Free radical-induced alterations in endothelial cell function

Free radical-induced injury to the arterial wall has been implicated in the pathogenesis and progression of atherosclerosis. To model the in vitro effects of free radicals on endothelial cell function, protein and lipid synthesis were measured after exposing cells to a superoxide generating system of xanthine (X = 100 μM) and xanthine oxidase (XO = 0.2 units). Total protein synthesis, measured by [³⁵S]methionine uptake, decreased by 87.65 ± 2.04% over 4 hr compared to controls (P < 0.05). Examination of lipid synthesis by high-performance liquid chromatography in cells prelabeled with either [³H]oleic acid or [³H]sodium acetate revealed alterations in all lipid classes. Phospholipid and neutral glyceride synthesis significantly decreased in a time- and dose-dependent fashion compared to controls (two-way ANOVA). In contrast, cholesterol synthesis and lipid peroxidation increased in a time- and dose-dependent fashion. When X = 200 μM and XO = 0.3 units, there was a statistically significant increase in cholesterol synthesis and lipid peroxidation within 24 hr (Tukey’s HSD). We conclude that there is evidence of endothelial cell injury as measured by decreases in protein, glyceride, and phospholipid synthesis. The concurrent increases in lipid peroxidation and cholesterol synthesis may explain the relationship between free radical injury and the pathogenesis of atherosclerosis.