Article

Curcumin Inhibits Osteoclastogenesis by Decreasing Receptor Activator of Nuclear Factor-kappa B Ligand (RANKL) in Bone Marrow Stromal Cells

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Abstract

Curcumin (diferuloylmethane), a pigment derived from turmeric, has anti-oxidant and anti-inflammatory activities. Accumulating evidence points to a biochemical link between increased oxidative stress and reduced bone density. Osteoclast formation was evaluated in co-cultures of bone marrow stromal cells (BMSC) and whole bone marrow cells (BMC). Expression of receptor activator of nuclear factor-kappaB ligand (RANKL) was analyzed at the mRNA and protein levels. Exposure to curcumin led to dose-dependent suppression of osteoclastogenesis in the coculture system, and to reduced expression of RANKL in IL-1alpha-stimulated BMSCs. Addition of RANKL abolished the inhibition of osteoclastogenesis by curcumin, whereas the addition of prostaglandin E2(PGE2) did not. The decreased osteoclastogenesis induced by curcumin may reduce bone loss and be of potential benefit in preventing and/or attenuating osteoporosis.

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... Curcumin is able to improve bone health in patients with osteoporosis by acting on multiple steps in the activation and differentiation of osteoclasts, and improving mineral density and mechanical properties. The potential mechanisms that have been proposed include inhibition of nuclear factor (NF)-κB, receptor activator of NF-κB ligand (RANKL), nitric oxide production, the generation of reactive oxygen species and inflammatory cytokine synthesis (38,39,47,50,51,60,61). ...
... By contrast, another study revealed that the administration of curcumin did not efficiently improve bone mineralization in ovariectomized rats, and indicated that curcumin affected the level of osteogenesis commitment, not osteoblast maturation (36). It has also been revealed that curcumin reduces the expression of RANKL and inhibits osteoclastogenesis by acting on BMSCs (61). This could be explained by the activity of curcumin as a scavenger of reactive oxygen species. ...
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The use of bone marrow mesenchymal stem cells (BMSCs) has great potential in cell therapy, particularly in the orthopedic field. BMSCs represent a valuable renewable cell source that have been successfully utilized to treat damaged skeletal tissue and bone defects. BMSCs can be induced to differentiate into osteogenic lineages via the addition of inducers to the growth medium. The present study examined the effects of all‑trans retinoic acid (ATRA) and curcumin on the osteogenic differentiation of mouse BMSCs. Morphological changes, the expression levels of the bone‑associated gene markers bone morphogenetic protein 2, runt‑related transcription factor and osterix during differentiation, an in vitro mineralization assay, and changes in osteocalcin expression revealed that curcumin supplementation promoted the osteogenic differentiation of BMSCs. By contrast, the application of ATRA increased osteogenic differentiation during the early stages, but during the later stages, it decreased the mineralization of differentiated cells. In addition, to the best of our knowledge, the present study is the first to examine the effect of curcumin on the osteogenic potency of mouse embryonic fibroblasts (MEFs) after reprogramming with human lim mineralization protein (hLMP‑3), which is a positive osteogenic regulator. The results revealed that curcumin‑supplemented culture medium increased hLMP‑3 osteogenic potency compared with that of MEFs cultured in the non‑supplemented medium. The present results demonstrate that enrichment of the osteogenic culture medium with curcumin, a natural osteogenic inducer, increased the osteogenic differentiation capacity of BMSCs as well as that of MEFs reprogrammed with hLMP‑3
... Although curcumin has a protective effect on bone remodeling 2,5,6,9,13,19,22) , appropriate therapeutic concentrations of curcumin are not well known as therapeutic drugs for osteoporosis. ...
... In addition to a variety of pharmacologic effects, including anti-inflammatory, anti-infectious and antioxidant activities, which are traditionally known 5,13,19) , recent studies investigated the protective effects of curcumin on the regulation of bone remodeling. It is well known that curcumin has action similar to bisphosphonate, the inhibition of osteoclastogenesis [4][5][6][7]9,23) . Ozaki et al. 10) showed that curcumin is a potent stimulator of osteoclast apoptosis and also an inhibitor of bone resorption caused by rabbit osteoclast. ...
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Although curcumin has a protective effect on bone remodeling, appropriate therapeutic concentrations of curcumin are not well known as therapeutic drugs for osteoporosis. The purpose of this study was to compare the bone sparing effect of treatment of low-dose and high-dose curcumin after ovariectomy in rats. Forty female Sprague-Dawley rats underwent either a sham operation (the sham group) or bilateral ovariectomy (OVX). The ovariectomized animals were randomly distributed among three groups; untreated OVX group, low-dose (10 mg/kg) curcumin administered group, and high-dose (50 mg/kg) curcumin group. At 4 and 8 weeks after surgery, serum biochemical markers of bone turnover were analyzed. Bone histomorphometric parameters of the 4th lumbar vertebrae were determined by micro-computed tomography (CT). In addition, mechanical strength was determined by a three-point bending test. High-dose curcumin group showed significantly lower osteocalcin, alkaline phosphatase, and the telopeptide fragment of type I collagen C-terminus concentration at 4 and 8 weeks compared with the untreated OVX group as well as low-dose curcumin group. In the analyses of micro-CT scans of 4th lumbar vertebrae, the high-dose curcumin treated group showed a significant increase in bone mineral densities (p=0.028) and cortical bone mineral densities (p=0.036) compared with the low-dose curcumin treated group. Only high-dose curcumin treated group had a significant increase of mechanical strength compared with the untreated OVX group (p=0.015). The present study results demonstrat that a high-dose curcumin has therapeutic advantages over a low-dose curcumin of an antiresorptive effect on bone remodeling and improving bone mechanical strength.
... This might be crucial to enhance the differentiation of osteoblasts (189). Also, curcumin slightly inhibited the enhancement of RANKL by IL-1a in human bone marrow stromal cells (190). Epigallocatechin-3-gallate is a flavonoid found abundantly in green tea. ...
Article
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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.
... Curcumin has been reported to inhibit osteoclastogenesis by decreasing RANKL signaling in bone marrow stromal cells. 21 Curcumin analogues (EF 31, ECMN909, and UBS109) with dosedependency (50-500 nM), which did not have cell toxicity, were found to have a suppressive effect on osteoclastogenesis, although the effect of curcumin was seen only at the highest dose (500 nM). RANKL, the key osteoclastogenic cytokine, is central to the formation of osteoclasts, the cells that resorb bone, through NF-kB signaling. ...
Article
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Bone homeostasis is maintained through a balance between osteoblastic bone formation and osteoclastic bone resorption. Bone loss is induced due to decreased osteoblastic bone formation and increased osteoclastic bone resorption with various pathologic states. Osteoporosis with its accompanying decrease in bone mass is widely recognized as a major public health problem. Pharmacologic and functional food factors may play a role in the prevention of bone loss with aging. This study was undertaken to determine the effect of curcumin analogues (curcumin, EF31, ECMN909, and UBS109), which were newly synthesized, on osteoblastogenesis and osteoclastogenesis in vitro. Among these compounds, UBS109 had a unique stimulatory effect on osteoblastic differentiation and mineralization. UBS109 stimulated both basal and bone morphogenic protein-2 (BMP2)-increased Smad-luciferase activity, the Smad signaling of which is related to osteoblastogenesis. Such an effect was not seen with other compounds. Moreover, UBS109 potently suppressed tumor necrosis factor-α (TNF-α)-increased osteoblastic nuclear factor kappa B (NF-κB)-luciferase activity. In addition, EF31, ECMN909, and UBS109 had a suppressive effect on osteoclastogenesis as compared with that of curcumin. ECMN909 and UBS109 potently inhibited the receptor activator of NF-κB (RANK) ligand (RANKL)-increased preosteoclastic NF-κB-luciferase activity, in which NF-κB signaling plays a pivotal role in osteoclastogenesis. In the present study, curcumin analogue UBS109 was found to have a stimulating effect on osteoblastogenesis and a suppressive effect on osteoclastogenesis in vitro, suggesting an anabolic effect of the compound on bone mass.
... Curcumin can improve multiple aspects of bone health in subjects with osteoporosis by acting on multiple steps in the activation and differentiation of osteoclasts, improving mineral density and mechanical properties. Mechanisms that have been proposed include inhibition of NF-κB, RANKL, NO production, generation of reactive oxygen species and inflammatory cytokine synthesis [36][37][38][39][40][41][42][43] . Through these mechanisms, curcumin can decrease osteoclast number, differentiation and activation. ...
Article
The Indian spice turmeric, in which the active and dominant biomolecule is curcumin, has been demonstrated to have significant medicinal properties, including anti-inflammatory and anti-neoplastic effects. This promise is potentially very applicable to musculoskeletal disorders, which are common causes of physician visits worldwide. Research at the laboratory, translational and clinical levels that supports the use of curcumin for various musculoskeletal disorders, such as osteoarthritis, osteoporosis, musculocartilaginous disorders, and sarcoma is here in comprehensively summarized. Though more phase I-III trials are clearly needed, thus far the existing data show that curcumin can indeed potentially be useful in treatment of the hundreds of millions worldwide who are afflicted by these musculoskeletal disorders. © 2015 Chinese Orthopaedic Association and Wiley Publishing Asia Pty Ltd.
... Other more recent antioxidant shown to affect osteoclasts include polyphenol extracts from dried plums [155], curcumerin [156], ascorbic acid [157], salvia miltorrhiza [158], coffee diterpene Kahweol [159], delthametrin [160], to name a few. The use of antioxidants from natural sources, such as fruits and vegetables, could be another way of inhibiting ROS. ...
... In many animal studies, the antioxidant (75) and anti-inflammatory (76), as well as the angiogenic and woundhealing effects of curcumin, by increasing the number of fibroblasts and promoting collagen synthesis (77), or by modulating urokinase plasminogen activator (uPA) expression (78), have been demonstrated. Interestingly, curcumin does not prevent alveolar bone resorption in vivo in rats (76), but inhibits RANKL-induced osteoclastogenesis in vitro (79). Guimarães et al also observed the lack of inhibition of bone resorption in an experimental model of lipopolysacharide (LPS)-induced periodontal disease (76), which is surprising, keeping in mind that curcumin was shown to significantly inhibit Porphyromonas gingivalis LPS-induced TNF-α and IL-1β production (80). ...
Article
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Curcumin has been shown to exert therapeutic or protective effects against a variety of diseases, such as cancer, pulmonary diseases, neurological, liver, metabolic, autoimmune, cardiovascular diseases and numerous other chronic ailments. Over 116 clinical studies on curcumin in humans were registered with the US National Institutes of Health in 2015. However, it is mystifying how curcumin can be so effective in the treatment of many diseases since it has very low water solubility and bioavailability. Furthermore, curcumin is not stable under various conditions; its degradation or condensation into different bioactive compounds may be responsible for its biological activities rather than curcumin itself. In this review, we provide evidence of curcumin degradation and condensation into different compounds which have or may have health benefits themselves. Literature reviews strongly suggest that these molecules contribute to the observed health benefits, rather than curcumin itself.
... Curcumin, as an anti-tumor agent, suppresses osteoclast formation in response to IL-1α by inhibiting the enzymes that generate ROS, thus inhibiting osteoclast formation [29]. Furthermore, curcumin-like denosumab, a monoclonal antibody for the treatment of osteoporosis, suppresses RANKL by inhibiting IKK and NF-KB activation or acts as a ROS scavenger to protect against bone destruction, decrease tumor burden, and also improve survival of osteosarcoma patients after chemotherapy [30]. ...
Article
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Osteosarcoma is a major form of malignant bone tumor that typically occurs in young adults and children. The combination of aggressive surgical strategies and chemotherapy has led to improvements in survival time, although individuals with recurrent or metastatic conditions still have an extremely poor prognosis. This disappointing situation strongly indicates that testing novel, targeted therapeutic agents is imperative to prevent the progression of osteosarcoma and enhance patient survival time. Curcumin, a naturally occurring phenolic compound found in Curcuma longa, has been shown to have a wide variety of anti-tumor, anti-oxidant, and anti-inflammatory activities in many types of cancers including osteosarcoma. Curcumin is a highly pleiotropic molecule that can modulate intracellular signaling pathways to regulate cell proliferation, inflammation, and apoptosis. These signaling pathways include RANK/RANKL, Notch, Wnt/β-catenin, apoptosis, autophagy, JAK/STAT, and HIF-1 pathways. Additionally, curcumin can regulate the expression of various types of microRNAs that are involved in osteosarcoma. Therefore, curcumin may be a potential candidate for the prevention and treatment of osteosarcoma. This comprehensive review not only covers the use of curcumin in the treatment of osteosarcoma and its anti-cancer molecular mechanisms but also reveals the novel delivery strategies and combination therapies with the aim to improve the therapeutic effect of curcumin.
... In fact, the effects of curcumin on bone cells have previously been investigated in vitro [6,7]. In co-cultures of bone marrow stromal cells (BMSC) and whole bone marrow cells (BMC), exposure to curcumin leads to dosedependent suppression of osteoclastogenesis in the coculture system and reduces the expression of RANKL in IL-1α-stimulated BMSCs [8]. Therefore, curcumin effects on bone microarchitecture in vivo warranted further evaluation. ...
Article
The present study aimed to investigate bone microarchitecture of the proximal tibia in glucocorticoidinduced osteoporosis (GIOP) mice, and the underlying molecular mechanisms of curcumin in DXM-induced osteoporosis were performed. DXM-treated facilitated to induce hypercalciuria in mice, and curcumin-treated showed a decrease in urine calcium. Curcumin reversed DXM-induced bone resorption, including an increase in serum OCN and a decrease in bone resorption markers CTX and TRAP-5b. H&E staining showed the increased disconnections and separation in trabecular bone network as well as the reduction of trabecular thickness throughout the proximal metaphysis of tibia in GIOP group. Importantly, curcumin reversed DXM-induced trabecular deleterious effects and stimulated bone remodeling. The further evidence showed that curcumin supplement significantly decreased the TRAP-positive stained area and inhibited the activity of OPG/RANKL/RANK signaling in the GIOP mice. Moreover, bioinformatics analysis suggested that miR-365 was a regulator of MMP9. The levels of miR-365 were markedly suppressed; however, curcumin treatment could reverse the downregulation of miR-365 in the tibia of GIOP mice. Simultaneously, the results demonstrated that the mRNA and protein expression of MMP-9 were significantly increased in GIOP mice compared with that of the control group. Curcumin treatment could suppress the expression of MMP-9 in the tibia of GIOP mice. The present study demonstrated the protective effects of curcumin against bone deteriorations in the experimentally DIOP mice, and the underlying mechanism was mediated, at least partially, through the activation of microRNA-365 via suppressing MMP9.
... Curcumin has several pharmacological and biological properties, and evidence has supported its potential protective function in osteoporosis [19][20]. Curcumin might decrease bone resorption by inhibition of osteoclast proliferation, differentiation, and activity as well as by promotion of osteoclast apoptosis [44][45][46][47]. Although no consistent conclusion has been reached concerning its benefits in osteogenesis, our present findings demonstrate that curcumin significantly decreases osteoblast apoptosis induced by H 2 O 2 with similar effectiveness as the antioxidant compound EUK134. ...
Article
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Background: Osteoblast apoptosis induced by oxidative stress plays a crucial role in the development and progression of osteoporosis. Curcumin, a natural antioxidant isolated from Curcuma longa, has highly protective effects against osteoporosis. However, the effects of curcumin on oxidative stress-induced osteoblast apoptosis remain unclear. This study aimed to explore the effect of curcumin on hydrogen peroxide (H2O2) induced osteoblast apoptosis and the underlying mechanisms. Methods: An osteoblastic cell line (Saos-2) was exposed to various concentrations of H2O2 with or without curcumin treatment. Cell viability was evaluated by MTT assays. The apoptosis rate was analyzed by flow cytometry and TUNEL assays. Mitochondrial ROS and membrane potential were determined using a fluorescence microscope. Mitochondrial respiratory enzyme activity was measured using a spectrophotometer. Protein levels were detected by western blotting. Results: Curcumin was cytoprotective because it greatly improved the viability of Saos-2 cells exposed to H2O2 and attenuated H2O2-induced apoptosis. Curcumin treatment also preserved the mitochondrial redox potential, decreased the mitochondrial oxidative status, and improved the mitochondrial membrane potential and functions. Furthermore, curcumin treatment markedly increased levels of phosphorylated protein kinase B (Akt) and phosphorylated glycogen synthase kinase-3β (GSK3β). Conclusion: Curcumin administration ameliorates oxidative stress-induced apoptosis in osteoblasts by preserving mitochondrial functions and activation of Akt-GSK3β signaling. These data provide experimental evidence supporting the clinical use of curcumin for prevention or treatment of osteoporosis.
... For the first time, our results showed that RANKL, RANK expression levels were lower in the experimental periodontitis rats submitted to curcumin compared with the vehicle group, which might illuminate that curcumin decreased alveolar bone loss in the experimental periodontitis rats, at least in part, via reduction of the osteoclast regulators' (RANKL/ RANK) expression. It has been reported that curcumin suppresses osteoclastogenesis in bone marrow stromal cells by decreasing RANKL expression [35]. Other studies also demonstrate that drugs inhibiting RANKL expression reduce the inflammation and alveolar bone loss in a P. gingivalis-induced periodontitis mice model [36] and a ligature-induced periodontitis rat model [29]. ...
Article
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Objective: Curcumin, an active ingredient of turmeric, is proved to be a potential candidate of controlling inflammation and bone resorption, but few reports are on the periodontitis. The purpose of this study was to evaluate whether the intra-gastric administration of curcumin could inhibit the inflammation and alveolar bone resorption in rats following ligature-induced experimental periodontitis. Materials and method: Male Wistar rats were randomly divided into three groups: no ligature placement and administration of vehicle, ligature placement and administration of vehicle, ligature placement and administration of curcumin. After the animals were sacrificed, their mandibles were collected for morphological, histological and immunohistochemical analysis; their gingival tissues were collected for cytokine measurements. Results: Bone resorption was significantly higher in the experimental periodontitis animals treated with vehicle compared with the curcumin-treated group or the control group. Furthermore, receptor activator of nuclear factor-κB ligand (RANKL), receptor activator of nuclear factor-κB (RANK), osteoprotegerin (OPG), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) expression levels were higher in the experimental periodontitis animals treated with vehicle compared with the curcumin treated group or the control group. CONCLUSIONS. Curcumin may decrease alveolar bone loss in the experimental periodontitis rats via suppressing the expression of RANKL/RANK/OPG and its anti-inflammatory properties.
... Curcumin is a component of Curcuma longa, and its rhizome has long been used as a food, spice, colorant, and herbal medicine. Curcumin has anti-inflammatory, 1,2) free radical scavenger-mediated antioxidant, 3,4) anticancer, 5,6) anti-allergy, 7,8) anti-arthritis, 9,10) anti-diabetes, 11) hepatoprotective, 12) neuroprotective, 13) antidepressant, 14) and muscle damage protective 15) physiological effects. With regard to chronic inflammation that is particularly associated with lifestyle-related diseases, many recent studies have investigated the inhibitory effects of curcumin on activated nuclear factor-kappaB (NF-κB), 16,17) and signal transducer and activator of transcription 3 (STAT3). ...
Article
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Curcumin, a polyphenol derived from the rhizome of the naturally occurring plant Curcuma longa, has various pharmacological actions such as antioxidant and anti-inflammatory effects. In this paper, we evaluated the role of its internal metabolite, curcumin β-D-glucuronide (curcumin monoglucuronide, CMG), by investigating curcumin kinetics and metabolism in the blood. Firstly, we orally administered highly bioavailable curcumin to rats to elucidate its kinetics, and observed not only the free-form of curcumin, but also, curcumin in a conjugated form, within the portal vein. We confirmed that curcumin is conjugated when it passes through the intestinal wall. CMG, one of the metabolites, was then orally administered to rats. Despite its high aqueous solubility compared to free-form curcumin, it was not well absorbed. In addition, CMG was injected intravenously into rats in order to assess its metabolic behavior in the blood. Interestingly, high levels of free-form curcumin, thought to be sufficiently high to be pharmacologically active, were observed. The in vivo antitumor effects of CMG following intravenous injection were then evaluated in tumor-bearing mice with the HCT116 human colon cancer cell line. The tumor volume within the CMG group was significantly less than that of the control group. Moreover, there was no significant loss of body weight in the CMG group compared to the control group. These results suggest that CMG could be used as an anticancer agent without the serious side effects that most anticancer agents have.
... Examples are given by polyphenols such as HCA, which exert inhibitory effects on osteoclastic cells formation induced by various osteoclastogenic factors Yamaguchi 2006b, 2007), by functioning as natural NF-jB antagonists, since they block the binding of RANKL to its receptor RANK and thus relieving the inhibitory action of TNF-a on the proanabolic SMAD pathway (Yamaguchi and Weitzmann 2009b;Yamaguchi 2012) (Fig. 6). Inhibition of RANKL has also been shown by treatment of human osteosarcoma cells (Lin et al. 2014) with Punica granatum fruit extract and in primary BMSCs (Oh et al. 2008) and osteoclast precursors (Huh et al. 2013) with curcumin and galangin (a flavonol found in Alpinia officinarum), thus inhibiting osteoclast formation. In an in vivo study involving women in postmenopause, intake of genistein downregulated RANKL expression and secretion, thus decreased RANKL/OPG ratio (Marini et al. 2008). ...
Article
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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.
... Another reason was that the expression of inflammatory factors such as interleukin-1α (IL-1α) and prostaglandin E2 (PGE2) was decreased by marsupialization could inhibit osteoclastogenesis in BMSCs (19). It has been showed that IL-1α and PGE2 evoked an increase in receptor activator of nuclear factor-κB ligand (RANKL) mRNA, and a decrease in osteoprotegerin (OPG) mRNA in BMSCs (20,21). All these factors may enhance the differentiated function of osteoblasts and bone formation. ...
Article
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Decompression has been considered a valuable tool for odontogenic cystic lesions to minimize cyst size with low morbidity and recurrence. However, whether decompression has a role in regulating stem cell properties of orofacial bone marrow stromal cells (BMSCs) around the cysts has not been fully investigated. The present study compared the stem cell marker profile and osteogenic differentiation potential of orofacial BMSCs prior to and following marsupialization (pre‑BMSCs vs. post‑BMSCs) in the same individuals. The results demonstrated that post‑BMSCs proliferated significantly faster, displayed higher colony‑forming unit‑fibroblast capacity and demonstrated higher expression of octamer binding protein 4, Nanog and SRY‑related HMG box 2 when compared with the pre‑BMSCs. Notably, the osteogenic potential was greater in the post‑BMSCs compared with in pre‑BMSCs, by demonstrating that the protein and mRNA expression levels of osteopontin, runt‑related transcription factor 2, osteocalcin, alkaline phosphatase and osterix were upregulated in pre‑BMSCs. Furthermore, the phosphorylated levels of extracellular signal‑regulated kinase and c‑Jun N‑terminal kinase were enhanced in post‑BMSCs. In conclusion, the study indicated that decompression influences the stem cell properties of orofacial BMSCs, and further studies are needed to verify the findings.
... This probably be due to bone anabolic or anti catabolic activity of these products. An in vitro studies [30], [31], [32] showed that Curcumin could stop osteoclastogenesis through suppression of RANKL activity completely, another in vivo studies [33], [34], [35], [36], [37] showed that using Curcumin could limit bone loss, improve remodeling and improve bone strength in osteoporosis animal models. For Cissus Quadrangularis an in vitro studies [38], [39], [40] showed its ability in promoting osteoblast proliferation and differentiation and as a potent antiosteoporotic substance in osteoporotic animal model [41], [42], [43]. ...
... As the principle active compound of Curcuma longa, it has been shown to interact with a wide variety of proteins, modifying their expression and regulating their functions. However, some inconsistent results have also been appeared about curcumin's beneficial effect [13,23]. Recently, the effect of curcumin on intracellular reactive oxy-gen species (ROS) formation and its potential roles have been widely investigated. ...
Article
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Scavenging of intracellular reactive oxygen species (ROS) is one of the potential mechanisms contributing to the protective effects of many antioxidants. Curcumin, a natural product, is an effective ROS scavenger. However, the role of its ROS scavenging ability in its cytoprotective action remains to be clarified. Herein, the protective effects of curcumin on hydrogen peroxide (H₂O₂)- and tert-butyl hydroperoxide-induced ROS formation and HepG2 cell injury were determined. HepG2 cells were pretreated with curcumin for 30 min and then treated with H₂O₂ (500 μM) or tert-butyl hydroperoxide (200 μM) for 24 h. Curcumin pretreatment dramatically decreased H₂O₂- and tert-butyl hydroperoxide-induced ROS production, but failed to suppress cytotoxicity of those compounds. H₂O₂ induced decreases in mitochondrial membrane potential (ΔΨm) and increases in DNA fragmentation could not be reversed by curcumin. Furthermore, curcumin enhanced expression of H₂O₂-induced pro-apoptotic protein Bax expression and inhibited expression of anti-apoptotic proteins Bcl-2 and Bcl-xL. In addition, curcumin significantly decreased p38MAPK and phospho-CDC-2 protein expression and increased phospho-p38MAPK, p42/44MAPK, and phospho-p42/44MAPK protein expression. These results suggest that short pretreatment and subsequent longer co-treatment of low concentrations of curcumin showed no obvious protective effect on H₂O₂-induced HepG₂ cell injury.
... Oral administration of curcumin inhibits osteoclast induced bone matrix degradation in insulin-dependent diabetic rat model [19]. It also prevented osteoclastogenesis by inhibiting NF-kb in RAW 264.7 cells [20]. Another study showed 50% decreased proliferation of MG-63 osteosarcoma cells but 80% increased viability of healthy osteoblast cells after treating with 10 mm curcumin [21]. ...
... It has been well-documented that curcumin can improve multiple aspects of bone health in subjects with osteoporosis through affecting mechanisms involved in the activation and differentiation of osteoclasts. These mechanisms include the inhibition of NF-κB, RANKL, NO production, ROS generation, and inflammatory cytokine synthesis [102][103][104][105][106][107][108][109]. By affecting these mechanisms, curcumin decreases the number of osteoclasts as well as their differentiation and activation, leading to shifting the balance between osteoblast and osteoclast activity in favor of osteoblasts. ...
Article
Curcumin is the principal polyphenolic compound present in turmeric with broad applications in tissue engineering and regenerative medicine. It has some important inherent properties with the potential to facilitate tissue healing, including anti‐inflammatory, anti‐oxidant, and antibacterial activities. Therefore, curcumin has been used for the treatment of various damaged tissues, especially wound injuries. There are different forms of curcumin, among which nano‐formulations are of a great importance in regenerative medicine. It is also important to design sophisticated delivery systems for controlled/localized delivery of curcumin to the target tissues and organs. Although there are many reports on the advantages of this compound, further research is required to fully explore its clinical usage. The review describes the physicochemical and biological properties of curcumin and the current state of the evidence on its applications in tissue engineering.
... However, TBP1901 suppressed SB plate thinning in 2 weeks. Some reports have shown that curcumin attenuates bone resorption by suppressing osteoclast proliferation [71] and osteoblast apoptosis [72]. This may be one of the reasons why the SB plate thinning was suppressed by TBP1901. ...
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Background: Curcumin has anti-inflammatory effects. However, curcumin is poorly water-soluble, and when administered orally, formscurcumin conjugates with poor efficacy.Curcumin monoglucuronide (TBP1901) is highly water-soluble and can existinthe free-form in a greater proportion than curcumin in vivo. This study aimed to evaluate the effectiveness of intra-articular TBP1901 injections fora rat model of osteoarthritis (OA). Methods: Sixty-four male Wistar rats (12weeks old) that had receivedthe destabilized medial meniscus(DMM) surgery, were randomly separatedinto the TBP1901 injectionandthe saline solution injection (control) group. They were sacrificedat 1, 2, 6, or 10weeks postoperatively(n = 8 for each). The TBP1901 (30mg/mL) andsaline solutionof 50μLwere administered to the knee joint through the patella tendon twice a week for the rats sacrificedat1 and 2weeks or once a week for at6 and 10weeks. The OA changes were evaluated by micro-computed tomography (micro-CT), histology, and immunohistochemical analysis. Results:Curcumin fluorescence was confirmed in the articular cartilageand synovium of rats with TBP1901 injections at all observation periods.The TBP1901injections significantly reducedthe synovial inflammation at 1 and 2 weeks and the expression of TNFα in thetibialarticular cartilage at 6 weeks postoperatively.Moreover, TBP1901 injections ameliorated the articular cartilage structure, the subchondral bone (SB) plate thickness, and perforations from 6 to 10 weeks.As a result, there were significant differencesbetween groups in OA scores, SB plate thickness, and perforations at 10 weeks postoperatively.In addition, osteophyte formation in the TBP1901group was significantly suppressed after 10 weeks. Conclusion: This study reports the first evidence that TBP1901 injections suppress inflammation and osteophyte formation, and ameliorate the articular cartilage and SB pathologies by absorption in the articular cartilage and synovium in a rat DMM model.Therefore, intra-articular injections of TBP1901may be effective in improving OA pathology.
... For instance, curcumin inhibited Toll-like receptor 4 (TLR4)-mediated signaling pathway and consequently suppressed macrophage polarizing towards M1, reducing the risk of chronic inflammation induced fibrotic encapsulation [24,29,31]. Moreover, curcumin alleviated the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast resorption [33,34] and enhanced osteo-differentiation of stem cells through activating phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor erythroid 2-related factor (Nrf2) signaling pathway [35]. Unfortunately, due to the low solubility and weak chemical stability [31], curcumin should to be loaded in drug-delivery system to keep long term release. ...
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To enhance corrosion resistance and osseointegration of Mg-based endosseous implants, novel coatings with self-healing and osteoimmunomodulation functions were fabricated on Mg. The coatings exhibited similar three-layered structure, comprising an inner layer of MgO, an interlayer of poly-L-lactide containing curcumin loaded F-encapsulated mesoporous silica nanocontainers (cFMSNs) and an outer layer of dicalcium phosphate dehydrate, while the amounts of cFMSNs contained in the interlayers were different (thus namely 5FMSN, 10FMSN, 20FMSN). Localized-electrochemical impedance spectroscopy, electrochemical and immersion tests were used to investigate self-healing property and corrosion resistance of the coatings, moreover, curcumin release, immunomodulation effects and osseointegration of these coatings were also assayed, together with cFMSNs-free coating (0FMSN). Due to the cFMSNs functioning as corrosion inhibitor, cFMSNs-contained coatings exhibited obvious self-healing property to enhance protection to Mg in vitro and in vivo compared to 0FMSN, and the enhancements were more pronounced with cFMSNs increase. cFMSNs-contained coatings sustainably released curcumin, and the accumulative curcumin concentration of the 20FMSN immersed physiological saline (PS) was 1.51 μM after 10 days of immersion, which was higher than those of the PS immersing 10FMSN (1.02 μM) and 5FMSN (0.31 μM). Owing to the released curcumin, cFMSNs-contained coatings significantly modulated the immune microenvironment towards favoring osteo-differentiation and extracellular matrix mineralization of bone marrow stem cells, consequently exhibited better osseointegration compared to 0FMSN. 20FMSN exhibited higher immunomodulatory efficiency compared to 10FMSN and 5FMSN, and thus achieved the best osseointegration in vivo. Our work paves an alternative way to design coatings on Mg for realizing improved clinical performance.
... We speculate that this lack of effect on bone resorption may be related with a time-delay to reach levels high enough for the biological effects of curcumin, since bone loss in the ligature model has been recently shown to occur already three days after placement of ligatures and stabilizes after the initial 11 days (56). These results are in contradiction with in vitro studies demonstrating that curcumin inhibits RANKL-induced osteoclastogenesis (57,58) and in striking contrast with the inhibition of bone resorption assessed in the distal femur in rats with experimentally-induced type 1 diabetes (59). We could not compare the dose of curcumin in this study, since the authors added curcumin directly to the rat chow and even though there is no objective quantification of the dose of curcumin, it was estimated in 120 mg/day (59), which is almost three times higher than our 100 mg/Kg/day (or approximately 45 mg/day in a 450 g rat). ...
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... The mechanism(s) by which curcumin slows down the disease activity in plasma cell dyscrasias is unclear. Previous studies have identified down-regulation of interleukin-6 (a growth factor for myeloma and also an inflammatory cytokine) and suppression of receptor activator of nuclear factor kappa-B ligand (RANKL) signaling as two possibilities [2][3][4]8] . In their recent review [9] , Vermorken et al have attributed the beneficial effect of curcumin to its potential anti-inflammatory action. ...
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Bone loss or osteoporosis, is a slow-progressing disease that results from dysregulation of pro-inflammatory cytokines. The FDA has approved number of drugs for bone loss prevention, nonetheless all are expensive and have multiple side effects. The nutraceuticals identified from dietary agents such as butein, cardamonin, coronarin D curcumin, diosgenin, embelin, gambogic acid, genistein, plumbagin, quercetin, reseveratrol, zerumbone and more, can modulate cell signaling pathways and reverse/slow down osteoporosis. Most of these nutraceuticals are inexpensive; show no side effect while still possessing anti-inflammatory properties. This review deals with various mechanisms of osteoporosis and how nutraceuticals can potentially prevent the bone loss.
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Objective Curcumin monoglucuronide (TBP1901) is highly water soluble and can convert to free form curcumin, which has pharmacological effects, on intravenous administration. This study aimed to investigate the effectiveness of TBP1901 intra-articular injections in an osteoarthritis (OA) rat model. Methods Sixty-four male Wistar rats (12 weeks old) who underwent destabilized medial meniscus (DMM) surgery were randomly separated into the TBP1901 injection or saline solution (control) injection group. They were sacrificed at 1, 2, 6, or 10 weeks postoperatively (weeks 1, 2, 6, and 10; n = 8 for each group). TBP1901 (30 mg/mL) or saline solution of 50 μL was injected into the knee joints twice a week during weeks 1 and 2 to investigate the effects in the acute phase of posttraumatic (PT) OA or once a week during weeks 6 and 10 to investigate it in the chronic phase of PTOA. Histology, immunohistochemistry, and micro-computed tomography were performed to evaluate the changes in OA. Results TBP1901 injections significantly reduced synovial inflammation at weeks 1 and 2, and tumor necrosis factor-α expression in the articular cartilage at week 6. The TBP1901 injections also significantly suppressed articular cartilage damage, subchondral bone (SB) plate thickening, SB plate perforation, and osteophyte formation at week 10. Conclusions TBP1901 intra-articular injections suppressed synovial inflammation in the acute phase of PTOA in DMM rats. In the chronic phase, TBP1901 suppresses articular cartilage damage and regulates SB plate changes.
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Osteoclasts, the multinucleated cells that resorb bone, develop from hematopoietic cells of monocyte/macrophage lineage. Osteoclast-like cells (OCLs) are formed by coculturing spleen cells with osteoblasts or bone marrow stromal cells in the presence of bone-resorbing factors. The cell-to-cell interaction between osteoblasts/stromal cells and osteoclast progenitors is essential for OCL formation. Recently, we purified and molecularly cloned osteoclastogenesis-inhibitory factor (OCIF), which was identical to osteoprotegerin (OPG). OPG/OCIF is a secreted member of the tumor necrosis factor receptor family and inhibits osteoclastogenesis by interrupting the cell-to-cell interaction. Here we report the expression cloning of a ligand for OPG/OCIF from a complementary DNA library of mouse stromal cells. The protein was found to be a member of the membrane-associated tumor necrosis factor ligand family and induced OCL formation from osteoclast progenitors. A genetically engineered soluble form containing the extracellular domain of the protein induced OCL formation from spleen cells in the absence of osteoblasts/stromal cells. OPG/OCIF abolished the OCL formation induced by the protein. Expression of its gene in osteoblasts/stromal cells was up-regulated by bone-resorbing factors. We conclude that the membrane-bound protein is osteoclast differentiation factor (ODF), a long-sought ligand mediating an essential signal to osteoclast progenitors for their differentiation into osteoclasts. ODF was found to be identical to TRANCE/RANKL, which enhances T-cell growth and dendritic-cell function. ODF seems to be an important regulator in not only osteoclastogenesis but also immune system.
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Tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE), a member of the TNF family expressed on activated T-cells, bone marrow stromal cells, and osteoblasts, regulates the function of dendritic cells (DC) and osteoclasts. The TRANCE receptor (TRANCE-R), recently identified as receptor activator of NF-kappabeta (RANK), activates NF-kappaB, a transcription factor critical in the differentiation and activation of those cells. In this report we identify the TNF receptor-associated factor (TRAF) family of signal transducers as important components of TRANCE-R-mediated NF-kappaB activation. Coimmunoprecipitation experiments suggested potential interactions between the cytoplasmic tail of TRANCE-R with TRAF1, TRAF2, TRAF3, TRAF5, and TRAF6. Dominant negative forms of TRAF2, TRAF5, and TRAF6 and an endogenous inhibitor of TRAF2, TRAF-interacting protein (TRIP), substantially inhibited TRANCE-R-mediated NF-kappaB activation, suggesting a role of TRAFs in regulating DC and osteoclast function. Overexpression of combinations of TRAF dominant negative proteins revealed competition between TRAF proteins for the TRANCE-R and the possibility of a TRAF-independent NF-kappaB pathway. Analysis of TRANCE-R deletion mutants suggested that the TRAF2 and TRAF5 interaction sites were restricted to the C-terminal 93 amino acids (C-region). TRAF6 also complexed to the C-region in addition to several regions N-terminal to the TRAF2 and TRAF5 association sites. Furthermore, transfection experiments with TRANCE-R deletion mutants revealed that multiple regions of the TRANCE-R can mediate NF-kappaB activation.
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The tumour-necrosis-factor-family molecule osteoprotegerin ligand (OPGL; also known as TRANCE, RANKL and ODF) has been identified as a potential osteoclast differentiation factor and regulator of interactions between T cells and dendritic cells in vitro. Mice with a disrupted opgl gene show severe osteopetrosis and a defect in tooth eruption, and completely lack osteoclasts as a result of an inability of osteoblasts to support osteoclastogenesis. Although dendritic cells appear normal, opgl-deficient mice exhibit defects in early differentiation of T and B lymphocytes. Surprisingly, opgl-deficient mice lack all lymph nodes but have normal splenic structure and Peyer's patches. Thus OPGL is a new regulator of lymph-node organogenesis and lymphocyte development and is an essential osteoclast differentiation factor in vivo.
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and acts as a decoy receptor in the RANK-RANKL signaling system (Fig. 8). In conclusion, osteoblasts/stromal cells are involved in all of the processes of osteoclast development, such as differentiation, survival, fusion, and activation of osteoclasts (Fig. 8). Osteoblasts/stromal cells can now be replaced with RANKL and M-CSF in dealing with the whole life of osteoclasts. RANKL, RANK, and OPG are three key molecules that regulate osteoclast recruitment and function. Further studies on these key molecules will elucidate the molecular mechanism of the regulation of osteoclastic bone resorption. This line of studies will establish new ways to treat several metabolic bone diseases caused by abnormal osteoclast recruitment and functions such as osteopetrosis, osteoporosis, metastatic bone disease, Paget's disease, rheumatoid arthritis, and periodontal bone disease.
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Studies in rodents have implicated various cytokines as paracrine mediators of increased osteoclastogenesis during estrogen deficiency, but increases in RANKL, the final effector of osteoclastogenesis, have not been demonstrated. Thus, we isolated bone marrow mononuclear cells expressing RANKL on their surfaces by two-color flow cytometry using FITC-conjugated osteoprotegerin-Fc (OPG-Fc-FITC) as a probe. The cells were characterized as preosteoblastic marrow stromal cells (MSCs), T lymphocytes, or B lymphocytes by using Ab's against bone alkaline phosphatase (BAP), CD3, and CD20, respectively, in 12 premenopausal women (Group A), 12 early postmenopausal women (Group B), and 12 age-matched, estrogen-treated postmenopausal women (Group C). Fluorescence intensity of OPG-Fc-FITC, an index of the surface concentration of RANKL per cell, was increased in Group B over Groups A and C by two- to threefold for MSCs, T cells, B cells, and total RANKL-expressing cells. Moreover, in the merged groups, RANKL expression per cell correlated directly with the bone resorption markers, serum C-terminal telopeptide of type I collagen and urine N-telopeptide of type I collagen, in all three cell types and inversely with serum 17beta-estradiol for total RANKL-expressing cells. The data suggest that upregulation of RANKL on bone marrow cells is an important determinant of increased bone resorption induced by estrogen deficiency.
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The recently cloned osteoclastogenesis inhibitory factor, or osteoprotegerin (OPG), has been shown to be a potent inhibitor of osteoclast formation. The inhibition is believed to be mediated through specific binding of OPG to a cell surface ligand on osteoblastic stromal cells. In this report we have studied the effect of the bone resorbing agent prostaglandin E2 (PGE2) on OPG mRNA levels in primary cultures of human bone marrow stroma cells (hBMSC). PGE2 dose- and time-dependently down-regulated the mRNA levels of OPG, as measured by RNAse protection assay. After 4 hours of stimulation with 1 microM PGE2, OPG mRNA levels were significantly decreased. The inhibitory effect was seen at and above 1 nM of PGE2. To elucidate whether the OPG mRNA levels are regulated via the proteinkinase A and/or the proteinkinase C pathways we stimulated cells with either forskolin (FSK) or phorbolic ester (PDbu) respectively. FSK (10 microM) decreased OPG mRNA levels to 50 % of control, whereas PE (10 nM) upregulated the mRNA levels to 250 % of control. These data show that PGE2 down-regulates the expression of OPG mRNA in hBMSC, probably via an increase in cAMP. This mechanism might be involved in PGE2-induced bone resorption.
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We studied the effects of PTH on the expression of tumor necrosis factor-related activation-induced cytokine (TRANCE), osteoprotegerin (OPG), and receptor activator of NF kappaB (RANK) messenger RNA (mRNA) in cultured murine bone marrow, calvaria, and osteoblasts. TRANCE, OPG, and RANK are recently identified regulators of osteoclast formation. Bone marrow cells were cultured with or without PTH(1-34) for 6 days. TRANCE, OPG, and RANK mRNA were measured by RT-PCR. In 6-day cultures, PTH stimulated the number of OCL/well in a dose-dependent manner. A time course showed significant (P < 0.01) increases in OCL/well after 24 h of PTH (100 ng/ml). TRANCE mRNA expression, like OCL formation, increased dose dependently and was maximal, with 10-100 ng/ml PTH. In contrast, OPG mRNA expression was decreased by 0.1 ng/ml PTH (40%) and completely abolished by 1 ng/ml. TRANCE mRNA expression was rapidly stimulated by PTH (maximal response at 1 h, 8.1-fold over control). Expression declined by 40% at 24 h but was still much greater than control at 6 days (4.6-fold) in a time-course study. PTH caused a transient stimulation of OPG mRNA at 1 h (2-fold), which returned to basal levels by 2 h. After 6 h, PTH completely inhibited OPG mRNA. There were only minor effects of PTH on RANK mRNA expression. PTH had less potent effects on TRANCE and OPG mRNA expression in calvaria organ cultures and osteoblasts. In mouse calvaria cultures, TRANCE expression was detectable in controls and was increased 2.9-fold by PTH at 24 h. PTH treatment of calvaria decreased OPG expression by 30% at 6 h. MC3T3 E-1 osteoblastic cells expressed minimal levels of TRANCE mRNA either before or after PTH treatment. OPG mRNA was present in MC3T3 E-1 cells, but levels were not modulated by PTH. In primary osteoblastic cells, PTH stimulated TRANCE mRNA expression 4-fold at 2 h and inhibited OPG mRNA expression by 46%. These results demonstrate a tight correlation between the ability of PTH to stimulate OCL formation in marrow culture and expression of TRANCE (r = 0.87, P < or = 0.05) and OPG mRNA (r = -0.88, P < or = 0.05). Reciprocal regulation of TRANCE and OPG mRNA by PTH preceded its effects on OCL formation by 18-23 h. Hence, it is likely that PTH regulates bone resorption, at least in part, via its effects on TRANCE and OPG expression.
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Curcumin is a potent inhibitor of the transcriptional factors activator protein-1 and nuclear factor-kappaB. Since transcriptional factors may play a functional role in the survival of osteoclasts, it was of interest to us to examine the effect of curcumin on osteoclast apoptosis. We observed that curcumin is a potent stimulator of this process in rabbit osteoclasts, as evidenced by morphological changes in nuclei and DNA fragmentation as criteria of apoptosis. The curcumin stimulation of the osteoclast apoptosis was dose-and treatment time-dependent. In addition, curcumin dramatically inhibited osteoclastic bone resorption, supporting our data that curcumin is a potent stimulator of osteoclast apoptosis.
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Oxidative stress may regulate cellular function in multiple pathological conditions, including atherosclerosis. One feature of the atherosclerotic plaque is calcium mineral deposition, which appears to result from the differentiation of vascular osteoblastic cells, calcifying vascular cells (CVC). To determine the role of oxidative stress in regulating the activity of CVC, we treated these cells with hydrogen peroxide (H(2)O(2)) or xanthine/xanthine oxidase (XXO) and assessed their effects on intracellular oxidative stress, differentiation, and mineralization. These agents increased intracellular oxidative stress as determined by 2,7 dichlorofluorescein fluorescence, and enhanced osteoblastic differentiation of vascular cells, based on alkaline phosphatase activity and mineralization. In contrast, H(2)O(2) and XXO resulted in inhibition of differentiation markers in bone osteoblastic cells, MC3T3-E1, and marrow stromal cells, M2-10B4, while increasing oxidative stress. In addition, minimally oxidized low-density lipoprotein (MM-LDL), previously shown to enhance vascular cell and inhibit bone cell differentiation, also increased intracellular oxidative stress in the three cell types. These effects of XXO and MM-LDL were counteracted by the antioxidants Trolox and pyrrolidinedithiocarbamate. These results suggest that oxidative stress modulates differentiation of vascular and bone cells oppositely, which may explain the parallel buildup and loss of calcification, seen in vascular calcification and osteoporosis, respectively.
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Enhanced osteoclastogenesis was observed in bone marrow-derived macrophage cells from 4-1BB-deficient mice than in those from wildtype mice. 4-1BB and 4-1BB ligand interaction may play a role at a certain stage of osteoclast formation through increased level of IL-10, a negative regulator of osteoclastogenesis. 4-1BB is an inducible T-cell costimulatory molecule and a member of the TNF receptor family. The expression pattern of 4-1BB and 4-1BB ligand (4-1BBL) has suggested that 4-1BB plays a role not only in various responses related to innate immunity but also in bone metabolism. Osteoclast formation was evaluated in bone marrow-derived macrophage cells (BMMs) from wildtype and 4-1BB-deficient (4-1BB-/-) mice. Expression of interleukin-10 (IL-10) during osteoclast formation was analyzed at the mRNA and protein levels. Expression of IL-10 was higher in RANKL-stimulated wildtype BMMs than 4-1BB-/- BMMs. When 4-1BBL was stimulated with 4-1BB-Fc fusion protein, the expression of IL-10 in BMMs increased. Neutralization of IL-10 was not as effective in preventing inhibition by IL-10 of osteoclast differentiation in 4-1BB-/- BMMs as in wildtype BMMs. When IL-10 was added to the culture medium, osteoclast formation was inhibited more efficiently in the 4-1BB-/- BMMs than in the wildtype BMMs. Interaction of 4-1BB and 4-1BBL stimulates IL-10 production through 4-1BBL signaling. 4-1BBL plays a role at a certain stage of osteoclast formation, and IL-10 may mediate this effect. The elevated level of osteoclastogenesis in 4-1BB-/- BMMs may thus be caused, in part, by a lower level of IL-10.
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Based on animal models, dietary polyphenols are predicted to be promising chemopreventive agents in humans. Allspice, clove, and thyme extracts as well as defined dietary polyphenolic compounds were, therefore, tested for their ability to activate mechanisms related to phase 1 enzymes, i.e., the PXR-regulated CYP3A4 promoter, and phase 2 enzymes, i.e. the EpRE-regulated promoters of gastrointestinal glutathione peroxidase (GI-GPx) and heme oxygenase-1 (HO-1), examples of Nrf2-regulated genes. From the compounds tested, clove and thyme extracts as well as curcumin and resveratrol activated the PXR. PXR activation correlated with the activation of the CYP3A4 promoter in the case of thyme extract, curcumin, and resveratrol, but not in the case of clove extract. Allspice extract, EGCG, and quercetin did not activate PXR but enhanced CYP3A4 promoter activity. Thyme extract and quercetin activated the EpRE of HO-1. Both significantly activated the GI-GPx promoter, effects that depended on a functional EpRE. Resveratrol did not activate the isolated EpRE but enhanced the GI-GPx promoter activity, whereas clove extract even inhibited it. It is concluded that individual polyphenols as well as polyphenol-rich plant extracts may affect phase 1 and 2 enzyme expression by distinct mechanisms that must be elucidated, before potential health effects can reliably be predicted.
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Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive-oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase, and inducible nitric oxide synthase (iNOS); it is an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C (PKC), EGF-receptor tyrosine kinase, and IkappaB kinase. Subsequently, curcumin inhibits the activation of NF-KB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs, and iNOS. It is considered that PKC, mTOR, and EGFR tyrosine kinase are the major upstream molecular targest for curcumin intervention, whereas the nuclear oncogenes such as c-jun, c-fos, c-myc, CDKs, FAS, and iNOS might act as downstream molecular targets for curcumin actions. It is proposed that curcumin might suppress tumor promotion through blocking signal transduction pathways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, whereas the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins play a pivotal role in the regulation of several basic cellular processes, including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of the ubiquitin-proteasome pathway.
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Halogenated and polycyclic aromatic hydrocarbons induce diverse biochemical responses through the transformation of a cytosolic aryl hydrocarbon receptor (AhR). In mouse hepatoma Hepa-1c1c7 cells, curcumin, a yellow pigment of Curcuma longa, did not inhibit the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced translocation of the AhR into the nucleus, but rather accelerated it. In the nucleus, curcumin inhibited the TCDD-induced heterodimerization of the AhR with an AhR nuclear translocator (Arnt), an essential partner for the transformation, and also dose-dependently inhibited the TCDD-evoked phosphorylation of both the AhR and Arnt. Moreover, curcumin significantly inhibited the TCDD-induced activation of protein kinase C (PKC), which is involved in the transformation, decreased the TCDD-induced DNA-binding activity of the AhR/Arnt heterodimer, and downregulated CYP1A1 expression. In a cell-free system, curcumin inhibited the binding of 3-methylcholanthrene, an AhR agonist, to the receptor. These results indicate that curcumin is able to bind to the AhR as a ligand, but suppresses its transformation by inhibiting the phosphorylation of AhR and Arnt, probably by PKC.
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Several lines of evidence indicate that the oxidative modification of protein and the subsequent accumulation of the modified proteins have been found in cells during aging, oxidative stress, and in various pathological states including premature diseases, muscular dystrophy, rheumatoid arthritis, and atherosclerosis. The important agents that give rise to the modification of a protein may be represented by reactive aldehydic intermediates, such as ketoaldehydes, 2-alkenals and 4-hydroxy-2-alkenals. These reactive aldehydes are considered important mediators of cell damage due to their ability to covalently modify biomolecules, which can disrupt important cellular functions and can cause mutations. Furthermore, the adduction of aldehydes to apolipoprotein B in low-density lipoproteins (LDL) has been strongly implicated in the mechanism by which LDL is converted to an atherogenic form that is taken up by macrophages, leading to the formation of foam cells. During the search for an endogenous inducer of cyclooxygenase-2 (COX-2), an inducible isoform responsible for high levels of prostaglandin production during inflammation and immune responses, 4-hydroxy-2-noennal (HNE), one of the most representative lipid peroxidation product, has been identified as the potential inducer of COX-2. In addition, the following study on the molecular mechanism of the COX-2 induction by HNE has unequivocally established that a serum component, which is eventually identified to be denatured LDL, is essential for COX-2 induction. Here I review current understanding of the mechanisms by which HNE in cooperation with the serum component activates gene expression of COX-2.