College of Fisheries, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
Aquat Toxicol. 2019 Sep;214:105240. doi: 10.1016/j.aquatox.2019.105240. Epub 2019 Jul 5.
Fish has a strong resistance to microcystins (MCs), cyclic heptapeptide cyanotoxins, known as endocrine disrupting chemicals (EDCs) which are released during cyanobacterial blooms and many laboratory and field studies have found the hepatic recovery of fish from the MCs exposure. The aim of the present study was to investigate the recovery mechanisms of reproductive function of adult zebrafish (Danio rerio) from microcystin-LR (MC-LR) exposure. Therefore, adult female zebrafish were exposed to 0, 1 or 50 μg/L of MC-LR for 21days and transferred to MC free water for another 21 days to investigate the recovery. After MC-LR exposure, marked histological lesions in the gonads, decreased the percentage of mature oocytes, decreased number of spawned eggs, decreased fertilization and hatching rates were observed. MC-LR exposure increased the concentration of 17β-estradiol (E2), testosterone (T) and vitellogenin (VTG) in female zebrafish. Some gene transcriptions of the hypothalamic-pituitary-gonad (HPG) axis significantly changed. The protein levels of 17βhsd and cyp19a remarkably increased in the MC-LR exposure groups. However, our laboratory observation also indicates that zebrafish transferred from microcystin exposure to toxin-free water and reared for 21 days exhibited a nearly complete recovery of reproductive functions, including histological structure, increased the percentage of matured oocytes and spawned eggs, stable hormone levels, well-balanced transcriptional and translational levels. These results indicate that after MC-LR exposure, the reproductive impairments in zebrafish are also reversible likewise hepatic recovery seen by different studies in fish. Future studies should be conducted to explore a better understanding of the recovery mechanisms of fish from microcystins exposure.
鱼类对微囊藻毒素（MCs）具有很强的抵抗力，MCs 是一种环状七肽的蓝藻毒素，被认为是内分泌干扰物（EDCs），在蓝藻水华期间会释放出来。许多实验室和现场研究发现，鱼类在暴露于 MC 后肝脏会恢复。本研究旨在探讨成年斑马鱼（Danio rerio）从微囊藻毒素-LR（MC-LR）暴露中恢复生殖功能的机制。因此，成年雌性斑马鱼暴露于 0、1 或 50μg/L 的 MC-LR 中 21 天，然后转移到不含 MC 的水中再暴露 21 天以进行恢复研究。MC-LR 暴露后，观察到性腺组织学损伤明显，成熟卵母细胞的比例降低，产卵量、受精率和孵化率均降低。MC-LR 暴露增加了雌性斑马鱼 17β-雌二醇（E2）、睾酮（T）和卵黄蛋白原（VTG）的浓度。下丘脑-垂体-性腺（HPG）轴的一些基因转录显著改变。MC-LR 暴露组 17βhsd 和 cyp19a 的蛋白水平显著增加。然而，我们实验室的观察也表明，从 MC 暴露转移到无毒素水中并再饲养 21 天的斑马鱼，其生殖功能几乎完全恢复，包括组织学结构、成熟卵母细胞和产卵量增加、激素水平稳定、转录和翻译水平平衡。这些结果表明，与不同鱼类研究中观察到的肝脏恢复一样，MC-LR 暴露后，斑马鱼的生殖损伤也是可逆的。未来的研究应该进一步探讨鱼类从 MC 暴露中恢复的机制。
