Hydrogen sulfide inhibits endothelial nitric oxide formation and receptor ligand-mediated Ca(2+) release in endothelial and smooth muscle cells

Abstract

Background: In the vascular system, ATP-sensitive K(+)-channels are a target for H2S. Recent evidence suggests that H2S may also modulate Na(+)- and Ca(2+)-permeable channels and intracellular Ca(2+) stores, but the influence of H2S on endothelial Ca(2+) dynamics and Ca(2+)-dependent activation of endothelial nitric oxide synthase (eNOS) is unclear. In this study, we investigated the effects of H2S on Ca(2+) signaling in endothelial and smooth muscle cells with special emphasis given to the role of H2S in modulating endothelial NO formation.

Methods: Experiments were performed with endothelial cells from porcine aorta, the human endothelial cell line HMEC-1, and smooth muscle cells from rat aorta and trachea. Mobilization of intracellular Ca(2+) and Ca(2+) entry was monitored with Fura-2. Activity of eNOS was determined as conversion of incorporated l-[(3)H]arginine into l-[(3)H]citrulline.

Results: Incubation of endothelial cells with the H2S donors sodium hydrogen sulfide (NaHS) and GYY4137 blocked activation of eNOS by the receptor agonist ATP but not by the Ca(2+) ionophore A23187. Data revealed that H2S inhibited ATP-induced release of Ca(2+) from intracellular stores indicating that H2S attenuates eNOS activity by blocking capacitative Ca(2+) entry. A similar inhibitory effect of H2S on ATP-induced Ca(2+) release and Ca(2+) entry was also observed in human microvascular endothelial cells and smooth muscle cells.

Conclusions: H2S antagonized Ca(2+) mobilization by receptor agonists and store-operated Ca(2+) entry thereby limiting eNOS activation and NO formation. The effect of H2S on Ca(2+) stores was not restricted to endothelial cells but was also observed in vascular and tracheal smooth muscle cells.

Keywords: ATP; Ca(2+); H(2)S; eNOS.