Nobuaki Sato

Publications (7)37.87 Total impact

• Article: New 19-nor-(20S)-1alpha,25-dihydroxyvitamin D3 analogs strongly stimulate osteoclast formation both in vivo and in vitro.

  Masahiro Sato, Yuko Nakamichi, Midori Nakamura, Nobuaki Sato, Tadashi Ninomiya, Akinori Muto, Hiroaki Nakamura, Hidehiro Ozawa, Yukiko Iwasaki, Emi Kobayashi, Masato Shimizu, Hector F DeLuca, Naoyuki Takahashi, Nobuyuki Udagawa
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  ABSTRACT: 2-Methylene-19-nor-(20S)-1alpha,25-dihydroxyvitamin D3 (2MD), an analog of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3], has been shown to strongly induce bone formation both in vitro and in vivo. We have synthesized four substituents at carbon 2 of 2MD (2MD analogs), four stereoisomers at carbon 20 of the respective 2MD analogs (2MD analog-C20 isomers) and four 2MD analogs with an oxygen atom at carbon 22 (2MD-22-oxa analogs) and examined their ability to stimulate osteoclastogenesis and induce hypercalcemia. 2MD analogs were 100 times as potent as 1alpha,25(OH)2D3 in stimulating the formation of osteoclasts in vitro and in inducing the expression of receptor activator of NF-kappaB ligand (RANKL) and 25-hydroxyvitamin D3-24 hydroxylase mRNAs in osteoblasts. The osteoclast-inducing activities of 2MD analog-C20 isomers and 2MD 22-oxa analogs were much weaker than those of 2MD analogs. In addition, the activity of a 2MD analog in inducing dentine resorption was much stronger than that of 1alpha,25(OH)2D3 in the pit formation assay. Affinities to the vitamin D receptor and transcriptional activities of these compounds did not always correlate with their osteoclastogenic activities. Osteoprotegerin-deficient (OPG-/-) mice provide a suitable model for investigating in vivo effects of 2MD analogs because they exhibit extremely high concentrations of serum RANKL. The same amounts of 2MD analogs and 1alpha,25(OH)2D3 were administered daily to OPG-/- mice for 2 days. The elevation in serum concentrations of RANKL and calcium was much greater in 2MD analog-treated OPG-/- mice than in 1alpha,25(OH)2D3-treated ones. A 2MD analog was much more potent than 1alpha,25(OH)2D3 in causing hypercalcemia and in increasing soluble RANKL with enhanced osteoclastogenesis even in wild-type mice. In contrast, the administration of the 2MD analog to c-fos-deficient mice failed to induce osteoclastogenesis and hypercalcemia. These results suggest that new substituents at carbon 2 of 2MD strongly stimulate osteoclast formation in vitro and in vivo, and that osteoclastic bone resorption is indispensable for their hypercalcemic action of 2MD analogs in vivo.
  Bone 03/2007; 40(2):293-304. · 4.02 Impact Factor
• Article: Signal transduction of lipopolysaccharide-induced osteoclast differentiation.

  Nobuyuki Udagawa, Nobuaki Sato, Shuhua Yang, Midori Nakamura, Teruhito Yamashita, Hiroshi Nakamura, Toshihide Noguchi
  Periodontology 2000 02/2007; 43:56-64. · 3.96 Impact Factor
• Article: [Bone destruction caused by osteoclasts].

  Teruhito Yamashita, Naoyuki Takahashi, Shuhua Yang, Nobuaki Sato, Nobuyuki Udagawa
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  ABSTRACT: Lipopolysaccharide (LPS) and muramyl dipeptide (MDP) are components of bacterial cell walls that cause innate immune responses and inflammation. Toll-like receptor 4 (TLR4) is a receptor for LPS and transduces signals through myeloid differentiation factor 88 (MyD88), which plays essential roles in the TLR/interleukin (IL)-1R signaling and activates MAP/ERK kinase (MEK)/ERK pathway to induce receptor activator of NF-kappaB ligand (RANKL) expression in osteoblasts. Osteoblasts express nucleotide oligomerization domain (NOD)2, an intracellular sensor for MDP, in response to LPS, IL-1 and TNF. NOD2 binds receptor-interacting protein (RIP2), a serine/threonine kinase which transduces NF-kappaB signaling. MDP synergistically enhances osteoclast formation induced by LPS, IL-1 and TNF through RANK ligand up-regulation in osteoblasts. TLR4 and NOD2 recognize bacterial components on cell surfaces and inside cells, respectively, and these signals up-regulate RANKL expression in osteoblasts, which results in enhancing osteoclast formation and function.
  Clinical calcium 03/2006; 16(2):234-40.
• Article: Muramyl dipeptide enhances osteoclast formation induced by lipopolysaccharide, IL-1 alpha, and TNF-alpha through nucleotide-binding oligomerization domain 2-mediated signaling in osteoblasts.

  Shuhua Yang, Naoyuki Takahashi, Teruhito Yamashita, Nobuaki Sato, Masahiro Takahashi, Makio Mogi, Takashi Uematsu, Yasuhiro Kobayashi, Yuko Nakamichi, Kiyoshi Takeda, Shizuo Akira, Haruhiko Takada, Nobuyuki Udagawa, Kiyofumi Furusawa
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  ABSTRACT: Muramyl dipeptide (MDP) is the minimal essential structural unit responsible for the immunoadjuvant activity of peptidoglycan. As well as bone-resorbing factors such as 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and PGE2, LPS and IL-1alpha stimulate osteoclast formation in mouse cocultures of primary osteoblasts and hemopoietic cells. MDP alone could not induce osteoclast formation in the coculture, but enhanced osteoclast formation induced by LPS, IL-1alpha, or TNF-alpha but not 1alpha,25(OH)2D3 or PGE2. MDP failed to enhance osteoclast formation from osteoclast progenitors induced by receptor activator of NF-kappaB ligand (RANKL) or TNF-alpha. MDP up-regulated RANKL expression in osteoblasts treated with LPS or TNF-alpha but not 1alpha,25(OH)2D3. Osteoblasts expressed mRNA of nucleotide-binding oligomerization domain 2 (Nod2), an intracellular sensor of MDP, in response to LPS, IL-1alpha, or TNF-alpha but not 1alpha,25(OH)2D3. Induction of Nod2 mRNA expression by LPS but not by TNF-alpha in osteoblasts was dependent on TLR4 and MyD88. MDP also enhanced TNF-alpha-induced osteoclast formation in cocultures prepared from Toll/IL-1R domain-containing adapter protein (TIRAP)-deficient mice through the up-regulation of RANKL mRNA expression in osteoblasts, suggesting that TLR2 is not involved in the MDP-induced osteoclast formation. The depletion of intracellular Nod2 by small interfering RNA blocked MDP-induced up-regulation of RANKL mRNA in osteoblasts. LPS and RANKL stimulated the survival of osteoclasts, and this effect was not enhanced by MDP. These results suggest that MDP synergistically enhances osteoclast formation induced by LPS, IL-1alpha, and TNF-alpha through RANKL expression in osteoblasts, and that Nod2-mediated signals are involved in the MDP-induced RANKL expression in osteoblasts.
  The Journal of Immunology 09/2005; 175(3):1956-64. · 5.79 Impact Factor
• Source

  Available from: PubMed Central

  Article: MyD88 but not TRIF is essential for osteoclastogenesis induced by lipopolysaccharide, diacyl lipopeptide, and IL-1alpha.

  Nobuaki Sato, Naoyuki Takahashi, Koji Suda, Midori Nakamura, Mariko Yamaki, Tadashi Ninomiya, Yasuhiro Kobayashi, Haruhiko Takada, Kenichiro Shibata, Masahiro Yamamoto, Kiyoshi Takeda, Shizuo Akira, Toshihide Noguchi, Nobuyuki Udagawa
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  ABSTRACT: Myeloid differentiation factor 88 (MyD88) plays essential roles in the signaling of the Toll/interleukin (IL)-1 receptor family. Toll-IL-1 receptor domain-containing adaptor inducing interferon-beta (TRIF)-mediated signals are involved in lipopolysaccharide (LPS)-induced MyD88-independent pathways. Using MyD88-deficient (MyD88-/-) mice and TRIF-deficient (TRIF-/-) mice, we examined roles of MyD88 and TRIF in osteoclast differentiation and function. LPS, diacyl lipopeptide, and IL-1alpha stimulated osteoclastogenesis in cocultures of osteoblasts and hemopoietic cells obtained from TRIF-/- mice, but not MyD88-/- mice. These factors stimulated receptor activator of nuclear factor-kappaB ligand mRNA expression in TRIF-/- osteoblasts, but not MyD88-/- osteoblasts. LPS stimulated IL-6 production in TRIF-/- osteoblasts, but not TRIF-/- macrophages. LPS and IL-1alpha enhanced the survival of TRIF-/- osteoclasts, but not MyD88-/- osteoclasts. Diacyl lipopeptide did not support the survival of osteoclasts because of the lack of Toll-like receptor (TLR)6 in osteoclasts. Macrophages expressed both TRIF and TRIF-related adaptor molecule (TRAM) mRNA, whereas osteoblasts and osteoclasts expressed only TRIF mRNA. Bone histomorphometry showed that MyD88-/- mice exhibited osteopenia with reduced bone resorption and formation. These results suggest that the MyD88-mediated signal is essential for the osteoclastogenesis and function induced by IL-1 and TLR ligands, and that MyD88 is physiologically involved in bone turnover.
  Journal of Experimental Medicine 10/2004; 200(5):601-11. · 13.85 Impact Factor
• Article: Suppression of osteoprotegerin expression by prostaglandin E2 is crucially involved in lipopolysaccharide-induced osteoclast formation.

  Koji Suda, Nobuyuki Udagawa, Nobuaki Sato, Masamichi Takami, Kanami Itoh, Je-Tae Woo, Naoyuki Takahashi, Kazuo Nagai
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  ABSTRACT: LPS is a potent stimulator of bone resorption in inflammatory diseases. The mechanism by which LPS induces osteoclastogenesis was studied in cocultures of mouse osteoblasts and bone marrow cells. LPS stimulated osteoclast formation and PGE(2) production in cocultures of mouse osteoblasts and bone marrow cells, and the stimulation was completely inhibited by NS398, a cyclooxygenase-2 inhibitor. Osteoblasts, but not bone marrow cells, produced PGE(2) in response to LPS. LPS-induced osteoclast formation was also inhibited by osteoprotegerin (OPG), a decoy receptor of receptor activator of NF-kappaB ligand (RANKL), but not by anti-mouse TNFR1 Ab or IL-1 receptor antagonist. LPS induced both stimulation of RANKL mRNA expression and inhibition of OPG mRNA expression in osteoblasts. NS398 blocked LPS-induced down-regulation of OPG mRNA expression, but not LPS-induced up-regulation of RANKL mRNA expression, suggesting that down-regulation of OPG expression by PGE(2) is involved in LPS-induced osteoclast formation in the cocultures. NS398 failed to inhibit LPS-induced osteoclastogenesis in cocultures containing OPG knockout mouse-derived osteoblasts. IL-1 also stimulated PGE(2) production in osteoblasts and osteoclast formation in the cocultures, and the stimulation was inhibited by NS398. As seen with LPS, NS398 failed to inhibit IL-1-induced osteoclast formation in cocultures with OPG-deficient osteoblasts. These results suggest that IL-1 as well as LPS stimulates osteoclastogenesis through two parallel events: direct enhancement of RANKL expression and suppression of OPG expression, which is mediated by PGE(2) production.
  The Journal of Immunology 03/2004; 172(4):2504-10. · 5.79 Impact Factor
• Article: p38 Mitogen-activated protein kinase is crucially involved in osteoclast differentiation but not in cytokine production, phagocytosis, or dendritic cell differentiation of bone marrow macrophages.

  Xiaotong Li, Nobuyuki Udagawa, Masamichi Takami, Nobuaki Sato, Yasuhiro Kobayashi, Naoyuki Takahashi
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  ABSTRACT: We previously reported that p38 MAPK signaling is required for osteoclast differentiation but not osteoclast function. Here we further investigated the role of p38 MAPK in the function and differentiation of mouse bone marrow macrophages (BMM phi), common precursors of osteoclasts and dendritic cells. Lipopolysaccharide (LPS) activated the p38 MAPK signaling pathway in BMM phi by sequential phosphorylation of MAPK kinase 3/6, p38 MAPK, and activating transcription factor-2. Treatment of BMM phi with SB203580, a p38 MAPK inhibitor, suppressed LPS-induced phosphorylation of activating transcription factor-2. LPS stimulated production of IL-1 beta, TNF alpha, and IL-6 in BMM phi, and SB203580 failed to inhibit the LPS-induced cytokine production. BMM phi incorporated latex beads via phagocytosis, and SB203580 had no effect on this phagocytosis. BMM phi differentiated into dendritic cells when treated with granulocyte macrophage colony-stimulating factor together with CD40 ligand, TNF alpha, or LPS, and SB203580 failed to inhibit this differentiation. Thus, p38 MAPK-mediated signals are not involved in either BMM phi function or BMM phi differentiation into dendritic cells. The differentiation of BMM phi into osteoclasts in response to receptor activator of nuclear factor-kappa B ligand or TNF alpha was strongly inhibited by SB203580. These findings emphasize the crucial roles of p38 MAPK-mediated signaling in osteoclast differentiation.
  Endocrinology 12/2003; 144(11):4999-5005. · 4.46 Impact Factor