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

J Bone Miner Res. 2002 Sep;17(9):1667-79. doi: 10.1359/jbmr.2002.17.9.1667.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / drug effects
  • Bone Marrow Cells / metabolism
  • Calcium Signaling
  • Carrier Proteins / genetics
  • Cell Line
  • Cyclic AMP / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Gene Expression / drug effects
  • Glycoproteins / genetics
  • Male
  • Membrane Glycoproteins / genetics
  • Mice
  • Mice, Inbred C57BL
  • Osteoclasts / cytology*
  • Osteoclasts / metabolism*
  • Osteoprotegerin
  • Parathyroid Hormone / pharmacology
  • Peptide Fragments / pharmacology
  • Protein Kinase C / metabolism
  • RANK Ligand
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptor Activator of Nuclear Factor-kappa B
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Parathyroid Hormone / genetics
  • Receptors, Parathyroid Hormone / metabolism*
  • Receptors, Tumor Necrosis Factor
  • Signal Transduction

Substances

  • Carrier Proteins
  • Glycoproteins
  • Membrane Glycoproteins
  • Osteoprotegerin
  • Parathyroid Hormone
  • Peptide Fragments
  • RANK Ligand
  • RNA, Messenger
  • Receptor Activator of Nuclear Factor-kappa B
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Parathyroid Hormone
  • Receptors, Tumor Necrosis Factor
  • TNFRSF11A protein, human
  • TNFRSF11B protein, human
  • TNFSF11 protein, human
  • Tnfrsf11a protein, mouse
  • Tnfrsf11b protein, mouse
  • Tnfsf11 protein, mouse
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C