title: Interferon regulatory factor-8 regulates bone metabolism by suppressing osteoclastogenesis.
abstract: Bone metabolism results from a balance between osteoclast-driven bone resorption and osteoblast-mediated bone formation. Diseases such as periodontitis and rheumatoid arthritis are characterized by increased bone destruction due to enhanced osteoclastogenesis. Here we report that interferon regulatory factor-8 (IRF-8), a transcription factor expressed in immune cells, is a key regulatory molecule for osteoclastogenesis. IRF-8 expression in osteoclast precursors was downregulated during the initial phase of osteoclast differentiation induced by receptor activator of nuclear factor-kappaB ligand (RANKL), which is encoded by the Tnfsf11 gene. Mice deficient in Irf8 showed severe osteoporosis, owing to increased numbers of osteoclasts, and also showed enhanced bone destruction after lipopolysaccharide (LPS) administration. Irf8-/- osteoclast precursors underwent increased osteoclastogenesis in response to RANKL and tumor necrosis factor-alpha (TNF-alpha). IRF-8 suppressed osteoclastogenesis by inhibiting the function and expression of nuclear factor of activated T cells c1 (NFATc1). Our results show that IRF-8 inhibits osteoclast formation under physiological and pathological conditions and suggest a model where downregulation of inhibitory factors such as IRF-8 contributes to RANKL-mediated osteoclastogenesis.
authors.affiliation: Department of Biochemistry, School of Dentistry, Showa University, Shinagawa, Tokyo, Japan.
authors.forename: Baohong
authors.initials: B
authors.lastname: Zhao
authors.forename: Masamichi
authors.initials: M
authors.lastname: Takami
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamada
authors.forename: Xiaogu
authors.initials: X
authors.lastname: Wang
authors.forename: Takako
authors.initials: T
authors.lastname: Koga
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Hu
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Tamura
authors.forename: Keiko
authors.initials: K
authors.lastname: Ozato
authors.forename: Yongwon
authors.initials: Y
authors.lastname: Choi
authors.forename: Lionel B
authors.initials: LB
authors.lastname: Ivashkiv
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takayanagi
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Kamijo
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D001842:Bone and Bones / Q000378:metabolism*; D002454:Cell Differentiation; D015536:Down-Regulation; D050835:Interferon Regulatory Factors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008070:Lipopolysaccharides / Q000633:toxicity; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D010024:Osteoporosis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D053245:RANK Ligand / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D000099185:Interferon Regulatory Factor-8
chemical_list: D050835:Interferon Regulatory Factors; D008070:Lipopolysaccharides; D053245:RANK Ligand; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D000099185:Interferon Regulatory Factor-8; C505689:Tnfsf11 protein, mouse