The effects of luteolin on osteoclast differentiation, function in vitro and ovariectomy-induced bone loss

Luteolin: A promising multifunctional natural flavonoid for human diseases

Natural products are closely associated with human health. Luteolin (LUT), a flavonoid polyphenolic compound, is widely found in fruits, vegetables, flowers, and herbs. It is noteworthy that LUT exhibits a variety of beneficial pharmacological properties and holds significant potential for clinical applications, particularly in antitumor, anti-convulsion, diabetes control, anti-inflammatory, neuroprotection, anti-oxidation, anti-cardiovascular, and other aspects. The potential mechanism of action has been partially elucidated, including the mediation of NF-κB, toll-like receptor, MAPK, Wnt/β-catenin, PI3K/Akt, AMPK/mTOR, and Nrf-2, among others. The review that aimed to comprehensively consolidate essential information on natural sources, pharmacological effects, therapeutic and preventive potential, as well as potential mechanisms of LUT. The objective is to establish a theoretical basis for the continued development and application of LUT.

Luteolin rescues postmenopausal osteoporosis elicited by OVX through alleviating osteoblast pyroptosis via activating PI3K-AKT signaling

BACKGROUND

Recently, osteoblast pyroptosis has been proposed as a potential pathogenic mechanism underlying osteoporosis, although this remains to be confirmed. Luteolin (Lut), a flavonoid phytochemical, plays a critical role in the anti-osteoporosis effects of many traditional Chinese medicine prescriptions. However, its protective impact on osteoblasts in postmenopausal osteoporosis (PMOP) has not been elucidated.

PURPOSE

This research aimed to determine the effect of Lut in ameliorating PMOP by alleviating osteoblast pyroptosis and sustaining osteogenesis.

STUDY DESIGN

This research was designed to investigate the novel mechanism of Lut in alleviating PMOP both in cell and animal models.

METHODS

Ovariectomy-induced PMOP models were established in mice with/without daily gavaged of 10 or 20 mg/kg body weight Lut. The impact of Lut on bone microstructure, metabolism and oxidative stress was evaluated with 0.104 mg/kg body weight Estradiol Valerate Tablets daily gavaged as positive control. Network pharmacological analysis and molecular docking were employed to investigate the mechanisms of Lut in PMOP treatment. Subsequently, the impacts of Lut on the PI3K/AKT axis, oxidative stress, mitochondria, and osteoblast pyroptosis were assessed. In vitro, cultured MC3T3-E1(14) cells were exposed to H2O2 with/without Lut to examine its effects on the PI3K/AKT signaling pathway, osteogenic differentiation, mitochondrial function, and osteoblast pyroptosis.

RESULTS

Our findings demonstrated that 20 mg/kg Lut, similar to the positive control drug, effectively reduced systemic bone loss and oxidative stress, and enhanced bone metabolism induced by ovariectomy. Network pharmacological analysis and molecular docking indicated that the PI3K/AKT axis was a potential target, with oxidative stress response and nuclear membrane function being key mechanisms. Consequently, the effects of Lut on the PI3K/AKT axis and pyroptosis were investigated. In vivo data revealed that the PI3K/AKT axis was deactivated following ovariectomy, and Lut restored the phosphorylation of key proteins, thereby reactivating the axis. Additionally, Lut alleviated osteoblast pyroptosis and mitochondrial abnormalities induced by ovariectomy. In vitro, Lut intervention mitigated the inhibition of the PI3K/AKT axis and osteogenesis, as well as H2O2-induced pyroptosis. Furthermore, Lut attenuated ROS accumulation and mitochondrial dysfunction. The effects of Lut, including osteogenesis restoration, anti-pyroptosis, and mitochondrial maintenance, were all reversed with LY294002 (a PI3K/AKT pathway inhibitor).

CONCLUSION

In summary, Lut could improve mitochondrial dysfunction, alleviate GSDME-mediated pyroptosis and maintain osteogenesis via activating the PI3K/AKT axis, offering a new therapeutic strategy for PMOP.

Exploring the anti-osteoporosis potential of Petroselinum crispum (Mill.) Fuss extract employing experimentally ovariectomized rat model and network pharmacology approach

One of the most prevalent secondary osteoporosis is ovariectomy-induced osteoporosis. Parsley (Petroselinum crispum) has potent estrogenic and antioxidant properties and was used traditionally in the treatment of amenorrhea and dysmenorrhea. The present study aimed to characterize parsley leaf extract (PLE) employing RP-HPLC-MS-MS/MS-based method and possible protective effect in ovariectomized (OVX)-induced osteoporosis in rats was assessed. Rats were randomly assigned into SHAM group, OVX group, PLE + OVX group (150 mg/kg/day, p.o), and estradiol benzoate (E2) + OVX group (30 μg/kg/day, s.c). After eight weeks following ovariectomy, biomarkers of bone strength, bone resorption, oxidative stress and histopathology were carried out. A network pharmacology approach investigated the key targets and potential mechanisms by of PLE metabolites against osteoporosis using databases: PubChem, BindingDB server, DisGeNET, ShinyGO, and KEGG Pathway. Moreover, FunRich 3.1.3, Cytoscape 3.10.0, and MOE 2019.0102 softwares were used for network pharmacology analysis and molecular docking studies. Flavones and hydroxycinnamic acid derivatives were predominant among 38 metabolites in PLE. It significantly restored bone strength and bone resorption biomarkers, osteocalcin (OST), oxidative stress biomarkers and histopathological alterations. The employed network pharmacology approach revealed that 14 primary target genes were associated with decreasing the severity of osteoporosis. Molecular docking revealed that cGMP-PKG signaling pathway has the highest fold enrichment and its downstream PDE5A. Luteolin, diosmetin, and isorhamnetin derivatives affected mostly osteoporosis targets. PLE exhibited protective action against ovariectomy-induced osteoporosis in rats and may be a promising therapy for premenopausal bone loss. cGMP-PKG signaling pathway could be a promising target for PLE in treating osteoporosis.

Integrating network pharmacology and experimental verification strategies to reveal the active ingredients and molecular mechanism of Tenghuang Jiangu Capsule against osteoporosis

Tenghuang Jiangu Capsule (THJGC) is a Chinese herbal formula used for the treatment of osteoporosis and osteoarthritis in China, but its mechanism for treating osteoporosis is not clear. The aim of this study was to investigate the therapeutic effect of THJGC on osteoporosis and its intrinsic mechanism through network pharmacology and experimental validation. Drugs and potential targets were obtained from several reliable databases through network pharmacology, and these targets were integrated and analyzed using bioinformatics and molecular docking strategies. Quercetin, lignans and kaempferol were identified as key components, and the key targets included Akt1, MAPKs, and CASP3. Subsequently, UPLC-MS/MS analysis confirmed the presence of components in THJGC for the treatment of osteoporosis. In addition, using ex vivo and in vivo models, it was confirmed that THJGC inhibited H2O2-induced ROS generation and apoptosis, and reduced OVX-induced bone loss in a mouse model of osteoporosis. Our data suggest that THJGC has antioxidant, bone formation-promoting, bone resorption-inhibiting, and MC3T3-E1 apoptosis-reducing effects, and thus has anti-osteoporotic properties. In conclusion, it may be a promising pharmacologic adjuvant treatment for osteoporosis.

Network Pharmacological Analysis and Animal Experimental Study on Osteoporosis Treatment with GuBen-ZengGu Granules

Aim

We explored the molecular pathway and material basis of GuBen-ZengGu granules (GBZGG) in treating osteoporosis using network pharmacology and animal experiments.

Methods

The effective active components and potential targets of GBZGG were obtained from the TCMSP database and BATMAN-TCM database. Disease-related genes were obtained from GeneCard, NCBI, and DisGeNET. Next, a protein interaction network was established using the STRING database, and core genes were screened using the MCODE module. Cytoscape 3.8.0 was used to construct the network of component-disease-pathway-target, and KEGG pathway enrichment analyses were performed using the clusterProfiler R package to predict the mechanism of GBZGG in treating osteoporosis. An osteoporosis rat model was established by ovarian excision (OVX), and the partial results of network pharmacology were experimentally verified.

Results

Pharmacodynamic results showed that GBZGG increased bone mineral density (BMD) and significantly improved the indexes of femur microstructure in model rats. The network pharmacology results showed that quercetin, luteolin, stigmasterol, angelicin, kaempferol, bakuchiol, bakuchiol, 7-O-methylisomucronulatum, isorhamnetin, formononetin, and beta-sitosterol are the major components of GBZGG, with MAPK1, AKT1, JUN, HSP90AA1, RELA, MAPK14, ESR1, RXRA, FOS, MAPK8, NCOA1, MYC, and IL-6 as its core targets for treating osteoporosis. Biological effects could be exerted by regulating the signaling pathways of fluid shear stress and the signaling pathways of atherosclerosis, advanced glycation end products (AGE-RAGE) of diabetic complications, prostate cancer, interleukin (IL-17), tumor necrosis factor (TNF), hepatitis B, mitogen-activated protein kinase (MAPK), etc. The results of animal experiments showed that GBZGG could reduce the serum levels of IL-6 and TNF-α, increase the expression of bone morphogenetic protein-2 (BMP-2) and runt-related transcription factor 2 (RUNX2) protein, and inhibit the activity of extracellular-regulated protein kinases (ERK1/2) and phosphorylation ERK1/2 (p-ERK1/2) protein.

Conclusion

GBZGG reduces the expression of ERK1/2 and p-ERK1/2 proteins and mRNAs through the inhibitory effects on IL-6 and TNF-α and negatively regulates the MAPK/ERK signaling pathway. The osteoporosis model showed that it effectively improved the loss of bone mass and destruction of bone microstructure in rats and maintained a positive balance for bone metabolism.

Equisetum arvense Inhibits Alveolar Bone Destruction in a Rat Model with Lipopolysaccharide (LPS)-Induced Periodontitis

Background and Aims

Equisetum arvense extract (EA) exerts various biological effects, including anti-inflammatory activity. The effect of EA on alveolar bone destruction has not been reported; therefore, we aimed to determine whether EA could inhibit alveolar bone destruction associated with periodontitis in a rat model in which periodontitis was induced using lipopolysaccharide from Escherichia coli (E. coli-LPS).

Methods

Physiological saline or E. coli-LPS or E. coli-LPS/EA mixture was topically administered into the gingival sulcus of the upper molar region of the rats. After 3 days, periodontal tissues of the molar region were collected. Immunohistochemistry was performed for cathepsin K, receptor activator of NF-κB ligand (RANKL), and osteoprotegerin (OPG). The cathepsin K-positive osteoclasts along the alveolar bone margin were counted. EA effects on the expression of the factors regulating osteoclastogenesis in osteoblasts with E. coli-LPS-stimulation were also examined in vitro.

Results

Treatment with EA significantly reduced the number of osteoclasts by decreasing the RANKL-expression and increasing OPG-expression in the periodontal ligament in the treatment group compared to the E. coli-LPS group. The in vitro study showed that the upregulation of p-IκB kinase α and β (p-IKKα/β), p-NF-κB p65, TNF-α, interleukin-6, and RANKL and downregulation of semaphorin 3A (Sema3A), β-catenin, and OPG in the osteoblasts with E. coli-LPS-stimulation improved with EA-treatment.

Conclusion

These findings demonstrated that topical EA suppressed alveolar bone resorption in the rat model with E. coli-LPS-induced periodontitis by maintaining a balance in RANKL/OPG ratio via the pathways of NF-κB, Wnt/β-catenin, and Sema3A/Neuropilin-1. Therefore, EA possesses the potential to prevent bone destruction through inhibiting osteoclastogenesis attributed to cytokine burst under plaque accumulation.

The combination of olive oil and Lepidium sativum improves the deleterious effects resulting from dexamethasone-induced osteoporosis in rats

Introduction

Osteoporosis is characterized by deterioration of bone microarchitecture and reduced bone mass and can increase the risk of fracture. To reduce this risk, the aim of this study was to compare the combination effects of olive oil and Lepidium sativum compared to the conventional drug therapy alendronate.

Methods

Osteoporosed-induced rat model was established by administration of dexamethasone in female adult albino rats. The serum level of Ca2+, P3+, and osteocalcin was assessed. In addition, histopathological changes and immunohistochemical expression of osteopontin within bone specimens were performed.

Results

Our results showed that a combination of olive oil and Lepidium sativum had a beneficial therapeutic effect in the treatment of osteoporosis as compared to alendronate therapy. This was demonstrated by increase of serum Ca2+, P3+, and osteocalcin levels in treated compared to control groups. Intriguingly, the highest effect was noticed in rats that received a combination of olive oil and Lepidium sativum compared to the individual treatment. This was reflected by an increase in the cortical bone thickness and a decrease in immunohistochemical expression of osteopontin compared to individual treated groups.

Conclusion

We concluded that the administration of a combination of olive oil and Lepidium sativum improves bone mineral health and intensity and reduces the risk of osteoporosis in a rat model.

Effect of Taraxaci Herba on Bone Loss in an OVX-Induced Model through the Regulation of Osteoclast Differentiation

Bone is a dynamic tissue that maintains homeostasis with a balance of osteoclasts for bone resorption and osteoblasts for bone formation. Women are deficient in estrogen after menopause, which promotes bone resorption due to excessive activity of osteoclasts, leading to osteoporosis. TH (also known as dandelion) is native to warm regions and has traditionally been used to treat gynecological diseases and inflammation. Menopause is a major cause of osteoporosis as it causes abnormal activity of osteoclasts, and various studies have shown that anti-inflammatory drugs have the potential to treat osteoporosis. We analyzed the effect of TH on osteoclast differentiation and the relevant mechanisms using RANKL. After administration of TH in a menopause-like rat model in which ovariectomy of the was rats carried out, changes in bone microstructure were analyzed via micro-CT, and the antiosteoporosis effect of TH was verified by a histological analysis. In addition, the pharmacological effects of TH in an animal model of osteoporosis were compared and analyzed with osteoporosis medications (17β-estradiol (E₂) and alendronate (ALN)). TH significantly inhibited the initial osteoclast differentiation via the NFATc1/c-Fos mechanism. In addition, bone density in the femur of osteoporotic rats was increased, and the expression of osteoclast-related factors in the serum and tissues was controlled. The results of this study provide objective evidence of the inhibitory effect of TH on osteoclastogenesis and OVX-induced bone loss.

Suppression of high bone remodelling by E'Jiao in ovariectomised rats

The current prevention options for postmenopausal osteoporosis are very limited. E'Jiao is a collagen-rich traditional Chinese medicine with the potential to prevent osteoporosis but more comprehensive investigations are lacking. This study aimed to investigate the skeletal protective effects of E'Jiao in a rat model of osteoporosis caused by ovariectomy. Female Sprague Dawley rats (n = 42) were randomly assigned into baseline, sham, ovariectomised (OVX) control, OVX-treated with low-dose (0.26 g/kg), medium dose (0.53 g/kg) and high dose E'Jiao (1.06 g/kg), as well as calcium carbonate (1% w/v) groups. Daily treatment through oral gavage was initiated 7 days after OVX. The rats were euthanised after eight weeks of treatment. Bone mineral density and content were measured at baseline, 1 and 2 months after treatment. Blood was collected for the measurement of bone remodelling markers. Femur and tibial bones were collected for histomorphometry and biomechanical strength analysis. Untreated OVX rats showed high bone remodelling marked by the increased bone formation and bone resorption markers, as well as increased mineralising surface/bone surface ratio. In addition, osteoclast surface and single-labelled surface were increased while mineral apposition rate was reduced in the untreated OVX rats. These changes were antagonised by E'Jiao at all doses. However, the structural, cellular and biomechanical parameters were not affected by ovariectomy and treatment. In conclusion, E'Jiao prevented high bone remodelling during oestrogen deficiency but a long-term study will be required to establish its effects on structural and biomechanical changes due to oestrogen deficiency.

Prophylactic Anti-Osteoporotic Effect of Matricaria chamomilla L. Flower Using Steroid-Induced Osteoporosis in Rat Model and Molecular Modelling Approaches

The anti-osteoporotic activity of ethanol extract from the Matricaria chamomilla L. flower was evaluated using steroid-induced osteoporosis in a rat model for the first time. Biochemical parameters such as serum calcium, phosphate, magnesium, creatinine, and alkaline phosphatase were assessed. At a 400 mg/kg body weight dose, the extract showed 54.01% and 27.73% reduction in serum calcium and phosphate ions serum levels, respectively. Meanwhile, it showed a 20% elevation in serum magnesium level, compared to the steroid-treated group. It also showed a significant decrease in creatinine and alkaline phosphatase levels, by 29.41% and 27.83%, respectively. The obtained results were further supported by biomechanical analyses, which revealed that a 400 mg/kg body weight dose of the flower extract increased bone strength and thickness. At the same time, it does not affect the bone length, compared to the diseased group. Histopathological examination revealed that the extract showed a significant increase in trabecular thickness, and it had restored the architecture of the cortical and trabecular structure with well-organized bone matrix. The possible inhibitory effect of the major phenolic compounds identified from the plant extract on cathepsin K was investigated using molecular docking. Rutin (4) had the best-fitting score within the active site, as evidenced by the free binding energy, (∆G = −54.19 Kcal/mol). ADMET/TOPKAT revealed that the examined compounds had variable pharmacodynamics and pharmacokinetic properties that could be improved to enhance the bioavailability during incorporation in various dosage forms. Thus, it can be concluded that this plant extract showed potential therapeutic benefits for osteoporosis.

Network pharmacology combined with GEO database identifying the mechanisms and molecular targets of Polygoni Cuspidati Rhizoma on Peri-implants

Peri-implants is a chronic disease leads to the bone resorption and loss of implants. Polygoni Cuspidati Rhizoma (PCRER), a traditional Chinese herbal has been used to treat diseases of bone metabolism. However, its mechanism of anti-bone absorption still remains unknown. We aimed to identify its molecular target and the mechanism involved in PCRER potential treatment theory to Peri-implants by network pharmacology. The active ingredients of PCRER and potential disease-related targets were retrieved from TCMSP, Swiss Target Prediction, SEA databases and then combined with the Peri-implants disease differential genes obtained in the GEO microarray database. The crossed genes were used to protein–protein interaction (PPI) construction and Gene Ontology (GO) and KEGG enrichment analysis. Using STRING database and Cytoscape plug-in to build protein interaction network and screen the hub genes and verified through molecular docking by AutoDock vina software. A total of 13 active compounds and 90 cross targets of PCRER were selected for analysis. The GO and KEGG enrichment analysis indicated that the anti-Peri-implants targets of PCRER mainly play a role in the response in IL-17 signaling, Calcium signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway among others. And CytoHubba screened ten hub genes (MMP9, IL6, MPO, IL1B, SELL, IFNG, CXCL8, CXCL2, PTPRC, PECAM1). Finally, the molecular docking results indicated the good binding ability with active compounds and hub genes. PCRER’s core components are expected to be effective drugs to treat Peri-implants by anti-inflammation, promotes bone metabolism. Our study provides new thoughts into the development of natural medicine for the prevention and treatment of Peri-implants.

Olive oil effectively mitigates ovariectomy-induced marrow adiposity assessed by MR spectroscopy in estrogen-deficient rabbits

BACKGROUND

Polyphenols in extra virgin olive oil (EVOO) have been found to reduce the expression of PPARγ2, inhibit adipocyte differentiation, and enhance the formation of osteoblasts from bone marrow stem cells. However, the underlying mechanisms of their action remain unknown.

PURPOSE

To determine the sequential effects of EVOO on marrow fat expansion induced by estrogen deprivation using 3.0-T proton magnetic resonance (MR) spectroscopy in an ovariectomy (OVX) rabbit model of postmenopausal bone loss over a six-month period.

MATERIAL AND METHODS

A total of 45 female New Zealand rabbits were equally divided into sham-operation, OVX controls, and OVX treated with EVOO for six months. Marrow fat fraction was measured by MR spectroscopy at baseline conditions, and three and six months postoperatively, respectively. Serum bone biomarkers, lumbar and femoral bone mineral density, microtomographic parameters, biomechanical properties, and quantitative parameters of marrow adipocytes were studied.

RESULTS

OVX was associated with marrow adiposity in a time-dependent manner, accompanied with increased bone turnover and impaired bone mass and trabecular microarchitecture. In OVX rabbits, EVOO markedly alleviated trabecular bone loss and reduced the accumulation of lipid droplets including adipocyte size, density, and areas of fat deposits in the bone marrow. EVOO prevented such changes in terms of both marrow adiposity and bone remodeling.

CONCLUSION

Early EVOO treatment may exert beneficial effects on bone by modulating marrow adiposity, which would support their protective effect against bone pathologies.

Re-appraising the role of flavonols, flavones and flavonones on osteoblasts and osteoclasts- A review on its molecular mode of action

Bone disorders have become a global concern illustrated with decreased bone mineral density and disruption in microarchitecture of natural bone tissue organization. Natural compounds that promote bone health by augmenting osteoblast functions and suppressing osteoclast functions has gained much attention and offer greater therapeutic value compared to conventional therapies. Amongst several plant-based molecules, flavonoids act as a major combatant in promoting bone health through their multi-faceted biological activities such as antioxidant, anti-inflammatory, and osteogenic properties. They protect bone loss by regulating the signalling cascades involved in osteoblast and osteoclast functions. Flavonoids augment osteoblastogenesis and inhibits osteoclastogenesis through their modulation of various signalling pathways. This review discusses the role of various flavonoids and their molecular mechanisms involved in maintaining bone health by regulating osteoblast and osteoclast functions.

The Role of Macronutrients, Micronutrients and Flavonoid Polyphenols in the Prevention and Treatment of Osteoporosis

Osteoporosis is considered an age-related disorder of the skeletal system, characterized primarily by decreased bone mineral density (BMD), microstructural quality and an elevated risk of fragility fractures. This silent disease is increasingly becoming a global epidemic due to an aging population and longer life expectancy. It is known that nutrition and physical activity play an important role in skeletal health, both in achieving the highest BMD and in maintaining bone health. In this review, the role of macronutrients (proteins, lipids, carbohydrates), micronutrients (minerals—calcium, phosphorus, magnesium, as well as vitamins—D, C, K) and flavonoid polyphenols (quercetin, rutin, luteolin, kaempferol, naringin) which appear to be essential for the prevention and treatment of osteoporosis, are characterized. Moreover, the importance of various naturally available nutrients, whether in the diet or in food supplements, is emphasized. In addition to pharmacotherapy, the basis of osteoporosis prevention is a healthy diet rich mainly in fruits, vegetables, seafood and fish oil supplements, specific dairy products, containing a sufficient amount of all aforementioned nutritional substances along with regular physical activity. The effect of diet alone in this context may depend on an individual’s genotype, gene-diet interactions or the composition and function of the gut microbiota.

Anti-Osteoporotic Mechanisms of Polyphenols Elucidated Based on In Vivo Studies Using Ovariectomized Animals

Polyphenols are widely known for their antioxidant activity, i.e., they have the ability to suppress oxidative stress, and this behavior is mediated by the autoxidation of their phenolic hydroxyl groups. Postmenopausal osteoporosis is a common health problem that is associated with estrogen deficiency. Since oxidative stress is thought to play a key role in the onset and progression of osteoporosis, it is expected that polyphenols can serve as a safe and suitable treatment in this regard. Therefore, in this review, we aimed to elucidate the anti-osteoporotic mechanisms of polyphenols reported by in vivo studies involving the use of ovariectomized animals. We categorized the polyphenols as resveratrol, purified polyphenols other than resveratrol, or polyphenol-rich substances or extracts. Literature data indicated that resveratrol activates sirtuin 1, and thereafter, suppresses osteoclastogenic pathways, such as the receptor activator of the nuclear factor kappa B (RANK) ligand (RANKL) pathway, and promotes osteoblastogenic pathways, such as the wingless-related MMTV integration site pathway. Further, we noted that purified polyphenols and polyphenol-rich substances or extracts exert anti-inflammatory and/or antioxidative effects, which inhibit RANKL/RANK binding via the NF-κB pathway, resulting in the suppression of osteoclastogenesis. In conclusion, antioxidative and anti-inflammatory polyphenols, including resveratrol, can be safe and effective for the treatment of postmenopausal osteoporosis based on their ability to regulate the imbalance between bone formation and resorption.

New bone-generative effect of Salvia officinalis L. in the expanded midpalatal suture : An in vivo and in vitro study

PURPOSE

The aims of this study were to evaluate the effects of systemic administration of Salvia officinalis Linnaeus (L.) leaf extract on new bone formation in the expanded premaxillary suture in rats in vivo and to examine the antioxidant effects and phenolic profile of Salvia officinalis (SO) leaf and root extracts in vitro.

METHODS

Fourteen male Sprague Dawley rats were allocated to two groups: SO group (n = 7) and control group (n = 7). An open-loop spring was attached to the upper incisors of each rat to expand the premaxillae. A 5-day expansion period followed by a 12-day retention period was observed. The rats in the SO group received systemic administration of 20 mg SO/kg/day via the orogastric route for 17 days. Histomorphometric examinations were carried out to examine the amount of new bone formation, number of capillaries, and intensity of inflammatory cell response. Immunohistochemical analysis was conducted to examine the number of osteoblasts and osteoclasts. Leaf and root extracts of SO were also analyzed for antioxidant activity and phenolic compounds in vitro.

RESULTS

Statistical analysis showed that the following were higher in the SO group than in the control group: new bone formation, number of osteoblasts and osteoclasts, intensity of inflammatory cell response (neutrophils, lymphocytes, and macrophages), and number of capillaries. The major compound identified in SO leaf extract was rosmarinic acid, while luteolin derivatives, salvianolic acid F, and medioresinol were also present.

CONCLUSIONS

Salvia officinalis L. from leaf extract provided antioxidant effects and stimulated enhanced new bone formation in the expanded midpalatal suture after maxillary expansion in rats.

Mechanism and Experimental Verification of Luteolin for the Treatment of Osteoporosis Based on Network Pharmacology

PURPOSE

To explore the molecular mechanism of luteolin in the treatment of osteoporosis (OP) by network pharmacological prediction and experimentation.

METHODS

The target proteins of luteolin were obtained with the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). OP-related proteins were extracted from the Comparative Toxicogenomics Database (CTD) and GeneCards and DisGeNET databases. We imported the common protein targets of luteolin and OP into the STRING database to obtain the relationships between the targets. The common target proteins of luteolin and OP were assessed by KEGG and GO enrichment analyses with the DAVID database. Animal experiments were conducted to verify the effect of luteolin on bone mineral density in ovariectomised (OVX) rats. Finally, the effects of luteolin on key signalling pathways were verified by cell experiments in vitro.

RESULTS

Forty-four targets of luteolin involved in the treatment of OP, including key target proteins such as TP53, AKT1, HSP90AA1, JUN, RELA, CASP3, and MAPK1, were screened. KEGG enrichment analysis found that luteolin inhibits OP by regulating the PI3K-Akt, TNF, oestrogen and p53 signalling pathways. The results of animal experiments showed that bone mass in the low-dose luteolin group (Luteolin-L group, 10 mg/kg), high-dose luteolin group (Luteolin-H group, 50 mg/kg) and positive drug group was significantly higher than that in the OVX group (P<0.05). Western blot (WB) analysis showed that the protein expression levels of Collagen I, Osteopontin and RUNX2 in bone marrow mesenchymal stem cells (BMSCs) cultured with 0.5, 1 and 5 μM luteolin for 48 h were significantly higher than those in the dimethyl sulfoxide (DMSO) group (P<0.05). In vitro cell experiments showed that the p-PI3K/PI3K and p-Akt/Akt expression ratios in BMSCs cultured with 0.5, 1 and 5 μM luteolin for 48 h were also significantly higher than those in the DMSO group (P<0.05).

CONCLUSIONS

Luteolin has multitarget and multichannel effects in the treatment of OP. Luteolin could reduce bone loss in OVX rats, which may be due to its ability to promote the osteogenic differentiation of BMSCs by regulating the activity of the PI3K-Akt signalling pathway.

Effects and mechanisms of natural plant active compounds for the treatment of osteoclast-mediated bone destructive diseases

Bone-destructive diseases, caused by overdifferentiation of osteoclasts, reduce bone mass and quality, and disrupt bone microstructure, thereby causes osteoporosis, Paget's disease, osteolytic bone metastases, and rheumatoid arthritis. Osteoclasts, the only multinucleated cells with bone resorption function, are derived from haematopoietic progenitors of the monocyte/macrophage lineage. The regulation of osteoclast differentiation is considered an effective target for the treatment of bone-destructive diseases. Natural plant-derived products have received increasing attention in recent years due to their good safety profile, the preference of natural compounds over synthetic drugs, and their potential therapeutic and preventive activity against osteoclast-mediated bone-destructive diseases. In this study, we reviewed the research progress of the potential antiosteoclast active compounds extracted from medicinal plants and their molecular mechanisms. Active compounds from natural plants that inhibit osteoclast differentiation and functions include flavonoids, terpenoids, quinones, glucosides, polyphenols, alkaloids, coumarins, lignans, and limonoids. They inhibit bone destruction by downregulating the expression of osteoclast-specific marker genes (CTSK, MMP-9, TRAP, OSCAR, DC-STAMP, V-ATPase d2, and integrin av3) and transcription factors (c-Fos, NFATc1, and c-Src), prevent the effects of local factors (ROS, LPS, and NO), and suppress the activation of various signalling pathways (MAPK, NF-κB, Akt, and Ca²⁺). Therefore, osteoclast-targeting natural products are of great value in the prevention and treatment of bone destructive diseases.

Flavonoids: Classification, Function, and Molecular Mechanisms Involved in Bone Remodelling

Flavonoids are polyphenolic compounds spotted in various fruits, vegetables, barks, tea plants, and stems and many more natural commodities. They have a multitude of applications through their anti-inflammatory, anti-oxidative, anti-carcinogenic properties, along with the ability to assist in the stimulation of bone formation. Bone, a rigid connective body tissue made up of cells embedded in a mineralised matrix is maintained by an assemblage of pathways assisting osteoblastogenesis and osteoclastogenesis. These have a significant impact on a plethora of bone diseases. The homeostasis between osteoblast and osteoclast formation decides the integrity and structure of the bone. The flavonoids discussed here are quercetin, kaempferol, icariin, myricetin, naringin, daidzein, luteolin, genistein, hesperidin, apigenin and several other flavonoids. The effects these flavonoids have on the mitogen activated protein kinase (MAPK), nuclear factor kappa β (NF-kβ), Wnt/β-catenin and bone morphogenetic protein 2/SMAD (BMP2/SMAD) signalling pathways, and apoptotic pathways lead to impacts on bone remodelling. In addition, these polyphenols regulate angiogenesis, decrease the levels of inflammatory cytokines and play a crucial role in scavenging reactive oxygen species (ROS). Considering these important effects of flavonoids, they may be regarded as a promising agent in treating bone-related ailments in the future.

Ethyl acetate extract of the Musa nana flower inhibits osteoclastogenesis and suppresses NF-κB and MAPK pathways

Banana flowers are consumed as a vegetable and traditionally used for managing several health problems including joint pain, a symptom of bone loss. Osteoclasts are key effector cells responsible for bone loss. Some flavonoids in banana flowers, such as quercetin and quercitrin, have been shown to be able to inhibit osteoclastogenesis. Whether banana flowers can inhibit osteoclast formation is unknown. In this study, we prepared the ethyl acetate fraction (FFE-EA) of an ethanolic extract of fresh flowers of Musa nana. Using UPLC-MS/MS analyses, 76 polyphenols were identified in FFE-EA. In RANKL-stimulated RAW264.7 macrophages, FFE-EA inhibited osteoclastogenesis and osteoclastic bone resorption. Mechanistic studies revealed that FFE-EA suppressed NF-κB and MAPK pathways, and lowered mRNA levels of osteoclast formation/function-related genes. These findings suggest that flowers of M. nana could be a source for formulating functional food that benefits bone health.

Inhibitory effects of luteolin and its derivatives on osteoclast differentiation and differences in luteolin production by Capsicum annuum varieties

Luteolin, an abundant flavonoid in the leaves of Capsicum annuum, has antioxidant activity and is, thus, a key chemical for promoting plant residue utilization, especially for the development of healthcare products. We assessed the inhibitory effect of luteolin and its glycosides on osteoclastic differentiation in human cells and found that the differentiation was effectively inhibited at noncytotoxic concentrations. We also screened 47 varieties of C. annuum for the accumulation of luteolin and apigenin to determine the prevalence of luteolin in diverse cultivars and identify varieties with high and/or selective luteolin production. The glycosides of luteolin and apigenin were found in all the tested varieties, with luteolin predominant over apigenin in most varieties. The identification and characterization of highly productive varieties of C. annuum is expected to be beneficial for the effective development of useful luteolin-based products from plant residues.

Paving Luteolin Therapeutic Potentialities and Agro-Food-Pharma Applications: Emphasis on In Vivo Pharmacological Effects and Bioavailability Traits

Luteolin is a naturally occurring secondary metabolite belonging to the class of flavones. As many other natural flavonoids, it is often found in combination with glycosides in many fruits, vegetables, and plants, contributing to their biological and pharmacological value. Many preclinical studies report that luteolin present excellent antioxidant, anticancer, antimicrobial, neuroprotective, cardioprotective, antiviral, and anti-inflammatory effects, and as a consequence, various clinical trials have been designed to investigate the therapeutic potential of luteolin in humans. However, luteolin has a very limited bioavailability, which consequently affects its biological properties and efficacy. Several drug delivery strategies have been developed to raise its bioavailability, with nanoformulations and lipid carriers, such as liposomes, being the most intensively explored. Pharmacological potential of luteolin in various disorders has also been underlined, but to some of them, the exact mechanism is still poorly understood. Given the great potential of this natural antioxidant in health, this review is aimed at providing an extensive overview on the in vivo pharmacological action of luteolin and at stressing the main features related to its bioavailability, absorption, and metabolism, while essential steps determine its absolute health benefits and safety profiles. In addition, despite the scarcity of studies on luteolin bioavailability, the different drug delivery formulations developed to increase its bioavailability are also listed here.

Study on the Mechanism of Salvia miltiorrhiza in the Treatment of Traumatic Bone Defects

Traumatic bone defect is one of the major orthopedic diseases in clinics, and its incidence is increasing year by year. And repairing traumatic bone defects is a very difficult problem in clinics at present. The surface of medical titanium-based alloy has good biological properties, and its implant has a certain role in promoting bone in bone tissue. However, titanium-based materials are biologically inert and have no biological activity. As a traditional Chinese medicine, Salvia miltiorrhiza has the efficacy of treating bone diseases and promoting bone healing. The curative effect can be better exerted by loading the traditional Chinese medicine active compound Salvia miltiorrhiza on the surface of the titanium implant in a certain way. At present, due to the complex chemical composition of Salvia miltiorrhiza, the mechanism of its use for the treatment of traumatic bone defects is still unclear. Therefore, in this study, we mainly discussed the potential target and mechanism of Salvia miltiorrhiza in the treatment of traumatic bone defects through network pharmacology, which may provide a scientific basis for the treatment of traumatic bone defects with Salvia miltiorrhiza loaded on the surface of medical titanium-based alloy. We screened out effective compounds and targets of Salvia miltiorrhiza and targets related to traumatic bone defects with the help of relevant databases. The targets of Salvia miltiorrhiza for traumatic bone defects were analyzed by STRING and GeneCards databases, and the results were visualized by constructing a compound-target network, protein-protein interaction network, and compound-target-disease network with Cytoscape 3.7.1 analysis software. Finally, the selected core targets carried out GO and KEGG enrichment. The results showed that 60 main active components were screened from Salvia miltiorrhiza Bunge, which could act on 149 targets. There were 33 active components and 70 targets related to traumatic bone defects, respectively. The core targets of Salvia miltiorrhiza in the treatment of traumatic bone defects were MAPK1, MAPK10, MAPK14, TGFB1, and TNF. The results of enrichment analysis showed that Salvia miltiorrhiza might treat traumatic bone defects through an osteogenic differentiation pathway.

Salvia officinalis Extract and 17β-Estradiol Suppresses Ovariectomy Induced Osteoporosis in Female Rats

&lt;b&gt;Background and Objective:&lt;/b&gt; Osteoporosis is a progressive metabolic disorder characterized by an impaired bone formation that leads to increased morbidity and mortality.&lt;i&gt; Salvia officinalis &lt;/i&gt;is a source of phytoestrogens that could help mitigate the risk of osteoporotic rat fracture by exerting sex hormones. Therefore, the present study was designed to investigate the curative effect of &lt;i&gt;Salvia officinalis &lt;/i&gt;Extract&lt;i&gt; &lt;/i&gt;(SOE) and&lt;i&gt; &lt;/i&gt;17β-estradiol (E&lt;sub&gt;2&lt;/sub&gt;) and their combination&lt;i&gt; &lt;/i&gt;on bone loss in female rats with ovariectomy-induced estrogen deficiency &lt;b&gt;Materials and Methods:&lt;/b&gt; Forty adult female albino rats were divided into five groups, which included Sham control (Sham), ovariectomy (OVX), OVX+SOE, OVX+E&lt;sub&gt;2&lt;/sub&gt; and OVX +SOE+E&lt;sub&gt;2&lt;/sub&gt;.&lt;i&gt; &lt;/i&gt;SOE (10 mL kg&lt;sup&gt;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) and E&lt;sub&gt;2&lt;/sub&gt; (30 μg kg&lt;sup&gt;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) had been daily gavaged in the OVX+SOE, OVX+E&lt;sub&gt;2&lt;/sub&gt; and OVX+SOE+E&lt;sub&gt;2&lt;/sub&gt;, respectively for 6-weeks. &lt;b&gt;Results:&lt;/b&gt; The model of ovariectomy resulted in osteoporosis as demonstrated by the decreased serum Ca, P, vitamin D, E&lt;sub&gt;2&lt;/sub&gt; level associated with a significant increase in PTH levels in comparison to the sham control group. Besides, OVX to rats caused up-regulation in the levels of CTX-1, P1NP, BALP, OC and RANKL comparable to the sham control group. Moreover, SOE and E&lt;sub&gt;2&lt;/sub&gt; significantly modulated the calciotropic parameters and improved all bone turnover markers as well as RANKL as compared to the OVX group. However, Histopathological and immunohistochemical results showed defective mineralization with the destruction of the bone matrix and increased TNF-α expression from the OVX group relative to the treated groups. &lt;b&gt;Conclusion:&lt;/b&gt; These results suggest that both SOE and E&lt;sub&gt;2&lt;/sub&gt; or their combined administration are efficient inhibitors against ovariectomy-induced bone loss in female rats.

Changes in Bone Metabolism and Antioxidant Defense Systems in Menopause-Induced Rats Fed Bran Extract from Dark Purple Rice (Oryza sativa L. Cv. Superjami)

Menopause is a matter of concern for women’s health due to a deficiency of female hormones; additionally, reactive oxygen species and aging can cause osteoporosis. Food becomes increasingly interesting as a menopausal woman’s alternative to hormone therapy. The effects of ethanol extracts from dark purple Superjami rice bran on bone metabolism and antioxidant defense systems in menopause-induced animal models were evaluated. Female rats underwent sham surgery or were ovariectomized to induce a menopause-like state. Rats were divided into a sham control group (SHAM), an ovariectomized control group (OVX), and an ovariectomized grou supplemented with Superjami rice bran extract group (OVX-S) and fed for 8 weeks. The OVX groups exhibited significantly more weight gain, amounts of bone turnover biochemical markers (alkaline phosphatase, osteocalcin, and C-terminal telopeptide), bone loss, lipid-peroxidation and oxidative stress than the SHAM group. However, Superjami bran extract added to the diet resulted in a significant reduction in body weight and lipid peroxidation, as well as enhanced bone metabolism and antioxidant enzyme activities, in ovariectomized rats. These results propound that extracts from Superjami rice bran have therapeutic potentiality against bone loss and oxidative stress in menopause-induced states and will be useful in preventing postmenopausal osteoporosis and oxidative damage.

Protective Effect of Ciclopirox against Ovariectomy-Induced Bone Loss in Mice by Suppressing Osteoclast Formation and Function

Postmenopausal osteoporosis is closely associated with excessive osteoclast formation and function, resulting in the loss of bone mass. Osteoclast-targeting agents have been developed to manage this disease. We examined the effects of ciclopirox on osteoclast differentiation and bone resorption in vitro and in vivo. Ciclopirox significantly inhibited osteoclast formation from primary murine bone marrow macrophages (BMMs) in response to receptor activator of nuclear factor kappa B ligand (RANKL), and the expression of genes associated with osteoclastogenesis and function was decreased. The formation of actin rings and resorption pits was suppressed by ciclopirox. Analysis of RANKL-mediated early signaling events in BMMs revealed that ciclopirox attenuates IκBα phosphorylation without affecting mitogen-activated protein kinase activation. Furthermore, the administration of ciclopirox suppressed osteoclast formation and bone loss in ovariectomy-induced osteoporosis in mice and reduced serum levels of osteocalcin and C-terminal telopeptide fragment of type I collagen C-terminus. These results indicate that ciclopirox exhibits antiosteoclastogenic activity both in vitro and in vivo and represents a new candidate compound for protection against osteoporosis and other osteoclast-related bone diseases.

Chrysin alleviates alteration of bone-remodeling markers in ovariectomized rats and exhibits estrogen-like activity in silico

BACKGROUND

Evidences are beginning to accrue that flavonoids, particularly phytoestrogens, could have beneficial effects against several age-related diseases linked to estrogen deficiency including postmenopausal osteoporosis.

METHODS

In this study, the effect of chrysin on selected bone-remodeling markers in ovariectomized rats and its estrogen-like activity in silico were investigated.

RESULTS

The data indicated that administration of chrysin at 50 mg/kg and 100 mg/kg for 6 weeks to OVX rats significantly (p < 0.05) prevented body weight gain and partially reverse uterine weight loss. In addition, treatment of OVX rats significantly (p < 0.01) increased femur dry weight, femur ash weight, bone ash calcium, and phosphorous levels in a dose-dependent manner. However, there was significant (p < 0.001) decline in serum estradiol level in all OVX rats compared to the sham-operated group. Interestingly, administration of chrysin significantly (p < 0.05) reversed the reduction of estradiol induced by ovariectomy compared to untreated OVX rats. Moreover, administration of chrysin to OVX rats significantly (p < 0.05) suppressed excessive elevation of bone-remodeling markers expression compared to untreated OVX rats. Similarly, molecular docking analysis revealed that chrysin interacts with both α and β estrogen receptors with exothermic binding energies of -229.83 kcal/Mol and -252.72 kcal/Mol, respectively, and also fits perfectly into the active site of both α and β estrogen receptors.

CONCLUSION

This study demonstrated that chrysin exhibits potential antiosteoporotic effects against bone loss in OVX rats through enhanced bone mineral contents and preventing excessive elevation of bone-remodeling markers and bone-resorbing cytokine.

3',4'-Dihydroxyflavonol Modulates the Cell Cycle in Cancer Cells: Implication as a Potential Combination Drug in Osteosarcoma

New agents are demanded to increase the therapeutic options for osteosarcoma (OS). Although OS is the most common bone cancer in children and adolescents, it is considered a rare disorder. Therefore, finding adjuvant drugs has potential to advance therapy for this disease. In this study, 3′,4′-dihydroxyflavonol (DiOHF) was investigated to assess the effects in OS cellular models in combination with doxorubicin (Dox). MG-63 and U2OS human OS cells were exposed to DiOHF and Dox and tested for cell viability and growth. To elucidate the inhibitory effects of DiOHF, additional studies were conducted to assess apoptosis and cell cycle distribution, gene expression quantification of cell cycle regulators, and cytokinesis-block cytome assay to determine nuclear division rate. DiOHF decreased OS cell growth and viability in a concentration-dependent manner. Its combination with Dox enabled Dox dose reduction in both cell lines, with synergistic interactions in U2OS cells. Although no significant apoptotic effects were detected at low concentrations, cytostatic effects were demonstrated in both cell lines. Incubation with DiOHF altered cell cycle dynamics and resulted in differential cyclin and cyclin-dependent kinase expression. Overall, this study presents an antiproliferative action of DiOHF in OS combination therapy via modulation of the cell cycle and nuclear division.

Systems pharmacology dissection of action mechanisms for herbs in osteoporosis treatment

Objective

Osteoporosis has become the biggest cause of non-fatal health issue. Currently, the limitations of traditional anti-osteoporosis drugs such as long-term ill-effects and drug resistance, have raised concerns toward complementary and alternative therapies, particularly herbal medicines and their natural active compounds. Thus, this study aimed to provide an integrative analysis of active chemicals, drug targets and interacting pathways of the herbs for osteoporosis treatment.

Methods

Here, we introduced a systematic pharmacology model, combining the absorption, distribution, metabolism, and excretion (ADME) screening model, drug targeting and network pharmacology, to probe into the therapeutic mechanisms of herbs in osteoporosis.

Results

We obtained 86 natural compounds with favorable pharmacokinetic profiles and their 58 targets from seven osteoporosis-related herbs. Network analysis revealed that they probably synergistically work through multiple mechanisms, such as suppressing inflammatory response, maintaining bone metabolism or improving organism immunity, to benefit patients with osteoporosis. Furthermore, experimental results showed that all the five compounds (calycosin, asperosaponin VI, hederagenin, betulinic acid and luteolin) enhanced osteoblast proliferation and differentiation in vitro, which corroborated the validity of this system pharmacology approach. Notably, gentisin and aureusidin among the identified compounds were first predicted to be associated with osteoporosis.

Conclusion

Herbs and their natural compounds, being characterized as the classical combination therapies, might be engaged in multiple mechanisms to coordinately improve the osteoporosis symptoms. This work may contribute to offer novel strategies and clues for the therapy and drug discovery of osteoporosis and other complex diseases.

Analysis of Molecular Mechanism of Erxian Decoction in Treating Osteoporosis Based on Formula Optimization Model

Osteoporosis (OP) is a highly prevalent orthopedic condition in postmenopausal women and the elderly. Currently, OP treatments mainly include bisphosphonates, receptor activator of nuclear factor kappa-B ligand (RANKL) antibody therapy, selective estrogen receptor modulators, teriparatide (PTH1-34), and menopausal hormone therapy. However, increasing evidence has indicated these treatments may exert serious side effects. In recent years, Traditional Chinese Medicine (TCM) has become popular for treating orthopedic disorders. Erxian Decoction (EXD) is widely used for the clinical treatment of OP, but its underlying molecular mechanisms are unclear thanks to its multiple components and multiple target features. In this research, we designed a network pharmacology method, which used a novel node importance calculation model to identify critical response networks (CRNs) and effective proteins. Based on these proteins, a target coverage contribution (TCC) model was designed to infer a core active component group (CACG). This approach decoded the mechanisms underpinning EXD's role in OP therapy. Our data indicated that the drug response network mediated by the CACG effectively retained information of the component-target (C-T) network of pathogenic genes. Functional pathway enrichment analysis showed that EXD exerted therapeutic effects toward OP by targeting PI3K-Akt signaling (hsa04151), calcium signaling (hsa04020), apoptosis (hsa04210), estrogen signaling (hsa04915), and osteoclast differentiation (hsa04380) via JNK, AKT, and ERK. Our method furnishes a feasible methodological strategy for formula optimization and mechanism analysis and also supplies a reference scheme for the secondary development of the TCM formula.

Agastache rugosa ethanol extract suppresses bone loss via induction of osteoblast differentiation with alteration of gut microbiota

PURPOSE

Osteoporosis is a metabolic skeletal disease characterized by bone loss and an increased risk of fractures. This study aimed to investigate the therapeutic effect of Agastache rugosa on postmenopausal osteoporosis and elucidate its mechanisms in modulating the bone status.

METHODS AND RESULTS

In the osteoblast differentiation process with MC3T3-E1 pre-osteoblasts, ethanol extract of Agastache rugosa (EEAR) and its compounds increased the expression of the proteins and genes of the osteoblast differentiation-related markers such as Runt-related transcription factor 2 (RUNX2) and β-catenin along with the elevation of calcium deposits. An ovariectomized mouse model was utilized to determine the impact of EEAR extract on postmenopausal osteoporosis. Twelve weeks of AR treatment suppressed the loss of bone strength, which was observed through micro-computed tomography. AR elevated osteogenic markers in the bone marrow cells, and collagen type 1 alpha 1 in the distal femoral bone. The results of the 16S rRNA gene sequencing analysis of cecal gut microbiomes demonstrated that AR reversed the ovariectomy-induced changes in the gut microbiomes.

CONCLUSION

Ethanol extract of Agastache rugosa has a therapeutic effect on postmenopausal osteoporosis via bone morphogenic protein, transforming growth factor β, and Wnt signaling pathway. It also increases the diversity of gut microbiota. Therefore, these data suggest that EEAR could be a potential candidate to treat postmenopausal osteoporosis.

Membrane Transport Proteins in Osteoclasts: The Ins and Outs

During bone resorption, the osteoclast must sustain an extraordinarily low pH environment, withstand immense ionic pressures, and coordinate nutrient and waste exchange across its membrane to sustain its unique structural and functional polarity. To achieve this, osteoclasts are equipped with an elaborate set of membrane transport proteins (pumps, transporters and channels) that serve as molecular ‘gatekeepers’ to regulate the bilateral exchange of ions, amino acids, metabolites and macromolecules across the ruffled border and basolateral domains. Whereas the importance of the vacuolar-ATPase proton pump and chloride voltage-gated channel 7 in osteoclasts has long been established, comparatively little is known about the contributions of other membrane transport proteins, including those categorized as secondary active transporters. In this Special Issue review, we provide a contemporary update on the ‘ins and outs’ of membrane transport proteins implicated in osteoclast differentiation, function and bone homeostasis and discuss their therapeutic potential for the treatment of metabolic bone diseases.

Emerging Natural-Product-Based Treatments for the Management of Osteoarthritis

Osteoarthritis (OA) is a complex degenerative disease in which joint homeostasis is disrupted, leading to synovial inflammation, cartilage degradation, subchondral bone remodeling, and resulting in pain and joint disability. Yet, the development of new treatment strategies to restore the equilibrium of the osteoarthritic joint remains a challenge. Numerous studies have revealed that dietary components and/or natural products have anti-inflammatory, antioxidant, anti-bone-resorption, and anabolic potential and have received much attention toward the development of new therapeutic strategies for OA treatment. In the present review, we provide an overview of current and emerging natural-product-based research treatments for OA management by drawing attention to experimental, pre-clinical, and clinical models. Herein, we review current and emerging natural-product-based research treatments for OA management.

Traditional Chinese Medicine and orthopedic biomaterials: Host of opportunities from herbal extracts

The role of Traditional Chinese Medicine (TCM), especially herbs or herbal extracts, in treating diseases has received increasing attention. This review focuses on the use of herbal extracts as signaling molecules and functional materials in the field of orthopedics, biomaterial science and bone tissue engineering strategies. A literature review using both Chinese and English references on herbs and herbal extracts based on TCM theory used in orthopedics and biomaterial science was performed. We discuss the efficacy of herbs, the active extracts from these herbs, the combination of herbal extracts and biomaterials and, finally, the application of herbal extracts to the biomaterials specific to orthopedics. Only a few studies have confirmed the feasibility of applying herbal extracts to biomaterials to improve the role of biomaterials and/or optimize drug delivery and release in orthopedics. In this context, this review reveals a new and promising direction for herbal extracts, where the use of herbal extracts based on TCM systemic treatment, can change the limited modern medicine view of biomaterials as "only for local treatment" when considering its efficacy.

Predicting and Exploring the Mechanisms of Erzhi Pill in Prevention and Treatment of Osteoporosis Based on Network Pharmacology and Zebrafish Experiments

Background

Erzhi Pill (EZP), a traditional Chinese medicine (TCM) prescription, has been widely applied to improve bone metabolism and treat osteoporosis (OP) in China. However, its effective constituents and mechanisms remain unclear.

Methods

By combining network pharmacology and zebrafish experiments, an integrative method was employed to address this problem. Firstly, the disease targets of OP were collected from two public gene databases. Secondly, the active compounds and drug targets of EZP were obtained from the traditional Chinese medicine systems pharmacology database and analysis platform (TCMSP). Thirdly, a drug-target-disease interaction network was constructed, and the key active components were identified by analyzing the topological characteristics of the network. Finally, these predicted results were tested by zebrafish experiments and compared with those from the literature. Specifically, quercetin as an important representative active component of EZP was applied to wild type and transgenic zebrafish larvae to assess its effects on skull mineralization and osteoplastic differentiation.

Results

Our study identified 72 active compounds, 220 targets and 166 signaling pathways probably involved in the prevention and treatment of OP by EZP, wherein quercetin, apigenin, daidzein, luteolin, ursolic acid and kaempferol could be the key compounds, while PI3K-Akt signaling pathway, TNF signaling pathway and IL-17 signaling pathway could be the key signaling pathways. The experiments indicated that quercetin attenuated both the decrease of skull mineralization and the inhibition of skull osteoplastic differentiation in zebrafish larvae trigged by dexamethasone.

Conclusion

Our study not only investigated potentially effective constituents and mechanisms of EZP in the prevention and treatment of OP, but also provided a reference for the in-depth research, development and application of TCM.

Does Panchatikta ghrita have anti-osteoporotic effect? Assessment in an experimental model in ovariectomized rats

BACKGROUND

Osteoporosis is a public health problem in the elderly wherein a decrease in bone mass and mineral density increases the at risk of fractures. Panchatikta Ghrita (PG) is a classical Ayurvedic formulation that may help slow bone degeneration.

OBJECTIVE

This experimental study was conducted to assess the efficacy of Panchatikta ghrita (PG) in protecting against postmenopausal osteoporosis in ovariectomized rats.

MATERIALS AND METHODS

The experiment was initiated after Institutional Animal Ethics Committee approval. 96 female Sprague Dawley rats were divided into 8 groups viz. sham control (NC), diseased control (DC), vehicle control (VC), 3 test drug (PG) groups (PG1, PG2 & PG3 - 0.9, 1.8 and 2.7gm/kg body weight respectively) and 2 standard control (SC) groups - SC1 received 17α-ethinylestradiol 1μg/kg/day while SC2 received alendronate (7mg/kg/week). Study medications were administereddaily for four months. Bone specific biomarkers viz. osteocalcin and TRAP-5b were estimated at baseline and end of study. Animals were sacrificed on day 121 and their femurs and tibiae were harvested for histomorphometric analysisand bone microarchitectural studies.

RESULTS

Serum osteocalcin and TRAP-5b showed significant increase (p < 0.001) in levels in DC group as compared to sham controls. All 3 doses of PG decreased bone specific biomarker levels with maximal effect seen with highest dose of PG similar to that seen with standard drugs. PG also significantly improved bone micro architectural parameters like bone mineral density and mineral content at higher dose levels. Decrease in osteoclasts and significant dose dependent increase in bone hardness and elasticity was seen with PG which was comparable to standard drugs.

CONCLUSION

PG increased bone mineral density and content, decreased turnover of bone specific biomarkers and osteoclast formation, indicating its protective effect against experimentally induced postmenopausal osteoporosis.

IL-4 absence triggers distinct pathways in apical periodontitis development

Dental pulp is a specialized tissue able to respond to infectious processes. Nevertheless, infection progress and root canal colonization trigger an immune-inflammatory response in tooth-surrounding tissues, leading to apical periodontitis and bone tissue destruction, further contributing to tooth loss. In order to shed some light on the effects of IL-4 on periradicular pathology development modulation, microtomographic, histological and proteomic analyses were performed using 60 mice, 30 wild type and 30 IL-4^-/^-. For that, 5 animals were used for microtomographic and histological analysis, and another 5 for proteomic analysis for 0, 7 and 21 days with/without pulp exposure. The periapical lesions were established in WT and IL-4^-/^- mice without statistical differences in their volume, and the value of p < 0.05 was adopted as significant in microtomographic and histological analyses. Regarding histological analysis, IL-4^-/^- mice show aggravation of pulp inflammation compared to WT. By using proteomic analysis, we have identified 32 proteins with increased abundance and 218 proteins with decreased abundance in WT animals after 21 days of pulp exposure, compared to IL-4^-/^- animals. However, IL-4^-/^- mice demonstrated faster development of apical periodontitis. These animals developed a compensatory mechanism to overcome IL-4 absence, putatively based on the identification of upregulated proteins related to immune system signaling pathways. Significance: IL-4 might play a protective role in diseases involving bone destruction and its activity may contribute to host protection, mainly due to its antiosteoclastogenic action.

Water Extract of Agastache rugosa Prevents Ovariectomy-Induced Bone Loss by Inhibiting Osteoclastogenesis

Estrogen deficiency in postmenopausal women causes homeostatic imbalance of bone, resulting in bone loss and osteoporosis. Agastache rugosa, a plant belonging to the Lamiaceae family, is an aromatic herb, and the leaves of this herb are widely used as food ingredients. Extracts of A. rugosa have various bioactivities including anti-HIV integration, anti-inflammatory, and anti-atherogenic properties. However, the beneficial effect of A. rugosa on bone has not been studied. Therefore, we investigated the effects of water extract of A. rugosa (WEAR) on osteoclast differentiation and estrogen deficiency-induced bone loss in ovariectomized (OVX) mice as an animal model for postmenopausal osteoporosis. The oral administration of WEAR remarkably improved OVX-induced trabecular bone loss and fat accumulation in the bone marrow. WEAR suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation in osteoclast precursor cells, subsequently inhibiting resorption activity on a bone mimetic surface. WEAR inhibited the expression of cellular oncogene fos (c-Fos) and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), key osteoclastogenic transcription factors, by decreasing RANKL-induced activation of mitogen-activated protein kinases (MAPKs), and nuclear factor-κB (NF-κB) pathways. We also identified seventeen phytochemicals present in WEAR, including five phenols and twelve flavonoids, and found eleven bioactive constituents that have anti-osteoclastogenic effects. Collectively, these results suggest that WEAR could be used to treat and prevent postmenopausal osteoporosis by suppressing osteoclastogenesis.

An herbal formula inhibits STAT3 signaling and attenuates bone erosion in collagen-induced arthritis rats

BACKGROUND

Receptor activator of NF-κB ligand (RANKL) facilitates differentiation of osteoclast precursors into osteoclasts, resulting in bone erosion in rheumatoid arthritis (RA) patients. Fibroblast-like synoviocytes (FLS) are the main cells for producing RANKL. Signal transducer and activator of transcription 3 (STAT3) signaling is activated in FLS of RA patients (RA-FLS), which has been linked to RANKL production. A two-herb formula (RL) comprising Rosae Multiflorae Fructus and Lonicerae Japonicae Flos is traditionally used for treating RA in China. We have found that a standardized ethanolic extract of RL (RLE for short) alleviates bone erosion in collagen-induced arthritis (CIA) rats.

PURPOSE

This study aimed to determine whether RLE inhibits RANKL production and osteoclastogenesis in cell and rat models, and to explore the involvement of the STAT3 pathway in this inhibition.

STUDY DESIGN AND METHODS

A CIA rat model, interleukin-6/soluble interleukin-6 receptor (IL-6/sIL-6R)-stimulated RA-FLS and a co-culture system (IL-6/sIL-6R-stimulated RA-FLS/peripheral blood mononuclear cells) were used to evaluate the effects of RLE. Micro-computed tomography analysis was used to observe bone erosion in CIA rats. Tartrate-resistant acid phosphatase staining was used to evaluate osteoclastogenesis. Western blotting and ELISA assays were employed to examine protein levels. RT-qPCR was used to detect mRNA levels. STAT3-over-activated RA-FLS were used to investigate the involvement of STAT3 signaling in the anti-osteoclastogenic effects of RLE.

RESULTS

RLE alleviated bone erosion in joints of CIA rats. In both synovial tissues of CIA rats and IL-6/sIL-6R-stimulated RA-FLS, RLE downregulated the protein level of RANKL. In the co-culture system, RLE significantly and dose-dependently inhibited IL-6/sIL-6R-induced osteoclastogenesis. Mechanistic studies revealed that RLE lowered the protein level of phospho-STAT3 (Tyr705) in synovial tissues of CIA rats. In IL-6/sIL-6R-stimulated RA-FLS, RLE inhibited the activation/phosphorylation of a STAT3 upstream kinase Janus kinase 2 (Tyr1007/1008) and STAT3 (Tyr705), decreased the nuclear localization of STAT3, lowered mRNA levels of STAT3-transcriptionally regulated genes IL-1β and TNF-α. RLE's inhibitory effects on RANKL production in RA-FLS gradually decreased when IL-6/sIL-6R doses increased. Over-activation of STAT3 diminished the inhibitory effects of RLE on RANKL production in IL-6/sIL-6R-stimulated RA-FLS, and attenuated the anti-osteoclastogenic effects of RLE in the co-culture system.

CONCLUSION

We, for the first time, demonstrated that suppressing STAT3 signaling contributes to the inhibition of RANKL production and osteoclastogenesis, and thereby supports the mechanisms responsible for the reduction in bone erosion in RLE-treated CIA rats. This study provides further pharmacological groundwork for developing RLE as a modern anti-arthritic drug, and supports the notion that targeting STAT3 signaling is a viable strategy for managing bone erosion.

Effects of Virgin Olive Oil on Bone Health in Ovariectomized Rats

Osteoporosis is a pressing concern facing public health, thus making research into the effects of nutrients on bone health particularly important. Evidence from preclinical studies using animal models and a limited number of studies in human suggests that olive oil (OO) is a protective agent for bone. The aim of this work is to study the effects of virgin olive oil (VOO) consumption by ovariectomized rats on bone health. A total of 48 6-month-old female Wistar rats weighing 320 ± 10 g (mean ± SD) were divided into the following groups: SHAM (n = 12), simulated intervention; OVX (n = 12), ovariectomized; OVX + 100 (n = 12), ovariectomized and treated with VOO (100 µL/day by oral gavage); and OVX + 200 (n = 12) ovariectomized and treated with VOO (200 µL/day by oral gavage), all over 3 months. Femoral (F) and lumbar (L) bone mineral density (FBMD and LBMD), microtomographic parameters, fractal dimension D2D and D3D, and biomechanical properties were studied. After 3 months of VOO treatment, although FBMD and LBMD were not affected, bone quality was improved, as the elasticity of bone and fractal dimension (complexity of bone) were more similar to healthy bone. Our results support the findings of previous research suggesting that dietary intake of olive oil may exert beneficial effect on some bone characteristics.

Polyphenol-Rich Foods and Osteoporosis

BACKGROUND

Osteoporosis is a metabolic disease affecting the bone mineral density and thus compromise the strength of the bones. Disease prevention through diet is the objective of the study and discussion. Among the several nutrients investigated, the intake of phenols seems to influence bone mineral density by acting as free radical scavengers, preventing oxidation-induced damage to bone cells. In addition, the growing understanding of the bone remodelling process supports the theory that inflammation significantly contributes to the etiopathogenesis of osteoporosis.

METHODS

To provide an overview of current evidence on polyphenol-rich foods and osteoporosis prevention we made a comprehensive review of the literature focusing on the state of art of the topic.

RESULTS

Some polyphenol-rich foods, including olive oil, fruit and vegetable, tea and soy, seem to be beneficial for preventing osteoporosis disease and its progression. The mechanism is still partly unknown and may involve different pathways which include inflammation and other disease reactions.

CONCLUSIONS

However, further research is needed to better understand the mechanisms regulating the molecular interaction between osteoporosis incidence and progression and polyphenol-rich foods. The current evidence suggests that dietary intervention with polyphenol rich foods may be useful to prevent incidence and progression of this condition.

Effect of Extra Virgin Olive Oil and Traditional Brazilian Diet on the Bone Health Parameters of Severely Obese Adults: A Randomized Controlled Trial

Dietary interventions can stabilize and/or reverse bone mass loss. However, there are no reports on its effects on bone mineral density (BMD) in severely obese people, despite the vulnerability of this group to bone loss. We examine the effect of extra virgin olive oil supplementation and the traditional Brazilian diet (DieTBra) on BMD and levels of calcium, vitamin D, and parathyroid hormone (PTH) in severely obese adults. A randomized controlled trial followed-up with severely obese adults (n = 111, with mean body mass index 43.6 kg/m2 ± 4.5 kg/m2) for 12 weeks. Study participants received either olive oil (52 mL/day), DieTBra, or olive oil + DieTBra (52 mL/day + DieTBra). BMD was assessed by total spine and hip dual-energy X-ray absorptiometry. After interventions, BMD means for total spine (p = 0.016) and total hip (p = 0.029) were higher in the DieTBra group than in the olive oil + DieTBra group. Final mean calcium levels were higher in the olive oil group compared to the olive oil + DieTBra group (p = 0.026). Findings suggest that DieTBra and extra virgin olive oil have positive effects on bone health in severely obese adults. The major study was registered at ClinicalTrials.gov (NCT02463435).

A butanolic fraction from the standardized stem extract of Cassia occidentalis L delivered by a self-emulsifying drug delivery system protects rats from glucocorticoid-induced osteopenia and muscle atrophy

We recently reported that a butanol soluble fraction from the stem of Cassia occidentalis (CSE-Bu) consisting of osteogenic compounds mitigated methylprednisone (MP)-induced osteopenia in rats, albeit failed to afford complete protection thus leaving a substantial scope for further improvement. To this aim, we prepared an oral formulation that was a lipid-based self-nano emulsifying drug delivery system (CSE-BuF). The globule size of CSE-BuF was in the range of 100–180 nm of diluted emulsion and the zeta potential was −28 mV. CSE-BuF enhanced the circulating levels of five osteogenic compounds compared to CSE-Bu. CSE-BuF (50 mg/kg) promoted bone regeneration at the osteotomy site and completely prevented MP-induced loss of bone mass and strength by concomitant osteogenic and anti-resorptive mechanisms. The MP-induced downregulations of miR29a (the positive regulator of the osteoblast transcription factor, Runx2) and miR17 and miR20a (the negative regulators of the osteoclastogenic cytokine RANKL) in bone was prevented by CSE-BuF. In addition, CSE-BuF protected rats from the MP-induced sarcopenia and/or muscle atrophy by downregulating the skeletal muscle atrogenes, adverse changes in body weight and composition. CSE-BuF did not impact the anti-inflammatory effect of MP. Our preclinical study established CSE-BuF as a prophylactic agent against MP-induced osteopenia and muscle atrophy.

Luteolin supports osteogenic differentiation of human periodontal ligament cells

Background

Previous research revealed that luteolin could improve the activation of alkaline phosphatase (ALP) and osteocalcin in mouse osteoblasts. We aimed to determine the effect of luteolin on osteogenic differentiation of periodontal ligament cells (PDLCs).

Methods

Cultured human PDLCs (HPDLCs) were treated by luteolin at 0.01, 0.1, 1, 10, 100 μmol/L, Wnt/β-catenin pathway inhibitor (XAV939, 5 μmol/L) alone or in combination with 1 μmol/L luteolin. Immunohistochemical staining was performed to ensure cells source. Cell activity and the ability of osteogenic differentiation in HPDLCs were determined by MTT, ALP and Alizarin Red S staining. Real-time Quantitative PCR Detecting System (qPCR) and Western blot were performed to measure the expressions of osteogenic differentiation-related genes such as bone morphogenetic protein 2 (BMP2), osteocalcin (OCN), runt-related transcription factor 2 (RUNX2), Osterix (OSX) and Wnt/β-catenin pathway proteins members cyclin D1 and β-catenin.

Results

Luteolin at concentrations of 0.01, 0.1, 1, 10, 100 μmol/L promoted cell viability, ALP activity and increased calcified nodules content in HPDLCs. The expressions of BMP2, OCN, OSX, RUNX2, β-catenin and cyclin D1 were increased by luteolin at concentrations of 0.01, 0.1, 1 μmol/L, noticeably, 1 μmol/L luteolin produced the strongest effects. In addition, XAV939 inhibited the expressions of calcification and osteogenic differentiation-related genes in HPDLCs, and 1 μmol/L luteolin availably decreased the inhibitory effect.

Conclusion

1 μmol/L luteolin accelerated osteogenic differentiation of HPDLCs via activating the Wnt/β-catenin pathway, which could be clinically applied to treat periodontal disease.

A Delphinidin-Enriched Maqui Berry Extract Improves Bone Metabolism and Protects against Bone Loss in Osteopenic Mouse Models

In our previous investigation, delphinidin, one of the most abundant anthocyanins found in vegetables and berry fruits, had been shown to inhibit osteoclasts and prevent bone loss in mouse models of osteoporosis. In the present study, we investigated whether a delphinidin glycoside-enriched maqui berry extract (MBE, Delphinol^®) exhibits beneficial effects on bone metabolism both in vitro and in vivo. MBE stimulated the osteoblastic differentiation of MC3T3-E1 cells, as indicated by enhanced mineralized nodule formation, and increased alkaline phosphatase activity, through the upregulation of bone morphogenetic protein 2 (Bmp2), runt-related transcription factor 2 (Runx2), osterix (Osx), osteocalcin (Ocn), and matrix extracellular phosphoglycoprotein (Mepe) mRNA expression. Immunostaining and immunoprecipitation assays demonstrated that MBE suppressed NF-κB transnucleation through acting as a superoxide anion/peroxynitrite scavenger in MC3T3-E1 cells. Simultaneously, MBE inhibited both osteoclastogenesis in primary bone marrow macrophages and pit formation by maturated osteoclasts on dentine slices. Microcomputed tomography (micro-CT) and bone histomorphometry analyses of femurs demonstrated that the daily ingestion of MBE significantly increased BV/TV (ratio of bone volume to tissue volume), Tb.Th (trabecular thickness), Tb.N (trabecular number), N.Nd/N.Tm (node to terminus ratio), OV/TV (ratio of osteoid volume to tissue volume), BFR/TV (bone formation rate per tissue volume), and significantly decreased Tb.Sp (trabecular separation), ES/BS (ratio of eroded surface to bone surface) and N.Oc/BS (number of osteoclast per unit of bone surface), compared to vehicle controls in osteopenic mouse models. These findings suggest that MBE can be a promising natural agent for the prevention of bone loss in osteopenic conditions by not only inhibiting bone resorption, but also stimulating bone formation.

Fermented Oyster Extract Prevents Ovariectomy-Induced Bone Loss and Suppresses Osteoclastogenesis

There is growing interest in bioactive substances from marine organisms for their potential use against diverse human diseases. Osteoporosis is a skeletal disorder associated with bone loss primarily occurring through enhanced osteoclast differentiation and resorption. Recently, we reported the anti-osteoclastogenic activity of fermented Pacific oyster (Crassostrea gigas) extract (FO) in vitro. The present study focused on investigating the anti-osteoporotic efficacy of FO in bone loss prevention in an experimental animal model of osteoporosis and elucidating the mechanism underlying its effects. Oral administration of FO significantly decreased ovariectomy-induced osteoclast formation and prevented bone loss, with reduced serum levels of bone turnover biomarkers including osteocalcin and C-terminal telopeptide fragment of type I collagen C-terminus (CTX). FO significantly suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced differentiation of bone marrow-derived macrophages (BMMs) into osteoclasts and attenuated the induction of osteoclast-specific genes required for osteoclastogenesis and bone resorption. Furthermore, FO inhibited RANKL-mediated IκBα and p65 phosphorylation in BMMs. Taken together, these results demonstrate that FO effectively suppresses osteoclastogenesis in vivo and in vitro, and that FO can be considered as a potential therapeutic option for the treatment of osteoporosis and osteoclast-mediated skeletal diseases.