Hyperbaric oxygen: a novel modality to ameliorate experimental colitis

AbstractBackground—Hyperbaric oxygen (HBO) has been suggested to be beneficial ininflammatory bowel disease but the mechanisms responsible for its therapeu tic eVects have not been elucidated.Aim—To assess the eVect of HBO treat ment on colonic damage in two models ofexperimental colitis, and to examine whether this eVect is mediated by modula tion of NO synthesis.Methods—Colitis was induced by either flushing the colon with 2 ml 5% acetic acidor intracolonic administration of 30 mg trinitrobenzenesulphonic acid (TNB) dis solved in 0.25 ml 50% ethanol. Rats were exposed to HBO (100% oxygen at 2.4 atmosphere absolute) for one hour twice on the day of colitis induction and once daily thereafter. Control rats were treated only with acetic acid or TNB. Rats were killed 24 hours after acetic acid adminis tration or one and seven days after TNB treatment. The colon was isolated, washed, and weighed, the lesion area was measured, and mucosal scrapings were processed for determination of myeloper oxidase (MPO) and NO synthase (NOS) activities, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) generation.Results—In control rats exposed for seven days to HBO, colonic NOS activity wassignificantly decreased by 61%, compared with its activity in untreated rats (2.93(0.17) nmol/g/min). HBO significantly re duced by 51 and 62% the extent of injuryinduced by acetic acid and TNB respec tively. The protection provided by HBOwas accompanied by a significant de crease in colonic weight, PGE2 generation,MPO, and NOS activities. In acetic acid colitis, LTB4 generation was also signifi cantly decreased.Conclusions—(1) HBO eVectively de creases colitis induced by acetic acid andTNB. (2) The decreased NOS activity induced by HBO suggests that reductionin NO generation may be among the mechanisms responsible for the anti inflammatory eVect of HBO. (3) HBO may be considered in the treatment of patients with refractory inflammatory bowel disease