Inducible nitric oxide synthase expression before and after eradication ofHelicobacter pylori in different forms of gastritis

An increased expression of inducible nitric oxide synthase (iNOS) has been observed in the inflamed human gastric mucosa as well as in some tumors. Th is observation suggests a pathobiological role of elevated NO production. T he purpose of this study was to compare the immunohistochemical iNOS expres sion in the different kinds of gastritis before and after the eradication o f Helicobacter pylori. We performed iNOS and H. pylori immunohistochemical staining and counted iNOS positive cells. We detected elevated expression o f iNOS around sites infected with H. pylori. iNOS expression in chemical ga stritis was strongly elevated in mucosal glands. After treatment, we found a significant difference in iNOS expression in patients with classical H. p ylori-induced antrum predominant gastritis and in patients with active auto immune gastritis. In the special case of progressed gastritis with intestin al metaplasia we found persistence of intestinal metaplasia, and we could n ot find a significant difference in the number of positive iNOS cells befor e and after treatment. The persistence of IM as a possibly precancerous les ion is probably at least in the antrum a source of continuous iNOS inductio n even after H. pylori eradication. (C) 2001 Federation of European Microbi ological Societies. Published by Elsevier Science B.V. All rights reserved.