Hepcidin is a 25 amino acid peptide produced in the liver whose expression is increased by iron loading and decreased in iron deficiency (Pigeon et al. 2001). This site of synthesis and the dramatic regulation by iron has led to the suggestion that hepcidin might be the master controller of iron metabolism, relaying information about the status of the body iron stores to the intestine and regulating absorption accordingly. The mode of action of hepcidin is still unclear. In this study we have utilised the Caco-2 cell model of human intestinal epithelial cells to investigate the possibility that hepcidin might interact directly with the epithelium.

Cells were cultured in Transwell plates for 21 days. For the final 24 h of the culture period, human synthetic hepcidin (30 µg ml^-1) was added to the basolateral medium. At the end of the incubation period cells were either used to measure ⁵⁵Fe transport across the Caco-2 cell monolayers, processed for Western blotting for the iron transport proteins DMT1 and IREG1, or used as a source of RNA to determine changes in transporter expression by Real-Time RT-PCR.

Following exposure to hepcidin, iron uptake across the apical membrane of Caco-2 cells was significantly decreased (control 453.3 ± 47.0 pmol cm^-2 h^-1; +hepcidin 268.3 ± 63.8 pmol cm^-2 h^-1, means ± S.E.M. n = 6, P = 0.04 Student’s unpaired t test). Efflux across the basolateral membrane was unaffected by hepcidin treatment. In agreement with the transport data, the expression of the apical membrane transporter DMT1 was decreased by hepcidin treatment at both the protein and mRNA level, whereas expression of IREG1, the basolateral efflux protein, was unaffected.