Stoker Tammy E, Wang Jun, Murr Ashley S, Bailey Jarod R, Buckalew Angela R
Neurotoxicology and Endocrine Toxicology Branch, Public Health and Integrated Toxicology Division, Center of Public Health and Environmental Assessments, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States.
Oak Ridge Institute for Science and Education, US Department of Energy, Oak Ridge, Tennessee 37831, United States.
Chem Res Toxicol. 2023 Mar 20;36(3):380-389. doi: 10.1021/acs.chemrestox.2c00339. Epub 2023 Feb 23.
Over the past decade, there has been increased concern for environmental chemicals that can target various sites within the hypothalamic-pituitary-thyroid axis to potentially disrupt thyroid synthesis, transport, metabolism, and/or function. One well-known thyroid target in both humans and wildlife is the sodium iodide symporter (NIS) that regulates iodide uptake into the thyroid gland, the first step of thyroid hormone synthesis. Our laboratory previously developed and validated a radioactive iodide uptake (RAIU) high-throughput assay in a stably transduced human NIS cell line (hNIS-HEK293T-EPA) to identify chemicals with potential for NIS inhibition. So far, we have tested over 2000 chemicals (US EPA's ToxCast chemical libraries PI_v2, PII, and e1K) and discovered a subset of chemicals that significantly inhibit iodide uptake in the hNIS assay. Here, we utilized this screening assay to test a set of 149 unique per- and polyfluoroalkyl substances (PFAS) (ToxCast PFAS library) for potential NIS inhibition. For this evaluation, the 149 blinded samples were screened in a tiered approach, first in an initial single-concentration (≤100 μM) RAIU assay and subsequent evaluation of the chemicals that produced ≥20% inhibition using multiconcentration (MC) response (0.001-100 μM) testing in parallel RAIU and cell viability assays. Of this set, 38 of the PFAS chemicals inhibited iodide uptake ≥20% in the MC testing with 25 displaying inhibition ≥50%. To prioritize the most potent PFAS NIS inhibitors in this set, chemicals were ranked based on outcomes of both iodide uptake and cytotoxicity and normalized to perchlorate, a known positive control. Consistent with previous findings, PFOS and PFHxS were again found to be potent NIS inhibitors, yet significant inhibition was also observed for several other screened PFAS chemicals. Although further studies are clearly warranted, this initial screening effort identifies NIS as a molecular target for potential thyroid disruption by this persistent and structurally diverse class of chemicals.
在过去十年中，人们越来越关注环境化学物质，这些物质可作用于下丘脑 - 垂体 - 甲状腺轴内的各个部位，从而有可能干扰甲状腺的合成、运输、代谢和/或功能。在人类和野生动物中，一种众所周知的甲状腺靶点是钠碘同向转运体（NIS），它调节碘进入甲状腺的摄取，这是甲状腺激素合成的第一步。我们实验室之前在稳定转导的人NIS细胞系（hNIS - HEK293T - EPA）中开发并验证了一种放射性碘摄取（RAIU）高通量检测方法，以识别具有抑制NIS潜力的化学物质。到目前为止，我们已经测试了2000多种化学物质（美国环保署的ToxCast化学物质库PI_v2、PII和e1K），并发现了一组在hNIS检测中能显著抑制碘摄取的化学物质。在此，我们利用这种筛选检测方法来测试一组149种独特的全氟和多氟烷基物质（PFAS）（ToxCast PFAS库）是否具有潜在的NIS抑制作用。对于此次评估，这149个盲样采用分层方法进行筛选，首先在初始单浓度（≤100 μM）的RAIU检测中进行筛选，随后对在平行的RAIU和细胞活力检测中产生≥20%抑制作用的化学物质使用多浓度（MC）响应（0.001 - 100 μM）测试进行评估。在这组物质中，38种PFAS化学物质在MC测试中抑制碘摄取≥20%，其中25种显示抑制作用≥50%。为了在这组物质中确定最有效的PFAS NIS抑制剂，根据碘摄取和细胞毒性的结果对化学物质进行排名，并以高氯酸盐（一种已知的阳性对照）进行标准化。与之前的研究结果一致，全氟辛烷磺酸（PFOS）和全氟己烷磺酸（PFHxS）再次被发现是强效的NIS抑制剂，但在其他几种筛选出的PFAS化学物质中也观察到了显著的抑制作用。尽管显然需要进一步研究，但这项初步筛选工作确定NIS是这一持久性且结构多样的化学物质类别潜在干扰甲状腺功能的分子靶点。
