H2S-induced gastric fundus smooth muscle tension potentiation is mediated by the phosphoinositide 3-kinase/Akt/endothelial nitric oxide synthase pathway

New Findings What is the central question of this study? The present study investigated the relationship between H2S and NO in regulation of gastric fundus tension. What is the main finding and its importance? Endogenous or exogenous H2S and NO have opposite effects on fundus tension, and H2S-induced gastric fundus tension enhancements are mediated by inhibition of NO generation through the phosphoinositide 3-kinase/Akt pathway. These results are very important in exploring the mechanism of physiological accommodation and accommodation disorder. Hydrogen sulphide (H2S) is considered a new gasotransmitter, along with NO and CO. It was recently confirmed that H2S and NO play important roles in the regulation of gastrointestinal smooth muscle tension. The present study was designed to elucidate the interactions between H2S and NO with respect to the regulation of gastric fundus smooth muscle tension using Western blotting, physiological and electrochemical techniques. Real-time H2S and NO generation was detected in gastric smooth muscle tissue. NaHS, an H2S donor, enhanced fundus smooth muscle tension, whereas SNP, an NO donor, decreased fundus smooth muscle tension in a dose-dependent manner. NaHS-induced increases in fundus smooth muscle tension were suppressed by L-NAME, an NO synthase inhibitor. Aminooxyacetic acid (AOAA), a cystathionine beta-synthase inhibitor, exerted inhibitory effects on fundus smooth muscle tension; these effects were also suppressed by L-NAME. Real-time NO generation was significantly potentiated by AOAA. Endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 and Akt phosphorylation at serine308 and threonine473 were significantly inhibited by NaHS. LY294002, a phosphoinositide 3-kinase inhibitor, blocked these NaHS-mediated effects. However, eNOS phosphorylation at serine1177 and Akt phosphorylation at serine308 and threonine473 were significantly potentiated by AOAA. Cystathionine beta-synthase siRNA interference significantly increased eNOS phosphorylation at serine 1177 and Akt phosphorylation at serine 308 and threonine 473. Cystathionine beta-synthase siRNA interference also increased total eNOS protein expression levels but did not significantly change total Akt kinase protein expression levels. These results suggest that H2S-induced enhancement of gastric fundus tension is mediated by inhibition of NO generation through the phosphoinositide 3-kinase/Akt pathway.