Proteomic analysis of upregulated proteins in Helicobacter pylori under oxidative stress induced by hydrogen peroxide

The development of gastric cancer was suggested to be associated with chronic inflammation as a consequence of Helicobacter pylori infection. Such inflammation-related oxidative stress induced by reactive oxygen species (ROS) in vivo may exert bidirectional effects on both hosts and H pylori. In this study, ROS-induced oxidative stress was mimicked by coculture of gastric epithelial cells with H pylori treated with hydrogen peroxide (H2O2). To investigate the effect of H2O2 on the proteome of H pylori, we performed two-dimensional polyacrylamide gel electrophoresis followed by liquid chromatography coupled with nano-electrospray ionization-tandem mass spectrometry (liquid chromatography mass spectrometry) and bioinformatics database analysis. The nine most overexpressed proteins consisted of three virulence factors, including cytotoxin-associated protein A (CagA), vacuolating cytotoxin (VacA), adherence-associated protein (AlpA), and two antioxidant enzymes alkylhydroperoxide reductase (AhpC) and catalase (KatA), plus one serine protease (HtrA), aconitate hydratase, and fumarate reductase. We have also confirmed the upregulation of virulence factors and antioxidant proteins in several H pylori strains isolated from patients of different clinical outcomes. Furthermore, it is noted that H pylori was found to decrease in infection rate and increase in proliferation after being exposed to H2O2. We also found that gastric epithelial cells can be protected from oxidative damage by H2O2 in the presence of H pylori. In conclusion, this study lends support to the supposition that ROS containing H2O2 as one of the major oxidative species can induce upregulation of virulence factors and antioxidant enzymes in H pylori, which may aid in the elucidation of inflammation leading to the development of gastric cancer from H pylori infection.