17-beta estradiol attenuates hypoxic induction of HIF-1alpha and erythropoietin in Hep3B cells

J Cardiovasc Pharmacol. 2004 Jul;44(1):93-100. doi: 10.1097/00005344-200407000-00013.


Hypoxia inducible factor-1 (HIF-1) is a heterodimeric transcription factor that regulates expression of several hypoxia-inducible genes, including erythropoietin (EPO), by binding to hypoxia response elements (HREs) in their promoters/enhancers. Previously, we have shown that 17-beta estradiol (E2-beta) attenuates hypoxic induction of EPO in rats. We hypothesized that this response is mediated by E2-beta-induced attenuation of HIF-1alpha activity/expression. To test this hypothesis, we performed reporter gene assays in Hep3B cells to assess E2-beta effects on hypoxia-induced activity of a reporter gene driven by the HRE from a cloned EPO-enhancer element. Immunocytochemistry and Western blots were additionally used to determine effects of E2-beta on hypoxic increases in HIF-1alpha and EPO immunoreactivity. Finally, we examined potential influences of E2-beta on HIF-1alpha mRNA levels by real-time PCR. Consistent with our hypothesis, E2-beta (100 pM) inhibited hypoxic increases in HRE-mediated reporter gene activity. Furthermore, the estrogen-receptor antagonist ICI 182,780 (25 microM) eliminated these inhibitory effects of E2-beta. E2-beta similarly attenuated hypoxic induction of both EPO and HIF-1alpha protein in an estrogen-receptor dependent manner, but was without effect on HIF-1alpha mRNA expression. These findings suggest a role for E2-beta to attenuate EPO expression by interfering with hypoxic increases in HIF-1alpha protein through an estrogen receptor-dependent mechanism.

Publication types

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

MeSH terms

  • Animals
  • Blotting, Western
  • Cells, Cultured
  • Erythropoietin / biosynthesis*
  • Estradiol / pharmacology*
  • Fluorescent Antibody Technique
  • Genes, Reporter / drug effects*
  • Hypoxia / metabolism*
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Polymerase Chain Reaction
  • Rats
  • Transcription Factors / biosynthesis*


  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Transcription Factors
  • Erythropoietin
  • Estradiol