polymyxin-b(1) and Hemolysis

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Bacteria; Cell Membrane; Cell Survival; Drug Design; Gram-Negative Bacteria; Gram-Positive Bacteria; HEK293 Cells; Hemolysis; Humans; Magnetic Resonance Spectroscopy; Microbial Sensitivity Tests; Molecular Dynamics Simulation; Peptides

Due to the threat of escalating multi-drug resistant gram-negative bacteria to human health and life, novel antimicrobial agents against gram-negative pathogens are urgently needed. As antimicrobial peptides are not prone to induce bacteria resistance, they are believed to be one kind of promising class of potential antimicrobial agent candidates to combat multi-drug resistant bacteria for long-term use. Jelleine-1, first isolated from the royal jelly of honeybees, is a typical amphiphilic antimicrobial peptide and shows broad antimicrobial spectrum and negligible toxicity. To promote its antimicrobial activity and extend its potential of clinical use against multi-drug resistant gram-negative bacteria, novel analogs of jelleine-1 were designed, synthesized and their antimicrobial functions and toxicity were examined in this study. Our results showed that fine tuning of the cationic charge, polarity, and basicity of the sequence through amino acids substitution at position 3, 5, 7 and maintaining position 1, 4, 6, 8 unchanged could improve the bioactivity of jelleine-1 significantly. Meanwhile, we also found that the substitution of phenylalanine by tryptophan also could improve the antimicrobial activity of jelleine-1. Among all the analogs, analog 15, which is enriched in arginine and leucine, showed the most potent antimicrobial activity against both gram-negative and gram-positive bacteria, especially to multi-drug resistant Pseudomonas aeruginosa in vivo and in vitro. In addition, analog 15 also showed potent inhibition of the formation of multi-drug resistant P. aeruginosa biofilm and negligible toxicity, which was certified by MTT, hemolysis, blood assay, and biochemical analysis.

Topics: Amino Acid Sequence; Animals; Antimicrobial Cationic Peptides; Bees; Biofilms; Cell Survival; Disease Models, Animal; Drug Resistance, Multiple, Bacterial; Fatty Acids; Gram-Negative Bacteria; Gram-Positive Bacteria; Hemolysis; Humans; Male; Mice; Microbial Sensitivity Tests; Oligopeptides; Permeability; Pseudomonas aeruginosa; Sepsis

Substrate-based sirtuin inhibitors target bacterial genome and RNA and provide a promising approach to address bacterial resistance issues, if cellular internalisation can be achieved. We designed N-trifluoroacetyl lysine and N-thioacetyl lysine peptides (KP 13, KP 15 and KP 24) as inhibitors of bacterial sirtuins and their cell-penetrating peptide conjugates Tat KP 13, Tat KP 15 and Tat KP 24. The conjugated peptides were successfully internalised and showed signs of bacterial transcription inhibition resulting in enhanced antibacterial potency against model Gram negative and Gram positive pathogens. Synergistic activity in combination with streptomycin and polymyxin B has also been established. These peptides were effective in inhibiting biofilm formation and eradicating preformed biofilms. Morphological analysis using both SEM and TEM showed bacterial membrane disruption. Calcein dye leakage analysis established the selectivity of these peptides to bacterial membranes. This study documents the first report of the application of substrate-based sirtuin inhibitors as antimicrobial therapeutics.

Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Biofilms; Cell Survival; Cell-Penetrating Peptides; Drug Design; Escherichia coli; Gram-Negative Bacteria; Gram-Positive Bacteria; Hemolysis; Humans; Lysine; Mice; Microbial Sensitivity Tests; Sirtuins; Staphylococcus aureus; Unilamellar Liposomes

Topics: Animals; Anti-Bacterial Agents; Bacteremia; Cell Membrane; Drug Design; Escherichia coli; Hemolysis; Male; Mice, Inbred C57BL; Microbial Sensitivity Tests; Molecular Structure; Pyrimidines; Rabbits; Staphylococcus aureus; Structure-Activity Relationship; Thiazoles; Thiophenes

We have designed de novo and synthesized ten 26-residue D-conformation amphipathic α-helical cationic antimicrobial peptides (AMPs), seven with "specificity determinants", which provide specificity for prokaryotic cells over eukaryotic cells. The ten AMPs contain five or six positively charged residues (d-Arg, d-Lys, d-Orn, l-Dab, or l-Dap) on the polar face to understand their role in hemolytic activity against human red blood cells and antimicrobial activity against seven Acinetobacter baumannii strains, resistant to polymyxin B and colistin, and 20 A. baumannii worldwide isolates from 2016 and 2017 with antibiotic resistance to 18 different antibiotics. AMPs with specificity determinants and with l-Dab and l-Dap residues on the polar face have essentially no hemolytic activity at 1000 μg/mL (380 μM), showing for the first time the importance of these unusual amino acid residues in solving long-standing hemolysis issues of AMPs. Specificity determinants maintained excellent antimicrobial activity in the presence of human sera.

Topics: Acinetobacter baumannii; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Drug Design; Erythrocytes; Hemolysis; Humans; Hydrophobic and Hydrophilic Interactions; Microbial Sensitivity Tests; Protein Conformation, alpha-Helical; Protein Structure, Secondary

Antimicrobial peptides are an important weapon against invading pathogens and are potential candidates as novel antibacterial agents, but their antifungal activities are not fully developed. In this study, a set of imperfectly amphipathic peptides was developed based on the imperfectly amphipathic palindromic structure R

Topics: Amino Acid Sequence; Animals; Antifungal Agents; Candida albicans; Cytoplasm; Drug Resistance, Fungal; HEK293 Cells; Hemolysis; Humans; Hydrophobic and Hydrophilic Interactions; Intracellular Membranes; Inverted Repeat Sequences; Mice; Models, Molecular; Peptides; Protein Conformation; RAW 264.7 Cells