Dataset Information

Laser-captured microglia in the Alzheimer's and Parkinson's brain reveal unique regional expression profiles and suggest a potential role for hepatitis B in the Alzheimer's brain.

ABSTRACT: Expression array data from dozens of laboratories, including our own, show significant changes in expression of many genes in Alzheimer's disease (AD) patients compared with normal controls. These data typically rely on brain homogenates, and information about transcripts specific to microglia and other central nervous system (CNS) cell types, which far outnumber microglia-specific transcripts, is lost. We therefore used single-cell laser capture methods to assess the full range of microglia-specific expression changes that occur in different brain regions (substantia nigra and hippocampus CA1) and disease states (AD, Parkinson's disease, and normal controls). Two novel pathways, neuronal repair and viral processing were identified. Based on KEGG analysis (Kyoto Encyclopedia of Genes and Genomes, a collection of biological pathways), one of the most significant viruses was hepatitis B virus (HBV) (false discovery rate < 0.00000001). Immunohistochemical analysis using HBV-core antibody in HBV-positive control, amnestic mild cognitive impairment, and HBV-positive AD cases show increased HBV immunoreactivity as disease pathology increases. These results are the first, to our knowledge, to show regional differences in human microglia. In addition, these data reveal new functions for microglia and suggest a novel risk factor for AD.

SUBMITTER: Mastroeni D

PROVIDER: S-EPMC6686891 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Laser-captured microglia in the Alzheimer's and Parkinson's brain reveal unique regional expression profiles and suggest a potential role for hepatitis B in the Alzheimer's brain.

Mastroeni Diego D Nolz Jennifer J Sekar Shobana S Delvaux Elaine E Serrano Geidy G Cuyugan Lori L Liang Winnie S WS Beach Thomas G TG Rogers Joseph J Coleman Paul D PD

Neurobiology of aging 20171101

Expression array data from dozens of laboratories, including our own, show significant changes in expression of many genes in Alzheimer's disease (AD) patients compared with normal controls. These data typically rely on brain homogenates, and information about transcripts specific to microglia and other central nervous system (CNS) cell types, which far outnumber microglia-specific transcripts, is lost. We therefore used single-cell laser capture methods to assess the full range of microglia-spe ...[more]

PMID: 29207277

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Project description:Alzheimer's disease (AD) is a devastating neurodegenerative disorder that threatens to reach epidemic proportions as our population ages. Although much research has examined molecular pathways associated with AD, relatively few such studies have focused on the disease's critical early stages. In a prior microarray study we correlated gene expression in hippocampus with degree of Alzheimer's disease and found close associations between upregulation of apparent glial transcription factor/epigenetic/tumor suppressor genes and incipient AD. The results suggested a new model in which AD pathology spreads along myelinated axons (Blalock et al., 2004). However, the microarray analyses were performed on RNA extracted from frozen hand-dissected hippocampal CA1 tissue blocks containing both gray and white matter, limiting the confidence with which transcriptional changes in gray matter could be distinguished from those in white matter. Here, we used laser capture microdissection (LCM) to exclude major white matter tracts while selectively collecting CA1 hippocampal gray matter from formalin-fixed, paraffin-embedded (FFPE) hippocampal sections of the same subjects assessed in our prior study. Microarray analyses of this gray matter-enriched tissue revealed many transcriptional changes similar to those seen in our past study and in studies by others, particularly for downregulated neuron-related genes. Additionally, the present analyses identified several previously undetected pathway alterations, including downregulation of molecules that stabilize ryanodine receptor Ca2+ release and upregulation of vasculature development. Conversely, we found a striking paucity of the upregulated changes in the putative glial and growth-related genes that had been strongly overrepresented in the prior mixed-tissue study. We conclude that FFPE tissue can be a reliable resource for microarray studies of brain tissue, that upregulation of growth-related epigenetic/transcription factors during incipient AD is predominantly localized in and around white matter (supporting our prior findings and model), and that novel alterations in vascular and ryanodine receptor-related pathways in gray matter are closely associated with incipient AD.

Project description:Alzheimer's disease (AD) is characterized by a sequence of pathological changes, which are commonly assessed in vivo using various brain imaging modalities such as magnetic resonance imaging (MRI) and positron emission tomography (PET). Currently, the most approaches to analyze statistical associations between regions and imaging modalities rely on Pearson correlation or linear regression models. However, these models are prone to spurious correlations arising from uninformative shared variance and multicollinearity. Notably, there are no appropriate multivariate statistical models available that can easily integrate dozens of multicollinear variables derived from such data, being able to utilize the additional information provided from the combination of data sources. Gaussian graphical models (GGMs) can estimate the conditional dependency from given data, which is conceptually expected to closely reflect the underlying causal relationships between various variables. Hence, we applied GGMs to assess multimodal regional brain alterations in AD. We obtained data from N = 972 subjects from the Alzheimer's Disease Neuroimaging Initiative. The mean amyloid load (AV45-PET), glucose metabolism (FDG-PET), and gray matter volume (MRI) were calculated for each of the 108 cortical and subcortical brain regions. GGMs were estimated using a Bayesian framework for the combined multimodal data and the resulted conditional dependency networks were compared to classical covariance networks based on Pearson correlation. Additionally, graph-theoretical network statistics were calculated to determine network alterations associated with disease status. The resulting conditional dependency matrices were much sparser (≈10% density) than Pearson correlation matrices (≈50% density). Within imaging modalities, conditional dependency networks yielded clusters connecting anatomically adjacent regions. For the associations between different modalities, only few region-specific connections were detected. Network measures such as small-world coefficient were significantly altered across diagnostic groups, with a biphasic u-shape trajectory, i.e., increased small-world coefficient in early mild cognitive impairment (MCI), similar values in late MCI, and decreased values in AD dementia patients compared to cognitively normal controls. In conclusion, GGMs removed commonly shared variance among multimodal measures of regional brain alterations in MCI and AD, and yielded sparser matrices compared to correlation networks based on the Pearson coefficient. Therefore, GGMs may be used as alternative to thresholding-approaches typically applied to correlation networks to obtain the most informative relations between variables.

Project description:BackgroundCycles of alcohol and stress are hypothesized to contribute to alcohol use disorders. How this occurs is poorly understood, although both alcohol and stress activate the neuroimmune system-the immune molecules and cells that interact with the nervous system. The effects of alcohol and stress on the neuroimmune system are mediated in part by peripheral signaling molecules. Alcohol and stress both enhance immunomodulatory molecules such as corticosterone and endotoxin to impact neuroimmune cells, such as microglia, and may subsequently impact neurons. In this study, we therefore examined the effects of acute and chronic ethanol (EtOH) on the corticosterone, endotoxin, and microglial and neuronal response to acute stress.MethodsMale Wistar rats were treated intragastrically with acute EtOH and acutely stressed with restraint/water immersion. Another group of rats was treated intragastrically with chronic intermittent EtOH and acutely stressed following prolonged abstinence. Plasma corticosterone and endotoxin were measured, and immunohistochemical stains for the microglial marker CD11b and neuronal activation marker c-Fos were performed.ResultsAcute EtOH and acute stress interacted to increase plasma endotoxin and microglial CD11b, but not plasma corticosterone or neuronal c-Fos. Chronic EtOH caused a lasting sensitization of stress-induced plasma endotoxin, but not plasma corticosterone. Chronic EtOH also caused a lasting sensitization of stress-induced microglial CD11b, but not neuronal c-Fos.ConclusionsThese results find acute EtOH combined with acute stress enhanced plasma endotoxin, as well as microglial CD11b in many brain regions. Chronic EtOH followed by acute stress also increased plasma endotoxin and microglial CD11b, suggesting a lasting sensitization to acute stress. Overall, these data suggest alcohol and stress interact to increase plasma endotoxin, resulting in enhanced microglial activation that could contribute to disease progression.

Project description:BackgroundMicroglia, the brain's principal immune cell, are increasingly implicated in Alzheimer's disease (AD), but the molecular interfaces through which these cells contribute to amyloid beta (Aβ)-related neurodegeneration are unclear. We recently identified microglial contributions to the homeostatic and disease-associated modulation of perineuronal nets (PNNs), extracellular matrix structures that enwrap and stabilize neuronal synapses, but whether PNNs are altered in AD remains controversial.MethodsExtensive histological analysis was performed on male and female 5xFAD mice at 4, 8, 12, and 18 months of age to assess plaque burden, microgliosis, and PNNs. Findings were validated in postmortem AD tissue. The role of neuroinflammation in PNN loss was investigated via LPS treatment, and the ability to prevent or rescue disease-related reductions in PNNs was assessed by treating 5xFAD and 3xTg-AD model mice with colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 to deplete microglia.FindingsUtilizing the 5xFAD mouse model and human cortical tissue, we report that PNNs are extensively lost in AD in proportion to plaque burden. Activated microglia closely associate with and engulf damaged nets in the 5xFAD brain, and inclusions of PNN material are evident in mouse and human microglia, while aggrecan, a critical PNN component, deposits within human dense-core plaques. Disease-associated reductions in parvalbumin (PV)+ interneurons, frequently coated by PNNs, are preceded by PNN coverage and integrity impairments, and similar phenotypes are elicited in wild-type mice following microglial activation with LPS. Chronic pharmacological depletion of microglia prevents 5xFAD PNN loss, with similar results observed following depletion in aged 3xTg-AD mice, and this occurs despite plaque persistence.InterpretationWe conclude that phenotypically altered microglia facilitate plaque-dependent PNN loss in the AD brain.FundingThe NIH (NIA, NINDS) and the Alzheimer's Association.

Project description:BACKGROUND:Parkinson's disease (PD) is characterized by selective degeneration of dopaminergic (DA) neurons of the substantia nigra pars compacta (SN) while neighboring ventral tegmental area (VTA) DA neurons are relatively spared. Mechanisms underlying the selective protection of the VTA and susceptibility of the SN are still mostly unknown. Here, we demonstrate the importance of balance between astrocytes and microglia in the susceptibility of SN DA neurons to the PD mimetic toxin 1-methyl-4-phenylpyridinium (MPP+). METHODS:Previously established methods were used to isolate astrocytes and microglia from the cortex (CTX), SN, and VTA, as well as embryonic midbrain DA neurons from the SN and VTA. The transcriptional profile of isolated microglia was examined for 21 canonical pro- and anti-inflammatory cytokines by qRT-PCR with and without MPP+ exposure. Homo- and heterotypic co-cultures of neurons and astrocytes were established, and the effect of altering the ratio of astrocytes and microglia in vitro on the susceptibility of midbrain DA neurons to the PD mimetic toxin MPP+ was investigated. RESULTS:We found that regionally isolated microglia (SN, VTA, CTX) exhibit basal differences in their cytokine profiles and that activation of these microglia with MPP+ results in differential cytokine upregulation. The addition of microglia to cultures of SN neurons and astrocytes was not sufficient to cause neurodegeneration; however, when challenged with MPP+, all regionally isolated microglia resulted in exacerbation of MPP+ toxicity which was alleviated by inhibition of microglial activation. Furthermore, we demonstrated that isolated VTA, but not SN, astrocytes were able to mediate protection of both SN and VTA DA neurons even in the presence of exacerbatory microglia; however, this protection could be reversed by increasing the numbers of microglia present. CONCLUSION:These results suggest that the balance of astrocytes and microglia within the midbrain is a key factor underlying the selective vulnerability of SN DA neurons seen in PD pathogenesis and that VTA astrocytes mediate protection of DA neurons which can be countered by greater numbers of deleterious microglia.

Dataset Information

Laser-captured microglia in the Alzheimer's and Parkinson's brain reveal unique regional expression profiles and suggest a potential role for hepatitis B in the Alzheimer's brain.

Publications

Laser-captured microglia in the Alzheimer's and Parkinson's brain reveal unique regional expression profiles and suggest a potential role for hepatitis B in the Alzheimer's brain.

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