magainin-2-peptide--xenopus and Shock--Septic

CA-MA is a hybrid antimicrobial peptide (AMP) derived from two naturally occurring AMPs, cecropin A and magainin 2. CA-MA shows strong antimicrobial activity against Gram-negative and Gram-positive bacteria but also exhibits cytotoxicity toward mammalian cells. Our objective was to identify CA-MA analogues with reduced cytotoxicity by systematic replacement of amino acids with positively charged R groups (His and Lys), aliphatic R groups (Leu), or polar R groups (Glu). Among the CA-MA analogues studied (CMA1 to -6), CMA3 showed the strongest antimicrobial activity, including against drug-resistant Escherichia coli and Pseudomonas aeruginosa strains isolated from hospital patients. CMA3 appeared to act by inducing pore formation (toroidal model) in the bacterial membrane. In cytotoxicity assays, CMA3 showed little cytotoxicity toward human red blood cells (hRBCs) or HaCaT cells. Additionally, no fluorescence was released from small or giant unilamellar vesicles exposed to 60 μM CMA3 for 80 s, whereas fluorescence was released within 35 s upon exposure to CA-MA. CMA3 also exerted strong lipopolysaccharide (LPS)-neutralizing activity in RAW 264.7 cells, and BALB/c mice exposed to LPS after infection by Escherichia coli showed improved survival after administration of one 0.5-mg/kg of body weight or 1-mg/kg dose of CMA3. Finally, in a mouse model of septic shock, CMA3 reduced the levels of proinflammatory factors, including both nitric oxide and white blood cells, and correspondingly reduced lung tissue damage. This study suggests that CMA3 is an antimicrobial/antiendotoxin peptide that could serve as the basis for the development of anti-inflammatory and/or antimicrobial agents with low cytotoxicity.

Topics: Amino Acid Sequence; Amino Acid Substitution; Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents, Non-Steroidal; Antimicrobial Cationic Peptides; Cell Line; Cell Membrane; Erythrocytes; Escherichia coli; Escherichia coli Infections; Humans; Keratinocytes; Lipopolysaccharides; Macrophages; Magainins; Male; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Nitric Oxide; Protein Engineering; Pseudomonas aeruginosa; Shock, Septic; Survival Analysis; Xenopus Proteins

The therapeutic efficacies of three polycationic peptides selected among the class of the magainins (magainin I, magainin II, and magainin II amide), alone and combined with piperacillin, were investigated in a rat model of septic shock. Rats were given an intraperitoneal injection of 2 x 10(10) CFU of Escherichia coli and randomized to receive intraperitoneally isotonic sodium chloride solution, 60 mg of piperacillin per kg of body weight, and 1 mg of each magainin per kg alone and combined with 60 mg of piperacillin per kg. The main outcome measures were bacterial growth in abdominal exudate and plasma, endotoxin and tumor necrosis factor alpha (TNF-alpha) concentrations in plasma, and lethality. Treatments with the magainins achieved significant reductions of bacterial growth and plasma endotoxin and TNF-alpha concentrations. In general, treatments with the combinations of magainins and piperacillin demonstrated the highest efficacies.

Topics: Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Disease Models, Animal; Drug Therapy, Combination; Gram-Negative Bacteria; Gram-Negative Bacterial Infections; Infusions, Parenteral; Magainins; Male; Microbial Sensitivity Tests; Piperacillin; Rats; Rats, Wistar; Shock, Septic; Treatment Outcome; Xenopus Proteins