Sphingosine kinase 1 regulates differentiation of human and mouse lung fibroblasts mediated by TGF-beta1

Am J Respir Cell Mol Biol. 2007 Oct;37(4):395-404. doi: 10.1165/rcmb.2007-0065OC. Epub 2007 Jul 19.


Transforming growth factor beta (TGF-beta) contributes to the progression of pulmonary fibrosis through up-regulation of alpha-smooth muscle actin (alpha-SMA) as lung myofibroblast differentiation. Bioactive sphingosine 1-phosphate (S1P) has been shown to mimic TGF-beta signals; however, the function of S1P in lung fibrotic process has not been well documented. We found, in a mouse model of bleomycin lung fibrosis, that SPHK1 and alpha-SMA were colocalized within lung fibrotic foci and that these expressions were significantly increased in primary cultured fibroblasts. Using human lung fibroblasts WI-38, we explored the rationale of sphingosine kinase (SPHK) with TGF-beta1 stimulation. SPHK inhibitors and small interference RNA (siRNA) targeted SPHK1 decreased alpha-SMA and fibronectin expression up-regulated by TGF-beta1. In the meantime, SPHK1 inhibition did not affect smad2 phosphorylation in response to TGF-beta1. Then we examined whether S1P receptors transactivation may affect TGF-beta signals. siRNA against S1P(2) and S1P(3), but not S1P(1), reduced alpha-SMA expression as well as Y-27632, Rho kinase inhibitor. We also detected activation of Rho GTPase upon stimulation of TGF-beta1 on the cell membrane where S1P(2) or S1P(3) was overexpressed. These data suggested that SPHK1 activation by TGF-beta1 leads to Rho-associated myofibroblasts differentiation mediated by transactivated S1P receptors in the lung fibrogenic process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bleomycin
  • Cell Differentiation / drug effects*
  • Cell Line
  • Enzyme Activation / drug effects
  • Female
  • Fibroblasts / cytology*
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology*
  • Gene Silencing
  • Humans
  • Lung / cytology*
  • Lung / drug effects
  • Lung / enzymology*
  • Mice
  • Mice, Inbred C57BL
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Protein Kinase Inhibitors / pharmacology
  • Pulmonary Fibrosis / chemically induced
  • Pulmonary Fibrosis / enzymology
  • Pulmonary Fibrosis / pathology
  • RNA, Small Interfering / metabolism
  • Receptors, Lysosphingolipid / genetics
  • Receptors, Lysosphingolipid / metabolism
  • Signal Transduction / drug effects
  • Smad2 Protein / metabolism
  • Transcriptional Activation / drug effects
  • Transforming Growth Factor beta1 / pharmacology*
  • Up-Regulation / drug effects
  • Up-Regulation / genetics
  • rho GTP-Binding Proteins / metabolism


  • Protein Kinase Inhibitors
  • RNA, Small Interfering
  • Receptors, Lysosphingolipid
  • Smad2 Protein
  • Transforming Growth Factor beta1
  • Bleomycin
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • rho GTP-Binding Proteins