title: Nitric oxide regulates receptor activator of nuclear factor-kappaB ligand and osteoprotegerin expression in bone marrow stromal cells.
abstract: Bone remodeling reflects an equilibrium between bone resorption and formation. The local expression of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in bone determines the entry of monoblastic precursors into the osteoclast lineage and subsequent bone resorption. Nitric oxide (NO) inhibits osteoclastic bone resorption in vitro and regulates bone remodeling in vivo. An interaction of NO with RANKL and OPG has not been studied. Here, we show that treatment of ST-2 murine stromal cells with the NO donor sodium nitroprusside (100 microm) for 24 h inhibited 1,25 dihydroxyvitamin D(3)-induced RANKL mRNA to less than 33 +/- 7% of control level, whereas OPG mRNA increased to 204 +/- 19% of control. NOR-4 replicated these NO effects. The effects of NO were dose dependent and associated with changes in protein levels: RANKL protein decreased and OPG protein increased after treatment with NO. PTH-induced RANKL expression in primary stromal cells was inhibited by sodium nitroprusside, indicating that the NO effect did not require vitamin D. NO donor did not change the stability of RANKL or OPG mRNAs, suggesting that NO affected transcription. Finally, cGMP, which can function as a second messenger for NO, did not reproduce the NO effect, nor did inhibition of endogenous guanylate cyclase prevent the NO effect on these osteoactive genes. The effect of NO to decrease the RANKL/OPG equilibrium should lead to decreased recruitment of osteoclasts and positive bone formation. Thus, drugs and conditions that cause local increase in NO formation in bone may have positive effects on bone remodeling.
authors.affiliation: Department of Medicine, Veterans Affairs Medical Center, VAMC-151, 1670 Clairmont Road, Decatur, GA 30033, USA. xfan@emory.edu
authors.forename: Xian
authors.initials: X
authors.lastname: Fan
authors.forename: Eileen
authors.initials: E
authors.lastname: Roy
authors.forename: Liping
authors.initials: L
authors.lastname: Zhu
authors.forename: Tamara C
authors.initials: TC
authors.lastname: Murphy
authors.forename: Cheryl
authors.initials: C
authors.lastname: Ackert-Bicknell
authors.forename: C Michael
authors.initials: CM
authors.lastname: Hart
authors.forename: Clifford
authors.initials: C
authors.lastname: Rosen
authors.forename: Mark S
authors.initials: MS
authors.lastname: Nanes
authors.forename: Janet
authors.initials: J
authors.lastname: Rubin
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics*; D002460:Cell Line; D006152:Cyclic GMP / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006023:Glycoproteins / Q000235:genetics*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D053244:Osteoprotegerin; D010281:Parathyroid Hormone / Q000494:pharmacology; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D018124:Receptors, Tumor Necrosis Factor; D017154:Stromal Cells / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D020030:Nitric Oxide Donors; D053244:Osteoprotegerin; D010281:Parathyroid Hormone; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D009599:Nitroprusside; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D002117:Calcitriol; D006152:Cyclic GMP