Study on the Effects of Curculigoside on Proliferation, Differentiation, and Calcification of Mouse Osteoblastic MC3T3-E1 Cells

Curculigoside Protects against Excess-Iron-Induced Bone Loss by Attenuating Akt-FoxO1-Dependent Oxidative Damage to Mice and Osteoblastic MC3T3-E1 Cells

Summary

The present investigation found that curculigoside (CUR) can prevent excess-iron-induced bone loss in mice and cells through antioxidation and inhibiting excess-iron-induced phosphorylation of the Akt-FoxO1 pathway. CUR can attenuate the decreasing of cell viability, enhance autophagy, potentiate the antioxidant effect, and reduce apoptosis in MC3T3-E1 cells treated with excess iron through regulating the expression of FoxO1 target gene.

Introduction

Oxidative stress induced by iron overload is an important factor involved in primary osteoporosis disease and iron overload-related diseases. Curculigoside (CUR), a phenolic glycoside found abundantly in Curculigo orchioides Gaertn., has been demonstrated to possess antioxidant and antiosteoporotic properties. The aim of the present study is to explore the underlying molecular mechanism of CUR on excess-iron-induced bone loss in mice and osteoblastic MC3T3-E1 cells.

Methods

An iron-overload mice model was used to study the protective effects of CUR on bone loss induced by oxidative stress. Serum bone metabolism markers and antioxidant enzymes were also measured. To explore the antioxidant mechanism of CUR, the MC3T3-E1 osteoblastic cell line was used.

Results

In vivo studies showed that BMD and microarchitectural parameters were improved after a 3-month administration of CUR. CUR improved the biochemical parameters related to bone metabolism and the expressions of Runx2, OCN, and type 1 collagen and increased the formation of bone-mineralized nodules in vitro. CUR also inhibited ROS generation and increased the activities of antioxidant enzymes both in vivo and in vitro treated with excess iron. CUR can upregulate the level of FoxO1 and Nrf2, downregulate the level of p53 and the phosphorylation level of FoxO1, improve nuclear translocation of FoxO1, probably by inhibiting the IGFR/AKT signaling pathway, then increased cell viability and autophagy, and reduced apoptosis of MC3T3-E1 cells treated with excess iron by regulating the expression of FoxO1 target genes MnSOD, Gadd45a, Bim, FasL, and Rab7.

Conclusions

These results demonstrated that CUR was able to alleviate bone loss induced by oxidative stress resulting from iron overload, suggesting its potential use for the treatment of primary osteoporosis and bone loss in iron-overload-related diseases.

Strontium‑containing α‑calcium sulfate hemihydrate promotes bone repair via the TGF‑β/Smad signaling pathway

Calcium phosphate-based bone substitutes have been widely used for bone repair, augmentation and reconstruction in bone implant surgery. While some of these substitutes have shown excellent biological efficacy, there remains a need to improve the performance of the current calcium phosphate-based bone substitutes. Strontium ions (Sr) can promote new osteogenesis, inhibit osteoclast formation and increase osteoconductivity. However, the therapeutic effect and mechanism of strontium-containing α-calcium sulfate hemihydrate (Sr-CaS) remains unclear. The present study created bone injuries in rats and treated the injuries with Sr-CaS. Then Cell Counting Kit-8, soft agar colony formation, flow cytometry, Transwell and Alizarin Red staining assays were performed to assess the bone cells for their proliferation, growth, apoptosis, invasion, and osteogenic differentiation abilities. The bone reconstructive states were measured by the microCT method, hematoxylin and eosin staining and Masson staining. Bone-related factors were analyzed by the reverse transcription-quantitative PCR assay; transforming growth factor (TGF)-β, mothers against decapentaplegic homolog (Smad)2/3 and β-catenin expression was measured by western blot analysis and osteocalcin (OCN) expression was assessed by immunohistochemistry. Sr-CaS did not significantly affect the proliferation and apoptosis of bone marrow stem cells (BMSCs), but did accelerate the migration and osteogenic differentiation of BMSCs in vitro. Sr-CaS promoted bone repair and significantly increased the values for bone mineral density, bone volume fraction, and trabecular thickness, but decreased trabecular spacing in vivo in a concentration-dependent manner. In addition, Sr-CaS dramatically upregulated the expression levels of genes associated with osteogenic differentiation (Runt-related transcription factor 2, Osterix, ALP, OCN and bone sialoprotein) both in vitro and in vivo. Sr-CaS also increased Smad2/3, TGF-β and phosphorylated-β-catenin protein expression in vitro and in vivo. These results indicated that materials that contain 5 or 10% Sr can improve bone defects by regulating the TGF-β/Smad signaling pathway.

Pharmacokinetic and Metabolism Studies of Curculigoside C by UPLC-MS/MS and UPLC-QTOF-MS

Pharmacokinetic and metabolism studies were carried out on curculigoside C (CC), a natural product with good antioxidant and neuroprotective effects, with the purpose of investigating the effects of the hydroxyl group at C-3' in curculigoside. A rapid and sensitive method with UPLC-MS was developed and fully validated for the first time in the pharmacokinetic analysis for quantification of CC in rat plasma. The assay was linear (R² > 0.9984) over the concentration range of 1⁻2500 ng/mL, with the lower limit of quantification (LLOQ) being 1 ng/mL. The intra-day and inter-day precision (expressed as relative standard deviation, RSD) ranged from 4.10% to 5.51% and 5.24% to 6.81%, respectively. The accuracy (relative error, RE) ranged from -3.28% to 0.56% and -5.83% to -1.44%, respectively. The recoveries ranged from 92.14% to 95.22%. This method was then applied to a pharmacokinetic study of rats after intragastric administration of 15, 30 and 60 mg/kg CC. The results revealed that CC exhibited rapid oral absorption (Tmax = 0.106 h, 0.111 h, and 0.111 h, respectively), high elimination (t1/2 = 2.022 h, 2.061 h, and 2.048 h, respectively) and low absolute bioavailability (2.01, 2.13, and 2.39%, respectively). Furthermore, an investigation on the metabolism of CC was performed by UPLC-QTOF-MSE. Twelve metabolites of CC from plasma, bile, urine and faeces of rats were confirmed. The main metabolic pathways of CC, which involve dehydration, glucosylation, desaturation, formylation, cysteine conjugation, demethylation and sulfonation, were profiled. In conclusion, this research has developed a sensitive quantitative method and demonstrated the metabolism of CC in vivo.

Curculigoside and polyphenol-rich ethyl acetate fraction of Molineria latifolia rhizome improved glucose uptake via potential mTOR/AKT activated GLUT4 translocation

Adipose tissue is one of the major organs responsible for rapid restoration of postprandial glucose fluxes. Being the major isoform of glucose transporter in adipose tissue, regulations of insulin-dependent GLUT4 trafficking have always been of research interest. The present study aimed to examine the molecular mechanisms underlying the efficacy of curculigoside and polyphenol-rich ethyl acetate fraction (EAF) of Molineria latifolia rhizome in triggering glucose uptake. We assessed the adipogenic potential and glucose uptake stimulatory activity of curculigoside and EAF by employing a murine 3T3-L1 adipocyte model. The transcriptional and translational expressions of selected intermediates in the insulin signalling pathway were evaluated. While curculigoside neither promoted adipogenesis nor activated peroxisome proliferator activated receptor gamma, treatment with polyphenol-rich EAF resulted otherwise. However, both treatments enhanced insulin-stimulated uptake of glucose. This was coupled with increased availability of GLUT4 at the plasma membrane of the differentiated adipocytes although the total GLUT4 protein level was unaffected. In addition, the treatment increased the phosphorylation of both AKT and mTOR, which have been reported to be associated with GLUT4 translocation. The present findings proposed that curculigoside and EAF increased glucose transport activity of 3T3-L1 adipocytes via GLUT4 translocation as a result of potential mTOR/AKT activation. The more potent efficacy observed with EAF suggested potential synergistic and multi-targeted action.

An LC-MS/MS method for determination of curculigoside with anti-osteoporotic activity in rat plasma and application to a pharmacokinetic study

A rapid, simple, selective and sensitive LC-MS/MS method was developed for the determination of curculigoside in rat plasma. The analytical procedure involves extraction of curculigoside and syringin (internal standard, IS) from rat plasma with a one-step extraction method by protein precipitation. The chromatographic resolution was performed on an Agilent XDB-C18 column (4.6 × 50 mm, 5 µm) using an isocratic mobile phase of methanol with 0.1% formic acid and H2 O with 0.1% formic acid (45:55, v/v) at a flow rate of 0.35 mL/min with a total run time of 2.0 min. The assay was achieved under the multiple-reaction monitoring mode using positive electrospray ionization. Method validation was performed according to US Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curve was linear over 4.00-4000 ng/mL (R = 0.9984) for curculigoside with a lower limit of quantification of 4.00 ng/mL in rat plasma. The intra- and inter-day precisions and accuracies were 3.5-4.6 and 0.7-9.1%, in rat plasma, respectively. The validated LC-MS/MS method was successfully applied to a pharmacokinetic study of curculigoside in rats after a single intravenous and oral administration of 3.2 and 32 mg/kg. The absolute bioavailability of curculigoside after oral administration was 1.27%.