Helicobacter pylori infection of rhesus monkeys is associated with down-regulation of H, K-ATPase a subunit mRNA

Abstract

Clinical studies and data from isolated gastric parietal cells suggest that acid secretion is inhibited by acute H pylori infection, leading to gastric hypochlorhydria. In addition, eradication of H. pylori is associated with increased acid secretion. The mechanism of these changes is unknown. Gastric acid secretion is mediated by the enzyme H,K-ATPase which exchanges luminal K+ for cytoplasmic H+. To test the hypothesis that H pylori infection has direct inhibitory effects on gastric H,K-ATPase a subunit (HKa) gene expression, we sought a correlation between H pylori infection and levels of HKa messenger RNA. Total RNA was isolated from gastric corpus biopsies of three rhesus monkeys (Macaca mulatta) with persistent H pylori infection and four uninfected monkeys. A 2I7 bp HKa cDNA template was made from monkey RNA using RT-PCR with primers based on human HKa cDNA. Using RNA polymerase, a 32p_ labeled anti-sense RNA was generated from the monkey HKa cDNA template. Relative HKa mRNA concentrations in the monkey gastric RNA samples were measured by ribonuclease protection assay (RPA), using measurement of constitutively-expressed 18S ribosomal RNA in the same samples to normalize the data. The radiographic intensities of HKa mRNA bands and of 18S rRNA bands on RPA phosphor imager electrophoretograms were quantitated by digital analysis. Gastric HKa mRNAlI8S rRNA band intensity ratios were consistently higher in biopsies from uninfected monkeys compared to persistently-infected animals. These results suggest that persistent H pylori infection of monkey gastric mucosa inhibits HKa synthesis by parietal cells, reducing cellular levels of functional H,KATPases and thus decreasing acid output. Assuming that these effects are reversible after treatment, the present observations also could explain the increased acid output observed in humans following eradication of H pylori. as well as the increased risk for gastroesophageal reflux disease associated with H. pylori eradication.