Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental condition with several identified risk factors, both genetic and non-genetic. Among these, prenatal exposure to valproic acid (VPA) has been extensively associated with the development of the disorder. The zebrafish, a cost- and time-effective model, is useful for studying ASD features. Using validated VPA-induced ASD zebrafish models, we aimed to provide new insights into VPA exposure effects during embryonic development and to identify new potential biomarkers associated with ASD-like features. Dose–response analyses were performed in vivo to study larval phenotypes and mechanisms underlying neuroinflammation, mitochondrial dysfunction, oxidative stress, microglial cell status, and motor behaviour. Wild-type and transgenic Tg(mpeg1:EGFP) zebrafish were water-exposed to VPA doses (5 to 500 µM) from 6 to 120 h post-fertilisation (hpf). Embryos and larvae were monitored daily to assess survival and hatching rates, and numerous analyses and tests were conducted from 24 to 120 hpf. VPA doses higher than 50 µM worsened survival and hatching rates, while doses of 25 µM or more altered morphology, microglial status, and larval behaviours. VPA 50 µM also affected mRNA expression of inflammatory cytokines and neurogenesis-related genes, mitochondrial respiration, and reactive oxygen species accumulation. The study confirmed that VPA alters brain homeostasis, synaptic interconnections, and neurogenesis-related signalling pathways, contributing to ASD aetiopathogenesis. Further studies are essential to identify novel ASD biomarkers for developing new drug targets and tailored therapeutic interventions for ASD.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social skills and the presence of repetitive and restricted behaviors and interests. The social behavior of the zebrafish (Danio rerio) makes this organism a valuable tool for modeling ASD in order to explore the social impairment typical of this disorder. In addition to transgenic models, exposure of zebrafish embryos to valproic acid (VPA) has been found to produce ASD-like symptoms. This review first sets out to examine the existing literature on adult social behavior in the zebrafish VPA-induced model of autism, and the authors also aim to identify the ideal VPA dosage able to induce a persistent and long-lasting ASD-like phenotype while minimizing the suffering and distress of research animals in compliance with the principles of replacement, refinement, and reduction (3Rs).

Autism Spectrum Disorder (ASD) is a multifactorial neurodevelopmental condition in which neuroinflammation, oxidative stress, and synaptic dysfunction act as converging mechanisms. Prenatal exposure to valproic acid (VPA), an antiepileptic drug and histone deacetylase inhibitor, is a recognized environmental risk factor associated with ASD-like phenotypes. Zebrafish, with conserved neuroimmune pathways, rapid development, and quantifiable social behavior, represents a robust model for investigating ASD pathophysiology and testing therapeutic candidates. This study aimed to assess if a previously selected concentration of VPA is capable of inducing persistent alterations from early development through adulthood, and to assess the potential of β-glucans, natural polysaccharides with antioxidant and immunomodulatory properties, to mitigate VPA-induced alterations. A multimodal approach included morphological evaluation, mitochondrial respiration, quantitative PCR of inflammatory markers, and behavioral assays targeting locomotion, anxiety-like responses, and social preference. Low-dose VPA (25 μM) induced developmental and behavioral difficulties, accompanied by a transient reduction in mitochondrial respiratory capacity. β-glucan supplementation attenuated selected VPA-induced alterations, including inflammatory gene-expression changes in larvae and behavioral alterations in adulthood. Overall, these findings provide preclinical evidence that β-glucans can modulate selected VPA-induced inflammatory, molecular and behavioral alterations and support further investigation of their potential effects in neurodevelopmental models.