Association between sialic acid, sialidase activity and cholesterol of lipid-containing circulating immune complexes in the blood serum of patients with atherosclerosis

Abstract

Atherosclerosis is the most common chronic non-infectious diseases, in the pathogenesis of which the accumulation of lipids in the subendothelial layer of the arteries and the local inflammatory reaction play a significant role. The source of lipid accumulation in the vascular wall is modified low-density lipoproteins. Desialylation is one of the known modifications that leads to the emergence of atherogenic properties in low-density lipoproteins. Enzymes that have sialidase activity circulate in human blood, i.e., the ability to cleave sialic acid from low-density lipoproteins. Desialylated low-density lipoproteins are autoantigens and induce the production of IgG autoantibodies, which form immune complexes with low-density lipoproteins, which aggravates the course of atherosclerosis. The purpose of the study was to establish associations between the levels of sialic acid in low-density lipoproteins, sialidase activity and the cholesterol content of lipid-containing circulating immune complexes in the blood serum of patients with atherosclerosis. Blood sera from patients with coronary heart disease were used as biological material to determine indicators of sialidase activity, cholesterol content of lipid-containing circulating immune complexes and sialic acid in low-density lipoproteins, which were isolated from blood serum. Serum samples were obtained from the laboratory of clinical biochemistry of the Institute of Clinical Cardiology, A.L. Myasnikov Federal State Budgetary Institution National Medical Research Center of Cardiology named after Academician E.I. Chazov as unutilized residues after performing routine biochemical tests. Fifty-one samples of blood serum and low-density lipoproteins isolated from it were analyzed. A significant positive relationship was revealed between the cholesterol content of circulating immune complexes and sialidase activity in the blood serum (r = 0.305 at p = 0.029). At the same time, no correlation was found between the content of sialic acid in low-density lipoproteins and sialidase activity in the blood serum, as well as between the cholesterol content of circulating immune complexes in the blood serum and sialic acid in low-density lipoproteins. It should be assumed that increased sialidase activity in the blood serum leads to the formation of desialylated immunogenic low-density lipoproteins with the subsequent appearance of autoantibodies and the formation of lipid-containing circulating immune complexes.