1 Capsaicin sensitive a erent nerves play an important role in gastric mucosal defensive mechanisms. Capsaicin stimulates a erent nerves and enhances the release of calcitonin gene-related peptide (CGRP), which seems to be the predominant neurotransmitter of spinal a erents in the rat stomach, exerting many pharmacological e ects by a direct mechanism or indirectly through second messengers such as nitric oxide (NO). 2 Lafutidine is a new type of anti-ulcer drug, possessing both an antisecretory e ect, exerted via histamine H 2 receptor blockade, and gastroprotective activities. Studies with certain antagonists or chemical dea erentation techniques suggest the gastroprotective actions of lafutidine to be mediated by capsaicin sensitive a erent nerves, but this is an assumption based on indirect techniques. In order to explain the direct relation of lafutidine to a erent nerves, we conducted the following studies.3 We determined CGRP and NO release from rat stomach and speci®c [ 3 H]-resiniferatoxin (RTX) binding to gastric vanilloid receptor subtype 1 (VR1), which binds capsaicin, using EIA, a microdialysis system and a radioreceptor assay, respectively. 4 Lafutidine enhanced both CGRP and NO release from the rat stomach induced by a submaximal dose of capsaicin, but had no e ect on speci®c [ 3 H]-RTX and capsaicin binding to VR1. 5 In conclusion, our ®ndings demonstrate that lafutidine modulates the activity of capsaicin sensitive a erent nerves in the rat stomach, which may be a key mechanism involved in its gastroprotective action.
Abstract.Helicobacter pylori (H. pylori) infection of gastric epithelial cells has been shown to induce interleukin (IL)-8 production, but the signal transduction mechanism leading to IL-8 production has not been clearly defined. Here, we investigate the role of protein kinase C (PKC) in the mechanism of induction of IL-8 release by H. pylori in human gastric epithelial cells. In MKN45 cells, H. pylori-induced IL-8 release was enhanced by treatment with PKC inhibitors (GF109203X and calphostin C) and PKC depletion, which completely inhibited PKC activity. Moreover, PKC inhibitors and PKC depletion increased extracellular signal-regulated kinase (ERK) activity and phosphorylation, but not calcium / calmodulin-dependent protein kinase II (CaMK II) activity, in response to H. pylori infection. PKC activated by H. pylori inhibited activation of ERK induced by H. pylori without affecting the CaMK II activity and negatively regulated IL-8 production in human gastric epithelial cells.
These results suggest that lafutidine inhibits IL-8 release by inhibiting H. pylori adherence to gastric epithelial cells, indicating a novel mechanism by which lafutidine protects against the mucosal inflammation associated with H. pylori infection.
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