Aggravating effect of cigarette smoke exposure on experimental colitis is associated with leukotriene B₄ and reactive oxygen metabolites

Background/Aims: Cigarette smoking is closely related to the development and recurrence of inflammatory bowel disease (IBD). The present study aimed to investigate the underlying mechanisms of the adverse action of cigarette smoke (CS) exposure on trinitrobenzene sulfonic acid (TNBS)-induced IBD. Methods: Rats were preexposed to CS once daily for 4 days before receiving a TNBS enema, and they were killed 24 h afterwards. The colonic myeloperoxidase (MPO) and xanthine oxidase (XO) activities, leukotriene B₄ (LTB₄) and glutathione (GSH) levels, as well as the production of reactive oxygen metabolites (ROMs) were measured. Results: CS preexposure significantly augmented the adverse effects of the TNBS enema on colonic damage and increase in MPO activity, while it did not significantly alter the XO activity. Meanwhile, the elevation of ROM production and LTB₄ concentration in colonic tissues after the TNBS enema was also markedly enhanced by CS exposure. In contrast, the depressive action of the TNBS enema on cellular antioxidant GSH levels was reduced further by CS exposure. Pretreatment with a specific LTB₄ antagonist, ONO-4057, protected against colonic damage, particularly in the CS group. Conclusion: CS exposure aggravated experimental IBD. This adverse action could be due to the depletion of GSH together with overproduction of LTB₄, followed by the accumulation of neutrophils and ROMs in the colonic tissue.