• Molecules and Cells
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• v.37 no.10
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• pp.747-752
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• 2014

Protein kinase C (PKC) family members phosphorylate a wide variety of protein targets and are known to be involved in diverse cellular signaling pathways. However, the role of PKC in receptor activator of NF-${\kappa}B$ ligand (RANKL) signaling has remained elusive. We now demonstrate that $PKC{\beta}$ acts as a positive regulator which inactivates glycogen synthase kinase-$3{\beta}$ (GSK-$3{\beta}$) and promotes NFATc1 induction during RANKL-induced osteoclastogenesis. Among PKCs, $PKC{\beta}$ expression is increased by RANKL. Pharmacological inhibition of $PKC{\beta}$ decreased the formation of osteoclasts which was caused by the inhibition of NFATc1 induction. Importantly, the phosphorylation of GSK-$3{\beta}$ was decreased by $PKC{\beta}$ inhibition. Likewise, down-regulation of $PKC{\beta}$ by RNA interference suppressed osteoclast differentiation, NFATc1 induction, and GSK-$3{\beta}$ phosphorylation. The administration of PKC inhibitor to the RANKL-injected mouse calvaria efficiently protected RANKL-induced bone destruction. Thus, the $PKC{\beta}$ pathway, leading to GSK-$3{\beta}$ inactivation and NFATc1 induction, has a key role in the differentiation of osteoclasts. Our results also provide a further rationale for $PKC{\beta}$'s therapeutic targeting to treat inflammation-related bone diseases.

• Journal of Veterinary Clinics
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• v.28 no.4
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• pp.387-393
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• 2011

Polygoni Multiflori Radix (PMR) a dried root tuber of Polygonum multiflorum Thunberg with bioactivities in bone metabolism is one of the most famous tonic traditional medicines in China, Japan and Korea.To observe the anti-osteoporotic effect of PMR, we observed the effects on proliferation and alkaline phosphatase (ALP) activity of primary osteoblasts, bone nodule formation, pit formation of osteoclasts and osteoclastogenesis in vitro. As the result of that, although PMR extracts have no meaningful changes on the the proliferation of primary osteoblasts, significant (p < 0.01) increases of ALP acitivity of osteoblasts were dose-dependently observed in all PMR extracts treated groups tested compared to that of vehicle control. It means that it enhanced the differentiation (ALP activity) and bone nodule formation of osteoblast. In addition, PMR extracts dose-dependently inhibits the pit formation and the number of multinucleated osteoclast-like cells (OCLs), osteoclastogenesis in vitro. Therefore these results show the possibility of PMR extracts as another anti-osteoporotic agents.

• BMB Reports
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• v.51 no.7
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• pp.356-361
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• 2018

Actin-binding LIM protein 1 (ABLIM1), a member of the LIM-domain protein family, mediates interactions between actin filaments and cytoplasmic targets. However, the role of ABLIM1 in osteoclast and bone metabolism has not been reported. In the present study, we investigated the role of ABLIM1 in the receptor activator of $NF-{\kappa}B$ ligand (RANKL)-mediated osteoclastogenesis. ABLIM1 expression was induced by RANKL treatment and knockdown of ABLIM1 by retrovirus infection containing Ablim1-specific short hairpin RNA (shAblim1) decreased mature osteoclast formation and bone resorption activity in a RANKL-dose dependent manner. Coincident with the downregulated expression of osteoclast differentiation marker genes, the expression levels of c-Fos and the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), critical transcription factors of osteoclastogenesis, were also decreased in shAblim1-infected osteoclasts during RANKL-mediated osteoclast differentiation. In addition, the motility of preosteoclast was reduced by ABLIM1 knockdown via modulation of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt/Rac1 signaling pathway, suggesting another regulatory mechanism of ABLIM1 in osteoclast formation. These data demonstrated that ABLIM1 is a positive regulator of RANKL-mediated osteoclast formation via the modulation of the differentiation and PI3K/Akt/Rac1-dependent motility.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.1
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• pp.109-114
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• 2011

Atractylodis Rhizoma Alba is commonly used herbal medicine and it has been known that has immuno-regualtory effects and anti-cancer effects. The inhibition of osteoclastogenesis is essential for the prevention and treatment of osteoporosis. The aim of this study was to evaluate the effects of Atractylodis Rhizoma Alba on osteoclast differentiation in vitro and on resorbing activity of osteoclast. Osteoclast formation was evaluated in bone marrow cells (BMC) in the presence or absence of Atractylodis Rhizoma Alba. The expression of c-fos, tartrate-resistant acid phosphatase (TRAP), OSCAR, DC-STAMP, cathepsin K, MafB and NFATc1 mRNA in osteoclast precursor were assessed by RT-PCR. The levels of TNF receptor-associated factor-6 (TRAF-6), c-fos and NFATc1 protein were assessed by Western blot analysis. Also the correlation with MAPKs and NF-${\kappa}B$ pathways were measured by using Western blot analysis. With bone resorption study, I tried to evaluate the inhibitory effects of Atractylodis Rhizoma Alba on mature osteoclast function. Atractylodis Rhizoma Alba inhibited the RANKL induced osteoclastic differentiation from bone marrow macrophage in a dose dependant manner without cellular toxicity. Gene expression of c-fos and NFATc1 was significantly down regulated with Atractylodis Rhizoma Alba treatment. Atractylodis Rhizoma Alba markedly inhibited the RANKL-induced osteoclastogenesis through suppression of nuclear factor kappa b (NF-${\kappa}B$) pathway, down stream pathway of p38, ERK and JNK pathway. Taken together, I concluded that Atractylodis Rhizoma Alba have beneficial effect on osteoporosis by inhibition of osteoclast differentiation and by inhibition of functioning osteoclast. Thus I expect that Atractylodis Rhizoma Alba could be a treatment option for osteoporosis.

• International Journal of Oral Biology
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• v.41 no.1
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• pp.9-15
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• 2016

Receptor activator of nuclear factor-${\kappa}B$ ligand (RANKL) is an osteoblast/stromal cell-derived essential factor for osteoclastogenesis. During endochondral bone formation, hypertrophic chondrocytes calcify cartilage matrix that is subsequently resorbed by osteoclasts in order to be replaced by new bone. Hypoxia-induced upregulation of RANKL expression has been previously demonstrated in an in vitro system using osteoblasts; however, the involved mechanism remains unclear in chondrocytes. In the present study, we investigated whether hypoxia regulates RANKL expression in ATDC5 cells, a murine chondrogenic cell line, and hypoxia-inducible factor-$1{\alpha}$ (HIF-$1{\alpha}$) mediates hypoxia-induced RANKL expression by transactivating the RANKL promoter. The expression levels of RANKL mRNA and protein, as well as HIF-$1{\alpha}$ protein, were significantly increased in ATDC5 cells under hypoxic condition. Constitutively active HIF-$1{\alpha}$ alone significantly increased the levels of RANKL expression under normoxic conditions, whereas dominant negative HIF-$1{\alpha}$ reduced hypoxia-induced RANKL expression. HIF-$1{\alpha}$ increased RANKL promoter reporter activity in a HIF-$1{\alpha}$ binding element-dependent manner in ATDC5 cells. Hypoxia-induced RANKL levels were much higher in differentiated ATDC5 cells, as compared to proliferating ATDC5 cells. These results suggested that under hypoxic conditions, HIF-$1{\alpha}$ mediates induction of RANKL expression in chondrocytes; in addition, hypoxia plays a role in osteoclastogenesis during endochondral bone formation, at least in part, through the induction of RANKL expression in hypertrophic chondrocytes.

• Biomolecules & Therapeutics
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• v.19 no.1
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• pp.70-76
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• 2011

Bone remodeling is a dynamic process involving a constant balance between osteoclast-induced bone resorption and osteoblast-induced bone formation. Osteoclasts play a crucial homeostatic role in skeletal modeling and remodeling, and destroy bone in many pathological conditions. Previously, we reported that the hexane soluble fraction of Ficus carica inhibited osteoclast differentiation. Poly unsaturated fatty acids, such as ethyl docosahexaenoate (E-DHA), docosahexaenoic acid (DHA), cis-11,14-eicosadienoic acid (EDA) and eicosapentaenoic acid (EPA), were identified from the hexane soluble fraction of Ficus carica. Among them, E-DHA most potently inhibited osteoclastogenesis in RAW264.7 cells. E-DHA reduced the activities of JNK and NF-$\kappa}B$. E-DHA suppressed the expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1). Interestingly, DHA increased the activity of alkaline phosphatase and expression of bone morphogenetic protein 2 (BMP2) more than E-DHA in MC3T3-E1 cells, suggesting that DHA may induce osteoblast differentiation. The data suggests that a combination of E-DHA and DHA has potential use in the treatment of diseases involving abnormal bone lysis, such as osteoporosis, rheumatoid arthritis and periodontal bone erosion.

• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.395-404
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• 2008

Purpose: Osteoprotegerin (OPG) is a secreted glycoprotein and a member of the tumor necrosis factor (TNF) receptor family that inhibits bone resorption by suppressing osteoclastogenesis. Gingival fibroblasts (GF) play a role in periodontal disease progression, and the purpose of this experiment was to evaluate influence of osteotropic factors on the expression of osteoprotegerin mRNA in these cells. Materials and Methods: In this experiment, the influence of osteoclastogenic factors, interleukin-1 beta (IL-$1{\beta}$), TNF-$\alpha$, prostanglandin E2 ($PEG_2$). parathyroid hormone (PTH) and 1$\alpha$, 25-dihydroxyvitamin $D_3$ on the expression of osteoprotegerin mRNA in GF was studied by Northern blot hybridization. Results: As expected, $PEG_2$ tended to inhibit OPG levels and this was most prominent at 24 hours of culture with $10^{-7}M$ of $PEG_2$. TNF-$\alpha$ at 10ng/ml and also at 25ng/ml decreased OPG levels to almost 30% of the control at 24 hours. This contrasts with reports of increased OPG levels from osteoblast/stromal cells and gingival fibroblasts stimulated by TNF-$\alpha$. Decrease of OPG levels with $PEG_2$ and TNF-$\alpha$ suggests a pathway whereby these mediators exert their resorptive effects. However, OPG levels were increased almost 3-fold at 24 hours with IL-1$\beta$(1 to 15ng/ml) and increased 1.4 fold with 24-hour treatment of $10^{-7}M$ PTH. Conclusion: Increase of OPG levels suggests that these 'osteoclastogenic' factors act in more complex ways and may act to inhibit bone resorption in inflammatory periodontitis. This result supports the role of OPG as a negative feedback mechanism in osteoclastic activity.

• YAKHAK HOEJI
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• v.59 no.5
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• pp.207-214
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• 2015

P2Y receptors, a type of P2 receptor family, are G-protein coupled receptors and 8 subtypes have been characterized ($P2Y_1$, $P2Y_2$, $P2Y_4$, $P2Y_6$, $P2Y_{11-14}$). Recently, several studies have shed light on the role of P2Y receptors in bone biology. Among them, little is known on the role of $P2Y_6$ receptor on osteoclast differentiation. Thus, we investigated the role of $P2Y_6$ receptor on osteoclastogenesis using $P2Y_6$ receptor selective antagonist, MRS 2578. When osteoblasts and bone marrow cells were co-cultured in the presence of $VitD_3$ and $PGE_2$, $P2Y_6$ antagonist increased the formation of TRAP positive osteoclasts. To elucidate the target cells of $P2Y_6$ antagonist, we first checked the effect of MRS 2578 on osteoblasts. Treatment of MRS 2578 did not affect OPG : RANKL mRNA ratio in osteoblasts. Next, we checked the effects of $P2Y_6$ antagonist on osteoclast precursors using mouse bone marrow macrophages (BMMs). Addition of MRS 2578 increased the number of osteoclasts in RANKL-treated BMMs. Although $P2Y_6$ antagonist had no effect on RANKL-induced NFATc1, c-Fos and MafB expression levels, it significantly stimulated RANKL-induced Blimp1 mRNA expression in BMMs. Taken together, these data indicate that $P2Y_6$ antagonist increases osteoclast formation by upregulation of Blimp1 expression.

• Molecules and Cells
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• v.38 no.1
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• pp.75-80
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• 2015

Osteoclasts are unique cells responsible for the resorption of bone matrix. MicroRNAs (miRNAs) are involved in the regulation of a wide range of physiological processes. Here, we examined the role of miR-26a in RANKL-induced osteoclastogenesis. The expression of miR-26a was upregulated by RANKL at the late stage of osteoclastogenesis. Ectopic expression of an miR-26a mimic in osteoclast precursor cells attenuated osteoclast formation, actin-ring formation, and bone resorption by suppressing the expression of connective tissue growth factor/CCN family 2 (CTGF/CCN2), which can promote osteoclast formation via upregulation of dendritic cell-specific transmembrane protein (DC-STAMP). On the other hand, overexpression of miR-26a inhibitor enhanced RANKL-induced osteoclast formation and function as well as CTGF expression. In addition, the inhibitory effect of miR-26a on osteoclast formation and function was prevented by treatment with recombinant CTGF. Collectively, our results suggest that miR-26a modulates osteoclast formation and function through the regulation of CTGF.

• The Journal of Korean Obstetrics and Gynecology
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• v.27 no.3
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• pp.12-27
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• 2014

Objectives: This study was performed to evaluate the effect of Guibi-tang water extract (GB) on osteoporosis. Methods: We examined the effect of GB on osteoclast differentiation using murine pre-osteoclastic RAW 264.7 cells treated with receptor activator of nuclear factor kappa-B ligand (RANKL). The effect of GB on osteoclast was measured by counting TRAP (+) multinucleated cells and measuring TRAP activity. The mRNA expressions of osteoclastogenesis-related genes (Cathepsin K, MMP-9, TRAP, NFATc1, MITF, TNF-${\alpha}$, IL-6, COX-2) were measured by real-time PCR. We examined the effect of GB on osteoblast proliferation, ALP activity, bone matrix protein synthesis and collagen synthesis using murine calvarial cell. Results: GB decreased the number of TRAP (+) multinucleated cells and inhibited TRAP activity in RANKL-stimulated RAW 264.7 cell. GB decreased the expression of genes related osteoclastogenesis such as Cathepsin K, MMP-9, TRAP, NFATc1, MITF, COX-2 in RANKL-stimulated RAW 264.7 cell. But GB did not decrease the expression of iNOS and increased the expression of TNF-${\alpha}$, IL-6 in RANKL-stimulated RAW 264.7 cell. These genes (iNOS, TNF-${\alpha}$, IL-6) are thought to be related with the inflammatory bone destruction. GB increased cell proliferation of rat calvarial cell and also increased ALP activity in rat calvarial cell. GB did not increase bone matrix protein synthesis but increased collagen synthesis in rat calvarial cell. Conclusions: This study suggests that GB may be effective in treating osteoporosis by inhibiting osteoclast differentiation and its related gene expression and by increasing osteoblast proliferation.