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N Kubodera

Publications and source records attributed to N Kubodera.

At least 19 recordsLinked to original sources
PubMed1998

Effect of combination treatment with a vitamin D analog (OCT) and a bisphosphonate (AHPrBP) in a nude mouse model of cancer-associated hypercalcemia.

Hypercalcemia represents one of the important paraneoplastic syndromes affecting morbidity and mortality of cancer patients. We and others have demonstrated that vitamin D analogs with little calcemic activities suppress the transcription of the parathyroid hormone-related peptide (PTHrP) gene, a major humor responsible for cancer hypercalcemia, and thereby prevent the development of hypercalcemic syndrome. The present study was undertaken: to compare the therapeutic efficacy of a vitamin D analog, 22-oxa-1,25-dihydroxyvitamin D3 (OCT), and a bisphosphonate (disodium 3-amino-1-hydroxypropylidene-1,1-bisphosphonate pentahydrate [AHPrBP]), an inhibitor of osteoclastic bone resorption, on cancer-induced hypercalcemia; and to see if the effect could be enhanced by combination treatment, using a nude mouse model implanted with a human pancreas carcinoma (FA-6). After a single intravenous administration, OCT (5 microg/kg of body weight [BW]) was as effective as AHPrBP (10 mg/kg of BW) in lowering blood ionized calcium levels in tumor-bearing nude mice, and their combination further enhanced the therapeutic effect. Although AHPrBP lost its efficacy after repeated injections, OCT was still effective after the third administration. The therapeutic effect of OCT in cancer hypercalcemia was observed in four other human tumors, including another pancreas carcinoma (PAN-7), two squamous cell carcinomas of the lung (KCC-C1 and LC-6), and a squamous carcinoma of the pharynx (PHA-1), all of which elaborated PTHrP into the circulation. Treatment with OCT resulted in a decrease in circulating PTHrP levels by approximately 50% in two representative models. However, the mechanism underlying the antihypercalcemic effect of OCT seemed complex, involving inhibition of PTHrP production, suppression of excessive bone resorption, and an antitumor activity. OCT also markedly inhibited the body weight loss with tumor growth, while AHPrBP, which exhibited a similar antihypercalcemic effect, was less effective than OCT in preventing cachexia. The anticachectic activity of their combination did not exceed that of OCT alone, suggesting a hypercalcemia-dependent as well as an independent mechanism of cancer cachexia. It is concluded that OCT may be useful, either as a single agent or in combination with bisphosphonates, for the treatment of cancer-associated hypercalcemia and cachexia.

Animals↗
PubMed1997

Transcriptional induction of cyclooxygenase-2 in osteoblasts is involved in interleukin-6-induced osteoclast formation.

Interleukin-6 (IL-6) induces osteoclast-like cell (osteoclast) formation in a dose-dependent fashion in cocultures of mouse bone marrow cells and osteoblastic cells when soluble IL-6 receptor (sIL-6R) is present. Simultaneous treatment with submaximal doses of IL-1alpha and IL-6 with sIL-6R caused marked induction of osteoclast formation and PGE2 synthesis. These effects were suppressed by adding neutralizing antibodies against IL-1alpha or IL-6R and were totally abolished by adding nonsteroidal antiinflammatory drugs, such as indomethacin and a selective cyclooxygenase-2 (COX-2) inhibitor (NS398). In mouse osteoblastic cells, both IL-1alpha and IL-6 with sIL-6R markedly induced messenger RNA expression of COX-2, but not COX-1, as determined by Northern blot analysis, and luciferase activity in cells stably transfected with a COX-2 promoter-luciferase fusion construct. IL-6 and sIL-6R, when added separately, did not stimulate COX-2 messenger RNA expression. Simultaneous addition of IL-1alpha and IL-6 with sIL-6R to osteoblast cultures cooperatively induced transcription of COX-2, which was associated with a marked increase in COX activity measured by the conversion of arachidonic acid into PGE2. The increased PGE2 synthesis by osteoblasts may play an important role in osteoclastogenesis induced by submaximal doses of IL-1 and IL-6.

Aging↗
PubMed1997

Synthetic studies of vitamin D analogs. XXIV. Synthesis of active vitamin D3 analogs substituted at the 2 beta-position and their preventive effects on bone mineral loss in ovariectomized rats.

Analogs related to 1 alpha,25-dihydroxy-2 beta-(3-hydroxypropoxy)vitamin D3 (ED-71) (4), oxa-type and carba-type analogs of vitamin D3 bearing substituents at the 2 beta-position of 1 alpha,25-dihydroxyvitamin D3 (1), were synthesized from the alpha-epoxides (6 and 13). Three analogs, ED-71 (4) and two carba-type analogs (16 and 26), showed potent preventive effects on bone mineral loss in pre-osteoporosis model rats. ED-71 (4) was concluded to be an optimized analog and a promising candidate for the treatment of osteoporosis.

Absorptiometry, Photon↗
PubMed1996

In vitro metabolism of the vitamin D analog, 22-oxacalcitriol, using cultured osteosarcoma, hepatoma, and keratinocyte cell lines.

Using four cultured cell models representing liver, keratinocyte, and osteoblast, we have demonstrated that the vitamin D analog, 22-oxacalcitriol is degraded into a variety of hydroxylated and side chain truncated metabolites. Four of these metabolic products have been rigorously identified by high pressure liquid chromatography, diode array spectrophotometry, and gas chromatography-mass spectrometry analysis as 24-hydroxylated and 26-hydroxylated derivatives as well as the cleaved molecules, hexanor-1alpha,20-dihydroxyvitamin D3 and hexanor-20-oxo-1alpha-hydroxyvitamin D3. Comparison with chemically synthesized standards has revealed the stereochemistry of the biological products. Although differences exist in the amounts of products formed with the different cell types, it is apparent that 22-oxacalcitriol is subject to metabolism by both vitamin D-inducible and noninducible enzymes. Time course studies suggest that the truncated 20-alcohol is derived from a side chain hydroxylated molecule via a hemiacetal intermediate and the 20-oxo derivative is likely formed from the 20-alcohol. Biological activity measurements of the metabolites identified in our studies are consistent with the view that these are catabolites and that the biological activity of 22-oxacalcitriol is due to the parent compound. These results are also consistent with recent findings of others that the biliary excretory form of 22-oxacalcitriol is a glucuronide ester of the truncated 20-alcohol.

Animals↗
PubMed1996

1,25-dihydroxyvitamin D3 and 22-oxacalcitriol prevent the decrease in vitamin D receptor content in the parathyroid glands of uremic rats.

Decreased content of the 1,25-dihydroxyvitamin D3 receptor (VDR) in parathyroid glands from patients and animals with chronic renal failure has been implicated in the pathogenesis of secondary hyperparathyroidism. In these studies, we examined the regulation of VDR by 1,25-dihydroxyvitamin D3 (1,25-D3) and 22-oxacalcitriol (OCT) in parathyroid glands of uremic rats. After eight weeks of renal failure, VDR content in parathyroid glands of uremic rats was decreased (400 +/- 42 vs. 729 +/- 47 fmol/mg protein in normal control rats, P < 0.05) and strongly correlated with serum 1,25-D3 levels (r = 0.829, P = 0.0001). Treatment with either 1,25-D3 or OCT prevented the decrease in VDR. We conclude that low serum 1,25-D3 levels, at least in part, account for the decrease in VDR content in parathyroid glands of uremic rats and that treatment with 1,25-D3 or OCT prevents this decrease ameliorating the development of secondary hyperparathyroidism.

Animals↗
PubMed1996

Synthetic studies of vitamin D analogs. XXII. Synthesis and antiproliferation activity of putative metabolites of 1 alpha, 25-dihydroxy-22-oxavitamin D3.

As putative metabolites of 1 alpha,25-dihydroxy-22-oxavitamin D3 (OCT), 24-hydroxylated OCT in 24(R) and 24(S) forms, 24-ketoOCT, 26-hydroxylated OCT in 25(S) and 25(R) forms, pentanorOCT and pentanor-ketoOCT were synthesized from the steroidal 20(S)-alcohol. Their antiproliferation activities towards human promyelocytic leukemia cells (HL-60 cells) are also reported. Oxidized derivatives at the C-24 position, 24-ketoOCT, 24(R)-hydroxylated OCT and 24(S)-hydroxylated OCT, showed activities comparable to or slightly weaker than that of OCT, while 26-hydroxylated OCT was less active than OCT. Truncated OCT, pentanor OCT and pentanor-ketoOCT, were inactive at 10(-7)-10(-10) M.

Animals↗
PubMed1995

Binding of vitamin D to low-density-lipoprotein (LDL) and LDL receptor-mediated pathway into cells.

The present study was undertaken to identify serum components other than vitamin D-binding proteins that bind to 1,25(OH)2 D3, and its analog. The binding rate of 1,25(OH)2 D3, 22-oxa-1,25(OH)2D3 (OCT) or 25(OH) D3 to total lipoprotein(TLP) represented 16.7%, 4.65%, and 3.11% of total counts added, respectively. Polyacrylamide gel electrophoresis of the TLP revealed that 1,25(OH)2 D3 and OCT were associated with LDL. The binding studies of OCT-bound LDL to the fibroblasts showed specific pathway to the cells mediated by LDL-receptor. These findings may have important implications in understanding the mechanisms of the diverse biological actions of 1,25(OH)2 D3 and in designing a novel delivery system for vitamin D analogs.

Apolipoprotein B-100↗
PubMed1994

The binding properties, with blood proteins, and tissue distribution of 22-oxa-1 alpha,25-dihydroxyvitamin D3, a noncalcemic analogue of 1 alpha, 25-dihydroxyvitamin D3, in rats.

The binding properties, with blood proteins, and tissue distribution of 22-oxa-1 alpha,25-dihydroxyvitamin (22-oxacalcitriol; OCT), a noncalcemic analogue of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], in rats were investigated. The binding affinity of OCT to plasma vitamin D binding protein (DBP) is extremely low and OCT mainly circulates in the blood as an intact form nonspecifically bound to lipoproteins especially to chylomicrons and low density lipoprotein (LDL). OCT intravenously injected into normal rats rats rapidly disappeared from the blood, and rapidly appeared in the bile as glucuronides of intact OCT and 1 alpha, 3 beta,20(S)-trihydroxy-9,10-secopregna-5,7,10(19)-triene (23,24,25,26, 27-pentanorOCT; pentanorOCT) as an OCT metabolite. When OCT or 1,25(OH)2D3 was injected into normal rats, significant amounts of OCT and 1,25(OH)2D3 were quickly detected in the thyroid and parathyroid glands, thymus, adrenals, liver, plasma, small intestine, kidneys, and calvaria. The detected amounts of OCT in the parathyroid glands, thymus, adrenals, liver, small intestine, and kidneys were significantly higher than the respective values for 1,25(OH)2D3 2 and/or 10 min after injection, while those of OCT in the plasma and calvaria were significantly lower than those of 1,25(OH)2D3. The in vivo rapid turn-over, nonspecific transportation, and incorporation of detectable amounts into the tissues are typical characteristics of OCT which may account for its specific activities.

Animals↗
PubMed1993

Differential effects of 1,25-(OH)2D3 and 22-oxacalcitriol on phosphate and calcium metabolism.

1,25-dihydroxyvitamin D3 has been used with success in the treatment of secondary hyperparathyroidism associated with chronic renal failure. However, frequently 1,25-(OH)2D3 induces hypercalcemia, especially in those patients ingesting large doses of calcium carbonate, precluding the administration of therapeutic doses of 1,25-(OH)2D3. In addition, control of serum phosphorus is a persistent problem in patients maintained on chronic hemodialysis and 1,25-(OH)2D3 treatment can aggravate the hyperphosphatemia. Thus, ideally an analog of 1,25-(OH)2D3 that can suppress PTH with minor effects on calcium (Ca) and phosphate (PO4) metabolism would be an ideal tool to control secondary hyperparathyroidism. We have shown that 22-oxa-1,25-(OH)2D3 (OCT), an analog of 1,25-(OH)2D3 with little calcemic activity, can suppress PTH mRNA in normal rats and in cultured bovine parathyroid cells with equipotency to 1,25-(OH)2D3. To further characterize the differential effects of 1,25-(OH)2D3 and OCT on Ca and PO4 metabolism we performed several experiments in intact and parathyroidectomized (PTX) rats. In metabolic studies in four groups of normal rats 1,25-(OH)2D3 treatment (8 ng/day) significantly increased the intestinal Ca absorption from 15.2 +/- 2.68% to 30.5 +/- 2.85% (P < 0.01), while the same dose of OCT had no effect. A dose of 200 ng/day of OCT increased intestinal Ca absorption similarly to the 8 ng/day dose of 1,25-(OH)2D3, from 10.6 +/- 2.49% to 24.8 +/- 2.35% (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The mechanism for the disparate actions of calcitriol and 22-oxacalcitriol in the intestine.

22-Oxacalcitriol (OCT) is one of several new analogs of vitamin D that retain many of the therapeutically useful properties of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], but have much less calcemic activity. In the present study we examined the actions of OCT on intestinal calcium absorption and calbindin D9k mRNA in vitamin D-deficient rats. After ip injection of OCT (1 microgram/kg), calcium absorption increased significantly by 2 h and was maximal at 4 h (2.5-fold above control), but returned to pretreatment levels by 16 h. In contrast, the same dose of 1,25-(OH)2D3 caused a 3-fold increase in calcium absorption, which lasted more than 48 h. The transient effect of OCT on calcium absorption was also observed when the analog was infused at a dose of 1 micrograms/kg.day for 3 days. At the end of the infusion period, calcium absorption was 3-fold higher than that in vehicle-infused controls, but fell to pretreatment levels by 24 h after removing the minipumps. The time courses for induction of calbindin D9k mRNA were similar for OCT and 1,25-(OH)2D3, with no change observed until more than 4 h after injection. However, calbindin mRNA levels returned to pretreatment values more rapidly in the OCT-treated rats. Consistent with these findings, we observed that a 1 microgram/kg dose of [3H] OCT was completely cleared by 4-6 h after injection. This was paralleled by a loss of [3H]OCT associated with the intestinal vitamin D receptor. The rapid clearance of OCT is probably due to its low affinity for the serum vitamin D-binding protein. This low affinity would also be expected to allow greater accessibility to target cells. In support of this, we found that higher amounts of OCT than 1,25-(OH)2D3 were associated with the intestinal vitamin D receptor after the injection of several doses of these tritiated ligands. In summary, our results indicate that the pharmacokinetic properties of OCT are responsible at least in part for its low calcemic activity. Furthermore, comparison of the transient elevation of calcium absorption by OCT with its more prolonged effects on PTH and calbindin D9k indicates that each action of vitamin D compounds has a distinct biological half-life. The short circulating half-life of OCT can exploit these differences to provide a therapeutic advantage in the treatment of vitamin D-responsive diseases.

Animals↗
PubMed1993

Differential catabolism of 22-oxacalcitriol and 1,25-dihydroxyvitamin D3 by normal human peripheral monocytes.

22-Oxacalcitriol [1,25-(OH)2-22oxa-D3] mimics the action of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in a variety of target tissues, including the systemic control of calcitriol metabolism. Similar to 1,25-(OH)2D3, 1,25-(OH)2-22oxa-D3 decreases the rate of 1,25-(OH)2D3 synthesis and accelerates its metabolic clearance rate. We have previously shown that in normal human monocytes, physiological concentrations of 1,25-(OH)2D3 and 1,25-(OH)2-22oxa-D3 determine identical suppression of 1,25-(OH)2D3 synthesis. Moreover, both sterols have a similar potency to induce vitamin D degradation through stimulation of the C24-hydroxylation pathway. In this study, we examined the ability of normal human monocytes to metabolize 1,25-(OH)2-22oxa-D3 and whether the enzymes involved are the same as those that catabolize 1,25-(OH)2D3. Time-course experiments demonstrated no detectable basal catabolic activity. However, exogenous 1,25-(OH)2D3 at physiological concentrations induced 1,25-(OH)2-22oxa-D3 degradation by normal human monocytes. Competition experiments showed that a 10-fold molar excess of unlabeled 1,25-(OH)2D3 inhibited tritiated-1,25-(OH)2-22oxa-D3 catabolism by 85%, whereas a 10-fold excess of unlabeled 1,25-(OH)2-22oxa-D3 reduced tritiated-1,25-(OH)2-22oxa-D3 catabolism by 33%. In contrast, although a 10-fold excess of unlabeled 1,25-(OH)2D3 reduced tritiated 1,25-(OH)2D3 catabolism by 60%, a 1000-fold excess of 1,25-(OH)2-22oxa-D3 was required to reduce tritiated 1,25-(OH)2D3 catabolism to this degree. The apparent Km for 1,25-(OH)2-22oxa-D3 was significantly higher than that of 1,25-(OH)2D3 (2.0 +/- 0.8 0.9 +/- 0.2 nM, respectively; P < 0.001) for the catabolic pathway induced by physiological concentrations of 1,25-(OH)2D3. Moreover, the presence of 0.65 nM 1,25-(OH)2D3 caused an additional increase in the Km for 1,25-(OH)2-22oxa-D3 (3.2 +/- 0.8 nM). These data suggest that 1,25-(OH)2-22oxa-D3 may be less accessible than 1,25-(OH)2D3 to the hydroxylases involved in vitamin D catabolism. The resulting prolonged biological half-life of the analog in certain target tissues may be involved in its selectivity.

Binding, Competitive↗
PubMed1993

Synthetic studies of vitamin D analogues. XIV. Synthesis and calcium regulating activity of vitamin D3 analogues bearing a hydroxyalkoxy group at the 2 beta-position.

Four vitamin D3 analogues (7a, 7b, 7c and 7d) bearing a hydroxyalkoxy group at the 2 beta-position were synthesized from the alpha-epoxide (5). The C-3 analogue (7b) showed the highest potency for elevating plasma calcium levels in rats. Furthermore, the 25-hydroxylated C-3 analogue (ED-71) (3), prepared from the 25-hydroxylated alpha-epoxide (9), significantly increased plasma calcium to levels much higher than those in rats administered 1 alpha,25-(OH)2-D3 (1).

Administration, Oral↗
PubMed1993

Synthetic studies of vitamin D analogues. XVII. Synthesis and differentiation-inducing activity of 1 alpha,24-dihydroxy-22-oxavitamin D3 analogues and their 20(R)-epimers.

Four vitamin D3 analogues, 1 alpha,24(S)- and 1 alpha,24(R)-dihydroxy-22-oxavitamin D3 (5 and 6) and their 20(R)-epimers (7 and 8) were synthesized from the 20(S)-alcohol (10). In tests of activity to induce differentiation of human myeloid leukemia cells (HL-60) to macrophages, 5 showed comparable activity to 1 alpha,25-dihydroxy-22-oxavitamin D3 (OCT) (2), and the other three analogues (6, 7 and 8) were less active than OCT (2). The binding properties of these analogues to the chick embryonic intestinal 1 alpha,25-dihydroxyvitamin D3 (1) receptor were evaluated. Furthermore, 20(R)-OCT (9) was synthesized and its biological properties were compared with those of OCT(2) and the 20(R)-epimers (7 and 8).

Animals↗
PubMed1992

Metabolism of 22-oxacalcitriol by a vitamin D-inducible pathway in cultured parathyroid cells.

Catabolism of 22-oxacalcitriol (OCT) in parathyroid cells was compared to that of the parent hormone, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Catabolism of both compounds was greatly accelerated by pretreatment of the cells with 1,25-(OH)2D3 or OCT. The rate of degradation of OCT was slightly greater than that of 1,25-(OH)2D3. Excess unlabeled OCT or 1,25-(OH)2D3 inhibited metabolism of both tritiated substrates. Ketoconazole, a cytochrome P450 inhibitor, blocked catabolism of both compounds. The major OCT metabolite appeared to be 1,20-dihydroxy-22,23,24,25,26,27-hexanor-vitamin D3 which was not active in suppressing PTH secretion. We conclude that OCT appears to be metabolized by the same vitamin D-inducible side chain oxidation pathway that catabolizes other vitamin D compounds and that its higher than expected suppression of PTH secretion is not due to slower cellular metabolism.

Animals↗
PubMed1992

Synthetic studies of vitamin D analogues. XI. Synthesis and differentiation-inducing activity of 1 alpha,25-dihydroxy-22-oxavitamin D3 analogues.

Six analogues of 1 alpha,25-dihydroxy-22-oxavitamin D3 (OCT) (2), 26,27-dimethyl OCT (5), 26,27-diethyl OCT (6), 24-norOCT (7), 24-homoOCT (8), 24-dihomoOCT (9), and 24-trihomoOCT (10) were synthesized from the 20(S)-alcohol (11) as the common starting material. In the activity inducing differentiation of human myeloid leukemia cells (HL-60) into macrophages, 26,27-dimethyl OCT (5) and 24-homoOCT (8) showed the highest activities. The binding properties of these analogues to the chick embryonic intestinal 1 alpha,25-dihydroxyvitamin D3 (1) receptor are also described.

Animals↗
PubMed1992

Production and specificity of anti-22-oxacalcitriol antisera.

22-Oxacalcitriol 3-hemiglutarate, a haptenic derivative of 22-oxacalcitriol, was synthesized to obtain a specific antibody for use in radioimmunoassay. Three antisera were elicited in rabbits against the hapten conjugated with bovine serum albumin, and their specificity was examined by cross-reaction study. One of the antisera was found to be satisfactorily specific, and expected to provide a radioimmunoassay useful for the pharmacokinetic study of 22-oxacalcitriol.

Animals↗
PubMed1992

Synthetic studies of vitamin D analogues. X. Synthesis and biological activities of 1 alpha,25-dihydroxy-21-norvitamin D3.

1 alpha,25-Dihydroxy-21-norvitamin D3 (3) was synthesized from 1 alpha-hydroxydehydroepiandrosterone (4). Certain biological properties of 3 were examined in comparison with those of 1 alpha,25-dihydroxyvitamin D3 (1) and 1 alpha,25-dihydroxy-21-nor-20-oxavitamin D3 (2) to evaluate the effect of the 21-methyl substituent on biological activities. The differentiation-inducing activity of 3 towards human myeloid leukemia cells was approximately one-fifth of that of 1, while in the binding affinity with chick intestinal cytosolic receptor, 3 was about one-tenth of that of 1. The rather weak effect of 3 on serum calcium levels in normal mice at a dosage of 500 micrograms/kg (intravenous administration) indicates that the essential importance of the 21-methyl moiety may lie in its effect on the regulation of calcium metabolism.

Animals↗