title: Activation of peroxisome proliferator-activated receptor gamma inhibits TNF-alpha-mediated osteoclast differentiation in human peripheral monocytes in part via suppression of monocyte chemoattractant protein-1 expression.
abstract: Tumor necrosis factor-alpha (TNF-alpha) plays critical roles in bone resorption at the site of inflammatory joints. The aim of this study is to evaluate the effect of peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonists, a new class of anti-inflammatory compounds, on TNF-alpha-mediated osteoclastogenesis in human monocytes. Human monocytes were differentiated into osteoclasts in the presence of TNF-alpha and macrophage colony-stimulating factor. Tartrate-resistant acid phosphatase (TRAP) staining and a pit formation assay using dentin were used for the identification of activated osteoclasts. The protein and gene expressions of transcription factors were determined by immunofluorescence and real-time RT-PCR analysis, respectively. TNF-alpha-induced osteoclast generation from human peripheral monocytes in a dose-dependent manner, and the induction was not inhibited by osteoprotegerin, a decoy receptor for receptor activator of NF-kappaB ligand. The addition of PPAR-gamma agonists, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) or ciglitazone, to the culture resulted in a remarkably reduced number of generated osteoclasts. In addition, both agonists inhibited the protein and gene expressions of nuclear factor of activated T-cell isoform c1 (NFATc1), c-Fos, c-Jun and NF-kappaB p65, which are known to be associated with osteoclastogenesis. GW9662, an antagonist of PPAR-gamma, fully rescued ciglitazone-induced inhibition, but did not affect 15d-PGJ2-induced inhibition. Monocyte chemoattractant protein-1 (MCP-1), a CC chemokine related to osteoclastogenesis, was induced during TNF-alpha-mediated osteoclast differentiation, and the neutralizing antibody to MCP-1 reduced osteoclast formation by about 40%. 15d-PGJ2 and ciglitazone blocked the induction of MCP-1 by TNF-alpha. Moreover, the addition of MCP-1 rescued the inhibition of TRAP-positive multinucleated cell (TRAP-MNCs) formation by 15d-PGJ2 and ciglitazone, although generated TRAP-MNCs had no capacity to resorb dentin slices. Our data demonstrate that 15d-PGJ2 and ciglitazone down-regulate TNF-alpha-mediated osteoclast differentiation in human cells, in part via suppression of the action of MCP-1. These PPAR-gamma agonists may be a promising therapeutic application for rheumatoid arthritis and inflammatory bone-resorbing diseases.
authors.affiliation: Department of Internal Medicine 1, Faculty of Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hounoki
authors.forename: Eiji
authors.initials: E
authors.lastname: Sugiyama
authors.forename: Saad Gad-Kamel
authors.initials: SG
authors.lastname: Mohamed
authors.forename: Kouichiro
authors.initials: K
authors.lastname: Shinoda
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Taki
authors.forename: Hekmat Osman
authors.initials: HO
authors.lastname: Abdel-Aziz
authors.forename: Muneharu
authors.initials: M
authors.lastname: Maruyama
authors.forename: Masashi
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Miyahara
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism*; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D047495:PPAR gamma / Q000378:metabolism*; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D053245:RANK Ligand / Q000378:metabolism; D045162:Thiazolidinediones / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: C477819:15-deoxyprostaglandin J2; D018932:Chemokine CCL2; D047495:PPAR gamma; D053245:RANK Ligand; D045162:Thiazolidinediones; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D015230:Prostaglandin D2; C039671:ciglitazone