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Folic acid supplementation rescues valproic acid-induced developmental neurotoxicity and behavioral alterations in
Maram Muhsen1, Jaclyn Youngs1, Anne Riu2
1Department of Intelligent Systems Engineering, Indiana University, Bloomington, Indiana, USA.
Insights
Valproic acid (VPA) exposure in zebrafish causes neurodevelopmental defects and behavioral issues. Folic acid (FA) supplementation effectively reversed most VPA-induced brain and motor neuron abnormalities, highlighting FA
Area of Science:
- Developmental Neuroscience
- Neurotoxicology
- Teratology
Background:
- Fetal exposure to valproic acid (VPA), an anticonvulsant, is linked to birth defects and neurodevelopmental problems.
- Understanding the precise neurotoxic mechanisms of VPA is crucial for developing preventative strategies.
- Zebrafish serve as a valuable model organism for studying developmental neurotoxicity due to their genetic tractability and optical transparency.
Purpose of the Study:
- To investigate the neurotoxic effects of VPA exposure on zebrafish embryos.
- To evaluate the potential of folic acid (FA) supplementation to counteract VPA-induced neurodevelopmental and behavioral deficits.
- To establish zebrafish as a model for studying VPA teratogenesis and screening for therapeutic interventions.
Main Methods:
- Zebrafish embryos from transgenic lines expressing neuronal green fluorescent protein were exposed to varying concentrations of VPA, with or without FA supplementation.
- Fluorescence microscopy was employed to assess structural alterations in brain regions, neuronal progenitor cells, and motor neuron neurite sprouting.
- A standardized zebrafish embryo twitching assay was utilized to quantify functional behavioral changes.
Main Results:
- VPA exposure induced concentration-dependent reductions in midbrain size, increased hindbrain midline gaps, and perturbed motor neuron neurite outgrowth.
- VPA significantly decreased neuronal progenitor cell numbers and altered embryonic motor behaviors, causing hyperactivity in darkness and hypoactivity in light.
- Folic acid supplementation successfully rescued VPA-induced defects in midbrain size and hindbrain midline, increased progenitor cell counts, and improved motor neuron sprouting and light-associated behaviors.
Conclusions:
- VPA exposure triggers specific neurotoxic effects and developmental abnormalities in zebrafish embryos.
- Folic acid supplementation demonstrates significant efficacy in reversing the majority of VPA-induced neurodevelopmental and behavioral defects.
- Zebrafish represent a robust and effective model for investigating VPA teratogenesis and for screening potential therapeutic countermeasures.
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 VPA-induced teratogenesis and to screen for countermeasures.
