All Publications

  • TREM1 disrupts myeloid bioenergetics and cognitive function in aging and Alzheimer disease mouse models. Nature neuroscience Wilson, E. N., Wang, C., Swarovski, M. S., Zera, K. A., Ennerfelt, H. E., Wang, Q., Chaney, A., Gauba, E., Ramos Benitez, J. A., Le Guen, Y., Minhas, P. S., Panchal, M., Tan, Y. J., Blacher, E., A Iweka, C., Cropper, H., Jain, P., Liu, Q., Mehta, S. S., Zuckerman, A. J., Xin, M., Umans, J., Huang, J., Durairaj, A. S., Serrano, G. E., Beach, T. G., Greicius, M. D., James, M. L., Buckwalter, M. S., McReynolds, M. R., Rabinowitz, J. D., Andreasson, K. I. 2024


    Human genetics implicate defective myeloid responses in the development of late-onset Alzheimer disease. A decline in peripheral and brain myeloid metabolism, triggering maladaptive immune responses, is a feature of aging. The role of TREM1, a pro-inflammatory factor, in neurodegenerative diseases is unclear. Here we show that Trem1 deficiency prevents age-dependent changes in myeloid metabolism, inflammation and hippocampal memory function in mice. Trem1 deficiency rescues age-associated declines in ribose 5-phosphate. In vitro, Trem1-deficient microglia are resistant to amyloid-β42 oligomer-induced bioenergetic changes, suggesting that amyloid-β42 oligomer stimulation disrupts homeostatic microglial metabolism and immune function via TREM1. In the 5XFAD mouse model, Trem1 haploinsufficiency prevents spatial memory loss, preserves homeostatic microglial morphology, and reduces neuritic dystrophy and changes in the disease-associated microglial transcriptomic signature. In aging APPSwe mice, Trem1 deficiency prevents hippocampal memory decline while restoring synaptic mitochondrial function and cerebral glucose uptake. In postmortem Alzheimer disease brain, TREM1 colocalizes with Iba1+ cells around amyloid plaques and its expression is associated with Alzheimer disease clinical and neuropathological severity. Our results suggest that TREM1 promotes cognitive decline in aging and in the context of amyloid pathology.

    View details for DOI 10.1038/s41593-024-01610-w

    View details for PubMedID 38539014

    View details for PubMedCentralID 4369837

  • Machine learning models of plasma proteomic data predict mood in chronic stroke and tie it to aberrant peripheral immune responses. Brain, behavior, and immunity Bidoki, N. H., Zera, K. A., Nassar, H., Drag, L. L., Mlynash, M., Osborn, E., Musabbir, M., Eun K Kim, D., Paula Mendez, M., Lansberg, M. G., Aghaeepour, N., Buckwalter, M. S. 2023


    Post-stroke depression is common, long-lasting and associated with severe morbidity and death, but mechanisms are not well-understood. We used a broad proteomics panel and developed a machine learning algorithm to determine whether plasma protein data can predict mood in people with chronic stroke, and to identify proteins and pathways associated with mood. We used Olink to measure 1,196 plasma proteins in 85 participants aged 25 and older who were between 5 months and 9 years after ischemic stroke. Mood was assessed with the Stroke Impact Scale mood questionnaire (SIS3). Machine learning multivariable regression models were constructed to estimate SIS3 using proteomics data, age, and time since stroke. We also dichotomized participants into better mood (SIS3 > 63) or worse mood (SIS3 ≤ 63) and analyzed candidate proteins. Machine learning models verified that there is indeed a relationship between plasma proteomic data and mood in chronic stroke, with the most accurate prediction of mood occurring when we add age and time since stroke. At the individual protein level, no single protein or set of proteins predicts mood. But by using univariate analyses of the proteins most highly associated with mood we produced a model of chronic post-stroke depression. We utilized the fact that this list contained many proteins that are also implicated in major depression. Also, over 80% of immune proteins that correlate with mood were higher with worse mood, implicating a broadly overactive immune system in chronic post-stroke depression. Finally, we used a comprehensive literature review of major depression and acute post-stroke depression. We propose that in chronic post-stroke depression there is over-activation of the immune response that then triggers changes in serotonin activity and neuronal plasticity leading to depressed mood.

    View details for DOI 10.1016/j.bbi.2023.08.002

    View details for PubMedID 37557961

  • Targeting VCAM1 to reduce neuroinflammation in ischemia-triggered vascular dementia. Alzheimer's & dementia : the journal of the Alzheimer's Association Zera, K. A., Peterson, T., Yousef, H., Lee, D., Wyss-Coray, T., Buckwalter, M. S. 1800; 17 Suppl 3: e053849


    BACKGROUND: Ischemia is a well-established contributor to vascular dementia. Indeed, the most common pathology in people with dementia is mixed, and over half of patients diagnosed with AD have demonstrable vascular pathologies. Ischemia induces an immune response which triggers secondary neurodegeneration remote to the initial lesion, and consequent cognitive decline. Ischemia-triggered vascular dementia is dependent on B-lymphocytes driving chronic neuroinflammation in adult mice. However, vascular dementia is most common in the aged, and there are key differences in inflammatory responses with age. Vascular cell adhesion molecule 1 (VCAM1) is an endothelial protein that facilitates vascular-immune crosstalk via interaction with very late antigen-4 (VLA-4). Soluble VCAM1 is elevated in stroke, vascular dementia, and normal aging in both people and mice. In aging mice, anti-VCAM1 ameliorates age-induced neuroinflammation and cognitive impairment. Although the mechanism is unclear, this is likely mediated via changes in endothelial cell activation and secretion of pro-inflammatory mediators. Therefore, we hypothesized that acute anti-VCAM1 treatment would reduce microgliosis and astrogliosis, while delayed treatment would reduce B and T lymphocyte infiltration in a mouse model of ischemia-triggered vascular dementia.METHOD: Adult (3-month-old) or aged (10-month-old) C57BL/6J mice (n=10-15/group) underwent permanent distal middle cerebral artery occlusion. Mice were dosed with anti-VCAM1 antibody either 4 hours or 4 days post-ischemia, and then sacrificed at 72 hours, 3 weeks or 6 weeks post-ischemia. Microgliosis and astrogliosis were quantified as percent area immunostained in the lesion border by CD68 and GFAP, respectively. B and T cell infiltration were quantified as percent lesion immunostained by B220, and CD3+ cells in the ischemic lesion, respectively.RESULT: Acute treatment reduced microgliosis 30% (p=0.0476) and astrogliosis 39% (p<0.03). In adults, delayed anti-VCAM1 significantly reduced B and T cell infiltration approximately 25% (p=0.0015) and 50% (p=0.0192), respectively. Similarly, in aged mice, delayed anti-VCAM1 significantly reduced B and T cell infiltration approximately 50% (p=0.0037) and 30% (p=0.0036), respectively. In contrast, early anti-VCAM1 had little or no effect on B or T cell infiltration.CONCLUSION: Together, these findings establish VCAM1 as a possible therapeutic target to ameliorate ischemia-induced neuroinflammation and consequent cognitive decline in a mouse model of vascular dementia.

    View details for DOI 10.1002/alz.053849

    View details for PubMedID 35108898

  • Brain profiling in murine colitis and human epilepsy reveals neutrophils and TNFalpha as mediators of neuronal hyperexcitability. Journal of neuroinflammation Barnes, S. E., Zera, K. A., Ivison, G. T., Buckwalter, M. S., Engleman, E. G. 2021; 18 (1): 199


    BACKGROUND: Patients with chronic inflammatory disorders such as inflammatory bowel disease frequently experience neurological complications including epilepsy, depression, attention deficit disorders, migraines, and dementia. However, the mechanistic basis for these associations is unknown. Given that many patients are unresponsive to existing medications or experience debilitating side effects, novel therapeutics that target the underlying pathophysiology of these conditions are urgently needed.METHODS: Because intestinal disorders such as inflammatory bowel disease are robustly associated with neurological symptoms, we used three different mouse models of colitis to investigate the impact of peripheral inflammatory disease on the brain. We assessed neuronal hyperexcitability, which is associated with many neurological symptoms, by measuring seizure threshold in healthy and colitic mice. We profiled the neuroinflammatory phenotype of colitic mice and used depletion and neutralization assays to identify the specific mediators responsible for colitis-induced neuronal hyperexcitability. To determine whether our findings in murine models overlapped with a human phenotype, we performed gene expression profiling, pathway analysis, and deconvolution on microarray data from hyperexcitable human brain tissue from patients with epilepsy.RESULTS: We observed that murine colitis induces neuroinflammation characterized by increased pro-inflammatory cytokine production, decreased tight junction protein expression, and infiltration of monocytes and neutrophils into the brain. We also observed sustained neuronal hyperexcitability in colitic mice. Colitis-induced neuronal hyperexcitability was ameliorated by neutrophil depletion or TNFalpha blockade. Gene expression profiling of hyperexcitable brain tissue resected from patients with epilepsy also revealed a remarkably similar pathology to that seen in the brains of colitic mice, including neutrophil infiltration and high TNFalpha expression.CONCLUSIONS: Our results reveal neutrophils and TNFalpha as central regulators of neuronal hyperexcitability of diverse etiology. Thus, there is a strong rationale for evaluating anti-inflammatory agents, including clinically approved TNFalpha inhibitors, for the treatment of neurological and psychiatric symptoms present in, and potentially independent of, a diagnosed inflammatory disorder.

    View details for DOI 10.1186/s12974-021-02262-4

    View details for PubMedID 34511110

  • T cells direct microglial repair of white matter after stroke. Trends in neurosciences Zera, K. A., Buckwalter, M. S. 2021


    A recent paper by Shi et al. defines the role of regulatory T cells (Tregs) in white matter recovery after ischemic stroke. This study elucidates the mechanisms by which Tregs direct microglia to alter their phenotype to support oligodendrogenesis, thereby improving white matter integrity and functional recovery after stroke in mice.

    View details for DOI 10.1016/j.tins.2021.07.005

    View details for PubMedID 34332802

  • The Local and Peripheral Immune Responses to Stroke: Implications for Therapeutic Development. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics Zera, K. A., Buckwalter, M. S. 2020


    The immune response to stroke is an exciting target for future stroke therapies. Stroke is a leading cause of morbidity and mortality worldwide, and clot removal (mechanical or pharmacological) to achieve tissue reperfusion is the only therapy currently approved for patient use. Due to a short therapeutic window and incomplete effectiveness, however, many patients are left with infarcted tissue that stimulates inflammation. Although this is critical to promote repair, it can also damage surrounding healthy brain tissue. In addition, acute immunodepression and subsequent infections are common and are associated with worse patient outcomes. Thus, the acute immune response is a major focus of researchers attempting to identify ways to amplify its benefits and suppress its negative effects to improve short-term recovery of patients. Here we review what is known about this powerful process. This includes the role of brain resident cells such as microglia, peripherally activated cells such as macrophages and neutrophils, and activated endothelium. The role of systemic immune activation and subsequent immunodepression in the days after stroke is also discussed, as is the chronic immune responses and its effects on cognitive function. The biphasic role of inflammation, as well as complex timelines of cell production, differentiation, and trafficking, suggests that the relationship between the acute and chronic phases of stroke recovery is complex. Gaining a more complete understanding of this intricate process by which inflammation is initiated, propagated, and terminated may potentially lead to therapeutics that can treat a larger population of stroke patients than what is currently available. The immune response plays a critical role in patient recovery in both the acute and chronic phases after stroke. In patients, the immune response can be beneficial by promoting repair and recovery, and also detrimental by propagating a pro-inflammatory microenvironment. Thus, it is critical to understand the mechanisms of immune activation following stroke in order to successfully design therapeutics.

    View details for DOI 10.1007/s13311-020-00844-3

    View details for PubMedID 32193840

  • Aged blood impairs hippocampal neural precursor activity and activates microglia via brain endothelial cell VCAM1 NATURE MEDICINE Yousef, H., Czupalla, C. J., Lee, D., Chen, M. B., Burke, A. N., Zera, K. A., Zandstra, J., Berber, E., Lehallier, B., Mathur, V., Nair, R. V., Bonanno, L. N., Yang, A. C., Peterson, T., Hadeiba, H., Merkel, T., Koerbelin, J., Schwaninger, M., Buckwalter, M. S., Quake, S. R., Butcher, E. C., Wyss-Coray, T. 2019; 25 (6): 988-+
  • Stabilization of the hypoxia-inducible transcription Factor-1 alpha (HIF-1 alpha) in thiamine deficiency is mediated by pyruvate accumulation TOXICOLOGY AND APPLIED PHARMACOLOGY Zera, K., Zastre, J. 2018; 355: 180–88


    Vitamin B1, or thiamine is a critical enzyme cofactor required for metabolic function and energy production. Thiamine deficiency (TD) is common in various diseases, and results in severe neurological complications due to diminished mitochondrial function, oxidative stress, excitotoxicity and inflammation. These pathological sequelae result in apoptotic cell death in both neurons and astrocytes in distinct regions, in particular the thalamus and mammillary bodies. Comparable histological injuries in patients with hypoxia/ischemia (H/I) have also been described, suggesting a congruency between the cellular responses to these stresses. Analogous to H/I, TD stabilizes and activates Hypoxia Inducible Factor-1α (HIF-1α) even without changes in physiological oxygen levels. However, the mechanism of HIF-1α stabilization in TD is currently unknown. Using a pyruvate assay, we have demonstrated that TD induces pyruvate accumulation in mouse primary astrocytes which correlates to an increase in HIF-1α expression. Additionally, we utilized an enzymatic assay for pyruvate dehydrogenase to demonstrate a reduction in catalytic activity during TD due to lack of available thiamine pyrophosphate cofactor, resulting in the observed pyruvate accumulation. Finally, a pyruvate kinase inhibitor which limited pyruvate accumulation was utilized to demonstrate the role of pyruvate accumulation in HIF-1α stabilization during TD. These results reveal that stabilization of HIF-1α protein in TD centralizes on pyruvate accumulation in mouse primary astrocytes due to metabolic disruption of PDH.

    View details for DOI 10.1016/j.taap.2018.07.004

    View details for Web of Science ID 000442193300019

    View details for PubMedID 30008376

  • Thiamine deficiency activates hypoxia inducible factor-1 alpha to facilitate pro-apoptotic responses in mouse primary astrocytes PLOS ONE Zera, K., Zastre, J. 2017; 12 (10): e0186707


    Thiamine is an essential enzyme cofactor required for proper metabolic function and maintenance of metabolism and energy production in the brain. In developed countries, thiamine deficiency (TD) is most often manifested following chronic alcohol consumption leading to impaired mitochondrial function, oxidative stress, inflammation and excitotoxicity. These biochemical lesions result in apoptotic cell death in both neurons and astrocytes. Comparable histological injuries in patients with hypoxia/ischemia and TD have been described in the thalamus and mammillary bodies, suggesting a congruency between the cellular responses to these stresses. Consistent with hypoxia/ischemia, TD stabilizes and activates Hypoxia Inducible Factor-1α (HIF-1α) under physiological oxygen levels. However, the role of TD-induced HIF-1α in neurological injury is currently unknown. Using Western blot analysis and RT-PCR, we have demonstrated that TD induces HIF-1α expression and activity in primary mouse astrocytes. We observed a time-dependent increase in mRNA and protein expression of the pro-apoptotic and pro-inflammatory HIF-1α target genes MCP1, BNIP3, Nix and Noxa during TD. We also observed apoptotic cell death in TD as demonstrated by PI/Annexin V staining, TUNEL assay, and Cell Death ELISA. Pharmacological inhibition of HIF-1α activity using YC1 and thiamine repletion both reduced expression of pro-apoptotic HIF-1α target genes and apoptotic cell death in TD. These results demonstrate that induction of HIF-1α mediated transcriptional up-regulation of pro-apoptotic/inflammatory signaling contributes to astrocyte cell death during thiamine deficiency.

    View details for DOI 10.1371/journal.pone.0186707

    View details for Web of Science ID 000413168100090

    View details for PubMedID 29045486

    View details for PubMedCentralID PMC5646851

  • Role of HIF-1 alpha in the hypoxia inducible expression of the thiamine transporter, SLC19A3 GENE Zera, K., Sweet, R., Zastre, J. 2016; 595 (2): 212–20


    Ensuring continuous intracellular supply of thiamine is essential to maintain metabolism. Cellular homeostasis requires the function of the membrane bound thiamine transporters THTR1 and THTR2. In the absence of increased dietary intake of thiamine, varying intracellular levels to meet metabolic demands during pathophysiological stressors, such as hypoxia, requires adaptive regulatory mechanisms to increase thiamine transport capacity. Previous work has established the up-regulation of SLC19A3 (THTR2) gene expression and activity during hypoxic stress through the activity of the hypoxia inducible transcription factor 1 alpha (HIF-1α). However, it is unknown whether HIF-1α acts directly or indirectly to trans-activate expression of SLC19A3. This work utilized the breast cancer cell line BT-474 treated with 1% O2 or a hypoxia chemical mimetic deferoxamine to determine the minimal promoter region of SLC19A3 responsible for hypoxia responsiveness. In silico sequence analysis determined two contiguous hypoxia responsive elements in close proximity to the transcriptional start site of the SLC19A3 gene. Using a HIF-1α transcriptional factor ELISA assay, HIF-1α was capable of binding to a dsDNA construct of the SLC19A3 minimal promoter. Chromatin immunoprecipitation assay established that SP1 was bound to the SLC19A3 minimal promoter region under normoxic conditions. However, HIF-1α binding to the minimal promoter region occurred during hypoxic treatments, while no SP1 binding was observed under these conditions. This work demonstrates the direct binding and activation of SLC19A3 expression by HIF-1α during hypoxic stress, suggesting an important adaptive regulatory role for HIF-1α in maintaining thiamine homeostasis.

    View details for DOI 10.1016/j.gene.2016.10.013

    View details for Web of Science ID 000388778500012

    View details for PubMedID 27743994

    View details for PubMedCentralID PMC5097002