Cysteine-rich antimicrobial peptides are abundant in animal and plant tissues involved in host defense. In insects, most are synthesized in the fat body, an organ analogous to the liver of vertebrates. From human urine, we characterized a cysteine-rich peptide with three forms differing by amino-terminal truncation, and we named it hepcidin (Hepc) because of its origin in the liver and its antimicrobial properties. Two predominant forms, Hepc20 and Hepc25, contained 20 and 25 amino acid residues with all 8 cysteines connected by intramolecular disulfide bonds. Reverse translation and search of the data bases found homologous liver cDNAs in species from fish to human and a corresponding human genomic sequence on human chromosome 19. The full cDNA by 5 rapid amplification of cDNA ends was 0.4 kilobase pair, in agreement with hepcidin mRNA size on Northern blots. The liver was the predominant site of mRNA expression. The encoded prepropeptide contains 84 amino acids, but only the 20 -25-amino acid processed forms were found in urine. Hepcidins exhibited antifungal activity against Candida albicans, Aspergillus fumigatus, and Aspergillus niger and antibacterial activity against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and group B Streptococcus. Hepcidin may be a vertebrate counterpart of cysteinerich antimicrobial peptides produced in the fat body of insects.Innate immunity relies on a variety of effector mechanisms to defend against microbial invasion. Among them are the abundant and widely distributed disulfide-linked cationic antimicrobial peptides found in both the plant and animal kingdoms. Generally, these peptides exhibit a broad range of activity against bacteria, fungi, protozoa, and enveloped viruses. Plants produce many cysteine-rich antimicrobial peptides including thionins, plant defensins, and the cysteine rich Ib-AMP 1-4 (1-3). In insects, cysteine-rich antimicrobial peptides are produced in the fat body (functional homologue of the mammalian liver) and transcriptionally induced and released into the hemolymph in response to infection or injury. These include insect defensins, heliomicin, drosomycin, and thanatin (4 -7). Mollusks also produce cationic and cysteine-rich antimicrobial peptides such as mytilin, mytimicin, and myticin (8). In mammals, similar antimicrobial peptides include ␣-and ␤-defensins and protegrins (9, 10).Like the insect fat body, the vertebrate liver is also centrally involved in innate immune response to infection. The "acute phase" response to infection or inflammation is a pattern of increased hepatic synthesis of many secreted proteins involved in host defense and the selective suppression of synthesis of other secreted proteins. In contrast to the abundant fat bodyderived antimicrobial peptides of insects, no vertebrate antimicrobial peptides originating in the liver have been described to date. In this work, we report the discovery of a novel hepatic antimicrobial peptide, hepcidin, whose processed form is found in urine. MATERIALS AND METHODSPur...

Hepcidin is a liver-made peptide proposed to be a central regulator of intestinal iron absorption and iron recycling by macrophages. In animal models, hepcidin is induced by inflammation and iron loading, but its regulation in humans has not been studied. We report that urinary excretion of hepcidin was greatly increased in patients with iron overload, infections, or inflammatory diseases. Hepcidin excretion correlated well with serum ferritin levels, which are regulated by similar pathologic stimuli. In vitro iron loading of primary human hepatocytes, however, unexpectedly down-regulated hepcidin mRNA, suggesting that in vivo regulation of hepcidin expression by iron stores involves complex indirect effects. Hepcidin mRNA was dramatically induced by interleukin-6 (IL-6) in vitro, but not by IL-1 or tumor necrosis factor ␣ (TNF-␣), demonstrating that human hepcidin is a type II acute-phase reactant. The linkage of hepcidin induction to inflammation in humans supports its proposed role as a key mediator of anemia of inflammation.

Recovery from blood loss requires a greatly enhanced supply of iron to support expanded erythropoiesis. After hemorrhage, suppression of the iron-regulatory hormone hepcidin allows increased iron absorption and mobilization from stores. We identified a new hormone, erythroferrone (ERFE), which mediates hepcidin suppression during stress erythropoiesis. ERFE is produced by erythroblasts in response to erythropoietin. ERFE-deficient mice fail to suppress hepcidin rapidly after hemorrhage and exhibit a delay in recovery from blood loss. ERFE expression is greatly increased in murine HbbTh3/+ thalassemia intermedia where it contributes to the suppression of hepcidin and systemic iron overload characteristic of this disease.

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