title: Extracellular ADP is a powerful osteolytic agent: evidence for signaling through the P2Y(1) receptor on bone cells.
abstract: There is increasing evidence that extracellular nucleotides act on bone cells via P2 receptors. This study investigated the action of ADP and 2-methylthioADP, a potent ADP analog with selectivity for the P2Y(1) receptor, on osteoclasts, the bone-resorbing multinuclear cells. Using three different assays, we show that ADP and 2-methylthioADP at nanomolar to submicromolar levels caused up to fourfold to sixfold increases in osteoclastic bone resorption. On mature rat osteoclasts, cultured for 1 day on polished dentine disks, peak effects on resorption pit formation were observed between 20 nM and 2 microM of ADP. The same concentrations of ADP also stimulated osteoclast and resorption pit formation in 10-day mouse marrow cultures on dentine disks. In 3-day explant cultures of mouse calvarial bones, the stimulatory effect of ADP on osteoclast-mediated Ca(2+) release was greatest at 5-50 microM and equivalent to the maximal effects of prostaglandin E(2). The ADP effects were blocked in a nontoxic manner by MRS 2179, a P2Y(1) receptor antagonist. Using in situ hybridization and immunocytochemistry, we found evidence for P2Y(1) receptor expression on both osteoclasts and osteoblasts; thus, ADP could exert its actions both directly on osteoclasts and indirectly via P2Y(1) receptors on osteoblasts. As a major ATP degradation product, ADP is a novel stimulator of bone resorption that could help mediate inflammatory bone loss in vivo.
authors.affiliation: Department of Anatomy and Developmental Biology, Autonomic Neuroscience Institute, University College London, London WC1E 6BT, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Hoebertz
authors.forename: S
authors.initials: S
authors.lastname: Meghji
authors.forename: G
authors.initials: G
authors.lastname: Burnstock
authors.forename: T R
authors.initials: TR
authors.lastname: Arnett
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001862:Bone Resorption; D001842:Bone and Bones / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1; D015398:Signal Transduction / Q000502:physiology; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology*
chemical_list: C111914:N(6)-methyl-2'-deoxyadenosine 3',5'-diphosphate; C546383:P2ry1 protein, mouse; C546384:P2ry1 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D013873:Thionucleotides; C002480:methylthio-ADP; D000244:Adenosine Diphosphate; D002118:Calcium