Abstract
Acute myocardial infarction (AMI) results from long-term diminished blood supply diminishment (ischemia) to the heart, and the main reason for ischemia is hypoxia. BCL2 interaction protein 3 (BNIP3) can be upregulated by hypoxia and participates in the mediation of hypoxia-activated apoptosis in cardiac myocyte death. The purpose of this study was to interrogate the mechanism of BNIP3 in hypoxia-activated cardiac myocyte injury. Cell viability and apoptosis were evaluated by Cell counting kit 8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), TdT-mediated dUTP Nick-End Labeling (TUNEL), and caspase-3 activity assays. Molecular interactions were assessed by RNA immunoprecipitation (RIP) and pull-down assays. Gene levels were assessed via quantitative real-time PCR and western blot. BNIP3 expression was upregulated by hypoxia in H9c2 cells. We found that circ-BNIP3 (hsa_circ_0005972), whose annotated gene was BNIP3, was induced by hypoxia and positively regulated BNIP3 expression. Knockdown of BNIP3 or circ-BNIP3 reversed the effect of hypoxia in attenuating H9c2 cell viability and inducing apoptosis. circ-BNIP3 sponged miRNA-27a-3p (miR-27a-3p) to upregulate BNIP3 expression. Moreover, eukaryotic translation initiation factor 4A3 (EIF4A3) bound with the upstream region of the circ-BNIP3 mRNA transcript and induced circ-BNIP3 expression in H9c2 cells. EIF4A3-induced circ-BNIP3 aggravated hypoxia-caused injury of H9c2 cells through targeting miR-27a-3p/BNIP3 pathway, indicating circ-BNIP3 as a new target for relieving hypoxia-induced injury of cardiac myocytes.