IUBMB Life, 48: 413–417, 1999 Copyright c ° 1999 IUBMB 1521-6543/99 $12.00 + .00 Original Research Article Oxidized Lipoproteins in Blood Plasma: Possible Marker of Atherosclerosis Progression Patricia Moriel, F´ abio S. Okawabata, and Dulcineia S. P. Abdalla Departamento de An´ alises Cl´ õnicas e Toxicol´ ogicas, Faculdade de Ci ˆ encias Farmac ˆ euticas, Universidade de S ˜ ao Paulo, S ˜ ao Paulo, S. P., C.P. 66083, CEP 05389-970, Brazil Summary Oxidized lipoproteins and antioxidants were detected during the course of hypercholesterolemia development in cholesterol-fed rab- bits. Lipid peroxides in blood plasma and very-low-, low-, and high- density lipoproteins (¯-VLDL, LDL, and HDL) were increased during the course of hypercholesterolemia. The content of phos- pholipid peroxides increased in ¯-VLDL and LDL in parallel to that of cholesterol, whereas the amount of ®-tocopherol was de- creased either in lipoproteins or blood plasma. Ascorbate and urate concentrations were also decreased. Lipid peroxides were positively correlated with volume and area of atherosclerotic lesions, suggest- ing a relation between the concentrations of lipid peroxides in blood plasma and the progression of atheromatous lesions. IUBMB Life, 48: 413–417, 1999 Keywords Antioxidants; atherosclerosis; hypercholesterolemia; lipid peroxides; oxidative stress; oxidized lipoproteins; rabbits. INTRODUCTION Atherosclerosis is a leading cause of mortality in industrial- ized countries. A high concentration of low-density lipoprotein (LDL) 1 is clearly an important risk factor for atherosclerosis. However, the precise mechanism(s) by which LDL promotes the development of the early fatty-streak lesion remains to be elucidated. In the recent past many studies have suggested that oxidatively modied LDL and other lipoproteins may have an important role in atherogenesis. The oxidation of the lipid moi- ety precedes and then contributes to the formation of the oxida- tively modied LDL that can be taken up by cells in a seemingly uncontrolled fashion, leading to foam cell formation (1). Received 5 February 1999; accepted 5 May 1999. Address correspondence to Dulcineia Saes Parra Abdalla. E-mail: dspa@usp.br. 1 Abbreviations: CE-OOH, cholesteryl hydroxy/hydroperoxide ; HDL, high- density lipoprotein; LDL, low-density lipoprotein; PL-OOH, phospholipi d hy- droxy/hydroperoxide ; TL-OOH, triglyceride hydroxy/hydroperoxide ; b -VLDL, b very-low-density lipoprotein. Antioxidants protect LDL lipids against peroxidation, and optimal levels of antioxidants should slow the progression of atherosclerosis. Studies have shown roles for antioxidants in atherosclerosis and hyperlipidemic states (2, 3). The determination of lipid peroxides in plasma and lipopro- teins recently became of clinical relevance in disorders such as atherosclerosis, where oxidative reactions had been suggested to play some fundamental pathogenic role. The contribution of the lipid peroxides in blood plasma to atherogenesis and atheroscle- rosis progression is still a controversial issue. Atherosclerosis induced in rabbits by cholesterol-rich diets is characterized by the formation of a lipoprotein designated b -VLDL, the density of which is similar to that of the VLDL fraction (1.006 < d < 1.019) but which is enriched with choles- terol ester and has an electrophoretic migration in the b -region. b -VLDL is an atherogenic particle: It promotes cholesterol es- ter accumulation in macrophages and adhesion of monocytes to endothelial cells. In this study, the concentrations of oxidized lipoproteins and the consumption of antioxidants in blood plasma during the course of hypercholesterolemia in cholesterol-fed rabbits were investigated. A positive correlation was found between the vol- ume and area of atherosclerotic lesions and the concentrations of lipid peroxides in blood plasma. EXPERIMENTAL PROCEDURES Animals. Twenty adult male New Zealand rabbits, weight- ing 2–3 kg, were used in this study. For 2 months they were fed a diet (Nutricoelhos Especial Purina, S˜ ao Paulo, Brazil) en- riched with 1% cholesterol (Sigma Chemical Co., St. Louis, MO). Blood was collected from the animals into tubes contain- ing EDTA (1 mg/ml) after 12 h of fasting before starting the enriched diet and after 15, 30, 45, and 60 days of cholesterol- enriched feeding. Lipoproteins were isolated by sequential ultra- centrifugation from plasma and dialyzed against pH 7.4 buffer (150 mM NaCl, 1.0 mM EDTA, 3 mM NaN 3 , and 10 mM Tris), 413