MicrorRNA Dysregulation Contributes To Vascular Cognitive Impairment By Targeting Microglial Activation And Neuroinflammation Response

Background:Post-ischemic microglial activation contributes to neuronal damage through the release of large amounts of proinflammatory cytokines. The involvement of microRNAs (miRNAs) in the pathogenesis of brain and central nervous system-related disorders has been previously studied.Aim:The aim of this study was to evaluate whether the production of proinflammatory cytokines is regulated by miRNAs.Methods:BV-2 and primary rat microglial cells were activated by exposure to oxygen-glucose deprivation (OGD). Cerebral ischemia was induced by the four-vessel occlusion (4-VO) and bilateral common carotid artery occlusion (BCCAO) in rats. Induction of proinflammatory and neurotoxic factors, such as tumor necrosis factor (TNF)-a, interleukin (IL)-1β and nitric oxide (NO), was assessed by ELISA, immunofluorence and Griess assay, respectively. Then the miRNA expression profiles of OGD-activated BV-2 cells were compared with the profiles of resting cells by miRNA microarray. BV-2 and primary rat microglia cells were transfected with miR-181c to evaluate its effects on TNF-a production following OGD. In addition, a luciferase reporter assay was conducted to confirm the direct targets of miR-181c.Results:OGD induced BV-2 microglial activation in vitro, as evidenced by overproduction of TNF-a, IL-1β and NO. Cerebral ischemia induced microglial activation and release of proinflammatory cytokines in the hippocampal CA1 region. We further found that OGD down-regulated miR-181c expression. We discovered that miR-181c could directly target the 3’-untranslated region (3’-UTR) of TNF-α mRNA, and suppress its mRNA and protein expressions. miR-181c could also inhibit NF-κB activation and the downstream production of proinflammatory mediators by suppressing TLR4 expression. Ectopic expression of miR-181c partially protected neurons from cell death caused by OGD-activated microglia. Lentiviral overexpression of miR-181c in CA1 subregion inhibited neuronal apoptosis and microglia activation following ischemia and cognitive impairment.Conclusions:Our data suggest an important role for microRNA in the regulation of microglial activation following ischemia/hypoxia and microglia-mediated neruonal injury, suggesting a novel miR-based intervention strategy for vascular cognitive impairment.