Whole gut lavage fluid interleukin-1β and interleukin-8 in smokers and non-smokers with Crohn's disease in clinical remission

Introduction. Smoking in patients with Crohns disease is associated with more frequent relapse. The mechanism responsible is unknown but a direct pro-inflammatory action on intestinal mucosa has been postulated. Mucosal inflammation in clinically inactive Crohns disease predicts forthcoming relapse. Whole gut lavage fluid obtained after bowel cleansing with a polyethylene glycol electrolyte solution is an assessment of gut inflammation and immunity. Aim. To assess whether whole gut lavage fluid interleukin-1beta and interleukin-8 differed between smokers and non-smokers with clinically inactive Crohns disease. Methods. A total of 34 patients with inactive Crohns disease (Crohns disease activity index <150 and whole gut lavage fluid IgG concentration of <10 mg/ml) underwent whole gut lavage with interleukin-1beta and interleukin-8 analysed by enzyme-linked immunosorbent assay Clinical details and blood markers of inflammation were collected. Results. In this series, 14 patients smoked (10 females, mean age 44.3 +/- 14.3 years], 20 did not (12 females, mean age 40.7 +/- 14.3). Surgical resection was more common in smokers (12/14 vs 8/20, p<0.008). Whole gut lavage fluid IgG was significantly lower, in smokers (median 1.5 mg/ml (range 1.0-8.0 mg/ml) vs median 3.5 mg/ml (range 1.0-7.0 mg/ml), p<0.05). Whole gut lavage fluid interleukin-1beta was also lower in smokers [median 14.5 pg/ml [range 272 pg/ml) vs 26 pg/ml (range 7-1700 pg/ml)], p<0.03. Conclusion. Markers of mucosal inflammation in inactive Crohns disease are lower in smokers than non-smokers. This is against the hypothesis that nicotine exerts a direct pro-inflammatory action via interleukin-1 beta and interleukin-8. Further research is required to elucidate the exact mechanisms involved.