IL-1β modulation of H,K-ATPase α-subunit gene transcription inHelicobacter pyloriinfection

Helicobacter pylori infection of the human gastric body induces hypochlorhydria by perturbing acid secretion. H. pylori inhibits parietal cell H,K-ATPase α-subunit (HKα) gene and protein expression, providing a mechanistic basis for clinical hypochlorhydria. Given that H. pylori infection increases gastric mucosal IL-1β, an acid secretory inhibitor, we investigated the role of IL-1β in H. pylori-mediated inhibition of HKα transcription. Human gastric adenocarcinoma (AGS) cells were transfected with promoter-reporter constructs containing human HKα 5′-flanking sequence deletions. IL-1β (10 ng/ml) had no effect on the transcriptional activity of six progressively shorter deletion constructs of the HKα promoter (HKα2179–HKα340) and significantly stimulated the activity of HKα206, HKα177, HKα165, and HKα102 deletion constructs (80%, 100%, 46%, and 35%, respectively). H. pylori inhibited the transcriptional activity of HKα2179, HKα206, HKα177, and HKα165; IL-1β relieved the H. pylori inhibition of HKα2179 and HKα206 activity but not HKα177 and HKα165 activity. AGS cell pretreatment with a MEK1/2 inhibitor prevented the IL-1β-mediated stimulation, but p38 and JNK pathway inhibitors did not. IL-1β mRNA levels in AGS cells were low and unaffected by H. pylori, and ELISAs of H. pylori-conditioned AGS culture media showed no measurable IL-1β secretion. These data indicate that an IL-1β-dependent cis-response element lies downstream of −206 nt in the HKα promoter and that IL-1β-mediated upregulation of HKα transcription is affected by an ERK1/2 kinase signal pathway. We conclude that an IL-1β-responsive HKα cis element positively regulates HKα gene transcription in shortened deletion constructs and that H. pylori-induced inhibition of HKα transcription is not mediated by IL-1β.