Abstract TP264: MicroRNA-15a/16-1 Antagomir Ameliorates Ischemic Brain Injury in Experimental Stroke

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MicroRNAs (miRs) are small endogenous RNA molecules that repress gene translation by hybridizing to 3’-UTRs of mRNAs. Accumulating evidence has shown that miRs play a critical regulatory role in the pathogenesis of ischemic stroke. MiR-15a and miR-16-1 are two highly conserved miRs, which act similarly by binding to their common mRNA targets, thus forming both a structural and functional cluster. Dysregulated plasma levels of miR-15a/16-1 have been reported in stroke patients. Inhibition of miR-15a has been shown to protect against myocardial infarction and selected by pharmaceutical companies as one of the most attractive miR-based therapeutics. Up to now, the essential role and therapeutic potential of the miR-15a/16-1 cluster in ischemic stroke are poorly understood. In this study, adult male miR-15a/16-1 knockout and wildtype mice were subjected to 45 min of middle cerebral artery occlusion (MCAO) and 72h of reperfusion. In a separate experiment, miR-15a/16-1 specific inhibitor (antagomir, 30 pmol/g) was injected into tail vein of stroke mice and the animals were allowed to survive for 72h. The neurological scores, brain infarct volume, and edema content were then evaluated and analyzed. To explore the underlying mechanism, inflammatory factors were measured by qPCR or ELISA and anti-apoptotic proteins were examined by western blotting. We found that genetic deletion of miR-15a/16-1 or intravenous delivery of miR-15a/16-1 antagomir significantly reduced cerebral infarct size, decreased brain edema and improved neurological outcomes in stroke mice. Mechanistically, treatment of miR-15a/16-1 antagomir significantly ameliorated the expression of several key inflammatory factors and increased the Bcl-2 and Bcl-w levels in the ischemic brain regions. These results demonstrated that pharmacological inhibition of miR-15a/16-1 reduces ischemic brain injury via both anti-apoptotic and anti-inflammatory mechanisms and the miR-15a/16-1 cluster is a novel therapeutic target for ischemic stroke.

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