Role of CYP2J2 in Xenobiotic Induced QT-prolongation

描述（由申请人提供）：本研究计划的长期目标是阐明CYP2J2在某些外源性药物延长QT间期和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碳三烯酸（EETs）。在各种细胞模型中，eet对心脏离子通道和qt周期的电生理影响已经得到了充分的证明。我们已经证明CYP2J2被70%与qt延长密切相关的药物所抑制。因此，CYP2J2抑制剂引起的组织EET(s)浓度的改变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，与扭转点相关的药物可以识别出强烈抑制CYP2J2，但在生理浓度下对hERG的影响很小。为了验证这一假设，我们设计了两个特定的目标，重点是描述CYP2J2抑制的生理效应，这些药物可导致重组系统和心脏微粒体中表达CYP2J2的转基因小鼠的QT-延长。第二种假设认为，抑制CYP2J2的药物通过降低EET水平来延长小鼠心肌细胞的动作电位，从而导致KATP电流的减少。为了验证第二个假设，我们开发了特异性目标3和4，以确定在特异性目标1和2中鉴定的强效CYP2J2抑制剂对小鼠的慢性治疗是否会导致小鼠心脏组织中内源性EETs水平的降低。最后，特异性目标4利用从野生型和转基因小鼠分离的心肌细胞的电生理研究来确定抑制CYP2J2对KATP电流和动作电位持续时间的影响。成功完成这些目标将首次证明代谢在扭转原性药物毒性机制中的重要性，通过表征位于药物和内源性底物代谢界面的独特酶（CYP2J2）的功能相互作用。

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.