title: 5-Hydroxy-3,6,7,8,3'4'-hexamethoxyflavone inhibits nitric oxide production in lipopolysaccharide-stimulated BV2 microglia via NF-κB suppression and Nrf-2-dependent heme oxygenase-1 induction.
abstract: In this study, we found that 5-hydroxy-3,6,7,8,3'4'-hexamethoxyflavone (5HHMF) from Hizikia fusiforme considerably inhibits lipopolysaccharide (LPS)-stimulated NO production by suppressing the expression of inducible NO synthase (iNOS) in BV2 microglia. In addition, 5HHMF blocked LPS-induced phosphorylation of IκB, resulting in suppression of the nuclear translocation of nuclear factor-κB (NF-κB) subunits, namely p65 and p50, which are important molecules involved in the regulation of iNOS expression. Pyrrolidine dithiocarbamate (PDTC), a specific NF-κB inhibitor, along with 20S proteasome inhibitor (PSI) significantly inhibited LPS-induced iNOS expression, which indirectly suggested that 5HHMF downregulated iNOS expression by suppressing NF-κB activity. Thus, we found that 5HHMF enhances heme oxygenase-1 (HO-1) expression via nuclear factor-erythroid 2-related factor 2 (Nrf2) activation. In addition, cobalt protoporphyrin (CoPP), a specific HO-1 inducer, predominantly suppressed LPS-induced NO production. In contrast, zinc protoporphyrin (ZnPP), a specific HO-1 inhibitor, showed a partial suppressive effect of 5HHMF on LPS-induced NO production. Further, 5HHMF increased specific DNA-binding activity of Nrf2, and transient knockdown with Nrf2 siRNA subsequently reversed 5HHMF-induced NO inhibition, which was followed by suppression of HO-1 activity. Taken together, our findings indicate that 5HHMF suppresses NO production through modulation of iNOS, consequently suppressing NF-κB activity and induction of Nrf2-dependent HO-1 activity.
authors.affiliation: Laboratory of Immunobiology, Department of Marine Life Sciences, Jeju National University, Jeju 690-756, Republic of Korea.
authors.forename: Chang-Hee
authors.initials: CH
authors.lastname: Kang
authors.forename: Min Jeong
authors.initials: MJ
authors.lastname: Kim
authors.forename: Min Jeong
authors.initials: MJ
authors.lastname: Seo
authors.forename: Yung Hyun
authors.initials: YH
authors.lastname: Choi
authors.forename: Wol Soon
authors.initials: WS
authors.lastname: Jo
authors.forename: Kyung-Tae
authors.initials: KT
authors.lastname: Lee
authors.forename: Yong Kee
authors.initials: YK
authors.lastname: Jeong
authors.forename: Gi-Young
authors.initials: GY
authors.lastname: Kim
mesh_terms: D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D047309:Flavones / Q000494:pharmacology*; D055785:Gene Knockdown Techniques; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D011524:Protoporphyrins / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D013859:Thiocarbamates / Q000494:pharmacology
chemical_list: D047309:Flavones; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495636:Nfe2l2 protein, mouse; D011524:Protoporphyrins; D011759:Pyrrolidines; D013859:Thiocarbamates; C521815:5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone; C017803:zinc protoporphyrin; C020972:pyrrolidine dithiocarbamic acid; C007095:cobaltiprotoporphyrin; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse