Abstract
BackgroundWhile 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.Methods16HBE14o- 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.ResultsA 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.ConclusionShort 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.
Highlights
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
The apical junctional complexes (AJCs) consist of the basolateral adherens junctions which are important for cell signaling and initiating cell-cell adhesion [12] while the apical tight junctions (TJs) are composed of the claudin family, tight junction-associated MARVEL proteins (TAMPs), and immunoglobulin-like proteins such as the junctional adhesion molecule family [13, 14]
Twenty four hours exposure to SRM 2975 causes increased cytoplasmic staining for Occludin in 16HBE14o- cells [17], while primary rat airway epithelial cells (AECs) and human A549 cells exposed to 20 μg/cm2 diesel particulate matter (DEP) for 3 h exhibited a reduction of Occludin present at the plasma membrane despite no change in Occludin protein levels in whole cell lysates [42]. Despite this possibility of Occludin reorganization following DEP exposure, our study demonstrated that a loss of Tricellulin through siRNA mediated knockdown can cause a significant decrease in barrier function as measured by both reduced transepithelial electrical resistance (TEER) and increased permeability to FITCDextran, suggesting that a loss of Tricellulin is sufficient to significantly impact barrier function
Summary
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. The AJCs consist of the basolateral adherens junctions which are important for cell signaling and initiating cell-cell adhesion [12] while the apical tight junctions (TJs) are composed of the claudin family, tight junction-associated MARVEL proteins (TAMPs), and immunoglobulin-like proteins such as the junctional adhesion molecule family [13, 14]. Due to their apical location, TJs regulate paracellular passage of ions and macromolecules across the epithelium. The TAMP family shares the four-pass transmembrane MARVEL domain and is composed of Occludin, Tricellulin (Tric), and MarvelD3 [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
