miR­124 inhibits cardiomyocyte apoptosis in myocardial ischaemia­reperfusion injury by activating mitochondrial calcium uniporter regulator 1.

Mitochondria­mediated apoptosis is the primary cause of cardiomyocyte death. Therefore, mitochondria are a key target for treating myocardial injury. Mitochondrial calcium uniporter regulator 1 (MCUR1)­mediated mitochondrial calcium homeostasis markedly promotes cell proliferation and resistance to apoptosis. However, whether MCUR1 is involved in regulation of cardiomyocyte apoptosis during myocardial ischaemia­reperfusion remains unknown. microRNA­124 (miR­124) is upregulated in cardiovascular disease, suggesting a key role for miR­124 in the cardiovascular system. Whether miR­124 affects cardiomyocyte apoptosis and myocardial infarction is not well understood. Western blot showed that miR­124 and MCUR1 were upregulated in cardiomyocyte apoptosis induced by hydrogen peroxide (H2O2). Flow cytometry assay of cell apoptosis showed that miR­124 inhibited cardiomyocyte apoptosis by activating MCUR1 following H2O2 treatment. The dual­luciferase reporter assay confirmed binding of miR­124 to MCUR1 3'­UTR and subsequent activation of MCUR1. FISH assay revealed the entry of miR­124 into the cell nucleus. Therefore, MCUR1 was identified as a novel target of miR­124, and it was shown that the miR­124­MCUR1 axis modulated cardiomyocyte apoptosis induced by H2O2 in vitro. The results indicated induced expression of miR­124 during acute myocardial infarction and its transport to the nucleus. In the nucleus, miR­124 transcriptionally activated MCUR1 by binding to its enhancers. These findings reveal a role of miR­124 as a biomarker for myocardial injury and infarction.