Acute exposure to 6PPD-Q at environmentally relevant concentrations induces lipid and energy metabolism dysregulation in rainbow trout

2-((4-Methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione (6PPD-Q), a ubiquitous transformation product of tire rubber antioxidants, has emerged as an aquatic pollutant of high ecotoxicological concern due to its extremely high acute toxicity to sensitive salmonid species. While recent toxicological studies have identified several pathways associated with acute toxicity, systemic lipid dysregulation in sensitive salmonids remains poorly characterized. Semi-quantitative untargeted lipidomics was employed to characterize lipidomic perturbations in surviving rainbow trout ( Oncorhynchus mykiss ), a species highly sensitive to 6PPD-Q, following acute exposure and to explore how these perturbations may contribute to adverse effects. Following a 24 h acute exposure to 6PPD-Q at environmentally relevant concentrations (0.45, 0.9, and 1.8 μg/L), significant oxidative stress was observed, evidenced by elevated reactive oxygen species, malondialdehyde levels, and increased antioxidant enzyme activities. Lipidomic analysis revealed extensive dysregulation of the lipid profile. This disruption was characterized by the accumulation of triglycerides (TG) and oxidized triglycerides (OxTG), alongside a selective decrease in diacylglycerols (DG) and phospholipids (PL) containing polyunsaturated fatty acids. Docosahexaenoic acid (DHA) and arachidonic acid (AA) were identified as the most affected species (DHA-PL and AA-PL). Furthermore, a significant reduction in mitochondria-associated lipids, specifically cardiolipin (CL) and coenzyme Q10 (CoQ10), was noted, which was consistent with previously reported mitochondrial impairment. These perturbations suggested that 6PPD-Q may be associated with suppressed fatty acid β-oxidation, resulting in TG accumulation. This study provides new insights into lipidomic perturbations associated with acute 6PPD-Q exposure and identifies specific OxTG species as candidate biomarkers for environmental monitoring and ecological risk assessment.