Trexler Andrew W, Knudsen Gabriel A, Nicklisch Sascha C T, Birnbaum Linda S, Cannon Ronald E
NCI Laboratory of Toxicology and Toxicokinetics, Research Triangl Park, North Carolina, 27709.
Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla 92093, California.
Toxicol Sci. 2019 Oct 1;171(2):463-472. doi: 10.1093/toxsci/kfz155.
2,4,6-Tribromophenol (TBP, CAS No. 118-79-6) is a brominated chemical used in the production of flame-retardant epoxy resins and as a wood preservative. In marine environments, TBP is incorporated into shellfish and consumed by predatory fish. Food processing and water treatment facilities produce TBP as a byproduct. 2,4,6-Tribromophenol has been detected in human blood and breast milk. Biologically, TBP interferes with estrogen and thyroid hormone signaling, which regulate important transporters of the blood-brain barrier (BBB). The BBB is a selectively permeable barrier characterized by brain microvessels which are composed of endothelial cells mortared by tight-junction proteins. ATP-binding cassette (ABC) efflux transporters on the luminal membrane facilitate the removal of unwanted endobiotics and xenobiotics from the brain. In this study, we examined the in vivo and ex vivo effects of TBP on two important transporters of the BBB: P-glycoprotein (P-gp, ABCB1) and Multidrug Resistance-associated Protein 2 (MRP2, ABCC2), using male and female rats and mice. 2,4,6-Tribromophenol exposure ex vivo resulted in a time- (1-3 h) and dose- (1-100 nM) dependent decrease in P-gp transport activity. MRP2 transport activity was unchanged under identical conditions. Immunofluorescence and western blotting measured decreases in P-gp expression after TBP treatment. ATPase assays indicate that TBP is not a substrate and does not directly interact with P-gp. In vivo dosing with TBP (0.4 µmol/kg) produced decreases in P-gp transport. Co-treatment with selective protein kinase C (PKC) inhibitors prevented the TBP-mediated decreases in P-gp transport activity.
2,4,6-三溴苯酚（TBP，化学物质登记号：118-79-6）是一种溴化化学品，用于生产阻燃环氧树脂并用作木材防腐剂。在海洋环境中，TBP会进入贝类体内并被掠食性鱼类摄取。食品加工和水处理设施会产生TBP作为副产物。在人体血液和母乳中已检测到2,4,6-三溴苯酚。从生物学角度来看，TBP会干扰雌激素和甲状腺激素信号传导，而这些信号传导调节着血脑屏障（BBB）的重要转运蛋白。血脑屏障是一种选择性渗透屏障，其特征是由紧密连接蛋白连接的内皮细胞组成的脑微血管。管腔膜上的ATP结合盒（ABC）外排转运蛋白有助于将不需要的内源性物质和外源性物质从大脑中清除。在本研究中，我们使用雄性和雌性大鼠及小鼠，研究了TBP对血脑屏障的两种重要转运蛋白：P-糖蛋白（P-gp，ABCB1）和多药耐药相关蛋白2（MRP2，ABCC2）的体内和体外作用。体外暴露于2,4,6-三溴苯酚会导致P-gp转运活性呈时间（1 - 3小时）和剂量（1 - 100 nM）依赖性降低。在相同条件下，MRP2转运活性未发生变化。免疫荧光和蛋白质印迹法检测到TBP处理后P-gp表达降低。ATP酶分析表明TBP不是底物，也不直接与P-gp相互作用。体内给予TBP（0.4 μmol/kg）会导致P-gp转运降低。与选择性蛋白激酶C（PKC）抑制剂共同处理可防止TBP介导的P-gp转运活性降低。
