title: An intact canonical NF-κB pathway is required for inflammatory gene expression in response to hypoxia.
abstract: Hypoxia is a feature of the microenvironment in a number of chronic inflammatory conditions due to increased metabolic activity and disrupted perfusion at the inflamed site. Hypoxia contributes to inflammation through the regulation of gene expression via key oxygen-sensitive transcriptional regulators including the hypoxia-inducible factor (HIF) and NF-κB. Recent studies have revealed a high degree of interdependence between HIF and NF-κB signaling; however, the relative contribution of each to hypoxia-induced inflammatory gene expression remains unclear. In this study, we use transgenic mice expressing luciferase under the control of NF-κB to demonstrate that hypoxia activates NF-κB in the heart and lungs of mice in vivo. Using small interfering RNA targeted to the p65 subunit of NF-κB, we confirm a unidirectional dependence of hypoxic HIF-1α accumulation upon an intact canonical NF-κB pathway in cultured cells. Cyclooxygenase-2 and other key proinflammatory genes are transcriptionally induced by hypoxia in a manner that is both HIF-1 and NF-κB dependent, and in mouse embryonic fibroblasts lacking an intact canonical NF-κB pathway, there is a loss of hypoxia-induced inflammatory gene expression. Finally, under conditions of hypoxia, HIF-1α and the p65 subunit of NF-κB directly bind to the cyclooxygenase-2 promoter. These results implicate an essential role for NF-κB signaling in inflammatory gene expression in response to hypoxia both through the regulation of HIF-1 and through direct effects upon target gene expression.
authors.affiliation: UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Susan F
authors.initials: SF
authors.lastname: Fitzpatrick
authors.forename: Murtaza M
authors.initials: MM
authors.lastname: Tambuwala
authors.forename: Ulrike
authors.initials: U
authors.lastname: Bruning
authors.forename: Bettina
authors.initials: B
authors.lastname: Schaible
authors.forename: Carsten C
authors.initials: CC
authors.lastname: Scholz
authors.forename: Annette
authors.initials: A
authors.lastname: Byrne
authors.forename: Aisling
authors.initials: A
authors.lastname: O'Connor
authors.forename: William M
authors.initials: WM
authors.lastname: Gallagher
authors.forename: Colin R
authors.initials: CR
authors.lastname: Lenihan
authors.forename: John F
authors.initials: JF
authors.lastname: Garvey
authors.forename: Katherine
authors.initials: K
authors.lastname: Howell
authors.forename: Padraic G
authors.initials: PG
authors.lastname: Fallon
authors.forename: Eoin P
authors.initials: EP
authors.lastname: Cummins
authors.forename: Cormac T
authors.initials: CT
authors.lastname: Taylor
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000276:immunology* / Q000473:pathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D018836:Inflammation Mediators / Q000502:physiology*; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018836:Inflammation Mediators; D016328:NF-kappa B; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human