Abstract-Because oleic acid is implicated in the antiatherogenic effects attributed to the Mediterranean diet, we investigated whether this fatty acid can modulate endothelial activation, ie, the concerted expression of gene products involved in leukocyte recruitment and early atherogenesis. We incubated sodium oleate with human umbilical vein endothelial cells for 0 to 72 hours, followed by coincubation of oleate with human recombinant tumor necrosis factor, interleukin (IL)-1␣, IL-1␤, IL-4, Escherichia coli lipopolysaccharide (LPS), or phorbol 12-myristate 13-acetate for a further 6 to 24 hours. The endothelial expression of vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and intercellular adhesion molecule-1 was monitored by cell surface enzyme immunoassays or flow cytometry, and steady-state levels of VCAM-1 mRNA were assessed by Northern blot analysis. At 10 to 100 mol/L for Ͼ24 hours, oleate inhibited the expression of all adhesion molecules tested. After a 72-hour incubation with oleate and a further 16-hour incubation with oleate plus 1 g/mL LPS, VCAM-1 expression was reduced by Ͼ40% compared with control. Adhesion of monocytoid U937 cells to LPS-treated endothelial cells was reduced concomitantly. Oleate also produced a quantitatively similar reduction of VCAM-1 mRNA levels on Northern blot analysis and inhibited nuclear factor-B activation on electrophoretic mobility shift assays. Incubation of endothelial cells with oleate for 72 hours decreased the relative proportions of saturated (palmitic and stearic) acids in total cell lipids and increased the proportions of oleate in total cell lipids without significantly changing the relative proportions of polyunsaturated fatty acids. Although less potent than polyunsaturated fatty acids in inhibiting endothelial activation, oleic acid may contribute to the prevention of atherogenesis through selective displacement of saturated fatty acids in cell membrane phospholipids and a consequent modulation of gene expression for molecules involved in monocyte recruitment. (Arterioscler Thromb Vasc Biol. 1999;19:220-228.)

Conclusions These results indicate that the single double bond present in oleic acid is a necessary and sufficient requirement for FA inhibition of endothelial activation. Since this occurred independent of the stimuli used and was present also with PMA, bypassing membrane receptors, these results point to an interference with a common signal transduction pathway for cytokine signaling. These results are accounted for by an inhibition of NF‐χB activation, here demonstrated at the same concentrations required for the inhibition of surface protein. Relevance of these observations to explaining the alleged beneficial antiatherogenic effects of the Mediterranean diet, in which oleic acid in olive oil is a major nutritional component, could lie in the relatively selective displacement of saturated FA by oleate addition to endothelial cells which was also shown to occur in our system. Thus, an increase in the unsaturation index in cell membranes by oleic acid‐rich diets is theoretically additive to the effects of polyunsaturated FA. By these mechanisms, monocyte recruitment in response to atherogenic stimuli might be decreased (3).