Lipoxin A4 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 epithelial barrier. Here, we investigated the impact of lipoxin A4 (LXA4), an eicosanoid with counterregulatory inflammatory roles, on PMN migration across cultured monolayers of the human intestinal epithelial cell line T84. Transepithelial migration of PMN was assessed in the apical-to-basolateral direction and in the basolateral-to-apical direction. In the apical-to-basolateral direction, preexposure of PMN to LXA4 (10 nM, 15 min) stimulated an 87 +/- 5% increase in transepithelial migration of PMN as determined by a PMN myeloperoxidase assay. The LXA4-elicited effect on transmigration was present throughout the 2-h assay period and was not secondary to LXA4 effects on epithelial monolayer integrity as judged by measurement of transepithelial resistance. PMN migration 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 LXA4 modulates transmigration in the two opposing directions were observed. 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 transmigration. The action of LXA4 was not sensitive to inhibitors of cyclooxygenase or specific leukotriene biosynthesis, but was sensitive to staurosporine, a protein kinase C inhibitor. These results suggest that migration of PMN across epithelia in the physiological direction may 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.