Hepcidin is an
antimicrobial peptide and regulator of
iron homeostasis which has two
isoforms in most fishes and some mammals. Previous studies have reported that the two
hepcidin isoforms have different roles. Hamp type-1 plays a regulatory role in
iron metabolism and hamp type-2 mostly performs an antimicrobial role. In this study, we found that Ctenopharyngodon idella (C. idella) have only one
hepcidin isoform (hamp type-1), which showed both broad-spectrum antibacterial and
iron regulatory functions. C. idella
hepcidin mature
peptide (hepcidin-25) and truncated
peptide (hepcidin-20) exhibited bactericidal activities against both Gram-positive and Gram-negative bacteria in a dose-dependent manner in part through membrane
rupture and binding to bacterial genomic
DNA. The data from challenge tests demonstrated that the administration of hepcidin-25 significantly reduced mortality rates of C. idella by A. hydrophila
infection, probably due to direct bactericidal activities of the
peptide and a reduction of
iron content in the fish serum. In addition, a comparison between hepcidin-20 and -25 suggests that the N terminal 5
amino acids play a critical role in reducing
iron content in fish serum. Our findings revealed an important role of hamp type-1 in maintaining
iron homeostasis and fighting against
bacterial infections, suggesting the
hepcidin has implications for the prevention and control of
bacterial infection in aquaculture.