SIRT3 mediates the antioxidant effect of hydrogen sulfide in endothelial cells

Oxidative stress is a key contributor to endothelial dysfunction and associated cardiovascular pathogenesis. Hydrogen sulfide (H₂S) is an antioxidant gasotransmitter that protects endothelial cells against oxidative stress. Sirtuin3 (SIRT3), which belongs to the silent information regulator 2 (SIR2) family, is an important deacetylase under oxidative stress. H₂S is able to regulate the activity of several sirtuins. The present study aims to investigate the role of SIRT3 in the antioxidant effect of H₂S in endothelial cells. Results: Cultured EA.hy926 endothelial cells were exposed to hydrogen peroxide (H₂O₂) as a model of oxidative stress-induced cell injury. GYY4137, a slow-releasing H₂S donor, improved cell viability, reduced oxidative stress and apoptosis, and improved mitochondrial function following H₂O₂ treatment. H₂S reversed the stimulation of MAPK phosphorylation, downregulation of SIRT3 mRNA and reduction of the superoxide dismutase 2 and isocitrate dehydrogenase 2 expression which were induced by H₂O₂. H₂S also increased activator protein 1 (AP-1) binding activity with SIRT3 promoter and this effect was absent in the presence of the specific AP-1 inhibitor, SR11302 or curcumin. Paraquat administration to mice induced a defected endothelium-dependent aortic vasodilatation and increased oxidative stress in both mouse aorta and small mesenteric artery, which were alleviated by GYY4137 treatment. This vasoprotective effect of H₂S was absent in SIRT3 knockout mice. Innovation: The present results highlight a novel role for SIRT3 in the protective effect of H₂S against oxidant damage in the endothelium both in vitro and in vivo. Conclusion: H₂S enhances AP-1 binding activity with the SIRT3 promoter, thereby upregulating SIRT3 expression and ultimately reducing oxidant-provoked vascular endothelial dysfunction.