Gut microbiota and neurotransmitter network underlies EHDPP-induced neurotoxicity in zebrafish.

Environmental pollutants are increasingly associated with neurological dysfunction, yet their underlying mechanisms remain poorly understood. Here, zebrafish were used to investigate the chronic lifelong neurotoxicity of 2-ethylhexyl diphenyl phosphate (EHDPP) exposure at two sublethal levels of 5 and 125 μg/L. EHDPP exposure induced pronounced sex-specific neurobehavioral deficits, with females exhibiting greater susceptibility to locomotor dysfunction, social impairment, and cognitive decline. Mechanistically, EHDPP reshaped the gut microbial community by enriching pro-inflammatory Gram-negative Fusobacteria while depleting beneficial Firmicutes and Bacteroidetes taxa, accompanied by intestinal barrier disruption, lipopolysaccharide translocation, intestinal inflammation, and blood-brain barrier impairment. These alterations further triggered microglia and astrocyte-mediated neuroinflammation and extensive disturbances in neurotransmitter metabolism, characterized by targeted detection of forty-two brain metabolites, particularly within tryptophan- and tyrosine-associated pathways. Integrated analyses of 16S gut microbiota sequencing, targeted brain metabolomics, and multi-dimensional behavioral tests revealed a coordinated regulatory network linking microbial dysbiosis, inflammatory signaling, neurotransmitter imbalance, and neurobehavioral abnormalities. Notably, dietary inulin supplementation effectively restored microbial homeostasis, alleviated peripheral and central inflammation and neurotransmitter disturbances, and ameliorated EHDPP-induced behavioral impairments, providing direct evidence that the gut-brain axis acts as a key mediator of EHDPP-induced neurotoxicity. Our study also highlights microbiota-targeted intervention as a potential strategy for mitigating pollutant-associated neurological disorders.