SICKLE RED-BLOOD-CELLS STIMULATE ENDOTHELIAL-CELL PRODUCTION OF EICOSANOIDS AND DIACYLGLYCEROL

The effects of sickle red cel-endothelial cell interaction on endothel ial cell arachidonic acid (AA) mobilization, eicosanoid release, and d iacylglycerol (DAG) production were evaluated by using bovine aortic e ndothelial eels. We have shown that coincubation of washed red blood c ells (RBCs) from patients with sickle cell disease with endothelial ce lls stimulate AA release (90% increase as compared with buffer control s, n = 8, p < 0.002). Released AA was mobilized from membrane phosphat idylcholine and phosphatidylserine and was converted to eicosanoids vi a the cyclooxygenase and lipoxygenase pathways in increased amounts in the presence of sickle erythrocytes. The production of prostacyclin a nd 15-hydroxyeicosatetraenoic acid (15-HETE) were increased by 78% (p < 0.01) and 103% (p < 0.025), respectively, as shown by both chromatog raphic and immunoassay procedures. Sickle erythrocytes also stimulated the hydrolysis of endothelial cell phosphoinositides, including phosp hatidylinositol-mono-phosphate (p < 0.03) and phosphatidylinositol-bis -phosphate (p < 0.006). This response was accompanied by a significant increase in the production of DAG (50% increase as compared with buff er control, n = 8, p < 0.025). In contrast, coincubation of washed ery throcytes from normal healthy donors with endothelial cells had no sig nificant effect on endothelial cell phospholipid turnover. When the si ckle RBC-induced biochemical changes in endothelial cells were contras ted with those observed with normal RBCs, the ability of sickle RBCs t o induce AA mobilization and the production of mono-HETEs and DAG was markedly increased (p = 0.05 to p < 0.025). Because 15-HETE is a pro-a dhesinogenic eicosanoid and DAG is an endogenous activator of protein kinase C, an enzyme involved in modulating cell surface adhesive prope rties, both 15-HETE and DAG could potentially play a role in the vascu lar pathophysiology of sickle cell disease.