Ghorbanzadeh Mehdi, van Ede Karin I, Larsson Malin, van Duursen Majorie B M, Poellinger Lorenz, Lücke-Johansson Sandra, Machala Miroslav, Pěnčíková Kateřina, Vondráček Jan, van den Berg Martin, Denison Michael S, Ringsted Tine, Andersson Patrik L
Department of Chemistry, Umeå University , SE-901 87 Umeå, Sweden.
Chem Res Toxicol. 2014 Jul 21;27(7):1120-32. doi: 10.1021/tx5001255. Epub 2014 Jun 18.
For a better understanding of species-specific relative effect potencies (REPs), responses of dioxin-like compounds (DLCs) were assessed. REPs were calculated using chemical-activated luciferase gene expression assays (CALUX) derived from guinea pig, rat, and mouse cell lines. Almost all 20 congeners tested in the rodent cell lines were partial agonists and less efficacious than 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). For this reason, REPs were calculated for each congener using concentrations at which 20% of the maximal TCDD response was reached (REP20TCDD). REP20TCDD values obtained for PCDD/Fs were comparable with their toxic equivalency factors assigned by the World Health Organization (WHO-TEF), while those for PCBs were in general lower than the WHO-TEF values. Moreover, the guinea pig cell line was the most sensitive as indicated by the 20% effect concentrations of TCDD of 1.5, 5.6, and 11.0 pM for guinea pig, rat, and mouse cells, respectively. A similar response pattern was observed using multivariate statistical analysis between the three CALUX assays and the WHO-TEFs. The mouse assay showed minor deviation due to higher relative induction potential for 2,3,7,8-tetrachlorodibenzofuran and 2,3,4,6,7,8-hexachlorodibenzofuran and lower for 1,2,3,4,6,7,8-heptachlorodibenzofuran and 3,3',4,4',5-pentachlorobiphenyl (PCB126). 2,3,7,8-Tetrachlorodibenzofuran was more than two times more potent in the mouse assay as compared with that of rat and guinea pig cells, while measured REP20TCDD for PCB126 was lower in mouse cells (0.05) as compared with that of the guinea pig (0.2) and rat (0.07). In order to provide REP20TCDD values for all WHO-TEF assigned compounds, quantitative structure-activity relationship (QSAR) models were developed. The QSAR models showed that specific electronic properties and molecular surface characteristics play important roles in the AhR-mediated response. In silico derived REP20TCDD values were generally consistent with the WHO-TEFs with a few exceptions. The QSAR models indicated that, e.g., 1,2,3,7,8-pentachlorodibenzofuran and 1,2,3,7,8,9-hexachlorodibenzofuran were more potent than given by their assigned WHO-TEF values, and the non-ortho PCB 81 was predicted, based on the guinea-pig model, to be 1 order of magnitude above its WHO-TEF value. By combining in vitro and in silico approaches, REPs were established for all WHO-TEF assigned compounds (except OCDD), which will provide future guidance in testing AhR-mediated responses of DLCs and to increase our understanding of species variation in AhR-mediated effects.
为了更好地理解物种特异性相对效应强度（REPs），对二噁英类化合物（DLCs）的反应进行了评估。使用源自豚鼠、大鼠和小鼠细胞系的化学激活荧光素酶基因表达试验（CALUX）计算REPs。在啮齿动物细胞系中测试的几乎所有20种同系物都是部分激动剂，且效力低于2,3,7,8-四氯二苯并 - 对 - 二噁英（TCDD）。因此，使用达到最大TCDD反应20%时的浓度计算每种同系物的REP20TCDD。多氯二苯并对二噁英/多氯二苯并呋喃（PCDD/Fs）获得的REP20TCDD值与其由世界卫生组织（WHO）指定的毒性当量因子（WHO-TEF）相当，而多氯联苯（PCBs）的REP20TCDD值总体低于WHO-TEF值。此外，豚鼠细胞系最为敏感，豚鼠、大鼠和小鼠细胞的TCDD 20%效应浓度分别为1.5、5.6和11.0 pM。在三种CALUX试验和WHO-TEFs之间使用多变量统计分析观察到类似的反应模式。小鼠试验显示出轻微偏差，原因是2,3,7,8-四氯二苯并呋喃和2,3,4,6,7,8-六氯二苯并呋喃的相对诱导潜力较高，而1,2,3,4,6,7,8-七氯二苯并呋喃和3,3',4,4',5-五氯联苯（PCB126）的相对诱导潜力较低。与大鼠和豚鼠细胞相比，2,3,7,8-四氯二苯并呋喃在小鼠试验中的效力高出两倍多，而小鼠细胞中PCB126的测量REP20TCDD（0.05）低于豚鼠（0.2）和大鼠（0.07）。为了为所有WHO-TEF指定的化合物提供REP20TCDD值，开发了定量构效关系（QSAR）模型。QSAR模型表明，特定的电子性质和分子表面特征在芳烃受体（AhR）介导的反应中起重要作用。计算机模拟得出的REP20TCDD值与WHO-TEF值总体一致，但有一些例外。QSAR模型表明，例如，1,2,3,7,8-五氯二苯并呋喃和1,2,3,7,8,9-六氯二苯并呋喃的效力高于其指定的WHO-TEF值，并且基于豚鼠模型预测，非邻位PCB 81比其WHO-TEF值高1个数量级。通过结合体外和计算机模拟方法，为所有WHO-TEF指定的化合物（除八氯二苯并二噁英外）建立了REPs，这将为未来测试DLCs的AhR介导反应提供指导，并增进我们对AhR介导效应中物种差异变化的理解。
