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/EBP alpha) and interleukin 6 (IL-6) have been shown to regulate hepcidin gene transcription. Aim: To investigate mechanisms underlying alcohol-induced disturbances in iron homeostasis by measuring the expression of hepcidin and C/EBPa 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/EBP alpha. The effect of alcohol on hepcidin and C/EBP alpha gene expression was also determined in isolated hepatocytes, HuH-7 cells and HepG2 cells treated with 50 mM ethanol, 200 mu M acetaldehyde, and/or 20 ng/ml IL-6. Results: Hepcidin and C/EBPa 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 (50mM) 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. Conclusion: The down-regulation of hepcidin and C/EBPa 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.