Role of CYP2J2 in Xenobiotic Induced QT-prolongation

描述(由申请人提供)：这项研究提案的长期目标是阐明CYP2J2在某些外源性药物延长QT、心脏毒性作用中的作用。CYP2J2在心肌细胞中含量丰富，参与花生四烯酸代谢为具有生物活性的环氧二十碳三烯酸(EETs)。在不同的细胞模型中，EETs对心脏离子通道和QT间期的电生理效应已经得到了很好的证明。我们已经证明，与QT延长密切相关的药物中，有70%能抑制细胞色素P450 2J2的表达。因此，CYP2J2抑制剂引起的组织EET(S)浓度的变化可能会对心肌细胞产生毒性作用。该项目围绕两个假设和四个具体目标展开。假设一指出，与尖端扭矩相关的药物可以被确定为强烈抑制CYP2J2，但在生理浓度下对HERG的影响很小。设计了两个特定的目标来验证这一假说，并重点描述了通过在重组系统中引起QT延长的药物和在心脏中表达CYP2J2的转基因小鼠的心脏微粒体中抑制CYP2J2的生理效应。第二种假设认为，抑制CYP2J2的药物通过降低EET水平而延长小鼠心肌细胞的动作电位，这反过来又导致KATP电流的减少。为了验证第二个假设，开发了特定的AIMS 3和4，以确定在特定的AIMS 1和2中确定的有效的CYP2J2抑制剂对小鼠的慢性治疗是否导致小鼠心肌组织中内源性EETS水平的减少，最后，特定的AIM 4利用从野生型和转基因小鼠分离的心肌细胞的电生理学研究来确定抑制CYP2J2对KATP电流和动作电位时程的影响。这些目标的成功完成将通过表征位于药物和内源性底物代谢界面的一种独特的酶(CYP2J2)的功能相互作用，首次证明代谢在致痛药物毒性机制中的重要性。 公共卫生相关性：本提案中描述的研究旨在了解医源性疾病的机制。有时，摄入食物中的某些药物或化学物质会干扰一种名为CYP2J2的酶的内源性功能，并可能导致心脏毒性。预测哪些药物具有调节CYP2J2活性的风险将有助于我们在这种心脏毒性发生之前将其预防，提高药物安全性，并减少药物的不良反应。

DESCRIPTION (provided by applicant): The long term objective of this research proposal is to elucidate the role of CYP2J2 in the QT- prolonging, cardiotoxic effect of certain xenobiotics. CYP2J2 is abundant in cardiac myocytes and is involved in the metabolism of arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs). EETs have well documented electrophysiological effects on cardiac ion channels and the QT-period in various cell models. We have demonstrated that CYP2J2 is inhibited by 70% of drugs that are strongly associated with QT-prolongation. Therefore, alterations in tissue EET(s) concentrations caused by CYP2J2 inhibitors could be expected to have toxic effects on cardiomyocytes. This project is developed around two hypotheses and four specific aims. Hypothesis one states that drugs associated with torsade de pointes can be identified that strongly inhibit CYP2J2, but have minimal effect on hERG at physiological concentrations. Two specific aims were designed to test this hypothesis and are focused on characterizing the physiological effect of CYP2J2 inhibition by drugs that cause QT- prolongation in both a recombinant system and cardiac microsomes from transgenic mice that express CYP2J2 in their hearts. The second hypothesis states that drugs that inhibit CYP2J2 contribute to prolongation of the action potential in mouse cardiac myocytes by reducing EET levels, which in turn leads to reduction in KATP currents. To test the second hypothesis, specific aims 3 and 4 were developed to determine if chronic treatment of mice with potent CYP2J2 inhibitors, identified in specific aims 1 and 2, leads to reduction in endogenous EETs levels in mouse cardiac tissue and finally specific aim 4 utilizes electrophysiological studies in cardiac myocytes isolated from wild type and transgenic mice to determine the consequences of inhibiting CYP2J2 on KATP currents and the action potential duration. Successful completion of these aims will demonstrate, for the first time, the importance of metabolism in the mechanism of toxicity of torsadogenic drugs, by characterizing the functional interactions of a unique enzyme (CYP2J2) that is situated at the interface of drug and endogenous substrate metabolism. PUBLIC HEALTH RELEVANCE: The research described in this proposal aims at understanding the mechanism of an iatrogenic disease. Sometimes ingesting certain drugs or chemicals in food interferes with the endogenous function of an enzyme, CYP2J2, and may precipitate cardiotoxicity. Predicting which drugs pose a risk of modulating CYP2J2 activity will aid us in preventing this cardiotoxicity before it occurs, improve drug safety, and reduce drug adverse effects.