Abstract TP252: MicroRNA-376a-5p Improves Outcome for Acute Ischemic Stroke After Endovascular Mechanical Reperfusion in Rat Model

Abstract

Background: MicroRNAs are involved in regulating cerebral ischemia process, but its underlying mechanism is unclear. The removal of intraluminal filament in the transient middle cerebral artery occlusion (tMCAO) model resulted in instantaneous recanalization, similar to endovascular thrombectomy in stroke. We previously showed microRNA-376a down-regulation in the ischemic brain in rat tMCAO model with hemorrhagic transformation. This study investigated the role of miR-376a-5p in cerebral ischemia and reperfusion injury after mechanical reperfusion. Methods: The intraluminal filament tMCAO model was established in rats with 2 hour ischemia followed by reperfusion. The expression of miR-376a-5p in the ischemic brain and blood were quantified. Intravenous miR-376a-5p agomir was delivered before reperfusion or after reperfusion. Infarct volume, brain water content, neurological score, blood-brain barrier (BBB) damage, and levels of miR-376a-5p, NADPH oxidase (NOX) 4, Caspase-3 and aquaporin-4 were determined at 24-hour after ischemia. Results: MiR-376a-5p levels in the infarction core and peri-infarct cortex were decreased at 3 hours after reperfusion in tMCAO model. The decreased levels of miR-376a in ischemic brain and blood lasted for 24 hours after ischemia. Intravenous miR-376a-5p agomir before and after reperfusion increased the expression of miR-376a and suppressed the up-regulation of NOX4, Caspase-3 and AQP-4 in the infarction core and peri-infarct cortex compared with the tMCAO group (p<0.01). Dual-luciferase reporter system showed that NOX4, Caspase-3, and AQP-4 were the direct target genes of miR-376a-5p. MiR-376a overexpression inhibited the up-regulation of reactive oxygen species and neuronal apoptosis in the peri-infarct cortex. Intravenous miR-376a agomir reduced infarct volume, brain edema and reperfusion-induced BBB breakdown at 24-hour after ischemia, resulting in improved neurological outcome (p<0.01). Conclusions: MiR-376a-5p overexpression protects against cerebral ischemia and reperfusion injury via downregulating NOX4, Caspase-3 and AQP-4. Infusion of miR-376a-5p agomir represents a novel adjunctive therapeutic strategy to improve outcome after mechanical reperfusion for acute stroke.