共查询到20条相似文献,搜索用时 15 毫秒
2.
The hormone 1alpha,25(OH)2vitamin D3 (1,25-D) produces biological responses via both genomic and rapid mechanisms. The genomic responses are linked to a nuclear receptor, while the rapid responses are believed to utilize other signal transduction pathways that are likely linked to a putative cell membrane receptor for 1,25-D. The natural seco-steroid, 1,25-D, is capable of facile rotation about its 6,7 single carbon bond to permit generation of a continuum of potential ligand shapes extending from the 6-s-cis (6C) to the 6-s-trans (6T). To identify the shape of the conformer(s) that can serve as agonists for the genomic and rapid responses, we synthesized two families of analogs that were locked in either the 6T or 6C conformation. We found that 6T-locked analogs were inactive or significantly less active than 1,25-D in both rapid responses (transcaltachia or the rapid stimulation of intestinal Ca2+ absorption in perfused chick intestine, stimulation of whole cell chloride currents in osteoblastic ROS 17/2.8 cells, and stimulation of phosphorylation of mitogen-activated protein kinase in promyelocytic NB4 leukemic cells) and in genomic responses (induction of osteocalcin in human MG-63 osteoblastic cells). For genomic responses, the 6C-locked analogs bound poorly to the nuclear receptor and were much less potent than 1,25-D. In contrast, the 6C-locked analogs were potent agonists of the three rapid responses studied and had activities equivalent to 1,25-D. These results demonstrate that the signal transduction pathways that support rapid and genomic responses can discriminate between different shapes of the conformationally flexible 1,25-D. 相似文献
3.
The sterol, 1,25-dihydroxyvitamin D 3 (1,25(OH) 2D 3), has immunosuppressive activity. The hormone inhibits the production of lymphokines (IL-2, IFN-γ) and monocyte-derived cytokine (IL-12) leading to inhibition of helper T cell subset type 1 (Th 1). When given in vivo, the hormone prevents the development of spontaneous and induced models of autoimmunity. Analogs of 1,25(OH) 2D 3, with reduced hypercalcemic effects, display an enhanced activity in autoimmunity compared to the sterol and prolong graft survival in experimental transplantation. This paper reviews our understanding of the cellular actions of the hormone and the therapeutic application of 1,25(OH) 2D 3 and analogs in autoimmunity and transplantation. 相似文献
4.
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
5.
1,25-Dihydroxyvitamin D 3, [1,25(OH) 2D 3], the biologically most active metabolite of vitamin D 3, is involved in the regulation of calcium homeostasis and bone metabolism. Recently, receptors for 1,25(OH) 2D 3 have also been shown in cells and tissues not directly related to calcium homeostasis. Experimental data obtained with leukemic and cancer cell lines, both in vitro and in vivo, showed the effects of 1,25(OH) 2D 3 on cell differentiation and proliferation. However, high doses of the sterol have to be used to observe these effects. Additional studies are needed to establish whether 1,25(OH) 2D 3 or suitable analogues have a therapeutic potential in malignant diseases without unacceptable toxicity like the development of hypercalcemia. 相似文献
7.
Adequate supply of vitamin D 3 is not sufficient for the prevention of post-menopausal osteoporosis, because of a tightly regulated critical step in formation of the most active vitamin D metabolite 1,25-dihydroxyvitamin D 3. Direct application of 1,25(OH) 2D 3, however, was effective in reducing fracture rate and increasing bone mineral density as has been shown in large clinical studies. Extracts from Solanum glaucophyllum and Trisetum flavescens plants containing 1,25(OH)2D3-glycosides were characterized by their vitamin D-activity in a quail eggshell bioassay and applied in an osteoporosis model in ovariectomized rats. An extract from the grass T. flavescens and a purified extract from S. glaucophyllum were characterized by the absence of alkaloids and the analytically determined content of 1,25(OH)2D3. In the ovariectomized rat model after 6 months duration, the bone metabolism relevant markers serum calcium, 1,25(OH)2D3, urinary crosslinks and calcium were measured. At termination tibial mineral content was determined and as imaging procedure micro-computerized tomography was applied. The bisphosphonate alendronate was used as a positive standard. While alendronate reduced bone resorption, as seen in a reduced urinary crosslink excretion, both vitamin D metabolite-containing extracts were able to improve bone mineral density by an enhanced calcium turnover. 相似文献
9.
After intravenous administration of the vitamin D 3 analog, 22-oxacalcitriol (OCT), to normal rats plasma metabolites were investigated by HPLC, GC-MS and LC-MS. Five side-chain oxidation metabolites, 24 R(OH)OCT, 24 S(OH)OCT, (25 R)-26(OH)OCT, (25 S)-26(OH)OCT and 24oxoOCT, were identified by comparison with the corresponding synthetic compounds. These side-chain oxidation metabolites were similar to those of calcitriol [1,25(OH) 2 vitamin D 3] described previously. Besides these five metabolites, two unique side-chain cleavage metabolites, 20 S(OH)-hexanor-OCT and 17,20 S(OH) 2-hexanor-OCT, were identified as main metabolites in plasma by GC-MS and LC-MS using a specific chemical reaction. Our studies suggest that OCT is extensively metabolized and circulates in blood as a number of metabolites as well as unchanged OCT. This metabolism includes both unique pathways of C 23-O 22 cleavage and 17-hydroxylation, in addition to the side-chain oxidation metabolites similar to those of 1,25-(OH) 2D 3. 相似文献
10.
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
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.
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
16.
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
17.
1,25-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]1,25-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
18.
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
19.
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
20.
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
|