College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, PR China.
College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, PR China; Engineering Research Center of Green development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Wuhan, 430070, PR China; Hubei Provincial Engineering Laboratory for Pond Aquaculture, Wuhan, 430070, PR China; Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, PR China.
Environ Pollut. 2024 Feb 1;342:123021. doi: 10.1016/j.envpol.2023.123021. Epub 2023 Nov 21.
The ecological risk posed by MCs-producing M. aeruginosa and elevated ammonia to fish in actual aquatic environments remains uncertain. To address this knowledge gap, we conducted simulations to investigate the endocrine-reproductive toxicity of prolonged exposure (45 d) to Microcystis aeruginosa (2 × 10^ cells/mL) and 30 mg/L total ammonia nitrogen (TAN) in zebrafish under environmentally relevant conditions. Our results showed that exposure to M. aeruginosa significantly inhibited the body weight, increased gonadosomatic index (GSI), delayed oocyte development, and disrupted endocrine hormonal balance (reduced gonadotropin-releasing hormone (GnRH), and increased estradiol (E2) and testosterone (T)). Mechanistically, it should be attributed to the over-expression of hypothalamic-pituitary-gonadal-liver (HPGL) axis-related genes (cyp11a and cyp17) induced by M. aeruginosa. On the other hand, TAN exposure caused mild damage to zebrafish ovarian tissue and promoted an increase of T levels by inducing the upregulation of steroid hormone synthesis gene (3βhsd) expression in the ovary. It is worth noting that the dysregulation of E2/T ratio in zebrafish ovaries may be attributed to the inhibition of cyp19a1a by both M. aeruginosa and TAN. These results were further confirmed by changes in steroidogenic enzymes activities in the M. aeruginosa or TAN treated groups. Our findings indicated that exposure to M. aeruginosa and TAN had adverse impacts on the reproductive system of zebrafish. And the combined exposure of M. aeruginosa and TAN had more severe effects on the body weight, GSI, pathological changes, hormone levels and HPGL-axis related gene expression in female zebrafish. These results provide compelling evidence regarding the potential risks for reproductive health associated with M. aeruginosa and TAN in eutrophic water bodies experiencing M. aeruginosa blooms, and contribute to the development of effective strategies for monitoring and managing these toxins in aquatic ecosystems.
富营养化水体中铜绿微囊藻水华爆发时，微囊藻产生的麻痹性贝类毒素和氨氮对鱼类的生态风险仍不确定。为了填补这一知识空白，我们进行了模拟实验，以研究在实际水生环境中，鱼类在微囊藻（2×10^cells/mL）和 30mg/L 总氨氮（TAN）的长期暴露（45d）下，内分泌-生殖毒性。结果表明，暴露于铜绿微囊藻会显著抑制鱼体体重，增加性腺指数（GSI），延迟卵母细胞发育，并破坏内分泌激素平衡（降低促性腺激素释放激素（GnRH），增加雌二醇（E2）和睾酮（T））。从机制上讲，这归因于铜绿微囊藻诱导的下丘脑-垂体-性腺-肝（HPGL）轴相关基因（cyp11a 和 cyp17）的过度表达。另一方面，TAN 暴露对斑马鱼卵巢组织造成轻微损伤，并通过诱导卵巢中类固醇激素合成基因（3βhsd）表达的上调，促进 T 水平的升高。值得注意的是，斑马鱼卵巢中 E2/T 比值的失调可能归因于铜绿微囊藻和 TAN 对 cyp19a1a 的抑制。这些结果通过微囊藻或 TAN 处理组中甾体生成酶活性的变化得到进一步证实。我们的研究结果表明，暴露于铜绿微囊藻和 TAN 会对斑马鱼的生殖系统产生不利影响。并且铜绿微囊藻和 TAN 的联合暴露对雌性斑马鱼的体重、GSI、病理变化、激素水平和 HPGL 轴相关基因表达有更严重的影响。这些结果为富营养化水体中铜绿微囊藻和 TAN 对生殖健康的潜在风险提供了有力证据，有助于开发监测和管理水生生态系统中这些毒素的有效策略。
