转化生长因子β受体在恶唑酮结肠炎中的表达及临床意义

Significance of transforming growth factor receptors expressing in oxazolone-induced colitis model in mice

目的探讨转化生长因子(TGF)β信号传导通路异常在结肠炎发病中可能的作用机制。方法第0、1天,Balb/c小鼠皮肤涂搽0.2ml3%的恶唑酮,第7天以0.15ml1%的恶唑酮灌肠,第10天处死小鼠,取制模成功的6只小鼠(实验组)及6只未经处理的小鼠(对照组)的结肠组织分别采用免疫组化和蛋白免疫印迹法定性和定量检测TGFβ受体(TGFβR)Ⅰ、TGFβRⅡ、Smad7(TGFβ信号传导的抑制性介质)的表达。结果实验组小鼠均于灌肠后24h内出现厌食,懒动,稀便,便血或大便隐血(+),体重减轻。TGFβRⅠ、TGFβRⅡ、Smad7在对照组主要都表达于结肠腺体上部,在实验组都表达于整个结肠腺体及固有层、黏膜下层。TGFβRⅠ、TGFβRⅡ、Smad7在对照组和实验组的表达量分别为3.40±1.25、21.71±6.97、8.95±2.12和6.49±2.18、4.40±3.34、17.92±6.80。结论恶唑酮结肠炎中TGFβRⅠ表达无改变,TGFβRⅡ表达减少,Smad7表达增高,故该结肠炎中存在TGFβ信号传导通路异常。该模型的病理表现及免疫学特征类似人类溃疡性结肠炎。

Objective To observe the expression of TGFβRⅠ,TGFβRⅡ and Smad7 in oxazolone-induced colitis of mice and to investigate the role of the TGFβ 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 TGFβRⅠ, TGFβRⅡ 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, TGFβRⅠ, TGFβⅡ 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 TGFβRⅠ, TGFβⅡ, Smad7 and the ratio of TGFβRⅠ/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 TGFβRⅡ and increased Smad7 expressions indicate the abnormality of TGFβ signal transduction in oxazolone-induced colitis. These pathologic and immunologic characteristics may resemble human ulcerative colitis.