The chromatin remodeling factor Arid1a cooperates with Jun/Fos to promote osteoclastogenesis by epigenetically upregulating Siglec15 expression.

Osteoporosis is characterized by an imbalance between osteoclast-mediated bone resorption and osteoblast-related bone formation, particularly increased osteoclastogenesis. However, the mechanisms by which epigenetic factors regulate osteoclast precursor differentiation during osteoclastogenesis remain poorly understood. Here, we show that the specific knockout of the chromatin remodeling factor Arid1a in bone marrow-derived macrophages (BMDMs) results in increased bone mass. The loss of Arid1a in BMDM inhibits cell-cell fusion and maturation of osteoclast precursors, thereby suppressing osteoclast differentiation. Mechanistically, Arid1a increases the chromatin access in the gene promoter region of sialic acid-binding Ig-like lectin 15 (Siglec15) by transcription factor Jun/Fos, which results in the upregulation of Siglec15 and promotion of osteoclast differentiation. However, the loss of Arid1a reprograms the chromatin structure to restrict Siglec15 expression in osteoclast precursors, thereby inhibiting BMDM differentiation into mature osteoclasts. Deleting Arid1a after ovariectomy (a model for postmenopausal bone loss) alleviated bone loss and maintained bone mass. In summary, epigenetic reprogramming mediated by Arid1a loss suppresses osteoclast differentiation and may serve as a promising therapeutic strategy for treating bone loss diseases.

Osteoporosis is a common disease, usually diagnosed by decreased bone density and increased fragility. The people with osteoporosis has higher risk of fractures. Nearly one third of the aged people will suffer from osteoporosis-related fractures and even lose their lives because of this. Therefore, there is an urgent need for early intervention and effective treatment options for osteoporosis in the aging population. Bone tissue is a highly dynamic tissue that undergoes continuous remodeling throughout an individual's entire life. The balance of remodeling depends on the bone formation mediated by osteoblasts and bone resorption by osteoclasts. When this balance is disrupted, osteoporosis occurs. Thus, the aim of our research is to explore the behind mechanism of this imbalance. Here, we demonstrate that the loss of Arid1a, a chromatin remodeler, leads to chromatin reprogramming that restricts access to promoters by transcription factors such as Jun/Fos, thereby suppressing osteoclast activation and bone resorption. Our findings offer insights into the epigenetic mechanisms underlying osteoporosis and suggest potential strategies for its prevention and treatment.

Comparative study in estrogen-depleted mice identifies skeletal and osteocyte transcriptomic responses to abaloparatide and teriparatide.

Osteocytes express parathyroid hormone (PTH)/PTH-related protein (PTHrP) receptors and respond to the PTHrP analog abaloparatide (ABL) and to the PTH 1-34 fragment teriparatide (TPTD), which are used to treat osteoporosis. Several studies indicate overlapping but distinct skeletal responses to ABL or TPTD, but their effects on cortical bone may differ. Little is known about their differential effects on osteocytes. We compared cortical osteocyte and skeletal responses to ABL and TPTD in sham-operated and ovariectomized mice. Administered 7 weeks after ovariectomy for 4 weeks at a dose of 40 µg/kg/d, TPTD and ABL had similar effects on trabecular bone, but ABL showed stronger effects in cortical bone. In cortical osteocytes, both treatments decreased lacunar area, reflecting altered peri-lacunar remodeling favoring matrix accumulation. Osteocyte RNA-Seq revealed that several genes and pathways were altered by ovariectomy and affected similarly by TPTD and ABL. Notwithstanding, several signaling pathways were uniquely regulated by ABL. Thus, in mice, TPTD and ABL induced a positive osteocyte peri-lacunar remodeling balance, but ABL induced stronger cortical responses and affected the osteocyte transcriptome differently. We concluded that ABL affected the cortical osteocyte transcriptome in a manner subtly different from TPTD, resulting in more beneficial remodeling/modeling changes and homeostasis of the cortex.

CircFam190a: a critical positive regulator of osteoclast differentiation via enhancement of the AKT1/HSP90ß complex.

The identification of key regulatory factors that control osteoclastogenesis is important. Accumulating evidence indicates that circular RNAs (circRNAs) are discrete functional entities. However, the complexities of circRNA expression as well as the extent of their regulatory functions during osteoclastogenesis have yet to be revealed. Here, based on circular RNA sequencing data, we identified a circular RNA, circFam190a, as a critical regulator of osteoclast differentiation and function. During osteoclastogenesis, circFam190a is significantly upregulated. In vitro, circFam190a enhanced osteoclast formation and function. In vivo, overexpression of circFam190a induced significant bone loss, while knockdown of circFam190a prevented pathological bone loss in an ovariectomized (OVX) mouse osteoporosis model. Mechanistically, our data suggest that circFam90a enhances the binding of AKT1 and HSP90ß, promoting AKT1 stability. Altogether, our findings highlight the critical role of circFam190a as a positive regulator of osteoclastogenesis, and targeting circFam190a might be a promising therapeutic strategy for treating pathological bone loss.

Ap-2ß regulates cranial osteogenic potential via the activation of Wnt/ß-catenin signaling pathway.

The skull is a fundamental bone that protects the development of brain and consists of several bony elements, such as the frontal and parietal bones. Frontal bone exhibited superior in osteogenic potential and regeneration of cranial defects compared to parietal bone. However, how this regional difference is regulated remains largely unknown. In this study, we identified an Ap-2ß transcriptional factor with a higher expression in frontal bone, but its molecular function in osteoblasts needs to be elucidated. We found that Ap-2ß knockdown in preosteoblasts leads to reduced proliferation, increased cell death and impaired differentiation. Through RNA-seq analysis, we found that Ap-2ß influences multiple signaling pathways including the Wnt pathway, and overexpression of Ap-2ß showed increased nuclear ß-catenin and its target genes expressions in osteoblasts. Pharmacological activation of Wnt/ß-catenin signaling using LiCl treatment cannot rescue the reduced luciferase activities of the ß-catenin/TCF/LEF reporter in Ap-2ß knockdown preosteoblasts. Besides, transient expression of Ap-2ß via the lentivirus system could sufficiently rescue the inferior osteogenic potential in parietal osteoblasts, while Ap-2ß knockdown in frontal osteoblasts resulted in reduced osteoblast activity, reduced active ß-catenin and target genes expressions. Taken together, our data demonstrated that Ap-2ß modulates osteoblast proliferation and differentiation through the regulation of Wnt/ß-catenin signaling pathway and plays an important role in regulating regional osteogenic potential in frontal and parietal bone.

Ugi Cascade Sequence for the Construction of 3-Pyrrolin-2-one Scaffolds: Anti-proliferation in Prostate Cancer Cells.

Herein, a small series of 3-pyrrolin-2-ones was efficiently synthesized through a three-step Ugi cascade sequence. This method features readily available substrates, simple aqueous workup procedures and good yields, dramatically improving generality of reaction. Importantly, the newly product N-benzyl-2-(3-(4-chlorophenyl)-4-methyl-2-oxo-2,5-dihydro-1H-pyrrol-1-yl)-2-phen-ylacetamide exhibited potent anti-proliferation in prostate cancer cell line through G1/S cell cycle arrest and targeted in PI3K/AKT/TSC2 signal pathway.

Norcantharidin ameliorates estrogen deficient-mediated bone loss by attenuating the activation of extracellular signal-regulated kinase/ROS/NLRP3 inflammasome signaling.

Osteoporosis, characterized by reduced bone mass, aberrant bone architecture, and elevated bone fragility, is driven by a disruption of bone homeostasis between bone resorption and bone formation. However, up to now, no drugs are perfect for osteoporosis treatment due to different defects. In this study, we demonstrated that norcantharidin (NCTD) could inhibit osteoclast formation and bone resorption by attenuating the ERK, ROS and NLRP3 inflammasomes pathways in vitro. Moreover, our in vivo study further confirms its preventive effects on estrogen-deficiency bone loss by inhibiting osteoclast formation and functions. Therefore, we could conclude that NCTD might be a potential candidates for the prevention and treatment of osteoporosis.

HemoglobinA1c Is a Risk Factor for Changes of Bone Mineral Density: A Mendelian Randomization Study.

Background: As a valuable blood glucose measurement, HemoglobinA1c (HbA1c) is of great clinical value for diabetes. However, in previous observational studies, studies on its effect on bone mineral density (BMD) have different results. This study aimed to use Mendelian randomization (MR) to assess the effect of HbA1c on bone mineral density and fracture risk, and try to further explore whether this association was achieved through glycemic or non-glycemic factors. Methods: Take HbA1c measurement as exposure, and BMD estimated from quantitative heel ultrasounds (eBMD) and bone fractures as outcomes. Two-Sample MR Analysis was conducted to assess the causal effect of HbA1C on heel BMD and risk fracture. Then, we performed the analysis using two subsets of these variants, one related to glycemic measurement and the other to erythrocyte indices. Results: Genetically increased HbA1C was associated with the lower heel eBMD [odds ratio (OR) 0.91 (95% CI 0.87, 0.96) per %-unit, P = 3 × 10-4(IVW)]. Higher HbA1C was associated with lower heel eBMD when using only erythrocytic variants [OR 0.87 (0.82, 0.93), P=2× 10-5(IVW)]; However, when using only glycemic variants, this casual association does not hold. In further MR analysis, we test the association of erythrocytic traits with heel eBMD. Conclusion: Our study revealed the significant causal effect of HbA1c on eBMD, and this causal link might achieve through non-glycemic pathways (erythrocytic indices).

Cepharanthine Ameliorates Chondrocytic Inflammation and Osteoarthritis via Regulating the MAPK/NF-κB-Autophagy Pathway.

Osteoarthritis is a worldwide joint disease caused by abnormal chondrocytic metabolism. However, traditional therapeutic methods aimed at anti-inflammation for early-stage disease are palliative. In the present study, we demonstrated that cepharanthine (CEP), extracted from the plant Stephania cepharantha, exerted protective medicinal efficacy on osteoarthritis for the first time. In our in vitro study, CEP suppressed the elevated expression of matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) and inducible nitric oxide synthase (iNOS) stimulated by IL-1ß or TNF-α by inhibiting the activation of MAPK and NF-κB signaling pathways, and upregulated the protein expression of aggrecan, collagen II, and Sox9. Also, CEP could reverse the reduced level of cellular autophagy in IL-1ß or TNF-α-induced chondrocytes, indicating that the protective effect of CEP on osteoarthritis was achieved by restoring MAPK/NF-κB-mediated autophagy. Furthermore, in a murine OA model, CEP mitigated cartilage degradation and prevented osteoarthritis in the CEP-treated groups versus the OA group. Hence, our results revealed the therapeutic prospect of CEP for anti-osteoarthritic treatment.

Phillyrin Prevents Ovariectomy-Induced Osteolysis by Inhibiting Osteoclast Differentiation.

Postmenopausal osteoporosis is a metabolic disease caused by an imbalance between osteoclasts and osteoblasts. At present, the drug strategy for treating postmenopausal osteoporosis has some limitations and is unable to satisfy the demands of patients. Phillyrin (Phil) is an herbal extract from Forsythiae Fructus, with an inhibitory effect on osteolysis. In this study, we described the role of Phil in ovariectomy-induced osteoporosis and its effect on osteoclast differentiation in vitro. Eighteen female C57BL/6 mice were randomly divided into three groups: sham group (sham surgery and injection with 0.9% normal saline), ovariectomized group (ovariectomy and injection with 0.9% normal saline), and Phil group (ovariectomy and injecting Phil with 100 mg/kg for 2 days). Mice were sacrificed after 6-week Phil administration and femurs were harvested for microcomputed tomography (micro-CT) and histomorphology analyses. In vitro, we used different concentrations of Phil to study its effect on osteoclastogenesis. The results showed that the BV/TV, Tb.Th, and Tb.N in trabecular bone were increased in the Phil group compared with the OVX group, and the trabecular bone mass was remarkably decreased in the OVX group compared with the sham group. The number of osteoclasts was increased in the OVX group compared to the sham group, and the number and area of osteoclasts were decreased in the Phil group compared to the control group. Compared with the OVX group, the number and area of osteoclasts were reduced in the Phil group. In conclusion, Phil could inhibit the formation of osteoclasts, promote the growth of bone trabecular, and relieve osteoporosis caused by ovariectomy, with a certain clinical adoption value.

Additive Effect of Parathyroid Hormone and Zoledronate Acid on Prevention Particle Wears-Induced Implant Loosening by Promoting Periprosthetic Bone Architecture and Strength in an Ovariectomized Rat Model.

Implant-generated particle wears are considered as the major cause for the induction of implant loosening, which is more susceptible to patients with osteoporosis. Monotherapy with parathyroid hormone (PTH) or zoledronate acid (ZOL) has been proven efficient for preventing early-stage periprosthetic osteolysis, while the combination therapy with PTH and ZOL has exerted beneficial effects on the treatment of posterior lumbar vertebral fusion and disuse osteopenia. However, PTH and ZOL still have not been licensed for the treatment of implant loosening to date clinically. In this study, we have explored the effect of single or combined administration with PTH and ZOL on implant loosening in a rat model of osteoporosis. After 12 weeks of ovariectomized surgery, a femoral particle-induced periprosthetic osteolysis model was established. Vehicle, PTH (5 days per week), ZOL (100 mg/kg per week), or combination therapy was utilized for another 6 weeks before sacrifice, followed by micro-CT, histology, mechanical testing, and bone turnover examination. PTH monotherapy or combined PTH with ZOL exerted a protective effect on maintaining implant stability by elevating periprosthetic bone mass and inhibiting pseudomembrane formation. Moreover, an additive effect was observed when combining PTH with ZOL, resulting in better fixation strength, higher periprosthetic bone mass, and less pseudomembrane than PTH monotherapy. Taken together, our results suggested that a combination therapy of PTH and ZOL might be a promising approach for the intervention of early-stage implant loosening in patients with osteoporosis.

Effect of Amniotic Membrane/Collagen-Based Scaffolds on the Chondrogenic Differentiation of Adipose-Derived Stem Cells and Cartilage Repair.

Objectives: Repairing articular cartilage damage is challenging. Clinically, tissue engineering technology is used to induce stem cell differentiation and proliferation on biological scaffolds to repair defective joints. However, no ideal biological scaffolds have been identified. This study investigated the effects of amniotic membrane/collagen scaffolds on the differentiation of adipose-derived stem cells (ADSCs) and articular cartilage repair. Methods: Adipose tissue of New Zealand rabbits was excised, and ADSCs were isolated and induced for differentiation. An articular cartilage defect model was constructed to identify the effect of amniotic membrane/collagen scaffolds on cartilage repair. Cartilage formation was analyzed by imaging and toluene blue staining. Knee joint recovery in rabbits was examined using hematoxylin and eosin, toluidine, safranine, and immunohistochemistry at 12 weeks post-operation. Gene expression was examined using ELISA, RT-PCR, Western blotting, and immunofluorescence. Results: The adipose tissue was effectively differentiated into ADSCs, which further differentiated into chondrogenic, osteogenic, and lipogenic lineages after 3 weeks' culture in vitro. Compared with platelet-rich plasmon (PRP) scaffolds, the amniotic membrane scaffolds better promoted the growth and differentiation of ADSCs. Additionally, scaffolds containing the PRP and amniotic membrane efficiently enhanced the osteogenic differentiation of ADSCs. The levels of COL1A1, COL2A1, COL10A1, SOX9, and ACAN in ADSCs + amniotic membrane + PRP group were significantly higher than the other groups both in vitro and in vivo. The Wakitani scores of the ADSC + amniotic membrane + PRP group were lower than that in ADSC + PRP (4.4 ± 0.44**), ADSC + amniotic membrane (2.63 ± 0.38**), and control groups (6.733 ± 0.21) at week 12 post-operation. Osteogenesis in rabbits of the ADSC + amniotic membrane + PRP group was significantly upregulated when compared with other groups. Amniotic membranes significantly promoted the expression of cartilage regeneration-related factors (SOX6, SOX9, RUNX2, NKX3-2, MEF2C, and GATA4). The ADSC + PRP + amniotic membrane group exhibited the highest levels of TGF-ß, PDGF, and FGF while exhibiting the lowest level of IL-1ß, IL6, and TNF-α in articular cavity. Conclusion: Amniotic membrane/collagen combination-based scaffolds promoted the proliferation and cartilage differentiation of ADSCs, and may provide a new treatment paradigm for patients with cartilage injury.

Genetic Associations Between IL-6 and the Development of Autoimmune Arthritis Are Gender-Specific.

Objectives: To find out the genetic association between IL6 and autoimmune arthritis. Methods: We performed a two-sample Mendelian randomization (MR) study using multiple genome-wide association studies (GWAS) datasets. Furthermore, a sex-stratified MR study was performed to identify sexual dimorphism in the association between IL6 and autoimmune arthritis. Then, LocusZoom plots were displayed based on the IL6R gene region to present evidence of genetic colocalization between diseases. Results: The MR result denoted a genetic association between the increased level of IL-6 signaling and risk of RA (ß=0.325, 95%CI 0.088, 0.561, p=7.08E-03) and AS (ß=1.240, 95%CI 0.495, 1.980, p=1.1E-03). Accordingly, sIL6R was found to have negatively correlation with the onset of RA (ß=-0.020, 95%CI -0.0320, -0.008, p=1.18E-03) and AS (ß=-0.125, 95%CI -0.177, -0.073, p=2.29E-06). However, no genetic association between IL6/sIL6R and PsA was detected. The gender-stratified MR analysis showed that IL6 was associated with AS in the male population, with RA in the female population, and with PsA in the male population. Additionally, ADAR, a gene identified by a sensitive test, could be the reason for the nonsignificant association between IL6 and PsA in a pooled population. Conclusion: Our findings showed that the overactive IL6 signal pathway led to autoimmune arthritis, especially in RA and AS. Sexual difference was also observed in IL6-intermediate susceptibility to autoimmune arthritis.

Vorinostat ameliorates IL-1α-induced reduction of type II collagen by inhibiting the expression of ELF3 in chondrocytes.

Osteoarthritis (OA) is a common joint disease that ultimately causes physical disability and imposes an economic burden on society. Cartilage destruction plays a key role in the development of OA. Vorinostat is an oral histone deacetylase (HDAC) inhibitor and has been used for the treatment of T-cell lymphoma. Previous studies have reported the anti-inflammatory effect of HDAC inhibitors in both in vivo and in vitro models. However, it is unknown whether vorinostat exerts a protective effect in OA. In this study, our results demonstrate that treatment with vorinostat prevents interleukin 1α (IL-1α)-induced reduction of type II collagen at both gene and protein levels. Treatment with vorinostat reduced the IL-1α-induced production of mitochondrial reactive oxygen species (ROS) in T/C-28a2 cells. Additionally, vorinostat rescued the IL-1α-induced decrease in the expression of the collagen type II a1 (Col2a1) gene and the expression of Sry-related HMG box 9 (SOX-9). Importantly, we found that vorinostat inhibited the expression of matrix metalloproteinase-13 (MMP-13), which is responsible for the degradation of type II collagen. Furthermore, vorinostat suppressed the expression of E74-like factor 3 (ELF3), which is a key transcription factor that plays a pivotal role in the IL-1α-induced reduction of type II collagen. Also, the overexpression of ELF3 abolished the protective effects of vorinostat against IL-1α-induced loss of type 2 collagen by inhibiting the expression of SOX-9 whilst increasing the expression of MMP-13. In conclusion, our findings suggest that vorinostat might prevent cartilage destruction by rescuing the reduction of type II collagen, mediated by the suppression of ELF3.

The combination of PLLA/PLGA/PCL composite scaffolds integrated with BMP-2-loaded microspheres and low-intensity pulsed ultrasound alleviates steroid-induced osteonecrosis of the femoral head.

Low-intensity pulsed ultrasound (LIPUS), which has been previously reported to promote bone repair, is proposed to be a noninvasive form of therapy for the treatment of osteonecrosis. Bone fillers made from composite scaffolds have been demonstrated to be effective for preventing bone defects such as osteonecrosis. The present study aimed to investigate whether the application of LIPUS combined with bone morphogenetic protein-2 (BMP-2)-loaded poly-L-lactic acid/polylactic-co-glycolic acid/poly-ε-caprolactone (PLLA/PLGA/PCL) composite scaffolds can improve recovery in a rat model of steroid-induced osteonecrosis of the femoral head (ONFH). BMP-2-loaded PLGA microspheres incorporated into PLLA/PLGA/PCL composite scaffolds were constructed. Bilateral femoral head LIPUS intervention was conducted in rats with steroid-induced ONFH. LIPUS intervention alone contributed to the alleviation of osteonecrosis, in addition to improving load-carrying capacity and accelerated bone formation, angiogenesis and differentiation. Subsequently, femoral head parameters and assessment of load-carrying capacity, bone formation-related factors, and angiogenesis- and differentiation-related factors were measured in rats with or without implanted BMP-2-loaded PLLA/PLGA/PCL composite scaffolds. LIPUS combined with the implantation of PLLA/PLGA/PCL composite scaffolds loaded with BMP-2 microspheres protected rats against steroid-induced ONFH and improved load-carrying capacity, bone formation, angiogenesis and differentiation. Together, these data support the use of BMP-2-loaded PLLA/PLGA/PCL composite scaffolds combined with LIPUS for ONFH as a potential alternative curative solution for treating bone diseases.

Carnosol attenuates RANKL-induced osteoclastogenesis in vitro and LPS-induced bone loss.

Osteolysis is characterized by the imbalance of bone remodeling triggered by excessive activation of osteoclasts, which ultimately leads to pathological bone destruction. Diseases caused by overactive osteoclasts, such as osteolysis around the prosthesis, periodontitis and osteoporosis, are clinically common but lack effective treatment. Therefore, exploring regimens that could specifically impair the formation and function of osteoclasts has become a breakthrough in the treatment of these diseases. Carnosol is a natural phenolic diterpene with anti-inflammatory, antibacterial, anti-tumor and antioxidant properties. In this study, we found that carnosol can impede RANKL-induced osteoclastogenesis via modulating the activation of NF-κb and JNK signaling pathways in vitro. Additionally, we confirmed that carnosol could alleviate bone loss in amurine model of LPS-induced inflammatory bone erosion in vivo. Thence, these findings demonstrate that carnosol may be a potentially effective regent for the treatment of osteoclast-related disorders.

Prognosis of prostate cancer and bone metastasis pattern of patients: a SEER-based study and a local hospital based study from China.

Prostate cancer (PCa) is the leading cause of cancer-related death among men worldwide. Knowledge of the prognostic factors of PCa and the bone metastasis pattern of patients would be helpful for patients and doctors. The data of 177,255 patients with prostate cancer diagnosed between 2010 and 2013 with at least five years of follow-up were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. Multivariate Cox regression analysis was used to determine the predictive value of patients' characteristics for survival after adjusting for other variates. Multivariate logistic regression analysis was used to evaluate the odds ratio of bone metastasis in PCa patients. The predictive value of age, race, marital status, and tumor characteristics were compared. The survival of patients with different socioeconomic statuses and bone metastasis statuses was compared by Kaplan-Meier analysis. A total of 1,335 patients with prostate cancer diagnosed between 2009 and 2015 were enrolled from the Second Affiliated Hospital of Zhejiang University School of Medicine. The survival of patients with different prostate-specific antigen (PSA) levels, Gleason scores, marital statuses and bone metastasis statuses was compared by Kaplan-Meier analysis. In SEER database, 96.74% of patients were 50 years of age or older. Multivariate Cox analysis revealed that for PCa patients, age at presentation, older age, single marital status, lower socioeconomic status, higher PSA level, T1 and N0 stage, and bone metastasis were independent risk factors for increased mortality. Multivariate logistic regression analysis revealed that patients who were married, were living in urban areas, had lower PSA levels, underwent surgery, and radiation had lower OR factors for bone metastasis. Asian or Pacific Islander, better socioeconomic status, lived in urban areas, married marital status, lower PSA levels and lower Gleason scores were better prognostic factors in PCa. Additionally, patients with single or divorced marital status, who were living in rural places had higher PSA levels, and T1 and N0 stages have a high OR for bone metastasis.

Catalpol suppresses osteoclastogenesis and attenuates osteoclast-derived bone resorption by modulating PTEN activity.

Excessive activation of osteoclast activity is responsible for many bone diseases, such as osteoporosis, rheumatoid arthritis, periprosthetic osteolysis, and periodontitis. Natural compounds that inhibit osteoclast formation and/or function have therapeutic potential for treating these diseases. Catalpol, a bioactive iridoid extracted from a traditional herbal medicine Rehmannia glutinosa, exhibits various pharmacological properties, including anti-inflammatory, antioxidant, antidiabetic, and antitumor effects. However, its effects on osteoclast formation and function remain unknown. In the present study, we showed that catalpol inhibited receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation and bone resorption, as well as the expression of osteoclast-related marker genes. The investigation of molecular mechanisms showed that catalpol upregulated phosphatase and tensin homolog (PTEN) activity by reducing its ubiquitination and degradation, subsequently suppressing RANKL-induced NF-κB and AKT signaling pathways, leading to an inhibition on NFATc1 induction. Furthermore, catalpol protected mice against inflammation- and ovariectomy-induced bone loss by inhibiting osteoclast activity in vivo. These results suggest that catalpol might be developed as a promising candidate for treating osteoclast-related bone diseases.

Stachydrine prevents LPS-induced bone loss by inhibiting osteoclastogenesis via NF-κB and Akt signalling.

Osteoclast overactivation-induced imbalance in bone remodelling leads to pathological bone destruction, which is a characteristic of many osteolytic diseases such as rheumatoid arthritis, osteoporosis, periprosthetic osteolysis and periodontitis. Natural compounds that suppress osteoclast formation and function have therapeutic potential for treating these diseases. Stachydrine (STA) is a bioactive alkaloid isolated from Leonurus heterophyllus Sweet and possesses antioxidant, anti-inflammatory, anticancer and cardioprotective properties. However, its effects on osteoclast formation and function have been rarely described. In the present study, we found that STA suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation and bone resorption, and reduced osteoclast-related gene expression in vitro. Mechanistically, STA inhibited RANKL-induced activation of NF-κB and Akt signalling, thus suppressing nuclear factor of activated T cells c1 induction and nuclear translocation. In addition, STA alleviated bone loss and reduced osteoclast number in a murine model of LPS-induced inflammatory bone loss. STA also inhibited the activities of NF-κB and NFATc1 in vivo. Together, these results suggest that STA effectively inhibits osteoclastogenesis both in vitro and in vivo and therefore is a potential option for treating osteoclast-related diseases.

Peimine suppresses interleukin­1ß­induced inflammation via MAPK downregulation in chondrocytes.

Osteoarthritis (OA) is the most common type of degenerative joint disease and secreted inflammatory molecules serve a pivotal role in it. Peimine has been reported to have anti­inflammatory activity. In order to investigate the potential therapeutic role of Peimine in OA, mouse articular chondrocytes were treated with IL­1ß and different doses of Peimine in vitro. The data revealed that Peimine not only suppressed IL­1ß­induced production of nitric oxide (NO) and prostaglandin E2, but also reduced the protein levels of inducible NO synthase (iNOS) and cyclooxygenase­2 (COX­2). In addition, Peimine inhibited the IL­1ß­induced mRNA expression of matrix metalloproteinase (MMP)­1, MMP­3, MMP­9, MMP­13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)­4 and ADAMTS­5. Furthermore, Peimine inhibited IL­1ß­induced activation of the mitogen­activated protein kinase (MAPK) pathway. The protective effect of Peimine on IL­1ß­treated chondrocytes was attenuated following activation of the MAPK pathway, as demonstrated by the increased expression levels of MMP­3, MMP­13, ADAMTS­5, iNOS and COX­2 compared with the Peimine group. The in vivo data suggested that Peimine limited the development of OA in the mouse model. In general, the data indicate that Peimine suppresses IL­1ß­induced inflammation in mouse chondrocytes by inhibiting the MAPK pathway, suggesting a promising therapeutic role for Peimine in the treatment of OA.