Department of Intelligent Systems Engineering, Indiana University, Bloomington, Indiana, USA.
Department of Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, Texas, USA.
Epilepsia. 2021 Jul;62(7):1689-1700. doi: 10.1111/epi.16915. Epub 2021 May 16.
Fetal exposure to the anticonvulsant drug valproic acid (VPA), used to treat certain types of epilepsy, increases the risk for birth defects, including neural tube defects, as well as learning difficulties and behavioral problems. Here, we investigated neurotoxic effects of VPA exposure using zebrafish as a model organism. The capacity of folic acid (FA) supplementation to rescue the VPA-induced neuronal and behavioral perturbations was also examined.
Zebrafish embryos of different transgenic lines with neuronal green fluorescent protein expression were exposed to increasing concentrations of VPA with or without FA supplementation. Fluorescence microscopy was used to visualize alterations in brain structures and neural progenitor cells, as well as motor neurons and neurite sprouting. A twitching behavioral assay was used to examine the functional consequences of VPA and FA treatment.
In zebrafish embryos, VPA exposure caused a decrease in the midbrain size, an increase in the midline gap of the hindbrain, and perturbed neurite sprouting of secondary motor neurons, in a concentration-dependent manner. VPA exposure also decreased the fluorescence intensity of neuronal progenitor cells in early developmental stages, indicating fewer cells. Furthermore, VPA exposure significantly altered embryonic twitching activity, causing hyperactivity in dark and hypoactivity in light. Supplementation of FA rescued the VPA-induced smaller midbrain size and hindbrain midline gap defects. FA treatment also increased the number of neuronal progenitor cells in VPA-treated embryos and salvaged neurite sprouting of the secondary motor neurons. FA rescued the VPA-induced alterations in twitching activity in light but not in dark.
We conclude that VPA exposure induces specific neurotoxic perturbations in developing zebrafish embryos, and that FA reversed most of the identified defects. The results demonstrate that zebrafish is a promising model to study VPA-induced teratogenesis and to screen for countermeasures.
用于治疗某些类型癫痫的抗惊厥药物丙戊酸（VPA）会使胎儿暴露于其中，从而增加出生缺陷的风险，包括神经管缺陷，以及学习困难和行为问题。在这里，我们使用斑马鱼作为模型生物来研究 VPA 暴露的神经毒性作用。还研究了叶酸（FA）补充剂是否有能力挽救 VPA 引起的神经元和行为紊乱。
用不同的具有神经元绿色荧光蛋白表达的转基因系的斑马鱼胚胎暴露于不同浓度的 VPA 中，同时或不补充 FA。荧光显微镜用于观察脑结构和神经祖细胞以及运动神经元和神经突发芽的变化。抽搐行为分析用于检查 VPA 和 FA 处理的功能后果。
在斑马鱼胚胎中，VPA 暴露以浓度依赖性方式导致中脑尺寸减小，后脑中线间隙增大，以及次级运动神经元的神经突发芽紊乱。VPA 暴露还降低了早期发育阶段神经元祖细胞的荧光强度，表明细胞数量减少。此外，VPA 暴露显著改变了胚胎抽搐活动，导致在黑暗中过度活跃，在光中活动减少。FA 补充挽救了 VPA 引起的较小中脑尺寸和后脑中线间隙缺陷。FA 处理还增加了 VPA 处理胚胎中神经元祖细胞的数量，并挽救了次级运动神经元的神经突发芽。FA 挽救了 VPA 引起的光中抽搐活动的改变，但不能挽救黑暗中的抽搐活动。
我们得出结论，VPA 暴露会在发育中的斑马鱼胚胎中引起特定的神经毒性紊乱，而 FA 逆转了大部分已识别的缺陷。结果表明，斑马鱼是研究 VPA 诱导的致畸作用和筛选对策的有前途的模型。
