Hypoxia induces autophagy in cardiomyocytes via a hypoxia-inducible factor 1-dependent mechanism

Hypoxia frequently accompanies such vascular disorders as atherosclerosis, thrombosis and ischemia/reperfusion injury. Myocardial ischemia/reperfusion, in particular, is a major contributor to cardiomyocyte impairment. Autophagy is a dynamic, self-catabolic process that has been implicated in a wide range of physiological processes and the pathogenesis of diverse diseases. The aim of the present study was to investigate the promotion of autophagy by hypoxia in a rat H9c2 heart cell line and determine the regulatory role of hypoxia-inducible factor 1 (HIF-1) in the hypoxia-induced autophagy in H9c2 cells, using quantitative green fluorescent protein-microtubule-associated protein 1 light chain 3 analysis and electron microscopy of autophagic vesicles. In addition, western blot and quantitative polymerase chain reaction analysis of autophagy-associated markers was conducted. In addition, the role of HIF-1-mediated autophagy in the hypoxia-induced impairment of H9c2 cells was examined, as a measure of cellular viability, using an MTT assay. The results demonstrated that autophagy was induced in H9c2 cells under hypoxia, and the autophagy induction triggered by hypoxia could be enhanced by HIF-1α overexpression and inhibited by HIF-1α knockdown. Furthermore, the HIF-1-mediated autophagy ameliorated the reduction in the H9c2 cell viability induced by hypoxia. These findings provide a novel insight into the hypoxic-ischemic injury to cardiomyocytes and give evidence for the occurrence of HIF-1-mediated autophagy in myocardial ischemia.