Alpha lipoic acid protects heart against myocardial ischemia–reperfusion injury through a mechanism involving aldehyde dehydrogenase 2 activation

Abstract

Recent studies demonstrate that alpha lipoic acid can prevent nitroglycerin tolerance by restoring aldehyde dehydrogenase 2 (ALDH2) activity and ALDH2-mediated detoxification of aldehydes is thought as an endogenous mechanism against ischemia–reperfusion injury. This study was performed to explore whether the cardioprotective effect of alpha lipoic acid was related to activation of ALDH2 and the underlying mechanisms. In a Langendorff model of ischemia–reperfusion in rats, cardiac function, activities of creatine kinase (CK) and ALDH2, contents of 4-hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) were measured. In a cell model of hypoxia–reoxygenation, the apoptosis, ALDH activity, reactive oxygen species level, 4-HNE and MDA contents were examined. In the isolated hearts, ischemia–reperfusion treatment led to cardiac dysfunction accompanied by an increase in 4-HNE and MDA contents. Pretreatment with lipoic acid significantly up-regulated myocardial ALDH2 activity concomitantly with an improvement of cardiac dysfunction and a decrease in 4-HNE and MDA contents, these effects were blocked by the inhibitor of ALDH2. Similarly, in the cultured cardiomyocytes, hypoxia–reoxygenation treatment induced apoptosis accompanied by an increase in the production of reactive oxygen species, 4-HNE and MDA. Administration of lipoic acid significantly up-regulated cellular ALDH2 activity concomitantly with a reduction in apoptosis, production of reactive oxygen species, 4-HNE and MDA, these effects were reversed in the presence of ALDH2 or PKCε inhibitors. Our results suggest that the cardioprotective effects of lipoic acid on ischemia–reperfusion injury are through a mechanism involving ALDH2 activation. The regulatory effect of lipoic acid on ALDH2 activity is dependent on PKCε signaling pathway.