Polystyrene nanoplastics impair epithelial barrier establishment and modulate extracellular vesicle release in human bronchial cells cultured at the air-liquid interface

The growing production of plastics has led to widespread environmental contamination by micro- and nanoplastics (MNPLs), raising increasing concern about their potential impact on human respiratory health. Among them, nanoplastics (NPs) can penetrate deeply into the lungs. However, their impact on human bronchial epithelial cells remains poorly characterized. Here, we assessed the effects of 40 nm polystyrene (PS)-NPs on human bronchial Calu-3 cells cultured at the air-liquid interface (ALI) during early epithelial establishment, a three-dimensional model representing a functionally immature or compromised airway epithelial barrier. Chronic exposure (120 h) to PS-NPs (12 and 120 µg/cm²) interfered with barrier establishment in a concentration- and time-dependent manner, as demonstrated by reduced transepithelial electrical resistance (TEER) and decreased expression of the junctional proteins E-cadherin and Zonula Occludens-1 (ZO-1). PS-NPs also promoted the release of multiple inflammatory mediators, with osteopontin (OPN), a recognized biomarker of air pollution exposure, together with IL-2 and IL-10, showing the most consistent increases across both epithelial compartments. Other cytokines displayed concentration- and compartment-dependent secretion patterns. This polarized secretion pattern suggests selective activation of epithelial signaling pathways and paracrine communication toward the submucosal milieu. Furthermore, PS-NPs were internalized by Calu-3 cells and packaged into extracellular vesicles (EVs), a process that may limit acute cellular damage while potentially enabling propagation of NP-induced signals. Overall, these findings indicate that PS-NP exposure perturbs epithelial barrier function and polarized intercellular communication under conditions mimicking a compromised airway epithelium, suggesting a mechanistic role for NPs as aggravating factors of pre-existing epithelial dysfunction