胰岛素通过mTORC2/SGK1途径上调肺泡上皮钠通道α亚基的作用机制

Mechanism of insulin in up-regulating epithelial sodium channelα-subunit via mTORC2/SGK1 signaling pathway

目的:研究mTORC2/SGK1在胰岛素上调肺泡上皮钠通道α亚基(α-ENaC)中的作用,阐明胰岛素促进小鼠急性肺损伤(ALI)时肺水肿清除的机制。方法:C57BL/6J小鼠随机分为对照组、脂多糖(LPS)组、胰岛素组、PP242(mTORC1/2抑制剂)组和雷帕霉素(特异性mTORC1抑制剂)组,每组10只。经相应处理后分别留取标本检测小鼠肺湿/干质量比(W/D)、肺泡液体清除率(AFC),HE染色观察肺组织病理学变化,Western blotting法检测肺组织中α-ENaC表达水平及pSGK1(Ser422)磷酸化水平。结果:与LPS组比较,胰岛素组小鼠肺组织病理评分、肺W/D明显降低(P<0.05),AFC明显增加(P<0.05)。与对照组比较,LPS组小鼠肺组织中α-ENaC蛋白表达水平明显降低(P<0.05);与LPS组比较,胰岛素组小鼠肺组织中α-ENaC蛋白表达水平和pSGK1(Ser422)磷酸化水平明显升高(P<0.05);与胰岛素组比较,PP242组小鼠肺组织中α-ENaC蛋白表达和pSGK1(Ser422)磷酸化水平明显降低(P<0.05)。结论:胰岛素通过mTORC2途径激活SGK1,上调α-ENaC表达,促进肺泡液体清除,对ALI/急性呼吸窘迫综合征(ARDS)的预后有一定的改善作用。

Objective To study the role of mTORC2/SGK1 signaling pathway in the up-regulation of alveolar epithelial sodium channelα-subunit（α-ENaC）by insulin,and to clarify the mechanism of insulin in promoting the lung edema clearance in the acute lung injury（ALI）mice.Methods The C57BL/6Jmice were randomly divided into control group,LPS group,insulin group（LPS＋insulin）,PP242 group（PP242＋ LPS＋insulin）and rapamycin group（rapamycin＋LPS＋insulin）,with 10 mice in each group.The lung wet/dry weight（W/D）ratios and alveolar fluid clearance（AFC）of the mice were detected.HE staining was used to observe the pathological changes of lung tissue.The protein expression levels ofα-ENaC and phosphorylated serum-and the levels of glucocorticoid-inducible kinase 1（SGK1）at Ser422 in lung tissue were determined by Western blotting method.Results Compared with LPS group,the lung injury score and W/D ratio in insulin group were decreased significantly（P〈0.05）and the AFC was increased significantly（P〈0.05）.The expression level ofα-ENaC protein in LPS group was decreased significantly compared with control group（P〈0.05）.The expression levels of bothα-ENaC protein and pSGK1（Ser422）in insulin group were significantly increased compared with LPS group（P〈0.05）.Compared with insulin group,theα-ENaC protein expression level and phosphorylated SGK1（Ser422）level in PP242 group were decreased（P〈0.05）.Conclusion Through mTORC2 pathway,insulin activates the SGK1 and up-regulates the expression ofα-ENaC protein to accelerate the AFC,which is beneficial to the prognosis of ALI/acute respiratory distress syndrome（ARDS）.