Cheng Chloe Y S, Slominski Andrzej T, Tuckey Robert C
School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA 6009, Australia.
Department of Dermatology, University of Alabama at Birmingham, AL, USA; VA Medical Center, Birmingham, AL, USA.
J Steroid Biochem Mol Biol. 2016 May;159:131-41. doi: 10.1016/j.jsbmb.2016.03.014. Epub 2016 Mar 9.
20S-Hydroxyvitamin D3 [20(OH)D3] is the biologically active major product of the action of CYP11A1 on vitamin D3 and is present in human plasma. 20(OH)D3 displays similar therapeutic properties to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], but without causing hypercalcaemia and therefore has potential for development as a therapeutic drug. CYP24A1, the kidney mitochondrial P450 involved in inactivation of 1,25(OH)2D3, can hydroxylate 20(OH)D3 at C24 and C25, with the products displaying more potent inhibition of melanoma cell proliferation than 20(OH)D3. CYP3A4 is the major drug-metabolising P450 in liver endoplasmic reticulum and can metabolise other active forms of vitamin D, so we examined its ability to metabolise 20(OH)D3. We found that CYP3A4 metabolises 20(OH)D3 to three major products, 20,24R-dihydroxyvitamin D3 [20,24R(OH)2D3], 20,24S-dihydroxyvitamin D3 [20,24S(OH)2D3] and 20,25-dihydroxyvitamin D3 [20,25(OH)2D3]. 20,24R(OH)2D3 and 20,24S(OH)2D3, but not 20,25(OH)2D3, were further metabolised to trihydroxyvitamin D3 products by CYP3A4 but with low catalytic efficiency. The same three primary products, 20,24R(OH)2D3, 20,24S(OH)2D3 and 20,25(OH)2D3, were observed for the metabolism of 20(OH)D3 by human liver microsomes, in which CYP3A4 is a major CYP isoform present. Addition of CYP3A family-specific inhibitors, troleandomycin and azamulin, almost completely inhibited production of 20,24R(OH)2D3, 20,24S(OH)2D3 and 20,25(OH)2D3 by human liver microsomes, further supporting that CYP3A4 plays the major role in 20(OH)D3 metabolism by microsomes. Since both 20,24R(OH)2D3 and 20,25(OH)2D3 have previously been shown to display enhanced biological activity in inhibiting melanoma cell proliferation, our results show that CYP3A4 further activates, rather than inactivates, 20(OH)D3.
20S-羟基维生素D3 [20(OH)D3] 是CYP11A1作用于维生素D3的生物活性主要产物，存在于人体血浆中。20(OH)D3具有与1,25-二羟基维生素D3 [1,25(OH)2D3] 相似的治疗特性，但不会引起高钙血症，因此具有开发成为治疗药物的潜力。CYP24A1是参与1,25(OH)2D3失活的肾线粒体细胞色素P450，它可以在C24和C25位将20(OH)D3羟化，其产物对黑色素瘤细胞增殖的抑制作用比20(OH)D3更强。CYP3A4是肝脏内质网中主要的药物代谢细胞色素P450，能够代谢维生素D的其他活性形式，因此我们研究了它代谢20(OH)D3的能力。我们发现CYP3A4将20(OH)D3代谢为三种主要产物，即20,24R-二羟基维生素D3 [20,24R(OH)2D3]、20,24S-二羟基维生素D3 [20,24S(OH)2D3] 和20,25-二羟基维生素D3 [20,25(OH)2D3]。20,24R(OH)2D3和20,24S(OH)2D3，而非20,25(OH)2D3，可被CYP3A4进一步代谢为三羟基维生素D3产物，但催化效率较低。在人肝微粒体中观察到20(OH)D3代谢产生的同样三种主要产物，即20,24R(OH)2D3、20,24S(OH)2D3和20,25(OH)2D3，其中CYP3A4是主要存在的细胞色素P450同工酶。添加CYP3A家族特异性抑制剂三乙酰竹桃霉素和阿扎环醇，几乎完全抑制了人肝微粒体产生20,24R(OH)2D3、20,24S(OH)2D3和20,25(OH)2D3，进一步证明CYP3A4在微粒体对20(OH)D3的代谢中起主要作用。由于先前已证明20,24R(OH)2D3和20,25(OH)2D3在抑制黑色素瘤细胞增殖方面具有增强的生物活性，我们的结果表明CYP3A4进一步激活而非失活20(OH)D3。
