Xie Liqiang, Yan Wei, Li Jing, Yu Liqin, Wang Jianghua, Li Guangyu, Chen Nan, Steinman Alan D
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China.
Institute of Agricultural Quality Standards & Testing Technology, Hubei Academy of Agricultural Sciences, Wuhan 430064, China.
Aquat Toxicol. 2015 Jul;164:16-22. doi: 10.1016/j.aquatox.2015.04.014. Epub 2015 Apr 13.
Recent studies have shown that cyanobacteria-derived microcystins (MCs) have the potential to disrupt endocrine systems. However, the effects of microcystin-RR (MC-RR) and their underlying mechanisms are poorly resolved in fish. In this study, MC-RR exposure through submersion caused serious developmental toxicity, such as growth delay and depressed heart rates in zebrafish larvae. We also detected decreased levels of thyroid hormones (THs), suggesting that MC-RR-triggered thyroid endocrine disruption might contribute to the growth impairment observed in developing zebrafish. To further our understanding of mechanisms of MC-RR-induced endocrine toxicity, quantitative real-time PCR (QPCR) analysis was performed on hypothalamic-pituitary-thyroid (HPT) axis related genes, i.e., corticotropin-releasing factor (CRF), thyroid-stimulating hormone (TSH), sodium/iodide symporter (NIS), thyroglobulin (TG), thyroid receptors (TRα and TRβ) and iodothyronine deiodinases (Dio1 and Dio2), of developing zebrafish embryos exposed to 0, 0.3, 1.0 or 3.0mgL(-1) MC-RR until 96h post-fertilization. Our results showed that transcription pattern of HPT axis related genes were greatly changed by MC-RR exposure, except TG gene. Furthermore, western blot was used to validate the results of gene expression. The results showed protein synthesis of TG was not affected, while that of NIS was significantly up-regulated, which are in accordance with gene expression. The overall results indicated that exposure to MC-RR can induce developmental toxicity, which might be associated with thyroid endocrine disruption in developing zebrafish larvae.
近期研究表明，蓝藻产生的微囊藻毒素（MCs）有扰乱内分泌系统的可能性。然而，微囊藻毒素-RR（MC-RR）对鱼类的影响及其潜在机制仍未完全明确。在本研究中，斑马鱼幼体通过浸泡接触MC-RR会导致严重的发育毒性，如生长迟缓以及心率降低。我们还检测到甲状腺激素（THs）水平下降，这表明MC-RR引发的甲状腺内分泌紊乱可能是斑马鱼幼体发育过程中生长受损的原因。为了进一步了解MC-RR诱导内分泌毒性的机制，我们对暴露于0、0.3、1.0或3.0mgL(-1) MC-RR直至受精后96小时的斑马鱼胚胎下丘脑-垂体-甲状腺（HPT）轴相关基因进行了定量实时PCR（QPCR）分析，这些基因包括促肾上腺皮质激素释放因子（CRF）、促甲状腺激素（TSH）、钠/碘同向转运体（NIS）、甲状腺球蛋白（TG）、甲状腺受体（TRα和TRβ）以及碘甲状腺原氨酸脱碘酶（Dio1和Dio2）。我们的结果显示，除TG基因外，MC-RR暴露极大地改变了HPT轴相关基因的转录模式。此外，我们还使用蛋白质免疫印迹法验证基因表达结果。结果显示TG的蛋白质合成未受影响，而NIS的蛋白质合成显著上调，这与基因表达结果一致。总体结果表明，暴露于MC-RR可诱导发育毒性，这可能与斑马鱼幼体发育过程中的甲状腺内分泌紊乱有关。
