title: Stimulation by TLR5 modulates osteoclast differentiation through STAT1/IFN-beta.
abstract: Osteoclasts are bone-resorbing cells that are differentiated from hemopoietic precursors of the monocyte-macrophage lineage. Stimulation of TLRs has been shown to positively or negatively modulate osteoclast differentiation, depending on the experimental condition. However, the molecular mechanism by which this modulation takes place remains unclear. In the present study, we examined the effects of flagellin, a specific microbial ligand of TLR5, on the receptor activator of NF-kappaB ligand (RANKL)-stimulated osteoclastogenesis. Flagellin suppressed RANKL induction of c-Fos protein expression in bone marrow-derived macrophages without affecting c-Fos mRNA expression. Ectopic overexpression of c-Fos and a constitutively active form of NFATc1 reversed the flagellin-induced anti-osteoclastogenic effect. The inhibitory effect of flagellin was mediated by IFN-beta production. Flagellin stimulated IFN-beta expression and release in bone marrow-derived macrophages, and IFN-beta-neutralizing Ab prevented the flagellin-induced c-Fos down-regulation and the anti-osteoclastogenic effect. IFN-beta gene induction by flagellin, LPS, or RANKL was dependent on STAT1 activation. Treatment with flagellin or RANKL stimulated STAT1 activation, and STAT1 deficiency or the JAK2 inhibitor AG490 dramatically prevented IFN-beta induction in response to flagellin or RANKL. In addition, STAT1 deficiency abolished the anti-osteoclastogenic effect induced by flagellin or LPS. In contrast, flagellin stimulated osteoclast differentiation in cocultures of osteoblasts and bone marrow cells without inducing IFN-beta. Thus, IFN-beta acts as a critical modulator of osteoclastogenesis in response to TLR5 activation.
authors.affiliation: Department of Cell and Developmental Biology, Dental Research Institute, School of Dentistry, Seoul National University, 28 Yeongon-Dong, Jongro-Gu, Seoul, Republic of Korea.
authors.forename: Hyunil
authors.initials: H
authors.lastname: Ha
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Ha-Neui
authors.initials: HN
authors.lastname: Kim
authors.forename: Han Bok
authors.initials: HB
authors.lastname: Kwak
authors.forename: Hyun-Man
authors.initials: HM
authors.lastname: Kim
authors.forename: Shee Eun
authors.initials: SE
authors.lastname: Lee
authors.forename: Joon Haeng
authors.initials: JH
authors.lastname: Rhee
authors.forename: Hong-Hee
authors.initials: HH
authors.lastname: Kim
authors.forename: Zang Hee
authors.initials: ZH
authors.lastname: Lee
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation / Q000235:genetics; D018920:Coculture Techniques; D005408:Flagellin / Q000494:pharmacology; D015870:Gene Expression; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism*; D053614:Janus Kinase 2 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D053245:RANK Ligand / Q000494:pharmacology; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D051198:Toll-Like Receptor 5 / Q000819:agonists*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D005408:Flagellin; D016899:Interferon-beta; D053614:Janus Kinase 2; D008070:Lipopolysaccharides; D016760:Proto-Oncogene Proteins c-fos; D053245:RANK Ligand; D050794:STAT1 Transcription Factor; D051198:Toll-Like Receptor 5; C494080:Stat1 protein, mouse; C476286:Ticam1 protein, mouse; C507926:Jak2 protein, mouse