Project description:Epigenetic mechanisms regulate distinct aspects of the inflammatory response in various immune cell types. Despite a central role for microglia in neuroinflammation and neurodegeneration little is known about their epigenetic regulation of the inflammatory response. We found that TET2 expression is increased in microglia upon stimulation with various inflammogens through a NF-kB-dependent pathway. RNA-seq analysis showed that TET2 modulates the transcriptional response of microglial cells to LPS.
Project description:Microglia are resident CNS immune cells that are active sensors in healthy brain and versatile effectors under pathological conditions. Cerebral ischemia induces a robust neuroinflammatory response that includes marked changes in the gene expression and phenotypic profile of a variety of endogenous CNS cell types (astrocytes, neurons, microglia) as well as an influx of leukocytic cells (neutrophils, macrophages, T-cells) from the periphery. Many molecules and conditions can trigger a transformation of ârestingâ (or surveying) microglia to an âactivatedâ (alerted/reactive) state. Here we review recent developments in the literature that relate to microglial activation in the experimental setting of in vitro and in vivo ischemia. We also present new data from our own laboratory demonstrating the direct effects of in vitro ischemic conditions on the microglial phenotype and genomic profile. Emphasis is placed on the role of specific molecular signaling systems such as hypoxia inducible factor-1 (HIF-1) and toll-like receptor-4 (TLR4) in regulating the microglial response in this setting. We then review histological and recent novel radiological data that confirms a key role for microglial activation in the setting of ischemic stroke in humans. We discuss recent progress in the pharmacological and molecular targeting of microglia in acute ischemic stroke. Finally, we explore how recent studies on ischemic preconditioning have increased interest in preemptively targeting microglial activation in order to reduce stroke severity. 12 arrays, 4 experimental groups, 3 replicates in each group, CN is control normoxia, CH is control hypoxia, TN is TLR4 knockout normoxia, TH is TLR4 knockout hypoxia.
Project description:The rapid accumulation of self-renewed polarized microglia in the penumbra is the critical neuroinflammatory process after the onset of ischemic stroke, leading to secondary demyelination and neuronal loss. HDAC3 has been reported to regulate cell proliferation of tumour cells and modulate neuroinflammation. However, the mechanism by which HDAC3 regulates microgliosis and microglial polarization remains ambiguous. Herein, we demonstrated that microglia-specific ablation of HDAC3 (HDAC3-miKO) ameliorated poststroke long-term functional and histological outcomes. Starting with unbiased RNA seq of microglia, we identified mitosis as the most significant process reversed by loss of HDAC3. Notably, HDAC3-miKO specifically inhibited the proliferation of M1-like microglia but not M2-like microglia, resulting in microglial transition to an M1-like state. Moreover, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) revealed that HDAC3 deletion induced drastic closing of accessible regions enriched with motifs for PU.1. Taken together, we uncovered for the first time that HDAC3/PU.1-mediated differential proliferation-related reprogramming in different microglia populations drives poststroke inflammatory state transition of microglia and thereby contributes to the pathophysiology of ischemic stroke.
Project description:The rapid accumulation of self-renewed polarized microglia in the penumbra is the critical neuroinflammatory process after the onset of ischemic stroke, leading to secondary demyelination and neuronal loss. HDAC3 has been reported to regulate cell proliferation of tumour cells and modulate neuroinflammation. However, the mechanism by which HDAC3 regulates microgliosis and microglial polarization remains ambiguous. Herein, we demonstrated that microglia-specific ablation of HDAC3 (HDAC3-miKO) ameliorated poststroke long-term functional and histological outcomes. Starting with unbiased RNA seq of microglia, we identified mitosis as the most significant process reversed by loss of HDAC3. Notably, HDAC3-miKO specifically inhibited the proliferation of M1-like microglia but not M2-like microglia, resulting in microglial transition to an M1-like state. Moreover, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) revealed that HDAC3 deletion induced drastic closing of accessible regions enriched with motifs for PU.1. Taken together, we uncovered for the first time that HDAC3/PU.1-mediated differential proliferation-related reprogramming in different microglia populations drives poststroke inflammatory state transition of microglia and thereby contributes to the pathophysiology of ischemic stroke.
Project description:Spinocerebellar ataxia type 6 (SCA6) is a dominantly inherited neurodegenerative disease caused by an expansion of a CAG repeat encoding a polyglutamine (PolyQ) tract in the Cav2.1 voltage-gated calcium channel. Pathologically, it is characterized by selective degeneration of cerebellar Purkinje cells (PCs), which are a common target for PolyQ-induced toxicity among several different SCAs. Mutant Cav2.1 confers toxicity mainly through a toxic gain-of-function mechanism, but subcellular site of expanded Cav2.1 toxicity is controversial and it remains elusive whether SCA6 shares pathogenic cascades with other SCAs. To gain insight into these problems, we studied the cerebellar gene expression patterns of young Sca6 MPI 118Q/118Q knockin (KI) mice, which express mutant Cav2.1 from endogenous locus and faithfully models human SCA6. Comparison of transcriptional changes with those of Sca1 154Q/2Q mice, a faithful KI mouse model of SCA1, revealed that transcriptional signatures in the MPI 118Q/118Q were distinct from those of Sca1 154Q/2Q. Examination of temporal profiles of candidate genes showed that upregulation of those associated with microglial activation was initiated before PC degeneration was apparent and augmented as the disease progressed. Histological analysis of the MPI 118Q/118Q cerebellum confirmed the presence of Iba-1 positive activated microglia. Moreover, predominance of M1-like pro-inflammatory microglia was observed and was concomitant with the increased expression of pro-inflammatory cytokines. These results suggest that the unique transcriptional response, which highlights upregulation of neuroinflammatory genes possibly associated with lysosomal involvement, may play a pivotal role in the pathogenesis. Modulation of innate immune system could pave the way for slowing the progression of SCA6. We used MPI 118Q/118Q and MPI 11Q/11Q mice for Sca6 KI model at six weeks old. Statistical analysis of differently expressed genes was performed using the Linear Models for Microarray Data (limma) package in R/Bioconductor.
Project description:Microglia-mediated neuroinflammatory response in the early brain injury after subarachnoid hemorrhage (SAH) has been reported to have an impact on progress and the mechanism is not completely understood. Here, we performed genome-wide transcriptome analysis of microglia purified from damaged hemisphere of adult mice at 3 days after SAH or sham operation. Robust transcriptional changes were observed between SAH-induced and healthy microglia, indicating rapid activation of microglia after suffering SAH. We identified 1576 differentially expressed genes (DEGs; 928 up-regulated and 648 down-regulated) in SAH-induced microglia compared with sham microglia, representing a strong alteration of the genome (6.85% of total ~23,000 genes). Functional enrichment of these DEGs indicated that cell division, inflammatory response, cytokine production and leukocyte chemotaxis were strongly activated in SAH-induced microglia. Moreover, we identified and proved the TLR2/IRF7 signaling axis was involved in regulation of this microglia-mediated inflammation in SAH mice, by performing flow cytometry, immunofluorescence. Together, these results provided a perspective of microglia-mediated neuroinflammatory response in the early stage of SAH and might give a new therapeutic target for SAH.
Project description:Understanding the respective role of microglia and infiltrating monocytes in neuroinflammatory conditions has recently seemed possible by the identification of a specific microglia signature. Here instead we provide evidence that peripheral macrophages may express some of the most commonly described microglia markers at some developmental stages or pathological conditions, in particular during chronic neuroinflammation. Further, our data support the hypothesis about phenotypic plasticity and convergence among distinct myeloid cells so that they may act as a functional unit rather than as different entities, boosting their mutual functions in different phases of disease. This holds relevant implications in the view of the growing use of myeloid cell therapies to treat brain disease in humans.
Project description:Microglia are tissue macrophages of the central nervous system (CNS) that control tissue homeostasis, and as such they are crucially important for organ integrity. Microglia dysregulation is thought to be causal for a group of neuropsychiatric, neurodegenerative and neuroinflammatory diseases, called ‘microgliopathies’. However, how the intracellular stimulation machinery in microglia is controlled is poorly understood. By using expression studies, we identified the ubiquitin-specific protease (Usp) 18 in white matter microglia that essentially contributes to microglial quiescence under homeostatic conditions. We further found that microglial Usp18 negatively regulated the activation of STAT1 and concomitant induction of interferon-induced genes thereby disabling the termination of IFN signalling. Unexpectedly, the Usp18-mediated feedback loop was independent from the catalytic domain of the protease but instead required the interacting region of Ifnar2. Additionally, the absence of Ifnar1 completely rescued microglial activation indicating a tonic IFN signal mediated by receptor interactions under non-diseased conditions. Finally, conditional depletion of Usp18 only in myeloid cells significantly enhanced the disease burden in a mouse model of CNS autoimmunity, increased axonal and myelin damage and determined the spatial distributions of CNS lesions that shared the same STAT1 signature as myeloid cells found in active multiple sclerosis (MS) lesions. These results identify Usp18 as novel negative regulator of microglia activation, demonstrate a protective role of the IFNAR pathway for microglia and establish Usp18 as potential therapeutic target for the treatment of MS. Primary microglia (WT, USP18ko and USP18_C61A mice) and BV-2 cells (treated with control siRNA or siRNA against USP18) were incubated with 500 U/ml IFN-b. At different timepoints (0h, 6h, and 24h) RNA samples were taken and analyzed via Microarray
Project description:Microglia are innate immune cells of the brain that perform phagocytic and inflammatory functions in disease conditions. Transcriptomic studies of acutely-isolated microglia have provided novel insights into their molecular and functional diversity in homeostatic and neurodegenerative disease states. State-of-the-art mass spectrometric methods can comprehensively characterize proteomic alterations in microglia in neurodegenerative disorders, potentially providing novel functionally-relevant molecular insights that are not provided by transcriptomics. However, proteomic profiling of adult primary microglia in neurodegenerative disease conditions has not been performed. We performed quantitative proteomic analyses of purified CD11b+ acutely-isolated microglia adult mice in normal, acute neuroinflammatory (LPS-treatment) and chronic neurodegenerative states (5xFAD model of Alzheimer’s disease [AD]) using tandem mass tag mass spectrometry. Differential expression analyses were performed to characterize specific microglial proteomic changes in 5xFAD mice and identify overlap with LPS-induced pro-inflammatory changes. Our results were also contrasted with existing proteomic data from wild-type mouse microglia and from existing microglial transcriptomic data from wild-type and 5xFAD mice. Neuropathological validation studies of select proteins were performed in human AD and 5xFAD brains. Of 4,133 proteins identified, 187 microglial proteins were differentially expressed in the 5xFAD mouse model of AD pathology, including proteins with previously known (Apoe, Clu and Htra1) as well as previously unreported relevance to AD biology (Cotl1 and Hexb). Proteins upregulated in 5xFAD microglia shared significant overlap with pro-inflammatory changes observed in LPS-treated mice. Several proteins increased in human AD brain were also upregulated by 5xFAD microglia (Aβ peptide, Apoe, Htra1, Cotl1 and Clu). Cotl1 was identified as a novel microglia-specific marker with increased expression and strong association with AD neuropathology. Apoe protein was also detected within plaque-associated microglia in which Apoe and Aβ were highly co-localized suggesting a role for Apoe in phagocytic clearance of Aβ. We report the first comprehensive comparative proteomic study of adult mouse microglia derived from acute neuroinflammatory and AD models, representing a valuable resource to the neuroscience research community. We highlight shared and unique microglial proteomic changes in acute neuroinflammatory, aging and AD mouse models in addition to identifying novel roles for microglial proteins in human neurodegeneration.
Project description:Tet2 regulates gene expression by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine. Profiling the genomic locations of 5-hydroxymethylcytosine after Tet2 manipulation can inform us of the targets of Tet2 regulation. We profiled hydroxymethylcytosine in Tet2 knockout neurons to determine the targets of Tet2 in neurons.