Effects of Thoron Inhalation and Cyclosporin A Treatment on Dextran Sulfate Sodium-Induced Oxidative Damage in Mice

Radon (222Rn; Rn) and thoron (220Rn; Tn) inhalation have been reported to enhance antioxidant activity in various organs. However, the effects of Tn on the colon have not been investigated. This study aimed to clarify the effects of Tn inhalation, alone and in combination with cyclosporin A (CsA), on dextran sulfate sodium (DSS)-induced colitis, and the accompanying oxidative stress, in mice. Male BALB/c mice were subjected to continuous 8-day Tn inhalation (c-Tn, 533±128 Bq/m3) or alternate-day Tn inhalation over the same period (f-Tn, 577±63Bq/m3), followed by treatment with 3% DSS and either CsA or vehicle for 7 days. Although the disease activity index (DAI) decreased significantly by day 2 in the c-Tn group, scores remained significantly higher than those in the f-Tn group. In the c-Tn group, superoxide dismutase and catalase activity in the colon were significantly elevated compared with those in sham controls. Thus, DSS-induced damage was effectively inhibited in the earlier stages by the c-Tn mode of inhalation than by the f-Tn mode. These findings suggest that continuous Tn inhalation more effectively attenuated early colitis symptoms than alternate-day inhalation, potentially through upregulation of antioxidant defenses. Tn and CsA showed no combined effects.