High extracellular inorganic phosphate concentration inhibits RANK-RANKL signaling in osteoclast-like cells.
In this work, we investigated the effect of inorganic phosphate (Pi) on the differentiation of monocyte/macrophage precursors into an "osteoclastic" phenotype, and we delineated the molecular mechanisms which could be involved in this phenomenon. This was achieved by stimulating human peripheral blood monocytic cells and RAW 264.7 monocyte-macrophage precursor cells to differentiate into osteoclast-like cells in the presence of receptor activator of NF-kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). RANKL has been previously reported to stimulate the signaling kinases ERK 1/2, p38, Akt, JNK, and the DNA-binding activity of the transcription factors AP-1 and NF-kappaB. Increase in extracellular Pi concentration (1.5-4.5 mM) dose-dependently inhibits both osteoclastic differentiation and bone resorption activity induced by RANKL and M-CSF. Pi was found to specifically inhibit the RANKL-induced JNK and Akt activation, while RANKL-induced p38 and ERK 1/2 phosphorylation were not significantly affected. Moreover, we found that Pi significantly reduced the RANKL-stimulated DNA-binding activity of NF-kappaB. The effects of Pi on osteoclast differentiation and DNA-binding activity of NF-kappaB were prevented by Foscarnet, a sodium-phosphate cotransport inhibitor, suggesting that the effects of Pi occur subsequently to its intake. These results demonstrate that Pi downregulates the differentiation of osteoclasts via a negative feedback exerted on RANK-RANKL signaling.
Mozar
Anaïs
A
INSERM, ERI-12, Amiens, France.
Haren
Nathalie
N
Chasseraud
Maud
M
Louvet
Loïc
L
Mazière
Cécile
C
Wattel
Alice
A
Mentaverri
Romuald
R
Morlière
Patrice
P
Kamel
Saïd
S
Brazier
Michel
M
Mazière
Jean C
JC
Massy
Ziad A
ZA
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D001862:Bone Resorption; D002454:Cell Differentiation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D017245:Foscarnet / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D010710:Phosphates / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism* / Q000494:pharmacology; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism*; D050608:Sodium-Phosphate Cotransporter Proteins / Q000037:antagonists & inhibitors; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor / Q000378:metabolism; D000071681:Tartrate-Resistant Acid Phosphatase; D018808:Transcription Factor AP-1 / Q000378:metabolism
D007527:Isoenzymes; D010710:Phosphates; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D050608:Sodium-Phosphate Cotransporter Proteins; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D051705:Sp3 Transcription Factor; D017245:Foscarnet; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase