Hepcidin Is Down‐regulated in Alcoholic Liver Injury: Implications for the Pathogenesis of Alcoholic Liver Disease

Abstract

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 α) 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/EBP α 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 α. The effect of alcohol on hepcidin and C/EBP α gene expression was also determined in isolated hepatocytes, HuH‐7 cells and HepG2 cells treated with 50 mM ethanol, 200 μ M acetaldehyde, and/or 20 ng/ml IL‐6. Results:Hepcidin and C/EBP α 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. Conclusion:The down‐regulation of hepcidin and C/EBP α 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.