Low-calcemic, efficacious, 1alpha,25-dihydroxyvitamin D3 analog QW-1624F2-2: calcemic dose-response determination, preclinical genotoxicity testing, and revision of A-ring stereochemistry.
ABSTRACT Based on an X-ray crystal structure determination, the A-ring stereochemistry of hybrid analog QW-1624F2-2 (1alpha-hydroxymethyl-16-ene-24,24-difluoro-25-hydroxy-26,27-bis-homovitamin D3) is revised to be 1alpha-CH2OH-3beta-OH. This analog is shown to be approximately 80-100 times less calciuric than the natural hormone 1alpha,25-dihydoxyvitamin D3. This analog is shown also to be non-genotoxic in three different standard assays.
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ABSTRACT: We demonstrated previously that daily injection for 3 days of the less calcemic vitamin D analogs: JK 1624 F(2)-2 (JKF) and QW 1624F(2)-2 (QW) followed by estradiol-17beta (E(2)) in female rats upregulated creatine kinase-specific activity (CK) in skeletal tissues. In this study, we evaluated both histomorphological and biochemical changes due to a regime of 4 days treatment with JKF or QW, followed by injection of E(2) on day 5, repeated for 2.5 months. Ovariectomized female rats (Ovx) were injected 2 weeks after surgery, with JKF or QW at 0.2 ng/g BW followed by injections of E(2) (1 microg/rat) on day 5 of each week for 2.5 months. Rats were sacrificed 24 h after the last injection and bones were analyzed. JKF alone decreased growth plate width, increased % total bone volume (%TBV), with no change in cortical thickness. In contrast, QW restored growth plate width and %TBV with no change in cortical thickness. Combined with E(2), JKF restored %TBV and growth plate width but with no change in cortical thickness, while QW restored significantly all parameters including cortical thickness. Moreover, there was also an increase in the responsiveness of CK to E(2) in epiphyseal cartilage and diaphyseal bone but not in uterus. Thus, vitamin D less calcemic analogs increased responsiveness to E(2) morphologically as well as biochemically. We, therefore, conclude that combined treatment of less calcemic analogs vitamin D and E(2) might be superior for treatment of bone damage caused by ovariectomy in female rats and might be applied for post-menopausal osteoporosis.Journal of Cellular Biochemistry 04/2007; 100(6):1406-14. DOI:10.1002/jcb.21143 · 3.37 Impact Factor
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ABSTRACT: Vitamin D receptors are widely expressed in the cardiovascular system, in which Vitamin D and its metabolites exert a variety of biological activities such as regulation of cellular proliferation and differentiation, cell calcium transients and cell energy metabolism in vitro. The latter is mediated through the control of the brain type creatine kinase specific activity (CK), which serves to provide a readily available reservoir for ATP generation under increased work-load. In the present study we undertook to assess the role of Vitamin D on energy metabolism in the rat heart and aorta in vivo by using CK, which is a key energy metabolizing enzyme and compare Vitamin D depleted and repleted animals. Vascular tissues from female or male Vitamin D-depleted rats showed 61-80% lower CK activity in the aorta (Ao) and left ventricle of the heart (Lv) than control, Vitamin D-replete rats. Moreover, neither estradiol-17beta (E2) nor dihydrotestosterone (DHT), which increases CK specific activity in Ao and Lv of intact female or male rats, respectively, were able to stimulate CK in Vitamin D-depleted rats. Treatment of intact female rats for 2 weeks or 2 months with the less-calcemic Vitamin D analogs JKF 1624F2-2 (JKF) or QW 1624F2-2 (QW) (Fig. 1), did not significantly affect CK specific activity. However, after pretreatment with these analogs, there was an up regulation of the E2-induced CK response in Ao and Lv. In intact female rats, all Vitamin D analogs also potentiated the in vivo CK response to the SERMs raloxifene (Ral) and tamoxifen (TAM) in Ao and Lv. However the inhibitory effect of Ral or TAM on E2-induced CK activity was lost after pretreatment with Vitamin D analogs. The non-calcemic analog CB 1093 (CB) induced a significant increase in estradiol receptor alpha (ERalpha) protein in both myocardial and aortic tissue from intact and from ovariectomized female rats. Collectively, these results indicate that Vitamin D analogs modulate cell energy homeostasis in vascular tissues through induction of CK and up regulation of the response and sensitivity of CK in vascular tissues to E2 and to SERMs, possibly through via an increase in ERalpha protein in female derived organs. These results corroborate our previous in vitro studies in human vascular cells and further suggest that the Vitamin D system plays an important physiological role in maintaining normal cell energy reservoir in the vasculature.The Journal of Steroid Biochemistry and Molecular Biology 12/2006; 101(4-5):232-8. DOI:10.1016/j.jsbmb.2006.06.023 · 4.05 Impact Factor
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ABSTRACT: Vitamin D seems to exert a protective effect against common cancers, although this does not correlate with circulating levels of active 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], indicating a more localized activation of vitamin D. The aim of this study was to investigate the significance of this in breast cancer. Quantitative reverse transcription-PCR analysis of mRNA expression was carried out for the vitamin D-activating enzyme 1alpha-hydroxylase, the catabolic enzyme 24-hydroxylase, and the vitamin D receptor in 41 tumors and paired nonneoplastic tissue as well as breast cancer cell lines. Immunohistochemistry was used to assess 1alpha-hydroxylase protein expression, and enzyme assays were used to quantify vitamin D metabolism. Expression of mRNA for 1alpha-hydroxylase (27-fold; P < 5 x 10(-11)), vitamin D receptor (7-fold; P < 1.5 x 10(-8)), and 24-hydroxylase (4-fold; P < 0.02) was higher in breast tumors. 1alpha-Hydroxylase enzyme activity was also higher in tumors (44.3 +/- 11.4 versus 12.4 +/- 4.8 fmol/h/mg protein in nonneoplastic tissue; P < 0.05). However, production of inactive 1,24,25-trihydroxyvitamin D3 was also significantly higher in tumors (84.8 +/- 11.7 versus 33.6 +/- 8.5 fmol/h/mg protein; P < 0.01). Antisense inhibition of 24-hydroxylase in vitro increased antiproliferative responses to 1,25(OH)2D3. These data indicate that the vitamin D-activating enzyme 1alpha-hydroxylase is up-regulated in breast tumors. However, dysregulated expression of 24-hydroxylase seems to abrogate the effects of local 1,25(OH)2D3 production in tumors by catalyzing catabolism to less active vitamin D metabolites. The enzymes involved in autocrine metabolism of vitamin D in breast tissue may therefore provide important targets for both the prevention and treatment of breast cancer.Clinical Cancer Research 05/2005; 11(9):3579-86. DOI:10.1158/1078-0432.CCR-04-2359 · 8.19 Impact Factor