title: Endotoxin (lipopolysaccharide) neutralization by innate immunity host-defense peptides. Peptide properties and plausible modes of action.
abstract: Binding of lipopolysaccharide (LPS) to macrophages results in proinflammatory cytokine secretion. In extreme cases it leads to endotoxic shock. A few innate immunity antimicrobial peptides (AMPs) neutralize LPS activity. However, the underlying mechanism and properties of the peptides are not yet clear. Toward meeting this goal we investigated four AMPs and their fluorescently labeled analogs. These AMPs varied in composition, length, structure, and selectivity toward cells. The list included human LL-37 (37-mer), magainin (24-mer), a 15-mer amphipathic alpha-helix, and its D,L-amino acid structurally altered analog. The peptides were investigated for their ability to inhibit LPS-mediated cytokine release from RAW264.7 and bone marrow-derived primary macrophages, to bind LPS in solution, and when LPS is already bound to macrophages (fluorescence spectroscopy and confocal microscopy), to compete with LPS for its binding site on the CD14 receptor (flow cytometry) and affect LPS oligomerization. We conclude that a strong binding of a peptide to LPS aggregates accompanied by aggregate dissociation prevents LPS from binding to the carrier protein lipopolysaccharide-binding protein, or alternatively to its receptor, and hence inhibits cytokine secretion.
authors.affiliation: Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Yosef
authors.initials: Y
authors.lastname: Rosenfeld
authors.forename: Niv
authors.initials: N
authors.lastname: Papo
authors.forename: Yechiel
authors.initials: Y
authors.lastname: Shai
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004731:Endotoxins / Q000737:chemistry*; D006801:Humans; D007113:Immunity, Innate; D015850:Interleukin-6 / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology*; D008264:Macrophages / Q000276:immunology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010455:Peptides / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D012842:Sarcoma Virus, Woolly Monkey; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: D004731:Endotoxins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D010455:Peptides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C504014:lipopolysaccharide-6B, Yersinia pestis