ANESTHETIC TOXICITY--MECHANISMS AND PREVENTION

麻醉毒性--机制与预防

• 批准号: 2770988
• 负责人: Evan D. Kharasch
• 金额: $ 22.39万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-30 至 2000-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2770988
• 关键词: active sites; anesthesia complication; clinical research; cytochrome P450; disulfiram; drug adverse effect; drug design /synthesis /production; drug interactions; drug metabolism; enzyme activity; enzyme inhibitors; enzyme mechanism; enzyme substrate complex; halothane; hepatotoxin; human subject; isozymes; laboratory rat; lipid peroxides; liver metabolism; nuclear magnetic resonance spectroscopy; oxygen tension; protein structure function; stereoisomer

DESCRIPTION (Adapted from the Investigator's Abstract): The overall objective of this research proposal is to enhance the safety of volatile anesthetics by diminishing or preventing their toxicity. Halothane, the most widely used anesthetic in the world, causes a rare but fatal fulminant hepatic necrosis. Moreover, it commonly causes altered postoperative mixed function oxidase activity. The toxicity of halothane, and other fluorinated anesthetics, is intrinsically linked to their metabolism by cytochrome P450. For example, the immunologic cascade culminating in fulminant hepatic necrosis ("halothane hepatitis") is initiated by P450-mediated halothane oxidation to products which bind to liver proteins, rendering them antigenic. P450 also activates halothane to free radicals which initiate lipid peroxidation, and catalyzes nephrotoxic fluoride ion release from fluorinated ethers. Specific human P450 isoforms responsible for anesthetic metabolism have been identified. P4502E1 catalyzes fluorinated ether defluorination and halothane oxidation to protein antigens, while P4503A4 catalyzes halothane reduction to free radicals. Certain volatile anesthetics, alone among the myriad protoxins and procarcinogens activated by P4502E1, are metabolized stereoselectively. Furthermore, P4502E1 metabolizes halothane aerobically but not anaerobically, while the converse occurs for P4503A4. One central hypothesis to be tested is that selective inactivation of the specific human cytochrome P450 isoforms responsible for anesthetic metabolism can be accomplished clinically, and that such inactivation will prevent anesthetic toxification. Disulfiram is an effective clinical inhibitor of P4502E1 and P4502E1-mediated anesthetic metabolism. However, clinical disulfiram P450 specificity and efficacy in preventing metabolism-based toxicity are unknown. Human studies will establish the specificity, safety and optimal disulfiram dosing regimen for clinical inhibition of P4502E1-mediated anesthetic toxicity. The ability of clinical P450 inhibitors, developed to diminish anesthetic metabolism, to prevent metabolism-based anesthetic toxicity will be investigated in vitro and in vivo in animals and humans. If the hypothesis is correct, then volatile anesthetic metabolism will be diminished, toxicity will be reduced or prevented, and the therapeutic index of volatile anesthetics dramatically enhanced. The second major hypothesis to be tested is that unique structural dynamic features of the P4502E1 and P4503A4 active sites restricts substrate binding and active site mobility, and that oxygen-dependent conformational changes have a critical modulatory role in these processes. Cloned, expressed human P450s 2E1 and 3A4 will be used in catalytic structure-activity studies with anesthetic stereoisomers and analogues, in concert with NMR studies of substrate-hemoprotein interactions, to test this hypothesis. If the hypothesis is correct, then unique insights into molecular mechanisms of substrate-protein interactions will be obtained. More importantly, potentially bioactivated anesthetics or protoxins may be rationally designed to avoid this metabolic hazard.

描述（根据调查员的摘要改编）：总体 该研究建议的目的是提高挥发性的安全性 通过减少或防止其毒性来麻醉。 Halothane， 世界上使用最广泛使用的麻醉剂会导致罕见但致命的暴发性 肝坏死。 此外，它通常会导致术后混合物改变 功能氧化酶活性。 氟烷和其他氟的毒性 麻醉药与细胞色素P450的代谢本质上相关。 例如，免疫学级联高潮肝的最终 坏死（“硫烷肝炎”）由P450介导的硫烷引发 氧化与结合肝蛋白的产品，使其氧化 抗原。 P450还将氟烷激活为启动的自由基 脂质过氧化，并催化肾毒性氟离子从 氟化物。 特定的人P450同工型负责麻醉 已经确定了代谢。 P4502E1催化氟醚 脱氟化和氟烷氧化蛋白抗原，而P4503A4 催化氟烷还原为自由基。 某些挥发性 麻醉药，仅在无数蛋白质和procarcinogen中激活 由P4502E1，立体选择性代谢。 此外，P4502E1 用氧而不是厌氧代谢，而相反 P4503A4发生。 一个要测试的中心假设是选择性 特定的人类细胞色素P450同工型的灭活 麻醉代谢可以在临床上完成，这样 失活将防止麻醉毒性。 二硫次是一个 P4502E1和P4502E1介导的麻醉剂的有效临床抑制剂 代谢。 但是，临床二硫仑P450的特异性和功效 预防基于代谢的毒性尚不清楚。 人类研究将 建立特异性，安全性和最佳二硫次给药方案 P4502E1介导的麻醉毒性的临床抑制作用。 能力 临床P450抑制剂，发展为减少麻醉代谢的发展 预防基于代谢的麻醉毒性将在体外研究 和动物和人的体内。 如果假设正确，则 挥发性麻醉代谢将降低，毒性将降低 或阻止的，以及挥发性麻醉药的治疗指数 增强。 要测试的第二个主要假设是独特的 P4502E1和P4503A4活动位点的结构动态特征 限制底物结合和主动站点的迁移率，并且 氧依赖性构象变化在 这些过程。 克隆，表达的人类P450S 2E1和3A4将使用 麻醉立体异构体的催化结构活性研究和 类似物，与底物 - 脱蛋白的NMR研究一致 相互作用，以检验这一假设。 如果假设正确，则 对底物 - 蛋​​白质相互作用的分子机制的独特见解 将获得。 更重要的是，潜在的生物活化麻醉药或 蛋白质可能是理性设计的，以避免这种代谢危害。