Cardioprotective Effect of Onion Extract against Ischemic Injury In vitro and In vivo

Abstract

"Cardiomyocyte apoptosis is one of the pathological features of ischemic heart desease (IHD) and is associated with thrombosis or other acute alterations of coronary atherosclerotic plaques. The mechanisms of these ischemia/reperfusion injuries have been suggested to involve reactive oxygen species (ROS). Allium family, including garlic and onion, are known to have a potential to reduce the detrimental effect of cardiovascular risk factors, and their beneficial roles are suggested to be associated with antioxidant mechanism. Compared to garlic, very few have been reported about the myocardial beneficial effect of onion. Based on these considerations, the present study was designed to test whether onion extract have cardioprotective effect against ischemic injury in H9c2 cell culture system and rat myocardial infarct model in vivo, and if so, whether the beneficial effect of onion is attributed to its antioxidant property. This study also investigated which component of onion extract is involved in the beneficial effect of onion extract. In H9c2 cells, onion extract markedly elicited cardioprotective effect against hypoxia-induced apoptotic death, demonstrated by its inhibitory effect on hypoxia-induced cytochrome c release, caspase-3 activation, and increase in TUNEL-positive cells. Onion extract also inhibited elevation of ROS generation induced by hypoxia. From inhibitory effects of onion extract and a well-known antioxidant trolox on hypoxia-induced decrease in mitochondrial membrane potential. it is suggested that antiapoptotic effect of onion extract is contributed to its antioxidant property, resulting in the inhibition of downstream mitochondrial death pathway. Cardioprotective effect of onion extract has been further demonstrated in rat myocardial infarct model in vivo, showing that administration of onion extract decreased infarct size and TUNEL-positive cells. Among components of onion extract, a major component quercetin showed a remarkable protective effect against ischemic injury in vitro and in vivo. The profile of the cardioprotective effect is same as in the case of onion extract. In conclusion, the results from this study suggest that onion extract has a significant cardioprotective effect contributed to antioxidant activity of its major component quercetin and that the signaling cascade of its antiapoptotic effect involves inhibition of mitochondrial death pathways, including loss of mitochondrial membrane potential, cytochrome c release and activation of caspase-3. "