Mitochondrial respiratory chain as a new target for anti-ischemic molecules

Vascular diseases like thrombosis, myocardial infarction, cerebral ischemia or chronic venous insufficiency affect a high proportion of the population. They are all associated with more or less pronounced ischemic conditions. We have previously shown that some venotropic drugs display an anti-ischemic activity, i.e. they prevent the hypoxia-induced decrease in ATP content in cultured cells. The effect is due to the fact that these molecules maintain mitochondrial respiratory activity during hypoxia. Among them is bilobalide. Starting from the 3D structure of bilobalide, we designed new molecules presenting the same chemical features. They were synthesized and tested for their biological activity. As the parent compound, two of them, malonic acid dicyclopent-2-enyl ester (MRC2P119) and 2-oxo-3-oxa-bicyclo[3.1.0]hexane-1-carboxylic acid allyl ester (MRC2P57), were able to markedly increase the respiratory control ratio of isolated mitochondria. They are able to prevent the inhibition of complex I by amytal and of complex III by myxothiazol, but not the uncoupling of the respiration by carbonylcyanide m-chlorophenyl hydrazone (m-CCP). Moreover, MRC2P119 and MRCP2P57 inhibit, in a dose-dependent way, the hypoxia-induced decrease in ATP content in endothelial cells as well as the subsequent activation of these cells as evidenced by an inhibition of the increase in neutrophil adherence to the endothelial cells induced by hypoxia. Finally, MRC2P119 prevent the hypoxia- and the hypoxia-reoxygenation-induced decrease in viability of SH-SY5Y neuroblastoma cells. In conclusion, we identified two new molecules, which display anti-ischemic properties when tested in vitro on endothelial and neuronal cell types. This anti-ischemic activity is probably due to a protection of complexes I and III of the mitochondrial respiratory chain.