Imbalance of the antioxidant network of mouse small intestinal mucosa after radiation exposure.

The aim of this study was to investigate acute variations in antioxidant defense systems in the intestinal mucosa after abdominal radiation exposure and the role played by radiation-induced inflammation in these variations. Antioxidant defense systems of mouse small intestinal mucosa were studied at 6 h and 4 days after abdominal radiation exposure. Superoxide dismutases, glutathione peroxidases, catalase, metallothioneins and thioredoxins were followed in terms of mRNA expression, protein expression and enzyme activities. Dexamethasone was administered to investigate the relationship between variations in mucosal antioxidant capacity and radiation-induced inflammation. Six hours after exposure, only mitochondrial-associated antioxidant systems were induced (the superoxide dismutase and thioredoxin 2). Four days after exposure, during the inflammatory phase, superoxide dismutases were decreased and modulations of the second line of the antioxidant network were also observed: Catalase was decreased and glutathione peroxidases and metallothioneins were induced. Dexamethasone treatment modulated only glutathione peroxidase expression and did not influence either metallothionein or superoxide dismutase expression. Our findings provide direct in vivo evidence that antioxidant mechanisms of the small intestinal mucosa were not markedly mobilized during the very acute tissue radiation response. During the radiation-induced acute inflammatory response, the antioxidant capacity appeared to be dependent on inflammatory status to a certain extent.