Diesel exhaust particle exposure reduces expression of the epithelial tight junction protein Tricellulin

Abstract

Background While exposure to diesel exhaust particles has been linked to aberrant immune responses in allergic diseases such as asthma, little attention has been paid to their effects on the airway epithelial barrier. In this study, we sought to determine the effect of diesel exhaust exposure on airway epithelial barrier function and composition using in vitro and in vivo model systems. Methods 16HBE14o- human bronchial epithelial cells were grown on collagen coated Transwell inserts and exposed to 5 to 50 μg/cm2 SRM 2975 diesel particulate matter (DEP) suspended in cell culture medium or vehicle controls. Changes in barrier function were assessed by measuring transepithelial electrical resistance (TEER) and permeability to 4 kDa FITC Dextran. Neonatal BALB/c mice were exposed to aerosolized DEP (255 ± 89 μg/m3; 2 h per day for 5 days) and changes in the tight junction protein Tricellulin were assessed 2 weeks post exposure. Results A six-hour incubation of epithelial cells with diesel exhaust particles caused a significant concentration-dependent reduction in epithelial barrier integrity as measured by decreased TEER and increased permeability to 4 kDa FITC-Dextran. This reduction in epithelial barrier integrity corresponded to a significant reduction in expression of the tight junction protein Tricellulin. siRNA mediated knockdown of Tricellulin recapitulated changes in barrier function caused by DEP exposure. Neonatal exposure to aerosolized DEP caused a significant reduction in lung Tricellulin 2 weeks post exposure at both the protein and mRNA level. Conclusion Short term exposure to DEP causes a significant reduction in epithelial barrier integrity through a reduction in the tight junction protein Tricellulin. Neonatal exposure to aerosolized DEP caused a significant and sustained reduction in Tricellulin protein and mRNA in the lung, suggesting that early life exposure to inhaled DEP may cause lasting changes in airway epithelial barrier function.

Carbon nanoparticles adversely affect CFTR expression and toxicologically relevant pathways

“…2d, e). Diesel engine exhaust particles showed similar responses in previous studies despite differences in particle composition as well as cell culture and exposure conditions 30,31 .…”

“…The values of a blank insert without cells were subtracted as the background value. assessed using 4 kDa FITC-Dextran (SIGMA) permeability as described previously 30 . Medium was removed from both compartments, cells and the wells washed with PBS.…”

“…Notably, we previously showed that these cells, similar to alveolar epithelial cells, respond to CNP exposure with pro-inflammatory signaling events which were also observed in vivo in exposed rodents 29 . Diesel exhaust particles showed effects on the barrier function of 16HBE14o- cells including reduced expression of tricellulin ( TRIC ), decreased transepithelial electrical resistance (TEER), increased fluorescein-isothiocyanate (FITC)-Dextran permeability 30 and altered occludin ( OCLN ) expression 31 . A transcriptomic analysis of 16HBE14o- cells exposed to airborne PM2.5 revealed upregulation of genes involved in xenobiotic metabolism and inflammatory pathways, which was predominantly attributed to the absorbed substances, like PAHs 32 .…”

Nrf2 Activation Protects Against Organic Dust and Hydrogen Sulfide Exposure Induced Epithelial Barrier Loss and K. pneumoniae Invasion

“…Permeability of the cellular monolayer was assessed by measuring the movement of the apically applied FITC-dextran across the cellular monolayer ( Smyth et al., 2020 ). NHBE cells were seeded in collagen coated 3 µm cell culture inserts with the expansion media in both the upper and lower compartment.…”

Air Pollution and the Airways: Lessons from a Century of Human Urbanization

“…It consists of fine particles (like PM 2.5 ) and ultrafine particles [137]. DEP exposure leads to a loss of epithelial barrier integrity, especially via a decrease in tricellulin, a tight junction both on mRNA and protein level, and specific compounds of DEP can lead to epithelial cell apoptosis [138,139]. The IL-33/ST2 axis has also been implicated in contributing to DEP-enhanced allergic airway responses.…”