Oak Ridge Institute for Science and Education Postdoctoral Fellow, Oak Ridge, Tennessee 37830, United States.
U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, Minnesota 55804, United States.
Chem Res Toxicol. 2024 Oct 21;37(10):1660-1669. doi: 10.1021/acs.chemrestox.4c00183. Epub 2024 Sep 13.
Thyroid hormone (TH) carrier proteins play an important role in distributing TH to target tissue as well as maintaining the balance of free versus bound TH in the blood. Interference with the TH carrier proteins has been identified as a potential mechanism of thyroid system disruption. To address the lack of data regarding chemicals binding to these carrier proteins and displacing TH, a fluorescence-based screening assay was utilized to screen over 1,400 chemicals from the U.S. EPA's ToxCast phase1_v2, phase 2, and e1k libraries for competitive binding to one of the carrier proteins, thyroxine-binding globulin. Initial screening at a single high concentration of 100 μM identified 714 chemicals that decreased signal of the bound fluorescent ligand by 20% or higher. Of these, 297 produced 50% or greater reduction in fluorescence and were further tested in concentration-response (0.004 to 150 μM) to determine relative potency. Ten chemicals were found to have EC50 values <1 μM, 63 < 10 μM, and 141 chemicals between 10 and 100 μM. Utilization of this assay contributes to expanding the number of assays available for identifying chemicals with the potential to disrupt TH homeostasis. These results support ranking and prioritization of chemicals to be tested to aid in the development of a framework for predicting effects from high-throughput data.
甲状腺激素（TH）载体蛋白在将 TH 分配到靶组织以及维持血液中游离和结合 TH 的平衡方面发挥着重要作用。干扰 TH 载体蛋白已被确定为甲状腺系统紊乱的潜在机制。为了解决缺乏有关与这些载体蛋白结合并置换 TH 的化学物质的数据的问题，利用基于荧光的筛选测定法，从美国环保局的 ToxCast phase1_v2、phase 2 和 e1k 库中筛选了超过 1400 种化学物质，以竞争性结合到一种载体蛋白-甲状腺素结合球蛋白上。在 100 μM 的单一高浓度下进行初步筛选，确定了 714 种化学物质，其结合荧光配体的信号降低了 20%或更高。其中，有 297 种化学物质使荧光降低了 50%或更高，并进一步在浓度反应（0.004 至 150 μM）中进行测试，以确定相对效力。发现有 10 种化学物质的 EC50 值<1 μM，63 种<10 μM，141 种在 10 至 100 μM 之间。该测定法的使用有助于增加可用于识别具有破坏 TH 动态平衡潜力的化学物质的测定法数量。这些结果支持对化学物质进行排名和优先级排序，以进行测试，从而有助于开发预测高通量数据产生的影响的框架。
