Human endothelial cells modulate granulocyte adherence and chemotaxis.

Although human endothelial cells (EC) and granulocytes interact in several ways, the factors that regulate such interactions are not well defined. In this study we found that EC and their products directly altered granulocyte adherence (GA) and chemotactic activity. The spontaneous adherence of granulocytes to human umbilical vein EC monolayers was significantly reduced at 5, 15 and 30 min if the granulocytes were preincubated with EC that were stimulated by rocking. At 30 min the spontaneous adherence of EC-preincubated granulocytes was 36% of that of control granulocytes (P = 0.004). The augmented adherence stimulated by FMLP was also decreased (54% of control) by preincubation of the granulocytes with rocked EC. The ability of stimulated EC to inhibit GA was attenuated when the EC monolayers that were used for preincubation with the granulocytes were pretreated with the cyclooxygenase inhibitor indomethacin. GA to unstimulated EC was not significantly altered by indomethacin or aspirin, suggesting that cyclooxygenase products do not influence GA under resting conditions. Preincubation of granulocytes with rocked EC monolayers or supernatant media from rocked EC monolayers diminished their chemotactic response to FMLP by 45 to 65. This inhibition was also attenuated by pretreatment of the EC with indomethacin. EC supernatant medium caused a rapid increase in granulocyte intracellular cyclic AMP, with a maximum increase to 200% of control at 1 min. These data indicate that stimulated EC release one or more arachidonic acid products that alter spontaneous and inflammatory mediator-stimulated granulocyte activity. Prostacyclin, a major cyclooxygenase product of EC arachidonate, depressed inflammatory mediator-augmented GA to EC monolayers and chemotaxis when present in nanomolar concentrations. We conclude that EC-derived prostacyclin, alone or in combination with other EC products, alters GA and chemotaxis stimulated by inflammatory mediators. This provides a mechanism by which EC may modulate granulocyte distribution as well as granulocyte responses that are influenced by adherence, such as the release of toxic oxygen metabolites and granular enzymes.