Engagement of ICAM‐1 mediates neutrophil crawling on the luminal surface of the intestinal epithelium and signals to regulate barrier function

Abstract

A hallmark of inflammatory mucosal diseases is transepithelial migration (TEM) of neutrophils (PMN) and subsequent accumulation in a lumenal space. TEM has been extensively modeled, but PMN interactions with apical epithelial ligands and resulting effects on epithelial barrier function remain poorly understood. We previously showed that interferon γ (IFNγ) treatment of T84 intestinal epithelial cells enhanced ICAM‐1 expression on the apical epithelial cell membrane, leading to increased PMN adhesion. Here we show that, after TEM, 59.3±7.6% of apically‐associated PMN exhibit crawling behavior. There was a 33% increase in PMN crawling on IFNγ treated T84 monolayers along with decreased crawling distance and velocity. These effects were ICAM‐1 specific, as they were reversible by treatment with anti‐ICAM‐1 antibody (Ab). Experiments modeling functional engagement of epithelial ICAM‐1 by Ab‐mediated crosslinking significantly impaired epithelial barrier, as determined by decreased transepithelial resistance, increased flux of FITC‐dextran (~2.5‐fold) and increased PMN TEM (~1.5‐fold). These findings were paralleled by actin rearrangement and decreased cell surface JAM‐A and E‐Cadherin. These results suggest that after TEM, PMN engagement of apically expressed epithelial ICAM‐1 results in signaling to alter barrier and subsequent recruitment of leukocytes.