Regulation of the hypoxia-inducible factor 1alpha by the inflammatory mediators nitric oxide and tumor necrosis factor-alpha in contrast to desferroxamine and phenylarsine oxide.
Hypoxic/ischemic conditions provoke activation of the hypoxia-inducible factor-1 (HIF-1), which functions as a transcription factor. HIF-1 is composed of the HIF-1alpha and -beta subunits, and stability regulation occurs via accumulation/degradation of HIF-1alpha with the notion that a prolyl hydroxylase accounts for changes in protein level. In addition, there is evidence that HIF-1 is up-regulated by diverse agonists during normoxia. We investigated the impact of inflammatory mediators nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) on HIF-1alpha regulation. For comparison, LLC-PK(1) cells were exposed to hypoxia, stimulated with desferroxamine (DFX, known to mimic hypoxia), and the thiol-cross-linking agent phenylarsine oxide (PAO). Although all stimuli elicited HIF-1alpha stabilization with differences in the time-dependent accumulation pattern, significant variations appeared with regard to signaling. With the use of a superoxide anion (O(2-)) generator, we established an O(2-)-sensitive pathway that blocked HIF-1alpha stabilization in response to NO and TNF-alpha while DFX- and PAO-evoked HIF-1alpha stabilization appeared O(2-)-insensitive. NO and TNF-alpha signaling required phosphorylation events, especially activation of the phosphatidylinositol 3-kinase/Akt, which is in contrast to DFX and PAO. Based on HIF-1-dependent luciferase reporter gene analysis, it was found that, in contrast to NO and TNF-alpha, PAO resembled a stimulus that induced a dysfunctional HIF-1 complex. These data indicate that diverse agonists activate HIF-1alpha under normoxic conditions by employing different signaling pathways.
Sandau
K B
KB
Faculty of Biology, University of Kaiserslautern, Erwin-Schrödinger-Strasse, 67663 Kaiserslautern, Germany.
Zhou
J
J
Kietzmann
T
T
Brüne
B
B
D000730:Androstadienes / Q000494:pharmacology; D001152:Arsenicals / Q000494:pharmacology*; D003676:Deferoxamine / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018836:Inflammation Mediators / Q000494:pharmacology*; D007668:Kidney / Q000098:blood supply; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D015427:Reperfusion Injury; D015398:Signal Transduction; D014157:Transcription Factors / Q000096:biosynthesis*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D015854:Up-Regulation; D000077191:Wortmannin
D000730:Androstadienes; D001152:Arsenicals; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018836:Inflammation Mediators; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C029341:oxophenylarsine; D009569:Nitric Oxide; D019833:Genistein; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D003676:Deferoxamine; D010100:Oxygen; D000077191:Wortmannin