ABSTRACT
Objective To observe the expression of TGF?RⅠ,TGF?RⅡ and Smad7 in oxazolone-induced colitis of mice and to investigate the role of the TGF? signal transduction on pathogenesis of colitis. Methods Balb/c mice were pre-sensitized by skin painting with 0.2 ml 3% oxazolone on day 0 and 1 followed by intrarectal administration of 0.15 ml 1% oxazolone on day 7. The mice were sacrificed after 3 days. Colitis was evaluated by macroscopic and microscopic examination. The expressions of TGF?RⅠ, TGF?RⅡ and Smad 7 were examined by immunohistochemical study and Western blot respectively. All the results were compared with the controls. Results Twenty-four hours after intrarectal administration of oxazolone, the mice presented anorexia, less moving, loose stool, hematochezia or occult blood(+) and weight loss. The macroscopic and microscopic scores in two groups were 0.17?0.41, 2.67?1.03 and 2.33?0.52, 8.17?0.75, respectively. In the normal intestine, TGF?RⅠ, TGF?Ⅱ and Smad7 were mainly co-localized on the upper part of the villus. However, their expression was not only throughout the villus including fundus of crypts, but also in the mononuclear cells of the lamina propria and submucosa in the experimental intestine. The amounts of TGF?RⅠ, TGF?Ⅱ, Smad7 and the ratio of TGF?RⅠ/Ⅱ in control and colitis groups were 3.40?1.25, 21.71?6.97, 8.95?2.12, 0.16?0.01 and 6.49?3.18, 4.40?3.34, 17.92?6.80, 2.14?1.61, respectively. Conclusions Decreased TGF?RⅡ and increased Smad7 expressions indicate the abnormality of TGF? signal transduction in oxazolone-induced colitis. These pathologic and immunologic characteristics may resemble human ulcerative colitis.