ROS mediate the hypoxic repression of the hepcidin gene by inhibiting C/EBPalpha and STAT-3.
Hepcidin, a liver peptide, systemically inhibits iron utilization and is downregulated under hypoxic conditions. However, little is known about the mechanism underlying the hypoxic suppression of hepcidin. Here, we tested the possibility that HIF-1 and ROS are involved in hepcidin regulation. Hepcidin mRNA, pre-mRNA, and protein levels were reduced in mouse livers and in HepG2 cells after hypoxic incubation, and HIF-1 overexpression and knock-down studies showed that hepcidin regulation is independent of HIF-1. On the other hand, ROS levels were significantly elevated in hypoxic HepG2 cells, and anti-oxidants prevented the hypoxic down-regulation of hepcidin. Conversely, a prooxidant, H(2)O(2), suppressed hepcidin expression in these cells even in normoxia. Of the various transcription factors examined, C/EBPalpha and STAT-3 were found to dissociate from hepcidin promoter under hypoxia, but to become fully engaged after anti-oxidant treatment. These results suggest that ROS repress the hepcidin gene by preventing C/EBPalpha and STAT-3 binding to hepcidin promoter during hypoxia.
Choi
Si-On
SO
Department of Pharmacology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-799, Republic of Korea.
Cho
Young-Suk
YS
Kim
Hye-Lim
HL
Park
Jong-Wan
JW
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D004229:Dithiothreitol / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D064451:Hepcidins; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000860:Hypoxia; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D016877:Oxidants / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
D023181:Antimicrobial Cationic Peptides; D022763:CCAAT-Enhancer-Binding Protein-alpha; D016166:Free Radical Scavengers; C578702:HAMP protein, human; C579599:Hamp protein, mouse; D064451:Hepcidins; D051793:Hypoxia-Inducible Factor 1; D016877:Oxidants; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor; D006861:Hydrogen Peroxide; D004229:Dithiothreitol; D000111:Acetylcysteine