高糖通过PI3K-AKT-mTOR信号通路增加足细胞自噬

High glucose increases podocyte autophagy through PI3K- AKT- mTOR signaling pathway

目的研究高糖引起足细胞自噬变化及其相关的信号机制。方法培养的足细胞被分为6组，正常浓度葡萄糖（NG）组、高浓度葡萄糖（HG）组、NG＋雷帕霉素（Rap）组、HG＋Rap组、NG＋LY294002组和HG＋LY294002组。观察自噬增强剂Rap和P13K抑制剂LY294002对高糖条件下培养的足细胞自噬和凋亡的影响。电镜和吖啶橙染色观察细胞内自噬体的形成；Western印迹检测自噬标志蛋白微管相关蛋白1轻链3（LC3）和自噬血管基因Beelin-1的表达；通过阻断自噬的信号通路观察磷脂酰肌醇3激酶-蛋白激酶B-哺乳动物雷帕霉素靶蛋白（P13K-AKT-mTOR）相关蛋白AKT和mTOR的磷酸化水平的改变。结果高糖可导致足细胞凋亡增加，促进足细胞内自噬体和自噬相关蛋白表达增加（均P〈0．05）。与高糖组相比，HG＋Rap组LC3-Ⅱ和Beelin-1的表达增加（均P〈0．05）；LY294002部分抑制高糖导致的LC3-Ⅱ和Beelin-1表达增加（均P〈0．05）。与高糖组相比，HG＋LY294002组足细胞内AKT磷酸化的水平增加（P〈0．05），mTOR的磷酸化水平降低（P〈0．01）；HG＋LY294002组足细胞的AKT和mTOR磷酸化水平较高糖组均降低（均P〈0．05）。结论高糖可促进足细胞的自噬和凋亡，推测高糖诱导的足细胞自噬作用部分通过P13K—AKT—mTOR信号通路调节实现的。

Objective To evaluate the effects of high glucose on autophagy and apoptosis of podocyte and explore the signaling pathway in high glucose- induce podocyte autophagy. Methods Differentiated mouse podocytes were exposed to high glucose（30 retool/L） or rapamycin （autophagy enhancer, 1 μg/L） or LY294002 （a selective PI3K inhibitor, 50 retool/L） for 24 h. The formations of autophagy were observed by electron microscopy and acridine orange staining. Apoptosis was evaluated by flow cytometry. The expression of autophagy protein LC3 - Ⅱ/I and Beclin - 1 as well as the phosphorylation of AKT and mTOR were examined by Western blotting analysis. Results High glucose induced podocytes apoptosis, increased autophagy and the expression of autophagy-associated proteins （all P 〈 0.05）. Rapamycin further increased the expression of LC3-Ⅱ and Beelin-1 protein （all P 〈 0.05）, but LY294002 inhibited partially the protein expression of LC3-Ⅱ and Beelin-1 induced by high glucose （both P 〈 0.05）. Treatment with rapamycin increased the phosphorylation of AKT, but reduced that of roTOR in podoeytes. Moreover, LY294002 inhibited phosphorylation of both AKT and mTOR （both P 〈 0.05）. Conclusions High glucose promotes podocyte autophagy and apoptosis. Highglucose-induced autophagy is mediated partly through PI3K-AKT-mTOR signaling pathway.