MicroRNA-195 protection against focal cerebral ischemia by targeting CX3CR1

OBJECTIVE: It has been reported that microRNA-195 (miR-195) protects against chronic brain injury induced by chronic brain hypoperfusion. However, neither the expression profile of miR-195 nor its potential role during acute ischemic stroke has been investigated. In this study, the authors' aim was to verify the mechanism of miR-195 in acute ischemic stroke. METHODS: The plasma levels of miR-195 expression were assessed using real-time PCR in 96 patients with acute ischemic stroke, and the correlation with the National Institutes of Health Stroke Scale score was evaluated. In addition, cerebral infarct volume, neurological score, and levels of miR-195 and CX3CL1/CX3CR1 mRNA and protein expression were assessed in mice subjected to middle cerebral artery occlusion (MCAO) with or without intra-cerebroventricular infusion of lentiviral vector. The inflammatory cytokines tumor necrosis factor-α (TNFα), interleukin (IL)-1β, and IL-6 of mouse brains after MCAO and BV2 cells treated with oxygen-glucose deprivation were measured using enzyme-linked immunosorbent assay, and apoptotic proteins were examined by Western blotting. Direct targeting of CX3CL1/CX3CR1 by miR-195 was determined by immunoblotting and dual luciferase assay. RESULTS: In ischemic stroke patients, miR-195 was significantly downregulated and expression levels of miR-195 in these patients negatively correlated with the National Institutes of Health Stroke Scale score. In mice after MCAO, miR-195 overexpression decreased infarct volume, alleviated neurological deficits, and most importantly, suppressed an inflammatory response. Meanwhile, miR-195 suppressed the expression of the inflammatory cytokines TNFα, IL-1β, and IL-6 in vitro and in vivo. The authors further discovered that both CX3CL1 and CX3CR1 are direct targets of miR-195, but miR-195 exerts neuroprotective roles mainly through inhibiting CX3CR1-mediated neuroinflammation and subsequent neuronal cell apoptosis. CONCLUSIONS: Taken together, these findings suggest that miR-195 promotes neuronal cell survival against chronic cerebral ischemic damage by inhibiting CX3CR1-mediated neuroinflammation. This indicates that miR-195 may represent a novel target that regulates neuroinflammation and brain injury, thus offering a new treatment strategy for cerebral ischemic disorders.