Crosstalk between hydrogen sulfide and nitric oxide in endothelial cells

Abstract

Hydrogen sulfide (H ₂S) and nitric oxide (NO) are major gasotransmitters produced in endothelial cells (ECs), contributing to the regulation of vascular contractility and structural integrity. Their interaction at different levels would have a profound impact on angiogenesis. Here, we showed that H ₂S and NO stimulated the formation of new microvessels. Incubation of human umbilical vein endothelial cells (HUVECs-926) with NaHS (a H ₂S donor) stimulated the phosphorylation of endothelial NO synthase (eNOS) and enhanced NO production. H ₂S had little effect on eNOS protein expression in ECs. L-cysteine, a precursor of H ₂S, stimulated NO production whereas blockage of the activity of H ₂S-generating enzyme, cystathionine gamma-lyase (CSE), inhibited this action. CSE knockdown inhibited, but CSE overexpression increased, NO production as well as EC proliferation. LY294002 (Akt/PI3-K inhibitor) or SB203580 (p38 MAPK inhibitor) abolished the effects of H ₂S on eNOS phosphorylation, NO production, cell proliferation and tube formation. Blockade of NO production by eNOS-specific siRNA or nitro-L-arginine methyl ester (L-NAME) reversed, but eNOS overexpression potentiated, the proliferative effect of H ₂S on ECs. Our results suggest that H ₂S stimulates the phosphorylation of eNOS through a p38 MAPK and Akt-dependent pathway, thus increasing NO production in ECs and vascular tissues and contributing to H ₂S-induced angiogenesis.