Suppressive effect of rebamipide, an antiulcer agent, against activation of human neutrophils exposed to formyl-methionyl-leucyl-phenylalanine

Abstract

Rebamipide, an antiulcer agent, has been shown to be able to prevent gastric mucosal injury resulting in part from activation of neutrophils. The mechanism of its suppressive action, however, remains to be established. The present study aimed to determine the effect of rebamipide on activation of isolated human neutrophils and to identify the signal transduction pathway involved in its regulation. In unstimulated cells, alkaline phosphatase activity was found residing in short rod-shaped intracellular granules. Upon stimulation with a chemotactic peptide formyl-methionyl-leucylphenylalanine, the granules fused to form elongated tubular structures and spherical vacuoles. Rebamipide inhibited reorganization of alkaline phosphatasecontaining granules along with upregulation of alkaline phosphatase activity and CD16, a marker of the granules. It also suppressed chemotaxis, an increase in intracellular calcium ion concentration, and NADPH oxidase activation in cells stimulated with formylmethionyl- leucyl-phenylalanine. In contrast, the drug showed no inhibitory action toward upregulation of alkaline phosphatase activity and CD16, and activation of NADPH oxidase in cells stimulated with phorbol myristate acetate, an activator of protein kinase C. These findings demonstrate that rebamipide exerts a broad spectrum of suppressive actions toward biological functions of human neutrophils stimulated with formylmethionyl- leucyl-phenylalanine, but not with phorbol myristate acetate, and suggest that the upstream point of protein kinase C is the signal transduction pathway involved in its regulation.