title: 1,2-Naphthoquinone suppresses lipopolysaccharide-dependent activation of IKKβ/NF-κB/NO signaling: an alternative mechanism for the disturbance of inducible NO synthase-catalyzed NO formation.
abstract: 1,2-Naphthoquinone (1,2-NQ) is an uncoupling agent for constitutive nitric oxide (NO) synthase (NOS), thereby inhibiting its catalytic activity. However, little information on whether this quinone can affect inducible NOS (iNOS) is available. To address this issue, we examined the effect of 1,2-NQ on lipopolysaccharide (LPS)-mediated induction of iNOS. Exposure of LPS-challenged RAW264.7 cells to 1,2-NQ resulted in decreased NO formation through a reduction in iNOS production. Under these conditions, LPS-induced activation of nuclear transcription factor-κB (NF-κB) coupled to phosphorylation of inhibitory κBα (IκBα) declined. Similar effects of 1,2-NQ were observed in the lungs of mice exposed to LPS. Using IκB kinase β (IKKβ)-transfected RAW264.7 cells and recombinant IKKβ protein, we found that 1,2-NQ diminished the phosphorylation of IκB by IKKβ enzymatic activity. Taken together, these results suggest that 1,2-NQ reduces iNOS-catalyzed NO production through 1) an uncoupling reaction, as reported previously, and/or 2) disruption of IKKβ/NF-κB signaling.
authors.affiliation: Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Daigo
authors.initials: D
authors.lastname: Sumi
authors.forename: Masako
authors.initials: M
authors.lastname: Akimori
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Inoue
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Takano
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kumagai
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002460:Cell Line; D024202:Electrophoretic Mobility Shift Assay; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009285:Naphthoquinones / Q000633:toxicity*; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
chemical_list: D008070:Lipopolysaccharides; D016328:NF-kappa B; D009285:Naphthoquinones; C482199:lipopolysaccharide, E coli O55-B5; D009569:Nitric Oxide; C040756:1,2-naphthoquinone; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051550:I-kappa B Kinase