AIM: To investigate the mucosal protective effect and the mechanisms of action of the anti-ulcer drug irsogladine maleate in gastric injury induced by indomethacin in rats.METHODS: Gastric mucosal injury was induced in male Hos:Donryu rats by oral administration of indomethacin at a dose of 48 mg/kg.One hour before indomethacin treatment,animals were orally pretreated with irsogladine maleate at doses of 1 mg/kg,3 mg/kg or 10 mg/kg.Four hours after indomethacin administration,the animals were sacrificed and their stomachs were rapidly removed and processed for the evaluation of gastric mucosal damage and the determination of the concentrations of tumor necrosis factor-α (TNF-α),interleukin-1β(IL-1β),IL-8 and myeloperoxidase (MPO) in mucosal tissues.RESULTS: Linear hemorrhagic mucosal lesions were observed primarily in the glandular stomach 4 h after oral administration of indomethacin.Pretreatment with irsogladine maleate markedly reduced the number and severity of these lesions in a dosedependent manner.The mucosal concentrations of proinflammatory cytokines (TNF-β,IL-1β,and IL-8)and MPO,which indicates the degree of mucosal infiltration by neutrophils,increased concomitantly with the occurrence of gastric injury in the indomethacintreated rats.Pretreatment with irsogladine maleate significantly decreased the levels of these inflammatory factors in gastric tissue elicited by indomethacin.CONCLUSION: The mucosal protective effects afforded by irsogladine maleate on gastric injury induced by indomethacin are mediated by inhibition of mucosal proinflammatory cytokine production and neutrophil infiltration,leading to suppression of mucosal inflammation and subsequent tissue destruction.