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 25 mg/kg) in mice induced rapid-onset pulmonary edema and neutrophilic inflammation, peaking within 24-48 h. Although 6-PPD was rapidly cleared from lung tissue within 24 h 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 168 h. 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 336 h. 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.