The novel mitochondria-targeted hydrogen sulfide (H(2)S) donors AP123 and AP39 protect against hyperglycemic injury in microvascular endothelial cells in vitro

The development of diabetic vascular complications is initiated, at least in part, by mitochondrial reactive oxygen species (ROS) production in endothelial cells. Hyperglycemia induces superoxide production in the mitochondria and initiates changes in the mitochondrial membrane potential that leads to mitochondrial dysfunction. Hydrogen sulfide (H(2)S) supplementation has been shown to reduce the mitochondrial oxidant production and shows efficacy against diabetic vascular damage in vivo. However, the half-life of H(2)S is very short and it is not specific for the mitochondria. We have therefore evaluated two novel mitochondria-targeted anethole dithiolethione and hydroxythiobenzamide H(2)S donors (AP39 and AP123 respectively) at preventing hyperglycemia-induced oxidative stress and metabolic changes in microvascular endothelial cells in vitro. Hyperglycemia (HG) induced significant increase in the activity of the citric acid cycle and led to elevated mitochondrial membrane potential. Mitochondrial oxidant production was increased and the mitochondrial electron transport decreased in hyperglycemic cells. AP39 and AP123 (30–300 nM) decreased HG-induced hyperpolarisation of the mitochondrial membrane and inhibited the mitochondrial oxidant production. Both H(2)S donors (30–300 nM) increased the electron transport at respiratory complex III and improved the cellular metabolism. Targeting H(2)S to mitochondria retained the cytoprotective effect of H(2)S against glucose-induced damage in endothelial cells suggesting that the molecular target of H(2)S action is within the mitochondria. Mitochondrial targeting of H(2)S also induced >1000-fold increase in the potency of H(2)S against hyperglycemia-induced injury. The high potency and long-lasting effect elicited by these H(2)S donors strongly suggests that these compounds could be useful against diabetic vascular complications.