Divergent effects of nicotine administration on cytokine levels in rat small bowel mucosa, colonic mucosa, and blood.

BACKGROUND Chronic nicotine administration has a dual effect on inflammatory bowel disease: augmentation of jejunitis and amelioration of colitis. We previously showed that chronic nicotine administration has divergent regional effects on small bowel and colonic mucosal mediators and blood flow. OBJECTIVE To examine the effects of nicotine administration on cytokine levels in normal rat small bowel mucosa, colonic mucosa, and blood. METHODS Male Sprague-Dawley rats weighing 200-250 g were given nicotine (12.5 micrograms/ml) that was dissolved in tap water. Rats were sacrificed on days 1, 2, 7 and 14 after nicotine initiation; blood was withdrawn, and small bowel and colon were resected, washed and weighed. Mucosal scrapings were extracted in 2 ml Krebs-Hemselest buffer for determination of interleukins-2, 6 and 10 using the Biosource International Immunoassay Kit. RESULTS Nicotine decreased IL-10 and increased IL-6 levels in small bowel mucosa (from 3.5 +/- 0.5 to 0.4 +/- 0.1 pg/ml and from 1.9 +/- 0.4 to 13.6 +/- 0.4 pg/ml respectively; P < 0.05). Nicotine decreased IL-2 levels in the colon (from 15.8 +/- 3.0 to 7.9 +/- 1.0 pg/ml; P < 0.05), having no effect on IL-10 or IL-6 levels. Rats treated with nicotine had lower IL-6 and IL-2 blood levels compared to control rats. CONCLUSIONS Nicotine has different regional effects on small bowel and colonic cytokine mucosal levels, which might explain some of its opposite effects on small bowel and colonic inflammation.