title: Endotoxin-neutralizing activity and mechanism of action of a cationic α-helical antimicrobial octadecapeptide derived from α-amylase of rice.
abstract: We have previously reported that AmyI-1-18, an octadecapeptide derived from α-amylase (AmyI-1) of rice, is a novel cationic α-helical peptide that exhibited antimicrobial activity against human pathogens, including Porphyromonas gingivalis, Pseudomonas aeruginosa, Propionibacterium acnes, Streptococcus mutans, and Candida albicans. In this study, to further investigate the potential functions of AmyI-1-18, we examined its inhibitory ability against the endotoxic activities of lipopolysaccharides (LPSs, smooth and Rc types) and lipid A from Escherichia coli. AmyI-1-18 inhibited the production of endotoxin-induced nitric oxide (NO), an inflammatory mediator, in mouse macrophages (RAW264) in a concentration-dependent manner. The results of a chromogenic Limulus amebocyte lysate assay illustrated that the ability [50% effective concentration (EC50): 0.17 μM] of AmyI-1-18 to neutralize lipid A was similar to its ability (EC50: 0.26 μM) to neutralize LPS, suggesting that AmyI-1-18 specifically binds to the lipid A moiety of LPS. Surface plasmon resonance analysis of the interaction between AmyI-1-18 and LPS or lipid A also suggested that AmyI-1-18 directly binds to the lipid A moiety of LPS because the dissociation constant (KD) of AmyI-1-18 with lipid A is 5.6×10(-10) M, which is similar to that (4.3×10(-10) M) of AmyI-1-18 with LPS. In addition, AmyI-1-18 could block the binding of LPS-binding protein to LPS, although its ability was less than that of polymyxin B. These results suggest that AmyI-1-18 expressing antimicrobial and endotoxin-neutralizing activities is useful as a safe and potent host defense peptide against pathogenic Gram-negative bacteria in many fields of healthcare.
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan; Center for Transdisciplinary Research, Niigata University, Niigata 950-2181, Japan. Electronic address: mtanig@eng.niigata-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Taniguchi
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Ochiai
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Matsushima
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Tajima
authors.affiliation: Department of Chemistry, Tokyo Dental College, Tokyo 101-0062, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kato
authors.affiliation: Graduate School of Technology, Niigata Institute of Technology, Niigata 945-1195, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Saitoh
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D020128:Inhibitory Concentration 50; D008050:Lipid A / Q000737:chemistry* / Q000494:pharmacology; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D012275:Oryza / Q000201:enzymology; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry*; D000067996:RAW 264.7 Cells; D000516:alpha-Amylases / Q000737:chemistry*
chemical_list: D000893:Anti-Inflammatory Agents; D023181:Antimicrobial Cationic Peptides; D008050:Lipid A; D010446:Peptide Fragments; D010940:Plant Proteins; D009569:Nitric Oxide; D000516:alpha-Amylases
keywords: Anti-inflammatory activity; Endotoxin-neutralizing peptide; LPS-binding activity; Lipid A-binding activity; Multi-functional peptide