Abstract 342: Naturally Occurring Modified Forms of LDL

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Electronegative LDL, small,dense LDL, and desialylated LDL circulating in the blood of patients were obtained by different methods. Naturally, the question arises what are the similarities and differences between these forms of LDL modification. We believe that multiple modified LDL particle (small, dense, electronegative, desialylated, etc.) occurs in blood. Ex vivo experiments have revealed mechanisms of multiple modification of LDL in the blood. Fraction of native LDL was isolated from blood plasma of healthy subjects. Blood serum of patients with assessed atherosclerosis was also obtained. LDL and serum were mixed and incubated for various periods at 37°C. After 1 hour incubation of native LDL with atherosclerotic serum desialylated LDL appears. After 3 hours, LDL becomes able to cause accumulation of cholesterol in cultured cells. After 6 hours, LDL demonstrates reduction of neutral lipids and phospholipids as well as reduction in its size. After 36 hours, an increase in the electronegativity of the lipoprotein particle is detected. After 48-72 hours, loss of α-tocopherol, increase of susceptibility to oxidation, and accumulation of lipid peroxidation products in LDL are observed. Thus, multiple modification of LDL is a cascade of sequential changes in lipoprotein particle, namely: desialylation, loss of lipids, size reduction, increase of electronegative charge, lipid peroxidation in LDL. Desialylation of LDL particle is one of the first or primary events of atherogenic modification. We have established that the reason of LDL desialylation is trans-sialidase. We found trans-sialidase activity in the blood of patients with atherosclerosis and other cardiovascular diseases. We have shown that human neuraminidases 2 and 4 possess trans-sialidase activity. On the other hand, selective inhibitors of viral sialidases suppress trans-sialidase activity in the blood of atherosclerotic patients. Thus, trans-sialidase causing atherogenic desialylation of LDL may be of both endogenous and exogenous origin. Supported by Russian Ministry of Education and Science (Project RFMEFI61614X0010).