Background: Proton pump inhibitors have been reported to modify the level of Helicobacter pylori gastritis. Aim: To quantitatively investigate the effect of a proton pump inhibitor on the mucosal neutrophil reaction. Methods: Forty-six H. pylori-infected patients (17 duodenal ulcer, 29 gastric ulcer) were enrolled. During endoscopic examination, biopsy samples were obtained from the antrum and the corpus. The tissue content of neutrophil myeloperoxidase was measured by enzyme-linked immunoabsorbent assay, and H. pylori infection was histologically assessed. A proton pump inhibitor was administered orally for 8 weeks. Results: In the patients as a whole, antral myeloperoxidase decreased significantly after proton pump inhibitor treatment, but corpus myeloperoxidase remained largely unchanged. In duodenal ulcer patients, myeloperoxidase significantly decreased in the antrum, but increased in the corpus. In gastric ulcer patients, a significant reduction was observed in antral myeloperoxidase, but corpus myeloperoxidase remained unchanged. In the antral myeloperoxidase > corpus myeloperoxidase subgroup (n = 24), antral myeloperoxidase significantly decreased, whereas corpus myeloperoxidase increased. No changes were observed at either site in the corpus myeloperoxidase > antral myeloperoxidase subgroup. Histology showed that the antral bacterial load of H. pylori decreased in all subgroups, but that it was mostly unchanged in the corpus. Conclusions: Proton pump inhibitor treatment stimulated the neutrophil reaction in the corpus mucosa of duodenal ulcer patients and of patients in whom antral neutrophil accumulation was more predominant than that of the corpus. This phenomenon may not be caused by increased bacterial density.
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