共查询到20条相似文献,搜索用时 250 毫秒
2.
Of the various risk factors contributing to osteoporosis, dietary/lifestyle factors are important. In a clinical study we reported that women with caffeine intakes >300 mg/day had higher bone loss and women with vitamin D receptor (VDR) variant, tt were at a greater risk for this deleterious effect of caffeine. However, the mechanism of how caffeine effects bone metabolism is not clear. 1,25-Dihydroxy vitamin D 3 (1,25(OH) 2D 3) plays a critical role in regulating bone metabolism. The receptor for 1,25(OH) 2D 3, VDR has been demonstrated in osteoblast cells and it belongs to the superfamily of nuclear hormone receptors. To understand the molecular mechanism of the role of caffeine in relation to bone, we tested the effect of caffeine on VDR expression and 1,25(OH) 2D 3 mediated actions in bone. We therefore examined the effect of different doses of caffeine (0.2, 0.5, 1.0 and 10 mM) on 1,25(OH) 2D 3 induced VDR protein expression in human osteoblast cells. We also tested the effect of different doses of caffeine on 1,25(OH) 2D 3 induced alkaline phosphatase (ALP) activity, a widely used marker of osteoblastic activity. Caffeine dose dependently decreased the 1,25(OH) 2D 3 induced VDR expression and at concentrations of 1 and 10 mM, VDR expression was decreased by about 50–70%, respectively. In addition, the 1,25(OH) 2D 3 induced alkaline phosphatase activity was also reduced at similar doses thus affecting the osteoblastic function. The basal ALP activity was not affected with increasing doses of caffeine. Overall, our results suggest that caffeine affects 1,25(OH) 2D 3 stimulated VDR protein expression and 1,25(OH) 2D 3 mediated actions in human osteoblast cells. 相似文献
3.
We employed genetically modified mice to examine the role of 1,25-dihydroxyvitamin D 3 [1,25(OH) 2D 3] on skeletal and calcium homeostasis. In mice expressing the null mutation for 25-hydroxyvitamin D 1 hydroxylase (1OHase −/−), or the vitamin D receptor (VDR −/−), 1,25(OH) 2D 3 and calcium were both required for optimal epiphyseal growth plate development, serum calcium and phosphorus alone were sufficient to mineralize skeletal tissue independent of 1,25(OH) 2D 3 and the VDR, and endogenous 1,25(OH) 2D 3 and the VDR were essential for baseline bone formation. In 2-week-old 1OHase −/− mice and in 2-week-old mice homozygous for the PTH null mutation(PTH −/−), PTH and 1,25(OH) 2D 3 were each found to exert independent and complementary effects on skeletal anabolism, with PTH predominantly affecting appositional trabecular bone growth and 1,25(OH) 2D 3 influencing both endochondral bone formation and appositional bone growth. Endogenous 1,25(OH) 2D 3 maintained serum calcium homeostasis predominantly by modifying intestinal and renal calcium transporters but not by producing net bone resorption. Administration of exogenous 1,25(OH) 2D 3 to double mutant PTH −/−1OHase −/− mice produced skeletal effects consistent with the actions of endogenous 1,25(OH) 2D 3. These studies reveal an important skeletal anabolic role for both endogenous and exogenous 1,25(OH) 2D 3 and point to a potential role for 1,25(OH) 2D 3 analogs in the treatment of disorders of bone loss. 相似文献
4.
1,25-dihydroxyvitamin D 3 (1,25-(OH) 2D 3) is known to be involved in regulating the proliferation of parathyroid cells and PTH synthesis through reactions involving its nuclear receptor. We evaluated the effects of 1,25-(OH) 2D 3 and its hexafluorinated analog, 26,26,26,27,27,27-hexafluoro-1,25-dihydroxyvitamin D 3 (26,27-F 6-1,25-(OH) 2D 3), on parathyroid cells. The 1,25-(OH) 2D 3 and 26,27-F 6-1,25-(OH) 2D 3 each inhibited [ 3H]thymidine incorporation and ornithine decarboxylase (ODC) activity, which is important in cell proliferation, in primary cultured bovine parathyroid cells. The inhibitory effect of 26,27-F 6-1,25-(OH) 2D 3 on PTH secretion from parathyroid cells was significantly more potent than that of 1,25-(OH) 2D 3 between 10 −11 M and 10 −8 M. Study of 26,27-F 6-1,25-(OH) 2D 3 metabolism in parathyroid cells in vitro elucidated its slower degradation than that of 1,25-(OH) 2D 3. After 48 h of incubation with [1 β- 3H]26,27-F 6-1,25-(OH) 2D 3, two HPLC peaks, one for [1 β- 3H]26,27-F 6-1,25-(OH) 2D 3, and a second larger peak for [1 β- 3H]26,27-F 6-1,23(S),25-(OH) 3D 3, were detected. No metabolites were detected after the same period of incubation with 1,25-(OH) 2[26,27- 3H]D 3. We observed that 26,27-F 6-1,23(S),25-(OH) 3D 3 was as potent as 1,25-(OH) 2D 3 in inhibiting the proliferation of parathyroid cells. Data suggest that the greater biological activity of 26,27-F6-1,25-(OH)2D3 is explained by its slower metabolisms and by the retention of the biological potency of 26,27-F6-1,25-(OH)2D3 even after 23(S)-hydroxylation. 相似文献
5.
Induction of growth arrest and differentiation by 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2D 3) occurs in non-malignant cell types but is often reduced in cancer cells. For example, androgen-independent prostate cancer cells, DU-145 and PC-3, are relatively insensitive to the anti-proliferative action of 1,25-(OH) 2D 3. This appears to be due to increased 1,25-(OH) 2D 3-metabolism, as a result of CYP24 enzyme-induction, which in turn leads to decreased anti-proliferative efficacy. In the in vitro rat kidney mitochondria assay, the 2-(4-hydroxybenzyl)-6-methoxy-3,4-dihydro-2 H-naphthalen-1-one (4) was found to be a potent inhibitor of Vitamin D 3 metabolising enzymes (IC 50 3.5 μM), and was shown to be a more potent inhibitor than the broad spectrum P450 inhibitor ketoconazole (IC 50 20 μM). The combination of the inhibitor and 1,25-(OH) 2D 3 caused a greater inhibition of proliferation in DU-145 cells than when treated with both agents alone. Examination of the regulation of VDR target gene mRNA in DU-145 cells revealed that co-treatment of 1,25-(OH) 2D 3 plus inhibitor of Vitamin D 3 metabolising enzymes co-ordinately upregulated CYP24, p21 waf1/cip1 and GADD45. 相似文献
6.
The affinity of purified human vitamin D-binding protein from serum (DBP) for 25-hydroxyvitamin D 3 (25-OHD 3) and 1,25-dihydroxyvitamin D 3 [1,25-(OH) 2D 3] was measured in the presence of free fatty acids (FFA), cholesterol, prostaglandins and several drugs. Mono- and polyunsaturated fatty acids markedly decreased the affinity of both 25-OHD 3 and 1,25-(OH) 2D 3 for DBP, whereas saturated fatty acids (stearic and arachidic acid), cholesterol, cholesterol esters, retinol, retinoic acid and prostaglandins (A 1 and E 1) did not affect the apparent affinity. Several chemicals known to decrease the binding of thyroxine to its plasma-binding protein did not affect the affinity of DBP. The apparent affinity of DBP for both 25-OHD3 and 1,25-(OH)2D3 decreased 2.4- to 4.6-fold in the presence of 36 μM of linoleic or arachidonic acid, respectively. Only a molar ratio of FFA:DBP higher than 10,000 was able to decrease the binding of 25-OHD3 to DBP by 20%. Much smaller ratio's of FFA:DBP (25 for arachidonic and 45 for oleic acid), however, decreased the binding of 1,25-(OH)2D3 to DBP. These latter ratio's are well within the physiological range. The addition of human albumin in a physiological albumin:DBP molar ratio did not impair the inhibitory effect of linoleic acid on the binding of [3H]25-OHD3 to DBP. The binding and bioavailability of vitamin D metabolites thus might be altered by mono- and polyunsaturated but not by saturated fatty acids. 相似文献
9.
1,25-Dihydroxyvitamin D 3 (1,25(OH) 2D 3) interacts with the Vitamin D 3 receptor (VDR) to modulate proliferation and apoptosis in a variety of cell types, including breast cancer cells. In this review, we discuss three issues related to the role of the VDR in growth control: first, whether mammary glands lacking VDR exhibit abnormal growth; second, whether the VDR is essential for induction of apoptosis by 1,25(OH) 2D 3; and third, whether VDR up-regulation can sensitize cells to 1,25(OH) 2D 3. Studies from our laboratory have demonstrated that mammary glands from VDR knockout (VDR KO) mice exhibit accelerated growth and branching during puberty, pregnancy and lactation as compared to wild-type (WT) mice. In addition, involution after weaning, a process driven by epithelial cell apoptosis, proceeds at a slower rate in VDR KO mice compared to WT mice. Using cells isolated from VDR KO and WT mice, we report that both normal and transformed mammary cells derived from WT mice are growth inhibited by 1,25(OH) 2D 3, however, cells derived from VDR KO mice are completely unresponsive to 1,25(OH) 2D 3. In human breast cancer cells, we have identified a variety of agents, including steroid hormones, phytoestrogens and growth factors, that up-regulate VDR expression and enhance sensitivity to 1,25(OH) 2D 3-mediated growth inhibition. Collectively, these studies support a role for 1,25(OH) 2D 3 and the VDR in negative growth regulation of both normal mammary gland and breast cancer cells. 相似文献
11.
1α,25-Dihydroxyvitamin D 3, an endogenous ligand with the highest affinity for the vitamin D receptor (VDR), was labeled with 11C for use in biological experiments. The radionuclide was incorporated via the reaction of [ 11C]methyllithium on a methyl ketone precursor in tetrahydrofuran at −10 °C. Deprotection of the labeled intermediate yielded 2.5–3 GBq [26,27- 11C]1α,25-dihydroxyvitamin D 3 [ 11C-1,25(OH) 2 D 3] with specific radioactivity averaging 100 GBq/μmol at the end of synthesis and HPLC purification. The entire process took 48 min from the end of radionuclide production. In vitro binding experiments in rachitic chick purified VDR demonstrated the high affinity binding of this novel tracer. Thus; 11C-1,25(OH) 2 D 3 is available for in vivo distribution studies and may be suitable for the positron emission tomography (PET) determination of VDR levels and occupancy in animals and humans. 相似文献
13.
The biologically active form of vitamin D, 1,25-dihydroxyvitamin D 3 (1,25(OH) 2D 3), regulates osteoblast proliferation and differentiation. Production of 1,25(OH) 2D 3 is catalysed by the enzyme 25-hydroxyvitamin D 3-1-hydroxylase (CYP27B1). Though highly expressed in the kidney, the CYP27B1 gene is also expressed in non-renal tissues including bone. It is hypothesised that local production of 1,25(OH) 2D 3 by osteoblasts plays an autocrine or paracrine role. The aim of this study was to investigate what factors regulate expression of the CYP27B1 gene in osteoblast cells. ROS 17/2.8 osteoblast cells were transiently transfected with plasmid constructs containing the 5′-flanking sequence of the human CYP27B1 gene fused to a luciferase reporter gene. Cells were treated with either parathyroid hormone (PTH), 1,25(OH) 2D 3, transforming growth factor-beta (TGF-β) or insulin-like growth factor-1 (IGF-1) and luciferase activity was measured 24 h later. The results showed that 1,25(OH) 2D 3 did not alter expression of the reporter construct, however treatment with PTH, IGF-1 and TGF-β decreased expression by 18, 53 and 58% respectively. The repressive action of TGF-β was isolated to the region between −531 and −305 bp. These data suggest that expression of the 5′-flanking region for the CYP27B1 gene in osteoblast cells may be regulated differently to that previously described in kidney cells. 相似文献
14.
This study examines the effect of 1,25-dihydroxyvitamin D 3 [1,25(OH) 2D 3], 24,25-dihydroxyvitamin D 3 [24,25(OH) 2D 3], two vitamin D analogues (KH 1060 and EB 1089, which are 20-epi-22-oxa and 22,24-diene-analogues, respectively), 9- cis retinoic acid and all- trans retinoic acid on proliferation of SH-SY5Y human neuroblastoma cells, after treatment for 7 days. Cell number did not change when the cells were incubated with 1, 10 or 100 nM 1,25(OH) 2D 3 or its derivatives, but significantly decreased in the presence of the two retinoids (0.001–10 μM final concentration). A synergistic inhibition was observed, when SH-SY5Y cells were treated combining 0.1 μM 9- cis retinoic acid and 10 nM 1,25(OH) 2D 3 or 10 nM KH 1060, and 1 μM 9- cis retinoic acid and 10 nM 1,25(OH) 2D 3 or 10 nM EB 1089. Acetylcholinesterase activity showed a significant increase, in comparison with controls, after treatment of the cells for 7 days with 0.1 or 1 μM 9- cis retinoic acid, alone or combined with 10 nM 1,25(OH) 2D 3 or 10 nM KH 1060 or 10 nM EB 1089. This increase was synergistic, combining 1 μM 9- cis retinoic acid and 10 nM 1,25(OH) 2D 3 or EB 1089. The levels of the c- myc encoded protein remarkably decreased after treatment of SH-SY5Y cells for 1, 3, 7 days with 0.1 and 1 μM 9- cis retinoic acid, alone or combined with 10 nM 1,25(OH) 2D 3 or 10 nM KH 1060 or 10 nM EB 1089. In particular, the association of 1 μM 9- cis retinoic acid and 10 nM 1,25(OH) 2D 3 or 10 nM EB 1089 resulted in a synergistic c- myc inhibition, in comparison with that obtained in the presence of the retinoid alone. These findings may have therapeutic implications in human neuroblastoma. 相似文献
15.
The economy of Ca utilization is under the control of vitamin D 3, particularly its active metabolite 1,25-dihydroxy cholecalciferol [1,25(OH) 2D 3]. In sufficient Ca absorption leads to tibial dyschondroplasia resulting in not attaining optimum body weight. Our earlier studies [T.P. Prema, N. Raghuramulu, Phytochemistry 37 (1994) 167] have shown that the Cestrum diurnum (CD) leaves contain vitamin D 3 metabolites. It was felt whether incorporation of CD as a source of 1,25(OH) 2D 3 could improve the Ca absorption in broilers. Four groups of 60 birds each were fed with either normal diet or normal diet + 0.25% CD or normal diet without vitamin D 3 or normal diet without vitamin D 3 + 0.25% CD leaf powder for 45 days. In subsample of six birds it was observed that incorporation of CD leaves in the feed had the maximal effect on all the parameters studied. The results indicate that the intestinal Ca transport as represented by Serosa/Mucosa (S/M) ratio was found to be significantly ( p < 0.01) higher in broilers fed diet with CD leaf powder and the 1 hydroxylase activity in kidney is significantly ( p < 0.001) higher in negative controls. On the other hand the supplementation of CD leaves enhanced the serum Ca, body weight, tibia weight, density and strength resulting in the disappearance of tibial dyschondroplasia. No lesions of toxicity were observed in any of the soft tissue examined. The results suggest that the incorporation of CD leaf powder in poultry feed could be beneficial to the poultry. 相似文献
16.
The ingestion of Solanum glaucophyllum ( SG) causes a calcinosis of cattle named Enteque Seco (ES). The toxic principle is the 1,25-(OH) 2D 3, mainly conjugated as glycoside. This study aims to validate a simple novel method of evaluation of the VDA of SG leaves. Aqueous extracts of SG were purified using C 18 minicolumns and assayed by RIA with an antibody raised in rabbits by injection of the acid—C22, 1-(OH)Vitamin D 3. Data were expresed as glycoside equivalent to 1,25-(OH) 2D 3 in ng/g of dry leaves. We compared this data with 1,25-(OH) 2D 3 levels measured, in the same samples, by liquid chromatography (HPLC) after enzyme cleavage. This procedure involved the incubation of SG leaves with rumen fluid, followed by C 18-OH solid phase extraction. The 1,25-(OH) 2D 3 fraction was run by HPLC and detection was achieved using a photodiode array detector. Data were expressed as micrograms of 1,25-(OH) 2D 3/g dry leaves. A significant regression of 1,25-(OH) 2D 3 levels ( Y) as a function of glycoside RIA 1,25-(OH) 2D 3 equivalents ( X) was found: Y = 12.02 + 0.35 X [ R = 0.81; P = 0,0002; N = 15], allowing us to conclude that this novel assay could be used to estimate the amount of this active principle contained in SG leaves. 相似文献
17.
Vitamin D is produced by exposure of 7-dehydrocholesterol in the skin to UV irradiation (UVR) and further converted in the skin to the biologically active metabolite, 1,25-dihydroxyvitamin D 3 (1,25(OH) 2D 3) and other compounds. UVR also results in DNA damage producing cyclobutane pyrimidine dimers (CPD). We previously reported that 1,25(OH) 2D 3 at picomolar concentrations, protects human skin cells from UVR-induced apoptosis, and decreases CPD in surviving cells. 1,25(OH) 2D 3 has been shown to generate biological responses via two pathways—the classical steroid receptor/genomic pathway or a rapid, non-genomic pathway mediated by a putative membrane receptor. Whether the rapid response pathway is physiologically relevant is unclear. A cis-locked, rapid-acting agonist 1,25(OH) 2lumisterol 3 (JN), entirely mimicked the actions of 1,25(OH) 2D 3 to reduce fibroblast and keratinocyte loss and CPD damage after UVR. The effects of 1,25(OH) 2D 3 were abolished by a rapid-acting antagonist, but not by a genomic antagonist. Skh:hr1 mice exposed to three times the minimal erythemal dose of solar-simulated UVR and treated topically with 1,25(OH) 2D 3 or JN immediately after UVR showed reduction in UVR-induced UVR-induced sunburn cells ( p < 0.01 and <0.05, respectively), CPD ( p < 0.01 for both) and immunosuppression ( p < 0.001 for both) compared with vehicle-treated mice. These results show for the first time an in vivo biological response mediated by a rapid-acting analog of the vitamin D system. The data support the hypothesis that 1,25(OH) 2D 3 exerts its photoprotective effects via the rapid pathway and raise the possibility that other D compounds produced in skin may contribute to the photoprotective effects. 相似文献
19.
Five heterometallic compounds with formulae [Ba(H 2O) 4Cr 2(μ-OH) 2( nta) 2] · 3H 2O (I), [M( bpy) 2(H 2O) 2] [Cr 2(OH) 2( nta) 2] · 7H 2O, where M 2+ = Zn, (II); Ni, (III); Co, (IV) and [Mn(H 2O) 3( bpy)Cr 2(OH) 2( nta) 2] · ( bpy) · 5H 2O (V); bpy = 2,2′-bipyridine, ( nta = nitrilotriacetate ion) have been prepared by reaction of I with the corresponding M II-sulfates in the presence of 2,2′-bipyridine. Substances I–V have been characterized by magnetic susceptibility measurements, EPR and X-ray determinations. I represents a 2D coordination polymer formed by coordination of centrosymmetrical dimeric chromium(III) units and Barium cations. The 10-coordinate Ba polyhedron is completed by four water molecules. Compounds II–IV are isostructural and consist of non-centrosymmetric dimeric anions [Cr 2(μ-OH) 2( nta) 2] 2−, complex cations [M II( bpy) 2(H 2O) 2] 2+ and solvate water molecules. The octahedral coordination of chromium atoms implies four donor atoms of the nta3− ligands and two bridging OH groups. Multiple hydrogen bonds of coordinated and solvate water molecules link anions and cations in a 3D network. A similar [Cr 2(μ-OH) 2( nta) 2] 2− unit is found in V. The bridging function is performed by a carboxylate oxygen atom of the nta ligand that leads to the formation of a trinuclear complex [Mn( bpy)(H 2O) 2Cr 2(μ-OH) 2( nta) 2]. Experimental and calculated frequency and temperature dependences of EPR spectra of these compounds are presented. The fine structure appearing on the EPR spectra of compound V is analyzed in detail at different temperatures. It is established that the main part of the EPR signals is due to the transitions in the spin states of a spin multiplet with S = 2. Analyses of experimental and calculated spectra confirm the absence of interaction between metal ions (M II) and Cr-dimers in complexes III and IV and the presence of weak Mn–Cr interactions in V. The temperature dependence of magnetic susceptibilities for I–V was fitted on the basis of the expression derived from isotropic Hamiltonian including a bi-quadratic exchange term. 相似文献
|