15-HYDROXYEICOSATETRAENOIC ACID INHIBITS NEUTROPHIL MIGRATION ACROSS CYTOKINE-ACTIVATED ENDOTHELIUM

15-hydroxyeicosatetraenoic acid (15-HETE) is an eicosanoid, formed by the actions of 15-lipoxygenase, epoxygenases, and cyclooxygenases on a rachidonic acid, whose tissue levels are often elevated during inflamm ation. The present study demonstrates that 15(S)-HETE is a potent inhi bitor of polymorphonuclear neutrophil (PMN) migration across cytokine- activated endothelium in vitro. 15(S)-HETE is rapidly esterified into PMN phospholipids, and we report that 15(S)-HETE- remodeled PMN displa yed blunted adhesion to, and migration across, human endothelial cells that had been activated with either interleukin-1 beta or tumor necro sis factor-alpha. Several lines of evidence suggested that 15(S)-HETE inhibited PMN transmigration by attenuating PMN responsiveness to endo thelial cell-derived platelet-activating factor (PAF). The inhibitory action of 15(S)-HETE on transmigration was not restricted by the profi le of adhesion molecules expressed by cytokine-activated endothelium. Interleukin-1 beta and tumor necrosis factor-alpha induce PAF producti on by endothelium, and PMN migration across cytokine-activated endothe lium was inhibited by a PAF receptor antagonist. PMN migration across endothelium in response to exogenous PAF was dramatically inhibited fo llowing exposure of PMN to 15(S)-HETE. Furthermore, 15(S)-HETE-remodel ed PMN displayed impaired cytoskeletal and adhesion responses when sti mulated by exogenous PAF, two pivotal events in PMN migration across a ctivated endothelium. 15(S)-HETE seemed to attenuate PMN responsivenes s to PAF by inhibiting membrane-associated signal transduction events. In keeping with this interpretation, remodeling of PMN phospholipids with 15(S)-HETE was associated with a sixfold reduction in the affinit y of specific high-affinity PAF receptors for their ligand and impaire d PAF-triggered IP3 generation. In contrast, PMN adhesion responses st imulated by calcium ionophore or activators of protein kinase C remain ed intact These results provide further evidence that 15(S)-HETE may b e an important endogenous inhibitor of PMN-endothelial cell interactio n that serves to limit or reverse neutrophil-mediated inflammation in vivo.