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Inflammation Research

, Volume 54, Issue 2, pp 66–73 | Cite as

Augmentation of the bactericidal activities of human cathelicidin CAP18/LL-37-derived antimicrobial peptides by amino acid substitutions

  • I. NagaokaEmail author
  • K. Kuwahara-Arai
  • H. Tamura
  • K. Hiramatsu
  • M. Hirata
Original Research Paper

Abstract.

Objective: Mammalian myeloid and epithelial cells express various peptide antibiotics (such as defensins and cathelicidins) that contribute to the innate host defense against invading micro-organisms. Among these, human cathelicidin CAP18/LL-37 (L1-S37) possesses potent antibacterial activities against Gram-positive and Gram-negative bacteria. In this study, to develop peptide derivatives with improved bactericidal actions, we utilized the amphipathic 18-mer peptide (K15–V32) of LL-37 as a template, and evaluated the activities of modified peptides.

Methods: Antibacterial activities of the peptides (0.022 ~ 4.4 μM corresponding to 0.1 ~ 10 μg/ml) were assessed by alamarBlueTM assay using Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa as target organisms. Furthermore, the membrane-permeabilization activities of the peptides were examined by using E. coli ML-35p as a target.

Results: By substituting E16 and K25 with two L residues, the hydrophobicity of the peptide (18-mer LL) was increased, and by further substituting Q22, D26 and N30 with three K residues, the cationicity of the peptide (18-mer LLKKK) was enhanced. Among peptide derivatives, 18-mer LLKKK exhibited the most potent antibacterial actions against S. aureus (methicillin-resistant and -sensitive), S. pneumoniae, S. pyogenes, E. coli and P. aeruginosa, and possessed the most powerful membrane-permeabilizing activities against E. coli ML-35p at the effective concentrations (p < 0.05, 18-mer LLKKK vs. 18-mer LL, 18-mer K15-V32 and LL-37).

Conclusions: Bactericidal activities of the amphipathic human CAP18/LL-37-derived 18-mer peptide can be augmented by modifying its hydrophobicity and cationicity, and 18-mer LLKKK is the most potent among peptide derivatives with therapeutic potential for Gram-positive and Gram-negative bacterial infections.

Key words.

Cathelicidin Antibacterial peptide Hydrophobicity Hydrophilicity Amino acid substitution 

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Copyright information

© Birkhäuser Verlag, Basel 2005

Authors and Affiliations

  • I. Nagaoka
    • 1
    Email author
  • K. Kuwahara-Arai
    • 2
  • H. Tamura
    • 3
  • K. Hiramatsu
    • 2
  • M. Hirata
    • 4
  1. 1.Department of Host Defense and Biochemical Research, School of MedicineJuntendo UniversityTokyoJapan
  2. 2.Department of Bacteriology, School of MedicineJuntendo UniversityTokyoJapan
  3. 3.Seikagaku CorporationTokyoJapan
  4. 4.Institute of Ohtaka Enzyme Co.HokkaidoJapan

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