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.

中文翻译：

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汉普1型通过直接杀灭微生物和调节草鱼（Ctenopharyngodon idella）中的铁代谢来促进抗菌素的防御。

铁调素是铁稳态的抗菌肽和调节剂，在大多数鱼类和某些哺乳动物中具有两种亚型。先前的研究已报道这两种铁调素同工型具有不同的作用。汉普1型在铁代谢中起调节作用，而汉普2型主要发挥抗菌作用。在这项研究中，我们发现Ctenopharyngodon idella（C. idella）仅具有一种hepcidin亚型（hamp 1型），它具有广谱抗菌和铁调节功能。C.idellahepcidin成熟肽（hepcidin-25）和截短肽（hepcidin-20）部分通过膜破裂和与细菌基因组DNA结合，表现出对革兰氏阳性和革兰氏阴性细菌的杀菌活性，呈剂量依赖性。挑战试验的数据表明，使用hepcidin-25可以显着降低嗜水气单胞菌对C. idella的死亡率。感染可能是由于该肽的直接杀菌活性以及鱼血清中铁含量的降低。此外，hepcidin-20和-25之间的比较表明，N末端5个氨基酸在降低鱼血清中的铁含量中起关键作用。我们的发现揭示了Hamp 1型在维持铁稳态和抵抗细菌感染中的重要作用，这表明铁调素对水产养殖中细菌感染的预防和控制具有重要意义。