Helicobacter pylori virulence factors affecting gastric proton pump expression and acid secretion

Acute Helicobacter pylori infection of gastric epithelial cells and human gastric biopsies represses H, K-ATPase alpha subunit (HK alpha) gene expression and inhibits acid secretion, causing transient hypochlorhydria and supporting gastric H. pylori colonization. Infection by H. pylori strains deficient in the cag pathogenicity island (cag PAI) genes cagL, cagE, or cagM, which do not transfer CagA into host cells or induce interleukin-8 secretion, does not inhibit HK alpha expression, nor does a cagA-deficient strain that induces IL-8. To test the hypothesis that virulence factors other than those mediating CagA translocation or IL-8 induction participate in HK alpha repression by activating NF-kappa B, AGS cells transfected with HK alpha promoter-Luc reporter constructs containing an intact or mutated NF-kappa B binding site were infected with wild-type H. pylori strain 7.13, isogenic mutants lacking cag PAI genes responsible for CagA translocation and/or IL-8 induction (cagA, cag zeta, cag epsilon, cagZ, and cag beta), or deficient in genes encoding two peptidoglycan hydrolases (slt and cag gamma). H. pylori-induced AGS cell HK alpha promoter activities, translocated CagA, and IL-8 secretion were measured by luminometry, immunoblotting, and ELISA, respectively. Human gastric biopsy acid secretion was measured by microphysiometry. Taken together, the data showed that HK alpha repression is independent of IL-8 expression, and that CagA translocation together with H. pylori transglycosylases encoded by slt and cag gamma participate in NF-kappa B-dependent HK alpha repression and acid inhibition. The findings are significant because H. pylori factors other than CagA and IL-8 secretion are now implicated in transient hypochlorhydria which facilitates gastric colonization and potential triggering of epithelial progression to neoplasia.