Ursodeoxycholic acid inhibits oxidative stress induced by bile acids and gastric acid in esophageal cell lines: Relevance to Barrett’s esophagus pathogenesis Free

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Objectives: Barrett's esophagus (BE) is a premalignant condition associated with elevated risk for the development of esophageal adenocarcinoma (ADCA). Previous studies indicated that oxidative damage contributes to the development of ADCA. We tested the hypothesis that bile acids and gastric acid, two components of refluxate, can induce oxidative stress and oxidative DNA damage. We speculate that effects of gastric acid and bile acids may be inhibited by treatment with the cytoprotective bile acid, ursodeoxycholic acid (UDCA).

Methods: Oxidative stress was evaluated by staining with an antibody to 8-hydroxy-deoxyguanosine (8-OH-dG) in BE tissues with different degrees of dysplasia. The levels of 8-OH-dG were also evaluated ex vivo in BE tissues incubated for 10 minutes with control medium and medium acidified to pH 4 and supplemented with 0.5mM bile acid cocktail. Furthermore, three esophageal cell lines (BE cells, normal squamous esophageal HET-1A cells and adenocarcinoma Seg-1 cells) were exposed for 1-10 minutes to control media, media containing bile acid cocktail, media acidified to pH 4, and media at pH 4 supplemented with 0.1mM bile acid cocktail and evaluated for induction of reactive oxygen species (ROS). In addition, the cells were treated as above but with 0.1 mM UDCA added to the media.

Results: Immunohistochemical analysis showed that 8-OH-dG is present at increased levels in epithelial cells of dysplastic BE. Incubation of BE tissues with a combination of a bile acid cocktail and low pH leads to the increased formation of 8-OH-dG. An increase in ROS occurs after exposure to pH 4 and a bile acid cocktail in all three cell lines and pH 4 treatment alone induced ROS in BE cells and HET-1A cells. These increases in ROS were inhibited by treatment with 0.1mM UDCA.

Conclusions: Oxidative DNA damage is present at increased levels in dysplastic BE tissue. Oxidative stress can be induced in esophageal tissues and cells by short exposures to bile acids and low pH. These alterations may underlie the development of BE and tumor progression. UDCA treatment may inhibit oxidative damage induced by cytotoxic bile acids and gastric acid.