Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.
Adenosine A1 Receptors Regulates RANKL-Induced Osteoclast Formation Via Regulation of c-fos and NFATc1 Expression.
He2, Wenjie, Wilder2, Tuere, Cronstein1, Bruce N.
Adenosine is a purine molecule necessary for normal cell metabolism and growth. Recent work from our laboratory using adenosine A1 -deficient mice has demonstrated that adenosine A1 receptors play a critical role in regulating bone turnover, raising the intriguing possibility of targeting A1 receptors for therapeutic advancement in osteoporosis and other bone diseases. In the present study, we investigated the mechanism by which A1 receptors regulate mouse osteoclast differentiation induced by macrophage-colony stimulating factor (M-CSF) and the receptor activator of NF-kappaB ligand (RANKL) from monocyte/macrophage cell lineage of bone marrow cells.
Osteoclast differentiation was studied in vitro as the M-CSF/RANKL stimulated formation of multinucleated (>3 nuclei), TRAP-positive cells from primary murine (C57Bl/6) bone marrow-derived precursors. Signaling events were studied by Western Blot for activated (phosphorylated) signaling molecules and changes in message were determined by RT-PCR.
As we have previously demonstrated, the A1receptor specific antagonist 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX) dose-dependently inhibited RANKL-stimulated tartrate-resistant acid phosphatase (TRAP)-positive osteoclast formation from bone marrow cells and the bone-resorptive activity of mature osteoclasts (p<0.001, n=3, IC50= 0.1mM). This inhibition is accompanied by reduction of osteoclast-specific target genes including MMP9, Integrin av, Integrin b3, Cathepsin K and TRAP (p<0.05, n=4). Furthermore, DPCPX inhibited accumulation of the RANKL-stimulated c-fos mRNA at day 3 in bone marrow cells (p<0.05, n=3); c-fos is a key transcription factor for the differentiation of osteoclasts. DPCPX also dose-dependently suppressed RANKL-induced gene expression of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) at day 4 in bone marrow cells (p<0.05, n=3). Among the RANK signaling MAPK pathways, DPCPX (1mM) inhibited phosphorylation of JNK (p<0.001, n=4), which is upregulated in response to RANKL in bone marrow macrophages.
Collectively, these data suggest that Adenosine A1 receptor blockade inhibits RANKL-induced osteoclast formation by inhibiting activation of JNK/c-Jun pathway, thereby suppressing the gene expression of c-fos and NFATc1 in osteoclast precursors. These results are consistent with the hypothesis that endogenously released adenosine, acting at A1 receptors, is critical for the expression and activation of critical signaling intermediates required for osteoclastogenesis. Moreover, these results further support the notion that blockade of adenosine A1 receptors may be useful in the treatment and prevention of osteoporosis and premature bone loss.
To cite this abstract, please use the following information:
He, Wenjie, Wilder, Tuere, Cronstein, Bruce N.; Adenosine A1 Receptors Regulates RANKL-Induced Osteoclast Formation Via Regulation of c-fos and NFATc1 Expression. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1469