LIPOXIN A(4) MODULATES TRANSMIGRATION OF HUMAN NEUTROPHILS ACROSS INTESTINAL EPITHELIAL MONOLAYERS

Neutrophil (PMN) migration across intestinal epithelial barriers, such as occurs in many disease states, results in modifications in epithel ial barrier. Here, we investigated the impact of lipoxin A4 (LXA4), an eicosanoid with counterregulatory inflammatory roles, on PMN migratio n across cultured monolayers of the human intestinal epithelial cell l ine T84. Transepithelial migration of PMN was assessed in the apical-t o-basolateral direction and in the basolateral-to-apical direction. In the apical-to-basolateral direction, preexposure of PMN to LXA4 (10 n M, 15 min) stimulated an 87 +/- 5% increase in transepithelial migrati on of PMN as determined by a PMN myeloperoxidase assay. The LXA4-elici ted effect on transmigration was present throughout the 2-h assay peri od and was not secondary to LXA4 effects on epithelial monolayer integ rity as judged by measurement of transepithelial resistance. PMN migra tion in the basolateral-to-apical direction was modulated by LXA4 with a comparable time- and concentration-dependence to that in the apical -to-basolateral direction. However, qualitative differences in how LXA 4 Modulates transmigration in the two opposing directions were observe d. In the basolateral-to-apical direction, preexposure of PMN to LXA4 (10 nM, 15 min) diminished PMN transepithelial migration by 33 +/- 4%. Structure-function studies revealed that LXA4 and 11-trans-LXA4 (50% of LXA4 effect), but not LXB4, inhibited basolateral-to-apical PMN tra nsmigration. The action of LXA4 was not sensitive to inhibitors of cyc looxygenase or specific leukotriene biosynthesis, but was sensitive to staurosporine, a protein kinase C inhibitor. These results suggest th at migration of PMN across epithelia in the physiological direction ma y be qualitatively different following PMN exposure to eicosanoids. We propose that such retention of PMN at this specific anatomic location may serve an important role in mucosal defense.