蛋白酶体抑制剂MG132对早期糖尿病肾病大鼠Smad7表达的影响

Effect of proteasome inhibitor MG132 on Smad7 expression in early diabetic nephropathy rat

目的观察蛋白酶体抑制剂MG132对早期糖尿病肾病大鼠的治疗作用及其对肾脏中Smad7蛋白表达的影响。方法将45只健康雄性Wistar大鼠随机分为正常对照组(NC组,n=10);糖尿病模型组35只,用链脲佐菌素诱导糖尿病大鼠模型后30只纳入实验,分为糖尿病组(DC组,n=10),MG132高浓度组(MH组,n=10),MG132低浓度组(ML组,n=10)。MH组与ML组给予MG132腹腔注射,NC组和DC组予以等量生理盐水腹腔注射,各组喂养至6周和8周时分别处死5只大鼠。处死前测量大鼠体重,心脏取血测空腹血糖。电镜观察肾脏超微结构变化,Western blot检测各组Smad7蛋白表达水平。结果 (1)各模型组较NC组体重明显减轻,空腹血糖显著升高(P<0.01);各模型组大鼠体重8周后较6周后减轻(P<0.05)。MH组、ML组较DC组体重增加(P<0.05);但各模型组间空腹血糖无统计学差异(P>0.05)。(2)电镜下各模型组均可见部分基底膜不规则增厚、足突间隙增宽或融合、内皮细胞水肿。以上改变MH组、ML组较DC组轻,MH组较ML组轻;各模型组8周病理改变与6周相比无明显减轻。(3)与NC组比较,DC组Smad7蛋白表达降低(P<0.01);与DC组比较,MH、ML组Smad7表达增加(P<0.05)。MH组较ML组Smad7蛋白表达显著增加(P<0.05);随时间延长,8周与6周间差异愈加显著(P<0.05)。结论糖尿病肾病时Smad7泛素化降解增加;蛋白酶体抑制剂MG132可抑制Smad7的泛素化降解,增加Smad7蛋白表达。

Objective To observe the therapeutic effect of proteasome inhibitor MG132 on the early diabetic nephropathy rat and the expression of the Smad7 protein in kidney.Methods 45 healthy male Wistar rats were randomly divided into normal control group(NC group,n=10),diabetic models group(n=35).30 rats in diabetes models group were internalized the experiment after being induced by streptozotion,and divided into diabetic group(DC group,n=10),the high MG132 concentration group(MH group,n=10),the low MG132 concentration group(ML group,n=10).MH group and ML group received MG132 by intraperitoneal injection,meanwhile,NC group and DC group were treated by equal normal saline intraperitoneal injection daily.Half of rats in each group were sacrificed at 6 weeks and 8 weeks after treatment.Body weight(BW)of the rats were measured,and heart blood samples were taken to measure the fasting plasma glucose(FPG),as the ultrastructure of rat kidney changes were observed by electron microscopic and the expression level of Smad7 protein was detected by Western blot.Results (1)In each model group,the BW decreased obviously,but the FPG increased significantly compared with NC group(P<0.01).While the BW of each model groups decreased at 8 weeks compared with 6 weeks(P<0.05),and that in MH,ML group increased compared with DC group(P<0.05);but there was no statistical difference among each model groups in FPG(P>0.05).(2)Under the electron microscope,in all model groups glomerular basement membrane was thickened,foot process gap was widen or fusion and endothelial cells were edematous partly.These changes of MH group were milder compare with ML group,while that in DC group were the most apparent.But there were no statistical significances between 8 weeks and 6 weeks in each group.(3)Compared with NC group,the expression of Smad7 decreased in DC group(P<0.01).After the rats were treated with MG132,there were statistical significances among MH and ML group(P<0.05).With time,the differences between 6 weeks and 8 weeks were more obvious(P<0.05).Conclusions The ubiquitin degradation of Smad7 increased in diabetic nephropathy.Proteasome inhibitor MG132 could inhibit Smad7 ubiquitin degradation and increase the expression of Smad7.