Cyclic antimicrobial peptides based on Limulus anti-lipopolysaccharide factor for neutralization of lipopolysaccharide

• Published in: Biochemical pharmacology Vol. 68; no. 7; pp. 1297 - 1307
• Main Authors: Andrä, Jörg, Lamata, Marta, Martinez de Tejada, Guillermo, Bartels, Rainer, Koch, Michel H.J., Brandenburg, Klaus
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-10-2004; Elsevier Science
• Subjects: Antimicrobial Cationic Peptides; Antimicrobial peptide; Arthropod Proteins; Biological and medical sciences; Cytokine induction; Humans; Invertebrate Hormones - pharmacology; LALF; Limulus test; Lipopolysaccharides - antagonists & inhibitors; Lipopolysaccharides - metabolism; LPS neutralization; Medical sciences; Neutralization Tests - methods; Peptides, Cyclic - chemical synthesis; Peptides, Cyclic - chemistry; Peptides, Cyclic - pharmacology; Pharmacology. Drug treatments; Phospholipids - metabolism; Tumor-necrosis-factor-α; MNC; Cytokine induction; FTIR; LPS neutralization; Limulus test; Tumor-necrosis-factor-α; FRET; LALF; LPS; Antimicrobial peptide; Cytokine; Pharmacology; Antimicrobial agent; Tumor necrosis factor; Arthropoda; Merostomata; Limulus; Lipopolysaccharide; Tumor-necrosis-factor-a; Invertebrata
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2004.05.054

Bacterial endotoxin (lipopolysaccharide, LPS) is responsible for the septic shock syndrom. 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 (
ξ) potential experiments exhibited a complete compensation of the negative charges of LPS, whereas for the other peptides a residual negative potential of −20 to −40
mV 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.