THROMBOTIC AND INFLAMMATORY CHANGES IN ENDOTHELIAL CELLS INCUBATED WITH LEUKOCYTES

Adhesion of leukocytes (WBC's) to vascular endothelial cells (EC's) is a component of inflammation, thrombosis and atherosclerosis. The purpose of this study was to assess the effect of WBC adhesion on the EC contribution to these pathologic events. Human WBC's were isolated and co-incubated with cultured human umbilical cord EC's. Supernatants and cell lysates (4 wells × 2) were obtained at 0.5,1,2, and 4 hours of incubation. EC's and WBC's (5 × 10⁵) were-incubated alone or in combination. Supernatants and cell lysates were assayed for leukotriene B4 (LTB4), the thromboxane metabolite thromboxane B2 (TXB2) and the prostacyclin metabolite 6-keto prostaglandin FT alpha (6 keto) by RIA. Cell lysates were analyzed for cell associated procoagulant activity (PCA) by an APTT procedure, for plasminogen activator inhibitor (PAI) by an amidolytic assay and for IL-1 by a T-cell co-stimulator assay. Cellular and supernatant LTB4 was unmeasurable for both WBC's and WBC/EC cultures. WBC TXB2 showed a time dependent elevation which was unaffected by EC's. IL-1 activity was measurable at 2 hours and reach 14 U/ml in WBC's and 6 U/ml in EC/WBC cultures. Co-incubation of WBC's with EC's induced a 200% increase in both supernatant and cell associated 6 keto concentrations compared to EC's incubated alone. EC's and WBC's produced no PCA when incubated alone. PCA activity of the EC/WBC co-cultures was measurable at 2 hours and was 300-1500 U/ml after 4 hours. Coincubated EC's had a 50% decrease in cell PAI, suggesting an increased release of inhibitor from the cells. The prostacyclin and PAI release -along with the delayed expression of PCA activity are responses similar to those expected after EC exposure to cytokines. A source of these cytokines appears to be the WBC's which secreted measurable amounts of IL-1. WBC released IL-1 was sufficient to induce biochemical changes in EC's which can stimulate coagulation (PCA synthesis), inhibit fibrinolysis (PAI release), and enhance inflammation (prostacyclin synthesis). These results suggest that the release of WBC IL-1 can be sufficient to produce pro-thrombotic and inflammatory changes in EC's which are similar to those observed with the addition of exogenous IL-1 to EC cultures.