The Role of Bronchial Epithelial Cell-Derived Extracellular Vesicles in Modulating Macrophage Function and COPD Progression

Abstract

Long-term exposure to fine particulate matter (PM2.5) is a major environmental risk factor for chronic obstructive pulmonary disease (COPD). PM2.5 directly damages bronchial epithelial cells and promotes pro-inflammatory signaling. Emerging evidence indicates that extracellular vesicles (EVs) released by stressed epithelial cells contribute to immune dysregulation. This study established an in vitro model to examine how PM2.5-induced epithelial EVs modulate macrophage function.

BEAS-2B cells were exposed to low and high PM2.5 concentrations, and EVs were isolated and characterised using nanoparticle tracking analysis, BCA protein quantification, and Western blotting. Time-dependent uptake of EVs by PMA-differentiated THP-1 macrophages was confirmed by fluorescence tracing. EVs alone did not alter macrophage viability or cytokine secretion, but under lipopolysaccharide (LPS) stimulation, EV pre-exposure modulated macrophage responses. These effects depended on EV source and exposure duration rather than concentration, and strong inflammatory stimulation (100 ng/mL LPS) diminished EV-mediated regulation. Notably, IL-6 and IL-8 secretion showed biphasic responses to EV dose, and the duration of EV treatment influenced macrophage signalling outcomes.

While a definitive macrophage polarization pattern could not be established, this work provides a basis for future studies into EV-mediated immune regulation. Overall, PM2.5 reduced epithelial viability, increased pro-inflammatory cytokine release, and may have altered EV cargo, thereby influencing macrophage behaviour in an inflammation-dependent manner. These findings highlight both the direct effects of PM2.5 on epithelial cells and the potential role of EV-mediated epithelial–macrophage communication in air-pollution-induced airway inflammation, offering insights relevant to COPD pathogenesis.