Reactive oxygen species activate the HIF-1alpha promoter via a functional NFkappaB site.
OBJECTIVE
Reactive oxygen species have been implicated as signaling molecules modulating the activity of redox-sensitive transcription factors such as nuclear factor kappa B (NF-kappaB). Recently, the transcription factor hypoxia-inducible factor-1 (HIF-1), known to mediate gene expression by hypoxia, has been found to be also activated by nonhypoxic factors in a redox-sensitive manner. We therefore aimed to elucidate the link between these 2 important redox-sensitive transcription factors.


RESULTS
In pulmonary artery smooth muscle cells, reactive oxygen species generated either by exogenous H2O2 or by a NOX4-containing NADPH oxidase stimulated by thrombin activated or induced NF-kappaB and HIF-1alpha. The reactive oxygen species-mediated HIF-1alpha induction occurred on the transcriptional level and was dependent on NF-kappaB. Transfection experiments with wild-type or mutant HIF-1alpha promoter constructs revealed the presence of a yet unidentified NF-kappaB binding element. Gel shift analyses and chromatin immunoprecipitation verified binding of NF-kappaB to this site. Furthermore, reactive oxygen species enhanced expression of plasminogen activator inhibitor-1, which was prevented by dominant-negative IkappaB or mutation of the HIF-1 binding site within the plasminogen activator inhibitor-1 promoter.


CONCLUSIONS
These findings show for the first time to our knowledge that reactive oxygen species directly link HIF-1alpha and NF-kappaB, implicating an important pathophysiological role of this novel pathway in disorders associated with elevated levels of reactive oxygen species.
Bonello
Steve
S
Experimental Pediatric Cardiology, Department of Pediatric Cardiology and Congenital Heart Disease, German Heart Center Munich at the TU Munich, Lazarettstr. 36, D-80636 Munich, Germany.
Zähringer
Christian
C
BelAiba
Rachida S
RS
Djordjevic
Talija
T
Hess
John
J
Michiels
Carine
C
Kietzmann
Thomas
T
Görlach
Agnes
A
D001665:Binding Sites; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism* / Q000502:physiology; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011651:Pulmonary Artery / Q000166:cytology; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology; D014158:Transcription, Genetic / Q000502:physiology
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016328:NF-kappa B; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D013917:Thrombin