Broad-spectrum activity of membranolytic cationic macrocyclic peptides against multi-drug resistant bacteria and fungi

• Published in: European journal of pharmaceutical sciences 2024-06, Vol.197, p.106776-106776, Article 106776
• Main Authors: Lohan, Sandeep, Konshina, Anastasia G., Tiwari, Rakesh K., Efremov, Roman G., Maslennikov, Innokentiy, Parang, Keykavous
• Format: Article
• Language: English
• Subjects: Antibiotics; Antifungal peptides; Antimicrobial peptides; Bacteria; Cyclic peptides; Drug resistance; Membranolytic; Molecular dynamics; Molecular hydrophobicity potential; Peptide-membrane interactions
• ISSN: 0928-0987; 1879-0720
• DOI: 10.1016/j.ejps.2024.106776

•A series of cyclic peptides composed of non-canonical amino acids were synthesized and characterized.•Peptides displayed broad-spectrum activity against multidrug-resistant bacteria and fungi.•Peptides showed rapid killing action and antibiofilm activity against resistant strains of bacteria and fungi.•Peptides displayed selective membranolytic action against bacterial membrane over the mammalian membrane.•Peptides showed high plasma stability and negligible signs of resistance development. The emergence of multidrug-resistant (MDR) strains causes severe problems in the treatment of microbial infections owing to limited treatment options. Antimicrobial peptides (AMPs) are drawing considerable attention as promising antibiotic alternative candidates to combat MDR bacterial and fungal infections. Herein, we present a series of small amphiphilic membrane-active cyclic peptides composed, in part, of various nongenetically encoded hydrophilic and hydrophobic amino acids. Notably, lead cyclic peptides 3b and 4b showed broad-spectrum activity against drug-resistant Gram-positive (MIC = 1.5–6.2 µg/mL) and Gram-negative (MIC = 12.5–25 µg/mL) bacteria, and fungi (MIC = 3.1–12.5 µg/mL). Furthermore, lead peptides displayed substantial antibiofilm action comparable to standard antibiotics. Hemolysis (HC50 = 230 µg/mL) and cytotoxicity (>70 % cell viability against four different mammalian cells at 100 µg/mL) assay results demonstrated the selective lethal action of 3b against microbes over mammalian cells. A calcein dye leakage experiment substantiated the membranolytic effect of 3b and 4b, which was further confirmed by scanning electron microscopy. The behavior of 3b and 4b in aqueous solution and interaction with phospholipid bilayers were assessed by employing nuclear magnetic resonance (NMR) spectroscopy in conjunction with molecular dynamics (MD) simulations, providing a solid structural basis for understanding their membranolytic action. Moreover, 3b exhibited stability in human blood plasma (t1/2 = 13 h) and demonstrated no signs of resistance development against antibiotic-resistant S. aureus and E. coli. These findings underscore the potential of these newly designed amphiphilic cyclic peptides as promising anti-infective agents, especially against Gram-positive bacteria. [Display omitted]