高糖通过转化生长因子β1-Smad信号传递途径诱导肾小管上皮细胞转分化

目的 通过观察高糖对肾小管上皮细胞转分化(EMT)的作用，探讨其与转化生长因子β1 (TGF-β1)的关系及糖尿病肾病肾小管间质纤维化的发病机制。 方法 以人肾小管上皮细胞株HKC细胞和高表达Smad7蛋白的HKC转染细胞株为研究对象。蛋白印迹法检测高糖(葡萄糖浓度分别为25和50 mmol/L)对α平滑肌肌动蛋白(α-SMA)、E钙黏蛋白 (E-cadherin)和纤连蛋白(FN)表达的影响。酶联免疫吸附(ELISA)法检测TGF-β1的水平。Boyden小室检测HKC细胞的迁移能力。抗TGF-β1抗体中和实验分析高糖对肾小管EMT作用及与TGF-β1的关系。 结果 持续的高糖作用(96 h)能够导致HKC表达α-SMA蛋白，其中25和50 mmol/L的葡萄糖分别增加表达α-SMA 2.8倍和8.2倍；降低E-cadherin的表达；刺激合成FN。25和50 mmol/L的葡萄糖刺激HKC 12 h后，细胞培养上清液中TGF-β1浓度分别为(408.5±198.6)和(939.3±311.8) ng/L，呈剂量依赖性。抗TGF-β1抗体能够显著抑制高糖导致的HKC高表达α-SMA蛋白和FN及降低E-cadherin表达的作用。高表达Smad7蛋白的HKC转染细胞株在高糖的持续作用下，不能表达α-SMA和FN蛋白，E-cadherin也未见降低。细胞迁移实验表明，25和50 mmol/L高糖能够增加HKC迁移至Boyden小室膜下侧面的细胞数(12.4±3.7)和（18.6±4.4)细胞/HP）]，与正常对照组(3.0±0.8)细胞/HP]差异有统计学意义(P < 0.01)。抗TGF-β1多克隆抗体能够部分抑制高糖(50 mmol/L)造成的HKC细胞向Boyden小室膜下侧面的迁移(11.9±5.2)细胞/HP]。高表达Smad7蛋白的HKC转染细胞株在高糖培养条件下迁移至Boyden小室膜下侧面的细胞数（4.3±1.2）细胞/HP]与正常对照组差异无统计学意义。 结论 高糖能够诱导肾小管EMT，此作用与高糖刺激该细胞合成TGF-β1有关，阻止Smad信号途径能够拮抗TGF-β1介导的肾小管EMT的作用。

High glucose induces renal epithelial-mesenchymal transition through transforming growth factor β1-Smad signaling pathway

Objective To investigate the effect of high glucose on renal tubular epithelial-mesenchymal transition,and to analyze the relationship between high glucose and transforming growth factor β1(TGF-β1)and the mechanism of renal interstitial fibrosis. Methods HKC and Smad7-overexpression HKC cells were grown in DMEM/F12 medium containing 5%～10%newborn calf serum.They were cultured for 16 h in free serum medium after 80%cells were adhered onto the surface of the flask.Afterwards,they were stimulated by high glucose(glucose concentration:25 mmol/L and 50 mmol/L).The expression of α-SMA,E-cadherin and fibronectin was detected by Western blot while the supernatant level of TGF-β1 was detected by ELISA.Cell motility and migration was evaluated using Boyden chamber motogenicity assay. Results In HKC induced by high glucose,the expression of α-SMA and fibronectin protein was highly upregulated while the expression of E-cadhefin protein was down-regulated.The expression of TGF-β1was up-regulated in a dose-dependent manner.These above-mentioned effects could be obviously inhibited by anti-TGF-β1 antibody.The protein expression of α-SMA,fibronectin and E-cadherin had no obvious change in Smad7-overexpression HKC induced by high glucose.HKC exhibited enhanced motility and invasive capacity in high glucose groups,compared to that in control group.Migrated cell counting was(12.4±3.7)and(18.6±4.4)cell/HP in 25 and 50 mmol/L glucose groups respectively. Conclusion High glucose may induce renal tubular epithelialmesenchymal transition through TGF-β1 pathway,which can be inhibited by blocking the Smad signal pathway.