Acute or repeated exposure of aerosolized flame retardants induces molecular and structural alterations in lung...

Organophosphate flame retardants (OPFRs) such as tributyl phosphate (TBP) are widely used industrial additives increasingly detected in the environment and human tissues, yet their inhalation toxicity remains poorly characterized. In this study, we employed the ex vivo porcine precision-cut lung slice (pPCLS) model to investigate the cytotoxic, oxidative stress, and structural effects of aerosolized TBP under both acute and repeated exposure conditions. Using the Vitrocell®, pPCLS were exposed to TBP aerosols at deposited surface concentrations (µg/cm²) within ranges commonly applied in ALI-based inhalation toxicology models and selected to simulate cumulative low-dose exposure scenarios reported for organophosphate flame retardants in indoor environments. Acute exposure (24 h) caused a reduction in tissue viability, increased reactive oxygen species (ROS) production, and enhanced caspase-3 activation, indicating mitochondrial stress and apoptosis induction. There is a potential tendency for markers (K-RAS, p53, and MMP-15) to increase. Histological analyses revealed disruption of extracellular matrix architecture. Repeated low-dose exposure (5 × 24 h) led to progressive tissue disorganization and early signs of fibrogenic remodeling, evidenced by increased collagen deposition, p53 expression, reduced tissue viability, and sustained oxidative stress. These findings suggest that cumulative subcytotoxic exposure to aerosolized TBP can initiate pathways associated with chronic pulmonary injury. The pPCLS model demonstrated high reproducibility, preserved lung architecture, and responsiveness to chemical insult, reinforcing its translational relevance for respiratory toxicology. Overall, our results provide mechanistic insight into TBP-induced lung toxicity and highlight precision-cut lung slices as a useful model for evaluating inhalation hazards of industrial chemicals.