Bone Resorption Function Research Articles

Isoginkgetin Inhibits RANKL-induced Osteoclastogenesis and Alleviates Bone Loss

Osteoporosis is characterized by excessive osteoclast activity leading to bone loss, decreased bone mineral density, and increased susceptibility to fractures. Through in vivo/vitro experiments, along with network pharmacology analysis, we aimed to explore the underlying mechanisms of Isoginkgetin (IGG) in inhibiting osteoclastogenesis, providing valuable insights for further research in the future. Firstly, we ascertained the safe concentration of IGG stimulation on BMMs, followed by a systematic exploration of the concentration gradient at which IGG inhibited osteoclastogenesis using TRAP analysis. An osteoporosis model was established to further validate the in vitro experimental findings by combining Micro-CT and immunohistochemical analysis. The results show that IGG did not exhibit cytotoxicity or proliferative effects on BMMs at concentrations equal to or less than 10 μM. Additionally, IGG inhibited the activity of osteoclastogenesis and bone resorption function at lower concentrations. RT-PCR and Western Blot results demonstrated that IGG could downregulate genes and proteins associated with osteoclastogenesis. The Western Blot results also showed that IGG inhibited the phosphorylation expression of P38, ERK, and P65 in the MAPK and NF-κB pathways. At the same time, it rescued the degradation of IκB-α at 15 and 60 min. IGG can also impact the relative expression levels of oxidative proteins such as SOD-1, HO-1, and catalase, thereby influencing cellular equilibrium and stress levels, ultimately inhibiting the formation of mature OC. In vivo experiments demonstrated that IGG alleviated bone loss caused by osteoclasts and improved relevant parameters of trabecular bone. So, IGG effectively attenuated osteoclastogenesis, and improved bone density, thereby portraying its role in osteoporosis management.

Damascenone inhibits osteoclastogenesis by epigenetically modulating Nrf2-mediated ROS scavenge and counteracts OVX-induced osteoporosis

BackgroundBone formation and resorption regulate bone homeostasis. Excessive osteoclastogenesis enhances bone resorption and causes osteoporosis. Although medicines targeting osteoclast have been developed, these drugs have several side effects. Natural compounds have advantages in safety and efficiency, making them potential candidates for osteoporosis treatment. PurposeThis study aims to elucidate the role of damascenone (Dama) in osteoclastogenesis and osteoporosis. Study design and methodsTo demonstrate the effect of Dama on osteoclast differentiation and function, we performed multiple in vitro experiments including TRAP staining, F-actin staining, bone slice resorption assay, real-time PCR, and western bolt. Further, ROS detection, network pharmacology, microscale thermophoresis assay, and ChIP assay were conducted to elucidate the underlying molecular mechanism. Finally, the in vivo effects of Dama were verified using an ovariectomy induced osteoporosis mice model. ResultsDama inhibited RANKL-induced osteoclast differentiation and bone resorptive function in vitro. The expression of osteoclast-related genes and activation of MAPKs and NF-κB signaling in osteoclast were also attenuated by Dama. Meanwhile, Dama reduced intracellular ROS level via up-regulating Nrf2 expression. Network pharmacology demonstrated that HDAC2 is the potential direct target of Dama. Dama inhibited HDAC2 function and increased H3K27ac level of Nrf2, which induced Nrf2 expression and activated ROS scavenging enzymes. Inhibiting NRF2 or activating HDAC2 attenuated the effect of Dama on osteoclastogenesis. Finally, Dama injection suppressed in vivo osteoclastogenesis and ameliorated bone loss induced by OVX. ConclusionDama attenuates osteoclastogenesis by epigenetically modulating Nrf2 expression and ROS scavenge. This study provides evidence for Dama being a potential treatment for osteoporosis.

Secreted protein TNA: a promising biomarker for understanding the adipose-bone axis and its impact on bone metabolism

BackgroundOsteoporosis (OP) is a systemic bone disease characterized by reduced bone mass and deterioration of bone microstructure, leading to increased bone fragility. Platelets can take up and release cytokines, and a high platelet count has been associated with low bone density. Obesity is strongly associated with OP, and adipose tissue can influence platelet function by secreting adipokines. However, the biological relationship between these factors remains unclear.MethodsWe conducted differential analysis to identify OP platelet-related plasma proteins. And, making comprehensive analysis, including functional enrichment, protein-protein interaction network analysis, and Friends analysis. The key protein, Tetranectin (TNA/CLEC3B), was identified through screening. Then, we analyzed TNA’s potential roles in osteogenic and adipogenic differentiation using multiple RNA-seq data sets and validated its effect on osteoclast differentiation and bone resorption function through in vitro experiments.ResultsSix OP-platelet-related proteins were identified via differential analysis. Then, we screened the key protein TNA, which was found to be highly expressed in adipose tissue. RNA-seq data suggested that TNA may promote early osteoblast differentiation. In vitro experiments showed that knockdown of TNA expression significantly increased the expression of osteoclast markers, thereby promoting osteoclast differentiation and bone resorption.ConclusionsWe identified TNA as a secreted protein that inhibits osteoclast differentiation and bone resorption. While, it potentially promoted early osteoblast differentiation from bioinformatic results. TNA may play a role in bone metabolism through the adipose-bone axis.

Identification of key biomarkers for early warning of diabetic retinopathy using BP neural network algorithm and hierarchical clustering analysis

Diabetic retinopathy is one of the most common microangiopathy in diabetes, essentially caused by abnormal blood glucose metabolism resulting from insufficient insulin secretion or reduced insulin activity. Epidemiological survey results show that about one third of diabetes patients have signs of diabetic retinopathy, and another third may suffer from serious retinopathy that threatens vision. However, the pathogenesis of diabetic retinopathy is still unclear, and there is no systematic method to detect the onset of the disease and effectively predict its occurrence. In this study, we used medical detection data from diabetic retinopathy patients to determine key biomarkers that induce disease onset through back propagation neural network algorithm and hierarchical clustering analysis, ultimately obtaining early warning signals of the disease. The key markers that induce diabetic retinopathy have been detected, which can also be used to explore the induction mechanism of disease occurrence and deliver strong warning signal before disease occurrence. We found that multiple clinical indicators that form key markers, such as glycated hemoglobin, serum uric acid, alanine aminotransferase are closely related to the occurrence of the disease. They respectively induced disease from the aspects of the individual lipid metabolism, cell oxidation reduction, bone metabolism and bone resorption and cell function of blood coagulation. The key markers that induce diabetic retinopathy complications do not act independently, but form a complete module to coordinate and work together before the onset of the disease, and transmit a strong warning signal. The key markers detected by this algorithm are more sensitive and effective in the early warning of disease. Hence, a new method related to key markers is proposed for the study of diabetic microvascular lesions. In clinical prediction and diagnosis, doctors can use key markers to give early warning of individual diseases and make early intervention.

PTHrP participates in the bone destruction of middle ear cholesteatoma via promoting macrophage differentiation into osteoclasts induced by RANKL.

Progressive bone resorption and destruction is one of the most critical clinical features of middle ear cholesteatoma, potentially leading to various intracranial and extracranial complications. However, the mechanisms underlying bone destruction in middle ear cholesteatoma remain unclear. This study aims to explore the role of parathyroid hormone-related protein (PTHrP) in bone destruction associated with middle ear cholesteatoma. A total of 25 cholesteatoma specimens and 13 normal external auditory canal skin specimens were collected from patients with acquired middle ear cholesteatoma. Immunohistochemical staining was used to detect the expressions of PTHrP, receptor activator for nuclear factor-kappa B ligand (RANKL), and osteoprotegerin (OPG) in cholesteatoma and normal tissues. Tartrate-resistant acid phosphatase (TRAP) staining was used to detect the presence of TRAP positive multi-nucleated macrophages in cholesteatoma and normal tissues. Mono-nuclear macrophage RAW264.7 cells were subjected to interventions, divided into a RANKL intervention group and a PTHrP+ RANKL co-intervention group. TRAP staining was used to detect osteoclast formation in the 2 groups. The mRNA expression levels of osteoclast-related genes, including TRAP, cathepsin K (CTSK), and nuclear factor of activated T cell cytoplasmic 1 (NFATc1), were measured using real-time polymerase chain reaction (real-time PCR) after the interventions. Bone resorption function of osteoclasts was assessed using a bone resorption pit analysis. Immunohistochemical staining showed significantly increased expression of PTHrP and RANKL and decreased expression of OPG in cholesteatoma tissues (all P<0.05). PTHrP expression was significantly positively correlated with RANKL, the RANKL/OPG ratio, and negatively correlated with OPG expression (r=0.385, r=0.417, r=-0.316, all P<0.05). Additionally, the expression levels of PTHrP and RANKL were significantly positively correlated with the degree of bone destruction in cholesteatoma (r=0.413, r=0.505, both P<0.05). TRAP staining revealed a large number of TRAP-positive cells, including multi-nucleated osteoclasts with three or more nuclei, in the stroma surrounding the cholesteatoma epithelium. After 5 days of RANKL or PTHrP+RANKL co-intervention, the number of osteoclasts was significantly greater in the PTHrP+RANKL co-intervention group than that in the RANKL group (P<0.05), with increased mRNA expression levels of TRAP, CTSK, and NFATc1 (all P<0.05). Scanning electron microscopy of bone resorption pits showed that the number (P<0.05) and size of bone resorption pits on bone slices were significantly greater in the PTHrP+RANKL co-intervention group compared with the RANKL group. PTHrP may promote the differentiation of macrophages in the surrounding stroma of cholesteatoma into osteoclasts through RANKL induction, contributing to bone destruction in middle ear cholesteatoma.

Dauricine attenuates ovariectomized-induced bone loss and RANKL-induced osteoclastogenesis via inhibiting ROS-mediated NF-κB and NFATc1 activity

BackgroundOsteoclast plays an important role in maintaining the balance between bone anabolism and bone catabolism. The abnormality of osteoclast is closely related to osteolytic bone diseases such as osteoporosis, rheumatoid arthritis and tumor bone metastasis. PurposeWe aim to search for natural compound that may suppress osteoclast formation and function. Study designIn this study, we assessed the impact of Dauricine (Dau) on the formation and function of osteoclasts in vitro, as well as its potential in preventing bone loss in an ovariectomy mouse model in vivo. MethodsMultiple in vitro experiments were carried out, including osteoclastogenesis, podosomal belt formation, bone resorption assay, RNA-sequencing, real-time quantitative PCR, ROS level detection, surface plasmon resonance assay, luciferase assay and western blot. To verify the effect in vivo, an ovariectomized mouse model (OVX model) was constructed, and bone parameters were measured using micro-CT and histology. Furthermore, metabolomics analysis was performed on blood serum samples from the OVX model. ResultsIn vitro experiments demonstrated that Dau inhibits RANKL-induced osteoclastogenesis, podosomal belt formation, and bone resorption function. RNA-sequencing results revealed that Dau significantly suppresses genes related to osteoclast. Functional enrichment analysis indicated that Dau's inhibition of osteoclasts may be associated with NF-κB signaling pathway and reactive oxygen metabolism pathway. Molecular docking, surface plasmon resonance assay and western blot analysis further confirmed that Dau inhibits RANKL-induced osteoclastogenesis by modulating the ROS/NF-κB/NFATc1 pathway. Moreover, administration of Dau to OVX-induced mice validated its efficacy in treating bone loss disease. ConclusionDau prevents OVX-induced bone loss by inhibiting osteoclast activity and bone resorption, potentially offering a new approach for preventing and treating metabolic bone diseases such as osteoporosis. This study provides innovative insights into the inhibitory effects of Dau in an in vivo OVX model and elucidates the underlying mechanism.

Myeloid-derived suppressor cell-derived osteoclasts with bone resorption capacity in the joints of arthritic SKG mice.

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature myeloid cells with immunosuppressive functions. It is known that MDSCs are expanded at inflammatory sites after migrating from bone marrow (BM) or spleen (Sp). In chronic inflammatory diseases such as rheumatoid arthritis (RA), previous reports indicate that MDSCs are increased in BM and Sp, but detailed analysis of MDSCs in inflamed joints is very limited. The purpose of this study is to characterize the MDSCs in the joints of mice with autoimmune arthritis. We sorted CD11b+Gr1+ cells from joints (Jo), bone marrow (BM) and spleen (Sp) of SKG mice with zymosan (Zym)-induced arthritis and investigated differentially expressed genes (DEGs) by microarray analysis. Based on the identified DEGs, we assessed the suppressive function of CD11b+Gr1+ cells from each organ and their ability to differentiate into osteoclasts. We identified MDSCs as CD11b+Gr1+ cells by flow cytometry and morphological analysis. Microarray analysis revealed that Jo-CD11b+Gr1+ cells had different characteristics compared with BM-CD11b+Gr1+ cells or Sp-CD11b+Gr1+ cells. Microarray and qPCR analysis showed that Jo-CD11b+Gr1+ cells strongly expressed immunosuppressive DEGs (Pdl1, Arg1, Egr2 and Egr3). Jo-CD11b+Gr1+ cells significantly suppressed CD4+ T cell proliferation and differentiation in vitro, which confirmed Jo-CD11b+Gr1+ cells as MDSCs. Microarray analysis also revealed that Jo-MDSCs strongly expressed DEGs of the NF-κB non-canonical pathway (Nfkb2 and Relb), which is relevant for osteoclast differentiation. In fact, Jo-MDSCs differentiated into osteoclasts in vitro and they had bone resorptive function. In addition, intra-articular injection of Jo-MDSCs promoted bone destruction. Jo-MDSCs possess a potential to differentiate into osteoclasts which promote bone resorption in inflamed joints, while they are immunosuppressive in vitro.

The Function and Mechanism of Anti-Inflammatory Factor Metrnl Prevents the Progression of Inflammatory-Mediated Pathological Bone Osteolytic Diseases.

Metrnl, recently identified as an adipokine, is a secreted protein notably expressed in white adipose tissue, barrier tissues, and activated macrophages. This adipokine plays a pivotal role in counteracting obesity-induced insulin resistance. It enhances adipose tissue functionality by promoting adipocyte differentiation, activating metabolic pathways, and exerting anti-inflammatory effects. Extensive research has identified Metrnl as a key player in modulating inflammatory responses and as an integral regulator of muscle regeneration. These findings position Metrnl as a promising biomarker and potential therapeutic target in treating inflammation-associated pathologies. Despite this, the specific anti-inflammatory mechanisms of Metrnl in immune-mediated osteolysis and arthritis remain elusive, warranting further investigation. In this review, we will briefly elaborate on the role of Metrnl in anti-inflammation function in inflammation-related osteolysis, arthritis, and pathological bone resorption, which could facilitate Metrnl's clinical application as a novel therapeutic strategy to prevent bone loss. While the pathogenesis of elbow stiffness remains elusive, current literature suggests that Metrnl likely exerts a pivotal role in its development.

Unveiling the potential of Butylphthalide: inhibiting osteoclastogenesis and preventing bone loss.

Osteoporosis, resulting from overactive osteoclasts and leading to elevated fracture risk, has emerged as a global public health concern due to the aging population. Therefore, inhibiting osteoclastogenesis and bone resorption function represents a crucial approach for preventing and treating osteoporosis. The purpose of this study was to examine the effects and molecular mechanisms of Butylphthalide (NBP) on the differentiation and function of osteoclasts induced by RANKL. Osteoclastogenesis was assessed through TRAP staining and bone slice assay. An animal model that underwent ovariectomy, simulating postmenopausal women's physiological characteristics, was established to investigate the impact of Butylphthalide on ovariectomy-induced bone loss. To delve deeper into the specific mechanisms, we employed Western blot, PCR, immunofluorescence, and immunohistochemical staining to detect the expression of proteins that are associated with the osteoclast signaling pathway. In this study, we found that Butylphthalide not only suppressed osteoclastogenesis and bone resorption in vitro but also significantly decreased TRAcP-positive osteoclasts and prevented bone loss in vivo. Further mechanistic experiments revealed that Butylphthalide reduces intracellular ROS in osteoclasts, inhibits the MAPK and NFATc1 signaling pathways, and downregulates the key genes and proteins of osteoclasts. This inhibits osteoclast formation and function. The reduction in ROS in osteoclasts is intricately linked to the activity of Butylphthalide-modulated antioxidant enzymes. Overall, NBP may offer a alternative treatment option with fewer side effects for skeletal diseases such as osteoporosis.

IL-17 promotes osteoclast-induced bone loss by regulating glutamine-dependent energy metabolism.

Osteoclasts consume an amount of adenosine triphosphate (ATP) to perform their bone resorption function in the development of osteoporosis. However, the mechanism underlying osteoclast energy metabolism has not been fully elucidated. In addition to glucose, glutamine (Glu) is another major energy carrier to produce ATP. However, the role of Glu metabolism in osteoclasts and the related molecular mechanisms has been poorly elucidated. Here we show that Glu is required for osteoclast differentiation and function, and that Glu deprivation or pharmacological inhibition of Glu transporter ASCT2 by V9302 suppresses osteoclast differentiation and their bone resorptive function. In vivo treatment with V9302 improved OVX-induced bone loss. Mechanistically, RNA-seq combined with in vitro and in vivo experiments suggested that Glu mediates the role of IL-17 in promoting osteoclast differentiation and in regulating energy metabolism. In vivo IL-17 treatment exacerbated OVX-induced bone loss, and this effect requires the participation of Glu or its downstream metabolite α-KG. Taken together, this study revealed a previously unappreciated regulation of IL-17 on energy metabolism, and this regulation is Glu-dependent. Targeting the IL-17-Glu-energy metabolism axis may be a potential therapeutic strategy for the treatment of osteoporosis and other IL-17 related diseases.

VSIG4 inhibits RANKL-induced osteoclastogenesis by enhancing Nrf2-dependent antioxidant response against reactive oxygen species production

Osteoporosis is a prevalent systemic skeletal disorder, particularly affecting postmenopausal women, primarily due to excessive production and activation of osteoclasts. However, the current anti-osteoporotic drugs utilized in clinical practice may lead to certain side effects. Therefore, it is necessary to further unravel the potential mechanisms regulating the osteoclast differentiation and to identify novel targets for osteoporosis treatment. This study revealed the most significant decline in VSIG4 expression among the VSIG family members. VSIG4 overexpression significantly inhibited RANKL-induced osteoclastogenesis and bone resorption function. Mechanistically, both western blot and immunofluorescence assay results demonstrated that VSIG4 overexpression attenuated the expression of osteoclast marker genes and dampened the activation of MAPK and NF-κB signaling pathways. Furthermore, VSIG4 overexpression could inhibit the generation of reactive oxygen species (ROS) and stimulate the expression of Nrf2 along with its downstream antioxidant enzymes via interaction with Keap1. Notably, a potent Nrf2 inhibitor, ML385, could reverse the inhibitory effect of VSIG4 on osteoclast differentiation. In line with these findings, VSIG4 overexpression also mitigated bone loss induced by OVX and attenuated the activation of osteoclasts in vivo. In conclusion, our results suggest that VSIG4 holds promise as a novel target for addressing postmenopausal osteoporosis. This is achieved by suppressing osteoclast formation via enhancing Nrf2-dependent antioxidant response against reactive oxygen species production.

Artemisinic acid attenuates osteoclast formation and titanium particle-induced osteolysis via inhibition of RANKL-induced ROS accumulation and MAPK and NF-κB signaling pathways.

Periprosthetic osteolysis (PPO) is the most common cause of joint arthroplasty failure. Its progression involves both biological and mechanical factors. Osteoclastogenesis induced by wear from debris-cell interactions, ultimately leading to excessive bone erosion, is considered the primary cause of PPO; therefore, targeting osteoclasts is a promising treatment approach. Currently available drugs have various side effects and limitations. Artemisinic acid (ArA) is a sesquiterpene isolated from the traditional herb Artemisia annua L. that has various pharmacological effects, such as antimalarial, anti-inflammatory, and antioxidant activities. Therefore, this study was aimed at investigating the effect of ArA on osteoclast formation and bone resorption function in vitro, as well as wear particle-induced osteolysis in vivo, and to explore its molecular mechanism of action. Here, we report that ArA inhibits RANKL-stimulated osteoclast formation and function. Mechanistically, ArA suppresses intracellular reactive oxygen species levels by activating the antioxidant response via nuclear factor erythroid-2-related factor 2 (Nrf2) pathway upregulation. It also inhibits the mitogen-activated kinases (MAPK) and nuclear factor-κB (NF-κB) pathways, as well as the transcription and expression of NFATc1 and c-Fos. In vivo experiments demonstrated that ArA reduces osteoclast formation and alleviates titanium particle-induced calvarial osteolysis. Collectively, our study highlights that ArA, with its osteoprotective and antioxidant effects, is a promising therapeutic agent for preventing and treating PPO and other osteoclast-mediated osteolytic diseases.

Urolithin A attenuates osteoclast differentiation and compensates for ovariectomy-induced bone loss in mice by inhibiting PI3K/AKT/mTOR signaling pathway

Backgrounds and purposesOsteoporosis (OP) is a debilitating illness distinguished by a reduction in bone density and microstructure, which leads to fragility, fracture risk, and increased mortality, particularly in the elderly and postmenopausal women. Growing evidence suggests that various plant derivatives could be a potential therapy for osteoporosis. Ellagic acid is a phenolic found naturally in extracts from plants such as pomegranate, blackberry and berry. In earlier research, ellagic acid (EA) was reported to have certain benefits on osteoporosis, however, EA was limited by its weak bioactivity. Urolithin A (UA), an ellagic acid metabolite present in the intestinal bacteria, which had a greater bioavailability. However, its therapeutic effects and mechanisms in osteoporosis remain to be explored. Study designIn this work, we explored about how UA affected the molecular processes of osteoclasts differentiation in vitro. We also performed the ovariectomy-induced osteoporotic mice model in order to evaluate how UA impacted the bone loss of osteoporosis. Methods1. TRAP staining analysis to examine the impact of UA on osteoclast differentiation. 2. RT-PCR for evaluating UA's impact on the expression of genes relevant to osteoclasts. Bone resorption experiment and scan by electron microscope in order to determine the impact of UA on osteoclast function. 3.Using western blotting, investigate the impact of UA on the osteoclast differentiation-related signaling pathway. 4. Developed an osteoporosis mouse model for evaluating the preventative impact of UA on bone loss after an ovariectomy. Results1. UA reduced osteoclast development in a dosage manner without cytotoxicity. 2. UA suppresses osteoclast-related gene expression as well as the function of osteoclast bone resorption. 3. UA regulates osteoclast development by decreasing PI3K/AKT/mTOR signaling pathway phosphorylation as well as Nfatc1 transcription and translation. 4. Animal study demonstrated that UA reduced bone loss in ovariectomy-induced osteoporotic mice. ConclusionUA reduced the development and bone resorption function of osteoclast, was shown as inhibiting expression of osteoclast-associated specific genes as well as the PI3K/AKT/mTOR signaling pathway and decreasing Nfatc1 expression. In vivo, UA prevented bone loss in ovariectomy-induced osteoporotic mice. Finally, UA shown tremendous promise in the prevention and treatment of osteoporosis.

Conditional knockout of PDK1 in osteoclasts suppressed osteoclastogenesis and ameliorated prostate cancer-induced osteolysis in murine model

BackgroundThe development and maintenance of normal bone tissue is maintained by balanced communication between osteoblasts and osteoclasts. The invasion of cancer cells disrupts this balance, leading to osteolysis. As the only bone resorbing cells in vivo, osteoclasts play important roles in cancer-induced osteolysis. However, the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1) in osteoclast resorption remains unclear.MethodsIn our study, we used a receptor activator of nuclear factor-kappa B (RANK) promoter‐driven Cre‐LoxP system to conditionally delete the PDK1 gene in osteoclasts in mice. We observed the effect of osteoclast‐specific knockout of PDK1 on prostate cancer-induced osteolysis. Bone marrow-derived macrophage cells (BMMs) were extracted and induced to differentiate osteoclasts in vitro to explore the role of PDK1 in osteoclasts.ResultsIn this study, we found that PDK1 conditional knockout (cKO) mice exhibited smaller body sizes when compared to the wild-type (WT) mice. Moreover, deletion of PDK1 in osteoclasts ameliorated osteolysis and rPDK1educed bone resorption markers in the murine model of prostate cancer-induced osteolysis. In vivo, we discovered that osteoclast‐specific knockout of suppressed RANKL-induced osteoclastogenesis, bone resorption function, and osteoclast-specific gene expression (Ctsk, TRAP, MMP-9, NFATc1). Western blot analyses of RANKL-induced signaling pathways showed that conditional knockout of PDK1 in osteoclasts inhibited the early nuclear factor κB (NF-κB) activation, which consequently suppressed the downstream induction of NFATc1.ConclusionThese findings demonstrated that PDK1 performs an important role in osteoclastogenesis and prostate cancer-induced osteolysis by modulating the PDK1/AKT/NF-κB signaling pathway.

Icaritin ameliorates RANKL-mediated osteoclastogenesis and ovariectomy-induced osteoporosis.

A rapidly aging society and longer life expectancy are causing osteoporosis to become a global epidemic. Over the last five decades, a number of drugs aimed at reducing bone resorption or restoring bone mass have been developed, but their efficacy and safety are limited. Icaritin (ICT) is a natural compound extracted from anti-osteoporosis herb Epimedium spp. and has been shown to inhibit osteoclast differentiation. However, the molecular mechanism by which ICT weaken RANKL-induced osteoclast differentiation has not been completely investigated. Here, we evaluated the anti-osteoclastogenic effect of ICT in vitro and the potential drug candidate for treating osteoporosis in vivo. In vitro study, ICT was found to inhibit osteoclast formation and bone resorption function via downregulating transcription factors activated T cell cytoplasm 1 (NFATc1) and c-fos, which further downregulate osteoclastogenesis-specific gene. In addition, the enhanced mitochondrial mass and function required for osteoclast differentiation was mitigated by ICT. The histomorphological results from an in vivo study showed that ICT attenuated the bone loss associated with ovariectomy (OVX). Based on these results, we propose ICT as a promising new drug strategy for osteoporosis that inhibits osteoclast differentiation.

Euonymus alatus (Thunb.) Siebold Prevents Osteoclast Differentiation and Osteoporosis.

Euonymus alatus (Thunb.) Siebold, a traditional medicinal plant, has been used in China and several other Asian countries to address a variety of health concerns. The extensive research conducted on E. alatus is driven by its diverse pharmacological applications. However, its biological effects on osteoclastogenesis and osteoporosis have not been previously studied. In this research, we investigated the impact of an ethanolic extract of E. alatus (EEEA) on osteoclast differentiation and function as well as estrogen deficiency-induced bone loss. We found that EEEA inhibits osteoclast differentiation by downregulating the expression of the receptor activator of nuclear factor-κB ligand (RANKL) in osteoclast-supporting cells and by directly impeding RANKL-mediated signaling pathways for osteoclastogenesis in precursor cells. In addition, EEEA inhibited the bone-resorptive function of mature osteoclasts in vitro. Furthermore, oral administration of EEEA significantly alleviated bone loss in an ovariectomy-induced osteoporosis mouse model. Additionally, we identified phytochemicals in EEEA that have suppressive effects on osteoclast differentiation and bone loss. Collectively, these results suggest that EEEA holds potential as a biotherapeutic candidate for anti-postmenopausal osteoporosis.

Anemoside B4 attenuates RANKL-induced osteoclastogenesis by upregulating Nrf2 and dampens ovariectomy-induced bone loss

Increased numbers and functional overactivity of osteoclasts are the pathological basis for bone loss diseases such as osteoporosis, which are characterized by cortical bone thinning, decreased trabecular bone quantity, and reduced bone mineral density. Effective inhibition of osteoclast formation and bone resorption are important means of treating such skeletal diseases. Anemoside B4 (AB4), the main active component of Pulsatilla chinensis, possesses a wide range of anti-inflammatory and immunoregulatory effects. However, its effect and mechanism in osteoclast differentiation remain unclear. In this study, we found through tartrate-resistant acidic phosphatase (TRAcP) staining and immunofluorescence staining that AB4 inhibited the differentiation, fusion, and bone-resorption functions of osteoclasts induced by receptor activator of nuclear factor κB ligand (RANKL) in vitro. Additionally, real time PCR (RT-qPCR) and western blot analysis showed AB4 downregulated the expression of osteoclast marker genes, including Nfatc1, Fos, and Ctsk, while upregulating Nrf2 expression. AB4 (5 mg/kg) alleviated bone loss in ovariectomized mice by inhibiting osteoclast formation. Furthermore, the knockout of Nrf2 weakened the inhibitory effects of AB4 on osteoclast formation and related gene expression. In summary, the results suggest AB4 can inhibit osteoclast differentiation and function by activating Nrf2 and indicate AB4 may be a candidate drug for osteoporosis.

Anti-osteoporosis mechanism of resistance exercise in ovariectomized rats based on transcriptome analysis: a pilot study.

Postmenopausal osteoporosis is the main cause of fractures in women.Resistance exercise has a positive effect on bone mineral density in postmenopausal osteoporosis patients, but its mechanism is unclear.The purpose of this study was to explore the mechanism of resistance exercise in improving ovariectomized osteoporotic rats based on the transcriptome sequencing technique. Eighteen female Sprague-Dawley rats were randomly divided into the sham-operated group, the non-exercise group, and the resistance exercise group.The rat model of postmenopausal osteoporosis was established by bilateral ovariectomy.Ten weeks after the operation, the resistance exercise group received 2 weeks of adaptive training, and 12 weeks of resistance exercise began in the 13th week.The rats were trained 5 days per week, in 4 sets of 3 repetitions per day.After the intervention, all rats were sacrificed, and the body weight, bone mineral density, trabecular bone microarchitecture, and bone biomechanics were examined.At the same time, RNA-seq and enrichment analysis of gene ontology and Kyoto Encyclopedia of Genes and Genomes were performed on the left tibias, followed by Elisa and RT-qPCR verification. It had been found that resistance exercise can effectively counteract the weight gain of ovariectomized osteoporotic rats, and has a good effect on bone mineral density and trabecular bone microarchitecture. Enrichment analysis showed that regulation of gene expression and osteoclast differentiation is the most closely related biological process and signaling pathway shared by RE/Ovx and NE/Ovx groups. Our results revealed that resistance exercise can play a role in inhibiting osteoclast activation and preventing the enhancement of osteoclast bone resorption function in ovariectomized osteoporotic rats by inhibiting Fos/Fosb-regulated TRAP activation and relieving Calcr inhibition, which has important application value in preventing bone loss caused by estrogen deficiency.

Time-resolved molecular measurements reveal changes in astronauts during spaceflight.

From the early days of spaceflight to current missions, astronauts continue to be exposed to multiple hazards that affect human health, including low gravity, high radiation, isolation during long-duration missions, a closed environment and distance from Earth. Their effects can lead to adverse physiological changes and necessitate countermeasure development and/or longitudinal monitoring. A time-resolved analysis of biological signals can detect and better characterize potential adverse events during spaceflight, ideally preventing them and maintaining astronauts' wellness. Here we provide a time-resolved assessment of the impact of spaceflight on multiple astronauts (n = 27) by studying multiple biochemical and immune measurements before, during, and after long-duration orbital spaceflight. We reveal space-associated changes of astronauts' physiology on both the individual level and across astronauts, including associations with bone resorption and kidney function, as well as immune-system dysregulation.

Activation of NLRP3 signaling contributes to cadmium-induced bone defects, associated with autophagic flux obstruction

Cadmium (Cd) is a widespread environmental and industrial pollutant to cause various bone metabolic diseases. Our former study reported that Cd promoted adipogenesis and inhibited osteogenic differentiation of primary bone marrow-derived mesenchymal stem cells (BMSCs) by NF-κB inflammation signaling and oxidative stress, and Cd-induced osteoporosis of long bone and compromised repair of cranial bone defect in vivo. However, the underlying mechanisms of Cd-induced bone damage remain elusive. In this study, we used Sprague Dawley (SD) rat and NLRP3-knockout mouse models to elucidate the exact effects and molecular mechanisms of Cd-induced bone damage and aging. Herein we found that the exposure of Cd preferentially targeted a few specific tissues such as bone and kidney. Cd triggered NLRP3 inflammasome pathways and the accumulation of autophagosomes of primary BMSCs, and also Cd stimulated the differentiation and bone resorption function of primary osteoclasts. Moreover, Cd not only activated ROS/NLRP3/caspase-1/p20/IL-1β pathways, but also influenced Keap1/Nrf2/ARE signaling. The data revealed that autophagy dysfunction and NLRP3 pathways synergistically mediated the impairments of Cd in bone tissues. Loss of NLRP3 function partially alleviated Cd-induced osteoporosis and craniofacial bone defect in the NLRP3-knockout mouse model. Furthermore, we characterized the protective effects and potential therapeutic targets of the combined treatment of anti-aging agents (rapamycin+melatonin+NLRP3 selective inhibitor MCC950) on Cd-induced bone damage and inflammatory aging. These results illuminate that ROS/NLRP3 pathways and autophagic flux obstruction are involved in the Cd-induced toxic actions of bone tissues. Collectively, our study unveils some therapeutic targets and the regulatory mechanism to prevent Cd-caused bone rarefaction. The findings improve the mechanistic understanding of environmental Cd exposure-caused bone metabolism disorders and tissue damage.