We have investigated structural changes of peptides related to antimicrobial peptide Halictine-1 (HAL-1) induced by interaction with various membrane-mimicking models with the aim to identify a mechanism of the peptide mode of action and to find a correlation between changes of primary/secondary structure and biological activity. Modifications in the HAL-1 amino acid sequence at particular positions, causing an increase of amphipathicity (Arg/Lys exchange), restricted mobility (insertion of Pro) and consequent changes in antimicrobial and hemolytic activity, led to different behavior towards model membranes. Secondary structure changes induced by peptide-membrane interaction were studied by circular dichroism, infrared spectroscopy, and fluorescence spectroscopy. The experimental results were complemented by molecular dynamics calculations. An α-helical structure has been found to be necessary but not completely sufficient for the HAL-1 peptides antimicrobial action. The role of alternative conformations (such as β-sheet, PPII or 310-helix) also seems to be important. A mechanism of the peptide mode of action probably involves formation of peptide assemblies (possibly membrane pores), which disrupt bacterial membrane and, consequently, allow membrane penetration.

• Keywords
• antibacterial peptides, circular dichroism, fluorescence, halictine, infrared spectroscopy,
• MeSH
• Anti-Bacterial Agents chemistry   metabolism   MeSH
• Phosphatidylcholines chemistry   MeSH
• Phosphatidylglycerols chemistry   MeSH
• Hydrophobic and Hydrophilic Interactions MeSH
• Antimicrobial Cationic Peptides chemistry   metabolism   MeSH
• Kinetics MeSH
• Protein Conformation, alpha-Helical MeSH
• Protein Conformation, beta-Strand MeSH
• Lipid Bilayers chemistry   MeSH
• Permeability MeSH
• Amino Acid Sequence MeSH
• Molecular Dynamics Simulation MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Phosphatidylcholines MeSH
• Phosphatidylglycerols MeSH
• Antimicrobial Cationic Peptides MeSH
• Lipid Bilayers MeSH

We examined the benefits of short linear α-helical antimicrobial peptides (AMPs) invented in our laboratory for treating bone infection and preventing microbial biofilm formation on model implants due to causative microorganisms of osteomyelitis. For this purpose, we introduced a model of induced osteomyelitis that utilizes human femur heads obtained from the hospital after their replacement with artificial prostheses. We found that the focus of the infection set up in the spongy part of this bone treated with AMP-loaded calcium phosphate cement was eradicated much more effectively than was the focus treated with antibiotics such as vancomycin or gentamicin loaded into the same cement. This contradicts the minimum inhibitory concentrations (MIC) values of AMPs and antibiotics against some bacterial strains obtained in standard in vitro assays. The formation of microbial biofilm on implants made from poly(methylmethacrylate)-based bone cement loaded with AMP was evaluated after the implants' removal from the infected bone sample. AMPs loaded in such model implants prevented microbial adhesion and subsequent formation of bacterial biofilm on their surface. Biofilms did form, on the other hand, on control implants made from the plain cement when these were implanted into the same infected bone sample. These results of the experiments performed in human bone tissue highlight the clinical potential of antimicrobial peptides for use in treating and preventing osteomyelitis caused by resistant pathogens.

• Keywords
• antimicrobial peptides, bone cement, femur heads, implant-related infections, osteomyelitis,
• Publication type
• Journal Article MeSH