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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dihydrotachysterol3, a reduced (or hydrogenated) analog of vitamin D3 in which the A ring has been rotate through 180 degrees , is, after hepatic 25-hydroxylation, converted in vivo to a dihydroxylated metabolite, termed peak H, which is at present unidentified but with good affinity for the vitamin D receptor. Although peak H is made in relatively large amounts in vivo, it has not yet been possible to synthesize it in vitro. Mass spectrometric evidence suggests that peak H is 25-hydroxylated and the presumption that it is a metabolite of 25-hydroxydihydrotachysterol3 was confirmed by the demonstration that radiolabeled peak H was formed in vivo in the rat after injection of 25-hydroxy-[10,19-3H]dihydrotachysterol3, produced from [10,19-3H]dihydrotachysterol3 in a hepatic cell model. The metabolism of 25-hydroxy-[10,19-3H]dihydrotachysterol3 was also studied in a rat osteosarcoma cell UMR-106, a known target cell for vitamin D, using high (11 microM) and low (10 nM) substrate concentrations. Metabolic products were isolated by lipid extraction, purified by high-performance liquid chromatography, and characterized by direct-probe mass spectrometry and gas chromatography/mass spectrometry. The formation of peak H from 25-hydroxydihydrotachysterol3 could not be demonstrated in UMR-106 cells. However, 25-hydroxydihydrotachysterol3 was metabolized to at least seven side-chain modified metabolites, each of which was extensively characterized and tentatively identified. It is concluded that the vitamin D enzyme system present in UMR-106 cells is able to metabolize dihydrotachysterol3 very efficiently to a series of metabolites but is incapable of producing peak H.
Steroids 1992 May
PMID:Metabolism of 25-hydroxydihydrotachysterol3 in bone cells in vitro. 133 6

24-Oxa-vitamin D3 (24-oxa-D3) and 24-oxa-1 alpha-hydroxyvitamin D3 were designed as possible inhibitors of the vitamin D metabolic activation pathway. Their affinity for the vitamin D receptor (from pig intestine) and human vitamin binding protein were reduced, and their potency to induce cell differentiation of human leukemia cells (HL 60) or osteosarcoma cells (MG 63) was markedly reduced (19% and 3%, respectively), in comparison with calcitriol. A single or chronic injection of 24-oxa-D3 had no biological activity, whereas chronic administration of 24-oxa-1 alpha-hydroxy-D3 showed weak agonist activity in rachitic chicks. When the 24-oxa-D3 was given prior to a single injection of vitamin D3, lower values of serum calcium (64% of the value obtained in vitamin D-treated animals), osteocalcin (52%), 25-(OH)D3 (45%) and duodenal calbindin-D 28K (9.4%) were found. When given chronically in a 100-fold more excess no clear antagonistic effects were observed. 24-Oxa-D3 is thus a new metabolic weak antagonist of vitamin D3, but adding a hydroxyl group at C-1 creates a weak agonist.
Steroids 1995 Jun
PMID:Antagonistic activity of 24-oxa-analogs of vitamin D. 767 83

The biological activity of 16-epoxy side-chain analogs of 1 alpha,25-dihydroxyvitamin D3, (1 alpha,25(OH)2D3) was evaluated in vitro and in vivo. Compared to 1 alpha,25(0H)2D3, all analogs had lower affinities for the pig duodenal vitamin D receptor and also for the human serum vitamin D binding protein. The in vitro effects on cell proliferation or differentiation of human promyeloid leukemia (induction of superoxide production in HL-60 cells), human osteosarcoma MG-63 cells (osteocalcin secretion), or human breast cancer cells (incorporation of thymidine in MCF-7 cells), was markedly inhibited by several epoxy analogs, compared to 1 alpha,25(OH)2D3, but the rank order of their activity widely varied among different cancer cells. The most potent analogs (24S,25S-24-hydroxy-25,26-epoxy-22-ene-1 alpha-OHD3, 25,26-epoxy-23-yne-1 alpha-OHD3, and 25,26-epoxy-23-yne-20-epi-1 alpha-OHD3 or compounds, 16, 5, and 7, respectively) were equipotent (16 and 5) or 30-fold (compound 7 on MG-63 cells) to 40-fold (compound 7 on MCF-7 cells) more active than 1 alpha,25-(OH)2D3. These analogs were nevertheless poorly antirachitic (< 3%) when tested in vitamin D-deficient chicks (using serum and bone calcium, serum osteocalcin and duodenal calbindin D-28K, as end points). Compound 7 was also 100-fold more active than 1 alpha,25-(OH)2D3 in inhibition of proliferation of human foreskin keratinocytes. Some epoxy analogs of 1 alpha,25-(OH)2D3 thus display interesting dissociations between their receptor affinity and their potency to induce cell differentiation, whereas their effect on cell proliferation/differentiation exceed their calcemic effects more than 100- to 1000-fold.
Steroids 1995 Apr
PMID:Biological evaluation of epoxy analogs of 1 alpha,25-dihydroxyvitamin D3. 853 86

Starting with (20S)-20-(p-toluenesulfonyl)oxymethyl-pregna-1, 5-dien-3 alpha-ol (4), we synthesized three vitamin D analogs in 10 to 11 steps: 1 alpha, 26-dihydroxy-27-nor-vitamin D3 (1), its 3-epi analog (2), and 2 beta-methoxy-1 alpha, 26-dihydroxy-27-nor-vitamin D3 (3). We tested the derivatives in the murine mesenchymal cell line C3H1OT1/2. All substances were less potent in inhibition of cell proliferation, inhibition of adipocyte differentiation, and induction of gene activation, and had a lower affinity to the vitamin D receptor than the native vitamin D3 metabolite 1.25(OH)2D3. The affinity of 1 to the vitamin D binding protein was about three times higher than that of 1.25(OH)2D3.
Steroids 1996 Oct
PMID:Synthesis and biological activities of 26-hydroxy-27-nor-derivatives of 1 alpha, 25-dihydroxyvitamin D3. 891 Sep 73

A synthesis and an in vitro evaluation of side chain-unsaturated analogs 3 and 4 of 24a, 24b-dihomo-1,25-dihydroxycholecalciferol (1) are described, Novel C23a, 24-vitamin D synthons (sulfone 10 and aldehyde 11) were used for the synthesis of analog 4 and for the efficient preparation of the parent compound 1. The synthetic approach developed allows the use of easily available side chain fragments, such as oxirane 12 or Wittig reagent 15 for the preparation of compound 1 and analog 4, respectively. Introduction of a 24aE double bond results in a selective, 1000-fold increase in the binding affinity of analog 4 for the vitamin D receptor, compared to the affinity of 1, whereas the affinity of 4 for the vitamin D-binding protein and the activity in stimulating the differentiation of human promyelocytic leukemia HL-60 cells remained largely unchanged.
Steroids 1997 Jul
PMID:Synthesis and in vitro evaluation of side chain-unsaturated analogs of 24a,24b-dihomo-1,25-dihydroxycholecalciferol. 925 95

Anomalous diequatorial epoxide ring opening of 1 beta, 2 beta-oxido-cholesta-5,7-diene-3 beta, 25-diol 1 produces the 1 beta-hydroxy-2 alpha-chloro-provitamin 2 and its corresponding 1 beta-hydroxy-provitamin 3. The provitamins 2 and 3 are transformed by irradiation and thermal isomerization to 2 alpha-chloro-1-epicalcitriol NS3 (4) and 1-epicalcitriol NS8 (5), respectively. These two A-ring derivatives were tested for their in vitro biological activity in the mesenchymal, murine cell line C3H10T1/2, and their effects were compared with those of the native vitamin D3 derivatives 25(OH)D3 and 1.25(OH)2D3. NS3 and NS8 showed marked differences in their affinity for the vitamin D binding protein (DBP) and in their ability to inhibit cell proliferation. NS8 has the ability to bind to a high-affinity DBP-binding site for which 25(OH)D3 has none affinity. The 2 alpha-chloro-substitution (NS3) prevents binding to the postulated noncompetitive, NS8-specific DBP-binding site and diminishes the affinity to the vitamin D receptor (VDR) and therefore diminishing NS3's biological abilities. The elucidation of the structure-function relationships at the DBP-binding-sites could have major impact on the development of new vitamin D3 derivatives with extended serum half-life.
Steroids 1998 Jan
PMID:Synthesis and biological activities of 2 alpha-chloro-1-epicalcitriol and 1-epicalcitriol. 943 92

Synthesis of novel C19-modified affinity and photoaffinity analogs of vitamin D3 and 25-hydroxyvitamin D3(25-OH-D3) is described. A key step in the synthesis is a Horner-Emmons reaction between C19-nor-cyclovitamin D3-C19-ketone or C19-nor-25-hydroxy-cyclovitamin D3-C19-ketone and diethyl cyanomethylphosphonate. Competitive radioligand binding assays with human serum vitamin D-binding protein (DBP) and 5E-[19-(2-bromoacetoxy)methyl]25-hydroxyvitamin D3 and 5E-25-hydroxyvitamin D3-19-methyl[(4-azido-2-nitro)phenyl]-glycinate, 25-OH-D3-analogs containing affinity and photoaffinity probes at C19-position, demonstrated that these compounds displaced radiolabeled 25-OH-D3 from the binding pocket of DBP in a dose-dependent manner. Thus, these affinity and photoaffinity analogs are potentially useful in determining the ligand binding site topographies of DBP and possibly the vitamin D receptor.
Steroids 1998 Apr
PMID:Synthesis and binding-analysis of 5E-[19-(2-bromoacetoxy)methyl]25-hydroxyvitamin D3 and 5E-25-hydroxyvitamin D3-19-methyl[(4-azido-2-nitro)phenyl]glycinate: novel C19-modified affinity and photoaffinity analogs of 25-hydroxyvitamin D3. 958 57

Calcitrol, 1,25 dihydroxyvitamin D3 (1,25-D3) has an important role in the antiproliferative and growth regulatory effects on normal and neoplastic cells (e.g. prostate cancer cells). 1,25-D3 binds to the vitamin D receptor (VDR), a member of the steroid receptor superfamily. Steroids, via intranuclear receptors, have been demonstrated to have high affinity binding to the nuclear matrix, the tissue specific scaffolding of the nucleus that is involved in the organization of DNA, replication and transcription. We hypothesized that the VDR interacts closely with the nuclear matrix in both human and rat tissues. In the studies described here, nuclear matrix proteins (NMP) were extracted from a number of rat and human tissues and immunoblot analysis performed using a rat anti-VDR antibody. The results from these studies reveal that the anti-VDR antibody detects six forms of the VDR in the NMP preparations: human testis demonstrated a protein of 57 and 52 kDa molecular weight compared with 57 and 37 kDa in the rat testis. Human prostate demonstrated proteins of 52 kDa compared to rat ventral (57 and 37 kDa) and dorsal prostate (52 and 26 kDa). Human and rat bladder NMP demonstrated a protein binding at 55 kDa and rat seminal vesicle NMP binding at 48 kDa. This is the first report of VDRs associated with the nuclear matrix. The varying molecular weight proteins reactive with the anti-VDR antibody within these tissues may represent different isoforms, proteolytic cleavage of a larger VDR or post-translational modification. The VDR-NMP interaction may be involved in the tissue specific actions of 1,25-D3 especially growth regulatory and antiproliferative effects.
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PMID:Association of vitamin D receptors with the nuclear matrix of human and rat genitourinary tissues. 974 21

Using 1 alpha,2 alpha-oxido-cholesta-5,7-diene-3 beta,25-diol (2) as a starting material, the provitamins of calcitriol with an additional 2 beta-chloro-, 2 beta-fluoro-, and 2 beta-methoxy-substituent (3,4,5) are obtained by transdiaxial opening of the oxirane ring with nucleophiles. An efficient irradiation process is described and used for the synthesis of the 2 beta-substituted calcitriols NS2 (2 beta-Cl), NS6 (2 beta-F), and NS7 (2 beta-OCH3). The affinity of these three vitamin D3 derivatives to the vitamin D receptor (VDR) and was determined. These three A-ring derivatives of 1,25(OH)2D3 were further tested for their proliferation-inhibitory and anti-adipogenic activity and gene regulatoric activity in the vitamin D3-sensitive, murine, mesenchymal cell line C3H10T1/2. The VDR-affinity of the 2 beta-chloro derivative, NS2 (2 beta-Cl), was identical to 1,25(OH)2D3 and its vitamin D binding protein (DBP)-affinity was in the range of 1,25(OH)2D3. NS2 inhibited the proliferation of C3H10T1/2(BMP-4)-cells in the presence of fetal calf serum (FCS) 9 times, and, in the absence of FCS, 111 times lower, as compared with 1,25(OH)2D3. The ID50 dose of adipogenesis-inhibition of NS2 was 13 times higher than the ID50 dose of 1,25(OH)2D3. NS6 (2 beta-F) displayed a slightly higher affinity than 1,25(OH)2D3 to the VDR and DBP-affinity. The proliferation-inhibitory activity in the presence of FCS was 90 times higher, as compared with 1,25(OH)2D3. In the FCS-free proliferation assay NS6 displayed an inhibitory activity in the range of 1,25(OH)2D3. NS6 showed an 5 times higher potency to inhibit (pre)adipocyte-differentiation in C3H10T1/2(BMP-4)-cells than 1,25(OH)2D3. NS7 (2 beta-OCH3) showed the lowest VDR-affinity and the highest DBP-affinity of the tested substances, as compared with 1,25(OH)2D3 (11 times lower and 35 times higher respectively). Its proliferation-inhibitory activity in the FCS-free medium was 9 times and in the FCS-containing assay 67 times lower in comparison with 1,25(OH)2D3. A 1250 times higher NS7-dose was needed to reach the anti-adipogenic potency of 1,25(OH)2D3. All tested substances displayed a similar ability to activate a vitamin D responsive element-regulated reporter gene compared to 1,25(OH)2D3 (NS2 and NS6: 1.3 times higher activity; NS7: 1,4 times lower activity).
Steroids 1998 Dec
PMID:Synthesis and biological activities of 2 beta-chloro-, 2 beta-fluoro-, and 2 beta-methoxy-1 alpha,25-dihydroxyvitamin D3. 987 Feb 60

1,25-(OH)2D3 (1,25) exerts its effects on growth plate chondrocytes through classical vitamin D (VDR) receptor-dependent mechanisms, resulting in mineralization of the extracellular matrix. Recent studies have shown that membrane-mediated mechanisms are involved as well. 1,25 targets cells in the prehypertrophic and upper hypertrophic zones of the costochondral cartilage growth plate (GC cells), resulting in increased specific activity of alkaline phosphatase (ALP), phospholipase A2 (PLA2), and matrix metalloproteinases (MMPs). At the cellular level, 1,25 action results in rapid changes in arachidonic acid (AA) release and re-incorporation, alterations in membrane fluidity and Ca ion flux, and increased prostaglandin E1 and E2 (PGE2) production. Protein kinase C (PKC) is activated in a phospholipase C (PLC) dependent-mechanism, due in part to the increased production of diacylglycerol (DAG). In addition, AA acts directly on the cell to increase PKC specific activity. AA also provides a substrate for cyclooxygenase (COX), resulting in PGE2 production. 1,25 mediates its effects through COX-1, the constitutive enzyme, but not COX-2, the inducible enzyme. Time course studies using specific inhibitors of COX-1 show that AA stimulates PKC activity and PKC then stimulates PGE2 production. PGE2 acts as a mediator of 1,25 action on the cells, also stimulating PKC activity. The rapid effects of 1,25 on PKC are nongenomic, occurring within 3 min and reaching maximal activation by 9 min. It promotes translocation of PKC to the plasma membrane. When 1,25 is incubated directly with isolated plasma membranes, PKCalpha is stimulated although PKCzeta is also present. In contrast, when isolated matrix vesicles (MVs) are incubated with 1,25, PKCzeta is inhibited and PKCalpha is unaffected. These membrane-mediated effects are due to the presence of a specific membrane vitamin D receptor (mVDR) that is distinct from the classical cytosolic VDR. Studies using 1,25 analogs with reduced binding affinity for the classical VDR, confirm that rapid activation of PKC by 1,25 is not VDR dependent. The membrane-mediated effects of 1,25 are critical to the regulation of events in the extracellular matrix produced by the chondrocytes. MVs are extracellular organelles associated with maturation of the matrix, preparing it for mineralization. MV composition is under genomic control, involving VDR-mechanisms. In the matrix, no new gene expression or protein synthesis can occur, however. Differential distribution of PKC isoforms and their nongenomic regulation by 1,25 is one way for the chondrocyte to control events at sites distant from the cell. GC cells contain 1a-hydroxylase and produce 1,25; this production is regulated by 1,25, 24,25, and dexamethasone. 1,25 stimulates MMPs in the MVs, resulting in increased proteoglycan degradation in mineralization gels, and increased activation of latent transforming growth factor-beta 1 (TGF-beta1).
Steroids
PMID:1,25-(OH)2D3 modulates growth plate chondrocytes via membrane receptor-mediated protein kinase C by a mechanism that involves changes in phospholipid metabolism and the action of arachidonic acid and PGE2. 1032 81


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