Project description:Microglia are resident immune cells of the brain that play important roles in mediating inflammatory responses in several neurological diseases via direct and indirect mechanisms. One indirect mechanism may involve extracellular vesicle (EV) release, so that the molecular cargo transported by microglia-derived EVs can have functional effects by facilitating intercellular communication. The molecular composition of microglia-derived EVs, and how microglial activation states impacts EV composition and EV-mediated effects in neuroinflammation, remain poorly understood. We hypothesize that microglia-derived EVs have unique molecular profiles that are determined by microglial activation state. Using size-exclusion chromatography to purify EVs from BV2 microglia, combined with proteomic (label-free quantitative mass spectrometry or LFQ-MS) and transcriptomic (mRNA and non-coding RNA seq) methods, we obtained comprehensive molecular profiles of microglia-derived EVs. LFQ-MS identified several classic EV proteins (tetraspanins, ESCRT machinery, and heat shock proteins), in addition to over 200 proteins not previously reported in the literature. Unique mRNA and microRNA signatures of microglia-derived EVs were also identified. After treating BV2 microglia with lipopolysaccharide (LPS), interleukin-10, or transforming growth factor beta, to mimic pro-inflammatory, anti-inflammatory, or homeostatic states, respectively, LFQ-MS and RNA seq revealed novel state-specific proteomic and transcriptomic signatures of microglia-derived EVs. Particularly, LPS treatment had the most profound impact on proteomic and transcriptomic compositions of microglia-derived EVs. Furthermore, we found that EVs derived from LPS-activated microglia were able to induce pro-inflammatory transcriptomic changes in resting responder microglia, confirming the ability of microglia-derived EVs to relay functionally-relevant inflammatory signals. These comprehensive microglia-EV molecular datasets represent important resources for the neuroscience and glial communities, and provide novel insights into the role of microglia-derived EVs in neuroinflammation.

Project description:Murine BV2 microglia cells were transfected either with siRNA negative control or siRNA against caspase-3 for 48h. Later on some the of the BV2 transfected cells were co-cultured with C6 glioma cells during 6h. We used the SA Biosciences Mouse Wound Healing PCR Array (PAMM-121Z) to quantitate gene expression of relevant genes related to the wound healing process Glioma cells recruit and exploit microglia, resident immune cells of the brain, for their proliferation and invasion capability. The underlying molecular mechanism used by glioma cells to transform microglia into a tumor-supporting phenotype remains elusive. Here, we report that glioma-induced microglia conversion is coupled to a reduction of basal microglial caspase-3 activity, increased S-nitrosylation of mitochondria-associated caspase-3 through inhibition of thioredoxin-2 activity, and demonstrate that caspase-3 inhibition regulates microglial tumor-supporting function. Further, we identified nitric oxide synthase-2 (NOS2) activity originating from the glioma cells as a driving stimulus in the control of microglial caspase-3 activity. Repression of glioma NOS2 expression in vivo led to reduction in both microglia recruitment and tumor expansion, whereas depletion of the microglial caspase-3 gene promoted tumor growth. This study provides evidence that the inhibition of Trx2-mediated denitrosylation of SNO-procaspase-3 is part of the microglial pro-tumoral activation pathway initiated by glioma cancer cells. qPCR gene expression profiling. Three independent experiments of siControl BV2 monoculture, siCaspase3 BV2 monoculture, siControl BV2 cocultured 6h with C6 glioma cells and siCaspase3 BV2 cocultured 6h with C6 glioma cells. Equal amount total RNA from each culture was used for the gene expression analysis. Please note that the raw data for three independent experiments (prior to averaging the data) is provided in the 'Raw_Data_File_with_the_Ct_values_for_3_indep_experiments.txt'.

Project description:Alzheimer’s Disease (AD) is the most common cause of dementia in the elderly population without a cure or early diagnostics currently available. Despite the demonstrated ability of extracellular vesicles (EVs) to spread tau and Aβ pathology in AD models and their potential utility as a diagnostic and treatment-monitoring tool, our knowledge of human brain EV subpopulations, their molecular composition and roles in disease progression is very limited. Genome-wide association studies linked multiple AD genetic risk factors to microglia-specific pathways suggesting a potential role of microglia-derived EVs in AD progression. Here we are presenting a method for isolation of microglial CD11b-positive small EVs from cryopreserved human brain tissue and multi-omics analysis of the EVs from the parietal cortex of 4 late-stage AD (Braak V-VI) and 3 age-matched normal/low pathology (NL) cases. We identified a total of 1000 proteins by quantitative proteomics, analyzed 594 individual lipid species by targeted lipidomics, and 105 miRNAs using a NanoString miRNA expression panel. We found significant reduction in abundance of homeostatic microglia markers, P2RY12 and TMEM119, and increased levels of disease associated microglia markers, FTH1 and TREM2, in microglial EVs from AD brain compared to NL cases. Protein tau abundance was also significantly higher in AD brain-derived microglial EVs. These changes were accompanied by upregulation of synaptic and neuron-specific proteins in the AD group. Levels of free-cholesterol were elevated in microglial EVs from AD brain. Lipidomic analysis also revealed a pro-inflammatory lipid profile, endolysosomal dysfunction and significant AD-associated decrease in levels of docosahexaenoic acid (DHA)-containing polyunsaturated lipids of different classes, suggesting a potential defect in acyl-chain remodeling. Several immune pathways and senescence were among the top pathways controlled by 4 miRNAs significantly upregulated in the AD group. Our data suggest that loss of the homeostatic microglia signature in late AD stages may accompany endolysosomal impairment and release of undigested neuronal and myelin debris, including tau, through extracellular vesicles. These data validate a method of isolation of small cell-type specific EVs from human brain tissue, suggests new potential EV-associated markers and disease-related pathways, and provides a framework for future large-scale multi-omics study.

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Glioblastoma Hijacks Microglial Gene Expression to Support Tumor Growth

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