Crosstalk of hypoxia-mediated signaling pathways in upregulating plasminogen activator inhibitor-1 expression in keloid fibroblasts

J Cell Physiol. 2004 Apr;199(1):89-97. doi: 10.1002/jcp.10452.


Keloids are skin fibrotic conditions characterized by an excess accumulation of extracellular matrix (ECM) components secondary to trauma or surgical injuries. Previous studies have shown that plasminogen activator inhibitor-1 (PAI-1) can be upregulated by hypoxia and may contribute to keloid pathogenesis. In this study we investigate the signaling mechanisms involved in hypoxia-mediated PAI-1 expression in keloid fibroblasts. Using Northern and Western blot analysis, transient transfections, and pharmacological agents, we demonstrate that hypoxia-induced upregulation of PAI-1 expression is mainly controlled by hypoxia inducible factors-1alpha (HIF-1alpha) and that hypoxia leads to a rapid and transient activation of phosphatidylinositol-3-kinase/Akt (PI3-K/Akt) and extracellular signal-regulated kinases 1/2 (ERK1/2). Treatment of cells with PI-3K/Akt inhibitor (LY294002) and tyrosine protein kinase inhibitor (genistein) significantly attenuated hypoxia-induced PAI-1 mRNA and protein expression as well as promoter activation, apparently via an inhibition of the hypoxia-induced stabilization of HIF-1alpha protein, attenuation of the steady-state level of HIF-1alpha mRNA, and its DNA-binding activity. Even though disruption of ERK1/2 signaling pathway by PD98059 abolished hypoxia-induced PAI-1 promoter activation and mRNA/protein expression in keloid fibroblasts, it did not inhibit the hypoxia-mediated stabilization of HIF-1alpha protein and the steady-state level of HIF-1alpha mRNA nor its DNA binding activity. Our findings suggest that a combination of several signaling pathways, including ERK1/2, PI3-K/Akt, and protein tyrosine kinases (PTKs), may contribute to the hypoxia-mediated induction of PAI-1 expression via activation of HIF-1alpha in keloid fibroblasts.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Blotting, Northern
  • Blotting, Western
  • DNA-Binding Proteins / drug effects
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology
  • Enzyme Inhibitors / pharmacology
  • Fibroblasts / metabolism*
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / physiology
  • Humans
  • Hypoxia / metabolism*
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Keloid / metabolism*
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism
  • Nuclear Proteins / drug effects
  • Nuclear Proteins / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Plasminogen Activator Inhibitor 1 / biosynthesis*
  • Promoter Regions, Genetic
  • Protein-Tyrosine Kinases / metabolism
  • RNA, Messenger / analysis
  • RNA, Messenger / drug effects
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Transcription Factors*
  • Transfection
  • Up-Regulation


  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Nuclear Proteins
  • Plasminogen Activator Inhibitor 1
  • RNA, Messenger
  • Transcription Factors
  • Phosphatidylinositol 3-Kinases
  • Protein-Tyrosine Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases