Effect of Disulfide Cyclization of Ultrashort Cationic Lipopeptides on Antimicrobial Activity and Cytotoxicity

Abstract

Ultrashort cationic lipopeptides (USCLs) are considered to be a promising class of antimicrobials with high activity against a broad-spectrum of microorganisms. However, the majority of these compounds are characterized by significant toxicity toward human cells, which hinders their potential application. To overcome those limitations, several approaches have been advanced. One of these is disulfide cyclization that has been shown to improve drug-like characteristics of peptides. In this article the effect of disulfide cyclization of the polar head of N-palmitoylated USCLs on in vitro biological activity has been studied. Lipopeptides used in this study consisted of three or four basic amino acids (lysine and arginine) and cystine in a cyclic peptide. In general, disulfide cyclization of the lipopeptides resulted in peptides with reduced cytotoxicity. Disulfide-cyclized USCLs exhibited improved selectivity between Candida sp., Gram-positive strains and normal cells in contrast to their linear counterparts. Interactions between selected USCLs and membranes were studied by molecular dynamics simulations using a coarse-grained force field. Moreover, membrane permeabilization properties and kinetics were examined. Fluorescence and transmission electron microscopy revealed damage to Candida cell membrane and organelles. Concluding, USCLs are strong membrane disruptors and disulfide cyclization of polar head can have a beneficial effect on its in vitro selectivity between Candida sp. and normal human cells.

Biological and Physico-Chemical Characteristics of Arginine-Rich Peptide Gemini Surfactants with Lysine and Cystine Spacers

“…It was found that the curves represent zero-order reaction kinetics ([E]>>[S]), especially after the first 15 min. Similar results were obtained for USCLs consisting of palmitic acid and cationic amino acid residues (lysine and arginine) [ 120 ] and other cationic antimicrobial peptides (e.g., NCP-3, ADP) [ 124 , 125 ].…”

“…In general, all surfactants permeabilize both IM and OM and exhibited comparable lithic action on membranes. Similar results were obtained in experiments with USCLs and other antimicrobial cationic peptides, but raising the peptide concentrations did not always lead to a more pronounced inner membrane disruption and can differ significantly between monomeric and dimerized antimicrobial peptides [ 120 , 127 ]. Presumably, this can be due to some specific interactions with enzymes, substrates, or reaction products.…”

“…In this study, the biofilm of C. glabrata turned out to be more resistant to lipopeptides than that of C. albicans , whereas the antimicrobial activity against planktonic cultures was similar between both strains. In our previous studies, MBEC of USCLs against biofilms were almost identical between these two strains [ 120 ]. It was noticed that amphotericin B, which disrupts the plasma membrane, preferentially affects germ tubes [ 121 ].…”

“…Lipopeptide hydrophobicity was determined as described previously [ 120 ]. To do this, a Waters Alliance e2695 system with a Waters 2998 PDA Detector (software-Empower 3, Waters, Milford, MA, USA) was used.…”

“…The MBECs were determined as described previously using 96-well polystyrene flat-bottom plates [ 15 , 120 ]. For this purpose, 24 h cultures of microorganisms were diluted to obtain a final density of 5.0 × 10 5 CFU/mL and 2.0 × 10 5 CFU/mL of bacteria and fungi, respectively.…”