Abstract: | Background—Hyperbaric oxygen (HBO) has beensuggested to be beneficial in inflammatory bowel disease but themechanisms responsible for its therapeutic effects have not been elucidated. Aim—To assess the effect of HBO treatment oncolonic damage in two models of experimental colitis, and to examinewhether this effect is mediated by modulation of NO synthesis. Methods—Colitis was induced by either flushing thecolon with 2 ml 5% acetic acid or intracolonic administration of 30 mg trinitrobenzenesulphonic acid (TNB) dissolved in 0.25 ml 50% ethanol. Rats were exposed to HBO (100% oxygen at 2.4 atmosphere absolute) forone 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 administration or one andseven days after TNB treatment. The colon was isolated, washed, andweighed, the lesion area was measured, and mucosal scrapings wereprocessed for determination of myeloperoxidase (MPO) and NO synthase(NOS) activities, prostaglandin E2 (PGE2) andleukotriene B4 (LTB4) generation. Results—In control rats exposed for seven days toHBO, colonic NOS activity was significantly decreased by 61%, comparedwith its activity in untreated rats (2.93 (0.17) nmol/g/min). HBOsignificantly reduced by 51 and 62% the extent of injury induced byacetic acid and TNB respectively. The protection provided by HBO wasaccompanied by a significant decrease in colonic weight,PGE2 generation, MPO, and NOS activities. In acetic acidcolitis, LTB4 generation was also significantly decreased. Conclusions—(1) HBO effectively decreases colitisinduced by acetic acid and TNB. (2) The decreased NOS activity inducedby HBO suggests that reduction in NO generation may be among the mechanisms responsible for the anti-inflammatory effect of HBO. (3) HBOmay be considered in the treatment of patients with refractory inflammatory bowel disease.
Keywords:hyperbaric oxygen; acetic acid colitis; trinitrobenzenesulphonic acid colitis; inflammatory bowel disease |