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A N Orekhov

Publications and source records attributed to A N Orekhov.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Intercellular communication studied by using the gap junctions in a primary cell culture of human aortic intima].

The rate of gap junction communication has been investigated in the primary culture of highly differentiated mesenchymal cells (subendothelial smooth muscle cells isolated from grossly normal and atherosclerotic areas of human aorta), and in poorly differentiated cells of mesenchymal origin (adult human skin fibroblasts as well as skin fibroblasts and aortic smooth muscle cells derived from human fetus). In cell cultures isolated from grossly normal and atherosclerotic aorta the number of cells coupled via gap junction increased with cell density and reached the plateau at a cell density of 50-70 cells/mm2. In cultures of normal aortic cells the number of coupled cells was significantly higher than in cultures of atherosclerotic cells. Gap junctional communication between cells loaded with lipid inclusions was lower that that between cells free of excess of intracellular lipids. In cultures of human skin fibroblasts the rate of intercellular communication was comparable to that in cultures of atherosclerotic cells. There was practically no cell-to-cell communication in cultures of fetal cells. It is hypothesized that the reduced gap junctional communication in atherosclerotic human aorta is associated with alterations in the degree of smooth muscle cell differentiation.

Adult↗
PubMed1995

Apolipoprotein B-bound lipids as a marker for evaluation of low density lipoprotein oxidation in vivo.

It has been generally accepted that oxidized low density lipoprotein (LDL) plays an important role in atherogenesis. However, oxidized LDL was not detected in patients' blood and the extent of LDL oxidation in vivo is unknown. We have suggested that LDL oxidation may lead to a formation of covalent links between lipids and apolipoprotein B. LDL were oxidized by copper ions, 2,2'-azobis-(2-aminopropane hydrochloride), sodium hypochlorite or by incubation with macrophages. Oxidized LDL were delipidated by repeated extraction with organic solvents. After mild alkaline hydrolysis protein-bound sterols were identified colorimetrically and by high-performance liquid chromatography. Protein-bound phospholipid residues were detected by nuclear magnetic resonance and colorimetric determination of phosphate. Using radiolabeled lipids it was also shown that free and esterified cholesterol, phospholipids, as well as triglyceride and free fatty acid residues can form covalent bonds with apolipoprotein B. The ability of lipids to bind to apolipoprotein B correlates with the degree of unsaturation of their fatty acids and depends on the nature of polar head of phospholipids. When LDL were oxidized with copper ions, the content of protein-bound lipids increased gradually up to 24 h of incubation, while the levels of conjugated dienes, hydroperoxides and thiobarbituric acid-reactive substances changed in varying manners. It has been demonstrated that the content of protein-bound sterols in multiple-modified desialylated LDL of patients with coronary atherosclerosis is higher than that in native LDL. Our results suggest that the level of protein-bound lipids may be a marker of LDL oxidation and can be used to evaluate the association of lipoprotein oxidation and atherogenesis.

Adult↗
PubMed1995

Naturally occurring modified low density lipoproteins are similar if not identical: more electronegative and desialylated lipoprotein subfractions.

Previous studies demonstrated that more electronegative low density lipoprotein (LDL) isolated from human blood by ion exchange chromatography has a chemical composition and physical properties similar to desialylated LDL obtained by lectin chromatography (Avogaro et al., 1988; Orekhov et al., 1989). In this study, sialic acid content and percentage of desialylated LDL in the electronegative LDL (LDL-) subfraction have been investigated. The sialic acid content of the LDL- was 2- to 6-fold lower than that of native LDL and close to that of desialylated LDL. In the native LDL subfraction, 83% of lipoprotein particles did not bind to the Ricinus communis agglutinin, indicating lack of terminal galactose, presumably appearing as a result of desialylation of LDL carbohydrate chains. By contrast, a major proportion of human LDL- (81%) was bound to the lectin. It was also found that the desialylated LDL subfraction consists of 88% LDL-. Native LDL did not affect the contents of free and esterified cholesterol in intimal cells cultured from grossly normal human aorta, while LDL- and desialylated LDL induced a 1.5- to 3-fold increase in the intracellular content of cholesteryl esters. Thus, LDL- is desialylated LDL which induces lipid accumulation in intimal cells. Our findings suggest that the LDL- particle is similar if not identical to the desialylated LDL particle.

Adult↗
PubMed1995

Gap junctional communication in primary culture of cells derived from human aortic intima.

Intercellular communication via gap junctions plays an important role in the regulation and homeostasis. The presence of gap junctions and the efficiency of their function directly correlates with the degree of cell differentiation in a tissue. In the present study, gap junctional communication has been investigated in a primary culture of highly differentiated mesenchymal cells (subendothelial smooth muscle cells isolated from grossly normal and atherosclerotic areas of human aorta) and in poorly differentiated cells of mesenchymal origin (adult human skin fibroblasts as well as skin fibroblasts and aortic smooth muscle cells, derived from human fetus). The fluorescent dye transfer technique was used in this study. In cell cultures isolated from grossly normal and atherosclerotic aorta, the number of cells coupled via gap junctions increased with cell density and reached a plateau at a cell density of 50 to 70 cells/mm2. In cultures of normal aortic cells the number of coupled cells was 23.0 +/- 4.1 per injected cell and was significantly higher than in cultures of atherosclerotic cells (16.4 +/- 2.1, p < 0.05). Gap junctional communication between cells loaded with lipid inclusions was 2.4-fold lower than between cells free of excess intracellular lipids. In cultures of human skin fibroblasts the rate of intercellular communication was lower than in cultures of normal aortic cells and was comparable to that in cultures of atherosclerotic cells. There was practically no cell-to-cell communication in cultures of fetal cells. It is hypothesized that the reduced gap junctional communication in atherosclerotic human aorta is associated with the alterations in the degree of smooth muscle cell differentiation and impairs the function of the intima in atherosclerosis.

Aorta↗
PubMed1995

Heterogeneity of smooth muscle cells in embryonic human aorta.

Cellular composition of aortas from 5- to 12-week and 18- to 28-week-old human embryos were investigated using immunocytochemistry, scanning and transmission electron microscopy. The aorta of the 5- to 12-week-old embryos consisted of three sublayers differing in cellular composition. The inner sublayer adjacent to the endothelium contained round and ovoid cells with synthetic phenotype. In the intermediate sublayer, spindle-like cells ultrastructurally similar to smooth muscle cells were found. Cells of the outer sublayer resembled fibroblasts or poorly differentiated mesenchymal cells. There were not definite morphological borders between sublayers. In the 18- to 28-week-old embryo aorta the intima was separated from media by internal elastic lamina. Intimal and innermost medial cells had predominately stellate shape and synthetic phenotype. The outer part of media contained spindle-like cells that had well developed contractile structures. Both the 5- to 12-week-old and the 18- to 28-week-old embryo aortic cells were positively stained for alpha-actin and myosin and negatively stained for macrophage antigens. Thus, the majority of embryo aortic cells appeared smooth muscle cells, however there was a regional difference in shape and synthetic state of these cells.

Aorta, Thoracic↗
PubMed1995

Diagnostic value of immune cholesterol as a marker for atherosclerosis.

BACKGROUND: The serum of patients with coronary atherosclerosis contains circulating immune complexes including low-density lipoproteins (LDLs). We have developed a technique for the evaluation of LDL content in circulating immune complexes by measuring total cholesterol levels in polyethylene glycol precipitates (immune cholesterol). In the present study, the value of immune cholesterol in the diagnosis of atherosclerosis was compared with that of other laboratory parameters, such as total cholesterol levels, triglycerides, LDL cholesterol, high-density lipoprotein cholesterol, lipoprotein(a), and apolipoproteins B and A-1. METHODS: Immune cholesterol and the other parameters were determined in blood samples from 200 patients with documented coronary and extracoronary atherosclerosis. Coronary atherosclerosis was assessed by coronary angiography; stenoses in the aortic arch and branches and in lower-limb arteries were evaluated by angiography and ultrasonography. RESULTS: Only immune cholesterol and the ratio of apolipoprotein B to apolipoprotein A-1 correlated significantly with the severity of coronary atherosclerosis. The accuracy of the diagnosis of coronary atherosclerosis by immune cholesterol was 78%, considerably higher than that of other laboratory parameters. Use of a combined parameter consisting of immune cholesterol, LDL cholesterol, and the patient's age increased the diagnostic accuracy to 81%. A high level of immune cholesterol is characteristic not only of coronary atherosclerosis but also of extracoronary atherosclerosis. The sensitivity, specificity and accuracy of the diagnosis of extracoronary atherosclerosis were even higher than those for coronary atherosclerosis. CONCLUSION: Immune cholesterol may be employed as a novel marker in the diagnosis of advanced atherosclerosis.

Adult↗
PubMed1995

Direct anti-atherosclerosis-related effects of garlic.

Direct anti-atherosclerosis-related effects of garlic were studied using cell culture. An aqueous extract from garlic powder (GPE) was added to smooth muscle cells cultured from atherosclerotic plaques of human aorta. During a 24-hour incubation, GPE significantly reduced the level of cholesteryl esters and free cholesterol in these cultured cells and inhibited their proliferative activity. In addition, GPE significantly reduced cholesterol accumulation and inhibited cell proliferation stimulated by blood serum taken from patients with angiographically assessed coronary atherosclerosis, i.e. GPE reduced atherogenic manifestations of patients' serum. Garlic effect on blood atherogenicity of patients with coronary atherosclerosis has also been studied ex vivo. Following a 24-hour incubation with cultured cells, patients' blood serum caused an increase of total cell cholesterol. Blood serum taken 2 hours after an oral administration of 300 mg garlic powder tablet caused substantially less cholesterol accumulation in cultured cells. This suggests that garlic powder manifests direct anti-atherogenic-related action not only in vitro but also in vivo.

Adult↗
PubMed1995

Modified (desialylated) low-density lipoprotein measured in serum by lectin-sorbent assay.

Modified low-density lipoprotein (LDL) with a low sialic acid content was found in the blood of patients with coronary atherosclerosis. This desialylated lipoprotein causes lipid accumulation in arterial smooth-muscle cells and stimulates cell proliferation and production of the extracellular matrix, i.e., induces all atherogenic manifestations at the cellular level. We have developed a lectin-sorbent assay for the determination of desialylated LDL in sera. The assay is based on the binding of desialylated LDL by immobilized Ricinus communis agglutinin with subsequent measurement of lipoprotein through use of anti-apolipoprotein (apo) B antibody. The assay is sensitive to desialylated apo B concentrations as low as 5 micrograms/L. The intraassay and interassay CVs were 4.8% and 11.3%, respectively. Comparison between the lectin-sorbent assay and a lectin chromatographic technique showed a good correlation. This determination of modified desialylated LDL in human serum with high accuracy and reproducibility may help establish the diagnostic value of this lipoprotein as a risk factor of atherosclerosis.

Adult↗
PubMed1994

Effect of lipoprotein(a) on lipid metabolism of cultured human intimal aortic cells.

The effect of Lp(a) on lipid metabolism in cells cultured from unaffected human aortic intima has been investigated. Lp(a) isolated from the blood of healthy subjects failed to alter intracellular neutral lipid content. On the other hand, Lp(a) obtained from coronary atherosclerosis patients induced a 1.5- to 2-5-fold increase in intracellular levels of free and esterified cholesterol and triglycerides. The sialic acid content of patients' Lp(a) was 2.5-fold lower as compared with that of healthy subjects' Lp(a). Healthy donors' Lp(a) in vitro desialylated with neuraminidase were able to accumulate lipids within the cells. Using lectin-chromatography on Ricinus Communis agglutinin-agarose, Lp(a) was divided into subfractions differing by sialic acid content. Desialylated (sialic acid-poor) Lp(a), but not sialylated lipoproteins, were capable of increasing the intracellular content of total cholesterol. Desialylated but not sialylated Lp(a) formed aggregates during incubation under cell culture conditions. Isolated aggregates of desialylated Lp(a) induced lipid accumulation in cells. Elimination of Lp(a) aggregates from cultural medium prevented the increase of intracellular lipids. Complexes of Lp(a) with the matrix components and antibodies increased lipid level in cultured cells. We assume that formation of large particles of desialylated Lp(a) aggregates or Lp(a)-containing complexes is a necessary step for lipid accumulation in human intimal cells.

Adult↗
PubMed1994

Sulfonylureas induce cholesterol accumulation in cultured human intimal cells and macrophages.

Using primary cultures of human smooth muscle intimal cells and mouse peritoneal macrophages it was demonstrated that oral hypoglycemic agents, sulfonylurea derivatives, at concentrations 10(-5)-10(-4) mol/l caused significant (by 25%-60%) intracellular total cholesterol accumulation. This in vitro atherogenic effect was confirmed in an ex vivo model. Sera from Type 2 diabetic patients, taken after sulfonylurea administration, acquired the ability to induce cholesterol accumulation in cultured cells. This enhanced atherogenic effect of patients' sera was observed for the next 2-4 h following the treatment and corresponded well to the pharmacokinetic characteristics of the tested drugs. The results suggest that sulfonylureas may exert a direct atherogenic action at the level of arterial cells, by increasing intracellular cholesterol content.

Adult↗
PubMed1994

Characterization of chemical composition of native and modified low density lipoprotein occurring in the blood of diabetic patients.

Low density lipoprotein (LDL) from Type 1 and Type 2 diabetic patients, unlike LDL from healthy subjects, caused a 1.5- to 2.5-fold increase in the cholesterol content of cells cultured from unaffected human aortic intima, i.e. possessed atherogenic potential. LDL were further divided into two subfractions by affinity chromatography on Ricinus communis agglutinin-agarose. The amount of bound LDL was significantly higher in diabetic patients as compared with healthy subjects. Bound LDLs differed from unbound ones by significantly lowered sialic acid content, i.e. were desialylated lipoproteins. Desialylated, but not sialylated LDL subfraction induced massive cholesterol accumulation in cultured cells. Desialylated LDL subfraction in diabetic patients was also characterized by a higher degree of nonenzymatic glycation as compared to LDL subfraction with normal sialic acid level. Desialylated LDL had significantly decreased levels of free and esterified cholesterol, triglycerides and phosphatidylcholine and elevated amounts of lysophosphatidylcholine. These disturbances in lipid constituent of LDL were weak in healthy subjects, but conspicuous in diabetic patients. The results of this study have shown that there is in vivo modified LDL subfraction in the blood of diabetic patients which is characterized by crucial changes in protein and lipid moiety and are able to induce massive cholesterol accumulation in cultured cells.

Cells, Cultured↗