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 Crohn's 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 Crohn's 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-1β and interleukin-8 differed between smokers and non-smokers with clinically inactive Crohn's disease. Methods. A total of 34 patients with inactive Crohn's disease (Crohn's disease activity index <150 and whole gut lavage fluid IgG concentration of <10 mg/ml) underwent whole gut lavage with interleukin-1β 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-1β was also lower in smokers (median 14.5 pg/ml (range 2-72 pg/ml) vs 26 pg/ml (range 7-1700 pg/ml)], p<0.03. Conclusion. Markers of mucosal inflammation in inactive Crohn's disease are lower in smokers than non-smokers. This is against the hypothesis that nicotine exerts a direct pro-inflammatory action via interleukin-1β and interleukin-8. Further research is required to elucidate the exact mechanisms involved.