Effect of Helicobacter pylori infection on cyclooxygenase‐2 expression in gastric antral mucosa

OBJECTIVE: Helicobacter pylori infection is a major etiological cause of chronic gastritis. Inducible cyclooxygenase (COX‐2) is an important regulator of mucosal inflammation. Recent studies indicate that expression of COX‐2 may contribute to gastro­intestinal carcinogenesis. The aim of this study was to investigate the effects of H. pylori infection and eradication therapy on COX‐2 expression in gastric antral mucosa. METHODS: Antral biopsies were taken from 46 H. pylori‐infected patients, who also had chronic gastritis, both before and after anti‐H. pylori treatment. The COX‐2 protein was stained by using immunohistochemical methods and COX‐2 expression was quantified as the percentage of epithelial cells expressing COX‐2. Gastritis and H. pylori infection status were graded according to the Sydney system. RESULTS: Cyclooxygenase‐2 expression was detected in the cytoplasm of gastric antral epithelial cells both before and after the eradication of H. pylori. Cyclooxygenase‐2 expression in mucosa with H. pylori infection was compared with the corresponding mucosa after successful H. pylori eradication (20.1 ± 13.1%vs 13.8 ± 5.9%; P < 0.05). At the same time, COX‐2 expression in H. pylori‐infected mucosa was com­pared with the normal controls (18.0 ± 14.1%vs 12.3 ± 4.6%, P < 0.05). Expression of COX‐2 was correlated with the degree of chronic inflammation (r= 0.78, P < 0.05). CONCLUSIONS: Our results showed that H. pylori infection leads to gastric mucosal overexpression of COX‐2 protein, suggesting that the enzyme is involved in H. pylori‐related gastric pathology in humans.