Structure-Activity Study of Vitamin D Analogues

To clarify the structure-function relationship of vitamin D analogues，we synthesized novel vitamin D analogues and evaluated their biological activities.(1)A series of singly dehydroxylated 19-nor-1α，25-dihydroxyvitamin D I D 23锡D2A-ring analogues were synthesized.The analogues could be clearly divided into two categories；one group，bearing1α-hydroxy or 3β-hydroxy groups in the A-ring，were potent differentiators and the second group，bearing1β-hydroxy or 3α-hydroxy groups，were potent stimulators of apoptosis。These findings will provide useful information not only for development of therapeutic agents for treatment of leukemia and other cancers.(2)Biological activities of a series of 2β-substituted analogues of 1α，25(OH)I D 22 II D2)D I D 23 II D 2 were evaluated。Binding affinity for VDR，transactivation potency on the target gene and VDR-mediated gene regulation of the hydroxyalkyl and hydroxyalkoxy2β-substituted analogues were almost comparable to those of 1α，25(OH)I D 22 D D…More y D23 I D 2，while the alkyl and alkenyl analogues were much less active than 1α，25(OH)I D 22 ii D 2.Furthermore，we found a promising candidate for preventive and therapeutic medicine of osteoporosis among these compounds.(3)The biological activity of two sets of ring A stereo isomers of 2-methyl-1α，25-dihydroxyvitamin D I D 23ii D2 and 2-methyl-20-epi-1α，25-dihydroxyvitamin D I D23 D2were evaluated.We found that2β-methyl-20-epi-3-epi-1β，25(OH)I D22个D 2D个D23个D23个D2is transcriptionally more active than1α，25(OH)个D22个D2D个个D23个D2despite lacking the 1α-hydroxyl group，which was believed to be essential for expressing VDR-mediated gene transcription.Since the C-20 natural counterpart，2β-methyl-3-epi-1β，25(OH)D 22个D 2D个D 23个D2，was almost completely biologically inactive，20-epimerization is probably responsible for activation of gene expression.(4)We found that binding affinity 1α，25(OH)I D22个D个D22个D2 and 1α，25(OH)25(OH)D 22 D 2 and 1α，25(OH)D 22 D D 2 D D 27 D 27 D 2 were much less active than 1α，25(OH)D 22 D 23 D 2 in these respects。This is the first finding concerning biological assessment of 1α，25(OH)I D22个D 2D个D22个D2，1α，25(OH)个D22个D2，1α，25(OH)个D22个个D2，1α，25(OH)个D22个个D2，24-epi-1α，25(OH)个D22个D2个D2，25(OH)个D22个D2and1α，25(OH)个D22个D2D27个D27个D 2at the molecular level，25(OH)Especially with regards to the structural differences at the 24R-or24S-methyl group and a double bond between carbons22 and 23 in the side chain of 1α，25(OH)I D 22 ii D derivatives.(5)The effects of 1α，25(OH)I D 22 ii D D I D 23 ii D 2 and its analogues on transmembrane Ca D 12核D 1 influx were examined in the growth phase of rat ostearcoma ROS 17/2.25(OH)D 22个D D 23个D2和its analogues modulate transmembrane Ca D12个D1influx in osteoblast-like cells by opening L-type Ca D12个D1 channels which can recognize 1α-hydroxy analogues as agonists and 1β-hydroxy analogues as antagonists.(6)We demonstrated that1α，25(OH)The vitamin D I D 23 D 2 receptor(VDR)specifically bound to the distal NFAT site in the human IL-2 promoter.Less：Less

To clarify the structure-function relationship of vitamin D analogues, we synthesized novel vitamin D analogues and evaluated their biological activities.(1) A series of singly dehydroxylated 19-nor-1α, 25-dihydroxyvitamin DィイD23ィエD2 A-ring analogues were synthesized. The analogues could be clearly divided into two categories ; one group, bearing 1α-hydroxy or 3β-hydroxy groups in the A-ring, were potent differentiators and the second group, bearing 1β-hydroxy or 3α-hydroxy groups, were potent stimulators of apoptosis. These findings will provide useful information not only for development of therapeutic agents for treatment of leukemia and other cancers.(2) Biological activities of a series of 2β-substituted analogues of 1α, 25(OH)ィイD22ィエD2)DィイD23ィエD2 were evaluated. Binding affinity for VDR, transactivation potency on the target gene and VDR-mediated gene regulation of the hydroxyalkyl and hydroxyalkoxy 2β-substituted analogues were almost comparable to those of 1α, 25(OH)ィイD22ィエD2Dィ … More イD23ィエD2, while the alkyl and alkenyl analogues were much less active than 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2. Furthermore, we found a promising candidate for preventive and therapeutic medicine of osteoporosis among these compounds.(3) The biological activity of two sets of ring A stereo isomers of 2-methyl-1α, 25-dihydroxyvitamin DィイD23ィエD2 and 2-methyl-20-epi-1α, 25-dihydroxyvitamin DィイD23ィエD2 were evaluated. We found that 2β-methyl-20-epi-3-epi-1β, 25(OH)ィイD22ィエD2DィイD23ィエD2 is transcriptionally more active than 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2 despite lacking the 1α-hydroxyl group, which was believed to be essential for expressing VDR-mediated gene transcription. Since the C-20 natural counterpart, 2β-methyl-3-epi-1β, 25(OH)ィイD22ィエD2DィイD23ィエD2, was almost completely biologically inactive, 20-epimerization is probably responsible for activation of gene expression.(4) We found that binding affinity 1α, 25(OH)ィイD22ィエD2DィイD22ィエD2 and 1α, 25(OH)ィイD22ィエD2DィイD24ィエD2 were almost comparable to the effects of 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2, while 24-epi-1α, 25(OH)ィイD22ィエD2DィイD22ィエD2 and 1α, 25(OH)ィイD22ィエD2DィイD27ィエD2 were much less active than 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2 in these respects. This is the first finding concerning biological assessment of 1α, 25(OH)ィイD22ィエD2DィイD22ィエD2, 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2, 1α, 25(OH)ィイD22ィエD2DィイD24ィエD2, 24-epi-1α, 25(OH)ィイD22ィエD2DィイD22ィエD2 and 1α, 25(OH)ィイD22ィエD2DィイD27ィエD2 at the molecular level, especially with regards to the structural differences at the 24R- or 24S-methyl group and a double bond between carbons 22 and 23 in the side chain of 1α, 25(OH)ィイD22ィエD2D derivatives.(5) The effects of 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2 and its analogues on transmembrane CaィイD12+ィエD1 influx were examined in the growth phase of rat osteosarcoma ROS17/2.8 cells.The results suggest that 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2 and its analogues modulate transmembrane CaィイD12+ィエD1 influx in osteoblast-like cells by opening L-type CaィイD12+ィエD1 channels which can recognize 1α-hydroxy analogues as agonists and 1β-hydroxy analogues as antagonists.(6) We demonstrated that 1α, 25(OH)ィイD22ィエD2DィイD23ィエD2-mediated suppressive effects on the inducible expression of cytokine genes in human T cells may, in part, be due to diminished activity of the transcription factor NFAT. The vitamin DィイD23ィエD2 receptor (VDR) specifically bound to the distal NFAT site in the human IL-2 promoter. Less