Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Osteoprotegerin (OPG) is a soluble decoy receptor that inhibits osteoclastogenesis and is closely associated with bone resorption processes. We have designed and determined the solution structures of potent OPG analogue peptides, derived from sequences of the cysteine-rich domain of OPG. The inhibitory effects of the peptides on osteoclastogenesis are dose-dependent (10(-6) M-10(-4) M), and the activity of the linear peptide at 10(-4) M is ten-fold higher than that of the cyclic OPG peptide. Both linear and cyclic peptides have a beta-turn-like conformation and the cyclic peptide has a rigid conformation, suggesting that structural flexibility is an important factor for receptor binding. Based on structural and biochemical information about RANKL and the OPG peptides, we suggest that complex formation between the peptide and RANKL is mediated by both hydrophobic and hydrogen bonding interactions. These results provide structural insights that should aid in the design of peptidyl-mimetic inhibitors for treating metabolic bone diseases caused by abnormal osteoclast recruitment.
Mol Cells 2008 May 31
PMID:Structure-function of the TNF receptor-like cysteine-rich domain of osteoprotegerin. 1844 24

Several epidemiological studies have reported that temporomandibular disorder is more prevalent in women, which suggests the involvement of sex hormones, such as estrogen, in the pathogenesis of this disease. PCR amplification and Western blotting were employed to target the expression of estrogen receptors (ERs) in human fibroblast-like synovial and ATDC5 cells. The effect of estrogen was investigated through the expression of RANKL, osteoprotegerin (OPG), M-CSF/CSF-1 and c-fms. We showed expression of M-CSF/ CSF-1 and c-fms, with time-dependent increase in both after the addition of estrogen. Based on previous studies reporting that M-CSF/CSF-1 regulates the proliferation and differentiation of hemopoietic progenitor cells into mature macrophages, we put forward a new hypothesis based on the increased inflammation and tendency of females to suffer more from temporomandibular disorder (TMD) in the presence of external exacerbating factors. Detection of RANKL and OPG in ATDC5 and expression of both in HFLS was confirmed with complete disappearance of the RANKL band, and marked increase in the expression of OPG after 1 h from the addition of estrogen.
Int J Mol Med 2008 Jun
PMID:Effect of estrogen on bone resorption and inflammation in the temporomandibular joint cellular elements. 1850 73

To understand the contribution of IL-6/IL-6R to subchondral bone and bone marrow abnormality in RA patients and the effects of tocilizumab on those abnormalities, we evaluated early change in a collagen-induced arthritis (CIA) monkey model with or without a single administration of tocilizumab. Six CIA cynomolgus monkeys received tocilizumab and 3 CIA monkeys received vehicle only. Their interphalangeal joints were analyzed using HE, silver impregnation (SI), or immunohistochemistry (RANKL) staining. The number of osteoclasts increased in the arthritis control but was suppressed in the tocilizumab-treated animals. Osteoblast/stromal cells of the arthritis control monkeys were of monolayer, while in the tocilizumab-treated monkeys, the cells were multi-layer or differentiated osteoblasts, and the meshwork of the reticulum fibers showed recovery in the SI. Hematopoietic marrow was replaced by interstitial fluid and reticulum fibers were eliminated in the arthritic model but showed recovery in the tocilizumab-treated animals. RANKL showed overproduction with arthritis and suppressed with tocilizumab treatment. The evidence indicates that IL-6/IL-6R is involved in subchondral bone and bone marrow change in RA patients. Tocilizumab treatment recovered changes in the CIA monkeys as a result of the co-differentiation between the osteoclasts and the osteoblast/stramal cells, at least partially through the suppression of RANKL overproduction.
Exp Mol Pathol 2008 Jun
PMID:Early effects of tocilizumab on bone and bone marrow lesions in a collagen-induced arthritis monkey model. 1851 Oct 40

A large body of evidence suggests that the immune system directly impacts bone physiology. We tested whether immune regulating hormones (IRH), 17beta-androstenediol (beta-AED), 7beta,17beta-androstenetriol (beta-AET) or the 17alpha-androstenediol (alpha-AED), and 7alpha,17beta-androstenetriol (alpha-AET) metabolites could directly influence bone remodeling in vitro using human fetal osteoblasts (FOB-9). The impact on bone remodeling was examined by comparing the ratio of RANKL/OPG gene expression in response to AED and AET compounds. The alpha-AED was found to significantly increase in the ratio of RANKL/OPG gene expression and altering the morphology of RANKL stained FOB-9 cells. Cell viability was assessed using a Live/Dead assay. Again alpha-AED was unique in its ability to reduce the proportion of viable cells, and to induce mild apoptosis of FOB-9 cells. Treatment of FOB-9 cells with WY14643, an activator of PPAR-alpha and -gamma, also significantly elevated the percentage of dead cells. This increase was abolished by co-treatment with GW9962, a specific inhibitor of PPAR-gamma. Analysis of PPAR-gamma mRNA by Quantitative RT-PCR and its activation by DNA binding demonstrated that alpha-AED increased PPAR-gamma activation by 19%, while beta-AED conferred a 37% decrease in PPAR-gamma activation. In conclusion, alpha-AED opposed beta-AED by elevating a bone resorption scenario in osteoblast cells. The increase in RANKL/OPG is modulated by an activation of PPAR-gamma that in turn caused mild apoptosis of FOB-9 cells.
J Steroid Biochem Mol Biol 2008 Jun
PMID:Effects of alpha/beta-androstenediol immune regulating hormones on bone remodeling and apoptosis in osteoblasts. 1851 51

To clarify the mechanisms of altered bone repair in the diabetic state, we investigated RANK, RANKL and OPG expression by immunohistochemistry and RT-PCR in the fracture sites of rats that were either healthy or made diabetic by alloxan. Histomorphometric analysis of the fracture site at 7 days after fracture revealed that diabetic rats (db) have significantly less hard tissue formation at the fracture site, compared to controls. The number of RANK, RANKL and OPG positive cells was decreased in the db group; however, the RANKL/OPG ratio was similar in controls and db at this time. At day 14, numbers of RANKL and OPG positive cells and the mRNA expression for these markers were higher in the control group than in db (P = 0.008). The RANKL/OPG ratio in the db group was greater than in controls. Our results demonstrate an imbalance of RANKL/OPG expression associated with diabetes that may contribute to the delay of fracture repair during the course of diabetes.
J Mol Histol 2008 Aug
PMID:Imbalance of RANK, RANKL and OPG expression during tibial fracture repair in diabetic rats. 1859 39

We investigated whether the effect of beta-cryptoxanthin (CRP) on osteoclastic cells formed in the mouse marrow culture system in vitro is enhanced by culture with zinc. Bone marrow cells were isolated from mice. The macrophage colony-stimulating factor (M-CSF)-dependent bone marrow macrophages were cultured in the presence of M-CSF (10 ng/ml) and receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL; 50 ng/ml) for 96 h. The osteoclastic cells formed were further cultured for 24 or 72 h in a medium containing either vehicle, CRP, zinc sulfate (zinc), or CRP plus zinc with or without M-CSF (10 ng/ml) and RANKL (50 ng/ml). The number of osteoclastic cells was significantly decreased after culture with the combination of CRP (10(-7) M) and zinc (10(-5) M) in the presence or absence of M-CSF and RANKL for 24 or 72 h as compared with the value for CRP or zinc alone. Agarose gel electrophoresis showed the presence of low-molecular weight deoxyribonucleic acid (DNA) fragments of adherent cells cultured with CRP (10(-7) M) plus zinc (10(-5) M) for 24 or 72 h in the presence of M-CSF and RANKL, indicating that the combination of the two chemicals induces apoptotic cell death. CRP plus zinc-induced decrease in osteoclastic cells was significantly inhibited in the presence of caspase-3 inhibitor (10(-8) or 10(-7) M). Culture with CRP (10(-7) M) plus zinc ((10(-5) M) for 24 or 72 h caused a significant increase in caspase-3 mRNA expression in the presence or absence of M-CSF and RANKL as compared with the value for each chemical alone. CRP plus zinc-induced increase in caspase-3 mRNA expression was completely inhibited in the presence of cycloheximide (10(-7) M), an inhibitor of protein synthesis, or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DBR; 10(-6) M), an inhibitor of transcription activity. The mRNA expression of tartrate-resistant acid phosphatase (TRACP) and cathepsin K was significantly decreased after culture with CRP plus zinc in the presence or absence of M-CSF and RANKL for 72 h as compared with CRP or zinc alone. Nuclear factor of activated T cells c1 (NFATc1) mRNA expression was significantly decreased after culture with CRP plus zinc in the presence or absence of M-CSF and RANKL for 72 h as compared with each chemical alone, while NF-kappaB mRNA expression was not significantly changed. This study demonstrated that the combination of CRP and zinc has potent suppressive effects on osteoclastic cells in vitro.
Int J Mol Med 2008 Aug
PMID:Combination of beta-cryptoxanthin and zinc has potent effects on apoptotic cell death and suppression of bone resorption-related gene expression in osteoclastic cells. 1863 77

Notch signaling plays a key role in various cell differentiation processes including bone homeostasis. However, the specific involvement of Notch in regulating osteoclastogenesis is still controversial. In the present study, we show that RANKL induces expression of Jagged1 and Notch2 in bone marrow macrophages during osteoclast differentiation. Suppression of Notch signaling by a selective gamma-secretase inhibitor or Notch2 short hairpin RNA suppresses RANKL-induced osteoclastogenesis. In contrast, induction of Notch signaling by Jagged1 or by ectopic expression of intracellular Notch2 enhances NFATc1 promoter activity and expression and promotes osteoclastogenesis. Finally, we found that Notch2 and p65 interact in the nuclei of RANKL-stimulated cells and that both proteins are recruited to the NFATc1 promoter, driving its expression. Taken together, our results show a new molecular cross talk between Notch and NF-kappaB pathways that is relevant in osteoclastogenesis.
Mol Cell Biol 2008 Oct
PMID:The association of Notch2 and NF-kappaB accelerates RANKL-induced osteoclastogenesis. 1871 Sep 34

The receptor subunit gp130 is utilized by a wide range of cytokines, many of which have critical functions in regulating the actions of osteoclasts and osteoblasts. In vitro studies have revealed remarkably consistent effects of many of these family members, specifically, actions on receptors in the osteoblast lineage that stimulate osteoblast differentiation and stimulate production of RANKL, thereby increasing the formation of osteoclasts. In contrast to this simple model of gp130 action on bone, deletion of cytokines or receptors that interact with gp130 reveal a range of bone phenotypes implicating critical roles for gp130 signaling in longitudinal bone growth, bone resorption and bone formation. In most cases, deletion of gp130, ligands or ligand-specific receptors interacting with gp130 causes a low level of bone formation; a high level of bone formation was only observed in gp130(Y757F/Y757F) mice, gp130 signaling mutants, where it is caused by a cell-lineage autonomous increase in osteoclast formation and an IL-6-dependent coupling pathway. On the other hand, the range of gene knockouts may cause either a reduction or an increase in osteoclast formation, and in many cases alterations in osteoclast size and ability to resorb bone. Since some knockouts are neonatal lethal, interpretation of ex vivo analyses and the contribution of each component to bone remodeling are not clearly defined, and there is still much work to be done before these questions can be resolved. Taken together these results indicate multiple roles for gp130 cytokines in controlling osteoblasts and osteoclast function, including paracrine roles to mediate signaling between these two cell types.
Mol Cell Endocrinol 2009 Oct 30
PMID:gp130 signaling in bone cell biology: multiple roles revealed by analysis of genetically altered mice. 1880 58

Osteoprotegerin (OPG) is a soluble tumor necrosis factor receptor family member, which potently inhibits RANKL-mediated osteoclastogenesis. Numerous constructs have been created for therapeutic purposes in which the heparin-binding and death homology domains of OPG were removed and the remaining peptide (amino acids 22-194) was fused to the Fc domain of human IgG1 (OPG-Fc). The administration of OPG-Fc efficiently counteracted bone loss in a variety of preclinical models of cancers. However, several in vitro studies have shown that native or recombinant full-length OPG not only neuralizes RANKL, but also the death-inducing ligand TRAIL, suggesting that OPG might potentially counteract the anti-tumor activity of TRAIL. Additional evidence suggests that full-length OPG possesses RANKL- and TRAIL-independent biological properties, mainly related to the promotion of endothelial cell survival and angiogenesis. Finally, breast tumor cells overexpressing OPG have shown increased bone metastatic potential in vivo. The relevance of these apparently conflicting findings in tumor cell biology is highlighted.
Cell Mol Life Sci 2009 Mar
PMID:Role of full-length osteoprotegerin in tumor cell biology. 1901 55

The OPG/RANKL/RANK system is important in the balance between bone formation and resorption. We used primary human osteoblasts (hOBs) cells to examine the impact of 17-beta-estradiol (E2) or/and 1,25-dihydroxyvitamin D (1,25D) in OPG/RANKL system in 28 post-menopausal (PM) women; (a) with hip fracture (OP) or (b) with osteoarthritis (OA). The hOB from OP patients proliferated slower during the first stage, than the OA women (31.5+/-2.6 and 21.4+/-1.3 days, respectively, p<0.05). The OP group secreted significantly higher OPG protein levels than the OA women (10.1+/-2.6 and 4.4+/-0.8pmol/L, respectively, p<0.05). The 1,25D and 1,25D+E2 induce an increase in RANKL and RANKL/OPG mRNA expression in OP patients above 200% (p<0.05). HOBs from the osteoporotic hip initially proliferate slower but after reaching the first cellular confluence, the proliferation rate is equal in both groups. Furthermore, hOBs from hips with OP present a higher protein secretion of OPG, and higher RANKL and RANKL/OPG expression ratio in response to 1,25D and 1,25D+E2, than hOBs from OA women. All this could suggest that the greater bone loss that characterizes OP patients can be mediated due to differences in the secretion and expression of the RANKL/OPG system in response to different stimuli.
J Steroid Biochem Mol Biol 2009 Jan
PMID:RANKL/OPG in primary cultures of osteoblasts from post-menopausal women. Differences between osteoporotic hip fractures and osteoarthritis. 1907 56


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>