Yan Saihong, Wu Huimin, Qin Jianhui, Zha Jinmiao, Wang Zijian
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, College of Fisheries, Huazhong Agriculture University, Wuhan 430070, China.
Environ Pollut. 2017 Jun;225:559-568. doi: 10.1016/j.envpol.2017.02.071. Epub 2017 Mar 16.
Halogen-free organophosphorus flame retardants are widespread in aquatic environments. Although it has been documented that they affect the behavior and reproduction of aquatic species, researches investigating cellular detoxification and the defense system in bivalves are scarce. In this study, adult Asian clams (C. fluminea) were exposed to tris (2-butoxyethyl) phosphate (TBEP) and tributyl phosphate (TBP) at 20, 200, and 2000 μg/L for 28 d. The results showed no noticeable difference in siphoning behavior. However, the siphoning behavior displayed a trend toward a slight decrease in the treatment groups. GR activity was markedly reduced compared with the control groups, whereas the levels of cyp4 significantly increased following the 2000 μg/L TBP treatments (p < 0.05). Moreover, the levels of gsts1 and gstm1 significantly decreased following all TBEP treatments and were significantly inhibited by 20 μg/L TBP (p < 0.05). The adverse effects on antioxidant enzymes suggested that C. fluminea mainly relies on the antioxidant system to reduce damage without an increase in MDA levels following exposure to a low concentration. Moreover, mRNA expression levels of heat shock proteins (hsp 22, 40, 60, 70, and 90) were significantly down-regulated with TBEP and TBP treatments lower than 200 μg/L (p < 0.05), whereas significant up-regulations were observed for hsp 22 and hsp 70 in response to 2000 μg/L TBP treatment (p < 0.05). Up-regulation of ATP-binding cassette (ABC) transporter genes (abcb1 and abcc1) showed that TBEP and TBP could activate the multixenobiotic resistance (MXR) system to discharge xenobiotics in C. fluminea, which kept its shell closed at high concentrations to prevent xenobiotic entry. Our results provide a new insight into the different mechanisms of cellular detoxification and the MXR system of C. fluminea in response to low and high concentrations of TBEP and TBP.
无卤有机磷阻燃剂在水生环境中广泛存在。尽管已有文献记载它们会影响水生物种的行为和繁殖，但针对双壳贝类细胞解毒和防御系统的研究却很少。在本研究中，成年亚洲蛤蜊（河蚬）分别暴露于浓度为20、200和2000μg/L的磷酸三（2-丁氧基乙基）酯（TBEP）和磷酸三丁酯（TBP）中，持续28天。结果显示，虹吸行为没有明显差异。然而，处理组的虹吸行为呈现出轻微下降的趋势。与对照组相比，谷胱甘肽还原酶（GR）活性显著降低，而在2000μg/L TBP处理后，细胞色素P450 4（cyp4）水平显著升高（p<0.05）。此外，在所有TBEP处理后，谷胱甘肽S-转移酶1（gsts1）和谷胱甘肽S-转移酶m1（gstm1）水平显著下降，并受到20μg/L TBP的显著抑制（p<0.05）。对抗氧化酶的不利影响表明，河蚬在暴露于低浓度污染物时，主要依靠抗氧化系统来减少损伤，且丙二醛（MDA）水平没有升高。此外，在低于200μg/L的TBEP和TBP处理下，热休克蛋白（hsp 22、40、60、70和90）的mRNA表达水平显著下调（p<0.05），而在2000μg/L TBP处理后，观察到hsp 22和hsp 70显著上调（p<0.05）。ATP结合盒（ABC）转运蛋白基因（abcb1和abcc1）的上调表明，TBEP和TBP可以激活河蚬的多药耐药（MXR）系统，以排出异生物质，河蚬在高浓度下会紧闭贝壳以防止异生物质进入。我们的研究结果为河蚬细胞解毒和MXR系统应对低浓度和高浓度TBEP及TBP的不同机制提供了新的见解。
