Acute Helicobacter pylori
infection of gastric epithelial cells and human gastric biopsies represses H,K-
ATPase α subunit (HKα) 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 HKα 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 HKα repression by activating NF-κB, AGS cells transfected with HKα promoter-Luc reporter constructs containing an intact or mutated NF-κB 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, cagζ, cagε, cagZ, and cagβ), or deficient in genes encoding two
peptidoglycan hydrolases (slt and cagγ). H. pylori-induced AGS cell HKα 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 HKα repression is independent of
IL-8 expression, and that CagA translocation together with H. pylori transglycosylases encoded by slt and cagγ participate in NF-κB-dependent HKα 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.