The Perinatal Pharmacology of the Nuclear Receptor

描述（由申请方提供）：这是R 01 HD 073070的重新提交，其是针对PAR-11-057提交的。我们的目标是了解围产期肝功能的核受体法尼醇X受体（FXR），特别是肝脏的后果FXR激活围产期发展。最近的研究表明，FXR激活具有多种治疗益处，因此，FXR已被广泛用作治疗靶点。以前关于FXR功能的大多数结论都依赖于成年动物的使用，而对FXR在围产期发育过程中的功能知之甚少。FXR的激活通过CYP 7A 1的转录抑制来抑制胆汁酸合成。据信，由于CYP 7A 1的基础表达较低，以及出生后早期肠肝胆汁酸再循环不足，围产期肝脏对胆汁酸池大小减少特别敏感。胆汁酸是已用于治疗肝胆疾病（包括某些儿科疾病）的临床药物。由于母亲使用胆汁酸药物和其他非胆汁酸FXR激活剂，也有大量的围产期FXR激活机会。因此，必须了解FXR的围产期药理学。我们的初步研究结果表明：1）FXR转基因小鼠的围产期激活导致肝毒性，部分致死性，炎症的迹象：2）FXR转基因的围产期毒性与胆汁酸分泌减少有关，可能是由于Cyp 7a 1的抑制; 3）围产期补充胆汁酸和/或维生素可减轻转基因鼠的肝毒性和部分致死性;（4）转基因小鼠的存活率受到明显影响，转基因母鼠喂养的转基因鼠仔存活率低于对照母鼠; 5）FXR的围产期毒性与成纤维细胞生长因子诱导的立即早期反应蛋白14（Fn 14），一种在新生儿肝脏中高度表达并与炎症有关的基因。在Fn 14基因启动子中鉴定出一个假定的FXR反应元件，表明Fn 14是FXR的转录靶点; 6）我们成功合成了6？ECDCA是一种有效的FXR激动剂，具有良好的生物利用度。根据我们的初步数据，我们假设FXR在围产期发育中具有以前未被认识到的作用。具体地说，我们假设FXR的激活可能对围产期发育期间的肝脏有毒，原因是：1）FXR的抑制， 胆汁酸的合成; 2）肠道维生素吸收不足; 3）围产期对胆汁酸池大小减少的超敏反应;以及4）母体FXR激活导致的“毒奶”。此外，FXR的围产期毒性可能是由于Fn 14的激活，FXR的一个新的转录靶点。我们提出了四个具体的目标来验证我们的假设：（1）确定围产期发育过程中FXR的基因激活是否对肝脏有毒性，以及围产期毒性是否会通过膳食补充胆汁酸和/或维生素来减轻;（2）为了确定在围产期发育期间FXR的药理学激活是否对肝脏有毒，以及药理学作用是否是FXR依赖性的;（3）确定FXR激活对围产期毒性的母体效应;以及（4）确定Fn 14是否是FXR的转录靶点以及Fn 14是否是FXR的围产期毒性所必需的。据我们所知，这项研究代表了第一次尝试系统地评价围产期药理学FXR。这项研究的结果将增加我们对FXR围产期功能的理解，这将为利用FXR的治疗益处提供更好的指导。* 本申请人同意并已申请资金参加NIH主办的为期两天的年度会议，重点是在马里兰州贝塞斯达的发展药理学。申请人也同意与其他研究者合作。

DESCRIPTION (provided by applicant): This is the resubmission of R01 HD073070, which was submitted in response to PAR-11-057. Our goal is to understand the perinatal liver function of the nuclear receptor farnesoid X receptor (FXR), especially the hepatic consequence of FXR activation during perinatal development. Recent studies have suggested multiple therapeutic benefits of FXR activation and as a result, FXR has been intensively pursued as a therapeutic target. The majority of the previous conclusions on the function of FXR have relied on the use of adult animals, whereas little is known about the function of FXR during the perinatal development. Activation of FXR suppresses bile acid synthesis through the transcriptional suppression of CYP7A1. It is believed that the perinatal livers are particularly sensitive to a decreased bile acid pool size because of a lower basal expression of CYP7A1, as well as the insufficient enterohepatic bile acid recirculation in the early postnatal period. Bile acids are clinical drugs that have been used to treat hepatobiliary diseases including certain pediatric disorders. There are also ample opportunities for perinatal activation of FXR as a result of maternal use of bile acid drugs and other non-bile acid FXR-activating agents. As such, it is imperative to understand the perinatal pharmacology of FXR. Our preliminary results show that: 1) Perinatal activation of FXR in transgenic mice resulted in hepatotoxicity, partial lethality, an signs of inflammation; 2) The perinatal toxicity of the FXR transgene was associated with a decreased biliary secretion of bile acids, likely due to the suppression of Cyp7a1; 3) Perinatal dietary supplement of bile acids and/or vitamins relived the hepatotoxicity and partial lethality o the transgenic pups; 4) There was a material effect on the survival of the transgenic mice, in which the transgenic pups nursed by transgenic dams had a worse survival than those nursed by control dams; 5) The perinatal toxicity of FXR was associated with the activation of the fibroblast growth factor-inducible immediate-early response protein 14 (Fn14), a gene highly expressed in the neonatal liver and implicated in inflammation. A putative FXR response element has been identified in the Fn14 gene promoter, suggesting Fn14 as a transcriptional target of FXR; and 6) we have successfully synthesized 6?-ECDCA, a potent FXR agonist with a favorable bioavailability. Based on our preliminary data, we hypothesize that FXR has a previously unrecognized role during perinatal development. Specifically, we hypothesize that activation of FXR might be toxic to the liver during perinatal development due to 1) the inhibition of bile acid synthesis; 2) a deficiency in intestinal vitamin absorption; 3) a perinatal hypersensitivity to decreased bile acid pool size; and 4) the "toxic milk" as a result of maternal FXR activation. Moreover, the perinatal toxicity of FXR might have been contributed to by the activation of Fn14, a novel transcriptional target of FXR. We propose four specific aims to test our hypotheses: (1) To determine whether a genetic activation of FXR during perinatal development is toxic to the liver, and whether the perinatal toxicity will be relieved by the dietay supplement of bile acids and/or vitamins; (2) To determine whether a pharmacological activation of FXR during perinatal development is toxic to the liver, and whether the pharmacological effect is FXR- dependent; (3) To determine the maternal effect of FXR activation on perinatal toxicity; and (4) To determine whether Fn14 is a transcriptional target of FXR and whether Fn14 is necessary for the perinatal toxicity of FXR. To our knowledge, this study represents the first attempt to systematically evaluate the perinatal pharmacology of FXR. Results from this study will increase our understanding of the perinatal function of FXR, which will offer better guidance in harnessing the therapeutic benefit of FXR. *This applicant agrees and has requested funds to participate in the annual NIH-sponsored two-day meetings focusing on Developmental Pharmacology in Bethesda, MD. This applicant also agrees to cooperate with other investigators.