miR-129-5p Ameliorates Ischemic Brain Injury by Binding to SIAH1 and Activating the mTOR Signaling Pathway

Aberrant expression of microRNAs (miRNAs) has been linked with ischemic brain injury (IBI), but the mechanistic actions behind the associated miRNAs remain to be determined. Of note, miR-129-5p was revealed to be downregulated in the serum of patients with IBI. In silico prediction identified a putative target gene, siah E3 ubiquitin protein ligase 1 (SIAH1), of miR-129-5p. Accordingly, this study plans to clarify the functional relevance of the interplay of miR-129-5p and SIAH1 in IBI. IBI was modeled by exposing human hippocampal neuronal cells to oxygen-glucose deprivation (OGD) in vitro and by occluding the middle cerebral artery (MCAO) in a mouse model in vivo. Apoptosis of hippocampal neuronal cells was assessed by annexin V-FITC/PI staining and TUNEL staining. The area of cerebral infarction was measured using TTC staining, along with neurological scoring on modeled mice. Loss of hippocampal neuronal cells in the peri-infarct area was monitored using Nissl staining. Downregulated miR-129-5p expression was found in OGD-induced hippocampal neuronal cells and MCAO-treated mice. Mechanistically, miR-129-5p was validated to target and inhibit SIAH1 through the application of dual-luciferase reporter assay. Additionally, enforced miR-129-5p inhibited the apoptosis of OGD-induced cells and decreased the cerebral infarct area, neurological scores and apoptosis of hippocampal neuronal cells by downregulating SIAH1 and activating the mTOR signaling pathway. Taken together, the results of this study reveal the important role and underlying mechanism of miR-129-5p in IBI, providing a promising biomarker for preventive and therapeutic strategies.