Molecular basis of interindividual variability in CYP2D6-mediated drug metabolism

 描述（由申请人提供）：非故意的药物过量或剂量不足是一个巨大的临床问题。CYP 2D 6介导的药物代谢的个体间差异较大是导致这一问题的关键因素，因为它是对给定剂量的CYP 2D 6底物产生不可预测的药物不良结局的原因。已知CYP 2D 6的遗传多态性部分解释了变异性，尤其是对于弱代谢者表型;然而，它们未能解释其余人群中的大多数变异性（约90%）。越来越多的证据表明，CYP 2D 6在转录水平上的差异调节在决定CYP 2D 6介导的药物代谢中起着关键作用。在健康人肝组织中，CYP 2D 6的mRNA水平与酶的活性高度相关。相关性水平与CYP 3A 4相似，CYP 3A 4是一种主要在转录水平上控制表达的基因。尽管有这些证据，但对CYP 2D 6转录的调控因素知之甚少。因此，我们对导致药物不良反应或药物依赖的个体间变异性的理解存在很大差距。 无效我们研究的长期目标是开发更好地预测个体中高度可变的CYP 2D 6活性的方法。我们的假设是，遗传和环境因素调节特定转录因子，小异源二聚体伴侣（SHP）的表达/活性，这反过来又改变CYP 2D 6的表达。我们进一步假设，这是部分负责CYP 2D 6表达的个体间变异性。我们的假设是基于我们最近在CYP 2D 6人源化转基因（Tg-CYP 2D 6）小鼠中发现SHP抑制CYP 2D 6表达。此外，增强SHP表达的化合物抑制肝CYP 2D 6表达，并且SHP和CYP 2D 6表达在人肝组织中呈负相关。这些数据有力地表明，SHP在调节CYP 2D 6表达中起关键作用，并且SHP的差异表达导致CYP 2D 6变异性。为了验证我们的假设，我们提出了以下具体目标：（1）确定SHP调节剂在Tg-CYP 2D 6小鼠中引起CYP 2D 6表达改变的程度，以及（2）鉴定解释人类肝脏组织中CYP 2D 6变异性的SHP调节剂。目前预测CYP 2D 6活性的努力完全依赖于CYP 2D 6基因型，无法解释大多数人群中CYP 2D 6的变异性。预计拟议的工作将揭示以前未知的CYP 2D 6变异性的贡献者（即控制SHP表达和/或活性的外在和遗传因素），从而提高预测CYP 2D 6活性的能力。我们相信，这将最终导致策略的发展，以尽量减少危险药物过量和剂量不足与CYP 2D 6底物的风险。

 DESCRIPTION (provided by applicant): Unintentional drug over- or under-dosing is an enormous clinical problem. The large interindividual variability in CYP2D6-mediated drug metabolism is a critical contributor to this problem, as it is responsible for the unpredictable occurrence of adverse drug outcomes in response to a given dose of a CYP2D6 substrate. It is known that genetic polymorphisms of CYP2D6 partially explain the variability, especially for the poor metabolizer phenotype; however, they fail to explain the majority of variability in the remaining population (~90%). Accumulating evidence strongly indicates that differential regulation of CYP2D6 at the transcriptional level plays a key role in determining CYP2D6-mediated drug metabolism. In healthy human liver tissues, mRNA levels of CYP2D6 were highly correlated with the enzyme's activity. The level of correlation was similar to that for CYP3A4, a gene whose expression is controlled mainly at the transcriptional level. Despite this evidence, factors governing CYP2D6 transcription are poorly understood. Thus, there is a substantial gap in our understanding of the interindividual variability that lead to adverse drug reactions or drug inefficacy. The long-term goal of our research is to develop approaches to better predict the highly variable CYP2D6 activity in individuals. Our hypothesis is that genetic and environmental factors regulate the expression/activity of a specific transcription factor, small heterodimer partner (SHP), which in turn alters CYP2D6 expression. We further hypothesize that this is in part responsible for the interindividual variability in CYP2D6 expression. Our hypothesis is based on our recent finding in CYP2D6-humanized transgenic (Tg-CYP2D6) mice that SHP represses CYP2D6 expression. Moreover, compounds enhancing SHP expression repress hepatic CYP2D6 expression, and SHP and CYP2D6 expression is negatively correlated in human liver tissues. These data strongly suggest that SHP plays a key role in regulating CYP2D6 expression and that differential expression of SHP leads to CYP2D6 variability. To test our hypothesis, we propose the following specific aims: (1) Determine the extent to which SHP modulators cause alterations of CYP2D6 expression in Tg-CYP2D6 mice, and (2) Identify SHP modulators that explain CYP2D6 variability in human liver tissues. Current efforts to predict CYP2D6 activity rely exclusively on the CYP2D6 genotypes and fail to explain CYP2D6 variability in the majority of the population. The proposed work is expected to reveal previously unknown contributors to CYP2D6 variability (namely extrinsic and genetic factors controlling the expression and/or activity of SHP) and, thus, improve the ability to predict CYP2D6 activity. We believe this will ultimately lead to the development of strategies to minimize the risk of dangerous drug over- and under-dosing with CYP2D6 substrates.