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

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.