* Department of Pharmacology and Toxicology, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands;
Toxicol Sci. 2013 Dec;136(2):382-91. doi: 10.1093/toxsci/kft198. Epub 2013 Sep 6.
Endocrine-disrupting chemicals (EDCs) are considered to cause testicular toxicity primarily via interference with steroid hormone function. Alternatively, EDCs could possibly exert their effects by interaction with ATP-binding cassette (ABC) transporters that are expressed in the blood-testis barrier. In this study, we investigated the effects of bisphenol A (BPA), tetrabromobisphenol A (TBBPA), bis(2-ethylhexyl) phthalate, mono(2-ethylhexyl) phthalate, perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS) on breast cancer resistance protein (BCRP), multidrug resistance proteins 1 and 4 (MRP1 and MRP4), and P-glycoprotein (P-gp) using membrane vesicles overexpressing these transporters. BPA solely inhibited BCRP activity, whereas TBBPA, PFOA, and PFOS inhibited all transporters tested. No effect was observed for the phthalates. Using transporter-overexpressing Madin-Darby canine kidney cells, we show that BPA and PFOA, but not TBBPA, are transported by BCRP, whereas none of the compounds were transported by P-gp. To investigate the toxicological implications of these findings, testosterone secretion and expression of steroidogenic genes were determined in murine Leydig (MA-10) cells upon exposure to the selected EDCs. Only BPA and TBBPA concentration dependently increased testosterone secretion by MA-10 cells to 6- and 46-fold of control levels, respectively. Inhibition of the Mrp's by MK-571 completely blocked testosterone secretion elicited by TBBPA, which could not be explained by coinciding changes in expression of steroidogenic genes. Therefore, we hypothesize that transporter-mediated efflux of testosterone precursors out of MA-10 cells is inhibited by TBBPA resulting in higher availability for testosterone production. Our data show the toxicological and clinical relevance of ABC transporters in EDC risk assessment related to testicular toxicity.
内分泌干扰化学物质（EDCs）被认为主要通过干扰类固醇激素功能引起睾丸毒性。或者，EDCs 可能通过与血睾屏障中表达的 ATP 结合盒（ABC）转运蛋白相互作用而发挥作用。在这项研究中，我们使用过表达这些转运蛋白的膜囊泡研究了双酚 A（BPA）、四溴双酚 A（TBBPA）、邻苯二甲酸二（2-乙基己基）酯、邻苯二甲酸单（2-乙基己基）酯、全氟辛酸（PFOA）和全氟辛烷磺酸（PFOS）对乳腺癌耐药蛋白（BCRP）、多药耐药蛋白 1 和 4（MRP1 和 MRP4）和 P-糖蛋白（P-gp）的影响。BPA 仅抑制 BCRP 活性，而 TBBPA、PFOA 和 PFOS 抑制所有测试的转运蛋白。邻苯二甲酸盐没有观察到影响。使用过表达转运蛋白的 Madin-Darby 犬肾细胞，我们表明 BPA 和 PFOA 但不是 TBBPA 由 BCRP 转运，而没有一种化合物由 P-gp 转运。为了研究这些发现的毒理学意义，我们在暴露于选定的 EDC 后，在小鼠 Leydig（MA-10）细胞中测定了睾酮分泌和类固醇生成基因的表达。只有 BPA 和 TBBPA 浓度依赖性地将 MA-10 细胞中的睾酮分泌增加至对照水平的 6 倍和 46 倍。MK-571 对 Mrp 的抑制完全阻断了 TBBPA 引起的睾酮分泌，这不能用类固醇生成基因表达的伴随变化来解释。因此，我们假设 TBBPA 抑制了 MA-10 细胞中睾酮前体的转运蛋白外排，从而增加了睾酮生成的可利用性。我们的数据表明，在与睾丸毒性相关的 EDC 风险评估中，ABC 转运蛋白具有毒理学和临床相关性。
