三氯生对中华大蟾蜍蝌蚪脂代谢的干扰及其作用机理研究

Triclosan (TCS) is broad-spectrum antimicrobial compound used extensively in personal care products. With the wide use of these products, TCS has been considered as a new ubiquitous pollutant in natural aquatic environments including surface water and ground water. TCS specifically inhibits the fatty acid synthesis in bacteria, and it has become evident that TCS also acts as a thyroid hormone disrupting chemical in non-target organisms. The purpose of this study is to reveal the underlying mechanism of TCS effects on lipid metabolism, according to functional characters of liver and thyroid gland in Bufo garagarizans tadpoles exposed to the TCS. Fatty acid compositions in liver were determined by GC-MS and mRNA expression levels of key genes involved in fatty acid metabolism were measured using quantitative real time polymerase chain reaction (qRT-PCR). In addition, ultrastructural characters of mitochondria and peroxisome in hepatocytes were examined using transmission electron microscopy. Finally, the level of thyroid hormone in blood serum, hepatic mRNA expression of thyroid hormone receptor (TR), typeⅡ and Ⅲ deiodinase (D2 and D3) were evaluated. According to the above results, the mechanisms of lipid metabolism response to TCS stress in Bufo garagarizans tadpoles were concluded. This study will provide academic data for understanding of the potential ecological risks of TCS in the water body.

三氯生作为一种广谱抗菌剂，在个人护理用品中被广泛添加。近年来，随着个人护理用品使用量增大，三氯生已经成为地表水和地下水的新型污染物之一。在细菌中，三氯生靶向干扰脂肪酸的合成；而在非靶向生物中，其具有甲状腺激素干扰效应。基于甲状腺激素在脂代谢中的调控作用，本研究拟对中华大蟾蜍(Bufo garagarizans)蝌蚪进行三氯生水体暴露，依据三氯生对肝脏和甲状腺的机能效应研究，阐明其对脂代谢干扰的作用机理。通过GC-MS测定肝脏脂肪酸组成，qRT-PCR分析脂肪酸代谢关键酶mRNA的表达水平，电镜观测肝细胞线粒体和过氧化物酶体的超微结构。此外，依据血液中甲状腺激素水平、肝脏中脱碘酶（D2和D3）及甲状腺激素受体TR mRNA表达水平等结果，揭示中华大蟾蜍蝌蚪脂肪酸代谢对三氯生胁迫的响应规律及其作用机理。本研究的实施有助于为水环境三氯生污染所造成的生态风险评价提供理论依据。

三氯生（TCS）作为一种广谱抗菌剂，在个人护理用品中被广泛添加。近年来，随着个人护理用品使用量增大，TCS已经成为地表水和地下水的新型污染物之一。本研究对中华大蟾蜍(Bufo garagarizans)蝌蚪进行TCS水体暴露，首先通过形态测量、qRT-PCR分析脱碘酶（D2和D3）及甲状腺激素受体TR mRNA表达水平，研究了TCS胁迫对中华大蟾蜍蝌蚪生长发育和甲状腺激素干扰效应的影响。结果表明，TCS胁迫对中华大蟾蜍蝌蚪生长发育具有一定的抑制作用，且中华大蟾蜍蝌蚪不同靶器官中D2、D3、TRα和TRβ的表达水平均受到一定影响，提示TCS对中华大蟾蜍蝌蚪产生一定的甲状腺激素干扰效应。其次，通过GC-MS测定肝脏脂肪酸组成，qRT-PCR分析脂肪酸代谢关键酶mRNA的表达水平，电镜观测肝脏的超微结构变化，揭示了中华大蟾蜍蝌蚪脂肪酸代谢对TCS胁迫的响应规律。结果显示，TCS暴露导致脂肪酸组成和SFA/MUFA/PUFA比例的改变；60-150 µg/L TCS处理组蝌蚪肝脏组织结构中色素巨噬细胞数目增多，胶原纤维沉积；超微结构的变化主要表现为线粒体基质电子密度增高和脂滴的聚集。此外，60-150 µg/L TCS处理组蝌蚪肝脏SOD、HSP 90、PHGPx、ACC、CPT2、PPARa、FAE、SCP的mRNA表达水平均显著降低，提示高浓度的TCS可导致肝脏组织结构受损并影响脂肪酸代谢，最终造成脂滴聚集，这可能是由于肝脏中氧化应激相关基因和脂肪酸代谢相关基因的表达受到干扰所致。本研究的结果有助于为水环境三氯生污染对两栖动物脂代谢的影响和潜在机理提供一定的理论依据。