Lateral membrane LXA4 receptors mediate LXA4's anti-inflammatory actions on intestinal epithelium

Lipoxin A(4) (LXA(4)) and its stable analogs downregulate chemokine secretion in polarized epithelia. This anti-inflammatory effect has been suggested to be mediated by the LXA(4) receptor (LXA(4)R),a G protein-coupled receptor. To determine whether LXA(4)R is expressed on the apical, basolateral, or both poles of intestinal epithelia, an NH2-terminal c-myc epitope tag was added to the human LXA(4)R cDNA and recombinant retroviruses were used to transduce polarized epithelial cells. In polarized T84 intestinal epithelial cells, c-myc-LXA(4)R was preferentially expressed on the basolateral surface as indicated by cell surface-selective biotinylation and confocal microscopy. Furthermore, expression of c-myc-LXA(4)R and a truncation mutant lacking the cytoplasmic terminus was primarily confined to the lateral subdomain. We also observed that the expression of myc-LXA(4) conferred enhanced downregulation of IL-8 expression in response to LXA(4) analog and that blockade of the CysLT1 receptor by montelukast did not prevent this response to LXA(4) analog. Thus LXA(4) generated in or near the paracellular space via neutrophil-epithelial interactions can rapidly act on epithelial LXA(4)R to downregulate epithelial promotion of intestinal inflammation.