Hypoxia-inducible factor-dependent production of profibrotic mediators by hypoxic hepatocytes

Authors

  • Bryan L. Copple,

    1. Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
    Search for more papers by this author
  • Juan J. Bustamante,

    1. Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
    Search for more papers by this author
  • Timothy P. Welch,

    1. Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
    Search for more papers by this author
  • Nam Deuk Kim,

    1. Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
    2. School of Pharmacy, Pusan National University, Busan, South Korea
    Search for more papers by this author
  • Jeon-Ok Moon

    1. Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
    2. School of Pharmacy, Pusan National University, Busan, South Korea
    Search for more papers by this author

Correspondence
Bryan L. Copple, PhD, Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, 4063 KLSIC, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
Tel: +913 588 7142
Fax: +913 588 7501
e-mail: bcopple@kumc.edu

Abstract

Background/Aims: During the development of liver fibrosis, mediators are produced that stimulate cells in the liver to differentiate into myofibroblasts and to produce collagen. Recent studies demonstrated that the transcription factor, hypoxia-inducible factor-1α (HIF-1α), is critical for upregulation of profibrotic mediators, such as platelet-derived growth factor-A (PDGF-A), PDGF-B and plasminogen activator inhibitor-1 (PAI-1) in the liver, during the development of fibrosis. What remains unknown is the cell type-specific regulation of these genes by HIF-1α in liver cell types. Accordingly, the hypothesis was tested that HIF-1α is activated in hypoxic hepatocytes and regulates the production of profibrotic mediators by these cells.

Methods: In this study, hepatocytes were isolated from the livers of control and HIF-1α- or HIF-1β-deficient mice and exposed to hypoxia.

Results: Exposure of primary mouse hepatocytes to 1% oxygen stimulated nuclear accumulation of HIF-1α and upregulated PAI-1, vascular endothelial cell growth factor and the vasoactive peptides adrenomedullin-1 (ADM-1) and ADM-2. In contrast, the levels of PDGF-A and PDGF-B mRNAs were unaffected in these cells by hypoxia. Exposure of HIF-1α-deficient hepatocytes to 1% oxygen only partially prevented upregulation of these genes, suggesting that other hypoxia-regulated transcription factors, such as HIF-2α, may also regulate these genes. In support of this, HIF-2α was activated in hypoxic hepatocytes, and exposure of HIF-1β-deficient hepatocytes to 1% oxygen completely prevented upregulation of PAI-1, vascular endothelial cell growth factor and ADM-1, suggesting that HIF-2α may also contribute to upregulation of these genes in hypoxic hepatocytes.

Conclusions: Collectively, our results suggest that HIFs may be important regulators of profibrotic and vasoactive mediators by hypoxic hepatocytes.

Ancillary