Perfluorooctanoic acid (PFOA) impairs motor neuron development and locomotor behavior in zebrafish larvae via ROS-mediated oxidative stress

• PFOA disrupts motor neuron axonal branching and network complexity in zebrafish larvae. • Early-life PFOA exposure elevates ROS and induces lipid peroxidation. • Oxidative stress is a key mechanism underlying PFOA-induced neurodevelopmental toxicity. • PFOA altered neurotransmission- and synapse-related gene expression. • Antioxidant NAC partially restores PFOA-induced locomotor deficits. Perfluorooctanoic acid (PFOA), a widespread per- and polyfluoroalkyl substance (PFAS), is increasingly recognized as a developmental neurotoxicant. Although prenatal exposure has been linked to behavioral impairments, the mechanistic basis involving oxidative stress and motor neuron dysfunction remains unclear. In this study, we investigated the effect of early-life PFOA exposure on locomotor behavior, motor neuron morphology, oxidative stress biomarkers, and neurodevelopment-relate gene expression. Zebrafish embryos (AB strain and Tg(hb9:eGFP)) were exposed to PFOA (0, 10, 100, 1000 μg/L) from 2 hours post-fertilization (hpf) to 168 hpf. Our results reveal that PFOA exposure led to a concentration-response reduction in locomotor activity at 168 hpf. In addition, motor neurons axonal arbor complexity was significantly decreased at 36 hpf. Further investigations showed that reactive oxygen species (ROS) levels were elevated in a concentration-dependent manner at 24 hpf, while malondialdehyde (MDA) content increased at 168 hpf, suggesting sustained lipid peroxidation. Moreover, the antioxidant protein Trx1 was up-regulated, together with perturbation of the transcriptional balance of antioxidant and pro-oxidant genes as well as neurodevelopment-related genes. Notably, N-acetylcysteine (NAC) co-treatment partially restored locomotor performance, supporting a central role of ROS-mediated oxidative stress in PFOA neurotoxicity. Collectively, these findings demonstrate that early-life PFOA exposure disrupts motor neuron development and behavior via redox imbalance and transcriptional dysregulation, providing new mechanistic insights into the developmental neurotoxicity of PFAS.