title: Fisetin inhibits osteoclastogenesis through prevention of RANKL-induced ROS production by Nrf2-mediated up-regulation of phase II antioxidant enzymes.
abstract: Osteoclasts (OCLs) are multinucleated bone-resorbing cells that are differentiated by stimulation with receptor activator of nuclear factor kappa-B ligand (RANKL) and macrophage colony-stimulating factor. We recently demonstrated that regulation of heme-oxygenase 1 (HO-1), a stress-induced cytoprotective enzyme, also functions in OCL differentiation. In this study, we investigated effects of fisetin, a natural bioactive flavonoid that has been reported to induce HO-1 expression, on the differentiation of macrophages into OCLs. Fisetin inhibited the formation of OCLs in a dose-dependent manner and suppressed the bone-resorbing activity of OCLs. Moreover, fisetin-treated OCLs showed markedly decreased phosphorylation of extracellular signal-regulated kinase, Akt, and Jun N-terminal kinase, but fisetin did not inhibit p38 phosphorylation. Fisetin up-regulated mRNA expression of phase II antioxidant enzymes including HO-1 and interfered with RANKL-mediated reactive oxygen species (ROS) production. Studies with RNA interference showed that suppression of NF-E2-related factor 2 (Nrf2), a key transcription factor for phase II antioxidant enzymes, rescued fisetin-mediated inhibition of OCL differentiation. Furthermore, fisetin significantly decreased RANKL-induced nuclear translocation of cFos and nuclear factor of activated T cells cytoplasmic-1 (NFATc1), which is a transcription factor critical for osteoclastogenic gene regulation. Therefore, fisetin inhibits OCL differentiation through blocking RANKL-mediated ROS production by Nrf2-mediated up-regulation of phase II antioxidant enzymes.
authors.affiliation: Division of Oral Pathopharmacology, Department of Developmental and Reconstructive Medicine, Nagasaki University Graduate School of Biomedical Sciences, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Sakai
authors.forename: Megumi
authors.initials: M
authors.lastname: Shimada-Sugawara
authors.forename: Yu
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Reiko
authors.initials: R
authors.lastname: Fumimoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fukuma
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Nishishita
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Okamoto
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tsukuba
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000517:prevention & control; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology*; D044948:Flavonols; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D051547:Heme Oxygenase-1 / Q000378:metabolism* / Q000502:physiology; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology; D008264:Macrophages / Q000166:cytology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D005419:Flavonoids; D044948:Flavonols; D051267:NF-E2-Related Factor 2; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; C495636:Nfe2l2 protein, mouse; D017382:Reactive Oxygen Species; D053246:Receptor Activator of Nuclear Factor-kappa B; D016173:Macrophage Colony-Stimulating Factor; D051547:Heme Oxygenase-1; C017875:fisetin