Inhibitory regulation of osteoclast differentiation by interleukin-3 via regulation of c-Fos and Id protein expression

Interleukin-3 (IL-3) is produced under various pathological conditions and is thought to be involved in the pathogenesis of inflammatory diseases; however, its function in bone homeostasis under normal conditions or nature of the downstream molecular targets remains unknown. Here we examined the effect of IL-3 on osteoclast differentiation from mouse and human bone marrow-derived macrophages (BMMs). Although IL-3 can induce osteoclast differentiation of multiple myeloma bone marrow cells, IL-3 greatly inhibited osteoclast differentiation of human BMMs isolated from healthy donors. These inhibitory effects of IL-3 were only observed at early time points (days 0 and 1). IL-3 inhibited the expression of c-Fos and NFATc1 in BMMs treated with RANKL. However, IL-3-mediated inhibition of osteoclast differentiation was not completely reversed by ectopic expression of c-Fos or NFATc1. Importantly, IL-3 induced inhibitor of DNA binding/differentiation (Id)1 in hBMMs, while Id2 were sustained during osteoclast differentiation of mBMMs treated with IL-3. Ectopic expression of NFATc1 in Id2-deficient BMMs completely reversed the inhibitory effect of IL-3 on osteoclast differentiation. Furthermore, inflammation-induced bone erosion was markedly inhibited by IL-3 administration. Taken together, our results suggest that IL-3 plays an inhibitory role in osteoclast differentiation by regulating c-Fos and Ids, and also exerts anti-bone erosion effects.     

Kirenol inhibits RANKL-induced osteoclastogenesis and prevents ovariectomized-induced osteoporosis via suppressing the Ca2+-NFATc1 and Cav-1 signaling pathways

BackgroundOsteoporosis is a threat to aged people who have excessive osteoclast activation and bone resorption, subsequently causing fracture and even disability. Inhibiting osteoclast differentiation and absorptive functions has become an efficient approach to treat osteoporosis, but osteoclast-targeting inhibitors available clinically remain rare. Kirenol (Kir), a bioactive diterpenoid derived from an antirheumatic Chinese herbal medicine Herba Siegesbeckiae, can treat collagen-induced arthritis in vivo and promote osteoblast differentiation in vitro, while the effects of Kir on osteoclasts are still unclear.PurposeWe explore the role of Kir on RANKL-induced osteoclastogenesis in vitro and bone loss in vivo.MethodsThe in vitro effects of Kir on osteoclast differentiation, bone resorption and the underlying mechanisms were evaluated with bone marrow-derived macrophages (BMMs). In vivo experiments were performed using an ovariectomy (OVX)-induced osteoporosis model.ResultsWe found that Kir remarkably inhibited osteoclast generation and bone resorption in vitro. Mechanistically, Kir significantly inhibited F-actinring formation and repressed RANKL-induced NF-κB p65 activation and p-p38, p-ERK and c-Fos expression. Moreover, Kir inhibited both the expression and nuclear translocation of NFATc1. Ca²⁺ oscillation and caveolin-1 (Cav-1) were also reduced by Kir during osteoclastogenesis in vitro. Consistent with these findings, 2–10 mg/kg Kir attenuated OVX-induced osteoporosis in vivo as evidenced by decreased osteoclast numbers and downregulated Cav-1 and NFATc1 expression.ConclusionsKir suppresses osteoclastogenesis and the Cav-1/NFATc1 signaling pathway both in vitro and in vivo and protects against OVX-induced osteoporosis. Our findings reveal Kir as a potential safe oral treatment for osteoporosis.     

Mollugin from Rubea cordifolia suppresses receptor activator of nuclear factor-κB ligand-induced osteoclastogenesis and bone resorbing activity in vitro and prevents lipopolysaccharide-induced bone loss in vivo

Osteopenic diseases, such as osteoporosis, are characterized by progressive and excessive bone resorption mediated by enhanced receptor activator of nuclear factor-κB ligand (RANKL) signaling. Therefore, downregulation of RANKL downstream signals may be a valuable approach for the treatment of bone loss-associated disorders. In this study, we investigated the effects of the naphthohydroquinone mollugin on osteoclastogenesis and its function in vitro and in vivo. Mollugin efficiently suppressed RANKL-induced osteoclast differentiation of bone marrow macrophages (BMMs) and bone resorbing activity of mature osteoclasts by inhibiting RANKL-induced c-Fos and NFATc1 expression. Mollugin reduced the phosphorylation of signaling pathways activated in the early stages of osteoclast differentiation, including the MAP kinase, Akt, and GSK3β and inhibited the expression of different genes associated with osteoclastogenesis, such as OSCAR, TRAP, DC-STAMP, OC-STAMP, integrin αν, integrin β3, cathepsin K, and ICAM-1. Furthermore, mice treated with mollugin showed significant restoration of lipopolysaccharide (LPS)-induced bone loss as indicated by micro-CT and histological analysis of femurs. Consequently, these results suggested that mollugin could be a novel therapeutic candidate for bone loss-associated disorders including osteoporosis, rheumatoid arthritis, and periodontitis.     

Akt induces osteoclast differentiation through regulating the GSK3β/NFATc1 signaling cascade

SHIP is an SH2-containing inositol-5-phosphatase expressed in hematopoietic cells. It hydrolyzes the PI3K product PI(3,4,5)P(3) and blunts the PI3K-initiated signaling pathway. Although the PI3K/Akt pathway has been shown to be important for osteoclastogenesis, the molecular events involved in osteoclast differentiation have not been revealed. We demonstrate that Akt induces osteoclast differentiation through regulating the GSK3β/NFATc1 signaling cascade. Inhibition of the PI3K by LY294002 reduces formation of osteoclasts and attenuates the expression of NFATc1, but not that of c-Fos. Conversely, overexpression of Akt in bone marrow-derived macrophages (BMMs) strongly induced NFATc1 expression without affecting c-Fos expression, suggesting that PI3K/Akt-mediated NFATc1 induction is independent of c-Fos during RANKL-induced osteoclastogenesis. In addition, we found that overexpression of Akt enhances formation of an inactive form of GSK3β (phospho-GSK3β) and nuclear localization of NFATc1, and that overexpression of a constitutively active form of GSK3β attenuates osteoclast formation through downregulation of NFATc1. Furthermore, BMMs from SHIP knockout mice show the increased expression levels of phospho-Akt and phospho-GSK3β, as well as the enhanced osteoclastogenesis, compared with wild type. However, overexpression of a constitutively active form of GSK3β attenuates RANKL-induced osteoclast differentiation from SHIP-deficient BMMs. Our data suggest that the PI3K/Akt/GSK3β/NFATc1 signaling axis plays an important role in RANKL-induced osteoclastogenesis.     

Prevention of wear particle-induced osteolysis by a novel V-ATPase inhibitor saliphenylhalamide through inhibition of osteoclast bone resorption

Wear particle-induced peri-implant loosening (Aseptic prosthetic loosening) is one of the most common causes of total joint arthroplasty. It is well established that extensive bone destruction (osteolysis) by osteoclasts is responsible for wear particle-induced peri-implant loosening. Thus, inhibition of osteoclastic bone resorption should prevent wear particle induced osteolysis and may serve as a potential therapeutic avenue for prosthetic loosening. Here, we demonstrate for the first time that saliphenylhalamide, a new V-ATPase inhibitor attenuates wear particle-induced osteolysis in a mouse calvarial model. In vitro biochemical and morphological assays revealed that the inhibition of osteolysis is partially attributed to a disruption in osteoclast acidification and polarization, both a prerequisite for osteoclast bone resorption. Interestingly, the V-ATPase inhibitor also impaired osteoclast differentiation via the inhibition of RANKL-induced NF-κB and ERK signaling pathways. In conclusion, we showed that saliphenylhalamide affected multiple physiological processes including osteoclast differentiation, acidification and polarization, leading to inhibition of osteoclast bone resorption in vitro and wear particle-induced osteolysis in vivo. The results of the study provide proof that the new generation V-ATPase inhibitors, such as saliphenylhalamide, are potential anti-resorptive agents for treatment of peri-implant osteolysis.     

Parthenolide inhibits osteoclast differentiation and bone resorbing activity by down-regulation of NFATc1 induction and c-Fos stability,during RANKL-mediated osteoclastogenesis

Parthenolide, a natural product derived from Feverfew, prevents septic shock and inflammation. We aimed to identify the effects of parthenolide on the RANKL (receptor activator of NF-κB ligand)-induced differentiation and bone resorbing activity of osteoclasts. In this study, parthenolide dose-dependently inhibited RANKL-mediated osteoclast differentiation in BMMs, without any evidence of cytotoxicity and the phosphorylation of p38, ERK, and IκB, as well as IκB degradation by RANKL treatment. Parthenolide suppressed the expression of NFATc1, OSCAR, TRAP, DC-STAMP, and cathepsin K in RANKL-treated BMMs. Furthermore, parthenolide down-regulated the stability of c-Fos protein, but could not suppress the expression of c-Fos. Overexpression of NFATc1 and c-Fos in BMMs reversed the inhibitory effect of parthenolide on RANKL-mediated osteoclast differentiation. Parthenolide also inhibited the bone resorbing activity of mature osteoclasts. Parthenolide inhibits the differentiation and bone-resolving activity of osteoclast by RANKL, suggesting its potential therapeutic value for bone destructive disorders associated with osteoclast-mediated bone resorption. [BMB Reports 2014; 47(8): 451-456]     

Icariin inhibits RANKL-induced osteoclastogenesis via modulation of the NF-κB and MAPK signaling pathways

The receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-RANK regulatory axis is a major regulator of osteoclast differentiation and activation. Icariin, a flavonol glycoside isolated from the Epimedium herb, has been reported to prevents bone loss in ovariectomized mice and inhibits wear particle-induced osteolysis. However, the molecular mechanism through which icariin inhibits RANKL-induced osteoclastogenesis has not been fully understood. Therefore, we aimed to investigate the effects of icariin on RANKL-induced osteoclastogenesis and to elucidate the mechanism underlying this effect. Our results showed that RANKL-induced osteoclastogenesis was inhibited by icariin in bone marrow macrophages (BMMs) and RAW264.7?cells, and that this effect was due to suppression of NF-κB and mitogen-activated protein kinase (MAPK) activation. In addition, icariin inhibited F-actin ring formation and attenuated the bone resorption ability of mature osteoclasts. Collectively, our results indicate that icariin may be a promising potential candidate for the treatment of osteolytic diseases such as osteoporosis. Moreover, our findings lay the foundation for understanding and intervening in osteoclast-related diseases at the molecular level.     

Jolkinolide B inhibits RANKL-induced osteoclastogenesis by suppressing the activation NF-κB and MAPK signaling pathways

Osteoclasts together with osteoblasts play pivotal roles in bone remodeling. The unique function and ability of osteoclasts to resorb bone makes them critical in both normal bone homeostasis and pathologic bone diseases such as osteoporosis and rheumatoid arthritis. Thus, new compounds that may inhibit osteoclastogenesis and osteoclast function may be of great value in the treatment of osteoclast-related diseases. In the present study, we examined the effect of jolkinolide B (JB), isolated from the root of Euphorbia fischeriana Steud on receptor activator of NF-κB ligand (RANKL)-induced osteoclast formation. We found that JB inhibited RANKL-induced osteoclast differentiation from bone marrow macrophages (BMMs) without cytotoxicity. Furthermore, the expression of osteoclastic marker genes, such as tartrate-resistant acid phosphatase (TRAP), cathepsin K (CtsK), and calcitonin receptor (CTR), was significantly inhibited. JB inhibited RANKL-induced activation of NF-κB by suppressing RANKL-mediated IκBα degradation. Moreover, JB inhibited RANKL-induced phosphorylation of mitogen-activated protein kinases (p38, JNK, and ERK). This study thus identifies JB as an inhibitor of osteoclast formation and provides evidence that JB might be an alternative medicine for preventing and treating osteolysis.     

Carboxypeptidase E Is a Novel Modulator of RANKL-Induced Osteoclast Differentiation

Osteoclasts are large polykaryons that have the unique capacity to degrade bone and are generated by the differentiation of myeloid lineage progenitors. To identify the genes involved in osteoclast development, we performed microarray analysis, and we found that carboxypeptidase E (CPE), a prohormone processing enzyme, was highly upregulated in osteoclasts compared with their precursors, bone marrow-derived macrophages (BMMs). Here, we demonstrate a novel role for CPE in receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation. The overexpression of CPE in BMMs increases the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear osteoclasts and the expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1), which are key regulators in osteoclastogenesis. Furthermore, employing CPE knockout mice, we show that CPE deficiency attenuates osteoclast formation. Together, our data suggest that CPE might be an important modulator of RANKL-induced osteoclast differentiation.