Abstract

BACKGROUND Prostaglandin endoperoxide synthase/cyclooxygenase (COX) is the key enzyme in gastric mucosal protection and repair but its cellular localisation in the human stomach is still unclear.

AIMS To investigate immunohistochemically the cellular distribution of COX-1 and COX-2 proteins in the human stomach with or without gastritis or ulceration.

PATIENTS AND METHODS Tissues were obtained by surgical resection of gastric ulcers associated with perforation (n=9) or by biopsy from Helicobacter pylori positive patients with gastric ulcers (n=45) and H pylori negative healthy subjects (n=15). COX expression was detected by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and light and electron microscopic immunohistochemistry.

RESULTS COX-2 mRNA and protein were detected in gastric ulcer tissues but not in intact gastric mucosa. COX-1 mRNA and protein were detected in the intact mucosa. COX-2 immunostaining was exclusively localised in macrophages and fibroblasts between necrotic and granulation tissues of the ulcer bed. The percentage of COX-2 expressing cells was significantly higher in open than in closed ulcers, and in gastritis than in gastric mucosa without H pylori infection. COX-1 immunoreactivity localised in lamina propria mesenchymal cells was similar in various stages of ulcer disease and in intact gastric mucosa. Electron microscopic immunohistochemistry revealed both COX-1 and COX-2 on the luminal surfaces of the endoplasmic reticulum and nuclear envelope of macrophages and fibroblasts.

CONCLUSIONS Our results showed that COX-2 protein was induced in macrophages and fibroblasts in gastric ulcers and H pylorirelated gastritis, suggesting its involvement in the tissue repair process.