Effect of cyclooxygenase-2 inhibition on human Helicobacter pylori gastritis: mechanisms underlying gastrointestinal safety and implications for cancer chemoprevention

Abstract

Cyclooxygenase (COX)-2 expression and prostaglandin production is increased by Helicobacter pylori infection. Non-selective COX inhibitors reduce prostaglandins and mucosal proliferation in infected mucosa and may reduce gastric cancer risk, but ulceration precludes their use. COX-2 inhibitors cause fewer ulcers and may be chemopreventive. Physiological studies of COX-2 inhibitors in humans with H. pylori infection have not been performed. Aim: To study the impact of COX-2 specific inhibition on gastric prostaglandin levels, H. pylori gastritis and proliferation. Methods: Twenty infected (eight males, 12 females; age 38 1.8) and six uninfected (four males, two females; age 36 3.5) healthy volunteers received rofecoxib 25 mg daily for 14 days. Endoscopic biopsies were evaluated for prostaglandin E 2 (PGE 2 ) content, gastritis and proliferation. Results: Before drug therapy, compared to uninfected, H. pylori -infected subjects had significantly higher: (a) gastric mucosal PGE 2 (pg mg tissue) in the gastric body and antrum, (b) H. pylori score in body and antrum and (c) mid-gland proliferation index in antrum and body. The COX-2 inhibitor did not significantly affect PGE 2 levels, gastritis scores or proliferation indices in the body or antrum in the H. pylori- positive or -negative subjects. Conclusion: The predominant source of increased gastric PGE 2 in H. pylori infection appears to be COX-1-derived. In non-ulcerated H. pylori gastritis, COX-2 inhibition does not affect cellular proliferation. Rofecoxib's lack of effect on gastric prostaglandin levels and proliferation in H. pylori -infected mucosa may explain the absence of an increased ulcer risk among COX-2 inhibitor users with H. pylori infection. The lack of significant effect on intermediate biomarkers raises uncertainty regarding the potential of specific COX-2 inhibitors for chemoprevention of gastric cancer.