Kaempferol attenuates particle-induced osteogenic impairment by regulating ER stress via the IRE1α-XBP1s pathway.

Periprosthetic osteolysis and subsequent aseptic loosening are the primary causes of failure following total joint arthroplasty. Wear particle-induced osteogenic impairment is recognized as an important contributing factor in the development of osteolysis, with endoplasmic reticulum (ER) stress emerging as a pivotal underlying mechanism. Hence, searching for potential therapeutic targets and agents capable of modulating ER stress in osteoblasts is crucial for preventing aseptic loosening. Kaempferol (KAE), a natural flavonol compound, has shown promising osteoprotective effects and anti-ER stress properties in diverse diseases. However, the influence of KAE on ER stress-mediated osteogenic impairment induced by wear particles remains unclear. In this study, we observed that KAE effectively relieved TiAl6V4 particles-induced osteolysis by improving osteogenesis in a mouse calvarial model. Furthermore, we demonstrated that KAE could attenuate ER stress-mediated apoptosis in osteoblasts exposed to TiAl6V4 particles, both in vitro and in vivo. Mechanistically, our results revealed that KAE mitigated ER stress-mediated apoptosis by upregulating the IRE1α-XBP1s pathway while concurrently partially inhibiting the IRE1α-regulated RIDD and JNK activation. Collectively, our findings suggest that KAE is a prospective therapeutic agent for treating wear particle-induced osteolysis and highlight the IRE1α-XBP1s pathway as a potential therapeutic target for preventing aseptic loosening.

Calycosin alleviates titanium particle-induced osteolysis by modulating macrophage polarization and subsequent osteogenic differentiation.

Periprosthetic osteolysis (PPO) caused by wear particles is one of the leading causes of implant failure after arthroplasty. Macrophage polarization imbalance and subsequent osteogenic inhibition play a crucial role in PPO. Calycosin (CA) is a compound with anti-inflammatory and osteoprotective properties. This study aimed to evaluate the effects of CA on titanium (Ti) particle-induced osteolysis, Ti particle-induced macrophage polarization and subsequent osteogenic deficits, and explore the associated signalling pathways in a Ti particle-stimulated calvarial osteolysis mouse model using micro-CT, ELISA, qRT-PCR, immunofluorescence and western blot techniques. The results showed that CA alleviated inflammation, osteogenic inhibition and osteolysis in the Ti particle-induced calvarial osteolysis mouse model in vivo. In vitro experiments showed that CA suppressed Ti-induced M1 macrophage polarization, promoted M2 macrophage polarization and ultimately enhanced osteogenic differentiation of MC3T3-E1 cells. In addition, CA alleviated osteogenic deficits by regulating macrophage polarization homeostasis via the NF-κB signalling pathway both in vivo and in vitro. All these findings suggest that CA may prove to be an effective therapeutic agent for wear particle-induced osteolysis.

Sesamin inhibits RANKL-induced osteoclastogenesis and attenuates LPS-induced osteolysis via suppression of ERK and NF-κB signalling pathways.

Infection by bacterial products in the implant and endotoxin introduced by wear particles activate immune cells, enhance pro-inflammatory cytokines production, and ultimately promote osteoclast recruitment and activity. These factors are known to play an important role in osteolysis as well as potential targets for the treatment of osteolysis. Sesamin has been shown to have a variety of biological functions, such as inhibiting inflammation, anti-tumour and involvement in the regulation of fatty acid and cholesterol metabolism. However, the therapeutic effect of sesamin on osteolysis and its mechanism remain unclear. Present studies shown that in the condition of in vitro, sesamin could inhibit osteoclastogenesis and bone resorption, as well as suppressing the expression of osteoclast-specific genes. Further studies on the mechanism suggest that the effect of sesamin on human osteoclasts was mediated by blocking the ERK and NF-κB signalling pathways. Besides, sesamin was found to be effective in treating LPS-induced osteolysis by decreasing the production of pro-inflammatory cytokines and inhibiting osteoclastogenesis in vivo. Sesamin was non-toxic to heart, liver, kidney, lung and spleen. Therefore, sesamin is a promising phytochemical agent for the therapy of osteolysis-related diseases caused by inflammation and excessive osteoclast activation.

Medication-related osteonecrosis of the lower jaw without osteolysis on computed tomography images.

INTRODUCTION: Surgery is the standard treatment for medication-related osteonecrosis of the jaw (MRONJ). This study reviewed patients with mandibular MRONJ who underwent surgical treatment, and in particular the characteristics of non-osteolytic MRONJ with no evidence of osteolysis on CT were described. MATERIALS AND METHODS: We conducted a retrospective study of patients with mandibular MRONJ who underwent surgery between January 2016 and September 2022. Various clinical and imaging factors regarding treatment outcomes were investigated and analyzed. Additionally, the disease course of non-osteolytic MRONJ was examined in detail. RESULTS: This study included 55 patients (66 surgeries) with a mean age of 74.7. The primary disease was osteoporosis (24 patients) and malignancy (31 patients); the type of antiresorptive agent was bisphosphonate (BP) in 21 patients and denosumab (DMB) in 26. BP was initially administered; however, it was changed to DMB in eight patients. Preoperatively, the cumulative cure rates for all 66 surgeries were 72.8% at 1 year and 77.3% at 2 years. Cure rates were significantly lower in patients with malignancy, those without osteolysis, and those who underwent sequestrum removal or marginal mandibulectomy than those with osteoporosis, osteolysis, and segmental mandibulectomy. Non-osteolytic MRONJ was observed in eight patients, all with malignancy and receiving high-dose DMB. Only two patients were cured after the initial surgery, and most patients ultimately underwent segmental mandibulectomy. CONCLUSIONS: Surgical treatment yielded good treatment outcomes in most patients with mandibular MRONJ; however, the cure rate was lower in patients with malignancy who showed no osteolysis on CT images.

Phillygenin prevents osteoclast differentiation and bone loss by targeting RhoA.

Forsythia suspensa tea is a popular traditional Chinese medicine decoction for its healthy and therapeutic benefits. However, its effects in bone metabolism were not clear. In recent study, we uncovered anti-osteoclastogenesis property of Phillygenin (Phi), a compound abundant in Forsythia suspensa leaves, and aimed to investigate the effect and mechanism of Phi on bone metabolism in vivo and in vitro. Lipopolysaccharides-induced murine calvaria osteolysis and ovariectomy-induced bone loss animal models were used to identify the bone-protective effect of Phi in vivo and micro-CT, pQCT, and TRAP staining were applied. We used CCK8, TUNEL, BrdU, and TRAP staining to evaluate the efficacy of Phi on the proliferation and formation of OCs in primary mBMMs. RNA sequence, activity-based protein profiling, molecular docking, G-LISA, and WB were used to inspect the target and underlying mechanism of Phi's actions in mBMMs. We found Phi significantly inhibited bone resorption in vivo and inhibited mBMMs osteoclastogenesis in vitro. Ras homolog gene family member A (RhoA) was identified as the direct target of Phi. It counteracted the effects of RhoA activator and acted as a RhoA inhibitor. By targeting RhoA, Phi modulated Rho-associated coiled-coil containing protein kinase 1 (ROCK1) activity and regulated its downstream NF-κB/NFATc1/c-fos pathway. Furthermore, Phi depressed the disassembling of F-actin ring through cofilin and myosin1a. Our findings provided Phi as a potential option for treating bone loss diseases by targeting RhoA and highlighted the importance of F. suspensa as a preventive approach in bone disorders.

PLGA nanoparticles engineering extracellular vesicles from human umbilical cord mesenchymal stem cells ameliorates polyethylene particles induced periprosthetic osteolysis.

The wear particle-induced dissolution of bone around implants is a significant pathological factor in aseptic loosening, and controlling prosthetic aseptic loosening holds crucial social significance. While human umbilical cord mesenchymal stem cell-derived exosomes (HucMSCs-Exos, Exos) have been found to effectively promote osteogenesis and angiogenesis, their role in periprosthetic osteolysis remains unexplored. To enhance their in vivo application, we engineered HucMSCs-Exos-encapsulated poly lactic-co-glycolic acid (PLGA) nanoparticles (PLGA-Exos). In our study, we demonstrate that PLGA-Exos stimulate osteogenic differentiation while inhibiting the generation of reactive oxygen species (ROS) and subsequent osteoclast differentiation in vitro. In vivo imaging revealed that PLGA-Exos released exosomes slowly and maintained a therapeutic concentration. Our in vivo experiments demonstrated that PLGA-Exos effectively suppressed osteolysis induced by polyethylene particles. These findings suggest that PLGA-Exos hold potential as a therapeutic approach for the prevention and treatment of periprosthetic osteolysis. Furthermore, they provide novel insights for the clinical management of osteolysis.

The Dopamine D1 Receptor Attenuates Titanium Particle-Induced Inhibition of Osteogenesis by Activating the Wnt Signaling Pathway.

Periprosthetic osteolysis (PPO), caused by wear particles, has become a major cause of joint replacement failure. Secondary surgery after joint replacement poses a serious threat to public health worldwide. Therefore, determining how to effectively inhibit wear particle-induced PPO has become an urgent issue. Recently, the interaction between osteogenic inhibition and wear particles at the biological interface of the implant has been found to be an important factor in the pathological process. Previous studies have found that the central nervous system plays an important role in the regulation of bone formation and bone remodeling. Dopamine (DA), an important catecholamine neurotransmitter, plays an integral role in the physiological and pathological processes of various tissues through its corresponding receptors. Our current study found that upregulation of dopamine first receptors could be achieved by activating the Wnt/ß-catenin pathway, improving osteogenesis in vivo and in vitro, and significantly reducing the inhibition of titanium particle-induced osteogenesis. Overall, these findings suggest that dopamine first receptor (D1R) may be a plausible target to promote osteoblast function and resist wear particle-induced PPO.

Alpinetin ameliorates bone loss in LPS-induced inflammation osteolysis via ROS mediated P38/PI3K signaling pathway.

BACKGROUND AND OBJECTIVE: Bone loss occurs in several inflammatory diseases because of chronic persistent inflammation that activates osteoclasts (OCs) to increase bone resorption. Currently available antiresorptive drugs have severe side effects or contraindications. Herein, we explored the effects and mechanism of Alpinetin (Alp) on receptor activator of nuclear factor κB ligand (RANKL)-mediated OCs differentiation, function, and in inflammatory osteolysis of mice. METHOD: Primary mouse bone marrow-derived macrophages (BMMs) induced by RANKL and macrophage colony-stimulating factor (M-CSF) were utilized to test the impact of Alp on OCs differentiation, function, and intracellular reactive oxygen species (ROS) production, respectively. Expression of oxidant stress relevant factors and OCs specific genes were assessed via real-time quantitative PCR. Further, oxidative stress-related factors, NF-κB, MAPK, PI3K/AKT/GSK3-ß, and NFATc1 pathways were examined via Western blot. Finally, LPS-induced mouse calvarial osteolysis was used to investigate the effect of Alp on inflammatory osteolysis in vivo. RESULT: Alp suppressed OCs differentiation and resorption function, and down-regulated the ROS production. Alp inhibited IL-1ß, TNF-α and osteoclast-specific gene transcription. It also blocked the gene and protein expression of Nox1 and Keap1, but enhanced Nrf2, CAT, and HO-1 protein levels. Additionally, Alp suppressed the phosphorylation of PI3K and P38, and restrained the expression of osteoclast-specific gene Nfatc1 and its auto-amplification, hence minimizing LPS-induced osteolysis in mice. CONCLUSION: Alp is a novel candidate or therapeutics for the osteoclast-associated inflammatory osteolytic ailment.

Corilagin attenuates osteoclastic osteolysis by enhancing HO-1 and inhibiting ROS.

Chinese herbal medicine has well-established therapeutic effects in various diseases. Corilagin (Cor), a gallic acid tannin in Phyllanthus niruri L., has anti-inflammatory and antioxidant effects in many diseases. However, its role in osteoclast-related bone diseases has not been determined. In vitro, bone marrow macrophages (BMMs) were extracted and isolated to differentiate into osteoclasts. The effects of Cor on osteoclast formation, bone resorption, and reactive oxygen species (ROS) production were performed. In addition, quantitative real-time polymerase chain reaction and western blot analysis were used to evaluate the effect of Cor on oxidative stress-related pathways, which are nuclear factors-κB ligand-receptor activator (RANKL) stimulates important downstream pathways. Furthermore, microcomputed tomography and bone histomorphometry were performed to analyze the therapeutic effect of Cor in mouse models of lipopolysaccharide (LPS)-mediated bone defects in vivo. Cor influenced the nuclear factor of activated T cells 1 (NFATc1) signaling pathway and reduced ROS in RANKL-treated osteoclasts, thereby inhibiting osteoclast formation and bone resorption. Moreover, Cor protected against LPS-mediated skull defects in vivo. In sum, our results confirm that Cor can inhibit osteoclastogenesis and intracellular oxidative stress. In addition, the inflammatory bone defect induced by LPS was also attenuated by Cor. Accordingly, Cor is a new candidate therapeutic agent for osteoclast-mediated osteolytic diseases.

Versicotide G suppresses osteoclastogenesis and prevents osteolysis.

Excessive formation and function of osteoclasts cause various osteolytic bone diseases. Natural products are a potential source for the discovery of new therapeutic candidates to treat bone destruction diseases. In this study, chemical informatics and bioassay guided examination of the marine-derived Aspergillus versicolor F77 fungus chemically resulted in the isolation of seven cyclopeptides, of which versicotides G-J (1-4) are new cyclohexapeptides. Their structures were identified by spectroscopic data in association with Marfey method and single crystal X-ray diffraction data for configurational assignments. Bioassay revealed that versicotide G (1, VG) is the most active among the analogs to suppress the receptor activator of nuclear factor-KB ligand (RANKL)-induced osteoclastogenesis in bone marrow derived monocytes (BMMs) without affecting BMMs viability. VG also suppressed RANKL-induced actin-ring formation and resorbing function of osteoclast dose-dependently. Mechanistically, VG attenuated RANKL-induced intracellular calcium elevation by inhibiting PLCγ1 phosphorylation and blocking the activation of downstream phosphatase calcineurin. In addition, VG abrogated the expression and translocation of nuclear factor of activated T cells cytoplasmic-1 (NFATc1), leading to the downregulation of the expression of osteoclast-specific genes and the abolishment of the osteoclast formation. In the in vivo test, VG suppressed osteoclast formation and bone loss in Ti-induced calvarial osteolytic mouse model.These findings imply that VG is a promising candidate for the remedy of bone destruction-related diseases.

The ketone body ß-hydroxybutyrate alleviates CoCrMo alloy particles induced osteolysis by regulating NLRP3 inflammasome and osteoclast differentiation.

BACKGROUND: Aseptic Loosening (AL) following periprosthetic osteolysis is the main long-term complication after total joint arthroplasty (TJA). However, there is rare effective treatment except for revision surgery, which is costly and painful to the patients. In recent years, the ketone body ß-hydroxybutyrate (BHB) has attracted much attention and has been proved to be beneficial in many chronic diseases. With respect to the studies on the ketone body ß-hydroxybutyrate (BHB), its anti-inflammatory ability has been widely investigated. Although the ketone body ß-hydroxybutyrate has been applied in many inflammatory diseases and has achieved considerable therapeutic efficacy, its effect on wear particles induced osteolysis is still unknown. RESULTS: In this work, we confirmed that the anti-inflammatory action of ß-hydroxybutyrate (BHB) could be reappeared in CoCrMo alloy particles induced osteolysis. Mechanistically, the ketone body ß-hydroxybutyrate (BHB) deactivated the activation of NLRP3 inflammasome triggered by CoCrMo alloy particles. Of note, this inhibitory action was independent of Gpr109a receptor as well as histone deacetylase (HDAC) suppression. Furthermore, given that butyrate, one kind of short chain fatty acid (SCFA) structurally related to ß-hydroxybutyrate (BHB), has been reported to be an inhibitor of osteoclast, thus we also investigate the effect of ß-hydroxybutyrate (BHB) on osteoclast, which was contributed to bone resorption. It was found that ß-hydroxybutyrate (BHB) did not only affect osteoclast differentiation, but also inhibit its function. Unlike the inflammasome, the effect of ß-hydroxybutyrate (BHB) on osteoclast may mainly rely on histone deacetylase (HDAC) suppression. CONCLUSIONS: In general, our study showed that the alleviation of osteolysis may owe to the effect of ß-hydroxybutyrate (BHB) on inflammasome deactivation and osteoclast.

Photoluminescent carbon dots (PCDs) from sour apple: a biocompatible nanomaterial for preventing UHMWPE wear-particle induced osteolysis via modulating Chemerin/ChemR23 and SIRT1 signaling pathway and its bioimaging application.

Photoluminescent nanomaterials have been widely employed in several biological applications both in vitro and in vivo. For the first time, we report a novel application of sour apple-derived photoluminescent carbon dots (PCDs) for reducing ultra-high molecular weight polyethylene (UHMWPE) wear particle-induced osteolysis using mouse calvarial model. Generally, aseptic prosthetic loosening seems to be a significant postoperative problem for artificial joints replacement, which is mainly contributed by UHMWPE-induced osteolysis. Hence, inhibiting osteoclastic bone-resorption could minimize UHMWPE-induced osteolysis for implant loosening. Prior to osteolysis studies, the prepared sour apple-derived PCDs were employed for bioimaging application. As expected, the prepared PCDs effectively inhibited the UHMWPE particle-induced osteoclastogenesis in vitro. The PCDs treatment effectively inhibited the UHMWPE-induced osteoclast differentiation, F-actin ring pattern, and bone resorption in vitro. Also, the PCDs reduced the UHMWPE-induced ROS stress as well as the expression level of pro-inflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-8. Further, the qPCR and western blot results hypothesized that PCDs inhibited the UHMWPE wear particle-induced osteolysis through suppressing chemerin/ChemR23 signaling and NFATc1 pathway, along with upregulation of SIRT1 expression. Overall, these findings suggest that the synthesized PCDs could be a potential therapeutic material for minimizing UHMWPE particle-induced periprosthetic osteolysis to avoid postoperative complications.

GSK-3ß suppression upregulates Gli1 to alleviate osteogenesis inhibition in titanium nanoparticle-induced osteolysis.

Wear particle-induced periprosthetic osteolysis (PPO) have become a major reason of joint arthroplasty failure and secondary surgery following joint arthroplasty and thus pose a severe threat to global public health. Therefore, determining how to effectively suppress particle-induced PPO has become an urgent problem. The pathological mechanism involved in the PPO signaling cascade is still unclear. Recently, the interaction between osteogenic inhibition and wear particles at the implant biological interface, which has received increasing attention, has been revealed as an important factor in pathological process. Additionally, Hedgehog (Hh)-Gli1 is a crucial signaling cascade which was regulated by multiple factors in numerous physiological and pathological process. It was revealed to exert a crucial part during embryonic bone development and metabolism. However, whether Hh-Gli1 is involved in wear particle-induced osteogenic inhibition in PPO remains unknown. Our present study explored the mechanism by which the Hh-Gli1 signaling cascade regulates titanium (Ti) nanoparticle-induced osteolysis. We found that Hh-Gli1 signaling was dramatically downregulated upon Ti particle treatment. Mechanistically, glycogen synthesis kinase 3ß (GSK-3ß) activation was significantly increased in Ti particle-induced osteogenic inhibition via changes in GSK-3ß phosphorylation level and was found to participate in the posttranslational modification and degradation of the key transcription factor Gli1, thus decreasing the accumulation of Gli1 and its translocation from the cytoplasm to the nucleus. Collectively, these findings suggest that the Hh-Gli1 signaling cascade utilizes a GSK3ß-mediated mechanism and may serve as a rational new therapeutic target against nanoparticle-induced PPO.

NOX4 blockade suppresses titanium nanoparticle-induced bone destruction via activation of the Nrf2 signaling pathway.

Periprosthetic osteolysis (PPO) triggered by wear particles is the most severe complication of total joint replacement (TJR) surgeries, representing the major cause of implant failure, which is public health concern worldwide. Previous studies have confirmed the specialized role of osteoclast-induced progressive bone destruction in the progression of PPO. Additionally, the reactive oxygen species (ROS) induced by wear particles can promote excessive osteoclastogenesis and bone resorption. Nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), a cellular enzyme, is considered to be responsible for the production of ROS and the formation of mature osteoclasts. However, NOX4 involvement in PPO has not yet been elucidated. Therefore, we investigated the mechanism by which NOX4 regulates osteoclast differentiation and the therapeutic effects on titanium nanoparticle-induced bone destruction. We found that NOX4 blockade suppressed osteoclastogenesis and enhanced the scavenging of intracellular ROS. Our rescue experiment revealed that nuclear factor-erythroid 2-related factor 2 (Nrf2) silencing reversed the effects of NOX4 blockade on ROS production and osteoclast differentiation. In addition, we found increased expression levels of NOX4 in PPO tissues, while NOX4 inhibition in vivo exerted protective effects on titanium nanoparticle-induced osteolysis through antiosteoclastic and antioxidant effects. Collectively, these findings suggested that NOX4 blockade suppresses titanium nanoparticle-induced bone destruction via activation of the Nrf2 signaling pathway and that NOX4 blockade may be an attractive therapeutic approach for preventing PPO.

Piperlongumine Inhibits Titanium Particles-Induced Osteolysis, Osteoclast Formation, and RANKL-Induced Signaling Pathways.

Wear particle-induced aseptic loosening is the most common complication of total joint arthroplasty (TJA). Excessive osteoclast formation and bone resorptive activation have been considered to be responsible for extensive bone destruction and prosthesis failure. Therefore, identification of anti-osteoclastogenesis agents is a potential therapy strategy for the treatment of aseptic loosening and other osteoclast-related osteolysis diseases. In the present study, we reported, for the first time, that piperlongumine (PL), a key alkaloid compound from Piper longum fruits, could significantly suppress the formation and activation of osteoclasts. Furthermore, PL effectively decreased the mRNA expressions of osteoclastic marker genes such as tartrate-resistant acid phosphatase (TRAP), calcitonin receptor (CTR), and cathepsin K (CTSK). In addition, PL suppressed the receptor activator of nuclear factor-κB ligand (RANKL)-induced activations of MAPKs (ERK, JNK and p38) and NF-κB, which down-regulated the protein expression of nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). Using a titanium (Ti) particle-induced calvarial osteolysis model, we demonstrated that PL could ameliorate Ti particle-induced bone loss in vivo. These data provide strong evidence that PL has the potential to treat osteoclast-related diseases including periprosthetic osteolysis (PPO) and aseptic loosening.

The USP14-NLRC5 pathway inhibits titanium particle-induced osteolysis in mice by suppressing NF-κB and PI3K/AKT activities.

Total hip arthroplasty (THA) is a widely-used surgical intervention for treating patients with end-stage degenerative and inflammatory osteoarthropathy. However, wear particles from the artificial titanium joint can induce osteolysis, limiting the long-term survivorship of THA. Monocyte/macrophage lineage cells are the key players in the response to wear particles, and the proinflammatory NF-κB and phosphoinositide 3-kinase (PI3K)-AKT Ser/Thr kinase (AKT)-signaling pathways have been shown to be the most important contributors to wear particle-induced osteolysis. In contrast, ubiquitin-specific protease 14 (USP14) specifically removes the polyubiquitin chains from the nucleotide-binding and oligomerization domain (NOD)-like receptor family Caspase recruitment domain (CARD)-containing 5 (NLRC5) and thereby enhances the NLRC5-mediated inhibition of NF-κB signaling. In this study, we aimed to clarify the role of the USP14-NLRC5 pathway in wear particle-induced osteolysis in vitro and in vivo We found that NLRC5 or USP14 overexpression inhibits titanium particle-induced proinflammatory tumor necrosis factor α (TNFα) production and NF-κB pathway activation, and it also decreases M1 macrophage polarization and PI3K/AKT pathway activation. Of note, NLRC5 and USP14 overexpression attenuated titanium particle-induced cranial osteolysis in mice. In conclusion, the findings of our study indicate that the USP14-NLRC5 pathway inhibits titanium particle-induced osteolysis by suppressing the NF-κB and PI3K/AKT pathways both in vitro and in vivo.

Carnosol suppresses RANKL-induced osteoclastogenesis and attenuates titanium particles-induced osteolysis.

Osteolysis is a common medical condition characterized by excessive activity of osteoclasts and bone resorption, leading to severe poor quality of life. It is essential to identify the medications that can effectively suppress the excessive differentiation and function of osteoclasts to prevent and reduce the osteolytic conditions. It has been reported that Carnosol (Car), isolated from rosemary and salvia, has anti-inflammatory, antioxidative, and anticancer effects, but its activity on osteolysis has not been determined. In this study, we found that Car has a strong inhibitory effect on the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation dose-dependently without any observable cytotoxicity. Moreover, Car can inhibit the RANKL-induced osteoclastogenesis and resorptive function via suppressing NFATc1, which is a result of affecting MAPK, NF-κB and Ca2+ signaling pathways. Moreover, the particle-induced osteolysis mouse model confirmed that Car could be effective for the treatment of bone loss in vivo. Taken together, by suppressing the formation and function of RANKL-induced osteoclast, Car, may be a therapeutic supplementary in the prevention or the treatment of osteolysis.

Naringin inhibits titanium particles-induced up-regulation of TNF-α and IL-6 via the p38 MAPK pathway in fibroblasts from hip periprosthetic membrane.

AIMS: Inflammatory responses to wear debris cause osteolysis that leads to aseptic loosening and hip arthroplasty failure. Wear debris stimulate macrophages and fibroblasts to secret proinflammatory cytokines, including TNF-α and IL-6, which have been specifically implicated in periprosthetic osteolysis and osteoclast differentiation. Naringin has anti-inflammatory effect in macrophages. Moreover, naringin inhibited osteoclastogenesis and wear particles-induced osteolysis. In this study, we examined the potential inhibitory effects of naringin on titanium (Ti) particle-induced proinflammatory cytokines secretion in fibroblasts and the possible underlying molecular mechanisms. MATERIALS AND METHODS: Fibroblasts were isolated from periprosthetic membrane at the time of revision surgery performed due to aseptic loosening after hip arthroplasty and were cultured in the presence or absence of Ti particles, naringin and mitogen-activated protein kinase (MAPK) inhibitors, PD98059 (a selective inhibitor of ERK), SP600125 (a selective inhibitor of JNK), and SB203580 (a selective inhibitor of p38). TNF-α and IL-6 assays were performed using enzyme-linked immunosorbent assay kits. The phosphorylation levels of p38 and nuclear factor kappa B p65 (NF-κB p65) were examined by western blot. RESULTS: Naringin or SB203580 pretreatment significantly suppressed the secretion of TNF-α and IL-6 induced by titanium particles in fibroblasts, while inhibition of ERK or JNK pathways showed no effect on production of TNF-α and IL-6. Moreover, naringin inhibited Ti particle-induced phosphorylation of p38 and p65. CONCLUSIONS: These results indicated that naringin could inhibit Ti particle-induced inflammation in fibroblasts by inhibiting p38 MAPK/NF-κB p65 activity and might be a potential drug for the treatment of inflammatory periprosthetic osteolysis after arthroplasty.

Oridonin ameliorates inflammation-induced bone loss in mice via suppressing DC-STAMP expression.

Currently, dendritic cell-specific transmembrane protein (DC-STAMP), a multipass transmembrane protein, is considered as the master regulator of cell-cell fusion, which underlies the formation of functional multinucleated osteoclasts. Thus, DC-STAMP has become a promising target for osteoclast-associated osteolytic diseases. In this study, we investigated the effects of oridonin (ORI), a natural tetracyclic diterpenoid compound isolated from the traditional Chinese herb Rabdosia  rubescens, on osteoclastogenesis in vivo and ex vivo. ICR mice were injected with LPS (5 mg/kg, ip, on day 0 and day 4) to induce inflammatory bone destruction. Administration of ORI (2, 10 mg·kg-1·d-1, ig, for 8 days) dose dependently ameliorated inflammatory bone destruction and dramatically decreased DC-STAMP protein expression in BMMs isolated from LPS-treated mice. Treatment of preosteoclast RAW264.7 cells with ORI (0.78-3.125 µM) dose dependently inhibited both mRNA and protein levels of DC-STAMP, and suppressed the following activation of NFATc1 during osteoclastogenesis. Knockdown of DC-STAMP in RAW264.7 cells abolished the inhibitory effects of ORI on RANKL-induced NFATc1 activity and osteoclast formation. In conclusion, we show for the first time that ORI effectively attenuates inflammation-induced bone loss by suppressing DC-STAMP expression, suggesting that ORI is a potential agent against inflammatory bone diseases.

Protocatechualdehyde inhibits receptor activator of nuclear factor kappa-B ligand-induced osteoclastogenesis and attenuates lipopolysaccharide-induced inflammatory osteolysis.

Inflammatory osteolysis as a consequence of chronic bacterial infection underlies several lytic bone conditions, such as otitis media, osteomyelitis, septic arthritis, periodontitis, periprosthetic infection, and aseptic loosening of orthopedic implants. In consideration of the lack of effective preventive or treatments options against infectious osteolysis, the exploitation of novel pharmacological compounds/agents is critically required. The present study assessed the effect of protocatechualdehyde (PCA), a natural occurring polyphenolic compound with diverse biological activities including but not limited to antibacterial and antiinflammatory properties, on nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in vitro and lipopolysaccharide (LPS)-induced bone loss in vivo. In the present study, it was found that PCA potently inhibited RANKL-induced osteoclast formation, fusion, and activation toward bone resorption in a dose-dependent manner via the suppression of the ERK/c-Fos/nuclear factor of activated T-cells, cytoplasmic 1 signaling axis. It was further demonstrated that the in vivo administration of PCA could effectively protect mice against the deleterious effects of LPS-induced calvarial bone destruction by attenuating osteoclast formation and activity in a dose-dependent manner. Collectively, these findings provided evidence for the potential therapeutic application of PCA in the prevention and treatment of infectious osteolytic conditions, and potentially other osteoclast-mediated bone diseases.