Stimulatory effect of undecylenic acid on mouse osteoblast differentiation

Natural compounds with bone-forming (or anabolic) activity have been recently focused on in bone research. The present study investigated the effect of undecylenic acid (UA) on osteoblast differentiation in mouse osteoblastic MC3T3-E1 subclone 4 cells and primary mouse calvarial cells. Low concentrations of UA (up to 5 microM) exhibited no cytotoxicity and significantly increased the expression and activity of alkaline phosphatase (early differentiation marker of osteoblast) and calcium deposition with the induction of expression of the osteocalcin gene in both cells. Interestingly, at low concentration of UA, the induction of NF-kappaB p65 translocation into nucleus and the up-regulation of AP-1 and NFATc1 transcript levels were also observed, suggesting that the stimulatory effect of UA on osteoblast differentiation could be mediated through the activation of transcription factors. Additionally, although the patterns of UA-induced activation of MAP kinases (JNK and p38) were not completely consistent with the increase of both ALP activity and calcium deposition by UA, MAP kinases might be partially involved in the biological function of UA during the early and late stages of osteoblast differentiation.

Machilin A isolated from Myristica fragrans stimulates osteoblast differentiation

This study evaluated the stimulatory effects of machilin A and structurally related lignans isolated from Myristica fragrans on osteoblast differentiation. In two IN VITRO osteoblast differentiation models, machilin A stimulated osteoblast differentiation via activation of p38 MAP kinase. Lignans isolated from Myristica fragrans also stimulated osteoblast differentiation in MC3T3-E1 cells; the lignans included macelignan, machilin F, nectandrin B, safrole, licarin A, licarin B, myristargenol, and meso-dihydroguaiaretic acid. These data suggest that lignans isolated from Myristica fragrans have anabolic activity in bone metabolism.

Anabolic activity of ursolic acid in bone: Stimulating osteoblast differentiation in vitro and inducing new bone formation in vivo

In the field of osteoporosis, there has been growing interest in anabolic agents that enhance bone mass and improve bone architecture. In this study, we demonstrated that the ubiquitous plant triterpenoid, ursolic acid, enhances differentiation and mineralization of osteoblasts in vitro. We found that ursolic acid induced the expression of osteoblast-specific genes with the activation of mitogen-activated protein kinases, nuclear factor-kappaB, and activator protein-1. Additionally, noggin, an antagonist of bone morphogenetic proteins (BMPs), inhibited ursolic acid-induced osteoblast differentiation. Noggin also inhibited the activation of Smad and the induction of BMP-2 mRNA expression by ursolic acid in the late stage of osteoblast differentiation. Importantly, ursolic acid was shown to have bone-forming activity in vivo in a mouse calvarial bone formation model. A high proportion of positive immunostaining of BMP-2 was found in the nuclear region of woven bone formed by ursolic acid. These results suggested that ursolic acid has the anabolic potential to stimulate osteoblast differentiation and enhance new bone formation.

Baicalein stimulates osteoblast differentiation via coordinating activation of MAP kinases and transcription factors

The identification of anabolic agents that directly stimulate bone formation has recently attracted greater interest. Here, baicalein was identified as a natural compound that stimulates the differentiation of mouse osteoblastic MC3T3-E1 subclone 4 cells. Baicalein induced the activation of NF-kappaB in the initiation stage of osteoblast differentiation, and it activated the MAP kinase/NF-kappaB signaling pathway and induced the expression of osteoblast differentiation markers in the early stage. In the late stage, baicalein stimulated the calcium deposition with the activation of MAP kinases and AP-1 family members such as Fra-1 and Fra-2. Another transcription factor, NFATc1, was slightly induced by baicalein in the late stage. Thus, baicalein could stimulate the osteoblast differentiation via the activation of complexly coordinated signaling pathways that include MAP kinases and transcription factors such as NF-kappaB, AP-1, and NFATc1.

Emodin accelerates osteoblast differentiation through phosphatidylinositol 3-kinase activation and bone morphogenetic protein-2 gene expression

Emodin is a naturally occurring anthraquinone present in the roots and bark of numerous plants of the genus Rhamnus. Here, we identified emodin as one of compounds activating the mRNA expression of bone morphogenetic protein (BMP)-2 in the differentiation process of mouse osteoblastic MC3T3-E1 subclone 4 cells. Without any effect on cell growth, the low concentration (up to 5 microM) of emodin highly induced the mRNA expression of BMP-2, the expression of alkaline phosphatase (an early marker of osteoblast differentiation), and the mineralization. Interestingly, emodin induced the activation of phosphatidylinositol 3-kinase (PI3K), Akt and mitogen-activated protein (MAP) kinases, but those inductions by emodin were completely inhibited by the PI3K inhibitor, LY294002, suggesting that the up-regulation of BMP-2 by emodin could be mediated through the activation of both Akt and MAP kinases by activating PI3K. Additionally, emodin-induced activation of NF-kappaB suggested that NF-kappaB might be required for its anabolic activity in part. In conclusion, the use of natural compounds with anabolic activity such as emodin could have a beneficial effect on bone health and this kind of studies further elucidate the pharmacological roles of natural compounds in the prevention of osteoporosis and provide the initiative in the early drug discovery and development for osteoporosis.

Novel small molecule induces p53-dependent apoptosis in human colon cancer cells

Using high-throughput screening with small-molecule libraries, we identified a compound, KCG165 [(2-(3-(2-(pyrrolidin-1-yl)ethoxy)-1,10b-dihydro-[1,2,4]triazolo[1,5-c]quinazolin-5(6H)-one)], which strongly activated p53-mediated transcriptional activity. KCG165-induced phosphorylations of p53 at Ser(6), Ser(15), and Ser(20)(,) which are all key residues involved in the activation and stabilization of p53. Consistent with these findings, KCG165 increased level of p53 protein and led to the accumulation of transcriptionally active p53 in the nucleus with the increased occupancy of p53 in the endogenous promoter region of its downstream target gene, p21(WAF1/CIP). Notably, KCG165-induced p53-dependent apoptosis in cancer cells. Furthermore, we suggested topoisomerase II as the molecular target of KCG165. Together, these results indicate that KCG165 may have potential applications as an antitumor agent.

Low concentration of 3-carene stimulates the differentiation of mouse osteoblastic MC3T3-E1 subclone 4 cells

Recently, natural products have gained more interest as alternative treatments for metabolic bone disorders and for the maintenance of bone health. In this study, the anabolic activities of 89 natural compounds were evaluated by measuring the amount of newly synthesized calcium in the differentiation process of mouse osteoblastic MC3T3-E1 subclone 4 cells. Of these compounds, a low concentration (up to 5 microm) of 3-carene, which is a bicyclic monoterpene in essential oils extracted from pine trees, was shown to stimulate significantly the activity and expression of alkaline phosphatase, an early phase marker of osteoblastic differentiation, on differentiation day 9. On day 15, it dramatically promoted the induction of calcium in a dose-dependent manner. The stimulatory effect of 3-carene on mineralization might be associated with its potential to induce the protein expression/activation of the mitogen-activated protein kinases and the transcript levels of osteoblast mineralization-related genes such as osteopontin and type I collagen. Further studies are needed to determine the precise mechanism, but the anabolic activity of 3-carene in bone metabolism suggested that the use of natural additives to the diet including essential oils could have a beneficial effect on bone health.

Profiling signalling pathways of the receptor activator of NF-kappaB ligand-induced osteoclast formation in mouse monocyte cells, RAW264.7

Cell-based signal chemical genomics can profile the signalling pathway for certain cellular events by using a target-known chemical library. To ascertain its usefulness, the receptor activator of NF-kappaB ligand (RANKL)-induced osteoclastogenesis in mouse monocyte/macrophage cells RAW264.7 was used as an in vitro experimental model. Of 180 target-known inhibitors/activators formatted in a 384-well plate, 8 chemicals were shown to inhibit the osteoclast formation, but 4 chemicals enhanced this process. A variety of references support, or possibly lead one to expect the effects of these 12 chemicals on the cellular process of osteoclastogenesis in RAW264.7 cells, but several signalling pathways were newly found in this study; for example, CA-074 Me inhibiting cathepsin B and nitrendipine blocking the calcium channel could have the potential to inhibit the osteoclast formation as well as bone resorption. This is a simple but very fast and powerful method of profiling the signalling pathway of certain cellular events. Signal chemical genomics could provide invaluable information for the exploration of new target signalling processes and further target-based drug discovery strategies.

Synthesis of novel chemical probes for the study of tanshinone binding proteins

Novel diazirine or biotin-labeled tanshinone probes were synthesized and evaluated for TRAP inhibitory activity against RANKL-induced osteoclastogenesis in RAW264.7 cells. We found that diazirine-labeled derivatives (18 and 20) are potent inhibitors of RANKL-induced osteoclastogenesis. IC50 values were 18.02 and 15.00 microM, respectively. These probes will be useful reagents for investigating tanshinone-proteins interactions.

Protein profiling and transcript expression levels of heat shock proteins in 17beta-estradiol-treated human MCF-7 breast cancer cells

Using proteomics, proteins regulated by 17beta-estradiol (E2) were identified in human MCF-7 breast cancer cells; 26 proteins including heat shock proteins (Hsps) were differentially regulated by E2 in cells cultured in serum-free condition. When the transcript levels of these proteins and another Hsps were measured by real-time PCR, the transcripts encoding 6 proteins (Hsp56, Hsp90alpha, Hsp110, protein disulfide isomerase related protein, XTP3-transactivated protein A and stathmin 1) were significantly up-regulated and that encoding aminoacylase 1 was down-regulated by E2 in cells cultured with or without serum. The protein profiling and transcript expression patterns of E2-regulated proteins including Hsps in MCF-7 cells suggested the involvement of these proteins in breast carcinogenesis. Proteins (or transcripts) whose expression pattern is altered by E2 might be potent targets for treating breast cancer patients.

Synthesis of a novel biotin-tagged photoaffinity probe for VEGF receptor tyrosine kinases

A novel biotin-tagged photoaffinity probe was synthesized and evaluated as a vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase inhibitor. The probe (2) is a potent VEGFR-2 inhibitor with an IC(50) value of 7.1 microM, and inhibits VEGF-induced proliferation in human umbilical vein endothelial cells (HUVEC), with an IC(50) value of 40.3 microM. This probe will be a useful reagent for investigating ligand-protein interactions.

Effective glycemic control achieved by transplanting non-viral cationic liposome-mediated VEGF-transfected islets in streptozotocin-induced diabetic mice

Hypoxic damage is one of the major causes of islet graft failure and VEGF is known to play a crucial role in revascularization. To address the effectiveness of a cationic lipid reagent as a VEGF gene carrier, and the beneficial effect of VEGF-transfected islets on glycemic control, we used effectene lipid reagent in a transfection experiment using mouse islets. Transfection efficiencies were highest for 4 microg/microgL cDNA and 25 microgL effectene and cell viabilities were also satisfactory under this condition, and the overproduction of VEGF mRNA and protein were confirmed from conditioned cells. A minimal number of VEGF-transfected islets (100 IEQ/animal) were transplanted into streptozotocin (STZ)-induced diabetic mice. Hyperglycemia was not controlled in the islet transplantation (IT)-alone group (0/8) (non- diabetic glucose mice number/total recipient mice number) or in the IT-pJDK control vector group (0/8). However, hyperglycemia was completely abrogated in the IT-pJDK-VEGF transduced group (8/8), and viable islets and increased VEGF-transfected grafts vascularization were observed in renal capsules.

Mitogenic estrogen metabolites alter the expression of 17beta-estradiol-regulated proteins including heat shock proteins in human MCF-7 breast cancer cells

Estrogen metabolites are carcinogenic. The comparative mitogenic activities of 17b-estradiol (E2) and four metabolites, 2-hydroxyestradiol (2-OHE2), 4-hydroxyestradiol (4-OHE2), 16a-hydroxyestrone (16a-OHE1) and 2-methoxyestradiol (2-ME), were determined in estrogen receptor(ER)-positive MCF-7 human breast cancer cells. Each of the E2 metabolites caused proliferation of the MCF-7 cells, but only E2 and 16a-OHE1 induced a greater than 20-fold increases in transcripts of the progesterone receptor (PR) gene, a classical ER-mediated gene. This suggests that the mitogenic action of E2 and 16a-OHE1 could result from their effects on gene expression via the ER. E2 metabolites altered the expression of E2-regulated proteins including heat shock proteins (Hsps). 16a-OHE1 and 2-ME as well as E2 increased levels of Hsp56, Hsp60, Hsp90a and Hsp110 transcripts, and the patterns of these inductions resembled that of PR. Hsp56 and Hsp60 protein levels were increased by all the E2 metabolites. Levels of the transcripts of 3 E2-upregulated proteins (XTP3-transactivated protein A, protein disulfide isomerase-associated 4 protein and stathmin 1) and an E2-downregulated protein (aminoacylase 1) were also affected by the E2 metabolites. These results suggest that the altered expression of Hsps (especially Hsp56 and Hsp60) by E2 metabolites such as E2, 16a-OHE1 and 2-ME could be closely linked to their mitogenic action.

Chemical regulation of abscisic acid catabolism in plants by cytochrome P450 inhibitors

Plant hormone abscisic acid (ABA) is an important factor for conferring drought stress resistance on plants. Therefore, small molecules that regulate ABA levels in plants can be useful both for investigating functions of ABA and for developing new plant growth regulators. Abscisic acid (ABA) catabolism in plants is primarily regulated by ABA 8'-hydroxylase, which is a cytochrome P450 (P450). We tested known P450 inhibitors containing a triazole group and found that uniconazole-P inhibited ABA catabolism in cultured tobacco Bright Yellow-2 cells. In a structure-activity study of uniconazole, we found a more effective ABA catabolic inhibitor (diniconazole) than uniconazole-P. Diniconazole, a fungicide, acted as a potent competitive inhibitor of recombinant Arabidopsis ABA 8'-hydroxylase, CYP707A3, in an in vitro assay. Diniconazole-treated plants retained a higher ABA content and higher transcription levels of ABA response genes during rehydration than did untreated plants and were more drought stress tolerant than untreated plants. These results strongly suggest that ABA catabolic inhibitors that target ABA 8'-hydroxylase can regulate the ABA content of plants and conferred drought stress resistance on plants. The optical resolution of diniconazole revealed that the S-form isomer, which is a weak fungicidal isomer, was more active as an ABA catabolic inhibitor than was the R-form isomer.

Regulation of fibroblast growth factor 2 and fibroblast growth factor receptors by transforming growth factor beta in human osteoblastic MG-63 cells

Fibroblast growth factor 2 (FGF-2) and its receptors (FGFRs) are important regulators of bone cell function. Although FGF-2 is a major modulator of bone cell function, its expression and regulation in human osteoblasts have not been investigated. We examined FGF-2 messenger RNA (mRNA) expression and regulation in the human osteosarcoma MG-63 cells. Northern analysis revealed that MG-63 cells expressed FGF-2 mRNA transcripts of 7, 4, 2.2, and 1.3 kilobases (kb). In the absence of serum, treatment with transforming growth factor beta (TGF-beta; 0.1-10 ng/ml) increased all FGF-2 mRNA transcripts. Maximal increase was seen with 1 ng/ml of TGF-beta. TGF-beta increased FGF-2 mRNA expression within 2 h and this was sustained for 24 h. Phorbal myristate acetate (PMA; 1 microM) also increased FGF-2 mRNA at 6 h. Time course studies showed that TGF-beta did not significantly alter FGFR1 or FGFR2 mRNA expression in MG-63 cells. Western blotting with anti-human FGF-2 revealed that MG-63 cells synthesize three isoforms of FGF-2 protein of approximately 18, 22/23, and 24 kDa, which were increased after either 6 h or 24 h of treatment with TGF-beta. Increased FGF-2 mRNA and protein expression in response to TGF-beta was markedly reduced by the protein kinase A (PKA) inhibitor H-89. Immunogold labeling of MG-63 cells treated with TGF-beta showed increased labeling for FGF-2 and FGFR2 in the nuclei. In contrast, TGF-beta treatment significantly decreased FGFR1 labeling in the nuclei. These data show that TGF-beta regulates FGF-2 gene expression in human osteosarcoma cells. Furthermore, TGF-beta modulates the cellular localization of FGF-2 and its receptors.

Selective interaction of triazole derivatives with DWF4, a cytochrome P450 monooxygenase of the brassinosteroid biosynthetic pathway, correlates with brassinosteroid deficiency in planta

Brassinazole, a synthetic chemical developed in our laboratory, is a triazole-type brassinosteroid biosynthesis inhibitor that induces dwarfism in various plant species. The target sites of brassinazole were investigated by chemical analyses of endogenous brassinosteroids (BRs) in brassinazole-treated Catharanthus roseus cells. The levels of castasterone and brassinolide in brassinazole-treated plant cells were less than 6% of the levels in untreated cells. In contrast, campestanol and 6-oxocampestanol levels were increased, and levels of BR intermediates with hydroxy groups on the side chains were reduced, suggesting that brassinazole treatment reduced BR levels by inhibiting the hydroxylation of the C-22 position. DWF4, which is an Arabidopsis thaliana cytochrome P450 isolated as a putative steroid 22-hydroxylase, was expressed in Escherichia coli, and the binding affinity of brassinazole and its derivatives to the recombinant DWF4 were analyzed. Among several triazole derivatives, brassinazole had both the highest binding affinity to DWF4 and the highest growth inhibitory activity. The binding affinity and the activity for inhibiting hypocotyl growth were well correlated among the derivatives. In brassinazole-treated A. thaliana, the CPD gene involved in BR biosynthesis was induced within 3 h, most likely because of feedback activation caused by the reduced levels of active BRs. These results indicate that brassinazole inhibits the hydroxylation of the C-22 position of the side chain in BRs by direct binding to DWF4 and that DWF4 catalyzes this hydroxylation reaction.

The effects of dexamethasone on insulin release and biosynthesis are dependent on the dose and duration of treatment

Complex results concerning the effect of glucocorticoids on insulin secretion have been reported. The aim of this study is to clarify the direct effects of glucocorticoids on pancreatic islets and to determine whether the effect of glucocorticoids on insulin biosynthesis or release is dependent on the dose and duration of treatment with glucocorticoid. Studies on insulin secretion and biosynthesis were performed with different concentrations (0, 1, 10, 100 nmol/l) and durations (1 and 6 h) of treatment with dexamethasone (dexa) in rat pancreatic islets. (1) One nmol/l dexa had no inhibitory effect on insulin secretion and biosynthesis. Ten and 100 nmol/l had an inhibitory effect on insulin secretion, which was mainly due to suppression of the first phase of insulin secretion. (2) Insulin content was significantly increased regardless of the concentration in 1-h treated islets. However, insulin content was markedly diminished with 100 nmol/l dexa in 6-h treated islets. (3) The preproinsulin mRNA expression of 6-h treated islets was suppressed in a dose-dependent manner. Our data revealed that, in the condition of short-term and low-dose glucocorticoid exposure, insulin secretion and biosynthesis are not affected. The secretory process of insulin seems to be the initial step of the inhibitory action of glucocorticoid. Both insulin release and biosynthesis are inhibited by chronic exposure to high dose dexamethasone. It can be concluded that glucocorticoid might be involved in the multisteps of insulin release and biosynthesis.

Routine measurement of serum calcitonin is useful for early detection of medullary thyroid carcinoma in patients with nodular thyroid diseases

BACKGROUND

Medullary thyroid carcinoma (MTC) is characterized by a high concentration of serum calcitonin. Routine measurement of serum calcitonin concentration has been advocated for detection of MTC among patients with nodular thyroid diseases. However, a minimal to moderate increase of serum calcitonin concentration has been frequently observed in diseases other than MTC. Fine-needle aspiration cytology (FNAC) is not a reliable method for detection of MTC. Therefore, we evaluated the usefulness of routine measurement of serum calcitonin concentration in patients with nodular thyroid diseases, and studied the validity of pentagastrin stimulation test and FNAC in these patients.

SUBJECTS AND METHODS

We performed routine measurement of serum calcitonin concentrations in 1,448 patients (male, 285, female, 1,163) with nodular thyroid diseases. The average age was 46 years (range, 14-86 years). Initial examination included thyroid examination, thyroid scan or ultrasonography, measurements of serum free triiodothyronine) (T3), free thyroxine (T4), thyrotropin (TSH) levels, and antithyroid autoantibodies. FNAC was performed in all patients who had palpable or visible thyroid nodule by ultrasonography, and pentagastrin stimulation test was performed in 39 patients who consented. Serum calcitonin concentration was measured with a two-site immunoradiometric assay using commercial kits. We also measured the serum calcitonin concentration in 407 healthy subjects without thyroid or nonthyroid diseases.

RESULTS

Serum calcitonin concentration was 10 pg/mL or less in 403 normal subjects (99.0 percentile), and 11-13 pg/mL in the remaining 4 subjects. We found that 56 (3.87%) of 1,448 patients with nodular thyroid diseases had serum calcitonin level above 10 pg/mL. Ten patients (0.69%) with histologically confirmed MTC were detected by the routine measurement of serum calcitonin. The prevalence of MTC was 5.2% in 194 patients with thyroid carcinoma. Five of 10 patients with MTC had basal serum calcitonin level above 100 pg/mL. The remaining 5 patients had minimal or moderate elevation of basal serum calcitonin (range, 12-86 pg/mL). Serum calcitonin concentration increased to more than 100 pg/mL by pentagastrin in all patients with MTC (2.4- to 37.7-fold increase). FNAC suggested MTC in only 2 patients (22.2%), and failed to diagnose MTC in 7 patients. FNAC was not performed in 1 patient with MTC, because he had no visible mass by ultrasonography.

CONCLUSION

These results suggested that routine measurement of serum calcitonin is useful in the early detection of MTC among patients with nodular thyroid diseases. Pentagastrin stimulation test may also be a reliable way for evaluating thyroid nodular patients with mild or moderate elevation of serum calcitonin concentrations. However, FNAC was not sensitive in detecting MTC. We recommend routine measurement of serum calcitonin concentration in patients with nodular thyroid diseases.

Treatment of dark-grown Arabidopsis thaliana with a brassinosteroid-biosynthesis inhibitor, brassinazole, induces some characteristics of light-grown plants

When a brassinosteroid biosynthesis inhibitor, brassinazole (Brz), was applied at concentrations ranging from 0.1 to 2 microM. Arabidopsis thaliana (L.) Heynh seedlings grown in the dark exhibited morphological features of light-grown plants, i.e. short hypocotyls, expanded cotyledons, and true leaves, in a dose-dependent manner. Control (non Brz-treated) seedlings grown in the dark for 40 d did not develop leaf primordia. However, treatment with the lowest concentration of Brz induced the development of leaf buds, although it hardly induced any short hypocotyls, and treatment with the highest concentration of Brz induced both short hypocotyls and leaves. Labeling experiments with the thymidine analogue 5-bromo-2'-deoxyuridine revealed that amplification of cell nuclei and organellar nucleoids is activated in the shoot apical meristems of dark-grown Brz-treated seedlings. These results suggest that Brz-treatment induces development of true leaves. Furthermore, condensation and scattering of plastid nucleoids, which is known to occur during the differentiation of etioplasts into chloroplasts, was observed in the plastids of dark-grown Brz-treated cotyledons. In addition, high levels of ribulose-1,5-bisphosphate carboxylase-oxygenase proteins accumulated in the plastids of the cotyledons. Electron microscopy showed that the plastids were etioplasts with a prolamellar body and few thylakoid membranes. These results suggest that Brz treatment in the dark induces the initial steps of plastid differentiation, which occur prior to the development of thylakoid membranes. This is a novel presumed function of brassinosteroids. These cytological changes seen in Brz-treated Arabidopsis were exactly the same as those seen in a brassinosteroid-biosynthesis-deficient mutant, det2, supporting the hypothesis that Brz has no side-effects except inhibiting brassinosteroid biosynthesis, and should prove a useful tool in clarifying the role of brassinosteroids.

Synthesis and biological activity of 4'-methoxy derivatives of abscisic acid

Replacing the 4'-carbonyl group of abscisic acid with a methoxy group does not affect the abscisic acid (ABA)-like activities of the product in barley aleurone protoplasts, although the reduction of ABA to 4'-hydroxyl derivatives significantly reduces the ABA-like activity of the products. This suggests that methoxy derivatives of abscisic acid might be used to produce probes for ABA binding proteins.