Crosstalk of hypoxia-mediated signaling pathways in upregulating plasminogen activator inhibitor-1 expression in keloid fibroblasts.
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.
Zhang
Qunzhou
Q
Department of Oral & Maxillofacial Surgery, Charles R. Drew University of Medicine and Science, Los Angeles, California 90059, USA.
Wu
Yidi
Y
Chau
Cindy H
CH
Ann
David K
DK
Bertolami
Charles N
CN
Le
Anh D
AD
D015152:Blotting, Northern; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007627:Keloid / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009687:Nuclear Proteins / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014157:Transcription Factors; D014162:Transfection; D015854:Up-Regulation
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases