title: Cyclic antimicrobial peptides based on Limulus anti-lipopolysaccharide factor for neutralization of lipopolysaccharide.
abstract: Bacterial endotoxin (lipopolysaccharide, LPS) is responsible for the septic shock syndrome. As potential therapeutic agents cyclic cationic antimicrobial peptides of different length, based on the Limulus anti-lipopolysaccharide factor (LALF), were synthesized, and their interaction with LPS was characterized physico-chemically and related to results in biological assays. All peptides inhibited the LPS-induced cytokine production in human mononuclear cells and the Limulus amebocyte lysate in a concentration-dependent way, with the peptide comprising the complete LPS-binding loop of the LALF (cLALF22) being the most effective. The peptides were neither cytotoxic nor hemolytic, except a slight effect of cLALF22. The peptides were able to displace Ca(2+) cations from a LPS monolayer, with cLALF22 being again most effective in accordance with results from isothermal titration calorimetry, in which saturation of binding was observed at an equimolar [cLALF22]:[LPS] ratio, and at a ratio 2-2.5 for the other peptides. For cLALF22, zeta (xi) potential experiments exhibited a complete compensation of the negative charges of LPS, whereas for the other peptides a residual negative potential of -20 to -40mV was found. X-ray diffraction experiments showed that the mixed unilamellar/cubic inverted aggregate structure of the lipid A part of LPS was converted into a multilamellar one. The gel to liquid crystalline phase transition of the acyl chains of LPS was changed upon cLALF22 binding, leading to a clear fluidization, which was not observed or only to a lesser degree for the other peptides. The affinity of the peptides for LPS led to a reduced binding of lipopolysaccharide-binding protein (LBP) to target membranes and hence to an inhibition of cytokine induction in human mononuclear cells.
authors.affiliation: Forschungszentrum Borstel, Leibniz-Zentrum für Medizin und Biowissenschaften, Biophysik, Parkallee 10, 23845 Borstel, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Andrä
authors.forename: Marta
authors.initials: M
authors.lastname: Lamata
authors.forename: Guillermo
authors.initials: G
authors.lastname: Martinez de Tejada
authors.forename: Rainer
authors.initials: R
authors.lastname: Bartels
authors.forename: Michel H J
authors.initials: MH
authors.lastname: Koch
authors.forename: Klaus
authors.initials: K
authors.lastname: Brandenburg
mesh_terms: D023181:Antimicrobial Cationic Peptides; D060829:Arthropod Proteins; D006801:Humans; D007447:Invertebrate Hormones / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009500:Neutralization Tests / Q000379:methods; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D010743:Phospholipids / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D060829:Arthropod Proteins; D007447:Invertebrate Hormones; D008070:Lipopolysaccharides; D010456:Peptides, Cyclic; D010743:Phospholipids; C034705:antilipopolysaccharide factor (Limulus)