Role of constitutive nitric oxide synthase S-nitrosylation in Helicobacter pylori-induced gastric mucosal cell apoptosis: effect of ghrelin.

Infection with H. pylori is a primary factor in the etiology of gastric disease, and the excessive NO generation and a massive rise in apoptosis are well recognized features that characterize the mucosal inflammatory responses to the bacterium and its lipopolysaccharide (LPS). Here, we report that H. pylori LPS-induced enhancement in gastric mucosal cell apoptosis and NO generation was associated with the suppression in constitutive nitric oxide synthase (cNOS) activity and a marked up-regulation in the activity of inducible nitric oxide synthase (iNOS). Further, we demonstrate that the detrimental effect of the LPS on cNOS was manifested in the enzyme protein S-nitrosylation, that was susceptible to suppression by iNOS inhibitor, 1400W. Moreover, we show that the countering effect of peptide hormone, ghrelin, on the LPS-induced changes in apoptosis and cNOS activity was reflected in the loss in cNOS S-nitrosylation and the increase in the enzyme phosphorylation. These findings demonstrate that the disturbances in gastric mucosal NO generation system caused by H. pylori result from the iNOS-derived NO suppression of cNOS activation through S-nitrosylation. We also report that ghrelin protection against H. pylori-induced gastric mucosal proapoptotic events involves cNOS activation manifested by the increase in enzyme protein phosphorylation and a decrease in its S-nitrosylation.