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Osteoporosis, a prevalent osteolytic condition worldwide, necessitates effective strategies to inhibit excessive bone resorption by curbing osteoclast hyperactivation. Liquiritin (LIQ), an flavanone derivative employed in acute lung injury and rheumatoid arthritis treatment, possesses an unclear role in addressing excessive bone resorption. In this investigation, we found that LIQ demonstrates the ability to inhibit osteoclast formation and the bone-resorbing activity induced by RANKL. At a specific concentration, LIQ significantly attenuated NF-κB-Luc activity induced by RANKL and curtailed NF-κB activation in RANKL-stimulated RAW264.7 cells, resulting in reduced IκB-α breakdown and diminished nuclear NF-κB levels. Furthermore, LIQ markedly inhibited RANKL-induced NFATc1 activation, as evidenced by diminished NFATc1 luciferase activity, reduced NFATc1 mRNA levels, and decreased nuclear NFATc1 protein levels. Subsequent experiments demonstrated that LIQ effectively restrained the RANKL-induced elevation of intracellular calcium as well as reactive oxygen species. Additionally, LIQ exhibited a downregulating effect on the expression of osteoclast-specific genes, which include Acp5, Cathepsin K, Atp6v0d2, Nfatc1, c-Fos, and Mmp9. Notably, our findings revealed the potential of LIQ to counteract decreased bone density in mice that underwent ovariectomy. Collectively, the data indicate that LIQ impedes osteoclast formation triggered by RANKL and the subsequent reduction in bone mass by mitigating ROS levels and suppressing the Ca2+/MAPK-NFATc1 signaling pathway, suggesting its promising candidacy as a therapeutic agent for RANKL-mediated osteoporosis. [ABSTRACT FROM AUTHOR]

Osteoporosis (OP), characterized by continuous bone loss and increased fracture risk, has posed a challenge to patients and society. Long-term administration of current pharmacological agents may cause severe side effects. Traditional medicines, acting as alternative agents, show promise in treating OP. Osthole, a natural coumarin derivative separated from Cnidium monnieri (L.) Cusson and Angelica pubescens Maxim. f., exhibits protective effects against the pathological development of OP. Osthole increases osteoblast-related bone formation and decreases osteoclast-related bone resorption, suppressing OP-related fragility fracture. In addition, the metabolites of osthole may exhibit pharmacological effectiveness against OP development. Mechanically, osthole promotes osteogenic differentiation by activating the Wnt/β-catenin and BMP-2/Smad1/5/8 signaling pathways and suppresses RANKL-induced osteoclastogenesis and osteoclast activity. Thus, osthole may become a promising agent to protect against OP development. However, more studies should be performed due to, at least in part, the uncertainty of drug targets. Further pharmacological investigation of osthole in OP treatment might lead to the development of potential drug candidates. [ABSTRACT FROM AUTHOR]

Charcot neuroarthropathy (CN) is a chronic, destructive, and painless damage of the skeletal system that affects the life quality of patients. CN, with an unclear mechanism, is characterized with invasive destruction of bones and a serious abnormality of bone metabolism. Unfortunately, development of an effective prevention and treatment strategy for CN is still a great challenge. Of note, recent studies providing an insight into the molecular mechanisms of bone metabolism and homeostasis have propelled development of novel CN therapeutic strategies. Therefore, this review aims to shed light on the pathogenesis, diagnosis, and treatment of CN. In particular, we highlight the eminent role of the osteoprotegerin (OPG)-receptor activator of nuclear factorκB (RANK)-RANK ligand (RANKL) system in the development of CN. Furthermore, we summarize and discuss the diagnostic biomarkers of CN as well as the potential pharmacological mechanisms of current treatment regimens from the perspective of bone metabolism. We believe that this review will enhance the current state of knowledge on the diagnosis, prevention, and therapeutic efficacy of CN. [ABSTRACT FROM AUTHOR]

Osteoclast is a hematopoietic precursor cell derived from the mononuclear macrophage cell line, which is the only cell with bone resorption function. Its abnormal activation can cause serious osteolysis related diseases such as rheumatoid arthritis, Paget's disease and osteoporosis. In recent years, the adverse effects caused by anabolic anti-osteolytic drugs have increased the interest of researchers in the potential therapeutic and preventive effects of natural plant derivatives and natural compounds against osteolytic diseases caused by osteoclasts. Natural plant derivatives and natural compounds have become major research hotspots for the treatment of osteolysis-related diseases due to their good safety profile and ability to improve bone. This paper provides an overview of recent advances in the molecular mechanisms of RANKL and downstream signaling pathways in osteoclast differentiation, and briefly outlines potential natural compounds with antiosteoclast activity and molecular mechanisms. [ABSTRACT FROM AUTHOR]

Denosumab is a monoclonal antibody that targets and inhibits the osteoclast activating factor receptor activator for nuclear factor-κB ligand (RANKL). It has been widely used in the treatment of osteoporosis, giant cell tumors of bone, and in the prevention of malignant skeletal-related events (SREs). We collected the research results and related MeSH terms of denosumab from 2011 to 2021 through the Web of Science and PubMed, respectively. The literature was visualized and analyzed by CiteSpace and bibliometric online analysis platforms. The MeSH terms were biclustered using the Bibliographic Co-Occurrence Analysis System (BICOMB) and graph clustering toolkit (gCLUTO). The results show that the number of denosumab-related annual publications had increased from 51 to 215, with the United States leading and Amgen Inc. being the most influential in the past 10 years. Articles published in the Journal of Bone and Mineral Research had the highest total citations. Three scholars from Shinshu University in Matsumoto, Yukio Nakamura, Takako Suzuki, and Hiroyuki Kato, joined the field relatively late but produced the most. The clinical comparison and combination of denosumab with other drugs in the treatment of osteoporosis was the most significant focus of research. Drug withdrawal rebound and management strategies have gained more attention and controversy recently. MeSH analysis revealed eight major categories of research hotspots. Among them, exploring the multiple roles of the RANK-RANKL-OPG system in tumor progression, metastasis, and other diseases is the potential direction of future mechanism research. It is a valuable surgical topic to optimize the perioperative drug administration strategy for internal spinal fixation and orthopedic prosthesis implantation. Taken together, the advantages of denosumab were broad and cost-effective. However, there were still problems such as osteonecrosis of the jaw, severe hypocalcemia, a high recurrence rate of giant cells in the treatment of bone and individual sarcoidosis, and atypical femoral fractures, which need to be adequately solved. [ABSTRACT FROM AUTHOR]

Bone-resorbing osteoclasts are essential for skeletal remodelling, and the hyperactive formation and function of osteoclasts are common in bone metabolic diseases, especially postmenopausal osteoporosis. Therefore, regulating the osteoclast differentiation is a major therapeutic target in osteoporosis treatment. Icariin has shown potential osteoprotective effects. However, existing studies have reported limited bioavailability of icariin, and the material basis of icariin for anti-osteoporosis is attributed to its metabolites in the body. Here, we compared the effects of icariin and its metabolites (icariside I, baohuoside I, and icaritin) on osteoclastogenesis by high-content screening followed by TRAP staining and identified baohuoside I (BS) with an optimal effect. Then, we evaluated the effects of BS on osteoclast differentiation and bone resorptive activity in both in vivo and in vitro experiments. In an in vitro study, BS inhibited osteoclast formation and bone resorption function in a dose-dependent manner, and the elevated osteoclastic-related genes induced by RANKL, such as NFATc1, cathepsin K, RANK, and TRAP, were also attenuated following BS treatment. In an in vivo study, OVX-induced bone loss could be prevented by BS through interrupting the osteoclast formation and activity in mice. Furthermore, mechanistic investigation demonstrated that BS inhibited osteoclast differentiation by ameliorating the activation of the MAPK and NF-kB pathways and reducing the expression of uPAR. Our study demonstrated that baohuoside I could inhibit osteoclast differentiation and protect bone loss following ovariectomy. [ABSTRACT FROM AUTHOR]

Osteoporosis is a serious public health problem that results in fragility fractures, especially in postmenopausal women. Because the current therapeutic strategy for osteoporosis has various side effects, a safer and more effective treatment is worth exploring. It is important to examine natural plant extracts during new drug design due to low toxicity. Mogrol is an aglycon of mogroside, which is the active component of Siraitia grosvenorii (Swingle) and exhibits anti-inflammatory, anticancer and neuroprotective effects. Here, we demonstrated that mogrol dose-dependently inhibited osteoclast formation and function. To confirm the mechanism, RNA sequencing (RNA-seq), real-time PCR (RT–PCR), immunofluorescence and Western blotting were performed. The RNA-seq data revealed that mogrol had an effect on genes involved in osteoclastogenesis. Furthermore, RT–PCR indicated that mogrol suppressed osteoclastogenesis-related gene expression, including CTSK, ACP5, MMP9 and DC-STAMP, in RANKL-induced bone marrow macrophages Western blotting demonstrated that mogrol suppressed osteoclast formation by blocking TNF receptor-associated factor 6 (TRAF6)-dependent activation of the mitogen-activated protein kinase nuclear factor-B (NF-κB) signaling pathway, which decreased two vital downstream transcription factors, the nuclear factor of activated T cells calcineurin-dependent 1 (NFATc1) and c-Fos proteins expression. Furthermore, mogrol dramatically reduced bone mass loss in postmenopausal mice. In conclusion, these data showed that mogrol may be a promising procedure for osteoporosis prevention or therapy. [ABSTRACT FROM AUTHOR]

Bone-resorbing osteoclasts are essential for skeletal remodelling, and the hyperactive formation and function of osteoclasts are common in bone metabolic diseases, especially postmenopausal osteoporosis. Therefore, regulating the osteoclast differentiation is a major therapeutic target in osteoporosis treatment. Icariin has shown potential osteoprotective effects. However, existing studies have reported limited bioavailability of icariin, and the material basis of icariin for anti-osteoporosis is attributed to its metabolites in the body. Here, we compared the effects of icariin and its metabolites (icariside I, baohuoside I, and icaritin) on osteoclastogenesis by high-content screening followed by TRAP staining and identified baohuoside I (BS) with an optimal effect. Then, we evaluated the effects of BS on osteoclast differentiation and bone resorptive activity in both in vivo and in vitro experiments. In an in vitro study, BS inhibited osteoclast formation and bone resorption function in a dose-dependent manner, and the elevated osteoclastic-related genes induced by RANKL, such as NFATc1, cathepsin K, RANK, and TRAP, were also attenuated following BS treatment. In an in vivo study, OVX-induced bone loss could be prevented by BS through interrupting the osteoclast formation and activity in mice. Furthermore, mechanistic investigation demonstrated that BS inhibited osteoclast differentiation by ameliorating the activation of the MAPK and NF-kB pathways and reducing the expression of uPAR. Our study demonstrated that baohuoside I could inhibit osteoclast differentiation and protect bone loss following ovariectomy.

Osteoporosis is a serious public health problem that results in fragility fractures, especially in postmenopausal women. Because the current therapeutic strategy for osteoporosis has various side effects, a safer and more effective treatment is worth exploring. It is important to examine natural plant extracts during new drug design due to low toxicity. Mogrol is an aglycon of mogroside, which is the active component of Siraitia grosvenorii (Swingle) and exhibits anti-inflammatory, anticancer and neuroprotective effects. Here, we demonstrated that mogrol dose-dependently inhibited osteoclast formation and function. To confirm the mechanism, RNA sequencing (RNA-seq), real-time PCR (RT–PCR), immunofluorescence and Western blotting were performed. The RNA-seq data revealed that mogrol had an effect on genes involved in osteoclastogenesis. Furthermore, RT–PCR indicated that mogrol suppressed osteoclastogenesis-related gene expression, including CTSK, ACP5, MMP9 and DC-STAMP, in RANKL-induced bone marrow macrophages Western blotting demonstrated that mogrol suppressed osteoclast formation by blocking TNF receptor-associated factor 6 (TRAF6)-dependent activation of the mitogen-activated protein kinase nuclear factor-B (NF-κB) signaling pathway, which decreased two vital downstream transcription factors, the nuclear factor of activated T cells calcineurin-dependent 1 (NFATc1) and c-Fos proteins expression. Furthermore, mogrol dramatically reduced bone mass loss in postmenopausal mice. In conclusion, these data showed that mogrol may be a promising procedure for osteoporosis prevention or therapy.

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.

Objective: Pharmacokinetics (PK), pharmacodynamics (PD), safety and immunogenicity studies were conducted to evaluate the bioequivalence of CMAB807, a biosimilar to denosumab (Prolia®), which is the only approved RANKL inhibitor for the treatment of osteoporosis. Methods: In this randomized, double-blind, single-dose phase I study, 132 healthy Chinese male subjects received a subcutaneous injection of 60 mg of CMAB807 or denosumab at a 1:1 ratio. The PK, PD, safety and immunogenicity results were assessed prior to and up to 126 days after administration. Results: The PK profiles of CMAB807 and denosumab were similar. The geometric mean ratios of the maximum concentration (Cmax), AUC0-t and AUCo-∞ were 102.41, 104.15 and 103.89%, respectively, and the 90% confidence interval was observed to be within 80.00–125.00%, which indicated the bioequivalence of CMAB807 and denosumab. The PD profiles of the two groups were also comparable. The production of the C-terminal cross-linking telopeptide of type I collagen (CTX1) was inhibited by up to 85% for 10 days, and this inhibition was sustained for up to 126 days in both the CMAB807 and denosumab groups. No subjects in the CMAB807 group, three subjects in the denosumab group before administration, and two subjects in the denosumab group after administration were positive for anti-drug antibody (ADA). Adverse events (AEs) were observed in 98.5% of subjects in both groups. The most common AE recorded was increased parathyroid hormone (PTH) levels, with incidences of 92.4 and 95.5% in the CMAB807 and denosumab groups, respectively. No clinically meaningful differences were observed in safety and immunogenicity between CMAB807 and denosumab. Conclusion: CMAB807 represents a new potential treatment option for patients with osteoporosis. C linical Trial Registration: https://clinicaltrials.gov (Registration No. NCT03925051), http://www.chinadrugtrial/org.cn/index.html (Registration No. CTR20190800). [ABSTRACT FROM AUTHOR]

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]

Receptor activator of nuclear factor-κB ligand (RANKL) has been found to induce osteoclastogenesis and bone resorption. However, the underlying molecular mechanisms remain unclear. Via conducting a series of biochemical experiments with in vitro cell lines, this study investigated the role and mechanism of NADPH oxidase 4 (Nox4) in RANKL-induced autophagy and osteoclastogenesis. In the current study, we found that RANKL dramatically induced autophagy and osteoclastogenesis, inhibition of autophagy with chloroquine (CQ) markedly attenuates RANKL-induced osteoclastogenesis. Interestingly, we found that the protein level of Nox4 was remarkably upregulated by RANKL treatment. Inhibition of Nox4 by 5-O-methyl quercetin or knockdown of Nox4 with specific shRNA markedly attenuated RANKL-induced autophagy and osteoclastogenesis. Furthermore, we found that Nox4 stimulated the production of nonmitochondrial reactive oxygen species (ROS), activating the critical unfolded protein response (UPR)-related signaling pathway PERK/eIF-2α/ATF4, leading to RANKL-induced autophagy and osteoclastogenesis. Blocking the activation of PERK/eIF-2α/ATF4 signaling pathway either by Nox4 shRNA, ROS scavenger (NAC) or PERK inhibitor (GSK2606414) significantly inhibited autophagy during RANKL-induced osteoclastogenesis. Collectively, this study reveals that Nox4 promotes RANKL-induced autophagy and osteoclastogenesis via activating ROS/PERK/eIF-2α/ATF4 pathway, suggesting that the pathway may be a novel potential therapeutic target for osteoclastogenesis-related disease.

Mentha arvensis L., is an aromatic herb that belongs to the Lamiaceae family and is widely used in medicinal applications, essential oil applications, and food flavoring. The extract of M. arvensis has been reported to exert sedative-hypnotic, anti-inflammatory, anti-fungal, and anti-bacterial effects. However, its effects on bone metabolism have not yet been studied. Here, we investigated the effects of the water extract of M. arvensis (WEMA) on osteoclast formation in vitro and bone loss in an ovariectomized mouse model. We found that WEMA inhibited osteoclast differentiation by directly acting on osteoclast precursor cells. WEMA inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced the expression of cellular oncogene fos (c-Fos) and nuclear factor of activated T cells c1 (NFATc1), crucial transcription factors for osteoclast differentiation, by suppressing RANKL-induced activation of early signaling pathways such as those of mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB). In addition, oral administration of WEMA suppressed ovariectomy-induced trabecular bone loss in mice. We additionally identified phytochemicals in WEMA that are known to have anti-osteoclastogenic or anti-osteoporotic properties. Collectively, these results suggest that WEMA is a promising herbal candidate that can be used to prevent or treat postmenopausal osteoporosis.

Receptor activator of nuclear factor-κB ligand (RANKL) has been found to induce osteoclastogenesis and bone resorption. However, the underlying molecular mechanisms remain unclear. Via conducting a series of biochemical experiments with in vitro cell lines, this study investigated the role and mechanism of NADPH oxidase 4 (Nox4) in RANKL-induced autophagy and osteoclastogenesis. In the current study, we found that RANKL dramatically induced autophagy and osteoclastogenesis, inhibition of autophagy with chloroquine (CQ) markedly attenuates RANKL-induced osteoclastogenesis. Interestingly, we found that the protein level of Nox4 was remarkably upregulated by RANKL treatment. Inhibition of Nox4 by 5-O-methyl quercetin or knockdown of Nox4 with specific shRNA markedly attenuated RANKL-induced autophagy and osteoclastogenesis. Furthermore, we found that Nox4 stimulated the production of nonmitochondrial reactive oxygen species (ROS), activating the critical unfolded protein response (UPR)-related signaling pathway PERK/eIF-2α/ATF4, leading to RANKL-induced autophagy and osteoclastogenesis. Blocking the activation of PERK/eIF-2α/ATF4 signaling pathway either by Nox4 shRNA, ROS scavenger (NAC) or PERK inhibitor (GSK2606414) significantly inhibited autophagy during RANKL-induced osteoclastogenesis. Collectively, this study reveals that Nox4 promotes RANKL-induced autophagy and osteoclastogenesis via activating ROS/PERK/eIF-2α/ATF4 pathway, suggesting that the pathway may be a novel potential therapeutic target for osteoclastogenesis-related disease. [ABSTRACT FROM AUTHOR]

Mentha arvensis L., is an aromatic herb that belongs to the Lamiaceae family and is widely used in medicinal applications, essential oil applications, and food flavoring. The extract of M. arvensis has been reported to exert sedative-hypnotic, anti-inflammatory, anti-fungal, and anti-bacterial effects. However, its effects on bone metabolism have not yet been studied. Here, we investigated the effects of the water extract of M. arvensis (WEMA) on osteoclast formation in vitro and bone loss in an ovariectomized mouse model. We found that WEMA inhibited osteoclast differentiation by directly acting on osteoclast precursor cells. WEMA inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced the expression of cellular oncogene fos (c-Fos) and nuclear factor of activated T cells c1 (NFATc1), crucial transcription factors for osteoclast differentiation, by suppressing RANKL-induced activation of early signaling pathways such as those of mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB). In addition, oral administration of WEMA suppressed ovariectomy-induced trabecular bone loss in mice. We additionally identified phytochemicals in WEMA that are known to have anti-osteoclastogenic or anti-osteoporotic properties. Collectively, these results suggest that WEMA is a promising herbal candidate that can be used to prevent or treat postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

Osteoporosis is a common disease characterized by a systemic impairment of bone mass and microarchitecture that results in fragility fractures. Severe bone loss due to osteoporosis triggers pathological fractures and consequently decreases the daily life activity and quality of life. Therefore, prevention of osteoporosis has become an important issue to be addressed. We have reported that the fungal secondary metabolite (+)-terrein (TER), a natural compound derived from Aspergillus terreus, has shown receptor activator of nuclear factor-κB ligand (RANKL)–induced osteoclast differentiation by suppressing nuclear factor of activated T-cell 1 (NFATc1) expression, a master regulator of osteoclastogenesis. TER has been shown to possess extensive biological and pharmacological benefits; however, its effects on bone metabolism remain unclear. In this study, we investigated the effects of TER on the femoral bone metabolism using a mouse-ovariectomized osteoporosis model (OVX mice) and then on RANKL signal transduction using mouse bone marrow macrophages (mBMMs). In vivo administration of TER significantly improved bone density, bone mass, and trabecular number in OVX mice (p < 0.01). In addition, TER suppressed TRAP and cathepsin-K expression in the tissue sections of OVX mice (p < 0.01). In an in vitro study, TER suppressed RANKL-induced phosphorylation of PKCα/βII, which is involved in the expression of NFATc1 (p < 0.05). The PKC inhibitor, GF109203X, also inhibited RANKL-induced osteoclastogenesis in mBMMs as well as TER. In addition, TER suppressed the expression of osteoclastogenesis-related genes, such as Ocstamp, Dcstamp, Calcr, Atp6v0d2, Oscar, and Itgb3 (p < 0.01). These results provide promising evidence for the potential therapeutic application of TER as a novel treatment compound against osteoporosis.

Bone erosion is the most evident pathological condition of rheumatoid arthritis (RA), which is the main cause of joint deformities and disability in RA patients. At present, the conventional RA drugs have not achieved satisfactory effect in improving bone erosion. ZhiJingSan (ZJS), which is a traditional Chinese prescription composed of scolopendra (dried body of Scolopendra subspinipes mutilans L. Koch, scolopendridae) and scorpion (dried body of Buthus martensii Karsch, Buthus), exhibits anti-rheumatism, analgesic and joint deformities improvement effects. This study aimed to assess the therapeutic effect of ZJS on RA bone erosion and to elucidate the underlying mechanism. The effect of ZJS on RA bone erosion was investigated in a murine model of bovine collagen-induced arthritis (CIA), and the underlying mechanism was investigated in vitro in an osteoclast differentiation cell model. Administration of ZJS delayed the onset of arthritis, alleviated joint inflammation, and attenuated bone erosion in the CIA mice. Meanwhile, ZJS decreased the serum levels of TNF-α, IL-6, and anti-bovine collagen II-specific antibodies. Furthermore, ZJS treatment reduced the number of osteoclasts and the expression of cathepsin K in the ankle joints of CIA mice. ZJS also inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation and the expression of MMP9 and cathepsin K in vitro. Mechanistically, ZJS blocked RANKL-induced p65 phosphorylation, nucleation, and inhibited the expression of downstream NFATc1 and c-Fos in bone marrow-derived macrophages (BMMs). Taken together, ZJS exerts a therapeutic effect on bone erosion in CIA mice by inhibiting RANKL/NF-κB-mediated osteoclast differentiation, which suggested that ZJS is a promising prescription for treating RA bone erosion.

Osteoporosis is a common disease characterized by a systemic impairment of bone mass and microarchitecture that results in fragility fractures. Severe bone loss due to osteoporosis triggers pathological fractures and consequently decreases the daily life activity and quality of life. Therefore, prevention of osteoporosis has become an important issue to be addressed. We have reported that the fungal secondary metabolite (+)-terrein (TER), a natural compound derived from Aspergillus terreus , has shown receptor activator of nuclear factor-κB ligand (RANKL)–induced osteoclast differentiation by suppressing nuclear factor of activated T-cell 1 (NFATc1) expression, a master regulator of osteoclastogenesis. TER has been shown to possess extensive biological and pharmacological benefits; however, its effects on bone metabolism remain unclear. In this study, we investigated the effects of TER on the femoral bone metabolism using a mouse-ovariectomized osteoporosis model (OVX mice) and then on RANKL signal transduction using mouse bone marrow macrophages (mBMMs). In vivo administration of TER significantly improved bone density, bone mass, and trabecular number in OVX mice (p < 0.01). In addition, TER suppressed TRAP and cathepsin-K expression in the tissue sections of OVX mice (p < 0.01). In an in vitro study, TER suppressed RANKL-induced phosphorylation of PKCα/βII, which is involved in the expression of NFATc1 (p < 0.05). The PKC inhibitor, GF109203X, also inhibited RANKL-induced osteoclastogenesis in mBMMs as well as TER. In addition, TER suppressed the expression of osteoclastogenesis-related genes, such as Ocstamp , Dcstamp , Calcr , Atp6v0d2 , Oscar , and Itgb3 (p < 0.01). These results provide promising evidence for the potential therapeutic application of TER as a novel treatment compound against osteoporosis. [ABSTRACT FROM AUTHOR]

Bone erosion is the most evident pathological condition of rheumatoid arthritis (RA), which is the main cause of joint deformities and disability in RA patients. At present, the conventional RA drugs have not achieved satisfactory effect in improving bone erosion. ZhiJingSan (ZJS), which is a traditional Chinese prescription composed of scolopendra (dried body of Scolopendra subspinipes mutilans L. Koch , scolopendridae) and scorpion (dried body of Buthus martensii Karsch, Buthus), exhibits anti-rheumatism, analgesic and joint deformities improvement effects. This study aimed to assess the therapeutic effect of ZJS on RA bone erosion and to elucidate the underlying mechanism. The effect of ZJS on RA bone erosion was investigated in a murine model of bovine collagen-induced arthritis (CIA), and the underlying mechanism was investigated in vitro in an osteoclast differentiation cell model. Administration of ZJS delayed the onset of arthritis, alleviated joint inflammation, and attenuated bone erosion in the CIA mice. Meanwhile, ZJS decreased the serum levels of TNF-α, IL-6, and anti-bovine collagen II-specific antibodies. Furthermore, ZJS treatment reduced the number of osteoclasts and the expression of cathepsin K in the ankle joints of CIA mice. ZJS also inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation and the expression of MMP9 and cathepsin K in vitro. Mechanistically, ZJS blocked RANKL-induced p65 phosphorylation, nucleation, and inhibited the expression of downstream NFATc1 and c-Fos in bone marrow-derived macrophages (BMMs). Taken together, ZJS exerts a therapeutic effect on bone erosion in CIA mice by inhibiting RANKL/NF-κB-mediated osteoclast differentiation, which suggested that ZJS is a promising prescription for treating RA bone erosion. [ABSTRACT FROM AUTHOR]

Bone metabolism is a physiological process that involves both osteoblasts and osteoclasts. Pathological changes of osteoclasts are commonly seen in osteoporosis diseases. Juglanin is a natural compound, reported to have an inhibitory effect on inflammation, oxidative stress and cancer progression. The purpose of this study is to explore the role that Juglanin plays on the osteoclast functions and underlying signaling pathways. In vitro study demonstrated that Juglanin had negative influence on osteoclastic differentiation by suppressing the transcription activity of osteoclastogenesis-related genes and proteins. To determine the underlying mechanism, Western blot was employed to show that Juglanin could significantly have negative effect on the phosphorylation of P50, P65, I-κB， ultimately suppressing the expression and transcriptional activity of nuclear factor of activated T cells (NFATc1). In vivo Juglanin treatment attenuate bone reducing in mice with removed ovary through suppressing osteoclast functioning. Taken together, our study demonstrated that in the molecular mechanism, JUG inhibited the expression of receptor activator of nuclear factor-κ B ligand (RANKL) induced NF - κ B signaling pathway, thus may play a vital part in preventing postmenopausal osteoporosis.

Cudratrixanthone U (CTU) is a prenylated xanthone compound isolated from Maclura tricuspidata Bureau (Moraceae). Prenylated xanthones have been reported to exhibit a variety of biological activities. However, the effects of prenylated xanthone on osteoclast differentiation and function are still unclear. Excessive bone resorption by osteoclasts is considered a major cause of diseases such as osteoporosis. Accordingly, suppression of excessive osteoclast formation and function is one of strategies for treating osteoclast related bone diseases. In this study, CTU inhibited osteoclast differentiation and function in RAW264.7 macrophages and BMM cells induced by receptor activator of nuclear factor-κB ligand (RANKL). CTU regulated the formation of TRAF6-TAK1 complex in RANKL-induced RAW264.7 macrophages and BMM cells. Osteoclast-specific genes including those encoding matrix metallopeptidase 9 (MMP-9), dendritic cell-specific transmembrane proteins (DC-STAMP), cathepsin K (CTSK) and chemokine CC motif ligand 4 (CCL4) play an important role in bone resorption and migration, and were effectively regulated by CTU. These results suggest that CTU is a potential therapeutic agent in osteoporosis.

Asiatic acid is a triterpenoid compound extracted from a medicinal plant Centella asiatica. It has been used as a highly efficient compound for the treatment of cancer and hyperlipidemia, as well as possessing potential antiinflammatory properties. However, its effects on bone metabolism and osteoporosis haven’t been reported. The purpose of our research were to reveal the biomolecular effects of asiatic acid on osteoclasts, and its underlying molecular mechanisms regulating its effects on receptor activator of NF-κB ligand (RANKL)-induced signaling pathways. We found that asiatic acid inhibited multinucleated tartrate-resistant acid phosphatase (TRAcP)-positive osteoclast differentiation and osteoclast induced bone loss. Real time PCR showed that asiatic acid reduced the expression of down-cascade target genes including Ctsk, Nfatc1, Calcr, and Atp6v0d2. Western blot and luciferase reporter gene assays revealed that asiatic acid inhibits RANKL mediated NF-κB and NFATc1 signalings. Further, in vivo study demonstrated asiatic acid attenuates estrogen deficiency-induced bone loss in ovariectomized mice. MicroCT and histology analyses revealed that osteoclast numbers were significantly suppressed in asiatic acid treated groups. Furthermore, serum levels of TRAcP and CTX-1 were downregulated in treated groups. Taken together, our data show that asiatic acid can inhibit osteoclastic formation and reduce OVX-induced bone resorption through RANKL-activated NF-κB or NFATc1 signaling, suggesting that asiatic acid may be a potential and effective natural compound for the therapy of excessive RANKL-related osteolytic diseases.

Cudratrixanthone U (CTU) is a prenylated xanthone compound isolated from Maclura tricuspidata Bureau (Moraceae). Prenylated xanthones have been reported to exhibit a variety of biological activities. However, the effects of prenylated xanthone on osteoclast differentiation and function are still unclear. Excessive bone resorption by osteoclasts is considered a major cause of diseases such as osteoporosis. Accordingly, suppression of excessive osteoclast formation and function is one of strategies for treating osteoclast related bone diseases. In this study, CTU inhibited osteoclast differentiation and function in RAW264.7 macrophages and BMM cells induced by receptor activator of nuclear factor-κB ligand (RANKL). CTU regulated the formation of TRAF6-TAK1 complex in RANKL-induced RAW264.7 macrophages and BMM cells. Osteoclast-specific genes including those encoding matrix metallopeptidase 9 (MMP-9), dendritic cell-specific transmembrane proteins (DC-STAMP), cathepsin K (CTSK) and chemokine CC motif ligand 4 (CCL4) play an important role in bone resorption and migration, and were effectively regulated by CTU. These results suggest that CTU is a potential therapeutic agent in osteoporosis. [ABSTRACT FROM AUTHOR]

Asiatic acid is a triterpenoid compound extracted from a medicinal plant Centella asiatica. It has been used as a highly efficient compound for the treatment of cancer and hyperlipidemia, as well as possessing potential antiinflammatory properties. However, its effects on bone metabolism and osteoporosis haven't been reported. The purpose of our research were to reveal the biomolecular effects of asiatic acid on osteoclasts, and its underlying molecular mechanisms regulating its effects on receptor activator of NF-κB ligand (RANKL)-induced signaling pathways. We found that asiatic acid inhibited multinucleated tartrate-resistant acid phosphatase (TRAcP)-positive osteoclast differentiation and osteoclast induced bone loss. Real time PCR showed that asiatic acid reduced the expression of down-cascade target genes including Ctsk , Nfatc1 , Calcr , and Atp6v0d2. Western blot and luciferase reporter gene assays revealed that asiatic acid inhibits RANKL mediated NF-κB and NFATc1 signalings. Further, in vivo study demonstrated asiatic acid attenuates estrogen deficiency-induced bone loss in ovariectomized mice. MicroCT and histology analyses revealed that osteoclast numbers were significantly suppressed in asiatic acid treated groups. Furthermore, serum levels of TRAcP and CTX-1 were downregulated in treated groups. Taken together, our data show that asiatic acid can inhibit osteoclastic formation and reduce OVX-induced bone resorption through RANKL-activated NF-κB or NFATc1 signaling, suggesting that asiatic acid may be a potential and effective natural compound for the therapy of excessive RANKL-related osteolytic diseases. [ABSTRACT FROM AUTHOR]

Given the limitations of existing therapeutic agents for treatment of postmenopausal osteoporosis, there still remains a need for more options with both efficacy and less adverse effects. Cistanche deserticola Y. C. Ma is known as a popular tonic herb traditionally used to treatment deficiency of kidney energy including muscle weakness in minority area of Asian counties. Based on the theory of “kidney dominate bone,” an ovariectomized (OVX) rat model of postmenopausal osteoporosis was used to evaluate the therapeutic effect of C. deserticola extract (CDE) on bone loss. Forty eight female Sprague-Dawley rats, aged about 12 weeks, were randomly assigned into six groups including sham group orally administrated with 0.5% carboxymethyl cellulose sodium (CMC-Na) (sham), positive group treated with 1 mg/kg of estradiol valerate (EV), low, moderate, and high dosage groups orally administrated with 200, 400, and 800 mg/kg/day of CDE, respectively. After 3 months of continuous intervention, CDE exhibited significant anti-osteoporotic activity evidenced by the enhanced total bone mineral density, ameliorated bone microarchitecture; increased alkaline phosphatase activity; decreased deoxypyridinoline, cathepsin K, tartrate-resistant acid phosphatase, and malondialdehyde levels; whereas the body, uterus, and vagina weights in OVX rats were not influenced by CDE intervention. In addition, a seemed contradictory phenomenon on levels of calcium and phosphorus between OVX and sham rats were observed and elucidated. Mechanistically, CDE significantly down-regulated the levels of TRAF6, RANKL, RANK, NF-κB, IKKβ, NFAT2, and up-regulated the phosphatidylinositol 3-kinase (PI3K), AKT, osteoprotegerin, and c-Fos expressions, which implied CDE could suppress RANKL/RANK-induced activation of downstream NF-κB and PI3K/AKT pathways, and ultimately, preventing activity of the key osteoclastogenic proteins NFAT2 and c-Fos. All of the data suggested CDE possessed potential anti-osteoporotic activity and this effect was, at least in part, involved in modulation of RANKL/RANK/TRAF6-mediated NF-κB and PI3K/AKT signaling as well as c-Fos and NFAT2 levels. Therefore, CDE may represent a useful promising remedy candidate for treatment of postmenopausal osteoporosis.

Given the limitations of existing therapeutic agents for treatment of postmenopausal osteoporosis, there still remains a need for more options with both efficacy and less adverse effects. Cistanche deserticola Y. C. Ma is known as a popular tonic herb traditionally used to treatment deficiency of kidney energy including muscle weakness in minority area of Asian counties. Based on the theory of "kidney dominate bone," an ovariectomized (OVX) rat model of postmenopausal osteoporosis was used to evaluate the therapeutic effect of C. deserticola extract (CDE) on bone loss. Forty eight female Sprague-Dawley rats, aged about 12 weeks, were randomly assigned into six groups including sham group orally administrated with 0.5% carboxymethyl cellulose sodium (CMC-Na) (sham), positive group treated with 1 mg/kg of estradiol valerate (EV), low, moderate, and high dosage groups orally administrated with 200, 400, and 800 mg/kg/day of CDE, respectively. After 3 months of continuous intervention, CDE exhibited significant anti-osteoporotic activity evidenced by the enhanced total bone mineral density, ameliorated bone microarchitecture; increased alkaline phosphatase activity; decreased deoxypyridinoline, cathepsin K, tartrate-resistant acid phosphatase, and malondialdehyde levels; whereas the body, uterus, and vagina weights in OVX rats were not influenced by CDE intervention. In addition, a seemed contradictory phenomenon on levels of calcium and phosphorus between OVX and sham rats were observed and elucidated. Mechanistically, CDE significantly down-regulated the levels of TRAF6, RANKL, RANK, NF-κB, IKKβ, NFAT2, and up-regulated the phosphatidylinositol 3-kinase (PI3K), AKT, osteoprotegerin, and c-Fos expressions, which implied CDE could suppress RANKL/RANK-induced activation of downstream NF-κB and PI3K/AKT pathways, and ultimately, preventing activity of the key osteoclastogenic proteins NFAT2 and c-Fos. All of the data suggested CDE possessed potential anti-osteoporotic activity and this effect was, at least in part, involved in modulation of RANKL/RANK/TRAF6-mediated NF-κB and PI3K/AKT signaling as well as c-Fos and NFAT2 levels. Therefore, CDE may represent a useful promising remedy candidate for treatment of postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

Bone homeostasis and resorption is regulated by the proper activation of osteoclasts, whose stimulation largely depends on the receptor activator of nuclear factor κB ligand (RANKL)-RANK signaling. Herein, for the first time, we showed that interferon regulatory factor (Irf)-3 was intimately involved in RANKL-induced osteoclast formation. In addition, hesperetin (Hes) derived from citrus fruit could inhibit RANKL-induced osteoclast differentiation and maturation among three types of osteoclast precursors with inhibited formation of F-actin rings and resorption pits on bone slices. More importantly, by using SP600125, a selective Jnk inhibitor, we showed that Hes was able to significantly attenuate the Jnk downstream expression of Irf-3 and c-Jun, thereby inactivating NF-κB/MAPK signaling and transcriptional factor NFATc-1, leading to suppression of osteoclast-specific genes, which resulted in impaired osteoclastogenesis and functionality. An ovariectomized (OVX) osteoporosis mouse model demonstrated that Hes could increase trabecular bone volume fractions (BV/TV), trabecular thickness, and trabecular number, whereas it decreased trabecular separation in OVX mice with well-preserved trabecular bone architecture and decreased levels of TRAP-positive osteoclasts. This is further evidenced by the diminished serum expression of bone resorption marker CTX and enhanced production of osteoblastic ALP in vivo. Taken together, these results suggested that Hes could inhibit Jnk-mediated Irf-3/c-Jun activation, thus attenuating RANKL-induced osteoclast formation and function both in vitro and in vivo.

Recent studies indicate that uPAR acts a crucial part in cell migration and the modulation of bone homeostasis. As a natural serine protease inhibitor, ulinastatin owns the capacity to reduce proinflammatory factors, downregulate the activation of NF-κB and mitogen-activated protein kinases (MAPKs) signaling pathways. Osteoclastogenesis has been demonstrated to be related with low-grade inflammation which involves cell migration, thus we speculate that ulinastatin may have a certain kind of impact on uPAR so as to be a potential inhibiting agent of osteoclastogenesis. In this research, we investigated the role which ulinastatin plays in RANKL-induced osteoclastogenesis both in vivo and in vitro. Ulinastatin inhibited osteoclast formation and bone resorption in a dose-dependent manner in primary bone marrow-derived macrophages (BMMs), and knockdown of uPAR could completely repress the formation of osteoclasts. At the molecular level, ulinastatin suppressed RANKL-induced activation of cathepsin K, TRAP, nuclear factor-κB (NF-κB) and MAPKs, and decreased the expression of uPAR. At the meantime, ulinastatin also decreased the expression of osteoclast marker genes, including cathepsin K, TRAP, RANK, and NFATc1. Besides, ulinastatin prevented bone loss in ovariectomized C57 mice by inhibiting the formation of osteoclasts. To sum up, this research confirmed that ulinastatin has the ability to inhibit osteoclastogenesis and prevent bone loss, and uPAR plays a crucial role in that process. Therefore, ulinastatin could be chosen as an effective alternative therapeutics for osteoclast-related diseases.

Bone metabolism is determined by a delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts. The imbalance due to over-activated osteoclasts plays an important role in various diseases. Activation of NF-κB and MAPK signaling pathways by receptor activator of nuclear factor -κB ligand (RANKL) is vital for osteoclastogenesis. Here, we for the first time explored the effects of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid found in the Glycyrrhiza glabra L roots, on RANKL-induced osteoclastogenesis, osteoclast functions and signaling pathways in vitro and in vivo. In bone marrow monocytes (BMMs) and RAW264.7 cells, 18β-GA inhibited osteoclastogenesis, decreased expression of TRAP, cathepsin K, CTR and MMP-9, blocked actin ring formation and compromised osteoclasts functions in a dose-dependent manner at an early stage with minimal effects on osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). For underlying molecular mechanisms, 18β-GA inhibited RANKL-induced phosphorylation of p65, p50, and IκB, blocked p65 nuclear translocation and decreased the DNA-binding activity of NF-κB. Besides, 18β-GA inhibited the activation of the MAPK pathways. Co-immunoprecipitation showed that 18β-GA treatment blocked RANK–TRAF6 association at an upstream site. In vivo, 18β-GA treatment inhibited ovariectomy-induced osteoclastogenesis and reduced bone loss in mice. Overall, our results demonstrated that 18β-GA inhibited RANKL-induced osteoclastogenesis by inhibiting RANK expression in preosteoclasts and blocking the binding of RANK and TRAF6 which lead to the inhibition of NF-κB and MAPK signaling pathways. 18β-GA is a promising novel candidate in the treatment of osteoclast-related diseases such as postmenopausal osteoporosis.

Bone homeostasis and resorption is regulated by the proper activation of osteoclasts, whose stimulation largely depends on the receptor activator of nuclear factor κB ligand (RANKL)-RANK signaling. Herein, for the first time, we showed that interferon regulatory factor (Irf)-3 was intimately involved in RANKL-induced osteoclast formation. In addition, hesperetin (Hes) derived from citrus fruit could inhibit RANKL-induced osteoclast differentiation and maturation among three types of osteoclast precursors with inhibited formation of F-actin rings and resorption pits on bone slices. More importantly, by using SP600125, a selective Jnk inhibitor, we showed that Hes was able to significantly attenuate the Jnk downstream expression of Irf-3 and c-Jun, thereby inactivating NF-κB/MAPK signaling and transcriptional factor NFATc-1, leading to suppression of osteoclast-specific genes, which resulted in impaired osteoclastogenesis and functionality. An ovariectomized (OVX) osteoporosis mouse model demonstrated that Hes could increase trabecular bone volume fractions (BV/TV), trabecular thickness, and trabecular number, whereas it decreased trabecular separation in OVX mice with well-preserved trabecular bone architecture and decreased levels of TRAP-positive osteoclasts. This is further evidenced by the diminished serum expression of bone resorption marker CTX and enhanced production of osteoblastic ALP in vivo. Taken together, these results suggested that Hes could inhibit Jnk-mediated Irf-3/c-Jun activation, thus attenuating RANKL-induced osteoclast formation and function both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Recent studies indicate that uPAR acts a crucial part in cell migration and the modulation of bone homeostasis. As a natural serine protease inhibitor, ulinastatin owns the capacity to reduce proinflammatory factors, downregulate the activation of NF-κB and mitogen-activated protein kinases (MAPKs) signaling pathways. Osteoclastogenesis has been demonstrated to be related with low-grade inflammation which involves cell migration, thus we speculate that ulinastatin may have a certain kind of impact on uPAR so as to be a potential inhibiting agent of osteoclastogenesis. In this research, we investigated the role which ulinastatin plays in RANKL-induced osteoclastogenesis both in vivo and in vitro. Ulinastatin inhibited osteoclast formation and bone resorption in a dose-dependent manner in primary bone marrow-derived macrophages (BMMs), and knockdown of uPAR could completely repress the formation of osteoclasts. At the molecular level, ulinastatin suppressed RANKL-induced activation of cathepsin K, TRAP, nuclear factor-κB (NF-κB) and MAPKs, and decreased the expression of uPAR. At the meantime, ulinastatin also decreased the expression of osteoclast marker genes, including cathepsin K, TRAP, RANK, and NFATc1. Besides, ulinastatin prevented bone loss in ovariectomized C57 mice by inhibiting the formation of osteoclasts. To sum up, this research confirmed that ulinastatin has the ability to inhibit osteoclastogenesis and prevent bone loss, and uPAR plays a crucial role in that process. Therefore, ulinastatin could be chosen as an effective alternative therapeutics for osteoclast-related diseases. [ABSTRACT FROM AUTHOR]

Bone metabolism is determined by a delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts. The imbalance due to over-activated osteoclasts plays an important role in various diseases. Activation of NF-κB and MAPK signaling pathways by receptor activator of nuclear factor -κB ligand (RANKL) is vital for osteoclastogenesis. Here, we for the first time explored the effects of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid found in the Glycyrrhiza glabra L roots, on RANKL-induced osteoclastogenesis, osteoclast functions and signaling pathways in vitro and in vivo. In bone marrow monocytes (BMMs) and RAW264.7 cells, 18β-GA inhibited osteoclastogenesis, decreased expression of TRAP, cathepsin K, CTR and MMP-9, blocked actin ring formation and compromised osteoclasts functions in a dose-dependent manner at an early stage with minimal effects on osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). For underlying molecular mechanisms, 18β-GA inhibited RANKL-induced phosphorylation of p65, p50, and IκB, blocked p65 nuclear translocation and decreased the DNA-binding activity of NF-κB. Besides, 18β-GA inhibited the activation of the MAPK pathways. Co-immunoprecipitation showed that 18β-GA treatment blocked RANK–TRAF6 association at an upstream site. In vivo, 18β-GA treatment inhibited ovariectomy-induced osteoclastogenesis and reduced bone loss in mice. Overall, our results demonstrated that 18β-GA inhibited RANKL-induced osteoclastogenesis by inhibiting RANK expression in preosteoclasts and blocking the binding of RANK and TRAF6 which lead to the inhibition of NF-κB and MAPK signaling pathways. 18β-GA is a promising novel candidate in the treatment of osteoclast-related diseases such as postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

Post-menopausal osteoporosis (PMOP) is a metabolic bone disorder characterized by low bone mass and micro-architectural deterioration of bone tissue. The over-activated osteoclastogenesis, which plays an important role in osteoporosis, has become an important therapeutic target. M54 was a bioactive derivative of the Chinese traditional herb matrine. We found that M54 could suppress RANKL-induced osteoclastogenesis in bone marrow mononuclear cells and RAW264.7 cells through suppressing NF-κB, PI3K/AKT, and MAPKs pathways activity in vitro, and prevent ovariectomy-induced bone loss in vivo. Our previous study has proved that ribosomal protein S5 (RPS5) was a direct target of M19, based on which M54 was synthesized. Thus we deduced that M54 also targeted RPS5. During osteoclastogenesis, the RPS5 level in RAW264.7 cells was significantly down-regulated while M54 could maintain its level. After RPS5 was silenced, the inhibitory effects of M54 on osteoclastogenesis were partially compromised, indicating that M54 took effects through targeting RPS5. In summary, M54 was a potential clinical medicine for post-menopause osteoporosis treatment, and RPS5 is a possible key protein in PMOP.

Pregnane X receptor (PXR) which belongs to the nuclear hormone receptor superfamily plays vital roles in several biological functions, especially in the inflammatory procedure. Besides that, PXR is revealed by recent studies to have essential effects on bone tissue. As an agonist of PXR, meclizine is a piperazine-derived histamine H1 antagonist, and has been frequently used for prevention and treatment of vomiting and nausea. Because osteoclastogenesis is characterized by the activation of inflammation-related signaling pathways, we speculated that meclizine may affect formation and function of osteoclast. In the present study, we explored the effect of meclizine on RANKL-induced osteoclastogenesis both in vivo and in vitro. In primary bone marrow-derived macrophages (BMMs), meclizine reduced osteoclast formation and bone resorption in a dose-dependent manner, while knockdown of PXR with siRNA partially abrogated the osteoclastogenesis inhibition of meclizine. On the one hand, at the molecular level, meclizine attenuated RANKL-induced activation of c-Fos, NFATc1, nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPKs), including ERK and p38, but not JNK. Meanwhile, meclizine reduced the expression of osteoclast-specific genes, including TRAP, MMP9, Cathepsin K and NFATc1. On the other hand, meclizine decreased OVX-induced bone loss by repressing osteoclast activity. In conclusion, our results indicated that meclizine inhibits osteoclastogenesis via regulation of several RANKL signaling pathways and PXR was involved in the processes. Therefore, meclizine may be considered as a novel therapeutic candidate for osteoclast-related diseases.

Periodontitis is a chronic inflammatory disease that damages the integrity of the tooth-supporting tissues, known as the periodontium, and comprising the gingiva, periodontal ligament and alveolar bone. In this study, the effects of nardosinone (Nd) on bone were tested in a model of lipopolysaccharide (LPS)-induced alveolar bone loss, and the associated mechanisms were elucidated. Nd effectively suppressed LPS-induced alveolar bone loss and reduced osteoclast (OC) numbers in vivo. Nd suppressed receptor activator of nuclear factor-κB ligand (RANKL)-mediated OC differentiation, bone resorption, and F-actin ring formation in a dose-dependent manner. Further investigation revealed that Nd suppressed osteoclastogenesis by suppressing the ERK and JNK signaling pathways, scavenging reactive oxygen species, and suppressing the activation of PLCγ2 that consequently affects the expression and/or activity of the OC-specific transcription factors, c-Fos and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). In addition, Nd significantly reduced the expression of OC-specific markers in mouse bone marrow-derived pre-OCs, including c-Fos, cathepsin K (Ctsk), VATPase d2, and Nfatc1. Collectively, these findings suggest that Nd has beneficial effects on bone, and the suppression of OC number implies that the effect is exerted directly on osteoclastogenesis.

Postmenopausal osteoporosis is a disease characterized by excessive osteoclastic bone resorption. Some anti-diabetic drugs were demonstrated for anti-osteoclastic bone-loss effects. The present study investigated the skeletal effects of chronic administration of sitagliptin, a dipeptidyl peptidase IV (DPP IV) inhibitor that is increasingly used for type 2 diabetes treatments, in an estrogen deficiency-induced osteoporosis and elucidated the associated mechanisms. This study indicated that sitagliptin effectively prevented ovariectomy-induced bone loss and reduced osteoclast numbers in vivo. It was also indicated that sitagliptin suppressed receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation, bone resorption, and F-actin ring formation in a manner of dose-dependence. In addition, sitagliptin significantly reduced the expression of osteoclast-specific markers in mouse bone-marrow-derived macrophages, including calcitonin receptor (Calcr), dendrite cell-specific transmembrane protein (Dc-stamp), c-Fos, and nuclear factor of activated T-cells cytoplasmic 1 (Nfatc1). Further study indicated that sitagliptin inhibited osteoclastogenesis by suppressing AKT and ERK signaling pathways, scavenging ROS activity, and suppressing the Ca2+ oscillation that consequently affects the expression and/or activity of the osteoclast-specific transcription factors, c-Fos and NFATc1. Collectively, these findings suggest that sitagliptin possesses beneficial effects on bone and the suppression of osteoclast number implies that the effect is exerted directly on osteoclastogenesis.

Post-menopausal osteoporosis (PMOP) is a metabolic bone disorder characterized by low bone mass and micro-architectural deterioration of bone tissue. The over-activated osteoclastogenesis, which plays an important role in osteoporosis, has become an important therapeutic target. M54 was a bioactive derivative of the Chinese traditional herb matrine. We found that M54 could suppress RANKL-induced osteoclastogenesis in bone marrow mononuclear cells and RAW264.7 cells through suppressing NF-κB, PI3K/AKT, and MAPKs pathways activity in vitro, and prevent ovariectomy-induced bone loss in vivo. Our previous study has proved that ribosomal protein S5 (RPS5) was a direct target of M19, based on which M54 was synthesized. Thus we deduced that M54 also targeted RPS5. During osteoclastogenesis, the RPS5 level in RAW264.7 cells was significantly down-regulated while M54 could maintain its level. After RPS5 was silenced, the inhibitory effects of M54 on osteoclastogenesis were partially compromised, indicating that M54 took effects through targeting RPS5. In summary, M54 was a potential clinical medicine for post-menopause osteoporosis treatment, and RPS5 is a possible key protein in PMOP. [ABSTRACT FROM AUTHOR]

Postmenopausal osteoporosis is a disease characterized by excessive osteoclastic bone resorption. Some anti-diabetic drugs were demonstrated for anti-osteoclastic bone-loss effects. The present study investigated the skeletal effects of chronic administration of sitagliptin, a dipeptidyl peptidase IV (DPP IV) inhibitor that is increasingly used for type 2 diabetes treatments, in an estrogen deficiency-induced osteoporosis and elucidated the associated mechanisms. This study indicated that sitagliptin effectively prevented ovariectomy-induced bone loss and reduced osteoclast numbers in vivo. It was also indicated that sitagliptin suppressed receptor activator of nuclear factor-kB ligand (RANKL)-mediated osteoclast differentiation, bone resorption, and F-actin ring formation in a manner of dose-dependence. In addition, sitagliptin significantly reduced the expression of osteoclast-specific markers in mouse bonemarrow- derived macrophages, including calcitonin receptor (Calcr), dendrite cellspecific transmembrane protein (Dc-stamp), c-Fos, and nuclear factor of activated T-cells cytoplasmic 1 (Nfatc1). Further study indicated that sitagliptin inhibited osteoclastogenesis by suppressing AKT and ERK signaling pathways, scavenging ROS activity, and suppressing the Ca2+ oscillation that consequently affects the expression and/or activity of the osteoclast-specific transcription factors, c-Fos and NFATc1. Collectively, these findings suggest that sitagliptin possesses beneficial effects on bone and the suppression of osteoclast number implies that the effect is exerted directly on osteoclastogenesis. [ABSTRACT FROM AUTHOR]

Osteoporosis (OP), characterized by continuous bone loss and increased fracture risk, has posed a challenge to patients and society. Long-term administration of current pharmacological agents may cause severe side effects. Traditional medicines, acting as alternative agents, show promise in treating OP. Osthole, a natural coumarin derivative separated from Cnidium monnieri (L.) Cusson and Angelica pubescens Maxim. f., exhibits protective effects against the pathological development of OP. Osthole increases osteoblast-related bone formation and decreases osteoclast-related bone resorption, suppressing OP-related fragility fracture. In addition, the metabolites of osthole may exhibit pharmacological effectiveness against OP development. Mechanically, osthole promotes osteogenic differentiation by activating the Wnt/β-catenin and BMP-2/Smad1/5/8 signaling pathways and suppresses RANKL-induced osteoclastogenesis and osteoclast activity. Thus, osthole may become a promising agent to protect against OP development. However, more studies should be performed due to, at least in part, the uncertainty of drug targets. Further pharmacological investigation of osthole in OP treatment might lead to the development of potential drug candidates., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Chen, Liao and Gan.)