Interleukin-1 Enhances the Ability of Cultured Human Umbilical Vein Endothelial Cells to Oxidize Linoleic Acid

Human umbilical vein endothelial cells (HUVEC) were treated with recombinant interleukin (IL)-1 beta, and the metabolism of exogenous linoleic acid was studied. High performance liquid chromatography, gas chromatography-mass spectrometry, and chiral analysis revealed that HUVEC enzymatically convert linoleic acid mainly into 13-(S)hydroxy-9(Z),11(E)-octadecadienoic (13-HODE) and 9-(R)hydroxy-10(E),12(Z)-octadecadienoic acids, which may isomerize toward all-trans compounds. IL-1 beta increased the formation of all octadecanoids in a time- and dose-dependent manner with similar EC50 (approximately 1 unit/ml). The apparent Km values of linoleic acid were 15.59 +/- 8.39 and 152.9 +/- 84 microM (p < 0.05) in IL-1 beta-treated cells and controls, respectively, indicating a higher substrate affinity in cells stimulated with IL-1 beta. Ratios of S/R enantiomers for the hydroxyoctadecanoids produced by untreated and IL-1 beta-treated cells were similar to those from isolated cyclooxygenases (COXs), whereas isolated 15-lipoxygenase yielded 13-HODE with a strict S configuration. The formation of octadecanoids was inhibited in a dose-dependent manner by several COX inhibitors in both controls and IL-1 beta-treated cells, COX2 selective inhibitors being more effective on IL-1 beta-treated cells than on controls. COX1 and COX2 protein levels increased less than 2-fold and 8-fold, respectively, after IL-1 beta treatment. The specificity of COX inhibitors was proven since they did not inhibit 13-HODE formation by human polymorphonuclear leukocytes. Overall, these results indicate that COXs are responsible for the oxidative metabolism of linoleic acid in HUVEC, and IL-1 beta increases it by inducing the expression of new enzyme, mainly COX2.