miR-9-5p attenuates ischemic stroke through targeting ERMP1-mediated endoplasmic reticulum stress

Ischemic stroke (IS) is a cerebrovascular disease with serious neurological function impairment, which may activate endoplasmic reticulum (ER) stress. However, the underlying regulatory mechanism of ER stress under IS remains unclear. miR-9-5p is enriched in the brain tissues and plays a role in the pathological process of IS. Therefore, the purpose of this study is to explore the effect of miR-9 on ER stress and underlying mechanism in IS. Here, a middle cerebral artery occlusion (MCAO) rat model was utilized to examine the alteration of brain pathology, and the expressions of miR-9 and ER stress-related proteins. Then SH-SY5Y cells with oxygen-glucose deprivation (OGD) were performed to further evaluate the functional role of miR-9 and preliminary mechanism. The results showed that miR-9 levels were decreased in the ischemic region of rats after MCAO. MCAO significantly increased the brain infract volume, reduced Nissl bodies and cell apoptosis, and increased ER stress-related proteins (ERMP1, GRP78, p-PERK, p-eIF2α and CHOP). Furthermore, overexpression of miR-9 by miR-9 mimics increased cell viability, inhibited LDH activity and cell apoptosis, and inactivated ER stress in OGD-neurons. Luciferase activity results showed that miR-9 negatively regulated ERMP1 expression by directly targeting ERMP1 3' UTR. Subsequently, we found that ERMP1 overexpression reversed the inhibition of miR-9 on GRP78-PERK-CHOP pathway in OGD neurons. In summary, our results suggest that the attenuation of miR-9 on ischemic injury may be involved in targeting ERMP1-mediated ER stress, which provides an available target for IS treatment.