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Osteoporosis, which typically affects postmenopausal women, is an osteolytic disease due to over-activation of osteoclasts. However, current drugs targeting osteoclast inhibition face various side effects, making natural compounds with great interest as alternative treatment options. Cycloastragenol (CAG) is a triterpenoid with multiple biological activities. Previously, CAG's activity against aging-related osteoporosis was reported, but the mechanisms of actions for the activities were not understood. This study demonstrated that CAG dose-dependently inhibited osteoclast formation in receptor activator of nuclear factor-κB ligand (RANKL)-stimulated bone marrow macrophage (BMMs). Mechanism studies showed that CAG inhibited NF-κB, calcium, and nuclear factor of activated T cells 1 (NFATc1) pathways. Additionally, CAG also promoted the nuclear factor-erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1)/anti-oxidative response element (ARE) pathway that scavenges reactive oxygen species (ROS). Furthermore, CAG was also found to prevent bone loss of postmenopausal osteoporosis (PMO) in a preclinical model of ovariectomized (OVX) mice. Collectively, our research confirms that CAG inhibits the formation and function of osteoclasts by regulating RANKL-induced intracellular signaling pathways, which may represent a promising alternative for the therapy of osteoclast-related disease. [ABSTRACT FROM AUTHOR]

The extravagant osteoclast formation and resorption is the main cause of osteoporosis. Inhibiting the hyperactive osteoclastic resorption is considered as an efficient treatment for osteoporosis. Rhaponticin (RH) is a small molecule that has been reported to possess anti-inflammatory, anti-allergic, anti-fibrotic, and anti-diabetic activities. However, the influence of RH on osteoclasts differentiation and function is still unclear. To this end, an array of assays including receptor activator of nuclear factor kappa-Β (NF-κB) ligand (RANKL) induced osteoclastogenesis, tartrate-resistant acidic phosphatase (TRAcP) staining, immunofluorescence, and hydroxyapatite resorption were performed in this study. It was found that RH had significant anti-catabolic effects by inhibiting osteoclastogenesis and bone resorption without cytotoxicity. Mechanistically, the expression of NADPH oxidase 1 (Nox1) was found to be suppressed and antioxidant enzymes including catalase, superoxide dismutase 2 (SOD-2), and heme oxygenase-1(HO-1) were enhanced following RH treatment, suggesting RH exhibited antioxidant activity by reducing the generation of reactive oxygen species (ROS) as well as enhancing the depletion of ROS. In addition, MAPKs, NF-κB, and intracellular Ca2+ oscillation pathways were significantly inhibited by RH. These changes led to the deactivation of osteoclast master transcriptional factor-nuclear factor of activated T cells 1 (NFATc1), as examined by qPCR and Western blot assay, which led to the decreased expression of downstream integrin β3, c-Fos, cathepsin K, and Atp6v0d2. These results suggested that RH could effectively suppress RANKL-regulated osteoclast formation and bone resorption. Therefore, we propose that RH can represent a novel natural small molecule for the treatment of osteoporosis by inhibiting excessive osteoclast activity. [ABSTRACT FROM AUTHOR]

This article was submitted to Experimental Pharmacology and Drug Discovery, a section of the journal Frontiers in Pharmacology. Postmenopausal osteoporosis (PMOP), which increases the risk of fracture, is the most common bone disease in women. PMOP not only increases the risk of death but also imposes a financial burden on countless families. At present, most of the drugs used to treat osteoporosis have significant side effects, so it is important to find effective anti-osteoporosis medications without major side effects. Sesamolin (Ses) is a kind of natural lignan extracted from sesame oil. Many researches have shown that Ses has anti-inflammatory, antioxidative, and anticancer effects, however it is still unknown whether it has any effect on osteoporosis. In this research, we explored the therapeutic effect of Ses in the process of osteoclast formation and bone resorption and found that Ses effectively inhibited osteoclast formation in vitro through TRAcP staining and hydroxyapatite resorption assays. Through Western blot analysis of the NF-κB pathway, MAPK pathway, c-Fos and NFATc1, it was found that Ses not only effectively inhibited the activation of NF-κB and MAPK signaling pathways induced by RANKL but also significantly reduced the protein expression of c-Fos and NFATc1. Several genes specifically expressed in osteoclasts were determined by qPCR, and Ses was also found to play a significant inhibitory role on the expression of these genes. Besides, an osteoporosis model induced in ovariectomized (OVX) mice was employed to verify that Ses could effectively reduce bone loss caused by estrogen deficiency in vivo. In conclusion, Ses showed promise as a new treatment for postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

Osteolytic skeletal disorders are caused by an imbalance in the osteoclast and osteoblast function. Suppressing the differentiation and resorptive function of osteoclast is a key strategy for treating osteolytic diseases. Dracorhodin perchlorate (D.P), an active component from dragon blood resin, has been used for facilitating wound healing and anti‐cancer treatments. In this study, we determined the effect of D.P on osteoclast differentiation and function. We have found that D.P inhibited RANKL‐induced osteoclast formation and resorbed pits of hydroxyapatite‐coated plate in a dose‐dependent manner. D.P also disrupted the formation of intact actin‐rich podosome structures in mature osteoclasts and inhibited osteoclast‐specific gene and protein expressions. Further, D.P was able to suppress RANKL‐activated JNK, NF‐κB and Ca2+ signalling pathways and reduces the expression level of NFATc1 as well as the nucleus translocation of NFATc1. Overall, these results indicated a potential therapeutic effect of D.P on osteoclast‐related conditions. [ABSTRACT FROM AUTHOR]

Osteolytic bone diseases, for example postmenopausal osteoporosis, arise from the imbalances between osteoclasts and osteoblasts in the bone remodeling process, whereby osteoclastic bone resorption greatly exceeds osteoblastic bone formation resulting in severe bone loss and deterioration in bone structure and microarchitecture. Therefore, the identification of agents that can inhibit osteoclast formation and/or function for the treatment of osteolytic bone disease has been the focus of bone and orthopedic research. Vindoline (Vin), an indole alkaloid extracted from the medicinal plant Catharanthus roseus , has been shown to possess extensive biological and pharmacological benefits, but its effects on bone metabolism remains to be documented. Our study demonstrated for the first time, that Vin could inhibit osteoclast differentiation from bone marrow macrophages (BMMs) precursor cells as well as mature osteoclastic bone resorption. We further determined that the underlying molecular mechanism of action of Vin is in part due to its inhibitory effect against the activation of MAPK including p38, JNK, and ERK and intracellular reactive oxygen species (ROS) production. This effect ultimately suppressed the induction of c-Fos and NFATc1, which consequently downregulated the expression of the genes required for osteoclast formation and bone resorption. Consistent with our in vitro findings, in vivo administration of Vin protected mice against ovariectomy (OVX)-induced bone loss and trabecular bone deterioration. These results provided promising evidence for the potential therapeutic application of Vin as a novel treatment option against osteolytic diseases. [ABSTRACT FROM AUTHOR]

Osteoporosis is the most common osteolytic disease characterized by excessive osteoclast formation and resultant bone loss, which afflicts millions of patients around the world. Astilbin, a traditional herb, is known to have anti‐inflammatory, antioxidant and antihepatic properties, but its role in osteoporosis treatment has not yet been confirmed. In our study, astilbin was found to have an inhibitory effect on the RANKL‐induced formation and function of OCs in a dose‐dependent manner without cytotoxicity. These effects were attributed to its ability to suppress the activity of two transcription factors (NFATc1 and c‐Fos) indispensable for osteoclast formation, followed by inhibition of the expression of bone resorption‐related genes and proteins (Acp5/TRAcP, CTSK, V‐ATPase‐d2 and integrin β3). Furthermore, we examined the underlying mechanisms and found that astilbin repressed osteoclastogenesis by blocking Ca2+ oscillations and the NF‐κB and MAPK pathways. In addition, the therapeutic effect of MA on preventing bone loss in vivo was further confirmed in an ovariectomized mouse model. Therefore, considering its ability to inhibit RANKL‐mediated osteoclastogenesis and the underlying mechanisms, astilbin might be a potential candidate for treating osteolytic bone diseases. [ABSTRACT FROM AUTHOR]

Osteoporosis is a bone disease characterized by increasing osseous fragility and fracture due to the reduced bone mass and microstructural degradation. Primary pharmacological strategies for the treatment of osteoporosis, hormone replacement treatment (HRT), and alendronate therapies may produce adverse side-effects and may not be recommended for long-term usage. Some classic and bone-specific natural Chinese medicine are very popularly used to treat osteoporosis and bone fracture effectively in clinical with their potential value in bone growth and development, but with few adverse side-effects. Current evidence suggests that the treatments appear to improve bone metabolism and attenuate the osteoporotic imbalance between bone formation and bone resorption at a cellular level by promoting osteoblast activity and inhibiting the effects of osteoclasts. The valuable therapies might, therefore, provide an effective and safer alternative to primary pharmacological strategies. Therefore, the purpose of this article is to comprehensively review these classic and bone-specific drugs in natural Chinese medicines for the treatment of osteoporosis that had been deeply and definitely studied and reported with both bone formation and antiresorption effects, including Gynochthodes officinalis (F.C.How) Razafim. & B.Bremer (syn. Morinda officinalis F.C.How), Curculigo orchioides Gaertn. , Psoralea corylifolia (L.) Medik Eucommia ulmoides Oliv. , Dipsacus inermis Wall. (syn. Dipsacus asperoides C.Y.Cheng & T.M.Ai), Cibotium barometz (L.) J. Sm. , Velvet Antler , Cistanche deserticola Ma , Cuscuta chinensis Lam., Cnidium monnieri (L.) Cusson, Epimedium brevicornum Maxim, Pueraria montana (Lour.) Merr. and Salvia miltiorrhiza Bunge., thus providing evidence for the potential use of alternative Chinese medicine therapies to effectively treat osteoporosis. [ABSTRACT FROM AUTHOR]

Prosthesis loosening is a highly troublesome clinical problem following total joint arthroplasty. Wear‐particle‐induced osteoclastogenesis has been shown to be the primary cause of periprosthetic osteolysis that eventually leads to aseptic prosthesis loosening. Therefore, inhibiting osteoclastogenesis is a promising strategy to control periprosthetic osteolysis. The possible mechanism of action of rhoifolin on osteoclastogenesis and titanium particle‐induced calvarial osteolysis was examined in this study. The in vitro study showed that rhoifolin could strongly suppress the receptor activators of nuclear factor‐κB (NF‐κB) ligand‐stimulated osteoclastogenesis, hydroxyapatite resorption, F‐actin formation, and the gene expression of osteoclast‐related genes. Western blot analysis illustrated that rhoifolin could attenuate the NF‐κB and mitogen‐activated protein kinase pathways, and the expression of transcriptional factors nuclear factor of activated T cells 1 (NFATc1) and c‐Fos. Further studies indicated that rhoifolin inhibited p65 translocation to the nucleus and the activity of NFATc1 and NF‐κB rhoifolin could decrease the number of tartrate‐resistant acid phosphate‐positive osteoclasts and titanium particle‐induced C57 mouse calvarial bone loss in vivo. In conclusion, our results suggest that rhoifolin can ameliorate the osteoclasts‐stimulated osteolysis, and may be a potential agent for the treatment of prosthesis loosening. [ABSTRACT FROM AUTHOR]

Osteoporosis is a class of metabolic bone disease caused by complexed ramifications. Overactivation of osteoclasts due to a sudden decreased estrogen level plays a pivotal role for postmenopausal women suffering from osteoporosis. Therefore, inhibiting osteoclast formation and function has become a major direction for the treatment of osteoporosis. Tiliroside (Tle) is a salutary dietary glycosidic flavonoid extracted from Oriental Paperbush flower, which has been reported to have an anti‐inflammation effect. However, whether Tle affects the osteoclastogenesis and bone resorption remains unknown. Herein, we demonstrate that Tle prevents bone loss in ovariectomy in mice and inhibits osteoclast differentiation and bone resorption stimulated by receptor activator of nuclear factor‐κB ligand (RANKL) in vitro. Molecular mechanism studies reveal that Tle reduces RANKL‐induced activation of mitogen‐activated protein kinase and T‐cell nuclear factor 1 pathways, and osteoclastogenesis‐related marker gene expression, including cathepsin K (Ctsk), matrix metalloproteinase 9, tartrate‐resistant acid phosphatase (Acp5), and Atp6v0d2. Our research indicates that Tle suppresses osteoclastogenesis and bone loss by downregulating the RANKL‐mediated signaling protein activation and expression. In addition, Tle inhibits intracellular reactive oxygen species generation which is related to the formation of osteoclasts. Therefore, Tle might serve as a potential drug for osteolytic disease such as osteoporosis. [ABSTRACT FROM AUTHOR]

Osteoporosis (OP) is a metabolic disease caused by multiple factors, which is characterized by a reduction of bone mass per unit volume and destruction of bone microstructure. Aberrant osteoclast function is the main cause of OP, therefore, regulating the differentiation and function of osteoclast is one of the treatment strategies for OP. Pectolinarigenin (PEC) is a medicinal implant isolated from Fragrant Eupatorium. Our experimental data showed that PEC was able to inhibit receptor activator of nuclear factor‐κB ligand (RANKL)‐induced osteoclastogenesis in vitro, by tartrate‐resistant acid phosphatase (TRAcP) staining, Fibrous actin ring formation, and hydroxyapatite resorption assays. In terms of mechanism, PEC inhibited the expression of the osteoclastogenesis‐related gene, including cathepsin K (Ctsk), matrix metalloproteinase 9 (Mmp9), and TRAcP (Acp5). Western blot analysis demonstrated that PEC could significantly block the activation of RANKL‐induced mitogen‐activated protein kinase signaling cascades and was able to suppress the protein expression of nuclear factor of activated T‐cells and c‐Fos. Meanwhile, the intracellular reactive oxygen species levels were also reduced by PEC in a concentration‐dependent manner. Further, PEC could prevent the ovariectomy‐induced bone loss in vivo. Summarizing all, our data suggested that PEC inhibits osteoclast formation and function and RANKL signaling pathways, and thus could potentially be used in the treatment the osteoclast‐related bone loss diseases. [ABSTRACT FROM AUTHOR]

Osteolytic bone diseases are closely linked to the over‐activation of osteoclasts and enhancement of bone resorption. It has become a major health issue in orthopedic practice worldwide. Inhibition of osteoclasts is proposed to be the main treatment for osteolytic disorders. Diosmetin (DIO) is a natural flavonoid with properties of antioxidant, anti‐infection, and antishock. The effect of DIO on osteoclast differentiation is poorly understood. In this study project, we found that DIO could inhibit osteoclastic formation induced by receptor activator of nuclear factor kappa‐B ligand (RANKL) in a dose‐dependent manner. The expression of the osteoclast differentiation marker genes, cathepsin K, nuclear factor of activated T‐cells 1 (NFATc1), Acp5, Ctr, Atp6v0d2, and Mmp9 were also decreased by the treatment of DIO. In addition, DIO attenuated the formation of actin ring and the ability of bone resorption. Further, the western blotting showed that DIO inhibits the phosphorylation of the mitogen‐activated protein kinases signaling pathway induced by RANKL, accompanied by the downregulation of NFATc1 and c‐Fos expression. We also found that DIO could reduce the accumulation of reactive oxygen species (ROS) induced by RANKL. In vivo, the study revealed that DIO can significantly reduce LPS‐induced osteolysis in mice. Collectively, our study shows that DIO can inhibit osteoclast formation and activation, and could serve as a potential therapeutic drug for osteolytic bone diseases. [ABSTRACT FROM AUTHOR]

Osteoporosis, arthritis, Peget's disease, bone tumor, periprosthetic joint infection, and periprosthetic loosening have a common characteristic of osteolysis, which is characterized by the enhanced osteoclastic bone resorptive function. At present, the treatment target of these diseases is to interfere with osteoclastic formation and function. Scutellarein (Scu), a flavonoids compound, can inhibit the progress of tumor and inflammation. However, the role of Scu in inflammatory osteolysis isn't elucidated clearly. Our study showed that Scu inhibited bone destruction induced by LPS in vivo and OC morphology and function induced by RANKL in vitro. Mechanistic studies revealed that Scu suppressed osteoclastic marker gene expression by RANKL‐induced, such as Ctsk9, Mmp9, Acp5, and Atp6v0d2. In addition, we found that the inhibition effects of osteoclastogenesis and bone resorption function of Scu were mediated via attenuating NF‐κB and NFAT signaling pathways. In conclusion, the results showed that Scu may become a potential new drug for the treatment of inflammatory osteolysis. Scutellarein could inhibit osteoclastogenesis and bone resorptive function via attenuating NF‐κB and NFAT signaling pathways. The results showed that Scu may become a potential new drug for the treatment of inflammatory osteolysis. [ABSTRACT FROM AUTHOR]

Excessive osteoclast formation and function are considered as the main causes of bone lytic disorders such as osteoporosis and osteolysis. Therefore, the osteoclast is a potential therapeutic target for the treatment of osteoporosis or other osteoclast‐related diseases. Helvolic acid (HA), a mycotoxin originally isolated from Aspergillus fumigatus , has been discovered as an effective broad‐spectrum antibacterial agent and has a wide range of pharmacological properties. Herein, for the first time, HA was demonstrated to be capable of significantly inhibiting receptor activator of nuclear factor‐κB ligand (RANKL)‐induced osteoclastogenesis and bone resorption in vitro by suppressing nuclear factor of activated T cells 1 (NFATc1) activation. This inhibition was followed by the dramatically decreased expression of NFATc1‐targeted genes including Ctr (encoding calcitonin receptor), Acp5 (encoding tartrate‐resistant acid phosphatase [TRAcP]), Ctsk (encoding cathepsin K), Atp6v0d2 (encoding the vacuolar H+ ATPase V0 subunit d2 [V‐ATPase‐d2]) and Mmp9 (encoding matrix metallopeptidase 9) which are osteoclastic‐specific genes required for osteoclast formation and function. Mechanistically, HA was shown to greatly attenuate multiple upstream pathways including extracellular signal‐regulated kinase (ERK) phosphorylation, c‐Fos signaling, and intracellular Ca 2+ oscillation, but had little effect on nuclear factor‐κB (NF‐κB) activation. In addition, HA also diminished the RANKL‐induced generation of intracellular reactive oxygen species. Taken together, our study indicated HA effectively suppressed RANKL‐induced osteoclast formation and function. Thus, we propose that HA can be potentially used in the development of a novel drug for osteoclast‐related bone diseases. Helvolic acid (HA), a mycotoxin originally isolated from Aspergillus fumigatus, is demonstrated to be capable of significantly inhibiting receptor activator of nuclear factor‐κB ligand (RANKL)‐induced osteoclastogenesis and bone resorption in vitro by suppressing nuclear factor of activated T cells 1 (NFATc1) activation without affecting nuclear factor‐κB (NF‐κB) activation. Mechanistically, HA greatly attenuated multiple upstream pathways of NFATc1, including extracellular‐signal‐regulated kinase (ERK) phosphorylation, c‐Fos signaling, and intracellular Ca2+oscillation. Taken together, HA can be potentially used in the development of a novel drug for osteoclast‐related bone diseases. [ABSTRACT FROM AUTHOR]

Postmenopausal osteoporosis (PMO) is a progressive bone disease characterized by the over‐production and activation of osteoclasts in elderly women. In our study, we investigated the anti‐osteoclastogenic effect of evodiamine (EVO) in vivo and in vitro, as well as the underlying mechanism. By using an in vitro bone marrow macrophage (BMM)‐derived osteoclast culture system, we found that EVO inhibited osteoclast formation, hydroxyapatite resorption and receptor activator of NF‐κB ligand (RANKL)‐induced osteoclast marker gene and protein expression. Mechanistically, we found that EVO inhibited the degradation and RANKL‐induced transcriptional activity of IκBα. RANKL‐induced Ca2+ oscillations were also abrogated by EVO. In vivo, an ovariectomized (OVX) mouse model was established to mimic PMO, and OVX mice received oral administration of either EVO (10 mg/kg) or saline every other day. We found that EVO can attenuate bone loss in OVX mice by inhibiting osteoclastogenesis. Taken together, our findings suggest that EVO suppresses RANKL‐induced osteoclastogenesis through NF‐κB and calcium signalling pathways and has potential value as a therapeutic agent for PMO. [ABSTRACT FROM AUTHOR]

Osteoporosis is the most common osteolytic disease characterized by excessive osteoclast formation and resultant bone loss, which afflicts millions of patients around the world. Madecassoside (MA), isolated from Centella asiatica, was reported to have anti‐inflammatory and antioxidant activities, but its role in osteoporosis treatment has not yet been confirmed. In our study, MA was found to have an inhibitory effect on the RANKL‐induced formation and function of OCs in a dose‐dependent manner without cytotoxicity. These effects were attributed to its ability to suppress the activity of two transcription factors (NFATc1 and c‐Fos) indispensable for osteoclast formation, followed by inhibition of the expression of bone resorption‐related genes and proteins (Acp5/TRAcP, CTSK, ATP6V0D2/V‐ATPase‐d2, and integrin β3). Furthermore, we examined the underlying mechanisms and found that MA represses osteoclastogenesis by blocking Ca2+ oscillations and the NF‐κB and MAPK pathways. In addition, the therapeutic effect of MA on preventing bone loss in vivo was further confirmed in an ovariectomized mouse model. Therefore, considering its ability to inhibit RANKL‐mediated osteoclastogenesis and the underlying mechanisms, MA might be a potential candidate for treating osteolytic bone diseases. [ABSTRACT FROM AUTHOR]

Osteoclasts are responsible for bone resorption during the process of bone remodeling. Increased osteoclast numbers and bone resorption activity are the main factors contributing to bone loss–related diseases such as osteoporosis. Therefore, modulating the formation and function of osteoclasts is critical for the effective treatment of osteolysis and osteoporosis. Kavain is the active ingredient extracted from the root of the kava plant, which possesses known anti‐inflammatory properties. However, the effects of kavain on osteoclastogenesis and bone resorption remain unclear. In this study, we found that kavain inhibits receptor activator of nuclear factor‐κB ligand (RANKL)–induced osteoclast differentiation and fusion using tartrate‐resistant acid phosphatase staining and immunofluorescence. Furthermore, kavain inhibited bone resorption performed by osteoclasts. Using reverse transcription‐polymerase chain reaction and western blot analysis, we found that kavain downregulates the expression of osteoclast marker genes, such as nuclear factor of activated T cells, cytoplasmic 1 (Nfatc1), v‐atpase d2 (Atp6v0d2), dendrocyte expressed seven transmembrane protein (Dcstamp), matrix metallopeptidase 9 (Mmp9), cathepsin K (Ctsk), and Acp5. Additionally, kavain repressed RANKL‐induced calcium oscillations, nuclear factor of activated T cells activation, and mitogen‐activated protein kinase phosphorylation, while leaving NF‐κB unaffected. We found no effects of kavain on either osteoblast proliferation or differentiation. Besides, kavain inhibited bone loss in ovariectomized mice by suppressing osteoclastogenesis. Collectively, these data suggest a potential use for kavain as a candidate drug for the treatment of osteolytic diseases. Kavain suppresses NFATc1 expression and phosphorylation of P38 and JNK, while leaving ERK and NF‐κB unaffected. Besides, kavain attenuates NFATc1 activation via modulating intracellular calcium oscillations, hence inhibits osteoclastogenesis. [ABSTRACT FROM AUTHOR]

Osteoporosis is a metabolic disease characterized by osteopenia and bone microstructural deterioration. Osteoclasts are the primary effector cells that degrade bone matrix and their abnormal function leads to the development of osteoporosis. Reactive oxygen species (ROS) accumulation during cellular metabolism promotes osteoclast proliferation and differentiation, therefore, playing an important role in osteoporosis. Cistanche deserticola polysaccharide (CDP) possesses antitumor, anti‐inflammatory, and antioxidant activity. However, the impact of CDP on osteoclasts is unclear. In this study, tartrate‐resistant acid phosphatase staining, immunofluorescence, reverse transcription‐polymerase chain reaction, and western blot analysis were utilized to demonstrate that CDP inhibited osteoclastogenesis and hydroxyapatite resorption. In addition, CDP also inhibited the expression of osteoclast maker genes including Ctsk, Mmp9, and Acp5 and had no effect on receptor activator of nuclear factor κB (RANK) expression. Mechanistic analyses revealed that CDP increases the expression of antioxidant enzymes to attenuate RANKL‐mediated ROS production in osteoclasts and inhibits nuclear factor of activated T cells and mitogen‐activated protein kinase activation. These results suggest that CDP may represent a candidate drug for the treatment of osteoporosis caused by excessive osteoclast activity. CDP suppresses RANKL‐induced ROS production, as well as NFATc1 and MAPK activation, hence inhibits osteoclastogenesis. [ABSTRACT FROM AUTHOR]

The dynamic balance between bone resorption and bone formation is crucial to maintain bone mass. Osteoclasts are key cells that perform bone resorption while osteoblasts and osteocytes function in bone formation. Osteoporosis, a bone metabolism disease characterized by bone loss and degradation of bone microstructure, occurs when osteoclastic bone resorption outstrips osteoblastic bone synthesis. The interaction between receptor activator of nuclear factor κB ligand (RANKL) and RANK on the surface of bone marrow macrophages promotes osteoclast differentiation and activation. In this study, we found that lumichrome, a photodegradation product of riboflavin, inhibits RANKL‐induced osteoclastogenesis and bone resorption as determined by tartrate‐resistant acid phosphatase staining, immunofluorescence, reverse transcription‐polymerase chain reaction, and western blot. Our results showed that lumichrome represses the expression of osteoclast marker genes, including cathepsin K (Ctsk) and Nfatc1. In addition, lumichrome suppressed RANKL‐induced calcium oscillations, NFATc1, NF‐κB, and MAPK signaling activation. Moreover, lumichrome promoted osteoblast differentiation at an early stage, as demonstrated by upregulated expression of osteoblast marker genes Alp, Runx2, and Col1a1. We also found that lumichrome reduces bone loss in ovariectomized mice by inhibiting osteoclastogenesis. In summary, our data suggest the potential of lumichrome as a therapeutic drug for osteolytic diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Our original research demonstrated that AZD1390 inhibited osteoclastogenesis in a concentration-dependent and time-dependent manner. • The inhibition is via the AKT/GSK3β/NFATc1 pathway and the ROS pathway. • The potential value of AZD1390 in the prevention of osteoporosis was demonstrated in an OVX animal model. As a common disease in modern society, osteoporosis is caused by osteoclast hyperactivation, leading to enhanced bone resorption. Reactive oxygen species (ROS) metobolism and nuclear factor-activated T cells 1 (NFATc1) activities are two crucial processes during osteoclastogenesis. AZD1390 (AZD), an inhibitor of ataxia telangiectasia mutated (ATM), has been reported for antitumor effects, but little is known about how it plays a function in metabolic bone disease. Here, we found that AZD inhibitsthe generation, function and ROS-scavenging enzyme activity of mature osteoclast induced by RANKL stimulation, in a dose-dependent manner.Mechanistic analysis shows thatAZD affects osteoclast function and differentiation by inhibiting RANKL-induced NFATc1 signaling pathway and by increasing ROS-scavenging enzymes production in oxidative stress pathways. Preclinical studies have shown that AZD protects against bone loss in an ovariectomy (OVX) mouse model. Finally, our data confirm that AZD may prevent OVX-induced bone loss by abrogating RANKL-induced AKT/GSK3β/NFATc1 signaling pathways, and by promoting the expression of ROS scavenging enzymes in oxidative stress pathways.Collectively, our research shows that AZD has the potential as a new therapeutic agent for osteoporosis. [ABSTRACT FROM AUTHOR]

Pathological fractures caused by osteolytic lesions seriously threaten the health of patients. Osteoclasts play important roles in bone resorption whose hyperfunction are closely related to osteolytic lesions. Studies on osteoclast differentiation and function assist in the prevention of excessive bone loss associated diseases. We screened a variety of natural compounds with anti-inflammatory effect and found that poria cocos polysaccharide (PCP) inhibited RANKL-induced osteoclast formation and bone resorption via TRAcP staining, immunofluorescence, RT-PCR and western blot. PCP down-regulated phosphorylation of STAT3, P38, ERK and JNK, and thus repressed the expression of NFAcT1 and c-Fos during RANKL-induced osteoclastogenesis. Besides, the expression of bone resorption related genes such as TRAcP and CTSK was suppressed by PCP. The results suggest that PCP can be invoked as a candidate for the treatment of osteolytic diseases by inhibiting osteoclastogenesis. [ABSTRACT FROM AUTHOR]

Note: ARC inhibits osteoclastogenesis by suppressing RANKL-induced MAPK (including JNKs and ERKs), calcium, and NFATc1 signaling pathway, as well as by promoting the expression of ROS scavenging enzymes in Nrf2/Keap1/ARE signaling pathway. Osteoporosis, characterized by disrupted bone resorption and formation, is viewed as a global health challenge. Arctiin (ARC) is a main component of Arctium lappa L, which exerts chemopreventive effects against various tumor cells. However, the role of ARC in bone remodeling is still unclear. Here, we first demonstrated that ARC inhibits osteoclast formation and bone resorption function induced by the receptor activator of nuclear factor-κB ligand (RANKL) in a dose- and time-dependent manner without exerting cytotoxic effects. Mechanistic analysis revealed that ARC not only suppresses RANKL-induced mitogen-activated protein kinase (MAPK) and calcium signaling pathways, but also enhances the expression of cytoprotective enzymes that are involved in scavenging reactive oxygen species (ROS). Further, ARC inhibits the activation of the major transcription factor nuclear factor of activated T cells 1 (NFATc1) during RANKL-induced osteoclast formation. Preclinical studies showed that ARC protects bone loss in an ovariectomy (OVX) mouse model. Conclusively, our data confirmed that ARC could potentially inhibit osteoclastogenesis by abrogating RANKL-induced MAPK, calcium, and NFATc1 signaling pathway, as well as by promoting the expression of ROS scavenging enzymes in Nrf2/Keap1/ARE signaling pathway, thereby 2 2 Atp6v0d2 preventing OVX-induced bone loss. Thus, ARC may serve as a novel therapeutic agent for the treatment of osteoporosis. [ABSTRACT FROM AUTHOR]

Postmenopausal osteoporosis and other osteolytic bone diseases are often caused by the elevation in osteoclastogenesis and/or increased osteoclastic bone resorption, leading to excessive bone loss. Hederagenin (Hed) is a pentacyclic triterpenoid saponin extracted from various natural medicinal plants and exhibits numerous biological activities and may offer benefits against bone-related conditions. We evaluated the effects of Hed on osteoclast formation and bone resorption in vitro and the in vivo therapeutic benefits in the mouse model of ovariectomy (OVX)-induced bone loss. In vitro, osteoclast formation were determined by TRAcp staining; bone resorption were examined using Hydroxyapatite resorption assay and Podosomal actin belt formation assay; Related molecular mechanisms were determined by western blot assay. Construction of OVX mice by bilateral oophorectomy to simulate bone loss in vivo. In vitro cellular assays showed that Hed inhibited RANKL-induced osteoclast formation and osteoclast bone (hydroxyapatite) resorption as well as marker gene expression from BMM culture. Mechanistically, Hed attenuated RANKL-induced intracellular reactive oxygen species (ROS) production, and MAPK signaling pathway (ERK and p38) activation which curbed the downstream induction of c-Fos and NFATc1. Consistent with the in vitro findings, Hed administration effectively protected OVX mice from bone loss by reducing osteoclast number and activity on bone surface. Our data provided promising evidence for the potential use of Hederagenin in the treatment of osteoclast-mediated osteolytic bone diseases such as postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]