GASTRIC ANTISECRETORY AND ANTIULCER ACTIONS OF INTERLEUKIN-1 - EVIDENCE FOR THE PRESENCE OF AN IMMUNE BRAIN GUT AXIS

Increasing evidence suggests that interleukin-1 (IL-1), a cytokine mainly produced by activated monocytes/macrophages, has various biological actions in addition to its immunological activities. In the present study, we examined the effects of IL-1 on gastric secretion and gastric ulcer formation in rats. Gastric secretion was assessed in conscious pylorus-ligated rats weighing approximately 200 g. The peripheral injection of IL-1 resulted in a dose-related inhibition of gastric acid output. The central injection of IL-1 similarly reduced gastric acid secretion at 100 times smaller doses than peripherally injected IL-1, suggesting that this gastric antisecretory action of IL-1 is mediated by the central nervous system. In addition, it was found that this inhibitory effect of IL-1, either peripherally or centrally administered, was still evident at 8 h after injection, indicating the long-lasting property of this IL-1 action. On the basis of these antisecretory actions of IL-1, we determined whether or not pretreatment with IL-1 would prevent experimentally induced gastric ulcer formation. As expected, the central administration of IL-1 dose-dependently suppressed the development of gastric mucosal lesions induced by water-immersion restraint stress, a well-established ulcerogenic procedure. These results clearly demonstrated that IL-1 has potent antisecretory and antiulcer effects that are mediated by the central nervous system. Moreover, these findings suggest that there may exist an "immune-brain-gut" axis, which is involved in the regulation of gastric secretion and mucosal homeostasis, especially under certain pathophysiological conditions that activate the immune system to release various cytokines including IL-1.