Objective: To investigate the mechanism by which fibroblasts with high WNT2b expression causes intestinal mucosa barrier disruption and promote the progression of inflammatory bowel disease (IBD).
Methods: Caco-2 cells were treated with 20% fibroblast conditioned medium or co-cultured with fibroblasts highly expressing WNT2b, with the cells without treatment with the conditioned medium and cells co-cultured with wild-type fibroblasts as the control groups. The changes in barrier permeability of Caco-2 cells were assessed by measuring transmembrane resistance and Lucifer Yellow permeability. In Caco-2 cells co-cultured with WNT2b-overexpressing or control intestinal fibroblasts, nuclear entry of β-catenin was detected with immunofluorescence assay, and the expressions of tight junction proteins ZO-1 and E-cadherin were detected with Western blotting. In a C57 mouse model of dextran sulfate sodium (DSS)-induced IBD-like enteritis, the therapeutic effect of intraperitoneal injection of salinomycin (5 mg/kg, an inhibitor of WNT/β-catenin signaling pathway) was evaluated by observing the changes in intestinal inflammation and detecting the expressions of tight junction proteins.
Results: In the coculture system, WNT2b overexpression in the fibroblasts significantly promoted nuclear entry of β-catenin (P < 0.01) and decreased the expressions of tight junction proteins in Caco-2 cells; knockdown of FZD4 expression in Caco-2 cells obviously reversed this effect. In DSS-treated mice, salinomycin treatment significantly reduced intestinal inflammation and increased the expressions of tight junction proteins in the intestinal mucosa.
Conclusion: Intestinal fibroblasts overexpressing WNT2b causes impairment of intestinal mucosal barrier function and can be a potential target for treatment of IBD.
目的: 探讨WNT2b高表达成纤维细胞破坏肠黏膜,促进炎症性肠病(IBD)进展的机制。
方法: 通过体外细胞共培养及条件培养,构建成纤维细胞对Caco-2细胞的作用模型。实验组为加入20%成纤维细胞条件培养基或与WNT2b高表达成纤维细胞共培养,对照组为不含条件培养基或与野生型成纤维细胞共培养,通过跨膜电阻和荧光黄渗透率测定,评估Caco-2细胞屏障通透性的变化。与WNT2b高表达或对照肠道成纤维细胞共培养后,使用免疫荧光法检测Caco-2细胞β-catenin入核情况,使用Western blot法检测ZO-1、E-Cadherin等紧密连接蛋白表达情况。采用DSS(葡聚糖硫酸钠)对C57小鼠进行类IBD肠炎造模,实验组使用Salinomycin(5 mg/kg,腹腔注射),对照组为对应溶剂生理盐水,分别对小鼠进行处理,评价该抑制剂对肠炎的治疗作用。
结果: 与对照组相比,过表达WNT2b基因可致成纤维细胞分泌WNT2b蛋白显著增加,并促进Caco-2细胞β-catenin入核(P < 0.01),紧密连接蛋白表达下降; Caco-2细胞中敲低FZD4表达可逆转这一作用。Salinomycin可明显减轻对DSS小鼠肠道炎症并使肠黏膜紧密连接蛋白表达增多。
结论: WNT2b高表达成纤维细胞破坏肠黏膜屏障功能,是治疗IBD的潜在靶点。
Keywords: WNT/β-catenin signaling pathway; WNT2b; fibroblasts; inflammatory bowel disease.