Dietary exposure of 17-alpha ethinylestradiol modulates physiological endpoints and gene signaling pathways in female largemouth bass (Micropterus salmoides)

17alpha-ethinylestradiol (EE2), used for birth control in humans, is a potent estrogen that is found in wastewater at low concentrations (ng/L). EE2 has the ability to interfere with the endocrine system of fish, affecting reproduction which can result in population level effects. The objective of this study was to determine if dietary exposure to EE2 would alter gene expression patterns and key pathways in the liver and ovary and whether these could be associated with reproductive endpoints in female largemouth bass (LMB) during egg development. Female LMB received 70 ng EE2/g feed (feed administered at 1% of body weight) for 60 days. EE2 dietary exposure significantly reduced plasma vitellogenin concentrations by 70%. Hepatosomatic and gonadosomatic indices were also decreased with EE2 feeding by 38.5% and 40%, respectively. Transcriptomic profiling revealed that there were more changes in steady-state mRNA levels in the liver compared to the ovary. Genes associated with reproduction were differentially expressed such as vitellogenin in the liver and aromatase in the gonad. In addition, a set of genes related with oxidative stress (e.g., glutathione reductase and glutathione peroxidase) were identified as altered in the liver and genes associated with the immune system (e.g., complement component 1, and macrophage-inducible C-type lectin) were altered in the gonad. In a follow-up study with 0.2 ng EE2/g feed for 60 days, similar phenotypic and gene expression changes were observed that support these findings with the higher concentrations. This study provides new insights into how dietary exposure to EE2 interferes with endocrine signaling pathways in female LMB during a critical period of reproductive oogenesis. Dietary exposure to EE2 would alter gene expression patterns and key pathways in the liver and ovary and these could be associated with reproductive endpoints in female largemouth bass during maturation. Female LMB received about 351 ng EE2 per day (from EE2-laced feed containing 70ng EE2/g feed) for 60 days.

17α-乙炔雌二醇（17alpha-ethinylestradiol，EE2）是一种强效雌激素，常用于人类避孕，在废水中以低浓度（纳克/升，ng/L）检出。EE2可干扰鱼类内分泌系统，影响其繁殖过程，进而引发种群层面的效应。本研究旨在探究膳食暴露于EE2是否会改变雌性大口黑鲈（Largemouth Bass，LMB）在卵子发育阶段肝脏与卵巢的基因表达模式及关键通路，且这些变化是否与繁殖终点相关。实验中，雌性大口黑鲈以占体重1%的投喂量摄入每克饲料含70 ng EE2的饵料，持续60天。结果显示，膳食暴露EE2可使血浆卵黄蛋白原浓度显著降低70%；肝脏体指数与性腺体指数也分别下降38.5%与40%。转录组分析显示，相较于卵巢，肝脏的稳态mRNA水平变化更为显著。与繁殖相关的基因出现差异表达，如肝脏中的卵黄蛋白原及性腺中的芳香化酶。此外，肝脏中还鉴定出与氧化应激相关的一系列基因（如谷胱甘肽还原酶、谷胱甘肽过氧化物酶）表达发生改变，而性腺中与免疫系统相关的基因（如补体成分1、巨噬细胞诱导型C型凝集素）表达亦出现异常。在后续开展的每克饲料含0.2 ng EE2的60天投喂实验中，同样观察到相似的表型与基因表达变化，验证了高浓度暴露下的实验结果。本研究为膳食暴露EE2如何在雌性大口黑鲈繁殖卵子发生的关键时期干扰内分泌信号通路提供了新的见解。膳食暴露EE2可改变雌性大口黑鲈在成熟阶段肝脏与卵巢的基因表达模式及关键通路，且这些变化或与其繁殖终点相关。本次实验中，雌性大口黑鲈每日通过每克含70 ng EE2的投喂饵料摄入约351 ng EE2，持续60天。