泛素蛋白酶体途径对高糖刺激的肾系膜细胞Smad7表达的影响

目的:观察不同浓度高糖刺激后大鼠肾系膜细胞胞内Smad泛素化调节因子－Smurf2和Smad7 的表达，并以蛋白酶体特异性抑制剂MG132作为阻断剂，探讨泛素化降解在Smad信号中的作用。方法：将体外培养的大鼠肾小球系膜细胞分别设正常对照组（葡萄糖浓度5.6 mmol/L）、20 mmol/L高糖组、30 mmol/L高糖组、30 mmol/L高糖加蛋白酶体抑制剂MG132组等。用细胞免疫荧光染色法及激光共聚焦显微镜检测各组细胞泛素连接酶Smurf2及Smad7的表达。结果：(1)正常组细胞Smurf2蛋白表达较弱（25.93±3.35），Smad7蛋白表达较强（64.09±7.43）。(2)高糖组Smurf2表达较正常组增强(P<0.05)，呈浓度依赖性，荧光灰度值分别为20 mmol/L高糖组（56.99±7.00）、30 mmol/L高糖组（96.36±9.19）；Smad7表达减弱(P<0.05)，呈浓度依赖性，分别为20 mmol/L高糖组（45.33±6.67）、30 mmol/L高糖组（30.20±4.41）。（3）30 mmol/L高糖组加入MG132后，Smurf2表达减弱、Smad7表达增强。结论：（1）高糖可诱导肾系膜细胞Smurf2表达增强，Smad7表达减弱。(2)MG132可阻止高糖所导致的上述变化。提示泛素－蛋白酶体途径参与了糖尿病肾病Smad通路的信号调节。

Effect of ubiquitin-proteasome pathway on expression of Smad7 in cultured glomerular mesangial cells induced by high concentration of glucose

AIM:To observe the expression of Smad7 and Smad ubiquition regulatory factor-Smurf2 in rat glomerular mesangial cells (GMC) stimulated by the high concentration of glucose, and to investigate the effect of the ubiquition on Smad signaling by adding MG132 as a proteasome differential inhibitor.METHODS:Cultured rat GMC were divided into normal group (the concentration of glucose:5.6 mmol/L), high glucose group (20 mmol/L, 30 mmol/L, respectively), therapy group (30 mmol/L glucose with MG132).The expressions of Smurf2 and Smad7 in each group were measured by indirect immunofluorescence and laser scanning confocal microscope.RESULTS:(1) The expression of Smurf2 in GMC in normal group was weak (25.93±3.35) whereas the expression of Smad7 was strong (64.09±7.43).(2) The expression of Smurf2 in high glucose group was stronger than that in normal group (P<0.05), in a concentration-dependent manner, 20 mmol/L high glucose (56.99±7.00), 30 mmol/L high glucose (96.36±9.19), respectively.The expression of Smad7 in high glucose group was weakened (P<0.05), 20 mmol/L high glucose (45.33±6.67), 30 mmol/L high glucose (30.20±4.41), respectively.(3) In therapy group, the expression of Smurf2 was found weakened and expression of Smad7 was enhanced.CONCLUSION:(1) High glucose increases the expression of Smurf2 and decreases the expression of Smad7 in glomerular mesangial cells.(2) Ubiquition-proteasome pathway (UPP) is related with the regulation of Smad signal transduction pathways in diabetic nephropathy.