Toxic effects of combined exposure to tebuconazole and perfluorooctanoic acid on Eisenia fetida: an assessment based on behavioral, biochemical, and molecular levels.

With the intensification of modern agricultural production activities and industrial development, the presence of pesticides and persistent organic pollutants in the soil environment has emerged as a global ecological challenge. However, the toxicological effects of co-exposure to pesticides and persistent organic pollutants (POPs) on non-target soil organisms have not yet been fully understood. In this study, a tripartite research framework integrating behavioral, biochemical, and molecular dynamics analyses was adopted to investigate the potential mechanisms underlying the combined toxicity of tebuconazole and perfluorooctanoic acid (PFOA) on Eisenia fetida (E. fetida). The results demonstrated that exposure to tebuconazole alone and co-exposure to tebuconazole and PFOA significantly affected the behavior of E. fetida, inhibited growth and development, and altered movement patterns. At the biochemical level, the antioxidant defense system exhibited functional compensation. In contrast, detoxification and neurotransmission pathways showed systemic impairment. Increasing PFOA concentrations enhanced several toxic responses under co-exposure conditions. Meanwhile, molecular dynamics simulations further suggested that tebuconazole and PFOA could interact with the active sites of target proteins, including superoxide dismutase, acetylcholinesterase, and glutathione S-transferases, and actin, through hydrophobic interactions and unique halogen bonds. These interactions were associated with alterations in protein conformational dynamics, suggesting their potential involvement in the regulation of antioxidant defense, detoxification processes, neurotransmission, and locomotor-related functions. Collectively, these findings provide molecular-level evidence for compound-protein interactions and enhance the understanding of toxicological responses associated with pesticide-POP co-exposure in soil organisms under chronic exposure conditions.