H3K14 hyperacetylation-mediated c-Myc binding to the miR-30a-5p gene promoter under hypoxia postconditioning protects senescent cardiomyocytes from hypoxia/reoxygenation injury

Our previous study reported that microRNA (miR)-30a-5p upregulation under hypoxia postconditioning (HPostC) exert a protective effect on aged H9C2 cells against hypoxia/reoxygenation injury via DNA methyltransferase 3B-induced DNA hypomethylation at the miR-30a-5p gene promoter. This suggests that miR-30a-5p may be a potential preventative and therapeutic target for ischemic heart disease in aged myocardium. The present study aimed to investigate the underlying mechanisms of miR-30a-5p transcription in aged myocardium in ischemic heart disease. Cardiomyocytes were treated with 8 mg/ml D-galactose for 9 days, and then exposed to hypoxic conditions. Cell viability was determined using a cell viability assay. Expression levels of histone deacetylase 2 (HDAC2), LC3B-II/I, beclin-1 and p62 were detected via reverse transcription-quantitative PCR and western blotting. Chromatin immunoprecipitation-PCR and luciferase reporter assays were performed to evaluate the effect of c-Myc binding and activity on the miR-30a-5p promoter in senescent cardiomyocytes following HPostC. It was found that HPostC enhanced the acetylation levels of H3K14 at the miR-30a-5p gene promoter in senescent cardiomyocytes, which attributed to the decreased expression of HDAC2. In addition, c-Myc could positively regulate miR-30a-5p transcription to inhibit senescent cardiomyocyte autophagy. Mechanically, it was observed that increased H3K14 acetylation level exposed to romidepsin facilitated c-Myc binding to the miR-30a-5p gene promoter region, which led to the increased transcription of miR-30a-5p. Taken together, these results demonstrated that HDAC2-mediated H3K14 hyperacetylation promoted c-Myc binding to the miR-30a-5p gene promoter, which contributed to HPostC senescent cardioprotection.