title: Activation of adenosine A(2A) receptor reduces osteoclast formation via PKA- and ERK1/2-mediated suppression of NFκB nuclear translocation.
abstract: OBJECTIVE
  We previously reported that adenosine, acting at adenosine A(2A) receptors (A(2A)R), inhibits osteoclast (OC) differentiation in vitro (A(2A)R activation OC formation reduces by half) and in vivo. For a better understanding how adenosine A(2A)R stimulation regulates OC differentiation, we dissected the signalling pathways involved in A(2A)R signalling.
  
  
  METHODS
  OC differentiation was studied as TRAP+ multinucleated cells following M-CSF/RANKL stimulation of either primary murine bone marrow cells or the murine macrophage line, RAW264.7, in presence/absence of the A(2A)R agonist CGS21680, the A(2A)R antagonist ZM241385, PKA activators (8-Cl-cAMP 100 nM, 6-Bnz-cAMP) and the PKA inhibitor (PKI). cAMP was quantitated by EIA and PKA activity assays were carried out. Signalling events were studied in PKA knockdown (lentiviral shRNA for PKA) RAW264.7 cells (scrambled shRNA as control). OC marker expression was studied by RT-PCR.
  
  
  RESULTS
  A(2A)R stimulation increased cAMP and PKA activity which and were reversed by addition of ZM241385. The direct PKA stimuli 8-Cl-cAMP and 6-Bnz-cAMP inhibited OC maturation whereas PKI increased OC differentiation. A(2A)R stimulation inhibited p50/p105 NFκB nuclear translocation in control but not in PKA KO cells. A(2A)R stimulation activated ERK1/2 by a PKA-dependent mechanism, an effect reversed by ZM241385, but not p38 and JNK activation. A(2A)R stimulation inhibited OC expression of differentiation markers by a PKA-mechanism.
  
  
  CONCLUSIONS
  A(2A)R activation inhibits OC differentiation and regulates bone turnover via PKA-dependent inhibition of NFκB nuclear translocation, suggesting a mechanism by which adenosine could target bone destruction in inflammatory diseases like rheumatoid arthritis.
authors: Department of Medicine, Division of Translational Medicine, NYU School of Medicine, New York, NY 10016, USA.
authors: Aránzazu
authors: A
authors: Mediero
authors: Miguel
authors: M
authors: Perez-Aso
authors: Bruce N
authors: BN
authors: Cronstein
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists / Q000494:pharmacology*; D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D052002:NF-kappa B p50 Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D043705:Receptor, Adenosine A2A / Q000737:chemistry / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D052002:NF-kappa B p50 Subunit; D047428:Protein Kinase Inhibitors; D043705:Receptor, Adenosine A2A; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; C073701:Nfkb1 protein, mouse; D000242:Cyclic AMP; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; C517758:Prkaca protein, mouse; D000241:Adenosine
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