The antagonism between 2-methyl-1,25-dihydroxyvitamin D3 and 2-methyl-20-epi-1,25-dihydroxyvitamin D3 in non-genomic pathway-mediated biological responses induced by 1alpha,25-dihydroxyvitamin D3 assessed by NB4 cell differentiation.
We synthesized all eight possible A-ring diastereomers of 2-methyl substituted analogs of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and also all eight A-ring diastereomers of 2-methyl-20-epi-1alpha,25(OH)2D3. Their biological activities, especially the antagonistic effect on non-genomic pathway-mediated responses induced by 1alpha,25(OH)2D3 or its 6-s-cis-conformer analog, 1alpha,25(OH)2-lumisterol3, were assessed using an NB4 cell differentiation system. Antagonistic activity was observed for the 1beta-hydroxyl diastereomers, including 2beta-methyl-1beta,25(OH)2D3 and 2beta-methyl-3-epi-1beta,25(OH)2D3. Very interestingly, 2beta-methyl-3-epi-1alpha,25(OH)2D3 also antagonized the non-genomic pathway, despite its 1alpha-hydroxyl group. Other 1alpha-hydroxyl diastereomers did not show antagonistic activity. 20-epimerization diminished the antagonistic effect of all of these analogs on the non-genomic pathway. These findings suggested that the combination of the 2-methyl substitution of the A-ring and 20-epimerization of the side chain could alter the biological activities in terms of antagonism of non-genomic pathway-mediated biological response. Based on a previous report, 2-methyl substitution alters the equilibrium of the A-ring conformation between the alpha- and beta-chair conformers. The 2beta-methyl diastereomers, which exhibited antagonism on non-genomic pathway-mediated response, were considered to prefer the beta-conformer. Further examination to elucidate the relationship between the altered ligand shape and receptors interaction will be important for molecular level understanding of the mechanism of antagonism of the non-genomic pathway.
Miura
Daishiro
D
Teijin Institute for Bio-Medical Research, Teijin Pharma Ltd., 4-3-2 Asahigaoka, Hino, Tokyo 191-8512, Japan.
Norman
Anthony W
AW
Mizwicki
Mathew T
MT
Fujishima
Toshie
T
Konno
Katsuhiro
K
Kittaka
Atsushi
A
Takayama
Hiroaki
H
Ishizuka
Seiichi
S
D002117:Calcitriol / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D006801:Humans; D011487:Protein Conformation; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D065668:Vitamin D3 24-Hydroxylase
C116441:2-methyl-1,25-dihydroxyvitamin D3; C502297:2-methyl-20-epi-1,25-dihydroxyvitamin D3; D018167:Receptors, Calcitriol; D014807:Vitamin D; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol