Exploring the fate of 6PPD in zebrafish (Danio rerio): Understanding toxicokinetics, biotransformation mechanisms, and metabolomic profiling at environmentally relevant levels

In recent years, N -(1,3-dimethylbutyl)- N′ -phenyl- p -phenylenediamine (6PPD) has attracted significant attention in environmental science, yet its behavior in biological systems remains poorly understood. This study involved a 28-day zebrafish exposure experiment at three concentrations (2, 20, and 200 μg/L), to investigate its physiologically based toxicokinetic (PBTK) properties, the formation of biotransformation products, and the metabolic characteristics of liver tissue. The results indicated that the liver and intestines are key organs for 6PPD accumulation, with tissue-specific distribution patterns. The biotransformation of 6PPD in the liver involves various phase I and phase II metabolic reactions, including hydroxylation, N -dealkylation, and sulfation processes. Furthermore, Metabolomics analysis revealed substantial changes in both the diversity and abundance of liver metabolites with increasing 6PPD concentrations, particularly in key biological processes such as lipid metabolism, amino acid metabolism, and redox balance. Notably, significant disruptions in sphingolipid and glycerophospholipid pathways suggest 6PPD may impair membrane fluidity and stability, potentially leading to membrane damage and dysfunction. Overall, this study provides crucial insights into the biological behavior of 6PPD in zebrafish, contributing essential knowledge for its ecotoxicological evaluation.