Cyclooxygenase-2 expression in gastric antral mucosa before and after eradication of Helicobacter pylori infection

OBJECTIVE: Helicobacter pylori (H. pylori) causes chronic gastritis. The inducible prostaglandin synthetase cyclooxygenase 2 (COX-2) plays an important role in inflammatory conditions. We hypothesized that H. pylori-associated chronic gastritis would express COX-2 protein. Our aim was to evaluate the effect of eradication of H. pylori infection on COX-2 expression in the antral mucosa of patients before and after antibiotic therapy. METHODS: Tissues were obtained from patients with non-ulcer dyspepia undergoing H. pylori eradication. Ten patients with proven H. pylori infection and subsequent successful eradication were studied. Three biopsies of antral mucosa were evaluated before and after H. pylori eradication. The amount of acute and chronic inflammation was quantitated. Immunohistochemical staining for COX-2 was expressed as a percentage of the total number of cells and correlated with the degree of chronic inflammation. RESULTS: Specific immunostaining for COX-2 was observed in antral mucosa of patients infected with H. pylori. Patchy cytoplasmic staining was seen in surface epithelial cells and strong cytoplasmic staining for COX-2 was seen in parietal cells. Spotty cytoplasmic staining for COX-2 was also seen in lamina propria plasma cells, as well as there being macrophages present in the germinal centers of lymphoid aggregates. COX-2 expression could be detected both before and after eradication of H. pylori. The mean percentage of cells staining for COX-2 was significantly higher in H. pylori-infected mucosa, compared with mucosa after successful H. pylori eradication (33.4% +/- 5.4 vs 18.9% +/- 3.3, p = 0.038). COX-2 immunostaining correlated best with the chronic inflammation score (r2 = 0.78, p < 0.001). There was a strong correlation for those subjects who were H. pylori infected, as well as for those who had successful H. pylori eradication. CONCLUSIONS: H. pylori associated acute and chronic antral inflammation was associated with immunohistochemical detection of COX-2 protein in epithelial cells, in addition to associated mononuclear cells and parietal cells. Expression was reduced, but not eliminated, in the epithelium after successful eradication of H. pylori. Despite the reduction in COX-2 expression after H. pylori eradication, expression of COX-2 in epithelial cells remained and strongly correlated with the extent of the chronic inflammatory cell infiltrate. The clinical implications of H. pylori-associated induction of COX-2 expression for patients on selective COX-2 inhibitors, in addition to the role of COX-2 in gastric carcinogenesis, deserve further study.