Hyperbaric oxygen therapy ameliorates TNBS-induced acute distal colitis in rats

Rogério S Parra, Alexandre H Lopes, Eleonora U Carreira, Marley R Feitosa, Fernando Q Cunha, Sérgio B Garcia, Thiago M Cunha, José J R da Rocha, Omar Féres

This study investigated the therapeutic effects of hyperbaric oxygen in experimental acute distal colitis focusing on its effect on the production of pro-inflammatory cytokines, nitric oxide and hypoxia-inducible factor 1alpha. Colitis was induced with a rectal infusion of 150 mg/kg of TNBS under anesthesia with Ketamine (50 mg/kg) and Xylazine (10 mg/kg). Control animals received only rectal saline. After colitis induction, animals were subjected to two sessions of hyperbaric oxygen and were then euthanized. The distal intestine was resected for macroscopic analysis, determination of myeloperoxidase activity, western-blotting analyses of inducible nitric oxide synthase and cyclooxygenase-2 expression and immunohistochemical analysis of hypoxia-inducible factor 1alpha and cyclooxygenase-2. Cytokines levels in the distal intestine were measured using an enzyme-linked immunosorbent assay. Hyperbaric oxygen therapy attenuated the severity of acute distal colitis, with reduced macroscopic damage score. This effect was associated with prevention in the increase of pro-inflammatory cytokine production; myeloperoxidase activity, in the expression of inducible nitric oxide synthase and cyclooxygenase-2. Finally, hyperbaric oxygen inhibited the acute distal colitis-induced up-regulation of hypoxia-inducible factor 1alpha. The results indicate that hyperbaric oxygen attenuates the severity of acute distal colitis through the down-regulation of pro-inflammatory events.