CIP4在肾间质纤维化中的表达及作用

Expression and function of CIP4 in renal interstitial fibrosis

目的 观察骨架调节蛋白CIP4（Cdc42 interacting protein-4）在肾纤维化过程中表达水平、细胞内定位及高表达的CIP4基因对人肾小管上皮细胞E钙黏蛋白（E-cadherin）、波形蛋白（vimentin）的表达和β连环素（β-catenin）酪氨酸磷酸化水平的影响.方法 体外实验以人近端肾小管上皮细胞（HK-2细胞）为研究对象,10 μg/L TGF-β1刺激72 h诱导HK-2细胞转分化;Western印迹法检测各组细胞内CIP4、E-cadherin、vimentin蛋白的表达;RT-PCR法检测细胞内CIP4 mRNA表达水平;激光共聚焦显微镜观察CIP4在细胞内定位.体内实验以SD大鼠为研究对象,5/6肾切除法制作慢性肾纤维化模型;常规检测BUN和Scr水平;Masson染色检测肾组织纤维化水平;免疫组化法检测肾组织内CIP4蛋白的表达和分布.脂质体法介导含野生型CIP4的重组真核表达质粒pcDNA3.1-CIP4或pcDNA3.1-Zeo（空载体）转染HK-2细胞,Wetern印迹法检查转染的效率.稳定转染成功后,Wetern印迹法检测正常组、pcDNA-CIP4转染组和空载体转染组细胞内E-cadherin、vimentin蛋白的表达和β-catenin酪氨酸磷酸化水平.结果 正常HK-2细胞表达E-cadherin和少量的CIP4,几乎不表达vimentin.TGF-β1干预组细胞vimentin蛋白表达增加（P＜0.05）,E-cadherin蛋白表达减少（P＜0.05）,CIP4 mRNA和蛋白表达均显著增多（P＜0.05）.CIP4在正常细胞内大部分在细胞膜,少量在细胞质,在转分化的HK-2细胞表达显著增多,并向细胞质和细胞核聚集.假手术组大鼠肾功能正常,肾组织内未见明显纤维化组织,CIP4在肾小管表达较少,肾小球内几乎不表达;模型组大鼠BUN和Scr增高,肾组织内可见明显纤维化组织,CIP4在肾小管表达明显增加.pcDNA3.1-CIP4转染组较正常组和空载体转染组细胞内CIP4表达增多（P＜0.05）,β-catenin酪氨酸磷酸化水平和vimentin蛋白表达增加（P＜0.05）,而E-cadherin蛋白表达减少（P＜0.05）.结论 CIP4高表达可能参与肾小管上皮细胞-间充质细胞转分化,促进肾间质纤维化.

Objective To observe the expression and localization of CIP4 （Cdc42 interacting protein-4） in the renal fibrosis and the effect of CIP4 on the expression of E-cadherin,vimentin and β-catenin tyrosine phosphorylation. Methods In vitro, the human tubular epithelial cells （HK-2 cell line） were cultured with 10 μg / L TGF-β1 for 72 h. The protein expressions of CIP4, E-cadherin, vimentin and β-catenin tyrosine phosphorylation were measured by Western blotting; the expression of CIP4 mRNA was detected by RT-PCR. The intracellular distribution of CIP4 was observe by confocal microscope. In vivo, Masson staining was used to evaluate the level of renal fibrosis; the expression and distribution of CIP4 in renal tissue were detected by immunohistochemistry. HK-2 cells were transfected with pcDNA3. 1-CIP via lipofectamine 2000. The expressions of E-cadherin, vimentin and β-catenin tyrosine phosphorylation level in the transfected cells were detected by Western blotting. Results The expressions of CIP4 mRNA and protein were up-regulated in renal tubular EMT cells. Most of CIP4 protein localized in cell membrane, and some was in cytoplasm. After stimulation by TGF-β1, the expression of CIP4 protein both in cytoplasm and nucleus was greatly increased （P 〈0.05）,especially in cytoplasm. In vivo, CIP4 was expressed in renal tubular epithelia, but little expressed in glomeruli. In renal from 5/6 nephrectomized rats, CIP4 expression was significantly increased. In the CIP4 transfectants, the expression of CIP4, vimentin and β-catenin tyrosine phosphorylation level were up-regulated （P 〈0.05）, but E-cadherin expression was suppressed （P 〈0.05）.Conclusion The overexpression of CIP4 is likely to take part in the epithelial-to-mesenchymal transition process, thereby promoting the renal fibrosis.