Pathophysiology and clinical relevance of Helicobacter pylori

Considerable knowledge has recently accumulated on the mechanism by which Helicobacter pylori (H. pylori) induces chronic gastritis. Although H. pylori is not an invasive bacterium, soluble surface constituents can provoke pepsinogen release from gastric chief cells or trigger local inflammation in the underlying tissue. Urease appears to be one of the prime chemoattractants for recruitment and activation of inflammatory cells. Release of cytokines, such as tumor necrosis factor alpha, interleukin 1 and 6, and oxygen radicals, leads to a further tissue inflammation accompanied by a potent systemic IgA and IgG type of immune response. Chronic inflammation and antigens on glandular epithelial cells lead to a progressive destruction with loss of the epithelial barrier function. Within the gastric mucosa, patches of intestinal metaplasia develop, which may be a risk factor for subsequent development of gastric carcinoma. Hyperacidity in duodenal ulcer patients induces gastric metaplasia in the duodenal bulb, which represents a target for H. pylori colonization and ulcer formation. H. pylori can be detected in the majority of patients with peptic ulcers and, compared to age-matched healthy people, it is also found more often in patients with dyspepsia and gastric carcinoma. Although H. pylori can be detected in healthy people, the marked reduction of the ulcer recurrence rate by eradication of H. pylori (80 percent versus 20 percent relapse within one year) suggests that H. pylori is a major risk factor for duodenal ulcer formation. The potential role of H. pylori in non-ulcer dyspepsia and carcinogenesis is under investigation. Current regimens aimed at eradicating H. pylori use a combination of several drugs that are potentially toxic. Since the risk of complications may exceed the potential benefit in most patients, eradication treatment should be limited to clinical trials and to patients with aggressive ulcer disease. New drug regimens, e.g., the combination of proton pump inhibitors with one antibiotic, may provide less toxic alternatives. Beyond ulcer treatment, effective and well-tolerated eradication regimens may have a place in prophylaxis of gastric carcinoma.