Novel β-Hairpin Antimicrobial Peptides Containing the β-Turn Sequence of -RRRF- Having High Cell Selectivity and Low Incidence of Drug Resistance

Abstract

The emergence of multidrug-resistant bacteria has dramatically increased the lethality, level of resistance, and difficulty of treatment. In this study, a series of new antimicrobial peptides (AMPs) based on the β-hairpin structure with the template (XY) 2 RRRF(YX) 2 -NH 2 (X: hydrophobic amino acids; Y: cationic amino acids) were synthesized; surprisingly, almost all of the new peptides have strong antibacterial activity and negligible hemolytic toxicity. Particularly, the therapeutic index (TI) values of F(RI)2R and F(KW)2K reached up to 115.9 and 70.7, respectively. In addition, they did not show induced drug resistance and inhibited the development of antibiotic resistance when combined and used with traditional antibiotics. In addition, their antibacterial mechanism was preliminarily studied. Moreover, the new peptides F(RI)2R and F(KW)2K showed excellent performance in the pulmonary bacterial infection model and low toxicity in mice. In conclusion, F(RI)2R and F(KW)2K are considered new antimicrobial alternatives to address the antimicrobial-resistance crisis.

Hydrophobicity Determines the Bacterial Killing Rate of α-Helical Antimicrobial Peptides and Influences the Bacterial Resistance Development

“…Also, the more hydrophobic peptides induced higher PI fluorescence intensity than the less hydrophobic peptides (AS4-1 < AS4-5 < AS4-9) (Figure D). The AMP-induced bacterial membrane permeabilization generally results in continuous fluorescent dye transmembrane translocation for a long time even after bacterial cell death. , In the present study, although AS4-1, AS4-5, and AS4-9 needed less than 120 min to kill the bacterial cells in killing kinetics assay (Figure A), we can find that the calcein and PI fluorescence intensity induced by them continuously increased with the time extension to 180 min. All the results above prove that hydrophobicity, rather than net charge, is the key structural parameter for α-helical AMPs to permeabilize the bacterial IM and lead to the subsequent cell lysis.…”

Temporin-GHb-Derived Peptides Exhibit Potent Antibacterial and Antibiofilm Activities against Staphylococcus aureus In Vitro and Protect Mice from Acute Infectious Pneumonia

“…The results demonstrated that GHb3K and GHbK4R not only have good antibacterial activity in vitro but also show better therapeutic efficacy than vancomycin in acute pneumonia in vivo. It was reported that F­(RI)­2R and F­(KW)­2K exhibited anti-infection effects in a mouse model of pulmonary infections by S. aureus . Although F­(RI)­2R and F­(KW)­2K showed remarkable efficacy in vivo, they were toxic to the lung and liver.…”

“…It was reported that F(RI)2R and F(KW)2K exhibited anti-infection effects in a mouse model of pulmonary infections by S. aureus. 44 Although F(RI)2R and F(KW)2K showed remarkable efficacy in vivo, they were toxic to the lung and liver. In comparison, GHb3K and GHbK4R exhibited superior bactericidal properties, low toxicity, and high stability.…”

“…The peptides were dissolved in deionized water, 50% TFE (mimicking the hydrophobic environment of microbial membrane), and 30 mM SDS (mimicking the negatively charged prokaryotic membrane) at a concentration of 0.4 mg/mL. 44 The peptide solution was added into a quartz cuvette with 0.1 cm path lengths. The spectrum was monitored by using a Chirascan spectropolarimeter (Applied Photophysics, Leatherhead, UK) from 190 to 250 nm.…”

To Fold or Not to Fold: Diastereomeric Optimization of an α-Helical Antimicrobial Peptide

“…Membrane disruptive antimicrobial peptides (AMPs), which occur naturally as part of the innate immune system, offer an opportunity to address multidrug-resistant (MDR) bacteria because of their unspecific mechanism of action, against which resistance does not occur easily. − Such AMPs are however unstable in serum and most often toxic owing to their membrane disruptive amphiphilic and usually α-helical structure triggering their antibacterial effect. Their properties can be improved by sequence optimization, − whereby the most versatile approach consists in introducing non-natural structural elements such as d -amino acids, − non-natural residues, β- or γ-amino acids, , isopeptide bonds, or entirely non-peptidic elements such as spermine or fatty acids. , A complete redesign of AMPs is also possible in the form of dimers, cyclic or bicyclic staples, − small molecules, peptoids, , foldamers, or dendrimers. , …”