Inducible nitric oxide synthase, anti-oxidant enzymes and Helicobacter pylori infection in gastritis and gastric precancerous lesions in humans

Chronic inflammation induced by Helicobacter pylori infection has been asso ciated with an increased risk of stomach cancer. We have analysed 167 stoma ch biopsies from 99 patients for H. pylori infection and immunohistochemica lly for the expression of inducible nitric oxide synthase (iNOS), catalase and superoxide dismutases (SODs) as markers of oxidative stress. Biopsies w ere graded as follows on the basis of histology: normal, superficial gastri tis, variable severity of atrophic gastritis with or without intestinal met aplasia, and dysplasia, iNOS was detected in inflammatory cells in all type s of gastritis with or without H. pylori infection and independently of its severity. In foveolar cells, iNOS was observed in similar to 25% of all bi opsies showing any type of gastritis, but in a markedly higher proportion o f dysplastic samples, Catalase and Mn-type SOD in inflammatory cells and ca talase in foveolar cells were more frequently observed in marked atrophic g astritis biopsies than in less severe gastritis, Individual differences wer e found in the expression of these enzymes within groups with the same seve rity of gastritis, Prolonged oxidative stress in severe gastritis and dyspl asia may play an important role in gastric carcinogenesis, through increase d damage of DNA and tissues by reactive oxygen and nitrogen species. (C) 19 98 Lippincott Williams & Wilkins.