INHIBITION OF STIMULUS-INDUCED ENDOTHELIAL-CELL INTERCELLULAR-ADHESION MOLECULE-1, E-SELECTIN, AND VASCULAR CELLULAR ADHESION MOLECULE-1 EXPRESSION BY ARACHIDONIC-ACID AND ITS HYDROXY AND HYDROPEROXY DERIVATIVES

Localized adhesion of peripheral blood leukocytes to the endothelial l ining is essential for their exit from the blood under both physiologi cal and pathological conditions. The establishment, development, and r esolution of the inflammatory response is regulated by an array of med iators, many of which remain to be categorized. These include arachido nic acid (20:4n-6) and its hydroperoxy (HPETE) and hydroxy (HETE) deri vatives, which are released during inflammation. The data show that hu man umbilical vein endothelial cells, pretreated with these fatty acid s, have a reduced ability to be stimulated by tumor necrosis factor-al pha (TNF-alpha) for enhanced neutrophil and monocyte adhesion; the ord er of inhibitory activity being 15-HPETE>15-HETE>20:4 (n-6). This fatt y acid-induced inhibitory activity was reflected in the ability of the mediators to decrease the TNF-alpha-induced expression of the followi ng endothelial adhesion molecules: intercellular adhesion molecule-1 ( ICAM-1), E-selectin, and Vascular cell adhesion molecule-1 (VCAM-1), m easured by both enzyme-linked immunosorbent assay and flow cytometric analysis. TNF-alpha-induced increased expression of ICAM-1, E-selectin , and VCAM-1 mRNA was significantly depressed by 15-HPETE. Constitutiv ely expressed ICAM-1 and ICAM-1 mRNAs were unchanged by the fatty acid s. The saturated fatty acid 20:0 and the methyl eater of 20:4(n-6) had no inhibitory activity. The binding of TNF-alpha to its receptors was not altered by these fatty acids. The fatty acids also inhibited the expression of ICAM-1 and E-selectin induced by phorbol 12-myristate 13 -acetate, showing that inhibition occurred at a post-TNF-alpha recepto r binding level. The 15-HPETE was found to inhibit the TNF-alpha-induc ed increase in adhesion molecule expression in the early stage of the incubation, but expression returned to normal after 18 hours. An effec t of 15-HPETE on the early cell signaling system was demonstrated by t he ability of this fatty acid to inhibit agonist-induced protein kinas e C translocation.