title: 17β-estradiol suppresses lipopolysaccharide-induced acute lung injury through PI3K/Akt/SGK1 mediated up-regulation of epithelial sodium channel (ENaC) in vivo and in vitro.
abstract: BACKGROUND
  17β-estradiol can suppress acute lung injury (ALI) and regulate alveolar epithelial sodium channel (ENaC). However the relationship between these two functions remains unclear. This study is conducted to assess the role of ENaC and the PI3K/Akt/SGK1 signaling pathway in 17β-estradiol therapy in attenuating LPS-induced ALI.
  
  
  METHODS
  ALI was induced in C57BL/J male mice by intratracheal administration of lipopolysaccharide (LPS). Concurrent with LPS administration, 17β-estradiol or sterile saline was administered to ALI model with or without the phosphoinositide 3-kinase (PI3K) inhibitor wortmannin. The lung histological changes, inflammatory mediators in bronchoalveolar lavage fluid (BALF), wet/dry weight ratio (W/D) and alveolar fluid clearance (AFC) were measured 4 hours after LPS challenge in vivo. For in vitro studies, LPS-challenged MLE-12 cells were pre-incubated with or without wortmannin for 30 minutes prior to 17β-estradiol treatment. Expression of ENaC subunits was assessed by reverse transcriptase PCR, western blot, cell surface biotinylation, and immunohistochemistry. The levels of phosphorylated Akt and SGK1 in lung tissue and lung cell lines were investigated by western blot.
  
  
  RESULTS
  17β-estradiol suppressed LPS-mediated ALI in mice by diminishing inflammatory mediators and enhancing AFC. 17β-estradiol promoted the expression and surface abundance of α-ENaC, and increased the levels of phosphorylated-Akt and phosphorylated-SGK1 following LPS challenge. This induction was abolished by the PI3K inhibitor wortmannin in vivo and in vitro.
  
  
  CONCLUSIONS
  17β-estradiol attenuates LPS-induced ALI not only by repressing inflammation, but also by reducing pulmonary edema via elevation of α-ENaC expression and membrane abundance. These effects were mediated, at least partially, via activation of the PI3K/Akt/SGK1 signaling pathway.
authors.forename: Di
authors.initials: D
authors.lastname: Qi
authors.forename: Jing
authors.initials: J
authors.lastname: He
authors.forename: Daoxin
authors.initials: D
authors.lastname: Wang
authors.forename: Wang
authors.initials: W
authors.lastname: Deng
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ye
authors.forename: Longhua
authors.initials: L
authors.lastname: Feng
mesh_terms: D055371:Acute Lung Injury / Q000139:chemically induced / Q000201:enzymology / Q000517:prevention & control*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002460:Cell Line; D019610:Cytoprotection; D004195:Disease Models, Animal; D004731:Endotoxins; D004789:Enzyme Activation; D053503:Epithelial Sodium Channels / Q000187:drug effects* / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D017874:Immediate-Early Proteins / Q000378:metabolism*; D018836:Inflammation Mediators / Q000378:metabolism; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011654:Pulmonary Edema / Q000139:chemically induced / Q000201:enzymology / Q000517:prevention & control; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D004731:Endotoxins; D053503:Epithelial Sodium Channels; D004958:Estradiol; D017874:Immediate-Early Proteins; D018836:Inflammation Mediators; D058539:Phosphatidylinositol 3-Kinase; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000099184:Serum-Glucocorticoid Regulated Kinases; C507047:Scnn1a protein, mouse; C044101:endotoxin, Escherichia coli