SummaryTo determine the effect of Helicobacter pylori CagA expression on interleukin-8 (IL-8) induction in AGS cells, cagA and five of its fragments from strains 147A and 147C that vary in the 3 ′ ′ ′ ′ repeat region were cloned into the eukaryotic expression plasmid pSP65SR α α α α . IL-8, but not RANTES or IL-I β β β β , levels were increased in AGS cells transfected with 147A-cagA and to a greater extent with 147C-cagA , compared with negative controls. The 5 ′ ′ ′ ′ b fragment from the two strains had similar effects, but the 3 ′ ′ ′ ′ d and e fragments from 147C CagA had greater effects than those from 147A-CagA. When the Western CagA-specific sequence (WSS) of 147C-cagA was replaced with East Asian CagA-specific sequence (ESS) and cloned into pSP65SR α α α α as an East/West chimera, there was no significant effect on IL-8 production. Use of specific inhibitors indicates that Src kinase activation, and the mitogen-activated protein (MAP) kinase and NF-κ κ κ κ B pathways are the major intermediates for CagA effects on IL-8 induction, but the p38 MAP kinase pathway has little effect. These results indicate a direct CagA effect on IL-8 induction by gastric epithelial cells, and indicate signal pathway loci that can be targeted for amelioration.

Because matrix metalloproteinases (MMPs) play roles in inflammatory tissue injury, we asked whether MMP secretion by gastric epithelial cells may contribute to gastric injury in response to signals involved in Helicobacter pylori-induced inflammation and/or cyclooxygenase inhibition. Tumor necrosis factor (TNF)-␣, interleukin (IL)-1␤, and epidermal growth factor (EGF) stimulated gastric cell MMP-1 secretion, indicating that MMP-1 secretion occurs in inflammatory as well as noninflammatory situations. MMP-1 secretion required activation of the MAPK Erk and subsequent protein synthesis but was down-regulated by the alternate MAPK, p38. In contrast, secretion of MMP-13 was stimulated by TNF-␣/IL-1␤ but not EGF and was Erk-independent and mediated by p38. MMP-13 secretion was more rapid (peak, 6 h) than MMP-1 (peak >30 h) and only partly depended on protein synthesis, suggesting initial release of a pre-existing MMP-13 pool. Therefore, MMP-1 and MMP-13 secretion are differentially regulated by MAPKs. MMP-1 secretion was regulated by E prostaglandins (PGEs) in an Erk-dependent manner. PGEs enhanced Erk activation and MMP-1 secretion in response to EGF but inhibited Erk and MMP-1 when TNF-␣ and IL-1␤ were the stimuli, indicating that the effects of PGEs on gastric cell responses are context-dependent. These data show that secretion of MMPs is differentially regulated by MAPKs and suggest mechanisms through which H. pylori infection and/or cyclooxygenase inhibition may induce epithelial cell signaling to contribute to gastric ulcerogenesis.

Because the mechanisms of Helicobacter pylori-induced gastric injury are incompletely understood, we examined the hypothesis that H. pylori induces matrix metalloproteinase-1 (MMP-1) secretion, with potential to disrupt gastric stroma. We further tested the role of CagA, an H. pylori virulence factor, in MMP