Quercetin, a flavonoid, inhibits the proliferation, differentiation, and mineralization of osteoblasts in vitro

A New Biomaterial Derived from Aloe vera-Acemannan from Basic Studies to Clinical Application

Aloe vera is a kind of herb rich in polysaccharides. Acemannan (AC) is considered to be a natural polysaccharide with good biodegradability and biocompatibility extracted from Aloe vera and has a wide range of applications in the biomedical field due to excellent immunomodulatory, antiviral, antitumor, and tissue regeneration effects. In recent years, clinical case reports on the application of AC as a novel biomedical material in tissue regenerative medicine have emerged; it is mainly used in bone tissue engineering, pulp-dentin complex regeneration engineering, and soft tissue repair, among other operations. In addition, multiple studies have proved that the new composite products formed by the combination of AC and other compounds have excellent biological and physical properties and have broader research prospects. This paper introduces the preparation process, surface structure, and application forms of AC; summarizes the influence of acetyl functional group content in AC on its functions; and provides a detailed review of the functional properties, laboratory studies, clinical cutting-edge applications, and combined applications of AC. Finally, the current application status of AC from basic research to clinical treatment is analyzed and its prospects are discussed.

The controlled release, bioactivity and osteogenic gene expression of Quercetin-loaded gelatin/tragacanth/ nano-hydroxyapatite bone tissue engineering scaffold

In this study, a Gelatin/Tragacanth/Nano-hydroxyapatite scaffold was fabricated via freeze-drying method. A highly porous scaffold with an average pore diameter of 142 µm and porosity of 86% was found by the micro-computed tomography. The mean compressive strength of the scaffold was about 1.5 MPa, a value in the range of the spongy bone. The scaffold lost 10 wt.% of its initial weight after 28 days soaking in PBS that shows a fair degradation rate for a bone tissue engineering scaffold. Apatite formation ability of the scaffold was confirmed via scanning electron microscopy, X-ray diffraction and Fourier transforming infrared spectroscopy, after 28 days soaking in simulated body fluid. The scaffold was able to deliver 93% of the loaded drug, Quercetin, during 120 h in phosphate-buffered solution, in a sustainable manner. The MTT assay using human bone mesenchymal stem cells showed 84% cell viability of the Quercetin-loaded scaffold. The expression of the osteogenic genes including Col I, Runx-2, BGLAP (gene of osteocalcin), bFGF, SP7 (gene of osterix) and SPP1 (gene of osteopontin) were all upregulated when Quercetin was loaded on the scaffold, which indicates the synergetic effect of the drug and the scaffold.

Apigenin Modulates AnxA6- and TNAP-Mediated Osteoblast Mineralization

Mineralization-competent cells like osteoblasts and chondrocytes release matrix vesicles (MVs) which accumulate Ca2+ and Pi, creating an optimal environment for apatite formation. The mineralization process requires the involvement of proteins, such as annexins (Anx) and tissue-nonspecific alkaline phosphatase (TNAP), as well as low molecular-weight compounds. Apigenin, a flavonoid compound, has been reported to affect bone metabolism, but there are doubts about its mechanism of action under physiological and pathological conditions. In this report, apigenin potency to modulate annexin A6 (AnxA6)- and TNAP-mediated osteoblast mineralization was explored using three cell lines: human fetal osteoblastic hFOB 1.19, human osteosarcoma Saos-2, and human coronary artery smooth muscle cells HCASMC. We compared the mineralization competence, the morphology and composition of minerals, and the protein distribution in control and apigenin-treated cells and vesicles. The mineralization ability was monitored by AR-S/CPC analysis, and TNAP activity was determined by ELISA assay. Apigenin affected the mineral structure and modulated TNAP activity depending on the concentration. We also observed increased mineralization in Saos-2 cells. Based on TEM-EDX, we found that apigenin influenced the mineral composition. This flavonoid also disturbed the intracellular distribution of AnxA6 and TNAP, especially blocking AnxA6 aggregation and TNAP attachment to the membrane, as examined by FM analysis of cells and TEM-gold analysis of vesicles. In summary, apigenin modulates the mineralization process by regulating AnxA6 and TNAP, as well as through various effects on normal and cancer bone tissues or atherosclerotic soft tissue.

Molecular and cellular outcomes of quercetin actions on healthy and tumor osteoblasts

There is a global trend in the use of natural bioactive compounds to complement conventional therapies in bone diseases. In this work, we studied the effects of the phytoestrogen quercetin (QUE) in healthy and tumor osteoblasts. We found that QUE (1 μM, 48 h) significantly increased the cell number and the viability of healthy human osteoblasts (hFOB cells) determined by a trypan blue and a MTS assay, respectively, among other concentrations tested. In addition, wound healing and cellular adhesion assays also demonstrated that 1 μM of QUE significantly stimulated both parameters in osteoblasts. Moreover, osteoblast differentiation was also triggered by QUE in an osteogenic medium by measuring alkaline phosphatase activity, calcium deposition, and collagen levels. Herein, a concentration of 0.01 μM of QUE showed an increment in these differentiation markers and an activation of AKT/GSK3β/β-catenin pathway, determined by a Western blot analysis. In addition, immunocytochemistry and subcellular fraction studies indicated an increase of β-catenin localization in the plasma membrane after QUE treatment. Otherwise, QUE (20-100 μM) decreased the cell number and the viability in tumor osteoblasts (ROS 17/2.8 cells) after 48 h. Furthermore, QUE (100 μM) decreased AKT(Ser473) and the pro-apoptotic protein BAD(Ser136) phosphorylation. In addition, the ERK1/2 phosphorylation increased leading to osteosarcoma cell death since pre-treatment with the MEK inhibitor PD98059 had reverted QUE effect. Altogether, these results indicate that to stimulate the osteoblastogenesis low concentrations of QUE are required; however, these concentrations are not effective in inhibiting the growth of tumor osteoblasts, for which higher concentrations are required.

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.

Quercetin promotes bone marrow mesenchymal stem cell proliferation and osteogenic differentiation through the H19/miR-625-5p axis to activate the Wnt/β-catenin pathway

Background

Quercetin and H19 can promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). However, whether quercetin regulates H19 expression to promote osteogenic differentiation of BMSCs is unclear.

Methods

BMSC proliferation, matrix mineralization, and alkaline phosphatase (ALP) activity were assessed using the Cell Counting Kit-8, ALP assay kit, and alizarin red staining kit, respectively. Expression of H19, miR-625-5p, BMP-2, osteocalcin, and RUNX2 were measured by qRT-PCR; β-catenin protein level was measured by western blotting.

Results

Quercetin promoted BMSC proliferation, enhanced ALP activity, and upregulated the expression of BMP-2, osteocalcin, and RUNX2 mRNAs, suggesting that it promoted osteogenic differentiation of BMSCs. Moreover, quercetin increased H19 expression, while the effect of quercetin on BMSCs was reversed by silencing H19 expression. Additionally, miR-625-5p, interacted with H19, was downregulated during quercetin-induced BMSC osteogenic differentiation, which negatively correlated with H19 expression. Silencing miR-625-5p expression promoted BMSC proliferation and osteogenic differentiation, whereas miR-625-5p overexpression weakened the effect of quercetin on BMSCs. Finally, quercetin treatment or downregulation of miR-625-5p expression increased β-catenin protein level in BMSCs. Upregulation or downregulation of miR-625-5p or H19 expression, respectively, inhibited β-catenin protein level in quercetin treated-BMSCs.

Conclusion

H19 promotes, while miR-625-5p inhibits BMSC osteogenic differentiation. Quercetin activates the Wnt/β-catenin pathway and promotes BMSC osteogenic differentiation via the H19/miR-625-5p axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03418-8.

Guava (Psidium guajava L.): a glorious plant with cancer preventive and therapeutic potential

Guava (Psidium guajava L.) tree (Myrtaceae family) bears fruit rich in vitamins, fiber, and other nutrients. While native to Latin America, guava is grown in many tropical and subtropical regions across the globe where it has long been used in traditional medicine to treat a myriad of ailments. Guava has been shown to exhibit a number of biological and pharmacological activities, such as antioxidant, anti-inflammatory, immunomodulatory, antimicrobial, antidiabetic, and anticancer properties. Several parts of the plant, including the leaves, fruits, seeds, peels, pulp, bark, and oil, produce phytochemicals with medicinal properties. Emerging research has found that guava bioactive phytochemicals exert antitumorigenic effects against various human malignancies through multiple mechanisms. While there are numerous individual studies that document the anticancer effects of guava constituents, an up-to-date, comprehensive, and critical review of available research data has not been performed. Therefore, the purpose of this review is to present a complete analysis of the cancer preventive and anticancer therapeutic potential of guava-derived products and guava constituents, with a focus on the cellular and molecular mechanisms of action. The bioavailability, pharmacokinetics, and toxicity of guava as well as limitations, challenges, and future directions of research have also been discussed.

The synergistic effects of quercetin-containing 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis in mesenchymal stem cells

BACKGROUND/PURPOSE

Several growth factors were proven to be effective in the treatment of bone defects and fractures and thus have great potential for bone regeneration applications. However, it needs low-temperature storage and transportation. This study aimed to investigate the herbal extract quercetin, a candidate for natural flavonoid compounds that have been reported to be involved in regulating inflammation and improving immunity and health.

METHODS

In this study, we prepared quercetin (Q)/mesoporous calcium silicate calcium sulfate (MSCS)/polycaprolactone (PCL) composite scaffolds using the 3D printing technique, where we immersed it in simulated body fluid (SBF) solution and soaked it for up to 60 days. The characteristics of quercetin scaffold were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), immunofluorescence, and Alizarin Red S staining.

RESULTS

We found precipitation of apatite on the surface of the scaffold. The in vitro results for cell proliferation, cytotoxicity, and immunofluorescence staining revealed that Wharton's jelly mesenchymal stem cells (WJMSCs) with a 2% quercetin (Q2) scaffold were significantly higher in number than with 1% quercetin (Q1) and MSCS scaffolds. The phalloidin staining of cell skeletons on the surface of Q2 revealed powerful cell-to-cell adhesion and high expression of green fluorescence. The Q2 scaffold also had the highest calcium deposit levels based on Alizarin Red S staining in all scaffolds. This indicated that quercetin was able to induce cell growth and mitosis, echoing the previous preliminary results.

CONCLUSION

Our initial results indicate that this natural herbal extract can be a good bone-based gene substitution for bone regeneration.

Effect of Quercetin 3-O-β-D-Galactopyranoside on the Adipogenic and Osteoblastogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stromal Cells

Natural products, especially phenols, are promising therapeutic agents with beneficial effects against aging-related complications such as osteoporosis. This study aimed to investigate the effect of quercetin 3-O-β-D-galactopyranoside (Q3G), a glycoside of a common bioactive phytochemical quercetin, on osteogenic and adipogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). hBM-MSCs were induced to differentiate into osteoblasts and adipocytes in the presence or absence of Q3G and the differentiation markers were analyzed to observe the effect. Q3G treatment stimulated the osteoblastogenesis markers: cell proliferation, alkaline phosphatase (ALP) activity and extracellular mineralization. In addition, it upregulated the expression of RUNX2 and osteocalcin protein as osteoblastogenesis regulating transcription factors. Moreover, Q3G treatment increased the activation of osteoblastogenesis-related Wnt and bone morphogenetic protein (BMP) signaling displayed as elevated levels of phosphorylated β-catenin and Smad1/5 in nuclear fractions of osteo-induced hBM-MSCs. The presence of quercetin in adipo-induced hBM-MSC culture inhibited the adipogenic differentiation depicted as suppressed lipid accumulation and expression of adipogenesis markers such as PPARγ, SREBP1c and C/EBPα. In conclusion, Q3G supplementation stimulated osteoblast differentiation and inhibited adipocyte differentiation in hBM-MSCs via Wnt/BMP and PPARγ pathways, respectively. This study provided useful information of the therapeutic potential of Q3G against osteoporosis mediated via regulation of MSC differentiation.

Quercetin as an Agent for Protecting the Bone: A Review of the Current Evidence

Quercetin is a flavonoid abundantly found in fruits and vegetables. It possesses a wide spectrum of biological activities, thus suggesting a role in disease prevention and health promotion. The present review aimed to uncover the bone-sparing effects of quercetin and its mechanism of action. Animal studies have found that the action of quercetin on bone is largely protective, with a small number of studies reporting negative outcomes. Quercetin was shown to inhibit RANKL-mediated osteoclastogenesis, osteoblast apoptosis, oxidative stress and inflammatory response while promoting osteogenesis, angiogenesis, antioxidant expression, adipocyte apoptosis and osteoclast apoptosis. The possible underlying mechanisms involved are regulation of Wnt, NF-κB, Nrf2, SMAD-dependent, and intrinsic and extrinsic apoptotic pathways. On the other hand, quercetin was shown to exert complex and competing actions on the MAPK signalling pathway to orchestrate bone metabolism, resulting in both stimulatory and inhibitory effects on bone in parallel. The overall interaction is believed to result in a positive effect on bone. Considering the important contributions of quercetin in regulating bone homeostasis, it may be considered an economical and promising agent for improving bone health. The documented preclinical findings await further validation from human clinical trials.

Diverse biological effects of glycosyltransferase genes from Tartary buckwheat

BACKGROUND

Tartary buckwheat (Fagopyrum tataricum) is an edible cereal crop whose sprouts have been marketed and commercialized for their higher levels of anti-oxidants, including rutin and anthocyanin. UDP-glucose flavonoid glycosyltransferases (UFGTs) play an important role in the biosynthesis of flavonoids in plants. So far, few studies are available on UFGT genes that may play a role in tartary buckwheat flavonoids biosynthesis. Here, we report on the identification and functional characterization of seven UFGTs from tartary buckwheat that are potentially involved in flavonoid biosynthesis (and have varying effects on plant growth and development when overexpressed in Arabidopsis thaliana.) RESULTS: Phylogenetic analysis indicated that the potential function of the seven FtUFGT proteins, FtUFGT6, FtUFGT7, FtUFGT8, FtUFGT9, FtUFGT15, FtUFGT40, and FtUFGT41, could be divided into three Arabidopsis thaliana functional subgroups that are involved in flavonoid biosynthesis of and anthocyanin accumulation. A significant positive correlation between FtUFGT8 and FtUFGT15 expression and anthocyanin accumulation capacity was observed in the tartary buckwheat seedlings after cold stress. Overexpression in Arabidopsis thaliana showed that FtUFGT8, FtUFGT15, and FtUFGT41 significantly increased the anthocyanin content in transgenic plants. Unexpectedly, overexpression of FtUFGT6, while not leading to enhanced anthocyanin accumulation, significantly enhanced the growth yield of transgenic plants. When wild-type plants have only cotyledons, most of the transgenic plants of FtUFGT6 had grown true leaves. Moreover, the growth speed of the oxFtUFGT6 transgenic plant root was also significantly faster than that of the wild type. At later growth, FtUFGT6 transgenic plants showed larger leaves, earlier twitching times and more tillers than wild type, whereas FtUFGT15 showed opposite results.

CONCLUSIONS

Seven FtUFGTs were isolated from tartary buckwheat. FtUFGT8, FtUFGT15, and FtUFGT41 can significantly increase the accumulation of total anthocyanins in transgenic plants. Furthermore, overexpression of FtUFGT6 increased the overall yield of Arabidopsis transgenic plants at all growth stages. However, FtUFGT15 shows the opposite trend at later growth stage and delays the growth speed of plants. These results suggested that the biological function of FtUFGT genes in tartary buckwheat is diverse.

An extract from Myracrodruon urundeuva inhibits matrix mineralization in human osteoblasts

ETHNOPHARMACOLOGICAL RELEVANCE

Phytotherapy based on plant-derived compounds is an alternative medicinal strategy for the relief of symptoms and the curing of diseases. The leaves of Myracrodruon urundeuva a medicinal plant also known as "aroeira", has been used in traditional medicine as healing, antiulcer and anti-inflammatory to treat skeletal diseases in Brazil, but its role in bone cell toxicity, as well as in bone formation, remains to be established.

AIM OF THE STUDY

We sought to determine the in vitro osteogenic effects of a hydroalcoholic M. urundeuva leaves extract in primary human osteoblasts.

MATERIALS AND METHODS

Cell viability, reactive oxygen species (ROS) production, alkaline phosphatase (ALP) activity and matrix mineralization were evaluated by MTT assay, DCFH-DA probe, colorimetric-based enzymatic assay and Alizarin Red-staining, respectively. Besides, the matrix metalloproteinase (MMP)-2 and progressive ankylosis protein homolog (ANKH) gene expression were determined by real-time RT-qPCR and MMP-2 activity by zymography.

RESULTS

Exposure of osteoblasts to M. urundeuva extract significantly decreased viability and increased reactive oxygen species (ROS) production, regardless of the extract concentration. The M. urundeuva extract at 10 μg/mL also downregulated matrix metalloproteinase (MMP)-2, while upregulating progressive ankylosis protein homolog (ANKH) gene expression. By contrast, the MMP-2 activity was unchanged. The M. urundeuva extract at 10 μg/mL also reduced alkaline phosphatase (ALP) activity and mineralization.

CONCLUSIONS

Overall, our findings suggest that the inhibition of osteogenic differentiation and matrix mineralization promoted by M. urundeuva may be due more to an increase in oxidative stress than to the modulation of MMP-2 and ANKH expression.

Mimicking growth factors: role of small molecule scaffold additives in promoting tissue regeneration and repair

The primary aim of tissue engineering scaffolds is to mimic the in vivo environment and promote tissue growth. In this quest, a number of strategies have been developed such as enhancing cell-material interactions through modulation of scaffold physico-chemical parameters. However, more is required for scaffolds to relate to the cell natural environment. Growth factors (GFs) secreted by cells and extracellular matrix (ECM) are involved in both normal repair and abnormal remodeling. The direct use of GFs on their own or when incorporated within scaffolds represent a number of challenges such as release rate, stability and shelf-life. Small molecules have been proposed as promising alternatives to GFs as they are able to minimize or overcome many shortcomings of GFs, in particular immune response and instability. Despite the promise of small molecules in various TE applications, their direct use is limited by nonspecific adverse effects on non-target tissues and organs. Hence, they have been incorporated within scaffolds to localize their actions and control their release to target sites. However, scanty rationale is available which links the chemical structure of these molecules with their mode of action. We herewith review various small molecules either when used on their own or when incorporated within polymeric carriers/scaffolds for bone, cartilage, neural, adipose and skin tissue regeneration.

4-Hydroxyderricin inhibits osteoclast formation and accelerates osteoblast differentiation

4-Hydroxyderricin (4-HD) is a major polyphenol of Angelica keiskei (Japanese name Ashitaba), exhibiting anti-allergic, anti-diabetic, anti-oxidant, and antitumor effects. The present study was designed to evaluate the effects of 4-HD on bone formation and maintenance by using cultured osteoclasts and osteoblasts. 4-HD did not affect cell proliferation of stromal ST2 cells and preosteoblast MC3T3-E1 cells at concentrations of 1–10 μM. This compound inhibited the formation of multinucleated osteoclasts from mouse splenic cells, and we identified a molecular pathway of osteoclast differentiation mediated by 4-HD, which led to inhibition of the expression of receptor activator of nuclear factor-κB ligand and macrophage-colony stimulating factor in ST2 cells. By contrast, 4-HD enhanced indices of osteoblast differentiation, such as alkaline phosphatase activity and calcium deposition by osteoblastic MC3T3-E1 cells, at concentrations of 1–10 μM. Furthermore, we found that 4-HD at 1 μM attenuated H₂O₂ levels in MC3T3-E1 cells. Our findings indicate that 4-HD may have critical effects on bone formation and maintenance.

Ethyl acetate and n-butanol fraction of Cissus quadrangularis promotes the mineralization potential of murine pre-osteoblast cell line MC3T3-E1 (sub-clone 4)

In a sequel to investigate osteogenic potential of ethanolic extract of Cissus quadrangularis (CQ), the present study reports the osteoblast differentiation and mineralization potential of ethyl acetate (CQ-EA) and butanol (CQ-B) extracts of CQ on mouse pre-osteoblast cell line MC3T3-E1 (sub-clone 4) with an objective to isolate an antiosteoporotic compound. Growth curve, proliferation, and viability assays showed that both the extracts were nontoxic to the cells even at high concentration (100 µg/ml). The cell proliferation was enhanced at low concentrations (0.1 µg/ml and 1 µg/ml) of both the extracts. They also upregulated the osteoblast differentiation and mineralization processes in MC3T3-E1 cells as reflected by expression profile of osteoblast marker genes such as RUNX2, Osterix, Collagen (COL1A1), Alkaline Phosphatase (ALP), Integrin-related Bone Sialoprotein (IBSP), Osteopontin (OPN), and Osteocalcin (OCN). CQ-EA treatment resulted in early differentiation and mineralization as compared with the CQ-B treatment. These findings suggest that low concentrations of CQ-EA and CQ-B have proliferative and osteogenic properties. CQ-EA, however, is more potent osteogenic than CQ-B.

Quercetin Inlaid Silk Fibroin/Hydroxyapatite Scaffold Promotes Enhanced Osteogenesis

There is a significant rise in the bone grafts demand worldwide to treat bone defects owing to continuous increase in conditions such as injury, trauma, diseases, or infections. Therefore, development of three-dimensional scaffolds has evolved as a reliable technology to address the current limitations for bone tissue regeneration. Mimicking the natural bone, in this study, we have designed a silk fibroin/hydroxyapatite scaffold inlaid with a bioactive phytochemical (quercetin) at different concentrations for promoting osteogenesis, especially focusing on quercetin ability for enhancing bone health. Characterization of the quercetin/silk fibroin/hydroxyapatite (Qtn/SF/HAp) scaffolds showed an increased pore size and irregular porous microstructure with good mechanical strength. The Qtn (low-content)/SF/HAp scaffold was found to be an efficient cell carrier facilitating cellular growth, osteogenic differentiation, and proliferation as compared to SF/HAp and Qtn (high-content)/SF/HAp scaffolds. However, Qtn (high-content)/SF/HAp was observed to inhibit cell proliferation without any effects on cell viability. In vitro and in vivo outcomes studied using bone marrow-derived mesenchymal stem cells (rBMSCs) confirm the cytocompatibility, osteogenic differentiation ability, and prominent upregulation of the bone-specific gene expressions for the rBMSCs-seeded Qtn/SF/HAp scaffolds. In particular, the implanted Qtn (low-content)/SF/HAp scaffolds at the bone defect site were found to be well-attached and amalgamated with the surrounding tissues with approximately 80% bone volume recovery at 6 weeks after surgery as compared with other groups. Based on the aforementioned observations highlighting the quercetin efficiency for bone regeneration, the as-synthesized Qtn (low-content)/SF/HAp scaffolds can be envisioned to provide a biomimetic bone-like microenvironment promoting rBMSCs differentiation into osteoblast, thus suggesting a potential alternative graft for high-performance regeneration of bone tissues.

Polyphenol uses in biomaterials engineering

Polyphenols are micronutrients obtained from diet that have been suggested to play an important role in health. The health benefits of polyphenols and their protective effects in food systems as antioxidant compounds are well known and have been extensively investigated. However, their functional roles as a "processing cofactor" in tissue engineering applications are less widely known. This review focuses on the functionality of polyphenols and their application in biomaterials. Polyphenols have been used to stabilize collagen and to improve its resistance to degradation in biological systems. Therefore, they have been proposed to improve the performance of biomedical devices used in cardiovascular systems by improving the mechanical properties of grafted heart valves, enhancing microcirculation through the relaxation of the arterial walls and improving the capillary blood flow and pressure resistance. Polyphenols have been found to stimulate bone formation, mineralization, as well as the proliferation, differentiation, and the survival of osteoblasts. These effects are brought about by the stimulatory effect of polyphenols on osteoblast cells and their protective effect against oxidative stress and inflammatory cytokines. In addition, polyphenols inhibit the differentiation of the osteoclast cells. Collectively, these actions lead to promote bone formation and to reduce bone resorption, respectively. Moreover, polyphenols can increase the cross-linking of dentine and hence its mechanical stability. Overall, polyphenols provide interesting properties that will stimulate further research in the bioengineering field.

Beneficial Effect of Jojoba Seed Extracts on Hyperglycemia-Induced Oxidative Stress in RINm5f Beta Cells

Hyperglycemia occurs during diabetes and insulin resistance. It causes oxidative stress by increasing reactive oxygen species (ROS) levels, leading to cellular damage. Polyphenols play a central role in defense against oxidative stress. In our study, we investigated the antioxidant properties of simmondsin, a pure molecule present in jojoba seeds, and of the aqueous extract of jojoba seeds on fructose-induced oxidative stress in RINm5f beta cells. The exposure of RINm5f beta cells to fructose triggered the loss of cell viability (-48%, p < 0.001) and disruption of insulin secretion (p < 0.001) associated with of reactive oxygen species (ROS) production and a modulation of pro-oxidant and antioxidant signaling pathway. Cell pre-treatments with extracts considerably increased cell viability (+86% p < 0.001) for simmondsin and +74% (p < 0.001) for aqueous extract and insulin secretion. The extracts also markedly decreased ROS (-69% (p < 0.001) for simmondsin and -59% (p < 0.001) for aqueous extract) and caspase-3 activation and improved antioxidant defense, inhibiting p22phox and increasing nuclear factor (erythroid-derived 2)-like 2 (Nrf2) levels (+70%, p < 0.001) for aqueous extract. Simmondsin had no impact on Nrf2 levels. The richness and diversity of molecules present in jojoba seed extract makes jojoba a powerful agent to prevent the destruction of RINm5f beta cells induced by hyperglycemia.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Impact of Phytochemicals and Dietary Patterns on Epigenome and Cancer

Cancer remains one of the leading causes of death around the world. Initially it is recognized as a genetic disease, but now it is known to involve epigenetic abnormalities along with genetic alterations. Epigenetics refers to heritable changes that are not encoded in the DNA sequence itself, but play an important role in the control of gene expression. It includes changes in DNA methylation, histone modifications, and RNA interference. Although it is heritable, environmental factors such as diet could directly influence epigenetic mechanisms in humans. This article will focus on the role of dietary patterns and phytochemicals that have been demonstrated to influence the epigenome and more precisely histone and non-histone proteins modulation by acetylation that helps to induce apoptosis and phosphorylation inhibition, which counteracts with cells proliferation. Recent developments discussed here enhance our understanding of how dietary intervention could be beneficial in preventing or treating cancer and improving health outcomes.

Eurycoma longifolia as a potential alternative to testosterone for the treatment of osteoporosis: Exploring time-mannered proliferative, differentiative and morphogenic modulation in osteoblasts

ETHNOPHARMACOLOGICAL RELEVANCE

Eurycoma longifolia (EL) has been well-studied traditionally as a chief ingredient of many polyherbal formulations for the management of male osteoporosis. It has also been well-recognised to protect against bone calcium loss in orchidectomised rats.

AIM OF THE STUDY

To evaluate the effects of EL on the time-mannered sequential proliferative, differentiative, and morphogenic modulation in osteoblasts compared with testosterone.

MATERIALS AND METHODS

Cell proliferation was analysed using MTS assay and phase contrast microscopy. Osteogenic differentiation of MC3T3-E1 cells was assessed through a series of characteristic assays which include crystal violet staining, alkaline phosphatase (ALP) activity and Van Gieson staining. Taken together, the bone mineralization of extra cellular matrix (ECM) was estimated using alizarin red s (ARS) staining, von kossa staining, scanning electron microscopic (SEM) and energy dispersive x-ray (EDX) analysis.

RESULTS

The cell proliferation data clearly revealed the efficiency of EL particularly at a dose of 25µg/mL, in improving the growth of MC3T3-E1 cells compared with the untreated cells. Data also showed the prominence of EL in significantly promoting ALP activity throughout the entire duration of treatment compared with the testosterone-treated cells. The osteogenic differentiation potential of EL was further explored by analysing mineralization data which revealed that the calcified nodule formation (calcium deposition) and phosphate deposition was more pronounced in cells treated with 25µg/mL concentration of EL at various time points compared with the untreated and testosterone treated cells. The scanning electron microscopic (SEM) analysis also revealed highest globular masses of mineral deposits (identified as white colour crystals) in the ECM of cultured cells treated with 25µg/mL concentration of EL.

CONCLUSION

Compared to testosterone, greater potential of EL in promoting the proliferation and osteogenic differentiation of MC3T3-E1 cells provides an in vitro basis for the prevention of male osteoporosis. Thus, we anticipate that EL can be considered as an alternative approach to testosterone replacement therapy (TRT) for the treatment of male osteoporosis.

New Target Sites for Treatment of Osteoporosis

In the last few years, much progress has been achieved in the discovery of new drug target sites for treatment of osteoporotic disorders, one of the main challenging diseases with a large burden for the public health systems. Among these new agents promoting bone formation, shifting the impaired equilibrium between bone anabolism and bone catabolism in the direction of bone synthesis are inorganic polymers, in particular inorganic polyphosphates that show strong stimulatory effects on the expression of bone anabolic marker proteins and hydroxyapatite formation. The bone-forming activity of these polymers can even be enhanced by combination with certain small molecules like quercetin, or if given as functionally active particles with certain divalent cations like strontium ions even showing by itself biological activity. This chapter summarizes recent developments in the search and development of novel anti-osteoporotic agents, with a particular focus on therapeutic approaches based on the potential application of inorganic polymers and combinations.

Ethanol Extract of Cissus quadrangularis Enhances Osteoblast Differentiation and Mineralization of Murine Pre-Osteoblastic MC3T3-E1 Cells

Traditional medicinal literature and previous studies have reported the possible role of Cissus quadrangularis (CQ) as an anti-osteoporotic agent. This study examines the effectiveness of CQ in promoting osteoblast differentiation of the murine pre-osteoblast cell line, MC3T3-E1. Ethanolic extract of CQ (CQ-E) was found to affect growth kinetics of MC3T3-E1 cells in a dosage-dependent manner. High concentrations of CQ-E (more than 10 μg/ml) have particularly adverse effects, while lower concentrations of 0.1 and 1 µg/ml were non-toxic and did not affect cell viability. Notably, cell proliferation was significantly increased at the lower concentrations of CQ-E. CQ-E treatment also augmented osteoblast differentiation, as reflected by a substantial increase in expression of the early osteoblast marker ALP activity, and at later stage, by mineralization of extracellular matrix compared to the control group. These findings suggest dose-dependent effect of CQ-E with lower concentrations exhibiting anabolic and osteogenic properties. J. Cell. Physiol. 232: 540-547, 2017. © 2016 Wiley Periodicals, Inc.

Quercetin-induced changes in femoral bone microstructure of adult male rabbits

Flavonoids are a group of plant metabolites with antioxidant effects. One of the most abundant flavonoids in the human diet is quercetin. It is found widely in fruits, vegetables and has a lot of beneficial effects on human health. Quercetin has a positive pharmacological effect on bone metabolism and it prevents the organism against bone loss. However, its impact on the size of basic structural units of the compact bone is still unknown. Therefore, the aim of present study was to investigate the impact of the quercetin on femoral bone microstructure in 5-month-old male rabbits. Five rabbits of Californian broiler line were randomly divided into two groups. In the experimental group (E group; n=3), animals were intramuscularly injected with quercetin at dose 1000 μg.kg-1 body weight (bw) for 90 days, 3 times per week. Two rabbits without quercetin administration served as a control group (C group). According to our results, intramuscular application of quercetin had an insignificant effect on cortical bone thickness in male rabbits. In these rabbits, changes in qualitative histological characteristics were present in the middle part of the compacta, where primary vascular longitudinal bone tissue was present and expanded there from the periosteum. Also, a lower number of secondary osteons was found in these animals. From the histomorphometrical point of view, significantly decreased sizes of primary osteons' vascular canals and secondary osteons (p <0.05) were found in rabbits administered by quercetin. Our findings indicate that subchronic administration of quercetin at the dose used in our study had considerable impact on both qualitative and quantitative histological characteristics of the compact bone in adult male rabbits.

Biphasic Response to Luteolin in MG-63 Osteoblast-Like Cells under High Glucose-Induced Oxidative Stress

BACKGROUND

Clinical evidence indicates the diabetes-induced impairment of osteogenesis caused by a decrease in osteoblast activity. Flavonoids can increase the differentiation and mineralization of osteoblasts in a high-glucose state. However, some flavonoids such as luteolin may have the potential to induce cytotoxicity in osteoblast-like cells. This study was performed to investigate whether a cytoprotective concentration range of luteolin could be separated from a cytotoxic concentration range in human MG-63 osteoblast-like cells in high-glucose condition.

METHODS

Cells were cultured in a normal- or high-glucose medium. Cell viability was determined with the MTT assay. The formation of intracellular reactive oxygen species (ROS) was measured using probe 2',7' -dichlorofluorescein diacetate, and osteogenic differentiation was evaluated with an alkaline phosphatase bioassay.

RESULTS

ROS generation, reduction in alkaline phosphatase activity, and cell death induced by high glucose were inhibited by lower concentrations of luteolin (EC50, 1.29±0.23 µM). Oxidative stress mediated by high glucose was also overcome by N-acetyl-L-cysteine. At high concentrations, luteolin caused osteoblast cell death in normal- and high-glucose states (IC50, 34±2.33 and 27±2.42 µM, respectively), as represented by increased ROS and decreased alkaline phosphatase activity.

CONCLUSION

Our results indicated that the cytoprotective action of luteolin in glucotoxic condition was manifested in much lower concentrations, by a factor of approximately 26 and 20, than was its cytotoxic activity, which occurred under normal or glucotoxic condition, respectively.

Quercetin reversed lipopolysaccharide-induced inhibition of osteoblast differentiation through the mitogen‑activated protein kinase pathway in MC3T3-E1 cells

Quercetin, a flavonoid found in onions and other vegetables, has potential inhibitory effects on bone resorption in vivo and in vitro. In our previous study it was identified that quercetin triggered the apoptosis of lipopolysaccharide (LPS)‑induced osteoclasts and inhibited bone resorption. Currently, little information is available detailing the effect of quercetin on osteoblast differentiation and bone formation in bacteria‑induced inflammatory diseases. The present study aimed to investigate the effect of quercetin on osteoblast differentiation in MC3T3‑E1 osteoblasts stimulated with LPS. LPS significantly downregulated the mRNA expression of osteoblast‑related genes in the MC3T3‑E1 cells. By contrast, quercetin significantly restored the LPS‑suppressed mRNA expression of osteoblast‑related genes in a dose‑dependent manner. Quercetin also restored the protein expression of Osterix in MC3T3‑E1 cells suppressed by LPS. Furthermore, quercetin selectively triggered the activation of the mitogen‑activated protein kinase (MAPK) pathway by enhancing the expression of extracellular signal-regulated kinase and reducing the expression of c‑Jun N‑terminal kinase. These data suggest that quercetin reversed the inhibition of osteoblast differentiation induced by LPS through MAPK signaling. These findings suggest that quercetin may be of potential use as a therapeutic agent to restore osteoblast function in bacteria‑induced bone diseases.

Effect of Salicornia herbacea on osteoblastogenesis and adipogenesis in vitro

Bone-related complications are among the highest concerning metabolic diseases in the modern world. Bone fragility and susceptibility to fracture increase with age and diseases like osteoporosis. Elevated adipogenesis in bone results in osteoporosis and loss of bone mass when coupled with lack of osteoblastogenesis. In this study the potential effect of Salicornia herbacea extract against osteoporotic conditions was evaluated. Adipogenesis inhibitory effect of S.herbacea has been evidenced by decreased lipid accumulation of differentiating cells and expression levels of crucial adipogenesis markers in 3T3-L1 pre-adipocytes. S.herbacea treatment reduced the lipid accumulation by 25% of the control. In addition, mRNA expression of peroxisome proliferator-activated receptor (PPAR)γ, CCAAT/enhancer-binding protein (C/EBP)α and sterol regulatory element binding protein (SREBP)1c were inhibited by the presence of S. herbacea. Bone formation enhancement effect of S.herbacea was also confirmed in MC3T3-E1 pre-osteoblasts. The presence of S. herbacea significantly elevated the alkaline phosphatase (ALP) activity by 120% at a concentration of 100 μg/mL in differentiating osteoblasts. S. herbacea also significantly increased the expression of osteoblastogenesis indicators, ALP, bone morphogenetic protein (BMP)-2, osteocalcin and collagen type I (collagen-I). In conclusion, S. herbacea possess potential to be utilized as a source of anti-osteoporotic agent that can inhibit adipogenesis while promoting osteoblastogenesis.

Effects of Watercress Containing Rutin and Rutin Alone on the Proliferation and Osteogenic Differentiation of Human Osteoblast-like MG-63 Cells

Most known osteoporosis medicines are effective for bone resorption, and so there is an increasing demand for medicines that stimulate bone formation. Watercress (N. officinale R. Br.) is widely used as a salad green and herbal remedy. This study analyzed a watercress extract using ultra-performance liquid chromatography/mass spectrometry, and identified a rutin as one of its major constituents. Osteogenic-related assays were used to compare the effects of watercress containing rutin (WCR) and rutin alone on the proliferation and differentiation of human osteoblast-like MG-63 cells. The reported data are expressed as percentages relative to the control value (medium alone; assigned as 100%). WCR increased cell proliferation to 125.0±4.0% (mean±SD), as assessed using a cell viability assay, and increased the activity of alkaline phosphatase, an early differentiation marker, to 222.3±33.8%. In addition, WCR increased the expression of collagen type I, another early differentiation marker, to 149.2±2.8%, and increased the degree of mineralization, a marker of the late process of differentiation, to 122.9±3.9%. Rutin alone also increased the activity of ALP (to 154.4±12.2%), the expression of collagen type I (to 126.6±6.2%), and the degree of mineralization (to 112.3±5.0%). Daidzein, which is reported to stimulate bone formation, was used as a positive control; the effects of WCR on proliferation and differentiation were significantly greater than those of daidzein. These results indicate that WCR and rutin can both induce bone formation via the differentiation of MG-63 cells. This is the first study demonstrating the effectiveness of either WCR or rutin as an osteoblast stimulant.

Isoquercitrin and polyphosphate co-enhance mineralization of human osteoblast-like SaOS-2 cells via separate activation of two RUNX2 cofactors AFT6 and Ets1

Isoquercitrin, a dietary phytoestrogen, is a potential stimulator of bone mineralization used for prophylaxis of osteoporotic disorders. Here we studied the combined effects of isoquercitrin, a cell membrane permeable 3-O-glucoside of quercetin, and polyphosphate [polyP], a naturally occurring inorganic polymer inducing bone formation, on mineralization of human osteoblast-like SaOS-2 cells. Both compounds isoquercitrin and polyP induce at non-toxic concentrations the mineralization process of SaOS-2 cells. Co-incubation experiments revealed that isoquercitrin (at 0.1 and 0.3μM), if given simultaneously with polyP (as Ca(2+) salt; at 3, 10, 30 and 100μM) amplifies the mineralization-enhancing effect of the inorganic polymer. The biomineralization process induced by isoquercitrin and polyP is based on two different modes of action. After incubation of the cells with isoquercitrin or polyP the expression of the Runt-related transcription factor 2 [RUNX2] is significantly upregulated. In addition, isoquercitrin causes a strong increase of the steady-state-levels of the two co-activators of RUNX2, the activating transcription factor 6 [ATF6] and the Ets oncogene homolog 1 [Ets1]. The activating effect of isoquercitrin occurs via a signal transduction pathway involving ATF6, and by that, is independent from the induction cascade initiated by polyP. This conclusion is supported by the finding that isoquercitrin upregulates the expression of the gene encoding for osteocalcin, while polyP strongly increases the expression of the Ets1 gene and of the alkaline phosphatase. We show that the two compounds, polyP and isoquercitrin, have a co-enhancing effect on bone mineral formation and in turn might be of potential therapeutic value for prevention/treatment of osteoporosis.

Apigenin inhibits osteoblastogenesis and osteoclastogenesis and prevents bone loss in ovariectomized mice

Polyphenol have been reported to have physiological effects with respect to alleviating diseases such as osteoporosis and osteopetrosis. We recently reported that the olive polyphenol hydroxytyrosol accelerates bone formation both in vivo and in vitro. The present study was designed to evaluate the in vivo and in vitro effects of apigenin (4′,5,7-trihydroxyflavone), one of the major polyphenols in olives and parsley, on bone formation by using cultured osteoblasts and osteoclasts and ovariectomized (OVX) mice, respectively. Apigenin markedly inhibited cell proliferation and indices of osteoblast differentiation, such as collagen production, alkaline phosphatase activity, and calcium deposition in osteoblastic MC3T3-E1 cells at concentrations of 1–10 μM. At 10 μM, apigenin completely inhibited the formation of multinucleated osteoclasts from mouse splenic cells. Moreover, injection of apigenin at 10 mg kg⁻¹ body weight significantly suppressed trabecular bone loss in the femurs of OVX mice. Our findings indicate that apigenin may have critical effects on bone maintenance in vivo.

Site-specific anticancer effects of dietary flavonoid quercetin

Food-derived flavonoid quercetin, widely distributed in onions, apples, and tea, is able to inhibit growth of various cancer cells indicating that this compound can be considered as a good candidate for anticancer therapy. Although the exact mechanism of this action is not thoroughly understood, behaving as antioxidant and/or prooxidant as well as modulating different intracellular signalling cascades may all play a certain role. Such inhibitory activity of quercetin has been shown to depend first of all on cell lines and cancer types; however, no comprehensive site-specific analysis of this effect has been published. In this review article, cytotoxicity constants of quercetin measured in various human malignant cell lines of different origin were compiled from literature and a clear cancer selective action was demonstrated. The most sensitive malignant sites for quercetin revealed to be cancers of blood, brain, lung, uterine, and salivary gland as well as melanoma whereas cytotoxic activity was higher in more aggressive cells compared to the slowly growing cells showing that the most harmful cells for the organism are probably targeted. More research is needed to overcome the issues of poor water solubility and relatively low bioavailability of quercetin as the major obstacles limiting its clinical use.

Quercitrin and taxifolin stimulate osteoblast differentiation in MC3T3-E1 cells and inhibit osteoclastogenesis in RAW 264.7 cells

Flavonoids are natural antioxidants that positively influence bone metabolism. The present study screened among different flavonoids to identify biomolecules for potential use in bone regeneration. For this purpose, we used MC3T3-E1 and RAW264.7 cells to evaluate their effect on cell viability and cell differentiation. First, different doses of chrysin, diosmetin, galangin, quercitrin and taxifolin were analyzed to determine the optimum concentration to induce osteoblast differentiation. After 48h of treatment, doses ≥100μM of diosmetin and galangin and also 500μM taxifolin revealed a toxic effect on cells. The same effect was observed in cells treated with doses ≥100μM of chrysin after 14 days of treatment. However, the safe doses of quercitrin (200 and 500μM) and taxifolin (100 and 200μM) induced bone sialoprotein and osteocalcin mRNA expression. Also higher osteocalcin secreted levels were determined in 100μM taxifolin osteoblast treated samples when compared with the control ones. On the other hand, quercitrin and taxifolin decreased Rankl gene expression in osteoblasts, suggesting an inhibition of osteoclast formation. Indeed, osteoclastogenesis suppression by quercitrin and taxifolin treatment was observed in RAW264.7 cells. Based on these findings, the present study demonstrates that quercitrin and taxifolin promote osteoblast differentiation in MC3T3-E1 cells and also inhibit osteoclastogenesis in RAW264.7 cells, showing a positive effect of these flavonoids on bone metabolism.

Assessment of the role of flavonoids for inducing osteoblast differentiation in isolated mouse bone marrow derived mesenchymal stem cells

Quercetin and rutin are common flavonoids in fruit and vegetables, and have been reported to affect bone development. However, the effect of flavonoids on osteoblast differentiation remains a matter of controversy. In the present study, mouse bone marrow mesenchymal stem cells (BMMSCs) were isolated and characterized for their use in osteoblast differentiation using two flavonoids, quercetin and rutin. BMMSCs were cultured in various concentrations of quercetin and rutin during the osteoblast differentiation period of 10 days. Both quercetin and rutin were found to up regulate the osteoblast differentiation in dose dependent manner, albeit to lesser extent in case of former than that of latter. Quercetin and rutin also increased alkaline phosphatase activity by about 150 and 240% and demonstrated mineralization up to 110 and 200% respectively as compared to control (which was considered as 100%). Further, both the flavonoids were also found to increase the expression of some of the prominent markers for differentiation of osteoblast like osteopontin, osterix, RunX2, osteoprotegerin and osteocalcin. The current data suggests that certain classes of flavonoids like rutin and quercetin can be used in the cure and management of osteodegenerative disorders due to their osteoblast specific differentiation activities.

Effects of silicon on osteoblast activity and bone mineralization of MC3T3-E1 cells

Previous studies have reported that dietary silicon (Si) intake is positively associated with bone health including bone mineral density. Although the amount of Si intake is high among trace elements in humans, how dietary Si affects bone formation at the cellular level is not well addressed. The purpose of this study was to investigate the role of Si in osteoblast activity and bone mineralization. MC3T3-E1 was cultured as mature osteoblasts and treated with sodium metasilicate (0, 1, 5, 10, 25, 50, and 100 μM) as a source of Si. After 7 days of treatment, 5 and 10 μM of sodium metasilicate significantly increased intracellular alkaline phosphatase activity (p < 0.05) when compared to the control. Additionally, all doses of sodium metasilicate (1, 5, 10, 25, 50, and 100 μM) increased mineralized nodule formation at 14 days of differentiation as evidenced by increased Alizarin Red S staining. In the analysis of gene expression, 50 μM of sodium metasilicate upregulated type I collagen (COL-I) compared to the control group. However, the increase of COL-I gene expression as a result of treatment with 1, 10, 25, and 100 μM of sodium metasilicate did not reach statistical significance. mRNA expression of insulin-like growth factor-I and receptor activator of NF-κB ligand was not significantly changed at any dose of sodium metasilicate (0, 1, 5, 10, 25, 50, and 100 μM). In light of the results, we conclude that Si has a positive effect on bone metabolism by enhancing osteoblast mineralization activity.

Transglutaminase inhibitors attenuate vascular calcification in a preclinical model

OBJECTIVE

In vitro, transglutaminase-2 (TG2)-mediated activation of the β-catenin signaling pathway is central in warfarin-induced calcification, warranting inquiry into the importance of this signaling axis as a target for preventive therapy of vascular calcification in vivo.

METHODS AND RESULTS

The adverse effects of warfarin-induced elastocalcinosis in a rat model include calcification of the aortic media, loss of the cellular component in the vessel wall, and isolated systolic hypertension, associated with accumulation and activation of TG2 and activation of β-catenin signaling. These effects of warfarin can be completely reversed by intraperitoneal administration of the TG2-specific inhibitor KCC-009 or dietary supplementation with the bioflavonoid quercetin, known to inhibit β-catenin signaling. Our study also uncovers a previously uncharacterized ability of quercetin to inhibit TG2. Quercetin reversed the warfarin-induced increase in systolic pressure, underlying the functional consequence of this treatment. Molecular analysis shows that quercetin diet stabilizes the phenotype of smooth muscle and prevents its transformation into osteoblastic cells.

CONCLUSIONS

Inhibition of the TG2/β-catenin signaling axis seems to prevent warfarin-induced elastocalcinosis and to control isolated systolic hypertension.

Bone mineral density, polyphenols and caffeine: a reassessment

Several studies have shown beneficial associations between tea consumption and bone mineral density (BMD) and fracture risk. Current investigations into potential mechanisms of benefit are focused upon the F and polyphenol components of tea. However, previous studies have pointed towards caffeine consumption as a potential risk factor for low BMD and high fracture risk. Tea, therefore, represents an interesting paradox as a mildly caffeinated beverage that may enhance bone health. Fruit and vegetable intake has also been associated with BMD, and it is now apparent that several fruit and vegetable components, including polyphenols, may contribute positively to bone health. Evidence surrounding the function(s) of polyphenol-rich foods in bone health is examined, along with more recent studies challenging the relevance of caffeine consumption to in vivo Ca balance. Plant foods rich in polyphenols such as tea, fruit and vegetables, as significant factors in a healthy diet and lifestyle, may have positive roles in bone health, and the negative role of caffeine may have been overestimated. The present review covers evidence of dietary mediation in positive and negative aspects of bone health, in particular the roles of tea, fruit and vegetables, and of caffeine, flavonoids and polyphenols as components of these foods. Since the deleterious effects of caffeine appear to have been overstated, especially in respect of the positive effects of flavonoids, it is concluded that a reassessment of the role of caffeinated beverages may be necessary.

Quercetin protects primary human osteoblasts exposed to cigarette smoke through activation of the antioxidative enzymes HO-1 and SOD-1

Smokers frequently suffer from impaired fracture healing often due to poor bone quality and stability. Cigarette smoking harms bone cells and their homeostasis by increased formation of reactive oxygen species (ROS). The aim of this study was to investigate whether Quercetin, a naturally occurring antioxidant, can protect osteoblasts from the toxic effects of smoking. Human osteoblasts exposed to cigarette smoke medium (CSM) rapidly produced ROS and their viability decreased concentration- and time-dependently. Co-, pre- and postincubation with Quercetin dose-dependently improved their viability. Quercetin increased the expression of the anti-oxidative enzymes heme-oxygenase- (HO-) 1 and superoxide-dismutase- (SOD-) 1. Inhibiting HO-1 activity abolished the protective effect of Quercetin. Our results demonstrate that CSM damages human osteoblasts by accumulation of ROS. Quercetin can diminish this damage by scavenging the radicals and by upregulating the expression of HO-1 and SOD-1. Thus, a dietary supplementation with Quercetin could improve bone matter, stability and even fracture healing in smokers.

Antiosteoporotic compounds from seeds of Cuscuta chinensis

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Cuscuta chinensis (Tu-Si-Zi, TSZ) have long been used for the treatment of osteoporosis in China and some Asian countries. The compounds in TSZ responsible for the antiosteoporotic activity are still poorly understood.

AIM OF THE STUDY

The present study was designed to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells.

MATERIALS AND METHODS

Osteoblast-like UMR-106 cells were used for bioactivity-guided isolation of the active compounds. The activity of alkaline phosphatase (ALP) in UMR-106 cells was measured by p-nitrophenyl sodium phosphate assay. The proliferation of UMR-106 cells was assayed by Alamar-Blue method. Estrogenic activity of the extracts and isolated compounds was evaluated by activation of estrogen response element (ERE) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 5×ERE luciferase reporter plasmid. Antiestrogenic activity of the extracts and isolated compounds were evaluated by activation of activator protein-1 (AP-1) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 6×AP-1 luciferase reporter plasmid.

RESULTS

ALP-guided fractionation led to the isolation of five known flavonoids, quercetin, kaempferol, isorhamnetin, hyperoside and astragalin from the crude ethanolic extract of TSZ. Further study showed that kaempferol and hyperoside significantly increased the ALP activity in UMR-106 cells. Astragalin promoted the proliferation of UMR-106 cells whereas other compounds had no such effect. The isolated compounds showed estrogenic activity but quercetin, kaempferol and isorhamnetin showed more potent ERβ agonist activity. However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ERα/β-mediated AP-1 reporter expression.

CONCLUSIONS

Our findings validated the clinical use of TSZ in the treatment of osteoporosis, and demonstrated that kaempferol and hyperoside are the active compounds in TSZ for the osteogenic effect.

Olive polyphenol hydroxytyrosol prevents bone loss

Polyphenols reportedly exert physiological effects against diseases such as cancer, arteriosclerosis, hyperlipidemia and osteoporosis. The present study was designed to evaluate the effects of oleuropein, hydroxytyrosol and tyrosol, the major polyphenols in olives, on bone formation using cultured osteoblasts and osteoclasts, and on bone loss in ovariectomized mice. No polyphenols markedly affected the proliferation of osteoblastic MC3T3-E1 cells at concentrations up to 10μM. Oleuropein and hydroxytyrosol at 10 to 100μM had no effect on the production of type I collagen and the activity of alkaline phosphatase in MC3T3-E1 cells, but stimulated the deposition of calcium in a dose-dependent manner. In contrast, oleuropein at 10 to 100μM and hydroxytyrosol at 50 to 100μM inhibited the formation of multinucleated osteoclasts in a dose-dependent manner. Furthermore, both compounds suppressed the bone loss of trabecular bone in femurs of ovariectomized mice (6-week-old BALB/c female mice), while hydroxytyrosol attenuated H(2)O(2) levels in MC3T3-E1 cells. Our findings indicate that the olive polyphenols oleuropein and hydroxytyrosol may have critical effects on the formation and maintenance of bone, and can be used as effective remedies in the treatment of osteoporosis symptoms.

Ulmosides A and B: flavonoid 6-C-glycosides from Ulmus wallichiana, stimulating osteoblast differentiation assessed by alkaline phosphatase

Chemical investigation of Ulmus wallichiana stem bark resulted in isolation and identification of three new compounds (2S,3S)-(+)-3',4',5,7-tetrahydroxydihydroflavonol-6-C-beta-D-glucopyranoside (1), (2S,3S)-(+)-4',5,7-trihydroxydihydroflavonol-6-C-beta-D-glucopyranoside (3) and 3-C-beta-D-glucopyranoside-2,4,6-trihydroxymethylbenzoate (8), together with five known flavonoid-6-C-glucosides (2, 4-7). Their structures were elucidated using 1D and 2D NMR spectroscopic analysis. The absolute stereochemistry in compounds 1 and 3 were established with the help of CD data analysis and comparison with the literature data analysis. All the isolated compounds (1-8) were assessed for promoting the osteoblast differentiation using primary culture of rat osteoblast as an in vitro system. Compounds 1-3 and 5 significantly increased osteoblast differentiation as assessed by alkaline phosphatase activity.

Dietary quercetin inhibits bone loss without effect on the uterus in ovariectomized mice

Quercetin is a major dietary flavonoid found in onions and other vegetables, and potentially has beneficial effects on disease prevention. In the present study, we demonstrate for the first time the effects of dietary quercetin on bone loss and uterine weight loss by ovariectomy in vivo. Female mice were ovariectomized (OVX) and were randomly allocated to 3 groups: a control diet or a diet with 0.25% (LQ) or 2.5% quercetin (HQ). After 4 weeks, dietary quercetin had no effects on uterine weight in OVX mice, but bone mineral density of the lumbar spine L4 and femur measured by peripheral quantitative computed tomography (pQCT) was higher in both the sham and the HQ groups than in the OVX group. Histomorphometric analysis showed that the HQ group restored bone volume (BV/TV) completely in distal femoral cancellous bone, but did not reduce the osteoclast surface area and osteoclast number when compared with the OVX group. In in-vitro experiments using mouse monocyte/macrophage cell line RAW264.7 cells, however, quercetin and its conjugate, quercetin-3-O-beta-D: -glucuronide dose-dependently inhibited the receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclast differentiation, and the RANKL-stimulated expression of osteoclast related genes was also inhibited by quercetin. The luciferase reporter assay showed that quercetin did not appear to have estrogenic activity through estrogen receptors. These results suggest that dietary quercetin inhibits bone loss without effect on the uterus in OVX mice and does not act as a potent inhibitor of osteoclastogenesis or as a selective estrogen receptor modulator in vivo.

Antiproliferative effects of quercetin through cell cycle arrest and apoptosis in human breast cancer MDA-MB-453 cells

To explore the anticancer effects of the flavonoid quercetin on human breast cancer MDA-MB-453 cells via cell cycle regulation and the induction of apoptosis, the antiproliferative effect of quercetin was first examined by MTT assay. When MDA-MB-453 cells were treated with quercetin for various periods of time (3-24 hrs) and at various doses (1-100 microM), cell growth decreased significantly in a time-and dose-dependent manner. To elucidate the mechanism underlying the antiproliferative effect of quercetin, cell cycle progression and the induction of apoptosis in MDA-MB-453 cells exposed to 100 microM quercetin for 24 hrs were investigated. Quercetin caused a remarkable increase in the number of sub-G1 phase cells, and an Annexin-V assay revealed that exposure to quercetin affected apoptosis. Moreover, treatment with quercetin increased Bax expression but decreased Bcl-2 expression. Cleaved caspase-3 and PARP expression was also increased by quercetin. Thus, quercetin has probable anticancer activity. Our results suggest the existence of multiple pathways for the induction of cell cycle arrest and apoptosis by quercetin.

Underlying mechanism of quercetin-induced cell death in human glioma cells

There has been considerable interest in recent years in the anti-tumor activities of flavonoids. Quercetin, a ubiquitous bioactive flavonoid, can inhibit proliferation and induce apoptosis in a variety of cancer cells. However, the precise molecular mechanism by which quercetin induces apoptosis in cancer cells is poorly understood. The present study was undertaken to examine the effect of quercetin on cell viability and to determine its underlying mechanism in human glioma cells. Quercetin resulted in loss of cell viability in a dose- and time-dependent manner and the decrease in cell viability was mainly attributed to cell death. Quercetin did not increase reactive oxygen species (ROS) generation and the quercetin-induced cell death was also not affected by antioxidants, suggesting that ROS generation is not involved in loss of cell viability. Western blot analysis showed that quercetin treatment caused rapid reduction in phosphorylation of extracellular signal-regulated kinase (ERK) and Akt. Transient transfection with constitutively active forms of MEK and Akt protected against the quercetin-induced loss of cell viability. Quercetin-induced depolarization of mitochondrial membrane potential. Caspase activity was stimulated by quercetin and caspase inhibitors prevented the quercetin-induced loss of cell viability. Quercetin resulted in a decrease in expression of survivin, antiapoptotic proteins. Taken together, these findings suggest that quercetin results in human glioma cell death through caspase-dependent mechanisms involving down-regulation of ERK, Akt, and survivin.

Effects of total flavonoids and flavonol glycosides from Epimedium koreanum Nakai on the proliferation and differentiation of primary osteoblasts

In a bioassay-guided drug screening for anti-osteoporosis activity, eight flavonol glycosides were isolated from Epimedium koreanum Nakai, which is traditionally widely used in China for the treatment of impotence and osteoporosis. The effects of total flavonoids and flavonol glycosides on the proliferation and differentiation of rat calvarial osteoblast-like cells were evaluated by the MTT method and measuring the activity of alkaline phosphatase (ALP activity). Total flavonoids (1.2 x10(-2) to 6.0 x10(-7) mg/ml) and flavonol glycosides (2.0 x10(-5) to 1.0 x10(-9) mol/l) exhibited a strong inhibition on the proliferation of primary osteoblasts at most concentrations. However, the total flavonoids and icariin significantly promoted the differentiation of primary osteoblasts. The results suggested that flavonoids from E. koreanum Nakai may improve the development of osteoblasts by promoting the ALP activity; and icariin might be one of the active constituents facilitating the differentiation of osteoblasts.