Antimicrobial activity of trout hepcidin

Area of Science:

• Biochemistry
• Antimicrobial Peptides
• Molecular Biology

Background:

• Hepcidin, a liver-produced peptide hormone, possesses antimicrobial properties and a conserved beta-sheet structure.
• Previous studies identified hepcidin expression in rainbow trout liver, inducible by iron and lipopolysaccharide (LPS).
• The role of hepcidin's conformation and oxidative state in its antimicrobial function requires further investigation.

Purpose of the Study:

• To analyze the importance of hepcidin's peptide conformation and oxidative state in its antimicrobial activity.
• To elucidate the mechanism of hepcidin's antimicrobial action, including its interaction with bacterial cells and DNA.
• To investigate the role of the N-terminal ATCUN motif in hepcidin's function.

Main Methods:

• Comparison of antimicrobial activity between reduced (alpha-helix) and oxidized (beta-sheet) hepcidin forms against Escherichia coli and Piscirickettsia salmonis.
• Confocal microscopy to determine intracellular localization of hepcidin in P. salmonis.
• Sytox permeation assays to assess membrane disruption.
• DNA hydrolysis assays using hepcidin, ascorbate, and CuCl2, with and without the N-terminal ATCUN motif.

Main Results:

• Oxidized hepcidin demonstrated greater antimicrobial efficacy than reduced hepcidin against both tested bacteria.
• Confocal analysis confirmed intracellular localization of hepcidin within P. salmonis, and membrane disruption was ruled out as the primary mechanism.
• Hepcidin induced DNA hydrolysis in the presence of ascorbate and CuCl2, dependent on its N-terminal ATCUN motif; a truncated variant lacked this activity.

Conclusions:

• Correct folding of hepcidin is essential for its antimicrobial activity.
• The N-terminal ATCUN motif is implicated in hepcidin's ability to induce oxidative damage to macromolecules like DNA.
• Hepcidin's antimicrobial mechanism involves intracellular action and potential oxidative damage, rather than membrane disruption.