Interleukin-1beta and tumor necrosis factor-alpha stimulate DNA binding of hypoxia-inducible factor-1.
The rate of transcription of several genes encoding proteins involved in O(2) and energy homeostasis is controlled by hypoxia-inducible factor-1 (HIF-1), a heterodimeric DNA binding complex composed of alpha and beta subunits. HIF-1 is considered the primary trans-acting factor for the erythropoietin (EPO) and vascular endothelial growth factor (VEGF) genes. Since EPO gene expression is inhibited by the proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), while no such effect has been reported with respect to the VEGF gene, we investigated the effects of IL-1beta and TNF-alpha on the activation of the HIF-1 DNA-binding complex and the amount of HIF-1alpha protein in human hepatoma cells in culture. Under normoxic conditions, both cytokines caused a moderate activation of HIF-1 DNA binding. In hypoxia, cytokines strongly increased HIF-1 activity compared with the effect of hypoxia alone. Only IL-1beta increased HIF-1alpha protein levels. In transient transfection experiments, HIF-1-driven reporter gene expression was augmented by cytokines only under hypoxic conditions. In contrast to their effect on EPO synthesis, neither IL-1beta nor TNF-alpha decreased VEGF production. The mRNA levels of HIF-1alpha and VEGF were unaffected. Thus, cytokine-induced inhibition of EPO production is not mediated by impairment of HIF-1 function. We propose that HIF-1 may be involved in modulating gene expression during inflammation.
Hellwig-Bürgel
T
T
Institut für Physiologie, Medizinische Universität zu Lübeck, Lübeck, Germany. Hellwig@physio.mu-luebeck.de
Rutkowski
K
K
Metzen
E
E
Fandrey
J
J
Jelkmann
W
W
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007375:Interleukin-1 / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007375:Interleukin-1; D009687:Nuclear Proteins; D014157:Transcription Factors; D004247:DNA