Foley Briana, Breaux Kristen, Shobair Mahmoud, Feshuk Madison, Richard Ann M, Thomas Russell S, Paul Friedman Katie, Deisenroth Chad
Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27711, USA.
Retired, EPA Emeritus.
Toxicol Sci. 2025 Jul 21. doi: 10.1093/toxsci/kfaf102.
The U.S. EPA has evaluated thousands of environmental chemicals within the ToxCast and Tox21 programs using high-throughput screening (HTS) assays for molecular targets across the hypothalamic-pituitary-thyroid axis. The thyroid stimulating hormone receptor (TSHR) is a critical regulator of thyroid development and function, and essential for thyroid hormone synthesis. Hundreds of chemicals have been identified as potential modulators of the TSHR in a Tox21 HTS assay, but the mechanistic and biological relevance to humans is uncertain. The objectives of this study were to select a subset of active chemicals from the Tox21 TSHR assay, screen for agonist or antagonist activity in human primary thyrocyte assays to evaluate mechanistic effects on the native TSHR, then extend screening to assess functional effects on thyroid hormone synthesis in human thyroid microtissues. A total of 72 (agonist mode) and 64 (antagonist mode) chemicals were selected for screening. A conventional two-dimensional screening assay was implemented as a primary screening strategy to evaluate thyroglobulin protein production as a biomarker for TSHR-dependent bioactivity in primary thyrocytes. Active chemicals were triaged for secondary screening in three-dimensional thyroid microtissue assays to evaluate the functional relevance to thyroid hormone synthesis. Final results revealed two agonist and 13 antagonist chemicals that demonstrated concordant activity across the two assay formats. The results support a strategic tiered testing paradigm whereby chemicals flagged for hazard potential from targeted HTS assays are evaluated in assays with enhanced biological relevance to the target tissue of interest to inform hazard characterization for putative thyroid disrupting chemicals in humans.
美国环境保护局（EPA）已在ToxCast和Tox21项目中，使用针对下丘脑 - 垂体 - 甲状腺轴分子靶点的高通量筛选（HTS）分析方法，对数千种环境化学物质进行了评估。促甲状腺激素受体（TSHR）是甲状腺发育和功能的关键调节因子，对甲状腺激素合成至关重要。在Tox21 HTS分析中，已鉴定出数百种化学物质为TSHR的潜在调节剂，但其与人类的作用机制和生物学相关性尚不确定。本研究的目的是从Tox21 TSHR分析中选择一组活性化学物质，在人原代甲状腺细胞分析中筛选激动剂或拮抗剂活性，以评估对天然TSHR的作用机制，然后扩展筛选以评估对人甲状腺微组织中甲状腺激素合成的功能影响。总共选择了72种（激动剂模式）和64种（拮抗剂模式）化学物质进行筛选。实施了传统的二维筛选分析作为主要筛选策略，以评估甲状腺球蛋白的产生，作为原代甲状腺细胞中TSHR依赖性生物活性的生物标志物。对活性化学物质进行分类，以便在三维甲状腺微组织分析中进行二次筛选，以评估其与甲状腺激素合成的功能相关性。最终结果显示，有两种激动剂和13种拮抗剂化学物质在两种分析形式中表现出一致的活性。这些结果支持了一种战略性分层测试范式，即对从靶向HTS分析中标记出具有潜在危害的化学物质，在与感兴趣的靶组织具有更高生物学相关性的分析中进行评估，以为人类中假定的甲状腺干扰化学物质的危害特征提供信息。
