Recombinant receptor activator of nuclear factor�κB exhibits more marked inhibitory effects on osteoclasts compared with recombinant osteoprotegerin in�vitro and in�vivo (original) (raw)
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Journal of Bone and Mineral Research, 2003
Osteoprotegerin (OPG) is a naturally occurring negative regulator of osteoclast differentiation, activation, and survival. We created a recombinant form of human OPG (rhOPG), with a sustained serum half-life, to achieve prolonged antiresorptive activity. This study describes the rapid and sustained antiresorptive effects that are achieved with a single treatment with rhOPG. Male Sprague-Dawley rats (10 weeks old) were given a single bolus intravenous injection of vehicle (PBS) or rhOPG (5 mg/kg). PBS-and rhOPG-treated rats (n ؍ 6/group) were killed at 0, 0.5, 1, 2, 5, 10, 20, and 30 days post-treatment. rhOPG-treated rats were compared with their age-matched controls. The main pharmacologic effect of rhOPG was a rapid (24 h) reduction in osteoclast surface in the tibia, which reached a nadir on days 5 and 10 (95% reduction vs. vehicle controls). Osteoclast surface remained significantly reduced 30 days after the single treatment with rhOPG. Tibial cancellous bone volume was significantly increased within 5 days of rhOPG treatment (23%) and reached a peak increase of 58% on day 30. Femoral bone mineral density was significantly increased in rhOPG-treated rats on days 10 and 20. Pharmacokinetic analysis revealed that serum concentrations of rhOPG remained at measurable levels throughout the 30-day study. These data show that a single intravenous injection of rhOPG in young growing rats causes significant gains in bone volume and density, which are associated with rapid and sustained suppression of osteoclastic bone resorption. (J Bone Miner Res 2003;18:852-858)
Journal of Bone and Mineral Research, 2009
RANKL is an essential mediator of bone resorption, and its activity is inhibited by osteoprotegerin (OPG). Transgenic (Tg) rats were engineered to continuously overexpress OPG to study the effects of continuous long-term RANKL inhibition on bone volume, density, and strength. Lumbar vertebrae, femurs, and blood were obtained from 1-yr-old female OPG-Tg rats (n = 32) and from age-matched wildtype (WT) controls (n = 23). OPG-Tg rats had significantly greater serum OPG (up to 260-fold) and significantly lower serum TRACP5b and osteocalcin compared with WT controls. Vertebral histomorphometry showed significant reductions in osteoclasts and bone turnover parameters in OPG-Tg rats versus WT controls, and these reductions were associated with significantly greater peak load in vertebrae tested through compression. No apparent differences in bone material properties were observed in OPG-Tg rat vertebrae, based on their unchanged intrinsic strength parameters and their normal linear relationship between vertebral bone mass and strength. Femurs from OPG-Tg rats were of normal length but showed mild osteopetrotic changes, including reduced periosteal perimeter (-6%) and an associated reduction in bending strength. Serum OPG levels in WT rats showed no correlations with any measured parameter of bone turnover, mass, or strength, whereas the supraphysiological serum OPG levels in OPG-Tg rats correlated negatively with bone turnover parameters and positively with vertebral bone mass and strength parameters. In summary, low bone turnover after 1 yr of OPG overexpression in rats was associated with increased vertebral bone mass and proportional increases in bone strength, with no evidence for deleterious effects on vertebral material properties.
Osteoprotegerin Regulates Bone Formation through a Coupling Mechanism with Bone Resorption
Endocrinology, 2003
Deficiency of osteoprotegerin (OPG), a soluble decoy receptor for receptor activator of nuclear factor-B ligand (RANKL), in mice induces osteoporosis caused by enhanced bone resorption, but also accelerates bone formation. We examined whether bone formation is coupled with bone resorption in OPG-deficient (OPG ؊/؊ ) mice using risedronate, an inhibitor of bone resorption. Histomorphometric analysis showed that bone formation-related parameters (e.g. mineral apposition rate and osteoblast surface/bone surface) in OPG ؊/؊ mice sharply decreased with suppression of bone resorption by daily injection of risedronate for 30 d. OPG ؊/؊ mice exhibited high serum alkaline phosphatase activity and osteocalcin con-centration, both of which were decreased to the levels in wildtype mice by the risedronate injection. Serum levels of RANKL were markedly elevated in OPG ؊/؊ mice, but were unaffected by risedronate. The ectopic bone formation induced by bone morphogenetic protein-2 implantation into OPG ؊/؊ mice was not accelerated even with a high turnover rate of bone, but attenuation of mineral density from the ectopic bone was more pronounced than that in wild-type mice. These results suggest that bone formation is coupled with bone resorption at local sites in OPG ؊/؊ mice, and that serum RANKL levels do not reflect this coupling. Abbreviations: ALP, Alkaline phosphatase; BMD, bone mineral density; OPG, osteoprotegerin; RANKL, receptor activator of nuclear factor-B ligand; rh, recombinant human; WT, wild-type.
2010
Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor B ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis. (Endocrine Reviews 29: 155-192, 2008) prostate cancer metastasis to bone J. RANKL and RANKL inhibition in animal models of multiple myeloma K. RANKL and RANKL inhibition in fracture and fracture repair IV. Role and Regulation of OPG/RANKL in the Human Skeleton A. Postmenopausal osteoporosis B. Men C. Glucocorticoid treatment D. Paget's disease of bone E. Rheumatoid arthritis V. Clinical Therapeutics Targeting the RANK/RANKL/OPG System A. Mechanism of action of denosumab B. Clinical studies of denosumab in postmenopausal women with osteoporosis
Osteogenic Effects of a Potent Src-over-Abl-Selective Kinase Inhibitor in the Mouse
Journal of Pharmacology and Experimental Therapeutics, 2011
Src-null mice have higher bone mass because of decreased bone resorption and increased bone formation, whereas Ablnull mice are osteopenic, because of decreased bone formation. Compound I, a potent inhibitor of Src in an isolated enzyme assay (IC 50 0.55 nM) and a Src-dependent cell growth assay, with lower activity on equivalent Abl-based assays, potently, but biphasically, accelerated differentiation of human mesenchymal stem cells to an osteoblast phenotype (1-10 nM). Compound I (Ն0.1 nM) also activated osteoblasts and induced bone formation in isolated neonatal mouse calvariae. Compound I required higher concentrations (100 nM) to inhibit differentiation and activity of osteoclasts. Transcriptional profiling (TxP) of calvaria treated with 1 M compound I revealed downregulation of osteoclastic genes and up-regulation of matrix genes and genes associated with the osteoblast phenotype, confirming compound I's dual effects on bone resorption and formation. In addition, calvarial TxP implicated calcitonin-related polypeptide,  (-CGRP) as a potential mediator of compound I's osteogenic effect. In vivo, compound I (1 mg/kg s.c.) increased vertebral trabecular bone volume 21% (microcomputed tomography) in intact female mice. Increased trabecular volume was also detected histologically in a separate bone, the femur, particularly in the secondary spongiosa (100% increase), which underwent a 171% increase in bone formation rate, a 73% increase in mineralizing surface, and a 59% increase in mineral apposition rate. Similar effects were observed in ovariectomized mice with established osteopenia. We conclude that the Src inhibitor compound I is osteogenic, presumably because of its potent stimulation of osteoblast differentiation and activation, possibly mediated by -CGRP.
Osteoprotegerin protects against generalized bone loss in tumor necrosis factor-transgenic mice
Arthritis and Rheumatism, 2003
ObjectiveTo investigate the role of tumor necrosis factor (TNF) in systemic bone loss of chronic inflammatory conditions, such as rheumatoid arthritis (RA), and to address the therapeutic potential of osteoclast blockade.To investigate the role of tumor necrosis factor (TNF) in systemic bone loss of chronic inflammatory conditions, such as rheumatoid arthritis (RA), and to address the therapeutic potential of osteoclast blockade.MethodsWe investigated systemic bone changes in human TNF transgenic (hTNFtg) mice, which spontaneously developed severe inflammatory arthritis.We investigated systemic bone changes in human TNF transgenic (hTNFtg) mice, which spontaneously developed severe inflammatory arthritis.ResultsOsteodensitometry revealed a significant decrease in trabecular bone mineral density (BMD) (−37%) in hTNFtg mice, and histomorphometry revealed a dramatic loss of bone volume (−85%) compared with wild-type controls. Osteoclast-covered bone surface and serum levels of deoxypyridinoline crosslinks were significantly elevated, suggesting increased osteoclast-mediated bone resorption in hTNFtg mice. Osteoprotegerin (OPG) completely blocked TNF-mediated bone loss by increasing BMD (+89%) and bone volume (+647%). Most strikingly, formation of primary spongiosa was dramatically increased (+563%) in hTNFtg mice after OPG treatment. Osteoclast-covered bone surface and serum levels of deoxypyridinoline crosslinks were significantly decreased by OPG, suggesting effective blockade of osteoclast-mediated bone resorption. OPG did not influence levels of hTNF, TNF receptor I (TNFRI), interleukin-1β (IL-1β), and IL-6. However, OPG decreased bone formation parameters (osteoblast-covered bone surface and serum osteocalcin levels), which were elevated in hTNFtg mice. In contrast to OPG, bisphosphonates and anti-TNF treatment did not affect generalized bone loss in hTNFtg mice. Anti-TNF, however, did not affect levels of TNF and TNFRI at the concentrations tested. These data indicate that generalized bone loss due to increased TNF can be blocked by OPG.Osteodensitometry revealed a significant decrease in trabecular bone mineral density (BMD) (−37%) in hTNFtg mice, and histomorphometry revealed a dramatic loss of bone volume (−85%) compared with wild-type controls. Osteoclast-covered bone surface and serum levels of deoxypyridinoline crosslinks were significantly elevated, suggesting increased osteoclast-mediated bone resorption in hTNFtg mice. Osteoprotegerin (OPG) completely blocked TNF-mediated bone loss by increasing BMD (+89%) and bone volume (+647%). Most strikingly, formation of primary spongiosa was dramatically increased (+563%) in hTNFtg mice after OPG treatment. Osteoclast-covered bone surface and serum levels of deoxypyridinoline crosslinks were significantly decreased by OPG, suggesting effective blockade of osteoclast-mediated bone resorption. OPG did not influence levels of hTNF, TNF receptor I (TNFRI), interleukin-1β (IL-1β), and IL-6. However, OPG decreased bone formation parameters (osteoblast-covered bone surface and serum osteocalcin levels), which were elevated in hTNFtg mice. In contrast to OPG, bisphosphonates and anti-TNF treatment did not affect generalized bone loss in hTNFtg mice. Anti-TNF, however, did not affect levels of TNF and TNFRI at the concentrations tested. These data indicate that generalized bone loss due to increased TNF can be blocked by OPG.ConclusionOPG may represent a potent tool for preventing generalized loss of bone mass in chronic inflammatory disorders, especially RA.OPG may represent a potent tool for preventing generalized loss of bone mass in chronic inflammatory disorders, especially RA.
Inhibition of osteoblastic bone formation by nuclear factor-κB
Nature Medicine, 2009
An imbalance in bone formation relative to bone resorption results in the net bone loss in osteoporosis and inflammatory bone diseases. While it is well known how bone resorption is stimulated, the molecular mechanisms that mediate impaired bone formation are poorly understood. Here we show that the time-and stage-specific inhibition of endogenous IκB kinase (IKK)/nuclear factor-kappa B (NF-κB) NF-κB in differentiated osteoblasts significantly increases trabecular bone mass and bone mineral density without affecting osteoclast activities in young mice. Moreover, the inhibition of IKK/NF-κB in differentiated osteoblasts maintains bone formation, thereby preventing osteoporotic bone loss induced by ovariectomy (OVX) in adult mice. The inhibition of IKK/NF-κB enhances the expression of Fra-1, an essential factor for bone matrix formation in vitro and in vivo. Taken together, our results suggest that targeting IKK/NF-κB may help to promote bone formation in the treatment of osteoporosis and other bone diseases. Postnatal skeletal growth and bone remodeling are highly coordinated processes that are primarily mediated by bone-forming osteoblasts and bone-resorbing osteoclasts1-3. To maintain normal bone homeostasis, bone resorption is delicately balanced with bone extracellular matrix deposition or bone formation, ensuring that new bone is generated Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Journal of applied oral science : revista FOB, 2018
Raloxifene is an antiresorptive drug, selective estrogen receptor modulator (SERM) used in the treatment of osteoporosis. Objective To evaluate proteins related to bone repair at the peri-implant bone in a rat model of osteoporosis treated with raloxifene. Material and Methods 72 rats were divided into three groups: SHAM (healthy animals), OVX (ovariectomized animals), and RLX (ovariectomized animals treated with raloxifene). Raloxifene was administered by gavage (1 mg/kg/day). Tibial implantation was performed 30 days after ovariectomy, and animals were euthanized at 14, 42, and 60 days postoperatively. Samples were collected and analyzed by immunohistochemical reactions, molecular analysis, and microtomographic parameters. Results RLX showed intense staining of all investigated proteins at both time points except for RUNX2. These results were similar to SHAM and opposite to OVX, showing mild staining. The PCR gene expression of OC and ALP values for RLX (P<0.05) followed by SHA...
Bone, 2011
Background: The mechanism for the uncoupling effects of Sr on bone remains to be evaluated. Osteoblasts play important roles in osteoclastogenesis through regulating receptor activated nuclear factor kappa B (RANK) ligand (RANKL) and osteoprotegerin (OPG) expression. We hypothesize that OPG plays an important role in the cross-talk between osteoclasts and osteoblasts in response to Sr treatment. Materials and methods: MC3T3E1 cells were treated with Sr chloride (0-3 mM) and conditioned media were collected at 24 h after the treatment. The effect of conditioned media on osteoclastogenesis was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and bone resorption pits analysis. OPG and RANKL mRNA expressions in osteoblastic cells and protein secretion in the conditioned media were analyzed with real-time PCR and ELISA assay, respectively. The role of OPG in Sr-mediated inhibition of osteoclastogenesis was further evaluated with anti-OPG antibody in pre-osteoclastic cells. The role of OPG in Sr-mediated uncoupling effects on osteoporotic bone was evaluated by an animal study. Ovariectomized rats were oral administrated with vehicle or Sr chloride for two months supplemented with anti-IgG antibody (control) or anti-OPG antibody. The effects of OPG neutralization after Sr treatment on bone metabolism were analyzed by microCT, bone histomorphometry and biochemical analysis. Results: The conditioned media derived from Sr-treated osteoblastic cells exerted a dose-dependent inhibitory effect on osteoclastic differentiation and resorptive activity in pre-osteoclastic cells. OPG mRNA expression and protein secretion in osteoblastic cells were significantly increased after Sr treatment. Neutralization with anti-OPG antibody abolished the inhibitory effect of conditioned media on RANKL-induced osteoclastogenesis. The uncoupling effects of Sr treatment on trabecular bone were evidenced by greater bone volume and trabecular number, greater osteoid surface and bone formation rate, while less osteoclast surface. These effects were attenuated by the OPG neutralization by anti-OPG antibody injection. Conclusion: The evidences from the in vitro and in vivo studies suggested that OPG played an important role in the uncoupling effect of Sr on bone metabolism, possibly by acting as a cross-talk molecule between osteoclasts and osteoblasts in response to Sr treatment.
Osteoprotegerin (OPG) is a decoy receptor for receptor activator of NF-B ligand (RANKL). We previously reported that OPG deficiency elevated the circulating level of RANKL in mice. Using OPG ؊/؊ mice, we investigated whether OPG is involved in the shedding of RANKL by cells expressing RANKL. Osteoblasts and activated T cells in culture released a large amount of RANKL in the absence of OPG. OPG or a soluble form of receptor activator of NF-B (the receptor of RANKL) suppressed the release of RANKL from those cells. OPG-and T cell-double-deficient mice showed an elevated serum RANKL level equivalent to that of OPG ؊/؊ mice, indicating that circulating RANKL is mainly derived from bone. The serum level of RANKL in OPG ؊/؊ mice was increased by ovariectomy or administration of 1␣,25-dihydroxyvitamin D 3. Expression of RANKL mRNA in bone, but not thymus or spleen, was increased in wild-type and OPG ؊/؊ mice by 1␣,25-dihydroxyvitamin D 3. These results suggest that OPG suppresses the shedding of RANKL from osteoblasts and that the serum RANKL in OPG ؊/؊ mice exactly reflects the state of bone resorption.