Single Tire-Derived Pollutant (6-PPD) Exposure Triggers Lung Injury and Mitochondrial Disruption in Mice.

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD) is a widely used tire antiozonant that has recently emerged as a global environmental concern. Although its aquatic toxicity is well documented, its respiratory toxicity in mammals remains poorly understood. We aimed to characterize the temporal progression of 6-PPD-induced pulmonary injury and elucidate the underlying molecular mechanisms, with a focus on mitochondrial homeostasis. A single exposure to 6-PPD (10 or 25mg/kg) in mice induced rapid-onset pulmonary edema and neutrophilic inflammation, peaking within 24-48h. Although 6-PPD was rapidly cleared from lung tissue within 24h and extrapulmonary organs showed only transient or no significant changes, pulmonary injury persisted. Lung weight remained significantly elevated, and foamy alveolar macrophages were observed up to 168h. Mechanistically, 6-PPD induced a state of mitochondrial dysfunction characterized by sustained Drp1-mediated fission and impaired autophagic degradation, evidenced by persistent accumulation of p62 (SQSTM1) and LC3-II up to 336h. Despite these structural alterations, ATP levels and antioxidant enzyme activities remained stable, indicating maintained metabolic function despite disrupted mitochondrial quality control. A single respiratory exposure to 6-PPD induced persistent lung injury that outlasted the presence of the parent compound. This effect was associated with disruption of mitochondrial quality control, highlighting mitochondrial dysfunction as a key mechanism of toxicity. These findings provide important insights for assessing inhalation risks of tire-derived pollutants and support the need for further studies under environmentally relevant exposure conditions.