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 (H2 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 H2 S is very short and it is not specific for the mitochondria. We have therefore evaluated two novel mitochondria-targeted anethole dithiolethione and hydroxythiobenzamide H2 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 (30-300nM) decreased HG-induced hyperpolarisation of the mitochondrial membrane and inhibited the mitochondrial oxidant production. Both H2 S donors (30-300nM) increased the electron transport at respiratory complex III and improved the cellular metabolism. Targeting H2 S to mitochondria retained the cytoprotective effect of H2 S against glucose-induced damage in endothelial cells suggesting that the molecular target of H2 S action is within the mitochondria. Mitochondrial targeting of H2 S also induced >1000-fold increase in the potency of H2 S against hyperglycemia-induced injury. The high potency and long-lasting effect elicited by these H2 S donors strongly suggests that these compounds could be useful against diabetic vascular complications.