全氟辛烷基磺酸钾(PFOS)和纳米氧化锌(Nano-ZnO)复合暴露对斑马鱼下丘脑-垂体-甲状腺轴功能的影响

Co-Exposure to PFOS and Nano-Zn O Disrupted the Hypothalamus-Pituitary-Thyroid Axis in Zebrafish Larvae

全氟辛烷基磺酸钾(PFOS)和纳米氧化锌(Nano-Zn O)广泛存在于环境中,但是它们复合暴露对水生生物的潜在毒性机制尚未明确。本文探讨PFOS和Nano-Zn O复合暴露对斑马鱼下丘脑-垂体-甲状腺轴(HPT轴)毒性的影响。将斑马鱼胚胎从孵化开始暴露于PFOS(0.2、0.4、0.8 mg·L^(-1))、Nano-Zn O(6.75、12.5、25 mg·L^(-1))、PFOS+Nano-Zn O(0.2+6.75、0.4+12.5、0.8+25 mg·L^(-1))溶液中15 d后,分析幼鱼的发育毒性,体内的甲状腺激素(甲状腺素(T4)和三碘甲状腺氨酸(T3)含量和与甲状腺有关基因(CRF、TSH、NIS、TG和TPO)的表达情况。结果发现复合暴露组与单独暴露组相比,前者显著诱导了幼鱼的畸形率,降低了幼鱼的存活率,并抑制了幼鱼的体长。复合暴露组显著增加了幼鱼体内T3含量,同时抑制体内T4的含量。与单独暴露组相比,复合暴露组显著诱导了CRF和NIS基因的表达,同时抑制了TSHβ和TG基因的表达。而TPO基因的表达水平在单独和复合暴露组中没有显著差异。本研究首次证明了PFOS和Nano-Zn O复合暴露对斑马鱼幼鱼甲状腺轴的干扰效果并对其进行了机制探讨。

Perfluorooctanesulphonic acid potassium salt（PFOS） and Zn O nanoparticles（Nano-Zn O） are widely distributed in the environment. However, the potential toxicity of co-exposure to PFOS and Nano-Zn O remains to be fully elucidated. Our present study investigated the effects of co-exposure to PFOS and Nano-Zn O on the hypothalamic-pituitary-thyroid（HPT） axis in zebrafish. The embryos were exposed to PFOS（0.2, 0.4, 0.8 mg·L^（-1）） single solutions, Nano-Zn O（6.75, 12.5, 25 mg·L^（-1）） single solutions and PFOS plus Nano-Zn O（0.2 ＋ 6.75, 0.4 ＋ 12.5, 0.8 ＋25 mg·L^（-1）） mixture solutions for 15 days. We analyzed development toxicity, the whole-body content of TH and the expression of genes（corticotropin-releasing factor（CRF）, thyroid-stimulating hormone（TSHβ）, sodium/iodide symporter（NIS）, thyroglobulin（TG）, thyroid peroxidase（TPO） related to the HPT axis. Compared with single-exposure groups, the body length and survival rate decreased, the malformation rates increased in co-exposure groups. The triiodothyronine（T3） levels increased and the thyroxine（T4） content decreased in co-exposure groups. Compared with the exposure to PFOS and Nano-Zn O alone, the expression of genes（CRF and NIS） significantly up-regulated and the expression of genes（TSHβ and TG） significantly down-regulated in co-exposure groups. In addition, the expression of TPO gene was unchanged in both the single and co-exposure groups. Our results were the first evidence for the thyroid-disrupting effects of PFOS and Nano-Zn O co-exposure in zebrafish. The results also provide insight into the mechanism of disruption of the thyroid status by PFOS and Nano-Zn O.