Crosstalk between hydrogen sulfide and nitric oxide in endothelial cells

Hydrogen sulfide (H₂S) 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 H₂S and NO stimulated the formation of new microvessels. Incubation of human umbilical vein endothelial cells (HUVECs‐926) with NaHS (a H₂S donor) stimulated the phosphorylation of endothelial NO synthase (eNOS) and enhanced NO production. H₂S had little effect on eNOS protein expression in ECs. L‐cysteine, a precursor of H₂S, stimulated NO production whereas blockage of the activity of H₂S‐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 H₂S 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 H₂S on ECs. Our results suggest that H₂S 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 H₂S‐induced angiogenesis.