Jin L, Davis M R, Kharasch E D, Doss G A, Baillie T A
Department of Medicinal Chemistry, University of Washington, Seattle 98195, USA.
Chem Res Toxicol. 1996 Mar;9(2):555-61. doi: 10.1021/tx950162m.
Recent studies have indicated that the nephrotoxicity of fluoromethyl 2,2-difluoro-1-(trifluoromethyl)vinyl ether ("Compound A"), a breakdown product of the inhaled anesthetic sevoflurane, may be mediated by a reactive intermediate(s) generated via the cysteine conjugate beta-lyase pathway. In order to gain a better understanding of glutathione (GSH)-dependent metabolism of Compound A, the present study was carried out with the primary goal of detecting and characterizing Compound A--GSH conjugates. By means of ionspray LC-MS/MS and NMR spectroscopy, a total of four GSH conjugates ("A1-A4") were identified from the bile of rats dosed intraperitoneally with Compound A. A1 and A2 were identified as two diastereomers of S-[1,1-difluoro-2-(fluoromethoxy)-2-(trifluoromethyl)ethyl]glutath ione, while A3 and A4 were identified as (E)- and (Z)-S-[1-fluoro-2-(fluoromethoxy)-2-(trifluoromethyl)-vinyl]glutat hione, respectively. Quantitative analyses indicated that approximately 29% of the administered dose of Compound A was excreted into the bile in the form of the above GSH conjugates over a period of 6 h. Studies conducted in vitro demonstrated that the reaction of Compound A with GSH was catalyzed by both rat liver cytosolic and microsomal glutathione S-transferases (GST), with the two enzyme systems exhibiting different product selectivities. Formation of these GSH conjugates also occurred nonenzymatically at an appreciable rate. These results indicate that spontaneous and enzyme-mediated conjugation with GSH represents a major pathway of metabolism of Compound A in rats. Conjugation of Compound A with GSH in vivo appeared to be catalyzed preferentially by microsomal rather than cytosolic GST, based on comparison of biliary, microsomal, and cytosolic metabolic profiles. By analogy with other haloalkenes, further metabolism of the corresponding cysteine conjugates of Compound A by renal cysteine conjugate beta-lyase may lead to the formation of reactive acylating agents, which would be expected to bind covalently to cellular macromolecules and cause organ-selective nephrotoxicity.
近期研究表明，吸入麻醉剂七氟醚的分解产物氟甲基 2,2 - 二氟 - 1 -（三氟甲基）乙烯基醚（“化合物A”）的肾毒性可能由通过半胱氨酸共轭β - 裂解酶途径产生的一种或多种反应性中间体介导。为了更好地理解化合物A的谷胱甘肽（GSH）依赖性代谢，本研究以检测和表征化合物A - GSH共轭物为主要目标展开。借助离子喷雾LC - MS/MS和核磁共振光谱，从腹腔注射化合物A的大鼠胆汁中总共鉴定出四种GSH共轭物（“A1 - A4”）。A1和A2被鉴定为S - [1,1 - 二氟 - 2 -（氟甲氧基）- 2 -（三氟甲基）乙基]谷胱甘肽的两种非对映异构体，而A3和A4分别被鉴定为（E）-和（Z）- S - [1 - 氟 - 2 -（氟甲氧基）- 2 -（三氟甲基）- 乙烯基]谷胱甘肽。定量分析表明，在6小时内，约29%的化合物A给药剂量以上述GSH共轭物的形式排泄到胆汁中。体外研究表明，化合物A与GSH的反应由大鼠肝细胞质和微粒体谷胱甘肽S - 转移酶（GST）催化，这两种酶系统表现出不同的产物选择性。这些GSH共轭物的形成也以可观的速率非酶促发生。这些结果表明，与GSH的自发和酶介导共轭是化合物A在大鼠体内代谢的主要途径。基于胆汁、微粒体和细胞质代谢谱的比较，化合物A在体内与GSH的共轭似乎优先由微粒体而非细胞质GST催化。与其他卤代烯烃类似，化合物A相应的半胱氨酸共轭物被肾半胱氨酸共轭β - 裂解酶进一步代谢可能导致反应性酰化剂的形成，预计这些酰化剂会与细胞大分子共价结合并导致器官选择性肾毒性。
