Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, 8600 Dübendorf, Switzerland.
EPF Lausanne, School of Architecture, Civil and Environmental Engineering, 1015 Lausanne, Switzerland.
Toxicol Sci. 2020 Aug 1;176(2):355-365. doi: 10.1093/toxsci/kfaa073.
Zebrafish (Danio rerio) early life stages offer a versatile model system to study the efficacy and safety of drugs or other chemicals with regard to human and environmental health. This is because, aside from the well-characterized genome of zebrafish and the availability of a broad range of experimental and computational research tools, they are exceptionally well suited for high-throughput approaches. Yet, one important pharmacokinetic aspect is thus far only poorly understood in zebrafish embryo and early larvae: their biotransformation capacity. Especially, biotransformation of electrophilic compounds is a critical pathway because they easily react with nucleophile molecules, such as DNA or proteins, potentially inducing adverse health effects. To combat such adverse effects, conjugation reactions with glutathione and further processing within the mercapturic acid pathway have evolved. We here explore the functionality of this pathway in zebrafish early life stages using a reference substrate (1-chloro-2,4-dinitrobenzene, CDNB). With this work, we show that zebrafish embryos can biotransform CDNB to the respective glutathione conjugate as early as 4 h postfertilization. At all examined life stages, the glutathione conjugate is further biotransformed to the last metabolite of the mercapturic acid pathway, the mercapturate, which is slowly excreted. Being able to biotransform electrophiles within the mercapturic acid pathway shows that zebrafish early life stages possess the potential to process xenobiotic compounds through glutathione conjugation and the formation of mercapturates. The presence of this chemical biotransformation and clearance route in zebrafish early life stages supports the application of this model in toxicology and chemical hazard assessment.
斑马鱼（Danio rerio）的早期生命阶段为研究药物或其他化学物质对人类和环境健康的功效和安全性提供了一个多功能的模型系统。这是因为除了斑马鱼特征明确的基因组和广泛的实验和计算研究工具外，它们还非常适合高通量方法。然而，到目前为止，斑马鱼胚胎和早期幼虫的一个重要药代动力学方面还了解甚少：它们的生物转化能力。特别是，亲电化合物的生物转化是一个关键途径，因为它们很容易与亲核分子（如 DNA 或蛋白质）反应，可能会引起不良的健康影响。为了对抗这种不良影响，已经进化出与谷胱甘肽的共轭反应以及在巯基尿酸途径中的进一步处理。在这里，我们使用参考底物（1-氯-2,4-二硝基苯，CDNB）来探索这条途径在斑马鱼早期生命阶段的功能。通过这项工作，我们表明斑马鱼胚胎早在受精后 4 小时就可以将 CDNB 生物转化为相应的谷胱甘肽共轭物。在所有检查的生命阶段，谷胱甘肽共轭物进一步被生物转化为巯基尿酸途径的最后代谢物，即缓慢排泄的巯基尿酸。能够在巯基尿酸途径中生物转化亲电化合物表明，斑马鱼早期生命阶段具有通过谷胱甘肽共轭和形成巯基尿酸来处理外来化合物的潜力。这种化学转化和清除途径在斑马鱼早期生命阶段的存在支持了该模型在毒理学和化学危害评估中的应用。
