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The microRNA miR-181c controls microglia-mediated neuronal apoptosis by suppressing tumor necrosis factor.

ABSTRACT: Post-ischemic microglial activation may contribute to neuronal damage through the release of large amounts of pro-inflammatory cytokines and neurotoxic factors. The involvement of microRNAs (miRNAs) in the pathogenesis of disorders related to the brain and central nervous system has been previously studied, but it remains unknown whether the production of pro-inflammatory cytokines is regulated by miRNAs.BV-2 and primary rat microglial cells were activated by exposure to oxygen-glucose deprivation (OGD). Global cerebral ischemia was induced using the four-vessel occlusion (4-VO) model in rats. Induction of pro-inflammatory and neurotoxic factors, such as tumor necrosis factor (TNF)-?, interleukin (IL)-1?, and nitric oxide (NO), were assessed by ELISA, immunofluorescence, and the Griess assay, respectively. The miRNA expression profiles of OGD-activated BV-2 cells were subsequently compared with the profiles of resting cells in a miRNA microarray. BV-2 and primary rat microglial cells were transfected with miR-181c to evaluate its effects on TNF-? production after OGD. In addition, a luciferase reporter assay was conducted to confirm whether TNF-? is a direct target of miR-181c.OGD induced BV-2 microglial activation in vitro, as indicated by the overproduction of TNF-?, IL-1?, and NO. Global cerebral ischemia/reperfusion injury induced microglial activation and the release of pro-inflammatory cytokines in the hippocampus. OGD also downregulated miR-181c expression and upregulated TNF-? expression. Overproduction of TNF-? after OGD-induced microglial activation provoked neuronal apoptosis, whereas the ectopic expression of miR-181c partially protected neurons from cell death caused by OGD-activated microglia. RNAinterference-mediated knockdown of TNF-? phenocopied the effect of miR-181c-mediated neuronal protection, whereas overexpression of TNF-? blocked the miR-181c-dependent suppression of apoptosis. Further studies showed that miR-181c could directly target the 3'-untranslated region of TNF-? mRNA, suppressing its mRNA and protein expression.Our data suggest a potential role for miR-181c in the regulation of TNF-? expression after ischemia/hypoxia and microglia-mediated neuronal injury.

SUBMITTER: Zhang L

PROVIDER: S-EPMC3488569 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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The microRNA miR-181c controls microglia-mediated neuronal apoptosis by suppressing tumor necrosis factor.

Zhang Li L Dong Lian-Yan LY Li Ya-Jian YJ Hong Zhen Z Wei Wen-Shi WS

Journal of neuroinflammation 20120906

<h4>Background</h4>Post-ischemic microglial activation may contribute to neuronal damage through the release of large amounts of pro-inflammatory cytokines and neurotoxic factors. The involvement of microRNAs (miRNAs) in the pathogenesis of disorders related to the brain and central nervous system has been previously studied, but it remains unknown whether the production of pro-inflammatory cytokines is regulated by miRNAs.<h4>Methods</h4>BV-2 and primary rat microglial cells were activated by e ...[more]

PMID: 22950459

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Project description:BACKGROUND:Programmed cell death, including apoptosis, mitochondria-mediated necrosis, and necroptosis, is critically involved in ischemic cardiac injury, pathological cardiac remodeling, and heart failure progression. Whereas apoptosis and mitochondria-mediated necrosis signaling is well established, the regulatory mechanisms of necroptosis and its significance in the pathogenesis of heart failure remain elusive. METHODS:We examined the role of tumor necrosis factor receptor-associated factor 2 (Traf2) in regulating myocardial necroptosis and remodeling using genetic mouse models. We also performed molecular and cellular biology studies to elucidate the mechanisms by which Traf2 regulates necroptosis signaling. RESULTS:We identified a critical role for Traf2 in myocardial survival and homeostasis by suppressing necroptosis. Cardiac-specific deletion of Traf2 in mice triggered necroptotic cardiac cell death, pathological remodeling, and heart failure. Plasma tumor necrosis factor ? level was significantly elevated in Traf2-deficient mice, and genetic ablation of TNFR1 largely abrogated pathological cardiac remodeling and dysfunction associated with Traf2 deletion. Mechanistically, Traf2 critically regulates receptor-interacting proteins 1 and 3 and mixed lineage kinase domain-like protein necroptotic signaling with the adaptor protein tumor necrosis factor receptor-associated protein with death domain as an upstream regulator and transforming growth factor ?-activated kinase 1 as a downstream effector. It is important to note that genetic deletion of RIP3 largely rescued the cardiac phenotype triggered by Traf2 deletion, validating a critical role of necroptosis in regulating pathological remodeling and heart failure propensity. CONCLUSIONS:These results identify an important Traf2-mediated, NF?B-independent, prosurvival pathway in the heart by suppressing necroptotic signaling, which may serve as a new therapeutic target for pathological remodeling and heart failure.

Project description:BackgroundControlling thrombin-driven microglial activation may serve as a therapeutic target for intracerebral hemorrhage (ICH). Here, we investigated microRNA (miRNA)-based regulation of thrombin-driven microglial activation using an in vitro thrombin toxicity model applied to primary human microglia.MethodsA miRNA array identified 22 differential miRNA candidates. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) identified miR-181c as the most significantly downregulated miRNA. TargetScan analysis identified mixed lineage leukemia-1 (MLL1) as a putative gene target for miR-181c. qRT-PCR was applied to assess tumor necrosis factor-alpha (TNF-α), miR-181c, and MLL1 levels following thrombin or proteinase-activated receptor-4-specific activating peptide (PAR4AP) exposure. Anti-TNF-α antibodies and tumor necrosis factor receptor (TNFR) silencing were employed to test TNF-α/TNFR dependence. A dual-luciferase reporter system and miR-181c mimic transfection assessed whether mir-181c directly binds to and negatively regulates MLL1. Nuclear factor kappa-B (NF-κB)-dependent luciferase reporter assays and NF-κB target gene expression were assessed in wild-type (MLL1+) and MLL1-silenced cells.ResultsThrombin or PAR4AP-induced miR-181c downregulation (p < 0.05) and MLL1 upregulation (p < 0.05) that were dependent upon TNF-α/TNFR. miR-181c decreased wild-type MLL1 3'-UTR luciferase reporter activity (p < 0.05), and a miR-181c mimic suppressed MLL1 expression (p < 0.05). Thrombin treatment increased, while miR-181c reduced, NF-κB activity and NF-κB target gene expression in both wild-type (MLL1+) and MLL1-silenced cells (p < 0.05).ConclusionsThrombin-induced, TNF-α/TNFR-dependent miR-181c downregulation promotes MLL1 expression, increases NF-κB activity, and upregulates NF-κB target gene expression. As miR-181c opposes thrombin's stimulation of pro-inflammatory NF-κB activity, miR-181c mimic therapy may show promise in controlling thrombin-driven microglial activation following ICH.

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The microRNA miR-181c controls microglia-mediated neuronal apoptosis by suppressing tumor necrosis factor.

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The microRNA miR-181c controls microglia-mediated neuronal apoptosis by suppressing tumor necrosis factor.

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