Myocardial infarction is the leading cause of death worldwide, and cardiomyocyte apoptosis during myocardial infarction and reperfusion is a significant factor of poor prognosis. As important regulatory molecules, biofunctions of circRNAs in the pathogenesis of myocardial infarction remain elusive. To confirm the expression level and biological function of circNFIX in cardiomyocytes upon oxidative stress. Divergent polymerase chain reaction and Sanger sequencing were performed to verify the circular structure. The stability of circNFIX was confirmed by RNase R treatment and actinomycin D assay. In order to simulate oxidative stress during myocardial infarction, H9c2 cells were subjected to hydrogen peroxide and hypoxia stimulation. In vivo, mouse models of myocardial ischemia were established. The biological function of circNFIX in cardiomyocytes was investigated through loss- and gain-of-function assays, and cardiomyocyte apoptosis level was detected by the terminal deoxyribonucleotidyl transferase-mediated TdT-mediated dUTP nick end labeling assay and Western blot. CircNFIX is abundant, conserved, and stable in H9c2 cells. The expression of circNFIX was significantly downregulated in cardiomyocytes subjected to oxidative stress. Enforced CircNFIX promotes H9c2 cells apoptosis induced by hydrogen peroxide, in sharp contrast to circNFIX knockdown. In this study, we found that circNFIX served as a pro-apoptosis factor in cardiomyocyte apoptosis. CircNFIX possesses potential to be the biomarker and therapeutic target in myocardial infarction.
Keywords: Cardiomyocyte apoptosis; Myocardial infarction; Oxidative stress; circNFIX.