TOXICOLOGICAL SIGNIFICANCE OF BILE SALT EXPORT PUMP

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。药物诱导的肝毒性通常表现为胆汁淤积、肝炎或两者兼而有之。胆汁淤积是由胆汁流动受损引起的，并表现出一系列胆汁淤积症状。许多药物已被发现诱发胆汁淤积。虽然许多因素可能有助于胆汁淤积，破坏小管分泌最近被认为是一个主要的决定性因素。遗传和生物化学研究已经确定，胆汁盐输出泵（BSEP）负责胆汁酸的分泌。BSEP功能降低或缺陷与遗传性和获得性胆汁淤积直接相关。拟议项目的长期目标是测试外源性物质对BSEP表达的调控是通过不同但功能相关的核受体途径通过转录调控实现的假设。该试验项目的具体目标包括：（1）确定外源性物质对BSEP表达的调控模式;（2）定位BSEP启动子中负责这些化学物质调控BSEP表达的顺式作用元件。第一个具体的目的是测试的假设，这些化学品的BSEP的表达调节是通过改变转录速率或mRNA的稳定性。提出了两种实验方法来检验这一假设：（a）将用这些化学品进行剂量反应和时间过程研究;（B）将用外源性物质和转录抑制剂共同处理细胞，并监测BSEP mRNA的水平。第二个具体的目的是测试的假设，这些化学物质的BSEP的转录调控是序列特异性的。设计了两种实验方法来检验这一假设：（a）制备含有潜在外源性反应元件的BSEP启动子，并测试其对这些化学物质的反应性;（B）制备BSEP启动子的缺失突变体，以定位调控表达的功能重要序列。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Drug-induced hepatotoxicity is generally presented as cholestasis, hepatitis, or both. Cholestasis is caused by impaired bile flow and exhibits a series of bile-stagnated symptoms. Many drugs have been found to induce cholestasis. Although many factors likely contribute to cholestasis, disrupted canalicular secretion is recently recognized as a major determinant factor. Genetic and biochemical studies have established that the bile salt export pump (BSEP) is responsible for the secretion of bile acids. Decreased or defective BSEP function is linked directly to hereditary and acquired cholestasis. The long-term goal of the proposed project is to test the hypothesis that the regulated expression of the BSEP by xenobiotics is achieved by transcription regulation through distinct but functionally related nuclear receptor pathways. The specific aims of this pilot project include: (1) to determine the regulatory modes of BSEP expression by xenobiotics; and (2) to locate cis-acting elements in the BSEP promoter responsible for the regulated expression of BSEP by those chemicals. The first specific aim is designed to test the hypothesis that the regulated expression of BSEP by these chemicals is achieved by either altering transcription rate or mRNA stability. Two experimental approaches are proposed to test this hypothesis: (a) dose-response and time course studies will be conducted with these chemicals; (b) and cells will be co-treated with xenobiotics and transcription inhibitors, and the level of BSEP mRNA will be monitored. The second specific aim is designed to test the hypothesis that transcription regulation of BSEP by these chemicals is sequence-specific. Two experimental approaches are designed to test the hypothesis: (a) A BSEP promoter containing potential xenobiotic-response elements will be prepared and tested for the responsiveness to these chemicals; and (b) deletion mutants of the BSEP promoter will be made to locate functionally important sequences for the regulated expression.