Interactions of polybrominated diphenyl ethers with the aryl hydrocarbon receptor pathway
Interactions of polybrominated diphenyl ethers with the aryl hydrocarbon receptor pathway
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DOI：
10.1093/toxsci/kfj186
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发表时间：
2006-07-01
影响因子：
3.8
通讯作者：
Van den Berg, M
中科院分区：
文献类型：
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作者：
Peters, AK;Nijmeijer, S;Van den Berg, M
多溴联苯醚（PBDEs）是溴化阻燃剂，已被用作各种消费品的添加剂。多溴联苯醚与其他多卤代芳烃（如某些多氯联苯）的结构相似，对芳烃受体表现出亲和力，这引起了人们对它们可能具有二恶英样特性的关注。我们研究了环境相关PBDE（BDE-47、-99、-100、-153、-154和-183）和“平面”同类物BDE-77结合和/或激活稳定转染的啮齿动物肝癌细胞系中AhR的能力，该细胞系具有AhR响应增强型绿色荧光蛋白（AhR-EGFP）报告基因（HlG1.1c3小鼠和H4 G1.1c2大鼠肝癌）。7-乙氧基试卤灵-O-脱乙基化（EROD）用作CYP 1A 1活性的标志物。通过它们抑制AhR-EGFP表达和EROD活性的能力来测量2，3，7，8-四氯-二苯并-p-二恶英（TCDD）诱导的响应的剂量特异性和溴化特异性抑制。个体暴露于这些多溴联苯醚不会导致AhR-EGFP或CYP 1A 1活性的诱导增加。溴化程度较低的多溴联苯醚对TCDD诱导的两种细胞系的活动都表现出最强的抑制作用。虽然测试的溴化程度最高的多溴二苯醚BDE-183抑制EROD活性，但它不影响AhR-EGFP表达的诱导。在将稳定转染的人肝癌细胞（异源反应元件[XRE]-HepG 2）暴露于这些多溴二苯醚后，观察到类似的发现，对XRE驱动的荧光素酶活性产生了小但具有统计学意义的激动作用。与TCDD的共同暴露再次导致拮抗效应，证实这些PBDEs对TCDD诱导的反应的抑制作用不仅是由于在受体水平上的直接相互作用，而且在DNA结合水平上。在用Gal 4-AhR构建体和相应的Gal 4-Luc报告基因瞬时转染的HepG 2细胞中，证实了BDE-99的这种拮抗作用。此外，染色质免疫沉淀试验进一步证实，BDE-99可与AhR结合，并在CYP 1A 1启动子的背景下激活AhR核转位和二恶英反应元件（DRE）结合。然而，BDE-99激活的AhR的反式激活功能似乎很弱。这些综合结果表明，多溴联苯醚结合，但不激活AhR-AhR核转位蛋白-XRE复合物。
Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that have been in use as additives in various consumer products. Structural similarities of PBDEs with other polyhalogenated aromatic hydrocarbons that show affinity for the aryl hydrocarbon receptor (AhR), such as some polychlorinated biphenyls, raised concerns about their possible dioxin-like properties. We studied the ability of environmentally relevant PBDEs (BDE-47, -99, -100, -153, -154, and -183) and the "planar" congener BDE-77 to bind and/or activate the AhR in stably transfected rodent hepatoma cell lines with an AhR-responsive enhanced green fluorescent protein (AhR-EGFP) reporter gene (HlG1.1c3 mouse and H4G1.1c2 rat hepatoma). 7-Ethoxyresorufin-O-deethylation (EROD) was used as a marker for CYP1A1 activity. Dose- and bromination-specific inhibition of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD)-induced responses was measured by their ability to inhibit the induction of AhR-EGFP expression and EROD activity. Individual exposure to these PBDEs did not result in any increase in induction of AhR-EGFP or CYP1A1 activity. The lower brominated PBDEs showed the strongest inhibitory effect on TCDD-induced activities in both cell lines. While the highest brominated PBDE tested, BDE-183, inhibited EROD activity, it did not affect the induction of AhR-EGFP expression. Similar findings were observed after exposing stably transfected human hepatoma (xenobiotic response element [XRE]-HepG2) cells to these PBDEs, resulting in a small but statically significant agonistic effect on XRE-driven luciferase activity. Co-exposure with TCDD resulted again in antagonistic effects, confirming that the inhibitory effect of these PBDEs on TCDD-induced responses was not only due to direct interaction at receptor level but also at DNA-binding level. This antagonism was confirmed for BDE-99 in HepG2 cells transiently transfected with a Gal4-AhR construct and the corresponding Gal4-Luc reporter gene. In addition, a chromatin immunoprecipitation assay further confirmed that BDE-99 could bind to the: AhR and activate the AhR nuclear translocation and dioxin responsive element (DRE) binding in the context of the CYP1A1 promoter. However, the transactivation function of the BDE-99-activated AhR seems to be very weak. These combined results suggest that PBDEs do bind but not activate the AhR-AhR nuclear translocator protein-XRE complex.