Overexpressed microRNA-539-5p inhibits inflammatory response of neurons to impede the progression of cerebral ischemic injury by histone deacetylase 1.

Several microRNAs (miRNAs or miRs) regulate cerebral ischemic injury outcomes; however, little is known about the role of miR-539-5p during cerebral ischemic injury or the postischemic state. Cerebral ischemic injury was modeled in vitro by exposing human cortical neurons to oxygen-glucose deprivation (OGD) and in vivo by occluding the middle cerebral artery (MCAO) in a rat model. The effects of miR-539-5p, histone deacetylase 1 (HDAC1), and early growth response 2 (EGR2) on cerebral ischemia were investigated using gain- and loss-of-function experiments. We identified changes in miR-539-5p, HDAC1, EGR2, and phosphorylated c-Jun NH2-terminal kinase (JNK). The interaction among miR-539-5p, HDAC1, and EGR2 was determined by dual luciferase reporter gene assay, chromatin immunoprecipitation, and coimmunoprecipitation. We also investigated the effects on cell viability and apoptosis and changes in inflammatory cytokine expression and spatial memory on MCAO rats. miR-539-5p and EGR2 were poorly expressed, while HDAC1 was highly expressed in OGD-treated HCN-2 cells. miR-539-5p targeted HDAC1, while HDAC1 prevented acetylation of EGR2 resulting in its downregulation and subsequent activation of the JNK pathway. Overexpression of miR-539-5p or EGR2 or silencing HDAC1 improved viability and reduced apoptosis of OGD-treated HCN-2 cells in vitro. Furthermore, overexpression of miR-539-5p improved spatial memory, while decreasing cell apoptosis and inflammation in MCAO rats. Collectively, these data suggest that miR-539-5p targets HDAC1 to upregulate EGR2, thus blocking the JNK signaling pathway, by which cerebral ischemic injury is alleviated.