Downregulation of miRNA-663b protects against hypoxia-induced injury in cardiomyocytes by targeting BCL2L1.

In the present study, the role of microRNA-663b (miR-663b) in cardiomyocyte injury was examined. Reverse transcription-quantitative PCR (RT-qPCR) was performed to detect miR-663b expression in hypoxia-induced H9c2 cells. The results revealed that miR-663b expression was significantly upregulated in hypoxia-induced H9c2 cells compared with control cells. TargetScan analysis and dual-luciferase reporter assays demonstrated that miR-663b directly targeted the B-cell lymphoma 2 like 1 (BCL2L1) gene. RT-qPCR and western blotting data indicated that BCL2L1 expression was significantly downregulated in hypoxia-induced H9c2 cells compared with control cells. Under hypoxic conditions, H9c2 cells were transfected with miR-663b inhibitor, inhibitor control, miR-663b inhibitor + control small interfering (si)RNA or miR-663b inhibitor + BCL2L1-siRNA for 48 h. ELISA against creatine kinase-muscle/brain (CK-MB) and cardiac troponin 1 (cTnI) demonstrated that the miR-663b inhibitor reduced CK-MD and cTnI release and increased mitochondrial viability when compared with hypoxia-treated cells. Additionally, the miR-663b inhibitor significantly increased H9c2 cell viability and decreased cell apoptosis under hypoxic conditions. The results of ELISA further revealed that the miR-663b inhibitor decreased the release of various inflammatory factors, including tumour necrosis factor α, interleukin (IL) 1β and IL-6 in H9c2 cells under hypoxic conditions. These changes were reversed following BCL2L1 knockdown. In conclusion, miR-663b inhibition protected cardiomyocytes against hypoxia-induced injury by targeting BCL2L1 and may potentially be a novel target for the treatment of patients with myocardial infarction.