Dual Action of Nitric Oxide in the Pathogenesis of Ischemia/Reperfusion-Induced Mucosal Injury in Mouse Stomach

Aim: We investigated the roles of NO/NOS isoforms in the pathogenesis of ischemia/reperfusion (I/R)-induced gastric injury in mouse stomachs. Methods: Under urethane anesthesia, the celiac artery was clamped, and then reperfusion was established 30 min later by removal of the clamp. After a 60-min reperfusion, the stomach was examined for macroscopic lesions. Results: Following I/R, hemorrhagic lesions were generated in the mucosa, although ischemia alone caused no visible damage. Prior administration of L-NAME (a nonselective NOS inhibitor) significantly aggravated these lesions, in a L-arginine-inhibitable manner. By contrast, the selective iNOS inhibitor 1400W significantly prevented the occurrence of I/R-induced gastric lesions. The mucosal MPO activity was increased after I/R, and this response was enhanced and attenuated by prior administration of L-NAME and 1400W, respectively. Interestingly, the later treatment with L-NAME, given 10 min before reperfusion, significantly reduced the severity of the I/R-induced gastric damage, in a L-arginine-dependent manner. The expression of iNOS mRNA was up-regulated in the stomach following I/R, with an increase of mucosal NO content, and the NO production was significantly inhibited by both L-NAME and 1400W. Conclusion: Endogenous NO plays a dual role in the pathogenesis of IR-induced gastric damage; NO/cNOS is protective while NO/iNOS is proulcerogenic during I/R.