Tracy T S, Marra C, Wrighton S A, Gonzalez F J, Korzekwa K R
Department of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown 26506, USA.
Biochem Pharmacol. 1996 Oct 25;52(8):1305-9. doi: 10.1016/0006-2952(96)00501-1.
Flurbiprofen, a non-steroidal anti-inflammatory drug (NSAID), is metabolized by both oxidation via the cytochrome P450 system and by glucuronidation. The major oxidative pathway in flurbiprofen metabolism is to a 4'-hydroxy metabolite, and recently we demonstrated that cytochrome P450 2C9 and its R144C variant were involved in this process (Tracy et al., Biochem Pharmacol 49: 1269-1275, 1995). Using complementary DNA (cDNA)-expressed cell systems, it has been demonstrated that at physiological concentrations of flurbiprofen there is a lack of involvement of P450s 1A2, 2C8, 2E1, and 3A4. In evaluating flurbiprofen as a potential probe for cytochrome P450 2C9, it is important to assess the involvement of additional P450s in this process. To this end, further studies were undertaken using specific inhibitors of P450 2C9 and P450 cDNA-expressed microsomes for P450 1A1, 2A6, 2B6, 2C19, and 2D6 to assess their potential involvement. We observed the inhibition of (R)- and (S)-flurbiprofen 4'-hydroxylation by an inhibitor of P450 2C9, sulfaphenazole (Ki = 0.07 and 0.06 microM, respectively), and the NSAID piroxicam (Ki = 10 and 7 microM, respectively). Furthermore, using microsomes from a lymphoblastoid cell line, we found that P450s 1A1, 2A6, 2B6, 2C19, and 2D6 were not involved in flurbiprofen hydroxylation at physiological concentrations of flurbiprofen. This finding is particularly important due to the sequence homology and potential substrate overlap of P450 2C9 and 2C19. These studies then provide additional evidence to suggest that P450 2C9 may be the only isoform involved to any substantial degree in flurbiprofen 4'-hydroxylation, and thus this reaction is useful as an in vitro probe for this particularly cytochrome P450 isoform and may be useful as an in vivo probe.
氟比洛芬是一种非甾体抗炎药（NSAID），可通过细胞色素P450系统氧化和葡萄糖醛酸化两种方式进行代谢。氟比洛芬代谢的主要氧化途径是生成一种4'-羟基代谢物，最近我们证明细胞色素P450 2C9及其R144C变体参与了这一过程（Tracy等人，《生物化学与药物学》49: 1269 - 1275，1995）。利用互补DNA（cDNA）表达细胞系统已证明，在氟比洛芬的生理浓度下，P450 1A2、2C8、2E1和3A4不参与其代谢。在评估氟比洛芬作为细胞色素P450 2C9的潜在探针时，评估其他P450在此过程中的参与情况很重要。为此，使用P450 2C9的特异性抑制剂以及P450 1A1、2A6、2B6、2C19和2D6的cDNA表达微粒体进行了进一步研究，以评估它们的潜在参与情况。我们观察到P450 2C9的抑制剂磺胺苯吡唑（Ki分别为0.07和0.06 microM）和非甾体抗炎药吡罗昔康（Ki分别为10和7 microM）对（R）-和（S）-氟比洛芬4'-羟基化的抑制作用。此外，使用来自淋巴母细胞系的微粒体，我们发现，在氟比洛芬的生理浓度下，P450 1A1、2A6、2B6、2C19和2D6不参与氟比洛芬的羟基化。由于P450 2C9和2C19的序列同源性以及潜在的底物重叠，这一发现尤为重要。这些研究进而提供了更多证据，表明P450 2C9可能是在氟比洛芬4'-羟基化过程中任何显著程度上唯一涉及的同工酶，因此该反应可作为这种特定细胞色素P450同工酶的体外探针，也可能作为体内探针。
