Effect of Helicobacter pylori-mediated inflammation on nonsteroidal anti-inflammatory drugs-induced gastric mucosal injury.

Helicobacter pylori (H. pylori) infection and nonsteroidal anti-inflammatory drugs (NSAIDs) are two major causes of gastric ulceration, but relation between H. pylori infection and use of these drugs in gastric mucosal injury is controversial. Neutrophils have been implicated in the pathogenesis of gastric mucosal damage induced by H. pylori or NSAIDs. H. pylori itself and H. pylori extract induce neutrophil activation, such as superoxide production, expression of adhesion molecule (CD11b/CD18) and transendothelial migration, capillary plugging. Several clinical and experimental studies demonstrated that the degree of H. pylori-induced gastric mucosal injury was closely correlated with the extents of H. pylori infection and of neutrophil infiltration, suggesting implication in extravascular neutrophils for H. pylori-induced gastric mucosal injury. On the other hand, aspirin promotes neutrophil-endothelial adhesive interactions via increasing CD11b/CD18, but not neutrophil migration to extravascular space. In addition, our recent in vivo study suggests that neutrophils adhering to the blood vessels, but not neutrophils migrating to the interstitium, are implicated in aspirin-induced gastric mucosal injury. Recently, we found that administration of aspirin to gerbils three weeks after H. pylori inoculation produced severe gastric mucosal injury via marked infiltration of neutrophils. In this animal model, pretreatment with anti-neutrophil serum, elastase inhibitor or scavengers of reactive oxygen species remarkably inhibited gastric mucosal injury. These results suggest that H. pylori infection potentiates aspirin-induced gastric mucosal injury by mechanisms that include accumulation of activated neutrophils.