Abstract
Ischemia-reperfusion (I/R) injury (IRI) is a common clinical consequence of myocardial infarction. Exendin-4 is a glucagon-like peptide-1 (GLP-1) analog that has been demonstrated to alleviate myocardial IRI. Autophagy, a lysosomal pathway balancing cell survival and cell death, is engaged in myocardial IRI. However, whether exendin-4 exerts a protective effect on myocardial IRI by modulating autophagy remains elusive. Herein, we investigated the effect of exendin-4 on autophagic flux and explored the underlying molecular mechanisms. Our data revealed that the autophagic flux was blocked in the human ventricular cardiomyocyte cell lines (AC16) subjected to oxygen glucose deprivation/reoxygenation (OGD/R) in vitro. Exendin-4 pre-treatment markedly restored the blocked autophagic flux induced by OGD/R through promoting nuclear translocation of TFEB and transcription of genes involving autophagy initiation, the effect of which was reversed by TFEB knockdown. The restoration of autophagic flux contributed to multiple beneficial effects of exendin-4 in cardiomyocytes, including reduction of oxidative stress, preservation of mitochondrial network as well as inhibition of cytochrome c leakage from mitochondrial permeability transition pore (MPTP) and the resulting apoptosis. Moreover, the administration of exendin-4 reduced infarct size and preserved cardiac function through its anti-apoptosis and antioxidative effects in vivo. These results shed some light on understanding the novel mechanism of exendin-4 as a protective agent against myocardial IRI.