Current Research and Scholarly Interests
Neuron death, stress, gene therapy
- Mechanisms of Neuron Death
BIO 151 (Aut)
BIO 84 (Win)
Independent Studies (15)
- Advanced Research Laboratory in Experimental Biology
BIO 199 (Aut, Spr, Sum)
- Bioengineering Problems and Experimental Investigation
BIOE 191 (Win, Spr, Sum)
- Directed Investigation
BIOE 392 (Aut, Win, Spr, Sum)
- Directed Reading in Biology
BIO 198 (Aut, Win, Spr, Sum)
- Directed Reading in Environment and Resources
ENVRES 398 (Aut, Win, Spr, Sum)
- Directed Reading in Neurosciences
NEPR 299 (Aut, Win, Spr, Sum)
- Directed Reading/Special Projects
HUMBIO 199 (Aut, Win, Spr)
- Directed Research in Environment and Resources
ENVRES 399 (Aut, Win, Spr, Sum)
- Directed Study
BIOE 391 (Aut, Spr, Sum)
- Graduate Research
BIO 300 (Aut, Win, Spr, Sum)
- Graduate Research
NEPR 399 (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Sum)
- Out-of-Department Directed Reading
BIO 198X (Sum)
- Out-of-Department Graduate Research
BIO 300X (Sum)
- Teaching of Biology
BIO 290 (Aut, Win, Spr)
- Advanced Research Laboratory in Experimental Biology
Prior Year Courses
- Human Behavioral Biology
BIO 150, HUMBIO 160 (Spr)
- Mechanisms of Neuron Death
BIO 151 (Aut)
BIO 84 (Win)
- Human Behavioral Biology
Graduate and Fellowship Programs
Biology (School of Humanities and Sciences) (Phd Program)
This Is Your Brain on Nationalism The Biology of Us and Them
2019; 98 (2): 42–47
View details for Web of Science ID 000458345300005
- Doubled-Edged Swords in the Biology of Conflict FRONTIERS IN PSYCHOLOGY 2018; 9
- THE HEALTH-WEALTH GAP SCIENTIFIC AMERICAN 2018; 319 (5): 63–67
Speculations on the Evolutionary Origins of System Justification
2018; 16 (2): 1474704918765342
For centuries, philosophers and social theorists have wondered why people submit voluntarily to tyrannical leaders and oppressive regimes. In this article, we speculate on the evolutionary origins of system justification, that is, the ways in which people are motivated (often nonconsciously) to defend and justify existing social, economic, and political systems. After briefly recounting the logic of system justification theory and some of the most pertinent empirical evidence, we consider parallels between the social behaviors of humans and other animals concerning the acceptance versus rejection of hierarchy and dominance. Next, we summarize research in human neuroscience suggesting that specific brain regions, such as the amygdala and the anterior cingulate cortex, may be linked to individual differences in ideological preferences concerning (in)equality and social stability as well as the successful navigation of complex, hierarchical social systems. Finally, we consider some of the implications of a system justification perspective for the study of evolutionary psychology, political behavior, and social change.
View details for DOI 10.1177/1474704918765342
View details for Web of Science ID 000435972500001
View details for PubMedID 29911406
The mTOR cell signaling pathway is crucial to the long-term protective effects of ischemic postconditioning against stroke.
2018; 676: 58–65
Ischemic postconditioning (IPostC) protects against stroke, but few have studied the pathophysiological mechanisms of its long-term protective effects. Here, we investigated whether the mTOR pathway is involved in the long-term protective effects of IPostC. Stroke was induced in rats by distal middle cerebral artery occlusion (dMCAo) combined with 30 min of bilateral common carotid artery (CCA) occlusion, and IPostC was induced after the CCA release. Injury size and behavioral tests were measured up to 3 weeks post stroke. We used rapamycin and mTOR shRNA lentiviral vectors to inhibit mTOR activities, while S6K1 viral vectors, a main downstream mTOR gene, were used to promote mTOR activities. We found that rapamycin administration abolished the long-term protective effects of IPostC. In addition, IPostC promoted the presynaptic growth associated protein 43 (GAP-43) and the postsynaptic protein 95 (PSD-95) levels at 1 week post-stroke, which were reduced by rapamycin. Furthermore, rapamycin reduced phosphorylated mTOR (p-mTOR) protein levels measured at 3 weeks after stroke. These results were confirmed by mTOR shRNA transfection. Moreover, we found that injection of S6K1 viral vectors promoted GAP-43 and PSD-95 protein levels. We conclude that mTOR may play a crucial, protective role in brain damage after stroke and contribute to the protective effects of IPostC.
View details for DOI 10.1016/j.neulet.2018.03.062
View details for PubMedID 29605662
Adult-generated neurons born during chronic social stress are uniquely adapted to respond to subsequent chronic social stress.
Chronic stress is a recognized risk factor for psychiatric and psychological disorders and a potent modulator of adult neurogenesis. Numerous studies have shown that during stress, neurogenesis decreases; however, during the recovery from the stress, neurogenesis increases. Despite the increased number of neurons born after stress, it is unknown if the function and morphology of those neurons are altered. Here we asked whether neurons in adult mice, born during the final 5 days of chronic social stress and matured during recovery from chronic social stress, are similar to neurons born with no stress conditions from a quantitative, functional and morphological perspective, and whether those neurons are uniquely adapted to respond to a subsequent stressful challenge. We observed an increased number of newborn neurons incorporated in the dentate gyrus of the hippocampus during the 10-week post-stress recovery phase. Interestingly, those new neurons were more responsive to subsequent chronic stress, as they showed more of a stress-induced decrease in spine density and branching nodes than in neurons born during a non-stress period. Our results replicate findings that the neuronal survival and incorporation of neurons in the adult dentate gyrus increases after chronic stress and suggest that such neurons are uniquely adapted in the response to future social stressors. This finding provides a potential mechanism for some of the long-term hippocampal effects of stress.
View details for DOI 10.1038/s41380-017-0013-1
View details for PubMedID 29311652
Psychiatric distress in animals versus animal models of psychiatric distress
2016; 19 (11): 1387-1389
The realm of human uniqueness steadily shrinks; reflecting this, other primates suffer from states closer to depression or anxiety than 'depressive-like' or 'anxiety-like behavior'. Nonetheless, there remain psychiatric domains unique to humans. Appreciating these continuities and discontinuities must inform the choice of neurobiological approach used in studying any animal model of psychiatric disorders. More fundamentally, the continuities reveal how aspects of psychiatric malaise run deeper than our species' history.
View details for Web of Science ID 000386539900004
View details for PubMedID 27786183
- Stress and the brain: individual variability and the inverted-U NATURE NEUROSCIENCE 2015; 18 (10): 1344-1346
Stress and glucocorticoids promote oligodendrogenesis in the adult hippocampus
2014; 19 (12): 1275-1283
Stress can exert long-lasting changes on the brain that contribute to vulnerability to mental illness, yet mechanisms underlying this long-term vulnerability are not well understood. We hypothesized that stress may alter the production of oligodendrocytes in the adult brain, providing a cellular and structural basis for stress-related disorders. We found that immobilization stress decreased neurogenesis and increased oligodendrogenesis in the dentate gyrus (DG) of the adult rat hippocampus and that injections of the rat glucocorticoid stress hormone corticosterone (cort) were sufficient to replicate this effect. The DG contains a unique population of multipotent neural stem cells (NSCs) that give rise to adult newborn neurons, but oligodendrogenic potential has not been demonstrated in vivo. We used a nestin-CreER/YFP transgenic mouse line for lineage tracing and found that cort induces oligodendrogenesis from nestin-expressing NSCs in vivo. Using hippocampal NSCs cultured in vitro, we further showed that exposure to cort induced a pro-oligodendrogenic transcriptional program and resulted in an increase in oligodendrogenesis and decrease in neurogenesis, which was prevented by genetic blockade of glucocorticoid receptor (GR). Together, these results suggest a novel model in which stress may alter hippocampal function by promoting oligodendrogenesis, thereby altering the cellular composition and white matter structure.
View details for DOI 10.1038/mp.2013.190
View details for Web of Science ID 000345423500005
View details for PubMedID 24514565
View details for PubMedCentralID PMC4128957
Toxoplasma gondii Is Dependent on Glutamine and Alters Migratory Profile of Infected Host Bone Marrow Derived Immune Cells through SNAT2 and CXCR4 Pathways
2014; 9 (10)
The obligate intracellular parasite, Toxoplasma gondii, disseminates through its host inside infected immune cells. We hypothesize that parasite nutrient requirements lead to manipulation of migratory properties of the immune cell. We demonstrate that 1) T. gondii relies on glutamine for optimal infection, replication and viability, and 2) T. gondii-infected bone marrow-derived dendritic cells (DCs) display both "hypermotility" and "enhanced migration" to an elevated glutamine gradient in vitro. We show that glutamine uptake by the sodium-dependent neutral amino acid transporter 2 (SNAT2) is required for this enhanced migration. SNAT2 transport of glutamine is also a significant factor in the induction of migration by the small cytokine stromal cell-derived factor-1 (SDF-1) in uninfected DCs. Blocking both SNAT2 and C-X-C chemokine receptor 4 (CXCR4; the unique receptor for SDF-1) blocks hypermotility and the enhanced migration in T. gondii-infected DCs. Changes in host cell protein expression following T. gondii infection may explain the altered migratory phenotype; we observed an increase of CD80 and unchanged protein level of CXCR4 in both T. gondii-infected and lipopolysaccharide (LPS)-stimulated DCs. However, unlike activated DCs, SNAT2 expression in the cytosol of infected cells was also unchanged. Thus, our results suggest an important role of glutamine transport via SNAT2 in immune cell migration and a possible interaction between SNAT2 and CXCR4, by which T. gondii manipulates host cell motility.
View details for DOI 10.1371/journal.pone.0109803
View details for Web of Science ID 000343941200074
View details for PubMedCentralID PMC4192591
Mammalian Target of Rapamycin Cell Signaling Pathway Contributes to the Protective Effects of Ischemic Postconditioning Against Stroke
2014; 45 (9): 2769-?
Whether the mammalian target of rapamycin (mTOR) pathway is protective against brain injury from stroke or is detrimental is controversial, and whether it is involved in the protective effects of ischemic postconditioning (IPC) against stroke is unreported. Our study focuses on the protective role of mTOR against neuronal injury after stroke with and without IPC.We used both an in vitro oxygen-glucose deprivation model with a mixed neuronal culture and hypoxic postconditioning, as well as an in vivo stroke model with IPC. Rapamycin, a specific pharmacological inhibitor of mTOR, and mTOR short hairpin RNA lentiviral vectors were used to inhibit mTOR activity. A lentiviral vector expressing S6K1, a downstream molecule of mTOR, was used to confirm the protective effects of mTOR. Infarct sizes were measured and protein levels were examined by Western blot.We report that stroke resulted in reduced levels of phosphorylated proteins in the mTOR pathway, including S6K1, S6, and 4EBP1, and that IPC increased these proteins. mTOR inhibition, both by the mTOR inhibitor rapamycin and by mTOR short hairpin RNA, worsened ischemic outcomes in vitro and in vivo and abolished the protective effects of hypoxic postconditioning and IPC on neuronal death in vitro and brain injury size in vivo. Overexpression of S6K1 mediated by lentiviral vectors significantly attenuated brain infarction.mTOR plays a crucial protective role in brain damage after stroke and contributes to the protective effects of IPC.
View details for DOI 10.1161/STROKEAHA.114.005406
View details for Web of Science ID 000341491500055
View details for PubMedID 25013017
View details for PubMedCentralID PMC4146669
Toxoplasma gondii influences aversive behaviors of female rats in an estrus cycle dependent manner
PHYSIOLOGY & BEHAVIOR
2014; 135: 98-103
The protozoan Toxoplasma gondii (T. gondii) manipulates the behavior of its rodent intermediate host to facilitate its passage to its feline definitive host. This is accomplished by a reduction of the aversive response that rodents show towards cat odors, which likely increases the predation risk. Females on average show similar changes as males. However, behaviors that relate to aversion and attraction are usually strongly influenced by the estrus cycle. In this study, we replicated behavioral effects of T. gondii in female rats, as well as expanded it to two novel behavioral paradigms. We also characterized the role of the estrus cycle in the behavioral effects of T. gondii on female rats. Uninfected females preferred to spend more time in proximity to rabbit rather than bobcat urine, and in a dark chamber rather than a lit chamber. Infected females lost both of these preferences, and also spent more time investigating social novelty (foreign bedding in their environment). Taken together, these data suggest that infection makes females less risk averse and more exploratory. Furthermore, this effect was influenced by the estrus cycle. Uninfected rats preferred rabbit urine to bobcat urine throughout the cycle except at estrus and metestrus. In contrast, infected rats lost this preference at every stage of the cycle except estrus. Commensurate with the possibility that this was a hormone-dependent effect, infected rats had elevated levels of circulating progesterone, a known anxiolytic.
View details for DOI 10.1016/j.physbeh.2014.05.036
View details for Web of Science ID 000341556800012
View details for PubMedID 24907696
Glucocorticoids increase excitotoxic injury and inflammation in the hippocampus of adult male rats.
2014; 100 (2-3): 129-140
Stress exacerbates neuron loss in many CNS injuries via the actions of adrenal glucocorticoid (GC) hormones. For some injuries, this GC endangerment of neurons is accompanied by greater immune cell activation in the CNS, a surprising outcome given the potent immunosuppressive properties of GCs.To determine whether the effects of GCs on inflammation contribute to neuron death or result from it, we tested whether nonsteroidal anti-inflammatory drugs could protect neurons from GCs during kainic acid excitotoxicity in adrenalectomized male rats. We next measured GC effects on (1) chemokine production (CCL2 and CINC-1), (2) signals that suppress immune activation (CX3CL1, CD22, CD200, and TGF-β), and (3) NF-κB activity.Concurrent treatment with minocycline, but not indomethacin, prevented GC endangerment. GCs did not substantially affect CCL2, CINC-1, or baseline NF-κB activity, but they did suppress CX3CL1, CX3CR1, and CD22 expression in the hippocampus - factors that normally restrain inflammatory responses.These findings demonstrate that cellular inflammation is not necessarily suppressed by GCs in the injured hippocampus; instead, GCs may worsen hippocampal neuron death, at least in part by increasing the neurotoxicity of CNS inflammation. © 2014 S. Karger AG, Basel.
View details for DOI 10.1159/000367849
View details for PubMedID 25228100
View details for PubMedCentralID PMC4304880
Akt isoforms differentially protect against stroke-induced neuronal injury by regulating mTOR activities
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2013; 33 (12): 1875-1885
Protein kinases Akt1 and Akt3 are considered to be more crucial to brain function than Akt2. We investigated the roles of Akt1 and Akt3 in stroke-induced brain injury and examined their interactions with the Akt/mTOR pathways. Focal ischemia was induced in rats. Lentiviral vectors expressing constitutively active Akt1 and Akt3 (cAkt1 and cAkt3) were injected into the ischemic cortex. Infarct sizes and gene and protein expressions in the Akt/mTOR pathways were evaluated. The results show that Akt1 and Akt3 proteins were degraded as early as 1 hour after stroke, whereas Akt2 proteins remained unchanged until 24 hours after stroke. Lentiviral-mediated overexpression of cAkt1 or cAkt3 reduced neuronal death after in vitro and in vivo ischemia. Interestingly, cAkt3 overexpression resulted in stronger protection than cAkt1 overexpression. Western blot analyses further showed that cAkt3 promoted significantly higher levels of phosphorylated Akt and phosphorylated mTOR than cAkt1. The mTOR inhibitor rapamycin blocked the protective effects of both cAkt1 and cAkt3. In conclusion, Akt isoforms are differentially regulated after stroke and Akt3 offers stronger protection than cAkt1 by maintaining Akt levels and promoting mTOR activity.
View details for DOI 10.1038/jcbfm.2013.132
View details for Web of Science ID 000328002200008
View details for PubMedID 23942361
View details for PubMedCentralID PMC3851893
Early Postnatal Handling Alters Glucocorticoid Receptor Concentrations in Selected Brain Regions
2013; 127 (5): 637-641
Norway rat pups were either handled (H) or undisturbed (nonhandled, NH) in the period between birth and weaning on Day 21. Following weaning, half of the animals in each group were housed socially (Soc), and half were housed in isolation (Isol). At 120-150 days of age, all animals were sacrificed, and the following regions were dissected and frozen at -70 °C until the time of assay: frontal cortex, hippocampus, hypothalamus, amygdala, septum, and pituitary. [3H]Dexamethasone (3H Dex) binding in each region was examined by an in vitro, cytosol, receptor assay. 3H Dex binding was significantly higher in the hippocampus of both H-Soc and H-Isol than in NH groups. In the frontal cortex, 3H Dex binding was higher in the H-Soc animals than in the H-Isol and NH-Isol animals. There were no significant handling or housing effects found in the amygdala, hypothalamus, septum, or pituitary. Thus, early postnatal handling appears to influence the development of the glucocorticoid receptor system in the hippocampus and frontal cortex. These results are discussed as providing a possible mechanism for some of the previously reported effects of early handling on the development of the pituitary-adrenal response to stress.
View details for DOI 10.1037/a0034187
View details for Web of Science ID 000325780300004
View details for PubMedID 24128353
Soluble TNF receptor 1-secreting ex vivo-derived dendritic cells reduce injury after stroke
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2013; 33 (9): 1376-1385
Inflammation is a major factor in the progression of damage after stroke and in the clinic, current therapies treat the clot, not the resulting damage. We have developed a novel method of protein delivery that exploits the migration ability of leukocytes after ischemic stroke (transient middle cerebral artery occlusion; tMCAO). In our studies, ex vivo-derived dendritic cells (exDCs) migrate to the inflamed rat brain soon after tMCAO onset and the number of cells that remain in the brain after injection is significantly correlated with the amount of local inflammation at the injury site. In addition, exDCs transduced to overexpress soluble tumor necrosis factor (TNF) receptor1 (sTNFR1) produce functional cargo that is secreted and that blocks TNF-α bioavailability in vitro. When delivered at 6 hours post-tMCAO reperfusion, sTNFR1-exDC-treated rats show significantly smaller infarct size and decreased inflammation compared with animals treated with exDCs transduced with GFP lentivirus. These studies indicate that cell-mediated delivery of proteins may be a promising new approach to reduce brain damage after acute neurologic insult.Journal of Cerebral Blood Flow & Metabolism advance online publication, 12 June 2013; doi:10.1038/jcbfm.2013.100.
View details for DOI 10.1038/jcbfm.2013.100
View details for Web of Science ID 000324126400009
View details for PubMedID 23756688
Spatial Memory and Long-Term Object Recognition Are Impaired by Circadian Arrhythmia and Restored by the GABA(A)Antagonist Pentylenetetrazole
2013; 8 (8)
Performance on many memory tests varies across the day and is severely impaired by disruptions in circadian timing. We developed a noninvasive method to permanently eliminate circadian rhythms in Siberian hamsters (Phodopussungorus) so that we could investigate the contribution of the circadian system to learning and memory in animals that are neurologically and genetically intact. Male and female adult hamsters were rendered arrhythmic by a disruptive phase shift protocol that eliminates cycling of clock genes within the suprachiasmatic nucleus (SCN), but preserves sleep architecture. These arrhythmic animals have deficits in spatial working memory and in long-term object recognition memory. In a T-maze, rhythmic control hamsters exhibited spontaneous alternation behavior late in the day and at night, but made random arm choices early in the day. By contrast, arrhythmic animals made only random arm choices at all time points. Control animals readily discriminated novel objects from familiar ones, whereas arrhythmic hamsters could not. Since the SCN is primarily a GABAergic nucleus, we hypothesized that an arrhythmic SCN could interfere with memory by increasing inhibition in hippocampal circuits. To evaluate this possibility, we administered the GABAA antagonist pentylenetetrazole (PTZ; 0.3 or 1.0 mg/kg/day) to arrhythmic hamsters for 10 days, which is a regimen previously shown to produce long-term improvements in hippocampal physiology and behavior in Ts65Dn (Down syndrome) mice. PTZ restored long-term object recognition and spatial working memory for at least 30 days after drug treatment without restoring circadian rhythms. PTZ did not augment memory in control (entrained) animals, but did increase their activity during the memory tests. Our findings support the hypothesis that circadian arrhythmia impairs declarative memory by increasing the relative influence of GABAergic inhibition in the hippocampus.
View details for DOI 10.1371/journal.pone.0072433
View details for Web of Science ID 000323734600019
View details for PubMedID 24009680
View details for PubMedCentralID PMC3756994
Glucocorticoid signaling in myeloid cells worsens acute CNS injury and inflammation.
journal of neuroscience
2013; 33 (18): 7877-7889
Glucocorticoid stress hormones (GCs) are well known for being anti-inflammatory, but some reports suggest that GCs can also augment aspects of inflammation during acute brain injury. Because the GC receptor (GR) is ubiquitously expressed throughout the brain, it is difficult to know which cell types might mediate these unusual "proinflammatory" GC actions. We examined this with cell type-specific deletion or overexpression of GR in mice experiencing seizure or ischemia. Counter to their classical anti-inflammatory actions, GR signaling in myeloid cells increased Iba-1 and CD68 staining as well as nuclear p65 levels in the injured tissue. GCs also reduced levels of occludin, claudin 5, and caveolin 1, proteins central to blood-brain-barrier integrity; these effects required GR in endothelial cells. Finally, GCs compromised neuron survival, an effect mediated by GR in myeloid and endothelial cells to a greater extent than by neuronal GR.
View details for DOI 10.1523/JNEUROSCI.4705-12.2013
View details for PubMedID 23637179
Derivation of Injury-Responsive Dendritic Cells for Acute Brain Targeting and Therapeutic Protein Delivery in the Stroke-Injured Rat
2013; 8 (4)
Research with experimental stroke models has identified a wide range of therapeutic proteins that can prevent the brain damage caused by this form of acute neurological injury. Despite this, we do not yet have safe and effective ways to deliver therapeutic proteins to the injured brain, and this remains a major obstacle for clinical translation. Current targeted strategies typically involve invasive neurosurgery, whereas systemic approaches produce the undesirable outcome of non-specific protein delivery to the entire brain, rather than solely to the injury site. As a potential way to address this, we developed a protein delivery system modeled after the endogenous immune cell response to brain injury. Using ex-vivo-engineered dendritic cells (DCs), we find that these cells can transiently home to brain injury in a rat model of stroke with both temporal and spatial selectivity. We present a standardized method to derive injury-responsive DCs from bone marrow and show that injury targeting is dependent on culture conditions that maintain an immature DC phenotype. Further, we find evidence that when loaded with therapeutic cargo, cultured DCs can suppress initial neuron death caused by an ischemic injury. These results demonstrate a non-invasive method to target ischemic brain injury and may ultimately provide a way to selectively deliver therapeutic compounds to the injured brain.
View details for DOI 10.1371/journal.pone.0061789
View details for Web of Science ID 000317893400111
View details for PubMedID 23613937
View details for PubMedCentralID PMC3627911
Toxoplasma gondii infection induces dendritic retraction in basolateral amygdala accompanied by reduced corticosterone secretion
DISEASE MODELS & MECHANISMS
2013; 6 (2): 516-520
Pathological anxiety is thought to reflect a maladaptive state characterized by exaggerated fear. Naturally occurring perturbations that reduce fear can be crucial in the search for new treatments. The protozoan parasite Toxoplasma gondii invades rat brain and removes the fear that rats have of cat odors, a change believed to be parasitic manipulation of host behavior aimed at increasing parasite transmission. It is likely that mechanisms employed by T. gondii can be used as a heuristic tool to understand possible means of fear reduction in clinical settings. Male Long-Evans rats were infected with T. gondii and compared with sham-infected animals 8 weeks after infection. The amount of circulating plasma corticosterone and dendritic arborization of basolateral amygdala principal neurons were quantified. Previous studies have shown that corticosterone, acting within the basolateral amygdala, enhances the fear response to environmental stimuli. Here we show that T. gondii infection causes a dendritic retraction in basolateral amygdala neurons. Such dendritic retraction is accompanied by lower amounts of circulating corticosterone, both at baseline and when induced by an aversive cat odor. The concerted effects of parasitism on two pivotal physiological nodes of the fear response provide an animal model relevant to interactions between stress hormones and amygdalar plasticity.
View details for DOI 10.1242/dmm.009928
View details for Web of Science ID 000317266500023
View details for PubMedID 23104989
View details for PubMedCentralID PMC3597033
Treponema pallidum Infection in the Wild Baboons of East Africa: Distribution and Genetic Characterization of the Strains Responsible
2012; 7 (12)
It has been known for decades that wild baboons are naturally infected with Treponema pallidum, the bacterium that causes the diseases syphilis (subsp. pallidum), yaws (subsp. pertenue), and bejel (subsp. endemicum) in humans. Recently, a form of T. pallidum infection associated with severe genital lesions has been described in wild baboons at Lake Manyara National Park in Tanzania. In this study, we investigated ten additional sites in Tanzania and Kenya using a combination of macroscopic observation and serology, in order to determine whether the infection was present in each area. In addition, we obtained genetic sequence data from six polymorphic regions using T. pallidum strains collected from baboons at two different Tanzanian sites. We report that lesions consistent with T. pallidum infection were present at four of the five Tanzanian sites examined, and serology was used to confirm treponemal infection at three of these. By contrast, no signs of treponemal infection were observed at the six Kenyan sites, and serology indicated T. pallidum was present at only one of them. A survey of sexually mature baboons at Lake Manyara National Park in 2006 carried out as part of this study indicated that roughly ten percent displayed T. pallidum-associated lesions severe enough to cause major structural damage to the genitalia. Finally, we found that T. pallidum strains from Lake Manyara National Park and Serengeti National Park were genetically distinct, and a phylogeny suggested that baboon strains may have diverged prior to the clade containing human strains. We conclude that T. pallidum infection associated with genital lesions appears to be common in the wild baboons of the regions studied in Tanzania. Further study is needed to elucidate the infection's transmission mode, its associated morbidity and mortality, and the relationship between baboon and human strains.
View details for DOI 10.1371/journal.pone.0050882
View details for Web of Science ID 000312794500017
View details for PubMedID 23284649
View details for PubMedCentralID PMC3527465
Corticosterone treatment impairs auditory fear learning and the dendritic morphology of the rat inferior colliculus
2012; 294 (1-2): 104-113
Stress leads to secretion of the adrenal steroid hormone corticosterone (CORT). The aim of this study was to determine the effects of chronic CORT administration on auditory and visual fear conditioning. Male Sprague-Dawley rats received CORT (400 mg/ml) in their drinking water for 10 consecutive days; this treatment induces stress levels of serum CORT. CORT impaired fear conditioning (F((1,28)) = 11.52, p < 0.01) and extinction (F((1,28)) = 4.86, p < 0.05) of auditory fear learning, but did not affect visual fear conditioning. In addition, we analyzed the CORT effects on the neuronal morphology of the inferior colliculus (flat neurons, auditory mesencephalon, a key brain area for auditory processing) and superior colliculus (wide-field neurons, related to visual processing) by Golgi stain. CORT decreased dendritic arborization of inferior colliculus neurons by approximately 50%, but did not affect superior colliculus neurons. Thus, CORT had more deleterious effects on the auditory fear processing than the visual system in the brain.
View details for DOI 10.1016/j.heares.2012.09.008
View details for Web of Science ID 000313088800012
View details for PubMedID 23088831
- Importance of a sense of control and the physiological benefits of leadership PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2012; 109 (44): 17730-17731
- Super Humanity SCIENTIFIC AMERICAN 2012; 307 (3): 40-43
Short-Term Enrichment Makes Male Rats More Attractive, More Defensive and Alters Hypothalamic Neurons
2012; 7 (5)
Innate behaviors are shaped by contingencies built during evolutionary history. On the other hand, environmental stimuli play a significant role in shaping behavior. In particular, a short period of environmental enrichment can enhance cognitive behavior, modify effects of stress on learned behaviors and induce brain plasticity. It is unclear if modulation by environment can extend to innate behaviors which are preserved by intense selection pressure. In the present report we investigate this issue by studying effects of relatively short (14-days) environmental enrichment on two prominent innate behaviors in rats, avoidance of predator odors and ability of males to attract mates. We show that enrichment has strong effects on both the innate behaviors: a) enriched males were more avoidant of a predator odor than non-enriched controls, and had a greater rise in corticosterone levels in response to the odor; and b) had higher testosterone levels and were more attractive to females. Additionally, we demonstrate decrease in dendritic length of neurons of ventrolateral nucleus of hypothalamus, important for reproductive mate-choice and increase in the same in dorsomedial nucleus, important for defensive behavior. Thus, behavioral and hormonal observations provide evidence that a short period of environmental manipulation can alter innate behaviors, providing a good example of gene-environment interaction.
View details for DOI 10.1371/journal.pone.0036092
View details for Web of Science ID 000305341500043
View details for PubMedID 22567125
View details for PubMedCentralID PMC3342313
Basolateral amygdala regulation of adult hippocampal neurogenesis and fear-related activation of newborn neurons
2012; 17 (5): 527-536
Impaired regulation of emotional memory is a feature of several affective disorders, including depression, anxiety and post-traumatic stress disorder. Such regulation occurs, in part, by interactions between the hippocampus and the basolateral amygdala (BLA). Recent studies have indicated that within the adult hippocampus, newborn neurons may contribute to support emotional memory, and that regulation of hippocampal neurogenesis is implicated in depressive disorders. How emotional information affects newborn neurons in adults is not clear. Given the role of the BLA in hippocampus-dependent emotional memory, we investigated whether hippocampal neurogenesis was sensitive to emotional stimuli from the BLA. We show that BLA lesions suppress adult neurogenesis, while lesions of the central nucleus of the amygdala do not. Similarly, we show that reducing BLA activity through viral vector-mediated overexpression of an outwardly rectifying potassium channel suppresses neurogenesis. We also show that BLA lesions prevent selective activation of immature newborn neurons in response to a fear-conditioning task. These results demonstrate that BLA activity regulates adult hippocampal neurogenesis and the fear context-specific activation of newborn neurons. Together, these findings denote functional implications for proliferation and recruitment of new neurons into emotional memory circuits.
View details for DOI 10.1038/mp.2011.71
View details for Web of Science ID 000303110800008
View details for PubMedID 21670733
Prokineticin 2 is an endangering mediator of cerebral ischemic injury
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (14): 5475-5480
Stroke causes brain dysfunction and neuron death, and the lack of effective therapies heightens the need for new therapeutic targets. Here we identify prokineticin 2 (PK2) as a mediator for cerebral ischemic injury. PK2 is a bioactive peptide initially discovered as a regulator of gastrointestinal motility. Multiple biological roles for PK2 have been discovered, including circadian rhythms, angiogenesis, and neurogenesis. However, the role of PK2 in neuropathology is unknown. Using primary cortical cultures, we found that PK2 mRNA is up-regulated by several pathological stressors, including hypoxia, reactive oxygen species, and excitotoxic glutamate. Glutamate-induced PK2 expression is dependent on NMDA receptor activation and extracellular calcium. Enriched neuronal culture studies revealed that neurons are the principal source of glutamate-induced PK2. Using in vivo models of stroke, we found that PK2 mRNA is induced in the ischemic cortex and striatum. Central delivery of PK2 worsens infarct volume, whereas PK2 receptor antagonist decreases infarct volume and central inflammation while improving functional outcome. Direct central inhibition of PK2 using RNAi also reduces infarct volume. These findings indicate that PK2 can be activated by pathological stimuli such as hypoxia-ischemia and excitotoxic glutamate and identify PK2 as a deleterious mediator for cerebral ischemia.
View details for DOI 10.1073/pnas.1113363109
View details for Web of Science ID 000302294700073
View details for PubMedID 22431614
View details for PubMedCentralID PMC3325724
Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice in Rats by Enhancing Attractiveness of Males
2011; 6 (11)
Females in various species typically avoid males infected with parasites, while parasite-free males advertise their status through conspicuous phenotypic traits. This process selects for heritable resistance and reduces direct exposure of the female to parasites. Coevolving parasites are likely to attempt to circumvent this obstacle. In this paper, we demonstrate a case of parasitic manipulation of host mate choice. We report that Toxoplasma gondii, a sexually transmitted infection of brown rats, enhances sexual attractiveness of infected males. Thus under some evolutionary niches, parasites can indeed manipulate host sexual signaling to their own advantage.
View details for DOI 10.1371/journal.pone.0027229
View details for Web of Science ID 000297154900092
View details for PubMedID 22073295
View details for PubMedCentralID PMC3206931
Predator Cat Odors Activate Sexual Arousal Pathways in Brains of Toxoplasma gondii Infected Rats
2011; 6 (8)
Cat odors induce rapid, innate and stereotyped defensive behaviors in rats at first exposure, a presumed response to the evolutionary pressures of predation. Bizarrely, rats infected with the brain parasite Toxoplasma gondii approach the cat odors they typically avoid. Since the protozoan Toxoplasma requires the cat to sexually reproduce, this change in host behavior is thought to be a remarkable example of a parasite manipulating a mammalian host for its own benefit. Toxoplasma does not influence host response to non-feline predator odor nor does it alter behavior on olfactory, social, fear or anxiety tests, arguing for specific manipulation in the processing of cat odor. We report that Toxoplasma infection alters neural activity in limbic brain areas necessary for innate defensive behavior in response to cat odor. Moreover, Toxoplasma increases activity in nearby limbic regions of sexual attraction when the rat is exposed to cat urine, compelling evidence that Toxoplasma overwhelms the innate fear response by causing, in its stead, a type of sexual attraction to the normally aversive cat odor.
View details for DOI 10.1371/journal.pone.0023277
View details for Web of Science ID 000294121300027
View details for PubMedID 21858053
View details for PubMedCentralID PMC3157360
- Sympathy for the CEO SCIENCE 2011; 333 (6040): 293-294
Transient Gastric Irritation in the Neonatal Rats Leads to Changes in Hypothalamic CRF Expression, Depression- and Anxiety-Like Behavior as Adults
2011; 6 (5)
A disturbance of the brain-gut axis is a prominent feature in functional bowel disorders (such as irritable bowel syndrome and functional dyspepsia) and psychological abnormalities are often implicated in their pathogenesis. We hypothesized that psychological morbidity in these conditions may result from gastrointestinal problems, rather than causing them.Functional dyspepsia was induced by neonatal gastric irritation in male rats. 10-day old male Sprague-Dawley rats received 0.1% iodoacetamide (IA) or vehicle by oral gavage for 6 days. At 8-10 weeks of age, rats were tested with sucrose preference and forced-swimming tests to examine depression-like behavior. Elevated plus maze, open field and light-dark box tests were used to test anxiety-like behaviors. ACTH and corticosterone responses to a minor stressor, saline injection, and hypothalamic CRF expression were also measured.Behavioral tests revealed changes of anxiety- and depression-like behaviors in IA-treated, but not control rats. As compared with controls, hypothalamic and amygdaloid CRF immunoreactivity, basal levels of plasma corticosterone and stress-induced ACTH were significantly higher in IA-treated rats. Gastric sensory ablation with resiniferatoxin had no effect on behaviors but treatment with CRF type 1 receptor antagonist, antalarmin, reversed the depression-like behavior in IA-treated ratsThe present results suggest that transient gastric irritation in the neonatal period can induce a long lasting increase in depression- and anxiety-like behaviors, increased expression of CRF in the hypothalamus, and an increased sensitivity of HPA axis to stress. The depression-like behavior may be mediated by the CRF1 receptor. These findings have significant implications for the pathogenesis of psychological co-morbidity in patients with functional bowel disorders.
View details for DOI 10.1371/journal.pone.0019498
View details for Web of Science ID 000290531100014
View details for PubMedID 21589865
View details for PubMedCentralID PMC3093391
An Insult-Inducible Vector System Activated by Hypoxia and Oxidative Stress for Neuronal Gene Therapy
TRANSLATIONAL STROKE RESEARCH
2011; 2 (1): 92-100
Gene therapy has demonstrated the protective potential of a variety of genes against stroke. However, conventional gene therapy vectors are limited due to the inability to temporally control their expression, which can sometimes lead to deleterious side effects. Thus, an inducible vector that can be temporally controlled and activated by the insult itself would be advantageous. Using hypoxia responsive elements (HRE) and antioxidant responsive elements (ARE), we have constructed an insult-inducible vector activated by hypoxia and reactive oxygen species (ROS). In COS7 cells, the inducible ARE-HRE-luciferase vectors are highly activated by oxygen deprivation, hydrogen peroxide treatment, and the ROS-induced transcription factor NF-E2-related factor 2 (Nrf2). Using a defective herpes virus, the neuroprotective potential of this inducible vector was tested by over-expressing the transcription factor Nrf2. In primary cortical cultures, expression of the inducible ARE-HRE-Nrf2 protects against oxygen glucose deprivation, similar to that afforded by the constitutively expressed Nrf2. This ARE+HRE vector system is advantageous in that it allows the expression of a transgene to be activated not only during hypoxia but also maintained after reperfusion, thus prolonging the transgene expression during an ischemic insult. This insult-inducible vector system will be a valuable gene therapy tool for activating therapeutic/protective genes in cerebrovascular diseases.
View details for DOI 10.1007/s12975-010-0060-2
View details for Web of Science ID 000304162800012
View details for PubMedID 21603078
View details for PubMedCentralID PMC3097421
RNAi-mediated Knockdown of Injury-induced Prokineticin 2 And Its Effects On Neuron Death
International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2011: E141–E141
View details for Web of Science ID 000287479400328
- Male African elephants (Loxodonta africana) queue when the stakes are high ETHOLOGY ECOLOGY & EVOLUTION 2011; 23 (4): 388-397
Glucocorticoids Exacerbate Lipopolysaccharide-Induced Signaling in the Frontal Cortex and Hippocampus in a Dose-Dependent Manner
JOURNAL OF NEUROSCIENCE
2010; 30 (41): 13690-13698
Although the anti-inflammatory actions of glucocorticoids (GCs) are well established, evidence has accumulated showing that proinflammatory GC effects can occur in the brain, in a poorly understood manner. Using electrophoretic mobility shift assay, real-time PCR, and immunoblotting, we investigated the ability of varying concentrations of corticosterone (CORT, the GC of rats) to modulate lipopolysaccharide (LPS)-induced activation of NF-κB (nuclear factor κB), expression of anti- and proinflammatory factors and of the MAP (mitogen-activated protein) kinase family [ERK (extracellular signal-regulated kinase), p38, and JNK/SAPK (c-Jun N-terminal protein kinase/stress-activated protein kinase)], and AKT. In the frontal cortex, elevated CORT levels were proinflammatory, exacerbating LPS effects on NF-κB, MAP kinases, and proinflammatory gene expression. Milder proinflammatory GCs effects occurred in the hippocampus. In the absence of LPS, elevated CORT levels increased basal activation of ERK1/2, p38, SAPK/JNK, and AKT in both regions. These findings suggest that GCs do not uniformly suppress neuroinflammation and can even enhance it at multiple levels in the pathway linking LPS exposure to inflammation.
View details for DOI 10.1523/JNEUROSCI.0303-09.2010
View details for Web of Science ID 000282874600015
View details for PubMedID 20943909
Gene therapy in rodent amygdala against fear disorders
EXPERT OPINION ON BIOLOGICAL THERAPY
2010; 10 (9): 1289-1303
Successful treatment of fear and anxiety disorders is presently a difficult task. A major limitation is the fact that underlying physiological mechanisms of fear and anxiety are only now beginning to be understood. As we obtain more information about mechanisms and brain circuits involved, treatment of these conditions will become increasingly realistic.Gene therapy is a promising treatment strategy that has several advantages over the more widely used pharmacological approaches. In this review we discuss the potential and limitation of gene therapy in the amygdala. This review concerns itself with papers published within the last 20 years in the field of gene therapy for fear and anxiety, and has been primarily conducted in rodent models.We present the current state of research into gene therapy for anxiety disorders, using a few case studies. The review will delineate challenges, limitations and opportunities for successful gene therapy.There are sizeable gains in knowledge about functioning of the fear system. This will inform future improvements in gene therapy approaches. An ideal gene therapy strategy will involve improvements in both delivery vectors and in design of therapeutic cargo.
View details for DOI 10.1517/14712598.2010.509341
View details for Web of Science ID 000281614500001
View details for PubMedID 20662544
Expression of chimeric estrogen-glucocorticoid-receptor in the amygdala reduces anxiety
2010; 1342: 33-38
The basolateral amygdala is critical for generating anxiety, and exposure to glucocorticoids induces anxiety. The demonstrated ability of glucocorticoids to cause dendritic expansion and increase excitability in the amygdala could help mediate the behavioral effects of glucocorticoids, and thus may be important therapeutic target for anxiety. In contrast, estrogen has the opposite effects of glucocorticoids in many domains. In this study, we employed a gene therapeutic approach to reduce anxiety and dendritic arborization of amygdaloid neurons of adult male Wistar rats. We used a herpes simplex viral vector to express a chimeric steroid receptor ("ERGR") which binds glucocorticoids yet transduces their actions into estrogenic effects. When expressed in the basolateral amygdala (BLA), ERGR reduced anxiety, as tested on elevated plus-maze and open field, without affecting conditioned fear, another amygdala-dependent behavior. Moreover, ERGR also blocked glucocorticoid-induced dendritic expansion of BLA neurons. Thus ERGR expression in the BLA provides a potential therapeutic against anxiety disorders.
View details for DOI 10.1016/j.brainres.2010.03.092
View details for Web of Science ID 000279717500004
View details for PubMedID 20381473
Neighbor effects of neurons bearing protective transgenes
2010; 1339: 70-75
Viral vectors bearing protective transgenes can decrease neurotoxicity after varied necrotic insults. A neuron that dies necrotically releases glutamate, calcium and reactive oxygen species, thereby potentially damaging neighboring neurons. This raises the possibility that preventing such neuron death via gene therapy can secondarily protect neighboring neurons that, themselves, do not express a protective transgene. We determined whether such "good neighbor" effects occur, by characterizing neurons that, while uninfected themselves, are in close proximity to a transgene-bearing neuron. We tested two genes whose overexpression protects against excitotoxicity: anti-apoptotic Bcl-2, and a calcium-activated K(+) channel, SK2. Using herpes simplex virus type 2-mediated transgene delivery to hippocampal cultures, we observed "good neighbor" effects on neuronal survival following an excitotoxic insult. However, in the absence of insult, "bad neighbor" effects could also occur (i.e., where being in proximity to a neuron constitutively expressing one of those transgenes is deleterious). We also characterized the necessity for cell-cell contact for these effects. These phenomena may have broad implications for the efficacy of gene overexpression strategies in the CNS.
View details for DOI 10.1016/j.brainres.2010.04.037
View details for Web of Science ID 000279041000008
View details for PubMedID 20417625
View details for PubMedCentralID PMC2885846
Manipulation of host behaviour by Toxoplasma gondii: what is the minimum a proposed proximate mechanism should explain?
2010; 57 (2): 88-94
The behavioural manipulation hypothesis posits that parasites can change the behaviour of hosts to increase the reproductive fitness of the parasite. The protozoan parasite Toxoplasma gondii fits this description well. Sexual reproduction occurs in the cat intestine, from which highly stable oocysts are excreted in faeces. Grazing animals, including rodents, can then ingest these oocysts. The parasite has evolved the capacity to abolish the innate fear that rodents have of the odours of cats, and to convert that fear into an attraction. This presumably increases the likelihood of the rodent being predated, thereby completing the parasite's life cycle. The behavioural syndrome produced by T. gondii does not have any precedent in neuroscience research. This is not a case where the normal functioning of fear system have been altered. This is not even the case of the altering of fear towards predator odours, while leaving other kinds of fear intact. This is an unprecedented example of one component of the fear being eliminated (and replaced by a novel attraction), while appearing to leave other domains unchanged. An understanding of the neurobiological effects of T. gondii is beginning to emerge. One possibility is T. gondii's preferential localisation to, and effects within the amygdala; this is particularly intriguing, given the role of this brain structure in the normal fear response. Obviously, far more must be understood, and the unique behavioural effects of T. gondii put very demanding constraints on any hypothesis we formulate to explain proximate neurobiological mechanisms.
View details for Web of Science ID 000279330700002
View details for PubMedID 20608470
Anti-Glucocorticoid Gene Therapy Reverses the Impairing Effects of Elevated Corticosterone on Spatial Memory, Hippocampal Neuronal Excitability, and Synaptic Plasticity
JOURNAL OF NEUROSCIENCE
2010; 30 (5): 1712-1720
Moderate release of the major stress hormones, glucocorticoids (GCs), improves hippocampal function and memory. In contrast, excessive or prolonged elevations produce impairments. Enzymatic degradation and reformation of GCs help to maintain optimal levels within target tissues, including the brain. We hypothesized that expressing a GC-degrading enzyme in hippocampal neurons would attenuate the negative impact of an excessive elevation in GC levels on synaptic physiology and spatial memory. We tested this by expressing 11-beta-hydroxysteroid dehydrogenase (type II) in dentate gyrus granule cells during a 3 d GC treatment followed by examination of synaptic responses in hippocampal slices or spatial performance in the Morris water maze. In adrenalectomized rats with basal GC replacement, additional GC treatments for 3 d reduced synaptic strength and promoted the expression of long-term depression at medial perforant path synapses, increased granule cell and CA1 pyramidal cell excitability, and impaired spatial reference memory (without influencing learning). Expression of 11-beta-hydroxysteroid dehydrogenase (type II), mostly in mature dentate gyrus granule cells, reversed the effects of high GC levels on granule cell and pyramidal cell excitability, perforant path synaptic plasticity, and spatial memory. These data demonstrate the ability of neuroprotective gene expression limited to a specific cell population to both locally and trans-synaptically offset neurophysiological disruptions produced by prolonged increases in circulating stress hormones. This report supplies the first physiological explanation for previously demonstrated cognitive sparing by anti-stress gene therapy approaches and lends additional insight into the hippocampal processes that are important for memory.
View details for DOI 10.1523/JNEUROSCI.4402-09.2010
View details for Web of Science ID 000274246700014
View details for PubMedID 20130180
View details for PubMedCentralID PMC3516494
Evidence for caspase effects on release of cytochrome c and AIF in a model of ischemia in cortical neurons
2010; 469 (2): 179-183
Neuronal apoptosis following ischemia can be mediated by a caspase-dependent pathway, which involves the mitochondrial release of cytochrome c that initiates a cascade of caspase activation. In addition, there is a caspase-independent pathway, which is mediated by the release of apoptosis-inducing factor (AIF). Using caspase inhibitor gene therapy, we investigated the roles of caspases on the mitochondrial release of cyt c and the release of AIF. Specifically, we used herpes simplex virus-1 amplicon vectors to ectopically express a viral caspase inhibitor (crmA or p35) in mixed cortical cultures exposed to oxygen/glucose deprivation. Overexpression of either crmA or p35 (but not the caspase-3 inhibitor DEVD) inhibited the release of AIF; this suggests that there can be cross-talk between the caspase-dependent and the ostensibly caspase-independent pathway. In addition, both crmA overexpression and DEVD inhibited cyt c release, suggesting a positive feedback loop involving activated caspases stimulating cyt c release.
View details for DOI 10.1016/j.neulet.2009.11.067
View details for Web of Science ID 000274508700001
View details for PubMedID 19944742
View details for PubMedCentralID PMC2826205
- Glucocorticoids can arm macrophages for innate immune battle BRAIN BEHAVIOR AND IMMUNITY 2010; 24 (1): 17-18
Changes in Brain MicroRNAs Contribute to Cholinergic Stress Reactions
13th International Symposium on Cholinergic Mechanisms
HUMANA PRESS INC. 2010: 47–55
Mental stress modifies both cholinergic neurotransmission and alternative splicing in the brain, via incompletely understood mechanisms. Here, we report that stress changes brain microRNA (miR) expression and that some of these stress-regulated miRs regulate alternative splicing. Acute and chronic immobilization stress differentially altered the expression of numerous miRs in two stress-responsive regions of the rat brain, the hippocampal CA1 region and the central nucleus of the amygdala. miR-134 and miR-183 levels both increased in the amygdala following acute stress, compared to unstressed controls. Chronic stress decreased miR-134 levels, whereas miR-183 remained unchanged in both the amygdala and CA1. Importantly, miR-134 and miR-183 share a common predicted mRNA target, encoding the splicing factor SC35. Stress was previously shown to upregulate SC35, which promotes the alternative splicing of acetylcholinesterase (AChE) from the synapse-associated isoform AChE-S to the, normally rare, soluble AChE-R protein. Knockdown of miR-183 expression increased SC35 protein levels in vitro, whereas overexpression of miR-183 reduced SC35 protein levels, suggesting a physiological role for miR-183 regulation under stress. We show stress-induced changes in miR-183 and miR-134 and suggest that, by regulating splicing factors and their targets, these changes modify both alternative splicing and cholinergic neurotransmission in the stressed brain.
View details for DOI 10.1007/s12031-009-9252-1
View details for Web of Science ID 000273753500008
View details for PubMedID 19711202
View details for PubMedCentralID PMC2807969
Resilience against predator stress and dendritic morphology of amygdala neurons
BEHAVIOURAL BRAIN RESEARCH
2009; 205 (2): 535-543
Individual differences in coping response lie at the core of vulnerability to conditions like post-traumatic stress disorder (PTSD). Like humans, not all animals exposed to severe stress show lasting change in affect. Predator stress is a traumatic experience inducing long-lasting fear, but not in all rodents. Thus, individual variation may be a cross species factor driving responsiveness to stressful events. The present study investigated neurobiological bases of variation in coping with severe stress. The amygdala was studied because it modulates fear and its function is affected by stress. Moreover, stress-induced plasticity of the amygdala has been related to induction of anxiety, a comorbid symptom of psychiatric conditions like PTSD. We exposed rodents to predator stress and grouped them according to their adaptability based on a standard anxiety test (the elevated plus maze). Subsequently we investigated if well-adapted (less anxious) and mal-adapted (extremely anxious) stressed animals differed in the structure of dendritic trees of their output neurons of the right basolateral amygdala (BLA). Two weeks after exposure to stress, well-adapted animals showed low anxiety levels comparable to unstressed controls, whereas mal-adapted animals were highly anxious. In these same animals, Golgi analysis revealed that BLA neurons of well-adapted rats exhibited more densely packed and shorter dendrites than neurons of mal-adapted or unstressed control animals, which did not differ. These data suggest that dendritic hypotrophy in the BLA may be a resilience marker against lasting anxiogenic effects of predator stress.
View details for DOI 10.1016/j.bbr.2009.08.014
View details for Web of Science ID 000271253100030
View details for PubMedID 19686780
The microtubule interacting drug candidate NAP protects against kainic acid toxicity in a rat model of epilepsy
JOURNAL OF NEUROCHEMISTRY
2009; 111 (5): 1252-1263
NAP (NAPVSIPQ, generic name, davunetide), a neuroprotective peptide in clinical development for neuroprotection against Alzheimer's disease and other neurodegenerative indications, has been recently shown to provide protection against kainic acid excitotoxicity in hippocampal neuronal cultures. In vivo, kainic acid toxicity models status epilepticus that is associated with hippocampal cell death. Kainic acid toxicity has been previously suggested to involve the microtubule cytoskeleton and NAP is a microtubule-interacting drug candidate. In the current study, kainic acid-treated rats showed epileptic seizures and neuronal death. Injection of NAP into the dentate gyrus partially protected against kainic acid-induced CA3 neuron death. Microarray analysis (composed of > 31 000 probe sets, analyzing over 30 000 transcripts and variants from over 25 000 well-substantiated rat genes) in the kainic acid-injured rat brain revealed multiple changes in gene expression, which were prevented, in part, by NAP treatment. Selected transcripts were further verified by reverse transcription coupled with quantitative real-time polymerase chain reaction. Importantly, among the transcripts regulated by NAP were key genes associated with proconvulsant properties and with long-lasting changes that underlie the epileptic state, including activin A receptor (associated with apoptosis), neurotensin (associated with proper neurotransmission) and the Wolfram syndrome 1 homolog (human, associated with neurodegeneration). These data suggest that NAP may provide neuroprotection in one of the most serious neurological conditions, epilepsy.
View details for DOI 10.1111/j.1471-4159.2009.06415.x
View details for Web of Science ID 000271496500016
View details for PubMedID 19799711
NAP protects against cyanide-related microtubule destruction
Inter-Academic Symposium on Neurobiology of Neuro-Psychiatric Diseases
SPRINGER WIEN. 2009: 1411–16
The peptide NAP (NAPVSIPQ) was shown to protect neurons against a wide variety of insults. Particularly, NAP was shown to be neuroprotective in vitro against cyanide in hippocampal cultures and against oxygen-glucose deprivation in hippocampal and cortical neuronal cultures. Cyanide causes energy depletion in the cell and destroys the cytoskeleton, and NAP has been shown before to protect the microtubule cytoskeleton. The current study explored the effect of NAP on cyanide-induced microtubule destruction in cerebral cortical cultures. Sodium cyanide (6.8 mM) reduced the number of neurons containing intact microtubules as identified by bIII-tubulin immunostaining. When sodium cyanide was added together with NAP (10(-14)-10(-12) M), complete protection was observed. Although the primary site of action of cyanide is considered to be the mitochondria, the current results involve microtubule destruction by cyanide toxicity that is completely reversed by NAP treatment.
View details for DOI 10.1007/s00702-009-0252-7
View details for Web of Science ID 000271417800009
View details for PubMedID 19551468
The Stressed CNS: When Glucocorticoids Aggravate Inflammation
2009; 64 (1): 33-39
Glucocorticoids (GCs) are hormones released during the stress response that are well known for their immunosuppressive and anti-inflammatory properties; however, recent advances have uncovered situations wherein they have effects in the opposite direction. The CNS is a particularly interesting example, both because of its unique immune environment, and because GCs affect immune responses differently in different brain regions. In this minireview we discuss the contexts wherein GCs increase CNS inflammation and point out directions for future investigation.
View details for DOI 10.1016/j.neuron.2009.09.032
View details for Web of Science ID 000271454400008
View details for PubMedID 19840546
Mineralocorticoid Receptor Overexpression in Basolateral Amygdala Reduces Corticosterone Secretion and Anxiety
2009; 66 (7): 686-690
The amygdala plays a critical role in the development of anxiety and the regulation of stress hormone secretion. Reciprocally, stress and stress hormones can induce amygdala hypertrophy, a phenomenon related to enhanced anxiety. As such, modulating amygdaloid function can potentially reduce maladaptive features of the stress response. The amygdala contains two kind of receptor for corticosteroids, the adrenal steroid hormone released during stress: glucocorticoid receptors (GRs) and mineralocorticoid receptors (MRs). Although high-affinity MRs are heavily occupied during basal conditions, low-affinity GRs are heavily occupied only by stress levels of glucocorticoids. Prolonged and heavy occupancy of GRs tends to mediate the deleterious effects of glucocorticoids on neurons, whereas MR occupancy tends to mediate beneficial effects.In this report, we overexpress MR in neurons of adult rat basolateral amygdala, with a herpes simplex viral vector coding for two copies of MR.Such overexpression reduced anxiety, as measured on an elevated plus-maze, and reduced the magnitude of glucocorticoid secretion after an acute stressor.Thus, increasing MR signaling in basolateral amygdala could be valuable in management of stress disorders.
View details for DOI 10.1016/j.biopsych.2009.04.016
View details for Web of Science ID 000269981700010
View details for PubMedID 19500777
NAP protects against cytochrome c release: Inhibition of the initiation of apoptosis
EUROPEAN JOURNAL OF PHARMACOLOGY
2009; 618 (1-3): 9-14
NAPVSIPQ (NAP), an 8 amino acid peptide derived from activity-dependent neuroprotective protein (ADNP), provides neuroprotection through interaction with microtubules. Previous results have demonstrated NAP protection against oxygen-glucose deprivation in hippocampal cells in culture. Furthermore, in vivo studies have shown that NAP reduces caspase 3 activation in rats subjected to permanent mid-cerebral artery occlusion (a rat model of stroke). Oxygen-glucose deprivation (ischemia) has been associated with microtubule breakdown and cytochrome c release from mitochondria leading to apoptosis. Here, NAP in concentrations ranging from 10(-14)M to 10(-8)M completely blocked cytochrome c release in cortical neurons subjected to oxygen-glucose deprivation. Furthermore, quantitative microscopy coupled to microtubule immunocytochemistry suggested that NAP prevented microtubule degradation under oxidative stress. As cytochrome c release is a known initiator of the apoptotic pathway, it is suggested that NAP inhibits the early events of apoptosis.
View details for DOI 10.1016/j.ejphar.2009.07.013
View details for Web of Science ID 000270110500002
View details for PubMedID 19619522
SK2 potassium channel overexpression in basolateral amygdala reduces anxiety, stress-induced corticosterone secretion and dendritic arborization
2009; 14 (9): 847-855
The basolateral amygdala is critical for generation of anxiety. In addition, exposure to both stress and glucocorticoids induces anxiety. Demonstrated ability of the amygdala to change in response to stress and glucocorticoids could thus be important therapeutic target for anxiety management. Several studies have reported a relationship between anxiety and dendritic arborization of the amygdaloid neurons. In this study we employed a gene therapeutic approach to reduce anxiety and dendritic arborization of the amygdala neurons. Specifically, we overexpressed SK2 potassium channel in the basolateral amygdala using a herpes simplex viral system. Our choice of therapeutic cargo was guided by the indications that activation of the amygdala might underlie anxiety and that SK2 could reduce neuronal activation by exerting inhibitory influence on action potentials. We report that SK2 overexpression reduced anxiety and stress-induced corticosterone secretion at a systemic level. SK2 overexpression also reduced dendritic arborization of the amygdala neurons. Hence, SK2 is a potential gene therapy candidate molecule that can be used against stress-related neuropsychiatric disorders such as anxiety.
View details for DOI 10.1038/mp.2009.9
View details for Web of Science ID 000269150100005
View details for PubMedID 19204724
View details for PubMedCentralID PMC2763614
Effects of overexpression of antioxidants on the release of cytochrome c and apoptosis-inducing factor in the model of ischemia
2009; 453 (3): 182-185
Apoptosis arises from neuronal damage following an ischemic insult. Apoptosis-inducing factor (AIF) is a protein released from mitochondria in response to pro-apoptotic signals which then translocates to the nucleus and triggers DNA fragmentation. In parallel with this, pro-apoptotic signals cause the release of cytochrome c from mitochondria, activating caspase-dependent apoptosis. During post-ischemic reperfusion, reactive oxygen species (ROS) are formed in excess in mitochondria and can play a role in initiating apoptosis. In cultures, ROS are formed during post oxygen glucose deprivation (OGD) normoxia/normoglycemia that is used as a model for ischemia. In this study, we delivered viral vectors to overexpress antioxidants (GPX, catalase, CuZnSOD, or MnSOD) in mixed cortical cultures, in order to investigate the effects of ROS-reduction on the release of cytochrome c and AIF. Overexpression of MnSOD, CuZnSOD, catalase or GPX all prevented AIF translocation from mitochondria to the nucleus. Potentially, this could reflect broadly non-specific protection due to reducing ROS load. Arguing against this, overexpression of the same antioxidants did not inhibit cytochrome c release. These findings suggest a specific interaction between ROS formation and the caspase-independent route of apoptosis.
View details for DOI 10.1016/j.neulet.2009.02.020
View details for Web of Science ID 000264946600012
View details for PubMedID 19429031
Prokineticin 2 Exacerbates Cerebral Ischemic Injury In Rats
American-Association-International-Stroke Conference 2009
LIPPINCOTT WILLIAMS & WILKINS. 2009: E213–E213
View details for Web of Science ID 000264709500527
Disruption of Fear Memory Through Dual-Hormone Gene Therapy
2009; 65 (5): 441-444
The basolateral complex of the amygdala (BLA) is uniquely affected by steroid hormones. Whereas glucocorticoids (GCs)--the adrenal hormones released during stress--increase the excitability of BLA neurons, estrogen decreases it.In this study, we used a vector designed to express a chimeric gene that contains the GC-binding domain of the GC receptor (GR) and the DNA binding domain of the estrogen receptor (ER) ("ER/GR") in infected neurons; as a result, it transduces GC signals into estrogenic ones. We microinfused ER/GR bilaterally into the BLA of rats to determine whether it would impair fear conditioning, a valuable BLA-dependent paradigm for studying the neural basis of emotional memory.Expression of ER/GR in the BLA caused robust expression of the transgene and a significant disruption of both auditory and contextual long-term fear memory consolidation, whereas fear learning and post-shock freezing remained intact.These data show that dual gene therapy with ER/GR might be a useful tool for understanding the role of steroid hormones in the storage of traumatic memories.
View details for DOI 10.1016/j.biopsych.2008.09.003
View details for Web of Science ID 000263455300013
View details for PubMedID 18973875
Blocking glucocorticoid and enhancing estrogenic genomic signaling protects against cerebral ischemia
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2009; 29 (1): 130-136
Glucocorticoids (GCs) and estrogen can modulate neuron death and dysfunction during neurological insults. Glucocorticoids are adrenal steroids secreted during stress, and hypersecretion of GCs during cerebral ischemia compromises the ability of hippocampal and cortical neurons to survive. In contrast, estrogen can be neuroprotective after cerebral ischemia. Here we evaluate the protective potential of a herpes viral vector expressing a chimeric receptor (ER/GR), which is composed of the ligand-binding domain of the GC receptor (GR) and the DNA-binding domain of the estrogen receptor-alpha (ER). This novel receptor can transduce an endangering GC signal into a protective estrogenic one. Using an in vitro oxygen glucose deprivation model (OGD), GCs exacerbated neuron death in primary cortical cultures, and this worsening effect was completely blocked by ER/GR expression. Moreover, blocking GC actions with a vector expressing a dominant negative GC receptor promoted neuron survival during postischemia, but not preischemia. Thus, gene therapeutic strategies to modulate GC and estrogen signaling can be beneficial during an ischemic insult.
View details for DOI 10.1038/jcbfm.2008.105
View details for Web of Science ID 000262110200015
View details for PubMedID 18797472
The Influence of Stress Hormones on Fear Circuitry
ANNUAL REVIEW OF NEUROSCIENCE
2009; 32: 289-313
Fear arousal, initiated by an environmental threat, leads to activation of the stress response, a state of alarm that promotes an array of autonomic and endocrine changes designed to aid self-preservation. The stress response includes the release of glucocorticoids from the adrenal cortex and catecholamines from the adrenal medulla and sympathetic nerves. These stress hormones, in turn, provide feedback to the brain and influence neural structures that control emotion and cognition. To illustrate this influence, we focus on how it impacts fear conditioning, a behavioral paradigm widely used to study the neural mechanisms underlying the acquisition, expression, consolidation, reconsolidation, and extinction of emotional memories. We also discuss how stress and the endocrine mediators of the stress response influence the morphological and electrophysiological properties of neurons in brain areas that are crucial for fear-conditioning processes, including the amygdala, hippocampus, and prefrontal cortex. The information in this review illuminates the behavioral and cellular events that underlie the feedforward and feedback networks that mediate states of fear and stress and their interaction in the brain.
View details for DOI 10.1146/annurev.neuro.051508.135620
View details for Web of Science ID 000268504100013
View details for PubMedID 19400714
Effects of enrichment predominate over those of chronic stress on fear-related behavior in male rats
STRESS-THE INTERNATIONAL JOURNAL ON THE BIOLOGY OF STRESS
2009; 12 (4): 305-312
The ability to discriminate between spatial contexts is crucial for survival. This ability can be succinctly tested in the paradigm of fear renewal. In this paradigm, a change of spatial context results in robust renewal of conditioned fear, even if the conditioned fear has been previously extinguished. Chronic stress and environmental enrichment are known to affect learning and memory in opposite directions, with the former generally being deleterious. In this study, we examined the effects of chronic stress and enrichment on fear renewal in rats. Fear was evaluated as freezing responses to an auditory conditioning stimulus initially associated with footshocks in context A; fear extinction was evaluated in a novel spatial context (B) without the conditioned stimulus, and renewal in a third context (C) with the auditory cue. Specifically, we aimed to test if environmental enrichment can oppose the effects of chronic stress on fear renewal. We exposed different groups of adult male Wistar rats (6-12 per group) to 10 days of chronic stress (immobilization for 2 h daily), 14 days of enrichment, or a combination of both. We report that chronic stress compromised fear extinction and renewal. In contrast, enrichment re-established fear renewal in chronically stressed rats. Enhanced contextual modulation of fear memories in animals experiencing environmental enrichment while stressed could reflect an adaptive response. This could allow greater flexibility to optimize vigilance in differing spatial contexts.
View details for DOI 10.1080/10253890802379955
View details for Web of Science ID 000268932300003
View details for PubMedID 19051124
Hippocampal-dependent learning requires a functional circadian system
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2008; 105 (40): 15593-15598
Decades of studies have shown that eliminating circadian rhythms of mammals does not compromise their health or longevity in the laboratory in any obvious way. These observations have raised questions about the functional significance of the mammalian circadian system, but have been difficult to address for lack of an appropriate animal model. Surgical ablation of the suprachiasmatic nucleus (SCN) and clock gene knockouts eliminate rhythms, but also damage adjacent brain regions or cause developmental effects that may impair cognitive or other physiological functions. We developed a method that avoids these problems and eliminates rhythms by noninvasive means in Siberian hamsters (Phodopus sungorus). The present study evaluated cognitive function in arrhythmic animals by using a hippocampal-dependent learning task. Control hamsters exhibited normal circadian modulation of performance in a delayed novel-object recognition task. By contrast, arrhythmic animals could not discriminate a novel object from a familiar one only 20 or 60 min after training. Memory performance was not related to prior sleep history as sleep manipulations had no effect on performance. The GABA antagonist pentylenetetrazol restored learning without restoring circadian rhythms. We conclude that the circadian system is involved in memory function in a manner that is independent of sleep. Circadian influence on learning may be exerted via cyclic GABA output from the SCN to target sites involved in learning. Arrhythmic hamsters may have failed to perform this task because of chronic inhibitory signaling from the SCN that interfered with the plastic mechanisms that encode learning in the hippocampus.
View details for DOI 10.1073/pnas.0808259105
View details for Web of Science ID 000260360500068
View details for PubMedID 18832172
View details for PubMedCentralID PMC2563080
Viral vector-mediated blockade of the endocrine stress-response modulates non-spatial memory
2008; 437 (1): 1-4
Stress results in the release of glucocorticoids (GCs) which at high levels, impair performance on hippocampus-dependent tasks. Estrogen is neurotrophic and can rescue stress-induced memory impairments. Here we report the use of a viral vector to overexpress a chimeric gene (ER/GR) that converts the deleterious effects of glucocorticoids into beneficial estrogenic effects. A short immobilization stress regimen was sufficient to impair non-spatial memory. In contrast, viral vector-mediated overexpression of ER/GR in the dentate gyrus of the hippocampus protected against stress-induced impairments of non-spatial memory. These data add to the growing evidence that increasing estrogenic signaling can protect against the impairing effects of stress on non-spatial memory.
View details for DOI 10.1016/j.neulet.2008.03.016
View details for Web of Science ID 000256201000001
View details for PubMedID 18423865
View details for PubMedCentralID PMC2492835
Acute corticosterone treatment is sufficient to induce anxiety and amygdaloid dendritic hypertrophy
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2008; 105 (14): 5573-5578
Stress is known to induce dendritic hypertrophy in the basolateral amygdala (BLA) and to enhance anxiety. Stress also leads to secretion of glucocorticoids (GC), and the BLA has a high concentration of glucocorticoid receptors. This raises the possibility that stress-induced elevation in GC secretion might directly affect amygdaloid neurons. To address the possible effects of GC on neurons of amygdala and on anxiety, we used rats treated either acutely with a single dose or chronically with 10 daily doses of high physiological levels of corticosterone (the rat-specific glucocorticoid). Behavior and morphological changes in neurons of BLA were measured 12 days after the initiation of treatment in both groups. A single acute dose of corticosterone was sufficient to induce dendritic hypertrophy in the BLA and heightened anxiety, as measured on an elevated plus maze. Moreover, this form of dendritic hypertrophy after acute treatment was of a magnitude similar to that caused by chronic treatment. Thus, plasticity of BLA neurons is sufficiently sensitive so as to be saturated by a single day of stress. The effects of corticosterone were specific to anxiety, as neither acute nor chronic treatment caused any change in conditioned fear or in general locomotor activity in these animals.
View details for Web of Science ID 000254893600052
View details for PubMedID 18391224
Anti-apoptotic therapy with a Tat fusion protein protects against excitotoxic insults in vitro and in vivo
2008; 210 (2): 602-607
A number of gene therapy approaches have been developed for protecting neurons from necrotic neurological insults. Such therapies are limited by the need for transcription and translation of the protective protein, delaying therapeutic impact. As an alternative, we explore the neuroprotective potential of protein therapy, using a fusion protein comprised of the death-suppressing BH4 domain of the Bcl-xL protein and the protein transduction domain of the human immunodeficiency virus Tat protein. This fusion protein decreased neurotoxicity caused by the excitotoxins glutamate and kainic acid in primary hippocampal cultures, and decreased hippocampal damage in vivo in an excitotoxic seizure model.
View details for DOI 10.1016/j.expneurol.2007.12.008
View details for Web of Science ID 000254894200033
View details for PubMedID 18207142
Hypothermia blacks beta-catenin degradation after focal ischemia in rats
2008; 1198: 182-187
Dephosphorylated and activated glycogen synthase kinase (GSK) 3beta hyperphosphorylates beta-catenin, leading to its ubiquitin-proteosome-mediated degradation. beta-catenin-knockdown increases while beta-catenin overexpression prevents neuronal death in vitro; in addition, protein levels of beta-catenin are reduced in the brain of Alzheimer's patients. However, whether beta-catenin degradation is involved in stroke-induced brain injury is unknown. Here we studied activities of GSK 3beta and beta-catenin, and the protective effect of moderate hypothermia (30 degrees C) on these activities after focal ischemia in rats. The results of Western blot showed that GSK 3beta was dephosphorylated at 5 and 24 h after stroke in the normothermic (37 degrees C) brain; hypothermia augmented GSK 3beta dephosphorylation. Because hypothermia reduces infarction, these results contradict with previous studies showing that GSK 3beta dephosphorylation worsens neuronal death. Nevertheless, hypothermia blocked degradation of total GSK 3beta protein. Corresponding to GSK 3beta activity in normothermic rats, beta-catenin phosphorylation transiently increased at 5 h in both the ischemic penumbra and core, and the total protein level of beta-catenin degraded after normothermic stroke. Hypothermia did not inhibit beta-catenin phosphorylation, but it blocked beta-catenin degradation in the ischemic penumbra. In conclusion, moderate hypothermia can stabilize beta-catenin, which may contribute to the protective effect of moderate hypothermia.
View details for DOI 10.1016/j.brainres.2008.01.007
View details for Web of Science ID 000254106400020
View details for PubMedID 18241848
View details for PubMedCentralID PMC2350209
An insult-inducible vector system activated by hypoxia inducible factor 1 (hif1) and reactive oxygen species
33rd International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2008: 727–28
View details for Web of Science ID 000252726100863
Overexpression of Mineralocorticoid and Transdominant Glucocorticoid Receptor Blocks the Impairing Effects of Glucocorticoids on Memory
2008; 18 (11): 1103-1111
It is well established that mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) influence hippocampal-dependent spatial memory. MRs are saturated in the presence of low corticosterone (CORT) levels; consequently receptor protein levels play a rate-limiting role in regulating the positive effects of MR-mediated gene transcription. In this study, viral vector-mediated transgene expression was used to simultaneously manipulate both MR and GR signaling. This approach allowed us to investigate the effects of spatially restricted overexpression of MR and a negative transdominant GR (TD) in the dentate gyrus (DG) subfield of the hippocampus, on short term and long term spatial memory in animals overexpressing one copy of MR or TD, two copies of MR ("MR/MR"), or one copy of each ("MR/TD"). Expression of transgenes did not influence the acquisition (learning) phase of the Morris water maze task. However, we found an overall enhancing effect of MR/MR expression on short term memory performance. In addition, rats expressing TD and MR/TD blocked the high CORT-induced impairments on long term spatial memory retrieval. These findings illustrate the potential beneficial effects of increasing MR signaling or decreasing GR signaling to enhance specific aspects of cognitive function.
View details for DOI 10.1002/hipo.20467
View details for Web of Science ID 000260914000005
View details for PubMedID 18651616
General versus specific actions of mild-moderate hypothermia in attenuating cerebral ischemic damage
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2007; 27 (12): 1879-1894
Mild or moderate hypothermia is generally thought to block all changes in signaling events that are detrimental to ischemic brain, including ATP depletion, glutamate release, Ca(2+) mobilization, anoxic depolarization, free radical generation, inflammation, blood-brain barrier permeability, necrotic, and apoptotic pathways. However, the effects and mechanisms of hypothermia are, in fact, variable. We emphasize that, even in the laboratory, hypothermic protection is limited. In certain models of permanent focal ischemia, hypothermia may not protect at all. In cases where hypothermia reduces infarct, some studies have overemphasized its ability to maintain cerebral blood flow and ATP levels, and to prevent anoxic depolarization, glutamate release during ischemia. Instead, hypothermia may protect against ischemia by regulating cascades that occur after reperfusion, including blood-brain barrier permeability and the changes in gene and protein expressions associated with necrotic and apoptotic pathways. Hypothermia not only blocks multiple damaging cascades after stroke, but also selectively upregulates some protective genes. However, most of these mechanisms are addressed in models with intraischemic hypothermia; much less information is available in models with postischemic hypothermia. Moreover, although it has been confirmed that mild hypothermia is clinically feasible for acute focal stroke treatment, no definite beneficial effect has been reported yet. This lack of clinical protection may result from suboptimal criteria for patient entrance into clinical trials. To facilitate clinical translation, future efforts in the laboratory should focus more on the protective mechanisms of postischemic hypothermia, as well as on the effects of sex, age and rewarming during reperfusion on hypothermic protection.
View details for Web of Science ID 000250957800001
View details for PubMedID 17684517
Characterization of monocyte chemoattractant protein-1 expression following a kainate model of status epilepticus
2007; 1182: 138-143
Brain injury due to seizure induces a robust inflammatory response that involves multiple factors. Although the expression of chemokines has been identified as a part of this response, there are remaining questions about their relative contribution to seizure pathogenesis. To address this, we report the expression profile of the chemokine, monocyte chemoattractant protein-1 (MCP-1, CCL2), during kainate-induced seizure in the rat hippocampus. Furthermore, we compare MCP-1 expression to the temporal profile of blood-brain barrier (BBB) permeability and immune cell recruitment at the injury site, since both of these events have been linked to MCP-1. We find that BBB permeability increased prior to upregulation of MCP-1, while MCP-1 upregulation and immune cell recruitment occurred concurrently, 7-13 h after opening of the BBB. Our findings support the following conclusions: (1) BBB opening to large proteins does not require MCP-1 upregulation; (2) Leukocyte immigration is not sufficient to induce BBB opening to large proteins; (3) MCP-1 upregulation likely mediates recruitment of macrophages/microglia and granulocytes during seizure injury, thus warranting further investigation of this chemokine.
View details for DOI 10.1016/j.brainres.2007.08.092
View details for Web of Science ID 000251702700014
View details for PubMedID 17950261
Viral caspase inhibitor p35, but not crmA, is neuroprotective in the ischemic penumbra following experimental stroke
2007; 149 (4): 804-812
Apoptosis, a predominant cause of neuronal death after stroke, can be executed in a caspase-dependent or apoptosis inducing factor (AIF)-dependent manner. Herpes simplex virus (HSV) vectors expressing caspase inhibitors p35 and crmA have been shown to be neuroprotective against various excitotoxic insults. Here we further evaluated the possible neuroprotective role of p35 and crmA in a rat stroke model. Overexpression of p35, but not crmA, significantly increased neuronal survival. Results of double immunofluorescence staining indicate that compared with neurons infected with crmA or control vectors, p35-infected neurons had less active caspase-3 expression, cytosolic cytochrome c and nuclear AIF translocation.
View details for DOI 10.1016/j.neuroscience.2007.07.030
View details for Web of Science ID 000251501700008
View details for PubMedID 17945431
View details for PubMedCentralID PMC2144739
Structural consequences of Kcna1 gene deletion and transfer in the mouse hippocampus
2007; 48 (11): 2023-2046
Mice lacking the Kv1.1 potassium channel alpha subunit encoded by the Kcna1 gene develop recurrent behavioral seizures early in life. We examined the neuropathological consequences of seizure activity in the Kv1.1(-/-) (knock-out) mouse, and explored the effects of injecting a viral vector carrying the deleted Kcna1 gene into hippocampal neurons.Morphological techniques were used to assess neuropathological patterns in hippocampus of Kv1.1(-/-) animals. Immunohistochemical and biochemical techniques were used to monitor ion channel expression in Kv1.1(-/-) brain. Both wild-type and knockout mice were injected (bilaterally into hippocampus) with an HSV1 amplicon vector that contained the rat Kcna1 subunit gene and/or the E. coli lacZ reporter gene. Vector-injected mice were examined to determine the extent of neuronal infection.Video/EEG monitoring confirmed interictal abnormalities and seizure occurrence in Kv1.1(-/-) mice. Neuropathological assessment suggested that hippocampal damage (silver stain) and reorganization (Timm stain) occurred only after animals had exhibited severe prolonged seizures (status epilepticus). Ablation of Kcna1 did not result in compensatory changes in expression levels of other related ion channel subunits. Vector injection resulted in infection primarily of granule cells in hippocampus, but the number of infected neurons was quite variable across subjects. Kcna1 immunocytochemistry showed "ectopic" Kv1.1 alpha channel subunit expression.Kcna1 deletion in mice results in a seizure disorder that resembles--electrographically and neuropathologically--the patterns seen in rodent models of temporal lobe epilepsy. HSV1 vector-mediated gene transfer into hippocampus yielded variable neuronal infection.
View details for DOI 10.1111/j.1528-1167.2007.01189.x
View details for Web of Science ID 000250816600003
View details for PubMedID 17651419
View details for PubMedCentralID PMC2752664
NAP protects hippocampal neurons against multiple toxins
2007; 28 (10): 2004-2008
The femtomolar-acting protective peptide NAP (NAPVSIPQ), derived from activity-dependent neuroprotective protein (ADNP), is broadly neuroprotective in vivo and in vitro in cerebral cortical cultures and a variety of cell lines. In the present study, we have extended previous results and examined the protective potential of NAP in primary rat hippocampal cultures, using microtubule-associated protein 2 (MAP2) as a measure for neuroprotection. Results showed that NAP, at femtomolar concentrations, completely protected against oxygen-glucose deprivation, and cyanide poisoning. Furthermore, NAP partially protected against kainic acid excitotoxicity. In summary, we have significantly expanded previous findings in demonstrating here direct neuroprotective effects for NAP on vital hippocampal neurons that are key participants in cognitive function in vivo.
View details for DOI 10.1016/j.peptides.2007.08.004
View details for Web of Science ID 000250326100010
View details for PubMedID 17869381
Conditions of protection by hypothermia and effects on apoptotic pathways in a rat model of permanent middle cerebral artery occlusion
JOURNAL OF NEUROSURGERY
2007; 107 (3): 636-641
Hypothermia is protective in stroke models, but findings from permanent occlusion models are conflicting. In this article the authors induced focal ischemia in rats by permanent distal middle cerebral artery (MCA) occlusion plus transient occlusion of the common carotid arteries (CCAs). This models a scenario in which the MCA remains occluded but partial reperfusion occurs through collateral vessels. The authors also determined whether hypothermia mediates ischemic damage by blocking apoptotic pathways.The left MCA was occluded permanently and the CCAs were reopened after 2 hours, leading to partial reperfusion in rats maintained at 37 degrees C, 33 degrees C (mild hypothermia), or 30 degrees C (moderate hypothermia) for 2 hours during and/or after CCA occlusion (that is, for a total of 2 or 4 hours of hypothermia or normothermia). Infarct size was measured 2 days after the stroke. Immunofluorescence staining and Western blot analysis were used to detect cytochrome c and apoptosis inducing factor (AIF) translocation.Four hours of prolonged mild hypothermia (33 degrees C) reduced the infarct size 22% in the model of permanent MCA occlusion, whereas 2 hours of such mild hypothermia maintained either during CCA occlusion or after CCA release did not attenuate ischemic damage. However, moderate hypothermia (30 degrees C) during CCA occlusion was significantly more protective than 4 hours of 33 degrees C (46% decrease in infarct size). Four hours of mild or moderate hypothermia reduced cytosolic cytochrome c release and both nuclear and cytosolic AIF translocation in the penumbra 2 days after stroke.These findings suggest that hypothermic neuroprotection might be achieved by blocking AIF and cytochrome c-mediated apoptosis.
View details for Web of Science ID 000249220100022
View details for PubMedID 17886565
The effects of toxoplasma infection on rodent behavior are dependent on dose of the stimulus
2007; 148 (2): 342-348
Parasite Toxoplasma gondii blocks the innate aversion of rats for cat urine, putatively increasing the likelihood of a cat predating a rat. This is thought to reflect an adaptive behavioral manipulation, because toxoplasma can reproduce only in cat intestines. While it will be adaptive for the parasite to cause an absolute behavioral change, fitness costs associated with the manipulation itself suggest that the change is optimized and not maximized. We investigate these conflicting suggestions in the present report. Furthermore, exposure to cat odor causes long-lasting acquisition of learnt fear in the rodents. If toxoplasma manipulates emotional valence of cat odor rather than just sensory response, infection should affect learning driven by the aversive properties of the odor. As a second aim of the present study, we investigate this assertion. We demonstrate that behavioral changes in rodents induced by toxoplasma infection do not represent absolute all-or-none effects. Rather, these effects follow a non-monotonous function dependent on strength of stimulus, roughly resembling an inverted-U curve. Furthermore, infection affects conditioning to cat odor in a manner dependent upon strength of unconditioned stimulus employed. Non-monotonous relationship between behavioral manipulation and strength of cat odor agrees with the suggestion that a dynamic balance exists between benefit obtained and costs incurred by the parasite during the manipulation. This report also demonstrates that toxoplasma affects emotional valence of the cat odor as indicated by altered learned fear induced by cat odor.
View details for DOI 10.1016/j.neuroscience.2007.06.021
View details for Web of Science ID 000249638100002
View details for PubMedID 17683872
View details for PubMedCentralID PMC2430144
Mineralocorticoid receptor overexpression differentially modulates specific phases of spatial and nonspatial memory
JOURNAL OF NEUROSCIENCE
2007; 27 (30): 8046-8052
Glucocorticoids (GCs) and stress modulate specific phases of information processing. The modulatory affects of GCs on hippocampal function are thought to be mediated by the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). The GR plays a critical role in mediating the impairing effects of GCs on hippocampal function. Conversely, activation of MR facilitates hippocampal function. The high affinity of MR for GCs suggests that the receptor protein levels play a key role in regulating the beneficial effects of MR-mediated gene transcription. Using herpes simplex vectors, we transiently increased MR levels in dentate gyrus granule cells, which in turn enhanced MR signaling. We then examined its effects on spatial and nonspatial memory consolidation and retrieval using the object placement and object recognition task. Additionally, we assessed whether an increased MR signal could block the impairing effects of high GCs on memory retrieval. Rats overexpressing MR displayed an enhancement in the consolidation of nonspatial memory relative to rats expressing green fluorescent protein and suggest the potential for gene transfer techniques for enhancing cognition during stress. Moreover, rats overexpressing MR were spared from the disruptive effects of high GCs on the retrieval of nonspatial memory. Thus, this study illustrates the critical role of MR in mediating the retrieval and consolidation of nonspatial memory.
View details for DOI 10.1523/JNEUROSCI.1187-07.2007
View details for Web of Science ID 000248484800017
View details for PubMedID 17652595
Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework
TOXICOLOGY AND APPLIED PHARMACOLOGY
2007; 222 (1): 122-128
Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines.
View details for DOI 10.1016/j.taap.2007.02.015
View details for Web of Science ID 000247853900013
View details for PubMedID 17459441
Behavioral changes induced by Toxoplasma infection of rodents are highly specific to aversion of cat odors
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2007; 104 (15): 6442-6447
The protozoan parasite Toxoplasma gondii blocks the innate aversion of rats for cat urine, instead producing an attraction to the pheromone; this may increase the likelihood of a cat predating a rat. This is thought to reflect adaptive, behavioral manipulation by Toxoplasma in that the parasite, although capable of infecting rats, reproduces sexually only in the gut of the cat. The "behavioral manipulation" hypothesis postulates that a parasite will specifically manipulate host behaviors essential for enhancing its own transmission. However, the neural circuits implicated in innate fear, anxiety, and learned fear all overlap considerably, raising the possibility that Toxoplasma may disrupt all of these nonspecifically. We investigated these conflicting predictions. In mice and rats, latent Toxoplasma infection converted the aversion to feline odors into attraction. Such loss of fear is remarkably specific, because infection did not diminish learned fear, anxiety-like behavior, olfaction, or nonaversive learning. These effects are associated with a tendency for parasite cysts to be more abundant in amygdalar structures than those found in other regions of the brain. By closely examining other types of behavioral patterns that were predicted to be altered we show that the behavioral effect of chronic Toxoplasma infection is highly specific. Overall, this study provides a strong argument in support of the behavioral manipulation hypothesis. Proximate mechanisms of such behavioral manipulations remain unknown, although a subtle tropism on part of the parasite remains a potent possibility.
View details for DOI 10.1073/pnas.0608310104
View details for Web of Science ID 000245737500062
View details for PubMedID 17404235
View details for PubMedCentralID PMC1851063
An inflammatory review of glucocorticoid actions in the CNS
BRAIN BEHAVIOR AND IMMUNITY
2007; 21 (3): 259-272
In recent years, the classic view that glucocorticoids, the adrenal steroids secreted during stress, are universally anti-inflammatory has been challenged at a variety of levels. It was first observed that under some circumstances, acute GC exposure could have pro-inflammatory effects on the peripheral immune response. More recently, chronic exposure to GCs has been found to have pro-inflammatory effects on the specialized immune response to injury in the central nervous system. Here we review the evidence that in some cases, glucocorticoids can increase pro-inflammatory cell migration, cytokine production, and even transcription factor activity in the brain. We consider how these unexpected effects of glucocorticoids can co-exist with their well-established anti-inflammatory properties, as well as the considerable clinical implications of these findings.
View details for DOI 10.1016/j.bbi.2006.11.006
View details for Web of Science ID 000244822100002
View details for PubMedID 17194565
Overexpression of a chimeric steroid receptor protects striatal neurons from cerebral ischemia
32nd International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2007: 547–47
View details for Web of Science ID 000244122600481
Gene therapy using SOD1 protects striatal neurons from experimental stroke
2007; 411 (1): 32-36
Reactive oxygen species contribute to neuronal death following cerebral ischemia. Prior studies using transgenic animals have demonstrated the neuroprotective effect of the antioxidant, copper/zinc superoxide dismutase (SOD1). In this study, we investigated whether SOD1 overexpression using gene therapy techniques in non-transgenic animals would increase neuronal survival. A neurotropic, herpes simplex virus-1 (HSV-1) vector containing the SOD1 gene was injected into the striatum either before or after transient focal cerebral ischemia. Striatal neuron survival at 2 days was improved by 52% when vector was delivered 12-15 h prior to ischemia and by 53% when vector delivery was delayed 2 h following ischemia. These data add to the growing literature, which suggests that an antioxidant approach, perhaps by employing gene therapy techniques, may be beneficial in the treatment of stroke.
View details for DOI 10.1016/j.neulet.2006.08.089
View details for Web of Science ID 000243153100007
View details for PubMedID 17110031
View details for PubMedCentralID PMC1716259
Phosphoinositide-3-kinase/Akt survival signal pathways are implicated in neuronal survival after stroke
2006; 34 (3): 249-269
In recent years, the phosphoinositide-3-kinase/Akt cell survival signaling pathway has been increasingly researched in the field of stroke. Akt activity is suggested to be upregulated by phosphorylation through the activation of receptor tyrosine kinases by growth factors. Although the upstream signaling components phosphoinositide-dependent protein kinase (PDK)1 and integrinlinked kinase enhance the activity of Akt, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) decreases it. Upon activation, Akt phosphorylates an array of molecules, including glycogen synthase kinase3beta (GSK3beta), forkhead homolog in rhabdomyosarcoma (FKHR), and Bcl-2-associated death protein, thereby blocking mitochondrial cytochrome c release and caspase activity. Generally, the level of Akt phosphorylation at site Ser 473 (P-Akt) transiently increases after focal ischemia, whereas the levels of phosphorylation of PTEN, PDK1, forkhead transcription factor, and GSK3beta decrease. Numerous compounds (such as growth factors, estrogen, free radical scavengers, and other neuroprotectants) reduce ischemic damage, possibly by upregulating P-Akt. However, preconditioning and hypothermia block ischemic damage by inhibiting an increase of P-Akt. Inhibition of the Akt pathway blocks the protective effect of preconditioning and hypothermia, suggesting the Akt pathway contributes to their protective effects and that the P-Akt level does not represent its true kinase activity. Together, attenuation of the Akt pathway dysfunction contributes to neuronal survival after stroke.
View details for Web of Science ID 000250119900008
View details for PubMedID 17308356
Enhancing cognition after stress with gene therapy
JOURNAL OF NEUROSCIENCE
2006; 26 (45): 11637-11643
Hippocampal function is essential for the acquisition, consolidation, and retrieval of spatial memory. High circulating levels of glucocorticoids (GCs), the adrenal steroid hormones secreted during stress, have been shown to impair both acquisition and retrieval and can either impair or enhance consolidation, depending on experimental conditions. In contrast, estrogen can enhance spatial memory performance and can block the deleterious effects of GCs on such performance. We therefore constructed a chimeric gene ("ER/GR") containing the hormone-binding domain of the GC receptor and the DNA binding domain of the estrogen receptor; as a result, ER/GR transduces deleterious GC signals into beneficial estrogenic ones. We show here that acute immobilization stress, before acquisition and retrieval phases, increases latencies for male rats in a hidden platform version of the Morris water maze. This impairment is blocked by hippocampal expression of the ER/GR transgene. ER/GR expression also blocks decreases in platform crossings caused by acute stress, either after acquisition or before retrieval. Three days of stress before acquisition produces an estrogen-like enhancement of performance in ER/GR-treated rats. Moreover, ER/GR blocks the suppressive effects of GCs on expression of brain-derived neurotrophic factor (BDNF), a growth factor central to hippocampal-dependent cognition and plasticity, instead producing an estrogenic increase in BDNF expression. Thus, ER/GR expression enhances spatial memory performance and blocks the impairing effects of GCs on such performance.
View details for DOI 10.1523/JNEUROSCI.3122-06.2006
View details for Web of Science ID 000241892700015
View details for PubMedID 17093085
Interrupting reperfusion as a stroke therapy: ischemic postconditioning reduces infarct size after focal ischemia in rats
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2006; 26 (9): 1114-1121
Cerebral ischemic preconditioning protects against stroke, but is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role in cerebral injury after stroke; we tested the hypothesis that interrupting reperfusion lessens ischemic injury. We found for the first time that such postconditioning with a series of mechanical interruptions of reperfusion significantly reduces ischemic damage. Focal ischemia was generated by permanent distal middle cerebral artery (MCA) occlusion plus transient bilateral common carotid artery (CCA) occlusion. After 30 secs of CCA reperfusion, ischemic postconditioning was performed by occluding CCAs for 10 secs, and then allowing for another two cycles of 30 secs of reperfusion and 10 secs of CCA occlusion. Infarct size was measured 2 days later. Cerebral blood flow (CBF) was measured in animals subjected to permanent MCA occlusion plus 15 mins of bilateral CCA occlusion, which demonstrates that postconditioning disturbed the early hyperemia immediately after reperfusion. Postconditioning dose dependently reduced infarct size in animals subjected to permanent MCA occlusion combined with 15, 30, and 60 mins of bilateral CCA occlusion, by reducing infarct size approximately 80%, 51%, and 17%, respectively. In addition, postconditioning blocked terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling-positive staining, a marker of apoptosis, in the penumbra 2 days after stroke. Furthermore, in situ superoxide detection using hydroethidine suggested that postconditioning attenuated superoxide products during early reperfusion after stroke. In conclusion, postconditioning reduced infarct size, most plausibly by blocking apoptosis and free radical generation. With further study it may eventually be clinically applicable for stroke treatment.
View details for DOI 10.1038/sj.jcbfm.9600348
View details for Web of Science ID 000240015300002
View details for PubMedID 16736038
Culture in animals: The case of a non-human primate culture of low aggression and high affiliation
2006; 85 (1): 217-233
View details for Web of Science ID 000243493900012
Social cultures among nonhuman primates
2006; 47 (4): 641-656
View details for Web of Science ID 000239829900005
Gene therapy in the nervous system with superoxide dismutase
2006; 1088: 12-18
Neuronal death following necrotic insults involves the generation of reactive oxygen species (ROS). We investigated the effects of antioxidant gene therapy on ROS accumulation after exposure to either sodium cyanide, kainic acid or oxygen glucose deprivation (OGD). Specifically, we generated herpes simplex virus-1 amplicon vector expressing the gene for the antioxidant enzyme CuZnSOD. Overexpression of this gene in primary hippocampal cultures resulted in increased enzymatic activity of the corresponding protein. CuZnSOD significantly protected hippocampal neurons against sodium cyanide insult and the subsequent lipid peroxidation. However, it did not protect against OGD- or kainic-acid-induced toxicity. Moreover, CuZnSOD significantly worsened the toxicity, hydrogen peroxide accumulation and lipid peroxidation induced by kainic acid. As a possible explanation for this surprising worsening, CuZnSOD overexpression increased glutathione peroxidase activity in the presence of sodium cyanide but had no effect on catalase or glutathione peroxidase activity in the presence of kainic acid. Thus, cells were unlikely to be able to detoxify the excess hydrogen peroxide produced as a result of the CuZnSOD overexpression. These studies can be viewed as a cautionary note concerning gene therapy intervention against necrotic insults.
View details for DOI 10.1016/j.brainres.2006.02.109
View details for Web of Science ID 000238512900002
View details for PubMedID 16630587
Sleep restriction suppresses neurogenesis induced by hippocampus-dependent learning
JOURNAL OF NEUROPHYSIOLOGY
2005; 94 (6): 4224-4233
Sleep deprivation impairs hippocampal-dependent learning, which, in turn, is associated with increased survival of newborn cells in the hippocampus. We tested whether the deleterious effects of sleep restriction on hippocampus-dependent memory were associated with reduced cell survival in the hippocampus. We show that sleep restriction impaired hippocampus-dependent learning and abolished learning-induced neurogenesis. Animals were trained in a water maze on either a spatial learning (hippocampus-dependent) task or a nonspatial (hippocampus-independent) task for 4 days. Sleep-restricted animals were kept awake for one-half of their rest phase on each of the training days. Consistent with previous reports, animals trained on the hippocampus-dependent task expressed increased survival of newborn cells in comparison with animals trained on the hippocampus-independent task. This increase was abolished by sleep restriction that caused overall reduced cell survival in all animals. Sleep restriction also selectively impaired spatial learning while performance in the nonspatial task was, surprisingly, improved. Further analysis showed that in both training groups fully rested animals applied a spatial strategy irrespective of task requirements; this strategy interfered with performance in the nonspatial task. Conversely, in sleep-restricted animals, this preferred spatial strategy was eliminated, favoring the use of nonspatial information, and hence improving performance in the nonspatial task. These findings suggest that sleep loss altered behavioral strategies to those that do not depend on the hippocampus, concomitantly reversing the neurogenic effects of hippocampus-dependent learning.
View details for DOI 10.1152/jn.00218.2005
View details for Web of Science ID 000233317100053
View details for PubMedID 16014798
Marked differences in the efficacy of post-insult gene therapy with catalase versus glutathione peroxidase
2005; 1063 (1): 27-31
It is now recognized that the generation of reactive oxygen species (ROS) following necrotic neurological insults plays a central role in the subsequent neuron death. A key step in ROS detoxification is the conversion of hydrogen peroxide to water and oxygen by either catalase (CAT) or glutathione peroxidase (GPX). We have previously shown that overexpression of CAT or GPX protects cultured neurons against subsequent excitotoxic insults. Because of the unpredictability of most acute neurological insults, gene therapy will most often need to be carried out after rather than in anticipation of an insult. Thus, we have tested whether herpes virus amplicon vectors expressing CAT or GPX still protect cultured hippocampal neurons from oxygen/glucose deprivation if introduced following an insult. CAT-expressing vectors were protective even when introduced 8 h post-insult. In contrast, there was no post-insult time window in which GPX overexpression protected. While CAT requires no cofactor, GPX action requires glutathione as a cofactor. Thus, we speculated that the post-insult decline in glutathione compromises the protective potential of GPX. Supporting this, reversing the post-insult glutathione decline with glutathione supplementation was neuroprotective.
View details for DOI 10.1016/j.brainres.2005.09.032
View details for Web of Science ID 000233797100004
View details for PubMedID 16257394
Akt contributes to neuroprotection by hypothermia against cerebral ischemia in rats
JOURNAL OF NEUROSCIENCE
2005; 25 (42): 9794-9806
Activation of the Akt/protein kinase B (PKB) kinase pathway can be neuroprotective after stroke. Akt is activated by growth factors via a phosphorylation-dependent pathway involving the kinases phosphoinositide 3 (PI3) kinase and phosphoinositide-dependent protein kinase-1 (PDK1) and is negatively regulated by phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Akt kinase blocks apoptosis by phosphorylating the substrates forkhead transcription factor (FKHR) and glycogen synthase kinase 3beta (GSK3beta). We found that intra-ischemic hypothermia (30 degrees C) reduced infarct size and improved functional outcomes up to 2 months. Changes in phosphorylation levels of Akt, as measured by Western blots and immunostaining, differed from levels of Akt activity measured in an in vitro assay in normothermic animals. Hypothermia blocked most of these changes and maintained Akt activity. Inhibition of PI3/Akt enlarged infarct size in hypothermic animals. Hypothermia improved phosphorylation of PDK1, PTEN, and FKHR. Hypothermia did not improve GSK3beta (Ser9) phosphorylation but blocked the nuclear translocation of phosphorylated beta-catenin (Ser33/37/Thr41) downstream of GSK3beta. Phosphorylation levels of PTEN, Akt, and Akt substrate decreased before apoptotic cytochrome c release and degradation of microtubule-associated protein-2, a marker of neuronal survival. Hypothermia may protect from ischemic damage in part by preserving Akt activity and attenuating the apoptotic effects of PTEN, PDK1, and FKHR.
View details for DOI 10.1523/JNEUROSCI.3163-05.2005
View details for Web of Science ID 000232669300024
View details for PubMedID 16237183
Biphasic cytochrome c release after transient global ischemia and its inhibition by hypothermia
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2005; 25 (9): 1119-1129
Hypothermia is effective in preventing ischemic damage. A caspase-dependent apoptotic pathway is involved in ischemic damage, but how hypothermia inhibits this pathway after global cerebral ischemia has not been well explored. It was determined whether hypothermia protects the brain by altering cytochrome c release and caspase activity. Cerebral ischemia was produced by two-vessel occlusion plus hypotension for 10 mins. Body temperature in hypothermic animals was reduced to 33 degrees C before ischemia onset and maintained for 3 h after reperfusion. Western blots of subcellular fractions revealed biphasic cytosolic cytochrome c release, with an initial peak at about 5 h after ischemia, which decreased at 12 to 24 h, and a second, larger peak at 48 h. Caspase-3 and -9 activity increased at 12 and 24 h. A caspase inhibitor, Z-DEVD-FMK, administered 5 and 24 h after ischemia onset, protected hippocampal CA1 neurons from injury and blocked the second cytochrome c peak, suggesting that caspases mediate this second phase. Hypothermia (33 degrees C), which prevented CA1 injury, did not inhibit cytochrome c release at 5 h, but reduced cytochrome c release at 48 h. Caspase-3 and -9 activity was markedly attenuated by hypothermia at 12 and 24 h. Thus, biphasic cytochrome c release occurs after transient global ischemia and mild hypothermia protects against ischemic damage by blocking the second phase of cytochrome c release, possibly by blocking caspase activity.
View details for DOI 10.1038/sj.jcbfm.9600111
View details for Web of Science ID 000231576100003
View details for PubMedID 15789032
Glucocorticoids worsen excitotoxin-induced expression of pro-inflammatory cytokines in hippocampal cultures
2005; 194 (2): 376-383
Glucocorticoids (GCs), the adrenal steroid hormones released during stress, have well-known anti-inflammatory actions. Despite that, there is increasing evidence that GCs are not uniformly anti-inflammatory in the injured nervous system and, in fact, can be pro-inflammatory. The present report continues this theme. Primary hippocampal cultures were treated with GC concentrations approximating basal, acute (1 h) stress or chronic (24 h) stress conditions and were then exposed to the excitotoxin kainic acid (KA). KA induced expression of the pro-inflammatory cytokines IL-1 beta and TNF-alpha, and chronic high dose GC exposure excacerbated this induction. In a second study, cultures were exposed to the physiological range of GC concentrations for 24 h prior to KA treatment. Low- to mid-range GC concentrations were anti-inflammatory, decreasing expression of IL-1 beta and TNF-alpha, while the highest GC doses either failed to be anti-inflammatory or even potentiated expression further. These findings add to the growing picture of these classically anti-inflammatory hormones potentially having pro-inflammatory effects in the injured CNS.
View details for DOI 10.1016/j.expneurol.2005.02.021
View details for Web of Science ID 000230876100008
View details for PubMedID 16022865
Estrogenic protection against gp120 neurotoxicity: Role of microglia
2005; 1046 (1-2): 130-136
HIV infection of the nervous system can cause neurotoxicity, and the glycoprotein gp120 of HIV seems to play a key role in this. gp120 is neurotoxic through a multi-cellular pathway, stimulating microglia to release excitotoxins, cytokines and reactive oxygen species, which then damage neurons. We have previously shown that estrogen decreases the neurotoxicity of gp120 in mixed neuronal/glial cultures. In this study, we determine whether estrogen a) decreases the collective neurotoxicity of the factors released by gp120-treated microglia, and/or b) enhances the ability of neurons to survive such factors. To do so, we established microglial cultures, mixed neuronal/glial hippocampal cultures, and neuron-enriched cultures, independently manipulating gp120 and estrogen exposure in each type of culture, and inducing neurotoxicity in neuron-containing cultures by introducing conditioned media from gp120-treated microglial cultures. We observe that estrogen can exert some small protective effects at the level of bolstering neuronal resistance, but that the bulk of its protective effects arise at the level of decreasing the neurotoxicity of factors released by microglia.
View details for DOI 10.1016/j.brainres.2005.03.049
View details for Web of Science ID 000229898600015
View details for PubMedID 15878158
The influence of social hierarchy on primate health
2005; 308 (5722): 648-652
Dominance hierarchies occur in numerous social species, and rank within them can greatly influence the quality of life of an animal. In this review, I consider how rank can also influence physiology and health. I first consider whether it is high- or low-ranking animals that are most stressed in a dominance hierarchy; this turns out to vary as a function of the social organization in different species and populations. I then review how the stressful characteristics of social rank have adverse adrenocortical, cardiovascular, reproductive, immunological, and neurobiological consequences. Finally, I consider how these findings apply to the human realm of health, disease, and socioeconomic status.
View details for DOI 10.1126/science.1106477
View details for Web of Science ID 000228810900036
View details for PubMedID 15860617
Environmental enrichment reduces A beta levels and amyloid deposition in transgenic mice
2005; 120 (5): 701-713
Cerebral deposition of beta-amyloid (Abeta) peptides is an invariant pathological hallmark in brains of patients with Alzheimer's disease (AD) and transgenic mice coexpressing familial AD-linked APP and PS1 variants. We now report that exposure of transgenic mice to an "enriched environment" results in pronounced reductions in cerebral Abeta levels and amyloid deposits, compared to animals raised under "standard housing" conditions. The enzymatic activity of an Abeta-degrading endopeptidase, neprilysin, is elevated in the brains of "enriched" mice and inversely correlated with amyloid burden. Moreover, DNA microarray analysis revealed selective upregulation in levels of transcripts encoded by genes associated with learning and memory, vasculogenesis, neurogenesis, cell survival pathways, Abeta sequestration, and prostaglandin synthesis. These studies provide evidence that environmental enrichment leads to reductions in steady-state levels of cerebral Abeta peptides and amyloid deposition and selective upregulation in levels of specific transcripts in brains of transgenic mice.
View details for DOI 10.1016/j.cell.2005.01.015
View details for Web of Science ID 000227771400015
View details for PubMedID 15766532
Hypothermia attenuates the decrease in phosphorylation of proteins in AKT cell signal pathway after permanent middle cerebral artery occlusion in rats
30th International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2005: 514–14
View details for Web of Science ID 000227523800492
Gene therapy in neurological disease.
Methods in molecular medicine
2005; 104: 75-88
Advances in the area of stroke and other neurodegenerative disorders have identified a variety of molecular targets for potential therapeutic intervention. The use of modified viral vectors has now made it possible to introduce foreign DNA into central nervous system cells, permitting overexpression of the protein of interest. A particular advantage of the herpes simplex system is that the herpes virus is neurotropic and is therefore suited for gene therapy to the nervous system. The vectors used by our group to date utilize an amplicon-based bipromoter system, which permits expression of both the gene of interest and a reporter gene. Using this strategy, we have been successful in transferring potentially neuroprotective genes to individual central nervous system cells. Using this approach, it is possible to show that gene therapy both before and after insult is feasible. Some limitations of this technique exist, the main one being delivery and extent of transfection. Although application to clinical stroke is probably remote, viral vector-mediated gene therapy provides a unique and powerful tool in the study of molecular mechanisms involved in brain injury.
View details for PubMedID 15454665
- Organismal stress and telomeric aging: An unexpected connection PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2004; 101 (50): 17323-17324
Gene expression profiles associated with survival of individual rat dentate cells after endogenous corticosteroid deprivation
EUROPEAN JOURNAL OF NEUROSCIENCE
2004; 20 (12): 3233-3243
Removal of circulating corticosterone by adrenalectomy (ADX) leads to apoptosis after 3 days in a small population of rat dentate granule neurons, whereas most surrounding cells remain viable. Interestingly, a specific expression profile is triggered in surviving granule cells that may enhance their survival. Hippocampal slices prepared 1, 2 or 3 days after ADX or sham operation were stained ex vivo with Hoechst 33258, which serves to identify apoptotic neurons. After electrophysiological analysis, multiple gene expression in surviving individual granule cells was assessed by linear antisense RNA amplification and hybridization to slot blots containing various neuronal cDNAs. Hierarchical clustering and principal component analysis was performed on two physiological variables and 14 mRNA ratios from ADX cells from every time point. Our results indicate that surviving 3-day ADX granule cells display lower membrane capacitance, lower relative N-methyl-d-aspartate (NMDA) R1 mRNA expression and higher relative mineralocorticoid receptor (MR), alpha1A voltage-gated Ca-channel, Bcl-2 and NMDA R2C mRNA expression. Some 1- and 2-day ADX cells cluster with these 3-day survivors; therefore, one or more components of their mRNA expression profile may represent predictive markers for apoptosis resistance. The functional relevance of two candidate genes was tested by in vivo local over-expression in the same model system; of these, Bcl-2 conferred partial protection when induced shortly before ADX. Therefore, removal of corticosteroids triggers a specific gene expression profile in surviving dentate granule cells; key components of this profile may be associated with their survival.
View details for DOI 10.1111/j.1460-9568.2004.03819.x
View details for Web of Science ID 000225686000003
View details for PubMedID 15610156
The frontal cortex and the criminal justice system
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
2004; 359 (1451): 1787-1796
In recent decades, the general trend in the criminal justice system in the USA has been to narrow the range of insanity defences available, with an increasing dependence solely on the M'Naghten rule. This states that innocence by reason of insanity requires that the perpetrator could not understand the nature of their criminal act, or did not know that the act was wrong, by reason of a mental illness. In this essay, I question the appropriateness of this, in light of contemporary neuroscience. Specifically, I focus on the role of the prefrontal cortex (PFC) in cognition, emotional regulation, control of impulsive behaviour and moral reasoning. I review the consequences of PFC damage on these endpoints, the capacity for factors such as alcohol and stress to transiently impair PFC function, and the remarkably late development of the PFC (in which full myelination may not occur until early adulthood). I also consider how individual variation in PFC function and anatomy, within the normative range, covaries with some of these endpoints. This literature is reviewed because of its relevance to issues of criminal insanity; specifically, damage can produce an individual capable of differentiating right from wrong but who, nonetheless, is organically incapable of appropriately regulating their behaviour.
View details for DOI 10.1098/rstb.2004.1547
View details for Web of Science ID 000225645700014
View details for PubMedID 15590619
Restructuring the neuronal stress response with anti-glucocorticoid gene delivery
2004; 7 (9): 947-953
Glucocorticoids, the adrenal steroids released during stress, compromise the ability of neurons to survive neurological injury. In contrast, estrogen protects neurons against such injuries. We designed three genetic interventions to manipulate the actions of glucocorticoids, which reduced their deleterious effects in both in vitro and in vivo rat models. The most effective of these interventions created a chimeric receptor combining the ligand-binding domain of the glucocorticoid receptor and the DNA-binding domain of the estrogen receptor. Expression of this chimeric receptor reduced hippocampal lesion size after neurological damage by 63% and reversed the outcome of the stress response by rendering glucocorticoids protective rather than destructive. Our findings elucidate three principal steps in the neuronal stress-response pathway, all of which are amenable to therapeutic intervention.
View details for DOI 10.1038/nn1296
View details for Web of Science ID 000223546700013
View details for PubMedID 15300253
Chaperones, protein aggregation, and brain protection from hypoxic/ischemic injury
JOURNAL OF EXPERIMENTAL BIOLOGY
2004; 207 (18): 3213-3220
Chaperones, especially the stress inducible Hsp70, have been studied for their potential to protect the brain from ischemic injury. While they protect from both global and focal ischemia in vivo and cell culture models of ischemia/reperfusion injury in vitro, the mechanism of protection is not well understood. Protein aggregation is part of the etiology of chronic neurodegenerative diseases such as Huntington's and Alzheimer's, and recent data demonstrate protein aggregates in animal models of stroke. We now demonstrate that overexpression of Hsp70 in hippocampal CA1 neurons reduces evidence of protein aggregation under conditions where neuronal survival is increased. We have also demonstrated protection by the cochaperone Hdj-2 in vitro and demonstrated that this is associated with reduced protein aggregation identified by ubiquitin immunostaining. Hdj-2 can prevent protein aggregate formation by itself, but can only facilitate protein folding in conjunction with Hsp70. Pharmacological induction of Hsp70 was found to reduce both apoptotic and necrotic astrocyte death induced by glucose deprivation or oxygen glucose deprivation. Protection from ischemia and ischemia-like injury by chaperones thus involves at least anti-apoptotic, anti-necrotic and anti-protein aggregation mechanisms.
View details for DOI 10.1242/jeb.01034
View details for Web of Science ID 000224132000014
View details for PubMedID 15299042
- Is impaired neurogenesis relevant to the affective symptoms of depression? BIOLOGICAL PSYCHIATRY 2004; 56 (3): 137-139
Dual-gene, dual-cell type therapy against an excitotoxic insult by bolstering neuroenergetics
JOURNAL OF NEUROSCIENCE
2004; 24 (27): 6202-6208
Increasing evidence suggests that glutamate activates the generation of lactate from glucose in astrocytes; this lactate is shuttled to neurons that use it as a preferential energy source. We explore this multicellular "lactate shuttle" with a novel dual-cell, dual-gene therapy approach and determine the neuroprotective potential of enhancing this shuttle. Viral vector-driven overexpression of a glucose transporter in glia enhanced glucose uptake, lactate efflux, and the glial capacity to protect neurons from excitotoxicity. In parallel, overexpression of a lactate transporter in neurons enhanced lactate uptake and neuronal resistance to excitotoxicity. Finally, overexpression of both transgenes in the respective cell types provided more protection than either therapy alone, demonstrating that a dual-cell, dual-gene therapy approach gives greater neuroprotection than the conventional single-cell, single-gene strategy.
View details for DOI 10.1523/JNEUROSCI.0805-04.2004
View details for Web of Science ID 000222491000018
View details for PubMedID 15240812
Reduced amyloid deposition and enhanced A beta-catabolism in FAD-linked APPSWE/PSI Delta E9 mice following exposure to environmental enrichment
9th International Conference on Alzheimers Disease and Related Disorders
ELSEVIER SCIENCE INC. 2004: S36–S36
View details for Web of Science ID 000223058700120
Glucocorticoids influence brain glycogen levels during sleep deprivation
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
2004; 286 (6): R1057-R1062
We investigated whether glucocorticoids [i.e., corticosterone (Cort) in rats] released during sleep deprivation (SD) affect regional brain glycogen stores in 34-day-old Long-Evans rats. Adrenalectomized (with Cort replacement; Adx+) and intact animals were sleep deprived for 6 h beginning at lights on and then immediately killed by microwave irradiation. Brain and liver glycogen and glucose and plasma glucose levels were measured. After SD in intact animals, glycogen levels decreased in the cerebellum and hippocampus but not in the cortex or brain stem. By contrast, glycogen levels in the cortex of Adx+ rats increased by 43% (P < 0.001) after SD, while other regions were unaffected. Also in Adx+ animals, glucose levels were decreased by an average of 28% throughout the brain after SD. Intact sleep-deprived rats had elevations of circulating Cort, blood, and liver glucose that were absent in intact control and Adx+ animals. Different responses between brain structures after SD may be due to regional variability in metabolic rate or glycogen metabolism. Our findings suggest that the elevated glucocorticoid secretion during SD causes brain glycogenolysis in response to energy demands.
View details for DOI 10.1152/ajpregu.00528.2003
View details for Web of Science ID 000221443600011
View details for PubMedID 14962825
Bcl-2 transfection via herpes simplex virus blocks apoptosis-inducing factor translocation after focal ischemia in the rat
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2004; 24 (6): 681-692
Apoptosis plays a critical role in many neurologic diseases, including stroke. Cytochrome c release and activation of various caspases are known to occur after focal and global ischemia. However, recent reports indicate that caspase-independent pathways may also be involved in ischemic damage. Apoptosis-inducing factor (AIF) is a novel flavoprotein that helps mediate caspase-independent apoptotic cell death. AIF translocates from mitochondria to nuclei where it induces caspase-independent DNA fragmentation. Bcl-2, a mitochondrial membrane protein, protects against apoptotic and necrotic death induced by different insults, including cerebral ischemia. In the present study, Western blots confirmed that AIF was normally confined to mitochondria but translocated to nuclei or cytosol 8, 24, and 48 hours after onset of ischemia. Overall, AIF protein levels also increased after stroke. Confocal microscopy further demonstrated that nuclear AIF translocation occurred in the peri-infarct region but not in the ischemic core where only some cytosolic AIF release was observed. Our data also suggest that AIF translocated into nuclei after cytochrome c was released into the cytosol. Bcl-2 transfection in the peri-infarct region blocked nuclear AIF translocation and improved cortical neuron survival.
View details for Web of Science ID 000221824000011
View details for PubMedID 15181376
Sleep deprivation effects on growth factor expression in neonatal rats: A potential role for BDNF in the mediation of delta power
JOURNAL OF NEUROPHYSIOLOGY
2004; 91 (4): 1586-1595
The sleeping brain differs from the waking brain in its electrophysiological and molecular properties, including the expression of growth factors and immediate early genes (IEG). Sleep architecture and homeostatic regulation of sleep in neonates is distinct from that of adults. Hence, the present study addressed the question whether the unique homeostatic response to sleep deprivation in neonates is reflected in mRNA expression of the IEG cFos, brain-derived nerve growth factor (BDNF), and basic fibroblast growth factor (FGF2) in the cortex. As sleep deprivation is stressful to developing rats, we also investigated whether the increased levels of corticosterone would affect the expression of growth factors in the hippocampus, known to be sensitive to glucocorticoid levels. At postnatal days 16, 20, and 24, rats were subjected to sleep deprivation, maternal separation without sleep deprivation, sleep deprivation with 2 h recovery sleep, or no intervention. mRNA expression was quantified in the cortex and hippocampus. cFos was increased after sleep deprivation and was similar to control level after 2 h recovery sleep irrespective of age or brain region. BDNF was increased by sleep deprivation in the cortex at P20 and P24 and only at P24 in the hippocampus. FGF2 increased during recovery sleep at all ages in both brain regions. We conclude that cortical BDNF expression reflects the onset of adult sleep-homeostatic response, whereas the profile of expression of both growth factors suggests a trophic effect of mild sleep deprivation.
View details for DOI 10.1152/jn.00894.2003
View details for Web of Science ID 000220086100016
View details for PubMedID 14668298
- A pacific culture among wild baboons: Its emergence and transmission PLOS BIOLOGY 2004; 2 (4): 534-541
A pacific culture among wild baboons: its emergence and transmission.
2004; 2 (4): E106-?
Reports exist of transmission of culture in nonhuman primates. We examine this in a troop of savanna baboons studied since 1978. During the mid-1980s, half of the males died from tuberculosis; because of circumstances of the outbreak, it was more aggressive males who died, leaving a cohort of atypically unaggressive survivors. A decade later, these behavioral patterns persisted. Males leave their natal troops at adolescence; by the mid-1990s, no males remained who had resided in the troop a decade before. Thus, critically, the troop's unique culture was being adopted by new males joining the troop. We describe (a) features of this culture in the behavior of males, including high rates of grooming and affiliation with females and a "relaxed" dominance hierarchy; (b) physiological measures suggesting less stress among low-ranking males; (c) models explaining transmission of this culture; and (d) data testing these models, centered around treatment of transfer males by resident females.
View details for PubMedID 15094808
Catalase over-expression protects striatal neurons from transient focal cerebral ischemia
2004; 15 (3): 413-416
Reactive oxygen species (ROS) play key roles in the cascade of brain injury after stroke, and strategies to increase the antioxidant defenses of neurons after stroke hold great promise. In this study we evaluate the neuroprotective potential of using a herpes simplex viral vector to over-express catalase in rats. Vector was microinfused into the striatum either prior to or after middle cerebral artery occlusion (MCAO). Catalase over-expression was protective (relative to control vector) when the vector was delivered 14-16 h prior to ischemia, but not when delivered after ischemia. Thus, the timing of catalase over-expression relative to ischemia is a critical variable determining its potential therapeutic value.
View details for DOI 10.1097/01.wnr.000011132738420.12
View details for Web of Science ID 000225140000006
View details for PubMedID 15094494
Mild postischemic hypothermia prolongs the time window for gene therapy by inhibiting cytochrome C release
2004; 35 (2): 572-577
We showed previously that Bcl-2 overexpression with the use of herpes simplex viral (HSV) vectors improved striatal neuron survival when delivered 1.5 hours after stroke but not when delivered 5 hours after stroke onset. Here we determine whether hypothermia prolongs the therapeutic window for gene therapy.Rats were subjected to focal ischemia for 1 hour. Hypothermia (33 degrees C) was induced 2 hours after insult and maintained for 3 hours. Five hours after ischemia onset, HSV vectors expressing Bcl-2 plus beta-gal or beta-gal alone were injected into each striatum. Rats were killed 2 days later.Striatal neuron survival of Bcl-2-treated, hypothermic animals was improved 2- to 3-fold over control-treated, hypothermic animals and Bcl-2-treated, normothermic animals. Neuron survival among normothermic, Bcl-2-treated animals was not different from control normothermics or control hypothermics. Double immunostaining of cytochrome c and beta-gal demonstrated that Bcl-2 plus hypothermia significantly reduced cytochrome c release.Postischemic mild hypothermia extended the time window for gene therapy neuroprotection using Bcl-2 and reduced cytochrome c release.
View details for DOI 10.1161/01.STR.0000110787.42083.58
View details for Web of Science ID 000188669500057
View details for PubMedID 14726551
Neurotoxic effects of polymorphonuclear granulocytes on hippocampal primary cultures
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2004; 101 (1): 331-336
Many neurological insults and neurodegenerative disorders are accompanied by an acute inflammatory reaction that can contribute to neuronal damage. This inflammation involves infiltration of bloodborne polymorphonuclear leukocytes (PMNs) into the injured brain area. The role of inflammation in brain injury, however, is controversial, because recent studies suggest that inflammation may actually be beneficial in the recovery from brain damage. Therefore, we investigated the effects of pathophysiologically relevant concentrations of PMNs in vitro on mixed hippocampal primary cultures. Rat PMNs and peripheral blood lymphocytes were isolated by density centrifugation and cocultured with hippocampal cells for 24-72 h plus or minus an excitotoxic insult (50 microM kainic acid) or 6-h oxygen glucose deprivation. Cell death was analyzed by immunocytochemistry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and neuron-specific [2,2'-azino-bis(ethylbenzothiazoline-6-sulfonic acid)] assay. After 3 days of coculture in the absence of insult, PMNs caused massive neuron loss and dramatic morphological changes in glial cells (astrocyte detachment, aggregation). Furthermore PMNs exacerbated kainic acid- and oxygen glucose deprivation-induced neuron death by 20-30%. The cytotoxic effect of PMNs required heterocellular contact and were ameliorated by protease inhibitors. Lymphocytes, on the other hand, were not neurotoxic, but, instead, increased astrocyte proliferation. These findings suggest that PMN might represent a harmful part of inflammation after brain injury that can contribute to secondary damage.
View details for DOI 10.1073/pnas.0303510101
View details for Web of Science ID 000187937200061
View details for PubMedID 14684829
Overexpression of calbindin D-28k in dentate gyrus granule cells alters mossy fiber presynaptic function and impairs hippocampal-dependent memory
2004; 14 (6): 701-709
Calcium is a key signaling ion for induction of synaptic plasticity processes that are believed to influence cognition. Mechanisms regulating activity-induced increases in neuronal calcium and related synaptic modifications are not fully understood. Moreover, involvement of specific synapses in discrete aspects of spatial learning remains to be elucidated. We used herpes simplex amplicons to overexpress calbindin D(28k) (CaBP) selectively in dentate gyrus (DG) granule cells. We then examined the effects on hippocampal network activity by recording evoked synaptic responses in vivo and in vitro and analyzing hippocampal-dependent behavior. Relative to Lac-Z- and sham-infected controls, CaBP overexpression increased mossy fiber (MF-CA3) excitatory postsynaptic potentials and reduced paired-pulse facilitation (PPF), suggesting an increase in presynaptic strength. Additionally, CaBP overexpression reduced long-term potentiation (LTP), caused a frequency-dependent inhibition of post-tetanic potentiation (PTP), and impaired spatial navigation. Thus, increasing CaBP levels selectively in the DG disrupts MF-CA3 presynaptic function and impairs spatial cognition. The results demonstrate the power of gene delivery in the study of the neural substrates of learning and memory and suggest that mossy fiber synaptic plasticity is critical for long-term spatial memory.
View details for DOI 10.1002/hipo.10210
View details for Web of Science ID 000223365200005
View details for PubMedID 15318329
- Social status and health in humans and other animals ANNUAL REVIEW OF ANTHROPOLOGY 2004; 33: 393-418
Mild hypothermia inhibits cytochrome c/caspase-mediated apoptosis after global cerebral ischemia in rats
29th International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2004: 249–49
View details for Web of Science ID 000187630500123
Over-expression of antioxidant enzymes protects cultured hippocampal and cortical neurons from necrotic insults
JOURNAL OF NEUROCHEMISTRY
2003; 87 (6): 1527-1534
There is now considerable knowledge concerning neuron death following necrotic insults, and it is believed that the generation of reactive oxygen species (ROS) and oxidative damage play a pivotal role in the neuron death. Prompted by this, we have generated herpes simplex virus-1 amplicon vectors over-expressing the genes for the antioxidant enzymes catalase (CAT) or glutathione peroxidase (GPX), both of which catalyze the degradation of hydrogen peroxide. Over-expression of each of these genes in primary hippocampal or cortical cultures resulted in increased enzymatic activity of the cognate protein. Moreover, each enzyme potently decreased the neurotoxicity induced by kainic acid, glutamate, sodium cyanide and oxygen/glucose deprivation. Finally, these protective effects were accompanied by parallel decreases in hydrogen peroxide accumulation and the extent of lipid peroxidation. These studies not only underline the key role played by ROS in the neurotoxicity of necrotic insults, but also suggest potential gene therapy approaches.
View details for DOI 10.1046/j.1471-4159.2003.02123.x
View details for Web of Science ID 000186912100021
View details for PubMedID 14713308
Stress and plasticity in the limbic system
2003; 28 (11): 1735-1742
The adult nervous system is not static, but instead can change, can be reshaped by experience. Such plasticity has been demonstrated from the most reductive to the most integrated levels, and understanding the bases of this plasticity is a major challenge. It is apparent that stress can alter plasticity in the nervous system, particularly in the limbic system. This paper reviews that subject, concentrating on: a) the ability of severe and/or prolonged stress to impair hippocampal-dependent explicit learning and the plasticity that underlies it; b) the ability of mild and transient stress to facilitate such plasticity; c) the ability of a range of stressors to enhance implicit fear conditioning, and to enhance the amygdaloid plasticity that underlies it.
View details for Web of Science ID 000185827500016
View details for PubMedID 14584827
Glutathione peroxidase overexpression inhibits cytochrome c release and proapoptotic mediators to protect neurons from experimental stroke
2003; 34 (10): 2489-2494
Ischemic injury and reperfusion increases superoxide (O2-) production and reduces the ability of neurons to scavenge free radicals, leading to the release of cytochrome c and apoptosis. Here we test whether overexpression with the use of gene therapy of the antioxidant glutathione peroxidase (Gpx), delivered before or after experimental stroke, is protective against ischemic injury.Sixty-two rats underwent middle cerebral artery occlusion for 1 hour. Defective herpes simplex viral vectors expressing Gpx/lacZ or lacZ alone (control) were delivered into each striatum 12 hours before or 2 or 5 hours after ischemia onset.Striatal neuron survival at 2 days was improved by 36% when Gpx was delivered 12 hours before ischemia onset, 26% with a 2-hour delay, and 25% when delayed 5 hours. After ischemia, Gpx overexpression significantly reduced cytosolic translocation of cytochrome c and increased the proportion of Bcl-2-positive cells compared with cells transfected with control vector. Bax and activated caspase-3, while present in control-transfected neurons after ischemia, were rarely noted in Gpx-transfected cells.Expression from these herpes simplex viral vectors begins 4 to 6 hours after injection, which suggests a 9- to 11-hour temporal therapeutic window for Gpx. This is the first study to show that overexpression of Gpx with the use of gene therapy protects against experimental stroke, even with postischemic transfection, and the neuroprotective mechanism involves attenuation of apoptosis-related events.
View details for DOI 10.1161/01.STR.0000091268.25816.19
View details for Web of Science ID 000185679100056
View details for PubMedID 14500933
The neuroprotective effects of virally-derived caspase inhibitors p35 and crmA following a necrotic insult
NEUROBIOLOGY OF DISEASE
2003; 14 (1): 1-9
Neuronal excitotoxicity causes energetic impairment and the ensuing cell death has historically been regarded as necrotic. Recent findings, however, indicate that apoptosis may participate in excitotoxicity. Here we examined the neuroprotective mechanisms of the well-characterized viral caspase inhibitors, p35 and crmA, following domoic acid-induced excitotoxicity in hippocampal neurons. We show that though p35 and crmA rescued neurons from toxicity, they did so under conditions of negligible caspase activation and morphological apoptosis. Thus, we characterized the novel neuroprotective effects of p35 and crmA and found that they attenuated the drop in the mitochondrial potential and blunted the decline in ATP levels. These data, to our knowledge, are the first detailed descriptions of the cell death mechanisms following domoic acid treatment of neurons. Moreover, in demonstrating the previously unexplored modulation of these processes, these data underline the capacity for classically "anti-apoptotic" proteins to alter other branches of cell death processes.
View details for DOI 10.1016/S0969-9961(03)00083-4
View details for Web of Science ID 000185438700001
View details for PubMedID 13678661
Potassium channel gene therapy can prevent neuron death resulting from necrotic and apoptotic insults
JOURNAL OF NEUROCHEMISTRY
2003; 86 (5): 1079-1088
Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate hyperexcitation and enhance neuron survival. Therefore, we overexpressed a small-conductance calcium-activated (SK2) or voltage-gated (Kv1.1) channel via viral vectors in cultured hippocampal neurons. We found that SK2 or Kv1.1 protected not only against kainate or glutamate excitotoxicity but also increased survival after sodium cyanide or staurosporine. In vivo overexpression of either channel in dentate gyrus reduced kainate-induced CA3 lesions. In hippocampal slices, the kainate-induced increase in granule cell excitability was reduced by overexpression of either channel, suggesting that these channels exert their protective effects during hyperexcitation. It is also important to understand any functional disturbances created by transgene overexpression alone. In the absence of insult, overexpression of Kv1.1, but not SK2, reduced baseline excitability in dentate gyrus granule cells. Furthermore, while no behavioral disturbances during spatial acquisition in the Morris water maze were observed with overexpression of either channel, animals overexpressing SK2, but not Kv1.1, exhibited a memory deficit post-training. This difference raises the possibility that the means by which these channel subtypes protect may differ. With further development, potassium channel vectors may be an effective pre-emptive strategy against necrotic insults.
View details for DOI 10.1046/j.1471-4159.2003.01880.x
View details for Web of Science ID 000184723000003
View details for PubMedID 12911616
Altering behavior with gene transfer in the limbic system
11th Annual Meeting of the International-Behavioral-Neuroscience-Society (IBNS)
PERGAMON-ELSEVIER SCIENCE LTD. 2003: 479–86
There is now sufficient knowledge of the workings of the limbic system to allow experimental manipulation of behaviors anchored in limbic function. While such manipulations have traditionally involved lesions, stimulation or pharmacological approaches, it has become plausible to use gene transfer technology to alter patterns of gene expression in the nervous system. In this review, I consider ways in which gene transfer has been used to alter limbic function. These involve altering (a) cognition, (b) the rewarding properties of addictive substances, (c) patterns of social affiliation, and (d) responses to stress.
View details for DOI 10.1016/S0031-9384(03)00153-7
View details for Web of Science ID 000185291300015
View details for PubMedID 12954442
gp120 neurotoxicity fails to induce heat shock defenses, while the over expression of hsp70 protects against gp120
BRAIN RESEARCH BULLETIN
2003; 61 (2): 183-188
gp120, the coat glycoprotein of HIV, can damage CNS neurons. This appears to mostly involve an indirect pathway in which gp120 infects microglia, triggering the release of cytokines and glutamatergic excitotoxins which then damage neurons. A well-characterized response of cells to insults is to mobilize the heat stress response, a defense that has a number of protective consequences. We tested the capacity of gp120, at a dose well-documented to be neurotoxic, to activate the heat shock response in cultures from cortex and hippocampus, two brain regions sensitive to the neurotoxic effects of gp120. We found that gp120 failed to induce expression of hsp70, hsp25 or hsp90 in cortical or hippocampal cultures, under conditions where induction can be demonstrated in response to other insults. The failure of gp120 to induce a heat shock response is significant because we subsequently demonstrated that such an induction would have been beneficial. Specifically, over expression of hsp70 with a herpes viral amplicon vector protected cultured hippocampal neurons from gp120 neurotoxicity.
View details for DOI 10.1016/S0361-9230(03)00113-8
View details for Web of Science ID 000184051800010
View details for PubMedID 12832005
Effects of glucocorticoids in the gp120-induced inhibition of glutamate uptake in hippocampal cultures
2003; 972 (1-2): 137-141
Studies examining the development of AIDS Related Dementia have concentrated on neurotoxic properties of the HIV viral coat protein, gp120. We have previously shown that this neurotoxicity can be exacerbated by glucocorticoids (GCs), the stress hormones secreted by the adrenal. Moreover, GCs also worsen several of the mechanisms mediating gp120 neurotoxicity, such as increased calcium flux, ROS generation, and energy depletion. Gp120 interferes with the reuptake of glutamate in glia cultures, another possible mechanism by which it can be neurotoxic. This paper examines the role of GCs in exacerbating this phenomenon. It was found that while GCs do not exacerbate the decrease in reuptake of glutamate in glia cultures, they do enhance the decrease in mixed neuronal cultures and this latter effect appears to be energy-dependent.
View details for DOI 10.1016/S0006-8993(03)02517-4
View details for Web of Science ID 000182946100015
View details for PubMedID 12711086
Glucocorticoids mediate the effects of sleep deprivation on brain glycogen and glucose levels
17th Annual Meeting of the Associated-Professional-Sleep-Societies
AMER ACAD SLEEP MEDICINE. 2003: A14–A15
View details for Web of Science ID 000182841100036
Prospects for the treatment of stroke using gene therapy.
Expert review of neurotherapeutics
2003; 3 (3): 357-372
Recent advances have demonstrated the use of gene therapy in the treatment of stroke in experimental animal models of focal ischemia, global ischemia and subarachnoid hemorrhage. Several different vectors for gene transfer have been studied including herpes simplex virus, adenovirus, adeno-associated virus and liposomes. Genetically modified cell lines (e.g., bone marrow-derived cells) have been studied for ex vivo gene therapy. The effects of gene transfer to several brain regions including the striatum, cortex, hippocampus, subarachnoid space and blood vessels are reviewed. Targets of gene therapy, such as molecular cascades after ischemia onset (Ca2+ influx, ATP loss, increased nitric oxide) and events associated with apoptosis are also reviewed, in addition to how gene transfer may be used to understand pathomechanisms underlying ischemic injury and the temporal therapeutic windows following ischemia within which protective effects of gene therapy have been achieved. The prospects for gene therapy for stroke are discussed in light of these findings and it is concluded that solutions to key technological problems will allow gene therapy to be a viable treatment modality.
View details for DOI 10.1586/14737184.108.40.2067
View details for PubMedID 19810903
Bcl-2 overexpression protects against neuron loss within the ischemic margin following experimental stroke and inhibits cytochrome c translocation and caspase-3 activity
JOURNAL OF NEUROCHEMISTRY
2003; 85 (4): 1026-1036
Bcl-2 protects against both apoptotic and necrotic death induced by several cerebral insults. We and others have previously demonstrated that defective herpes simplex virus vectors expressing Bcl-2 protect against various insults in vitro and in vivo, including cerebral ischemia. Because the infarct margin may be a region that is most amenable to treatment, we first determined whether gene transfer to the infarct margin is possible using a focal ischemia model. Since ischemic injury with and without reperfusion may occur by different mechanisms, we also determined whether Bcl-2 protects against focal cerebral ischemic injury either with or without reperfusion in rats. Bax expression, cytochrome c translocation and activated caspase-3 expression were also assessed. Viral vectors overexpressing Bcl-2 were delivered to the infarct margin. Reperfusion resulted in larger infarcts than permanent occlusion. Bcl-2 overexpression significantly improved neuron survival in both ischemia models. Bcl-2 overexpression did not alter overall Bax expression, but inhibited cytosolic accumulation of cytochrome c and caspase-3 activation. Thus, we provide the first evidence that gene transfer to the infarct margin is feasible, that overexpression of Bcl-2 protects against damage to the infarct margin induced by ischemia with and without reperfusion, and that Bcl-2 overexpression using gene therapy attenuates apoptosis-related proteins. This suggests a potential therapeutic strategy for stroke.
View details for DOI 10.1046/j.1471-4159.2003.01756.x
View details for Web of Science ID 000182476400020
View details for PubMedID 12716434
Serum leptin levels as a marker for a syndrome X-like condition in wild baboons
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2003; 88 (3): 1234-1240
We measured serum leptin levels in two groupings of wild male baboons, one with access to abundant quantities of food from gardens and garbage dumps near human habitations (Garbage; n = 11) and one without access (No Garbage; n = 10). A Garbage subgroup had high leptin levels (Garbage HL), whereas the rest of the Garbage group had low leptin levels (Garbage LL) similar to those in the No Garbage group. The Garbage HL individuals were obese, with higher mass, body mass index, and leptin to mass ratios; were insulin to resistant, with elevations in serum insulin, glucose, and insulin to glucose ratios; and were hyperlipidemic. This syndrome X-like condition occurred only in the Garbage HL subset. The Garbage LL subset did not differ from the No Garbage individuals in mass, body mass index, leptin to mass ratio, insulin, glucose, or insulin to glucose ratios. The highest cholesterol levels, however, occurred in the Garbage LL individuals, suggesting that susceptibility to hyperlipidemia is distinguishable from susceptibility to obesity and insulin resistance. The differences were not explained by age or social status. These results show that a subgroup of wild baboons is susceptible to developing obesity and insulin resistance and that this susceptibility is not related to age or social rank.
View details for DOI 10.1210/jc.2002-021695
View details for Web of Science ID 000181545700045
View details for PubMedID 12629112
Novel glucocorticoid effects on acute inflammation in the CNS
JOURNAL OF NEUROCHEMISTRY
2003; 84 (4): 705-716
The CNS can mount an inflammatory reaction to excitotoxic insults that contributes to the emerging brain damage. Therefore, anti-inflammatory drugs should be beneficial in neurological insults. In contrast, glucocorticoids (GCs), while known for their anti-inflammatory effects, can exacerbate neurotoxicity in the hippocampus after excitotoxic insults. We investigated the effect of GCs on the inflammatory response after a neurological insult. Intact control (INT; intact stress response GC profile), adrenalectomized/GC-supplemented (ADX; low basal GC profile) and GC-treated (COR; chronically high GC profile) rats were injected with kainic acid into the hippocampal CA3 region. Lesion size was determined 8-72 h later. The inflammatory response was characterized using immunohistochemistry, RNAse protection assay and ELISA. The INT and COR rats developed larger CA3 lesions than ADX rats. We found that GCs surprisingly caused an increase in relative numbers of inflammatory cells (granulocytes, monocytes/macrophages and microglia). Additionally, mRNA and protein (IL-1beta and TNF-alpha) levels of the pro-inflammatory cytokines IL-1alpha, IL-1beta and TNF-alpha were elevated in COR rats compared with INT and ADX rats. These data strongly question the traditional view of GCs being uniformly anti-inflammatory and could further explain how GCs worsen the outcome of neurological insults.
View details for DOI 10.1046/j.0022-3042.2003.01604.x
View details for Web of Science ID 000180742400009
View details for PubMedID 12562515
Gene therapy for psychiatric disorders
AMERICAN JOURNAL OF PSYCHIATRY
2003; 160 (2): 208-220
There has been tremendous progress in developing techniques for manipulating genetic material, and the birth of gene therapy as a discipline has been one consequence of this. Most considerations of gene therapy in the nervous system have focused on attempts to transfer novel genes in for the purpose of protecting neurons from neurological insults. In this review, the author considers the progress in that field and the possible application of related gene therapy approaches to the far more difficult task of buffering against a psychiatric disorder. As an emphasis, the author reviews how the biology of psychiatric disorders is so often one of vulnerability to particular environments. Because of this context dependency, it would be likely that many possible gene therapeutic interventions would need to be context dependent as well. Thus, the author considers the plausibility of developing gene vector therapies that use conditional expression systems, in particular ones whose expression would be induced by the same environmental perturbations that exacerbate psychiatric symptoms themselves. In particular, the author considers the role of stress as a predisposing factor in certain psychiatric disorders and the ways in which stress signals can be harnessed as inducers of conditional expression systems in gene therapy.
View details for Web of Science ID 000180788300002
View details for PubMedID 12562564
Gene therapy and hypothermia for stroke treatment
6th International Conference on Neuroprotective Agents
NEW YORK ACAD SCIENCES. 2003: 54–68
We have previously reported studies of gene therapy using a neurotropic herpes simplex viral (HSV) vector system containing bipromoter vectors to transfer various protective genes to neurons. Using this system in experimental models of stroke, cardiac arrest, and excitotoxicity, we found that it is possible to enhance neuron survival against such cerebral insults by overexpressing genes that target various facets of injury. Among the genes we studied, the anti-apoptotic protein BCL-2 improved neuron survival following various insults, and was protective even when administered after stroke onset. BCL-2 is thought to protect cells from apoptotic death by preventing cytochrome c release from the mitochondria and subsequent caspase activation. We and others have established that cooling the brain by a few degrees markedly reduces ischemic injury and improves neurologic deficits in models of cerebral ischemia and trauma. This hypothermic neuroprotection is also associated with BCL-2 upregulation in some instances. Furthermore, hypothermia suppresses many aspects of apoptotic death including cytochrome c release, caspase activation, and DNA fragmentation. Here we show that two different kinds of protective therapies, BCL-2 overexpression and hypothermia, both inhibit aspects of apoptotic cell death cascades, and that a combination treatment can prolong the temporal therapeutic window for gene therapy.
View details for Web of Science ID 000184303000006
View details for PubMedID 12853295
Are subordinates always stressed? A comparative analysis of rank differences in cortisol levels among primates
HORMONES AND BEHAVIOR
2003; 43 (1): 67-82
Among primate species there is pronounced variation in the relationship between social status and measures of stress physiology. An informal meta-analysis was designed to investigate the basis of this diversity across different primate societies. Species were included only if a substantial amount of published information was available regarding both social behavior and rank-related differences in stress physiology. Four Old World and three New World species met these criteria, including societies varying from small-group, singular cooperative breeders (common marmoset and cotton top tamarin) to large-troop, multi-male, multi-female polygynous mating systems (rhesus, cynomolgus, talapoin, squirrel monkeys, and olive baboon). A questionnaire was formulated to obtain information necessary to characterize the stress milieu for individuals in particular primate societies. We standardized cortisol values within each species by calculating the ratio of basal cortisol concentrations of subordinates to those of dominants in stable dominance hierarchies and expressing the ratio as a percentage (relative cortisol levels). The meta-analysis identified two variables that significantly predicted relative cortisol levels: subordinates exhibited higher relative cortisol levels when they (1). were subjected to higher rates of stressors, and (2). experienced decreased opportunities for social (including close kin) support. These findings have important implications for understanding the different physiological consequences of dominant and subordinate social status across primate societies and how social rank may differ in its behavioral and physiological manifestations among primate societies.
View details for DOI 10.1016/S0018-506X(02)00037-5
View details for Web of Science ID 000182658400010
View details for PubMedID 12614636
- Neuroprotective gene therapy against acute neurological insults NATURE REVIEWS NEUROSCIENCE 2003; 4 (1): 61-69
HSV-mediated Bcl-2 transfection blocks apoptosis inducing factor (AIF) translocation after focal ischemia in rat
28th International Stroke Conference
LIPPINCOTT WILLIAMS & WILKINS. 2003: 241–41
View details for Web of Science ID 000180251100077
The exacerbation of hippocampal excitotoxicity by glucocorticoids is not mediated by apoptosis
2003; 77 (1): 24-31
Both endogenous and exogenous glucocorticoids (GCs) are known to cause apoptosis in a number of peripheral tissues and in some cases in the CNS. Additionally, GCs can exacerbate the neuron loss associated with such acute neurological insults as hypoxia-ischemia, excitotoxicity, and metabolic disruption. This exacerbation is accompanied by increased accumulation of glutamate in the synapse, excessive cytosolic calcium, and increased oxygen radical activity, markers usually attributed to pathways of necrotic cell death. It is also known that acute insults can involve apoptotic mediators. In this context, one outstanding question that has received little attention is whether the exacerbation of insult-mediated cell death in neurons is apoptotic in mechanism. In this study we investigate whether the GC-mediated exacerbation of hippocampal excitotoxicity in culture involves apoptosis. Specifically, we show that while the magnitude of hippocampal neuron death caused by the excitotoxin kainic acid is indeed worsened in the presence of GCs, there is no evidence of increased markers of apoptosis. Specifically, we show that neither kainic acid nor GCs alone, or in combination, cause activation of caspase 3, a critical executor of insult-induced apoptosis. Furthermore, while kainic acid causes a significant incidence of apoptotic nuclear condensation, the incidence of this morphological indicator of apoptosis is not worsened by GCs. Thus, GCs appear to augment excitotoxic death in hippocampal neurons without augmenting the occurrence of apoptosis. We suggest that this finding is to be expected, given some energetic features of GC action and the energetic demands of apoptosis.
View details for DOI 10.1159/000068337
View details for Web of Science ID 000181770500004
View details for PubMedID 12624538
Protection against gp120-induced neurotoxicity by an array of estrogenic steroids
2002; 958 (2): 272-276
gp120, the coat protein of HIV, can be neurotoxic and is thought to contribute to AIDS-related dementia complex. Such toxicity involves activation of glutamate receptors, mobilization of free cytosolic calcium, and generation of oxygen radicals. We have previously shown that the estrogen 17beta-estradiol, in concentrations of 100 nM or higher, lessens the neurotoxicity of gp120 in hippocampal and cortical cultures, blunts gp120-induced calcium mobilization, and lessens the oxidative consequences. In this study, we examined the protective potential of other estrogens. We found gp120 neurotoxicity in hippocampal cultures to be significantly lessened by estrone, equilin and estriol, although with an order of magnitude less potent than 17beta-estradiol. We also found all four estrogens to blunt gp120-induced calcium mobilization, with estriol being more efficacious than the other three estrogens. These findings give insight both into the mechanisms of estrogenic protection (e.g. receptor-dependent versus independent actions) as well as into the potential therapeutic use of estrogens against AIDS-related dementia complex.
View details for Web of Science ID 000180087300006
View details for PubMedID 12470862
Glucocorticoids and central nervous system inflammation
JOURNAL OF NEUROVIROLOGY
2002; 8 (6): 513-528
Glucocorticoids (GCs) are well known for their anti-inflammatory and immunosuppressive properties in the periphery and are therefore widely and successfully used in the treatment of autoimmune diseases, chronic inflammation, or transplant rejection. This led to the assumption that GCs are uniformly anti-inflammatory in the periphery and the central nervous system (CNS). As a consequence, GCs are also used in the treatment of CNS inflammation. There is abundant evidence that an inflammatory reaction is mounted within the CNS following trauma, stroke, infection, and seizure, which can augment the brain damage. However an increasing number of studies indicate that the concept of GCs being universally immunosuppressive might be oversimplified. This article provides a review of the current literature, showing that under certain circumstances GCs might fail to have anti-inflammatory effects and sometimes even enhance inflammation.
View details for DOI 10.1080/13550280290100914
View details for Web of Science ID 000180306600006
View details for PubMedID 12476346
Neuroprotective effects of bcl-2 overexpression in hippocampal cultures: interactions with pathways of oxidative damage
JOURNAL OF NEUROCHEMISTRY
2002; 83 (4): 914-923
Overexpression of bcl-2protects neurons from numerous necrotic insults, both in vitro and in vivo. While the bulk of such protection is thought to arise from Bcl-2 blocking cytochrome c release from mitochondria, thereby blocking apoptosis, the protein can target other steps in apoptosis, and can protect against necrotic cell death as well. There is evidence that these additional actions may be antioxidant in nature, in that Bcl-2 has been reported to protect against generators of reactive oxygen species (ROS), to increase antioxidant defenses and to decrease levels of ROS and of oxidative damage. Despite this, there are also reports arguing against either the occurrence, or the importance of these antioxidant actions. We have examined these issues in neuron-enriched primary hippocampal cultures, with overexpression of bcl-2 driven by a herpes simplex virus amplicon: (i) Bcl-2 protected strongly against glutamate, whose toxicity is at least partially ROS-dependent. Such protection involved reduction in mitochondrially derived superoxide. Despite that, Bcl-2 had no effect on levels of lipid peroxidation, which is thought to be the primary locus of glutamate-induced oxidative damage; (ii) Bcl-2 was also mildly protective against the pro-oxidant adriamycin. However, it did so without reducing levels of superoxide, hydrogen peroxide or lipid peroxidation; (iii) Bcl-2 protected against permanent anoxia, an insult likely to involve little to no ROS generation. These findings suggest that Bcl-2 can have antioxidant actions that may nonetheless not be central to its protective effects, can protect against an ROS generator without targeting steps specific to oxidative biochemistry, and can protect in the absence of ROS generation. Thus, the antioxidant actions of Bcl-2 are neither necessary nor sufficient to explain its protective actions against these insults in hippocampal neurons.
View details for Web of Science ID 000179046200019
View details for PubMedID 12421364
Glucocorticoid exacerbation of gp120 neurotoxicity: Role of microglia
2002; 177 (1): 151-158
Gp120 protein, part of the HIV coat, may be a causative agent in AIDS-Related Dementia (ARD) because of its demonstrated neurotoxicity in vitro and in vivo. There are two possible mechanisms for this toxicity, namely through release of toxins from the microglia or through direct action on neuronal chemokine receptors. In tissue culture, glucocorticoids (GCs), the adrenal steroids released during stress, exacerbate gp120 neurotoxicity. In this paper, we examine the means by which GCs may increase toxicity, focusing on interactions with microglia and glia. Media from microglia treated with gp120 was toxic to neurons but not to glia. The effects of GCs upon the extent of gp120-induced release of toxins by microglia seemed to be dependent on the time of exposure to the hormone. Twenty-four-hour exposure of microglia to GCs decreased the toxicity of gp120-treated microglial conditioned media. In contrast, longer-term GC exposure enhanced neurotoxicity. There also appeared to be a component of gp120 neurotoxicity in hippocampal cultures that was exacerbated by GCs, independent of the amount of microglia present. Thus, GCs appear to act at a number of different sites in the multi-cellular pathway to exacerbate the neurotoxic effects of gp120.
View details for DOI 10.1006/exnr.2002.7956
View details for Web of Science ID 000178263600014
View details for PubMedID 12429218
Gene transfer of HSP72 protects cornu ammonis 1 region of the hippocampus neurons from global ischemia: Influence of Bcl-2
ANNALS OF NEUROLOGY
2002; 52 (2): 160-167
We investigated whether HSV gene transfer of HSP72 in vivo and in vitro: (1) protected cornu ammonis 1 region of the hippocampus neurons from global cerebral ischemia; and (2) affected Bcl-2 expression. HSV vectors expressing HSP72 and beta-galactosidase (reporter) or beta-galactosidase only (control vector) were injected into cornu ammonis 1 region of the hippocampus 15 hours before induction of global cerebral ischemia (n = 10) and sham-operated rats (n = 8). HSP72 vector-treated rats displayed significantly more surviving transfected neurons (X-gal-positive, 31 +/- 8) compared with control vector-treated rats (10 +/- 4) after global cerebral ischemia. Sham-operated rats displayed similar numbers of X-gal-positive neurons (HSP72 vector 18 +/- 8 vs control vector 20 +/- 7). The percentage of beta-galactosidase and Bcl-2 coexpressing neurons in HSP72-treated rats after global cerebral ischemia (84 +/- 4%) was greater than that in control vector-treated rats (58 +/- 9%). The percentage of beta-galactosidase and Bcl-2 coexpressing neurons in sham-operated rats was similar in HSP72 (93 +/- 7%) and in control vector-treated rats (88 +/- 12%). HSP72 vector transfection led to 12 times as much Bcl-2 expression as the control vector in uninjured hippocampal neuronal cultures. In injured (oxygen-glucose deprivation) hippocampal neuron cultures, HSP72 vector transfection led to 2.8 times as much Bcl-2 expression as control vector. We show that HSP72 overexpression protects cornu ammonis 1 region of the hippocampus neurons from global cerebral ischemia, and that this protection may be mediated in part by increased Bcl-2 expression.
View details for DOI 10.1002/ana.10264
View details for Web of Science ID 000177140000005
View details for PubMedID 12210785
Disruptive effects of glucocorticoids on glutathione peroxidase biochemistry in hippocampal cultures
JOURNAL OF NEUROCHEMISTRY
2002; 82 (1): 118-125
Glucocorticoids (GCs), the adrenal steroids secreted during stress, compromise the ability of hippocampal neurons to survive various necrotic insults. We have previously observed that GCs enhance the hippocampal neurotoxicity of reactive oxygen species and, as a potential contributor to this, decrease the activity of the antioxidant enzyme, glutathione peroxidase (GSPx). In this report, we have studied the possible mechanisms underlying this GC effect upon GSPx in primary hippocampal cultures and have observed several results. (i) Corticosterone (the GC of rats) decreased glutathione levels; this was predominately a result of a decrease in levels of reduced glutathione (GSH), the form of glutathione which facilitates GSPx activity. (ii) Corticosterone also decreased levels of NADPH; this may help explain the effect on GSH as NADPH is required for regeneration of GSH from oxidized glutathione. (iii) However, the corticosterone effect on total glutathione levels could not just be caused by the NADPH effect, as there were also reduced levels of oxidized glutathione. (iv) Corticosterone caused a small but significant decrease in GSPx activity over a range of glucose concentrations; this occurred under circumstances of an excess of glutathione as a substrate, suggesting a direct effect of corticosterone on GSPx activity. (v) This corticosterone effect was likely to have functional implications, in that enhancement of GSPx activity (to the same magnitude as activity was inhibited by corticosterone) by GSPx overexpression protected against an excitotoxin. Thus, GCs have various effects, both energetic and non-energetic in nature, upon steps in GSPx biochemistry that, collectively, may impair hippocampal antioxidant capacity.
View details for Web of Science ID 000176438900014
View details for PubMedID 12091472
- Distributing behaviors of the Orangutan SCIENTIFIC AMERICAN 2002; 286 (6): 60-65
Male orangutan subadulthood: A new twist on the relationship between chronic stress and developmental arrest
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY
2002; 118 (1): 25-32
Both in the wild and in captivity, a marked and enduring arrest of secondary sexual developmental occurs in some male orangutans (Pongo pygmaeus) (Kingsley  The Orang-Utan: Its Biology and Conservation, The Hague: Junk; Utami ). Researchers have hypothesized that chronic stress, perhaps related to aggression from mature males, causes endocrine changes altering growth and maturation rates in these males (Maple  Orangutan Behavior, New York: Van Nostrand Reinhold; Graham  Orangutan Biology, Oxford: Oxford University Press). In this study, urine samples were collected over a 3-year period from 23 captive male orangutans to test the hypothesis that developmentally arrested male orangutans have an endocrine profile consistent with chronic stress. Three study males were juveniles, seven were arrested adolescents, six were developing adolescents, and seven were mature adults. Morning samples were analyzed by radioimmunoassay for levels of the stress hormones cortisol and prolactin, and group hormone profiles were compared by analysis of variance. Results indicate that developing adolescent male orangutans have a significantly higher stress hormone profile than juvenile, developmentally arrested adolescent, or adult males. These results imply that the arrest of secondary sexual development in some male orangutans is not stress-induced, but instead perhaps an adaptation for stress avoidance during the adolescent or "subadult" period. These data, together with previously reported data on levels of gonadotropins, testicular steroids, and growth-related hormones, define endocrine profiles associated with alternative reproductive strategies for males with and males without secondary sexual features (Maggioncalda et al. , .
View details for DOI 10.1002/ajpa.10074
View details for Web of Science ID 000175077700003
View details for PubMedID 11953942
Effects of food availability on serum insulin and lipid concentrations in free-ranging baboons
AMERICAN JOURNAL OF PRIMATOLOGY
2002; 57 (1): 13-19
The relationship between food availability and metabolic physiology was studied in groups of free-ranging baboons (Papio spp.) living in the Amboseli National Park and the Masai Mara National Reserve of Kenya. Three groups subsisted entirely on natural forage, while two other groups lived near tourist facilities and often consumed food wastes from these lodges. The refuse provided a very accessible food source with relatively high caloric density. Consumption of the refuse was associated with reduced locomotion. Sexually mature individuals from all five groups were sedated surreptitiously in the early morning and blood samples were collected. Compared to animals foraging exclusively in the wild, animals that supplemented their diet with the refuse items had two- to threefold elevations in serum insulin concentrations, as well as increased total cholesterol (C), HDL-C, and VLDL+LDL-C levels. No sex differences in physiological measures were observed except in body mass. Elevated serum insulin, and cholesterol and lipoprotein concentrations influence the development of cardiovascular disease and have been shown to be subject to dietary manipulation and exercise under controlled conditions. The present results suggest potentially deleterious effects of a highly accessible, calorically dense food source, and associated reduction of physical activity for baboons living in an otherwise natural environment.
View details for DOI 10.1002/ajp.1083
View details for Web of Science ID 000175326700002
View details for PubMedID 11977122
Stress and depression: possible links to neuron death in the hippocampus
2002; 4 (2): 117-128
Recent intriguing reports have shown an association between major depression and selective and persistent loss of hippocampal volume, prompting considerable speculation as to its underlying causes. In this paper we focus on the hypothesis that overt hippocampal neuron death could cause this loss and review current knowledge about how hippocampal neurons die during insults. We discuss (a) the trafficking of glutamate and calcium during insults; (b) oxygen radical generation and programmed cell death occurring during insults; (c) neuronal defenses against insults; (d) the role of energy availability in modulating the extent of neuron loss following such insults. The subtypes of depression associated with hippocampal atrophy typically involve significant hypersecretion of glucocorticoids, the adrenal steroids secreted during stress. These steroids have a variety of adverse affects, direct and indirect, in the hippocampus. Thus glucocorticoids may play a contributing role toward neuron death. We further discuss how glucocorticoids cause or exacerbate cellular changes associated with hippocampal neuron loss in the context of the events listed above.
View details for Web of Science ID 000175195800005
View details for PubMedID 12071509
Effect of GP120 on glutathione peroxidase activity in cortical cultures and the interaction with steroid hormones
JOURNAL OF NEUROCHEMISTRY
2002; 81 (2): 277-284
GP120 (the protein component of the HIV viral coat) is neurotoxic and may contribute to the cell loss associated with AIDS-related dementia. Previously, it has been shown in rat cortical mixed cultures that gp120 increased the accumulation of hydrogen peroxide and superoxide, two reactive oxygen species (ROS). We now demonstrate that gp120 increased activity of the key antioxidant glutathione peroxidase (GSPx), presumably as a defensive mechanism against the increased ROS load. Both estrogen and glucocorticoids (GCs), the adrenal steroid released during stress, blunted this gp120 effect on GSPx activity. The similar effects of estrogen and of GCs are superficially surprising, given prior demonstrations that GCs exacerbated and estrogens protected against gp120 neurotoxicity. We find that these similar effects of estrogen and GCs on GSPx regulation arose, in fact, from very different routes, which are commensurate with these prior reports. Specifically, estrogen has demonstrated antioxidant properties that may prevent the ROS increase (therefore acting as a neuroprotective agent) and rendered unnecessary the compensatory GSPx increased activity. To verify this we have added H2O2 to estrogen + gp120-treated cells, and GSPx activity was increased. However, with addition of H2O2 to GCs + gp120-treated cells there was no increase in activity. GCs appeared to decrease enzyme production and or activity and therefore under insult conditions ROS levels rose in the cell resulting in increased neurotoxicity. Overexpression of GSPx enzyme via herpes vector system reversed the GCs-induced loss of enzyme and eliminated the GCs exacerbation of gp120 neurotoxicity.
View details for Web of Science ID 000175059800007
View details for PubMedID 12064474
HSV-mediated delivery of virally derived anti-apoptotic genes protects the rat hippocampus from damage following excitotoxicity, but not metabolic disruption
2002; 9 (3): 214-219
Studies utilizing gene delivery to the nervous system indicate that various strategies are protective following acute neurological insults such as seizure and stroke. We have found that inhibitors of apoptosis are protective against excitotoxicity and heat stress but not energetic impairment in vitro. Here we studied the neuroprotective efficacy in vivo of these mediators: viral genes (crmA, p35, gamma34.5 KsBcl-2) that have evolved to suppress suicidal host responses to infection, by inhibiting apoptosis. We investigated these effects by utilizing modified herpes vectors to deliver the anti-apoptotic agents intracerebrally and examined them in the face of excitotoxic and metabolic insults. We found that p35 and gamma34.5 reduced by 45% a hippocampal CA3 lesion caused by kainic acid, while crmA and KsBcl-2 did not. None of the inhibitors protected the dentate gyrus of the hippocampus following 3-acetylpyridine, a hypoglycemia model, but we found crmA to worsen the damage. These data are similar to our results in neuronal cultures where the inhibitors protected against the excitotoxin domoic acid, but not against the metabolic poison, cyanide. Together, the results suggest that inhibitors of various apoptotic elements are capable of protecting under acute insult conditions both in vitro and in vivo, suggesting possible future therapeutic applications.
View details for DOI 10.1038/sj/gt/3301642
View details for Web of Science ID 000173966500008
View details for PubMedID 11859425
Mild post-ischemic hypothermia prolongs the time window for gene therapy
LIPPINCOTT WILLIAMS & WILKINS. 2002: 347–47
View details for Web of Science ID 000173147700101
Upregulation of Bcl-2 in CA1 neurons protected from global cerebral ischemia by HSP72 gene transfer
LIPPINCOTT WILLIAMS & WILKINS. 2002: 355–56
View details for Web of Science ID 000173147700150
Gene therapy against neurological insults: sparing neurons versus sparing function
TRENDS IN NEUROSCIENCES
2001; 24 (12): 695-700
Increasing knowledge of neuron death mediators has led to gene therapy techniques for neuroprotection. Overexpression of numerous genes enhances survival after necrotic or neurodegenerative damage. Nonetheless, although encouraging, little is accomplished if a neuron is spared from death, but not from dysfunction. This article reviews neuroprotection experiments that include some measure of function, and synthesizes basic principles relating to its maintenance. Variations in gene delivery systems, including virus-type and latency between damage onset and vector delivery, probably impact the therapeutic outcome. Additionally, functional sparing might depend on factors related to insult severity, neuron type involved or the step in the death cascade that is targeted.
View details for Web of Science ID 000172508500010
View details for PubMedID 11718873
Memory retrieval impairment induced by hippocampal CA3 lesions is blocked by adrenocortical suppression
2001; 4 (12): 1169-1171
There is evidence that in rats, partial hippocampal lesions or selective ablation of the CA3 subfield can disrupt retrieval of spatial memory and that hippocampal damage disinhibits hypothalamic-pituitary-adrenocortical (HPA)-axis activity, thereby elevating plasma levels of adrenocorticotropin and corticosterone. Here we report evidence that attenuation of CA3 lesion-induced increases in circulating corticosterone levels with the synthesis inhibitor metyrapone, administered shortly before water-maze retention testing, blocks the impairing effects of the lesion on memory retrieval. These findings suggest that elevated adrenocortical activity is critical in mediating memory retrieval deficits induced by hippocampal damage.
View details for DOI 10.1038/nn766
View details for Web of Science ID 000172525000010
View details for PubMedID 11713467
Sleep deprivation elevates plasma corticosterone levels in neonatal rats
2001; 315 (1-2): 29-32
Plasma corticosterone (CORT) levels were measured after short periods of sleep deprivation in rats at postnatal days 12, 16, 20, and 24. There was an age-dependent increase in basal CORT levels and sleep deprivation significantly elevated CORT at all ages compared to non-sleep deprived controls. The levels of CORT after sleep deprivation in P16, P20 and P24 animals were similar, resulting in an age-dependent decrease of the magnitude of the response. Sleep deprived P12 animals had lower levels of CORT. However, the observed response to sleep deprivation suggests that sleep loss is a significant stressor at this age. These observations suggest that younger animals are more sensitive to the effects of mild sleep deprivation than older ones.
View details for Web of Science ID 000172434800008
View details for PubMedID 11711207
Overexpression of HSP72 after induction of experimental stroke protects neurons from ischemic damage
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
2001; 21 (11): 1303-1309
The 72-kD inducible heat shock protein (HSP72) can attenuate cerebral ischemic injury when overexpressed before ischemia onset. Whether HSP72 overexpression is protective when applied after ischemia onset is not known, but would have important clinical implications. Fifty-seven rats underwent middle cerebral artery occlusion for 1 hour. Defective herpes simplex viral (HSV) vectors expressing hsp72 with lacZ as a reporter were delivered 0.5, 2, and 5 hours after ischemia onset into each striatum. Control animals received an identical vector containing only lacZ. Striatal neuron survival at 2 days was improved by 23% and 15% when HSP72 vectors were delayed 0.5 and 2 hours after ischemic onset, respectively ( P < 0.05). However, when delayed by 5 hours, HSP72 overexpression was no longer protective. This is the first demonstration that HSP72 gene transfer even after ischemia onset is neuroprotective. Because expression from these HSV vectors begins 4 to 6 hours after injection, this suggests that the temporal therapeutic window for HSP72 is at least 6 hours after ischemia onset. Future strategies aimed at enhancing HSP72 expression after clinical stroke may be worth pursuing. The authors suggest that in the future HSP72 may be an effective treatment for stroke.
View details for Web of Science ID 000172087000006
View details for PubMedID 11702045
- Depression, antidepressants, and the shrinking hippocampus PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2001; 98 (22): 12320-12322
Interactions among ascorbate, dehydroascorbate and glucose transport in cultured hippocampal neurons and glia
2001; 916 (1-2): 127-135
There is an increasing recognition of the damaging role played by oxygen radicals in mediating necrotic neuronal injury. As such, it becomes important to understand the transport mechanisms that help maintain appropriate levels of small molecule antioxidants such as ascorbate in the brain. It has long been known that the transport of dehydroascorbate (DHA) into a variety of cell types is accomplished through the Glut-1 glucose transporter. In this paper, we characterize interactions among the transports of ascorbate, DHA and glucose in hippocampal cultures. We find: (a) sodium-dependent transport of ascorbate in mixed neuronal/glial, pure glial, and neuron-enriched hippocampal cultures; in contrast, we observed no such transport of DHA; (b) such ascorbate transport appeared to be independent of the glucose transporter, in that glucose did not compete for such transport, and overexpression of the Glut-1 glucose transporter did not alter ascorbate uptake; (c) in contrast, ascorbate, at concentrations ranging from 1 to 20 mM inhibited 2-dexogyglucose transport in mixed, glial and enriched neuronal hippocampal cultures; (d) potentially, ascorbate, by acting as an electron donor, could impair the function of molecules involve in the transport or metabolism of glucose. We observed mild inhibition of glucose transport by one unrelated electron donor (glutathione). Moreover, transport was also inhibited by an ascorbate analog which is not an electron donor. Thus, we conclude that ascorbate transport in hippocampal neurons and glia occurs independent of the glucose transporter but that, nevertheless, ascorbate, at concentrations generally thought to be supraphysiological, has the potential for disrupting glucose transport.
View details for Web of Science ID 000171812300015
View details for PubMedID 11597599
Gene therapy and the aging nervous system
MECHANISMS OF AGEING AND DEVELOPMENT
2001; 122 (14): 1555-1563
In recent years, the first attempts have been made to apply gene transfer technology to protect neurons from death following neurological insults. There has been sufficient progress in this area that it becomes plausible to consider similar gene therapy approaches meant to delay aspects of aging of the nervous system. In this review, we briefly consider such progress and how it might be applied to the realm of the aging brain. Specifically, we consider: (a) the means of delivery of such therapeutic genes; (b) the choice of such genes; and (c) technical elaborations in gene delivery systems which can more tightly regulate the magnitude and duration of transgene protection.
View details for Web of Science ID 000170788600005
View details for PubMedID 11511396
Calbindin overexpression buffers hippocampal cultures from the energetic impairments caused by glutamate
2001; 911 (1): 37-42
A dramatic rise in free cytosolic calcium concentration is thought to be a central event in the pathogenesis of glutamate excitotoxicity in neurons. We have previously demonstrated that gene transfer of the calcium-binding protein calbindin D28k via a Herpes simplex amplicon vector decreases the rise in intracellular calcium and promotes cell survival following glutamatergic challenge. This study explores the effect of calbindin transgene expression on cellular metabolism following glutamate excitotoxicity. Because excitotoxic insults are often energetic in nature, and because calcium sequestering and extrusion place heavy energy demands on a cell, we hypothesized that calbindin overexpression may help preserve cellular energy levels during an insult. We overexpressed calbindin in primary hippocampal cultures, using a Herpes simplex amplicon vector system. We found that calbindin overexpression protected neurons from the decline in ATP levels, mitochondrial potential and metabolic rate following a glutamatergic insult. These results indicate that calbindin expression helps preserve cellular energy state following glutamate excitotoxicity. This illustrates the energetic load placed on neurons by increased free cytosolic calcium and may help explain the neuroprotective effects of calbindin.
View details for Web of Science ID 000170753500005
View details for PubMedID 11489442
Neuroprotective effects of an adenoviral vector expressing the glucose transporter: a detailed description of the mediating cellular events
2001; 908 (1): 49-57
Considerable knowledge exists concerning the events mediating neuron death following a necrotic insult; prompted by this, there have now been successful attempts to use gene therapy approaches to protect neurons from such necrotic injury. In many such studies, however, it is not clear what sequence of cellular events connects the overexpression of the transgene with the enhanced survival. We do so, exploring the effects of overexpressing the Glut-1 glucose transporter with an adenoviral vector in hippocampal cultures challenged with the excitotoxin kainic acid (KA). Such overexpression enhanced glucose transport, attenuated the decline in ATP concentrations, decreased the release of excitatory amino acid neurotransmitters, and decreased the total free cytosolic calcium load. Commensurate with these salutary effects, neuronal survival was enhanced with this gene therapy intervention. Thus, the neuroprotective effects of this particular gene therapy occurs within the known framework of the mechanisms of necrotic neuronal injury.
View details for Web of Science ID 000170095100005
View details for PubMedID 11457430
Gene therapy for treatment of cerebral ischemia using defective herpes simplex viral vectors
2001; 23 (5): 543-552
Significant advances have been made over the past few years concerning the cellular and molecular events underlying neuron death. Recently, it is becoming increasingly clear that some of the genes induced during cerebral ischemia may actually serve to rescue the cell from death. However, the injured cell may not be capable of expressing protein at levels high enough to be protective. One of the most exciting arenas of such interventions is the use of viral vectors to deliver potentially neuroprotective genes at high levels. Neurotrophic herpes simplex viral strains are an obvious choice for gene therapy to the brain, and we have utilized bipromoter vectors that are capable of transferring various genes to neurons. Using this system in experimental models of stroke, cardiac arrest and excitotoxicity, we have found that it is possible to enhance neuron survival against such cerebral insults by over-expressing genes that target various facets of injury. These include energy restoration by the glucose transporter (GLUT-1), buffering calcium excess by calbindin, preventing protein malfolding or aggregation by stress proteins and inhibiting apoptotic death by BCL-2. We show that in some cases, gene therapy is also effective after the onset of injury, and also address whether successful gene therapy necessarily spares function. Although gene therapy is limited to the few hundred cells the vector is capable of transfecting, we consider the possibility of such gene therapy becoming relevant to clinical neurology in the future.
View details for Web of Science ID 000169864400016
View details for PubMedID 11474812
Differential sensitivity of murine astrocytes and neurons from different brain regions to injury
2001; 169 (2): 416-424
Different brain regions show differential vulnerability to ischemia in vivo. Despite this, little work has been done to compare vulnerability of brain cells isolated from different brain regions to injury. Relatively pure neuronal and astrocyte cultures were isolated from mouse cortex, hippocampus, and striatum. Astrocyte vulnerability to 6 h oxygen-glucose deprivation was greatest in striatum (81.8 +/- 4.6% cell death), intermediate in hippocampus (59.8 +/- 4.8%), and least in cortex (37.0 +/- 3.5%). In contrast neurons deprived of oxygen and glucose for 3 h showed greater injury to cortical neurons (71.1 +/- 5.2%) compared to striatal (39.0 +/- 3.1%) or hippocampal (39.0 +/- 5.3%) neurons. Astrocyte injury from glucose deprivation or H(2)O(2) exposure was significantly greater in cells from cortex than from striatum or hippocampus. Neuronal injury resulting from serum deprivation was greater in cortical neurons than in those from striatum or hippocampus, while excitotoxic neuronal injury was equivalent between regions. Antioxidant status and apoptosis-regulatory genes were measured to assess possible underlying differences. Glutathione was higher in astrocytes and neurons isolated from striatum than in those from hippocampus. Superoxide dismutase activity was significantly higher in striatal astrocytes, while glutathione peroxidase activity and superoxide did not differ by brain region. Bcl-x(L) was significantly higher in striatal astrocytes than in astrocytes from other brain regions and higher in striatal and hippocampal neurons than in cortical neurons. Both neurons and astrocytes isolated from different brain regions demonstrate distinct patterns of vulnerability when placed in primary culture. Antioxidant state and levels of expression of bcl-x(L) can in part account for the differential injury observed. This suggests that different protective strategies may have different efficacies depending on brain region.
View details for Web of Science ID 000169189800019
View details for PubMedID 11358455
Neuroprotection with herpes simplex vectors expressing virally derived anti-apoptotic agents
2001; 901 (1-2): 12-22
A large body of literature dealing with neurotoxicity has focused on trying to define the exact nature of cell death following a neurological insult. While there is some debate in the field, it has been shown that a number of neurons in a given population can respond to an acute insult stimulus by activating the apoptotic cascade. To what extent, however, these insults result in the classical manifestations of either apoptosis or necrosis, or whether a mixture of the two results, is highly controversial, in part dependent on the particular system utilized. In this paper, we investigate the role of particular apoptotic signals in cultured rat hippocampal neurons, following acute excitotoxicity, metabolic poisoning, and heat stress. In particular, we examine these effects by utilizing a modified herpes simplex viral vector to specifically deliver viral anti-apoptotic genes. We have selected a battery of viral genes (crmA, p35, gamma34.5, KsBcl-2) that have evolved to suppress suicidal host responses to infection. We examine these inhibitors in the face of the above classes of insults and report that each viral agent tested has a unique profile in its ability to protect hippocampal neurons following acute neurological insults. Specifically, the effects of domoic acid excitotoxicity can be alleviated only with crmA, p35 and gamma34.5 whereas all genes tested can protect against heat stress. Conversely, no genes tested can protect against metabolic poisoning by cyanide. Such a study helps us to further understand the nature of apoptotic signals in different insults.
View details for Web of Science ID 000168768800002
View details for PubMedID 11368945
Interactions among glucose, lactate and adenosine regulate energy substrate utilization in hippocampal cultures
2001; 899 (1-2): 134-141
Glucose is the major energy source during normal adult brain activity. However, it appears that glial-derived lactate is preferred as an energy substrate by neurons following hypoxia-ischemia. We examined factors influencing this switch in energetic bias from glucose to lactate in cultured hippocampal neurons, focusing on the effects of the physiological changes in lactate, glucose and adenosine concentrations seen during hypoxia-ischemia. We show that with typical basal concentrations of lactate and glucose, lactate had no effect on glucose uptake. However, at the concentrations of these metabolites found after hypoxia-ischemia, lactate inhibited glucose uptake. Reciprocally, glucose had no effect on lactate utilization regardless of glucose and lactate concentrations. Furthermore, we find that under hypoglycemic conditions adenosine had a small, but significant, inhibitory effect on glucose uptake. Additionally, adenosine increased lactate utilization. Thus, the relative concentrations of glucose, lactate and adenosine, which are indicative of the energy status of the hippocampus, influence which energy substrates are used. These results support the idea that after hypoxia-ischemia, neurons are biased in the direction of lactate rather than glucose utilization and this is accomplished through a number of regulatory steps.
View details for Web of Science ID 000168403600013
View details for PubMedID 11311874
Calbindin D28K overexpression protects striatal neurons from transient focal cerebral ischemia
2001; 32 (4): 1028-1035
Increased intracellular calcium accumulation is known to potentiate ischemic injury. Whether endogenous calcium-binding proteins can attenuate this injury has not been clearly established, and existing data are conflicting. Calbindin D28K (CaBP) is one such intracellular calcium buffer. We investigated whether CaBP overexpression is neuroprotective against transient focal cerebral ischemia.Bipromoter, replication-incompetent herpes simplex virus vectors that encoded the genes for cabp and, as a reporter gene, lacZ were used. Sprague-Dawley rats received bilateral striatal injections of viral vector 12 to 15 hours before ischemia onset. With the use of an intraluminal occluding suture, animals were subjected to 1 hour of middle cerebral artery occlusion followed by 47 hours of reperfusion. Brains were harvested and stained with X-gal (to visualize beta-galactosidase, the gene product of lacZ). The number of remaining virally transfected, X-gal-stained neurons in both the ischemic and contralateral striata were counted and expressed as the percentage of surviving neurons in the ischemic striatum relative to the contralateral nonischemic striatum.Striatal neuron survivorship among cabp-injected animals was 53.5+/-4.1% (n=10) versus 26.8+/-5.4% among those receiving lacZ (n=9) (mean+/-SEM; P<0.001).We conclude that viral vector-mediated overexpression of CaBP leads to neuroprotection in this model of central nervous system injury. This is the first demonstration that CaBP overexpression protects neurons in a focal stroke model.
View details for Web of Science ID 000167951300038
View details for PubMedID 11283407
Gene therapy effectiveness differs for neuronal survival and behavioral performance
2001; 8 (8): 579-585
If neuronal gene therapy is to be clinically useful, it is necessary to demonstrate neuroprotection when the gene is introduced after insult. We now report equivalent neuronal protection if calbindin D(28K) gene transfer via herpes simplex virus amplicon vector occurs immediately, 30 min, or 1 h after an excitotoxic insult, but not after a 4 h delay. Behavioral performance was evaluated for immediate and 1 h delay groups using a hippocampal-dependent task. Despite equivalent magnitude and pattern of sparing of neurons with the immediate and 1 h delay approaches, the delay animals took a significantly longer time after insult to return to normal performance.
View details for Web of Science ID 000168265600001
View details for PubMedID 11320403
Mechanisms of estrogenic protection against gp120-induced neurotoxicity
2001; 168 (2): 385-391
gp120, an HIV coat glycoprotein that may play a role in AIDS-related dementia complex (ADC), induces neuronal toxicity characterized by NMDA receptor activation, accumulation of intracellular calcium, and downstream degenerative events including generation of reactive oxygen species and lipid peroxidation. We have previously demonstrated estrogenic protection against gp120 neurotoxicity in primary hippocampal cultures. We here characterize the mechanism of protection by blocking the classical cytosolic estrogen receptors and by measuring oxidative end points including accumulation of extracellular superoxide and lipid peroxidation. Despite blocking ERalpha and ERbeta with 1 microM tamoxifen, we do not see a decrease in the protection afforded by 100 nM 17 beta-estradiol against 200 pM gp120. Additionally, 17alpha-estradiol, which does not activate estrogen receptors, protects to the same extent as 17beta-estradiol. 17beta-Estradiol does, however, decrease gp120-induced lipid peroxidation and accumulation of superoxide. Together the data suggest an antioxidant mechanism of estrogen protection that is independent of receptor binding.
View details for Web of Science ID 000167904100019
View details for PubMedID 11259126
Cellular defenses against excitotoxic insults
JOURNAL OF NEUROCHEMISTRY
2001; 76 (6): 1601-1611
The cellular events mediating necrotic neuron death are now reasonably well understood, and involve excessive extracellular accumulation of glutamate and free cytosolic calcium. When such necrotic neurological insults occur, neurons are not passively buffeted, but instead mobilize a variety of defenses in an attempt to decrease the likelihood of neuron death, or to decrease the harm to neighboring neurons (by decreasing the likelihood of inflammation). This review considers some of these defenses, organizing them along the lines of those which decrease neuronal excitability, decrease extracellular glutamate accumulation, decrease cytosolic calcium mobilization, decrease calcium-dependent degenerative events, enhance neuronal energetics, and bias a neuron towards apoptotic, rather than necrotic, death. Although these are currently perceived as a disparate array of cellular adaptations, some experimental approaches are suggested that may help form a more unified subdiscipline of cellular defenses against neurological insults. Such an advance would help pave the way for the rational design of therapeutic interventions against necrotic insults.
View details for Web of Science ID 000167514500001
View details for PubMedID 11259476
Gene therapy for treatment of cerebral ischemia using defective herpes simplex viral vectors
5th International Conference on Neuroprotective Agents
NEW YORK ACAD SCIENCES. 2001: 340–357
Significant advances have been made over the past few years concerning the cellular and molecular events underlying neuron death. Recently, it is becoming increasingly clear that some of genes induced during cerebral ischemia may actually serve to rescue the cell from death. However, the injured cell may not be capable of expressing protein at high enough levels to be protective. One of the most exciting arenas of such interventions is the use of viral vectors to deliver potentially neuroprotective genes at high levels. Neurotropic herpes simplex viral (HSV) strains are an obvious choice for gene therapy to the brain, and we have used bipromoter vectors that are capable of transferring various genes to neurons. Using this system in experimental models of stroke, cardiac arrest, and excitotoxicity, we have found that it is possible to enhance neuron survival against such cerebral insults by overexpressing genes that target various facets of injury. These include energy restoration by the glucose transporter (GLUT-1), buffering calcium excess by calbindin, preventing protein malfolding or aggregation by stress proteins and inhibiting apoptotic death by BCL-2. We show that in some cases, gene therapy is also effective after the onset of injury, and also address whether successful gene therapy necessarily spares function. Although gene therapy is limited to the few hundred cells the vector is capable of transfecting, we consider the possibility of such gene therapy becoming relevant to clinical neurology in the future.
View details for Web of Science ID 000172028600039
View details for PubMedID 11462790
- Atrophy of the hippocampus in posttraumatic stress disorder: How and when? HIPPOCAMPUS 2001; 11 (2): 90-91
Bcl-2 overexpression protects against neuron loss in peri-infarct regions following experimental stroke
LIPPINCOTT WILLIAMS & WILKINS. 2001: 326–27
View details for Web of Science ID 000166234300127
Sparing of neuronal function postseizure with gene therapy
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2000; 97 (23): 12804-12809
Numerous studies have demonstrated that gene therapy interventions can protect neurons from death after neurological insults. In nearly all such studies, however, "protection" consists of reduced neurotoxicity, with no demonstrated preservation of neuronal function. We used a herpes simplex virus-1 system to overexpress either the Glut-1 glucose transporter (GT) (to buffer energetics), or the apoptosis inhibitor Bcl-2. Both decreased hippocampal neuron loss to similar extents during excitotoxic insults in vitro and in vivo. However, the mediating mechanisms and consequences of the two interventions differed. GT overexpression attenuated early, energy-dependent facets of cell death, blocking oxygen radical accumulation. Bcl-2 expression, in contrast, blocked components of death downstream from the energetic and oxidative facets. Most importantly, GT- but not Bcl-2-mediated protection preserved hippocampal function as assessed spatial maze performance. Thus, gene therapeutic sparing of neurons from insult-induced death does not necessarily translate into sparing of function.
View details for Web of Science ID 000165225800082
View details for PubMedID 11058147
View details for PubMedCentralID PMC18845
Gene therapies that enhance hippocampal neuron survival after an excitotoxic insult are not equivalent in their ability to maintain synaptic transmission
2000; 166 (1): 180-189
Research shows that overexpression of cytoprotective genes can spare neurons from necrotic death, but few studies have addressed the functional status of surviving neurons. Overexpression of a brain glucose transporter, Glut-1, or the anti-apoptotic protein, Bcl-2, in rats decreases the size of hippocampal lesions produced by kainic acid (KA) treatment. In animals in which KA-induced lesions are reduced to similar extents by Glut-1 or Bcl-2 overexpression, spatial learning is spared by Glut-1, but not Bcl-2. We postulated that Glut-1 and Bcl-2 act differently to protect hippocampal function and investigated the effects of vector overexpression on synaptic physiology after KA treatment. Three days after KA and vector delivery to the dentate gyrus, mossy fiber-CA3 (MF-CA3) population excitatory postsynaptic potentials (EPSPs) were recorded in vitro. In addition to producing a lesion in area CA3, KA treatment reduced baseline MF-CA3 synaptic strength, posttetanic potentiation (PTP), and long-term potentiation (LTP). A similar reduction in the KA-induced lesion was produced by overexpression of Glut-1 or Bcl-2. Glut-1, but not Bcl-2, attenuated the impairments in synaptic strength and PTP. Overexpression of Glut-1 or Bcl-2 preserved LTP after KA treatment. Results indicate greater protection of MF-CA3 synaptic transmission with overexpression of Glut-1 compared to Bcl-2 and suggest that not all neuroprotective gene therapy techniques are equivalent in their ability to spare function.
View details for Web of Science ID 000165119800016
View details for PubMedID 11031094
The effects of steroid hormones in HIV-related neurotoxicity: A mini review
2000; 48 (9): 881-893
This review examines the interaction of steroid hormones, glucocorticoids and estrogen, and gp120, a possible causal agent of acquired immune deficiency syndrome-related dementia complex. The first part of the review examines the data and mechanisms by which gp120 may cause neurotoxicity and by which these steroid hormones effect cell death in general. The second part of the review summarizes recent experiments that show how these steroid hormones can modulate the toxic effects of gp120 and glucocorticoids exacerbating toxicity, and estrogen decreasing it. We then examine the limited in vivo and clinical data relating acquired immune deficiency syndrome-related dementia complex and steroid hormones and speculate on the possible clinical significance of these findings with respect to acquired immune deficiency syndrome-related dementia complex.
View details for Web of Science ID 000165099700003
View details for PubMedID 11074226
The possibility of neurotoxicity in the hippocampus in major depression: A primer on neuron death
Conference on Depression in the 21st Century: New Insight into Drug Development and Neurobiology
ELSEVIER SCIENCE INC. 2000: 755–65
A number of studies indicate that prolonged, major depression is associated with a selective loss of hippocampal volume that persists long after the depression has resolved. This review is prompted by two ideas. The first is that overt neuron loss may be a contributing factor to the decrease in hippocampal volume. As such, the first half of this article reviews current knowledge about how hippocampal neurons die during insults, focusing on issues related to the trafficking of glutamate and calcium, glutamate receptor subtypes, oxygen radical generation, programmed cell death, and neuronal defenses. This is meant to orient the reader toward the biology that is likely to underlie any such instances of neuron loss in major depression. The second idea is that glucocorticoids, the adrenal steroids secreted during stress, may play a contributing role to any such neuron loss. The subtypes of depression associated with the hippocampal atrophy typically involve significant hypersecretion of glucocorticoids, and the steroid has a variety of adverse effects in the hippocampus, including causing overt neuron loss. The second half of this article reviews the steps in this cascade of hippocampal neuron death that are regulated by glucocorticoids.
View details for Web of Science ID 000165056200006
View details for PubMedID 11063972
Glucocorticoids and hippocampal atrophy in neuropsychiatric disorders
ARCHIVES OF GENERAL PSYCHIATRY
2000; 57 (10): 925-935
An extensive literature stretching back decades has shown that prolonged stress or prolonged exposure to glucocorticoids-the adrenal steroids secreted during stress-can have adverse effects on the rodent hippocampus. More recent findings suggest a similar phenomenon in the human hippocampus associated with many neuropsychiatric disorders. This review examines the evidence for hippocampal atrophy in (1) Cushing syndrome, which is characterized by a pathologic oversecretion of glucocorticoids; (2) episodes of repeated and severe major depression, which is often associated with hypersecretion of glucocorticoids; and (3) posttraumatic stress disorder. Key questions that will be examined include whether the hippocampal atrophy arises from the neuropsychiatric disorder, or precedes and predisposes toward it; whether glucocorticoids really are plausible candidates for contributing to the atrophy; and what cellular mechanisms underlie the overall decreases in hippocampal volume. Explicit memory deficits have been demonstrated in Cushing syndrome, depression, and posttraumatic stress disorder; an extensive literature suggests that hippocampal atrophy of the magnitude found in these disorders can give rise to such cognitive deficits.
View details for Web of Science ID 000089650300001
View details for PubMedID 11015810
- Stress hormones: Good and bad Symposium on Neuroscience 2000: a New Era of Discovery ACADEMIC PRESS INC ELSEVIER SCIENCE. 2000: 540–42
Trends in neurosciences
2000; 23 (9): 411-?
View details for PubMedID 10941189
Long-term expression driven by herpes simplex virus type-1 amplicons may fail due to eventual degradation or extrusion of introduced transgenes
2000; 165 (1): 58-65
In gene therapy applications employing herpes simplex virus amplicon-based vectors, a prevailing problem is the down-regulation of transgene expression over time. We have applied a combined immunocytochemistry and fluorescent in situ hybridization method to determine whether down-regulation of transgene expression at the single-cell level correlates with loss of vector DNA from the host cell nucleus. Utilizing separate fluorescent labels (i.e., rhodamine, fluorescein, and 4',6'-diamidino-2-phenlindole), we were able to simultaneously detect transgenes, their products, and their locations relative to the nuclear compartment of a single cell. Detection of the reporter gene lacZ and its encoded protein beta-galactosidase (beta-gal) was accomplished in in vivo experiments of the dentate gyrus of rats. A time course study of the expression of the transgene post-stereotactic microinfusion up to 60 days was made. Expression reached maximal levels within 12-24 h after infection, and lacZ presence was reduced to less than 3% of its maximal levels within 36 h after infection. In comparing days 1 and 60 post-stereotactic microinfusion, only one-fifth of the original DNA was observed in the area of a 100-mm radius around the site of microinfusion at day 60. Moreover, by comparing the locations of the reporter gene in cells that expressed the encoded protein versus those that did not, we found that introduced transgenes were preferentially localized in the nuclear periphery of down-regulated host cells, compared to expressing host cells. These results suggest that nuclear compartmentalization may play a role in the down-regulation of our reporter gene by means of peripheralization, extrusion, and/or degradation.
View details for DOI 10.1006/exnr.2000.7454
View details for Web of Science ID 000089295300006
View details for PubMedID 10964485
Neuroprotective potential of a viral vector system induced by a neurological insult
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2000; 97 (16): 9270-9275
Gene transfer into neurons via viral vectors for protection against acute necrotic insults has generated considerable interest. Most studies have used constitutive vector systems, limiting the ability to control transgene expression in a dose-dependent, time-dependent, or reversible manner. We have constructed defective herpes simplex virus vectors designed to be induced by necrotic neurological insults themselves. Such vectors contain a synthetic glucocorticoid-responsive promoter, taking advantage of the almost uniquely high levels of glucocorticoids-adrenal stress steroids-secreted in response to such insults. We observed dose-responsive and steroid-specific induction by endogenous and synthetic glucocorticoids in hippocampal cultures. Induction was likely to be rapid enough to allow transgenic manipulation of relatively early steps in the cascade of necrotic neuron death. The protective potential of such a vector was tested by inclusion of a neuroprotective transgene (the Glut-1 glucose transporter). Induction of this vector by glucocorticoids decreased glutamatergic excitotoxicity in culture. Finally, both exogenous glucocorticoids and excitotoxic seizures induced reporter gene expression driven from a glucocorticoid-responsive herpes simplex virus vector in the hippocampus in vivo.
View details for Web of Science ID 000088608000091
View details for PubMedID 10908682
View details for PubMedCentralID PMC16857
Glucocorticoids exacerbate insult-induced declines in metabolism in selectively vulnerable hippocampal cell fields
2000; 870 (1-2): 109-117
Glucocorticoids (GCs), the adrenal steroids released during stress, can compromise the ability of hippocampal neurons to survive necrotic neurological insults. This GC-induced endangerment has energetic facets, in that it can be attenuated with energy supplementation. In the present report, we studied the effects of GCs on the metabolic response of specific hippocampal cell fields to necrotic insults. We used silicon microphysiometry, which allows indirect measurement of metabolism in real time in tissue explants. Aglycemia caused a significant decline in metabolism in dentate gyrus explants, but not in CA1 or CA3 explants. When coupled with our prior report of cyanide disrupting metabolism only in CA1 explants, and the glutamatergic excitotoxin kainic acid disrupting metabolism only in CA3 explants, this demonstrates that microphysiometry can detect the selective regional vulnerability that characterizes the hippocampal response to these necrotic insults. We then examined the effects of GCs on the response to these insults, monitoring explants taken from rats that were adrenalectomized, intact, or treated with corticosterone (the GC of rats) that produced circulating levels equivalent to those of major stressors. Increased exposure to GCs worsened the decline in metabolism in dentate gyrus explants induced by hypoglycemia, and in CA1 explants induced by cyanide (after eliminating the effects of glial release of lactate for the support of neuronal metabolism). Thus, GCs worsen the metabolic consequences of necrotic insults in hippocampal explants.
View details for Web of Science ID 000087951500013
View details for PubMedID 10869507
Limitations in the neuroprotective potential of gene therapy with Bcl-2
2000; 859 (2): 202-206
Considerable attention has focused on the therapeutic transfer of genes with viral vectors into neurons for the purpose of protecting against neurological insults. A number of papers have reported that overexpression of the anti-apoptotic protein Bcl-2 can protect neurons both in vitro and in vivo against a variety of necrotic insults. An emerging literature suggests that the availability of energy tends to modulate a neuron towards dying apoptotically, rather than necrotically, in the aftermath of an insult. This suggests that an anti-apoptotic protein such as Bcl-2 should be minimally protective, at best, against purely energetic insults. In support of this idea, we report that overexpression of Bcl-2 with a herpes simplex viral vector fails to protect hippocampal neurons, either in vitro or in vivo, against the electron transport uncoupler 3-acetylpyridine (3AP). As a positive control, the same vector significantly protected against the excitotoxin kainic acid. This finding supports the view that neurotoxicity induced by 3AP is likely to have only minimal apoptotic facets. On a broader level, it suggests some limitations in the neuroprotective potential of gene therapy with Bcl-2.
View details for Web of Science ID 000086080600003
View details for PubMedID 10719065
An adenoviral vector expressing the glucose transporter protects cultured striatal neurons from 3-nitropropionic acid
2000; 859 (1): 21-25
Considerable interest has focused on the possibility of using gene transfer techniques to introduce protective genes into neurons around the time of necrotic insults. We have previously used herpes simplex virus amplicon vectors to overexpress the rat brain glucose transporter, Glut-1 (GT), and have shown it to protect against a variety of necrotic insults both in vitro and in vivo, as well as to buffer neurons from the steps thought to mediate necrotic injury. It is critical to show the specificity of the effects of any such transgene overexpression, in order to show that protection arises from the transgene delivered, rather than from the vector delivery system itself. As such, we tested the protective potential of GT overexpression driven, in this case, by an adenoviral vector, against a novel insult, namely exposure of primary striatal cultures to the metabolic poison, 3-nitropropionic acid (3NP). We observed that GT overexpression buffered neurons from neurotoxicity induced by 3NP.
View details for Web of Science ID 000085998400003
View details for PubMedID 10720611
A cautionary note: The actions of adenosine agonists and antagonists may be reversed under certain conditions in primary cultures
BRAIN RESEARCH BULLETIN
2000; 51 (4): 307-312
It is now generally accepted that adenosine has a neuroprotective role in the central nervous system. Agonists of adenosine such as 2-chloroadenosine (2-ClA) have been shown to be neuroprotective, while antagonists such as 8-phenyltheophylline (8-PT) increase neurotoxicity. However, paradoxical results have been reported with adenosine analogues, especially with respect to length of time of administration. We observe similarly contradictory findings with respect to 2-ClA and 8-PT actions in primary hippocampal cultures exposed to glutamate or kainic acid. We found 8-PT and 2-ClA had antagonist and agonist actions, respectively, only with acute (1 h) treatment; with chronic treatment (24 h), 2-ClA had no effects, while 8-PT had significant agonist actions. We also show that with variations in the type of culturing system, concentration, and pH that 8-PT's neurotoxic antagonist actions could be dramatically changed. We, therefore, present this paper as a cautionary note in experimenting with adenosine analogues.
View details for Web of Science ID 000085638900003
View details for PubMedID 10704780
Glucocorticoids exacerbate the deleterious effects of gp120 in hippocampal and cortical explants
JOURNAL OF NEUROCHEMISTRY
2000; 74 (3): 1000-1007
Glucocorticoids (GCs), the adrenal steroids secreted during stress, can compromise the ability of hippocampal neurons to survive numerous necrotic insults. We have previously observed that GCs worsen the deleterious effects of gp120, the glycoprotein of the acquired immune deficiency syndrome virus, which can indirectly damage neurons and which is thought to play a role in the neuropathological features of human immunodeficiency virus infection. Specifically, GCs augment gp120-induced calcium mobilization, ATP depletion, decline in mitochondrial potential, and neurotoxicity in fetal monolayer cultures from a number of brain regions. In the present report, we demonstrate a similar gp120/GC synergy in adult hippocampal and cortical explants. We generated explants from rats that were either adrenalectomized, adrenally intact, or intact and treated with corticosterone to produce levels seen in response to major stressors. Metabolic rates in explants were then indirectly assessed with silicon microphysiometry, and cytosolic calcium concentrations were assessed with fura-2 fluorescent microscopy. We observed that basal levels of GCs tonically augment the disruptive effects of gp120 on metabolism in the CA1 cell field of the hippocampus and in the cortex. Moreover, raising GC concentrations into the stress range exacerbated the ability of gp120 to mobilize cytosolic calcium in a number of hippocampal cell fields. Finally, we observed that the synthetic GC prednisone had similarly exacerbating effects on gp120. Thus, GCs can worsen the deleterious effects of gp120 in a system that is more physiologically relevant than the fetal monolayer culture and in a region-specific manner.
View details for Web of Science ID 000085335500012
View details for PubMedID 10693930
How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions
2000; 21 (1): 55-89
The secretion of glucocorticoids (GCs) is a classic endocrine response to stress. Despite that, it remains controversial as to what purpose GCs serve at such times. One view, stretching back to the time of Hans Selye, posits that GCs help mediate the ongoing or pending stress response, either via basal levels of GCs permitting other facets of the stress response to emerge efficaciously, and/or by stress levels of GCs actively stimulating the stress response. In contrast, a revisionist viewpoint posits that GCs suppress the stress response, preventing it from being pathologically overactivated. In this review, we consider recent findings regarding GC action and, based on them, generate criteria for determining whether a particular GC action permits, stimulates, or suppresses an ongoing stress-response or, as an additional category, is preparative for a subsequent stressor. We apply these GC actions to the realms of cardiovascular function, fluid volume and hemorrhage, immunity and inflammation, metabolism, neurobiology, and reproductive physiology. We find that GC actions fall into markedly different categories, depending on the physiological endpoint in question, with evidence for mediating effects in some cases, and suppressive or preparative in others. We then attempt to assimilate these heterogeneous GC actions into a physiological whole.
View details for Web of Science ID 000086512800005
View details for PubMedID 10696570
Alzheimer's disease and some speculations about the evolution of its modifiers
Conference on Towards a Comprehensive Theory for Alzheimers Disease
NEW YORK ACAD SCIENCES. 2000: 99–103
In this paper we consider the evolution of Alzheimer's-like neuropathology in the aging primate brain. In particular, we examine the evolutionary pressures that have likely selected for the neuroprotective effects of estrogen and of the apolipoprotein E2 and E3 isoforms. We analyze this in the context of the altricial nature of new-born primates, their long period of dependency on competent maternal care, and the requirement of cognitive intactness for such competency.
View details for Web of Science ID 000171966500016
View details for PubMedID 11193810
The role of gene therapy in acute cerebral ischemia
8th International Symposium on Pharmacology of Cerebral Ischemia
WISSENSCHAFTLICHE verlagsgesellschaft mbh. 2000: 457–472
View details for Web of Science ID 000168184000045
Growth hormone and thyroid stimulating hormone concentrations in captive male orangutans: Implications for understanding developmental arrest
AMERICAN JOURNAL OF PRIMATOLOGY
2000; 50 (1): 67-76
There are two morphs of reproductive male in orangutans. Both morphs span the age range from adolescent to adult, but "subadult" males are smaller in size and lack secondary sexual features. In this study, urine samples were collected over a 2 year period from 23 captive male orangutans in order to define the endocrinology of this apparent arrest of secondary sexual development. Three males were juveniles, 3 to 5 years of age; seven males showed no secondary sexual trait development and were over 7 years of age; six males were in the process of developing secondary sexual features, with the youngest male being 6 years of age; and seven males were fully mature adults. Morning samples were analyzed by radioimmunoassay for levels of growth hormone (GH) and thyroid-stimulating hormone (TSH) and group hormone profiles were compared by analysis of variance. GH is the primary hormone of growth and development and its increase in teenage boys is associated with the adolescent growth spurt. TSH stimulates the thyroid to produce and secrete hormones that have metabolic effects and required for normal growth and development. Results show that arrested adolescent male orangutans have a GH level about 1/3 that of developing adolescents (P = .0006). TSH levels do not differ significantly between arrested and developing adolescents. These data complement other endocrine data showing significantly lower levels of sex steroids and luteinizing hormone (LH) in arrested males than developing males [Maggioncalda, 1995a,b; Maggioncalda et al., 1999]. Together with documented behavioral differences between reproductive males with and without secondary sexual features, these endocrine data support the hypothesis that in male orangutans there are alternative developmental pathways and corresponding alternative reproductive strategies.
View details for Web of Science ID 000083814300006
View details for PubMedID 10588436
Gene therapy using viral vectors for acute neurologic insults
1999; 53 (9): 1922-1931
Enormous knowledge has emerged concerning the cellular and molecular events underlying necrotic neuron death after seizure, hypoxia-ischemia, or hypoglycemia. This has allowed the design of rational therapies to protect neurons at such times. One of the most exciting arenas of such interventions is the use of viral vectors to deliver neuroprotective genes. This review considers the progress in this nascent discipline. Neuroprotection has been demonstrated against a variety of in vitro and in vivo rodent models of necrotic insults with vectors overexpressing genes that target various facets of injury. These have included the energetic components, calcium excess, accumulation of reactive oxygen species, protein malfolding, inflammation, and triggering of apoptosis (i.e., programmed cell death) in a subset of cells. A number of caveats, subtleties, and pressing questions concerning this literature then are considered. These include whether these gene therapy interventions actually prevent, rather than merely delay, neuron death; the extent to which the effects of such vectors on neuronal cell biology is actually understood; the potential adverse effects of the use of such vectors; and whether sparing a neuron from death with one of these interventions spares function as well. Finally, we consider the likelihood of such gene therapy becoming relevant to clinical neurology in the near future.
View details for Web of Science ID 000084255300005
View details for PubMedID 10599759
The neuroprotective potential of heat shock protein 70 (HSP70)
MOLECULAR MEDICINE TODAY
1999; 5 (12): 525-531
In response to many metabolic disturbances and injuries, including stroke, neurodegenerative disease, epilepsy and trauma, the cell mounts a stress response with induction of a variety of proteins, most notably the 70-kDa heat shock protein (HSP70). Whether stress proteins are neuroprotective has been hotly debated, as these proteins might be merely an epiphenomenon unrelated to cell survival. Only recently, with the availability of transgenic animals and gene transfer, has it become possible to overexpress the gene encoding HSP70 to test directly the hypothesis that stress proteins protect cells from injury. A few groups have now shown that overproduction of HSP70 leads to protection in several different models of nervous system injury. This review will cover these studies, along with the potential mechanisms by which HSP70 might mediate cellular protection.
View details for Web of Science ID 000083729600007
View details for PubMedID 10562718
Delivery of herpes simplex virus amplicon-based vectors to the dentate gyrus does not alter hippocampal synaptic transmission in vivo
1999; 6 (10): 1679-1684
Herpes simplex virus type-1 (HSV) amplicon vectors containing neuroprotective genes can alter cell physiology and enhance survival following various insults. However, to date, little is known about effects of viral infection itself (independent of the gene delivered) on neuronal physiology. Electrically-evoked synaptic responses are routinely recorded to measure functional alterations in the nervous system and were used here to assess the potential capability of HSV vectors to disrupt physiology of the hippocampus (a forebrain structure involved in learning that is highly susceptible to necrotic insult, making it a frequent target in gene therapy research). Population excitatory post-synaptic potentials (EPSPs) were recorded in the dentate gyrus (DG) and in area CA3 in vivo 72 h after infusion of an HSV vector expressing a reporter gene (lacZ) or vehicle into the DG. Evoked perforant path (PP-DG) or mossy fiber (MF-CA3) EPSPs slope values measured across input/output (I/O) curves were not altered by infection. Paired-pulse facilitation at either recording site was also unaffected. X-gal-positive granule cells surrounded the recording electrode (PP-DG recording) and stimulating electrode tracts (MF-CA3 recording) in animals that received vector, suggesting that we had measured function, at least in part, in infected neurons. Because of the negative electrophysiological result, we sought to deliver a gene with an HSV amplicon which would affect the measured endpoints, as a positive control. Delivery of calbindin D28kpotentiated PP-DG synaptic strength, indicating that our recording system could detect alterations due to vector expression. Thus, the data indicate that HSV vectors are benign, in regard to effects on synaptic function, and support the use of these vectors as a safe method to deliver selected genes to the central nervous system.
View details for Web of Science ID 000082957100006
View details for PubMedID 10516716
Glucocorticoids, stress, and their adverse neurological effects: relevance to aging
1999; 34 (6): 721-732
Glucocorticoids, the adrenal steroids secreted during stress, while critical for successful adaptation to acute physical stressors, can have a variety of deleterious effects if secreted in excess. It has come to be recognized that glucocorticoid excess can have adverse effects in the nervous system, particularly the hippocampus. These effects include disruption of synaptic plasticity, atrophy of dendritic processes, compromising the ability of neurons to survive a variety of coincident insults and, at an extreme, overt neuron death. This review considers the current cellular and molecular bases underlying these adverse glucocorticoid actions, and their relevance to brain aging.
View details for Web of Science ID 000083016100001
View details for PubMedID 10579633
The Alzheimer's lottery
1999; 108 (7): 22-?
View details for Web of Science ID 000082165100015
Calbindin D-28K gene transfer via herpes simplex virus amplicon vector decreases hippocampal damage in vivo following neurotoxic insults
JOURNAL OF NEUROCHEMISTRY
1999; 73 (3): 1200-1205
Increases in cytoplasmic Ca2+ concentration ([Ca2+]i) can lead to neuron death. Preventing a rise in [Ca2+]i by removing Ca2+ from the extracellular space or by adding Ca2+ chelators to the cytosol of target cells ameliorates the neurotoxicity associated with [Ca2+]i increases. Another potential route of decreasing the neurotoxic impact of Ca2+ is to overexpress one of the large number of constitutive calcium-binding proteins. Previous studies in this laboratory demonstrated that overexpression of the gene for the calcium-binding protein calbindin D28K, via herpes simplex virus (HSV) amplicon vector, increases the survival of hippocampal neurons in vitro following energetic or excitotoxic insults but not following application of sodium cyanide. We now report that in vivo hippocampal infection with the calbindin D28K HSV vector increases neuronal survival in the dentate gyrus after application of the antimetabolite 3-acetylpyridine and increases transsynaptic neuronal survival in area CA3 following kainic acid neurotoxicity. The protective effects of infection with the calbindin D28K vector in an intact brain may prove to be beneficial during changes in Ca2+ homeostasis caused by neurological trauma associated with aging and certain neurological diseases.
View details for Web of Science ID 000082037000035
View details for PubMedID 10461912
Glucocorticoid modulation of gp120-induced effects on calcium-dependent degenerative events in primary hippocampal and cortical cultures
1999; 158 (1): 164-170
The HIV coat protein gp120 has been implicated in damaging the nervous system and may play a role in AIDS-related dementia complex. The glycoprotein triggers the release of a glutamatergic agent from infected microglia and macrophages, causing NMDA receptor- and calcium-dependent excitotoxic damage to neurons. We have previously shown that glucocorticoids, the adrenal steroids secreted during stress, worsen gp120 neurotoxicity and calcium mobilization in various brain regions. This study explores events down-stream of gp120-induced calcium mobilization, specifically, generation of reactive oxygen species (ROS) and subsequent lipid peroxidation, destruction of the cytoskeleton through spectrin proteolysis, and the glucocorticoid modulation of these events in primary hippocampal cultures. We observe that 200 pM gp120 causes a significant accumulation of ROS, including superoxide, and of lipid peroxidation. Counter to our predictions, pretreatment with the glucocorticoid corticosterone (CORT) did not worsen the effects of gp120 on ROS accumulation, but did increase lipid peroxidation. We also observed that neither gp120 alone nor gp120 plus CORT caused detectable proteolysis of the cytoskeletal protein spectrin, whose breakdown has been shown to be a damaging consequence of calcium excess in other models of necrotic neuronal injury.
View details for Web of Science ID 000081561800016
View details for PubMedID 10448428
Quantification of neuron survival in monolayer cultures using an enzyme-linked immunosorbent assay approach, rather than by cell counting
1999; 267 (1): 21-24
The determination of neurotoxicity in monolayer mixed cultures has traditionally necessitated the time consuming and subjective procedure of counting neurons. In this paper, we propose a modification of an immunohistochemical staining method with a neuron-specific antibody against MAP2, that allows for quantification of neuron number to be done using an enzyme-linked immunosorbent assay (ELISA) plate reader. This new procedure involves the use of the compound 2,3'-azino-bis(ethylbenzothiazoline-6-sulphonic acid) (ABTS) at the last stage of the staining procedure. We employed two neurotoxicity models (the excitotoxin kainic acid and the interactions between gp120, the glycoprotein of HIV, and the stress hormone corticosterone) to compare the results obtained with this new method and the old method of immunohistochemical staining followed by 3,3'-daminobenzidine (DAB) and the counting of neurons. The ABTS/ELISA method was found to be a fast, reliable and objective procedure for the quantification of neurotoxicity.
View details for Web of Science ID 000080531100006
View details for PubMedID 10400239
Reproductive hormone profiles in captive male orangutans: Implications for understanding developmental arrest
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY
1999; 109 (1): 19-32
For many years researchers have described some male orangutans as "subadult." These males are of adolescent to adult age and are reproductive, but have little to no secondary sexual trait development. Until now the only endocrine study of this arrest of secondary sexual trait development was performed by Kingsley (1982, 1988). She found that "subadult" or arrested males have lower testosterone levels than similar age developing adolescents or adult males. In this study, urine samples were collected over a two-year period from 23 captive male orangutans in order to more fully define male endocrine profiles. Three study males were juveniles, seven were arrested adolescents, six were developing adolescents, and seven were mature adults. Morning samples were analyzed by radioimmunoassay for levels of testicular steroids and gonadotropins and group hormone profiles were compared by analysis of variance. Results illustrate that arrested adolescent orangutans have significantly lower testosterone and dihydrotestosterone (DHT) levels than developing adolescents, but significantly higher levels than juveniles. Luteinizing hormone (LH) levels also differed between arrested and developing adolescents, with arrested males having lower levels. However, follicle stimulating hormone (FSH) levels were similar in both morphs of adolescent male. The overall hormone profiles for arrested and developing adolescent male orangutans suggest that arrested males lack levels of LH, testosterone, and DHT necessary for development of secondary sexual traits. However, they have sufficient testicular steroids, LH, and FSH to fully develop primary sexual function and fertility. These endocrine data help define alternative developmental pathways in male orangutans. The authors discuss the relationship between these developmental pathways and male orangutan reproductive strategies, and hypothesize about their prepubertal socioendocrine determination.
View details for Web of Science ID 000080140700003
View details for PubMedID 10342462
In vivo characterization of 11 beta-hydroxysteroid dehydrogenase in rat hippocampus using glucocorticoid neuroendangerment as an endpoint
1999; 69 (2): 138-144
11beta-Hydroxysteroid dehydrogenase (11beta-HSD) is the enzyme responsible for the interconversion of corticosterone (CORT) to 11-dehydrocorticosterone (11-DHC). CORT is an adrenal hormone secreted during the stress response and it has widespread effects in many different target tissues. In addition, CORT can exacerbate damage caused by neurological insults, such as kainic acid-induced seizures. In addition to its protective role in the kidney, 11beta-HSD is also thought to play a role in steroid regulation in the brain. However, it is not known whether the enzyme is acting in vivo as a reductase or a dehydrogenase. If the enzyme is working as a reductase, converting 11-DHC to CORT, it has the potential to exacerbate neurotoxicity due to other agents. On the other hand, 11beta-HSD could be neuroprotective if the enzyme is acting as a dehydrogenase, deactivating CORT by converting it into 11-DHC. To characterize the enzyme in vivo, we have utilized glucocorticoid neuroendangerment in the hippocampus as an indirect assay of 11beta-HSD function. We have shown that 11-DHC can exacerbate kainic acid toxicity in adrenalectomized (ADX) rats and this exacerbation is blocked by the 11beta-HSD antagonist, carbenoxolone; these findings suggest that 11beta-HSD is working as a reductase in ADX rats. The presumptive reductase activity found in ADX rats was derived from both hippocampal and peripheral forms of the enzyme. In the presence of physiological levels of glucocorticoids, reductase activity was decreased and no dehydrogenase activity was detected. The present study demonstrates that 11beta-HSD reductase activity, both in vivo and in vitro, occurs only in the presence of low levels of circulating glucocorticoids.
View details for Web of Science ID 000078916900008
View details for PubMedID 9986927
An outsider's commentary.
Advances in mind-body medicine
1999; 15 (1): 72-75
View details for PubMedID 10955978
- Gene therapy for acute neurological insults. Neurology 1999: 1922
Glucocorticoids interact with gp120 in causing neurotoxicity in striatal cultures
1998; 808 (2): 305-309
A significant subset of HIV-positive patients suffer from AIDS-Related Dementia Complex (ADC), an array of neurologic and neuropsychologic impairments. The HIV coat protein gp120 has been implicated in the deleterious neurologic consequences of HIV infection, damaging neurons through a glutamatergic and calcium-dependent pathway. We have previously reported that glucocorticoids, the adrenal steroids secreted during stress, can exacerbate the neurotoxic and calcium-mobilizing effects of gp120 in hippocampal and cortical cultures. Because both the symptomatology of ADC, as well as the neuropathologic profile of post-mortem HIV brains suggests an involvement of the striatum, we examined whether glucocorticoids could also augment the damaging effects of gp120 in primary striatal cultures. We observe that neither gp120 nor the glucocorticoid corticosterone, when administered alone, cause neurotoxicity or mobilization of free cytosolic calcium; however, a combination of the two caused significant toxicity and neuron death. This, along with our prior findings of gp120-glucocorticoid interactions, is striking, given the heavy clinical use of synthetic glucocorticoids for management of pulmonary complications of HIV infection.
View details for Web of Science ID 000076693200019
View details for PubMedID 9767177
Gene therapy with HSP72 is neuroprotective in rat models of stroke and epilepsy
ANNALS OF NEUROLOGY
1998; 44 (4): 584-591
Brain areas damaged by stroke and seizures express high levels of the 72-kd heat shock protein (HSP72). Whether HSP72 represents merely a marker of stress or plays a role in improving neuron survival in these cases has been debated. Some induced tolerance experiments have provided correlative evidence for a neuroprotective effect, and others have documented neuroprotection in the absence of HSP72 synthesis. We report that gene transfer therapy with defective herpes simplex virus vectors overexpressing hsp72 improves neuron survival against focal cerebral ischemia and systemic kainic acid administration. HSP72 overexpression improved striatal neuron survival from 62.3 to 95.4% in rats subjected to 1 hour of middle cerebral artery occlusion, and improved survival of hippocampal dentate gyrus neurons after systemic kainic acid administration, from 21.9 to 64.4%. We conclude that HSP72 may participate in processes that enhance neuron survival during transient focal cerebral ischemia and excitotoxin-induced seizures.
View details for Web of Science ID 000076316300002
View details for PubMedID 9778256
Gene transfer of calbindin D-28k cDNA via herpes simplex virus amplicon vector decreases cytoplasmic calcium ion response and enhances neuronal survival following glutamatergic challenge but not following cyanide
JOURNAL OF NEUROCHEMISTRY
1998; 71 (3): 1013-1023
Excitatory amino acid overstimulation of neurons can lead to a marked rise in cytoplasmic Ca2+ concentration ([Ca2+])i) and be followed by neuron death from hours to days later. If the rise in [Ca2+]i is prevented, either by removing Ca2+ from the extracellular environment or by placing Ca2+ chelators in the cytosol of the stimulated cells, the neurotoxicity associated with excitotoxins can be ameliorated. We have recently shown that neurons infected with a herpes simplex virus amplicon vector expressing cDNA for calbindin D28k responded to hypoglycemia with decreased [Ca2+]i and increased survival relative to controls. We now report that vector-infected neurons respond to glutamatergic insults with lower [Ca2+]i than controls and with increased survival. Infected neurons exposed to sodium cyanide did not respond with lower [Ca2+]i than controls, nor did they demonstrate increased survival postinsult. We examine these results in light of our earlier report and in the context of the potential of vectors like this for neuronal gene therapy.
View details for Web of Science ID 000075478400013
View details for PubMedID 9721726
Energy dependency of glucocorticoid exacerbation of gp120 neurotoxicity
JOURNAL OF NEUROCHEMISTRY
1998; 71 (3): 1187-1193
The HIV envelope glycoprotein, gp120, a well documented neurotoxin, may be involved in AIDS-related dementia complex. gp120 works through an NMDA receptor- and calcium-dependent mechanism to damage neurons. We have previously demonstrated that both natural and synthetic glucocorticoids (GCs) exacerbate gp120-induced neurotoxicity and calcium mobilization in hippocampal mixed cultures. GCs, steroid hormones secreted during stress, are now shown to work in conjunction with gp120 to decrease ATP levels and to work synergistically with gp120 to decrease the mitochondrial potential in hippocampal cultures. Furthermore, energy supplementation blocked the ability of GCs to worsen gp120's effects on neuronal survival and calcium mobilization. A GC-induced reduction in glucose transport in hippocampal neurons, as previously documented, may contribute to this energetic dependency. These results may have clinical significance, considering the common treatment of severe cases of Pneumocystis carinii pneumonia, typical of HIV infection, with large doses of synthetic GCs.
View details for Web of Science ID 000075478400031
View details for PubMedID 9721744
Glucocorticoids may alter antioxidant enzyme capacity in the brain: kainic acid studies
1998; 791 (1-2): 215-222
Glucocorticoids (GCs) predispose hippocampal neurons to damage during metabolic stressors. One component of hippocampal GC-endangerment may be changes in neuronal defenses against oxidative challenge. Previous experiments showed a decrease in basal levels of copper/zinc superoxide dismutase (Cu/Zn SOD) and glutathione peroxidase (GSPx) in the brain of rats treated with GCs [L. McIntosh, K. Hong, R. Sapolsky, Glucocorticoids may alter antioxidant enzyme capacity in the brain: baseline studies, 1997.]. In this study we administered the excitotoxin kainic acid (KA) to generate reactive oxygen species (ROS) in the brain, and monitored the activity of four antioxidant enzymes over 24 h in GC-free and GC-supplemented rats. We tested the response pattern in three regions of the brain (hippocampus, cortex, cerebellum) and the liver as a peripheral control. In the hippocampus, KA induced Cu/Zn SOD and catalase, but GCs prevented the induction of catalase and maintained the lowered GSPx activity seen previously in the baseline studies. In the cortex, KA induced Cu/Zn SOD, Mn SOD and catalase activity, but there was no significant GC effect. There was no response to KA in the cerebellum, but GCs decreased GSPx activity. In the liver, KA produced a rise in Cu/Zn SOD and catalase activity, and GC-treated animals showed a slower return to baseline. These experiments indicate that the impairment of antioxidant enzyme defenses, particularly the hippocampal peroxidases, could be a component of GC-mediated neuroendangerment.
View details for Web of Science ID 000073802600026
View details for PubMedID 9593900
Glucocorticoids may alter antioxidant enzyme capacity in the brain: baseline studies
1998; 791 (1-2): 209-214
Glucocorticoids (GCs), the adrenal steroids secreted during stress, have been shown to increase the vulnerability of hippocampal neurons to metabolic insults, potentially by altering the neuronal defense capacity against oxidative damage. These experiments assessed the effect of long term in vivo GC supplementation on basal activity of the antioxidant enzymes copper/zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD), catalase, and glutathione peroxidase (GSPx). Kinetic enzyme studies were done using brain tissue from the hippocampus, cortex, cerebellum, and also from liver as a peripheral control. Cu/Zn SOD activity was significantly lower in all brain regions of GC-treated rats, but higher in the liver. Mn SOD activity was unaffected by treatment. Catalase in the brain appeared largely unaffected by GC treatment, although liver catalase was significantly decreased. GSPx activity was significantly decreased by GCs at high peroxide levels in all tissues. These results indicate that the presence of GCs may lower the antioxidant capacity of tissues in a region-specific manner, and that the deficit may not appear until the tissue is challenged with supranormal levels of oxidative products (as seen with GSPx).
View details for Web of Science ID 000073802600025
View details for PubMedID 9593898
Darting terrestrial primates in the wild: A primer
AMERICAN JOURNAL OF PRIMATOLOGY
1998; 44 (2): 155-167
While a goal of many field primatologists is to observe subjects in as undisturbed a setting as possible, it is often necessary to anesthetize animals for any of a variety of reasons. In this paper, we review techniques for anesthetizing wild primates, based on our experience with more than a thousand such procedures carried out on baboons in East Africa. We consider the following: 1) rationales for anesthetizing a wild primate; 2) systems for the delivery of anesthetic and choice of anesthetic; 3) the darting process itself and issues relevant to the period between darting and the safe removal of the animal; 4) handling of an anesthetized primate; 5) medical complications associated with darting; 6) when to reanesthetize an animal; 7) the process of recovery from anesthesia and release of an awake animal; 8) safety issues for humans. The range of information that can be obtained through field anesthetizations, when carried out successfully, as well as the potential benefit for the animals involved, can be enormous. However, this process is not trivial from the standpoint of the dangers involved to both the subjects and to humans and because of the potential disruption of social behavior to the group. As such, anesthetizations in the field should not be carried out without a strong rationale and without a tremendous priority given to the safety and care of all involved.
View details for Web of Science ID 000071775200006
View details for PubMedID 9503127
Hypercortisolism associated with social subordinance or social isolation among wild baboons
ARCHIVES OF GENERAL PSYCHIATRY
1997; 54 (12): 1137-1143
The phenomena of basal hypercortisolism and of dexamethasone resistance have long intrigued biological psychiatrists, and much is still unknown as to the causes and consequences of such adrenocortical hyperactivity in various neuropsychiatric disorders. We have analyzed basal cortisol concentrations and adrenocortical responsiveness to dexamethasone in a population of wild baboons living in a national park in Kenya. We tested whether social subordinance in a primate is associated with dexamethasone resistance. Furthermore, we examined whether individual differences in adrenocortical measurements were predicted by the extent of social affiliation in these animals.Seventy yellow baboons (Papio cynocephalus) were anesthetized and injected with 5 mg of dexamethasone; the cortisol response was monitored for 6 hours. The animals were of both sexes in a range of ages and had known ranks in the dominance hierarchies within their troops. Extensive behavioral data were available for a subset of 12 adult males who were anesthetized under circumstances that also allowed for the determination of basal cortisol concentrations.The socially subordinate baboons were less responsive to dexamethasone than were the dominant ones; as one manifestation of this, postdexamethasone cortisol values were more than 3 times higher in the dozen lowest-ranking animals compared with the dozen highest. In addition, socially isolated males had elevated basal cortisol concentrations and showed a trend toward relative dexamethasone resistance.Our findings indicate that social status and degree of social affilitation can influence adrenocortical profiles; specifically, social subordinance or social isolation were associated in our study with hypercortisolism or feedback resistance.
View details for Web of Science ID A1997YJ96900011
View details for PubMedID 9400351
Insulin-like growth factor I is suppressed in socially subordinate male baboons
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
1997; 273 (4): R1346-R1351
Insulin-like growth factor (IGF) I is a potent growth-promoting and anabolic hormone with major roles in cellular growth and differentiation, protein metabolism and muscle physiology, wound healing, erythropoiesis, and immune stimulation. Few, if any, studies have examined social or psychological factors that could give rise to individual differences in IGF-I levels. As part of a long-term psychoendocrine study of a population of male baboons living freely in a national reserve in East Africa, we examined the relationship between social rank and IGF-I concentrations. We observed that social subordinance was associated with a relative suppression of IGF-I concentrations; no rank-related differences in concentrations of IGF-II or IGF-binding protein were observed. Extensive psychoendocrine literature suggests that the individual differences in IGF-I profiles were a consequence, rather than a cause, of the rank difference. We were able to rule out a number of possible proximal explanations for the rank-IGF-I correlation: 1) the correlation was not a function of age (which involves both an adolescent spurt in IGF-I concentrations as well as a decline in concentrations in aged individuals); 2) the IGF-I suppression in subordinate individuals could not be explained by the basal hypercortisolism typical of such subordinate animals; and 3) neither differences in the quality or quantity of food consumed, in basal testosterone concentrations, nor in genetics could explain the rank difference. Although the mediating mechanisms responsible for this rank difference were not discernible in this study, the magnitude of difference in IGF-I levels among baboons of differing ranks might be of physiological significance.
View details for Web of Science ID A1997YA44700018
View details for PubMedID 9362298
- The importance of a well-groomed child SCIENCE 1997; 277 (5332): 1620-1621
Increased expression of calbindin D-28k via herpes simplex virus amplicon vector decreases calcium ion mobilization and enhances neuronal survival after hypoglycemic challenge
JOURNAL OF NEUROCHEMISTRY
1997; 69 (3): 1039-1047
Disruption of Ca2+ homeostasis often leads to neuron death. Recently, the function of calcium-binding proteins as neuronal Ca2+ buffers has been debated. We tested whether calbindin D28k functions as an intracellular Ca2+ buffer by constructing bicistronic herpes simplex virus vectors to deliver rat calbindin cDNA to hippocampal neurons in vitro. Neurons were infected with vectors delivering calbindin or a negative control or were mock-infected. After 12 or 24 h of hypoglycemia, infected cells were made aglycemic during fura-2 calcium ratiometric imaging. In response to this challenge, neuronal overexpressing calbindin had less Ca2+ mobilized as compared with negative controls or mock-infected cells. Cells were assayed for survival after 12- or 24-h hypoglycemia or aglycemia. The calbindin vector decreased neuronal death due to hypoglycemia but not aglycemia. Here we demonstrate, in response to hypoglycemic challenge, both decreased Ca2+ mobilization and increased survival of cells infected with the calbindin vector.
View details for Web of Science ID A1997XR46700017
View details for PubMedID 9282926
Endocrine modulation of the neurotoxicity of gp120: Implications for AIDS-related dementia complex
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1997; 94 (17): 9457-9462
HIV infection often involves the development of AIDS-related dementia complex, a variety of neurologic, neuropsychologic, and neuropathologic impairments. A possible contributor to AIDS-related dementia complex is the HIV envelope glycoprotein gp120, which damages neurons via a complex glutamate receptor- and calcium-dependent cascade. We demonstrate an endocrine modulation of the deleterious effects of gp120 in primary hippocampal and cortical cultures. Specifically, we observe that gp120-induced calcium mobilization and neurotoxicity are exacerbated by glucocorticoids, the adrenal steroids secreted during stress. Importantly, this deleterious synergy can occur between gp120 and synthetic glucocorticoids (such as prednisone or dexamethasone) that are used clinically in high concentrations to treat severe cases of the Pneumocystis carinii pneumonia typical of HIV infection. Conversely, we also observe that estradiol protects neurons from the deleterious actions of gp120, reducing toxicity and calcium mobilization.
View details for Web of Science ID A1997XR76500098
View details for PubMedID 9256504
Herpes simplex viral vectors expressing Bcl-2 are neuroprotective when delivered after a stroke
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
1997; 17 (7): 740-744
Considerable interest has focused on the possibility of using viral vectors to deliver genes to the central nervous system for the purpose of decreasing necrotic neuronal injury. To that end, we have previously shown that a herpes simplex virus (HSV) vector expressing Bcl-2 could protect neurons from ischemia. In that study, vector was delivered before the ischemia. However, for such gene therapy to be of clinical use, vectors must be protective even if delivered after the onset of the insult. In the present study, we show that an HSV vector expressing Bcl-2 protects striatal neurons when delivered after focal ischemia. Rats were exposed to middle cerebral artery occlusion for 1 hour, followed by reperfusion, and damage was assessed 48 hours later. Delivery of the Bcl-2 vector 30 minutes after reperfusion (i.e., 1.5 hours after ischemia onset) prevented any significant loss of virally-targeted neurons in the striatum. In contrast, in rats microinfused with a vector only expressing a reporter gene, a highly significant loss of neurons occurred. By 4 hours into the reperfusion period (5 hours after ischemia onset), delivery of the Bcl-2 vector was no longer protective. These data show the efficacy of postinsult gene therapy strategies for the brain, underline the finite length of this temporal therapeutic window, and support the growing evidence attesting to the neuroprotective potential of Bcl-2.
View details for Web of Science ID A1997XR34500003
View details for PubMedID 9270490
- Gene therapy for the nervous system SCIENTIFIC AMERICAN 1997; 276 (6): 116-120
Application of silicon microphysiometry to tissue slices: Detection of metabolic correlates of selective vulnerability
1997; 752 (1-2): 99-106
The silicon microphysiometer is a recently developed instrument which measures rates of proton efflux in real time from small numbers of cultured cells. Since the main products of cellular metabolism are lactic acid and carbon dioxide, this instrument affords an indirect but sensitive measure of cellular metabolism. We previously described the use of the instrument with primary neuronal cultures (Raley-Susman, K.M., Miller, K.R., Owicki, J.C. and Sapolsky, R.M., Effects of excitotoxin exposure on metabolic rate of primary hippocampal cultures: application of silicon microphysiometer to neurobiology, J. Neurosci., 12 (1992) 773-780). In the present report, we adapt the instrument for the indirect measurement of metabolism in tissue slices. In initial studies, we demonstrate stable measures of metabolism with low background noise in hippocampal slices. In addition, measures were relatively insensitive to slice thickness, preparation time or the possible contribution of contaminating bacteria. We then demonstrate the ability to detect metabolic correlates of selective vulnerability in individual hippocampal cell fields. Specifically, we observe a metabolic response to kainic acid that was selective for CA3-derived tissue, and a response to cyanide that was selective for CA1-derived tissue. This corresponds to the well-known vulnerability of CA3 and CA1 to excitotoxic and ischemic insults, respectively. Finally, we show that glucocorticoids, stress-sensitive steroid hormones which are known to exacerbate the toxicity in kainic acid in CA3 neurons, exacerbate the metabolic effects of this excitotoxin as well; in this case, the steroid manipulation was carried out in rats prior to killing. Thus, this instrument represents a complement to more traditional approaches for assessing metabolism in specific brain regions and it can potentially be used for a broad variety of studies with animals of differing ages and pre-mortem manipulations.
View details for Web of Science ID A1997WT62300011
View details for PubMedID 9106445
Defective herpes simplex virus vectors expressing the rat brain stress-inducible heat shock protein 72 protect cultured neurons from severe heat shock
JOURNAL OF NEUROCHEMISTRY
1997; 68 (3): 961-969
Recently, preinduction of the heat shock response has been shown to protect CNS neurons undergoing various stressful insults, e.g., heat, ischemia, or exposure to excitotoxins. However, it is not known which of the proteins induced by the heat shock response mediate the protective effects. Previous correlative evidence points to a role for the highly stress-induced 72-kDa heat shock protein (hsp72). However, it is not known whether hsp72 expression alone can protect against a range of acute neuronal insults. We constructed a herpes simplex virus-1 vector carrying the rat brain stress-inducible hsp72 gene and the Escherichia coli lacZ (marker) gene. Infection with the vector caused hippocampal neurons to coexpress hsp72 and beta-galactosidase. Infection with a control vector led to marker gene expression only. Overexpression of hsp72 protected cultured hippocampal neurons against a heat shock but not against the metabolic toxin 3-nitropropionic acid or the excitotoxin glutamate. This is the first published report of protection following heat shock protein transfection in CNS neurons.
View details for Web of Science ID A1997WJ84200009
View details for PubMedID 9048741
McEwen-Induced Modulation of Endocrine History: A Partial Review.
Stress (Amsterdam, Netherlands)
1997; 2 (1): 1–12
In endless facets of physiology, there are points of homeostatic balance, such that too much or too litttle of something can both be deleterious (i.e., an "inverse U" pattern). This is particularly true when considering glucocorticoids (GCs), the adrenals steroid secreted during stress. In the first part of this paper, I review a number of realms in which a paucity and an excess of GCs are both damaging. Some findings are classical (for example, concerning GC effects upon body weight), while some are quite recent and have considerable implications for both physiology and pathophysiology (for example, inverse U's of GC actions in the realm of immunity and neuronal survival). The second part of the review considers the far thornier issue of how such inverse U's of GC actions are generated on a cellular and molecular level. One solution that has evolved, primarily in the hippocampus within the nervous system, involves the presence of two different types of receptors for GCs within the same cells; so long as the two receptors have very different affinities and mediate opposing effects on some cellular endpoint, an inverse U will emerge. The second solution, found in a number of peripheral tissues, involves GCs having opposing effects on the amount of some signal being generated (e.g., an immune cytokine) and the sensitivity of target tissues to that signal; under conditions that appear to be physiologically relevant, inverse U's emerge from this pattern as well. The final section of this review considers the enormous role played by Bruce McEwen in the emergence of this literature. I suggest that while much of this obviously has to do with the facts that have come from his group, another substantial contribution is from his steadying and supportive personality, the veritable embodiment of homeostatic balance.
View details for PubMedID 9787251
Styles of male social behavior and their endocrine correlates among low-ranking baboons
AMERICAN JOURNAL OF PRIMATOLOGY
1997; 42 (1): 25-39
We have previously studied the relationship between social subordinance (by approach-avoidance criteria) and physiology among male olive baboons (Papio anubis) living freely in a national park in Africa. In stable hierarchies, subordinate individuals have elevated basal glucocorticoid concentrations and a blunted glucocorticoid response to stress, as well as a prompt suppression of testosterone concentrations during stress. These facets have been interpreted as reflecting the chronic stress of social subordinance. In the present report, we find these endocrine features do not mark all subordinate individuals. Instead, endocrine profiles differed among subordinate males as a function of particular stylistic traits of social behavior. A subset of subordinate males was identified who had significantly high rates of consortships, a behavior usually shown only by high-ranking males. Such behavior predicted the beginning transition to dominance, as these males were significantly more likely than other subordinates to have moved to the dominant half of the hierarchy over the subsequent 3 years. In keeping with this theme of emerging from subordinance, these individuals had also significantly larger glucocorticoid stress-responses, another feature typical of dominant males. However, these subordinate males also had significantly elevated basal glucocorticoid concentrations; it is suggested that this reflects the stressfulness of their overt and precocious strategy of reproductive competition. In support of this, subordinate males with high rates of covert "stolen copulations" did not show elevated basal glucocorticoid concentrations. A second subset of subordinate males were the most likely to initiate fights are to displace aggression onto a third party after losing a fight. these males had significantly or near-significantly elevated testosterone concentrations, compared to the remaining subordinate cohort. Moreover, these males had significantly lower basal glucocorticoid concentrations; this echoes an extensive literature showing that the availability of a displacement behavior (whether aggressive or otherwise) after a stressor decreases glucocorticoid secretion. In support of this interpretation suggesting that it was the initiation of these aggressive acts which attenuated glucocorticoid secretion, there was no association between glucocorticoid concentrations and participation (independent of initiation) in aggressive interactions. Thus, these findings suggest that variables other than rank alone may be associated with distinctive endocrine profiles, and that even in the face of a social stressor (such as subordinance), particular behavioral styles may attenuate the endocrine indices of stress.
View details for Web of Science ID A1997WT68900002
View details for PubMedID 9108969
- 'The Trouble With Testosterone' and Other Essays on the Biology of the Human Predicament. Scribner 1997
Glucocorticoids increase the accumulation of reactive oxygen species and enhance adriamycin-induced toxicity in neuronal culture
1996; 141 (2): 201-206
Glucocorticoids (GCs), the adrenal steroids secreted during stress, are known to affect diverse processes involving reactive oxygen species, from exacerbation of ischemic damage to alteration of antioxidant enzyme activities. To determine whether GCs have a direct effect on oxidative processes, we constructed a dose-response curve using adriamycin, an oxygen radical generator, in primary neuronal cultures. In cultures derived from the hippocampus, which has the greatest concentration of corticosteroid receptors in the brain, higher levels of GCs significantly increased adriamycin toxicity, while not being toxic themselves. In cortical cultures, which contain lesser amounts of corticosteroid receptors, GCs had no effect on the adriamycin dose-response. Surprisingly, when tested with dichlorofluorescein for levels of reactive oxygen species (ROS), GCs increased ROS by approximately 10% basally and at all adriamycin doses in both hippocampal and cortical cultures. Thus, greater generation of ROS does not account for the increased susceptibility of the hippocampus to oxidative damage.
View details for Web of Science ID A1996VK39300005
View details for PubMedID 8812153
Endocrine modulators of necrotic neuron death
1996; 6 (4): 481-491
In recent years, there has been extraordinary progress in understanding the cellular and molecular cascades that mediate neuron death following necrotic insults. With this knowledge has come the recognition of ways in which these cascades can be modulated by extrinsic factors, altering the likelihood of subsequent neuron death. In this review, we consider the ability of a variety of hormones to modulate necrotic death cascades. Specifically, we will examine the ability of the stress hormones glucocorticoids and corticotropin-releasing factor, of thyroid hormone, and of pre-ischemic exposure to catecholamines to augment necrotic neuron death. In contrast, estrogen, insulin and postischemic exposure to catecholamines appear to decrease necrotic neuron death. We review the heterogeneous mechanisms that are likely to mediate these hormone effects, some possible clinical implications and the therapeutic potentials of these findings.
View details for Web of Science ID A1996VQ89700012
View details for PubMedID 8944318
Glucocorticoids may enhance oxygen radical-mediated neurotoxicity
5th Meeting of the International-Neurotoxicology-Association
ELSEVIER SCIENCE BV. 1996: 873–82
Modern populations are constantly exposed to a variety of compounds in the workplace and the environment that promote formation of reactive oxygen species (ROS) within susceptible tissues. Due to its high oxygen consumption, the brain may be particularly vulnerable to oxidative damage and degeneration. Agents that impact cellular oxidative homeostasis would therefore be expected to alter the toxicity of ROS generating compounds. We are testing this hypothesis using endogenous stress hormones, glucocorticoids, to perturb neuronal homeostasis, and adriamycin to generate ROS. Glucocorticoids (GCs) are hormones secreted by the adrenals in response to stress, and are also prescribed clinically to control inflammatory and autoimmune disorders in millions of people annually. Therefore, high GC levels may not be uncommon in individuals exposed to low levels of toxic compounds. Also, GCs appear to act on cellular pathways relevant to ROS as seen by their potentiation of neurodegeneration following insults such as stroke, hypoglycemia and seizure. Using rat primary neuronal culture, we determined neuronal susceptibility to adriamycin toxicity by cell counting (using MAP-2 staining). Dichlorofluorescein fluorescence confirmed ROS generation after adriamycin administration. Physiological levels of GCS (up to mM concentrations) in the culture media exacerbated both adriamycin toxicity and ROS generation. We hypothesize that GCs may exacerbate the toxicity of three neurotoxins whose mechanisms of action overlap GC pathways.
View details for Web of Science ID A1996WP10200036
View details for PubMedID 9086511
Inducible gene expression from defective herpes simplex virus vectors using the tetracycline-responsive promoter system
MOLECULAR BRAIN RESEARCH
1996; 41 (1-2): 200-209
Herpes simplex virus-based amplicon vectors have been used for gene transfer into cultured neurons and the adult CNS. Since constitutive expression of a foreign gene or overexpression of an endogenous gene may have deleterious effects, the ability to control temporal expression would be advantageous. To achieve inducible gene expression, we have incorporated the tetracycline-responsive promoter system into amplicon vectors and showed, both in vitro and in vivo, that expression can be modulated by tetracycline. Using the firefly luciferase as the reporter gene, maximal repression by tetracycline in hippocampal cultures was about 50-fold. Withdrawal of tetracycline derepressed gene expression, reaching maximal levels within 10-12 h. In contrast, addition of tetracycline to cultures without prior tetracycline exposure inhibited gene expression rapidly; luciferase activity was reduced to less than 8% within 24 h. In adult rat hippocampus, vectors expressing luciferase or the Escherichia coli lacZ were repressed by tetracycline 9- and 60-fold, respectively. Maximum gene expression from the vectors occurred 2-3 days post-infection and declined thereafter. Such decline impeded further induction of expression by withdrawing tetracycline. This study demonstrates the feasibility of incorporating a powerful inducible promoter system into HSV vectors. The development of such an inducible viral vector system for gene transfer into the adult CNS might prove to be of experimental and therapeutic value.
View details for Web of Science ID A1996VF39200026
View details for PubMedID 8883953
- Why stress is bad for your brain SCIENCE 1996; 273 (5276): 749-750
Hippocampal cell death.
1996; 272 (5266): 1249b-51b
View details for PubMedID 17832183
Hippocampal cell death.
1996; 272 (5266): 1249-1251
View details for PubMedID 8650531
Energy and glutamate dependency of 3-nitropropionic acid neurotoxicity in culture
1996; 138 (2): 298-304
3-Nitropropionic acid (3-NP) irreversibly inhibits the activity of the mitochondrial enzyme succinate dehydrogenase, leading to selective striatal lesions when administered in vivo. We studied the effects of 3-NP on dissociated cultures of neurons and glia with the following findings: (a) 3-NP killed cultured striatal neurons with a median lethal dose of 2.5 mM after 20 h of incubation in 20.0 mM glucose medium. Despite its selective toxicity in vivo, cultured striatal, hippocampal, septal, and hypothalamic neurons were similarly sensitive to 3-NP incubation. (b) 3-NP's effects were remarkably energy substrate dependent, with the median lethal dose dropping over an order of magnitude when glucose concentrations were lowered to 3.0 mM, a condition that was itself nontoxic. Cultures exposed to 3-NP had a far greater sensitivity to energy availability than those exposed to glutamate. (c) Recent work suggests that 3-NP toxicity may be partially mediated by excitotoxins. Our experiments show that neither kynurenic acid, a nonspecific glutamate receptor antagonist, nor the NMDA-receptor antagonist, DL-2-amino-7-phosphonoheptanoic acid, either in combination or alone, reduced 3-NP toxicity in striatal cultures. However, the noncompetitive NMDA antagonist MK-801 did attenuate 3-NP toxicity.
View details for Web of Science ID A1996UF07800013
View details for PubMedID 8620928
Overexpression of the glucose transporter gene with a Herpes simplex viral vector protects striatal neurons against stroke
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
1996; 16 (2): 181-185
Herpes simplex virus vectors bearing a glucose transporter (GT) gene and a marker gene were found to protect neurons against a 1-h focal ischemic insult. Rats receiving the GT vector v alpha22beta gal alpha4GT exhibited a 67.4 +/- 35.3% survival of virally targeted neurons in the ischemic hemisphere compared with the contralateral control (n = 7), whereas rats receiving a control vector exhibited only 32.8 +/- 17.9% survival (n = 9). This significant improvement in survival (105%, p=0.022) suggests that energy failure is an important contributor to the neuropathology of ischemic damage in the striatum, and that it can be alleviated by gene transfer. This is the first demonstration of protection against ischemic cerebral injury by the direct transfer of GT genes to neurons.
View details for Web of Science ID A1996TW39300001
View details for PubMedID 8594048
Overexpression of bcl-2 with herpes simplex virus vectors protects CNS neurons against neurological insults in vitro and in vivo
JOURNAL OF NEUROSCIENCE
1996; 16 (2): 486-496
Previous studies have demonstrated that overexpression of the proto-oncogene bcl-2 can protect neuron and neuron-like cell lines from growth factor deprivation, calcium ionophores, glutamate excitotoxicity, hypoglycemia, free radicals, and lipid peroxidation. To determine whether Bcl-2 exhibits a similar protective effect in CNS neurons, we generated defective herpes simplex virus (HSV) vectors capable of overexpressing Bcl-2 in primary cultures and in the intact brain. Infection of hippocampal cultures with Bcl-2 vectors enhanced neuron survivorship after exposure to adriamycin, a potent oxygen radical generator. Furthermore, dichlorofluorescein measurements indicated that there was a significant reduction in the accumulation of oxygen radicals associated with this insult. Bcl-2 vectors also enhanced survival in cultured neurons after exposure to glutamate and hypoglycemia. Most significantly, the in vivo delivery of the vector protected neurons against adriamycin toxicity in the dorsal horn of the dentate gyrus and focal ischemia in the striatum.
View details for Web of Science ID A1996TP51900007
View details for PubMedID 8551333
Autofluorescence as a confound in the determination of calcium levels in hippocampal slices using fura-2AM dye
1996; 706 (2): 283-288
Recent publications have reported calcium level determinations in slices of brain using imaging techniques and the dye fura-2AM. In general these studies ignore or deal only perfunctorily with the problem of autofluorescence in slices. This confound, which is a result of the pyridine nucleotides that are normally present in tissue, has been previously reported to interfere with Ca2+ measurements in slices. Because these pyridine compounds are involved in cell metabolism, the fluorescence intensity is labile over time following experimental manipulations. We were studying Ca2+ levels in hippocampal slices using standard imaging techniques. We found significant and variable autofluorescence at the wavelengths used for calcium determination which interfered with data interpretation in fura-treated slices. The intensity of this autofluorescence is an additive effect and is not large enough to be observed when imaging monolayers. In this paper we present a method for conducting experiments and analyzing data that decreases interference from autofluorescence. Experiments were carried out on both slices bulk loaded with fura-2AM and slices loaded with control buffer. A point to point subtraction of the control slice values gave representative calcium fluorescence values. Hippocampal slices were challenged with sodium cyanide or kainic acid. The metabolic response, seen in the fura-free slices, and the calcium response varied within and between these two treatments. Regional differences in the hippocampal sub fields were also demonstrated in response to the two treatments. These corresponded to known regional vulnerabilities to cyanide and kainate. We conclude that autofluorescence in slices need be considered when determining calcium concentrations using fura-2AM.
View details for Web of Science ID A1996TT52500014
View details for PubMedID 8822368
Stress, Glucocorticoids, and Damage to the Nervous System: The Current State of Confusion.
Stress (Amsterdam, Netherlands)
1996; 1 (1): 1–19
An extensive literature demonstrates that glucocorticoids (GCs), the adrenal steroids secreted during stress, can have a broad range of deleterious effects in the brain. The actions occur predominately, but not exclusively, in the hippocampus, a structure rich in corticosteroid receptors and particularly sensitive to GCs. The first half of this review considers three types of GC effects: a) GC-induced atrophy, in which a few weeks' exposure to high GC concentrations or to stress causes reversible atrophy of dendritic processes in the hippocampus; b) GC neurotoxicity where, over the course of months, GC exposure kills hippocampal neurons; c) GC neuroendangerment, in which elevated GC concentrations at the time of a neurological insult such as a stroke or seizure impairs the ability of neurons to survive the insult. The second half considers the rather confusing literature as to the possible mechanisms underlying these deleterious GC actions. Five broad themes are discerned: a) that GCs induce a metabolic vulnerability in neurons due to inhibition of glucose uptake; b) that GCs exacerbate various steps in a damaging cascade of glutamate excess, calcium mobilization and oxygen radical generation. In a review a number of years ago, I concluded that these two components accounted for the deleterious GC effects. Specifically, the energetic vulnerability induced by GCs left neurons metabolically compromised, and less able to carry out the costly task of containing glutamate, calcium and oxygen radicals. More recent work has shown this conclusion to be simplistic, and GC actions are shown to probably involve at least three additional components: c) that GCs impair a variety of neuronal defenses against neurologic insults; d) that GCs disrupt the mobilization of neurotrophins; e) that GCs have a variety of electrophysiological effects which can damage neurons. The relevance of each of those mechanisms to GC-induced atrophy, neurotoxicity and neuroendangerment is considered, as are the likely interactions among them.
View details for PubMedID 9807058
- Excitotoxic neuron death, acidotic endangerment, and the paradox of acidotic protection CELLULAR AND MOLECULAR MECHANISMS OF ISCHEMIC BRAIN DAMAGE 1996; 71: 237-245
- DO THE SALUTARY EFFECTS OF FOOD RESTRICTION OCCUR BECAUSE OF OR DESPITE OF THE ACCOMPANYING HYPERADRENOCORTICISM NEUROBIOLOGY OF AGING 1995; 16 (5): 849-850
DEFECTIVE HERPES-SIMPLEX VIRUS VECTORS EXPRESSING THE RAT-BRAIN GLUCOSE-TRANSPORTER PROTECT CULTURED NEURONS FROM NECROTIC INSULTS
JOURNAL OF NEUROCHEMISTRY
1995; 65 (2): 842-850
Because neurons are postmitotic, they are irreplaceable once they succumb to necrotic insults such as hypoglycemia, ischemia, and seizure. A paucity of energy can exacerbate the toxicities of these insults; thus, a plausible route to protect neurons from necrotic injury would be to enhance their glucose uptake capability. We have demonstrated previously that defective herpes simplex virus (HSV) vectors overexpressing the rat brain glucose transporter (GT) gene (gt) can enhance glucose uptake in adult rat hippocampus and in hippocampal cultures. Furthermore, we have observed that such vectors can maintain neuronal metabolism during hypoglycemia and reduce kainic acid-induced seizure damage. In this study, we have developed bicistronic vectors that coexpressed gt and Escherichia coli lacZ as a reporter gene, which allows us to identify directly neurons that are infected with the vectors. Overexpression of GT from these vectors protected cultured hippocampal, spinal cord, and septal neurons against various necrotic insults, including hypoglycemia, glutamate, and 3-nitropropionic acid. Our observations demonstrate the feasibility of using HSV vectors to protect neurons from necrotic insults. Although this study has concentrated on the delivery of gt, other genes with therapeutic or protective capability might also be used.
View details for Web of Science ID A1995RJ65700048
View details for PubMedID 7616244
HERPES-SIMPLEX VIRUS VECTORS OVEREXPRESSING THE GLUCOSE-TRANSPORTER GENE PROTECT AGAINST SEIZURE-INDUCED NEURON LOSS
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1995; 92 (16): 7247-7251
We have generated herpes simplex virus (HSV) vectors vIE1GT and v alpha 4GT bearing the GLUT-1 isoform of the rat brain glucose transporter (GT) under the control of the human cytomegalovirus ie1 and HSV alpha 4 promoters, respectively. We previously reported that such vectors enhance glucose uptake in hippocampal cultures and the hippocampus. In this study we demonstrate that such vectors can maintain neuronal metabolism and reduce the extent of neuron loss in cultures after a period of hypoglycemia. Microinfusion of GT vectors into the rat hippocampus also reduces kainic acid-induced seizure damage in the CA3 cell field. Furthermore, delivery of the vector even after onset of the seizure is protective, suggesting that HSV-mediated gene transfer for neuroprotection need not be carried out in anticipation of neurologic crises. Using the bicistronic vector v alpha 22 beta gal alpha 4GT, which coexpresses both GT and the Escherichia coli lacZ marker gene, we further demonstrate an inverse correlation between the extent of vector expression in the dentate and the amount of CA3 damage resulting from the simultaneous delivery of kainic acid.
View details for Web of Science ID A1995RM72200024
View details for PubMedID 7638175
View details for PubMedCentralID PMC41316
ADRENOCORTICOTROPIN SECRETAGOG RELEASE - STIMULATION BY FRUSTRATION AND PARADOXICALLY BY REWARD PRESENTATION
1995; 676 (1): 151-156
Colchicine blockade of axonal transport from the paraventricular nucleus to the median eminence was used to indirectly infer adrenocorticotropin (ACTH) secretagog release in response to a reward presentation and the psychological stressor of frustration. After training rats to drink at the same time of day for 30 min for 2-3 weeks, basal arginine vasopressin (AVP), but not corticotropin-releasing factor (CRF) or oxytocin (OT), concentrations were elevated. The frustration of presenting empty water bottles resulted in increased corticosterone concentrations. Concordantly, CRF, AVP, and OT contents in the median eminence decreased compared to controls. All three secretagogs are thus apparently involved in the corticosterone response to frustration. As expected, water presentation decreased both ACTH and corticosterone. Paradoxically, however, CRF, AVP, and OT contents also decreased compared to controls. The discrepancy of ACTH and corticosterone concentrations declining despite release of secretagogs cannot be explained by decreased adrenal or pituitary sensitivities since both exogenous ACTH and CRF elevated corticosterone and ACTH, respectively, in rewarded rats. Secretagog release, therefore, may not always be associated with stimulation of ACTH release.
View details for Web of Science ID A1995QQ47100015
View details for PubMedID 7796164
HERPES-SIMPLEX VIRUS VECTOR SYSTEM - ANALYSIS OF ITS IN-VIVO AND IN-VITRO CYTOPATHIC EFFECTS
JOURNAL OF NEUROSCIENCE METHODS
1995; 57 (2): 205-215
With its natural propensity to infect and establish life-long latency in neurons, herpes simplex virus type 1 (HSV-1) has been successfully employed by various laboratories as vectors for gene transfer into neurons. However, analysis of its cytopathic effects in vivo and in vitro has been limited. In this study, we examined the cytopathic effects of 2 HSV-1 alpha 4 mutants (ts756 and d120) on adult rat hippocampus and striatum and of d120 on hippocampal neurons in culture. We assessed damage by stringent counting of surviving neurons after infection and demonstrated that while neither ts756 nor d120 infection resulted in any gross anatomical or behavioral changes of the animals, ts756, but not d120, produced a significant amount of damage in the CA4 cell field and dentate gyrus of the hippocampus. Thus, since crude examination is insufficient to detect subtle but significant degrees of neuron loss, the cytopathic effects of HSV or any vector system must be carefully analyzed. Furthermore, we also observed that uninfected cell lysates damaged neurons, both in vivo and in vitro. This cytotoxicity occurred within the first 24 h post-inoculation and probably arose through the activation of glutamate receptors. For the preparation of HSV vectors, purification of the virus from soluble cellular components by a simple pelleting step can significantly decrease such acute toxicity.
View details for Web of Science ID A1995QU14500010
View details for PubMedID 7609584
PATTERNS OF ADRENOCORTICOTROPIN SECRETAGOG RELEASE IN RESPONSE TO SOCIAL INTERACTIONS AND VARIOUS DEGREES OF NOVELTY
1995; 20 (2): 183-191
Colchicine blockade of axonal transport from the paraventricular nucleus to the median eminence was used to indirectly infer ACTH secretagog release in response to the psychological stressors of social interactions and various degrees of novelty. Placing a rat in a new cage with either the smell or presence of a novel conspecific decreased arginine vasopressin and oxytocin (OT) contents, but not corticotropin-releasing factor content. Secretagog contents were unchanged in rats in their home cages faced with a novel conspecific. Secretagog release during social stress is thus primarily a function of being in a novel setting. For different degrees of novelty, rats were placed in either a novel cage, a novel bucket, or a novel bucket smelling of another rat. Whereas secretagog contents were unchanged with a novel cage, OT content alone decreased in response to both the bucket and the unclean bucket. Despite a graded corticosterone response, there was no distinction in the OT response, suggesting that the colchicine technique cannot accurately reflect gradations of stressors.
View details for Web of Science ID A1995PU09900006
View details for PubMedID 7899537
- Social subordinance as a marker of hypercortisolism - Some unexpected subtleties 1st World Congress on Stress NEW YORK ACAD SCIENCES. 1995: 626–639
GLUCOCORTICOIDS INCREASE EXTRACELLULAR [H-3] D-ASPARTATE OVERFLOW IN HIPPOCAMPAL CULTURES DURING CYANIDE-INDUCED ISCHEMIA
1994; 654 (1): 8-14
Glucocorticoids (GCs), the adrenal steroid hormones secreted during stress, exacerbate neuronal death in the hippocampus during ischemia. Since ischemia brain damage is ascribed to an elevated level of extracellular excitatory amino acids (EAAs), this study was undertaken to investigate the effect of GCs on EAA homeostasis in hippocampal cell cultures during the insult of cyanide exposure. Using D-[2,3-3H]aspartic acid ([3H]D-Asp) as a tracer, we found that corticosterone (CORT, the physiological GC in rats) increased the accumulation of extracellular [3H]D-Asp by 25% in hippocampal cultures during cyanide-induced ischemia. CORT had no effect on the release of [3H]D-Asp. Instead, analysis of [3H]D-Asp uptake kinetics indicates that CORT decreased the maximum uptake rate and the Michaelis constant by 44% and 50%, respectively, in cells treated with cyanide. It is concluded that, during cyanide-induced ischemia, CORT might enhance extracellular overflow of [3H]D-Asp by decreasing its uptake, thereby endangering neurons.
View details for Web of Science ID A1994PB98900002
View details for PubMedID 7982101
PHYSIOLOGICAL ELEVATIONS OF GLUCOCORTICOIDS POTENTIATE GLUTAMATE ACCUMULATION IN THE HIPPOCAMPUS
JOURNAL OF NEUROCHEMISTRY
1994; 63 (2): 596-602
Glucocorticoids (GCs) are secreted during stress and can damage the hippocampus over the course of aging and impair the capacity of hippocampal neurons to survive excitotoxic insults. Using microdialysis, we have previously observed that GCs augment the extracellular accumulation of glutamate and aspartate in the hippocampus following kainic acid-induced seizures. In that study, adrenalectomized rats maintained on minimal GC concentrations were compared with those exposed to GCs elevated to near-pharmacological levels. We wished to gain insight into the physiological relevance of these observations. Thus, we have examined the effects of GCs over the normal physiological range on glutamate and aspartate profiles; this was done by implanting adrenalectomized rats with GC-secreting pellets, which produce stable and controllable circulating GC concentrations. We observe that incremental increases in GC concentrations cause incremental increases in glutamate accumulation before the kainic acid insult, as well as in the magnitude of the glutamate response to kainic acid. Elevating GC concentrations from the circadian trough to peak doubled cumulative glutamate accumulation, whereas a rise into the stress range caused a fourfold increase in accumulation. Similar, although smaller, effects also occurred with aspartate accumulation (as well as with taurine but not glutamine accumulation). These data show that the highly elevated GC concentrations that accompany neurological insults such as seizure or hypoxia-ischemia will greatly exacerbate the glutamate accumulation at that time. Furthermore, stress levels of GCs augmented glutamate accumulation even in the absence of an excitotoxic insult, perhaps explaining how sustained stress itself damages the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1994NZ01700026
View details for PubMedID 7913489
DEXAMETHASONE RESISTANCE AMONG NONHUMAN-PRIMATES ASSOCIATED WITH A SELECTIVE DECREASE OF GLUCOCORTICOID RECEPTORS IN THE HIPPOCAMPUS AND A HISTORY OF SOCIAL INSTABILITY
1994; 60 (2): 134-140
We have studied some of the neuroendocrine and social correlates of dexamethasone resistance in a nonhuman primate population. Subjects were 51 male Macaca fascicularis monkeys with known behavioral histories and who had been given dexamethasone (DEX) suppression tests a week prior to killing. We compared the subset of monkeys who were most DEX responsive (post-DEX cortisol values of 3.1 +/- 0.5 micrograms/dl) versus a DEX-resistant subset (cortisol values of 9.2 +/- 2.0 micrograms/dl); we found two features that distinguished these groups: (a) DEX-resistant monkeys had significantly fewer available glucocorticoid receptor (GR) binding sites in the hippocampus; they did not differ in numbers of mineralocorticoid receptor (MR) sites in the hippocampus, nor in numbers for either receptor in the cortex or hypothalamus as a whole. (b) Animals had resided for a number of years in social groups that were either stable or were repeatedly destabilized by changing of group membership; the latter has been shown to constitute a sustained stressor. DEX-resistant animals were more than twice as likely to have come from an unstable group as were DEX-responsive monkeys. Rodent studies have shown that sustained stress can cause a selective downregulatory decrease in the numbers of hippocampal corticosteroid receptors, and that such a loss is associated with DEX resistance. The present data suggest similar associations in the primate, and may be of relevance to the DEX resistance observed in a subset of human depressives.
View details for Web of Science ID A1994NZ44700003
View details for PubMedID 7969770
GLUCOCORTICOIDS ACCELERATE ATP LOSS FOLLOWING METABOLIC INSULTS IN CULTURED HIPPOCAMPAL-NEURONS
1994; 646 (2): 303-306
Glucocorticoids (GCs), adrenal steroids released during stress, can damage the hippocampus outright and increase hippocampal vulnerability to metabolic insults. Changes in ATP levels were measured in response to aglycemia and to cyanide in cultured hippocampal neurons that had been exposed to high- and low-GC conditions. GCs did not depress baseline ATP levels but did accelerate the rate of the decline in ATP concentrations observed during the metabolic insults. These results support the hypothesis that GCs increase neuronal vulnerability by disrupting cellular metabolism and agree with similar findings in hippocampal astrocytes.
View details for Web of Science ID A1994NM41600019
View details for PubMedID 8069678
CHARACTERIZATION OF MINERALOCORTICOID AND GLUCOCORTICOID RECEPTORS IN PRIMATE BRAIN
1994; 637 (1-2): 303-307
Characteristics of neural corticosteroid receptors were studied in 51 adrenally-intact macaque monkeys using a modification of a corticosteroid receptor assay developed in this laboratory for rodent studies. Using cortisol as a ligand, two receptor subtypes could be distinguished and with similar Kd's to those observed in rodents, as measured with corticosterone. The time course showed maximum binding for mineralocorticoid receptors at 24 h and for glucocorticoid at 4 h. There were regional differences in the number of available binding sites for each receptor type, as well as an inverse correlation between the concentration of cortisol in the blood at the time of death and the number of available binding sites. In general this paper emphasizes the similarities between such receptors in primate and those in other species, similarities that could be detected despite the technical constraints of studying tissue taken from non-adrenalectomized animals.
View details for Web of Science ID A1994MY43600040
View details for PubMedID 8180810
- THE PHYSIOLOGICAL RELEVANCE OF GLUCOCORTICOID ENDANGERMENT OF THE HIPPOCAMPUS Conference on Brain Corticosteroid Receptors: Studies on the Mechanism, Function, and Neurotoxicity of Corticosteroid Action NEW YORK ACAD SCIENCES. 1994: 294–307
GLUCOCORTICOID EFFECTS ON NEURONAL DEVELOPMENT AND VITALITY
37th Benzon Symposium on Brain Lesions in the Newborn: Hypoxic and Haemodynamic Pathogenesis
MUNKSGAARD. 1994: 257–268
View details for Web of Science ID A1994BA54U00018
POTENTIAL BEHAVIORAL-MODIFICATION OF GLUCOCORTICOID DAMAGE TO THE HIPPOCAMPUS
BEHAVIOURAL BRAIN RESEARCH
1993; 57 (2): 175-182
Glucocorticoids (GCs), the adrenal steroids secreted during stress, can damage the hippocampus, a principal neural target site for GCs. The extent of cumulative exposure to GCs influences the rate of neuron loss in the aging hippocampus, such that stress can accelerate senescent hippocampal degeneration. Moreover, under circumstances where GC exposure is insufficient to damage neurons, the hormones impair the capacity of neurons to survive neurological insults such as hypoxia-ischemia, seizure, or hypoglycemia. Considerable progress has been made in understanding how GCs endanger hippocampal neurons. The effect is a direct one, in that the endangerment is mediated by GC receptors and occurs in cultured hippocampal neurons. The endangerment is energetic in nature--the insults worsened by GCs represent energetic crises, and the GC endangerment is prevented by supplementation of neurons with energy substrates. As the likely mechanism by which GCs induce an energetic vulnerability, the steroids inhibit glucose transport in hippocampal neurons and glia. As a result of this effect of GCs upon energetics is that neurons are less capable of the costly task of containing the damaging fluxes of glutamate and calcium triggered by the neurological insults. Thus, following such insults, GCs disrupt glutamate removal and elevate synaptic glutamate concentrations, enhance the magnitude and duration of the subsequent mobilization of free cytosolic calcium, and exacerbate the magnitude of calcium-dependent degenerative events. Thus, stress has the capacity to damage the hippocampus and exacerbate the toxicity of some common neurological disorders; nevertheless, some behavioral interventions are known to cause sustained diminution of GC concentrations, and thus have the potential to protect the hippocampus from these deleterious effects.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1993MQ47100008
View details for PubMedID 8117422
SENESCENT DECLINE IN SERUM DEHYDROEPIANDROSTERONE-SULFATE CONCENTRATIONS IN A POPULATION OF WILD BABOONS
JOURNALS OF GERONTOLOGY
1993; 48 (5): B196-B200
The physiologic functions of dehydroepiandrosterone sulfate (DS), a precursor of androgens and estrogen and the most abundant steroid in the circulation, are unknown. Nevertheless, numerous studies have shown that low concentrations of DS are correlated with a variety of metabolic and cardiovascular diseases in human beings, and administration of DS to experimental animals is associated with protection from similar diseases. Thus, the marked decline in DS concentrations with age in human beings may be of considerable functional significance. However, because of the difficulties in studying any heterogeneous human population, it has been difficult to assess the extent to which the DS decline with age is confounded by any of a number of factors (e.g., smoking, level of activity, genetics, diet, medication and disease). We studied the effects of age on DS concentrations in a well-characterized population of wild yellow baboons living freely in a national park in East Africa. Study of these animals circumvents many of the confounds just noted. In examining animals ranging in age from juvenile status to old age, we observed a robust decline in DS concentrations with age. The magnitude of the decline is approximately equal in both sexes. In addition, the decline is similar in comparing two baboon groups which have fully natural diets with one group which forages heavily on garbage from people.
View details for Web of Science ID A1993LY22600024
View details for PubMedID 8366259
CORTICOSTERONE EXACERBATES KAINATE-INDUCED ALTERATIONS IN HIPPOCAMPAL TAU IMMUNOREACTIVITY AND SPECTRIN PROTEOLYSIS INVIVO
JOURNAL OF NEUROCHEMISTRY
1993; 61 (1): 57-67
Aberrant elevations in intracellular calcium levels, promoted by the excitatory amino acid glutamate, may be a final common mediator of the neuronal damage that occurs in hypoxic-ischemic and seizure disorders. Glutamate and altered neuronal calcium homeostasis have also been proposed to play roles in more chronic neurodegenerative disorders, including Alzheimer's disease. Any extrinsic factors that may augment calcium levels during such disorders may significantly exacerbate the resulting damage. Glucocorticoids (GCs), the adrenal steroid hormones released during stress, may represent one such extrinsic factor. GCs can exacerbate hippocampal damage induced by excitotoxic seizures and hypoxia-ischemia, and we have observed recently that GCs elevate intracellular calcium levels in hippocampal neurons. We now report that the excitotoxin kainic acid (KA) can elicit antigenic changes in the microtubule-associated protein tau similar to those seen in the neurofibrillary tangles of Alzheimer's disease. KA induced a transient increase in the immunoreactivity of hippocampal CA3 neurons towards antibodies that recognize aberrant forms of tau (5E2 and Alz-50). The tau immunoreactivity appeared within 3 h of KA injection, preceded extensive neuronal damage, and subsequently disappeared as neurons degenerated. KA also caused spectrin breakdown, indicating the involvement of calcium-dependent proteases. Physiological concentrations of corticosterone (the species-typical GC of rats) enhanced the neuronal damage induced by KA and, critically, enhanced the intensity of tau immunoreactivity and spectrin breakdown. Moreover, the GC enhancement of spectrin proteolysis was prevented by energy supplementation, supporting the hypothesis that GC disruption of calcium homeostasis in the hippocampus is energetic in nature. Taken together, these findings demonstrate that neurofibrillary tangle-like alterations in tau, and spectrin breakdown, can be induced by excitatory amino acids and exacerbated by GCs in vivo.
View details for Web of Science ID A1993LH22700006
View details for PubMedID 8515288
CL-/HCO3- EXCHANGE FUNCTION DIFFERS IN ADULT AND FETAL-RAT HIPPOCAMPAL-NEURONS
1993; 614 (1-2): 308-314
We studied Cl-/HCO3- exchange function in acutely dissociated single hippocampal neurons from adult and fetal day 18 rat using a fluorescent intracellular pH (pHi) indicator dye. The presence of Cl-/HCO3- exchange activity was assayed by observing the elevation in pHi upon acute reversal of the Cl- gradient. Resting intracellular pH in acutely dissociated neurons of both adult and fetal tissue was significantly higher than that of cultured fetal hippocampal neurons (day 10-12 in culture). Acute removal of extracellular Cl- caused a rapid and reversible increase in pHi by 0.25 pH units in adult neurons but had virtually no effect in similarly dissociated fetal neurons. Cl-/HCO3- exchange activity was also undetectable in fetal cultured hippocampal neurons. The mRNA for the anion exchanger AE3 is expressed abundantly in adult rodent neurons. AE3 is a potential candidate molecule for the observed Cl-/HCO3- exchange activity. In situ hybridization was used to monitor expression of the AE3 gene in these two age groups. We found that both adult and fetal neurons express AE3 mRNA. These results indicate that AE3 may not function as a Cl-/HCO3- exchanger in fetal neurons, in contrast to its possible role in the adult brain.
View details for Web of Science ID A1993LJ04400040
View details for PubMedID 8348323
INHIBITION OF ACIDIFICATION RATE IN CULTURED FIBROBLASTS BY GLUCOCORTICOIDS - APPLICATION OF SILICON MICROPHYSIOMETRY TO ENDOCRINOLOGY
HORMONE AND METABOLIC RESEARCH
1993; 25 (5): 264-267
A recently-developed semiconductor-based instrument, the silicon microphysiometer, allows for realtime, sensitive quantification of cellular metabolism in small numbers of cultured cells with relative case. This is accomplished by detecting the extrusion into the extracellular space of acidic metabolic products of glycolysis, respiration, and ATP hydrolysis, including lactic acid, CO2, and protons. In the present report, we use microphysiometry to observe that glucocorticoids inhibit metabolic rate (as assessed indirectly by a change in the extracellular acidification rate) in fibroblasts (minimal effective dose of 1 nM of corticosterone), whereas 1 microM each estradiol, progesterone and testosterone failed to do so. We suggest that this inhibition of metabolism is secondary to the well-established inhibition of glucose transport and of protein synthesis in fibroblasts by glucocorticoids.
View details for Web of Science ID A1993LE73000007
View details for PubMedID 8330861
ALTERING CENTRAL-NERVOUS-SYSTEM PHYSIOLOGY WITH A DEFECTIVE HERPES-SIMPLEX VIRUS VECTOR EXPRESSING THE GLUCOSE TRANSPORTER GENE
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1993; 90 (8): 3655-3659
Because of their postmitotic nature, neurons are difficult subjects for gene transfer. To circumvent this, we have used a defective herpes simplex virus vector to overexpress the rat brain glucose transporter (GT) gene under the control of the human cytomegalovirus ie1 promoter. This vector, designated vIE1GT, was propagated using a herpes simplex virus type 1 temperature-sensitive mutant, ts756. GT expressed from vIE1GT was readily immunoprecipitated from membrane fractions of vIE1GT-infected Vero cells. By using indirect double immunofluorescence techniques, vIE1GT was shown to be capable of enhancing GT expression in cultured hippocampal neurons and glia. Glucose transport in such vIE1GT-infected cultures was increased approximately 2-fold relative to controls. The efficacy of this system in vivo was then tested by microinjection of vIE1GT into adult rat hippocampus. When examined 2 days later, GT expression from vIE1GT was demonstrated in hippocampal neurons by in situ hybridization; a small but significant increase in glucose transport was detected in tissue immediately surrounding the injection site by 2-deoxy[14C]glucose uptake and autoradiography. Such injections did not cause marked cytopathology. Thus, this approach can be used to alter central nervous system physiology in vitro and in vivo.
View details for Web of Science ID A1993KX81600112
View details for PubMedID 8386379
View details for PubMedCentralID PMC46360
CORTICOSTERONE IMPAIRS HIPPOCAMPAL NEURONAL CALCIUM REGULATION - POSSIBLE MEDIATING MECHANISMS
1993; 602 (1): 84-90
Corticosterone (CORT), the predominant glucocorticoid of rats which is secreted during stress, increases hippocampal neuronal vulnerability to excitotoxins, hypoxia-ischemia, and hypoglycemia in an energy-dependent manner. A mechanism for this endangerment could be the CORT-induced impairment of hippocampal neuronal calcium regulation. We have shown that CORT causes an energy-dependent prolonged elevation of cytosolic free calcium ([Ca2+]i) in response to kainic acid stimulation in cultured hippocampal neurons. That study utilized the calcium-sensitive dye fluo-3, which is unsuitable for determination of basal [Ca2+]i. The present study circumvents that limitation by using the dye fura-2 AM. We have replicated the previous demonstration that CORT potentiates the [Ca2+]i response to KA; we have also observed that CORT elevates basal [Ca2+]i concentrations. Furthermore, we have observed that the mechanism for this CORT impairment of calcium regulation involves a reduction in stimulus-induced calcium efflux. Energy-dependent disruptions in neuronal calcium regulation, such as induced by CORT, have been associated with subsequent neurotoxicity. Thus, the CORT-induced impairment of hippocampal neuronal calcium regulation could be the mechanism for the neuronal vulnerability and toxicity evident following CORT treatment and stress.
View details for Web of Science ID A1993KK30200012
View details for PubMedID 8448661
- ENDOCRINOLOGY ALFRESCO - PSYCHOENDOCRINE STUDIES OF WILD BABOONS 1991 Laurentian Hormone Conference ACADEMIC PRESS INC. 1993: 437–468
PATTERNS OF ADRENOCORTICOTROPIN SECRETAGOG RELEASE WITH HYPOGLYCEMIA, NOVELTY, AND RESTRAINT AFTER COLCHICINE BLOCKADE OF AXONAL-TRANSPORT
1993; 132 (1): 199-204
Colchicine blockade of axonal transport from the paraventricular nucleus to the median eminence was used to indirectly infer hypothalamic ACTH secretagog release in awake rats. Median eminence contents of CRF, arginine vasopressin (AVP) and oxytocin (OT) were determined by RIA after insulin-induced hypoglycemia, restraint, and novelty. Insulin decreased circulating glucose concentrations and increased ACTH and corticosterone values. Median eminence CRF and AVP content declined but OT content did not. Both novelty and restraint stressors increased circulating ACTH and corticosterone concentrations. Secretagog measurements indicated decreases in OT content without concomitant decreases in either CRF or AVP with both stressors. These results indicate that: 1) colchicine blockade of axonal transport is useful in studying patterns of secretagog release in animals undergoing psychological stressors; 2) in contrast to physical stressors, OT appears to be a major component of the hypothalamic-pituitary-adrenal response to psychological stress; 3) the patterns of secretagog release differ with regards to physical and psychological stressors.
View details for Web of Science ID A1993KH62500029
View details for PubMedID 7678213
ENDOCRINE FEATURES OF GLUCOCORTICOID ENDANGERMENT IN HIPPOCAMPAL ASTROCYTES
1993; 57 (1): 7-13
Metabolic insults, such as ischemia or hypoglycemia, typically cause severe neuronal injury in the hippocampus and this cell vulnerability can be exacerbated by glucocorticoid (GC) exposure. This endangerment can also be demonstrated in vitro in both neurons and astrocytes. Direct GC effects on cell physiology thus appear to play a role, but the actual mechanism remains unclear. In order to clarify whether GCs act as damaging agents via a 'classical' steroid route, we examined the temporal features and steroid-specificity of this synergy in hippocampal astrocyte cultures derived from E18 fetal rats. A 24-hour pretreatment with corticosterone (CORT), the principal GC in the rat, enhanced both hypoxic and hypoglycemic cell damage, as measured by lactate dehydrogenase assay. This damaging effect was abolished when CORT exposure was reduced to 8 or 4 h prior to the hypoglycemic or hypoxic treatment, respectively. A 24-hour exposure to several nonGC steroids also failed to enhance hypoxic cell damage. The damaging effect of CORT was attenuated if steroid exposure occurred during the hypoglycemic insult and was absent in both hypoxic and hypoglycemic paradigms if CORT exposure was limited to the recovery period. These results suggest that GCs aggravate metabolic astrocyte injury via classical hormonal effects that are steroid-specific, receptor-mediated, and emerge slowly after prolonged steroid exposure.
View details for Web of Science ID A1993KU36800002
View details for PubMedID 8479618
POSSIBLE MECHANISM BY WHICH STRESS ACCELERATES GROWTH OF VIRALLY DERIVED TUMORS
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1992; 89 (22): 11084-11087
Stress accelerates the growth of certain types of tumors. Here we report a possible metabolic mechanism underlying this phenomenon. Some early features of transformation include increased number of glucose transporters and greatly enhanced rates of glucose uptake; this adaptation accommodates the vast energy demands needed for neoplastic growth. In contrast, glucocorticoids, a class of steroid hormones secreted during stress, inhibit glucose transport in various tissues; this is one route by which circulating glucose concentrations are raised during stress. We reasoned that should transformed cells become resistant to this inhibitory action of glucocorticoids, such cells would gain preferential access to these elevated concentrations of glucose. In agreement with this, we observed that Fujinami sarcoma virus-transformed fibroblasts became resistant to this glucocorticoid action both in vitro and in the rat. As a result, under conditions where glucocorticoids exerted catabolic effects upon nontransformed fibroblasts (inhibition of metabolism and ATP concentrations), the opposite occurred in the virally transformed cells. We observe that this glucocorticoid resistance upon transformation cannot be explained by depletion of glucocorticoid receptors; previous studies have suggested that transformation causes an alteration in trafficking of such receptors. Because of this resistance of transformed fibroblasts to the inhibitory effects of glucocorticoids upon glucose transport, glucose stores throughout the body are, in effect, preferentially shunted to such tumors during stress.
View details for Web of Science ID A1992JY87400108
View details for PubMedID 1438318
CORTISOL CONCENTRATIONS AND THE SOCIAL SIGNIFICANCE OF RANK INSTABILITY AMONG WILD BABOONS
1992; 17 (6): 701-709
Previous work has shown that dominant primates in stable social hierarchies in a number of species often have low basal cortisol concentrations, relative to subordinate individuals. In contrast, this trait appears to be lost during periods of social instability, probably reflecting the psychological stressfulness of the instability. The present study examined whether basal cortisol concentrations were elevated not only when the overall hierarchy was unstable, but also were elevated in individuals which, within a stable hierarchy, were nevertheless in the process of their own rank shifting. Study subjects were a population of male olive baboons living freely in a national reserve in East Africa, which could be anesthetized under conditions allowing for determination of basal cortisol concentrations. The instability of a particular rank was quantified by determining the percentage of dominance interactions that represented a reversal of the already established direction of dominance. Highly unstable relationships with the rest of the males in the hierarchy did not predict elevated basal cortisol concentrations in an individual. Instead, it was the stability of interactions with males close in rank (within three steps in the hierarchy of the individual) which predicted cortisol concentrations: the greater the percentage of interactions that were reversals with the three nearest lower-ranking males, the higher the basal cortisol concentrations in an individual. In general, high rates of such reversal interactions indicated that the male was being challenged for his more dominant position.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1992KL03600017
View details for PubMedID 1287688
STRESS, GLUCOCORTICOIDS, AND AGING
AGING-CLINICAL AND EXPERIMENTAL RESEARCH
1992; 4 (3): 197-210
Attention has long been focused on the relationship between stress and aging, both under the guise of stress as an accelerator of normal aging and of aging as a time of impaired ability to cope with stress. This review examines the considerable amount of evidence in support of these views. We address these ideas with respect to glucocorticoids, the adrenal steroid hormones secreted during stress. In particular, we concentrate on three model systems: 1) programmed senescence in marsupial mice and semelparous fish as mediated by glucocorticoid excess; 2) glucocorticoid hypersecretion in rats and its role in damaging the aging brain; and 3) potential human and primate adrenocortical dysfunction during aging. We discuss physical and cognitive consequences of adrenocortical dysfunction in these systems, and how they may relate to human aging.
View details for Web of Science ID A1992JP60800003
View details for PubMedID 1420403
CORTICOSTERONE ENHANCES KAINIC ACID-INDUCED CALCIUM ELEVATION IN CULTURED HIPPOCAMPAL-NEURONS
JOURNAL OF NEUROCHEMISTRY
1992; 59 (3): 1033-1040
Corticosterone, a steroid secreted during stress, increases hippocampal neuronal vulnerability to excitotoxins, hypoxia-ischemia, and antimetabolites. Energy supplementation and N-methyl-D-aspartate receptor antagonists prevent this corticosterone-enhanced neurotoxicity. Because neuronal calcium regulation is energy dependent and a large calcium influx accompanies N-methyl-D-aspartate receptor activation, we investigated whether corticosterone exacerbates the elevation of hippocampal neuronal calcium induced by the glutamatergic excitotoxin kainic acid. Corticosterone caused a 23-fold increase in the magnitude of the calcium response to kainic acid, a sevenfold increase in the peak magnitude of the calcium response, and a twofold increase in calcium recovery time. This corticosterone effect may be energetic in nature as corticosterone decreases hippocampal neuronal glucose transport. Glucose supplementation reduced the corticosterone effect on the magnitude and peak magnitude of the calcium response to kainic acid. Glucose reduction, by the approximate magnitude by which corticosterone inhibits glucose transport, mimicked the corticosterone effect on the peak magnitude of the calcium response to kainic acid. Thus, corticosterone increases calcium after kainic acid exposure in hippocampal neurons in an energy-dependent manner. Elevated calcium is strongly implicated in stimulating neurotoxic cascades during other energetic insults and may be the mechanism for the corticosterone-induced hippocampal neuronal vulnerability and toxicity.
View details for Web of Science ID A1992JJ44200029
View details for PubMedID 1645163
GLUCOCORTICOIDS EXACERBATE HYPOXIC AND HYPOGLYCEMIC HIPPOCAMPAL INJURY INVITRO - BIOCHEMICAL CORRELATES AND A ROLE FOR ASTROCYTES
JOURNAL OF NEUROCHEMISTRY
1992; 59 (1): 137-146
The acute secretion of glucocorticoids is critical for responding to physiological stress. Under normal circumstances these hormones do not cause acute neuronal injury, but they have been shown to enhance ischemic and seizure-induced neuronal injury in the rat brain. Using fetal rat hippocampal cultures, we asked whether hypoxic and hypoglycemic cell damage in vitro could be exacerbated by direct exposure to corticosterone (CORT). Each of these insults alone damaged neuronal cells, whereas 4-6 h of hypoxic treatment could damage age-matched astrocytes if glucose was reduced or omitted. Ischemic-like injury to both cell types could be attenuated by pretreatment with high (30 mM) glucose. Exposure to 100 nM CORT did not affect cell viability under control conditions but enhanced both hypoxic and hypoglycemic neuronal injury. In both cases, pretreatment with high glucose abolished this CORT-mediated synergy. In astrocyte cultures, CORT exacerbated both hypoxic and hypoglycemic injury and this effect was also attenuated by high-glucose pretreatment. Identical 24-h CORT treatment caused a 13% reduction in glucose uptake in astrocytes and a 38% reduction in glycogen content, without affecting the level of intracellular glucose. Thus, CORT could endanger both neurons and astrocytes in mixed hippocampal cultures and this effect emerged only under conditions of substrate depletion. The metabolic disruption in astrocytes by CORT further suggests that the ability of CORT to exacerbate neuronal injury may be due in part to impaired glial cell function.
View details for Web of Science ID A1992HZ29000017
View details for PubMedID 1613495
GLUCOCORTICOIDS EXACERBATE KAINIC ACID-INDUCED EXTRACELLULAR ACCUMULATION OF EXCITATORY AMINO-ACIDS IN THE RAT HIPPOCAMPUS
JOURNAL OF NEUROCHEMISTRY
1992; 58 (5): 1730-1735
Glucocorticoids (GCs) compromise the ability of hippocampal neurons to survive various insults, and do so, at least in part, by exacerbating steps in the glutamate/N-methyl-D-aspartate (NMDA)/calcium cascade of damage. As evidence, GCs impair uptake of glutamate by hippocampal astrocytes, the GC endangerment of the hippocampus is NMDA receptor dependent, and GCs exacerbate kainic acid (KA)-induced calcium mobilization. These observations predict that GCs should also exacerbate KA-induced accumulation of extracellular glutamate and aspartate. To test this, adrenalectomized rats were given replacement GCs in either the low or high physiological range. Three days later, rats were anesthetized and 1 mM KA was infused through a dialysis probe placed in the dorsal hippocampus. Extracellular amino acid concentrations in the dialysate were then assessed by HPLC. After KA infusion, high-GC rats (30 +/- 3 micrograms/dl) had significantly elevated concentrations of glutamate and aspartate compared with low-GC rats (all less than 0.95 micrograms/dl). The glutamate accumulation was due to GCs raising pre-KA concentrations, whereas the aspartate accumulation was due to GCs exacerbating the KA-induced rise. Glutamine concentrations were unaffected by KA, whereas the high-GC regimen elevated glutamine concentrations both before and after KA. Taurine concentrations rose after infusion of KA, but were unaffected by GC regime, whereas alanine concentrations were unaffected by either manipulation. Serine concentrations were unaffected by KA, but were depressed both before and after KA in high-GC rats.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1992HN27400018
View details for PubMedID 1560229
EFFECTS OF EXCITOTOXIN EXPOSURE ON METABOLIC-RATE OF PRIMARY HIPPOCAMPAL CULTURES - APPLICATION OF SILICON MICROPHYSIOMETRY TO NEUROBIOLOGY
JOURNAL OF NEUROSCIENCE
1992; 12 (3): 773-780
Increasing evidence implicates glutamate receptor over-stimulation in the neurotoxicity associated with a host of metabolic insults, including seizures and hypoxia-ischemia. To begin to understand more completely the role of energy metabolism in the mechanism of neuron death following excitatory amino acid exposure, we investigated the effects of kainic acid exposure on metabolic rate in cultured hippocampal cells using a recently developed silicon microphysiometer. The device gives a continual real-time measure of metabolism in relatively small numbers of cells, as assessed by efflux of protons generated at least in part by ATP hydrolysis and lactic acid production. In the first half of this report, we characterize the feasibility of using this device for measuring cellular metabolism in hippocampal cultures. Metabolic rate in both astrocytes and neurons was readily detectable, with a high signal-to-noise ratio. The rate was proportional to the number of cells and was sensitive to metabolic enhancement or depression. We then utilized this device to study metabolic responses to the excitotoxin kainic acid. We observed a receptor-mediated, dose-dependent increase in metabolic rate upon stimulation by kainic acid, with an EC50 of approximately 100 microM. Exposure to toxic levels of kainic acid for 10 min produced an initial elevation (for 2 hr) in metabolic rate and then a gradual decline in metabolism over the next 8 hr that preceded a measurable loss of cell viability. This study further delineates a time window for the onset of kainic acid-induced damage. The results clearly show the feasibility of using silicon microphysiometry for assessing metabolism of brain cultures and for exploring the relationship between metabolism and synaptic activation.
View details for Web of Science ID A1992HJ35300008
View details for PubMedID 1545239
DO GLUCOCORTICOID CONCENTRATIONS RISE WITH AGE IN THE RAT
NEUROBIOLOGY OF AGING
1992; 13 (1): 171-174
While the secretion of glucocorticoids by the adrenal gland is essential for survival of various stressors, glucocorticoid excess can be pathogenic. This two-edged quality to glucocorticoid action makes it of interest whether glucocorticoid concentrations change with age. Numerous studies have examined this in the rat but have failed to reach consensus. The present report analyzes this literature and concludes that the lack of consensus cannot be attributed to strain or sex differences or differences in the point in the circadian cycle at which rats were studied. Instead, it appears that a critical variable is how truly "basal" (i.e., unstressed) basal samples were; in studies in which basal glucocorticoid concentrations in young control subjects were in a range reflecting unstressed basal conditions, there is a robust increase in hormone concentrations with age. In contrast, the bulk of studies reporting no increase with age were those in which young subjects had elevated basal glucocorticoid concentrations (perhaps reflecting the method and speed of obtaining the blood sample, the social conditions of the rat housing, and/or the recency with which there was a disturbance in the animal room). Thus, it appears that once this source of variability is recognized and factored out, there is a considerable increase in basal glucocorticoid concentrations in aged rats.
View details for Web of Science ID A1992GY12600024
View details for PubMedID 1542376
INHIBITION OF GLUCOCORTICOID SECRETION BY THE HIPPOCAMPAL-FORMATION IN THE PRIMATE
JOURNAL OF NEUROSCIENCE
1991; 11 (12): 3695-3704
Inhibition of the adrenocortical axis by glucocorticoids (GCs) occurs at both hypothalamic and suprahypothalamic sites. In the rat, the hippocampus has been shown to be an essential suprahypothalamic site. The present study shows that the hippocampal system serves a similar role in the nonhuman primate. Bilateral lesions that included the hippocampal formation and the parahippocampal cortex; the hippocampal formation, parahippocampal cortex, and the amygdala; or the fornix all produced GC hypersecretion in cynomolgus monkeys. The hypersecretion occurred throughout the day. Moreover, these lesions were also associated with dexamethasone resistance (i.e., GC hypersecretion following administration of the synthetic GC dexamethasone). The hypersecretion could not be attributed to acute surgical trauma, because neither circumscribed lesions of the amygdala nor conjoint lesions of the perirhinal and parahippocampal cortex produced adrenocortical abnormalities. Finally, in agreement with data derived from the rat, the GC hypersecretion following hippocampal lesions was transient. Secretory activity returned to normal levels by 6-15 months in all operated groups. Thus, the primate hippocampal system appears to share some neuroendocrine functions with the rodent.
View details for Web of Science ID A1991GV17600002
View details for PubMedID 1744687
INCIDENCE OF HYPERCORTISOLISM AND DEXAMETHASONE RESISTANCE INCREASES WITH AGE AMONG WILD BABOONS
1991; 30 (10): 1008-1016
While many features of the adrenocortical axis are unchanged with age in humans, there is a pattern of senescent hypercortisolism. This occurs basally, following threshold doses of dexamethasone, and in synergy with depression or Alzheimer's disease. An understanding of neuroendocrine aging is important, for both its gerontological implications, and determination of normative values for comparison with neuropsychiatric states. We have investigated whether aging is associated with hypercortisolism in a population of wild primates. The subjects were 108 yellow baboons (Papio cynocephalus) that have been under long-term study of Amboseli National Park in Kenya. Animals were anesthetized by blowgun under similar circumstances that allow for determination of basal cortisol concentrations. Sixty minutes later, 5.0 mg dexamethasone was administered to each animal, and cortisol determinations were made on serum collected immediately before administration and 6 hr later. Basal cortisol concentrations rose with age (p less than 0.028; r = 0.23). This occurred in a nonprogressive manner, in that there were no differences in concentrations among the youngest three quartiles of animals, whereas animals in the oldest quartile (older than approximately 16 years) had significantly higher values. In addition, there was a significant increase in postdexamethasone cortical concentrations with age (p less than 0.01; r = 0.31). This feature emerged progressively with age in both sexes. A number of possible artifactual causes of this senescent pattern could be eliminated, including medication confound, coincident disease, and body weight. These findings suggest that hypercortisolism and glucocorticoid feedback resistance might be general features of primate aging.
View details for Web of Science ID A1991GQ04800005
View details for PubMedID 1756195
LONG-TERM ADRENALECTOMY CAUSES LOSS OF DENTATE GYRUS AND PYRAMIDAL NEURONS IN THE ADULT HIPPOCAMPUS
1991; 114 (2): 246-249
A growing literature suggests that the hippocampus can be damaged by glucocorticoids, the adrenal steroids secreted during stress. Thus, considerable interest was generated by recent reports that prolonged elimination of glucocorticoids by adrenalectomy (ADX) damages hippocampal dentate gyrus neurons. To date, this phenomenon has only been observed in rats of peripubertal age or younger; moreover, reports differ considerably as to the magnitude of the damage induced. Therefore, we examined this issue in rats ADXd at 5 months of age. Three months later, there was a significant 26% loss of dentate neurons in a subset of rats. In agreement with these previous reports, this subset had attenuated weight gain and electrolyte imbalances, suggestive of complete removal of the adrenals and accessory adrenal tissue. As a novel observation, we also observed significant (19%) loss of CA4 pyramidal neurons. Thus, both severe under- or overexposure to glucocorticoids can be deleterious to a number of hippocampal neuron types.
View details for Web of Science ID A1991GK85200008
View details for PubMedID 1748198
GLUCOCORTICOIDS INHIBIT GLUCOSE-TRANSPORT AND GLUTAMATE UPTAKE IN HIPPOCAMPAL ASTROCYTES - IMPLICATIONS FOR GLUCOCORTICOID NEUROTOXICITY
JOURNAL OF NEUROCHEMISTRY
1991; 57 (4): 1422-1428
Glucocorticoids (GCs), the adrenal steroid hormones secreted during stress, can damage the hippocampus and impair its capacity to survive coincident neurological insults. This GC endangerment of the hippocampus is energetic in nature, as it can be prevented when neurons are supplemented with additional energy substrates. This energetic endangerment might arise from the ability of GCs to inhibit glucose transport into both hippocampal neurons and astrocytes. The present study explores the GC inhibition in astrocytes. (1) GCs inhibited glucose transport approximately 15-30% in both primary and secondary hippocampal astrocyte cultures. (2) The parameters of inhibition agreed with the mechanisms of GC inhibition of glucose transport in peripheral tissues: A minimum of 4 h of GC exposure were required, and the effect was steroid specific (i.e., it was not triggered by estrogen, progesterone, or testosterone) and tissue specific (i.e., it was not triggered by GCs in cerebellar or cortical cultures). (3) Similar GC treatment caused a decrease in astrocyte survival during hypoglycemia and a decrease in the affinity of glutamate uptake. This latter observation suggests that GCs might impair the ability of astrocytes to aid neurons during times of neurologic crisis (i.e., by impairing their ability to remove damaging glutamate from the synapse).
View details for Web of Science ID A1991GF10000044
View details for PubMedID 1680166
ENERGETICS AND NEURON DEATH - HIBERNATING BEARS OR STARVING REFUGEES
NEUROBIOLOGY OF AGING
1991; 12 (4): 348-349
The argument is made that the evidence for "use it or lose it" in neuronal loss during aging is rather weak. The first half of the commentary focuses on the distinctly "wear and tear" flavor to the mechanism of action of excitotoxins, and the broad range of cases of neuron loss in which they play a role. The second half challenges the "use it or lose it" interpretation of the phenomenon of glucocorticoid-induced neuron death.
View details for Web of Science ID A1991GB99500018
View details for PubMedID 1961369
REGULATION OF INTRACELLULAR PH IN CULTURED HIPPOCAMPAL-NEURONS BY AN AMILORIDE-INSENSITIVE NA+/H+ EXCHANGER
JOURNAL OF BIOLOGICAL CHEMISTRY
1991; 266 (5): 2739-2745
Regulation of intracellular pH (pHi) in single cultured rat hippocampal neurons was investigated using the fluorescent pHi indicator dye bis-carboxyethylcarboxyfluorescein. Resting pHi was dependent on the presence of bicarbonate and external Na+ but was not altered significantly by removal of Cl- or treatment with the anion exchange inhibitor diisothiocyanatostilbene-2,2'-disulfonate. Recovery of pHi from acute acid loading was due, in large part, to a pharmacologically distinct variant of the Na+/H+ antiporter. In nominally HCO3(-)-free solutions, this recovery exhibited a saturable dose dependence on extracellular Na+ (Km = 23-26 mM) or Li+. The antiporter was activated by decreasing pHi and was unaffected by collapse of the membrane potential with valinomycin. Like the Na+/H+ antiporter described in other cell systems, the hippocampal activity was inhibited by harmaline, but in sharp contrast, neither amiloride nor its more potent 5-amino-substituted analogues were able to prevent the recovery from an acid load. These data indicate that Na(+)-dependent mechanisms dominate pHi regulation in hippocampal neurons and suggest a role for a novel variant of the Na+/H+ antiporter.
View details for Web of Science ID A1991EX60000013
View details for PubMedID 1847131
- TESTICULAR FUNCTION, SOCIAL RANK AND PERSONALITY AMONG WILD BABOONS PSYCHONEUROENDOCRINOLOGY 1991; 16 (4): 281-293
A. E. Bennett Award paper. Adrenocortical function, social rank, and personality among wild baboons.
1990; 28 (10): 862-878
View details for PubMedID 2268690
GLUCOCORTICOID ENDANGERMENT OF HIPPOCAMPAL-NEURONS IS NMDA-RECEPTOR DEPENDENT
1990; 532 (1-2): 7-12
The adrenal stress hormones glucocorticoids (GCs) impair the ability of hippocampal neurons to survive neurological insults, including hypoxia-ischemia and seizure. These insults are thought to be toxic via a cascade of excessive synaptic concentrations of excitatory neurotransmitters (e.g. glutamate), activation of the NMDA receptor, and pathologic mobilization of cytosolic calcium post-synaptically. We tested whether GCs exacerbate these insults by exacerbating this 'NMDA cascade'. We sought a toxin which damaged independently of the NMDA cascade, and whose toxicity was enhanced by GCs. After testing a number of neurotoxins, we found that the antimetabolite 3-acetylpyridine (3AP) fit this requirement. We then tested if blockade of the NMDA receptor blocks the ability of GCs to enhance 3AP toxicity. Hippocampi were microinfused with 160 micrograms of 3AP. Elevating circulating GC concentrations to the range seen during major stressors for a week before and after microinfusion caused a significant increase in 3AP-induced damage (when compared to adrenalectomized rats kept GC-free for the same period). Infusing the NMDA receptor blocker APV with 3AP did not alter the toxicity in adrenalectomized rats. However, APV reduced 3AP-induced damage in GC-treated rats to levels seen in adrenalectomized rats. This suggests that GCs endanger hippocampal neurons by enhancing glutamatergic signals and/or enhancing vulnerability to such signals. As a possible explanation for this observation, GCs inhibit glucose uptake into hippocampal neurons, and numerous steps in the NMDA cascade are exacerbated when neuronal energy stores are diminished.
View details for Web of Science ID A1990EK05900002
View details for PubMedID 2149301
HIPPOCAMPAL DAMAGE ASSOCIATED WITH PROLONGED GLUCOCORTICOID EXPOSURE IN PRIMATES
JOURNAL OF NEUROSCIENCE
1990; 10 (9): 2897-2902
In the laboratory rat and guinea pig, glucocorticoids (GCs), the adrenal steroids that are secreted during stress, can damage the hippocampus and exacerbate the hippocampal damage induced by various neurological insults. An open question is whether GCs have similar deleterious effects in the primate hippocampus. In fact, we showed that sustained and fatal stress was associated with preferential hippocampal damage in the vervet monkey; however, it was not possible to determine whether the excessive GC secretion that accompanied such stress was the damaging agent. The present study examines this possibility. Pellets of cortisol (the principal GC of primates) were stereotaxically implanted into hippocampi of 4 vervet monkeys; contralateral hippocampi were implanted with cholesterol pellets as a control. One year later at postmortem, preferential damage occurred in the cortisol-implanted side. In the cholesterol side, mild cell layer irregularity was noted in 2 of 4 cases. By contrast in the cortisol-exposed hippocampi, all cases had at least 2 of the following neuropathologic markers: cell layer irregularity, dendritic atrophy, soma shrinkage and condensation, or nuclear pyknosis. Damage was severe in some cases, and was restricted to the CA3/CA2 cellfield. This anatomical distribution of damage, and the cellular features of the damage agree with that observed in instances of GC-induced toxicity in the rodent hippocampus, and of stress-induced toxicity in the primate hippocampus. These observations suggest that sustained GC exposure (whether due to stress, Cushings syndrome or exogenous administration) might damage the human hippocampus.
View details for Web of Science ID A1990DY54400004
View details for PubMedID 2398367
GLUCOCORTICOIDS INHIBIT GLUCOSE-TRANSPORT IN CULTURED HIPPOCAMPAL-NEURONS AND GLIA
1990; 52 (1): 57-64
A classical action of glucocorticoids (GCs) is to inhibit glucose uptake into various peripheral tissues. Two recent reports suggest that GCs do the same in the brain. Because of the in vivo nature of those studies, it was impossible to determine whether this inhibition occurred at the blood-brain barrier, and/or within neurons and glia themselves. In order to answer this and other mechanistic questions, we examined the effects of GCs on glucose transport in primary brain cultures. We established that uptake of 14C-2-deoxyglucose into hippocampal cultures was linear over a 15-min period and was inhibited by D-glucose and the uptake inhibitor cytochalasin B. Using this system, we found the following. (1) Both corticosterone and dexamethasone inhibited uptake into cultures containing both neurons and glia. (2) The effect was dose-dependent; steroid concentrations in the nanomolar range inhibited uptake from 20 to 33%. The effect was time-dependent, with more than 4 h of steroid exposure needed for inhibition. (3) Non-GC steroids did not inhibit uptake. (4) The GC inhibition seemed to be mediated by the type II (glucocorticoid) corticosteroid receptor. The effect was blocked by a type II, but not a type I (mineralocorticoid) receptor antagonist. Moreover, corticosterone inhibited only at concentrations well above the Kd for the type I receptor. Finally, aldosterone inhibited transport when applied at concentrations that bound heavily to type II receptors. (5) Corticosterone did not inhibit uptake in hypothalamic, cerebellar or cortical cultures, despite the presence of corticosteroid receptors in these cultures. (6) GCs inhibited uptake in both neuron- and glia-enriched hippocampal cultures.
View details for Web of Science ID A1990DP32700010
View details for PubMedID 2118608
MECHANISTIC DISTINCTIONS BETWEEN EXCITOTOXIC AND ACIDOTIC HIPPOCAMPAL DAMAGE IN AN INVITRO MODEL OF ISCHEMIA
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
1990; 10 (4): 527-535
Excitotoxicity is believed to underlie the selective loss of vulnerable neurons after transient ischemia, while lactic acidosis seems to be the principal feature and probable cause of tissue infarcts. Primary hippocampal cultures containing both neurons and astrocytes derived from fetal rats were used to examine the relative contributions of and interactions between excitotoxic and acidotic cell injury. Hypoxia-induced damage was energy dependent and involved the N-methyl-D-aspartate (NMDA) receptor. Glucose above 1 mM could completely protect against hypoxia-induced injury in a pH range of 7.4-6.5, while the NMDA receptor antagonist D,L-2-amino-5-phosphonovaleric acid (500 microM) during the posthypoxic period provided only partial protection in the absence of glucose. Astrocyte cultures were undamaged by ischemic-like treatment in this pH range, suggesting that hypoxia-induced cell death in mixed cultures was restricted to neurons. Lowering the extracellular pH to 7.0 and 6.5 caused no neuronal damage in normoxic controls, but in each case provided significant protection against hypoxic neuronal injury. In contrast, a second type of neurotoxicity was observed after a 6-h exposure to pH 6.0, while exposure to pH 5.5 was required to kill astrocytes. This acidotic damage appeared to be energy independent and did not involve the NMDA receptor. These results suggest that excitotoxic neuron death has an energetic component and that acidosis may produce both protective and damaging effects in the hippocampus during ischemic insults.
View details for Web of Science ID A1990DK16400008
View details for PubMedID 1971825
GLUCOCORTICOID ENDANGERMENT OF THE HIPPOCAMPUS - TISSUE, STEROID AND RECEPTOR SPECIFICITY
1990; 51 (6): 613-618
Glucocorticoids (GCs) can damage the hippocampus when exposure is prolonged, as well as impair the capacity of hippocampal neurons to survive various neurological insults. We have recently demonstrated that GCs impair the capacity of primary hippocampal cultures to survive many of these same insults. Using this culture system, we have characterized the features with which the GC corticosterone (CORT) impairs the capacity of these cells to survive the excitotoxin kainic acid. The GC endangerment seems to be mediated by the type II, but not type I corticosteroid receptor. As evidence for type II involvement, endangerment of cells was caused by CORT concentrations in the kilodalton range for the type II receptor, and also by the type II ligand dexamethasone; moreover, the endangerment was blocked by a type II antagonist. In contrast, a type I antagonist was not protective. Cultures contained both type I and II receptors. The effect was GC-specific, as cultures were endangered by CORT, cortisol and dexamethasone, but not by non-GC steroids. GCs did not exacerbate kainic acid damage in cerebeller or hypothalamic cultures, despite the presence of corticosteroid receptors. This agrees with the in vivo data showing that the GC exacerbation of neurological insults is either exclusive to or predominant in the hippocampus.
View details for Web of Science ID A1990DJ27600001
View details for PubMedID 2113998
HYPERCORTISOLISM AND ITS POSSIBLE NEURAL BASES
1990; 27 (9): 937-952
As is clear from the pages of this journal, biological psychiatrists remain fascinated by the phenomenon of dexamethasone (DEX) resistance and the hypercortisolism of various neuropsychiatric disorders. The mere existence of the endocrine abnormalities attests to the biological reality of these disorders. Furthermore, progress continues in using the occurrence of these endocrine defects as both diagnostic and prognostic markers of disease subtypes. Progress has also been made in understanding the mechanisms underlying the endocrine defects. The adrenocortical axis is vastly complex, involving multiple hypothalamic-releasing factors under CNS control, shifting pituitary and adrenal sensitivies to hormonal signals, and feedback regulation at all three levels. What defects within this system produce DEX resistance and hypercortisolism? In this paper, we review data suggesting that the endocrine problems is, at least in part, neural in nature. Drawing upon a rodent literature, we will also suggest some models by which this can occur. The hypercortisolism found in cases of affective disorders, anorexia nervosa, Alzheimer's disease, among the very aged or the chronically stressed, is not a uniform phenomenon. Basal cortisol concentrations can be elevated in all or part of the circadian cycle. Resistance to glucocorticoid (GC) feedback inhibition (as typically demonstrated by DEX resistance) can occur; the resistance can be complete, or occur as early escape from DEX suppression. Finally, elevated basal cortisol concentrations and DEX resistance can occur independently of each other. Until the end of this review, we will conveniently refer to these variants of adrenocortical hyperactivity as "hypercortisolism." In addition, rather than using the term "hypercortisolism" for the rat, we will use "hyperadrenocorticism" (as they secrete corticosterone, rather than cortisol).
View details for Web of Science ID A1990CZ06000001
View details for PubMedID 2185849
HIPPOCAMPAL GLUTAMINE-SYNTHETASE - INSENSITIVITY TO GLUCOCORTICOIDS AND STRESS
AMERICAN JOURNAL OF PHYSIOLOGY
1990; 258 (5): E894-E897
Glucocorticoids enhance the neurotoxic potential of several insults to the rat hippocampus that involve overactivation of glutamatergic synapses. These hormones also stimulate the synthesis of glutamine synthetase (GS) in peripheral tissue. Because this enzyme helps regulate glutamate metabolism in the central nervous system, glucocorticoid induction of GS in the brain may underlie the observed synergy. We have measured GS activity in the hippocampus and skeletal muscle (plantaris) of adult rats after bilateral adrenalectomy (ADX), corticosterone (Cort) replacement, or stress. No significant changes in GS were observed in hippocampal tissue, whereas muscle GS was significantly elevated after Cort treatment or stress and was reduced after ADX. These results suggest that Cort-induced shifts in GS activity probably do not explain Cort neurotoxicity, although the stress-induced rise in muscle GS may be relevant to certain types of myopathy.
View details for Web of Science ID A1990DE09700043
View details for PubMedID 1970712
GLUCOCORTICOID FEEDBACK INHIBITION OF ADRENOCORTICOTROPIC HORMONE SECRETAGOGUE RELEASE - RELATIONSHIP TO CORTICOSTEROID RECEPTOR OCCUPANCY IN VARIOUS LIMBIC SITES
1990; 51 (3): 328-336
Feedback inhibition of the adrenocortical axis by circulating glucocorticoids occurs at the pituitary and CNS sites. In the CNS, both hypothalamic and suprahypothalamic sites have been implicated as mediators of glucocorticoid feedback activity. In the present experiments, we have attempted to identify specific CNS regions mediating the feedback and to characterize which hypothalamic adrenocorticotropic hormone secretagogues are under glucocorticoid inhibitory control. Adrenalectomized rats were presented with a delayed feedback signal in the form of systemic infusion with corticosterone or dexamethasone. Hypophysialportal concentrations of corticotropin-releasing factor (CRF), arginine vasopressin (AVP), and oxytocin (OT) were determined before and during a hypotensive stressor in the face of varying levels of feedback. The rats were then killed, and the extent of total, type I, and type II corticosteroid receptor occupancy in hippocampus, hypothalamus, and amygdala was determined. The following observations were made: (1) increased hippocampal corticosteroid receptor occupancy was associated with suppressed adrenocorticotropic hormone secretagogue concentrations; (2) the major, significant predictor of initial (prehypotensive) concentrations of CRF, AVP, and OT was the extent of occupancy of hippocampal type II receptors, often in combination with occupancy of hippocampal type I or hypothalamic receptors; (3) secretion of CRF induced by hypotension was best predicted by hippocampal type I and type II receptor occupancy (stress-induced OT secretion was best predicted by hippocampal type II and hypothalamic receptor occupancy), and (4) the 'shape' of the hippocampal type II receptor occupancy versus initial AVP concentration curve suggested a nonlinear, threshold type of relationship, implying tight hippocampal regulation of AVP secretion.
View details for Web of Science ID A1990CQ17400014
View details for PubMedID 2157997
MILD ACIDOSIS PROTECTS HIPPOCAMPAL-NEURONS FROM INJURY INDUCED BY OXYGEN AND GLUCOSE DEPRIVATION
1990; 506 (2): 343-345
Hippocampal neurons are extremely sensitive to ischemic injury; two plausible mechanisms have been implicated in mediating such damage. The first involves overexposure of neurons to excitatory N-methyl-D-aspartate (NMDA) receptor agonists, which mobilize damaging concentrations of intracellular calcium; the second involves the generation of damaging tissue acidosis. A recent report shows that exposure to pH 6.6 can block NMDA-induced calcium currents in hippocampal neurons. This suggests that moderate acidity might protect against NMDA-mediated neurotoxicity and ischemic injury in vivo. We have observed such projection in vitro using primary hippocampal cultures. At an extracellular pH of 7.4, 6 h of glucose-free anoxia caused delayed and profound damage to neurons which was partially attenuated by the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV). Dropping the pH to 6.5 provided virtually complete protection against this insult. Thus, acidosis need not be viewed exclusively as a damaging component of ischemic insults.
View details for Web of Science ID A1990CL25500029
View details for PubMedID 2154291
- STRESS IN THE WILD SCIENTIFIC AMERICAN 1990; 262 (1): 116-123
- GLUCOCORTICOIDS, HIPPOCAMPAL DAMAGE AND THE GLUTAMATERGIC SYNAPSE PROGRESS IN BRAIN RESEARCH 1990; 86: 13-23
ELEVATION OF HYPOPHYSEAL PORTAL CONCENTRATIONS OF ADRENOCORTICOTROPIN SECRETAGOGUES AFTER FORNIX TRANSECTION
1989; 125 (6): 2881-2887
Glucocorticoid feedback inhibition at the level of the brain is extremely complex, involving feedback at both hypothalamic and suprahypothalamic levels. The hippocampus has been implicated as a suprahypothalamic mediator of such feedback, based on numerous lesion, stimulation, and steroid implantation studies. These reports, however, predated the isolation and characterization of CRF and recognition of the multifactorial control of ACTH release. Thus, it is not clear which hypothalamic ACTH secretagogues are under inhibitory control of the hippocampus. To answer this, we measured hypophysialportal concentrations of CRF, arginine vasopressin, and oxytocin in rats with fornix transections, which disrupt hippocampal communication with the hypothalamus. Hypophysial-portal blood was collected in rats exposed to either low or high circulating corticosterone concentrations in the presence or absence of the coincident stressor of hypotension. We observed that fornix transection produced hypersecretion of all three secretagogues. However, the pattern of hypersecretion differed for each as follows: 1) fornix transection did not affect either initial CRF secretion or the magnitude of the stress response, but made rats resistant to a high feedback signal during stress; 2) fornix transection led to initial arginine vasopressin hypersecretion, which remained sensitive to a high feedback signal; and 3) fornix transection led to initial oxytocin hypersecretion as well as resistance to a high corticosterone feedback signal during hypotension.
View details for Web of Science ID A1989CB90300013
View details for PubMedID 2555130
HYPERCORTISOLISM AMONG SOCIALLY SUBORDINATE WILD BABOONS ORIGINATES AT THE CNS LEVEL
ARCHIVES OF GENERAL PSYCHIATRY
1989; 46 (11): 1047-1051
Recent studies suggest that the hypercortisolism and dexamathasone resistance of depression arise, at least in part, at the level of the brain, ie, cortisol-releasing factor (CRF) and/or other corticotropin-secretagogues are hypersecreted. This article suggests a similar cause of the hypercortisolism of social subordinance. Two troops of wild olive baboons, living freely in the Serengeti Ecosystem of East Africa, have been under long-term study. Consistently, in stable dominance hierachies, subordinate males are hypercortisolemic relative to dominant animals. Furthermore, hypercortisolemic males are dexamethasone resistant. There are no rank-related difference in cortisol clearance or adrenal sensitivity to corticotropin, suggesting a pituitary and/or neural locus of the hypercortisolism. Subordinate males were shown to secrete less corticotropin in response to a CRF-challenge than did dominant males. Following the logic used in similar studies with depressives, if subordinate males were hypercortisolemic despite decreased pituitary sensitivity to CRF, then this implies that the hyperactivity of the adrenocortical axis is driven at the level of the brain. Furthermore, subordinate males were hyporesponsive to CRF after administration of metyrapone, which blocks cortisol secretion and disinhibits the pituitary from feedback inhibition. Thus, the pituitary appears to have lost sensitivity to CRF itself in these low-ranking males. These observations are interpreted in light of behavioral data suggesting that these subordinate males are under sustained social stress.
View details for Web of Science ID A1989AY08200010
View details for PubMedID 2554841
VENN DIAGRAMS AND NEURONAL VULNERABILITY
NEUROBIOLOGY OF AGING
1989; 10 (5): 613-614
Greenamyre and Young note that there is poor correlation between which hippocampal regions are damaged in Alzheimer's disease and which have the highest concentrations of NMDA receptors. They conclude that EAAs can thus only be necessary, but not sufficient to explain Alzheimer's damage. We note that this is in fact probably the rule rather than the exception: some of the most credible agents which damage neurons are merely necessary, but not sufficient to explain selective neuronal vulnerability.
View details for Web of Science ID A1989AV35400082
View details for PubMedID 2812238
STATUS EPILEPTICUS INDUCED HIPPOCAMPAL DAMAGE IS MODULATED BY GLUCOSE AVAILABILITY
1989; 97 (1-2): 157-162
Kainic acid administration induces status epilepticus seizures in the rat which damage CA1 and CA3 hippocampal neurons. Rats made hypoglycemic prior to seizure had enhanced volumes of damage, when compared to normo- or hyperglycemic rats. The mild hypoglycemia was not in the range which, itself, typically produces hippocampal damage. This suggests that limited energy availability compromised the ability of neurons to survive seizures. Our data also suggest that the CA1 damage seen after status epilepticus is not hypoxic-ischemic in origin, since elevating pre-seizure glucose concentrations to a range which typically exacerbates hypoxic-ischemic CA1 damage did not augment status-epilepticus CA1 damage.
View details for Web of Science ID A1989T180900028
View details for PubMedID 2919000
CHEMICAL ADRENALECTOMY REDUCES HIPPOCAMPAL DAMAGE INDUCED BY KAINIC ACID
1988; 473 (1): 175-180
Glucocorticoids (GCs), the adrenal steroids secreted during stress, have numerous catabolic effects which include damage to neurons of the hippocampus, a principal neural target site for the steroids. In the rat, the extent of GC exposure over the lifespan is a major determinant of the rate of hippocampal neuron death during aging. GCs also modulate the severity of hippocampal damage in the rat following insults such as seizure or hypoxia-ischemia. As evidence, exogenous GCs exacerbate, while adrenalectomy attenuates hippocampal damage after these insults. Thus, it is possible that diminution of endogenous GC secretion might protect the human hippocampus after similar neurological insults; adrenalectomy under such circumstances is obviously not a viable clinical option. We demonstrate the protective effects of transient chemical adrenalectomy with the GC synthesis inhibitor, metyrapone. Rats were microinfused with the excitotoxin kainic acid in order to induce status epilepticus seizures; this insult caused a significant GC stress-response. Attenuation of that response with metyrapone reduced the CA3 hippocampal damage produced by kainic acid. Metyrapone did not change the intensity of seizures, but rather, apparently, changed the capacity of neurons to withstand the seizure. Thus, metyrapone, which is used safely and efficaciously in other clinical contexts, might prove protective of the brain following seizure in the human.
View details for Web of Science ID A1988R529500024
View details for PubMedID 3208122
GLUCOCORTICOID TOXICITY IN THE HIPPOCAMPUS - INVITRO DEMONSTRATION
1988; 453 (1-2): 367-371
Glucocorticoids (GCs) disrupt the energy metabolism of neurons of the hippocampus, and thus leave them more vulnerable to a variety of damaging metabolic insults. In this manner, GCs appear to influence the rate of hippocampal neuron loss during aging in the rat, as well as the severity of hippocampal damage following hypoxia-ischemia or seizure. These GC actions could be secondary to their multitudinous peripheral actions. The present report, however, suggests that GCs directly endanger hippocampal neurons. Glucocorticoid-induced sensitization of neurons to damaging toxins was demonstrated in vitro. The viability of primary cultures of dispersed fetal rat hippocampal neurons was assessed following exposure to a variety of neurotoxins. Prior incubation of the cultures with the rodent-typical GC, corticosterone, significantly decreased neuronal viability in the face of the toxins. Such compounds included the glutaminergic excitotoxin kainic acid, the antimetabolite 3-acetylpyridine and the superoxide radical generator paraquat. As little as 10(-9) M corticosterone could potentiate damage, a concentration equivalent to low basal values in vivo. Higher concentrations of corticosterone could potentiate damage even further; these corticosterone concentrations were not themselves damaging. Administration of glucose increased neuronal viability in the face of the GC/toxin combination, without increasing viability following toxin alone. This suggests that a critical feature of the action of GCs on neurons might be the inhibition of glucose utilization (which is a hallmark of peripheral GC action).
View details for Web of Science ID A1988N952300044
View details for PubMedID 3401775
POSTMORTEM DECAY IN GLUCOCORTICOID BINDING IN HUMAN AND PRIMATE BRAIN
1988; 448 (1): 182-185
Numerous studies of glucorticoid receptors in the rodent brain suggest that similar studies of normal or diseased human brains might be informative. However, a major confound in quantification of such receptors is their possible decay during the lagtime between death and autopsy. We find evidence for such decay. Assay conditions were optimized in a number of ways to remove endogenous glucocorticoids occupying receptors at the time of death. Despite this, [3H]dexamethasone binding in 3-4.5 h postmortem human hippocampus was approximately half that of fresh human primate tissue, while no binding was detectable in 12-24 h postmortem material. In support of the idea of postmortem decay of these receptors, binding in slices of primate temporal cortex left at room temperature declined approximately 50% by 6 h postmortem.
View details for Web of Science ID A1988N225500023
View details for PubMedID 3390714
STRESS-INDUCED SUPPRESSION OF LUTEINIZING-HORMONE CONCENTRATIONS IN WILD BABOONS - ROLE OF OPIATES
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
1988; 66 (4): 722-726
Numerous stressors disrupt male reproductive physiology; previous studies of a population of wild baboons, living freely in a national park in East Africa, indicated that the stress of anesthetization by phencyclidine darting decreased both LH secretion and testicular sensitivity to LH. This study was undertaken to determine the mechanism(s) of the decreased LH secretion in these animals. Neither stress-induced glucocorticoid nor catecholamine release was responsible, since neither blockade of glucocorticoid secretion with the adrenal steroidogenesis inhibitor metyrapone nor blockade of catecholamine secretion with the sympathetic ganglionic blocking drug chlorisondamine prevented the stress-induced decline in serum LH concentrations. Administration of the opiate receptor antagonist naloxone (0.5 mg/kg BW), however, not only prevented the decline, but also transiently elevated serum LH concentrations, suggesting that opiates play a role in tonic as well as stress-induced decreases in LH secretion. Administration of a small dose of naloxone (0.03 mg/kg BW) commensurate with occupancy of only mu-opiate receptors slowed the stress-induced decline in LH concentrations, as did administration of the kappa-receptor antagonist MR 1452. These data suggest that opiates inhibit LH release via the combined occupancy of both mu- and kappa-receptors.
View details for Web of Science ID A1988M692400011
View details for PubMedID 2831246
Individual differences and the stress response: studies of a wild primate.
Advances in experimental medicine and biology
1988; 245: 399-411
View details for PubMedID 3228021
STRESS AND GLUCOCORTICOIDS IN AGING
ENDOCRINOLOGY AND METABOLISM CLINICS OF NORTH AMERICA
1987; 16 (4): 965-980
This article has considered two themes that have permeated the gerontologic literature--namely, that aging is a time of decreased efficiency in responding to stress and that chronic stress can accelerate aspects of aging. Given the restricted framework of considering adrenocortical function (as a component of the stress response) and glucocorticoid over-exposure (as a component of chronic stress), there is considerable evidence for both of these ideas. The capacity of glucocorticoids to damage the rat hippocampus slowly over the life span and the glucocorticoid hypersecretion that seems to ensue during aging as a result of such hippocampal damage support these long-standing ideas. It should be noted that these two components interact with each other--excessive glucocorticoid secretion damages the hippocampus, and hippocampal damage produces excessive glucocorticoid secretion. This dysregulatory cascade appears to be a normal part of aging in the rat. The role of glucocorticoids in triggering programmed aging and death, while quite dramatic, is probably a phylogenetically rare event; it remains to be seen if the dysregulatory cascade of glucocorticoid excess in the rat is of relevance to aging in other species. Numerous published studies suggest that this cascade is not an obligatory aspect of normal human aging; rather, it appears to be a significant factor in the explanation of some features of pathologies associated with human aging.
View details for Web of Science ID A1987L577500009
View details for PubMedID 3322822
2ND GENERATION QUESTIONS ABOUT SENESCENT NEURON LOSS
NEUROBIOLOGY OF AGING
1987; 8 (6): 547-548
Coleman and Flood's review emphasizes the emerging consensus about the magnitude and location of senescent neuron loss. The nature of the findings point to the most pressing questions to ask next. These concern the mechanisms of selective neuron death and of compensation for the death, the functional consequences of neuronal shrinkage and loss of neuronal density, and the sources of individual variability in these factors.
View details for Web of Science ID A1987L224500007
View details for PubMedID 3431627
SOCIAL SUBORDINANCE IN WILD BABOONS IS ASSOCIATED WITH SUPPRESSED HIGH-DENSITY LIPOPROTEIN-CHOLESTEROL CONCENTRATIONS - THE POSSIBLE ROLE OF CHRONIC SOCIAL STRESS
1987; 121 (5): 1605-1610
Atherosclerosis and coronary heart disease are promoted by elevated serum low density lipoprotein cholesterol (LDL-C) and are retarded by increased high density lipoprotein cholesterol (HDL-C). Considerable variability in these lipoproteins has been observed in studies of captive animals subjected to extensive experimental manipulations, or by epidemiological studies of human beings. We have examined these variables in wild male baboons living undisturbed in their natural habitat in the Serengeti Ecosystem of East Africa. Among socially subordinate males, HDL-C and apolipoprotein A-I concentrations were significantly reduced by 31% and 25%, respectively, compared to concentrations in dominant individuals. There were no social rank differences in VLDL + LDL-C or its apolipoprotein (Apo B). Differences in age, sex hormone concentrations, rank-related diet, body weight, or gene pools were unlikely to explain this rank-related pattern. However, diminished HDL-C concentrations were associated with elevated basal cortisol concentrations, suggesting that exposure of subordinate individuals to elevated levels of social stressors could cause lower HDL-C concentrations.
View details for Web of Science ID A1987K659600003
View details for PubMedID 3665834
Maturation of the adrenocortical stress response: neuroendocrine control mechanisms and the stress hyporesponsive period.
1986; 396 (1): 64-76
During the first two weeks of life rat pups show a markedly reduced adrenocortical response to stress, and this period of adrenocortical quiescence has been termed the 'stress non-responsive period' (SNRP). The adaptive value of the SNRP can be understood in terms of the effects of glucocorticoids on CNS development: excessively high or low corticoid levels are associated with abnormal neural and behavioral development. We have attempted to explain adrenocortical activity during this period in terms of the unique pattern of glucocorticoid-receptor concentrations that exist in the brain and pituitary of the neonatal rat. This pattern of receptor concentrations results in a negative-feedback condition at the level of the brain and pituitary that ensures the low, stable corticoid levels that appear to be optimal for neuronal development in glucocorticoid-sensitive brain regions.
View details for PubMedID 3011218
[3H]dexamethasone binding in the limbic brain of the fetal rat.
1985; 355 (2): 297-300
The pituitary-adrenal system in the fetal rat is relatively well-developed and during the later part of fetal life circulating corticosterone levels are comparable to those seen in adults. Shortly after birth the adrenal gland regresses and corticosterone levels decrease dramatically. In this paper we report evidence for a similar developmental pattern for the glucocorticoid receptor system within the limbic brain. Thus, glucocorticoid receptor concentrations are higher during the fetal period than during early postnatal life. Moreover, the specificity and the affinity with which glucocorticoid receptors bind [3H]dexamethasone are, according to our data, indistinguishable from those found in the limbic brain of the adult rat.
View details for PubMedID 4084786
The development of the glucocorticoid receptor system in the rat limbic brain. I. Ontogeny and autoregulation.
1985; 350 (1-2): 159-164
In order to characterize the development of the glucocorticoid receptor system in the brain, we examined [3H]dexamethasone binding in rat pups at various ages. Using an in vitro, cytosol, receptor assay we found evidence for low levels of glucocorticoid receptors perinatally with a subsequent increase in receptor concentrations that began by about the end of the first week of life. We have also shown that receptors during this period have a ligand specificity similar to that of receptors in adult animals. The postnatal increase in receptor levels parallels an increase in circulating corticosterone titers. Thus, receptor and hormone levels increase coincidentally. In adult animals, however, increasing levels of corticosterone are associated with a decrease in receptor levels and vice versa, such that corticosterone is thought to regulate its own receptor (i.e. autoregulation). This suggested an absence of autoregulation during development. We then determined hippocampal receptor concentrations of rats treated for 5 days with corticosterone, or adrenalectomized (ADX) 5 days prior to assay, examining whether up- or down-regulation occurs throughout development. In adults corticosterone treatment decreased (-45%) and long-term adrenalectomy increased (211%) glucocorticoid receptor concentrations. In contrast, at the youngest age tested (Day 10), the effects of manipulations of corticosterone titers on receptor concentrations were negligible. The potential for autoregulation emerged gradually throughout development. Thus, it appears that corticosterone regulation of its own receptors emerges only by about the time of puberty, and that this permits an increase in receptor levels to occur despite the concurrently increasing levels of circulating corticosterone.
View details for PubMedID 3986609
The development of the glucocorticoid receptor system in the rat limbic brain. III. Negative-feedback regulation.
1985; 350 (1-2): 169-173
In the neonatal rat, there are parallel increases with age in the concentrations of glucocorticoid receptors in the limbic system, and in the sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis to negative-feedback inhibition by circulating glucocorticoids. We speculated that the increasing receptor concentrations may mediate this increasing sensitivity of the HPA axis to the suppressive effects of glucocorticoids. To examine this idea we treated rats with exogenous corticosterone from days 29 to 34, resulting in a down-regulation of glucocorticoid receptors in the brain at Day 35 to levels similar to those of younger animals. Subjects whose maturational increase in receptors was reversed in this manner were less sensitive to feedback inhibition of glucocorticoids. Specifically, compared to controls they continued to secrete corticosterone after the end of stress, and were relatively insensitive to the suppressive effects of the synthetic glucocorticoid, dexamethasone, on corticosterone titers. Our data specifically implicate the hippocampus in modulating feedback sensitivity, as down-regulation was extensive in this structure, and did not occur in the septum, amygdala, hypothalamus or pituitary.
View details for PubMedID 3986611
The development of the glucocorticoid receptor system in the rat limbic brain. II. An autoradiographic study.
1985; 350 (1-2): 165-168
We report here the results of an autoradiographic analysis of the postnatal development of the hippocampal glucocorticoid receptor system in the rat brain. Quantitative analysis of the autoradiograms revealed a varied pattern of gradual development towards adult receptor concentrations during the second week of life. Receptor concentrations in the dentate gyrus increased dramatically between Days 9 and 15, while the changes during this period in the pyramidal layers of Ammon's horn seemed to reflect both structural changes in these regions as well as increases in receptor concentrations.
View details for PubMedID 3986610