Aggregation of modified low-density lipoprotein as factor strengthening atherogenic

Abstract

The purpose. This study shows the effect of low-density lipoprotein (LDL) aggregation on accumulation of intracellular cholesterol, evaluates an influence of intracellular LDL accumulation on cholesterol accumulation that depends on the LDL particle size. Methods. For this study, LDL were obtained from healthy persons and patients with cardiovascular disease. The LDL fraction with density of 1.019—1.065 g/ml was received by blood serum ultracentrifugation using the two-phase method. As a model to study the effect of aggregation of LDL, a culture of human monocytes/macrophages was used, CD14+ cells were isolated from whole blood by monocyte isolation kit "Miltenyi Biotech". Study of capture and degradation of LDL by macrophages was performed using ¹²⁵I-labeled LDL. The intracellular cholesterol content was measured by extraction of lipids from cells by a mixture of hexane-isopropanol (volume ratio 3:2). The concentration of cholesterol in the samples was measured by spectrophotometry using a kit for determination of total cholesterol (Fluitest CHOL, Analyticon Biotechnologies AG). Results. It was shown that LDL aggregation influenced accumulation of intracellular cholesterol. Significant differences were found when comparing the ability to aggregate LDL from healthy persons and that from patients with cardiovascular disease. It has been shown that native LDL are not aggregated in 6 hours of incubation, whereas there was 3—3.5 fold increase in the average particle size of the multiply-modified low-density lipoprotein (mmLDL) after 6 hours of incubation and 6.5—7 fold increase in 24 hours. Conclusion. The circulating multiply-modified low-density lipoproteins are a source of intracellular cholesterol in the intima of blood vessels. For the diagnosis and treatment of atherosclerosis, it is very important to understand the mechanisms of intracellular lipid accumulation and to study the characteristics of LDL, as well as to identify ways to increase the atherogenic potential of LDL. The results show the dependence of LDL ability to cause intracellular accumulation of cholesterol on the particle size.