[The relationship between adherens junction and tight junction and clinical symptoms in patients with diarrhea predominant irritable bowel syndrome].

Objective: To investigate the association between adherens junction proteins E-cadherin and β-catenin and tight junction protein claudin-2 and clinical symptoms in patients with diarrhea predominant irritable bowel syndrome (IBS-D). Methods: Cecal biopsy tissues were collected from IBS-D patients (n=26) according to Rome Ⅲ criterion and healthy controls (n=26). The duration of symptoms, abdominal pain score and mean weekly bowel movements were recorded. Colorectal dilatation combined with restraint stress were applied to establish visceral hypersensitivity rat model. Abdominal contraction reflex (AWR) was applied to assess the visceral sensitivity in rats. The stool frequency within 1 hour was recorded after establishing the rat model. The expression of E-cadherin、β-catenin and claudin-2 were assessed by Western blot and immunofluorescence microscopy. Intercellular ultrastructure was observed by transmission electron microscopy. Results: Compared with the healthy controls, the protein expression of E-cadherin and β-catenin in cecal epithelium in IBS-D patients were significantly lower (P=0.015 and P=0.005, respectively), while claudin-2 was significantly higher (P=0.000). Reduced E-cadherin and β-catenin expression was associated high abdominal pain score (r=-0.463, P=0.017 and r=-0.407, P=0.039). The lower expression of β-catenin was associated with longer duration of symptoms (r=-0.458, P=0.019). The protein expression of E-cadherin and ß-catenin in the cecal epithelium of the visceral hypersensitivity rats were significantly lower (P=0.004 and P=0.003, respectively), while claudin-2 was significantly higher (P=0.008). Reduced E-cadherin and ß-catenin expression was associated high visceral sensitivity in IBS-D rats (r=-0.639, P=0.047 and r=-0.888, P=0.001). Conclusions: Intercellular ultrastructure alterations well as cecal β-catenin and E-cadherin protein expression decrease and are associated with high abdominal pain score in IBS-D patients and hypersensitivity rats. β-catenin is further associated with prolonged duration of symptoms in IBS-D patients. The expression of E-cadherin and β-catenin may play a vital role in visceral sensitivity and intestinal barrier dysfunction in IBS-D.目的： 探讨黏附连接蛋白E-cadherin、β-catenin及紧密连接蛋白Claudin-2与腹泻型肠易激综合征（IBS-D）患者腹痛及症状持续时间之间的关系。 方法： 根据罗马Ⅲ标准，收集26例IBS-D患者和26例健康对照的回盲部组织标本，记录肠易激综合征（IBS）症状持续时间、腹痛评分及每周排便的次数。20只SD大鼠随机分为两组，模型组和对照组各10只，采用结直肠扩张联合束缚应激的方法构建内脏高敏感大鼠模型，采用腹部收缩反射（AWR）评估大鼠敏感性，记录造模成功后1 h内大鼠排便颗粒数。分别采用蛋白印迹和免疫荧光法检测E-cadherin、β-catenin及Claudin-2的表达和分布，用透射电镜观察细胞间隙改变。 结果： IBS-D患者肠黏膜E-cadherin、β-catenin蛋白表达明显低于健康对照组（P=0.015和P=0.005），而Claudin-2蛋白表达明显高于健康对照组（P=0.000）；免疫荧光观察和透射电镜可见IBS-D患者细胞间紧密连接和黏附连接结构破坏；E-cadherin、β-catenin低表达与IBS-D的腹痛评分呈负相关（分别为r=-0.463，P=0.017和r=-0.407，P=0.039），β-catenin低表达与IBS-D腹痛持续时间呈负相关（r=-0.458，P=0.019）。内脏高敏感大鼠肠黏膜E-cadherin、β-catenin蛋白表达明显低于对照组（P=0.004和P=0.003），而Claudin-2蛋白表达明显高于对照组（P=0.008）；E-cadherin、β-catenin低表达与IBS大鼠的内脏高敏感呈负相关（r=-0.639，P=0.047和r=-0.888，P=0.001）。 结论： IBS-D患者和内脏高敏感大鼠的回盲部黏附连接和紧密连接的微观结构和蛋白表达发生改变，E-cadherin、β-catenin蛋白表达降低，其与IBS-D患者腹痛评分相关，和大鼠内脏高敏感相关，β-catenin更与IBS-D患者腹痛持续时间相关。黏附连接蛋白E-cadherin、β-catenin改变可能在IBS内脏高敏感及肠黏膜屏障障碍中发挥重要作用。.