葡聚糖硫酸钠诱导炎症性肠病大鼠结肠黏膜紧密连接蛋白表达及其通透性的改变

目的：建立葡聚糖硫酸钠（DSS）诱导的大鼠炎症性肠病（IBD）模型，观察其肠上皮紧密连接蛋白表达以及结肠黏膜通透性的变化。方法：将雄性Sprague-Dawley（SD）大鼠随机分为对照组和IBD模型组，每组27只，通过使用3% DSS持续经饮水途径饲养大鼠6 d后恢复正常饮水14 d建立IBD模型，对照组自由饮水。分别于DSS处理后第7天、第14天和第21天观察结肠黏膜病理变化，第21天取结肠组织标本检测髓过氧化物酶活性；采用Ussing chamber检测结肠上皮通透性；通过real-time PCR和Western blot从转录水平和翻译水平分析肠上皮紧密连接蛋白表达。结果：IBD模型组大鼠出现腹泻、便血、体重下降，炎症集中在远端结肠，表现为隐窝脓肿，炎症细胞浸润。与对照组比较，IBD模型组大鼠结肠髓过氧化物酶活性显著增加（P<0.01），肠上皮跨膜电阻抗值和跨膜电势差显著降低（P<0.01），短路电流值明显增加（P<0.01）；Real-time PCR和Western blot的结果均提示正常大鼠尚未检测出claudin2的表达，IBD模型组 claudin2 mRNA及蛋白表达阳性；IBD模型组 occludin、claudin3、ZO-1 mRNA及蛋白表达水平均显著低于对照组（P<0.01）。结论：IBD大鼠结肠黏膜屏障功能受损，多种紧密蛋白表达改变，其中紧密连接蛋白表达变化可能在慢性修复期IBD屏障受损发病机制中起到重要作用。

Changes in tight junction protein expression and permeability of colon mucosa in rats with dextran sulfate sodium-induced inflammatory bowel disease

Objective To develop an experimental rat model of inflammatory bowel disease(IBD) by administration of dextran sulfate sodium(DSS),and to observe changes in the tight junction protein expression and permeability of colon mucosa.Methods Male Sprague-Dawley(SD) rats were randomly divided into control(n=27) and IBD model groups(n=27).In the IBD model group,IBD was induced by 6-day administration of 3% DSS in water followed by 14-day administration of water only.The control group was fed with water only.Pathological changes in colon mucosae were observed on days 7,14 and 21 after DSS administration.Colon tissue specimens were collected on day 21 for measuring myeloperoxidase(MPO) activity.The transepithelial electric resistance(TEER),transepithelial potential difference(TEPD) and short circuit current(Isc) of the specimens were measured by Ussing chamber.Real-time PCR and Western blot were used to measure the mRNA and protein expression of tight junction proteins in colon epithelia.Results In the IBD model group,diarrhea,hemafecia and weight loss were seen.Inflammation occurred mainly in the distal colon and was characterized by crypt abscess and inflammatory cell infiltration.The IBD model group showed significantly increased MPO activity(P<0.01),significantly decreased TEER(P<0.01) and TEPD(P<0.01),and significantly increased Isc(P<0.01) compared with the control group.No claudin 2 expression of mRNA and protein was detected in the control group,and they were expressed in the IBD model group.The expression levels of claudin 3,occludin and ZO-1 in the IBD model group were significantly decreased compared with in the control group(P<0.01).Conclusions IBD rats show colonic barrier dysfunction and changes in the expression of tight junction proteins.The changes in the expression of tight junction proteins may contribute to colonic barrier dysfunction in cases of IBD in the chronic recovery stage.