Protective effect of microRNA‑340‑5p against oxygen‑glucose deprivation/reperfusion in PC12 cells through targeting neuronal differentiation 4.

The expression levels of microRNA (miR)‑340‑5p are reportedly decreased in the peripheral blood during acute ischemic stroke; however, the direct effect and mechanism of action of miR‑340‑5p in ischemic stroke remains largely unknown. The present study aimed to investigate the effects of miR‑340‑5p, and its mechanism of action, on PC12 cells following oxygen‑glucose deprivation/reperfusion (OGD/R) induction. OGD/R‑induced PC12 cells served as the cellular model and subsequently, mRNA expression levels of miR‑340‑5p and neuronal differentiation 4 (Neurod4) were analyzed using reverse transcription‑quantitative PCR. Tumor necrosis factor‑α, interleukin (IL)‑1β and IL‑6 expression levels were detected using ELISA kits, and flow cytometry was used to determine the rate of cellular apoptosis. In addition, a nitric oxide (NO) synthase activity assay kit was used to detect NO levels and a NADPH assay kit was used to measure NADPH levels. Western blotting was also performed to analyze protein expression levels of bax, bcl‑2, cleaved caspase 3 and phosphorylated endothelial NOS (eNOS), and the target gene of miR‑340‑5p was predicted using TargetScan software and verified using a dual‑luciferase reporter assay. The expression levels of miR‑340‑5p were decreased in PC12 cells following OGD/R induction and Neurod4 was identified as a target gene of miR‑340‑5p. In addition, miR‑340‑5p overexpression reduced inflammation, apoptotic rate, NO production and NADPH levels, in addition to increasing eNOS expression in PC12 cells following OGD/R induction. Notably, the overexpression of Neurod4 reversed the aforementioned effects of miR‑340‑5p on PC12 cells following OGD/R induction. In conclusion, the findings of the present study suggested that miR‑340‑5p may protect PC12 cells against OGD/R through targeting Neurod4, which could provide important implications for the treatment of ischemia‑reperfusion injury based on miR‑340‑5p expression levels in vivo.