Hypoxia rapidly activates HIF-3alpha mRNA expression.
The role of the hypoxia-inducible factor (HIF) subunits 1alpha and 1beta in cellular response to hypoxia is well established, whereas little is known about HIF-2alpha and HIF-3alpha with respect to organ distribution and transcriptional regulation by hypoxia. We investigated mRNA levels of all HIF subunits and of their target genes erythropoietin (EPO) and glucose-transporter 1 (GLUT1) in rats undergoing systemic hypoxia for 30 or 120 min by quantitative real-time RT-PCR. In normoxia, persistently high mRNA levels of all HIF subunits were detected in cerebral cortex, hippocampus, and lung; the heart contained the lowest amounts. Hypoxia did not affect mRNA levels of HIF-1alpha, -1beta, and -2alpha. HIF-3alpha mRNA levels increased in all organs examined after 2 h of hypoxia. A significant rise of EPO and GLUT1 mRNA levels occurred in cortex, heart, liver, and kidney after 2 h of hypoxia, indicating activation of the HIF system. Protein levels of all HIF subunits, determined in brain and lung by immunoblotting, showed a marked increase corresponding to the duration of hypoxia. Our results suggest that induction at the transcriptional level is a unique feature of HIF-3alpha, which therefore may represent a rapidly reacting component of the HIF system in protection against hypoxic damage.
Heidbreder
Marc
M
Institute of Experimental and Clinical Pharmacology and Toxicology, University Luebeck, Ratzeburger Allee 160, D-23538 Luebeck, Germany. heidbred@medinf.mu-luebeck.de
Fröhlich
Frederike
F
Jöhren
Olaf
O
Dendorfer
Andreas
A
Qadri
Fatimunnisa
F
Dominiak
Peter
P
D000818:Animals; D051017:Apoptosis Regulatory Proteins; D051792:Basic Helix-Loop-Helix Proteins; D015687:Cell Hypoxia; D004921:Erythropoietin / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D051272:Glucose Transporter Type 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007700:Kinetics; D008297:Male; D008957:Models, Genetic; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009928:Organ Specificity; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D012097:Repressor Proteins; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D000099162:Endothelial PAS Domain-Containing Protein 1
D051017:Apoptosis Regulatory Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004921:Erythropoietin; D051272:Glucose Transporter Type 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099162:Endothelial PAS Domain-Containing Protein 1; C116973:HIF3A protein, human; C424683:Hif3a protein, rat; C495679:Slc2a1 protein, rat