Cyclic adenosine monophosphate/protein kinase A mediates parathyroid hormone/parathyroid hormone-related protein receptor regulation of osteoclastogenesis and expression of RANKL and osteoprotegerin mRNAs by marrow stromal cells.
Parathyroid hormone (PTH) is a major regulator of osteoclast formation and activation, effects that are associated with reciprocal up- and down-regulation of RANKL and osteoprotegerin (OPG), respectively. The roles of specific downstream signals generated by the activated PTH/PTH-related protein (PTHrP) receptor (PTH1R), such as cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) and phospholipase C/protein kinase C (PLC/PKC), in controlling RANKL and OPG expression and osteoclastogenesis remain uncertain. In MS1 conditionally transformed clonal murine marrow stromal cells, which support PTH-induced osteoclast formation from cocultured normal spleen cells, PTH(1-34) increased RANKL and macrophage colony-stimulating factor (M-CSF) mRNA expression and decreased that of OPG when present continuously for 7-20 days at 37 degrees C in the presence of dexamethasone (Dex). In cells precultured for 7 days and then treated with PTH(1-34), similar reciprocal regulation of RANKL and OPG occurred, maximally at 6-24 h, that was of greater amplitude than the changes induced by chronic (7-10 days) PTH exposure. These acute effects of PTH(1-34) were mimicked by PKA stimulators (8-bromoadenosine [8Br]-cAMP or forskolin [FSK]), blocked by the PKA inhibitor Rp-cAMPs but unaffected by the PKC inhibitor GF109203X. Amino-truncated PTH(1-34) analogs PTH(5-34) and PTH(7-34) neither increased cAMP production in MS1 cells nor regulated RANKL or OPG mRNA. Reciprocal RANKL/OPG mRNA regulation was induced in MS1 cells by PTH(3-34) but only at high concentrations that also increased cAMP. The highly PKA-selective PTH analog [Gly1,Arg19]human PTH(1-28) exerted effects similar to PTH(1-34) on RANKL and OPG mRNAs and on osteoclast formation, both in MS1/spleen cell cocultures and in normal murine bone marrow cultures. The direct PKC stimulator 12-O-tetradecanoylphorbol-13-acetate (PMA) did not induce RANKL mRNA in MS1 cells, but it did up-regulate OPG mRNA and also antagonized osteoclast formation induced by PTH(1-34) in both MS1/spleen cocultures and normal bone marrow cultures. Thus, cAMP/PKA signaling via the PTH1R is the primary mechanism for controlling RANKL-dependent osteoclastogenesis, although direct PKC activation may negatively regulate this effect of PTH by inducing expression of OPG.
Kondo
Hisatomo
H
Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
Guo
Jun
J
Bringhurst
F Richard
FR
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006023:Glycoproteins / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism*; D053244:Osteoprotegerin; D010281:Parathyroid Hormone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D053245:RANK Ligand; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B; D044168:Receptor, Parathyroid Hormone, Type 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D018016:Receptors, Parathyroid Hormone / Q000235:genetics / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D015398:Signal Transduction
D002352:Carrier Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D044168:Receptor, Parathyroid Hormone, Type 1; D018160:Receptors, Cytoplasmic and Nuclear; D018016:Receptors, Parathyroid Hormone; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C