Data from: Maternal stress-associated cortisol stimulation may protect embryos from cortisol excess in zebrafish

Abnormal embryo cortisol level causes developmental defects and poor survival in zebrafish (Danio rerio). However, no study has demonstrated that maternal stress leads to higher embryo cortisol content in zebrafish. We tested the hypothesis that maternal stress-associated elevation in cortisol levels increases embryo cortisol content in this asynchronous breeder. Zebrafish mothers were fed cortisol-spiked food for 5 days, to mimic maternal stress, followed by daily breeding for 10 days to monitor temporal embryo cortisol content. Cortisol treatment increased mean embryo yield, but the daily fecundity was variable among the groups. Embryo cortisol content was variable in both groups over a 10-day period. A transient elevation in cortisol levels was observed in the embryos from cortisol-fed mothers only on day 3, but not on subsequent days. We tested whether excess cortisol stimulates 11βHSD2 expression in ovarian follicles as a means to regulate embryo cortisol deposition. Cortisol treatment in vitro increased 11β HSD2 levels sevenfold, and this expression was regulated by actinomycin D and cycloheximide suggesting tight regulation of cortisol levels in the ovarian follicles. We hypothesize that cortisol-induced upregulation of 11βHSD2 activity in the ovarian follicles is a mechanism restricting excess cortisol incorporation into the eggs during maternal stress.

胚胎皮质醇水平异常会导致斑马鱼（Danio rerio）出现发育缺陷与存活率降低。然而，目前尚无研究证实斑马鱼的母体应激会使其胚胎皮质醇含量升高。本研究针对该异步产卵鱼类，验证了「母体应激相关的皮质醇水平升高会提升胚胎皮质醇含量」这一假说。实验通过向斑马鱼亲鱼投喂添加皮质醇的饲料5天以模拟母体应激，随后连续10天每日开展产卵实验，以监测胚胎皮质醇含量的动态变化。结果显示，皮质醇处理提升了胚胎的平均产量，但各组的单日繁殖力存在差异；在10天的实验周期内，两组的胚胎皮质醇含量均存在波动。仅在实验第3天，投喂皮质醇饲料的亲鱼所产胚胎的皮质醇水平出现一过性升高，后续天数未观察到此现象。本研究进一步探究了过量皮质醇是否会通过刺激卵巢滤泡的11βHSD2 (11β-羟基类固醇脱氢酶2) 表达，以调控胚胎皮质醇的沉积。体外皮质醇处理可使11βHSD2的表达水平上调7倍，且该表达受放线菌素D与环己酰亚胺调控，这表明卵巢滤泡对皮质醇水平存在精密调控。本研究提出假说：母体应激时，卵巢滤泡中皮质醇诱导的11βHSD2活性上调，是限制过量皮质醇进入卵子的调控机制。