Calcium regulating activity of 24a-homo-24,24-difluoro-1 alpha,25-dihydroxyvitamin D3 and 26,27-dimethyl-24,24-difluoro-1 alpha,25-dihydroxyvitamin D3

Up-regulation of transporters and enzymes by the vitamin D receptor ligands, 1alpha,25-dihydroxyvitamin D3 and vitamin D analogs, in the Caco-2 cell monolayer

The effects of 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] on gene expression and function were studied in Caco-2 cells. Microarray analyses, real-time quantitative polymerase chain reactions, and Western blotting were used to determine the mRNA and protein expression of transporters and enzymes after 1,25(OH)(2)D(3) or vehicle (0.1% ethanol) treatment for 1, 3, 6, and 10 days. The mRNA and protein expressions of the apical sodium-dependent bile acid transporter, oligopeptide transporter 1, multidrug resistance-associated protein (MRP) 3, and sulfotransferase 1E1 remained unchanged with 1,25(OH)(2)D(3) treatment, whereas those for CYP3A4, multidrug resistance protein 1, and MRP2 were significantly increased (P < 0.05). 1,25(OH)(2)D(3) treatment significantly enhanced MRP4 protein expression by increasing protein stability without affecting mRNA expression, as confirmed in cycloheximide experiments. Marked increase in 6beta-hydroxylation of testosterone by CYP3A4 was also observed in the 6-day 1,25(OH)(2)D(3)-treated (100 nM) cell lysate. The transport of [(3)H]digoxin, the P-glycoprotein (P-gp) substrate, after treatment with 100 nM 1,25(OH)(2)D(3) for 3 days revealed a higher apparent permeability (P(app)) value in the basal (B)-to-apical (A) direction over that of vehicle treatment (15.1 +/- 0.53 x 10(-6) versus 11.8 +/- 0.58 x 10(-6) cm/s; P < 0.05), whereas the P(app) in the A-to-B direction was unchanged; the efflux ratio was increased (from 5.8 to 8.0). Reduced cellular retention of 5-(and-6)-carboxy-2',7'-dichlorofluorescein, suggestive of higher MRP2 activity, was observed in the 3-day 100 nM 1,25(OH)(2)D(3)-treated cells over controls. Higher protein expression of CYP3A4, MRP2, P-gp, and MRP4 was also observed after a 6-day treatment with other vitamin D analogs (100 nM 1alpha-hydroxyvitamin D(3),1alpha-hydroxyvitamin D(2) or Hectorol, and 25-hydroxyvitamin D(3)) in Caco-2 cells, suggesting a role of 1,25(OH)(2)D(3) and analogs in the activation of enzymes and transporters via the vitamin D receptor.

Improved and efficient synthesis of 1alpha-hydroxy-[6-(2)H] and 1alpha-hydroxy-[6,19,19-(2)H]vitamin D3 derivatives

Improved and efficient procedures for deuterium-labeling at the 6,19,19 positions of 1alpha-hydroxyvitamin D3 derivatives via its sulfur dioxide-adduct by using a base-catalyzed H-D exchange reaction are described. Application of the known procedure using tBuOK/DMF-D2O, which is effective for labeling vitamin D3 derivatives, to 1alpha-hydroxy compounds gave only poor results because of isomerization and decomposition. We found that this procedure is improved by the use of iPrONa/iPrOD. During this study, we also found that the 6-monodeuterated product was selectively obtained when MeONa/CD3OD was employed instead of iPrONa/iPrOD. On the other hand, simple addition of 1,3-dimethyl-2-imidazolidinone as a co-solvent to the above conditions was effective for 1alpha,25-dihydroxy compounds. These improved procedures were successfully applied to the synthesis of 1alpha-hydroxy-[6,19,19-(2)H]vitamin D3 derivatives 4 and 1alpha-hydroxy-[6-(2)H]vitamin D3 derivatives 6 from the corresponding 1alpha-hydroxyvitamin D3 derivatives 1 via its sulfur dioxide-adducts 2, 3 and 5 in good over-all yield with high deuterium incorporation.

Elongation of the side chain of analogs of 1 alpha,25-dihydroxyvitamin D3 prevents osteopenia in a rat model

Five analogs of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] [1], 26,27-dimethyl-1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2(Me)2D3] [2], 26,27-dimethyl-1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2(Et)2D3] [3], 26,27-dipropyl-1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2(Pr)2D3] [4], 26,27-dimethyl-24,24-difluoro-1 alpha,25-dihydroxyvitamin D3 [24F2-1,25(OH)2(Me)2D3], and [5] 24a-homo-24,24-difluoro-1 alpha,25- dihydroxyvitamin D3 [24aF2-homo-1,25(OH)2D3] were investigated to clarify the possibility that prevents osteopenia induced in rats by ovariectomy and sciatic neurotomy. The objective of our studies was to determine whether these analogs may be effective for treatment of subjects with osteoporosis. 1,25(OH)2(Me)2D3, 24F2-1,25(OH)2(Me)2D3, and 24aF2-homo-1,25(OH)2D3 prevented decreases in bone mineral density (BMD) of the femur, as measured by dual energy X-ray absorptiometry (DXA). The potency of 1,25(OH)2(Me)2D3 in this test was higher than that of 1,25(OH)2D3. The potencies of 24F2-1,25(OH)2(Me)2D3 and 24aF2-homo-1,25(OH)2D3 were similar to that of 1,25(OH)2D3. On the other hand, though 1,25(OH)2(Et)2D3 and 1,25(OH)2(Pr)2D3 had a preventive effect on the decrease in BMD, the potency of two analogs was lower than that of 1,25(OH)2D3. Decreases in cortical and trabecular bone areas of the femur were prevented by three analogs of 1,25(OH)2D3, 1,25(OH)2(Me)2D3, 24F2-1,25(OH)2(Me)2D3, and 24aF2-homo-1,25(OH)2D3. Serum calcium (Ca) concentration was elevated at the last administration of three analogs of 1,25(OH)2D3, 1,25(OH)2(Me)2D3, 24F2-1,25(OH)2-(Me)2D3 and 24aF2-homo-1,25(OH)2D3.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium regulating activity of 26,27-dimethyl analog of 24R,25-dihydroxyvitamin D3

To determine the possibility that methyl substitution in 26- and 27-positions of 24R,25-dihydroxyvitamin D3 [24,25(OH)2D3] alters activities of the original compound, the effects of 24,25(OH)2D3 on calcium (Ca) regulating activity were compared with those of its methyl analog [24,25(OH)2(CH3)2D3] in addition to 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. 24,25(OH)2D3 at 10(-6) M and 24,25(OH)2(CH3)2D3 at 10(-7) M and above significantly stimulated both bone resorption in neonatal mouse calvaria cultures and formation of osteoclast-like multinucleated cells (MNC) in mouse bone marrow cultures. A stimulative effect of 1,25(OH)2D3 on bone resorption and MNC formation was recognized in very low concentrations (10(-11) M and above). Although a potency of 24,25(OH)2(CH3)2D3 in stimulating bone calcium (Ca) mobilization and intestinal Ca transport was higher than that of 24,25(OH)2D3, the potencies of both compounds were similar to that of 1,25(OH)2D3 unlike in vitro experiments. As 1,24R,25-trihydroxy-26,27-dimethylvitamin D3 showed almost the same effect as 24,25(OH)2(CH3)2D3, the dihydroxy form is suggested to be hydroxylated at 1 alpha position and converted to trihydroxy form in vitamin D-deficient rats. From these results, methyl substitution in 26- and 27-position of 24,25(OH)2D3 was found to elevate Ca regulating activity of the original compound. In addition, it is suggested that the basis for a similarity in potency between 1,25(OH)2D3 and 24,25(OH)2D3 or its dimethyl analog in vitamin D-deficient rats is likely the result of 1 alpha-hydroxylation.