Inhibition of miR-181a protects female mice from transient focal cerebral ischemia by targeting astrocyte estrogen receptor-α

Whether the effect of miR-181a is sexually dimorphic in stroke is unknown. Prior work showed protection of male mice with miR-181a inhibition. Estrogen receptor-alpha (ER alpha) is an identified target of miR181 in endometriurn. Therefore we investigated the separate and joint effects of miR-181a inhibition and 17 beta-estradiol (E2) replacement after ovariectomy. Adult female mice were ovariectomized and implanted with an E2- or vehicle containing capsule for 14d prior to 1 h middle cerebral artery occlusion (MCAO). Each group received either miR-181a antagomir or mismatch control by intracerebroventricular injection 24 h before MCAO. After MCAO neurologic deficit and infarct volume were assessed. Primary male and female astrocyte cultures were subjected to glucose deprivation with miR-181a inhibitor or transfection control, and E2 or vehicle control, with/without ESR alpha knockdown with small interfering RNA. Cell death was assessed by propidium iodide staining, and lactate dehydrogenase assay. A miR-181a/ER alpha target site blocker (TSB), with/without miR-181a mimic, was used to confirm targeting of ER alpha by miR-181a in astrocytes. Individually, miR-181a inhibition or E2 decreased infarct volume and improved neurologic score in female mice, and protected male and female astrocyte cultures. Combined miR-181a inhibition plus E2 afforded greater protection of female mice and female astrocyte cultures, but not in male astrocyte cultures. MiR-181a inhibition only increased ER alpha levels in vivo and in female cultures, while ERa knockdown with siRNA increased cell death in both sexes. Treatment with ER alpha TSB was strongly protective in both sexes. In conclusion, the results of the present study suggest miR-181a inhibition enhances E2-mediated stroke protection in females in part by augmenting ER alpha production, a mechanism detected in female mice and female astrocytes. Sex differences were observed with combined miR-181a inhibition/E2 treatment, and miR181a targeting of ER alpha. (C) 2017 Elsevier Inc. All rights reserved.