Zoledronate and high glucose levels influence osteoclast differentiation and bone absorption via the AMPK pathway

Integrated phytochemistry and network pharmacology analysis to reveal effective substances and mechanisms of Bushen Quhan Zhiwang decoction in the treatment of rheumatoid arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Bushen Quhan Zhiwang decoction (BQZD), a formula in traditional Chinese medicine (TCM), effectively delays bone destruction in rheumatoid arthritis (RA) patients. However, its chemical constituents, absorbed components, and metabolites remain unrevealed, and its mechanism in treating bone destruction in RA needs further investigation.

AIM OF THE STUDY

Our objective is to identify the chemical constituents, absorbed components, and metabolites of BQZD and explore the potential mechanisms of BQZD in treating bone destruction in RA.

MATERIALS AND METHODS

This study systematically identified the chemical constituents, absorbed components, and metabolites of BQZD using ultra-performance liquid chromatography with Q-Exactive Orbitrap mass spectrometry combined with parallel reaction monitoring. The absorbed components and metabolites were subjected to network pharmacology analysis to predict the potential mechanisms of BQZD in treating bone destruction in RA. The in vivo anti-osteoclastogenic and underlying mechanism were further verified in collagen-induced arthritis (CIA) rats.

RESULTS

A total of 182 compounds were identified in BQZD, 27 of which were absorbed into plasma and organs and 42 metabolites were identified in plasma and organs. The KEGG analysis revealed that MAPK signaling pathway was highly prioritized. BQZD treatment attenuated paw swelling and the arthritis index; suppressed synovial hyperplasia, bone destruction, and osteoclast differentiation; and inhibited the levels of TNF-α, IL-1β, and IL-6 in CIA rats. Mechanically, BQZD significantly decreased the protein expression levels of TRAF6, NFATc1, p-JNK, and p-p38, which might be related to 9 absorbed components and 1 metabolite.

CONCLUSION

This study revealed the key active components and metabolites of BQZD. BQZD exhibits bone-protective effects via TRAF6/p38/JNK MAPK pathway, which may be associated with 9 absorbed components and 1 metabolite.

Effect of a single dose of zoledronic acid on bone mineral density and trabecular bone score in Indian postmenopausal osteoporotic women with and without type 2 diabetes mellitus - A prospective cohort pilot study

PURPOSE

The objectives were to study the effect of a single dose of intravenous (IV) zoledronic acid (ZA) on changes in bone mineral density (BMD) (lumbar spine (LS), hip, & distal forearm), trabecular bone score (TBS) and bone turnover markers (BTMs) in postmenopausal osteoporotic women with and without diabetes over 12 months.

METHODS

Patients were divided into two groups: type 2 diabetes mellitus (T2DM) (n = 40) and non-DM (n = 40). Both groups received a single dose of 4 mg IV ZA at baseline. The BMD with TBS and BTMs (β-CTX, sclerostin, P1NP) were measured at baseline, six months, and 12 months.

RESULTS

At baseline, BMD in all three sites was similar in both groups. T2DM patients were older and had lower BTMs than non-DM patients. The mean increase in LS-BMD (gram/cm2) at 12 months in T2DM and the non-DM group was 3.6 ± 4.7% and 6.2 ± 4.7 %, respectively (P = 0.01). However, the age adjusted mean difference in LS BMD increment between two groups at one year was - 2.86 % (-5.02% to -0.69%), P = 0.01. There was a comparable change in BMD at other two sites, BTMs, and TBS in both the groups over one year follow-up.

CONCLUSION

The gain in the LS-BMD was significantly lower in T2DM group compared to non-DM subjects over 12 months after a single IV infusion of 4 mg ZA. The explanation for this could be low bone turnover in diabetes subjects at baseline.

Zoledronate Promotes Peri-Implant Osteogenesis in Diabetic Osteoporosis by the AMPK Pathway

Together with diabetic osteoporosis (DOP), diabetes patients experience poor peri-implant osteogenesis following implantation for dentition defects. Zoledronate (ZOL) is widely used to treat osteoporosis clinically. To evaluate the mechanism of ZOL for the treatment of DOP, experiments with DOP rats and high glucose-grown MC3T3-E1 cells were used. The DOP rats treated with ZOL and/or ZOL implants underwent a 4-week implant-healing interval, and then microcomputed tomography, biomechanical testing, and immunohistochemical staining were performed to elucidate the mechanism. In addition, MC3T3-E1 cells were maintained in an osteogenic medium with or without ZOL to confirm the mechanism. The cell migration, cellular actin content, and osteogenic differentiation were evaluated by a cell activity assay, a cell migration assay, as well as alkaline phosphatase, alizarin red S, and immunofluorescence staining. The mRNA and protein expression of adenosine monophosphate-activated protein kinase (AMPK), phosphorylated AMPK (p-AMPK), osteoprotegerin (OPG), receptor activator of nuclear factor kappa B ligand (RANKL), bone morphogenetic protein 2 (BMP2), and collagen type I (Col-I) were detected using real-time quantitative PCRs and western blot assays, respectively. In the DOP rats, ZOL markedly improved osteogenesis, enhanced bone strength and increased the expression of AMPK, p-AMPK, and Col-I in peri-implant bones. The in vitro findings showed that ZOL reversed the high glucose-induced inhibition of osteogenesis via the AMPK signaling pathway. In conclusion, the ability of ZOL to promote osteogenesis in DOP by targeting AMPK signaling suggests that therapy with ZOL, particularly simultaneous local and systemic administration, may be a unique approach for future implant repair in diabetes patients.

mTOR Signaling Pathway in Bone Diseases Associated with Hyperglycemia

The interplay between bone and glucose metabolism has highlighted hyperglycemia as a potential risk factor for bone diseases. With the increasing prevalence of diabetes mellitus worldwide and its subsequent socioeconomic burden, there is a pressing need to develop a better understanding of the molecular mechanisms involved in hyperglycemia-mediated bone metabolism. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that senses extracellular and intracellular signals to regulate numerous biological processes, including cell growth, proliferation, and differentiation. As mounting evidence suggests the involvement of mTOR in diabetic bone disease, we provide a comprehensive review of its effects on bone diseases associated with hyperglycemia. This review summarizes key findings from basic and clinical studies regarding mTOR's roles in regulating bone formation, bone resorption, inflammatory responses, and bone vascularity in hyperglycemia. It also provides valuable insights into future research directions aimed at developing mTOR-targeted therapies for combating diabetic bone diseases.

Annexin A2 Improves the Osteogenic Differentiation of Mesenchymal Stem Cells Exposed to High-Glucose Conditions through Lessening the Senescence

Osteoporosis is frequently found in chronic diabetic patients, and it results in an increased risk of bone fractures occurring. The underlying mechanism of osteoporosis in diabetic patients is still largely unknown. Annexin A2 (ANXA2), a family of calcium-binding proteins, has been reported to be involved in many biological process including bone remodeling. This study aimed to investigate the role of ANXA2 in mesenchymal stem cells (MSCs) during in vitro osteoinduction under high-glucose concentrations. Osteogenic gene expression, calcium deposition, and cellular senescence were determined. The high-glucose conditions reduced the osteogenic differentiation potential of the MSCs along with the lower expression of ANXA2. Moreover, the high-glucose conditions increased the cellular senescence of the MSCs as determined by senescence-associated β-galactosidase staining and the expression of p16, p21, and p53 genes. The addition of recombinant ANXA2 could recover the glucose-induced deterioration of the osteogenic differentiation of the MSCs and ameliorate the glucose-induced cellular senescence of the MSCs. A Western blot analysis revealed an increase in p53 and phosphorylated p53 (Ser 15), which was decreased by recombinant ANXA2 in MSC osteoblastic differentiation under high-glucose conditions. Our study suggested that the alteration of ANXA2 in high-glucose conditions may be one of the plausible factors in the deterioration of bones in diabetic patients by triggering cellular senescence.

Zoledronate promotes osteoblast differentiation in high-glucose conditions via the p38MAPK pathway

Zoledronate (ZOL) were found to inhibit bone resorption in an animal model of diabetes, high glucose concentrations have been shown to decreased the osteogenesis-related gene expression. But the molecular mechanism by which high glucose levels affect osteoblasts and the effects of ZOL on osteoblast differentiation in a high-glucose environment remain unclear. Therefore, we aimed to investigate the effect of ZOL on osteoblast differentiation in a high-glucose environment and determine the responsible mechanism. Cell proliferation was detected by MTT assay, and cell differentiation was evaluated by immunofluorescence staining for alkaline phosphatase expression, alizarin red staining, cytoskeletal arrangement, and actin fiber formation. Real-time PCR and western blot analyses were performed to detect the mRNA and protein expression of p38MAPK, phosphorylated (p)-p38MAPK, CREB, p-CREB, collagen (COL) I, osteoprotegerin (OPG), and RANKL. The results showed that cell proliferation activity did not differ among the groups. But high glucose inhibited osteoblast differentiation; actin fiber formation; and p38MAPK, p-p38MAPK, CREB, p-CREB, COL I, and OPG expression, while promoting RANKL expression. However, we found that treatment with ZOL reversed these effects of high glucose. And further addition of a p38MAPK inhibitor led to inhibition of osteoblast differentiation and actin fiber formation, and lower p38MAPK, p-p38MAPK, CREB, p-CREB, COL I, and OPG expression than in the high glucose +ZOL group with higher RANKL expression than in the high glucose +ZOL group. Collectively, this study demonstrates that high glucose inhibits the differentiation of osteoblasts, and ZOL could partly overcome these effects by regulating p38MAPK pathway activity.

The role of circadian rhythm in osteoporosis; a review

Osteoporosis is characterized by a high incidence rate, with significant effects on people’s lives. The underlying mechanisms are complex, with no treatments for the condition. Recent studies have indicated that melatonin can be used to treat osteoporosis by promoting osteoblast proliferation and differentiation, and inhibiting osteoclast differentiation. Specifically, in vivo mechanisms are initiated by stabilizing biological rhythms in bone tissue. In healthy organisms, these biological rhythms are present in bone tissue, and are characterized by bone formation during the day, and bone resorption at night. When this rhythm is disrupted, osteoporosis occurs. Thus, taking appropriate medication at different times of the day could produce different effects on osteoporosis rhythms. In this review, we characterized these processes, and provided treatments and management strategies for individuals with osteoporosis.

How zoledronic acid improves osteoporosis by acting on osteoclasts

Osteoporosis is called a silent disease, because it is difficult to detect until comprehensive examinations for osteoporosis are performed or osteoporotic fractures occur. Zoledronic acid is currently the first-line anti-osteoporotic drug, with good efficacy and treatment compliance. A major advantage of zoledronic acid is that intravenous zoledronic acid often guarantees a therapeutic effect for up to 1 year after infusion. The reasons why zoledronic acid is effective in improving osteoporosis are that it can inhibit osteoclast differentiation and induce osteoclast apoptosis, thus suppressing bone resorption and increasing bone density. The story between zoledronic acid and osteoclasts has been written long time ago. Both the canonical receptor activator of the receptor activator of nuclear factor-κB ligand (RANKL) pathway and the non-canonical Wnt pathway are the main pathways by which zoledronic acid inhibits osteoclast differentiation. Farnesyl pyrophosphate synthase (FPPS), reactive oxygen species (ROS), and ferroptosis that was first proposed in 2012, are all considered to be closely associated with zoledronic acid-induced osteoclast apoptosis. Here, we provide a brief review of the recent progress on the study of zoledronic acid and osteoclasts, and hope to elaborate how zoledronic acid improves osteoporosis by acting on osteoclasts.

Network pharmacology-based strategy for predicting therapy targets of Sanqi and Huangjing in diabetes mellitus

BACKGROUND

A comprehensive literature search shows that Sanqi and Huangjing (SQHJ) can improve diabetes treatment in vivo and in vitro, respectively. However, the combined effects of SQHJ on diabetes mellitus (DM) are still unclear.

AIM

To explore the potential mechanism of Panax notoginseng (Sanqi in Chinese) and Polygonati Rhizoma (Huangjing in Chinese) for the treatment of DM using network pharmacology.

METHODS

The active components of SQHJ and targets were predicted and screened by network pharmacology through oral bioavailability and drug-likeness filtration using the Traditional Chinese Medicine Systems Pharmacology Analysis Platform database. The potential targets for the treatment of DM were identified according to the DisGeNET database. A comparative analysis was performed to investigate the overlapping genes between active component targets and DM treatment-related targets. We constructed networks of the active component-target and target pathways of SQHJ using Cytoscape software and then analyzed the gene functions. Using the STRING database to perform an interaction analysis among overlapping genes and a topological analysis, the interactions between potential targets were identified. Gene Ontology (GO) function analyses and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were conducted in DAVID.

RESULTS

We screened 18 active components from 157 SQHJ components, 187 potential targets for active components and 115 overlapping genes for active components and DM. The network pharmacology analysis revealed that quercetin, beta-sitosterol, baicalein, etc. were the major active components. The mechanism underlying the SQHJ intervention effects in DM may involve nine core targets (TP53, AKT1, CASP3, TNF, interleukin-6, PTGS2, MMP9, JUN, and MAPK1). The screening and enrichment analysis revealed that the treatment of DM using SQHJ primarily involved 16 GO enriched terms and 13 related pathways.

CONCLUSION

SQHJ treatment for DM targets TP53, AKT1, CASP3, and TNF and participates in pathways in leishmaniasis and cancer.

Porphyromonas gingivalis Induces Bisphosphonate-Related Osteonecrosis of the Femur in Mice

One of the most prominent characteristics of bisphosphonate-related osteonecrosis of the jaw(BRONJ) is its site-specificity. Osteonecrosis tends to occur specifically in maxillofacial bones, in spite of a systemic administration of the medicine. Previous studies suggested rich blood supply and fast bone turnover might be reasons for BRONJ. Yet, a sound scientific basis explaining its occurrence is still lacking. The present study aimed to explore the role of Porphyromonas gingivalis (P. gingivalis), an important oral pathogen, on the site-specificity of bisphosphonate-induced osteonecrosis and to elucidate its underlying mechanism. Mice were intraperitoneally injected with zoledronic acid (ZA) or saline for 3 weeks. In the third week, the right mandibular first molars were extracted and circular bone defects with a diameter of 1 mm were created in right femurs. After the operation, drug administration was continued, and P. gingivalis suspension was applied to the oral cavities and femur defects. The mice were killed after four or eight weeks postoperatively. The right mandibles and femurs were harvested for micro-CT and histological analyses. A poor healing of bone defects of both jaws and femurs was noted in mice injected with both ZA and P. gingivalis. Micro-CT analysis showed a decreased bone volume, and histological staining showed an increased number of empty osteocyte lacunae, a decreased collagen regeneration, an increased inflammatory infiltration and a decreased number of osteoclasts. In addition, the left femurs were collected for isolation of osteoclast precursors (OCPs). The osteoclastogenesis potential of OCPs was analyzed in vitro. OCPs extracted from mice of ZA-treated groups were shown to have a lower osteoclast differentiation potential and the expression level of related genes and proteins was declined. In conclusion, we established a mouse model of bisphosphonate-related osteonecrosis of both the jaw and femur. P. gingivalis could inhibit the healing of femur defects under the administration of ZA. These findings suggest that P. gingivalis in the oral cavity might be one of the steering compounds for BRONJ to occur.

Effects of Type 2 Diabetes Mellitus on Osteoclast Differentiation, Activity, and Cortical Bone Formation in POSTmenopausal MRONJ Patients

Osteoporosis is a common metabolic bone disease in patients with diabetes, which can develop simultaneously with type 2 diabetes (T2D) in postmenopausal women. Bisphosphonate (BP) is administered to patients with both conditions and may cause medication-related osteonecrosis of the jaw (MRONJ). It affects the differentiation and function of osteoclasts as well as the thickness of the cortical bone through bone mineralization. Therefore, this study aimed to investigate the effects of T2D on osteoclast differentiation and activity as well as cortical bone formation in postmenopausal patients with MRONJ. Tissue samples were collected from 10 patients diagnosed with T2D and stage III MRONJ in the experimental group and from 10 patients without T2D in the control group. A histological examination was conducted, and the expression of dendritic cell-specific transmembrane protein (DC-STAMP) and tartrate-resistant acid phosphatase (TRAP) was assessed. Cortical bone formation was analyzed using CBCT images. The number of TRAP-positive osteoclasts and DC-STAMP-positive mononuclear cells was significantly less in the experimental group (p < 0.05). Furthermore, the thickness and ratio of cortical bone were significantly greater in the experimental group (p < 0.05). In conclusion, T2D decreased the differentiation and function of osteoclasts and increased cortical bone formation in postmenopausal patients with MRONJ.

Elevated lncRNA MIAT in peripheral blood mononuclear cells contributes to post-menopausal osteoporosis

Inflammatory cytokines contribute to the development of osteoporosis with sophisticated mechanisms. Globally alteration of long-chain non-coding RNA was screened in osteoporosis, while we still know little about their functional role in the inflammatory cytokine secretion. In this study, we collected the peripheral blood mononuclear cells (PBMCs) from post-menopausal osteoporosis patients to measure lncRNA MIAT (lncMIAT) expression levels, and explored the molecular mechanism of lncMIAT induced inflammatory cytokine secretion. We identified increased lncMIAT expression in the PBMCs of post-menopausal osteoporosis patients, which was an important predictive biomarker for the diagnosis. LncMIAT expression in PBMCs was positively correlated with the inflammatory cytokine secretion. Mechanism study indicated that lncMIAT increased the expression levels of p38MAPK by crosstalk with miR-216a in PBMCs. The lncMIAT/miR-216a/p38MAPK signaling contributed predominantly to the increased inflammatory cytokine secretion in the PBMCs from postmenopausal osteoporosis. In conclusion, we identified that increased lncMIAT in PBMCs induced inflammatory cytokine secretion, which contributed to the development of post-menopausal osteoporosis. lncMIAT/miR-216a axis was critical for the regulation of AMPK/p38MAPK signaling, which may be a promising therapeutic target for osteoporosis treatment by inflammatory cytokine inhibition.

Metabolomics Coupled with Pathway Analysis Provides Insights into Sarco-Osteoporosis Metabolic Alterations and Estrogen Therapeutic Effects in Mice

Postmenopausal osteoporosis (PMOP) and sarcopenia are common diseases that predominantly affect postmenopausal women. In the occurrence and development of these two diseases, they are potentially pathologically connected with each other at various molecular levels. However, the application of metabolomics in sarco-osteoporosis and the metabolic rewiring happening throughout the estrogen loss-replenish process have not been reported. To investigate the metabolic alteration of sarco-osteoporosis and the possible therapeutical effects of estradiol, 24 mice were randomly divided into sham surgery, ovariectomy (OVX), and estradiol-treated groups. Three-dimensional reconstructions and histopathology examination showed significant bone loss after ovariectomy. Estrogen can well protect against OVX-induced bone loss deterioration. UHPLC-Q-TOF/MS was preformed to profile semi- polar metabolites of skeletal muscle samples from all groups. Metabolomics analysis revealed metabolic rewiring occurred in OVX group, most of which can be reversed by estrogen supplementation. In total, 65 differential metabolites were identified, and pathway analysis revealed that sarco-osteoporosis was related to the alterations in purine metabolism, glycerophospholipid metabolism, arginine biosynthesis, tryptophan metabolism, histidine metabolism, oxidative phosphorylation, and thermogenesis, which provided possible explanations for the metabolic mechanism of sarco-osteoporosis. This study indicates that an UHPLC-Q-TOF/MS-based metabolomics approach can elucidate the metabolic reprogramming mechanisms of sarco-osteoporosis and provide biological evidence of the therapeutical effects of estrogen on sarco-osteoporosis.

Titanium Implants and Local Drug Delivery Systems Become Mutual Promoters in Orthopedic Clinics

Titanium implants have always been regarded as one of the gold standard treatments for orthopedic applications, but they still face challenges such as pain, bacterial infections, insufficient osseointegration, immune rejection, and difficulty in personalizing treatment in the clinic. These challenges may lead to the patients having to undergo a painful second operation, along with increased economic burden, but the use of drugs is actively solving these problems. The use of systemic drug delivery systems through oral, intravenous, and intramuscular injection of various drugs with different pharmacological properties has effectively reduced the levels of inflammation, lowered the risk of endophytic bacterial infection, and regulated the progress of bone tumor cells, processing and regulating the balance of bone metabolism around the titanium implants. However, due to the limitations of systemic drug delivery systems-such as pharmacokinetics, and the characteristics of bone tissue in the event of different forms of trauma or disease-sometimes the expected effect cannot be achieved. Meanwhile, titanium implants loaded with drugs for local administration have gradually attracted the attention of many researchers. This article reviews the latest developments in local drug delivery systems in recent years, detailing how various types of drugs cooperate with titanium implants to enhance antibacterial, antitumor, and osseointegration effects. Additionally, we summarize the improved technology of titanium implants for drug loading and the control of drug release, along with molecular mechanisms of bone regeneration and vascularization. Finally, we lay out some future prospects in this field.

MicroRNA miR-874-3p inhibits osteoporosis by targeting leptin (LEP)

MicroRNAs (miRNAs) regulate osteogenic differentiation and influence osteoporosis (OP). The aim of this study was to determine the potential role of miR-874-3p in OP. The expression levels of miR-874-3p and leptin (LEP) in the femoral neck trabeculae of 35 patients with or without OP were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The effects of miR-874-3p or LEP on the cell proliferation and alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osterix (OSX) levels were observed by upregulating miR-874-3p in human bone marrow mesenchymal stem cells (hBMSCs). Additionally, calcium deposition levels were evaluated using alizarin red staining (ARS). Molecular mechanisms of miR-874-3p and LEP underlying the osteogenic differentiation of hBMSCs were also evaluated using bioinformatics analysis, luciferase reporter assays, and RNA pull-down assays. The miR-874-3p levels were significantly lower in the femoral neck trabeculae of patients with OP than those of the control group, while the opposite was observed regarding the levels of LEP. Expression levels of miR-874-3p in hBMSCs were upregulated during osteogenic differentiation, while those of LEP were downregulated. Moreover, miR-874-3p upregulation promoted ALP, RUNX2, OCN, and OSX mRNA expression, cell proliferation, and calcium deposition in hBMSCs. LEP was found to be a target gene of miR-874-3p. Overexpression of LEP inhibited the expression of osteoblast markers and reversed the effect of osteogenic differentiation induced by the upregulation of miR-874-3p. In conclusion, miR-874-3p promoted the proliferation and differentiation of hBMSCs by downregulating the expression of LEP, thus inhibiting OP.

Abbreviations : miRNAs: microRNAs; OP: osteoporosis; hBMSCs: human Bone Marrow Mesenchymal stem cells; LEP: leptin; DEGs: differentially expressed genes

miRNA-7062-5p Promoting Bone Resorption After Bone Metastasis of Colorectal Cancer Through Inhibiting GPR65

Bone metastasis is positively associated with a poor prognosis in patients with colorectal cancer (CRC). CRC always leads to osteolytic change, which is regulated by aberrant activation of osteoclasts. MicroRNAs are remarkedly involved in metastasis of CRC; however, their role in bone metastasis of CRC is still unclear. The aim of this study is to find key microRNAs that are critical to bone resorption in bone metastasis of CRC. In this study, bone metastasis model was established through intratibially injecting CT-26 cells or MC-38 cells. Tartrate-resistant acid phosphatase (TRAP) staining was performed to explore the osteoclastogenesis of primary early osteoclast precursors (OCPs) after stimulation by CT-26 conditioned medium (CM). Then, microarray assay was performed to find differentially expressed miRNAs and mRNAs. The target gene of miRNA was confirmed by dual-luciferase analysis. The effect of miRNA, its target gene on osteoclastogenesis, and involved pathways were explored by Western blot, immunofluorescence analysis, and TRAP staining. Finally, the effect of miRNA on bone resorption in vivo was observed. miRNA-7062-5p was upregulated in early OCPs cultured in CT-26 CM or MC-38 CM. GPR65 was proven to be the target gene of miRNA-7062-5p. Overexpression of GPR65 can rescue the osteoclastogenesis caused by miRNA-7062-5p through activation of AMPK pathway. Local injection of miRNA-7062-5p inhibitors efficiently improved the bone resorption. Our study found the role of miRNA-7062-5p in regulating osteoclast formation, and our findings provided a potential therapeutic target in treatment of bone metastasis of CRC.

Hexosamine Biosynthetic Pathway-Derived O-GlcNAcylation Is Critical for RANKL-Mediated Osteoclast Differentiation

O-linked-N-acetylglucosaminylation (O-GlcNAcylation) performed by O-GlcNAc transferase (OGT) is a nutrient-responsive post-translational modification (PTM) via the hexosamine biosynthetic pathway (HBP). Various transcription factors (TFs) are O-GlcNAcylated, affecting their activities and significantly contributing to cellular processes ranging from survival to cellular differentiation. Given the pleiotropic functions of O-GlcNAc modification, it has been studied in various fields; however, the role of O-GlcNAcylation during osteoclast differentiation remains to be explored. Kinetic transcriptome analysis during receptor activator of nuclear factor-kappaB (NF-κB) ligand (RANKL)-mediated osteoclast differentiation revealed that the nexus of major nutrient metabolism, HBP was critical for this process. We observed that the critical genes related to HBP activation, including Nagk, Gfpt1, and Ogt, were upregulated, while the global O-GlcNAcylation was increased concomitantly during osteoclast differentiation. The O-GlcNAcylation inhibition by the small-molecule inhibitor OSMI-1 reduced osteoclast differentiation in vitro and in vivo by disrupting the translocation of NF-κB p65 and nuclear factor of activated T cells c1 (NFATc1) into the nucleus by controlling their PTM O-GlcNAcylation. Furthermore, OSMI-1 had a synergistic effect with bone target therapy on osteoclastogenesis. Lastly, knocking down Ogt with shRNA (shOgt) mimicked OSMI-1’s effect on osteoclastogenesis. Targeting O-GlcNAcylation during osteoclast differentiation may be a valuable therapeutic approach for osteoclast-activated bone diseases.

Bisphosphonates Reduce Smoking-Induced Osteoporotic-Like Alterations by Regulating RANKL/OPG in an Osteoblast and Osteoclast Co-Culture Model

Co-culture models have become mandatory for obtaining better insights into bone homeostasis, which relies on the balance between osteoblasts and osteoclasts. Cigarette smoking (CS) has been proven to increase the risk of osteoporosis; however, there is currently no proven treatment for osteoporosis in smokers excluding cessation. Bisphosphonates (BPs) are classical anti-osteoclastic drugs that are commonly used in examining the suitability of bone co-culture systems in vitro as well as to verify the response to osteoporotic stimuli. In the present study, we tested the effects of BPs on cigarette smoke extract (CSE)-affected cells in the co-culture of osteoblasts and osteoclasts. Our results showed that BPs were able to reduce CSE-induced osteoporotic alterations in the co-culture of osteoblasts and osteoclasts such as decreased matrix remodeling, enhanced osteoclast activation, and an up-regulated receptor activator of nuclear factor (NF)-kB-ligand (RANKL)/osteoprotegerin (OPG) ratio. In summary, BPs may be an effective alternative therapy for reversing osteoporotic alterations in smokers, and the potential mechanism is through modulation of the RANKL/OPG ratio.

Melatonin inhibits RANKL‑induced osteoclastogenesis through the miR‑882/Rev‑erbα axis in Raw264.7 cells

Melatonin, secreted in a typical diurnal rhythm pattern, has been reported to prevent osteoporosis; however, its role in osteoclastogenesis remains unclear. In the present study, the ability of melatonin to inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and the associated mechanism were investigated. Raw264.7 cells were cultured with RANKL (100 ng/ml) and macrophage colony-stimulating factor (M-CSF; 30 ng/ml) for 7 days, and tartrate-resistant acid phosphatase (TRAP) staining was used to detect osteoclastogenesis following treatment with melatonin. In addition, the effect of melatonin on cathepsin K and microRNA (miR)-882 expression was investigated via western blotting and reverse transcription-quantitative PCR. Melatonin significantly inhibited RANKL-induced osteoclastogenesis in Raw264.7 cells. From bioinformatics analysis, it was inferred that nuclear receptor subfamily 1 group D member 1 (NR1D1/Rev-erbα) may be a target of miR-882. In vitro, melatonin upregulated Rev-erbα expression and downregulated miR-882 expression in the osteoclastogenesis model. Rev-erbα overexpression boosted the anti-osteoclastogenesis effects of melatonin, whereas miR-882 partially diminished these effects. The present results indicated that the miR-882/Rev-erbα axis may serve a vital role in inhibiting osteoclastogenesis following RANKL and M-CSF treatment, indicating that Rev-erbα agonism or miR-882 inhibition may represent mechanisms through which melatonin prevents osteoporosis.

Various pathways of zoledronic acid against osteoclasts and bone cancer metastasis: a brief review

Zoledronic acid (ZA) is one of the most important and effective class of anti-resorptive drug available among bisphosphonate (BP), which could effectively reduce the risk of skeletal-related events, and lead to a treatment paradigm for patients with skeletal involvement from advanced cancers. However, the exact molecular mechanisms of its anticancer effects have only recently been identified. In this review, we elaborate the detail mechanisms of ZA through inhibiting osteoclasts and cancer cells, which include the inhibition of differentiation of osteoclasts via suppressing receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK) pathway, non-canonical Wnt/Ca2+/calmodulin dependent protein kinase II (CaMKII) pathway, and preventing of macrophage differentiation into osteoclasts, in addition, induction of apoptosis of osteoclasts through inhibiting farnesyl pyrophosphate synthase (FPPS)-mediated mevalonate pathway, and activation of reactive oxygen species (ROS)-induced pathway. Furthermore, ZA also inhibits cancer cells proliferation, viability, motility, invasion and angiogenesis; induces cancer cell apoptosis; reverts chemoresistance and stimulates immune response; and acts in synergy with other anti-cancer drugs. In addition, some new ways for delivering ZA against cancer is introduced. We hope this review will provide more information in support of future studies of ZA in the treatment of cancers and bone cancer metastasis.

[Zoledronate regulates osteoclast differentiation and bone resorption in high glucose through p38 MAPK pathway]

OBJECTIVE

To investigate the effect of zoledronate (ZOL) on osteoclast differentiation and bone resorption under high glucose, and the regulation mechanism of p38 mitogen activated kinase (p38 MAPK) signaling pathway in this process.

METHODS

RAW264.7 cells were divided into four groups: low group, high group, low+ZOL group and high+ZOL group after induced into osteoclasts. Cell proliferation activity was determined by MTT assay. The migration of RAW264.7 cells were examined Optical microscopy. Immunofluorescence microscopy was used to observe the cytoskeleton and sealing zones of osteoclasts. After adding group 5: high + ZOL + SB203580 group, trap staining was used to identify the number of positive osteoclasts in each group. The number and area of resorption lacunae were observed by SEM. The mRNA and protein expression of osteoclast related factors were detected by real-time PCR and Western blotting.

RESULTS

The cells in the 5 groups showed similar proliferative activity. High glucose promoted the migration of RAW264.7 cells (P < 0.05), inhibited the clarity of cytoskeleton and the formation of sealing zones in the osteoclasts. Exposure to high glucose significantly lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP, and inhibited osteoclast differentiation and bone absorption (P < 0.05). Treatment with ZOL obviously suppressed the migration ability of RAW264.7 cells, further reduced the clarity of the cytoskeleton, inhibited the formation of sealing zones of the osteoclasts, lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK, and TRAP (P < 0.05), and inhibited osteoclast differentiation and bone absorption. Treatment with SB203580 obviously inhibited osteoclast differentiation and bone resorption and the expressions of P38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP (P < 0.05).

CONCLUSIONS

High glucose inhibits osteoclast differentiation and bone resorption. ZOL inhibits osteoclast differentiation and bone resorption in high-glucose conditions by regulating p38 MAPK pathway, which can be a new pathway for ZOL to regulate diabetic osteoporosis.

The phytoestrogen glabrene prevents osteoporosis in ovariectomized rats through upregulation of the canonical Wnt/β-catenin signaling pathway

This study systematically investigated the effects of phytoestrogen glabrene on postmenopausal osteoporosis in an ovariectomy (OVX) rat model. Glabrene administration (25, 50, and 100 mg/kg) for 13 weeks can significantly slow down the body weight gain and slightly increase the uterus weight of OVX rats. The increased levels of U-Ca, U-P levels, urine DPD/creatinine, serum ALP, OCN, triglycerides, and total cholesterol induced by OVX were dramatically inhibited in rats, whereas no difference occurred for S-Ca and S-P in all groups. Furthermore, glabrene can enhance bone mineral density of the right femur, fourth-lumbar vertebra and tibia and improve biomechanical parameters, such as femoral neck loading force, three-point bending of the tibia, and vertebral compression in OVX rats. Moreover, glabrene greatly suppressed the expression of TRAP protein but increased OPG and BGP protein expression in tibia tissue of OVX rats. In addition, OVX-induced reduction of Lrp-5, β-catenin, Runx2, and Osx protein expression was all restored by glabrene treatment. The present study indicated that glabrene might be a potential alternative medicine for the prevention and treatment of postmenopausal osteoporosis via activation of the Wnt/β-catenin signaling pathway.

Proteomic study of in vitro osteogenic differentiation of mesenchymal stem cells in high glucose condition

Patients with diabetes have been widely reported to be at an increased risk of secondary osteoporosis. Osteoporosis is caused by an imbalance in bone remodeling due to increased bone resorption and/or decreased osteoblast-dependent bone formation. In this study, mesenchymal stem cells (MSCs) were used as a disease model to determine the effects of high glucose levels on MSC-osteoblast development. The results indicated that under high glucose conditions, MSCs had reduced cell viability and increased number of β-galactosidase-positive cells. Furthermore, in vitro osteogenesis was shown to be reduced in MSCs cultured in osteogenic differentiation medium at 10, 25, and 40 mM glucose as demonstrated by Alizarin red S staining and alkaline phosphatase activity assay. Moreover, a proteomic study was performed in MSCs cultured with 25 and 40 mM glucose. The proteomic results demonstrated that 12 proteins were up- and downregulated in bone marrow-derived mesenchymal stem cells cultured with high glucose in a dose-dependent manner. The findings presented here contribute to our understanding of the mechanism of diabetes mellitus responsible for bone loss. However, the exact mechanism of action of hyperglycemia on bone deformability requires additional studies.

AMP-activated protein kinase (AMPK) regulates autophagy, inflammation and immunity and contributes to osteoclast differentiation and functionabs

Osteoclasts are multinucleated giant cells, responsible for bone resorption. Osteoclast differentiation and function requires a series of cytokines to remove the old bone, which coordinates with the induction of bone remodelling by osteoblast-mediated bone formation. Studies have demonstrated that AMP-activated protein kinase (AMPK) play a negative regulatory role in osteoclast differentiation and function. Research involving AMPK, a nutrient and energy sensor, has primarily focused on osteoclast differentiation and function; thus, its role in autophagy, inflammation and immunity remains poorly understood. Autophagy is a conservative homoeostatic mechanism of eukaryotic cells, and response to osteoclast differentiation and function; however, how it interacts with inflammation remains unclear. Additionally, based on the regulatory function of different AMPK subunits for osteoclast differentiation and function, its activation is regulated by upstream factors to perform bone metabolism. This review summarises the critical role of AMPK-mediated autophagy, inflammation and immunity by upstream and downstream signalling during receptor activator of nuclear factor kappa-B ligand-induced osteoclast differentiation and function. This pathway may provide therapeutic targets for bone-related diseases, as well as function as a biomarker for bone homoeostasis.