TGF-β1及其信号蛋白在大鼠腹膜纤维化模型腹膜组织中的表达及可能作用

目的了解TGFβ1/Smads信号蛋白在高浓度葡萄糖透析液及炎症所致大鼠腹膜纤维化模型腹膜组织中的表达及在腹膜纤维化发生中的可能作用。方法24只SD雄性大鼠(180～200g)随机分为4组,每组6只。正常对照组,大鼠不做任何处理;LPS组,LPS用生理盐水稀释为0.6mg/100ml,在第1、3、5、7日按0.6mg/kg体重腹腔注射;4.25%透析液组,大鼠给予每日腹腔注射100ml/kg体重高糖透析液;LPS+4.25%透析液组,除每日腹腔注射100ml/kg体重高糖透析液外,LPS用4.25%透析液稀释为0.6mg/100ml,在第1、3、5、7日按0.6mg/kg体重腹腔注射;于实验第28天杀检动物,取壁层和脏层腹膜组织行光镜及电镜检查。用RTPCR及间接免疫荧光、Western杂交的方法检测αSMA、TGFβ1、Smad3、Smad7、pSmad2/3、ColⅠmRNA和蛋白的表达水平。结果Masson染色显示,与正常对照组比较,4W时各组壁层腹膜组织明显增厚,有大量胶原沉积,其中LPS+4.25%透析液组厚度最为显著(vsLPS组:42μm±3μmvs35μm±4μm,P=0.007,vs4.25%透析液组,42μm±3μmvs20μm±4μm,P=0.000);与正常对照组比较,三组αSMA、ColⅠ和TGFβ1、Smad3、pSmad2/3在脏层腹膜组织中的表达水平显著上调,上述变化以LPS+4.25%透析液组改变最为显著,TGFβ1mRNA为正常对照组的2倍,Smad3mRNA为正常对照组的1.8倍;与正常对照组比较,抑制性信号蛋白Smad7mRNA和蛋白表达水平在其他三组也有不同程度的上调,但Western杂交结果显示,pSmad/Smad7蛋白比值仍明显升高;电镜结果显示,除正常对照组外,各组间皮细胞均有损伤,LPS+4.25%透析液组的间皮细胞损伤最为明显,而且胞浆中出现明显的肌丝和密体。结论TGFβ1/Smads信号蛋白的活化是高浓度葡萄糖透析液和LPS导致大鼠腹膜发生纤维化的共同作用途径。高浓度葡萄糖透析液和LPS可能协同作用通过TGFβ1/Smads通路刺激腹膜间皮细胞转分化,介导腹膜纤维化的发生。

The role of TGF-beta1/Smads in the development of peritoneal fibrosis induced by high glucose peritoneal dialysate and LPS

OBJECTIVE: To investigate the expression and the potential role of TGF-beta/Smads in peritoneal fibrosis induced by high glucose dialysate and LPS in rats. METHODS: 24 male Sprague-Dawley rats were randomly allocated into four groups: control group, normal rats; LPS group: rats were treated with intraperitoneal injection of LPS (0.6 mg/kg body weight) on days 1, 3, 5, 7; dialysate Group: rats were treated with daily intraperitoneal injection of 4.25% peritoneal dialysate (100 ml/kg body weight) for 4 weeks; LPS + dialysate Group: daily intraperitoneal injection of 4.25% dialysate combined with four times injection of LPS (0.6 mg/kg body weight on days 1, 3, 5, 7) for 4 weeks. The parietal thickness was measured with masson stain. The expression of alpha-SMA, TGF-beta1, Smad 2/3, Smad 7 and ColI in peritoneal membrane was detected with confocal microscope by immuno-flurence, Western-blot and RT-PCR. RESULTS: Masson stain show the parietal thickness of the rats in all groups was significantly increased compared with control group and collagen deposition was evident in the thickened submesthelial compact zone. Parietal thickness of the rats in LPS + dialysate Group was most (vs LPS group: 41.5 +/- 3.3 microm vs 34.70 +/- 3.6 microm, P = 0.007, vs dialysate Group, 41.5 +/- 3.3 microm vs 20.2 +/- 3.6 microm, P = 0.000). The expression of alpha-SMA, Col I, TGF-beta1, Smad 3 was up-regulated in protein and mRNA level and the protein level of phosphorylated-Smad 2/3 was increased significantly. The most significant changes were found in LPS + dialysate Group. Compared with control group the mRNA and protein level of Smad7 was increased, but the protein ratio of phosphorylated Smad/Smad 7 in all groups was higher. Under electro-microscope, the mesothelial cells in LPS + dialysate Group had myofibroblast morphology with the presence of large bundles of actin microfilaments and dense bodies within the cytoplasm. CONCLUSIONS: High concentration glucose dialysate or LPS contributes to peritoneal fibrosis by stimulating TGF-beta/Smads signaling. 4.25% peritoneal dialysate can coordinate with LPS to activate TGF-beta/Smads signaling pathway and induce mesenchymal transdifferention and peritoneal fibrosis.