Pathway-level secretome modulation in bronchial epithelial spheroids following indoor dust exposure

As humans spend most of their time indoors, they are continuously exposed to an array of indoor air pollutants. While exposure to individual indoor air pollutants may often occur at low levels, cumulative exposure to indoor air pollutants contributes substantially to the human exposome. Chronic inhalation of indoor air pollutants has been associated with multiple respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), and respiratory infections. In this study, the cellular effects of an acute indoor dust exposure using a three-dimensional airway epithelial model were investigated. Bronchial epithelial cells (16HBE14o-) were cultured as spheroids and exposed to reference indoor dust (SRM 2585; 0-200 µg/mL) for 24 h. Metabolic activity, intracellular reactive oxygen species (ROS) levels, inflammatory cytokine secretion, and secretome profiles were assessed. Indoor dust exposure did not induce morphological alterations or significant reductions in metabolic activity. Instead, a concentration-dependent increase in intracellular ROS was observed. Cytokine analysis revealed selective cytokine modulation, while untargeted proteomics identified limited changes in individual protein abundance. Instead, pathway-level analyses revealed enrichment of epithelial differentiation-related pathways. Overall, these findings suggest that a 24 h indoor dust exposure may elicit subtle cellular responses rather than overt cytotoxicity or inflammatory activation. This study highlights the applicability of integrating functional, immunological, and proteomics-based approaches with 3D airway models to investigate cellular responses to complex environmental particle mixtures. However, direct extrapolation to human exposure scenarios is limited by uncertainties regarding effective cellular dose, particle localization and environmental representativeness. Therefore, these findings should be interpreted as exploratory, hypothesis-generating observations.