title: Overexpression of PTEN suppresses lipopolysaccharide-induced lung fibroblast proliferation, differentiation and collagen secretion through inhibition of the PI3-K-Akt-GSK3beta pathway.
abstract: BACKGROUND
  Abnormal and uncontrolled proliferation of lung fibroblasts may contribute to pulmonary fibrosis. Lipopolysaccharide (LPS) can induce fibroblast proliferation and differentiation through activation of phosphoinositide3-Kinase (PI3-K) pathway. However, the detail mechanism by which LPS contributes to the development of lung fibrosis is not clearly understood. To investigate the role of phosphatase and tensin homolog (PTEN), a PI3-K pathway suppressor, on LPS-induced lung fibroblast proliferation, differentiation, collagen secretion and activation of PI3-K, we transfected PTEN overexpression lentivirus into cultured mouse lung fibroblasts with or without LPS treatment to evaluate proliferation by MTT and Flow cytometry assays. Expression of PTEN, alpha-smooth muscle actin (alpha-SMA), glycogen synthase kinase 3 beta (GSK3beta) and phosphorylation of Akt were determined by Western-blot or real-time RT-PCR assays. The PTEN phosphorylation activity was measured by a malachite green-based assay. The content of C-terminal propeptide of type I procollagen (PICP) in cell culture supernatants was examined by ELISA.
  
  
  RESULTS
  We found that overexpression of PTEN effectively increased expression and phosphatase activity of PTEN, and concomitantly inhibited LPS-induced fibroblast proliferation, differentiation and collagen secretion. Phosphorylation of Akt and GSK3beta protein expression levels in the LPS-induced PTEN overexpression transfected cells were significantly lower than those in the LPS-induced non-transfected cells, which can be reversed by the PTEN inhibitor, bpV(phen).
  
  
  CONCLUSIONS
  Collectively, our results show that overexpression and induced phosphatase activity of PTEN inhibits LPS-induced lung fibroblast proliferation, differentiation and collagen secretion through inactivation of PI3-K-Akt-GSK3beta signaling pathways, which can be abrogated by a selective PTEN inhibitor. Thus, expression and phosphatase activity of PTEN could be a potential therapeutic target for LPS-induced pulmonary fibrosis. Compared with PTEN expression level, phosphatase activity of PTEN is more crucial in affecting lung fibroblast proliferation, differentiation and collagen secretion.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: He
authors.forename: Yuxiao
authors.initials: Y
authors.lastname: Deng
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Yongming
authors.initials: Y
authors.lastname: Chen
authors.forename: Shunpeng
authors.initials: S
authors.lastname: Xing
authors.forename: Xianyuan
authors.initials: X
authors.lastname: Zhao
authors.forename: Jia
authors.initials: J
authors.lastname: Ding
authors.affiliation: Department of Anesthesiology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 1630 Dong Fang Road, Shanghai 200127, China. gaoyuanshsmu@163.com.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Xiangrui
authors.initials: X
authors.lastname: Wang