Synthesis of 28,28,28-trideutero-25-hydroxydihydrotachysterol2.

As part of our program on synthesis of labeled vitamin D metabolites and analogs, we describe here an efficient and versatile synthetic approach to 28,28,28-trideutero- 25-hydroxydihydrotachysterol2 where isotopic labeling was incorporated stereoselectively in the last step of the synthesis. This deuterated compound will allow the study this analog in vitro or in vivo and to measure AT10-like compounds in serum by LC-MS/MS.

Vitamin D deficiency in community-acquired pneumonia: low levels of 1,25(OH)2 D are associated with disease severity.

OBJECTIVES: We aimed to explore the association between vitamin D levels and the severity, mortality and microbiological etiology of community-acquired pneumonia. METHODS: Vitamin D levels (both, the reservoir form 25-OH and the activated form 1,25-OH2) of 300 randomly selected patients with community-acquired pneumonia due to pre-specified pathogens included in the German competence network (CAPNETZ) study were measured. Prior to statistical analysis, values of 25-OH and 1,25-OH2 were power-transformed to achieve parametric distribution. All further analyses were performed with seasonally and age adjusted values. RESULTS: There was only a modest (Spearman Coefficient 0.38) positive correlation between 25-OH and 1,25-OH2. For 1,25-OH2 but not 25-OH, the general linear model revealed a significant inverse correlation between serum concentration and CURB score (p = 0.011). Liver and respiratory co-morbidity were associated with significantly lower 25-OH values and renal co-morbidity with significantly lower 1,25-OH2 values. No significant differences of 1,25-OH2 or 25-OH between different pathogens (influenza virus, Legionella spp., Streptococcus pneumoniae) were detected. CONCLUSION: For 1,25-OH2, we found a significant and independent (controlled for age, season and pathogen) negative correlation to pneumonia severity. Therefore, supplementation of non-activated vitamin D to protect from pneumonia may be non-sufficient in patients that have a decreased capacity to hydroxylate 25-OH to 1,25-OH2.

1,25(OH)(2)D(3) blocks TNF-induced monocytic tissue factor expression by inhibition of transcription factors AP-1 and NF-kappaB.

An essential coagulation factor, tissue factor (TF), is rapidly expressed by human monocytes when exposed to a variety of agonists, such as lipopolysaccharide or tumor necrosis factor (TNF). We previously found that 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and its potent synthetic analogs downregulate TF and upregulate thrombomodulin expression on monocytic cells, counteracting the effects of TNF at the level of transcription. The human TF gene has characteristic binding sequences for activator protein-1 (AP-1) (c-Jun/c-Fos), nuclear factor-kappaB (NF-kappaB), Sp-1, and early growth response factor-1 (Egr-1). In this study, we investigated the regulatory mechanisms by which 1,25(OH)(2)D(3) inhibits TNF-induced TF expression in human monocytic cells. 1,25(OH)(2)D(3) reduced basal and TNF-induced TF activities. Gel-shift assay and luciferase assay with the respective reporter vectors showed that 1,25(OH)(2)D(3) reduced basal and TNF-induced activities of the nuclear proteins AP-1 and NF-kappaB, but not Egr-1. 1,25(OH)(2)D(3) inhibited TNF-induced phosphorylation of c-Jun without affecting phosphorylation of the other pathways. On the other hand, 1,25(OH)(2)D(3) directly inhibited nuclear binding and activities of NF-kappaB in the nucleus without affecting phosphorylation of the NF-kappaB activation pathway. These results indicate that 1,25(OH)(2)D(3) suppresses basal and TNF-induced TF expression in monocytic cells by inhibition of AP-1 and NF-kappaB activation pathways, but not of Egr-1. Our results may help to elucidate the regulatory mechanisms of 1,25(OH)(2)D(3) in TF induction, and may have physiological significance in the clinical challenge to use potential 1,25(OH)(2)D(3) analogs in antithrombotic therapy as well as immunomodulation and antineoplastic therapy of leukemia.

Prevalence and correction of 25(OH) vitamin D deficiency in peritoneal dialysis patients.

BACKGROUND: Peritoneal dialysis (PD) patients are at risk for 25(OH) vitamin D deficiency due to effluent loss in addition to traditional risk factors. OBJECTIVES: To measure 25(OH) vitamin D deficiency in prevalent PD patients, to evaluate a replacement dose, and to determine the effects of correction. METHODS: 25(OH) vitamin D levels were drawn on prevalent PD patients. Patients deficientin 25(OH) vitamin D were given ergocalciferol, 50000 IU orally once per week for 4 weeks. Patients scored muscle weakness, bone pain, and fatigue on a scale of 0 (none) to 5 (severe). Serum calcium, phosphate, parathyroid hormone (PTH), and 25(OH) vitamin D, and 1,25(OH)2 vitamin D levels were obtained before and after treatment. RESULTS: 25(OH) vitamin D levels were measured in 29 PD patients. Deficiency (<15 ng/mL) was found in 28/29 (97%); 25/29 (86%) had undetectable levels (<7 ng/mL). One course of ergocalciferol corrected the deficiency in all but 1 patient, who required a second course. Scores for muscle weakness and bone pain fell from pre- to posttreatment (p < 0.001). 1,25(OH)2 vitamin D levels rose post ergocalciferol (from 20 to 26 pg/mL, n = 20, p = 0.09). Serum calcium, phosphate, and PTH levels did not change with ergocalciferol. CONCLUSIONS: Most PD patients had marked 25(OH) vitamin D deficiency, which was readily and safely corrected with one course of 50000 IU ergocalciferol, having no effect on serum calcium, phosphorus, or PTH, but complaints of muscle weakness and bone pain decreased. A prospective, placebo-controlled double-blinded study is needed to determine whether replacement of 25(PH) vitamin D is beneficial in PD patients.

Potent suppression of the parathyroid glands by hydroxylated metabolites of dihydrotachysterol(2).

BACKGROUND: Dihydrotachysterol(2), a licensed pharmaceutical, is hydroxylated to 25-hydroxydihydrotachysterol(2) (25(OH)DHT(2)) and 1 alpha,25-dihydroxydihydrotachysterol(2) (1 alpha,25(OH)(2)DHT(2)) in man. We have compared the biological activity of these metabolites with calcitriol and the 'non-calcaemic' analogue, 22-oxacalcitriol (OCT) in bovine parathyroid cell cultures and in rats. METHODS: The effect of each sterol on parathyroid hormone (PTH) secreted by primary bovine parathyroid cells was measured. High-performance liquid chromotography and gas chromotography-mass spectrometry were used to investigate in vitro 25(OH)DHT(2) metabolism. Rats were given a single intraperitoneal injection or five daily injections of each sterol, and changes in ionized calcium and PTH were measured. RESULTS: In vitro, all sterols suppressed PTH significantly. Calcitriol and OCT were of similar potency, but 1 alpha, 25(OH)(2)DHT(2) and 25(OH)DHT(2) required higher concentrations to suppress PTH equally. We were unable to detect metabolism of 25(OH)DHT(2) to 1 alpha,25(OH)(2)DHT(2) in vitro. In rats, a single dose of 0.5 microg/rat of calcitriol increased ionized calcium at 30 and 40 h (statistically significant at 48 h). 50 microg of OCT and 1 alpha,25(OH)(2)DHT(2) did not cause significant hypercalcaemia at 48 h, although 1 alpha,25(OH)(2)DHT(2) caused hypercalcaemia at 30 h. In contrast, 50 microg of 25(OH)DHT(2) caused hypercalcaemia at 48 h but not at 30 h. Five daily doses of 0.001 microg/rat of calcitriol caused a significant rise in calcium and a 50% fall in PTH. OCT and 1 alpha,25(OH)(2)DHT(2) at 0.025 and 0.5 microg/rat respectively caused similar suppression of PTH but without hypercalcaemia. CONCLUSION: 1 alpha,25(OH)(2)DHT(2) and 25(OH)DHT(2) are potent suppressors of PTH in vitro and in vivo. 25(OH)DHT(2) may be active by virtue of its pseudo-1 alpha-hydroxyl group. Hypercalcaemia caused by a single dose of 1 alpha,25(OH)(2)DHT(2) appeared to be more transient than calcitriol. Five daily doses of 1 alpha, 25(OH)(2)DHT(2) and OCT could achieve 50% suppression of PTH without significant increments in ionized calcium. In contrast, suppression of PTH by calcitriol was associated with significant increments in ionized calcium. These data suggest that like OCT, 1 alpha, 25(OH)(2)DHT(2) can dissociate calcaemic actions from parathyroid-suppressing actions in a manner that may be therapeutically useful.

Effects of new analogues of vitamin D on bone cells: implications for treatment of uremic bone disease.

BACKGROUND: The use of calcitriol in the treatment of uremic hyperparathyroidism and renal osteodystrophy is limited in many patients by hypercalcemic side-effects. New less calcemic analogues of calcitriol are being developed, and some are under clinical evaluation. To investigate whether these compounds possess important differences in their action on bone cells, we have studied their effects [with and without parathyroid hormone (PTH)] on the release and synthesis of the resorptive osteotropic cytokine, interleukin-6 (IL-6). METHODS: MG 63 and SaOS-2 human osteoblastic cell lines were cultured for 6 or 24 hours in media containing calcitriol, the sterols of interest, or 1-34 synthetic PTH. IL-6 release was assayed by commercially available enzyme-linked immunosorbent assay. IL-6 mRNA levels were assessed by reverse transcriptase-polymerase chain reaction. RESULTS: We found that calcitriol and paricalcitol behaved in a similar fashion, resulting in increased IL-6 release only at higher concentrations (10(-7) to 10(-9) M). In contrast, 22-oxacalcitriol and 1,25-dihydroxydihydrotachysterol2 stimulated release to a similar extent but at concentrations three to four orders of magnitude lower (10(-11) to 10(-13) M), despite being less potent as suppressers of parathyroid function than calcitriol. Studies of IL-6 mRNA showed a similar pattern of concentration and cell line-dependent transcription. CONCLUSIONS: Compounds stimulating IL-6 release at concentrations achievable during the treatment of uremic hyperparathyroidism might favor continuing linked bone formation and resorption and thereby avoid adynamic bone disease while still allowing profound suppression of PTH.

In vivo dihydrotachysterol2 metabolism in normal man: 1 alpha- and 1 beta-hydroxylation of 25-hydroxydihydrotachysterol2 and effects on plasma parathyroid hormone and 1 alpha,25-dihydroxyvitamin D3 concentrations.

It has recently been shown that in the rat, dihydrotachysterol (DHT) is extensively metabolized in the side-chain in vivo along pathways similar to those of vitamin D. In addition 25-hydroxy-DHT2 [25OHDHT2] is hydroxylated at C1, producing both 1 alpha- and 1 beta- hydroxy compounds. An in vivo study in 1988 demonstrated that in normal adult subjects receiving oral DHT2, plasma 1 alpha,25-dihydroxyvitamin D [1,25-(OH)2D] concentrations fell, but with unchanged plasma PTH levels. Down-regulation of 1,25-(OH)2D3 production by 25-(OH)DHT2 or some other unknown metabolite was also suggested as an explanation for these observations. To investigate whether either of the newly characterized 1 alpha,25- or 1 beta,25-(OH)2DHT2 was formed in vivo in normal man, DHT2 (approximately 1 mg/day, orally) was administered to healthy volunteers (three males and one female). Plasma was analyzed by high performance liquid chromatography and gas chromatography-mass spectrometry, demonstrating the formation of both 1 alpha,25- and 1 beta,25-(OH)2DHT2 in vivo in normal human subjects. Plasma levels of 1,25-(OH)2D3, PTH, ionized and total calcium, inorganic phosphate, and alkaline phosphatase were monitored. The plasma concentrations of DHT2, 25OHDHT2, and 1 alpha,25- and 1 beta,25-(OH)2DHT2 were measured by gas chromatography-mass spectrometry. In all volunteers, plasma ionized calcium increased slightly during DHT2 administration; 1,25-(OH)2D3 and PTH concentrations fell. Plasma levels of DHT2 and its metabolites rose over the same period. The average fall in the level of plasma 1,25-(OH)2D (60-70 pmol/L) was mirrored by a rise in the concentration of 1 alpha,25-(OH)2DHT2 (550 pmol/L). This ratio is appropriate, because it has previously been shown that in a reconstituted COS cell, 1 alpha,25-(OH)2DHT3 has roughly one tenth the potency of 1,25-(OH)2D3. At maximum concentration, the ratios of DHT2/25OHDHT2/1 beta,25-(OH)2DHT2/1 alpha,25-(OH)2DHT2 were approximately 10:1:2:0.1. The concentration of 1 beta,25-(OH)2DHT2 was greater than that of 25OHDHT2, and the ratio of 1 alpha,25- to 1 beta,25-(OH)2DHT2 (1:20) was substantially lower than that in rat plasma (3:10). The data presented here suggest that the active DHT2 metabolite in man is 1 alpha,25-(OH)2DHT2 and that the fall in plasma 1,25-(OH)2D seen during DHT therapy may be partly the result of suppressed PTH secretion.

[Plasma renin activity in tachistin-stimulated hypercalcemia and under the effect of chlorazine]. / Plazmena reninova aktivnost pri stimulirana chrez takhistin khiperkaltsiemiia i pri prilozhenie na khlorazin.

The aim of the present study was to elucidate the correlation between the Renin secretion and increased Plasma Calcium concentration and the role of Calmodulin in this process. Plasma Renin activity was determined radioimmunologically in 31 white rats, that were grouped as follows: group I - 7 controls loaded for 6 days perorally with 0.5 ml/200 g b.w. glycerin and injected i.m. for 6 days with 0.1 ml/200 g b.w. with 0.9% NaCl; group II - 8 rats, treated for 6 days with Tachistin 0.0025 mg/200 g b.w., dissolved in glycerin 0.5 ml/200 g b.w.; group III - 5 rats, treated with Tachistin 0.005 mg/200 g b.w. in the same manner; group IV - 5 rats injected i.m. with Chlorazin 0.5 mg/200 g b.w. for 6 days; group V - 6 rats, loaded with double dose Tachistin and with Chlorazin 0.5 mg/200 g b.w. for 6 days. Blood samples were taken intracardially on the seventh day from the beginning of the experiment and were analyzed with kits of Sorin-Biomedica-Italy. Our results suggest that the hypercalcemia induced by Tachistin caused a dose-dependent increase of PRA and Ca-Calmodulin complex is the dominant second messenger of Renin secretion.

In vivo metabolism of the vitamin D analog, dihydrotachysterol. Evidence for formation of 1 alpha,25- and 1 beta,25-dihydroxy-dihydrotachysterol metabolites and studies of their biological activity.

Dihydrotachysterol (DHT), a reduced vitamin D analog in which the A-ring has been rotated through 180 degrees is a biologically active molecule which can be used to study the structural requirements for the calcemic and cell differentiating properties of the vitamin D hormone, 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), as well as to investigate the specificity of the enzyme systems that catalyze the formation of this hormone. In this study we showed that dihydrotachysterol was metabolized in vivo into a significant polar metabolite observed on straight-phase high performance liquid chromatography (HPLC) which subsequently split into two peaks on reverse-phase HPLC. These two metabolites were identified by HPLC and gas chromatography-mass spectrometry techniques as 1 alpha,25-(OH)2DHT and 1 beta,25-(OH)2DHT. This pair of metabolites was formed from either DHT2 or DHT3. Standard 1 alpha,25-(OH)2DHTs were generated in vitro from chemically synthesized 1-hydroxydihydrotachysterol precursors using a liver hepatoma cell system. Both 1 alpha,25-(OH)2D2 and 1 alpha,25-(OH)2DHT3 showed a binding affinity to the mammalian vitamin D receptor only 50-100 less than 1 alpha,25-(OH)2D3 whereas 1 beta,25-(OH)2DHTs showed poor binding. On the other hand 1 beta,25-(OH)2DHT3 bound to the rat vitamin D transport protein (DBP) with stronger affinity than did 1 alpha,25-(OH)2DHT3. When tested in a COS-1 cell transfection assay system using a rat osteocalcin vitamin D responsive element coupled to a growth hormone reporter gene, 1 alpha,25-(OH)2DHT3 showed a biological activity only 10 times lower than 1 alpha,25-(OH)2D3. It is therefore suggested that 1 alpha,25-(OH)2DHT probably represents the metabolite of DHT responsible for some of its in vivo effects although we cannot rule out in vivo effects of other metabolites identified. Our studies suggest that 1 alpha,25-dihydroxylated DHTs represent a promising novel group of vitamin D analogs worthy of study for cell differentiation as well as calcemic properties.

Polar metabolites of dihydrotachysterol3 in the rat. Comparison with in vitro metabolites of 1 alpha,25-dihydroxydihydrotachysterol3.

The metabolism of 25-hydroxydihydrotachysterol3 (25-OH-DHT3) to more polar metabolites was investigated in vivo in the rat and compared with the in vitro metabolism of 1 alpha,25-dihydroxy-DHT3 (1 alpha,25-(OH)2DHT3) in the osteosarcoma cell line UMR 106. Rats were given 2 mg of DHT3 in divided doses at 0 and 6 hr. Plasma was collected 24 hr after the initial dose, extracted, separated, and polar metabolites purified by HPLC. A number of polar metabolites were formed in vivo with mass spectrometric characteristics which suggested that they were derived from a previously isolated metabolite of 25-OH-DHT3, T3/H. Of these, four were isolated and identified as 24-oxo-T3/H, 24-hydroxy-T3/H, 26-hydroxy-T3/H and the 26,23-lactone of T3/H. In view of the identification of T3/H as a mixture of 1 alpha- and 1 beta-hydroxylated 25-OH-DHT3, osteosarcoma cells (UMR 106) were incubated with chemically synthesized 1 alpha,25-(OH)2DHT3 in an attempt to determine from which component of the T3/H mixture these metabolites were derived. Again, more polar metabolites were formed and five of these were isolated by lipid extraction, purified by HPLC and identified as 24-oxo-1 alpha,25-(OH)2DHT3, 1 alpha,23,25-(OH)3DHT3, 24-oxo-1 alpha,23,25-(OH)3DHT3, 1 alpha,24,25-(OH)3DHT3 and 1 alpha,25,26-(OH)3DHT3. Three of the in vitro metabolites were similar to those found in rat plasma but only two of these metabolites were available in sufficient amounts to allow comparison. The chromatographic characteristics, using HPLC and gas chromatography, of these two pairs of metabolites (24-oxo and 24-hydroxy) were examined and it was demonstrated that they were not the same. It is therefore suggested that the polar metabolites formed in vivo are in fact metabolites of the T3/Hb component (1 beta,25-(OH)2DHT3) rather than the T3/Ha component (1 alpha,25-(OH)2DHT3). Supporting evidence for this suggestion was obtained when a small quantity of 1 beta,25-(OH)2DHT3, obtained from chemically synthesized 1 beta-OH-DHT3 by incubation with Hep 3B cells, was further incubated in the osteosarcoma UMR 106 system. Preliminary studies indicated that the putative 24-oxo and 24-hydroxy metabolites formed from 1 beta,25-(OH)2DHT3 had chromatographic and mass spectral properties almost indistinguishable from those of corresponding metabolites of T3/H formed in vivo. All the metabolites formed in vivo and in vitro are components of two metabolic pathways described previously for 25-hydroxyvitamin D3 and also for 25-OH-DHT3.

Isolation and identification of seven metabolites of 25-hydroxydihydrotachysterol3 formed in the isolated perfused rat kidney: a model for the study of side-chain metabolism of vitamin D.

The in vivo metabolism of dihydrotachysterol3, an analogue of vitamin D3 and a potent calcemic factor, has been studied in the rat. This in vivo metabolism is compared to the in vitro metabolism of 25-hydroxydihydrotachysterol3 in the perfused rat kidney. Using mass spectrometry and ultraviolet spectroscopy, we have identified seven novel metabolites derived from 25-hydroxydihydrotachysterol3. The seven compounds represent intermediates on two renal pathways (24-oxidation and 26,23-lactone formation) also observed for 25-hydroxyvitamin D3. No evidence was found for the renal synthesis of a 1-hydroxylated metabolite of 25-hydroxydihydrotachysterol3 analogous to the hormone 1,25-dihydroxyvitamin D3. Two of the compounds formed in vitro, 24,25-dihydroxydihydrotachysterol3 and 25-hydroxydihydrotachysterol 26,23-lactone, were also formed in vivo. In vivo studies also revealed the formation of two other unidentified metabolites which are presumed to be formed nonrenally and may be calcemic factors. This work shows that dihydrotachysterol3 metabolism is complex and probably utilizes the same side-chain enzymes as vitamin D3. In addition, our work also confirms that intermediates postulated to lie on pathways to 26,23-lactone in the vitamin D3 series are also formed for the side chain in dihydrotachysterol3.

Isolation and identification of 25-hydroxydihydrotachysterol2 1 alpha,25-dihydroxydihydrotachysterol2 and 1 beta,25-dihydroxydihydrotachysterol2.

Three metabolites of orally administered dihydrotachysterol2 have been isolated in impure form from serum of rats. These metabolites have been identified as 25-hydroxydihydrotachysterol2 and two epimers of formula 1-ambo,25-dihydroxydihydrotachysterol2 by means of gas chromatography-mass spectrometry and ultraviolet absorption spectrometry. For the first time this provides evidence for 9,10-seco steroid hydroxylation at pseudo C3. The stereochemistry of the 1-hydroxyl group of the two epimers could be established tentatively by quantitative comparison of the mass spectra of their respective trimethylsilyl derivatives. Since purity requirements were not achieved, biological activities could not be determined.