%0 Journal Article
%T Regulation of ENaC-mediated alveolar fluid clearance by insulin via PI3K/Akt pathway in LPS-induced acute lung injury
%A Wang Deng
%A Chang-Yi Li
%A Jin Tong
%A Wei Zhang
%A Dao-Xin Wang
%J Respiratory Research
%D 2012
%I BioMed Central
%R 10.1186/1465-9921-13-29
%X A model of ALI (LPS at a dose of 5.0 mg/kg) with non-hyperglycemia was established in Sprague-Dawley rats receiving continuous exogenous insulin by micro-osmotic pumps and wortmannin. The lungs were isolated for measurement of bronchoalveolar lavage fluid(BALF), total lung water content(TLW), and AFC after ALI for 8 hours. Alveolar epithelial type II cells were pre-incubated with LY294002, Akt inhibitor and SGK1 inhibitor 30 minutes before insulin treatment for 2 hours. The expressions of ¦Á-,¦Â-, and ¦Ã-ENaC were detected by immunocytochemistry, reverse transcriptase polymerase chain reaction (RT-PCR) and western blotting.In vivo, insulin decreased TLW, enchanced AFC, increased the expressions of ¦Á-,¦Â-, and ¦Ã-ENaC and the level of phosphorylated Akt, attenuated lung injury and improved the survival rate in LPS-induced ALI, the effects of which were blocked by wortmannin. Amiloride, a sodium channel inhibitor, significantly reduced insulin-induced increase in AFC. In vitro, insulin increased the expressions of ¦Á-,¦Â-, and ¦Ã-ENaC as well as the level of phosphorylated Akt but LY294002 and Akt inhibitor significantly prevented insulin-induced increase in the expression of ENaC and the level of phosphorylated Akt respectively. Immunoprecipitation studies showed that levels of Nedd4-2 binding to ENaC were decreased by insulin via PI3K/Akt pathway.Our study demonstrated that insulin alleviated pulmonary edema and enhanced AFC by increasing the expression of ENaC that dependent upon PI3K/Akt pathway by inhibition of Nedd4-2.Actue lung injury(ALI), the early stage of acute respiratory distress syndrome (ARDS), is a devastating clinical syndrome characterized by alveolar epithelial injury leading to non-cardiogenic pulmonary edema of flooding protein-rich fluid in the alveolar spaces with a mortality of approach 40%[1,2]. In vivo, alveolar fluid volume is determined by alveolar fluid clearance (AFC), the balance of transepithelial Na+ transport [3]. AFC was impaired in ALI and
%K Alveolar fluid clearance
%K Akt
%K Epithelial sodium channel
%K Insulin
%K Phosphatidylinositol 3-kinase
%K Acute lung injury
%U http://respiratory-research.com/content/13/1/29