Developmental Regulation of Drug Processing Genes

描述(申请人提供)：尽管最近在了解药物加工基因的表达模式和调控机制方面取得了快速进展，即成人体内的药物代谢酶和转运体，但在儿科阶段对此知之甚少。其长期目标是了解药物加工基因的个体调控机制，以便在儿童中实现有效和安全的药物治疗。已知有几个因素对正常发育至关重要，包括肝细胞核因子11(HNF11)、法尼类X受体(FXR)、生长激素(GH)信号转导和表观遗传影响。HNF11是肝脏早期发育的主要调节者，调节肝脏中大量药物加工基因的表达。胆汁酸信号通路的启动主要通过FXR介导，是围产期肝脏发育的标志。GH是出生后肝脏基因表达和成熟所必需的。转录因子对靶基因的可及性在很大程度上取决于组蛋白和DNA序列的甲基化/乙酰化状态。初步研究表明，在发育中的小鼠肝脏中，药物加工基因和转录因子以不同的动态模式表达，并与表观遗传特征相关。本研究的目的是阐明药物加工基因在小鼠体内表达的调控机制。这项提议的基本原理是，它的成功完成将产生基本知识，这些知识将成为进一步了解人类儿科药理学的基础。中心假说是：药物加工基因的发育调控是由激素调节的一系列事件，激素激活转录因子来修改表观遗传特征并调节基因表达。这一假设将在两个目标中得到检验。目的1确定药物加工基因的个体表达模式及其与转录因子和表观遗传学特征的相关性。将检测主要I/II期酶和药物转运体在雄性小鼠肝脏和肠道和肾脏中的相对mRNA表达，并与转录因子和染色体修饰(全基因组DNA甲基化和组蛋白修饰)的表达相关联。目的2利用相同的工作策略，阐明转录因子和生长激素在HNF11基因缺失、FXR基因缺失和生长激素缺乏症(LIT/LIT)小鼠体内药物加工基因在肝脏中的表达。这项研究是新颖的，因为它将使用全基因组方法来阐明激素和转录因子的变化如何调节药物加工基因的表观遗传特征和肝脏个体表达。这项研究意义重大，因为对儿科阶段肝脏药物加工基因的调控知之甚少。这项研究的结果将：1)提供有关药物加工基因和核受体在肝脏、肾脏和肠道中的个体发生表达模式的基础知识；2)有助于了解围产期激素和核受体的变化如何通过调节表观遗传特征，影响药物加工基因的阶段特异性和长期表达。 与公共卫生相关：拟议的研究具有重要意义，但在治疗药物的吸收、分布、新陈代谢和排泄中起重要作用的基因的发育表达模式的调节机制领域尚未得到充分研究。因此，这一发现有望应用于提高儿科药理学的有效性和安全性。

DESCRIPTION (provided by applicant): Despite recent rapid progress in understanding the expression patterns and regulatory mechanisms of drug processing genes, namely drug metabolizing enzymes and transporters in adults, little is known about these in the pediatric period. The long-term goal is to understand mechanisms of ontogenic regulation of drug processing genes, so that efficacious and safe drug treatments can be achieved in children. Several factors are known to be essential for normal development, including hepatocyte nuclear factor 11 (HNF11), farnesoid X receptor (FXR), growth hormone (GH) signaling, and epigenetic influences. HNF11, a master regulator of early liver development, regulates hepatic expression of a large battery of drug processing genes. Initiation of bile-acid signaling pathways, mediated largely via the FXR, is a hallmark of perinatal liver development. GH is essential for postnatal hepatic gene expression and maturation. The accessibility of transcription factors to the target genes is largely determined by the methylation/acetylation status of histones and DNA sequences. Preliminary studies illustrate that in developing mouse livers, drug processing genes and transcription factors are expressed in distinct dynamic patterns and correlate with epigenetic signatures. The objective of this proposal is to elucidate the regulatory mechanisms of ontogenic expression of drug processing genes in mice. The rationale of this proposal is that its successful completion will generate basic knowledge that will serve as the foundation for further understanding pediatric pharmacology in humans. The central hypothesis is: developmental regulation of drug processing genes is a sequential event regulated by hormones, which activate transcription factors to modify epigenetic signatures and regulate gene expression. This hypothesis will be tested in 2 aims. Aim 1 will determine the ontogenic expression patterns of drug processing genes and the correlation with transcription factors and epigenetic signatures. The relative mRNA expression of major phase I/II enzymes and drug transporters in male mouse livers versus intestine and kidney will be examined, and correlated with expression of transcription factors and chromosome modifications (genome-wide DNA methylation and histone modifications). Aim 2 will elucidate roles of transcription factors and GH in determining ontogenic hepatic expression of drug processing genes in HNF11-null, FXR-null, and GH deficiency (lit/lit) mice using the same working strategy. This study is novel, because it will use a genome-wide approach to elucidate how alterations of hormones and transcription factors modulate epigenetic signatures and hepatic ontogenic expression of drug processing genes. This study is significant, because little is known about the regulation of hepatic drug processing genes in pediatric stages. Results from this study will: 1) provide basic knowledge on the ontogenic expression patterns of drug processing genes and nuclear receptors in liver, kidney, and intestine; and 2) help to understand how perinatal alterations in hormones and nuclear receptors, via modulating epigenetic signatures, affect stage-specific and long-term expression of drug processing genes. PUBLIC HEALTH RELEVANCE: The proposed studies are of importance and an under-investigated area of regulatory mechanisms of the developmental expression patterns of genes important in the absorption, distribution, metabolism, and excretion of therapeutic drugs. Thus, the findings are expected to be applicable to the improvement of efficacy and safety of pediatric pharmacology.