Folic acid supplementation rescues valproic acid‐induced developmental neurotoxicity and behavioral alterations in zebrafish embryos

Abstract

Objective: 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. Methods: 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. Results: 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. Significance: 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 VPAinduced teratogenesis and to screen for countermeasures. |MUHSEN Et al.

Folic Acid Rescues Valproic Acid-Induced Morphogenesis Inhibition in Neural Rosettes Derived From Human Pluripotent Stem Cells

“…Studies have found that FA has a protective effect on the neurotoxicity of VPA ( Muhsen et al, 2021 ), we hypothesized that FA is a feasible candidate for preventing VPA-induced embryonic neurogenesis abnormalities. To further investigate whether FA supplementation could ameliorate the VPA-induced negative effect, we cotreated hPSCs with VPA1 μM and FA10 μM, defined as FV group ( Supplementary Figure 2A ).…”

Micronutrient imbalance and common phenotypes in neural tube defects

“…Both models are relatively high throughput for in vivo work and would make an excellent platform for testing the effect of multiple micronutrients independently or together. For example, it was recently shown that zebrafish embryos exposed to VPA had smaller midbrains and hindbrain midline gap; however, when the VPA-treated embryos were also given folic acid the brain size increased, and midline gap decreased (Muhsen et al, 2021). Although NTC in these models does not mimic human NTC as well as mouse, the relative quickness and accessibility make them an excellent model to test many conditions (Nikolopoulou et al, 2017).…”

Self-organized anteroposterior regionalization of early midbrain and hindbrain using micropatterned human embryonic stem cells

“…VPA has been known to be teratogenic since the early 1980s 34 and exposure to VPA during human embryo development has been found tightly linked to neural tube defects 35 and malformations in the midbrain and hindbrain 38,39,50,51 , as well as neurological disorders such as severe cognitive defects, autism spectrum disorder, and schizophrenia 52,53 . Recently, cytoskeletal protein MARCKSL1, which is an actin-stabilizing protein essential for dendrite morphogenesis and synapse maturation, has been identified to mediate VPA-induced morphological defects in developing neurons 54 .…”

“…Several teratogens have been identified that disrupt the midbrain/hindbrain development [34][35][36][37] . For example, valproic acid (VPA) exposure during embryo development causes neural tube defects and other types of malformations such as smaller midbrain size and an increase in the midline gap of the hindbrain 38,39 . It also decreases the proliferation of neuronal progenitor cells in early development 38 .…”

“…For example, valproic acid (VPA) exposure during embryo development causes neural tube defects and other types of malformations such as smaller midbrain size and an increase in the midline gap of the hindbrain 38,39 . It also decreases the proliferation of neuronal progenitor cells in early development 38 . In addition, recent clinical studies show that exposure to isotretinoin during pregnancy was linked to midbrain/hindbrain development malformations featured as disproportionately long midbrain and dysplasia of the quadrigeminal plate and vermis and disrupted AP axis patterning 37,[40][41][42][43] .…”