磷酸化Smad3对糖尿病大鼠肾组织SnoN表达的影响

摘要

Objective To explore the effect of phosphorylated Sma and Mad Homologue 3 (Smad3) on expression of transcription co-repressor Ski-related protein N (SnoN) protein in the kidney of diabetes mellitus (DM) rats.Methods The DM rats were induced by intraperitoneal injection of streptozotocin (STZ).Rats in different groups were killed at 2, 4, 8, 12, 16 and 24 weeks, respectively, after inducing DM.Meanwhile, the rats in age-matched groups as normal control were treated at the same period.Glucose and protein in urine collected within 24 hours were measured by biochemistry methods.PAS staining was used to observe the renal pathological changes.The protein levels of phosphorylated Smad3, SnoN, transforming growth factor-β1 ( TGF-β1 ), Smad2/3 and anaphase promoting complex (APC) in renal tissues were examined by immunohistochemical staining and Western blotting.The RT-PCR was employed to determine the expression of SnoN mRNA in renal cortex.Results Levels of blood glucose and 24 h-urine protein were remarkably increased in DM rats as compared with controls.The protein levels of phosphorylated Smad3, TGF-β1 and Smad2/3 were significantly up-regulated in the kidney of DM rats.There was a significant decrease of SnoN protein from DM4 week, the SnoN mRNA levels was unchanged in each diabetes group.Conclusions Phosphorylated Smad3 and APC may play a key role in the ubiquitin of SnoN protein.%目的 探讨磷酸化Smad3(p-Smad3)在糖尿病(DM)大鼠肾组织SnoN蛋白表达的影响.方法 链脲佐菌素诱发大鼠DM模型,分为DM2、4、8、12、16和24 w组(n=6),每组均设鼠龄匹配的正常对照组(n=6).生化方法测血糖和24 h尿蛋白;PAS染色观察肾组织病理学改变;免疫组化检测肾组织SnoN、Smad2/3和E3泛素连接酶APC10蛋白的表达;Western印迹方法动态观察肾皮质SnoN、p-Smad3、转化生长因子-β1(TGF-β1)和Smad2/3蛋白的表达;RT-PCR检测SnoN mRNA.结果 DM各组大鼠血糖和24 h尿蛋白较正常对照组均显著升高; SnoN和Smad2/3阳性染色主要见于肾小管上皮细胞,DM 2 w起 Smad2/3和 p-Smad3蛋白表达多于正常对照组,DM 4 w起 SnoN蛋白少于正常对照组;各DM组肾组织TGF-β1、Smad2/3和APC10 蛋白表达均多于正常对照组;DM各组SnoN mRNA与正常组相比差异无统计学意义.结论 糖尿病肾病发病过程中p-Smad3可能与APC一起介导了SnoN蛋白的泛素化降解过程.