A Novel Molecular Mechanism of IKKε-Mediated Akt/mTOR Inhibition in the Cardiomyocyte Autophagy after Myocardial Infarction

Abstract

Autophagy of cardiomyocytes after myocardial infarction (MI) is an important factor affecting the prognosis of MI. Excessive autophagy can lead to massive death of cardiomyocytes, which will seriously affect cardiac function. IKKε plays a crucial role in the occurrence of autophagy, but the functional role in MI remains largely unknown. To evaluate the impact of IKKε on the autophagy of cardiomyocytes after MI, MI was induced by surgical left anterior descending coronary artery ligation in IKKε knockout (KO) mice and wild-type (WT) mice. Starvation of H9c2 cells with IKKε siRNA and rescued with IKKε overexpressed afterwards to test the mechanism of IKKε in autophagy in vitro. Our results demonstrated that the expression of IKKε was upregulated in mice myocardial tissues which were consistent with cardiomyocyte autophagy after MI. Significantly, the IKKε KO mice showed increased infarct size, decreased viable cardiomyocytes, and exacerbated cardiac dysfunction when compared with the wild-type mice. Western blot and electron micrography analysis also revealed that loss of IKKε induces excessive cardiomyocyte autophagy and reduced the expression of p-Akt and p-mTOR. Similar results were observed in IKKε siRNA H9c2 cells in vitro which were under starvation injury. Notably, the levels of p-Akt and p-mTOR can restore in IKKε rescued cells. In conclusion, our results indicated that IKKε protects cardiomyocyte survival by reduced autophagy following MI via regulation of the Akt/mTOR signaling pathway. Thus, our study suggests that IKKε might represent a potential therapeutic target for the treatment of MI.