title: HIF-1 is expressed in normoxic tissue and displays an organ-specific regulation under systemic hypoxia.
abstract: Adaptation to hypoxia is regulated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor consisting of an oxygen-regulated alpha subunit and a constitutively expressed beta subunit. Although HIF-1 is regulated mainly by oxygen tension through the oxygen-dependent degradation of its alpha subunit, in vitro it can also be modulated by cytokines, hormones and genetic alterations. To investigate HIF-1 activation in vivo, we determined the spatial and temporal distribution of HIF-1 in healthy mice subjected to varying fractions of inspiratory oxygen. Immunohistochemical examination of brain, kidney, liver, heart, and skeletal muscle revealed that HIF-1alpha is present in mice kept under normoxic conditions and is further increased in response to systemic hypoxia. Moreover, immunoblot analysis showed that the kinetics of HIF-1alpha expression varies among different organs. In liver and kidney, HIF-1alpha reaches maximal levels after 1 h and gradually decreases to baseline levels after 4 h of continuous hypoxia. In the brain, however, HIF-1alpha is maximally expressed after 5 h and declines to basal levels by 12 h. Whereas HIF-1beta is constitutively expressed in brain and kidney nuclear extracts, its hepatic expression increases concomitantly with HIF-1alpha. Overall, HIF-1alpha expression in normoxic mice suggests that HIF-1 has an important role in tissue homeostasis.
authors.affiliation: Liver Laboratories, University of Birmingham, Birmingham, UK. d.m.stroka@bham.ac.uk
authors.forename: D M
authors.initials: DM
authors.lastname: Stroka
authors.forename: T
authors.initials: T
authors.lastname: Burkhardt
authors.forename: I
authors.initials: I
authors.lastname: Desbaillets
authors.forename: R H
authors.initials: RH
authors.lastname: Wenger
authors.forename: D A
authors.initials: DA
authors.lastname: Neil
authors.forename: C
authors.initials: C
authors.lastname: Bauer
authors.forename: M
authors.initials: M
authors.lastname: Gassmann
authors.forename: D
authors.initials: D
authors.lastname: Candinas
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002467:Cell Nucleus / Q000737:chemistry / Q000187:drug effects; D003593:Cytoplasm / Q000737:chemistry / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000097:blood; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D000860:Hypoxia / Q000503:physiopathology*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D004921:Erythropoietin; D010100:Oxygen