Inhibitory effects of arachidonic acid (20:4,n-6) and its monohydroperoxy- and hydroxy-metabolites on procoagulant activity in endothelial cells Original Research Article

The procoagulant response of endothelium to pathophysiological agents such as tumour necrosis factor α (TNFα) and phorbol myristate acetate (PMA) alters the expression of proteins such as tissue factor. The modulation of such procoagulant activity (PCA) by the polyunsaturated fatty acid arachidonic acid (20:4,n-6) and its 15-hydroperoxy (15-HPETE) and 15-hydroxy (15-HETE) metabolites was examined since this may have important implications in cardiovascular disease and atherosclerosis. Treatment of human umbilical vein endothelial cells (HUVEC) for 30 min with 20:4, 15-HPETE or 15-HETE before induction of PCA with TNFα (100 U) or PMA (10−7M) caused a significant inhibition of PCA. This inhibition was seen at 2–5 μM fatty acids. Dose response curves with TNFα indicated that the inhibition was greatest at higher concentrations of TNFα (≥250U TNFα/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 I125-labelled TNFα to its surface receptors on HUVEC, suggesting that the effect of these fatty acids was not mediated by events at the cell surface receptor level. In support of this, these fatty acids were found to inhibit PCA induced by PMA which bypasses cell surface receptors to activate protein kinase C directly. There was no alteration in the cell surface expression of tissue factor by these fatty acids, suggesting that the inhibition of PCA seen with these fatty acids does not result from a decrease in the synthesis of tissue factor. These findings have important clinical consequences in cardiovascular disease and atherosclerosis.