Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, USA.
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC, USA.
Aquat Toxicol. 2014 Sep;154:71-9. doi: 10.1016/j.aquatox.2014.05.007. Epub 2014 May 16.
Firemaster 550 (FM550) is an additive flame retardant mixture used within polyurethane foam and is increasingly found in house dust and the environment due to leaching. Despite the widespread use of FM550, very few studies have investigated the potential toxicity of its ingredients during early vertebrate development. In the current study, we sought to specifically investigate mono-substituted isopropylated triaryl phosphate (mITP), a component comprising approximately 32% of FM550, which has been shown to cause cardiotoxicity during zebrafish embryogenesis. Previous research showed that developmental defects are rescued using an aryl hydrocarbon receptor (AHR) antagonist (CH223191), suggesting that mITP-induced toxicity was AHR-dependent. As zebrafish have three known AHR isoforms, we used a functional AHR2 knockout line along with AHR1A- and AHR1B-specific morpholinos to determine which AHR isoform, if any, mediates mITP-induced cardiotoxicity. As in silico structural homology modeling predicted that mITP may bind favorably to both AHR2 and AHR1B isoforms, we evaluated AHR involvement in vivo by measuring CYP1A mRNA and protein expression following exposure to mITP in the presence or absence of CH223191 or AHR-specific morpholinos. Based on these studies, we found that mITP interacts with both AHR2 and AHR1B isoforms to induce CYP1A expression. However, while CH223191 blocked mITP-induced CYP1A induction and cardiotoxicity, knockdown of all three AHR isoforms failed to block mITP-induced cardiotoxicity in the absence of detectable CYP1A induction. Overall, these results suggest that, while mITP is an AHR agonist, mITP causes AHR-independent cardiotoxicity through a pathway that is also antagonized by CH223191.
FM550 是一种用于聚氨酯泡沫的添加型阻燃剂混合物，由于浸出作用，它在房屋灰尘和环境中越来越常见。尽管 FM550 被广泛使用，但很少有研究调查其成分在早期脊椎动物发育过程中的潜在毒性。在目前的研究中，我们试图专门研究单取代异丙基三芳基磷酸酯（mITP），它是 FM550 的大约 32%的组成部分，已被证明在斑马鱼胚胎发生过程中引起心脏毒性。先前的研究表明，使用芳香烃受体（AHR）拮抗剂（CH223191）可以挽救发育缺陷，这表明 mITP 诱导的毒性依赖于 AHR。由于斑马鱼有三个已知的 AHR 同工型，我们使用了一个功能 AHR2 敲除系，以及 AHR1A 和 AHR1B 特异性的 morpholino，以确定哪个 AHR 同工型（如果有的话）介导 mITP 诱导的心脏毒性。由于计算机模拟结构同源建模预测 mITP 可能与 AHR2 和 AHR1B 同工型都有良好的结合能力，我们通过在存在或不存在 CH223191 或 AHR 特异性 morpholino 的情况下，测量 mITP 暴露后 CYP1A mRNA 和蛋白质表达，来评估 AHR 在体内的参与情况。基于这些研究，我们发现 mITP 与 AHR2 和 AHR1B 同工型相互作用，诱导 CYP1A 表达。然而，虽然 CH223191 阻断了 mITP 诱导的 CYP1A 诱导和心脏毒性，但在没有检测到 CYP1A 诱导的情况下，敲低所有三种 AHR 同工型都未能阻断 mITP 诱导的心脏毒性。总的来说，这些结果表明，尽管 mITP 是 AHR 激动剂，但 mITP 通过一种也被 CH223191 拮抗的途径引起 AHR 非依赖性心脏毒性。
