Antibiotics are losing effectiveness as bacteria become resistant to conventional drugs. To find new alternatives, antimicrobial peptides (AMPs) are rationally designed with different lengths, charges, hydrophobicities (
- Award ID(s):
- 1659476
- NSF-PAR ID:
- 10188712
- Date Published:
- Journal Name:
- International Journal of Molecular Sciences
- Volume:
- 20
- Issue:
- 21
- ISSN:
- 1422-0067
- Page Range / eLocation ID:
- 5289
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
H ), and hydrophobic moments (μH), containing only three types of amino acids: arginine, tryptophan, and valine. Six AMPs with low minimum inhibitory concentrations (MICs) and <25% toxicity to mammalian cells are selected for biophysical studies. Their secondary structures are determined using circular dichroism (CD), which finds that the % α‐helicity of AMPs depends on composition of the lipid model membranes (LMMs): gram‐negative (G(−)) inner membrane (IM) >gram‐positive (G(+))> Euk33 (eukaryotic with 33 mol% cholesterol). The two most effective peptides, E2‐35 (16 amino acid [AA] residues) and E2‐05 (22 AAs), are predominantly helical in G(–) IM and G(+) LMMs. AMP/membrane interactions such as membrane elasticity, chain order parameter, and location of the peptides in the membrane are investigated by low‐angle and wide‐angle X‐ray diffuse scattering (XDS). It is found that headgroup location correlates with efficacy and toxicity. The membrane bending modulusK Cdisplays nonmonotonic changes due to increasing concentrations of E2‐35 and E2‐05 in G(–) and G(+) LMMs, suggesting a bacterial killing mechanism where domain formation causes ion and water leakage. -
Abstract Each year, thousands of patients die from antimicrobial‐resistant bacterial infections that fail to respond to conventional antibiotic treatment. Antimicrobial polymers are a promising new method of combating antibiotic‐resistant bacterial infections. We have previously reported the synthesis of a series of narrow‐spectrum peptidomimetic antimicrobial polyurethanes that are effective against Gram‐negative bacteria, such as
; however, these polymers are not effective against Gram‐positive bacteria, such asEscherichia coli . With the aim of understanding the correlation between chemical structure and antibacterial activity, we have subsequently developed three structural variants of these antimicrobial polyurethanes using post‐polymerization modification with decanoic acid and oleic acid. Our results show that such modifications converted the narrow‐spectrum antibacterial activity of these polymers into broad‐spectrum activity against Gram‐positive species such asStaphylococcus aureus , however, also increasing their toxicity to mammalian cells. Mechanistic studies of bacterial membrane disruption illustrate the differences in antibacterial action between the various polymers. The results demonstrate the challenge of balancing antimicrobial activity and mammalian cell compatibility in the design of antimicrobial polymer compositions. © 2019 Society of Chemical IndustryS. aureus -
Abstract Antimicrobial peptides (AMPs) are found throughout most kingdoms of life, are an important part of host immunity, and have been shown to act synergistically in various organisms to ameliorate bacterial infections. Herein, we report the synergistic behavior observed between two AMPs, Sub5 and CP10A, against
E. coli . In addition, enhanced synergistic activity againstE. coli andMRSA 43300 for two derivatives of Sub5, extended with the amino‐terminal copper and nickel (ATCUN) binding motif, is observed when dosed together with CP10A, while displaying little cytotoxicity towards human dermal fibroblasts. All three combinations of peptides co‐localized within bacterial cells as evidenced by fluorescence confocal microscopy. Investigations into the mechanism of synergy shows that all peptides indirectly damage DNA within cells, while only the ATCUN derivatives can oxidize phospholipids. Combinations of peptides were also shown to upregulate the concentration of reactive oxygen species within bothE. coli andMRSA 43300 . These results suggest that the production of reactive oxygen species is an important aspect mechanistically and further highlights the potential of these metallopeptides to aid in the treatment of antibiotic‐resistant infections. -
The threat of antibiotic resistance warrants the discovery of agents with novel antimicrobial mechanisms. Antimicrobial peptides (AMPs) directly disrupting bacterial membranes may overcome resistance to traditional antibiotics. AMP development for clinical use has been mostly limited to topical application to date. We developed a rational framework for systematically addressing this challenge using libraries composed of 86 novel Trp- and Arg-rich engineered peptides tested against clinical strains of the most common multidrug-resistant bacteria known as ESKAPE pathogens. Structure-function correlations revealed minimum lengths (as low as 16 residues) and Trp positioning for maximum antibacterial potency with mean minimum inhibitory concentration (MIC) of 2–4 μM and corresponding negligible toxicity to mammalian cells. Twelve peptides were selected based on broad-spectrum activity against both gram-negative and -positive bacteria and <25% toxicity to mammalian cells at maximum test concentrations. Most of the selected PAX remained active against the colistin-resistant clinical strains. Of the selected peptides, the shortest (the 16-residue E35) was further investigated for antibacterial mechanism and proof-of-concept in vivo efficacy. E35 killed an extensively-resistant isolate of Pseudomonas aeruginosa (PA239 from the CDC, also resistant to colistin) by irreversibly disrupting the cell membranes as shown by propidium iodide incorporation, using flow cytometry and live cell imaging. As proof of concept, in vivo toxicity studies showed that mice tolerated a systemic dose of up to 30 mg/kg peptide and were protected with a single 5 mg/kg intravenous (IV) dose against an otherwise lethal intraperitoneal injection of PA239. Efficacy was also demonstrated in an immune-compromised Klebsiella pneumoniae infection model using a daily dose of 4mg/kg E35 systemically for 2 days. This framework defines the determinants of efficacy of helical AMPs composed of only cationic and hydrophobic amino acids and provides a path for a potential departure from the restriction to topical use of AMPs toward systemic application.more » « less
-
null (Ed.)Abstract Background Though many plant defensins exhibit antibacterial activity, little is known about their antibacterial mode of action (MOA). Antimicrobial peptides with a characterized MOA induce the expression of multiple bacterial outer membrane modifications, which are required for resistance to these membrane-targeting peptides. Mini-Tn 5-lux mutant strains of Pseudomonas aeruginosa with Tn insertions disrupting outer membrane protective modifications were assessed for sensitivity against plant defensin peptides. These transcriptional lux reporter strains were also evaluated for lux gene expression in response to sublethal plant defensin exposure. Also, a plant pathogen, Pseudomonas syringae pv. syringae was modified through transposon mutagenesis to create mutants that are resistant to in vitro MtDef4 treatments. Results Plant defensins displayed specific and potent antibacterial activity against strains of P. aeruginosa . A defensin from Medicago truncatula , MtDef4, induced dose-dependent gene expression of the aminoarabinose modification of LPS and surface polycation spermidine production operons. The ability for MtDef4 to damage bacterial outer membranes was also verified visually through fluorescent microscopy. Another defensin from M. truncatula , MtDef5, failed to induce lux gene expression and limited outer membrane damage was detected with fluorescent microscopy. The transposon insertion site on MtDef4 resistant P. syringae pv. syringae mutants was sequenced, and modifications of ribosomal genes were identified to contribute to enhanced resistance to plant defensin treatments. Conclusions MtDef4 damages the outer membrane similar to polymyxin B, which stimulates antimicrobial peptide resistance mechanisms to plant defensins. MtDef5, appears to have a different antibacterial MOA. Additionally, the MtDef4 antibacterial mode of action may also involve inhibition of translation.more » « less