Neurotoxic effects of 2,4-DCP in adult zebrafish: A behavioral, biochemical, and genetic approach.

2,4-Dichlorophenol (2,4-DCP) is a persistent and toxic metabolite derived from the degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and other chlorinated compounds, representing an emerging environmental concern. Despite evidence of its toxicity, its neurotoxic effects in adult organisms remain poorly understood. This study aimed to evaluate the behavioral, biochemical, and molecular responses of adult zebrafish (Danio rerio) following 14-day exposure to environmentally relevant (30 μg L-1) and high (300 μg L-1) concentrations of 2,4-DCP. Behavioral analyses revealed decreased locomotor activity and increased anxiety-like responses in exposed fish, as well as impaired social preference at the higher concentration. Biochemical assays indicated elevated lactate dehydrogenase (LDH) and glutathione S-transferase (GST) activities, suggesting disturbance in pathways related to redox balance and cellular damage. Molecular analyses demonstrated downregulation of dopaminergic (drd1, th1) and neuroplasticity (bdnf) genes, along with reduced expression of pro-inflammatory cytokines (tnfa, il-6). Together, these results indicate that 2,4-DCP induces neurobehavioral alterations likely mediated by dopaminergic dysfunction, alterations in redox-related pathways, and altered neuroimmune-related signaling. The findings reinforce the ecological and toxicological relevance of 2,4-DCP as a neurotoxic pollutant and the need for further investigations into its long-term and multigenerational effects in aquatic species.