Sa1783 Nicotine Ameliorates Colonic Inflammation via Down-Regulation of Vascular Endothelial Cell Adhesion Molecules

Abstract

Background Ulcerative colitis (UC) is an intractable disease. Lymphocytes migration to colonic mucosa through endotherial venule like vessel is considered to be largely involved in pathophysiology of UC, and anti-adhesion molecule therapy is one of the established therapy. Although smoking has been reported to have a beneficial effect on UC, pathophysiology of nicotine from the point of lymphocytes trafficking is not studied. We investigated the involvement of nicotine in the colonic inflammation in the following three studies: 1) in vitro effect of nicotine on vascular endothelial cells, 2) in vivo effect of nicotine on inflamed mucosa of murine colitis model, and 3) intravital observation of lymphocyte migration to microvessels. Method 1) Microvascular endothelial cell line, bEnd3, was used. The bEnd3 cells (2x105) were cultured for 3days, and were treated with 5ng/ml TNFα and/or 200μg/ ml nicotine for 5 hours. Degree of mRNA expression of ICAM-1, VCAM-1 and MAdCAM1 was determined by quantitative RT-PCR. 2) C57BL/6J mice were used. For induction of colitis, mice were treated with 3% dextran sodium sulfate (DSS, 40kDa) in drinking water for 7 days. In some group, mice were treated with 0.1mg/ml nicotine in drinking water for 7 days. Disease activity of colitis was assessed by DAI score. We measured mRNA expressions of VCAM-1, ICAM-1 and MAdCAM-1 in the colonic tissue. 3) C57BL/6J mice were treated with 0.1mg/ml nicotine in drinking water 1 day after 3% DSS treatment for 7 days. Mice were injected FITC-labeld lymphocytes (3x107 dissoleved in 0.3ml) obtained from spleen of another mouse, via cervical vein. Microcirculation in the colonic mucosa was observed with a fluorescence microscope. Lymphocytes that moved outside the vessel were counted as transmigrated cells. Result In in vitro study, expression of ICAM-1, VCAM-1 andMAdCAM1 was increased by TNFα. Increase in expression of ICAM-1 by TNFα was not changed by nicotine. However, increase in expression of VCAM-1 and MAdCAM-1 was significantly attenuated by nicotine. In in vivo study, nicotine improved DAI score. Nicotine alone treatment did not affect expression of ICAM-1, VCAM-1 and MAdCAM-1, and DSS treatment significantly increased them. Addition of nicotine treatment to DSS significantly attenuated the increased expression of VCAM-1 and MAdCAM-1 induced by DSS, and tended to inhibit ICAM-1, although not statistically significant. By intravital observation, DSS increased the number of lymphocytes adhering to vascular endothelium and migrating out of vessel. Increase in lymphocytes migration was attenuated by nicotine. Conclusion Microvascular endothelial expression of adhesion molecules, especially VCAM-1 and MAdCAM-1 was significantly inihibited by exposure to nicotine. Down-regulation of vascular adhesion molecules by nicotine may play one of attenuative roles in colonic inflammation.