Neutrophil‐epithelial contact disrupts epithelial barrier function and is dependent on protease‐activated receptors (PAR)‐1 and ‐4

Neutrophil (PMN) infiltration through mucosal surfaces is a hallmark of inflammatory diseases and contributes to epithelial injury. Past research has shown that PMN contact increases epithelial permeability and induces epithelial signaling events prior to transepithelial migration. In this study we sought to better characterize the mechanisms that influence the disruption of epithelial barrier function induced by PMN contact. In the presence of a transepithelial fMLP gradient, PMN contact with basolateral surfaces of intestinal epithelial (T84 & SK‐CO15) monolayers resulted in decreased transepithelial electrical resistance (TER) and correlated with diminished levels of tight junction proteins occludin and ZO‐1, but not E‐cadherin. Pre‐incubation with 1mM AEBSF (serine protease inhibitor) prevented the decrease in TER induced by PMN contact. Conversely, incubation with 10μg/ml PMN elastase and proteinase‐3, but not cathepsin G, decreased TER. Treatment of epithelial monolayers with 50μM PAR agonists TFLLR (PAR‐1)/SLIGRL (PAR‐2)/AYPGKF (PAR‐4), or 5μM antagonists SCH79797 (PAR‐1)/P4pal‐10 (PAR‐4) also prevented the decrease in TER induced by PMN contact. Collectively, these findings suggest that activation of PAR signaling events by PMN proteases may enhance epithelial permeability and facilitate passage of migrating PMN through the paracellular space. (CAG/CIHR/Axcan Pharma Inc/NIH)