Seah Quee Ming, New Lee-Sun, Chan Eric C Y, Boelsterli Urs A
Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Drug Metab Lett. 2008 Aug;2(3):153-7. doi: 10.2174/187231208785425791.
We used immortalized human hepatocytes to study the bioactivation of leflunomide and the metabolic degradation to its major metabolite, A77 1726. Both leflunomide and A77 1726 caused a time- and concentration-dependent increase in LDH release. The cytotoxicity of leflunomide, but not that of A77 1726, was prevented by the pan-CYP inhibitor, 1-aminobenzotriazole, indicating that an oxidative metabolite(s) was responsible for the cell injury. LC/MS/MS analysis revealed that leflunomide was rapidly degraded in hepatocytes biphasically (t((1/2))(a) = 1.5 h, t((1/2)) >24 h), but much slower in cell-free medium (t((1/2)) >24 h). In contrast, the generation of A77 1726 occurred at a similar rate in cells and cell-free systems. In conclusion, leflunomide was rapidly metabolized in human hepatocytes to A77 1726, but its toxicity was dependent on other, CYP-dependent intermediates.
我们使用永生化人肝细胞来研究来氟米特的生物活化及其向主要代谢物A77 1726的代谢降解。来氟米特和A77 1726均导致乳酸脱氢酶（LDH）释放呈时间和浓度依赖性增加。泛CYP抑制剂1-氨基苯并三唑可预防来氟米特的细胞毒性，但不能预防A77 1726的细胞毒性，这表明一种氧化代谢物是细胞损伤的原因。液相色谱/串联质谱（LC/MS/MS）分析显示，来氟米特在肝细胞中迅速双相降解（t((1/2))(a)=1.5小时，t((1/2))>24小时），但在无细胞培养基中降解慢得多（t((1/2))>24小时）。相比之下，A77 1726在细胞和无细胞系统中的生成速率相似。总之，来氟米特在人肝细胞中迅速代谢为A77 1726，但其毒性取决于其他依赖CYP的中间体。
