Tobacco smoke induces epithelial barrier dysfunction via receptor EphA2 signaling

Abstract

Erythropoietin-producing human hepatocellular carcinoma (Eph) receptors are the largest family of receptor tyrosine kinases (RTKs) that mediate various cellular and developmental processes. The degrees of expression of these key molecules control the cell-cell interactions. Although the role of Eph receptors and their ligand Ephrins is well studied in developmental processes, their function in tobacco smoke (TS)-induced epithelial barrier dysfunction is unknown. We hypothesized that TS may induce permeability in bronchial airway epithelial cell (BAEpC) monolayer by modulating receptor EphA2 expression, actin cytoskeleton, adherens junction, and focal adhesion proteins. Here we report that in BAEpCs, acute TS exposure significantly upregulated EphA2 and EphrinA1 expression, disrupted the actin filaments, decreased E-cadherin expression, and increased protein permeability, whereas the focal adhesion protein paxillin was unaffected. Silencing the receptor EphA2 expression with silencing interference RNA (siRNA) significantly attenuated TS-induced hyperpermeability in BAEpCs. In addition, when BAEpC monolayer was transfected with EphA2-expressing plasmid and treated with recombinant EphrinA1, the transepithelial electrical resistance decreased significantly. Furthermore, TS downregulated E-cadherin expression and induced hyperpermeability across BAEpC monolayer in a Erk1/Erk2, p38, and JNK MAPK-dependent manner. TS induced hyperpermeability in BAEpC monolayer by targeting cell-cell adhesions, and interestingly cell-matrix adhesions were unaffected. The present data suggest that TS causes significant damage to the BAEpCs via induction of EphA2 and downregulation of E-cadherin. Induction of EphA2 in the BAEpCs exposed to TS may be an important signaling event in the pathogenesis of TS-induced epithelial injury.

Inhibition of EphA2/EphrinA1 signal attenuates lipopolysaccharide-induced lung injury

“…Also, immunofluorescence study supported the possibility of enhancing E-cadherin with EphA2 mAb. Further studies are needed to determine whether up-regulated E-cadherin expression and reduced protein leakage after EphA2 mAb posttreatment is associated with reduced Erk phosphorylation or activated PKC pathway, as reported by previous studies [35,36].…”

“…He et al [35] reported that LPS induces epithelial barrier dysfunction through the regulation of E-cadherin intracellular trafficking. Nasreen et al [36] demonstrated that EphA2 and EphrinA1 expression levels were increased in bronchial airway epithelial cells exposed to tobacco smoke, and this may be an important event preceding down-regulation of E-cadherin expression and MAPKdependent hyperpermeability.…”

EphA2 Receptor Signaling Mediates Inflammatory Responses in Lipopolysaccharide-Induced Lung Injury

“…Eph receptors and ephrin ligands represent the largest family of receptor tyrosine kinases that regulate important processes during embryonic neuronal development, angiogenesis and oncogenesis 1 2 . Emerging evidence suggests that Eph/ephrin plays a key role in inflammation 3 and previous studies have established the role of EphA2 in postnatal lung injury 9 10 11 15 .…”

“…Considering that the expression of ephrinA1 is induced by some cytokines 25 26 , ligand-mediated activation of the EphA2 receptor is expected to be accelerated in lung injury. Recent research reported that EphA2 expression induced by tobacco smoke exposure in bronchial airway epithelial cells was dependent on MAPK (ERK, p38, and JNK) signaling 15 . Determining whether EphA2 signaling communicates with these additional mechanisms in LPS-induced lung inflammation will require further investigation.…”

Using Drugs to Probe the Variability of Trans-Epithelial Airway Resistance

“…For example, it has been proposed that chronicity in asthma may be cued by an initial genetic and or environmental propensity that lowers TER, facilitating epithelial penetration that subsequently drives irreversible airway remodelling [ 2 ]. The clinical importance of TER is further illustrated by recent data suggesting that cigarette smoke, inhaled pollutants or acid exposure due to gastro-oesophageal reflux can all dysregulate tight junctional proteins by signalling through ion channels and/or acid sensors [ 3 – 5 ]. Furthermore, in Cystic Fibrosis (CF), mutation of one apical channel, the CF transmembrane conductance regulator (CFTR), disturbs a regulatory (proteostasis) network that, inter alia , controls TER [ 6 ].…”