Wilson Lindsay B, McClure Ryan S, Waters Katrina M, Simonich Michael T, Tanguay Robyn L
Department of Environmental and Molecular Toxicology, Sinnhuber Aquatic Research Laboratory, Oregon State University, Corvallis, OR, United States.
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States.
Front Toxicol. 2022 Aug 25;4:950503. doi: 10.3389/ftox.2022.950503. eCollection 2022.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants and are associated with human disease. Canonically, many PAHs induce toxicity via activation of the aryl hydrocarbon receptor (AHR) pathway. While the interaction between PAHs and the AHR is well-established, understanding which AHR-regulated transcriptional effects directly result in observable phenotypes and which are adaptive or benign is important to better understand PAH toxicity. Retene is a frequently detected PAH in environmental sampling and has been associated with AHR2-dependent developmental toxicity in zebrafish, though its mechanism of toxicity has not been fully elucidated. To interrogate transcriptional changes causally associated with retene toxicity, we conducted whole-animal RNA sequencing at 48 h post-fertilization after exposure to eight retene concentrations. We aimed to identify the most sensitive transcriptomic responses and to determine whether this approach could uncover gene sets uniquely differentially expressed at concentrations which induce a phenotype. We identified a concentration-response relationship for differential gene expression in both number of differentially expressed genes (DEGs) and magnitude of expression change. Elevated expression of at retene concentrations below the threshold for teratogenicity suggested that while expression is a sensitive biomarker of AHR activation, it may be too sensitive to serve as a biomarker of teratogenicity. Genes differentially expressed at only non-teratogenic concentrations were enriched for transforming growth factor-β (TGF-β) signaling pathway disruption while DEGs identified at only teratogenic concentrations were significantly enriched for response to xenobiotic stimulus and reduction-oxidation reaction activity. DEGs which spanned both non-teratogenic and teratogenic concentrations showed similar disrupted biological processes to those unique to teratogenic concentrations, indicating these processes were disrupted at low exposure concentrations. Gene co-expression network analysis identified several gene modules, including those associated with PAHs and AHR2 activation. One, Module 7, was strongly enriched for AHR2-associated genes and contained the strongest responses to retene. Benchmark concentration (BMC) of Module seven genes identified a median BMC of 7.5 µM, nearly the highest retene concentration with no associated teratogenicity, supporting the hypothesis that Module seven genes are largely responsible for retene toxicity.
多环芳烃（PAHs）是普遍存在的环境污染物，与人类疾病相关。通常，许多PAHs通过激活芳烃受体（AHR）途径诱导毒性。虽然PAHs与AHR之间的相互作用已得到充分证实，但了解哪些AHR调节的转录效应直接导致可观察到的表型，哪些是适应性的或良性的，对于更好地理解PAH毒性很重要。惹烯是环境采样中经常检测到的一种PAH，与斑马鱼中AHR2依赖性发育毒性有关，但其毒性机制尚未完全阐明。为了探究与惹烯毒性因果相关的转录变化，我们在受精后48小时暴露于八种惹烯浓度下进行了全动物RNA测序。我们旨在确定最敏感的转录组反应，并确定这种方法是否能够揭示在诱导表型的浓度下独特差异表达的基因集。我们在差异表达基因（DEGs）数量和表达变化幅度方面都确定了差异基因表达的浓度-反应关系。在低于致畸阈值的惹烯浓度下，[此处原文可能缺失具体基因名称]表达升高，这表明虽然[此处原文可能缺失具体基因名称]表达是AHR激活的敏感生物标志物，但它可能过于敏感，无法作为致畸性的生物标志物。仅在非致畸浓度下差异表达的基因在转化生长因子-β（TGF-β）信号通路破坏方面富集，而仅在致畸浓度下鉴定出的DEGs在对外源生物刺激的反应和还原-氧化反应活性方面显著富集。跨越非致畸和致畸浓度的DEGs显示出与致畸浓度特有的生物过程类似的破坏，表明这些过程在低暴露浓度下就被破坏。基因共表达网络分析确定了几个基因模块，包括与PAHs和AHR2激活相关的模块。其中一个模块，即模块7，在与AHR2相关的基因方面强烈富集，并包含对惹烯最强的反应。模块7基因的基准浓度（BMC）确定中位数BMC为7.5µM，几乎是没有相关致畸性的最高惹烯浓度，支持了模块7基因在很大程度上负责惹烯毒性的假设。
