Hydrogen Sulfide Protects HUVECs against Hydrogen Peroxide Induced Mitochondrial Dysfunction and Oxidative Stress

BACKGROUND: Hydrogen sulfide (H(2)S) has been shown to have cytoprotective effects in models of hypertension, ischemia/reperfusion and Alzheimer's disease. However, little is known about its effects or mechanisms of action in atherosclerosis. Therefore, in the current study we evaluated the pharmacological effects of H(2)S on antioxidant defenses and mitochondria protection against hydrogen peroxide (H(2)O(2)) induced endothelial cells damage. METHODOLOGY AND PRINCIPAL FINDINGS: H(2)S, at non-cytotoxic levels, exerts a concentration dependent protective effect in human umbilical vein endothelial cells (HUVECs) exposed to H(2)O(2). Analysis of ATP synthesis, mitochondrial membrane potential (ΔΨm) and cytochrome c release from mitochondria indicated that mitochondrial function was preserved by pretreatment with H(2)S. In contrast, in H(2)O(2) exposed endothelial cells mitochondria appeared swollen or ruptured. In additional experiments, H(2)S was also found to preserve the activities and protein expressions levels of the antioxidants enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in H(2)O(2) exposed cells. ROS and lipid peroxidation, as assessed by measuring H(2)DCFDA, dihydroethidium (DHE), diphenyl-l-pyrenylphosphine (DPPP) and malonaldehyde (MDA) levels, were also inhibited by H(2)S treatment. Interestingly, in the current model, D, L-propargylglycine (PAG), a selective inhibitor of cystathionine γ-lyase (CSE), abolished the protective effects of H(2)S donors. INNOVATION: This study is the first to show that H(2)S can inhibit H(2)O(2) mediated mitochondrial dysfunction in human endothelial cells by preserving antioxidant defences. SIGNIFICANCE: H(2)S may protect against atherosclerosis by preventing H(2)O(2) induced injury to endothelial cells. These effects appear to be mediated via the preservation of mitochondrial function and by reducing the deleterious effects of oxidative stress.