Dataset Information

MiR-30a Positively Regulates the Inflammatory Response of Microglia in Experimental Autoimmune Encephalomyelitis.

ABSTRACT: Multiple sclerosis (MS) is a classical inflammatory demyelinating disease of the central nervous system (CNS). Microglia are the main resident immune cells in the CNS and are closely associated with the pathogenesis of MS. In the present study, we found that miR-30a was highly expressed in jellyfish-like microglia in chronic active lesions of MS patients, as well as in the microglia of mice with experimental autoimmune encephalomyelitis (EAE) at the chronic phase. In vitro, the conditioned supernatant of mouse microglia overexpressing miR-30a promoted the apoptosis of oligodendrocyte precursor cells (OPCs), and inhibited OPC differentiation. In vivo, overexpressing miR-30a in transplanted microglia exacerbated the progression of EAE. Overexpression and knock-down experiments in primary cultured mouse microglia showed that miR-30a increased the expression of IL-1? and iNOS, which are pro-inflammatory, while inhibiting the expression of Ym-1 and CD206. Mechanistically, miR-30a inhibited the expression of Ppargc1b, which is the co-activator of peroxisome proliferator-activated receptor gamma, resulting in pro-inflammatory effects. Our work shows that miR-30a is an important regulator of the inflammatory response in microglia, and may be a promising therapeutic target for inflammatory diseases like MS in the CNS.

SUBMITTER: Fang X

PROVIDER: S-EPMC5725374 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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MiR-30a Positively Regulates the Inflammatory Response of Microglia in Experimental Autoimmune Encephalomyelitis.

Fang Xue X Sun Dingya D Wang Zhihong Z Yu Zhongwang Z Liu Weili W Pu Yingyan Y Wang Dan D Huang Aijun A Liu Mingdong M Xiang Zhenghua Z He Cheng C Cao Li L

Neuroscience bulletin 20170717 6

Multiple sclerosis (MS) is a classical inflammatory demyelinating disease of the central nervous system (CNS). Microglia are the main resident immune cells in the CNS and are closely associated with the pathogenesis of MS. In the present study, we found that miR-30a was highly expressed in jellyfish-like microglia in chronic active lesions of MS patients, as well as in the microglia of mice with experimental autoimmune encephalomyelitis (EAE) at the chronic phase. In vitro, the conditioned super ...[more]

PMID: 28717866

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Project description:BACKGROUND:Toll-like receptor 4 (TLR4) is well known for activating the innate immune system; however, it is also highly expressed in adaptive immune cells, such as CD4+ T-helper 17 (Th17) cells, which play a key role in multiple sclerosis (MS) pathology. However, the function and governing mechanism of TLR4 in Th17 remain unclear. METHODS:The changes of TLR4 in CD4+ T cells from MS patients and experimental autoimmune encephalomyelitis (EAE) mice were tested. TLR4-deficient (TLR4-/-) naïve T cells were induced in vitro and transferred into Rag1-/- mice to measure Th17 differentiation and EAE pathology. DNA sequence analyses combining with deletion fragments and mutation analyses, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA) were used to explore the mechanism of TLR4 signaling pathway in regulating Th17 differentiation. RESULTS:The levels of TLR4 were increased in CD4+ Th17 cells both from MS patients and EAE mice, as well as during Th17 differentiation in vitro. TLR4-/- CD4+ naïve T cells inhibited their differentiation into Th17, and transfer of TLR4-/- CD4+ naïve T cells into Rag1-/- mice was defective in promoting EAE, characterized by less demyelination and Th17 infiltration in the spinal cord. TLR4 signal enhanced Th17 differentiation by activating RelA, downregulating the expression of miR-30a, a negative regulator of Th17 differentiation. Inhibition of RelA activity increased miR-30a level, but decreased Th17 differentiation rate. Furthermore, RelA directly regulated the expression of miR-30a via specific binding to a conserved element of miR-30a gene. CONCLUSIONS:TLR4-/- CD4+ naïve T cells are inadequate in differentiating to Th17 cells both in vitro and in vivo. TLR4-RelA-miR-30a signal pathway regulates Th17 differentiation via direct binding of RelA to the regulatory element of miR-30a gene. Our results indicate modulating TLR4-RelA-miR-30a signal in Th17 may be a therapeutic target for Th17-mediated neurodegeneration in neuroinflammatory diseases.

Project description:Myelin-associated inhibitory factors within the central nervous system (CNS) are considered to be one of the main obstacles for axonal regeneration following disease or injury. The nogo receptor 1 (NgR1) has been well documented to play a key role in limiting axonal regrowth in the injured and diseased mammalian CNS. However, the role of nogo receptor in immune cell activation during CNS inflammation is yet to be mechanistically elucidated. Microglia/macrophages are immune cells that are regarded as pathogenic contributors to inflammatory demyelinating lesions in multiple sclerosis (MS). In this study, the animal model of MS, experimental autoimmune encephalomyelitis (EAE) was induced in ngr1+/+ and ngr1-/- female mice following injection with the myelin oligodendrocyte glycoprotein (MOG35-55) peptide. A fate-map analysis of microglia/macrophages was performed throughout spinal cord sections of EAE-induced mice at clinical scores of 0, 1, 2 and 3, respectively (increasing locomotor disability) from both genotypes, using the CD11b and Iba1 cell markers. Western immunoblotting using lysates from isolated spinal cord microglia/macrophages, along with immunohistochemistry and flow cytometric analysis, was performed to demonstrate the expression of nogo receptor and its two homologs during EAE progression. Myelin protein engulfment during EAE progression in ngr1+/+ and ngr1-/- mice was demonstrated by western immunblotting of lysates from isolated spinal cord microglia/macrophages, detecting levels of Nogo-A and MOG. The numbers of M1 and M2 microglia/macrophage phenotypes present in the spinal cords of EAE-induced ngr1+/+ and ngr1-/- mice, were assessed by flow cytometric analysis using CD38 and Erg-2 markers. A significant difference in microglia/macrophage numbers between ngr1+/+ and ngr1-/- mice was identified during the progression of the clinical symptoms of EAE, in the white versus gray matter regions of the spinal cord. This difference was unrelated to the expression of NgR on these macrophage/microglial cells. We have identified that as EAE progresses, the phagocytic activity of microglia/macrophages with myelin debris, in ngr1-/- mice, was enhanced. Moreover, we show a modulation from a predominant M1-pathogenic to the M2-neurotrophic cell phenotype in the ngr1-/- mice during EAE progression. These findings suggest that CNS-specific macrophages and microglia of ngr1-/- mice may exhibit an enhanced capacity to clear inhibitory molecules that are sequestered in inflammatory lesions.

Project description:Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b+ myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from spinal cord of IFN-γ-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen promoted a significantly higher induction of CD4+ regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-β secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1high MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1highPD-L1lowCD11b+Ly6G- cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1highPD-L1low MG). Amelioration of clinical symptoms and induction of CX3CR1highPD-L1low MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-γ promoted the induction of homeostatic CX3CR1highPD-L1low MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE.

Dataset Information

MiR-30a Positively Regulates the Inflammatory Response of Microglia in Experimental Autoimmune Encephalomyelitis.

Publications

MiR-30a Positively Regulates the Inflammatory Response of Microglia in Experimental Autoimmune Encephalomyelitis.

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