INHIBITORY EFFECTS OF ARACHIDONIC-ACID (20 4,N-6) AND ITS MONOHYDROPEROXY-METABOLITE AND HYDROXY-METABOLITE ON PROCOAGULANT ACTIVITY IN ENDOTHELIAL-CELLS/

The procoagulant response of endothelium to pathophysiological agents such as tumour necrosis factor alpha (TNF alpha) and phorbol myristate acetate (PMA) alters the expression of proteins such as tissue factor . The modulation of such procoagulant activity (PCA) by the polyunsatu rated fatty acid arachidonic acid (20:4,n-6) and its 15-hydroperoxy (1 5-HPETE) and 15-hydroxy (15-HETE) metabolites was examined since this may have important implications in cardiovascular disease and atherosc lerosis. Treatment of human umbilical vein endothelial cells (HUVEC) f or 30 min with 20:4, 15-HPETE or 15-HETE before induction of PCA with TNF alpha (100 U) or PMA (10(-7)M) caused a significant inhibition of PCA. This inhibition was seen at 2-5 mu M fatty acids. Dose response c urves with TNF alpha indicated that the inhibition was greatest at hig her concentrations of TNF alpha (greater than or equal to 250U TNF alp ha/ml). The mode of administration of the fatty acid was not critical as fatty acids presented as DPC-fatty acid micelles or solubilised in ethanol gave similar inhibitions of PCA. 20:4, 15-HPETE or 15-HETE did not alter the binding of I-125-labelled TNF alpha to its surface rece ptors on HUVEC, suggesting that the effect of these fatty acids was no t mediated by events at the cell surface receptor level. In support of this, these fatty acids were found to inhibit PCA induced by PMA whic h bypasses cell surface receptors to activate protein kinase C directl y. There was no alteration in the cell surface expression of tissue fa ctor by these fatty acids, suggesting that the inhibition of PCA seen with these fatty acids does not result from a decrease in the synthesi s of tissue factor. These findings have important clinical consequence s in cardiovascular disease and atherosclerosis.