A stable cyclized antimicrobial peptide derived from LL-37 with host immunomodulatory effects and activity against uropathogens

Abstract

The increasing antibiotic resistance among uropathogenic bacteria warrants alternative therapeutic strategies. We demonstrate the potential of the synthetic peptide CD4-PP, designed by dimerization and backbone cyclization of the shortest antimicrobial region of human cathelicidin, LL-37. CD4-PP is active against clinical and type strains of common uropathogens Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa at concentrations substantially below cellular cytotoxic levels and induced membrane deformation and leakage in E. coli and P. aeruginosa. Furthermore, CD4-PP treatment prevented the formation of new biofilm and dissolved mature biofilm created by E. coli and P. aeruginosa and targeted curli amyloid in E. coli biofilms. In addition, CD4-PP also induced production of LL-37 by uroepithelial cells and increased the expression of tight junction proteins claudin-14 and occludin. During uroepithelial cell infection, CD4-PP significantly reduced uropathogen survival when treatment was given at the start of infection. Low micromolar of CD4-PP treatment initiated after 2 h was successful with all tested species, except P. aeruginosa where CD4-PP was unable to reduce survival, which could be attributed by early biofilm formation. Finally, we demonstrated that urinary catheter pieces coated with saline fluid supplemented with CD4-PP reduced the attachment of E. coli, giving it a potential clinical application.

A Synthetic Cyclized Antimicrobial Peptide with Potent Effects against Drug-Resistant Skin Pathogens

“…The peptide induced the formation of blebs and ruffling of the bacterial surface compared with controls (Figure A–F). The blebbing pattern was comparable with what we had previously observed for E. coli . This suggests that CD4-PP has similar bacterial membrane deformation potential against both Gram-negative and Gram-positive bacteria.…”

“…CD4-PP was designed as a backbone cyclic dimer peptide based on the shortest antimicrobial sequence of LL-37, , called KR-12 . Two KR-12 units were then connected using linkers of four amino acids into a seamless chain of peptide bonds.…”

“…However, while these examples share a cyclic backbone, they represent different structural classes: RTD-1 and protegrin are both β-sheet peptides, while cyclotides may be described as more globular peptides, and they are all constrained by disulfide bonds. In contrast, the design of CD4-PP is based on two α-helical peptide monomers, whose structure is maintained when the peptide is in contact with lipid (cell) membranes …”

Peptide Stability Is Important but Not a General Requirement for Antimicrobial and Antibiofilm Activity In Vitro and In Vivo

“…19 White et al reported that an improved form of the cyclic KR-12 peptide shows promising results as a new antibiofilm agent. 38 In all these studies, peptide engineering to enhance peptide stability was an important part of the research. How peptide stability might influence the experimental outcomes is not well understood.…”

“…C10-KR8d, made in d -amino acids, is highly selective and potent . White et al reported that an improved form of the cyclic KR-12 peptide shows promising results as a new antibiofilm agent . In all these studies, peptide engineering to enhance peptide stability was an important part of the research.…”