Production of 1α,25-Dihydroxy-3-epi-vitamin D3 in two rat osteosarcoma cell lines (UMR 106 and ROS 17/2.8): existence of the C-3 epimerization pathway in ROS 17/2.8 cells in which the C-24 oxidation pathway is not expressed

Siu-Caldera, Mei-Ling; Sekimoto, H; Weiskopf, Andrew; Vouros, Paul; Muralidharan, K.; Okamura, William H.; Bishop, June E.; Norman, Anthony W.; Uskoković, Milan R.; Schuster, Inge; Reddy, G. Satyanarayana

doi:10.1016/s8756-3282(99)00019-8

Cited by 50 publications

(40 citation statements)

References 38 publications

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“…8). To the best of our knowledge, this is the first definite structural assignment of the C-25 dehydrates of OCT. Siu-Caldera et al (22) Two possible metabolic routes from OCT to dehydrates can be considered; one via the direct C-25 dehydration, and the other via the C-24 and C-26 hydroxylation. The latter route via the CYP24 metabolic pathway seems unlikely because the dehydration of hydroxyl groups at positions C-24/C-25 or C-25/ C-26 has not been found in the metabolism of steroid hormones.…”

Section: Discussionmentioning

confidence: 99%

“…Rat osteosarcoma ROS 17/2.8 cells, in which the C-24 oxidation pathway is not active, has been shown to metabolize 1␣,25(OH) 2 D 3 via the C-3 epimerization pathway (22). In contrast, the perfused rat kidney and human promyelocytic leukemia cell line HL-60, in which the C-23/C-24 hydroxylation pathways are highly expressed, do not metabolize 1␣,25(OH) 2 D 3 to via the C-3 epimerization pathway (22,35). These findings imply that C-3 epimerization pathway is cell-selective and contributes to the metabolism of vitamin D in concert with the C-23/C-24 hydroxylation pathways.…”

Section: Discussionmentioning

confidence: 99%

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Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Kamao¹,

Tatematsu²,

Hatakeyama³

et al. 2003

Journal of Biological Chemistry

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22-Oxacalcitriol (OCT) isOCT is a synthetic analog, which has an oxygen atom at position 22, and has received government approval for use as an agent for the treatment of secondary hyperparathyroidism and psoriasis in Japan. OCT is rapidly cleared from the circulation due to its extremely low affinity for DBP (9, 10), and binds the chicken vitamin D receptor (VDR) with an approximately 8-fold lower affinity than 1␣,25(OH) 2 D 3 (11). However, OCT inhibits growth of psoriatic fibroblasts and enhances the immune response more effectively than 1␣,25(OH) 2 D 3 (12, 13). In contrast, OCT has reduced calcemic effects both in terms of mobilizing calcium from bone and in stimulating intestinal calcium transport in vitamin D-deficient and normal rats (14, 15). Recently, Kato and co-workers (16) reported that OCT induced interaction of the VDR with a transcriptional factor TIF-2, but not with other transcriptional factors such as SRC-1 and AIB-1, while 1␣,25(OH) 2 D 3 induced interactions of the VDR with all of the three co-factors tested. These factors such as metabolic clearance, tissue-specific distribution, cellular uptake, intracellular metabolism, and transcriptional regulation could contribute to differences in biological activity. Recently, the metabolism of OCT has been studied in primary parathyroid cells (17) and keratinocytes (18) as well as osteosarcoma, hepatoma, and keratin cell lines (19). In all these systems, OCT is degraded into hydroxylated and sidechain truncated metabolites, 1␣,20(OH) 2 D 3 and hexanor-20-oxo-1␣-hydroxyvitamin D 3 (20-oxo-1␣(OH)D 3 ). However, despite relatively large amounts of products from OCT (19), the structures and properties of the less polar metabolites have not yet been clarified. In the case of 1␣,25(OH) 2 D 3 , one of these less polar metabolites has been identified as 3-epi-1␣,25(OH) 2 D 3 , in which a hydroxyl group at C-3 of the A-ring is epimerized from the ␤ to the ␣ position (20, 21). The C-3 epimerization of 1␣,25(OH) 2 D 3 occurs in vitro (20 -22) and in vivo (23), and is a highly tissue-specific/cell differentiation-dependent process * This work was supported in part by a grants-in-aid for scientific research from the Ministry of Education, Science, Sports and Culture of Japan, a grant for cooperative research administered by the Japan Private School Promotion Foundation, and a grant-in-aid from the Ministry of Health and Welfare of Japan. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.‡ ‡ To whom correspondence should be addressed: Dept. of Hygienic Sciences, Kobe Pharmaceutical University, 4-19-1 Motoyamakita-machi, Higashinada-ku, Kobe 658-8558, Japan.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Kamao¹,

Tatematsu²,

Hatakeyama³

et al. 2003

Journal of Biological Chemistry

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“…[13][14][15] In the present study, we compared the metabolic fate of the four 1a,2-methyl diastereomers with that of 1a,25(OH) 2 D 3 in rat osteosarcoma cells (UMR 106) which have been shown to express both the C-24 oxidation and the C-3 epimerization pathways. 16) We hereby report the results of these studies. The cells were cotransfected with a luciferase reporter plasmid (pGVB2 vector) containing a human osteocalcin gene promoter including a VDRE and the luciferase activity was measured.…”

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confidence: 89%

Metabolism of 2-Methyl Analogs of 1α,25-Dihydroxyvitamin D<sub>3</sub> in Rat Osteosarcoma Cells (UMR 106)

Rao

Siu-Caldera

Sekimoto

et al. 2002

Biological & Pharmaceutical Bulletin

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The secosteroid hormone, 1a,25-dihydroxyvitamin D 3 [1a,25(OH) 2 D 3 ] has a wide range of activities: in addition to its classical role in calcium homeostasis, 1a,25(OH) 2 D 3 is also involved in inhibiting proliferation and inducing differentiation of various normal and cancer cells. 1) To investigate the structure-function relationship and to develop potential therapeutic agents for the treatment of cancer, psoriasis and osteoporosis a large number of analogs of 1a,25(OH) 2 D 3 with structural modifications of both the side chain and the A-ring have been synthesized and biologically evaluated. Biological activity studies of these various synthetic analogs of 1a,25(OH) 2 D 3 have shown that many of them possessed highly potent, selective activities. 1)The activities of 1a,25(OH) 2 D 3 and its potent synthetic analogs are known to be primarily vitamin D receptor (VDR) mediated. The structure-function studies of the vitamin D molecule 2) have shown that the 1a,3b-configuration of hydroxyl groups is crucial for effective binding to the VDR and thus for full expression of the vitamin D activity, and epimerization of each hydroxyl group dramatically decreases the activity by about 100 times for 1b and 10 times for 3a 3,4) due to lack of affinity for VDR. We recently synthesized all eight possible A-ring diastereomers of 2-methyl-1a,25(OH) 2 D 3 (these analogs contain a methyl group on C-2 of the A-ring, and differ from each other in the stereochemistry of the methyl group on C-2 and the hydroxyl groups on C-1 and C-3) in order to investigate the structure-function relationship of the natural hormone and demonstrated that in addition to the C-1 and C-3 hydroxyl groups, the configuration of the 2-methyl group also considerably alters the activity.5-7) The 2-methyl analogs show unique biological properties. For example, the VDR binding affinities exhibited by the 1a-isomers are significantly higher than those exhibited by the 1b-isomers. Furthermore, out of all the 1a-isomers, the 2a-methyl isomers, when compared to the corresponding 2b-methyl isomers, showed much higher potency in inducing differentiation of HL-60 cells (Table 1) indicating that the 2a-methyl group enhances the VDR affinity whereas the 2b-methyl group decreases the VDR affinity. Our further studies have shown that the 2a-methyl isomers bearing 1a,3b-hydroxyl groups which strongly induced cell differentiation, failed to stimulate apoptosis. In contrast, the 2b-methyl isomers bearing 1b and 3a-hydroxyl groups which failed to induce differentiation of HL-60 cells, strongly stimulated apoptosis (Fig. 1). These findings indicate that the structural requirement for inducing apoptosis of HL-60 cells was clearly different from that for inducing differentiation of these cells. 8,9) Thus, all these findings suggest that a simple modification such as addition of a methyl group to the hormone can lead to a potent analog and the potency is highly dependent on the configuration not only of the C-1 and C-3 hydroxy groups but also of the 2-methyl group. At present ...

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“…1␣,25(OH) 2 D 3 has potent anti-proliferative and cell differentiation-inducing activities in addition to its role in calcium homeostasis. After the expression of various biological activities, 1␣,25(OH) 2 D 3 is further metabolized through the C-24 (3-6)/C-23 (7-10) oxidation pathways and the C-3 epimerization pathway (11)(12)(13)(14). The C-24 oxidation pathway, initiated by C-24 hydroxylation, leads to the conversion of 1␣,25(OH) 2 D 3 into a side chain cleavage product, calcitroic acid (4,5).…”

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confidence: 99%

“…The C-3 epimerization of 1␣,25(OH) 2 D 3 was observed in human colon carcinoma-derived Caco-2 cells (11), bovine parathyroid cells (12), rat osteoblastic UMR 106 and Ros17/2.8 cells (13), and various cultured cell lines (14). From these studies, the C-3 epimerization pathway is assumed to be cell-selective.…”

mentioning

confidence: 99%

C-3 Epimerization of Vitamin D3 Metabolites and Further Metabolism of C-3 Epimers

Kamao

Tatematsu

Hatakeyama

et al. 2004

Journal of Biological Chemistry

127

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1, 2). 1␣,25(OH) 2 D 3 has potent anti-proliferative and cell differentiation-inducing activities in addition to its role in calcium homeostasis. After the expression of various biological activities, 1␣,25(OH) 2 D 3 is further metabolized through the C-24 (3-6)/C-23 (7-10) oxidation pathways and the C-3 epimerization pathway (11-14). The C-24 oxidation pathway, initiated by C-24 hydroxylation, leads to the conversion of 1␣,25(OH) 2 D 3 into a side chain cleavage product, calcitroic acid (4, 5). The C-23 oxidation pathway, initiated by C-23 hydroxylation, leads to the formation of 1␣,25(OH) 2 D 3 -26,23-lactone (7-10). The newly discovered C-3 epimerization pathway leads to the conversion of the configuration of the hydroxyl group at C-3 of the A-ring and produces 3-epi-1␣,25(OH) 2 D 3 from 1␣,25(OH) 2 D 3 . In view of this modification at the A-ring, the C-3 epimerization pathway is quite different from side chain oxidation pathways.The C-3 epimerization of 1␣,25(OH) 2 D 3 was observed in human colon carcinoma-derived Caco-2 cells (11), bovine parathyroid cells (12), rat osteoblastic UMR 106 and Ros17/2.8 cells (13), and various cultured cell lines (14). From these studies, the C-3 epimerization pathway is assumed to be cell-selective. It was considered that the C-3 epimerization pathway is cell differentiation-related in Caco-2 cells, because 3-epi-1␣,25 (OH) 2 D 3 was only observed in confluent, quiescent Caco-2 cells, not proliferating Caco-2 cells (11). 3-Epi-1␣,25(OH) 2 D 3 was also isolated as a circulating metabolite of 1␣,25(OH) 2 D 3 in rats treated with pharmacological doses of 1␣,25(OH) 2 D 3 (15). In addition, synthetic analogs of 1␣,25(OH) 2 D 3 , e.g. 22-oxacalcitriol (16), 20-epi-1␣,25(OH) 2 D 3 (17), and 1␣,25(OH) 2 -16-ene-23-yne-D 3 (18), have been reported to be metabolized to their * This work was supported in part by a grant-in-aid for scientific research from the Ministry of Education, Science, Sports, and Culture of Japan, a grant for Cooperative Research administered by the Japan Private School Promotion Foundation, and a grant-in-aid from the Ministry of Health and Welfare of Japan. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.§ § To whom correspondence should be addressed: Dept.

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Production of 1α,25-Dihydroxy-3-epi-vitamin D3 in two rat osteosarcoma cell lines (UMR 106 and ROS 17/2.8): existence of the C-3 epimerization pathway in ROS 17/2.8 cells in which the C-24 oxidation pathway is not expressed

Cited by 50 publications

References 38 publications

Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Metabolism of 2-Methyl Analogs of 1α,25-Dihydroxyvitamin D<sub>3</sub> in Rat Osteosarcoma Cells (UMR 106)

C-3 Epimerization of Vitamin D3 Metabolites and Further Metabolism of C-3 Epimers

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Production of 1α,25-Dihydroxy-3-epi-vitamin D3 in two rat osteosarcoma cell lines (UMR 106 and ROS 17/2.8): existence of the C-3 epimerization pathway in ROS 17/2.8 cells in which the C-24 oxidation pathway is not expressed

Cited by 50 publications

References 38 publications

Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Two Novel Metabolic Pathways of 22-Oxacalcitriol (OCT)

Metabolism of 2-Methyl Analogs of 1&alpha;,25-Dihydroxyvitamin D<sub>3</sub> in Rat Osteosarcoma Cells (UMR 106)

C-3 Epimerization of Vitamin D3 Metabolites and Further Metabolism of C-3 Epimers

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Metabolism of 2-Methyl Analogs of 1α,25-Dihydroxyvitamin D<sub>3</sub> in Rat Osteosarcoma Cells (UMR 106)