title: Insulin upregulates the expression of epithelial sodium channel in vitro and in a mouse model of acute lung injury: role of mTORC2/SGK1 pathway.
abstract: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by proteinaceous pulmonary edema and severe arterial hypoxemia with a mortality of approximately 40%. Stimulation of epithelial sodium channel (ENaC) promotes Na(+) transport, a rate-limiting step for pulmonary edema reabsorption. Insulin is known to participate in the ion transport; however, its role in pulmonary edema clearance and the regulatory mechanism involved have not been fully elucidated. In the current study, in a lipopolysaccharide-based mouse model of ALI, we found that insulin alleviated pulmonary edema by promoting ENaC-mediated alveolar fluid clearance through serum and glucocorticoid induced kinase-1 (SGK1). In alveolar epithelial cells, insulin increased the expression of α-, β-, and γ-ENaC, which was blocked by the mammalian target of rapamycin complex 2 (mTORC2) inhibitor or knockdown of Rictor (a necessary component of mTORC2), and SGK1 inhibitor, respectively. In addition, an immunoprecipitation study demonstrated that SGK1(Ser422) phosphorylation, the key step for complete SGK1 activation by insulin, was conducted through PI3K/mTORC2 pathway. Finally, we testified the role of mTORC2 in vivo by demonstrating that PP242 prevented insulin-stimulated SGK1 activation and ENaC increase during ALI. The data revealed that during ALI, insulin stimulates alveolar fluid clearance by upregulating the expression of α-, β-, and γ-ENaC at the cell surface, which was, at least, partially through activating mTROC2/SGK1 signaling pathway.
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Jing
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Di
authors.initials: D
authors.lastname: Qi
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China. Electronic address: submitmail@126.com.
authors.forename: Dao-Xin
authors.initials: DX
authors.lastname: Wang
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Deng
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ye
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Long-Hua
authors.initials: LH
authors.lastname: Feng
authors.affiliation: Department of Respiratory Medicine, West China Hospital of Sichuan University, 37 Guoxue Lane, Wuhou District, Chengdu, Sichuan 610041, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Department of Respiratory Medicine, Second Affiliated Hospital of Chongqing Medical University, 76 Linjiang Road, Yuzhong District, Chongqing 400010, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Emergency, Yongchuan Affiliated Hospital of Chongqing Medical University, 439 Xuanhua Road, Yongchuan District, Chongqing 402160, China.
authors.forename: Chun-Rong
authors.initials: CR
authors.lastname: Zhang
mesh_terms: D055371:Acute Lung Injury / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D053503:Epithelial Sodium Channels; D007004:Hypoglycemic Agents; D017874:Immediate-Early Proteins; D007328:Insulin; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D058570:TOR Serine-Threonine Kinases; D000099184:Serum-Glucocorticoid Regulated Kinases
keywords: Acute lung injury; Alveolar fluid clearance; Epithelial sodium channel; Insulin; Mammalian target of rapamycin complex; Serum and glucocorticoid-induced kinase-1