Helicobacter pylori and H₂O₂ increase AP endonuclease-1/redox factor-1 expression in human gastric epithelial cells

Background & Aims: Helicobacter pylori infection causes inflammation, accumulation of reactive oxygen species, and oxidative DNA damage in the gastric mucosa. Apurinic/apyrimidinic endonuclease-1 (APE-1)/redox factor-1 (Ref-1) repairs damaged DNA and reductively activates transcription factors, including activator protein-1. Considering that H. pylori generate reactive oxygen species and that reactive oxygen species modulate APE-1/Ref-1 in other cell types, we examined the effect of H. pylori, oxidative stress, and antioxidants on APE-1/Ref-1 expression in human gastric epithelial cells. Methods: Human gastric epithelial cell lines or cells isolated from mucosal biopsy samples were stimulated with H. pylori, Campylobacter jejuni, and/or H ₂O ₂ in the presence or absence of antioxidants. APE-1/Ref-1 expression was assayed by Western blot or reverse-transcription polymerase chain reaction, and its cellular distribution was determined by using indirect conventional and confocal immunofluorescence. New protein synthesis was detected by [S ³⁵]methionine labeling. APE-1/Ref-1 function was assessed by using a luciferase-linked reporter construct containing 3 activator protein 1 binding sites. Results: APE-1/Ref-1 protein and messenger RNA were detected in resting gastric epithelial cells. APE-1/Ref-1 protein expression was increased after stimulation with H ₂O ₂ or live cag pathogenicity island-bearing H. pylori, but not cag pathogenicity island-negative H. pylori or C. jejuni. H. pylori- or reactive oxygen species-mediated increases in APE-1/Ref-1 expression involved de novo protein synthesis that was inhibited by antioxidants. H. pylori or H ₂O ₂ also induced nuclear accumulation of APE-1/Ref-1, and overexpression of APE-1/Ref-1 increased activator protein 1 binding activity. Conclusions: The data show that H. pylori or reactive oxygen species enhance APE-1/Ref-1 protein synthesis and nuclear accumulation in human gastric epithelial cells and implicate APE-1/Ref-1 in the modulation of the pathogenesis of H. pylori infection.