Molecular characterization of an antimicrobial peptide LEAP-2 in Onychostoma macrolepis: Expression pattern,...

Antimicrobial peptides (AMPs) as the host's antimicrobial source are promising candidates for the development of novel antibacterial agents. Our study identified and analyzed the LEAP-2 gene from the cavefish - Onychostoma macrolepis (OmLEAP-2), and antimicrobial activity of OmLEAP-2 was assessed through both in vivo and in vitro experiments. The OmLEAP-2 encodes 92 amino acids with a hydrophobic surface (LAMMPWY) and two disulfide bonds. Following A. hydrophila infection, OmLEAP-2 expression was up-regulated in the liver, spleen and intestine in Onychostoma macrolepis. Recombinant OmLEAP-2 protein exhibited dose-dependent antimicrobial activity against both Gram-negative and Gram-positive bacteria, particularly A. hydrophila and A. veronii. OmLEAP-2 overexpression not only reduced bacterial load and increased survival rate, but also suppressed expression of TNF-α and IL-1β in A. hydrophila-infected Onychostoma macrolepis. Furthermore, OmLEAP-2 regulated iron metabolism by increasing liver iron levels, altering serum iron content, and modulating iron-related genes (fpn1 and hepcidin) expression. Collectively, these findings demonstrate that OmLEAP-2 exhibits broad-spectrum antibacterial activity against aquatic pathogens and shows potential as a therapeutic peptide for treating bacterial disease.