Genotoxic and oxidative damage induced by Helicobacter pylori in Meriones unguiculatus.

Infection with Helicobacter pylori has been shown to be at the origin of various gastric pathologies. However, it has not yet been established whether the etiology of such diseases, particularly of gastric cancer, is related to the production of free radicals or to mutagenesis. The aim of this study was to determine whether a six-month infection with Helicobacter pylori increased the amount of lipid peroxidation, nitric oxide, and DNA damage in Mongolian gerbils (Meriones unguiculatus). H. pylori was characterized genotypically and administered orally to the animals. Four tests were applied to identify the presence of bacteria at one, two, four, and six months after the inoculation, namely, isolation and identification in culture, the urease test, the ELISA assay, and immunohistochemical staining of gastric biopsies. The infection was considered to be successful when three of the above-mentioned tests were positive. The infection occurred in 30% of the animals in the first month after the H. pylori inoculation and in 60-70% of the animals in the later stages. Levels of malondialdehyde, nitric oxide, and DNA damage (using the "comet" assay) were determined in the gastric tissue of the animals at one, two, four, and six months. We found statistically significant increases in malondialdehyde and nitric oxide levels from the second month on. The comet assay in animals infected with H. pylori showed a significant increase in the mean tail length throughout the observation period. We conclude that our results support the assumption that oxidative damage and DNA breakage produced by the infection with H. pylori are some of the initial alterations occurring in the development of gastric diseases.