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1.
1,25(OH)2D3 receptor regulation and 1,25(OH)2D3 effects in primary cultures of growth cartilage cells of the rat 总被引:2,自引:0,他引:2
G. Klaus J. Merke H. Eing U. Hügel P. Milde H. Reichel E. Ritz O. Mehls 《Calcified tissue international》1991,49(5):340-348
Summary Vitamin D deficiency leads to disturbed calcification of growth cartilage and enlargement of growth plate, illustrating that
chondrocytes are a target for vitamin D. This observation prompted an investigation of 1,25(OH)2D3 receptor expression and action of vitamin D metabolites on chondrocyte proliferation. In primary cultures of tibial growth
cartilage of male SD rats (80 g), specific binding of [3H]-1,25(OH)2D3 is noted in both the logarithmic growth phase and at confluence (Nmax 12780 molecules/cell versus 4368 molecules/cell). Scatchard analysis revealed the presence of a single class of noninteracting
binding sites. KD was 10−11 M irrespective of growth phase. The binding macromolecule had a sedimentation coefficient of 3.5 S. Interaction with DNA
was demonstrated by DNA cellulose affinity chromatography. In immunohistology, growth cartilage cells (rabbit tibia) expressed
nuclear 1,25(OH)2D3 receptors most prominently in the proliferative and hypertrophic zone. This corresponds to binding data which showed highest
Nmax in the proliferating cartilage. 1,25(OH)2D3 in the presence of delipidated fetal calf serum (FCS) had a biphasic effect on cell proliferation and density, i.e., stimulation
at 10−12 M and dose-dependent inhibition at 10−10 M and below. Inhibition was specific and not seen with 24,25(OH)2D3 or dexamethasone. Growth phase-dependent 1,25(OH)2D3 receptor expression and effects of 1,25(OH)2D3 on chondrocyte proliferation point to a role of vitamin D in the homeostasis of growth cartilage. 相似文献
2.
G. G. Langston L. D. Swain Z. Schwartz F. Del Toro R. Gomez Barbara D. Boyan 《Calcified tissue international》1990,47(4):230-236
Summary Vitamin D3 metabolites have been shown to affect proliferation, differentiation, and maturation of cartilage cells. Previous studies
have shown that growth zone chondrocytes respond primarily to 1,25(OH)2D3 whereas resting zone chondrocytes respond primarily to 24,25(OH)2D3. To examine the role of calcium in the mechanism of hormone action, this study examined the effects of the Ca ionophore A23187,
1,25(OH)2D3, and 24,25(OH)2D3 on Ca influx and efflux in growth zone chondrocytes and resting zone chondrocytes derived from the costochondral junction
of 125 g rats. Influex was measured as incorporation of45Ca. Efflux was measured as release of45Ca from prelabeled cultures into fresh media. The pattern of45Ca influx in unstimulated (control) cells over the incubation period was different in the two chondrocyte populations, whereas
the pattern of efflux was comparable. A23187 induced a rapid influx of45Ca in both types of chondrocytes which peaked by 3 minutes and was over by 6 minutes. Influx was greatest in the growth zone
chondrocytes. Addition of 10−8–10−9 M 1,25(OH)2D3 to growth zone chondrocyte cultures results in a dose-dependent increase in45Ca influx after 15 minutes. Efflux was stimulated by these concentrations of hormone throughout the incubation period. Addition
of 10−6–10−7 M 24,25(OH)2D3 to resting zone chondrocytes resulted in an inhibition in ion efflux between 1 and 6 minutes, with no effect on influx during
this period. Efflux returned to control values between 6 and 15 minutes.45Ca influx was inhibited by these concentrations of hormone from 15 to 30 minutes. These studies demonstrate that changes in
Ca influx and efflux are metabolite specific and may be a mechanism by which vitamin D metabolites directly regulated chondrocytes
in culture. 相似文献
3.
Summary The ability of 1,25(OH)2D3 and of 24,25(OH)2D3 to prevent or to heal rickets in chicks was evaluated by studies of plasma biochemistry, growth plate histology, bone morphometry
and microradiography, and bone mineralization. 1,25(OH)2D3 at a dose of 100 ng/day produced fewest abnormalities compared with vitamin D3-treated control chicks. Bone growth was slightly greater than vitamin D3-treated controls in chicks given a lower dose of this metabolite; the reverse was observed in chicks given a higher dose.
24,25(OH)2D3 was less effective than 1,25(OH)2D3 in preventing rickets even at doses as high as 400 ng/day. Treatment of rachitic chicks with doses of 24,25(OH)2D3 up to 300 ng/day produced no healing effect on the bone lesions, in marked contrast to the beneficial effects observed with
1,25(OH)2D3. 相似文献
4.
Summary The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (2.3×10-12-1.4×10-6 [M]) on alkaline phosphatase, collagen, and cell proliferation were examined in primary cultured hypertrophic chondrocytes prepared from the distal epiphyseal growth plate of the tibias of 12-day chick embryos. 1,25(OH)2D3 showed time- and dose-dependent inhibitory effects on the alkaline phosphatase and collagen levels. The inhibition of alkaline phosphatase activity became detectable at 2×10-11 [M] and reached 10% of control at 10-7 [M]. The concentration of 1,25(OH)2D3 giving a 50% inhibition of the enzyme level was approximately 3×10-10 [M]. Of the two extracellular collagen pools, a cell-associated matrix pool showed a more dramatic decrease (to 10% of control) than a culture medium pool (to 50% of control) at increased 1,25(OH)2D3 concentrations. The degree of inhibition was different for each type of chondrocyte-specific collagen (types II, IX, X, and XI). Types II and IX were inhibited in a parallel manner to only 60–80% of control. On the other hand, types X and XI were more greatly reduced up to 10% of control, and their dose-dependent inhibitory curves were similar to that of alkaline phosphatase. On cell proliferation, 1,25(OH)2D3 had a biphasic effect: stimulation at 10-10–10-8 [M] and inhibition at higher levels. The results revealed the significant involvement of 1,25(OH)2D3 in the metabolism of two probable calcification-related products, alkaline phosphatase and type X collagen. 相似文献
5.
Tom D Thacher Philip R Fischer Michael O Obadofin Michael A Levine Ravinder J Singh John M Pettifor 《Journal of bone and mineral research》2010,25(9):1988-1995
Children with calcium‐deficiency rickets may have increased vitamin D requirements and respond differently to vitamin D2 and vitamin D3. Our objective was to compare the metabolism of vitamins D2 and D3 in rachitic and control children. We administered an oral single dose of vitamin D2 or D3 of 1.25 mg to 49 Nigerian children—28 with active rickets and 21 healthy controls. The primary outcome measure was the incremental change in vitamin D metabolites. Baseline serum 25‐hydroxyvitamin D [25(OH)D] concentrations ranged from 7 to 24 and 15 to 34 ng/mL in rachitic and control children, respectively (p < .001), whereas baseline 1,25‐dihydroxyvitamin D [1,25(OH)2D] values (mean ± SD) were 224 ± 72 and 121 ± 34 pg/mL, respectively (p < .001), and baseline 24,25‐dihydroxyvitamin D [24,25(OH)2D] values were 1.13 ± 0.59 and 4.03 ± 1.33 ng/mL, respectively (p < .001). The peak increment in 25(OH)D was on day 3 and was similar with vitamins D2 and D3 in children with rickets (29 ± 17 and 25 ± 11 ng/mL, respectively) and in control children (33 ± 13 and 31 ± 16 ng/mL, respectively). 1,25(OH)2D rose significantly (p < .001) and similarly (p = .18) on day 3 by 166 ± 80 and 209 ± 83 pg/mL after vitamin D2 and D3 administration, respectively, in children with rickets. By contrast, control children had no significant increase in 1,25(OH)2D (19 ± 28 and 16 ± 38 pg/mL after vitamin D2 and D3 administration, respectively). We conclude that in the short term, vitamins D2 and D3 similarly increase serum 25(OH)D concentrations in rachitic and healthy children. A marked increase in 1,25(OH)2D in response to vitamin D distinguishes children with putative dietary calcium‐deficiency rickets from healthy children, consistent with increased vitamin D requirements in children with calcium‐deficiency rickets. © 2010 American Society for Bone and Mineral Research 相似文献
6.
Krohn K Haffner D Hügel U Himmele R Klaus G Mehls O Schaefer F 《Calcified tissue international》2003,73(4):400-410
Growth plate chondrocytes are affected by 1,25(OH)2D3 and androgens, which may critically interact to regulate proliferation and differentiation during the male pubertal growth spurt. We investigated possible interactions of 1,25(OH)2D3 and the non-aromatizable androgen dihydrotestosterone (DHT) in primary chondrocyte cultures from young male rats. DHT and 1,25(OH)2D3 independently stimulated DNA synthesis and cell proliferation in a dose-dependent manner with maximally effective doses of [10-8 M] and [10-12 M], respectively. Both DHT and 1,25(OH)2D3 stimulated the expression and release of IGF-I, and the proliferative effects of each hormone were prevented by an IGF-I antibody. DHT and 1,25(OH)2D3 increased messenger RNAs (mRNAs) of their cognate receptors and of IGF-I receptor mRNA (IGF-I-R). 1,25(OH)2D3 also stimulated mRNA of the androgen receptor (AR), whereas DHT did not affect mRNA of the vitamin-D receptor (VDR). Coincubation with both steroid hormones did not stimulate receptor mRNAs more than either hormone alone. The proliferative effects of DHT and 1,25(OH)2D3 were completely inhibited by simultaneous incubation with both hormones, despite potentiation of IGF-I synthesis. In contrast, both hormones synergistically stimulated cell differentiation as judged by alkaline phosphatase activity, collagen X mRNA, and matrix calcification in long-term experiments. We conclude that DHT and 1,25(OH)2D3 interact with respect to chondrocyte proliferation and cell differentiation. The proliferative effects of both hormones are mediated by local IGF-I synthesis. Simultaneous coincubation with both hormones blunts the proliferative effect exerted by either hormone alone, in favor of a more marked stimulation of cell differentiation. 相似文献
7.
Daniel T. Baran Sook Won Lee O. D. Jo Louis V. Avioli 《Calcified tissue international》1982,34(1):165-168
Summary Classic (type I) renal tubular acidosis in children is attended by growth retardation and rickets, abnormalities that can
be corrected by alkali therapy alone. We have employed the NH4Cl-treated rachitic chick as a model to investigate vitamin D metabolism in the acidotic state. NH4Cl ingestion for 96 h was associated with a rise in serum calcium, a significant decrease in blood pH (7.42+0.08 vs 7.30±0.08,P<0.005), decreased [3H]1,25(OH)2D3 following [3H]25OHD D3 injections, and enhanced metabolic clearance of administered [3H]1,25(OH)2D3. The data collectively suggest that metabolic acidosis in the chick alters the production and degradation of 1,25(OH)2D3. 相似文献
8.
Yulin Zhou Jining Wang Peter J Malloy Zdenek Dolezel David Feldman 《Journal of bone and mineral research》2009,24(4):643-651
Hereditary vitamin D‐resistant rickets (HVDRR) is a rare recessive genetic disorder caused by mutations in the vitamin D receptor (VDR). In this study, we examined the VDR in a young girl with clinical features of HVDRR including rickets, hypophosphatemia, and elevated serum 1,25(OH)2D. The girl also had total alopecia. Two mutations were found in the VDR gene: a nonsense mutation (R30X) in the DNA‐binding domain and a unique 3‐bp in‐frame deletion in exon 6 that deleted the codon for lysine at amino acid 246 (ΔK246). The child and her mother were both heterozygous for the 3‐bp deletion, whereas the child and her father were both heterozygous for the R30X mutation. Fibroblasts from the patient were unresponsive to 1,25(OH)2D3 as shown by their failure to induce CYP24A1 gene expression, a marker of 1,25(OH)2D3 responsiveness. [3H]1,25(OH)2D3 binding and immunoblot analysis showed that the patient's cells expressed the VDRΔK246 mutant protein; however, the amount of VDRΔK246 mutant protein was significantly reduced compared with wildtype controls. In transactivation assays, the recreated VDRΔK246 mutant was unresponsive to 1,25(OH)2D3. The ΔK246 mutation abolished heterodimerization of the mutant VDR with RXRα and binding to the coactivators DRIP205 and SRC‐1. However, the ΔK246 mutation did not affect the interaction of the mutant VDR with the corepressor Hairless (HR). In summary, we describe a patient with compound heterozygous mutations in the VDR that results in HVDRR with alopecia. The R30X mutation truncates the VDR, whereas the ΔK246 mutation prevents heterodimerization with RXR and disrupts coactivator interactions. 相似文献
9.
Satoshi Suda Naoyuki Takahashi Toshimasa Shinki Noboru Horiuchi Akira Yamaguchi Shusaku Yoshiki Shoji Enomoto Dr. Tatsuo Suda 《Calcified tissue international》1985,37(1):82-90
Summary The role of vitamin D in the maturation of epiphyseal chondrocytes was investigated in the developing chick embryo. Cartilage
tissues were divided into two parts: resting cartilage and growth cartilage. A cytosol component to which 1α,25-dihydroxyvitamin
D3 (1α,25(OH)2D3) is specifically bound first appeared in the growth cartilage on day 15, rapidly increased, and attained a maximum on day
19. The calcium content of the growth cartilage also began to increase on day 15 and continued to increase in parallel with
the 1α,25(OH)2D3 receptor levels. Glycosaminoglycan (GAG) synthesis by the growth cartilage cells increased from day 11–17 and rapidly declined
thereafter reciprocally with the increase in calcium and receptor levels. In the resting cartilage, no cytosol receptor for
1α,25(OH)2D3 was detected up to hatching time. The calcium content and GAG synthesis in the resting cartilage were very low and did not
change appreciably throughout development. No receptor-like macromolecule for 24R,25-dihydroxyvitamin D3 (24R,25(OH)2D3) was recognized in either the resting or growth cartilage. 1α,25(OH)2D3 added to the culture of chondrocytes from the epiphyseal growth cartilage inhibited GAG synthesis and stimulated its release
from the cell layer into the medium in a dose-dependent manner. Thesein vitro effects of 1α,25(OH)2D3 were not observed in chondrocytes obtained from 13-day-old growth cartilage and 19-day-old resting cartilage. 25-Hydroxyvitamin
D3 and 24R,25(OH)2D3 had no effect on chondrocytes in any of the preparations. These results suggest that 1α,25(OH)2D3 is directly involved in the maturation of chondrocytes and possibly in the calcification of growth cartilage. 相似文献
10.
《BONE》2014
We present a brother and sister with severe rickets, alopecia and highly elevated serum levels of 1,25-dihydroxyvitamin D (1,25-(OH)2D3). Genomic sequencing showed a homozygous point mutation (A133G) in the vitamin D receptor gene, leading to an amino acid change in the DNA binding domain (K45E), which was described previously. Hereditary vitamin D resistant rickets (HVDRR) was diagnosed. Functional studies in skin biopsy fibroblasts confirmed this. 1,25-(OH)2D3 reduced T helper (Th) cell population-specific cytokine expression of interferon γ (Th1), interleukins IL-17A (Th17) and IL-22 (Th17/Th22) in peripheral blood mononuclear cells (PBMCs) from the patient's parents, whereas IL-4 (Th2) levels were higher, reflecting an immunosuppressive condition. None of these factors were regulated by 1,25-(OH)2D3 in PBMCs from the boy. At present, both patients (boy is 23 years of age, girl is 7) have not experienced any major immune-related disorders. Although both children developed alopecia, the girl did so earlier than the boy. The boy showed complete recovery from the rickets at the age of 17 and does not require any vitamin D supplementations to date.In conclusion, we characterized two siblings with HVDRR, due to a mutation in the DNA binding domain of VDR. Despite a defective T cell response to vitamin D, no signs of any inflammatory-related abnormalities were seen, thus questioning an essential role of vitamin D in the immune system. Despite the fact that currently medicine is not required, close monitoring in the future of these patients is warranted for potential recurrence of vitamin D dependence and diagnosis of (chronic) inflammatory-related diseases. 相似文献
11.
D. D. Dean B. D. Boyan O. E. Muniz D. S. Howell Z. Schwartz 《Calcified tissue international》1996,59(2):109-116
Matrix vesicles are extracellular organelles produced by cells that mineralize their matrix. They contain enzymes that are
associated with calcification and are regulated by vitamin D metabolites in a cell maturation-dependent manner. Matrix vesicles
also contain metalloproteinases that degrade proteoglycans, macromolecules known to inhibit calcificationin vitro, as well as plasminogen activator, a proteinase postulated to play a role in activation of latent TGF-\. In the present study,
we examined whether matrix vesicle metalloproteinase and plasminogen activator are regulated by 1,25(OH)2D3 and 24,25 (OH)2D3. Matrix vesicles and plasma membranes were isolated from fourth passage cultures of resting zone chondrocytes that had been
incubated with 1010-10-7 M24,25(OH)2D3 or growth zone chondrocytes incubated with 10-11-l0-8 M 1,25(OH)2D3, and their alkaline phosphatase, active and total neutral metalloproteinase, and plasminogen activator activities determined.
24,25(OH)2D3 increased alkaline phosphatase by 35–60%, decreased active and total metalloproteinase by 75%, and increased plasminogen
activator by fivefold in matrix vesicles from resting zone chondrocyte cultures. No effect of vitamin D treatment was observed
in plasma membranes isolated from these cultures. In contrast, 1,25(OH)2D3 increased alkaline phosphatase by 35–60%, but increased active and total metalloproteinase three- to fivefold and decreased
plasminogen activator by as much as 75% in matrix vesicles isolated from growth zone chondrocyte cultures. Vitamin D treatment
had no effect on plasma membrane alkaline phosphatase or metalloproteinase, but decreased plasminogen activator activity.
The results demonstrate that neutral metalloproteinase and plasminogen activator activity in matrix vesicles are regulated
by vitamin D metabolites in a cell maturation-specific manner. In addition, they support the hypothesis that 1,25(OH)2D3 regulation of matrix vesicle function facilitates calcification by increasing alkaline phosphatase and phospholipase A2 specific activities as well as metalloprotemases which degrade proteoglycans. 相似文献
12.
Background : 1α,25‐dihydroxyvitamin D3 (1,25[OH]2D3) has been shown to inhibit the proliferation of various cancer cells including colon, prostate, melanoma, osteosarcoma and breast cancer. Methods : The human hepatoma cell line (HepG2) was cultured with 1,25(OH)2D3 or one of two analogues EB1089 or CB1093 for various durations. Cellular proliferation was measured by uptake of [3H]thymidine, and cell numbers were determined by trypan blue exclusion counting. Results : 1,25(OH)2D3, EB1089 and CB1093 all inhibited proliferation of HepG2 by up to 90% after 5 days of treatment, compared to the untreated controls. Decreased proliferation was associated with an approximately 50% reduction in cell numbers at concentrations of up to 10–10 mol/L after 5 days of treatment with 1,25(OH)2D3. Cell proliferation rapidly recovered in cultures treated with lower concentrations of 1,25(OH)2D3 (10–10 and 10–11 mol/L) when 1,25(OH)2D3 was removed from the cultures by placing cells in serum containing medium without 1,25(OH)2D3. When HepG2 cells were treated with 10–8 mol/L 1,25(OH)2D3 for 5 weeks, there was still significant inhibition of proliferation, although at week 5 there was 66% inhibition compared to 93% at the end of week 1. Conclusions : 1,25(OH)2D3, EB1089 and CB1093 all significantly inhibit the proliferation of HepG2 hepatoblastoma cells, with EB1089 being the most potent at lower concentrations. Inhibition can be maintained for at least 4 weeks, but is reversed after removal of vitamin D3. 相似文献
13.
Summary The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], exerts its biological effects by binding to a cytosolic receptor protein. Such a protein has been demonstrated in vitamin
D3 target organs including fetal rat calvariae and more recently in rat osteogenic sarcoma cells. In this study we have compared
the binding of 25-hydroxyvitamin D3 [25(OH)D3] and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] to that of 1,25-(OH)2D3 in fetal rat calvariae and osteogenic sarcoma (OS) cells. Sucrose density sedimentation, DNA-cellulose chromatography, and
intracellular uptake studies have been employed to evaluate these interactions.
In cytosol preparations from calvariae, [3H]-1,25(OH)2D3 bound to a 3.3S macromolecule and to a much greater extent to a 5.8S macromolecule while both [3H]25(OH)D3 and [3H]24,25(OH)2D3 bound to the 5.8S macromolecule. By incubating intact calvariae and OS cells with labeled metabolites and thus establishing
binding intracellularly prior to cell disruption, we have found that the 3.3S protein which has high specificity for 1,25(OH)2D3 occurs inside the cells; the 5.8S protein, however, does not occur inside the cells but is generated after cell disruption.
The [3H]-1,25(OH)2D3-receptor complex adsorbed to DNA-cellulose and was eluted from this affinity resin at 0.28M KCl. In contrast, [3H]25(OH)D3 and [3H]-24,25(OH)2D3 binding activity did not adsorb to DNA-cellulose. We conclude that, in contrast to the 3.3S protein, the 5.8S macromolecule
does not fulfill receptor criteria but is rather generated by the experimental manipulation of the bone cells. Our data suggest
that the vitamin D3 actions on bone are mediated only via the 3.3S receptor, and hence quantitative but not qualitative differences of the effects
of the various metabolites are feasible.
With technical assistance by M. Larsen, D. Meler, and M. LaFrance. 相似文献
14.
J. Rubin X. Fan D. Thornton R. Bryant D. Biskobing 《Calcified tissue international》1996,59(4):291-296
Macrophage colony stimulating factor (MCSF) is important for formation of osteoclasts. We investigated the ability of 1,25(OH)2D3 to regulate osteoblast production of MCSF. Mouse calvarial osteoblasts were cultured for 2 days ± 1,25(OH)2D3. Since 1,25(OH)2D3 decreased osteoblast proliferation by 17.6 ± 1% at 10 nM and 11 ± 4% at 1 nM, the effect of growth rate on MCSF secretion
was examined. Limiting cell proliferation by serum did not affect MCSF production. 1,25(OH)2D3 (1 nM) increased MCSF production (U/105 cells) maximally by 68 ± 33% (n = 3) with an ED50 for 1,25(OH)2D3 of 5 × 10−11 M. To investigate effects of 1,25(OH)2D3 on MCSF gene regulation, RT-PCR primers were designed to identify the mRNA coding for the membrane-bound isoform of MCSF.
Simultaneous RT-PCR of glyceraldehyde-phosphate dehydrogenase (GAP) allowed semiquantitative assessment of MCSF mRNA between
treatment groups expressed as the MCSF/GAP RT-PCR product ratio; both MCSF and GAP (+) primers were labeled with 32P-ATP for phosphorimage quantitation. The membrane-bound MCSF/GAP PCR product ratio was not affected by proliferative rate
when growth was limited by [serum]. The MCSF/GAP RT-PCR product ratio was dose dependently increased by 1,25(OH)2D3, maximally at 1 nM at 2.2 ± 0.2 = fold (n = 10). 1,25 (OH)2D3 also increased the expression of an RT-PCR MCSF/GAP product ratio which represented the secreted isoform of MCSF. The ability
of 1,25(OH)2D3 to pretranslationally regulate expression of membrane-bound osteoblast MCSF may be important in osteoblast:osteoclast interactions.
Received: 12 August 1995 / Accepted: 25 March 1996 相似文献
15.
Summary Binding of [3H] 1,25 (OH)2D3 and effects of 1,25 (OH)2D3 on cell ultrastructure were evaluated in vascular smooth muscle cells (VSMC) primary cultures (aortic media). Specific reversible
binding of [3H] 1,25 (OH)2D3 by a 3.5 S macromolecule with DNA binding, KD 6.2×10−10M and Nmax 16 fmol/mg protein was demonstrated. Incubation of VSMC with 10−8 M 1,25 (OH)2D3, but not 25 (OH)D3, in the presence of 10% FCS for up to three weeks caused rapid reversible appearance in the cytoplasm of membrane-bounded
electron-dense lysosomal particles which on electronspectroscopic imaging contained Ca and Pi. VSMC are targets for vitamin
D. 相似文献
16.
S. C. Miller B. P. Halloran H. F. DeLuca S. Yamada H. Takayama W. S. S. Jee 《Calcified tissue international》1981,33(1):489-497
Summary To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological
methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical
of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment
with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially
reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal
primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone
parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no
role in the modeling and mineralization of bone. 相似文献
17.
18.
1,25‐Dihydroxyvitamin D3 [1,25(OH)2D3] has many noncalcemic actions that rest on inhibition of proliferation and promotion of differentiation in malignant and normal cell types. 1,25(OH)2D3 stimulates osteoblast differentiation of human marrow stromal cells (hMSCs), but little is known about the effects of 25‐hydroxyvitamin D3 [25(OH)D3] on these cells. Recent evidence shows that hMSCs participate in vitamin D metabolism and can activate 25(OH)D3 by CYP27B1/1α‐hydroxylase. These studies test the hypothesis that antiproliferative and prodifferentiation effects of 25(OH)D3 in hMSCs depend on CYP27B1. We studied hMSCs that constitutively express high (hMSCshi‐1α) or low (hMSCslo‐1α) levels of CYP27B1 with equivalent expression of CYP24A1 and vitamin D receptor. In hMSCshi‐1α, 25(OH)D3 reduced proliferation, downregulated proliferating cell nuclear antigen (PCNA), upregulated p21Waf1/Cip1, and decreased cyclin D1. Unlike 1,25(OH)2D3, the antiapoptotic effects of 25(OH)D3 on Bax and Bcl‐2 were blocked by the P450 inhibitor ketoconazole. The antiproliferative effects of 25(OH)D3 in hMSCshi‐1α and of 1,25(OH)2D3 in both samples of hMSCs were explained by cell cycle arrest, not by increased apoptosis. Stimulation of osteoblast differentiation in hMSCshi‐1α by 25(OH)D3 was prevented by ketoconazole and upon transfection with CYP27B1 siRNA. These data indicate that CYP27B1 is required for 25(OH)D3's action in hMSCs. Three lines of evidence indicate that CYP27B1 is required for the antiproliferative and prodifferentiation effects of 25(OH)D3 on hMSCs: Those effects were not seen (1) in hMSCs with low constitutive expression of CYP27B1, (2) in hMSCs treated with ketoconazole, and (3) in hMSCs in which CYP27B1 expression was silenced. Osteoblast differentiation and skeletal homeostasis may be regulated by autocrine/paracrine actions of 25(OH)D3 in hMSCs. © 2011 American Society for Bone and Mineral Research. 相似文献
19.
Simon Wöhrle Christine Henninger Olivier Bonny Anne Thuery Noemie Beluch Nancy E Hynes Vito Guagnano William R Sellers Francesco Hofmann Michaela Kneissel Diana Graus Porta 《Journal of bone and mineral research》2013,28(4):899-911
Fibroblast growth factor 23 (FGF23) is a circulating factor secreted by osteocytes that is essential for phosphate homeostasis. In kidney proximal tubular cells FGF23 inhibits phosphate reabsorption and leads to decreased synthesis and enhanced catabolism of 1,25‐dihydroxyvitamin D3 (1,25[OH]2D3). Excess levels of FGF23 cause renal phosphate wasting and suppression of circulating 1,25(OH)2D3 levels and are associated with several hereditary hypophosphatemic disorders with skeletal abnormalities, including X‐linked hypophosphatemic rickets (XLH) and autosomal recessive hypophosphatemic rickets (ARHR). Currently, therapeutic approaches to these diseases are limited to treatment with activated vitamin D analogues and phosphate supplementation, often merely resulting in partial correction of the skeletal aberrations. In this study, we evaluate the use of FGFR inhibitors for the treatment of FGF23‐mediated hypophosphatemic disorders using NVP‐BGJ398, a novel selective, pan‐specific FGFR inhibitor currently in Phase I clinical trials for cancer therapy. In two different hypophosphatemic mouse models, Hyp and Dmp1‐null mice, resembling the human diseases XLH and ARHR, we find that pharmacological inhibition of FGFRs efficiently abrogates aberrant FGF23 signaling and normalizes the hypophosphatemic and hypocalcemic conditions of these mice. Correspondingly, long‐term FGFR inhibition in Hyp mice leads to enhanced bone growth, increased mineralization, and reorganization of the disturbed growth plate structure. We therefore propose NVP‐BGJ398 treatment as a novel approach for the therapy of FGF23‐mediated hypophosphatemic diseases. © 2013 American Society for Bone and Mineral Research. 相似文献
20.
M. Eguchi K. Shibata F. Wada H. Kawamura T. Shimauchi E. Shiota Y. Sugioka 《International orthopaedics》1987,11(1):77-82
Summary When HEBP (1-hydroxyethylidene-1, 1-biphosphonic acid) was administered to young rats in large doses over a short period rickets was consistently produced. When HEBP was administered concomitantly with 1,25 (OH)2D3 or calcitonin (CT), calcification appeared in the growth-plate cartilage where there had been an increase in thickness due to the inhibition of calcification.This experiment was done in an attempt to clarify differences in the calcification-promoting mechanisms of 1,25 (OH)2D3 and CT. The serum alkaline phosphatase level was reduced in rats with an accelerated calcification following the administration of 1,25 (OH)2D3, but there was no reduction in the serum alkaline phosphatase level in rats in which the calcification was accelerated by the administration of CT. The mode of appearance of calcification in the growth-plate cartilage by 1,25 (OH)2D3 or CT differed, depending on the time of administration.These results suggest that mechanisms involved in the enhancement of calcification by 1,25 (OH)2D3 and CT differ in cases where rickets are induced by HEBP.
Résumé Lorsqu'on administre à de jeunes rats de l'HEBP (acide 1-hydroxyéthylène-1,1-biphosphonique) à fortes doses et sur une courte période, on constate l'apparition d'un rachitisme à bonne reproductibilité. Dans le cas d'une administration concomitante d'HEBP et de 1,25 (OH)2 D3 ou de calcitonine (CT), apparaît une calcification du cartilage de croissance là où celui-ci s'était épaissi à la suite de l'inhibition de la calcification.Cette expérience a été réalisée pour tenter de préciser les différences entre les mécanismes accélérant la calcification par l'1,25 (OH)2 D3 our par la calcintonine. Le taux de phosphatase alcaline baisse chez les rats dont la calcification a été accélérée par le 1,25 (OH)2 D3 tandis que l'administration de CT, qui accélère également la calcification, ne provoque aucune baisse du taux de phosphatase alcaline du sérum. Le mode d'apparition de la calcification du cartilage de croissance par le 1,25 OH2 D3 ou par la CT dépend de le la durée d'administration.Ces résultats indiquent que les mécanismes d'accélération de la calcification du 1,25 (OH)2 D3 et de la CT sont différents lorsque le rachitisme est provoqué par l'HEBP.相似文献