U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA.
U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, MN 55804, USA.
Toxicol In Vitro. 2021 Mar;71:105073. doi: 10.1016/j.tiv.2020.105073. Epub 2020 Dec 29.
The iodide recycling enzyme, iodotyrosine deiodinase (IYD), is a largely unstudied molecular mechanism through which environmental chemicals can potentially cause thyroid disruption. This highly conserved enzyme plays an essential role in maintaining adequate levels of free iodide for thyroid hormone synthesis. Thyroid disruption following in vivo IYD inhibition has been documented in mammalian and amphibian models; however, few chemicals have been tested for IYD inhibition in either in vivo or in vitro assays. Presented here are the development and application of a screening assay to assess susceptibility of IYD to chemical inhibition. With recombinant human IYD enzyme, a 96-well plate in vitro assay was developed and then used to screen over 1800 unique substances from the U.S. EPA ToxCast screening library. Through a tiered screening approach, 194 IYD inhibitors were identified (inhibited IYD enzyme activity by 20% or greater at target concentration of 200 μM). 154 chemicals were further tested in concentration-response (0.032-200 μM) to determine IC and rank-order potency. This work broadens the coverage of thyroid-relevant molecular targets for chemical screening, provides the largest set of chemicals tested for IYD inhibition, and aids in prioritizing chemicals for targeted in vivo testing to evaluate thyroid-related adverse outcomes.
碘循环酶，即碘酪氨酸脱碘酶（IYD），是一种尚未被充分研究的分子机制，环境化学物质可能通过该机制对甲状腺造成破坏。这种高度保守的酶在维持甲状腺激素合成所需的游离碘水平方面发挥着重要作用。在哺乳动物和两栖动物模型中，已经记录了体内 IYD 抑制后甲状腺功能紊乱的现象；然而，在体内或体外试验中，只有少数化学物质被测试过对 IYD 的抑制作用。本文介绍了一种筛选试验的开发和应用，以评估 IYD 对化学抑制的敏感性。利用重组人 IYD 酶，开发了一种 96 孔板体外试验，并随后用于筛选来自美国 EPA ToxCast 筛选文库的 1800 多种独特物质。通过分层筛选方法，确定了 194 种 IYD 抑制剂（在 200μM 的目标浓度下，抑制 IYD 酶活性 20%或更多）。进一步对 154 种化学物质进行浓度反应（0.032-200μM）测试，以确定 IC 和排序效力。这项工作拓宽了用于化学筛选的甲状腺相关分子靶标的覆盖范围，提供了最大的一组经过测试的 IYD 抑制剂，并有助于为有针对性的体内测试确定化学物质的优先级，以评估与甲状腺相关的不良后果。
