The Secretome of Human Bronchial Epithelial Cells Exposed to Fine Atmospheric Particles Induces Fibroblast Proliferation

Abstract

Chronic exposure to particulate pollution is suspected to exacerbate inflammatory respiratory diseases such as asthma characterized by an airway remodelling involving fibrosis. Our study aims to investigate whether the secretome from human bronchial epithelial (HBE) cells exposed to fine particulate matter (PM) induces fibroblast proliferation. Primary HBE cells grown on air liquid interface were repeatedly exposed to fine PM at 5 and 10 µg/cm² (four treatments, 48 hours apart) and maintained in culture for five weeks. Collected basolateral culture medium was used as a conditioned medium for the subsequent treatment of fibroblasts. We observed that the conditioned medium collected from HBE cells treated with fine PM increased the growth rate of fibroblasts compared to the conditioned medium collected from control HBE cells. Fibroblast phenotype assessed by the observation of the vimentin network was well preserved. The mitogenic effect of conditioned medium was reduced in the presence of anti-epidermal growth factor receptor (EGFR), anti-amphiregulin or anti-TGFa, underlining the role of EGFR ligands in fibroblast proliferation. When fibroblasts were co-cultured with HBE cells treated once with fine PM, they exhibited a higher growth rate than fibroblasts co-cultured with non-treated HBE cells. Altogether these data show that the exposure of HBE cells to fine PM induced the production of EGFR ligands in sufficient amount to stimulate fibroblast proliferation providing insight into the role of PM in airway remodelling

Role of air pollutants in airway epithelial barrier dysfunction in asthma and COPD

“…Of note, PM-induced EGFR activation in AECs was shown to induce airway epithelial barrier disruption in AECs [ 54 , 55 ]. Non-toxic doses of whole PM 2.5 , and organic extract of PM 2.5 mainly containing PAH, were shown to increase the release of the EGFR ligand amphiregulin over 24 h up to 48 h post-exposure in AECs in vitro [ 56 , 57 ]. This increased release of EGFR ligands upon PM exposure was reported to be dependent on metalloproteinases such as metalloproteinase 17 (ADAM17) also known as (TNF-α)-converting enzyme (TACE) [ 58 ], which proteolytically cleaves the active form of amphiregulin.…”

Effects of Pristine and Nitrogen-Doped Multi-Walled Carbon Nanotubes on Human Lung Epithelial and Fibroblast Cells

“…Two primary approaches fall within this category for nanotoxicology assessments. The first is to treat one cell type with the material of interest, collect media after exposure, centrifuge it to remove extraneous nanoparticles (if interested in only studying soluble cell mediators), and apply the conditioned media in empirically determined ratios to another cell line in order to address unidirectional cell-cell communication [14][15][16]. Although this method somewhat lessens the need to identify cell media-compatible cell lines compared to co-culture, it has limitations.…”

“…These systems typically rely upon identifying two or more biologically relevant cell lines that would likely communicate in vivo, are compatible in culture, and maintain cell phenotypic activity. Proposed pulmonary culture systems have included alveolar epithelial-endothelial [19], epithelial-fibroblast [14,18,[20][21][22][23], macrophage-epithelial [24,25], and epithelial-macrophage-dendritic [26,27], all of which ask and answer specific research questions. They also typically rely upon the use of removable Transwell® membranes or similar on which one or two cell types can be seeded, as well as another cell line in the basolateral chamber of the Transwell® receiving dish.…”