Frank M. Longo, MD, PhD

All Publications

• Organ aging signatures in the plasma proteome track health and disease. Nature Oh, H. S., Rutledge, J., Nachun, D., Pálovics, R., Abiose, O., Moran-Losada, P., Channappa, D., Urey, D. Y., Kim, K., Sung, Y. J., Wang, L., Timsina, J., Western, D., Liu, M., Kohlfeld, P., Budde, J., Wilson, E. N., Guen, Y., Maurer, T. M., Haney, M., Yang, A. C., He, Z., Greicius, M. D., Andreasson, K. I., Sathyan, S., Weiss, E. F., Milman, S., Barzilai, N., Cruchaga, C., Wagner, A. D., Mormino, E., Lehallier, B., Henderson, V. W., Longo, F. M., Montgomery, S. B., Wyss-Coray, T. 2023; 624 (7990): 164-172

  Abstract

  Animal studies show aging varies between individuals as well as between organs within an individual1-4, but whether this is true in humans and its effect on age-related diseases is unknown. We utilized levels of human blood plasma proteins originating from specific organs to measure organ-specific aging differences in living individuals. Using machine learning models, we analysed aging in 11 major organs and estimated organ age reproducibly in five independent cohorts encompassing 5,676 adults across the human lifespan. We discovered nearly 20% of the population show strongly accelerated age in one organ and 1.7% are multi-organ agers. Accelerated organ aging confers 20-50% higher mortality risk, and organ-specific diseases relate to faster aging of those organs. We find individuals with accelerated heart aging have a 250% increased heart failure risk and accelerated brain and vascular aging predict Alzheimer's disease (AD) progression independently from and as strongly as plasma pTau-181 (ref. 5), the current best blood-based biomarker for AD. Our models link vascular calcification, extracellular matrix alterations and synaptic protein shedding to early cognitive decline. We introduce a simple and interpretable method to study organ aging using plasma proteomics data, predicting diseases and aging effects.

  View details for DOI 10.1038/s41586-023-06802-1

  View details for PubMedID 38057571

  View details for PubMedCentralID PMC10700136

• Modulation of the p75 neurotrophin receptor in the PS19 tauopathy mouse model regulates transcription profiles and inter-cellular communication across multiple populations of non-neuronal cells Butler, R. R., Yang, T., Han, C., Le Guen, Y., Tran, K. C., Lallani, S., Liu, H., Leng, S., Massa, S. M., Longo, F. M. WILEY. 2023

  View details for DOI 10.1002/alz.080789

  View details for Web of Science ID 001197662100003

• Targeting Endogenous Mechanisms of Brain Resilience for the Treatment and Prevention of Alzheimer's Disease. The journal of prevention of Alzheimer's disease Shanks, H. R., Onuska, K. M., Massa, S. M., Schmitz, T. W., Longo, F. M. 2023; 10 (4): 699-705

  Abstract

  Alzheimer's disease is a neurodegenerative disorder which contributes to millions of cases of dementia worldwide. The dominant theoretical models of Alzheimer's disease propose that the brain passively succumbs to disruptions in proteostasis, neuronal dysfunction, inflammatory and other processes, ultimately leading to neurodegeneration and dementia. However, an emerging body of evidence suggests that the adult brain is endowed with endogenous mechanisms of resilience which may enable individuals to remain cognitively intact for years despite underlying pathology. In this brief review, we discuss evidence from basic neuroscience and clinical research which demonstrates the existence of endogenous molecular signaling pathways that can promote resilience to neurodegeneration. The p75 neurotrophin receptor provides one such pathway of resilience due to its role as a fundamental signaling switch which determines neuronal survival or degeneration. We highlight a series of preclinical studies targeting the p75 neurotrophin receptor in mouse models which demonstrate resilience to amyloid. We briefly discuss the design and goals of a recent clinical trial of p75 neurotrophin receptor modulation in patients with mild to moderate Alzheimer's disease. Unique challenges for developing therapeutics and biomarkers which are optimized for targeting and detecting endogenous mechanisms of resilience are also discussed. Altogether, this review motivates further trial work of therapeutics modulating the p75 neurotrophin receptor and other deep biology targets.

  View details for DOI 10.14283/jpad.2023.110

  View details for PubMedID 37874090

• Modulation of p75<SUP>NTR</SUP> on mesenchymal stem cells increases their vascular protection in retinal ischemia-reperfusion mouse model Elshaer, S. L., Park, H., Pearson, L., Hill, W. D., Longo, F. M., El-Remessy, A. B. MARY ANN LIEBERT, INC. 2023: A71

  View details for Web of Science ID 001090964000048

• Senolytic therapy for Alzheimer's disease. Nature medicine Longo, F. M., Massa, S. M. 2023

  View details for DOI 10.1038/s41591-023-02541-y

  View details for PubMedID 37758897

  View details for PubMedCentralID 6260915

• Senolytic therapy for Alzheimer's disease NATURE MEDICINE Longo, F. M., Massa, S. M. 2023

  View details for DOI 10.1038/s41591-023-02541

  View details for Web of Science ID 001076629700002

• Pharmacological Co-Activation of TrkB and TrkC Receptor Signaling Ameliorates Striatal Neuropathology and Motor Deficits in Mouse Models of Huntington's Disease. Journal of Huntington's disease Simmons, D. A., Belichenko, N. P., Longo, F. M. 2023

  Abstract

  Loss of neurotrophic support in the striatum, particularly reduced brain-derived neurotrophic factor (BDNF) levels, contributes importantly to Huntington's disease (HD) pathogenesis. Another neurotrophin (NT), NT-3, is reduced in the cortex of HD patients; however, its role in HD is unknown. BDNF and NT-3 bind with high affinity to the tropomyosin receptor-kinases (Trk) B and TrkC, respectively. Targeting TrkB/TrkC may be an effective HD therapeutic strategy, as multiple links exist between their signaling pathways and HD degenerative mechanisms. We developed a small molecule ligand, LM22B-10, that activates TrkB and TrkC to promote cell survival.This study aimed to determine if upregulating TrkB/TrkC signaling with LM22B-10 would alleviate the HD phenotype in R6/2 and Q140 mice.LM22B-10 was delivered by concomitant intranasal-intraperitoneal routes to R6/2 and Q140 mice and then motor performance and striatal pathology were evaluated.NT-3 levels, TrkB/TrkC phosphorylation, and AKT signaling were reduced in the R6/2 striatum; LM22B-10 counteracted these deficits. LM22B-10 also reduced intranuclear huntingtin aggregates, dendritic spine loss, microglial activation, and degeneration of dopamine- and cyclic AMP-regulated phosphoprotein with a molecular weight of 32 kDa (DARPP-32) and parvalbumin-containing neurons in the R6/2 and/or Q140 striatum. Moreover, both HD mouse models showed improved motor performance after LM22B-10 treatment.These results reveal an NT-3/TrkC signaling deficiency in the striatum of R6/2 mice, support the idea that targeting TrkB/TrkC alleviates HD-related neurodegeneration and motor dysfunction, and suggest a novel, disease-modifying, multi-target strategy for treating HD.

  View details for DOI 10.3233/JHD-230589

  View details for PubMedID 37638447

• Delivery of BDNF through a Pluripotent Stem Cell-Based Platform Ameliorates Behavioral Deficits in a Mouse Model of Huntington's Disease Selvaraj, S., Simmons, D. A., Chen, T., Cao, G. Y., Camelo, T. S., McHugh, T. M., Gonzalez, S., Martin, R. M., Simanauskaite, J. M., Uchida, N., Longo, F. M., Porteus, M. H. CELL PRESS. 2023: 18

  View details for Web of Science ID 001045144200034

• Open drug discovery in Alzheimer's disease. Alzheimer's & dementia (New York, N. Y.) Axtman, A. D., Brennan, P. E., Frappier-Brinton, T., Betarbet, R., Carter, G. W., Fu, H., Gileadi, O., Greenwood, A. K., Leal, K., Longo, F. M., Mangravite, L. M., Edwards, A. M., Levey, A. I., Emory‐Sage‐SGC TREAT‐AD Center 2023; 9 (2): e12394

  Abstract

  Alzheimer's disease (AD) drug discovery has focused on a set of highly studied therapeutic hypotheses, with limited success. The heterogeneous nature of AD processes suggests that a more diverse, systems-integrated strategy may identify new therapeutic hypotheses. Although many target hypotheses have arisen from systems-level modeling of human disease, in practice and for many reasons, it has proven challenging to translate them into drug discovery pipelines. First, many hypotheses implicate protein targets and/or biological mechanisms that are under-studied, meaning there is a paucity of evidence to inform experimental strategies as well as high-quality reagents to perform them. Second, systems-level targets are predicted to act in concert, requiring adaptations in how we characterize new drug targets. Here we posit that the development and open distribution of high-quality experimental reagents and informatic outputs-termed target enabling packages (TEPs)-will catalyze rapid evaluation of emerging systems-integrated targets in AD by enabling parallel, independent, and unencumbered research.

  View details for DOI 10.1002/trc2.12394

  View details for PubMedID 37215505

• Myeloid deficiency of the intrinsic clock protein BMAL1 accelerates cognitive aging by disrupting microglial synaptic pruning. Journal of neuroinflammation Iweka, C. A., Seigneur, E., Hernandez, A. L., Paredes, S. H., Cabrera, M., Blacher, E., Pasternak, C. T., Longo, F. M., de Lecea, L., Andreasson, K. I. 2023; 20 (1): 48

  Abstract

  Aging is associated with loss of circadian immune responses and circadian gene transcription in peripheral macrophages. Microglia, the resident macrophages of the brain, also show diurnal rhythmicity in regulating local immune responses and synaptic remodeling. To investigate the interaction between aging and microglial circadian rhythmicity, we examined mice deficient in the core clock transcription factor, BMAL1. Aging Cd11bcre;Bmallox/lox mice demonstrated accelerated cognitive decline in association with suppressed hippocampal long-term potentiation and increases in immature dendritic spines. C1q deposition at synapses and synaptic engulfment were significantly decreased in aging Bmal1-deficient microglia, suggesting that BMAL1 plays a role in regulating synaptic pruning in aging. In addition to accelerated age-associated hippocampal deficits, Cd11bcre;Bmallox/lox mice also showed deficits in the sleep-wake cycle with increased wakefulness across light and dark phases. These results highlight an essential role of microglial BMAL1 in maintenance of synapse homeostasis in the aging brain.

  View details for DOI 10.1186/s12974-023-02727-8

  View details for PubMedID 36829230

  View details for PubMedCentralID 8157517

• Reduced expression of the cell intrinsic clock protein Bmal1 in myeloid cells accelerates cognitive decline and alters microglial function in aging mice Iweka, C., Seigneur, E., Latif-Hernandez, A., Paredes, S., Cabrera, M., Blacher, E., Wang, Q., Longo, F., DeLecea, L., Andreasson, K. AMER SOC CELL BIOLOGY. 2023: 761

  View details for Web of Science ID 001051001303275

• Performance of a fully-automated Lumipulse plasma phospho-tau181 assay for Alzheimer's disease. Alzheimer's research & therapy Wilson, E. N., Young, C. B., Ramos Benitez, J., Swarovski, M. S., Feinstein, I., Vandijck, M., Le Guen, Y., Kasireddy, N. M., Shahid, M., Corso, N. K., Wang, Q., Kennedy, G., Trelle, A. N., Lind, B., Channappa, D., Belnap, M., Ramirez, V., Skylar-Scott, I., Younes, K., Yutsis, M. V., Le Bastard, N., Quinn, J. F., van Dyck, C. H., Nairn, A., Fredericks, C. A., Tian, L., Kerchner, G. A., Montine, T. J., Sha, S. J., Davidzon, G., Henderson, V. W., Longo, F. M., Greicius, M. D., Wagner, A. D., Wyss-Coray, T., Poston, K. L., Mormino, E. C., Andreasson, K. I. 2022; 14 (1): 172

  Abstract

  BACKGROUND: The recent promise of disease-modifying therapies for Alzheimer's disease (AD) has reinforced the need for accurate biomarkers for early disease detection, diagnosis and treatment monitoring. Advances in the development of novel blood-based biomarkers for AD have revealed that plasma levels of tau phosphorylated at various residues are specific and sensitive to AD dementia. However, the currently available tests have shortcomings in access, throughput, and scalability that limit widespread implementation.METHODS: We evaluated the diagnostic and prognostic performance of a high-throughput and fully-automated Lumipulse plasma p-tau181 assay for the detection of AD. Plasma from older clinically unimpaired individuals (CU, n = 463) and patients with mild cognitive impairment (MCI, n = 107) or AD dementia (n = 78) were obtained from the longitudinal Stanford University Alzheimer's Disease Research Center (ADRC) and the Stanford Aging and Memory Study (SAMS) cohorts. We evaluated the discriminative accuracy of plasma p-tau181 for clinical AD diagnosis, association with amyloid beta peptides and p-tau181 concentrations in CSF, association with amyloid positron emission tomography (PET), and ability to predict longitudinal cognitive and functional change.RESULTS: The assay showed robust performance in differentiating AD from control participants (AUC 0.959, CI: 0.912 to 0.990), and was strongly associated with CSF p-tau181, CSF Abeta42/Abeta40 ratio, and amyloid-PET global SUVRs. Associations between plasma p-tau181 with CSF biomarkers were significant when examined separately in Abeta+ and Abeta- groups. Plasma p-tau181 significantly increased over time in CU and AD diagnostic groups. After controlling for clinical diagnosis, age, sex, and education, baseline plasma p-tau181 predicted change in MoCA overall and change in CDR Sum of Boxes in the AD group over follow-up of up to 5 years.CONCLUSIONS: This fully-automated and available blood-based biomarker assay therefore may be useful for early detection, diagnosis, prognosis, and treatment monitoring of AD.

  View details for DOI 10.1186/s13195-022-01116-2

  View details for PubMedID 36371232

• Modulation of p75 neurotrophin receptor (p75NTR) with LM11A-31 improves neurovascular damage in diabetic stroke Ismael, S., Longo, F., Bix, G., Ishrat, T. SAGE PUBLICATIONS INC. 2022: 219

  View details for Web of Science ID 000802263300369

• Chronic partial TrkB activation reduces seizures and mortality in a mouse model of Dravet syndrome. Proceedings of the National Academy of Sciences of the United States of America Gu, F., Parada, I., Yang, T., Longo, F. M., Prince, D. A. 2022; 119 (7)

  Abstract

  Dravet syndrome (DS) is one of the most severe childhood epilepsies, characterized by intractable seizures and comorbidities including cognitive and social dysfunction and high premature mortality. DS is mainly caused by loss-of-function mutations in the Scn1a gene encoding Nav1.1 that is predominantly expressed in inhibitory parvalbumin-containing (PV) interneurons. Decreased Nav1.1 impairs PV cell function, contributing to DS phenotypes. Effective pharmacological therapy that targets defective PV interneurons is not available. The known role of brain-derived neurotrophic factor (BDNF) in the development and maintenance of interneurons, together with our previous results showing improved PV interneuronal function and antiepileptogenic effects of a TrkB receptor agonist in a posttraumatic epilepsy model, led to the hypothesis that early treatment with a TrkB receptor agonist might prevent or reduce seizure activity in DS mice. To test this hypothesis, we treated DS mice with LM22A-4 (LM), a partial agonist at the BDNF TrkB receptor, for 7 d starting at postnatal day 13 (P13), before the onset of spontaneous seizures. Results from immunohistochemistry, Western blot, whole-cell patch-clamp recording, and invivo seizure monitoring showed that LM treatment increased the number of perisomatic PV interneuronal synapses around cortical pyramidal cells in layer V, upregulated Nav1.1 in PV neurons, increased inhibitory synaptic transmission, and decreased seizures and the mortality rate in DS mice. The results suggest that early treatment with a partial TrkB receptor agonist may be a promising therapeutic approach to enhance PV interneuron function and reduce epileptogenesis and premature death in DS.

  View details for DOI 10.1073/pnas.2022726119

  View details for PubMedID 35165147

• Post-stroke administration of the p75 neurotrophin receptor modulator, LM11A-31, attenuates chronic changes in brain metabolism, increases neurotransmitter levels, and improves recovery. The Journal of pharmacology and experimental therapeutics Nguyen, T. V., Crumpacker, R. H., Calderon, K. E., Garcia, F. G., Zbesko, J. C., Frye, J. B., Gonzalez, S., Becktel, D. A., Yang, T., Tavera-Garcia, M. A., Morrison, H. W., Schnellmann, R. G., Longo, F. M., Doyle, K. P. 2021

  Abstract

  The aim of this study was to test whether post-stroke oral administration of a small molecule p75 neurotrophin receptor(p75NTR) modulator (LM11A-31) can augment neuronal survival and improve recovery in a mouse model of stroke. Mice were administered LM11A-31 for up to 12 weeks, beginning 1 week after stroke. Metabolomic analysis revealed that after 2 weeks of daily treatment, mice that received LM11A-31 were distinct from vehicle treated mice by principal component analysis and had higher levels of serotonin, acetylcholine, and dopamine in their ipsilateral hemisphere. LM11A-31 treatment also improved redox homeostasis by restoring reduced glutathione. It also offset a stroke induced reduction in glycolysis by increasing acetyl-CoA. There was no effect on cytokine levels in the infarct. At 13 weeks following stroke, adaptive immune cell infiltration in the infarct was unchanged in LM11A-31 treated mice, indicating that LM11A-31 does not alter the chronic inflammatory response to stroke at the site of the infarct. However, LM11A-31 treated mice had less brain atrophy, neurodegeneration, tau pathology, and microglial activation in other regions of the ipsilateral hemisphere. These findings correlated with improved recovery of motor function on a ladder test, improved sensorimotor and cognitive abilities on a nest construction test, and less impulsivity in an open field test. These data support small molecule modulation of the p75 neurotrophin receptor for preserving neuronal health and function during stroke recovery. Significance Statement The findings from this study introduce the p75 neurotrophin receptor as a novel small molecule target for promotion of stroke recovery. Given that LM11A-31 is in clinical trials as a potential therapy for Alzheimer's disease, it could be considered as a candidate for assessment in stroke or vascular dementia studies.

  View details for DOI 10.1124/jpet.121.000711

  View details for PubMedID 34893553

• Small molecule modulation of TrkB and TrkC neurotrophin receptors prevents cholinergic neuron atrophy in an Alzheimer's disease mouse model at an advanced pathological stage. Neurobiology of disease Gonzalez, S., McHugh, T. L., Yang, T., Syriani, W., Massa, S. M., Longo, F. M., Simmons, D. A. 2021: 105563

  Abstract

  Degeneration of basal forebrain cholinergic neurons (BFCNs) in the nucleus basalis of Meynert (NBM) and vertical diagonal band (VDB) along with their connections is a key pathological event leading to memory impairment in Alzheimer's disease (AD). Aberrant neurotrophin signaling via Trks and the p75 neurotrophin receptor (p75NTR) contributes importantly to BFCN dystrophy. While NGF/TrkA signaling has received the most attention in this regard, TrkB and TrkC signaling also provide trophic support to BFCNs and these receptors may be well located to preserve BFCN connectivity. We previously identified a small molecule TrkB/TrkC ligand, LM22B-10, that promotes cell survival and neurite outgrowth in vitro and activates TrkB/TrkC signaling in the hippocampus of aged mice when given intranasally, but shows poor oral bioavailability. An LM22B-10 derivative, PTX-BD10-2, with improved oral bioavailability has been developed and this study examined its effects on BFCN atrophy in the hAPPLond/Swe (APPL/S) AD mouse model. Oral delivery of PTX-BD10-2 was started after appreciable amyloid and cholinergic pathology was present to parallel the clinical context, as most AD patients start treatment at advanced pathological stages. PTX-BD10-2 restored cholinergic neurite integrity in the NBM and VDB, and reduced NBM neuronal atrophy in symptomatic APPL/S mice. Dystrophy of cholinergic neurites in BF target regions, including the cortex, hippocampus, and amygdala, was also reduced with treatment. Finally, PTX-BD10-2 reduced NBM tau pathology and improved the survival of cholinergic neurons derived from human induced pluripotent stem cells (iPSCs) after amyloid-beta exposure. These data provide evidence that targeting TrkB and TrkC signaling with PTX-BD10-2 may be an effective disease-modifying strategy for combating cholinergic dysfunction in AD. The potential for clinical translation is further supported by the compound's reduction of AD-related degenerative processes that have progressed beyond early stages and its neuroprotective effects in human iPSC-derived cholinergic neurons.

  View details for DOI 10.1016/j.nbd.2021.105563

  View details for PubMedID 34838668

• Suppression of HIV-associated Macrophage Activation by a p75 Neurotrophin Receptor Ligand. Journal of neuroimmune pharmacology : the official journal of the Society on NeuroImmune Pharmacology Killebrew, D. A., Williams, K. S., Xie, Y., Longo, F., Meeker, R. B. 2021

  Abstract

  Previous studies indicated that nerve growth factor (NGF) and proNGF differentially regulate the phenotype of macrophages and microglia via actions at tropomyosin receptor kinase A (TrkA) and p75 neurotrophin receptors (p75NTR), respectively. The ability of HIV gp120 and virions to induce the secretion of factors toxic to neurons was suppressed by NGF and enhanced by proNGF, suggesting the potential for neurotrophin based "anti-inflammatory" interventions. To investigate the "anti-inflammatory" potential of the p75NTR ligand, LM11A-31, we treated cultured macrophages and microglia with HIV gp120 in the presence or absence of the ligand and evaluated the morphological phenotype, intrinsic calcium signaling, neurotoxic activity and proteins in the secretome. LM11A-31 at 10nM was able to suppress the release of neurotoxic factors from both monocyte-derived macrophages (MDM) and microglia. The protective effects correlated with a shift in morphology and a unique secretory phenotype rich in growth factors that overrode the actions of HIV gp120. The protein pattern was generally consistent with anti-inflammatory, phagocytic and tissue remodeling functions. Although the toxic factor(s) and the source of the neuroprotection were not identified, the data indicated that an increased degradation of NGF induced by HIV gp120 was likely to contribute to neuronal vulnerability. Although substantial work is still needed to reveal the functions of many proteins in the mononuclear phagocyte secretome, such as growth and differentiation factors, the data clearly indicate that the ligand LM11A-31 has excellent therapeutic potential due to its ability to induce a more protective phenotype that restricts activation by HIV.

  View details for DOI 10.1007/s11481-021-10002-x

  View details for PubMedID 34296391

• Modulation of p75(NTR) on Mesenchymal Stem Cells Improves Angiogenic Secretome and Vascular Protection in Retinal Ischemia-Reperfusion El-Remessy, A. B., Elshaer, S., Park, H., Pearson, L., Hill, W., Longo, F. M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2021

  View details for Web of Science ID 000690761600238

• Neuroimaging, Urinary, and Plasma Biomarkers of Treatment Response in Huntington's Disease: Preclinical Evidence with the p75NTR Ligand LM11A-31. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics Simmons, D. A., Mills, B. D., Butler Iii, R. R., Kuan, J., McHugh, T. L., Akers, C., Zhou, J., Syriani, W., Grouban, M., Zeineh, M., Longo, F. M. 2021

  Abstract

  Huntington's disease (HD) is caused by an expansion of the CAG repeat in the huntingtin gene leading to preferential neurodegeneration of the striatum. Disease-modifying treatments are not yet available to HD patients and their development would be facilitated by translatable pharmacodynamic biomarkers. Multi-modal magnetic resonance imaging (MRI) and plasma cytokines have been suggested as disease onset/progression biomarkers, but their ability to detect treatment efficacy is understudied. This study used the R6/2 mouse model of HD to assess if structural neuroimaging and biofluid assays can detect treatment response using as a prototype the small molecule p75NTR ligand LM11A-31, shown previously to reduce HD phenotypes in these mice. LM11A-31 alleviated volume reductions in multiple brain regions, including striatum, of vehicle-treated R6/2 mice relative to wild-types (WTs), as assessed with in vivo MRI. LM11A-31 also normalized changes in diffusion tensor imaging (DTI) metrics and diminished increases in certain plasma cytokine levels, including tumor necrosis factor-alpha and interleukin-6, in R6/2 mice. Finally, R6/2-vehicle mice had increased urinary levels of the p75NTR extracellular domain (ecd), a cleavage product released with pro-apoptotic ligand binding that detects the progression of other neurodegenerative diseases; LM11A-31 reduced this increase. These results are the first to show that urinary p75NTR-ecd levels are elevated in an HD mouse model and can be used to detect therapeutic effects. These data also indicate that multi-modal MRI and plasma cytokine levels may be effective pharmacodynamic biomarkers and that using combinations of these markers would be a viable and powerful option for clinical trials.

  View details for DOI 10.1007/s13311-021-01023-8

  View details for PubMedID 33786806

• Establishing a Data Science Unit in an Academic Medical Center: An Illustrative Model. Academic medicine : journal of the Association of American Medical Colleges Desai, M., Boulos, M., Pomann, G. M., Steinberg, G. K., Longo, F. M., Leonard, M., Montine, T., Blomkalns, A. L., Harrington, R. A. 2021

  Abstract

  The field of data science has great potential to address critical questions relevant for academic medical centers. Data science initiatives are consequently being established within academic medicine. At the cornerstone of such initiatives are scientists who practice data science. These scientists include biostatisticians, clinical informaticians, database and software developers, computational scientists, and computational biologists. Too often, however, those involved in the practice of data science are viewed by academic leadership as providing a noncomplex service to facilitate research and further the careers of other academic faculty. The authors contend that the success of data science initiatives relies heavily on the understanding that the practice of data science is a critical intellectual contribution to the overall science conducted at an academic medical center. Further, careful thought by academic leadership is needed for allocation of resources devoted to the practice of data science. At the Stanford University School of Medicine, the authors have developed an innovative model for a data science collaboratory based on 4 fundamental elements: an emphasis on collaboration over consultation; a subscription-based funding mechanism that reflects commitment by key partners; an investment in the career development of faculty who practice data science; and a strong educational component for data science members in team science and for clinical and translational investigators in data science. As data science becomes increasingly essential to learning health systems, centers that specialize in the practice of data science are a critical component of the research infrastructure and intellectual environment of academic medical centers.

  View details for DOI 10.1097/ACM.0000000000004079

  View details for PubMedID 33769342

• Restoring metabolism of myeloid cells reverses cognitive decline in ageing. Nature Minhas, P. S., Latif-Hernandez, A., McReynolds, M. R., Durairaj, A. S., Wang, Q., Rubin, A., Joshi, A. U., He, J. Q., Gauba, E., Liu, L., Wang, C., Linde, M., Sugiura, Y., Moon, P. K., Majeti, R., Suematsu, M., Mochly-Rosen, D., Weissman, I. L., Longo, F. M., Rabinowitz, J. D., Andreasson, K. I. 2021

  Abstract

  Ageing is characterized by the development of persistent pro-inflammatory responses that contribute to atherosclerosis, metabolic syndrome, cancer and frailty1-3. The ageing brain is also vulnerable to inflammation, as demonstrated by the high prevalence of age-associated cognitive decline and Alzheimer's disease4-6. Systemically, circulating pro-inflammatory factors can promote cognitive decline7,8, and in the brain, microglia lose the ability to clear misfolded proteins that are associated with neurodegeneration9,10. However, the underlying mechanisms that initiate and sustain maladaptive inflammation with ageing are not well defined. Here we show that in ageing mice myeloid cell bioenergetics are suppressed in response to increased signalling by the lipid messenger prostaglandin E2 (PGE2), a major modulator of inflammation11. In ageing macrophages and microglia, PGE2 signalling through its EP2 receptor promotes the sequestration of glucose into glycogen, reducing glucose flux and mitochondrial respiration. This energy-deficient state, which drives maladaptive pro-inflammatory responses, is further augmented by a dependence of aged myeloid cells on glucose as a principal fuel source. In aged mice, inhibition of myeloid EP2 signalling rejuvenates cellular bioenergetics, systemic and brain inflammatory states, hippocampal synaptic plasticity and spatial memory. Moreover, blockade of peripheral myeloid EP2 signalling is sufficient to restore cognition in aged mice. Our study suggests that cognitive ageing is not a static or irrevocable condition but can be reversed by reprogramming myeloid glucose metabolism to restore youthful immune functions.

  View details for DOI 10.1038/s41586-020-03160-0

  View details for PubMedID 33473210

• Modulation of p75NTR on Mesenchymal Stem Cells Increases Their Vascular Protection in Retinal Ischemia-Reperfusion Mouse Model. International journal of molecular sciences Elshaer, S. L., Park, H. S., Pearson, L. n., Hill, W. D., Longo, F. M., El-Remessy, A. B. 2021; 22 (2)

  Abstract

  Mesenchymal stem cells (MSCs) are a promising therapy to improve vascular repair, yet their role in ischemic retinopathy is not fully understood. The aim of this study is to investigate the impact of modulating the neurotrophin receptor; p75NTR on the vascular protection of MSCs in an acute model of retinal ischemia/reperfusion (I/R). Wild type (WT) and p75NTR-/- mice were subjected to I/R injury by increasing intra-ocular pressure to 120 mmHg for 45 min, followed by perfusion. Murine GFP-labeled MSCs (100,000 cells/eye) were injected intravitreally 2 days post-I/R and vascular homing was assessed 1 week later. Acellular capillaries were counted using trypsin digest 10-days post-I/R. In vitro, MSC-p75NTR was modulated either genetically using siRNA or pharmacologically using the p75NTR modulator; LM11A-31, and conditioned media were co-cultured with human retinal endothelial cells (HREs) to examine the angiogenic response. Finally, visual function in mice undergoing retinal I/R and receiving LM11A-31 was assessed by visual-clue water-maze test. I/R significantly increased the number of acellular capillaries (3.2-Fold) in WT retinas, which was partially ameliorated in p75NTR-/- retinas. GFP-MSCs were successfully incorporated and engrafted into retinal vasculature 1 week post injection and normalized the number of acellular capillaries in p75NTR-/- retinas, yet ischemic WT retinas maintained a 2-Fold increase. Silencing p75NTR on GFP-MSCs coincided with a higher number of cells homing to the ischemic WT retinal vasculature and normalized the number of acellular capillaries when compared to ischemic WT retinas receiving scrambled-GFP-MSCs. In vitro, silencing p75NTR-MSCs enhanced their secretome, as evidenced by significant increases in SDF-1, VEGF and NGF release in MSCs conditioned medium; improved paracrine angiogenic response in HREs, where HREs showed enhanced migration (1.4-Fold) and tube formation (2-Fold) compared to controls. In parallel, modulating MSCs-p75NTR using LM11A-31 resulted in a similar improvement in MSCs secretome and the enhanced paracrine angiogenic potential of HREs. Further, intervention with LM11A-31 significantly mitigated the decline in visual acuity post retinal I/R injury. In conclusion, p75NTR modulation can potentiate the therapeutic potential of MSCs to harness vascular repair in ischemic retinopathy diseases.

  View details for DOI 10.3390/ijms22020829

  View details for PubMedID 33467640

• Genome-wide analysis of common and rare variants via multiple knockoffs at biobank scale, with an application to Alzheimer disease genetics. American journal of human genetics He, Z., Le Guen, Y., Liu, L., Lee, J., Ma, S., Yang, A. C., Liu, X., Rutledge, J., Losada, P. M., Song, B., Belloy, M. E., Butler, R. R., Longo, F. M., Tang, H., Mormino, E. C., Wyss-Coray, T., Greicius, M. D., Ionita-Laza, I. 2021

  Abstract

  Knockoff-based methods have become increasingly popular due to their enhanced power for locus discovery and their ability to prioritize putative causal variants in a genome-wide analysis. However, because of the substantial computational cost for generating knockoffs, existing knockoff approaches cannot analyze millions of rare genetic variants in biobank-scale whole-genome sequencing and whole-genome imputed datasets. We propose a scalable knockoff-based method for the analysis of common and rare variants across the genome, KnockoffScreen-AL, that is applicable to biobank-scale studies with hundreds of thousands of samples and millions of genetic variants. The application of KnockoffScreen-AL to the analysis of Alzheimer disease (AD) in 388,051 WG-imputed samples from the UK Biobank resulted in 31 significant loci, including 14 loci that are missed by conventional association tests on these data. We perform replication studies in an independent meta-analysis of clinically diagnosed AD with 94,437 samples, and additionally leverage single-cell RNA-sequencing data with 143,793 single-nucleus transcriptomes from 17 control subjects and AD-affected individuals, and proteomics data from 735 control subjects and affected indviduals with AD and related disorders to validate the genes at these significant loci. These multi-omics analyses show that 79.1% of the proximal genes at these loci and 76.2% of the genes at loci identified only by KnockoffScreen-AL exhibit at least suggestive signal (p < 0.05) in the scRNA-seq or proteomics analyses. We highlight a potentially causal gene in AD progression, EGFR, that shows significant differences in expression and protein levels between AD-affected individuals and healthy control subjects.

  View details for DOI 10.1016/j.ajhg.2021.10.009

  View details for PubMedID 34767756

• Improved neurocognitive performance in FIV infected cats following treatment with the p75 neurotrophin receptor ligand LM11A-31. Journal of neurovirology Fogle, J. E., Hudson, L. n., Thomson, A. n., Sherman, B. n., Gruen, M. n., Lacelles, B. D., Colby, B. M., Clary, G. n., Longo, F. n., Meeker, R. B. 2021

  Abstract

  HIV rapidly infects the central nervous system (CNS) and establishes a persistent viral reservoir within microglia, perivascular macrophages and astrocytes. Inefficient control of CNS viral replication by antiretroviral therapy results in chronic inflammation and progressive cognitive decline in up to 50% of infected individuals with no effective treatment options. Neurotrophin based therapies have excellent potential to stabilize and repair the nervous system. A novel non-peptide ligand, LM11A-31, that targets the p75 neurotrophin receptor (p75NTR) has been identified as a small bioavailable molecule capable of strong neuroprotection with minimal side effects. To evaluate the neuroprotective effects of LM11A-31 in a natural infection model, we treated cats chronically infected with feline immunodeficiency virus (FIV) with 13 mg/kg LM11A-31 twice daily over a period of 10 weeks and assessed effects on cognitive functions, open field behaviors, activity, sensory thresholds, plasma FIV, cerebrospinal fluid (CSF) FIV, peripheral blood mononuclear cell provirus, CD4 and CD8 cell counts and general physiology. Between 12 and 18 months post-inoculation, cats began to show signs of neural dysfunction in T maze testing and novel object recognition, which were prevented by LM11A-31 treatment. Anxiety-like behavior was reduced in the open field and no changes were seen in sensory thresholds. Systemic FIV titers were unaffected but treated cats exhibited a log drop in CSF FIV titers. No significant adverse effects were observed under all conditions. The data indicate that LM11A-31 is likely to be a potent adjunctive treatment for the control of neurodegeneration in HIV infected individuals.

  View details for DOI 10.1007/s13365-021-00956-2

  View details for PubMedID 33661457

• Small molecule modulation of the p75 neurotrophin receptor inhibits multiple amyloid beta-induced tau pathologies. Scientific reports Yang, T., Tran, K. C., Zeng, A. Y., Massa, S. M., Longo, F. M. 2020; 10 (1): 20322

  Abstract

  Longitudinal preclinical and clinical studies suggest that Abeta drives neurite and synapse degeneration through an array of tau-dependent and independent mechanisms. The intracellular signaling networks regulated by the p75 neurotrophin receptor (p75NTR) substantially overlap with those linked to Abeta and to tau. Here we examine the hypothesis that modulation of p75NTR will suppress the generation of multiple potentially pathogenic tau species and related signaling to protect dendritic spines and processes from Abeta-induced injury. In neurons exposed to oligomeric Abeta in vitro and APP mutant mouse models, modulation of p75NTR signaling using the small-molecule LM11A-31 was found to inhibit Abeta-associated degeneration of neurites and spines; and tau phosphorylation, cleavage, oligomerization and missorting. In line with these effects on tau, LM11A-31 inhibited excess activation of Fyn kinase and its targets, tau and NMDA-NR2B, and decreased Rho kinase signaling changes and downstream aberrant cofilin phosphorylation. In vitro studies with pseudohyperphosphorylated tau and constitutively active RhoA revealed that LM11A-31 likely acts principally upstream of tau phosphorylation, and has effects preventing spine loss both up and downstream of RhoA activation. These findings support the hypothesis that modulation of p75NTR signaling inhibits a broad spectrum of Abeta-triggered, tau-related molecular pathology thereby contributing to synaptic resilience.

  View details for DOI 10.1038/s41598-020-77210-y

  View details for PubMedID 33230162

• Restoration of motor learning in a mouse model of Rett syndrome following long-term treatment with a novel small-molecule activator of TrkB DISEASE MODELS & MECHANISMS Adams, I., Yang, T., Longo, F. M., Katz, D. M. 2020; 13 (11)

  Abstract

  Reduced expression of brain-derived neurotrophic factor (BDNF) and impaired activation of the BDNF receptor, tropomyosin receptor kinase B (TrkB; also known as Ntrk2), are thought to contribute significantly to the pathophysiology of Rett syndrome (RTT), a severe neurodevelopmental disorder caused by loss-of-function mutations in the X-linked gene encoding methyl-CpG-binding protein 2 (MeCP2). Previous studies from this and other laboratories have shown that enhancing BDNF expression and/or TrkB activation in Mecp2-deficient mouse models of RTT can ameliorate or reverse abnormal neurological phenotypes that mimic human RTT symptoms. The present study reports on the preclinical efficacy of a novel, small-molecule, non-peptide TrkB partial agonist, PTX-BD4-3, in heterozygous female Mecp2 mutant mice, a well-established RTT model that recapitulates the genetic mosaicism of the human disease. PTX-BD4-3 exhibited specificity for TrkB in cell-based assays of neurotrophin receptor activation and neuronal cell survival and in in vitro receptor binding assays. PTX-BD4-3 also activated TrkB following systemic administration to wild-type and Mecp2 mutant mice and was rapidly cleared from the brain and plasma with a half-life of ∼2 h. Chronic intermittent treatment of Mecp2 mutants with a low dose of PTX-BD4-3 (5 mg/kg, intraperitoneally, once every 3 days for 8 weeks) reversed deficits in two core RTT symptom domains - respiration and motor control - and symptom rescue was maintained for at least 24 h after the last dose. Together, these data indicate that significant clinically relevant benefit can be achieved in a mouse model of RTT with a chronic intermittent, low-dose treatment paradigm targeting the neurotrophin receptor TrkB.

  View details for DOI 10.1242/dmm.044685

  View details for Web of Science ID 000598339900005

  View details for PubMedID 33361117

• Small-molecule modulation of the p75 neurotrophin receptor inhibits a wide range of tau molecular pathologies and their sequelae in P301S tauopathy mice. Acta neuropathologica communications Yang, T., Liu, H., Tran, K. C., Leng, A., Massa, S. M., Longo, F. M. 2020; 8 (1): 156

  Abstract

  In tauopathies, phosphorylation, acetylation, cleavage and other modifications of tau drive intracellular generation of diverse forms of toxic tau aggregates and associated seeding activity, which have been implicated in subsequent synaptic failure and neurodegeneration. Suppression of this wide range of pathogenic species, seeding and toxicity mechanisms, while preserving the physiological roles of tau, presents a key therapeutic goal. Identification and targeting of signaling networks that influence a broad spectrum of tau pathogenic mechanisms might prevent or reverse synaptic degeneration and modify disease outcomes. The p75 neurotrophin receptor (p75NTR) modulates such networks, including activation of multiple tau kinases, calpain and rhoA-cofilin activity. The orally bioavailable small-molecule p75NTR modulator, LM11A-31, was administered to tauP301S mice for 3months starting at 6months of age, when tau pathology was well established. LM11A-31 was found to reduce: excess activation of hippocampal cdk5 and JNK kinases and calpain; excess cofilin phosphorylation, tau phosphorylation, acetylation and cleavage; accumulation of multiple forms of insoluble tau aggregates and filaments; and, microglial activation. Hippocampal extracts from treated mice had substantially reduced tau seeding activity. LM11A-31 treatment also led to a reversal of pyramidal neuron dendritic spine loss, decreased loss of dendritic complexity and improvement in performance of hippocampal behaviors. These studies identify a therapeutically tractable upstream signaling module regulating a wide spectrum of basic mechanisms underlying tauopathies.

  View details for DOI 10.1186/s40478-020-01034-0

  View details for PubMedID 32891185

• Partial Activation of TrkB Receptors Corrects Interneuronal Calcium Channel Dysfunction and Reduces Epileptogenic Activity in Neocortex following Injury. Cerebral cortex (New York, N.Y. : 1991) Gu, F., Parada, I., Yang, T., Longo, F. M., Prince, D. A. 2020

  Abstract

  Decreased GABAergic inhibition due to dysfunction of inhibitory interneurons plays an important role in post-traumatic epileptogenesis. Reduced N-current Ca2+ channel function in GABAergic terminals contributes to interneuronal abnormalities and neural circuit hyperexcitability in the partial neocortical isolation (undercut, UC) model of post-traumatic epileptogenesis. Because brain-derived neurotrophic factor (BDNF) supports the development and maintenance of interneurons, we hypothesized that the activation of BDNF tropomyosin kinase B (TrkB) receptors by a small molecule, TrkB partial agonist, PTX BD4-3 (BD), would correct N channel abnormalities and enhance inhibitory synaptic transmission in UC cortex. Immunocytochemistry (ICC) and western blots were used to quantify N- and P/Q-type channels. We recorded evoked (e)IPSCs and responses to N and P/Q channel blockers to determine the effects of BD on channel function. Field potential recordings were used to determine the effects of BD on circuit hyperexcitability. Chronic BD treatment 1) upregulated N and P/Q channel immunoreactivity in GABAergic terminals; 2) increased the effects of N or P/Q channel blockade on evoked inhibitory postsynaptic currents (eIPSCs); 3) increased GABA release probability and the frequency of sIPSCs; and 4) reduced the incidence of epileptiform discharges in UC cortex. The results suggest that chronic TrkB activation is a promising approach for rescuing injury-induced calcium channel abnormalities in inhibitory terminals, thereby improving interneuronal function and suppressing circuit hyperexcitability.

  View details for DOI 10.1093/cercor/bhz254

  View details for PubMedID 32488246

• Therapeutic Intervention of p75(NTR) With LM11A-31 Protects Against Systemic and Retinal Inflammation And Visual Impairment In A Model of Diabetic Retinopathy El-Remessy, A. B., Mohamed, R., Pearson, L., Longo, F. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2020

  View details for Web of Science ID 000554495703231

• Editorial: Next-Generation Alzheimer's Therapeutics: Leveraging Deep Biology. The journal of prevention of Alzheimer's disease Longo, F. M., Massa, S. M. 2020; 7 (3): 138-139

  View details for DOI 10.14283/jpad.2020.30

  View details for PubMedID 32463062

• Next-generation Alzheimer's Therapeutics: Leveraging Deep Biology JPAD-JOURNAL OF PREVENTION OF ALZHEIMERS DISEASE Longo, F. M., Massa, S. M. 2020

  View details for DOI 10.14283/jpad.2020.30

  View details for Web of Science ID 000530980000001

• Non-Amyloid Approaches to Disease Modification for Alzheimer's Disease: An EU/US CTAD Task Force Report JPAD-JOURNAL OF PREVENTION OF ALZHEIMERS DISEASE Gauthier, S., Aisen, P. S., Cummings, J., Detke, M. J., Longo, F. M., Raman, R., Sabbagh, M., Schneider, L., Tanzi, R., Tariot, P., Weiner, M., Touchon, J., Vellas, B., Abushakra, S., Alam, J., Andrieu, S., Bansal, A., Baudler, M., Bell, J., Beraud, M., Bittner, T., Haeberlein, S., Bullain, S., Cantillon, M., Carrillo, M., Castrillo-Viguera, C., Cheung, I., Coelho, J., Di Giusto, D., Doody, R., Dwyer, J., Egan, M., Ewen, C., Fisher, C., Gold, M., Hampel, H., He, P., Hendrix, S., Henley, D., Irizarry, M., Iwata, A., Iwatsubo, T., Keeley, M., Kerchner, G., Kinney, G., Kolb, H., Kosco-Vilbois, M., Kramer, L., Kurzman, R., Lannfelt, L., Lawson, J., Li, J., Mintun, M., Navikas, V., Novak, G., Osswald, G., Ostrowitzki, S., Porsteinsson, A., Rubino, I., Salloway, S., Schindler, R., Sekiya, H., Selkoe, D., Siemers, E., Sims, J., Sipe, L., Sol, O., Sperling, R., Stephens, A., Streffer, J., Suhy, J., Swanson, C., Tamagnan, G., Teng, E., Tolar, M., Traber, M., Vergallo, A., Von Hehn, C., Vradenburg, G., Walker, J., Wunderlich, G., Yaari, R., Yang, H., Zago, W., Zoda, T., EU US CTAD Task Force 2020

  View details for DOI 10.14283/jpad.2020.18

  View details for Web of Science ID 000523070800001

• Non-Amyloid Approaches to Disease Modification for Alzheimer's Disease: An EU/US CTAD Task Force Report. The journal of prevention of Alzheimer's disease Gauthier, S., Aisen, P. S., Cummings, J., Detke, M. J., Longo, F. M., Raman, R., Sabbagh, M., Schneider, L., Tanzi, R., Tariot, P., Weiner, M., Touchon, J., Vellas, B. 2020; 7 (3): 152-157

  Abstract

  While amyloid-targeting therapies continue to predominate in the Alzheimer's disease (AD) drug development pipeline, there is increasing recognition that to effectively treat the disease it may be necessary to target other mechanisms and pathways as well. In December 2019, The EU/US CTAD Task Force discussed these alternative approaches to disease modification in AD, focusing on tau-targeting therapies, neurotrophin receptor modulation, anti-microbial strategies, and the innate immune response; as well as vascular approaches, aging, and non-pharmacological approaches such as lifestyle intervention strategies, photobiomodulation and neurostimulation. The Task Force proposed a general strategy to accelerate the development of alternative treatment approaches, which would include increased partnerships and collaborations, improved trial designs, and further exploration of combination therapy strategies.

  View details for DOI 10.14283/jpad.2020.18

  View details for PubMedID 32420298

  View details for PubMedCentralID PMC7223540

• Small molecule modulation of the p75 neurotrophin receptor suppresses age- and genotype-associated neurodegeneration in HIV gp120 transgenic mice. Experimental neurology Xie, Y. n., Seawell, J. n., Boesch, E. n., Allen, L. n., Suchy, A. n., Longo, F. M., Meeker, R. B. 2020: 113489

  Abstract

  The persistence of HIV in the central nervous system leads to cognitive deficits in up to 50% of people living with HIV even with systemic suppression by antiretroviral treatment. The interaction of chronic inflammation with age-associated degeneration places these individuals at increased risk of accelerated aging and other neurodegenerative diseases and no treatments are available that effectively halt these processes. The adverse effects of aging and inflammation may be mediated, in part, by an increase in the expression of the p75 neurotrophin receptor (p75NTR) which shifts the balance of neurotrophin signaling toward less protective pathways. To determine if modulation of p75NTR could modify the disease process, we treated HIV gp120 transgenic mice with a small molecule ligand designed to engage p75NTR and downregulate degenerative signaling. Daily treatment with 50 mg/kg LM11A-31 for 4 months suppressed age- and genotype-dependent activation of microglia, reduced expression of p75NTR, increased microtubule associated protein-2 (MAP-2), reduced dendritic varicosities and slowed the loss of parvalbumin immunoreactive neurons in the hippocampus. An age related accumulation of microtubule associated protein Tau was identified in the hippocampus in extracellular clusters that co-expressed p75NTR suggesting a link between Tau and p75NTR. Although the significance of the relationship between p75NTR and Tau is unclear, a decrease in Tau-1 immunoreactivity as gp120 mice entered old age (>16 months) suggests that the Tau may transition to more pathological modifications; a process blocked by LM11A-31. Overall, the effects of LM11A-31 are consistent with strong neuroprotective and anti-inflammatory actions that have significant therapeutic potential.

  View details for DOI 10.1016/j.expneurol.2020.113489

  View details for PubMedID 33007293

• Soluble TREM2 is elevated in Parkinson's disease subgroups with increased CSF tau. Brain : a journal of neurology Wilson, E. N., Swarovski, M. S., Linortner, P. n., Shahid, M. n., Zuckerman, A. J., Wang, Q. n., Channappa, D. n., Minhas, P. S., Mhatre, S. D., Plowey, E. D., Quinn, J. F., Zabetian, C. P., Tian, L. n., Longo, F. M., Cholerton, B. n., Montine, T. J., Poston, K. L., Andreasson, K. I. 2020

  Abstract

  Parkinson's disease is the second most common neurodegenerative disease after Alzheimer's disease and affects 1% of the population above 60 years old. Although Parkinson's disease commonly manifests with motor symptoms, a majority of patients with Parkinson's disease subsequently develop cognitive impairment, which often progresses to dementia, a major cause of morbidity and disability. Parkinson's disease is characterized by α-synuclein accumulation that frequently associates with amyloid-β and tau fibrils, the hallmarks of Alzheimer's disease neuropathological changes; this co-occurrence suggests that onset of cognitive decline in Parkinson's disease may be associated with appearance of pathological amyloid-β and/or tau. Recent studies have highlighted the appearance of the soluble form of the triggering receptor expressed on myeloid cells 2 (sTREM2) receptor in CSF during development of Alzheimer's disease. Given the known association of microglial activation with advancing Parkinson's disease, we investigated whether CSF and/or plasma sTREM2 differed between CSF biomarker-defined Parkinson's disease participant subgroups. In this cross-sectional study, we examined 165 participants consisting of 17 cognitively normal elderly subjects, 45 patients with Parkinson's disease with no cognitive impairment, 86 with mild cognitive impairment, and 17 with dementia. Stratification of subjects by CSF amyloid-β and tau levels revealed that CSF sTREM2 concentrations were elevated in Parkinson's disease subgroups with a positive tau CSF biomarker signature, but not in Parkinson's disease subgroups with a positive CSF amyloid-β biomarker signature. These findings indicate that CSF sTREM2 could serve as a surrogate immune biomarker of neuronal injury in Parkinson's disease.

  View details for DOI 10.1093/brain/awaa021

  View details for PubMedID 32065223

• Oral Administration of the p75 Neurotrophin Receptor Modulator, LM11A-31, Improves Erectile Function in a Mouse Model of Cavernous Nerve Injury. The journal of sexual medicine Yin, G. N., Ock, J. n., Limanjaya, A. n., Minh, N. N., Hong, S. S., Yang, T. n., Longo, F. M., Ryu, J. K., Suh, J. K. 2020

  Abstract

  Radical prostatectomy for prostate cancer can not only induce cavernous nerve injury (CNI), but also causes cavernous hypoxia and cavernous structural changes, which lead to a poor response to phosphodiesterase 5 inhibitors.To investigate the therapeutic effect of oral administration of LM11A-31, a small molecule p75 neurotrophin receptor (p75NTR) ligand and proNGF antagonist, in a mouse model of bilateral CNI, which mimics nerve injury-induced erectile dysfunction after radical prostatectomy.8-week-old male C57BL/6 mice were divided into sham operation and CNI groups. Each group was divided into 2 subgroups: phosphate-buffered saline and LM11A-31 (50 mg/kg/day) being administered once daily starting 3 days before CNI via oral gavage. 2 weeks after CNI, we measured erectile function by electrical stimulation of the bilateral cavernous nerve. The penis was harvested for histologic examination and Western blot analysis. The major pelvic ganglia was harvested and cultured for assays of ex vivo neurite outgrowth.Intracavernous pressure, neurovascular regeneration in the penis, in vivo or ex vivo functional evaluation, and cell survival signaling were measured.Erectile function was decreased in the CNI group (44% of the sham operation group), while administration of LM11A-31 led to a significant improvement of erectile function (70% of the sham operation group) in association with increased neurovascular content, including cavernous endothelial cells, pericytes, and neuronal processes. Immunohistochemical and Western blot analyses showed significantly increased p75NTR expression in the dorsal nerve of CNI mice, which was attenuated by LM11A-31 treatment. Protein expression of active PI3K, AKT, and endothelial nitric oxide synthase was increased, and cell death and c-Jun N-terminal kinase signaling was significantly attenuated after LM11A-31 treatment. Furthermore, LM11A-31 promoted neurite sprouting in cultured major pelvic ganglia after lipopolysaccharide exposure.LM11A-31 may be used as a strategy to treat erectile dysfunction after radical prostatectomy or in men with neurovascular diseases.Unlike biological therapeutics, such as proteins, gene therapies, or stem cells, the clinical application of LM11A-31 would likely be relatively less complex and low cost. Our study has some limitations. Future studies will assess the optimal dosing and duration of the compound. Given its plasma half-life of approximately 1 hour, it is possible that dosing more than once per day will provide added efficacy.Specific inhibition of the proNGF-p75NTR degenerative signaling via oral administration of LM11A-31 represents a novel therapeutic strategy for erectile dysfunction induced by nerve injury. Yin GN, Ock J, Limanjaya A, et al. Oral Administration of the p75 Neurotrophin Receptor Modulator, LM11A-31, Improves Erectile Function in a Mouse Model of Cavernous Nerve Injury. J Sex Med 2020;XX:XXX-XXX.

  View details for DOI 10.1016/j.jsxm.2020.10.015

  View details for PubMedID 33243690

• Modulation of the p75 neurotrophin receptor using LM11A-31 prevents diabetes-induced retinal vascular permeability in mice via inhibition of inflammation and the RhoA kinase pathway DIABETOLOGIA Elshaer, S. L., Alwhaibi, A., Mohamed, R., Lemtalsi, T., Coucha, M., Longo, F. M., El-Remessy, A. B. 2019; 62 (8): 1488–1500

  View details for DOI 10.1007/s00125-019-4885-2

  View details for Web of Science ID 000475698900018

• Nerve Growth Factor Pathobiology During the Progression of Alzheimer's Disease FRONTIERS IN NEUROSCIENCE Mufson, E. J., Counts, S. E., Ginsberg, S. D., Mahady, L., Perez, S. E., Massa, S. M., Longo, F. M., Ikonomovic, M. D. 2019; 13

  View details for DOI 10.3389/fnins.2019.00533

  View details for Web of Science ID 000473285000001

• Methotrexate chemotherapy impairs adaptive myelination through altered BDNF-TrkB signaling Geraghty, A. C., Gibson, E., Ghanem, R., Greene, J., Yang, T., Ni, L., Greenberg, M., Longo, F., Monje, M. WILEY. 2019: E329

  View details for Web of Science ID 000502867402005

• Nerve Growth Factor Pathobiology During the Progression of Alzheimer's Disease. Frontiers in neuroscience Mufson, E. J., Counts, S. E., Ginsberg, S. D., Mahady, L., Perez, S. E., Massa, S. M., Longo, F. M., Ikonomovic, M. D. 2019; 13: 533

  Abstract

  The current review summarizes the pathobiology of nerve growth factor (NGF) and its cognate receptors during the progression of Alzheimer's disease (AD). Both transcript and protein data indicate that cholinotrophic neuronal dysfunction is related to an imbalance between TrkA-mediated survival signaling and the NGF precursor (proNGF)/p75NTR-mediated pro-apoptotic signaling, which may be related to alteration in the metabolism of NGF. Data indicate a spatiotemporal pattern of degeneration related to the evolution of tau pathology within cholinotrophic neuronal subgroups located within the nucleus basalis of Meynert (nbM). Despite these degenerative events the cholinotrophic system is capable of cellular resilience and/or plasticity during the prodromal and later stages of the disease. In addition to neurotrophin dysfunction, studies indicate alterations in epigenetically regulated proteins occur within cholinotrophic nbM neurons during the progression of AD, suggesting a mechanism that may underlie changes in transcript expression. Findings that increased cerebrospinal fluid levels of proNGF mark the onset of MCI and the transition to AD suggests that this proneurotrophin is a potential disease biomarker. Novel therapeutics to treat NGF dysfunction include NGF gene therapy and the development of small molecule agonists for the cognate prosurvival NGF receptor TrkA and antagonists against the pan-neurotrophin p75NTR death receptor for the treatment of AD.

  View details for DOI 10.3389/fnins.2019.00533

  View details for PubMedID 31312116

  View details for PubMedCentralID PMC6613497

• Receptor dependence of BDNF actions in superficial dorsal horn: relation to central sensitization and actions of macrophage colony stimulating factor JOURNAL OF NEUROPHYSIOLOGY Boakye, P. A., Rancic, V., Whitlock, K. H., Simmons, D., Longo, F. M., Ballanyi, K., Smith, P. A. 2019; 121 (6): 2308–22

  View details for DOI 10.1152/jn.00839.2018

  View details for Web of Science ID 000472050000029

• Receptor-dependence of BDNF Actions in Superficial Dorsal Horn; Relation to Central Sensitization and Actions of Macrophage Colony Stimulating Factor 1 (CSF-1). Journal of neurophysiology Boakye, P. A., Rancic, V., Whitlock, K. H., Simmons, D., Longo, F. M., Ballanyi, K., Smith, P. A. 2019

  Abstract

  Peripheral nerve injury elicits an enduring increase in the excitability of the spinal dorsal horn. This change, which contributes to the development of neuropathic pain, is a consequence of release and prolonged exposure of dorsal horn neurons to various neurotrophins and cytokines. We have shown in rats that nerve injury increases excitatory synaptic drive to excitatory neurons but decreases drive to inhibitory neurons. Both effects, which contribute to an increase in dorsal horn excitability, appear to be mediated by microglial-derived BDNF. We have used multiphoton Ca2+ imaging and whole-cell recording of spontaneous EPSC's in defined medium organotypic cultures of GAD67-GFP+ mice spinal cord to determine the receptor dependence of these opposing actions of BDNF. In mice, as in rats, BDNF enhances excitatory transmission onto excitatory neurons. This is mediated via presynaptic TrkB and p75 neurotrophin receptors and exclusively by postsynaptic TrkB. By contrast with findings from rats, in mice BDNF does not decrease excitation of inhibitory neurons. The cytokine, macrophage colony stimulating factor 1 (CSF-1) has also been implicated in the onset of neuropathic pain. Nerve injury provokes its de novo synthesis in primary afferents, its release in spinal cord and activation of microglia. We now show that CSF-1 increases excitatory drive to excitatory neurons via a BDNF-dependent mechanism and decreases excitatory drive to inhibitory neurons via BDNF-independent processes. Our findings complete missing steps in the cascade of events whereby peripheral nerve injury instigates increased dorsal horn excitability in the context of central sensitization and the onset of neuropathic pain.

  View details for PubMedID 30995156

• Early life stress disrupts intestinal homeostasis via NGF-TrkA signaling NATURE COMMUNICATIONS Wong, H., Qin, H., Tsang, S., Zuo, X., Che, S., Chow, C., Li, X., Xiao, H., Zhao, L., Huang, T., Lin, C., Kwan, H., Yang, T., Longo, F. M., Lyu, A., Bian, Z. 2019; 10

  View details for DOI 10.1038/s41467-019-09744-3

  View details for Web of Science ID 000464494100014

• Early life stress disrupts intestinal homeostasis via NGF-TrkA signaling. Nature communications Wong, H. L., Qin, H., Tsang, S. W., Zuo, X., Che, S., Chow, C. F., Li, X., Xiao, H., Zhao, L., Huang, T., Lin, C. Y., Kwan, H. Y., Yang, T., Longo, F. M., Lyu, A., Bian, Z. 2019; 10 (1): 1745

  Abstract

  Early childhood is a critical period for development, and early life stress may increase the risk of gastrointestinal diseases including irritable bowel syndrome (IBS). In rodents, neonatal maternal separation (NMS) induces bowel dysfunctions that resemble IBS. However, the underlying mechanisms remain unclear. Here we show that NMS induces expansion of intestinal stem cells (ISCs) and their differentiation toward secretory lineages including enterochromaffin (EC) and Paneth cells, leading to EC hyperplasia, increased serotonin production, and visceral hyperalgesia. This is reversed by inhibition of nerve growth factor (NGF)-mediated tropomyosin receptor kinase A (TrkA) signalling, and treatment with NGF recapitulates the intestinal phenotype of NMS mice in vivo and in mouse intestinal organoids in vitro. Mechanistically, NGF transactivates Wnt/beta-catenin signalling. NGF and serotonin are positively correlated in the sera of diarrhea-predominant IBS patients. Together, our findings provide mechanistic insights into early life stress-induced intestinal changes that may translate into treatments for gastrointestinal diseases.

  View details for PubMedID 30988299

• Modulation of the p75 neurotrophin receptor suppresses age-related basal forebrain cholinergic neuron degeneration SCIENTIFIC REPORTS Xie, Y., Meeker, R. B., Massa, S. M., Longo, F. M. 2019; 9

  View details for DOI 10.1038/s41598-019-41654-8

  View details for Web of Science ID 000462462800039

• Modulation of the p75 neurotrophin receptor suppresses age-related basal forebrain cholinergic neuron degeneration. Scientific reports Xie, Y., Meeker, R. B., Massa, S. M., Longo, F. M. 2019; 9 (1): 5273

  Abstract

  Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) is linked to cognitive impairment. The p75 neurotrophin receptor (p75NTR) has been proposed to mediate neuronal degeneration in aging. Therefore, we tested the hypothesis that modifying p75NTR function would prevent or reverse aging-related neuronal degeneration using LM11A-31, a small molecule p75NTR modulator that downregulates degenerative and upregulates trophic receptor-associated signaling. Morphological analysis in mice showed loss of BFCN area detectable by 18 months of age. Oral administration of LM11A-31 from age 15 to 18 months resulted in a dose-related preservation of BFCN area and one month of treatment from 17 to 18 months also preserved cell area. To evaluate reversal of established neuronal atrophy, animals were treated from 21 to 25 months of age. Treatment was associated with an increase of cell size to a mean area larger than that observed at 18 months, accompanied by increases in mean MS/VDB neurite length, as well as increased cholinergic fiber density and synaptophysin pre-synaptic marker levels in the hippocampus. These findings support the idea that modulation of p75NTR activity can prevent and potentially reverse age-associated BFCN degeneration. Moreover, this may be achieved therapeutically with orally bioavailable agents such as LM11A-31.

  View details for PubMedID 30918278

• Modulation of the p75 neurotrophin receptor using LM11A-31 prevents diabetes-induced retinal vascular permeability in mice via inhibition of inflammation and the RhoA kinase pathway. Diabetologia Elshaer, S. L., Alwhaibi, A. n., Mohamed, R. n., Lemtalsi, T. n., Coucha, M. n., Longo, F. M., El-Remessy, A. B. 2019

  Abstract

  Breakdown of the inner blood-retinal barrier (BRB) is an early event in the pathogenesis of diabetic macular oedema, that eventually leads to vision loss. We have previously shown that diabetes causes an imbalance of nerve growth factor (NGF) isoforms resulting in accumulation of its precursor proNGF and upregulation of the p75 neurotrophin receptor (p75NTR), with consequent increases in the activation of Ras homologue gene family, member A (RhoA). We also showed that genetic deletion of p75NTR in diabetes preserved the BRB and prevented inflammatory mediators in retinas. This study aims to examine the therapeutic potential of LM11A-31, a small-molecule p75NTR modulator and proNGF antagonist, in preventing diabetes-induced BRB breakdown. The study also examined the role of p75NTR/RhoA downstream signalling in mediating cell permeability.Male C57BL/6 J mice were rendered diabetic using streptozotocin injection. After 2 weeks of diabetes, mice received oral gavage of LM11A-31 (50 mg kg-1 day-1) or saline (NaCl 154 mmol/l) for an additional 4 weeks. BRB breakdown was assessed by extravasation of BSA-AlexaFluor-488. Direct effects of proNGF were examined in human retinal endothelial (HRE) cells in the presence or absence of LM11A-31 or the Rho kinase inhibitor Y-27632.Diabetes triggered BRB breakdown and caused significant increases in circulatory and retinal TNF-α and IL-1β levels. These effects coincided with significant decreases in retinal NGF and increases in vascular endothelial growth factor and proNGF expression, as well as activation of RhoA. Interventional modulation of p75NTR activity through treatment of mouse models of diabetes with LM11A-31 significantly mitigated proNGF accumulation and preserved BRB integrity. In HRE cells, treatment with mutant proNGF (10 ng/ml) triggered increased cell permeability with marked reduction of expression of tight junction proteins, zona occludens-1 (ZO-1) and claudin-5, compared with control, independent of inflammatory mediators or cell death. Modulating p75NTR significantly inhibited proNGF-mediated RhoA activation, occludin phosphorylation (at serine 490) and cell permeability. ProNGF induced redistribution of ZO-1 in the cell wall and formation of F-actin stress fibres; these effects were mitigated by LM11A-31.Targeting p75NTR signalling using LM11A-31, an orally bioavailable receptor modulator, may offer an effective, safe and non-invasive therapeutic strategy for treating macular oedema, a major cause of blindness in diabetes.

  View details for PubMedID 31073629

• Loss of Adaptive Myelination Contributes to Methotrexate Chemotherapy-Related Cognitive Impairment. Neuron Geraghty, A. C., Gibson, E. M., Ghanem, R. A., Greene, J. J., Ocampo, A. n., Goldstein, A. K., Ni, L. n., Yang, T. n., Marton, R. M., Paşca, S. P., Greenberg, M. E., Longo, F. M., Monje, M. n. 2019

  Abstract

  Activity-dependent myelination is thought to contribute to adaptive neurological function. However, the mechanisms by which activity regulates myelination and the extent to which myelin plasticity contributes to non-motor cognitive functions remain incompletely understood. Using a mouse model of chemotherapy-related cognitive impairment (CRCI), we recently demonstrated that methotrexate (MTX) chemotherapy induces complex glial dysfunction for which microglial activation is central. Here, we demonstrate that remote MTX exposure blocks activity-regulated myelination. MTX decreases cortical Bdnf expression, which is restored by microglial depletion. Bdnf-TrkB signaling is a required component of activity-dependent myelination. Oligodendrocyte precursor cell (OPC)-specific TrkB deletion in chemotherapy-naive mice results in impaired cognitive behavioral performance. A small-molecule TrkB agonist rescues both myelination and cognitive impairment after MTX chemotherapy. This rescue after MTX depends on intact TrkB expression in OPCs. Taken together, these findings demonstrate a molecular mechanism required for adaptive myelination that is aberrant in CRCI due to microglial activation.

  View details for DOI 10.1016/j.neuron.2019.04.032

  View details for PubMedID 31122677

• Reduced cognitive deficits after FLASH irradiation of whole mouse brain are associated with less hippocampal dendritic spine loss and neuroinflammation. Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology Simmons, D. A., Lartey, F. M., Schüler, E. n., Rafat, M. n., King, G. n., Kim, A. n., Ko, R. n., Semaan, S. n., Gonzalez, S. n., Jenkins, M. n., Pradhan, P. n., Shih, Z. n., Wang, J. n., von Eyben, R. n., Graves, E. E., Maxim, P. G., Longo, F. M., Loo, B. W. 2019

  Abstract

  To evaluate the impact of ultra-rapid FLASH mouse whole brain irradiation on hippocampal dendritic spines and neuroinflammation, factors associated with cognitive impairment after brain irradiation.We administered 30 Gy whole brain irradiation to C57BL6/J mice in sub-second (FLASH) vs. 240 s conventional delivery time keeping all other parameters constant, using a custom configured clinical linac. Ten weeks post-irradiation, we evaluated spatial and non-spatial object recognition using novel object location and object recognition testing. We measured dendritic spine density by tracing Golgi-stained hippocampal neurons and evaluated neuroinflammation by CD68 immunostaining, a marker of activated microglia, and expression of 10 pro-inflammatory cytokines using a multiplex immunoassay.At ten weeks post-irradiation, compared to unirradiated controls, conventional delivery time irradiation significantly impaired novel object location and recognition tasks whereas the same dose given in FLASH delivery did not. Conventional delivery time, but not FLASH, was associated with significant loss of dendritic spine density in hippocampal apical dendrites, with a similar non-significant trend in basal dendrites. Conventional delivery time was associated with significantly increased CD68-positive microglia compared to controls whereas FLASH was not. Conventional delivery time was associated with significant increases in 5 of 10 pro-inflammatory cytokines in the hippocampus (and non-significant increases in another 3), whereas FLASH was associated with smaller increases in only 3.Reduced cognitive impairment and associated neurodegeneration were observed with FLASH compared to conventional delivery time irradiation, potentially through decreased induction of neuroinflammation, suggesting a promising approach to increasing therapeutic index in radiation therapy of brain tumors.

  View details for DOI 10.1016/j.radonc.2019.06.006

  View details for PubMedID 31253467

• A Small Molecule TrkB Neurotrophin Receptor Partial Agonist as Possible Treatment for Experimental Nonarteritic Anterior Ischemic Optic Neuropathy CURRENT EYE RESEARCH Shariati, M., Kumar, V., Yang, T., Chakraborty, C., Barres, B., Longo, F., Liao, Y. 2018; 43 (12): 1489-1499

  View details for DOI 10.1080/02713683.2018.1508726

  View details for Web of Science ID 000449997800011

• A Small Molecule TrkB Neurotrophin Receptor Partial Agonist as Possible Treatment for Experimental Nonarteritic Anterior Ischemic Optic Neuropathy. Current eye research Ali Shariati, M., Kumar, V., Yang, T., Chakraborty, C., Barres, B. A., Longo, F. M., Liao, Y. J. 2018: 1–11

  Abstract

  PURPOSE: Brain-derived neurotrophic factor (BDNF) and activation of its high affinity receptor tropomyosin kinase (Trk) B promote retinal ganglion cells (RGCs) survival following injury. In this study, we tested the effects of LM22A-4, a small molecule TrkB receptor-specific partial agonist, on RGC survival in vitro and in experimental nonarteritic anterior ischemic optic neuropathy (AION), the most common acute optic neuropathy in those older than 50years.METHODS: We assessed drug effects on immunopanned, cultured RGCs and calculated RGC survival and assessed TrkB receptor activation by mitogen-activated protein (MAP) kinase translocation. To assess effects in vivo, we induced murine AION and treated the animals with one intravitreal injection and three-week systemic treatment. We measured drug effects using serial spectral-domain optical coherence tomography (OCT) and quantified retinal Brn3A+ RGC density three weeks after ischemia.RESULTS: In vitro, LM22A-4 significantly increased the survival of cultured RGCs at day 2 (95% CI control: 8.4-13.6; LM22A-4: 23.7-30.3; BDNF: 24.3-29.9; P≤0.0001), similar to the effect of the endogenous TrkB receptor ligand BDNF. There was also significant nuclear and cytoplasmic translocation of MAP kinase (95% CI control: 0.9-6.8; LM22A-4: 38.8-84.4; BDNF: 64.0-93.0; P=0.0002), a known downstream event of TrkB receptor activation. Following AION, LM22A-4 treatment led to significant preservation of the ganglion cell complex (95% CI: AION-PBS: 66.8-70.7%; AION-LM22A-4: 70.0-73.1; P=0.03) and total retinal thickness (95% CI: AION-PBS: 185-196%; AION-LM22A-4: 195-203; P=0.002) as measured by OCT compared with non-treated eyes. There was also significant rescue of the Brn3A+ RGC density on morphometric analysis of whole mount retinae (95% CI control: 2360-2629; AION-PBS: 1647-2008 cells/mm2; AION-LM22A-4: 1958-2216 cells/mm2; P=0.02).CONCLUSIONS: TrkB receptor partial agonist LM22A-4 promoted survival of cultured RGCs in vitro by TrkB receptor activation, and treatment in vivo led to increased survival of RGCs after optic nerve ischemia, providing support that LM22A-4 may be effective therapy to treat ischemic optic neuropathy.ABBREVIATIONS: AION: anterior ischemic optic neuropathy, BDNF: Brain-derived neurotrophic factor, GCC: ganglion cell complex, MAP: mitogen-activated protein, OCT: spectral-domain optical coherence tomography, OD: right eye, ON: optic nerve, ONH: optic nerve head, OS: left eye, RGC: retinal ganglion cell; Trk: tropomyosin kinase.

  View details for PubMedID 30273053

• Alzheimer's associated amyloid and tau deposition co-localizes with a homeostatic myelin repair pathway in two mouse models of post-stroke mixed dementia ACTA NEUROPATHOLOGICA COMMUNICATIONS Nguyen, T. V., Hayes, M., Zbesko, J. C., Frye, J. B., Congrove, N. R., Belichenko, N. P., McKay, B. S., Longo, F. M., Doyle, K. P. 2018; 6: 100

  Abstract

  The goal of this study was to determine the chronic impact of stroke on the manifestation of Alzheimer's disease (AD) related pathology and behavioral impairments in mice. To accomplish this goal, we used two distinct models. First, we experimentally induced ischemic stroke in aged wildtype (wt) C57BL/6 mice to determine if stroke leads to the manifestation of AD-associated pathological β-amyloid (Aβ) and tau in aged versus young adult wt mice. Second, we utilized a transgenic (Tg) mouse model of AD (hAPP-SL) to determine if stroke leads to the worsening of pre-existing AD pathology, as well as the development of pathology in brain regions not typically expressed in AD Tg mice. In the wt mice, there was delayed motor recovery and an accelerated development of cognitive deficits in aged mice compared to young adult mice following stroke. This corresponded with increased brain atrophy, increased cholinergic degeneration, and a focal increase of Aβ in areas of axonal degeneration in the ipsilateral hemisphere of the aged animals. By contrast, in the hAPP-SL mice, we found that ischemia induced aggravated behavioral deficits in conjunction with a global increase in Aβ, tau, and cholinergic pathology compared to hAPP-SL mice that underwent a sham stroke procedure. With regard to a potential mechanism, in both models, we found that the stroke-induced Aβ and tau deposits co-localized with increased levels of β-secretase 1 (BACE1), along with its substrate, neuregulin 1 (NGR1) type III, both of which are proteins integral for myelin repair. Based on these findings, we propose that the chronic sequelae of stroke may be ratcheting-up a myelin repair pathway, and that the consequent increase in BACE1 could be causing an inadvertent cleavage of its alternative substrate, AβPP, resulting in greater Aβ seeding and pathogenesis.

  View details for PubMedID 30249297

• Unsolicited Patient Complaints Identify Physicians with Evidence of Neurocognitive Disorders AMERICAN JOURNAL OF GERIATRIC PSYCHIATRY Cooper, W. O., Martinez, W., Domenico, H. J., Callahan, S., Kirkby, B. P., Finlayson, A. R., Foster, J. J., Johnson, T. M., Longo, F. M., Merrill, D. G., Jacobs, M. L., Pichert, J. W., Catron, T. F., Moore, I. N., Webb, L. E., Karrass, J., Hickson, G. B. 2018; 26 (9): 927–36

  Abstract

  Determine whether words contained in unsolicited patient complaints differentiate physicians with and without neurocognitive disorders (NCD).We conducted a nested case-control study using data from 144 healthcare organizations that participate in the Patient Advocacy Reporting System program. Cases (physicians with probable or possible NCD) and two comparison groups of 60 physicians each (matched for age/sex and site/number of unsolicited patient complaints) were identified from 33,814 physicians practicing at study sites. We compared the frequency of words in patient complaints related to an NCD diagnostic domain between cases and our two comparison groups.Individual words were all statistically more likely to appear in patient complaints for cases (73% of cases had at least one such word) compared to age/sex matched (8%, p < 0.001 using Pearson's χ2 test, χ2 = 30.21, df = 1) and site/complaint matched comparisons (18%, p < 0.001 using Pearson's χ2 test, χ2 = 17.51, df = 1). Cases were significantly more likely to have at least one complaint with any word describing NCD than the two comparison groups combined (conditional logistic model adjusted odds ratio 20.0 [95% confidence interval 4.9-81.7]).Analysis of words in unsolicited patient complaints found that descriptions of interactions with physicians with NCD were significantly more likely to include words from one of the diagnostic domains for NCD than were two different comparison groups. Further research is needed to understand whether patients might provide information for healthcare organizations interested in identifying professionals with evidence of cognitive impairment.

  View details for PubMedID 30146001

• TSPO-PET imaging using [F-18]PBR06 is a potential translatable biomarker for treatment response in Huntington's disease: preclinical evidence with the p75(NTR) ligand LM11A-31 HUMAN MOLECULAR GENETICS Simmons, D. A., James, M. L., Belichenko, N. P., Semaan, S., Condon, C., Kuan, J., Shuhendler, A. J., Miao, Z., Chin, F. T., Longo, F. M. 2018; 27 (16): 2893–2912

  View details for DOI 10.1093/hmg/ddy202

  View details for Web of Science ID 000441102800010

• TSPO-PET Imaging Using [18F]PBR06 is a Potential Translatable Biomarker for Treatment Response in Huntington's Disease: Preclinical Evidence with the p75NTR Ligand LM11A-31. Human molecular genetics Simmons, D. A., James, M. L., Belichenko, N. P., Semaan, S., Condon, C., Kuan, J., Shuhendler, A. J., Miao, Z., Chin, F. T., Longo, F. M. 2018

  Abstract

  Huntington's Disease (HD) is an inherited neurodegenerative disorder that has no cure. HD therapeutic development would benefit from a non-invasive translatable biomarker to track disease progression and treatment response. A potential biomarker is using positron emission tomography (PET) imaging with a translocator protein 18kDa (TSPO) radiotracer to detect microglial activation, a key contributor to HD pathogenesis. The ability of TSPO-PET to identify microglial activation in HD mouse models, essential for a translatable biomarker, or therapeutic efficacy in HD patients or mice is unknown. Thus, this study assessed the feasibility of utilizing PET imaging with the TSPO tracer, [18F]PBR06, to detect activated microglia in multiple HD mouse models and to monitor response to treatment with LM11A-31, a p75NTR ligand known to reduce neuroinflammation in HD mice. [18F]PBR06-PET detected microglial activation in striatum, cortex and hippocampus of vehicle-treated R6/2 mice at a late disease stage and, notably, also in early and mid-stage symptomatic BACHD mice. After oral administration of LM11A-31 to R6/2 and BACHD mice, [18F]PBR06-PET discerned the reductive effects of LM11A-31 on neuroinflammation in both HD mouse models. [18F]PBR06-PET signal had a spatial distribution similar to ex vivo brain autoradiography and correlated with microglial activation markers: increased IBA-1 and TSPO immunostaining/blotting and striatal levels of cytokines IL-6 and TNFalpha. These results suggest [18F]PBR06-PET as a surrogate marker of therapeutic efficacy in HD mice with high potential as a translatable biomarker for preclinical and clinical HD trials.

  View details for PubMedID 29860333

• Partial TrkB receptor activation suppresses cortical epileptogenesis through actions on parvalbumin interneurons NEUROBIOLOGY OF DISEASE Gu, F., Parada, I., Yang, T., Longo, F. M., Prince, D. A. 2018; 113: 45–58

  Abstract

  Post-traumatic epilepsy is one of the most common and difficult to treat forms of acquired epilepsy worldwide. Currently, there is no effective way to prevent post-traumatic epileptogenesis. It is known that abnormalities of interneurons, particularly parvalbumin-containing interneurons, play a critical role in epileptogenesis following traumatic brain injury. Thus, enhancing the function of existing parvalbumin interneurons might provide a logical therapeutic approach to prevention of post-traumatic epilepsy. The known positive effects of brain-derived neurotrophic factor on interneuronal growth and function through activation of its receptor tropomyosin receptor kinase B, and its decrease after traumatic brain injury, led us to hypothesize that enhancing trophic support might improve parvalbumin interneuronal function and decrease epileptogenesis. To test this hypothesis, we used the partial neocortical isolation ('undercut', UC) model of posttraumatic epileptogenesis in mature rats that were treated for 2 weeks, beginning on the day of injury, with LM22A-4, a newly designed partial agonist at the tropomyosin receptor kinase B. Effects of treatment were assessed with Western blots to measure pAKT/AKT; immunocytochemistry and whole cell patch clamp recordings to examine functional and structural properties of GABAergic interneurons; field potential recordings of epileptiform discharges in vitro; and video-EEG recordings of PTZ-induced seizures in vivo. Results showed that LM22A-4 treatment 1) increased pyramidal cell perisomatic immunoreactivity for VGAT, GAD65 and parvalbumin; 2) increased the density of close appositions of VGAT/gephyrin immunoreactive puncta (putative inhibitory synapses) on pyramidal cell somata; 3) increased the frequency of mIPSCs in pyramidal cells; and 4) decreased the incidence of spontaneous and evoked epileptiform discharges in vitro. 5) Treatment of rats with PTX BD4-3, another partial TrkB receptor agonist, reduced the incidence of bicuculline-induced ictal episodes in vitro and PTZ induced electrographic and behavioral ictal episodes in vivo. 6) Inactivation of TrkB receptors in undercut TrkBF616A mice with 1NMPP1 abolished both LM22A-4-induced effects on mIPSCs and on increased perisomatic VGAT-IR. Results indicate that chronic activation of the tropomyosin receptor kinase B by a partial agonist after cortical injury can enhance structural and functional measures of GABAergic inhibition and suppress posttraumatic epileptogenesis. Although the full agonist effects of brain-derived neurotrophic factor and tropomyosin receptor kinase B activation in epilepsy models have been controversial, the present results indicate that such trophic activation by a partial agonist may potentially serve as an effective therapeutic option for prophylactic treatment of posttraumatic epileptogenesis, and treatment of other neurological and psychiatric disorders whose pathogenesis involves impaired parvalbumin interneuronal function.

  View details for PubMedID 29408225

• Glial scars are permeable to the neurotoxic environment of chronic stroke infarcts NEUROBIOLOGY OF DISEASE Zbesko, J. C., Nguyen, T. V., Yang, T., Frye, J., Hussain, O., Hayes, M., Chung, A., Day, W., Stepanovic, K., Krumberger, M., Mona, J., Longo, F. M., Doyle, K. P. 2018; 112: 63–78

  Abstract

  Following stroke, the damaged tissue undergoes liquefactive necrosis, a stage of infarct resolution that lasts for months although the exact length of time is currently unknown. One method of repair involves reactive astrocytes and microglia forming a glial scar to compartmentalize the area of liquefactive necrosis from the rest of the brain. The formation of the glial scar is a critical component of the healing response to stroke, as well as other central nervous system (CNS) injuries. The goal of this study was to evaluate the toxicity of the extracellular fluid present in areas of liquefactive necrosis and determine how effectively it is segregated from the remainder of the brain. To accomplish this goal, we used a mouse model of stroke in conjunction with an extracellular fluid toxicity assay, fluorescent and electron microscopy, immunostaining, tracer injections into the infarct, and multiplex immunoassays. We confirmed that the extracellular fluid present in areas of liquefactive necrosis following stroke is toxic to primary cortical and hippocampal neurons for at least 7 weeks following stroke, and discovered that although glial scars are robust physical and endocytic barriers, they are nevertheless permeable. We found that molecules present in the area of liquefactive necrosis can leak across the glial scar and are removed by a combination of paravascular clearance and microglial endocytosis in the adjacent tissue. Despite these mechanisms, there is delayed atrophy, cytotoxic edema, and neuron loss in regions adjacent to the infarct for weeks following stroke. These findings suggest that one mechanism of neurodegeneration following stroke is the failure of glial scars to impermeably segregate areas of liquefactive necrosis from surviving brain tissue.

  View details for PubMedID 29331263

• Microglial complement receptor 3 regulates brain A beta levels through secreted proteolytic activity JOURNAL OF EXPERIMENTAL MEDICINE Czirr, E., Castello, N. A., Mosher, K. I., Castellano, J. M., Hinkson, I. V., Lucin, K. M., Baeza-Raja, B., Ryu, J. K., Li, L., Farina, S. N., Belichenko, N. P., Longo, F. M., Akassoglou, K., Britschgi, M., Cirrito, J. R., Wyss-Coray, T. 2017; 214 (4): 1081-1092

  Abstract

  Recent genetic evidence supports a link between microglia and the complement system in Alzheimer's disease (AD). In this study, we uncovered a novel role for the microglial complement receptor 3 (CR3) in the regulation of soluble β-amyloid (Aβ) clearance independent of phagocytosis. Unexpectedly, ablation of CR3 in human amyloid precursor protein-transgenic mice results in decreased, rather than increased, Aβ accumulation. In line with these findings, cultured microglia lacking CR3 are more efficient than wild-type cells at degrading extracellular Aβ by secreting enzymatic factors, including tissue plasminogen activator. Furthermore, a small molecule modulator of CR3 reduces soluble Aβ levels and Aβ half-life in brain interstitial fluid (ISF), as measured by in vivo microdialysis. These results suggest that CR3 limits Aβ clearance from the ISF, illustrating a novel role for CR3 and microglia in brain Aβ metabolism and defining a potential new therapeutic target in AD.

  View details for DOI 10.1084/jem.20162011

  View details for Web of Science ID 000398051100015

  View details for PubMedID 28298456

• [F-18]GE-180 PET Detects Reduced Microglia Activation After LM11A-31 Therapy in a Mouse Model of Alzheimer's Disease THERANOSTICS James, M. L., Belichenko, N. P., Shuhendler, A. J., Hoehne, A., Andrews, L. E., Condon, C., Nguyen, T. V., Reiser, V., Jones, P., Trigg, W., Rao, J., Gambhir, S. S., Longo, F. M. 2017; 7 (6): 1422-1436

  Abstract

  Microglial activation is a key pathological feature of Alzheimer's disease (AD). PET imaging of translocator protein 18 kDa (TSPO) is a strategy to detect microglial activation in vivo. Here we assessed flutriciclamide ([(18)F]GE-180), a new second-generation TSPO-PET radiotracer, for its ability to monitor response to LM11A-31, a novel AD therapeutic in clinical trials. AD mice displaying pathology were treated orally with LM11A-31 for 3 months. Subsequent [(18)F]GE-180-PET imaging revealed significantly lower signal in cortex and hippocampus of LM11A-31-treated AD mice compared to those treated with vehicle, corresponding with decreased levels of TSPO immunostaining and microglial Iba1 immunostaining. In addition to detecting decreased microglial activation following LM11A-31 treatment, [(18)F]GE-180 identified activated microglia in AD mice with greater sensitivity than another second-generation TSPO radiotracer, [(18)F]PBR06. Together, these data demonstrate the promise of [(18)F]GE-180 as a potentially sensitive tool for tracking neuroinflammation in AD mice and for monitoring therapeutic modulation of microglial activation.

  View details for DOI 10.7150/thno.17666

  View details for PubMedID 28529627

• A small-molecule TrkB ligand restores hippocampal synaptic plasticity and object location memory in Rett syndrome mice. Disease models & mechanisms Li, W. n., Bellot-Saez, A. n., Phillips, M. L., Yang, T. n., Longo, F. M., Pozzo-Miller, L. n. 2017; 10 (7): 837–45

  Abstract

  Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in methyl-CpG-binding protein-2 (MECP2), a transcriptional regulator of many genes, including brain-derived neurotrophic factor (BDNF). BDNF levels are reduced in RTT autopsy brains and in multiple brain areas of Mecp2-deficient mice. Furthermore, experimental interventions that increase BDNF levels improve RTT-like phenotypes in Mecp2 mutant mice. Here, we characterized the actions of a small-molecule ligand of the BDNF receptor TrkB in hippocampal function in Mecp2 mutant mice. Systemic treatment of female Mecp2 heterozygous (HET) mice with LM22A-4 for 4 weeks improved hippocampal-dependent object location memory and restored hippocampal long-term potentiation (LTP). Mechanistically, LM22A-4 acts to dampen hyperactive hippocampal network activity, reduce the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs), and reduce the frequency of spontaneous tetrodotoxin-resistant Ca2+ signals in Mecp2 mutant hippocampal neurons, making them comparable to those features observed in wild-type neurons. Together, these observations indicate that LM22A-4 is a promising therapeutic candidate for the treatment of hippocampal dysfunction in RTT.

  View details for PubMedID 28679669

• A small molecule p75NTR ligand normalizes signalling and reduces Huntington's disease phenotypes in R6/2 and BACHD mice. Human molecular genetics Simmons, D. A., Belichenko, N. P., Ford, E. C., Semaan, S., Monbureau, M., Aiyaswamy, S., Holman, C. M., Condon, C., Shamloo, M., Massa, S. M., Longo, F. M. 2016; 25 (22): 4920-4938

  View details for DOI 10.1093/hmg/ddw316

  View details for PubMedID 28171570

  View details for PubMedCentralID PMC5418739

• Neurotrophin receptor signaling as a therapeutic target for Huntington's Disease. CNS & neurological disorders drug targets Simmons, D. A., Longo, F. M., Massa, S. M. 2016: -?

  Abstract

  Effective non-genetic disease modifying treatments for Huntington's disease (HD) will necessarily target multiple diverse neurodegenerative processes triggered by mutant huntingtin. Neurotrophin receptors are well-positioned for this task as they regulate signaling pathways that largely overlap with signaling networks contributing to HD-related synaptic dysfunction, glial activation, excitotoxicity, and other degenerative processes. This review will discuss the contributions of disrupted neurotrophin receptor-related signaling to primary HD neuropathologies, and prospects for harnessing this signaling to develop therapeutics to counteract HD degenerative mechanisms. Application of the native protein ligands has been challenging pharmacologically, but progress has been made with the advent of small molecule compounds that can selectively bind to and activate specific Trk receptors or p75NTR to promote trophic and/or inhibit degenerative signaling in cell populations preferentially affected in HD.

  View details for PubMedID 27823570

• A small molecule TrkB/TrkC neurotrophin receptor co-activator with distinctive effects on neuronal survival and process outgrowth. Neuropharmacology Yang, T., Massa, S. M., Tran, K. C., Simmons, D. A., Rajadas, J., Zeng, A. Y., Jang, T., Carsanaro, S., Longo, F. M. 2016; 110: 343-361

  Abstract

  Neurotrophin (NT) receptors are coupled to numerous signaling networks that play critical roles in neuronal survival and plasticity. Several non-peptide small molecule ligands have recently been reported that bind to and activate specific tropomyosin-receptor-kinase (Trk) NT receptors, stimulate their downstream signaling, and cause biologic effects similar to, though not completely overlapping, those of the native NT ligands. Here, in silico screening, coupled with low-throughput neuronal survival screening, identified a compound, LM22B-10, that, unlike prior small molecule Trk ligands, binds to and activates TrkB as well as TrkC. LM22B-10 increased cell survival and strongly accelerated neurite outgrowth, superseding the effects of brain-derived neurotrophic factor (BDNF), NT-3 or the two combined. Additionally, unlike the NTs, LM22B-10 supported substantial early neurite outgrowth in the presence of inhibiting glycoproteins. Examination of the mechanisms of these actions suggested contributions of the activation of both Trks and differential interactions with p75(NTR), as well as a requirement for involvement of the Trk extracellular domain. In aged mice, LM22B-10 activated hippocampal and striatal TrkB and TrkC, and their downstream signaling, and increased hippocampal dendritic spine density. Thus, LM22B-10 may constitute a new tool for the study of TrkB and TrkC signaling and their interactions with p75(NTR), and provides groundwork for the development of ligands that stimulate unique combinations of Trk receptors and activity patterns for application to selected neuronal populations and deficits present in various disease states.

  View details for DOI 10.1016/j.neuropharm.2016.06.015

  View details for PubMedID 27334657

• The Neurotrophic Factor Receptor p75 in the Rat Dorsolateral Striatum Drives Excessive Alcohol Drinking. journal of neuroscience Darcq, E., Morisot, N., Phamluong, K., Warnault, V., Jeanblanc, J., Longo, F. M., Massa, S. M., Ron, D. 2016; 36 (39): 10116-10127

  Abstract

  Brain-derived neurotrophic factor (BDNF) signaling in the dorsolateral striatum (DLS) keeps alcohol intake in moderation. For example, activation of the BDNF receptor tropomyosin receptor kinase B (TrkB) in the DLS reduces intake in rats that consume moderate amounts of alcohol. Here, we tested whether long-term excessive consumption of alcohol produces neuroadaptations in BDNF signaling in the rat DLS. We found that BDNF was no longer able to gate alcohol self-administration after a history of repeated cycles of binge alcohol drinking and withdrawal. We then elucidated the possible neuroadaptations that could block the ability of BDNF to keep consumption of alcohol in moderation. We report that intermittent access to 20% alcohol in a two-bottle choice paradigm that models excessive alcohol drinking produces a mobilization of DLS p75 neurotrophin receptor (p75NTR), whose activities oppose those of the Trk receptors, including TrkB. These neuroadaptations were not observed in the DLS of rats exposed to continuous access to 10% alcohol or in rats consuming sucrose. Furthermore, short hairpin RNA (shRNA)-mediated knockdown of the p75NTR gene in the DLS, as well as intra-DLS infusion or systemic administration of the p75NTR modulator, LM11A-31, significantly reduced binge drinking of alcohol. Together, our results suggest that excessive alcohol consumption produces a change in BDNF signaling in the DLS, which is mediated by the recruitment of p75NTR. Our data also imply that modulators of p75NTR signaling could be developed as medications for alcohol abuse disorders.Neuroadaptations gate or drive excessive, compulsive alcohol drinking. We previously showed that brain-derived neurotrophic factor and its receptor, TrkB, in the dorsolateral striatum (DLS), are part of an endogenous system that keeps alcohol drinking in moderation. Here, we show that a history of excessive alcohol intake produces neuroadaptations in the DLS that preclude BDNF's ability to gate alcohol self-administration in rats by the recruitment of the low-affinity neurotrophin receptor, p75NTR, whose activities opposes those of the Trk receptors. Finally, we show that the administration of the p75NTR modulator, LM11A-31, significantly reduces excessive alcohol intake suggesting that the drug may be developed as a new treatment for alcohol abuse disorders.

  View details for DOI 10.1523/JNEUROSCI.4597-14.2016

  View details for PubMedID 27683907

  View details for PubMedCentralID PMC5039257

• A small molecule p75NTR ligand normalizes signalling and reduces Huntington's disease phenotypes in R6/2 and BACHD mice. Human molecular genetics Simmons, D. A., Belichenko, N. P., Ford, E. C., Semaan, S., Monbureau, M., Aiyaswamy, S., Holman, C. M., Condon, C., Shamloo, M., Massa, S. M., Longo, F. M. 2016

  Abstract

  Decreases in the ratio of neurotrophic versus neurodegenerative signaling play a critical role in Huntington's disease (HD) pathogenesis and recent evidence suggests that the p75 neurotrophin receptor (NTR) contributes significantly to disease progression. p75(NTR) signaling intermediates substantially overlap with those promoting neuronal survival and synapse integrity and with those affected by the mutant huntingtin (muHtt) protein. MuHtt increases p75(NTR)-associated deleterious signaling and decreases survival signaling suggesting that p75(NTR) could be a valuable therapeutic target. This hypothesis was investigated by examining the effects of an orally bioavailable, small molecule p75(NTR) ligand, LM11A-31, on HD-related neuropathology in HD mouse models (R6/2, BACHD). LM11A-31 restored striatal AKT and other pro-survival signaling while inhibiting c-Jun kinase (JNK) and other degenerative signaling. Normalizing p75(NTR) signaling with LM11A-31 was accompanied by reduced Htt aggregates and striatal cholinergic interneuron degeneration as well as extended survival in R6/2 mice. The p75(NTR) ligand also decreased inflammation, increased striatal and hippocampal dendritic spine density, and improved motor performance and cognition in R6/2 and BACHD mice. These results support small molecule modulation of p75(NTR) as an effective HD therapeutic strategy. LM11A-31 has successfully completed Phase I safety and pharmacokinetic clinical trials and is therefore a viable candidate for clinical studies in HD.

  View details for PubMedID 27638888

• The BDNF Valine 68 to Methionine Polymorphism Increases Compulsive Alcohol Drinking in Mice That Is Reversed by Tropomyosin Receptor Kinase B Activation BIOLOGICAL PSYCHIATRY Warnault, V., Darcq, E., Morisot, N., Phamluong, K., Wilbrecht, L., Massa, S. M., Longo, F. M., Ron, D. 2016; 79 (6): 463-473

  Abstract

  The valine 66 to methionine (Met) polymorphism within the brain-derived neurotrophic factor (BDNF) sequence reduces activity-dependent BDNF release and is associated with psychiatric disorders in humans. Alcoholism is one of the most prevalent psychiatric diseases. Here, we tested the hypothesis that this polymorphism increases the severity of alcohol abuse disorders.We generated transgenic mice carrying the mouse homolog of the human Met66BDNF allele (Met68BDNF) and used alcohol-drinking paradigms in combination with viral-mediated gene delivery and pharmacology.We found that Met68BDNF mice consumed excessive amounts of alcohol and continued to drink despite negative consequences, a hallmark of addiction. Importantly, compulsive alcohol intake was reversed by overexpression of the wild-type valine68BDNF allele in the ventromedial prefrontal cortex of the Met68BDNF mice or by systemic administration of the tropomyosin receptor kinase B agonist, LM22A-4.Our findings suggest that carrying this BDNF allele increases the risk of developing uncontrolled and excessive alcohol drinking that can be reversed by directly activating the BDNF receptor, tropomyosin receptor kinase B. Importantly, this work identifies a potential therapeutic strategy for the treatment of compulsive alcohol drinking in humans carrying the Met66BDNF allele.

  View details for DOI 10.1016/j.biopsych.2015.06.007

  View details for Web of Science ID 000370023900008

  View details for PubMedID 26204799

  View details for PubMedCentralID PMC4676961

• Novel p75 neurotrophin receptor ligand stabilizes neuronal calcium, preserves mitochondrial movement and protects against HIV associated neuropathogenesis EXPERIMENTAL NEUROLOGY Meeker, R. B., Poulton, W., Clary, G., Schriver, M., Longo, F. M. 2016; 275: 182-198

  Abstract

  Human immunodeficiency virus (HIV) rapidly penetrates into the brain and establishes a persistent infection of macrophages/microglia. Activation of these cells by HIV results in the secretion of soluble factors that destabilize neuronal calcium homeostasis, encourage oxidative stress and result in neural damage. This damage is thought to underlie the cognitive-motor dysfunction that develops in many HIV-infected patients. Studies have suggested that neurotrophins may protect neurons from the toxic effects of HIV-associated proteins. To better understand the pathogenic mechanisms and the neuroprotective potential of neurotrophin ligands, we evaluated neuronal damage, calcium homeostasis and mitochondrial functions after exposure of cultured rat neurons directly to HIV gp120 or to conditioned medium from human monocyte-derived macrophages treated with gp120. We then assessed the ability of a new non-peptide p75 neurotrophin receptor ligand, LM11A-31, to stabilize calcium homeostasis and prevent the development of pathology. Each toxic challenge resulted in a delayed accumulation of intracellular calcium coupled to a decrease in the rate of calcium clearance from the cell. The delayed calcium accumulation correlated with the development of focal dendritic swellings (beading), cytoskeletal damage and impaired movement of mitochondria. Addition of LM11A-31 to the cultures at nanomolar concentrations eliminated cell death, significantly reduced the pathology, suppressed the delayed accumulation of calcium and restored mitochondrial movements. The potent neuroprotection and the stabilization of calcium homeostasis indicate that LM11A-31 may have excellent potential for the treatment of HIV-associated neurodegeneration.

  View details for DOI 10.1016/j.expneurol.2015.09.012

  View details for Web of Science ID 000367420500020

  View details for PubMedCentralID PMC4688079

• Neuroprotective Strategies for Alzheimer's Disease Prevention and Therapy DEVELOPING THERAPEUTICS FOR ALZHEIMER'S DISEASE: PROGRESS AND CHALLENGES Simmons, D. A., Yang, T., Massa, S. M., Longo, F. M., Wolfe, M. S. 2016: 437-458

  View details for DOI 10.1016/B978-0-12-802173-6.00016-2

  View details for Web of Science ID 000471782300018

• Novel p75 neurotrophin receptor ligand stabilizes neuronal calcium, preserves mitochondrial movement and protects against HIV associated neuropathogenesis. Experimental neurology Meeker, R. B., Poulton, W., Clary, G., Schriver, M., Longo, F. M. 2016; 275 Pt 1: 182-98

  Abstract

  Human immunodeficiency virus (HIV) rapidly penetrates into the brain and establishes a persistent infection of macrophages/microglia. Activation of these cells by HIV results in the secretion of soluble factors that destabilize neuronal calcium homeostasis, encourage oxidative stress and result in neural damage. This damage is thought to underlie the cognitive-motor dysfunction that develops in many HIV-infected patients. Studies have suggested that neurotrophins may protect neurons from the toxic effects of HIV-associated proteins. To better understand the pathogenic mechanisms and the neuroprotective potential of neurotrophin ligands, we evaluated neuronal damage, calcium homeostasis and mitochondrial functions after exposure of cultured rat neurons directly to HIV gp120 or to conditioned medium from human monocyte-derived macrophages treated with gp120. We then assessed the ability of a new non-peptide p75 neurotrophin receptor ligand, LM11A-31, to stabilize calcium homeostasis and prevent the development of pathology. Each toxic challenge resulted in a delayed accumulation of intracellular calcium coupled to a decrease in the rate of calcium clearance from the cell. The delayed calcium accumulation correlated with the development of focal dendritic swellings (beading), cytoskeletal damage and impaired movement of mitochondria. Addition of LM11A-31 to the cultures at nanomolar concentrations eliminated cell death, significantly reduced the pathology, suppressed the delayed accumulation of calcium and restored mitochondrial movements. The potent neuroprotection and the stabilization of calcium homeostasis indicate that LM11A-31 may have excellent potential for the treatment of HIV-associated neurodegeneration.

  View details for DOI 10.1016/j.expneurol.2015.09.012

  View details for PubMedID 26424436

  View details for PubMedCentralID PMC4688079

• B-Lymphocyte-Mediated Delayed Cognitive Impairment following Stroke. journal of neuroscience Doyle, K. P., Quach, L. N., Solé, M., Axtell, R. C., Nguyen, T. V., Soler-Llavina, G. J., Jurado, S., Han, J., Steinman, L., Longo, F. M., Schneider, J. A., Malenka, R. C., Buckwalter, M. S. 2015; 35 (5): 2133-2145

  Abstract

  Each year, 10 million people worldwide survive the neurologic injury associated with a stroke. Importantly, stroke survivors have more than twice the risk of subsequently developing dementia compared with people who have never had a stroke. The link between stroke and the later development of dementia is not understood. There are reports of oligoclonal bands in the CSF of stroke patients, suggesting that in some people a B-lymphocyte response to stroke may occur in the CNS. Therefore, we tested the hypothesis that a B-lymphocyte response to stroke could contribute to the onset of dementia. We discovered that, in mouse models, activated B-lymphocytes infiltrate infarcted tissue in the weeks after stroke. B-lymphocytes undergo isotype switching, and IgM, IgG, and IgA antibodies are found in the neuropil adjacent to the lesion. Concurrently, mice develop delayed deficits in LTP and cognition. Genetic deficiency, and the pharmacologic ablation of B-lymphocytes using an anti-CD20 antibody, prevents the appearance of delayed cognitive deficits. Furthermore, immunostaining of human postmortem tissue revealed that a B-lymphocyte response to stroke also occurs in the brain of some people with stroke and dementia. These data suggest that some stroke patients may develop a B-lymphocyte response to stroke that contributes to dementia, and is potentially treatable with FDA-approved drugs that target B cells.

  View details for DOI 10.1523/JNEUROSCI.4098-14.2015

  View details for PubMedID 25653369

• PET Imaging of Translocator Protein (18 kDa) in a Mouse Model of Alzheimer's Disease Using N-(2,5-Dimethoxybenzyl)-2-18F-Fluoro-N-(2-Phenoxyphenyl)Acetamide. Journal of nuclear medicine : official publication, Society of Nuclear Medicine James, M. L., Belichenko, N. P., Nguyen, T. V., Andrews, L. E., Ding, Z., Liu, H., Bodapati, D., Arksey, N., Shen, B., Cheng, Z., Wyss-Coray, T., Gambhir, S. S., Longo, F. M., Chin, F. T. 2015; 56 (2): 311-316

  Abstract

  Herein we aimed to evaluate the utility of N-(2,5-dimethoxybenzyl)-2-(18)F-fluoro-N-(2-phenoxyphenyl)acetamide ((18)F-PBR06) for detecting alterations in translocator protein (TSPO) (18 kDa), a biomarker of microglial activation, in a mouse model of Alzheimer's disease (AD).Wild-type (wt) and AD mice (i.e., APP(L/S)) underwent (18)F-PBR06 PET imaging at predetermined time points between the ages of 5-6 and 15-16 mo. MR images were fused with PET/CT data to quantify (18)F-PBR06 uptake in the hippocampus and cortex. Ex vivo autoradiography and TSPO/CD68 immunostaining were also performed using brain tissue from these mice.PET images showed significantly higher accumulation of (18)F-PBR06 in the cortex and hippocampus of 15- to 16-mo-old APP(L/S) mice than age-matched wts (cortex/muscle: 2.43 ± 0.19 vs. 1.55 ± 0.15, P < 0.005; hippocampus/muscle: 2.41 ± 0.13 vs. 1.55 ± 0.12, P < 0.005). And although no significant difference was found between wt and APP(L/S) mice aged 9-10 mo or less using PET (P = 0.64), we were able to visualize and quantify a significant difference in (18)F-PBR06 uptake in these mice using autoradiography (cortex/striatum: 1.13 ± 0.04 vs. 0.96 ± 0.01, P < 0.05; hippocampus/striatum: 1.266 ± 0.003 vs. 1.096 ± 0.017, P < 0.001). PET results for 15- to 16-mo-old mice correlated well with autoradiography and immunostaining (i.e., increased (18)F-PBR06 uptake in brain regions containing elevated CD68 and TSPO staining in APP(L/S) mice, compared with wts).(18)F-PBR06 shows great potential as a tool for visualizing TSPO/microglia in the progression and treatment of AD.

  View details for DOI 10.2967/jnumed.114.141648

  View details for PubMedID 25613536

• Role of CSPG receptor LAR phosphatase in restricting axon regeneration after CNS injury NEUROBIOLOGY OF DISEASE Xu, B., Park, D., Ohtake, Y., Li, H., Hayat, U., Liu, J., Selzer, M. E., Longo, F. M., Li, S. 2015; 73: 36-48

  Abstract

  Extracellular matrix molecule chondroitin sulfate proteoglycans (CSPGs) are highly upregulated in scar tissues and form a potent chemical barrier for CNS axon regeneration. Recent studies support that the receptor protein tyrosine phosphatase σ (PTPσ) and its subfamily member leukocyte common antigen related phosphatase (LAR) act as transmembrane receptors to mediate CSPG inhibition. PTPσ deficiency increased regrowth of ascending axons into scar tissues and descending corticospinal tract (CST) axons into the caudal spinal cord after spinal cord injury (SCI). Pharmacological LAR inhibition enhanced serotonergic axon growth in SCI mice. However, transgenic LAR deletion on axon growth in vivo and role of LAR in regulating regrowth of other fiber tracts have not been studied. Here, we studied role of LAR in restricting regrowth of injured descending CNS axons in deficient mice. LAR deletion increased regrowth of serotonergic axons into scar tissues and caudal spinal cord after dorsal over-hemitransection. LAR deletion also stimulated regrowth of CST fibers into the caudal spinal cord. LAR protein was upregulated days to weeks after injury and co-localized to serotonergic and CST axons. Moreover, LAR deletion improved functional recovery by increasing BMS locomotor scores and stride length and reducing grid walk errors. This is the first transgenic study that demonstrates crucial role of LAR in restricting regrowth of injured CNS axons.

  View details for DOI 10.1016/j.nbd.2014.08.030

  View details for Web of Science ID 000346328100004

  View details for PubMedID 25220840

• A strategy for analyzing bond strength and interaction kinetics between Pleckstrin homology domains and PI(4,5)P2 phospholipids using force distance spectroscopy and surface plasmon resonance ANALYST Malkovskiy, A. V., Wagh, D. A., LONGO, F. M., Rajadas, J. 2015; 140 (13): 4558-4565

  Abstract

  Phospholipids are important membrane components involved in diverse biological activities ranging from cell signaling to infection by viral particles. A thorough understanding of protein-phospholipid interaction dynamics is thus crucial for deciphering basic cellular processes as well as for targeted drug discovery. For any specific phospholipid-protein binding experiment, various groups have reported different binding constants, which are strongly dependent on applied conditions of interactions. Here, we report a method for accurate determination of the binding affinity and specificity between proteins and phospholipids using a model interaction between PLC-δ1/PH and phosphoinositide phospholipid PtdIns(4,5)P2. We developed an accurate Force Distance Spectroscopy (FDS)-based assay and have attempted to resolve the problem of variation in the observed binding constant by directly measuring the bond force. We confirm the FDS findings of a high bond strength of ∼0.19 ± 0.04 nN by Surface Plasmon Resonance (SPR) data analysis, segregating non-specific interactions, which show a significantly lower K(D) suggesting tight binding.

  View details for DOI 10.1039/c5an00498e

  View details for Web of Science ID 000356171400028

  View details for PubMedID 26040325

• Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75(NTR) NEUROTOXICOLOGY Friesland, A., Weng, Z., Duenas, M., Massa, S. M., Longo, F. M., Lu, Q. 2014; 45: 81-90

  Abstract

  Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP-2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP-2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that blocks proNGF binding to p75(NTR) or activates SHP-2 tyrosine phosphatase downstream of NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

  View details for DOI 10.1016/j.neuro.2014.09.005

  View details for Web of Science ID 000346955100009

  View details for PubMedID 25277379

• Acute administration of the small-molecule p75(NTR) ligand does not prevent hippocampal neuron loss or development of spontaneous seizures after pilocarpine-induced status epilepticus. Journal of neuroscience research Grabenstatter, H. L., Carlsen, J., Raol, Y. H., Yang, T., HUND, D., Cruz Del Angel, Y., White, A. M., Gonzalez, M. I., LONGO, F. M., Russek, S. J., Brooks-Kayal, A. R. 2014; 92 (10): 1307-1318

  Abstract

  Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are initially expressed in a precursor form (e.g., pro-BDNF) and cleaved to form mature BDNF (mBDNF). After pilocarpine-induced status epilepticus (SE), increases in neurotrophins regulate a wide variety of cell-signaling pathways, including prosurvival and cell-death machinery in a receptor-specific manner. Pro-BDNF preferentially binds to the p75 neurotrophin receptor (p75(NTR) ), whereas mBDNF is the major ligand of the tropomyosin-related kinase receptor. To elucidate a potential role for p75(NTR) in acute stages of epileptogenesis, rats were injected prior to and at onset of SE with LM11A-31, a small-molecule ligand that binds to p75(NTR) to promote survival signaling and inhibit neuronal cell death. Modulation of early p75(NTR) signaling and its effects on electrographic SE, SE-induced neurodegeneration, and subsequent spontaneous seizures were examined after LM11A-31 administration. Despite an established neuroprotective effect of LM11A-31 in several animal models of neurodegenerative disorders (e.g., Alzheimer's disease, traumatic brain injury, and spinal cord injury), high-dose LM11A-31 administration prior to and at onset of SE did not reduce the intensity of electrographic SE, prevent SE-induced neuronal cell injury, or inhibit the progression of epileptogenesis. Further studies are required to understand the role of p75(NTR) activation during epileptogenesis and in seizure-induced cell injury in the hippocampus, among other potential cellular pathologies contributing to the onset of spontaneous seizures. Additional studies utilizing more prolonged treatment with LM11A-31 are required to reach a definite conclusion on its potential neuroprotective role in epilepsy.

  View details for DOI 10.1002/jnr.23402

  View details for PubMedID 24801281

• Acute Administration of the Small-Molecule p75(NTR) Ligand Does Not Prevent Hippocampal Neuron Loss or Development of Spontaneous Seizures After Pilocarpine-Induced Status Epilepticus JOURNAL OF NEUROSCIENCE RESEARCH Grabenstatter, H. L., Carlsen, J., Raol, Y. H., Yang, T., HUND, D., Del Angel, Y. C., White, A. M., Gonzalez, M. I., LONGO, F. M., Russek, S. J., Brooks-Kayal, A. R. 2014; 92 (10): 1307-1318

  Abstract

  Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are initially expressed in a precursor form (e.g., pro-BDNF) and cleaved to form mature BDNF (mBDNF). After pilocarpine-induced status epilepticus (SE), increases in neurotrophins regulate a wide variety of cell-signaling pathways, including prosurvival and cell-death machinery in a receptor-specific manner. Pro-BDNF preferentially binds to the p75 neurotrophin receptor (p75(NTR) ), whereas mBDNF is the major ligand of the tropomyosin-related kinase receptor. To elucidate a potential role for p75(NTR) in acute stages of epileptogenesis, rats were injected prior to and at onset of SE with LM11A-31, a small-molecule ligand that binds to p75(NTR) to promote survival signaling and inhibit neuronal cell death. Modulation of early p75(NTR) signaling and its effects on electrographic SE, SE-induced neurodegeneration, and subsequent spontaneous seizures were examined after LM11A-31 administration. Despite an established neuroprotective effect of LM11A-31 in several animal models of neurodegenerative disorders (e.g., Alzheimer's disease, traumatic brain injury, and spinal cord injury), high-dose LM11A-31 administration prior to and at onset of SE did not reduce the intensity of electrographic SE, prevent SE-induced neuronal cell injury, or inhibit the progression of epileptogenesis. Further studies are required to understand the role of p75(NTR) activation during epileptogenesis and in seizure-induced cell injury in the hippocampus, among other potential cellular pathologies contributing to the onset of spontaneous seizures. Additional studies utilizing more prolonged treatment with LM11A-31 are required to reach a definite conclusion on its potential neuroprotective role in epilepsy.

  View details for DOI 10.1002/jnr.23402

  View details for Web of Science ID 000340504500008

  View details for PubMedCentralID PMC4134742

• Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75(NTR.) Neurotoxicology Friesland, A., Weng, Z., Duenas, M., Massa, S. M., Longo, F. M., Lu, Q. 2014

  Abstract

  Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP-2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP-2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that blocks proNGF binding to p75(NTR) or activates SHP-2 tyrosine phosphatase downstream of NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

  View details for DOI 10.1016/j.neuro.2014.09.005

  View details for PubMedID 25277379

• Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75(NTR.) Neurotoxicology Friesland, A., Weng, Z., Duenas, M., Massa, S. M., Longo, F. M., Lu, Q. 2014

  Abstract

  Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP-2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP-2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that blocks proNGF binding to p75(NTR) or activates SHP-2 tyrosine phosphatase downstream of NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

  View details for DOI 10.1016/j.neuro.2014.09.005

  View details for PubMedID 25277379

• A BDNF loop-domain mimetic acutely reverses spontaneous apneas and respiratory abnormalities during behavioral arousal in a mouse model of Rett syndrome. Disease models & mechanisms Kron, M., Lang, M., Adams, I. T., Sceniak, M., Longo, F., Katz, D. M. 2014; 7 (9): 1047-1055

  Abstract

  Reduced levels of brain-derived neurotrophic factor (BDNF) are thought to contribute to the pathophysiology of Rett syndrome (RTT), a severe neurodevelopmental disorder caused by loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2). In Mecp2 mutant mice, BDNF deficits have been associated with breathing abnormalities, a core feature of RTT, as well as with synaptic hyperexcitability within the brainstem respiratory network. Application of BDNF can reverse hyperexcitability in acute brainstem slices from Mecp2-null mice, suggesting that therapies targeting BDNF or its receptor, TrkB, could be effective at acute reversal of respiratory abnormalities in RTT. Therefore, we examined the ability of LM22A-4, a small-molecule BDNF loop-domain mimetic and TrkB partial agonist, to modulate synaptic excitability within respiratory cell groups in the brainstem nucleus tractus solitarius (nTS) and to acutely reverse abnormalities in breathing at rest and during behavioral arousal in Mecp2 mutants. Patch-clamp recordings in Mecp2-null brainstem slices demonstrated that LM22A-4 decreases excitability at primary afferent synapses in the nTS by reducing the amplitude of evoked excitatory postsynaptic currents and the frequency of spontaneous and miniature excitatory postsynaptic currents. In vivo, acute treatment of Mecp2-null and -heterozygous mutants with LM22A-4 completely eliminated spontaneous apneas in resting animals, without sedation. Moreover, we demonstrate that respiratory dysregulation during behavioral arousal, a feature of human RTT, is also reversed in Mecp2 mutants by acute treatment with LM22A-4. Together, these data support the hypothesis that reduced BDNF signaling and respiratory dysfunction in RTT are linked, and establish the proof-of-concept that treatment with a small-molecule structural mimetic of a BDNF loop domain and a TrkB partial agonist can acutely reverse abnormal breathing at rest and in response to behavioral arousal in symptomatic RTT mice.

  View details for DOI 10.1242/dmm.016030

  View details for PubMedID 25147297

  View details for PubMedCentralID PMC4142725

• Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice. Nature medicine Villeda, S. A., Plambeck, K. E., Middeldorp, J., Castellano, J. M., Mosher, K. I., Luo, J., Smith, L. K., Bieri, G., Lin, K., Berdnik, D., Wabl, R., Udeochu, J., Wheatley, E. G., Zou, B., Simmons, D. A., Xie, X. S., Longo, F. M., Wyss-Coray, T. 2014; 20 (6): 659-663

  Abstract

  As human lifespan increases, a greater fraction of the population is suffering from age-related cognitive impairments, making it important to elucidate a means to combat the effects of aging. Here we report that exposure of an aged animal to young blood can counteract and reverse pre-existing effects of brain aging at the molecular, structural, functional and cognitive level. Genome-wide microarray analysis of heterochronic parabionts--in which circulatory systems of young and aged animals are connected--identified synaptic plasticity-related transcriptional changes in the hippocampus of aged mice. Dendritic spine density of mature neurons increased and synaptic plasticity improved in the hippocampus of aged heterochronic parabionts. At the cognitive level, systemic administration of young blood plasma into aged mice improved age-related cognitive impairments in both contextual fear conditioning and spatial learning and memory. Structural and cognitive enhancements elicited by exposure to young blood are mediated, in part, by activation of the cyclic AMP response element binding protein (Creb) in the aged hippocampus. Our data indicate that exposure of aged mice to young blood late in life is capable of rejuvenating synaptic plasticity and improving cognitive function.

  View details for DOI 10.1038/nm.3569

  View details for PubMedID 24793238

  View details for PubMedCentralID PMC4224436

• TrkB Neurotrophin Receptor Activation with Pharmacophore as Possible Treatment for Experimental Ischemic Optic Neuropathy Shariati, M., Ma, J., Longo, F., Yang, T., Barres, B., Chakraborty, C., Liao, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2014

  View details for Web of Science ID 000433205505245

• Small Molecule p75(NTR) Ligands Reduce Pathological Phosphorylation and Misfolding of Tau, Inflammatory Changes, Cholinergic Degeneration, and Cognitive Deficits in A beta PPL/S Transgenic Mice JOURNAL OF ALZHEIMERS DISEASE Nguyen, T. V., Shen, L., Vander Griend, L., Quach, L. N., Belichenko, N. P., Saw, N., Yang, T., Shamloo, M., Wyss-Coray, T., Massa, S. M., Longo, F. M. 2014; 42 (2): 459-483

  Abstract

  The p75 neurotrophin receptor (p75NTR) is involved in degenerative mechanisms related to Alzheimer's disease (AD). In addition, p75NTR levels are increased in AD and the receptor is expressed by neurons that are particularly vulnerable in the disease. Therefore, modulating p75NTR function may be a significant disease-modifying treatment approach. Prior studies indicated that the non-peptide, small molecule p75NTR ligands LM11A-31, and chemically unrelated LM11A-24, could block amyloid-β-induced deleterious signaling and neurodegeneration in vitro, and LM11A-31 was found to mitigate neuritic degeneration and behavioral deficits in a mouse model of AD. In this study, we determined whether these in vivo findings represent class effects of p75NTR ligands by examining LM11A-24 effects. In addition, the range of compound effects was further examined by evaluating tau pathology and neuroinflammation. Following oral administration, both ligands reached brain concentrations known to provide neuroprotection in vitro. Compound induction of p75NTR cleavage provided evidence for CNS target engagement. LM11A-31 and LM11A-24 reduced excessive phosphorylation of tau, and LM11A-31 also inhibited its aberrant folding. Both ligands decreased activation of microglia, while LM11A-31 attenuated reactive astrocytes. Along with decreased inflammatory responses, both ligands reduced cholinergic neurite degeneration. In addition to the amelioration of neuropathology in AD model mice, LM11A-31, but not LM11A-24, prevented impairments in water maze performance, while both ligands prevented deficits in fear conditioning. These findings support a role for p75NTR ligands in preventing fundamental tau-related pathologic mechanisms in AD, and further validate the development of these small molecules as a new class of therapeutic compounds.

  View details for DOI 10.3233/JAD-140036

  View details for Web of Science ID 000341572000012

• A Small Molecule p75NTR Ligand, LM11A-31, Reverses Cholinergic Neurite Dystrophy in Alzheimer's Disease Mouse Models with Mid- to Late-Stage Disease Progression. PloS one Simmons, D. A., Knowles, J. K., Belichenko, N. P., Banerjee, G., Finkle, C., Massa, S. M., Longo, F. M. 2014; 9 (8): e102136

  Abstract

  Degeneration of basal forebrain cholinergic neurons contributes significantly to the cognitive deficits associated with Alzheimer's disease (AD) and has been attributed to aberrant signaling through the neurotrophin receptor p75 (p75NTR). Thus, modulating p75NTR signaling is considered a promising therapeutic strategy for AD. Accordingly, our laboratory has developed small molecule p75NTR ligands that increase survival signaling and inhibit amyloid-β-induced degenerative signaling in in vitro studies. Previous work found that a lead p75NTR ligand, LM11A-31, prevents degeneration of cholinergic neurites when given to an AD mouse model in the early stages of disease pathology. To extend its potential clinical applications, we sought to determine whether LM11A-31 could reverse cholinergic neurite atrophy when treatment begins in AD mouse models having mid- to late stages of pathology. Reversing pathology may have particular clinical relevance as most AD studies involve patients that are at an advanced pathological stage. In this study, LM11A-31 (50 or 75 mg/kg) was administered orally to two AD mouse models, Thy-1 hAPPLond/Swe (APPL/S) and Tg2576, at age ranges during which marked AD-like pathology manifests. In mid-stage male APPL/S mice, LM11A-31 administered for 3 months starting at 6-8 months of age prevented and/or reversed atrophy of basal forebrain cholinergic neurites and cortical dystrophic neurites. Importantly, a 1 month LM11A-31 treatment given to male APPL/S mice (12-13 months old) with late-stage pathology reversed the degeneration of cholinergic neurites in basal forebrain, ameliorated cortical dystrophic neurites, and normalized increased basal forebrain levels of p75NTR. Similar results were seen in female Tg2576 mice. These findings suggest that LM11A-31 can reduce and/or reverse fundamental AD pathologies in late-stage AD mice. Thus, targeting p75NTR is a promising approach to reducing AD-related degenerative processes that have progressed beyond early stages.

  View details for DOI 10.1371/journal.pone.0102136

  View details for PubMedID 25153701

  View details for PubMedCentralID PMC4143160

• Small molecule p75NTR ligands reduce pathological phosphorylation and misfolding of tau, inflammatory changes, cholinergic degeneration, and cognitive deficits in AßPP(L/S) transgenic mice. Journal of Alzheimer's disease : JAD Nguyen, T. V., Shen, L., Vander Griend, L., Quach, L. N., Belichenko, N. P., Saw, N., Yang, T., Shamloo, M., Wyss-Coray, T., Massa, S. M., Longo, F. M. 2014; 42 (2): 459-483

  Abstract

  The p75 neurotrophin receptor (p75NTR) is involved in degenerative mechanisms related to Alzheimer's disease (AD). In addition, p75NTR levels are increased in AD and the receptor is expressed by neurons that are particularly vulnerable in the disease. Therefore, modulating p75NTR function may be a significant disease-modifying treatment approach. Prior studies indicated that the non-peptide, small molecule p75NTR ligands LM11A-31, and chemically unrelated LM11A-24, could block amyloid-β-induced deleterious signaling and neurodegeneration in vitro, and LM11A-31 was found to mitigate neuritic degeneration and behavioral deficits in a mouse model of AD. In this study, we determined whether these in vivo findings represent class effects of p75NTR ligands by examining LM11A-24 effects. In addition, the range of compound effects was further examined by evaluating tau pathology and neuroinflammation. Following oral administration, both ligands reached brain concentrations known to provide neuroprotection in vitro. Compound induction of p75NTR cleavage provided evidence for CNS target engagement. LM11A-31 and LM11A-24 reduced excessive phosphorylation of tau, and LM11A-31 also inhibited its aberrant folding. Both ligands decreased activation of microglia, while LM11A-31 attenuated reactive astrocytes. Along with decreased inflammatory responses, both ligands reduced cholinergic neurite degeneration. In addition to the amelioration of neuropathology in AD model mice, LM11A-31, but not LM11A-24, prevented impairments in water maze performance, while both ligands prevented deficits in fear conditioning. These findings support a role for p75NTR ligands in preventing fundamental tau-related pathologic mechanisms in AD, and further validate the development of these small molecules as a new class of therapeutic compounds.

  View details for DOI 10.3233/JAD-140036

  View details for PubMedID 24898660

• A Small Molecule TrkB Ligand Reduces Motor Impairment and Neuropathology in R6/2 and BACHD Mouse Models of Huntington's Disease. journal of neuroscience Simmons, D. A., Belichenko, N. P., Yang, T., Condon, C., Monbureau, M., Shamloo, M., Jing, D., Massa, S. M., Longo, F. M. 2013; 33 (48): 18712-18727

  Abstract

  Loss of neurotrophic support in the striatum caused by reduced brain-derived neurotrophic factor (BDNF) levels plays a critical role in Huntington's disease (HD) pathogenesis. BDNF acts via TrkB and p75 neurotrophin receptors (NTR), and restoring its signaling is a prime target for HD therapeutics. Here we sought to determine whether a small molecule ligand, LM22A-4, specific for TrkB and without effects on p75(NTR), could alleviate HD-related pathology in R6/2 and BACHD mouse models of HD. LM22A-4 was administered to R6/2 mice once daily (5-6 d/week) from 4 to 11 weeks of age via intraperitoneal and intranasal routes simultaneously to maximize brain levels. The ligand reached levels in the R6/2 forebrain greater than the maximal neuroprotective dose in vitro and corrected deficits in activation of striatal TrkB and its key signaling intermediates AKT, PLCγ, and CREB. Ligand-induced TrkB activation was associated with a reduction in HD pathologies in the striatum including decreased DARPP-32 levels, neurite degeneration of parvalbumin-containing interneurons, inflammation, and intranuclear huntingtin aggregates. Aggregates were also reduced in the cortex. Notably, LM22A-4 prevented deficits in dendritic spine density of medium spiny neurons. Moreover, R6/2 mice given LM22A-4 demonstrated improved downward climbing and grip strength compared with those given vehicle, though these groups had comparable rotarod performances and survival times. In BACHD mice, long-term LM22A-4 treatment (6 months) produced similar ameliorative effects. These results support the hypothesis that targeted activation of TrkB inhibits HD-related degenerative mechanisms, including spine loss, and may provide a disease mechanism-directed therapy for HD and other neurodegenerative conditions.

  View details for DOI 10.1523/JNEUROSCI.1310-13.2013

  View details for PubMedID 24285878

• A Small Molecule p75(NTR) Ligand Protects Neurogenesis After Traumatic Brain Injury STEM CELLS Shi, J., Longo, F. M., Massa, S. M. 2013; 31 (11): 2561-2574

  Abstract

  The p75 neurotrophin receptor (p75(NTR)) influences the proliferation, survival, and differentiation of neuronal precursors and its expression is induced in injured brain, where it regulates cell survival. Here, we test the hypotheses that pharmacologic modulation of p75(NTR) signaling will promote neural progenitor survival and proliferation, and improve outcomes of traumatic brain injury (TBI). LM11A-31, an orally available, blood-brain barrier-permeant small-molecule p75(NTR) signaling modulator, significantly increased proliferation and survival, and decreased JNK phosphorylation, in hippocampal neural stem/progenitor cells in culture expressing wild-type p75(NTR), but had no effect on cells expressing a mutant neurotrophin-unresponsive form of the receptor. The compound also enhanced the production of mature neurons from adult hippocampal neural progenitors in vitro. In vivo, intranasal administration of LM11A-31 decreased postinjury hippocampal and cortical neuronal death, neural progenitor cell death, gliogenesis, and microglial activation, and enhanced long-term hippocampal neurogenesis and reversed spatial memory impairments. LM11A-31 diminished the postinjury increase of SOX2-expressing early progenitor cells, but protected and increased the proliferation of endogenous polysialylated-neural cell adhesion molecule positive intermediate progenitors, and restored the long-term production of mature granule neurons. These findings suggest that modulation of p75(NTR) actions using small molecules such as LM11A-31 may constitute a potent therapeutic strategy for TBI.

  View details for DOI 10.1002/stem.1516

  View details for Web of Science ID 000327025600025

  View details for PubMedID 23940017

• A small molecule p75(NTR) ligand prevents cognitive deficits and neurite degeneration in an Alzheimer's mouse model. Neurobiology of aging Knowles, J. K., Simmons, D. A., Nguyen, T. V., Vander Griend, L., Xie, Y., Zhang, H., Yang, T., Pollak, J., Chang, T., Arancio, O., Buckwalter, M. S., Wyss-Coray, T., Massa, S. M., Longo, F. M. 2013; 34 (8): 2052-2063

  Abstract

  The p75 neurotrophin receptor (p75(NTR)) is associated with multiple mechanisms linked to Alzheimer's disease (AD); hence, modulating its function might confer therapeutic effects. In previous in vitro work, we developed small molecule p75(NTR) ligands that inhibited amyloid-β-induced degenerative signaling and prevented neurite degeneration. In the present study, a prototype p75(NTR) ligand, LM11A-31, was administered orally to the Thy-1 hAPP(Lond/Swe) (APP(L/S)) AD mouse model. LM11A-31 reached brain concentrations known to inhibit degenerative signaling without toxicity or induction of hyperalgesia. It prevented deficits in novel object recognition after 2.5 months and, in a separate cohort, deficits in Y-maze performance after 3 months of treatment. Stereology studies found that the number and size of basal forebrain cholinergic neurons, which are normal in APP(L/S) mice, were unaffected. Neuritic dystrophy, however, was readily apparent in the basal forebrain, hippocampus and cortex, and was significantly reduced by LM11A-31, with no effect on amyloid levels. These studies reveal that p75(NTR) is an important and tractable in vivo drug target for AD, with LM11A-31 representing a novel class of therapeutic candidates.

  View details for DOI 10.1016/j.neurobiolaging.2013.02.015

  View details for PubMedID 23545424

• Optimizing the use of CROs by academia and small companies. Nature reviews. Drug discovery Lane, R. F., Friedman, L. G., Keith, C., Braithwaite, S. P., Frearson, J. A., Lowe, D. A., Longo, F. M., Refolo, L. M., Watterson, D. M., Tsaioun, K., Shineman, D. W., Fillit, H. M. 2013; 12 (7): 487-8

  View details for DOI 10.1038/nrd4057

  View details for PubMedID 23812255

• Small-molecule modulation of neurotrophin receptors: a strategy for the treatment of neurological disease. Nature reviews. Drug discovery Longo, F. M., Massa, S. M. 2013; 12 (7): 507-25

  Abstract

  Neurotrophins and their receptors modulate multiple signalling pathways to regulate neuronal survival and to maintain axonal and dendritic networks and synaptic plasticity. Neurotrophins have potential for the treatment of neurological diseases. However, their therapeutic application has been limited owing to their poor plasma stability, restricted nervous system penetration and, importantly, the pleiotropic actions that derive from their concomitant binding to multiple receptors. One strategy to overcome these limitations is to target individual neurotrophin receptors — such as tropomyosin receptor kinase A (TRKA), TRKB, TRKC, the p75 neurotrophin receptor or sortilin — with small-molecule ligands. Such small molecules might also modulate various aspects of these signalling pathways in ways that are distinct from the programmes triggered by native neurotrophins. By departing from conventional neurotrophin signalling, these ligands might provide novel therapeutic options for a broad range of neurological indications.

  View details for PubMedID 23977697

• Small-molecule modulation of neurotrophin receptors: a strategy for the treatment of neurological disease NATURE REVIEWS DRUG DISCOVERY Longo, F. M., Massa, S. M. 2013; 12 (7): 507-525

  Abstract

  Neurotrophins and their receptors modulate multiple signalling pathways to regulate neuronal survival and to maintain axonal and dendritic networks and synaptic plasticity. Neurotrophins have potential for the treatment of neurological diseases. However, their therapeutic application has been limited owing to their poor plasma stability, restricted nervous system penetration and, importantly, the pleiotropic actions that derive from their concomitant binding to multiple receptors. One strategy to overcome these limitations is to target individual neurotrophin receptors — such as tropomyosin receptor kinase A (TRKA), TRKB, TRKC, the p75 neurotrophin receptor or sortilin — with small-molecule ligands. Such small molecules might also modulate various aspects of these signalling pathways in ways that are distinct from the programmes triggered by native neurotrophins. By departing from conventional neurotrophin signalling, these ligands might provide novel therapeutic options for a broad range of neurological indications.

  View details for DOI 10.1038/nrd4024

  View details for Web of Science ID 000321110600016

• TrkB Neurotrophin Receptor Activation with Pharmacophore as Possible Treatment for Anterior Ischemic Optic Neuropathy Liao, Y., Lee, G., Ma, J., Yang, T., Chakraborty, C., Barres, B., Longo, F., Shariati, M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2013

  View details for Web of Science ID 000436232901104

• P75 NEUROTROPHIN RECEPTOR MODULATION AND JAK/STAT INHIBITION: ROLE IN THE PROGRESSION OF EPILEPSY IN THE PILOCARPINE RAT MODEL Grabenstatter, H. L., Del Angel, C. Y., Carlsen, J., Yang, T., White, A. M., Longo, F. M., Russek, S. J., Brooks-Kayal, A. R. WILEY-BLACKWELL. 2013: 52

  View details for Web of Science ID 000320472000147

• Role of RhoA in Cisplatin-Induced Neurotoxicity Friesland, A., Duenas, M., Weng, Z., Longo, F. M., Chen, Y., Lu, Q. FEDERATION AMER SOC EXP BIOL. 2013

  View details for Web of Science ID 000319883504578

• Differential effects of cisplatin on lung cancer cells and primary neurons: roles of small GTPase RhoA Weng, Z., Friesland, A., Lu, Z., Chen, Y., Longo, F. M., Boykin, C., Lu, Q. FEDERATION AMER SOC EXP BIOL. 2013

  View details for Web of Science ID 000319883502614

• Oral Administration of a Small Molecule Targeted to Block proNGF Binding to p75 Promotes Myelin Sparing and Functional Recovery after Spinal Cord Injury JOURNAL OF NEUROSCIENCE Tep, C., Lim, T. H., Ko, P. O., Getahun, S., Ryu, J. C., Goettl, V. M., Massa, S. M., Basso, M., Longo, F. M., Yoon, S. O. 2013; 33 (2): 397-410

  Abstract

  The lack of effective therapies for spinal cord injury points to the need for identifying novel targets for therapeutic intervention. Here we report that a small molecule, LM11A-31, developed to block proNGF-p75 interaction and p75-mediated cell death crosses the blood-brain barrier efficiently when delivered orally. Administered starting 4 h postinjury, LM11A-31 promotes functional recovery without causing any toxicity or increased pain in a mouse model of spinal contusion injury. In both weight-bearing open-field tests and nonweight-bearing swim tests, LM11A-31 was effective in improving motor function and coordination. Such functional improvement correlated with a >50% increase in the number of surviving oligodendrocytes and myelinated axons. We also demonstrate that LM11A-31 indeed inhibits proNGF-p75 interaction in vivo, thereby curtailing the JNK3-mediated apoptotic cascade. These results thus highlight p75 as a novel therapeutic target for an orally delivered treatment for spinal cord injury.

  View details for DOI 10.1523/JNEUROSCI.0399-12.2013

  View details for Web of Science ID 000313569600003

  View details for PubMedID 23303920

• Delayed Administration of a Small Molecule Tropomyosin-Related Kinase B Ligand Promotes Recovery After Hypoxic-Ischemic Stroke STROKE Han, J., Pollak, J., Yang, T., Siddiqui, M. R., Doyle, K. P., Taravosh-Lahn, K., Cekanaviciute, E., Han, A., Goodman, J. Z., Jones, B., Jing, D., Massa, S. M., Longo, F. M., Buckwalter, M. S. 2012; 43 (7): 1918-1924

  Abstract

  Stroke is the leading cause of long-term disability in the United States, yet no drugs are available that are proven to improve recovery. Brain-derived neurotrophic factor stimulates neurogenesis and plasticity, processes that are implicated in stroke recovery. It binds to both the tropomyosin-related kinase B and p75 neurotrophin receptors. However, brain-derived neurotrophic factor is not a feasible therapeutic agent, and no small molecule exists that can reproduce its binding to both receptors. We tested the hypothesis that a small molecule (LM22A-4) that selectively targets tropomyosin-related kinase B would promote neurogenesis and functional recovery after stroke.Four-month-old mice were trained on motor tasks before stroke. After stroke, functional test results were used to randomize mice into 2 equally, and severely, impaired groups. Beginning 3 days after stroke, mice received LM22A-4 or saline vehicle daily for 10 weeks.LM22A-4 treatment significantly improved limb swing speed and accelerated the return to normal gait accuracy after stroke. LM22A-4 treatment also doubled both the number of new mature neurons and immature neurons adjacent to the stroke. Drug-induced differences were not observed in angiogenesis, dendritic arborization, axonal sprouting, glial scar formation, or neuroinflammation.A small molecule agonist of tropomyosin-related kinase B improves functional recovery from stroke and increases neurogenesis when administered beginning 3 days after stroke. These findings provide proof-of-concept that targeting of tropomyosin-related kinase B alone is capable of promoting one or more mechanisms relevant to stroke recovery. LM22A-4 or its derivatives might therefore serve as "pro-recovery" therapeutic agents for stroke.

  View details for DOI 10.1161/STROKEAHA.111.641878

  View details for PubMedID 22535263

• Suppression of Immunodeficiency Virus-Associated Neural Damage by the p75 Neurotrophin Receptor Ligand, LM11A-31, in an In Vitro Feline Model JOURNAL OF NEUROIMMUNE PHARMACOLOGY Meeker, R. B., Poulton, W., Feng, W., Hudson, L., Longo, F. M. 2012; 7 (2): 388-400

  Abstract

  Feline immunodeficiency virus (FIV) infection like human immunodeficiency virus (HIV), produces systemic and central nervous system disease in its natural host, the domestic cat, that parallels the pathogenesis seen in HIV-infected humans. The ability to culture feline nervous system tissue affords the unique opportunity to directly examine interactions of infectious virus with CNS cells for the development of models and treatments that can then be translated to a natural infectious model. To explore the therapeutic potential of a new p75 neurotrophin receptor ligand, LM11A-31, we evaluated neuronal survival, neuronal damage and calcium homeostasis in cultured feline neurons following inoculation with FIV. FIV resulted in the gradual appearance of dendritic beading, pruning of processes and shrinkage of neuronal perikarya in the neurons. Astrocytes developed a more activated appearance and there was an enhanced accumulation of microglia, particularly at longer times post-inoculation. Addition of 10 nM LM11A-31, to the cultures greatly reduced or eliminated the neuronal pathology as well as the FIV effects on astrocytes and microglia. LM11A-31 also, prevented the development of delayed calcium deregulation in feline neurons exposed to conditioned medium from FIV treated macrophages. The suppression of calcium accumulation prevented the development of foci of calcium accumulation and beading in the dendrites. FIV replication was unaffected by LM11A-31. The strong neuroprotection afforded by LM11A-31 in an infectious in vitro model indicates that LM11A-31 may have excellent potential for the treatment of HIV-associated neurodegeneration.

  View details for DOI 10.1007/s11481-011-9325-0

  View details for Web of Science ID 000304164400010

  View details for PubMedID 22161560

• Thy1-hAPP(Lond/Swe+) mouse model of Alzheimer's disease displays broad behavioral deficits in sensorimotor, cognitive and social function. Brain and behavior Faizi, M., Bader, P. L., Saw, N., Nguyen, T. V., Beraki, S., Wyss-Coray, T., Longo, F. M., Shamloo, M. 2012; 2 (2): 142-154

  Abstract

  Alzheimer's disease (AD), the most common form of dementia, is an age-dependent progressive neurodegenerative disorder. β-amyloid, a metabolic product of the amyloid precursor protein (APP), plays an important role in the pathogenesis of AD. The Thy1-hAPP(Lond/Swe+) (line 41) transgenic mouse overexpresses human APP751 and contains the London (V717I) and Swedish (K670M/N671L) mutations. Here, we used a battery of behavioral tests to evaluate general activity, cognition, and social behavior in six-month-old male Thy1-hAPP(Lond/Swe+) mice. We found hyperactivity in a novel environment as well as significant deficits in spontaneous alternation behavior. In fear conditioning (FC), Thy1-hAPP(Lond/Swe+) mice did not display deficits in acquisition or in memory retrieval in novel context of tone-cued FC, but they showed significant memory retrieval impairment during contextual testing in an identical environment. Surprisingly, in a standard hidden platform water maze, no significant deficit was detected in mutant mice. However, a delayed-matching-to-place paradigm revealed a significant deficit in Thy1-hAPP(Lond/Swe+) mice. Lastly, in the social novelty session of a three-chamber test, Thy1-hAPP(Lond/Swe+) mice exhibited a significantly decreased interest in a novel versus a familiar stranger compared to control mice. This could possibly be explained by decreased social memory or discrimination and may parallel disturbances in social functioning in human AD patients. In conclusion, the Thy1-hAPP(Lond/Swe+) mouse model of AD displayed a behavioral phenotype that resembles, in part, the cognitive and psychiatric symptoms experienced in AD patients.

  View details for DOI 10.1002/brb3.41

  View details for PubMedID 22574282

  View details for PubMedCentralID PMC3345358

• Thy1-hAPP(Lond/Swe+) mouse model of Alzheimer's disease displays broad behavioral deficits in sensorimotor, cognitive and social function BRAIN AND BEHAVIOR Faizi, M., Bader, P. L., Saw, N., Nguyen, T. V., Beraki, S., Wyss-Coray, T., Longo, F. M., Shamloo, M. 2012; 2 (2): 142-154

  Abstract

  Alzheimer's disease (AD), the most common form of dementia, is an age-dependent progressive neurodegenerative disorder. β-amyloid, a metabolic product of the amyloid precursor protein (APP), plays an important role in the pathogenesis of AD. The Thy1-hAPP(Lond/Swe+) (line 41) transgenic mouse overexpresses human APP751 and contains the London (V717I) and Swedish (K670M/N671L) mutations. Here, we used a battery of behavioral tests to evaluate general activity, cognition, and social behavior in six-month-old male Thy1-hAPP(Lond/Swe+) mice. We found hyperactivity in a novel environment as well as significant deficits in spontaneous alternation behavior. In fear conditioning (FC), Thy1-hAPP(Lond/Swe+) mice did not display deficits in acquisition or in memory retrieval in novel context of tone-cued FC, but they showed significant memory retrieval impairment during contextual testing in an identical environment. Surprisingly, in a standard hidden platform water maze, no significant deficit was detected in mutant mice. However, a delayed-matching-to-place paradigm revealed a significant deficit in Thy1-hAPP(Lond/Swe+) mice. Lastly, in the social novelty session of a three-chamber test, Thy1-hAPP(Lond/Swe+) mice exhibited a significantly decreased interest in a novel versus a familiar stranger compared to control mice. This could possibly be explained by decreased social memory or discrimination and may parallel disturbances in social functioning in human AD patients. In conclusion, the Thy1-hAPP(Lond/Swe+) mouse model of AD displayed a behavioral phenotype that resembles, in part, the cognitive and psychiatric symptoms experienced in AD patients.

  View details for DOI 10.1002/brb3.41

  View details for Web of Science ID 000209173900005

  View details for PubMedCentralID PMC3345358

• A TrkB Small Molecule Partial Agonist Rescues TrkB Phosphorylation Deficits and Improves Respiratory Function in a Mouse Model of Rett Syndrome JOURNAL OF NEUROSCIENCE Schmid, D. A., Yang, T., Ogier, M., Adams, I., Mirakhur, Y., Wang, Q., Massa, S. M., Longo, F. M., Katz, D. M. 2012; 32 (5): 1803-1810

  Abstract

  Rett syndrome (RTT) results from loss-of-function mutations in the gene encoding the methyl-CpG-binding protein 2 (MeCP2) and is characterized by abnormal motor, respiratory and autonomic control, cognitive impairment, autistic-like behaviors and increased risk of seizures. RTT patients and Mecp2-null mice exhibit reduced expression of brain-derived neurotrophic factor (BDNF), which has been linked in mice to increased respiratory frequency, a hallmark of RTT. The present study was undertaken to test the hypotheses that BDNF deficits in Mecp2 mutants are associated with reduced activation of the BDNF receptor, TrkB, and that pharmacologic activation of TrkB would improve respiratory function. We characterized BDNF protein expression, TrkB activation and respiration in heterozygous female Mecp2 mutant mice (Het), a model that recapitulates the somatic mosaicism for mutant MECP2 found in typical RTT patients, and evaluated the ability of a small molecule TrkB agonist, LM22A-4, to ameliorate biochemical and functional abnormalities in these animals. We found that Het mice exhibit (1) reduced BDNF expression and TrkB activation in the medulla and pons and (2) breathing dysfunction, characterized by increased frequency due to periods of tachypnea, and increased apneas, as in RTT patients. Treatment of Het mice with LM22A-4 for 4 weeks rescued wild-type levels of TrkB phosphorylation in the medulla and pons and restored wild-type breathing frequency. These data provide new insight into the role of BDNF signaling deficits in the pathophysiology of RTT and highlight TrkB as a possible therapeutic target in this disease.

  View details for DOI 10.1523/JNEUROSCI.0865-11.2012

  View details for Web of Science ID 000299977200026

  View details for PubMedID 22302819

• Leukocyte Common Antigen-Related Phosphatase Is a Functional Receptor for Chondroitin Sulfate Proteoglycan Axon Growth Inhibitors JOURNAL OF NEUROSCIENCE Fisher, D., Xing, B., Dill, J., Li, H., Hoang, H. H., Zhao, Z., Yang, X., Bachoo, R., Cannon, S., Longo, F. M., Sheng, M., Silver, J., Li, S. 2011; 31 (40): 14051-14066

  Abstract

  Chondroitin sulfate proteoglycans (CSPGs) are a family of extracellular matrix molecules with various functions in regulating tissue morphogenesis, cell division, and axon guidance. A number of CSPGs are highly upregulated by reactive glial scar tissues after injuries and form a strong barrier for axonal regeneration in the adult vertebrate CNS. Although CSPGs may negatively regulate axonal growth via binding and altering activity of other growth-regulating factors, the molecular mechanisms by which CSPGs restrict axonal elongation are not well understood. Here, we identified a novel receptor mechanism whereby CSPGs inhibit axonal growth via interactions with neuronal transmembrane leukocyte common antigen-related phosphatase (LAR). CSPGs bind LAR with high affinity in transfected COS-7 cells and coimmunoprecipitate with LAR expressed in various tissues including the brain and spinal cord. CSPG stimulation enhances activity of LAR phosphatase in vitro. Deletion of LAR in knock-out mice or blockade of LAR with sequence-selective peptides significantly overcomes neurite growth restrictions of CSPGs in neuronal cultures. Intracellularly, CSPG-LAR interaction mediates axonal growth inhibition of neurons partially via inactivating Akt and activating RhoA signals. Systemic treatments with LAR-targeting peptides in mice with thoracic spinal cord transection injuries induce significant axon growth of descending serotonergic fibers in the vicinity of the lesion and beyond in the caudal spinal cord and promote locomotor functional recovery. Identification of LAR as a novel CSPG functional receptor provides a therapeutic basis for enhancing axonal regeneration and functional recovery after CNS injuries in adult mammals.

  View details for DOI 10.1523/JNEUROSCI.1737-11.2011

  View details for Web of Science ID 000295805500002

  View details for PubMedID 21976490

  View details for PubMedCentralID PMC3220601

• LAR IS A FUNCTIONAL RECEPTOR FOR CSPG AXON GROWTH INHIBITORS 29th Annual National Neurotrauma Symposium Li, S., Fisher, D., Xing, B., Li, H., Hoang, H., Cannon, S., Longo, F., Sheng, M., Silver, J. MARY ANN LIEBERT INC. 2011: A2–A3

  View details for Web of Science ID 000292457600027

• The p75 neurotrophin receptor is expressed by adult mouse dentate progenitor cells and regulates neuronal and non-neuronal cell genesis BMC NEUROSCIENCE Bernabeu, R. O., Longo, F. M. 2010; 11

  Abstract

  The ability to regulate neurogenesis in the adult dentate gyrus will require further identification and characterization of the receptors regulating this process. In vitro and in vivo studies have demonstrated that neurotrophins and the p75 neurotrophin receptor (p75NTR) can promote neurogenesis; therefore we tested the hypothesis that p75NTR is expressed by adult dentate gyrus progenitor cells and is required for their proliferation and differentiation.In a first series of studies focusing on proliferation, mice received a single BrdU injection and were sacrificed 2, 10 and 48 hours later. Proliferating, BrdU-positive cells were found to express p75NTR. In a second series of studies, BrdU was administered by six daily injections and mice were sacrificed 1 day later. Dentate gyrus sections demonstrated a large proportion of BrdU/p75NTR co-expressing cells expressing either the NeuN neuronal or GFAP glial marker, indicating that p75NTR expression persists at least until early stages of maturation. In p75NTR (-/-) mice, there was a 59% decrease in the number of BrdU-positive cells, with decreases in the number of BrdU cells co-labeled with NeuN, GFAP or neither marker of 35%, 60% and 64%, respectively.These findings demonstrate that p75NTR is expressed by adult dentate progenitor cells and point to p75NTR as an important receptor promoting the proliferation and/or early maturation of not only neural, but also glial and other cell types.

  View details for DOI 10.1186/1471-2202-11-136

  View details for Web of Science ID 000284326600001

  View details for PubMedID 20961458

  View details for PubMedCentralID PMC2987811

• Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents JOURNAL OF CLINICAL INVESTIGATION Massa, S. M., Yang, T., Xie, Y., Shi, J., Bilgen, M., Joyce, J. N., Nehama, D., Rajadas, J., Longo, F. M. 2010; 120 (5): 1774-1785

  Abstract

  Brain-derived neurotrophic factor (BDNF) activates the receptor tropomyosin-related kinase B (TrkB) with high potency and specificity, promoting neuronal survival, differentiation, and synaptic function. Correlations between altered BDNF expression and/or function and mechanism(s) underlying numerous neurodegenerative conditions, including Alzheimer disease and traumatic brain injury, suggest that TrkB agonists might have therapeutic potential. Using in silico screening with a BDNF loop-domain pharmacophore, followed by low-throughput in vitro screening in mouse fetal hippocampal neurons, we have efficiently identified small molecules with nanomolar neurotrophic activity specific to TrkB versus other Trk family members. Neurotrophic activity was dependent on TrkB and its downstream targets, although compound-induced signaling activation kinetics differed from those triggered by BDNF. A selected prototype compound demonstrated binding specificity to the extracellular domain of TrkB. In in vitro models of neurodegenerative disease, it prevented neuronal degeneration with efficacy equal to that of BDNF, and when administered in vivo, it caused hippocampal and striatal TrkB activation in mice and improved motor learning after traumatic brain injury in rats. These studies demonstrate the utility of loop modeling in drug discovery and reveal what we believe to be the first reported small molecules derived from a targeted BDNF domain that specifically activate TrkB.We propose that these compounds constitute a novel group of tools for the study of TrkB signaling and may provide leads for developing new therapeutic agents for neurodegenerative diseases.

  View details for DOI 10.1172/JCI41356

  View details for Web of Science ID 000277248000041

  View details for PubMedID 20407211

  View details for PubMedCentralID PMC2860903

• The p75 Neurotrophin Receptor Promotes Amyloid-beta(1-42)-Induced Neuritic Dystrophy In Vitro and In Vivo JOURNAL OF NEUROSCIENCE Knowles, J. K., Rajadas, J., Nguyen, T. V., Yang, T., LeMieux, M. C., Griend, L. V., Ishikawa, C., Massa, S. M., Wyss-Coray, T., Longo, F. M. 2009; 29 (34): 10627-10637

  Abstract

  Oligomeric forms of amyloid-beta (Abeta) are thought to play a causal role in Alzheimer's disease (AD), and the p75 neurotrophin receptor (p75(NTR)) has been implicated in Abeta-induced neurodegeneration. To further define the functions of p75(NTR) in AD, we examined the interaction of oligomeric Abeta(1-42) with p75(NTR), and the effects of that interaction on neurite integrity in neuron cultures and in a chronic AD mouse model. Atomic force microscopy was used to ascertain the aggregated state of Abeta, and fluorescence resonance energy transfer analysis revealed that Abeta oligomers interact with the extracellular domain of p75(NTR). In vitro studies of Abeta-induced death in neuron cultures isolated from wild-type and p75(NTR-/-) mice, in which the p75(NTR) extracellular domain is deleted, showed reduced sensitivity of mutant cells to Abeta-induced cell death. Interestingly, Abeta-induced neuritic dystrophy and activation of c-Jun, a known mediator of Abeta-induced deleterious signaling, were completely prevented in p75(NTR-/-) neuron cultures. Thy1-hAPP(Lond/Swe) x p75(NTR-/-) mice exhibited significantly diminished hippocampal neuritic dystrophy and complete reversal of basal forebrain cholinergic neurite degeneration relative to those expressing wild-type p75(NTR). Abeta levels were not affected, suggesting that removal of p75(NTR) extracellular domain reduced the ability of excess Abeta to promote neuritic degeneration. These findings indicate that although p75(NTR) likely does not mediate all Abeta effects, it does play a significant role in enabling Abeta-induced neurodegeneration in vitro and in vivo, establishing p75(NTR) as an important therapeutic target for AD.

  View details for DOI 10.1523/JNEUROSCI.0620-09.2009

  View details for PubMedID 19710315

• Signaling Through Rho GTPase Pathway as Viable Drug Target CURRENT MEDICINAL CHEMISTRY Lu, Q., Longo, F. M., Zhou, H., Massa, S. M., Chen, Y. 2009; 16 (11): 1355-1365

  Abstract

  Signaling through the Rho family of small GTPases has been increasingly investigated for their involvement in a wide variety of diseases such as cardiovascular, pulmonary, and neurological disorders as well as cancer. Rho GTPases are a subfamily of the Ras superfamily proteins which play essential roles in a number of biological processes, especially in the regulation of cell shape change, cytokinesis, cell adhesion, and cell migration. Many of these processes demonstrate a common theme: the rapid and dynamic reorganization of actin cytoskeleton of which Rho signaling has now emerged as a major switch control. The involvement of dynamic changes of Rho GTPases in disease states underscores the need to produce effective inhibitors for their therapeutic applications. Fasudil and Y-27632, with many newer additions, are two classes of widely used chemical compounds that inhibit Rho kinase (ROCK), an important downstream effector of RhoA subfamily GTPases. These inhibitors have been successful in many preclinical studies, indicating the potential benefit of clinical Rho pathway inhibition. On the other hand, except for Rac1 inhibitor NSC23766, there are few effective inhibitors directly targeting Rho GTPases, likely due to the lack of optimal structural information on individual Rho-RhoGEF, Rho-RhoGAP, or Rho-RhoGDI interaction to achieve specificity. Recently, LM11A-31 and other derivatives of peptide mimetic ligands for p75 neurotrophin receptor (p75(NTR)) show promising effects upstream of Rho GTPase signaling in neuronal regeneration. CCG-1423, a chemical compound showing profiles of inhibiting downstream of RhoA, is a further attempt for the development of novel pharmacological tools to disrupt Rho signaling pathway in cancer. Because of a rapidly growing number of studies deciphering the role of the Rho proteins in many diseases, specific and potent pharmaceutical modulators of various steps of Rho GTPase signaling pathway are critically needed to target for therapeutic intervention in cardiovascular disease, neurological disorders, and cancer progression.

  View details for Web of Science ID 000265692300004

  View details for PubMedID 19355891

• Stabilizing intracellular calcium regulation with novel neurotrophin mimetics provides potent neuroprotection against gp120-induced macrophage toxins Meeker, R. B., Poulton, W., Moore, L., Massa, S. M., Longo, F. M. TAYLOR & FRANCIS INC. 2009: 58-59

  View details for Web of Science ID 000270278700122

• Neurotrophin Mimetics reverse effects of HIV gp120 on Macrophages and Microglia Killebrew, D. A., Poulton, W., Longo, F. M., Massa, S. M., Meeker, R. B. TAYLOR & FRANCIS INC. 2009: 42-43

  View details for Web of Science ID 000270278700092

• Small Molecule, Non-Peptide p75(NTR) Ligands Inhibit A beta-Induced Neurodegeneration and Synaptic Impairment PLOS ONE Yang, T., Knowles, J. K., Lu, Q., Zhang, H., Arancio, O., Moore, L. A., Chang, T., Wang, Q., Andreasson, K., Rajadas, J., Fuller, G. G., Xie, Y., Massa, S. M., Longo, F. M. 2008; 3 (11)

  Abstract

  The p75 neurotrophin receptor (p75(NTR)) is expressed by neurons particularly vulnerable in Alzheimer's disease (AD). We tested the hypothesis that non-peptide, small molecule p75(NTR) ligands found to promote survival signaling might prevent Abeta-induced degeneration and synaptic dysfunction. These ligands inhibited Abeta-induced neuritic dystrophy, death of cultured neurons and Abeta-induced death of pyramidal neurons in hippocampal slice cultures. Moreover, ligands inhibited Abeta-induced activation of molecules involved in AD pathology including calpain/cdk5, GSK3beta and c-Jun, and tau phosphorylation, and prevented Abeta-induced inactivation of AKT and CREB. Finally, a p75(NTR) ligand blocked Abeta-induced hippocampal LTP impairment. These studies support an extensive intersection between p75(NTR) signaling and Abeta pathogenic mechanisms, and introduce a class of specific small molecule ligands with the unique ability to block multiple fundamental AD-related signaling pathways, reverse synaptic impairment and inhibit Abeta-induced neuronal dystrophy and death.

  View details for DOI 10.1371/journal.pone.0003604

  View details for Web of Science ID 000265134200003

  View details for PubMedID 18978948

  View details for PubMedCentralID PMC2575383

• A common motif targets huntingtin and the androgen receptor to the proteasome JOURNAL OF BIOLOGICAL CHEMISTRY Chandra, S., Shao, J., Li, J. X., Li, M., Longo, F. M., Diamond, M. I. 2008; 283 (35): 23950-23955

  Abstract

  Huntington disease derives from a critically expanded polyglutamine tract in the huntingtin (Htt) protein; a similar polyglutamine expansion in the androgen receptor (AR) causes spinobulbar muscular atrophy. AR activity also plays an essential role in prostate cancer. Molecular mechanisms that regulate Htt and AR degradation are not well understood but could have important therapeutic implications. We find that a pentapeptide motif (FQKLL) within the Htt protein regulates its degradation and subcellular localization to cytoplasm puncta. Disruption of the motif by alanine substitution at the hydrophobic residues increases the steady state level of the protein. Pulsechase analyses indicate that the motif regulates degradation. A similar motif (FQNLF) has corresponding activities in the AR protein. Transfer of the Htt motif with five flanking amino acids on either side to YFP reduces the steady state YFP level by rendering it susceptible to proteasome degradation. This work defines a novel proteasome-targeting motif that is necessary and sufficient to regulate the degradation of two disease-associated proteins.

  View details for DOI 10.1074/jbc.M800467200

  View details for Web of Science ID 000258638900050

  View details for PubMedID 18586675

  View details for PubMedCentralID PMC2527109

• Anti-cancer drug induced neurotoxicity and identification of Rho pathway signaling modulators as potential neuroprotectants NEUROTOXICOLOGY James, S. E., Burden, H., Burgess, R., Xie, Y., Yang, T., Massa, S. M., Longo, F. M., Lu, Q. 2008; 29 (4): 605-612

  Abstract

  Many chemotherapy drugs are known to cause significant clinical neurotoxicity, which can result in the early cessation of treatment. To identify and develop more effective means of neuroprotection it is important to understand the toxicity of these drugs at the molecular and cellular levels. In the present study, we examine the effects of paclitaxel (taxol), cisplatin, and methotrexate on primary rat neurons including hippocampal, cortical, and dorsal horn/dorsal root ganglion neuronal cultures. We found that all of these anti-cancer drugs induce substantial neurotoxicity evidenced by neurite degeneration. The neurons are capable of recovering after treatment withdrawal, but taxol exerts a biphasic effect that results in the collapse of processes days after treatment is withdrawn. After cisplatin and methotrexate treatment, we observed the degeneration of neuronal processes including the reduction of dendritic branching, length, and altered growth cone formation, indicating an abnormal arrangement of the actin cytoskeleton consistent with the involvement of Rho family small GTPases. Inhibiting RhoA downstream effector p160 ROCK/Rho kinase using Y-27632, or activating p75 neurotrophin receptor (p75 NTR) using non-peptide mimetic LM11A-31, were able to reverse the degeneration caused by cisplatin and methotrexate. Therefore, the neurotoxicity resulting from exposure to the anti-cancer drugs cisplatin and methotrexate can be alleviated by inhibiting Rho signaling pathway.

  View details for DOI 10.1016/j.neuro.2008.04.008

  View details for Web of Science ID 000257819500006

  View details for PubMedID 18539332

  View details for PubMedCentralID PMC2615238

• Small Molecule Modulation of p75 Neurotrophin Receptor Functions CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS Longo, F. M., Massa, S. M. 2008; 7 (1): 63-70

  Abstract

  Ligand-independent and/or proNGF-induced p75(NTR) signaling has emerged as a potential major contributor to a number of pathological states, including axotomy-induced death, motor neuron degeneration, neuronal degeneration in Alzheimer's disease and oligodendrocyte death following spinal cord injury. A long standing goal in the neurotrophin field has been the development of non-peptide, small molecules capable of functioning as specific ligands at neurotrophin receptors such as p75(NTR) to promote desired biological outcomes. Synthetic peptides modeled on neurotrophin protein domains have been found to bind to and activate various neurotrophin receptors, raising the possibility that active, non-peptide, small molecule ligands might also be identified; however, traditional high-throughput screening approaches have been largely ineffective in identifying such compounds. Using pharmacophores derived from the structure of loop 1 of nerve growth factor, non-peptide, small molecules that function as p75(NTR) ligands to promote survival and block proNGF-induced death have recently been identified. Small molecule p75(NTR) ligands, with high potency and specificity, may provide novel therapeutic approaches for neurodegenerative diseases, neurotrauma and other pathologic states.

  View details for Web of Science ID 000262654300008

  View details for PubMedID 18289033

• E-cadherin promotes retinal ganglion cell neurite outgrowth in a protein tyrosine phosphatase-mu-dependent manner MOLECULAR AND CELLULAR NEUROSCIENCE Oblander, S. A., Ensslen-Craig, S. E., Longo, F. M., Brady-Kalnay, S. M. 2007; 34 (3): 481-492

  Abstract

  During development of the visual system, retinal ganglion cells (RGCs) require cell-cell adhesion molecules and extracellular matrix proteins for axon growth. In this study, we demonstrate that the classical cadherin, E-cadherin, is expressed in RGCs from E6 to E12 and promotes neurite outgrowth from all regions of the chick retina at E6, E8 and E10. E-cadherin is also expressed in the optic tectum. E-cadherin adhesion blocking antibodies specifically inhibit neurite outgrowth on an E-cadherin substrate. The receptor-type protein tyrosine phosphatase, PTPmu, associates with E-cadherin. In this manuscript, we demonstrate that antisense-mediated down-regulation of PTPmu, overexpression of catalytically inactive PTPmu and perturbation of endogenous PTPmu using a specific PTPmu inhibitor peptide results in a substantial reduction in neurite outgrowth on E-cadherin. Taken together, these findings demonstrate that E-cadherin is an important adhesion molecule for chick RGC neurite outgrowth and suggest that PTPmu expression and catalytic activity are required for outgrowth on an E-cadherin substrate.

  View details for DOI 10.1016/j.mcn.2006.12.002

  View details for Web of Science ID 000244909200018

  View details for PubMedID 17276081

• Small molecule neurotrophin receptor ligands: Novel strategies for targeting Alzheimer's disease mechanisms 7th International Conference on Alzheimers Disease Drug Discovery Longo, F. M., Yang, T., Knowles, J. K., Xie, Y., Moore, L. A., Massa, S. M. BENTHAM SCIENCE PUBL LTD. 2007: 503–6

  Abstract

  A number of factors limit the therapeutic application of neurotrophin proteins, such as nerve growth factor (NGF) and brain-derived growth factor (BDNF), for Alzheimer's and other neurodegenerative diseases. These factors include unfavorable pharmacological properties typical of proteins and the pleiotropic effects mediated by protein-ligand interactions with p75(NTR), Trk, and sortilin neurotrophin receptors. Targeted modulation of p75(NTR) provides a strategy for preventing degeneration without promoting TrkA-mediated deleterious effects, and targeted activation of TrkB might achieve more favorable neurotrophic effects than those achieved by concomitant activation of p75(NTR) and TrkB. The discovery of small molecules functioning as ligands at specific neurotrophin receptors has made possible for the first time approaches for modulating selected components of neurotrophin signaling processes for the purpose of modulating underlying Alzheimer's disease mechanisms.

  View details for Web of Science ID 000253592000002

  View details for PubMedID 18220511

• Neuroprotective effects of small, non-peptide neurotrophin mimetics in neural cultures challenged with gp120 or feline immunodeficiency virus Meeker, R. B., Poulton, W., Feng, W., Massa, S. M., Longo, F. M. TAYLOR & FRANCIS INC. 2007: 103-104

  View details for Web of Science ID 000250754000202

• Mechanisms of pain during development: Receptor protein tyrosine phosphatases. Gonzalez-Brito, M., Bixby, J., Longo, F. LIPPINCOTT WILLIAMS & WILKINS. 2006: A36

  View details for DOI 10.1097/00003246-200612002-00127

  View details for Web of Science ID 000242540400128

• LAR protein tyrosine phosphatase receptor associates with TrkB and modulates neurotrophic signaling pathways JOURNAL OF NEUROBIOLOGY Yang, T., Massa, S. M., Longo, F. M. 2006; 66 (13): 1420-1436

  Abstract

  The identities of receptor protein tyrosine phosphatases (PTPs) that associate with Trk protein tyrosine kinase (PTK) receptors and modulate neurotrophic signaling are unknown. The leukocyte common antigen-related (LAR) receptor PTP is present in neurons expressing TrkB, and like TrkB is associated with caveolae and regulates survival and neurite outgrowth. We tested the hypothesis that LAR associates with TrkB and regulates neurotrophic signaling in embryonic hippocampal neurons. Coimmunoprecipitation and coimmunostaining demonstrated LAR interaction with TrkB that is increased by BDNF exposure. BDNF neurotrophic activity was reduced in LAR-/- and LAR siRNA-treated LAR+/+ neurons and was augmented in LAR-transfected neurons. In LAR-/- neurons, BDNF-induced activation of TrkB, Shc, AKT, ERK, and CREB was significantly decreased; while in LAR-transfected neurons, BDNF-induced CREB activation was augmented. Similarly, LAR+/+ neurons treated with LAR siRNA demonstrated decreased activation of Trk and AKT. LAR is known to activate the Src PTK by dephosphorylation of its negative regulatory domain and Src transactivates Trk. In LAR-/- neurons, or neurons treated with LAR siRNA, phosphorylation of the Src regulatory domain was increased (indicating Src inactivation), consistent with a role for Src in mediating LAR's ability to up-regulate neurotrophic signaling. Interactions between LAR, TrkB, and Src were further confirmed by the findings that Src coimmunoprecipitated with LAR, that the Src inhibitor PP2 blocked the ability of LAR to augment TrkB signaling, and that siRNA-induced depletion of Src decreased LAR interaction with TrkB. These studies demonstrate that receptor PTPs can associate with Trk complexes and promote neurotrophic signaling and point to receptor PTP-based strategies as a novel approach for modulating neurotrophin function.

  View details for DOI 10.1002/neu.20291

  View details for Web of Science ID 000241903700003

  View details for PubMedID 17013927

• Modulation of p75(NTR)-dependent motor neuron death by a small non-peptidyl mimetic of the neurotrophin loop 1 domain EUROPEAN JOURNAL OF NEUROSCIENCE Pehar, M., Cassina, P., Vargas, M. R., Xie, Y., Beckman, J. S., Massa, S. M., Longo, F. M., Barbeito, L. 2006; 24 (6): 1575-1580

  Abstract

  The p75 neurotrophin receptor (p75NTR) is expressed by degenerating spinal motor neurons in amyotrophic lateral sclerosis (ALS). The mature and pro-form of nerve growth factor (NGF) activate p75NTR to trigger motor neuron apoptosis. However, attempts to modulate p75NTR-mediated neuronal death in ALS models by downregulating or antagonizing p75NTR with synthetic peptides have led to only modest results. Recently, a novel ligand of p75NTR, compound LM11A-24, has been identified. It is a non-peptidyl mimetic of the neurotrophin loop 1 domain that promotes hippocampal neuron survival through p75NTR and exerts protection against p75NTR-mediated apoptosis of oligodendrocytes induced by proNGF. Thus, LM11A-24 appears to activate p75NTR-linked survival but not death mechanisms, and may interfere with the ability of neurotrophins to induce apoptosis. Given these findings, we hypothesized that LM11A-24 might be a particularly potent inhibitor of motor neuron degeneration. We examined the effects of LM11A-24 on apoptosis of cultured rat embryonic motor neurons. Interestingly, in contrast to the effects observed in hippocampal cultures, LM11A-24 was unable to prevent motor neuron apoptosis induced by trophic factor deprivation. However, picomolar concentrations of LM11A-24 prevented p75NTR-dependent motor neuron death induced by either exogenous addition of NGF or spinal cord extracts from symptomatic superoxide dismutase-1G93A mice, in the presence of low steady-state concentrations of nitric oxide. LM11A-24 also inhibited motor neuron death induced by NGF-producing reactive astrocytes in co-culture conditions. These studies suggest that modulation of p75NTR by small molecule ligands targeting this receptor might constitute a novel strategy for preventing motor neuron degeneration.

  View details for DOI 10.1111/j.1460-9568.2006.05040.x

  View details for Web of Science ID 000240660800007

  View details for PubMedID 17004921

• Protein-tyrosine phosphatase (PTP) wedge domain peptides - A novel approach for inhibition of PTP function and augmentation of protein-tyrosine kinase function JOURNAL OF BIOLOGICAL CHEMISTRY Xie, Y., Massa, S. M., Ensslen-Craig, S. E., Major, D. L., Yang, T., Tisi, M. A., Derevyanny, V. D., Runge, W. O., Mehta, B. P., Moore, L. A., Brady-Kalnay, S. M., Longo, F. M. 2006; 281 (24): 16482-16492

  Abstract

  Inhibition of protein-tyrosine phosphatases (PTPs) counterbalancing protein-tyrosine kinases (PTKs) offers a strategy for augmenting PTK actions. Conservation of PTP catalytic sites limits development of specific PTP inhibitors. A number of receptor PTPs, including the leukocyte common antigen-related (LAR) receptor and PTPmu, contain a wedge-shaped helix-loop-helix located near the first catalytic domain. Helix-loop-helix domains in other proteins demonstrate homophilic binding and inhibit function; therefore, we tested the hypothesis that LAR wedge domain peptides would exhibit homophilic binding, bind to LAR, and inhibit LAR function. Fluorescent beads coated with LAR or PTPmu wedge peptides demonstrated PTP-specific homophilic binding, and LAR wedge peptide-coated beads precipitated LAR protein. Administration of LAR wedge Tat peptide to PC12 cells resulted in increased proliferation, decreased cell death, increased neurite outgrowth, and augmented Trk PTK-mediated responses to nerve growth factor (NGF), a phenotype matching that found in PC12 cells with reduced LAR levels. PTPmu wedge Tat peptide had no effect on PC12 cells but blocked the PTPmu-dependent phenotype of neurite outgrowth of retinal ganglion neurons on a PTPmu substrate, whereas LAR wedge peptide had no effect. The survival- and neurite-promoting effect of the LAR wedge peptide was blocked by the Trk inhibitor K252a, and reciprocal co-immunoprecipitation demonstrated LAR/TrkA association. The addition of LAR wedge peptide inhibited LAR co-immunoprecipitation with TrkA, augmented NGF-induced activation of TrkA, ERK, and AKT, and in the absence of exogenous NGF, induced activation of TrkA, ERK, and AKT. PTP wedge domain peptides provide a unique PTP inhibition strategy and offer a novel approach for augmenting PTK function.

  View details for DOI 10.1074/jbc.M603131200

  View details for Web of Science ID 000238165700038

  View details for PubMedID 16613844

• Small, nonpeptide p75(NTR) ligands induce survival signaling and inhibit proNGF-induced death JOURNAL OF NEUROSCIENCE Massa, S. M., Xie, Y., Yang, T., Harrington, A. W., Kim, M. L., Yoon, S. O., Kraemer, R., Moore, L. A., Hempstead, B. L., Longo, F. M. 2006; 26 (20): 5288-5300

  Abstract

  Studies showing that neurotrophin binding to p75NTR can promote cell survival in the absence of Trk (tropomyosin-related kinase) receptors, together with recent structural data indicating that NGF may bind to p75NTR in a monovalent manner, raise the possibility that small molecule p75NTR ligands that positively regulate survival might be found. A pharmacophore designed to capture selected structural and physical chemical features of a neurotrophin domain known to interact with p75NTR was applied to in silico screening of small molecule libraries. Small, nonpeptide, monomeric compounds were identified that interact with p75NTR. In cells showing trophic responses to neurotrophins, the compounds promoted survival signaling through p75NTR-dependent mechanisms. In cells susceptible to proneurotrophin-induced death, compounds did not induce apoptosis but inhibited proneurotrophin-mediated death. These studies identify a unique range of p75NTR behaviors that can result from isolated receptor liganding and establish several novel therapeutic leads.

  View details for DOI 10.1523/JNEUROSCI.3547-05.2006

  View details for Web of Science ID 000237608400002

  View details for PubMedID 16707781

• Downregulation of the LAR protein tyrosine phosphatase receptor is associated with increased dentate gyrus neurogenesis and an increased number of granule cell layer neurons MOLECULAR AND CELLULAR NEUROSCIENCE Bernabeu, R., Yang, T., Xie, Y. M., Mehta, B., Ma, S. Y., Longo, F. M. 2006; 31 (4): 723-738

  Abstract

  Growth factors stimulating neurogenesis act through protein tyrosine kinases which are counterbalanced by protein tyrosine phosphatases (PTPs); thus, downregulation of progenitor PTP function might provide a novel strategy for promoting neurogenesis. We tested the hypotheses that the leukocyte common antigen-related (LAR) PTP is present in adult dentate gyrus progenitors, and that its downregulation would promote neurogenesis. In adult mice, LAR immunostaining was present in Ki-67- and PCNA-positive subgranular zone cells. At 1 h post-BrdU administration, LAR-/- mice demonstrated an approximately 3-fold increase in BrdU- and PCNA-positive cells, indicating increased progenitor proliferation. At 1 day and 4 weeks following 6 days of BrdU administration, LAR-/- mice exhibited a significant increase in BrdU and NeuN colabeled cells consistent with increased neurogenesis. In association with increased neurogenesis in LAR-/- mice, stereological analysis revealed a significant 37% increase in the number of neurons present in the granule cell layer. In cultured progenitor clones derived from LAR+/+ mice, LAR immunostaining was present in PCNA- and BrdU-positive cells. Progenitor clones derived from adult LAR-/- hippocampus or LAR+/+ clones made LAR-deficient with LAR siRNA demonstrated increased proliferation and, under differentiation conditions, increased proportions of Tuj1- and MAP2-positive cells. These studies introduce LAR as the first PTP found to be expressed in dentate progenitors and point to inhibition of LAR as a potential strategy for promoting neurogenesis. These findings also provide a rare in vivo demonstration of an association between increased dentate neurogenesis and an expanded population of granule cell layer neurons.

  View details for DOI 10.1016/j.mcn.2006.01.003

  View details for Web of Science ID 000236659600012

  View details for PubMedID 16488625

• Small molecule approaches for promoting neurogenesis. Current Alzheimer research Longo, F. M., Yang, T., Xie, Y., Massa, S. M. 2006; 3 (1): 5-10

  Abstract

  The discovery of small molecules capable of promoting neurogenesis will contribute to the elucidation of the physiological roles of neurogenesis and to novel therapeutic approaches. Small molecule development can be targeted to the promotion of precursor proliferation, survival, migration or maturation and might be applied to augmenting physiological neurogenesis already present in the dentate gyrus or subventricular zone/olfactory bulb or to normally non-neurogenic regions relevant to neuropathological states. Current small molecule discovery can be assessed from the perspective of the following categories: compounds modulating physiological signaling pathways regulating neurogenesis including the sonic hedgehog, bone morphogenic protein Wnt/,-catenin, Notch and chemokine systems; growth factor mimetics; protein tyrosine phosphatase inhibitors; existing drugs including antidepressants, lithium, valproate, sildenafil and statins; hormones, steroids and peptides; and neurotransmitter receptor agonists and antagonists. Unbiased, high throughput screening will likely lead to the discovery of additional active compounds and the recognition of novel mechanisms regulating neurogenesis. A major therapeutic challenge will consist of the identification of molecular targets and mechanisms relatively specific for precursor cells of interest.

  View details for PubMedID 16472196

• Identification of an ectodomain within the LAR protein tyrosine phosphatase receptor that binds homophilically and activates signalling pathways promoting neurite outgrowth EUROPEAN JOURNAL OF NEUROSCIENCE Yang, T., Yin, W. N., Derevyanny, V. D., Moore, L. A., Longo, F. M. 2005; 22 (9): 2159-2170

  Abstract

  Elucidation of mechanisms by which receptor protein tyrosine phosphatases (PTPs) regulate neurite outgrowth will require characterization of ligand-receptor interactions and identification of ligand-induced signalling components mediating neurite outgrowth. The first identified ligand of the leucocyte common antigen-related (LAR) receptor PTP consists of a 99-residue ectodomain isoform, termed LARFN5C, which undergoes homophilic binding to LAR and promotes neurite outgrowth. We employed peptide mapping of LARFN5C to identify an active neurite-promoting domain of LAR. A peptide mimetic consisting of 37 residues (L59) and corresponding to the fifth LAR fibronectin type III (FNIII) domain prevented LARFN5C homophilic binding, demonstrated homophilic binding to itself and promoted neurite outgrowth of mouse E16-17 hippocampal neurons and of dorsal root ganglia explants. Response to L59 was partially lost when using neurons derived from LAR-deficient (-/-) mice or neurons treated with LAR siRNA, consistent with homophilic interaction of L59 with LAR. L59 neurite-promoting activity was decreased in the presence of inhibitors of Src, Trk, PLCgamma, PKC, PI3K and MAPK. L59 activated Src (a known substrate of LAR), FAK and TrkB and also activated downstream signalling intermediates including PKC, ERK, AKT and CREB. BDNF augmented the maximal neurite-promoting activity of L59, a finding consistent with the presence of shared and distinct signalling pathways activated by L59 with BDNF and L59 with TrkB. These studies are the first to identify an ectodomain of LAR (located within the fifth FNIII domain) capable of promoting neurite outgrowth and point to novel approaches for promotion of neurite outgrowth.

  View details for DOI 10.1111/j.1460-9568.2005.04403.x

  View details for Web of Science ID 000232978500004

  View details for PubMedID 16262654

• Neurotrophin receptor-based strategies for Alzheimer's disease. Current Alzheimer research Longo, F. M., Massa, S. M. 2005; 2 (2): 167-169

  Abstract

  The traditional perspective of applying neurotrophins in the context of Alzheimer's disease is based on the premise that neurotrophins are capable of upregulating cholinergic function and of rendering neurons less vulnerable to certain processes causing degeneration. Factors limiting the therapeutic application of neurotrophin proteins include their poor pharmacological properties and their pleiotropic effects mediated by interaction with Trk, p75NTR and sortilin receptors. Recent studies suggesting and that pro-forms of neurotrophins accumulating in Alzheimer's and other pathological states cause cell death, that p75NTR modulates amyloid beta- and injury-induced neurodegeneration and that small molecules can be created that bind specifically to individual neurotrophin receptors point to novel strategies by which neurotrophin receptors might be targeted in Alzheimer's and other neuropathological states.

  View details for PubMedID 15974914

• Neurotrophin Small Molecule Mimetics: Candidate Therapeutic Agents for Neurological Disorders Curr Med Chem - CNS Agents Longo FM, Xie Y, Massa SM 2005; 5: 29-41
• Neurotrophin-based strategies for neuroprotection JOURNAL OF ALZHEIMERS DISEASE Longo, F. M., Massa, S. M. 2004; 6 (6): S13-S17

  Abstract

  Neurotrophins activate a number of signaling pathways relevant to neuroprotection; however, their poor pharmacological properties and their pleiotropic effects resulting from interaction with the p75(NTR)-Trk-sortilin three-receptor signaling system limit therapeutic application. While local application of neurotrophin proteins addresses some of the pharmacological challenges, selective targeting of neurotrophin receptors might allow for more selective application of neurotrophin receptor signaling modulation. Recent studies have supported the feasibility of developing non-peptidyl small molecules that mimic specific domains of neurotrophins and modulate signaling of specific neurotrophin receptors. The expression of p75(NTR) by populations of neurons most vulnerable in Alzheimer's disease and the linkage of p75(NTR) signaling to aberrant signaling mechanisms occurring in this disorder, point to potential applications for p75(NTR)-based small molecule strategies. Small molecules targeted to p75(NTR) in the settings of neurodegenerative disease and other forms of neural injury might serve to inhibit death signaling, block proNGF-mediated degenerative signaling and minimize deleterious effects promoted by pharmacologically upregulated Trk signaling.

  View details for Web of Science ID 000227211900004

  View details for PubMedID 15665408

• Neuroprotective strategies in Alzheimer's disease. NeuroRx : the journal of the American Society for Experimental NeuroTherapeutics Longo, F. M., Massa, S. M. 2004; 1 (1): 117-127

  Abstract

  In addition to strategies designed to decrease amyloid beta (A beta) levels, it is likely that successful Alzheimer's disease (AD) therapeutic regimens will require the concomitant application of neuroprotective agents. Elucidation of pathophysiological processes occurring in AD and identification of the molecular targets mediating these processes point to potential high-yield neuroprotective strategies. Candidate neuroprotective agents include those that interact specifically with neuronal targets to inhibit deleterious intraneuronal mechanisms triggered by A beta and other toxic stimuli. Strategies include creating small molecules that block A beta interactions with cell surface and intracellular targets, down-regulate stress kinase signaling cascades, block activation of caspases and expression of pro-apoptotic proteins, and inhibit enzymes mediating excessive tau protein phosphorylation. Additional potential neuroprotective compounds include those that counteract loss of cholinergic function, promote the trophic state and plasticity of neurons, inhibit accumulation of reactive oxygen species, and block excitotoxicity. Certain categories of compounds, such as neurotrophins or neurotrophin small molecule mimetics, have the potential to alter neuronal signaling patterns such that several of these target actions might be achieved by a single agent.

  View details for PubMedID 15717012

• A candidate chimeric mammalian mRNA transcript is derived from distinct chromosomes and is associated with nonconsensus splice junction motifs DNA AND CELL BIOLOGY Zhang, C., Xie, Y. M., Martignetti, J. A., Yeo, T. T., Massa, S. M., Longo, F. M. 2003; 22 (5): 303-315

  Abstract

  The process of creating chimeric mRNA transcripts derived from separately transcribed genes via known spliceosome mechanisms is termed trans-splicing, and has been primarily described in lower eukaryotes. Isolation of cDNA clones containing sequences from distinct genes has raised the possibility of trans-splicing across distinct genes in mammalian systems; however, the possibility of cloning artifacts or splicing via nonspliceosome mechanisms has been difficult to rule out. In most cases, the absence of corresponding genomic clones has limited assessment of splice donor and acceptance sites and associated intronic elements that would be expected to participate in spliceosome-based reactions. We have previously reported a cDNA clone encoding the rat Leukocyte Common Antigen-Related (LAR) tyrosine phosphatase receptor that contains an alternative 3' UTR. In the present study Northern, RT-PCR and RNase protection assays verified the existence of developmentally regulated 3' UTR alternative splicing of LAR transcripts in vivo. FISH and radiation hybrid mapping demonstrated that loci encoding LAR and its alternative 3' UTR are present on distinct chromosomes, raising the possibility that alternatively spliced transcripts resulted from trans-splicing. Exon/intron analysis of corresponding genomic clones revealed nonconsensus splice junctions along with elements known to promote both cis- and trans-splicing. Verification in a mammalian in vivo system of chimeric transcripts derived from distinct genes along with identification of atypical nonconsensus-associated genomic elements points to the novel possibilities of atypical spliceosome-based trans-splicing or nonconventional, nonspliceosome-based mechanisms leading to chimeric transcripts.

  View details for Web of Science ID 000184158200002

  View details for PubMedID 12941158

• Leukocyte antigen-related protein tyrosine phosphatase receptor: A small ectodomain isoform functions as a homophilic ligand and promotes neurite outgrowth JOURNAL OF NEUROSCIENCE Yang, T., Bernabeu, R., Xie, Y. M., Zhang, J. S., Massa, S. M., Rempel, H. C., LONGO, F. M. 2003; 23 (8): 3353-3363

  Abstract

  The identities of ligands interacting with protein tyrosine phosphatase (PTP) receptors to regulate neurite outgrowth remain mainly unknown. Analysis of cDNA and genomic clones encoding the rat leukocyte common antigen-related (LAR) PTP receptor predicted a small, approximately 11 kDa ectodomain isoform, designated LARFN5C, containing a novel N terminal followed by a C-terminal segment of the LAR fifth fibronectin type III domain. RT-PCR and Northern blot analysis confirmed the presence of LARFN5C transcripts in brain. Transfection of COS cells with LARFN5C-Fc cDNA resulted in expression of the predicted protein, and Western blot analysis verified expression of approximately 11 kDa LARFN5C protein in vivo and its developmental regulation. Beads coated with rLARFN5C demonstrated aggregation consistent with homophilic binding, and pull-down and immunoprecipitation assays demonstrated that rLARFN5C associates with the LAR receptor. rLARFN5C binding to COS cells was dependent on LAR expression, and rLARFN5C binding to LAR +/+ hippocampal neurons was fivefold greater than that found by using LAR-deficient (-/-) neurons. Substratum-bound rLARFN5C had potent neurite-promoting effects on LAR +/+ neurons, with a fivefold loss in potency with the use of LAR -/- neurons. rLARFN5C in solution at low nanomolar concentrations inhibited neurite outgrowth induced by substratum-bound rLARFN5C, consistent with receptor-based function. These studies suggest that a small ectodomain isoform of a PTP receptor can function as a ligand for the same receptor to promote neurite outgrowth.

  View details for Web of Science ID 000182475200030

  View details for PubMedID 12716943

• Alzheimer's therapeutics - Neurotrophin domain small molecule mimetics JOURNAL OF MOLECULAR NEUROSCIENCE Massa, S. M., Xie, Y. M., LONGO, F. M. 2003; 20 (3): 323-326

  Abstract

  Factors limiting the therapeutic application of neurotrophins to neurodegenerative diseases include poor stability and CNS penetration. Moreover, certain neurotrophin effects, such as promotion of neuronal death via interaction with the p75NTR receptor, might further limit their application. We have proposed that development of small molecule mimetics of neurotrophins might serve to overcome these limitations. In previous work, our laboratory established the proof-of-principle that mimetics of specific nerve growth factor (NGF) domains could prevent neuronal death. Peptidomimetics of the loop 1 domain prevent death via p75NTR-dependent signaling and peptidomimetics of the loop 4 domain prevent death via Trk-related signaling. In current work we are designing pharmacophore queries corresponding to loop domains 1 or 4 that incorporate features of the NGF crystal structure along with features derived from peptidomimetic structure-activity-relationships. Screening of in silico databases containing non-peptide, small molecules has identified a number of candidate NGF domain mimetics. Preliminary assessment of these compounds using neurotrophin bioassays indicates that several are capable of preventing neuronal death. Ongoing studies will determine whether these compounds act via p75NTR or Trk receptors.

  View details for Web of Science ID 000185578800017

  View details for PubMedID 14501015

• Modulation of Alzheimer-like synaptic and cholinergic deficits in transgenic mice by human apolipoprotein E depends on isoform, aging, and overexpression of amyloid beta peptides but not on plaque formation JOURNAL OF NEUROSCIENCE Buttini, M., Yu, G. Q., Shockley, K., Huang, Y. D., Jones, B., Masliah, E., Mallory, M., Yeo, T., LONGO, F. M., Mucke, L. 2002; 22 (24): 10539-10548

  Abstract

  The most frequent human apolipoprotein (apo) E isoforms, E3 and E4, differentially affect Alzheimer's disease (AD) risk (E4 > E3) and age of onset (E4 < E3). Compared with apoE3, apoE4 promotes the cerebral deposition of amyloid beta (Abeta) peptides, which are derived from the amyloid precursor protein (APP) and play a central role in AD. However, it is uncertain whether Abeta deposition into plaques is the main mechanism by which apoE isoforms affect AD. We analyzed murine apoE-deficient transgenic mice expressing in their brains human APP (hAPP) and Abeta together with apoE3 or apoE4. Because cognitive decline in AD correlates better with decreases in synaptophysin-immunoreactive presynaptic terminals, choline acetyltransferase (ChAT) activity, and ChAT-positive fibers than with plaque load, we compared these parameters in hAPP/apoE3 and hAPP/apoE4 mice and singly transgenic controls at 6-7, 12-15, and 19-24 months of age. Brain aging in the context of high levels of nondeposited human Abeta resulted in progressive synaptic/cholinergic deficits. ApoE3 delayed the synaptic deficits until old age, whereas apoE4 was not protective at any of the ages analyzed. Old hAPP/apoE4 mice had more plaques than old hAPP/apoE3 mice, but synaptic/cholinergic deficits preceded plaque formation in hAPP/apoE4 mice. Moreover, despite their different plaque loads, old hAPP/apoE4 and hAPP/apoE3 mice had comparable synaptic/cholinergic deficits, and these deficits were found not only in the hippocampus but also in the neocortex, which in most mice contained no plaques. Thus, apoE3, but not apoE4, delays age- and Abeta-dependent synaptic deficits through a plaque-independent mechanism. This difference could contribute to the differential effects of apoE isoforms on the risk and onset of AD.

  View details for Web of Science ID 000179861100008

  View details for PubMedID 12486146

• ProNGF induces p75-mediated death of oligodendrocytes following spinal cord injury NEURON Beattie, M. S., Harrington, A. W., LEE, R., Kim, J. Y., Boyce, S. L., LONGO, F. M., Bresnahan, J. C., Hempstead, B. L., Yoon, S. O. 2002; 36 (3): 375-386

  Abstract

  The neurotrophin receptor p75 is induced by various injuries to the nervous system, but its role after injury has remained unclear. Here, we report that p75 is required for the death of oligodendrocytes following spinal cord injury, and its action is mediated mainly by proNGF. Oligodendrocytes undergoing apoptosis expressed p75, and the absence of p75 resulted in a decrease in the number of apoptotic oligodendrocytes and increased survival of oligodendrocytes. ProNGF is likely responsible for activating p75 in vivo, since the proNGF from the injured spinal cord induced apoptosis among p75(+/+), but not among p75(-/-), oligodendrocytes in culture, and its action was blocked by proNGF-specific antibody. Together, these data suggest that the role of proNGF is to eliminate damaged cells by activating the apoptotic machinery of p75 after injury.

  View details for Web of Science ID 000178877700008

  View details for PubMedID 12408842

• Alzheimer's therapeutics - Neurotrophin small molecule mimetics JOURNAL OF MOLECULAR NEUROSCIENCE Massa, S. M., Xie, Y. M., Longo, F. M. 2002; 19 (1-2): 107-111

  Abstract

  A substantial portion of neuronal populations undergoing degeneration in Alzheimer's and other neurodegenerative disorders express neurotrophin receptors. Neurotrophin small molecule mimetics constitute candidate compounds that might be useful in preventing or delaying loss of neuronal function, neural networks or neuronal death in neurodegenerative states. We are testing the hypothesis that pharmacophores based on a combination of the crystal structures of neurotrophins and structure-activity relationships of active neurotrophin peptidomimetics can be used to screen small molecule libraries to identify non-peptide small molecules with neurotrophin agonist or antagonist activity. In preliminary screens using pharmacophores based on two nerve growth factor (NGF) loop domains, a number of small molecules have been identified that display neurotrophic activity using in vitro bioassays. Current studies are focused on determining whether these small molecules function via neurotrophin receptors and whether they activate neurotrophin signaling cascades. Assessment of structure-activity relationships between active and inactive small molecules will allow modification of pharmacophores and provide a basis for the iterative process if identifying compounds with increased potency and efficacy. A collection of such compounds will provide a basis for synthesis of compounds with targeted pharmacological properties.

  View details for Web of Science ID 000177794700018

  View details for PubMedID 12212765

• Alzheimer's therapeutics: Neurotrophin small molecule mimetics 1st Annual Investigators Meeting Massa, S. M., Xie, Y. M., LONGO, F. M. SPRINGER PUBLISHING CO. 2002: 147–155

  View details for Web of Science ID 000180452600018

• Psychological impact of news of genetic risk for Huntington disease AMERICAN JOURNAL OF MEDICAL GENETICS Horowitz, M. J., Field, N. P., Zanko, A., Donnelly, E. F., Epstein, C., Longo, F. 2001; 103 (3): 188-192

  Abstract

  A one-year longitudinal study was conducted investigating the psychological effects of the news of genetic testing for the Huntington disease (HD) gene. Participants were assessed at baseline (before obtaining news of test results) and at three, six, and 12 months after test results on stress-specific symptom measures. Among carriers of the HD gene, a considerable number (55%) showed evidence of neurological impairment at baseline, indicative of HD. Also noteworthy, these individuals had significantly higher psychological symptom scores at baseline than carriers without neurological impairment or noncarriers. Despite this, these individuals were no more aware of their carrier status at baseline than carriers without HD symptoms or noncarriers. Furthermore, the psychological symptom levels of HD carriers with neurological impairment remained elevated across the follow-up assessments. Results for noncarriers and carriers without HD neurological symptoms were consistent with the findings of previous studies indicating that news of genetic testing for the HD gene had limited detrimental impact. The clinical implications of the results are discussed.

  View details for Web of Science ID 000171277000002

  View details for PubMedID 11745989

• The leukocyte common antigen-related protein tyrosine phosphatase receptor regulates regenerative neurite outgrowth in vivo JOURNAL OF NEUROSCIENCE Xie, Y. M., Yeo, T. T., Zhang, C., Yang, T., Tisi, M. A., Massa, S. M., Longo, F. M. 2001; 21 (14): 5130-5138

  Abstract

  Drosophila and leech models of nervous system development demonstrate that protein tyrosine phosphatase (PTP) receptors regulate developmental neurite outgrowth. Whether PTP receptors regulate neurite outgrowth in adult systems or in regenerative states remains unknown. The leukocyte common antigen-related (LAR) receptor is known to be present in rodent dorsal root ganglion (DRG) neurons; therefore, the well established model of postcrush sciatic nerve regeneration was used to test the hypothesis that LAR is required for neurite outgrowth in the adult mammalian nervous system. In uninjured sciatic nerves, no differences in nerve morphology and sensory function were detected between wild-type and LAR-deficient littermate transgenic mice. Sciatic nerve crush resulted in increased LAR protein expression in DRG neurons. In addition, nerve injury led to an increase in the proportion of LAR protein isoforms known to have increased binding affinity to neurite-promoting laminin-nidogen complexes. Two weeks after nerve crush, morphological analysis of distal nerve segments in LAR-deficient transgenic mice demonstrated significantly decreased densities of myelinated fibers, decreased axonal areas, and increased myelin/axon area ratios compared with littermate controls. Electron microscopy analysis revealed a significant twofold reduction in the density of regenerating unmyelinated fibers in LAR-/- nerves distal to the crush site. Sensory testing at the 2 week time point revealed a corresponding 3 mm lag in the proximal-to-distal progression of functioning sensory fibers along the distal nerve segment. These studies introduce PTP receptors as a major new gene family regulating regenerative neurite outgrowth in vivo in the adult mammalian system.

  View details for Web of Science ID 000169692800022

  View details for PubMedID 11438588

• Stress induces zinc finger immediate early genes in the rat adrenal gland BRAIN RESEARCH Honkaniemi, J., Zhang, J. S., LONGO, F. M., Sharp, F. R. 2000; 877 (2): 203-208

  Abstract

  The secretion of steroid hormones from the adrenal cortex as well as cathecolamines from the adrenal medulla is stimulated by stress. In this study, we studied the effect of capsaicin-induced stress on the expression of the immediate-early genes (IEGs) NGFI-A, -B, -C, egr-2, -3 and Nurr1 in the rat adrenal gland using in situ hybridization. All of these IEGs except egr-2 were rapidly induced in the adrenal cortex and medulla. The temporal patterns of the IEG induction in medulla varied significantly. NGFI-A was induced in medulla within 15 min after stress, NGFI-B, egr-3 and Nurr1 were induced by 30 min, whereas NGFI-C was induced by 2 h. Surprisingly, only NGFI-B and Nurr1 were induced in the glucocorticoid secreting regions of zonae reticularis and fasciculata of the cortex, starting 15 min after the stress. All of the inducible IEGs were induced in the aldosterone secreting zona glomerulosa 15-30 min after the capsaicin injection. NGFI-A, NGFI-B and Nurr1 expression persisted for 6 h. Since the IEGs studied had major differences in their temporospatial induction pattern, they are likely to be induced by distinct stress-elicited factors and have separate target genes and roles in stress-induced glucocorticoid and catecholamine secretion.

  View details for Web of Science ID 000089388500010

  View details for PubMedID 10986333

• Nerve growth factor (NGF) loop 4 dimeric mimetics activate ERK and AKT and promote NGF-like neurotrophic effects JOURNAL OF BIOLOGICAL CHEMISTRY Xie, Y. M., Tisi, M. A., Yeo, T. T., LONGO, F. M. 2000; 275 (38): 29868-29874

  Abstract

  Previous work indicating that nerve growth factor (NGF) protein loops 2 and 4 interact with TrkA receptors raise the possibility that small molecule mimetics corresponding to TrkA-interacting domains that have NGF agonist activity can be developed. We applied our previously developed strategy of dimeric peptidomimetics to address the hypothesis that loop 4 small molecule dimeric mimetics would activate TrkA-related signal transduction and mimic NGF neurotrophic effects in a structure-specific manner. A loop 4 cyclized peptide dimer demonstrated NGF-like neurotrophic activity, whereas peptides with scrambled sequence, added or substituted residues, or cyclized in monomeric form were inactive. Activity was blocked by the TrkA inhibitors K252a and AG879 but not by NGF p75 receptor blocking antibody. Dimeric, but not monomeric, peptides partially blocked NGF activity. This profile was consistent with that of a NGF partial agonist. ERK and AKT phosphorylation was stimulated only by biologically active peptides and was blocked by K252a. The ERK inhibitor U0126 blocked the neurite- but not the survival-promoting activity of both NGF and active peptide. These studies support the proof of concept that small molecule NGF loop 4 mimetics can activate NGF signaling pathways and can mimic death-preventing and neurite-promoting effects of NGF. This finding will guide the rational design of NGF single-domain mimetics and contribute to elucidating NGF signal transduction mechanisms.

  View details for Web of Science ID 000089439800093

  View details for PubMedID 10896671

• Downregulation of LAR tyrosine phosphatase prevents apoptosis and augments NGF-induced neurite outgrowth JOURNAL OF NEUROBIOLOGY Tisi, M. A., Xie, Y. M., Yeo, T. T., Longo, F. M. 2000; 42 (4): 477-486

  Abstract

  The identity of the protein tyrosine phosphatases (PTPs) regulating cell death and responses to neurotrophins during neural development remain unknown. To determine if the leukocyte common antigen-related (LAR) PTP regulates these processes, PC12 cells were made LAR-deficient via stable transfection with an LAR antisense transgene. LAR-deficient cells demonstrated a stable novel phenotype, including a two-fold increase in nerve growth factor- but not fibroblast growth factor-induced neurite outgrowth. Upon serum-deprivation, LAR-deficient cells exhibited a two- to three-fold decrease in cell death. The findings that an endogenous PTP promotes cell death and counter-regulates neurotrophin actions introduce a major new receptor gene family to neurotrophic processes and suggest novel strategies for preventing cell death and augmenting neurotrophin function.

  View details for Web of Science ID 000085656200008

  View details for PubMedID 10699984

• Leukocyte common-antigen-related tyrosine phosphatase receptor: altered expression of mRNA and protein in the New England Deaconess Hospital rat line exhibiting spontaneous pheochromocytoma CARCINOGENESIS Yang, T., Martignetti, J. A., Massa, S. M., Longo, F. M. 2000; 21 (2): 125-131

  Abstract

  Regulation of cell proliferation by protein tyrosine phosphatases (PTPs) suggests that PTPs are important tumor suppressor genes. The gene encoding the leukocyte common-antigen-related (LAR) PTP receptor maps to chromosome 1p32-33, a region in which loss of heterozygosity is associated with human pheochromocytoma and other neuroectodermal tumors. The rat pheochromocytoma PC12 cell line was originally derived from the transplantable P259 tumor originating from the New England Deaconess Hospital (NEDH) line of Wistar inbred rats. Compared with their Wistar counterparts, 1-2-year-old NEDH rats exhibit a high incidence of spontaneous pheochromocytomas. This study investigates whether levels of LAR transcripts and protein are altered in NEDH adrenal tissue prior to tumor onset. In addition, alternative splicing of an LAR extracellular domain [LAR alternatively spliced element-c (LASE-c)], regulating LAR interaction with extracellular matrix components, was examined. These changes in LAR expression and alternative splicing were hypothesized to be more pronounced in tumor tissue and PC12 cells. Northern blot analysis demonstrated the presence of the approximately 5 kb LAR transcript in all cell lines examined, except PC12. In adrenal medulla tissue harvested from 2-3-month-old rats, LAR approximately 8 and approximately 5 kb transcript expression was decreased in NEDH compared with Wistar samples. RT-PCR demonstrated increased splicing of the LASE-c 27 bp alternatively spliced insert in the LAR extracellular domain in NEDH adrenal medulla tissue. Even greater LASE-c splicing was detected in adrenal medulla tumor tissue derived from 12-month-old NEDH rats and in PC12 cells. Western blot analysis demonstrated decreased levels of LAR protein and increased levels of LASE-c containing LAR protein isoforms in NEDH adrenal medulla tissue. These studies demonstrate that patterns of altered LAR expression present in PC12 cells and in pheochromocytoma tumor tissue are also present in adrenal tissue predisposed to a high incidence of spontaneous pheochromocytoma.

  View details for Web of Science ID 000085503400001

  View details for PubMedID 10657947

• Neurotrophin small-molecule mimetics 8th International Symposium on Neural Regeneration Xie, Y. M., LONGO, F. M. ELSEVIER SCIENCE BV. 2000: 333–347

  View details for Web of Science ID 000169388600029

  View details for PubMedID 11105692

• Gene expression along the cerebral-spinal axis after regional gene delivery HUMAN GENE THERAPY Meuli-Simmen, C., Liu, Y., Yeo, T. T., Liggitt, D., Tu, G. H., Yang, T., Meuli, M., Knauer, S., Heath, T. D., LONGO, F. M., Debs, R. J. 1999; 10 (16): 2689-2700

  Abstract

  We demonstrate here that intracerebroventricular or spinal cord (intrathecal) injection of either plasmid DNA alone or cationic liposome: DNA complexes (CLDCs) produces significant levels of expression of both reporter genes and biologically relevant genes in nonparenchymal cells lining both the brain and the spinal cord. Gene expression was identified both within the spinal cord and the brain after intracerebroventricular or intrathecal injection of either CLDCs or plasmid DNA alone. Intracerebroventricular or intrathecal injection of CLDCs containing the beta-galactosidase (beta-Gal) gene produced patchy, widely scattered areas of beta-Gal expression. The chloramphenicol acetyltransferase (CAT) reporter gene product reached peak levels between 24 hr and 1 week postinjection, and was still present at significant levels 3 weeks after a single intracerebroventricular or intrathecal injection. Intrathecal injection of the human granulocyte colony-stimulating factor (G-CSF) gene produced high levels of hG-CSF activity in both the spinal cord and the brain. Intracerebroventricular injection of CLDCs containing the murine nerve growth factor (NGF) gene increased mNGF levels in the hippocampus, a target region for cholinergic neurons in the medial septum, and increased cholinergic neurotransmitter synthetic enzyme choline acetyltransferase (ChAT) activity within the brain, a well-characterized effect of both purified and recombinant NGF protein. These findings indicate that intracerebroventricular or intrathecal injection of CLDCs can produce significant levels of expression of biologically and therapeutically relevant genes within the CNS. Efficient gene transfer into the CNS will facilitate the evaluation of gene function and regulation within the brain and spinal cord. We attempted to transfer and express genes within the brain and spinal cord by direct CNS injection of either DNA alone or CLDCs into the intraventricular and subarachnoid compartments. We show that intracerebroventricular or spinal cord (intrathecal) injection of either plasmid DNA alone or CLDCs produces significant levels of expression of both reporter genes and biologically relevant genes in nonparenchymal cells lining both the brain and the spinal cord. Intrathecal injection of the hG-CSF gene produced high levels of hG-CSF activity in both the spinal cord and the brain. Intracerebroventricular injection of CLDCs containing the murine NGF gene increased mNGF levels in the hippocampus, and increased cholinergic neurotransmitter synthetic enzyme ChAT activity within the brain. Locoregional diffusion of gene products expressed by transfected meningeal lining cells into brain and spinal cord parenchyma could potentially target secreted proteins within brain and spinal cord regions relevant to neuropathological states while limiting peripheral side effects.

  View details for Web of Science ID 000083522200013

  View details for PubMedID 10566897

• Leukocyte common antigen-related tyrosine phosphatase receptor: Increased expression and neuronal-type splicing in breast cancer cells and tissue MOLECULAR CARCINOGENESIS Yang, T., Zhang, J. S., Massa, S. M., Han, X. L., LONGO, F. M. 1999; 25 (2): 139-149

  Abstract

  The findings that protein tyrosine phosphatases (PTPs) regulate cell proliferation, response to growth factors, and cellular adhesion and the discovery that mutations in PTP genes are associated with breast cancer suggest that altered expression of PTPs contributes to the breast cancer cell phenotype. The leukocyte common antigen-related (LAR) PTP receptor is a prototype member of the class of PTP receptors containing cell adhesion domains. Full-length constitutively spliced LAR transcripts are expressed in breast and other tissues, whereas alternatively spliced isoforms are preferentially expressed in the nervous system. As a first step in evaluating the hypothesis that LAR-type PTPs influence breast cancer cell behavior, LAR expression and neuronal-type alternative splicing were examined in normal and breast cancer cell lines and tissues. Northern blot analysis demonstrated markedly increased LAR mRNA levels in breast cancer cell lines and tissues. Western blot analysis showed a greater than tenfold increase in LAR protein levels in breast cancer tissues. Reverse transcription-polymerase chain reaction was used to assess alternative splicing of extracellular and proximal membrane exons. Differential patterns of extracellular alternative splicing were found in normal versus carcinoma cell lines and tissues. Western blot analysis demonstrated increased levels of LAR protein isoforms encoded by alternatively spliced transcripts in breast cancer cell lines. This study is the first demonstration of increased LAR mRNA and LAR protein expression in breast cancer tissue and nontransformed cell lines and helps to elucidate the role of LAR in human breast cancer. The differential patterns of alternative splicing of LAR transcripts introduce LAR isoforms as candidate markers for future studies correlating differential gene expression and tumor behavior.

  View details for Web of Science ID 000080628100007

  View details for PubMedID 10365916

• Electromagnetic fields influence NGF activity and levels following sciatic nerve transection JOURNAL OF NEUROSCIENCE RESEARCH Longo, F. M., Yang, T., Hamilton, S., Hyde, J. F., Walker, J., Jennes, L., Stach, R., Sisken, B. F. 1999; 55 (2): 230-237

  Abstract

  Pulsed electromagnetic fields (PEMF) have been shown to increase the rate of nerve regeneration. Transient post-transection loss of target-derived nerve growth factor (NGF) is one mechanism proposed to signal induction of early nerve regenerative events. We tested the hypothesis that PEMF alter levels of NGF activity and protein in injured nerve and/or dorsal root ganglia (DRG) during the first stages of regeneration (6-72 hr). Rats with a transection injury to the midthigh portion of the sciatic nerve on one side were exposed to PEMF or sham control PEMF for 4 hr/day for different time periods. NGF-like activity was determined in DRG, in 5-mm nerve segments proximal and distal to the transection site and in a corresponding 5-mm segment of the contralateral nonoperated nerve. NGF-like activity of coded tissue samples was measured in a blinded fashion using the chick DRG sensory neuron bioassay. Overall, PEMF caused a significant decrease in NGF-like activity in nerve tissue (P < 0.02, repeated measures analysis of variance, ANOVA) with decreases evident in proximal, distal, and contralateral nonoperated nerve. Unexpectedly, transection was also found to cause a significant (P=0.001) 2-fold increase in DRG NGF-like activity between 6 and 24 hr postinjury in contralateral but not ipsilateral DRG. PEMF also reduced NGF-like activity in DRG, although this decrease did not reach statistical significance. Assessment of the same nerve and DRG samples using ELISA and NGF-specific antibodies confirmed an overall significant (P < 0.001) decrease in NGF levels in PEMF-treated nerve tissue, while no decrease was detected in DRG or in nerve samples harvested from PEMF-treated uninjured rats. These findings demonstrate that PEMF can affect growth factor activity and levels, and raise the possibility that PEMF might promote nerve regeneration by amplifying the early postinjury decline in NGF activity.

  View details for Web of Science ID 000078190200010

  View details for PubMedID 9972825

• LAR tyrosine phosphatase receptor: proximal membrane alternative splicing is coordinated with regional expression and intraneuronal localization MOLECULAR BRAIN RESEARCH Honkaniemi, J., Zhang, J. S., Yang, T., Zhang, C., Tisi, M. A., LONGO, F. M. 1998; 60 (1): 1-12

  Abstract

  Examination of null-mutant Drosophila and Leukocyte Common Antigen-Related (LAR)-deficient transgenic mice has demonstrated that the LAR protein tyrosine phosphatase (PTP) receptor promotes neurite outgrowth. In the absence of known ligands, the mechanisms by which LAR-type PTP receptors are regulated are unknown. We hypothesized that an alternatively spliced eleven amino acid proximal membrane segment of LAR (LAR alternatively spliced element-a; LASE-a) contributes to regulation of LAR function. Human, rat and mouse LAR cDNA sequences demonstrated that the predicted eleven amino acid inserts in rat and mouse are identical and share nine of eleven residues with the human insert. LASE-a splicing led to the introduction of a Ser residue into LAR at a position analogous to Ser residues undergoing regulated phosphorylation in other PTPs. In-situ studies revealed increasingly region-specific expression of LASE-a containing LAR transcripts during postnatal development. RT-PCR analysis of cortical and hippocampal tissue confirmed that the proportion of LAR transcripts containing LASE-a decreases during development. Immunostaining of cultured PC12 cells, cerebellar granule neurons, dorsal root ganglia and sciatic nerve sections with antibody directed against the LASE-a insert demonstrated signal in cell bodies but little if any along neurites. In contrast, staining with antibody directed to a separate domain of LAR showed accumulation of LAR along neurites. The findings that LASE-a splicing is conserved across human, rat and mouse, that the LASE-a insert introduces a Ser at a site likely to be targeted for regulated phosphorylation and that developmentally regulated splicing is coordinated with specific regional and intraneuronal localization point to important novel potential mechanisms regulating LAR-type tyrosine phosphatase receptor function in the nervous system.

  View details for Web of Science ID 000076149100001

  View details for PubMedID 9748473

• LAR tyrosine phosphatase receptor: A developmental isoform is present in neurites and growth cones and its expression is regional- and cell-specific MOLECULAR AND CELLULAR NEUROSCIENCE Zhang, J. S., Honkaniemi, J., Yang, T., Yeo, T. T., LONGO, F. M. 1998; 10 (5-6): 271-286

  Abstract

  Transgenic mice and Drosophila mutant studies demonstrate that the leukocyte common antigen-related (LAR) protein tyrosine phosphatase (PTPase) receptor is required for formation of neural networks. We assessed the hypothesis that alternative splicing of the LAR extracellular region contributes to this function by establishing temporospatial expression patterns of LAR isoforms containing an alternatively spliced extracellular nine amino acid segment (LAR alternatively spliced element-c; LASE-c). LASE-c was present in multiple alternatively spliced and truncated LAR transcripts. In contrast to LAR isoforms without LASE-c, levels of LAR transcripts and protein isoforms containing LASE-c were primarily present during development, suggesting a mechanism for developmental regulation of LAR function. In situ analysis demonstrated increasingly region- and cell-specific expression of LASE-c during maturation. Immunostaining revealed LASE-c-containing LAR protein along neurites and in growth cones. The discovery of highly regulated, temporospatial extracellular domain alternative splicing of LAR-type PTPase receptors points to a novel mechanism by which these receptors might influence network formation.

  View details for Web of Science ID 000073548600005

  View details for PubMedID 9604206

• LAR Tyrosine Phosphatase Receptor: A Developmental Isoform Is Present in Neurites and Growth Cones and Its Expression Is Regional- and Cell-Specific. Molecular and cellular neurosciences Zhang, Honkaniemi, Yang, Yeo, Longo 1998; 10 (5/6): 271-286

  Abstract

  Transgenic mice and Drosophila mutant studies demonstrate that the leukocyte common antigen-related (LAR) protein tyrosine phosphatase (PTPase) receptor is required for formation of neural networks. We assessed the hypothesis that alternative splicing of the LAR extracellular region contributes to this function by establishing temporospatial expression patterns of LAR isoforms containing an alternatively spliced extracellular nine amino acid segment (LAR alternatively spliced element-c; LASE-c). LASE-c was present in multiple alternatively spliced and truncated LAR transcripts. In contrast to LAR isoforms without LASE-c, levels of LAR transcripts and protein isoforms containing LASE-c were primarily present during development, suggesting a mechanism for developmental regulation of LAR function. In situ analysis demonstrated increasingly region- and cell-specific expression of LASE-c during maturation. Immunostaining revealed LASE-c-containing LAR protein along neurites and in growth cones. The discovery of highly regulated, temporospatial extracellular domain alternative splicing of LAR-type PTPase receptors points to a novel mechanism by which these receptors might influence network formation. Copyright 1998 Academic Press.

  View details for PubMedID 9618218

• Absence of p75(NTR) causes increased basal forebrain cholinergic neuron size, choline acetyltransferase activity, and target innervation JOURNAL OF NEUROSCIENCE Yeo, T. T., CHUACOUZENS, J., Butcher, L. L., Bredesen, D. E., Cooper, J. D., Valletta, J. S., Mobley, W. C., LONGO, F. M. 1997; 17 (20): 7594-7605

  Abstract

  Emerging evidence suggests that the p75 neurotrophin receptor (p75NTR) mediates cell death; however, it is not known whether p75NTR negatively regulates other neuronal phenotypes. We found that mice null for p75NTR displayed highly significant increases in the size of basal forebrain cholinergic neurons, including those that are TrkA-positive. Cholinergic hippocampal target innervation also was increased significantly. Activity of the cholinergic neurotransmitter synthetic enzyme choline acetyltransferase (ChAT) was increased in both the medial septum and hippocampus. Upregulation of these cholinergic features was not associated with increased basal forebrain or hippocampal target NGF levels. In contrast, striatal cholinergic neurons, which do not express p75NTR, showed no difference in neuronal number, size, or ChAT activity between wild-type and p75NTR null mutant mice. These findings indicate that p75NTR negatively regulates cholinergic neuronal phenotype of the basal forebrain cholinergic neurons, including cell size, target innervation, and neurotransmitter synthesis.

  View details for Web of Science ID A1997XZ44900003

  View details for PubMedID 9315882

• Trinucleotide repeats in transgenic mice: New insights NEUROSCIENTIST LONGO, F. M., Massa, S. M. 1997; 3 (5): 273-275

  View details for Web of Science ID A1997XZ57800007

• Aldose reductase inhibition increases CNTF-like bioactivity and protein in sciatic nerves from galactose-fed and normal rats DIABETES Mizisin, A. P., Calcutt, N. A., DiStefano, P. S., Acheson, A., LONGO, F. M. 1997; 46 (4): 647-652

  Abstract

  The impact of exaggerated polyol pathway flux on ciliary neurotrophic factor (CNTF)-like bioactivity and expression of CNTF in rat sciatic nerve was examined after 2 months of galactose intoxication. Polyol content was elevated (P < 0.001) and motor nerve conduction velocity reduced (P < 0.05) in galactose-fed rats compared with control animals or control and galactose-fed rats treated with the aldose reductase inhibitor (ARI) Ponalrestat. CNTF-like bioactivity in the galactose-fed group was reduced to 30% of that assayed in the control group (P < 0.001). ARI treatment significantly increased CNTF-like bioactivity by 60% compared with the untreated galactose group (P < 0.05) but did not restore it to control levels. Unexpectedly, bioactivity in ARI-treated control animals was increased by nearly 250% compared with untreated controls (P < 0.005). In addition to the deficit in CNTF bioactivity in untreated galactose rats, the expression of protein, but not of mRNA, was reduced (P < 0.05). In ARI-treated control and galactose-fed rats, the expression of CNTF peptide was significantly enhanced above control levels (both P < 0.05). Concomitant with the reduction in CNTF levels, there was a shift in the axonal size-frequency distribution of myelinated fibers toward smaller axons in galactose-fed rats that was prevented by ARI treatment. Since galactose feeding has little impact on levels of CNTF mRNA, these observations suggest that deficits in CNTF-like bioactivity may result from a posttranscriptional modification of neurotrophic protein expression or turnover. Unlike other functional and structural disorders in galactose neuropathy, factors other than polyol accumulation may contribute to the deficit in CNTF-like bioactivity.

  View details for Web of Science ID A1997WP64400015

  View details for PubMedID 9075806

• Synthetic NGF peptide derivatives prevent neuronal death via a p75 receptor-dependent mechanism JOURNAL OF NEUROSCIENCE RESEARCH LONGO, F. M., MANTHORPE, M., Xie, Y. M., VARON, S. 1997; 48 (1): 1-17

  Abstract

  Cyclized peptides corresponding to beta-loop regions of NGF were purified by HPLC and assayed for neurotrophic activity using DRG neurons. Peptides with the highest activity corresponded to loop region 29-35, a domain likely to interact with the p75 receptor. Unexpectedly, activity was confined to late-eluting HPLC fractions containing peptide multimers and primarily promoted neuronal survival without neurite outgrowth. Directed synthesis of dimer and monomer cyclized peptides demonstrated that dimers acted as partial NGF agonists in that they had both survival-promoting and NGF-inhibiting activity while monomer and linear peptides were inactive. Dimer activity was not affected by the Trk inhibitor K252a but was blocked by p75 receptor antibody and absent using p75 null mutant neurons. These studies suggest that region 29-35 peptide derivatives inhibit neuronal death via a structure- and p75-dependent mechanism.

  View details for Web of Science ID A1997WQ34600001

  View details for PubMedID 9086177

• Deficient LAR expression decreases basal forebrain cholinergic neuronal size and hippocampal cholinergic innervation JOURNAL OF NEUROSCIENCE RESEARCH Yeo, T. T., Yang, T., Massa, S. M., Zhang, J. S., Honkaniemi, J., Butcher, L. L., LONGO, F. M. 1997; 47 (3): 348-360

  Abstract

  A role in neural development for protein tyrosine phosphatase (PTPase) receptors has been suggested by the finding of aberrant neurite outgrowth in Drosophila mutants lacking functional leukocyte common antigen-related (LAR) PTPase receptors; however, PTPase functions in the mammalian nervous system remain to be established. In transgenic mice containing a gene trap in the LAR gene, only trace expression of full-length LAR transcripts was found. In these mice, the size of basal forebrain cholinergic neurons was significantly reduced and cholinergic innervation of the dentate gyrus was markedly decreased. These findings constitute the first demonstration of an aberrant neuronal phenotype in a mammalian PTPase mutant and support the hypothesis that LAR-type PTPase receptors function to establish and/or maintain neuronal networks.

  View details for Web of Science ID A1997WG30600013

  View details for PubMedID 9039657

• Minimized hormones grow in stature NATURE BIOTECHNOLOGY LONGO, F. M., Mobley, W. C. 1996; 14 (9): 1092-1092

  View details for Web of Science ID A1996VF84300027

  View details for PubMedID 9631056

• CLONING OF RAT GRP75, AN HSP70-FAMILY MEMBER, AND ITS EXPRESSION IN NORMAL AND ISCHEMIC BRAIN JOURNAL OF NEUROSCIENCE RESEARCH Massa, S. M., LONGO, F. M., Zuo, J., Wang, S., Chen, J., Sharp, F. R. 1995; 40 (6): 807-819

  Abstract

  Following metabolic stress a variety of gene products are induced in cells in the brain, some of which may protect the tissue from subsequent stresses. The heat shock proteins (hsps), in particular hsp70, have been widely studied in this context, but evidence for the involvement of known hsps in protection of the CNS is inconclusive. We have therefore undertaken the search for other stress-induced proteins which may mitigate ischemic injury. Beginning with degenerate RT-PCR, we have isolated a rat-brain cDNA encoding a protein highly similar to human grp75, a mitochondrial member of the hsp70-family of stress proteins. It is also highly similar to two non-mitochondrial proteins; mortalin, a senescence-related gene product, and pbp74, a protein implicated in B-cell peptide processing. Sequence structure and phylogenetic analyses predict mitochondrial localization and induction by a calcium ionophore and glucose deprivation in PC12 cells support its identification as rat grp75. In situ analysis of normal brain reveals an unusual distribution, with very high expression in neurons of the basal forebrain, reticular and subthalamic nuclei, globus pallidus, amygdala and elsewhere. grp75-mRNA is upregulated following focal brain ischemia in a distinctive fashion. When the degree of injury is small, induction occurs in the area of injury, similar to the pattern observed for hsp70. However, when the injury is extensive, hsr is upregulated in neurons outside the ischemic area. The induction of grp75 may represent a sensitive marker of metabolically compromised tissue.

  View details for Web of Science ID A1995QW01500011

  View details for PubMedID 7629893

• LAR TYROSINE PHOSPHATASE RECEPTOR - ALTERNATIVE SPLICING IS PREFERENTIAL TO THE NERVOUS-SYSTEM, COORDINATED WITH CELL-GROWTH AND GENERATES NOVEL ISOFORMS CONTAINING EXTENSIVE CAG REPEATS JOURNAL OF CELL BIOLOGY Zhang, J. S., LONGO, F. M. 1995; 128 (3): 415-431

  Abstract

  Receptor-linked tyrosine phosphatases regulate cell growth by dephosphorylating proteins involved in tyrosine kinase signal transduction. The leukocyte common antigen-related (LAR) tyrosine phosphatase receptor has sequence similarity to the neural cell adhesion molecule N-CAM and is located in a chromosomal region (1p32-33) frequently altered in neuroectodermal tumors. To understand the function of receptor-linked tyrosine phosphatases in neural development, we sought to identify LAR isoforms preferentially expressed in the nervous system and cellular processes regulating LAR alternative splicing. We report here the isolation of a series of rat LAR cDNA clones arising from complex combinatorial alternative splicing, not previously demonstrated for the tyrosine phosphatase-receptor gene family in general. Isoforms included: (a) deletions of the fourth, sixth and seventh fibronectin type III-like domains; (b) an alternatively spliced novel cassette exon in the fifth fibronectin type III-like domain; (c) two alternatively spliced novel cassette exons in the juxtamembrane region; (d) a retained intron in the extracellular region with in-frame stop codons predicting a secreted LAR isoform; and (e) an LAR transcript including an alternative 3' untranslated region containing multiple stretches of tandem CAG repeats up to 21 repeats in length. This number of repeats was in the range found in normal alleles of genes in which expansions of repeats are associated with neurodegenerative disease and the genetic phenomenon of anticipation. RT-PCR and Northern analysis demonstrated that LAR alternative splicing occurred preferentially in neuromuscular tissue in vivo and in neurons compared to astrocytes in vitro and was developmentally regulated. Alternative splicing was also regulated in PC12 cells by NGF, in 3T3 fibroblasts by cell confluence and in sciatic nerve and muscle subsequent to nerve transection. Western blot analysis demonstrated that alternatively spliced cassette exons result in the presence of corresponding amino acid segments of LAR protein in vivo. These studies suggest specialized functions of LAR isoforms in the nervous system and support our hypothesis that LAR-like tyrosine phosphatase receptors play a role in neural development and regeneration.

  View details for Web of Science ID A1995QD39800016

  View details for PubMedID 7844155

• WILL CILIARY NEUROTROPHIC FACTOR SLOW PROGRESSION OF MOTOR-NEURON DISEASE ANNALS OF NEUROLOGY LONGO, F. M. 1994; 36 (2): 125-127

  View details for Web of Science ID A1994PB26000001

  View details for PubMedID 8053646

• LEUKOCYTE COMMON ANTIGEN-RELATED RECEPTOR-LINKED TYROSINE PHOSPHATASE - REGULATION OF MESSENGER-RNA EXPRESSION JOURNAL OF BIOLOGICAL CHEMISTRY LONGO, F. M., Martignetti, J. A., LEBEAU, J. M., Zhang, J. S., Barnes, J. P., Brosius, J. 1993; 268 (35): 26503-26511

  Abstract

  Receptor-linked tyrosine phosphatases regulate cell growth by dephosphorylating proteins involved in tyrosine kinase signal transduction. Within this gene family, the leukocyte common antigen-related (LAR) gene is of particular interest with respect to the nervous system because it has sequence similarity to the neural cell adhesion molecule N-CAM and is located in a chromosomal region (1p32-33) frequently deleted in neuroectodermal tumors. However, immunostaining has detected LAR in non-neural tissues, but not in the central nervous system, peripheral neurons, or adrenal medulla. In this study, rat brain cDNA library LAR clones corresponding to cytoplasmic and 3'-untranslated regions of human LAR were identified. Using probes derived from these clones, high stringency Northern blots revealed approximately 8 kilobase and variable length tissue- and cell-specific LAR transcripts in cortex, brainstem, cerebellum, spinal cord, peripheral tissues, and cultured neural, glial, and pheochromocytoma cells. In situ hybridization showed expression by brain and dorsal root ganglion neurons. LAR expression was developmentally regulated in a region-dependent manner. Changes in LAR expression were also found during nerve growth factor-induced PC12 pheochromocytoma cell differentiation and with contact-mediated inhibition of fibroblast growth. These observations and studies demonstrating neurotrophins functioning via tyrosine kinase receptors suggest that LAR represents an additional mechanism regulating neural development.

  View details for Web of Science ID A1993MK42500073

  View details for PubMedID 8253779

• INDUCTION OF GLUCOSE-REGULATED PROTEIN (GRP78) AND INDUCIBLE HEAT-SHOCK PROTEIN (HSP70) MESSENGER-RNAS IN RAT-BRAIN AFTER KAINIC ACID SEIZURES AND FOCAL ISCHEMIA NEUROCHEMISTRY INTERNATIONAL Wang, S., LONGO, F. M., Chen, J., Butman, M., Graham, S. H., Haglid, K. G., Sharp, F. R. 1993; 23 (6): 575-582

  Abstract

  Specific probes were obtained using PCR cloning from rat brain for the 78 kDa glucose regulated (grp78), inducible 72 kDa (hsp70) as well as constitutive 73 kDa (hsc73) heat shock mRNAs. Grp78 and hsc73 were expressed in normal rat brain whereas hsp70 was not. Subcutaneous injection kainic acid (10 mg/kg) produced seizures and induced all three mRNAs. The induction of grp78 and hsp70 mRNAs occurred within 2 h, peaked between 6-8 h, persisted for 48 h, and returned to control levels by 72 h. Expression of the grp78 and hsp70 mRNAs after focal ischemia progressively increased with occlusion durations from 15-120 min in the cerebral cortex. Though grp78 and hsp70 mRNAs were induced modestly in the striatum by 15 min of ischemia, longer durations of ischemia were characterized by little change in the grp78 mRNA levels and relatively lower levels of hsp70 expression. This result indicates that progressive increases in the duration of ischemia in brain, prior to infarction, may produce proportional increases in transcription of the heat shock genes. However, once the duration of ischemia is long enough to produce infarction, this severely limits the availability of ATP which blocks transcription of the heat shock genes. In conclusion, concurrent induction of the heat shock genes suggests that kainic acid seizures and focal ischemia induce several different stress responses in brain cells caused by denaturation of proteins, changes of protein synthesis, and changes of protein glycosylation.

  View details for Web of Science ID A1993MH79700009

  View details for PubMedID 8281126

• CDNA CLONING AND EXPRESSION OF STRESS-INDUCIBLE RAT HSP70 IN NORMAL AND INJURED RAT-BRAIN JOURNAL OF NEUROSCIENCE RESEARCH LONGO, F. M., Wang, S., Narasimhan, P., Zhang, J. S., Chen, J., Massa, S. M., Sharp, F. R. 1993; 36 (3): 325-335

  Abstract

  A reverse transcriptase-polymerase chain reaction (RT-PCR) product obtained from ischemic rat brain RNA was used to screen a rat ischemic forebrain cDNA library for a cDNA clone containing the entire open reading frame for the inducible hsp70. The coding sequence for the rat hsp70 cDNA demonstrated significant similarities with the human hsp70 of Hunt and Morimoto (Proc Natl Acad Sci 82:6455-6459, 1985) and the mouse hsp70 of Hunt and Calderwood (Gene 87:199-204, 1990). The rat inducible hsp70 and constitutive hsc73 sequences are distinct. There was a low level of hsp70 mRNA expression in normal rat brain as in found in other tissues. hsp70 mRNA was markedly induced in rat brain 8 hours following global ischemia and kainic acid-induced seizures. Northern blots showed a approximately 2.9kb hsp70 mRNA band from control, kainic acid, and ischemic brains. RT-PCR confirmed the presence of hsp70 mRNA in normal rat brain. Since there are at least five human and six mouse inducible hsp70 genes known, many other rat hsp70 genes probably exist that could function in different cells or organelles or be induced under different circumstances.

  View details for Web of Science ID A1993MC79000009

  View details for PubMedID 8271311

• PROLONGED INCREASES IN NEUROTROPHIC ACTIVITY ASSOCIATED WITH KAINATE-INDUCED HIPPOCAMPAL SYNAPTIC REORGANIZATION NEUROSCIENCE Lowenstein, D. H., SEREN, M. S., LONGO, F. M. 1993; 56 (3): 597-604

  Abstract

  Synaptic reorganization occurs in the hippocampus following various forms of seizure activity and injury, and may contribute to epileptogenesis. To address the hypothesis that neurotrophic factors play an inductive role in synaptic reorganization following seizures, we directly measured neurotrophic activity in rat hippocampal extracts after kainate injection or prolonged stimulation of the perforant path. Serial dilutions of hippocampal extracts were added to cultures of chick dorsal root ganglia, which are known to require trophic support from nerve growth factor and other neurotrophins, or ciliary ganglia neurons, which require trophic support from ciliary neurotrophic factor. Neurotrophic activity was significantly increased in hippocampal extracts harvested from 12 h to 2 months after kainate treatment, with the peak effect seen at seven days. This neurotrophic activity was substantially blocked by an anti-nerve growth factor antibody. Extracts at seven days also showed a significant increase in ciliary neurotrophic factor-like activity. Sulfide/silver histochemistry, which stains dentate granule cell axon terminals, revealed that mossy fiber sprouting was evident two weeks following kainate treatment and increased progressively over the next two to six weeks. Perforant path stimulation that produced hyperexcitability in the dentate gyrus, but no sprouting, failed to induce changes in neurotrophic activity. These results suggest there are significant increases in neurotrophic factors following kainate-induced seizures, and the increases may be related to kainate-induced hippocampal injury rather than seizures per se. Furthermore, the timecourse of increased neurotrophic activity parallels that of mossy fiber reorganization, and is consistent with the hypothesis that neurotrophic factors play a role in the injury-induced synaptic reorganization seen in epilepsy.

  View details for Web of Science ID A1993LZ85700008

  View details for PubMedID 8255423

• HEAT-SHOCK PROTEINS USED TO SHOW THAT HALOPERIDOL PREVENTS NEURONAL INJURY PRODUCED BY KETAMINE, MK801, AND PHENCYCLIDINE ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Sharp, F. R., Butman, M., Wang, S., Koistinaho, J., Graham, S. H., Sagar, S. M., Berger, P., LONGO, F. M. 1993; 679: 288-290

  View details for Web of Science ID A1993LG18800027

  View details for PubMedID 8512190

• HEAT-SHOCK PROTEINS USED TO SHOW THAT HALOPERIDOL PREVENTS NEURONAL INJURY PRODUCED BY KETAMINE, MK801, AND PHENCYCLIDINE CONF ON MARKERS OF NEURONAL INJURY AND DEGENERATION Sharp, F. R., Butman, M., Wang, S., Koistinaho, J., Graham, S. H., Sagar, S. M., Berger, P., LONGO, F. M. NEW YORK ACAD SCIENCES. 1993: 288–290

  View details for Web of Science ID A1993BY50G00027

• HALOPERIDOL PREVENTS INDUCTION OF THE HSP70 HEAT-SHOCK GENE IN NEURONS INJURED BY PHENCYCLIDINE (PCP), MK801, AND KETAMINE JOURNAL OF NEUROSCIENCE RESEARCH Sharp, F. R., Butman, M., Wang, S., Koistinaho, J., Graham, S. H., Sagar, S. M., Noble, L., Berger, P., LONGO, F. M. 1992; 33 (4): 605-616

  Abstract

  The non-competitive NMDA receptor antagonists, PCP (phencyclidine), MK801, and ketamine produce psychosis in humans and abnormal vacuoles in posterior cingulate and retrosplenial rat cortical neurons. We show that PCP (> or = 5 mg/kg), MK801 (> or = 0.1 mg/kg), and ketamine (> 20 mg/kg) induce hsp70 mRNA and HSP70 heat shock protein in these vacuolated, injured neurons, and PCP also induces hsp70 in injured neocortical, piriform, and amygdala neurons. The PCP, MK801, and ketamine drug induced injury occurs in 30 day and older rats, but not in 0-20 day old rats, and is prevented by prior administration of the antipsychotic drugs haloperidol and rimcazole. Since haloperidol and rimcazole block dopamine and sigma receptors, and since M1 muscarinic cholinergic receptor antagonists also prevent the injury produced by PCP, MK801, and ketamine, future studies will be needed to determine whether dopamine, sigma, M1, or other receptors mediate the injury.

  View details for Web of Science ID A1992JZ84900012

  View details for PubMedID 1484394

• TROPHIC ACTIONS OF RECOMBINANT HUMAN NERVE GROWTH-FACTOR ON CULTURED RAT EMBRYONIC CNS CELLS EXPERIMENTAL NEUROLOGY Knusel, B., BURTON, L. E., LONGO, F. M., Mobley, W. C., Koliatsos, V. E., Price, D. L., HEFTI, F. 1990; 110 (3): 274-283

  Abstract

  NGF is a neurotrophic factor for basal forebrain cholinergic neurons and may serve to counteract the cholinergic deficits that are observed in Alzheimer's disease. Prior to the introduction of clinical trials, it is essential that recombinant human NGF (rhNGF) be produced and that its actions on target cells in the CNS be demonstrated. We prepared rhNGF and examined its actions on fetal rat brain neurons in culture including, in particular, the cholinergic neurons of the basal forebrain. rhNGF was more potent in increasing choline acetyltransferase (ChAT) activity in septal cultures than NGF purified from mouse salivary glands (mNGF). ED50s of the beta-NGF dimers were 4.9 pM for rhNGF and 12.4 pM for mNGF. The maximal ChAT activity response was achieved at approximately 35 pM with both NGFs and their efficacies were not significantly different. The two NGFs were not additive in effect. Identical to the results with mNGF, rhNGF strongly enhanced the intensity of ChAT immunostaining in septal cultures. Neither rhNGF nor mNGF affected the appearance of the cultures under phase-contrast illumination. Survival of cells at very low plating density on polyornithine/laminin-coated culture dishes was not affected by rhNGF or mNGF. Protein content and the uptake of GABA were also unaffected. At concentrations of up to 10 micrograms/ml, rhNGF did not significantly increase uptake of dopamine into cultures of ventral mesencephalon. We conclude that rhNGF produces potent and selective actions on cholinergic neurons of the basal forebrain as previously shown for mNGF.

  View details for Web of Science ID A1990EP12000005

  View details for PubMedID 2249737

• DIRECT SEQUENCING OF PCR PRODUCTS USING THE MAXAM-GILBERT METHOD GENETIC ANALYSIS-BIOMOLECULAR ENGINEERING Stamm, S., LONGO, F. M. 1990; 7 (5): 142-143

  Abstract

  Direct sequencing of polymerase chain reaction (PCR) products by using the Maxam-Gilbert method is described. In this method, one of the primers is end labeled. Thus it is possible to sequence the reaction product directly following purification using this chemical method.

  View details for Web of Science ID A1990EK26800010

  View details for PubMedID 2091696

• NERVE GROWTH-FACTOR INDUCES GENE-EXPRESSION OF THE PRION PROTEIN AND BETA-AMYLOID PROTEIN-PRECURSOR IN THE DEVELOPING HAMSTER CENTRAL-NERVOUS-SYSTEM PROGRESS IN BRAIN RESEARCH MCKINLEY, M. P., LONGO, F. M., Valletta, J. S., Rahbar, F., NEVE, R. L., Prusiner, S. B., Mobley, W. C. 1990; 86: 227-238

  View details for Web of Science ID A1990GW81200020

  View details for PubMedID 1982367

• NERVE GROWTH-FACTOR INDUCES GENE-EXPRESSION OF THE PRION PROTEIN AND BETA-AMYLOID PROTEIN-PRECURSOR IN THE DEVELOPING HAMSTER CENTRAL-NERVOUS-SYSTEM SYMP ON MOLECULAR AND CELLULAR MECHANISMS OF NEURONAL PLASTICITY IN AGING AND ALZHEIMERS DISEASE MCKINLEY, M. P., LONGO, F. M., Valletta, J. S., Rahbar, F., NEVE, R. L., Prusiner, S. B., Mobley, W. C. ELSEVIER SCIENCE PUBL B V. 1990: 227–238

  View details for Web of Science ID A1990BU86Z00020

• THE INVITRO BIOLOGICAL EFFECT OF NERVE GROWTH-FACTOR IS INHIBITED BY SYNTHETIC PEPTIDES CELL REGULATION LONGO, F. M., Vu, T. K., Mobley, W. C. 1990; 1 (2): 189-195

  Abstract

  Nerve growth factor (NGF)1 is a neurotrophic polypeptide that acts via specific receptors to promote the survival and growth of neurons. To delineate the NGF domain(s) responsible for eliciting biological activity, we synthesized small peptides corresponding to three regions in NGF that are hydrophilic and highly conserved. Several peptides from mouse NGF region 26-40 inhibited the neurite-promoting effect of NGF on sensory neurons in vitro. Inhibition was sequence-specific and could be overcome by increasing the concentration of NGF. Moreover, peptide actions were specific for NGF-mediated events in that they failed to block the neurotrophic activity of ciliary neuronotrophic factor (CNTF) or phorbol 12-myristate 13-acetate (PMA). In spite of the inhibition of NGF activity, peptides did not affect the binding of radiolabeled NGF. These studies define one region of NGF that may be required for neurotrophic activity.

  View details for Web of Science ID A1990DM09600003

  View details for PubMedID 2100197

• DEVELOPMENTAL REGULATION OF NERVE GROWTH-FACTOR AND ITS RECEPTOR IN THE RAT CAUDATE PUTAMEN NEURON Mobley, W. C., Woo, J. E., Edwards, R. H., Riopelle, R. J., LONGO, F. M., Weskamp, G., OTTEN, U., Valletta, J. S., Johnston, M. V. 1989; 3 (5): 655-664

  Abstract

  In prior studies, nerve growth factor (NGF) administration induced a robust, selective increase in the neurochemical differentiation of caudate-putamen cholinergic neurons. In this study, expression of NGF and its receptor was examined to determine whether endogenous NGF might serve as a neurotrophic factor for these neurons. The temporal pattern of NGF gene expression and the levels of NGF mRNA and protein were distinct from those found in other brain regions. NGF and high-affinity NGF binding were present during cholinergic neurochemical differentiation and persisted into adult-hood. An increase in NGF binding during the third postnatal week was correlated with increasing choline acetyltransferase activity. The data are consistent with a role for endogenous NGF in the development and, possibly, the maintenance of caudate-putamen cholinergic neurons.

  View details for Web of Science ID A1989CC19000013

  View details for PubMedID 2561975

• NERVE REGENERATION THROUGH ARTIFICIAL TUBULAR IMPLANTS PROGRESS IN NEUROBIOLOGY Fields, R. D., LEBEAU, J. M., LONGO, F. M., Ellisman, M. H. 1989; 33 (2): 87-?

  View details for Web of Science ID A1989AQ59100001

  View details for PubMedID 2678271

• WHITE MATTER DISEASE IN AIDS - FINDINGS AT MR IMAGING RADIOLOGY OLSEN, W. L., LONGO, F. M., Mills, C. M., Norman, D. 1988; 169 (2): 445-448

  Abstract

  A review of the magnetic resonance (MR) images of 365 patients with acquired immunodeficiency syndrome (AIDS) revealed that 112 (31%) had signal abnormalities confined to the white matter. Four patterns were observed: (a) diffuse: widespread involvement of a large area; (b) patchy: localized involvement with ill-defined margins; (c) focal: well-defined areas of involvement; and (d) punctate: small foci less than 1 cm in diameter. Clinical or pathologic findings were available in 60 of the 112 patients and were correlated with the white matter patterns seen on MR images. The diffuse pattern correlated with AIDS dementia complex (ADC), which was the most common clinical diagnosis. Patchy or punctate lesions may be seen with ADC but are less common. Focal white matter lesions were not seen in patients with ADC but were seen in all six patients with progressive multifocal leukoencephalopathy, in both patients with lymphoma, and in one patient with toxoplasmosis. The authors conclude that white matter lesions are are common in AIDS and are often secondary to direct infection of the brain with human immunodeficiency virus, which causes the ADC and usually produces a diffuse white matter pattern. Biopsy is probably not indicated in these patients. Focal white matter lesions suggest a focal infection or tumor, and biopsy may be warranted.

  View details for Web of Science ID A1988Q497400032

  View details for PubMedID 3174991

• DELAYED NERVE REGENERATION IN STREPTOZOTOCIN DIABETIC RATS MUSCLE & NERVE LONGO, F. M., Powell, H. C., Lebeau, J., Gerrero, M. R., Heckman, H., Myers, R. R. 1986; 9 (5): 385-393

  Abstract

  Nerve regeneration across a 10-mm gap was delayed in streptozotocin diabetic rats 3 and 4 weeks after transecting the sciatic nerve. Opposite ends of each cut nerve were introduced into a silicone tube, leaving a 10-mm gap. Electron microscopy was used to evaluate the progress of regeneration in sections at 2-mm intervals across the 10-mm gap. After 3 weeks, control axons had bridged the 10-mm gap, and myelin sheaths extended for 6-8 mm. By contrast, axons and their myelin sheaths were seen no further than 2 mm from the proximal stump in diabetic animals. By 4 weeks, axons had bridged the gap in diabetics; however, they appeared immature and showed dystrophic changes. The findings suggest that although regeneration does occur in diabetic nerves, it is significantly delayed and qualitatively impaired.

  View details for Web of Science ID A1986C513300001

  View details for PubMedID 2941683

• ABNORMAL NERVE REGENERATION IN GALACTOSE NEUROPATHY JOURNAL OF NEUROPATHOLOGY AND EXPERIMENTAL NEUROLOGY Powell, H. C., LONGO, F. M., LEBEAU, J. M., Myers, R. R. 1986; 45 (2): 151-160

  Abstract

  Nerve regeneration across a 10 mm gap through an implanted silicone tube was delayed in galactose-fed rats two and four weeks after transecting the nerve. This experimental metabolic neuropathy resembles diabetic neuropathy in which nerve regeneration is also delayed. Experiments were performed by introducing opposite ends of divided sciatic nerves into close-fitting silicone tubes, leaving a 10 mm gap. Growth of neurites across this gap was monitored by electron microscopy performed in sections at regular intervals of 2 mm from proximal to distal stumps. After two weeks some difference was apparent; axons advanced 1.4 +/- 0.4 mm in galactose-fed rats versus 3.5 +/- 1.5 mm in controls. Myelination did not progress beyond 1 mm in galactose-fed rats. Differences were greater between the two groups at four weeks. The growth of axons in galactose rats was 3.5 +/- 0.2 mm versus 9.4 +/- 0.1 mm in control nerves. In addition the size of the regenerating stump was much greater in control rats. Qualitative differences were also noticed during electron microscopic comparison of control and galactose-treated rats. The dystrophic axons seen in treated rats had abnormal electron-dense organelles, lamellated bodies, vesicles and tubular structures, as well as numerous glycogen granules. Abnormalities of spatial orientation were also noted. Unlike control axons which grew parallel with the long axis of the tube, regenerating axons in experimental animals were seen deviating from the axis at 90 degrees angles. Both immature sprouts and myelinating axons showed abnormal plasticity. Ultrastructural differences were also noted in Schwann cells, macrophages and vessels.

  View details for Web of Science ID A1986A129400005

  View details for PubMedID 3950655

• NEURONOTROPHIC ACTIVITIES IN CEREBROSPINAL-FLUID OF HEAD TRAUMA PATIENTS EXPERIMENTAL NEUROLOGY LONGO, F. M., Selak, I., Zovickian, J., MANTHORPE, M., VARON, S., U, H. S. 1984; 84 (1): 207-218

  Abstract

  Neuronotrophic factors (NTFs) are agents required for neurons to survive in tissue culture. In this study, we investigated the presence of NTFs in cerebrospinal fluid (CSF) of patients with central nervous system (CNS) injury. Cerebrospinal fluid was collected from 15 patients with acute CNS lesions in whom ventricular catheters had been placed to monitor and to facilitate the control of intracranial pressure. Neuronotrophic activity within the CSF was assayed using cultures of neurons derived from fetal rat hippocampus and embryonic chick cerebral cortex. Cerebrospinal fluid from all 15 patients contained NTFs which supported the survival of rat hippocampal neurons. Survival of chick cortex neurons was supported by eight of nine CSF samples. In the 11 patients from whom consecutive CSF samples were available, NTF activity assayed in rat hippocampal cultures tended to decrease during the first several days after CNS injury. In CSF collected from three patients by lumbar puncture for diagnosis of "nontraumatic" conditions, no NTFs were detectable. NTFs supporting hippocampal neurons were also detected in extracts of blood clot obtained from normal volunteers. Neuronotrophic activity in the CSF was heat sensitive, nondialyzable, and macromolecular, suggesting its association with a protein(s). These observations suggested that (i) NTFs are detectable in human CSF after CNS injury, (ii) NTFs appear in response to the injury itself, and (iii) at least some human NTFs can support the survival in culture of nonhuman CNS neurons.

  View details for Web of Science ID A1984SL49100016

  View details for PubMedID 6705885

• NEURITE-PROMOTING FACTORS AND EXTRACELLULAR-MATRIX COMPONENTS ACCUMULATING INVIVO WITHIN NERVE REGENERATION CHAMBERS BRAIN RESEARCH LONGO, F. M., HAYMAN, E. G., Davis, G. E., RUOSLAHTI, E., ENGVALL, E., MANTHORPE, M., VARON, S. 1984; 309 (1): 105-117

  Abstract

  The outgrowth of neurites from cultured neurons can be induced by the extracellular matrix glycoproteins, fibronectin and laminin, and by polyornithine-binding neurite-promoting factors (NPFs) derived from culture media conditioned by Schwann, or other cultured cells. We have examined the occurrence of fibronectin, laminin and NPFs during peripheral nerve regeneration in vivo. A previously established model of peripheral nerve regeneration was used in which a transected rat sciatic nerve regenerates through a silicone chamber bridging a 10 mm interstump gap. The distribution of fibronectin and laminin during regeneration was assessed by indirect immunofluorescence. Seven days after nerve transection the regenerating structure within the chamber consisted primarily of a fibrous matrix which stained with anti-fibronectin but not anti-laminin. At 14 days, cellular outgrowths from the proximal and distal stumps (along which neurites grow) had entered the fibronectin-containing matrix, consistent with a role of fibronectin in promoting cell migration. Within these outgrowths non-vascular as well as vascular cells stained with anti-fibronectin and anti-laminin. Within the degenerated distal nerve segment, cell characteristic of Bungner bands (rows of Schwann cells along which regenerating neurites extend) stained with anti-fibronectin and laminin. The fluid surrounding the regenerating nerve was found to contain NPF activity for cultured ciliary ganglia neurons which markedly increased during the period of neurite growth into the chamber. In previous studies using this particular neurite-promoting assay, laminin but to a much lesser extent fibronectin also promoted neurite outgrowth.(ABSTRACT TRUNCATED AT 250 WORDS)

  View details for Web of Science ID A1984TH18200010

  View details for PubMedID 6488001

• NEURONOTROPHIC ACTIVITIES ACCUMULATE INVIVO WITHIN SILICONE NERVE REGENERATION CHAMBERS BRAIN RESEARCH LONGO, F. M., MANTHORPE, M., Skaper, S. D., Lundborg, G., VARON, S. 1983; 261 (1): 109-116

  View details for Web of Science ID A1983QC95500013

  View details for PubMedID 6839146

• SPATIAL-TEMPORAL PROGRESS OF PERIPHERAL-NERVE REGENERATION WITHIN A SILICONE CHAMBER - PARAMETERS FOR A BIOASSAY JOURNAL OF COMPARATIVE NEUROLOGY Williams, L. R., LONGO, F. M., Powell, H. C., Lundborg, G., VARON, S. 1983; 218 (4): 460-470

  Abstract

  The spatial-temporal progress of peripheral nerve regeneration across a 10-mm gap within a silicone chamber was examined with the light and electron microscope at 2-mm intervals. A coaxial, fibrin matrix was observed at 1 week with a proximal-distal narrowing that extended beyond the midpoint of the chamber. At 2 weeks, Schwann cells, fibroblasts, and endothelial cells had migrated into the matrix from both nerve stumps. There was a delay of 7-14 days after nerve transection and chamber implantation before regenerating axons appeared in the chamber. At 2 weeks, nonmyelinated axons were seen only in the proximal 1-5 mm of the chamber in association with Schwann cells. Axons reached the distal stump by 3 weeks and a proximal-distal gradient of myelination was observed. These observations define the parameters of a morphologic assay for regeneration in this chamber model which can be used to investigate cellular and molecular mechanisms underlying the success of peripheral nerve regeneration.

  View details for Web of Science ID A1983RC61300008

  View details for PubMedID 6619324

• TEMPORAL CHANGES OF NEURONOTROPHIC ACTIVITIES ACCUMULATING INVIVO WITHIN NERVE REGENERATION CHAMBERS EXPERIMENTAL NEUROLOGY LONGO, F. M., Skaper, S. D., MANTHORPE, M., Williams, L. R., Lundborg, G., VARON, S. 1983; 81 (3): 756-769

  Abstract

  The presence of neuronotrophic factors (NTFs) in noninjured sciatic nerve extract and the course of their accumulation from 3 h to 30 days after nerve transection was examined. Rat sciatic nerves were transected and their proximal and distal stumps sutured into the openings of cylindrical silicone chambers leaving a 10-mm interstump gap. Previous studies had shown that regeneration occurs in chambers containing both stumps but is absent in chambers lacking the distal stump. Chambers became completely filled with fluid 10 to 12 h after implantation. Fluid from chambers without nerve stumps (open-ended) implanted adjacent to nerve-containing chambers had markedly lower trophic activities than those containing one or both stumps. In fluid collected from chambers containing both proximal and distal nerve stumps, the highest titers of NTFs directed to sensory neurons were measured at 3 h posttransection whereas the highest titers of NTFs directed to sympathetic and spinal cord neurons were detected at 1 and 3 days, respectively. Chambers containing only the proximal or only the distal stumps showed similar temporal dynamics for sensory and sympathetic NTFs. Sensory and sympathetic neuronotrophic activity in extracts of proximal and distal stumps followed a similar temporal course to those in chamber fluid. Extracts of nonlesion nerve segments 5 mm from the transection site contained higher sensory and lower sympathetic trophic activity than extracts including the transection site. Spinal cord activity was undetectable in all extracts. Antiserum to nerve growth factor had no effect on fluid or extracts containing high sensory or sympathetic activities. These observations suggested that (i) some NTFs may be present in normal nerves and others may be synthesized or accumulated in response to nerve injury, (ii) sensory, sympathetic, and spinal cord NTFs are separate agents and immunochemically distinct from nerve growth factor, (iii) NTFs predominantly originate from nerve stumps rather than from surrounding fluid, and (iv) proximal and distal nerve stumps accumulate and release NTFs at similar rates.

  View details for Web of Science ID A1983RH10300020

  View details for PubMedID 6884483

• ENDOGENOUS AND EXOGENOUS FACTORS SUPPORT NEURONAL SURVIVAL AND CHOLINE-ACETYLTRANSFERASE ACTIVITY IN EMBRYONIC SPINAL-CORD CULTURES BRAIN RESEARCH MANTHORPE, M., Luyten, W., LONGO, F. M., VARON, S. 1983; 267 (1): 57-66

  Abstract

  Dissociated 4-day (stage 23) chick embryo lumbar cord cells were cultured at low or high cell densities for 1 or 5 days in the presence or absence of added spinal neuronotrophic factor (supplied as RN22 Schwannoma conditioned medium, RCM). In low density, 1-day cultures neuronal survival was dependent on added RCM whereas by 5 days no neurons survived, even in the presence of RCM. In high density 1-day cultures a substantial neuronal population could survive even without added RCM and a large proportion of this neuronal population would survive for 5 days. When conditioned media from high density lumbar cord cultures was supplied to low density unsupplemented cultures, a similar level of 5-day neuronal survival resulted. However, no neurons survived in RCM-supplemented 5-day high density cultures, indicating the presence in RCM of a material toxic for the neurons. Both the RCM and the high density lumbar culture-conditioned medium supported considerable choline acetyltransferase activity indicating the presence within these cultures of motoneurons.

  View details for Web of Science ID A1983QS81900005

  View details for PubMedID 6860950

• LAMININ PROMOTES NEURITIC REGENERATION FROM CULTURED PERIPHERAL AND CENTRAL NEURONS JOURNAL OF CELL BIOLOGY MANTHORPE, M., ENGVALL, E., RUOSLAHTI, E., LONGO, F. M., Davis, G. E., VARON, S. 1983; 97 (6): 1882-1890

  Abstract

  The ability of axons to grow through tissue in vivo during development or regeneration may be regulated by the availability of specific neurite-promoting macromolecules located within the extracellular matrix. We have used tissue culture methods to examine the relative ability of various extracellular matrix components to elicit neurite outgrowth from dissociated chick embryo parasympathetic (ciliary ganglion) neurons in serum-free monolayer culture. Purified laminin from both mouse and rat sources, as well as a partially purified polyornithine-binding neurite promoting factor (PNPF-1) from rat Schwannoma cells all stimulate neurite production from these neurons. Laminin and PNPF-1 are also potent stimulators of neurite growth from cultured neurons obtained from other peripheral as well as central neural tissues, specifically avian sympathetic and sensory ganglia and spinal cord, optic tectum, neural retina, and telencephalon, as well as from sensory ganglia of the neonatal mouse and hippocampal, septal, and striatal tissues of the fetal rat. A quantitative in vitro bioassay method using ciliary neurons was used to (a) measure and compare the specific neurite-promoting activities of these agents, (b) confirm that during the purification of laminin, the neurite-promoting activity co-purifies with the laminin protein, and (c) compare the influences of antilaminin antibodies on the neurite-promoting activity of laminin and PNPF-1. We conclude that laminin and PNPF-1 are distinct macromolecules capable of expressing their neurite-promoting activities even when presented in nanogram amounts. This neurite-promoting bioassay currently represents the most sensitive test for the biological activity of laminin.

  View details for Web of Science ID A1983RT38400026

  View details for PubMedID 6643580

• NEURONOTROPHIC ACTIVITY IN BRAIN WOUNDS OF THE DEVELOPING RAT - CORRELATION WITH IMPLANT SURVIVAL IN THE WOUND CAVITY BRAIN RESEARCH MANTHORPE, M., NIETOSAMPEDRO, M., Skaper, S. D., Lewis, E. R., Barbin, G., LONGO, F. M., Cotman, C. W., VARON, S. 1983; 267 (1): 47-56

  Abstract

  Neuronotrophic activity accumulates in a wound cavity created in the entorhinal/occipital cortex of developing rats. These trophic factors support the survival of neurons in monolayer cultures of chick embryo spinal cord, ciliary ganglion, sympathetic ganglion and dorsal root ganglion, as well as of mouse dorsal root ganglion. Trophic activity was very low both in non-injured brain tissue and in the wound cavity 1 day post-lesion, but it increased 15- to 300-fold during the subsequent 2-5 days. Together with the trophic activity in the wound fluid were other substances which interfered with the survival of spinal cord neurons. The neuronotrophic factors appeared to be proteins immunologically distinct from mouse submaxillary nerve growth factor. Fragments of rat embryo corpus striatum placed in the cortical wound cavity immediately after its formation showed very poor subsequent survival and no innervation of the host hippocampus. However, if implantation was delayed by 3 or 6 days with respect to the time at which the receiving cavity was made, the survival was greatly improved and innervation of the host took place. The time course for the accumulation of the trophic factors in the cavity paralleled the delay leading to increased survival of brain grafts. It is suggested that the neuronotrophic activity accumulating in the wound cavity during the delay period may be responsible for the increased survival of the implants.

  View details for Web of Science ID A1983QS81900004

  View details for PubMedID 6860949

• Spinal cord neuronotrophic factors (SCNTFs): I. Bioassay of schwannoma and other conditioned media. Brain research LONGO, F. M., MANTHORPE, M., VARON, S. 1982; 255 (2): 277-294

  Abstract

  We present a procedure for the dissociation and growth in serum-free defined culture medium of 4-day chick embryo lumbar spinal cord (LC4) neurons. LC4 neurons will not survive for even 24 h without the addition of trophic supplements (putative spinal cord neuronotrophic factors, SCNTFs). Serum-free medium conditioned over chick embryo heart and skeletal muscle, mouse Schwann and rat RN22 Schwannoma cell cultures were found to contain SCNTF activity which could be quantitated using a convenient neuronal survival bioassay. RN22 conditioned medium also contains polyornithine-binding neurite promoting factors (PNPFs) which can be physically separated from SCNTF. When SCNTF and PNPF were presented to LC4 neurons individually or in combination (i) SCNTF, but not PNPF, supported neuronal survival whereas (ii) PNPF, but not SCNTF, induced neurite production. When LC4 neurons were grown in SCNTF alone, nearly all of them exhibited a flattened, circular, 'fried-egg' morphology. The subsequent addition of PNPF caused these cells to extend long neurites with characteristic terminal growth-cone-like structures.

  View details for PubMedID 7055725

• INVIVO REGENERATION OF CUT NERVES ENCASED IN SILICONE TUBES - GROWTH ACROSS A 6-MILLIMETER GAP JOURNAL OF NEUROPATHOLOGY AND EXPERIMENTAL NEUROLOGY Lundborg, G., Gelberman, R. H., LONGO, F. M., Powell, H. C., VARON, S. 1982; 41 (4): 412-422

  Abstract

  We describe an experimental in vivo system for studying peripheral nerve regeneration, in which the proximal stump of a transected nerve regrows through a transparent silicone chamber toward the distal stump. Physical separation permits examination of the effects of the humoral and/or cellular influences from the distal stump on regenerating fibers before they invade the distal segment itself. A small segment of the rat sciatic nerve was resected, leaving a 6 mm gap which was then encased by a cylindrical silicone chamber. Within the first weeks, a nerve trunk regenerated along the central axis of the chamber bridged the gap between the proximal and distal stumps. When the distal nerve stump was omitted from the distal opening of the chamber, only a thin structure with a few small-caliber fibers extended across the gap. In each instance regenerating nerve appeared as a cord-like structure completely surrounded by clear fluid, a feature which permits easy collection of the extracellular fluid for analysis of its chemical properties and biological activity. This feature also allows in vivo manipulation of the humoral environment in which nerve regeneration occurs.

  View details for Web of Science ID A1982NX92500004

  View details for PubMedID 7086464

• NERVE REGENERATION IN SILICONE CHAMBERS - INFLUENCE OF GAP LENGTH AND OF DISTAL STUMP COMPONENTS EXPERIMENTAL NEUROLOGY Lundborg, G., Dahlin, L. B., Danielsen, N., Gelberman, R. H., LONGO, F. M., Powell, H. C., VARON, S. 1982; 76 (2): 361-375

  View details for Web of Science ID A1982NN60700012

  View details for PubMedID 7095058

• Growth factors and motor neurons. Advances in neurology VARON, S., MANTHORPE, M., LONGO, F. M. 1982; 36: 453-472

  View details for PubMedID 7180691

• BRAIN INJURY CAUSES A TIME-DEPENDENT INCREASE IN NEURONOTROPHIC ACTIVITY AT THE LESION SITE SCIENCE NIETOSAMPEDRO, M., Lewis, E. R., Cotman, C. W., MANTHORPE, M., Skaper, S. D., Barbin, G., LONGO, F. M., VARON, S. 1982; 217 (4562): 860-861

  Abstract

  A cavity was made in the brain (entorhinal cortex) of developing or adult rats, and a small piece of Gelfoam was emplaced to collect fluid secreted into the wound. The neuronotrophic activity of the fluid was assayed with sympathetic and parasympathetic neurons in culture. The results show that wounds in the brain of developing or adult rats stimulate the accumulation of neuronotrophic factors and that the activity of these factors increases over the first few days after infliction of the damage.

  View details for Web of Science ID A1982PC11800039

  View details for PubMedID 7100931

• NERVE REGENERATION MODEL AND TROPHIC FACTORS INVIVO BRAIN RESEARCH Lundborg, G., LONGO, F. M., VARON, S. 1982; 232 (1): 157-161

  Abstract

  The proximal stump of a transected rat sciatic nerve has been observed to regenerate through a cylindrical silicone chamber across a 10 mm gap to the distal stump. The fluid filling such in vivo chambers contains trophic factors that ensure in vitro survival and growth of at least sensory neurons from rodent dorsal root ganglia--as already demonstrated for fluid generated in vitro from Schwann and other cell cultures.

  View details for Web of Science ID A1982MY42300013

  View details for PubMedID 7055692

• COMPARATIVE FEATURES OF SPINAL NEURONOTROPHIC FACTORS IN FLUIDS COLLECTED INVITRO AND INVIVO JOURNAL OF NEUROSCIENCE RESEARCH MANTHORPE, M., LONGO, F. M., VARON, S. 1982; 8 (2-3): 241-250

  Abstract

  Survival in monolayer culture of 4-day (stage 23) chick embryo lumbar spinal cord neurons can be regulated by two opposing activities. One, spinal neuronotrophic activity, promotes neuronal survival; and the other, spinal neuronotoxic activity, eliminates the neurons from the culture even when the trophic support is present at an optimal concentration. Quantitative microbioassays for each activity are presented and used to measure the relative amounts of each agent within different sources including glial, muscle, and spinal cord cell-conditioned media and fluid collected from peripheral and central nervous tissue lesions. Although both activities were present in all of the sources tested, their concentrations in the wound fluids were orders of magnitude greater than in the conditioned media. The fluid-derived trophic activities were inactivated by heat and trypsin and nondialyzable, whereas all of the conditioned media-derived trophic activities were heat- and trypsin-resistant and dialyzable.

  View details for Web of Science ID A1982PV92500013

  View details for PubMedID 7154113

• NERVE REGENERATION ACROSS AN EXTENDED GAP - A NEUROBIOLOGICAL VIEW OF NERVE REPAIR AND THE POSSIBLE INVOLVEMENT OF NEURONOTROPHIC FACTORS JOURNAL OF HAND SURGERY-AMERICAN VOLUME Lundborg, G., Dahlin, L. B., Danielsen, N., Hansson, H. A., Johannesson, A., LONGO, F. M., VARON, S., Engin, D. 1982; 7 (6): 580-587

  Abstract

  We have compared the anatomic and functional regeneration of a transected sciatic nerve following regrowth from its proximal stump through either preformed empty mesothelial chambers or autologous nerve grafts bridging a 10 mm gap. Within the mesothelial chambers an organized multifascicular nerve trunk forms between the proximal and distal stumps. After 3 months, distal segment cross sections from the mesothelial chamber and nerve graft groups did not differ with respect to axonal density or distribution of axonal diameters. Mean conduction velocities across the gaps were also similar, although the nerve graft group had a wider distribution of velocities. Little or no regeneration was evident when the gap between the nerve stumps was left empty. These results suggest that if the regrowing proximal stump is in an appropriate environment, it can form a well organized and oriented nerve trunk. In the mesothelial chambers, the regenerating nerve is surrounded by a loose cellular stroma and a small amount of interstitial fluid, which was found to contain trophic activity for cultured rodent sensory neurons. Such factors may also support nerve regeneration in vivo.

  View details for Web of Science ID A1982PP37900008

  View details for PubMedID 7175129

• SPINAL-CORD NEURONOTROPHIC FACTORS (SCNTFS) .1. BIOASSAY OF SCHWANNOMA AND OTHER CONDITIONED MEDIA DEVELOPMENTAL BRAIN RESEARCH LONGO, F. M., MANTHORPE, M., VARON, S. 1982; 3 (2): 277-294

  View details for Web of Science ID A1982NB13800010

• RELATION OF SOMAL LIPID-SYNTHESIS TO THE FAST AXONAL-TRANSPORT OF PROTEIN AND LIPID BRAIN RESEARCH LONGO, F. M., Hammerschlag, R. 1980; 193 (2): 471-485

  Abstract

  The role of somal lipid synthesis in the fast axonal transport of protein and lipid was examined in vitro utilizing spinal/sciatic nerve preparations of bullfrog. Inhibition of phospholipid synthesis in dorsal root ganglia by the amphiphilic cation, fenfluramine (0.1-2.0 mM) was monitored as decreased incorporation of [3H]choline into phosphatidyl choline. This inhibition was directly proportional to a decrease in the amount of [3H]protein undergoing fast axonal transport, the two variables being related by a slope close to unity. [3H]Choline-labeled lipid undergoing fast transport in the axon was unaffected by inhibition of somal phospholipid synthesis. Levels of fenfluramine up to 1.0 mM had no effect on uptake or incorporation of [3H]leucine. Selective exposure of desheathed nerve trunks to 1.0 mM fenfluramine had no effect on [3H]protein translocation, indicating that local phospholipid synthesis is not required to maintain ongoing transport in the axon. Inhibition of cholesterol synthesis in the ganglia with the analog 20,25-diazacholesterol also resulted in depression of [3H]protein transport. Since synthesis of both phospholipid and cholesterol are required at the level of the ganglion, it is suggested that the initiation of fast axonal transport of protein is dependent on the assembly of lipoprotein structures in the soma.

  View details for Web of Science ID A1980JX56900011

  View details for PubMedID 6155973