Hepcidin is down-regulated in alcoholic liver injury: implications for the pathogenesis of alcoholic liver disease.
BACKGROUND
Alcoholic liver disease is known to be associated with abnormal iron homeostasis, and iron metabolism itself is regulated by the liver-derived peptide hepcidin. Both CCAAT enhancer binding protein alpha (C/EBPalpha) and interleukin 6 (IL-6) have been shown to regulate hepcidin gene transcription.


OBJECTIVE
To investigate mechanisms underlying alcohol-induced disturbances in iron homeostasis by measuring the expression of hepcidin and C/EBPalpha mRNA using in vivo and in vitro models of alcoholic liver injury.


METHODS
Male rats were pair-fed an alcoholic liquid diet for 12 weeks. RT-PCR was performed on liver tissue using specific primers for hepcidin and C/EBPalpha. The effect of alcohol on hepcidin and C/EBPalpha gene expression was also determined in isolated hepatocytes, HuH-7 cells and HepG2 cells treated with 50 mM ethanol, 200 microM acetaldehyde, and/or 20 ng/ml IL-6.


RESULTS
Hepcidin and C/EBPalpha mRNA expression were significantly decreased in alcohol-fed rats compared with pair-fed controls (6-fold p < 0.001 and 2.2-fold p < 0.0002 reduction, respectively) and hepatic lipid peroxidation was increased by 32.5% (p < 0.05) in alcohol-fed rats compared with controls. Hepcidin gene expression was not altered significantly in cells cultured in the presence of 50 mM ethanol. Following 24 hour stimulation by IL-6, there was a 4-fold increase in hepcidin expression in hepatocytes and a 9-fold increase in HuH-7 cells. Ethanol (50 mM) attenuated the IL-6-induced increase in hepcidin expression in HuH-7 cells (9-fold to a 4-fold increase) but not in hepatocytes. Acetaldehyde had no effect on hepcidin gene expression in cells in culture.


CONCLUSIONS
The down-regulation of hepcidin and C/EBPalpha gene expression shown in vivo implies disturbed iron sensing contributing to the hepatosiderosis seen in alcoholic liver disease, possibly by mechanisms involving the IL-6 signaling cascade.
Bridle
Kimr
K
Southern Medical School, University of Queensland, Brisbane, Australia.
Cheung
Ting-Kin
TK
Murphy
Theresel
T
Walters
Margaretm
M
Anderson
Gregoryj
G
Crawford
Darrellh G
DG
Fletcher
Linda M
LM
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics*; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D005235:Fatty Liver, Alcoholic / Q000235:genetics* / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology; D064451:Hepcidins; D006706:Homeostasis / Q000235:genetics; D015850:Interleukin-6 / Q000235:genetics; D007501:Iron / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic / Q000235:genetics*
D023181:Antimicrobial Cationic Peptides; D022763:CCAAT-Enhancer-Binding Protein-alpha; C578703:Hamp protein, rat; D064451:Hepcidins; D015850:Interleukin-6; D012333:RNA, Messenger; D007501:Iron