Biomedical subjects

A N Orekhov

Publications and source records attributed to A N Orekhov.

At least 73 records · Page 4Linked to original sources

PubMed1993

Modified low density lipoprotein from diabetic patients causes cholesterol accumulation in human intimal aortic cells.

Fifty-five serum samples from 99 Type 1 and 71 serum samples from 81 Type 2 diabetic patients (56% and 88%, respectively) brought about a 1.5-3.5-fold increase in total cholesterol content of cultured human intimal aortic cells. This atherogenic effect did not correlate with patient's age, diabetes duration or plasma lipid levels, and was mainly due to low density lipoprotein (LDL). Cholesterol accumulation in cells incubated with LDL highly correlated with that in cells exposed to corresponding patient's serum (r = 0.872 and r = 0.811, P < 0.0001, in Type 1 and Type 2 diabetic patients, respectively). In LDL from diabetic patients the sialic acid content was decreased by an average of 30% (P < 0.05), as compared with healthy subjects, and the fructosyl lysine content was increased by an average of 25% (P < 0.05). Atherogenic effect of patients' LDL significantly correlated with their fructosyl lysine content (P < 0.0001) and negatively correlated with sialic acid content (P < 0.0001). Two LDL fractions were further separated from the total LDL preparation by affinity chromatography on Ricinus communis agglutinin-agarose. The bound (desialylated) LDL fraction was characterized by an increased fructosyl lysine content and the altered neutral lipid and phospholipid composition, while non-bound (sialylated) LDL fraction did not differ from normal LDL. Desialylated, but not sialylated, LDL fraction induced massive cholesterol accumulation in cultured cells. In conclusion, the cholesterol accumulating effect of diabetic patients' blood sera is mainly related to atherogenic low density lipoprotein fraction, which is modified in various ways--by increased non-enzymatic glycosylation, desialylation and alterations in lipid composition. This multiple-modified LDL may contribute to the premature atherosclerosis development in diabetes mellitus.

Adolescent↗

PubMed1993

Characteristics of low-density lipoprotein subfractions from patients with coronary artery disease.

BACKGROUND: The low-density lipoprotein (LDL) of patients with coronary artery disease (CAD) has been reported to enhance cholesterol ester accumulation in aortic cells. The LDL of patients with CAD also has a higher mean density than the LDL of healthy subjects, indicating a different subspecies distribution. Because these density differences may be associated with altered metabolism and atherogenicity of LDL, we studied the properties and effects of isolated LDL subfractions on cell lipid metabolism and cholesterol accumulation. METHODS: Plasma pools of patients with angiographically proven CAD (A) and healthy controls (C) were used to isolate and fractionate LDL into five subfractions (1 to 5, from the lowest to the highest density) by gradient ultracentrifugation. Each of the LDL subfractions was analyzed for particle diameter, chemical composition, sialic acid content, and their effect on lipid content and cholesterol esterification in arterial cell and macrophage cultures, respectively. RESULTS: The chemical compositions of the respective subfractions revealed no differences between patients and controls, except that the sialic acid content was reduced in dense LDL subfractions, especially in the samples from patients with CAD (fractions A3, A4, A5, and C5). LDL subfractions with reduced sialic acid content also enhanced the incorporation of [14C]-oleate into cholesterol esters in mouse peritoneal macrophage cultures (fractions A4, A5, and C5) and increased the cholesterol ester content in primary cultures of human aortic intimal cells (fractions A3, A4, A5, and C5). CONCLUSIONS: The results suggest that the dense LDL subfractions of patients with CAD are atherogenic by promoting intracellular cholesterol ester accumulation. The results also suggest that the atherogenicity is associated with reduced sialic acid content of the LDL subspecies.

Adult↗

PubMed1993

[The antiatherosclerotic effect of verapamil in a cell culture of human aortic intima].

Verapamil was examined for effects on atherosclerotic manifestations in cultured human aortic intimal cells. Addition of verapamil in a concentration of 10(-6)-10(-4) M to the cultured cells isolated from aortic atherosclerotic areas led to lower cellular lipids, suppressed cell proliferation and inhibited synthesis of collagen and cholesterol esters 24 hours after incubation. Verapamil also prevented atherogenic serum-induced accumulation of cholesterol in the cells isolated from normal aortic intimal areas. No decrease in cellular cholesterol levels was observed when the cells had been incubated with verapamil in the medium containing lipid-free serum. The findings suggest that the atherosclerotic effect of verapamil, which was seen in the experiments with animals, can be determined by the action of this drug on cellular processes.

Aorta↗

PubMed1993

Autoantibodies against low-density lipoprotein and atherogenic potential of blood.

Blood serum of ischaemic heart disease patients possesses an atherogenic potential which manifests itself in the accumulation of cholesterol in cultured smooth muscle cells of human aorta and in mouse peritoneal macrophages. Recently it was found that serum atherogenicity is associated with the presence in the blood of modified (desialylated) low-density lipoprotein (LDL) and of autoantibodies against LDL (anti-LDL). In the blood, anti-LDL and LDL form circulating immune complexes (CIC). Blood serum atherogenic potential is directly related to the content of LDL cholesterol or apolipoprotein B in CIC. The present study elucidates the effect of LDL and anti-LDL concentrations on the atherogenic properties of blood serum. After the addition of exogenic LDL, in certain atherogenic sera a significant increase in CIC cholesterol as well as the increase of serum atherogenic potential revealed in cell culture were registered. In these sera free anti-LDL capable of binding to exogenous LDL were detected. In other atherogenic sera and in all non-atherogenic sera, the LDL increase failed to be accompanied by any changes in the CIC cholesterol. In these sera no free anti-LDL were detected. The addition of exogenous anti-LDL into non-atherogenic sera was accompanied by 2.5-fold increase in CIC cholesterol and by the appearance of atherogenic properties in these sera. Affinity chromatography was used to remove anti-LDL from atherogenic sera. This removal was accompanied by 2.5- to 3-fold decrease in the CIC cholesterol up to the level characteristic of non-atherogenic serum of healthy donors. The removal of anti-LDL led to disappearance of serum atherogenic properties. From these data we assume that the CIC LDL level and, consequently, serum atherogenic potential is to a considerable degree determined by anti-LDL concentration in the serum.

Adult↗

PubMed1993

Carbohydrate composition of protein and lipid components in sialic acid-rich and -poor low density lipoproteins from subjects with and without coronary artery disease.

Low density lipoprotein (LDL) from patients with coronary heart disease (CHD) caused 78-286% increase in accumulation of cholesterol in human aortic subendothelial cells compared to 2-17% caused by LDL from normal subjects. Ricin-Sepharose affinity chromatography was used to separate LDL into two subfractions, one sialic acid-rich (SAR) and the other sialic acid-poor (SAP). SAP-LDL from CHD patients caused 156-307% increase in accumulation of cellular cholesterol, whereas SAR-LDL from these patients caused only 14-21% increase. SAP-LDL from normal healthy subjects caused 50-86% increased accumulation, whereas their SAR-LDL induced only 2-12% increase. Carbohydrate analysis of SAP-LDL protein isolated from four CHD patients revealed mean values of 59, 25, 61, and 11 nmoles of N-acetyl glucosamine, galactose, mannose, and sialic acid per mg protein, respectively. Mean values for SAR-LDL protein from these patients were 59, 31, 77, and 24 nmol/mg protein, respectively. Analysis of SAP-LDL protein from four normal healthy subjects indicated respective mean values of 58, 29, 72, and 22 nmol/mg, whereas SAR-LDL protein from normals contained 59, 29, 72, and 29 nmol/mg. The carbohydrate content of LDL lipids represents about 25% of the total carbohydrate present in the lipoprotein. The mean values for SAP-LDL lipids from four CHD patients were about 2, 2, 18, 18, and 2 nmol/mg protein for N-acetyl galactosamine, N-acetyl glucosamine, galactose, glucose, and sialic acid, respectively. The mean values for SAR-LDL lipids from these patients were 3, 4, 34, 41, and 5 nmol/mg, respectively. Analysis of SAP-LDL lipids from four normal healthy subjects indicated respective mean values of 4, 6, 30, 31, and 3 nmol/mg, whereas SAR-LDL lipids from these subjects contained 6, 9, 41, 46, and 7 nmol/mg. These results suggest that the different biological properties of SAR-LDL and SAP-LDL are related to their different carbohydrate compositions.

Blood Proteins↗

PubMed1992

Influence of a cholesterol rich diet in rabbits on the formation of PGI2 and TXA2.

In the study was investigated whether the formation of prostanoids is changed in the different regions of aorta or in clotting whole blood in dependence on development of atherosclerosis. For this question New Zealand rabbits were fed for different periods with a cholesterol rich diet (0.5%). At the end of the different dietary periods the animals were killed and the following parameters estimated: blood: levels of total cholesterol, HDLcholesterol, VLDLcholesterol, cholesterol in the beta-migrating lipoprotein fraction, serum lipid peroxides, TXB2 formation capacity of clotting whole blood; aorta: surface of intima covered with fatty streaks, free and esterified cholesterol, triglycerides, collagen, formation of 6-keto-PGF1a and TXB2 by abdominal and thoracic aortas. The lipid parameter demonstrated a relatively strong correlation with the duration of cholesterol rich diet or the macroscopically detectable atherosclerosis, but the prostanoid formation remained unchanged.

Animals↗

PubMed1992

Lipid-laden white blood cells in the circulation of patients with coronary heart disease.

The total lipid content of white blood cells from healthy donors and patients with angiographically documented atherosclerosis of coronary arteries (CHD patients) was determined by flow cytofluorometry. The cells of donors were homogeneous with respect to intracellular lipid level. However, two subpopulations of white blood cells were identified in CHD patients based on their lipid content. The first population was identical to cells of donors with regard to lipid content, whereas cells of the second subpopulation (10 to 60% of the total cell number) had a four- to eightfold greater amount of intracellular lipid. The main classes of lipids accumulated in these cells were triglycerides and cholesteryl esters. It is postulated that the occurrence of lipid-laden cells in the blood may be used as an indicator of the presence of atherosclerotic lesions in human coronary arteries.

Adult↗

PubMed1992

Beta-blockers: propranolol, metoprolol, atenolol, pindolol, alprenolol and timolol, manifest atherogenicity on in vitro, ex vivo and in vivo models. Elimination of propranolol atherogenic effects by papaverine.

The addition of the beta-blockers propranolol, metoprolol, atenolol, pindolol, alprenolol and timolol to a culture of peritoneal macrophages or smooth muscle cells induced an increase in the intracellular cholesterol content. Blood serum obtained from a rabbit after a peroral administration of beta-blockers also induced cholesterol accumulation. This property of drug or blood serum obtained after peroral administration is conventionally referred to as atherogenic potential or atherogenicity. Regular administration of propranolol during a 21-day period evoked stable atherogenicity of rabbit blood serum. This was accompanied by stimulation of manifestations of atherosclerosis in the aorta deendothelialized with a balloon catheter. Propranolol increased neointimal thickening, lipid accumulation, an increase in cell number and in the collagen content. In vitro, the combination of propranolol with papaverine eliminated the atherogenic effect of propranolol which manifested itself as stimulation of cholesterol accumulation in cultured cells. Simultaneous peroral administration of propranolol and papaverine prevented the appearance of serum atherogenicity. Papaverine eliminated neointimal thickening, an increase in cell number and in the lipid and collagen contents evoked by propranolol. Papaverine itself had no effect on these parameters. Thus, the atherogenicity of propranolol as well as capacity of papaverine to eliminate beta-blocker atherogenicity revealed in cell culture was confirmed in vivo. We hope that these results may be useful in the development of new drugs and optimization of antiatherosclerotic drug therapy.

Adrenergic beta-Antagonists↗

PubMed1992

Stellate cells of aortic intima: I. Human and rabbit.

Stellate cells hitherto accounted exclusively in the innermost elastic-hyperplastic layer were already reported to inhabit human aortic intima. The present paper shows that most of these cells are situated just beneath the endothelium. Stellate cells also appear in the deendothelialization-induced myointimal thickening of rabbit aorta. In the myointimal thickening these cells were revealed in the direct proximity to the endothelium. A conclusion is available that the previously demonstrated polymorphism of human aortic intimal cells may be reproduced in a simple experimental model, which gives new possibilities for the study of the cellular polymorphism in the vessel wall.

Adult↗

PubMed1992

Stellate cells of aortic intima: II. Arborization of intimal cells in culture.

The present study analyzed effects of different cAMP-elevators on cell morphology in primary culture of human intimal and medial cells from grossly normal and atherosclerotic areas. In primary culture of human aortic cells adenylate cyclase activator forskolin and other cAMP elevators induced arborization of cells, i.e. they reversibly changed the shape of cells. This resulted in the formation of thin branching processes and in the concentration of cytoplasm around the nucleus. In the culture, the shape of the arborized cells resembled that of stellate ones detected in the aortic intima in situ. The arborization of cells was accompanied by destruction of myofilaments. Due to cAMP elevators' effect, most of the arborized cells were exhibited in the cultures isolated from the elastic-hyperplastic layer of the intima. The number of arborized cells was significantly less in the cultures isolated from the musculo-elastic layer and still lesser in those isolated from media. We failed to reveal any significant difference in the number of arborized cells cultured from fatty streaks, atherosclerotic plaques and grossly normal aortic areas. Obtained results suggest that the previously revealed polymorphism of human aortic intimal cells may be accounted for by the cell shape transformations underlined by the mechanism similar to that of arborization in vitro.

Actins↗

PubMed1992

The atherogenic effect of lupus sera: systemic lupus erythematosus-derived immune complexes stimulate the accumulation of cholesterol in cultured smooth muscle cells from human aorta.

The influence of systemic lupus erythematosus (SLE) patients' sera on lipid accumulation in the cultured smooth muscle cells (SMC) from unaffected human aortic intima was examined. It was demonstrated that the cholesterol uptake in the SMC cultured in the presence of SLE sera is 1.5- to 6-fold higher than in the cells cultured with normal human sera (NHS) obtained from healthy donors. Incubation of the SMC with circulating immune complexes (CIC) isolated from lupus sera by precipitation with 2.5% polyethylene glycol 6000 (PEG) caused a 3- to 4-fold rise in the intracellular cholesterol level. The atherogenic effect of lupus sera, as well as isolated CIC, strongly correlated (r = 0.98) with the low density lipoprotein (LDL) content in the PEG-precipitated CIC. The cholesterol level in cultured SMC also increased 2- to 3-fold when growth medium was supplemented with LDL, DNA, and anti-DNA autoantibodies (IgG) affinity isolated from lupus sera. Using immunofluorescent staining, it was shown that the addition of a DNA-anti-DNA IgG mixture to the growth medium, together with NHS, stimulated LDL incorporation in the SMC. The results of double-label staining suggest the formation of LDL-DNA-IgG complexes which seem to be entrapped in cells more actively than free LDL. The composition of PEG-precipitated CIC was studied by electrophoresis and immunoblotting. Significant amounts of apolipoprotein B, as well as low molecular weight DNA and immunoglobulins, were found in SLE-derived CIC. The data obtained suggest that the atherogenic effect of human lupus sera in vitro is generally due to the appearance of LDL-containing immune complexes. Different mechanisms possibly involved in the lupus atherogenesis are discussed.

Adult↗

PubMed1992

Three types of naturally occurring modified lipoproteins induce intracellular lipid accumulation due to lipoprotein aggregation.

Low density lipoprotein (LDL) from patients with coronary atherosclerosis and diabetes mellitus as well as in vitro desialylated LDL, glycosylated LDL, and lipoprotein (a) caused a twofold to fourfold rise in cholesteryl ester in cultured human blood monocytes and intimal smooth muscle cells isolated from normal aorta. Native LDL from healthy subjects failed to induce intracellular lipid accumulation. We have demonstrated by laser correlative photometry and gel filtration chromatography that in vivo and in vitro modified lipoproteins form aggregates under cell culture conditions. The degree of modified lipoprotein aggregation directly correlated with the ability of these lipoproteins to elevate the cholesteryl ester content of cultured cells. Modified lipoprotein aggregates isolated by gel filtration induced a threefold to fivefold elevation in cellular cholesteryl ester content. Aggregates of 125I-modified LDL were taken up and degraded fivefold to sevenfold more effectively as compared with nonaggregated lipoproteins. The uptake and degradation of 125I-labeled aggregates were strongly inhibited by unlabeled aggregates, latex beads, and cytochalasin B but not by native or acetylated LDL. These data indicate that uptake of lipoprotein aggregates occurred by phagocytosis. Obtained results suggest that modified lipoprotein aggregation may be the key condition for lipid accumulation.

Cells, Cultured↗

PubMed1992

Three types of naturally occurring modified lipoproteins induce intracellular lipid accumulation in human aortic intimal cells--the role of lipoprotein aggregation.

Blood monocytes or intimal smooth muscle cells from normal aorta were incubated with low density lipoprotein (LDL) from patients with coronary atherosclerosis, or with LDL from diabetic patients, or with lipoprotein(a) (Lp(a)). In each case there was a 2- to 4-fold rise in the intracellular cholesteryl ester content. LDL from healthy subjects failed to induce intracellular lipid accumulation in these cells. LDL from patients with coronary atherosclerosis, LDL from diabetic patients, and Lp(a) form aggregates under cell culture conditions. The ability of these lipoproteins to increase the cholesteryl ester content of cultured cells is directly correlated to the degree of lipoprotein aggregation. When aggregates were removed from the lipoprotein preparations by filtration, the latter became less effective in promoting intracellular lipid accumulation. Incubation of cells with lipoprotein aggregates, isolated by gel filtration, induced a 3- to 5-fold elevation of the cellular cholesteryl ester content. These results suggest that LDL from atherosclerotic patients, or LDL from diabetic patients, or Lp(a) have a tendency to form aggregates and that these aggregates are avidly taken up by intimal smooth muscle cells followed by lipid accumulation. This aggregation tendency may play a role in atherogenesis.

Aorta↗

PubMed1992

Use of cell culture for optimisation of direct antiatherogenic therapy with verapamil.

The potential of verapamil to prevent atherogenesis induced by atherogenic serum in cell culture was investigated. Smooth muscle cells were cultured from human aortic intima and incubated with blood serum from patients with coronary artery disease. Only serum causing a significant rise in total cholesterol content in cultured cells during a 24-hour incubation period was used. The addition of verapamil to cells decreased serum-induced cholesterol accumulation. The maximum antiatherogenic effect of verapamil in vitro was recorded at 10(-5) to 10(-4) mol/L. Blood serum obtained from patients before and after oral verapamil administration was added to cultured cells. The atherogenic potential of serum obtained after verapamil administration was significantly lower than the predose value. To optimise direct antiatherogenic therapy with verapamil, the minimum dose that produced the maximum effect was established as 30 to 40mg. Using a 40mg dose, the maximum effect of oral verapamil was observed 3 hours after administration. A second 40mg dose was given 5 hours after the first dose, when the blood serum atherogenic potential was about 40% of the predose value and rising. This second dose maintained the atherogenic potential of serum at about 40%. Thus, to decrease atherogenic potential of serum and to maintain it at a low level, verapamil should be administered at a dose of 40mg 5 times daily with a 4- to 5-hour interval between doses.

Administration, Oral↗

PubMed1992

[The effect of calcium antagonists on cholesterol metabolism in human aortal intima cells and macrophage lines].

Effects of two Ca-antagonists, verapamil and nifedipine, on the total cellular cholesterol content and accumulation, as well as on the synthesis and hydrolysis of cholesteryl esters in human aortic intimal smooth muscle cells and P388D1 cell line have been studied. Verapamil and nifedipine used at 10(-6) M and higher concentrations decreased the total cellular cholesterol content (by 25-40%) in intimal cells isolated from atherosclerotic lesions without any effect on the cholesterol content in normal intimal cells or P388D1 cells. At 2 x 10(-5) M verapamil and nifedipine prevented the accumulation of cholesterol induced by atherogenic blood serum or atherogenic low density lipoproteins in both types of cells. At 10(-5) M and higher concentrations verapamil and nifedipine inhibited (2-3-fold) cholesteryl ester synthesis in intimal cells and, used at 10(-6) M and higher doses, in P388D1 cells as well. Verapamil and nifedipine (2 x 10(-5) M) enhanced the hydrolysis of cholesteryl esters in both types of cells. The Ca-channel agonist Bay K8644 had no effect on cholesteryl ester synthesis, nor did it suppress its inhibition by Ca-antagonist. The beta-receptor blocker propranolol induced the accumulation of cholesterol in intimal cells and inhibited the synthesis and hydrolysis of cholesterol esters in these cells. The data obtained suggest that the antiatherosclerotic action of Ca-blockers is determined by their ability to reduce the cellular cholesterol content which is suggested to be the result of enhanced hydrolysis of cellular cholesteryl esters.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

[Carbohydrate composition of native and desialylated low density lipoproteins in the plasma of patients with coronary atherosclerosis].

The monosaccharide content was examined in apoprotein B and lipids of total low density lipoprotein (LDL) preparations isolated from the blood of healthy individuals and patients with coronary atherosclerosis, as well as in desialylated and sialylated LDL obtained by affinity chromatography on Ricinus Communis Agglutinin-agarose. The glycoconjugates of total apoprotein-B of healthy subjects' LDL were found to consist of N-acetylglycosamine, galactose, mannose and sialic acid in a molar ratio of 2:1:2.5:1. The content of protein-bound neutral sugars was the same in healthy subjects and patients, while there was a lower sialic acid amount in the patients. The level of protein-bound sialic acid in patients' desialylated LDL was 2- to 3-fold lower than that in sialylated LDL. In contrast to apoprotein-B glycoconjugated, the lipid-bound carbohydrate chains of total LDL preparations had N-acetylgalactosamine and glucose, but not mannose. In total LDL from patients, the content of all lipid-bound carbohydrates was 1.5- to 4-fold lower than that in LDL from healthy subjects. In healthy subjects and in patients alike, the neutral sugar content of a lipid subfraction of desialylated LDL was lower than in those of sialylated LDL. It is concluded that atherogenic desialylated LDL differ from non-atherogenic sialylated LDL in neutral sugar levels.

Amino Sugars↗

PubMed1992

[The structure of the endothelialized and nonendothelialized areas of myointimal thickening of the rabbit aorta].

De-endothelialization of the abdominal aorta of the rabbit was performed with a balloon catheter. As a result, a partially endothelialized myointimal thickening was formed consisting of smooth myocytes and macrophages. As compared with the zone devoid of the endothelium the endothelialized zone was characterized by less thickness and by the presence of an additional elastic membrane. Great amount of leukocytes and solitary thrombocytes were adhesed just in the place of contact. In the center of nonendothelialized zone no adhesion was observed. In the zone covered by the endothelium smooth myocytes of the synthetic and contractile phenotype were seen with similar frequency. The nonendothelialized zone was presented mainly by smooth myocytes of the synthetic phenotype and macrophages. The myointimal thickening of the rabbit aorta might be considered as an informative model for analysis of myoendothelial interactions.

Animals↗

PubMed1992

[Effects of lovastatin therapy on the level of low density lipoproteins and atherogenic potential of serum in patients with ischemic heart disease and hypercholesterolemia].

The serum atherogenic potential in patients with coronary heart disease (CHD) concurrent with hypercholesterolemia (LDL cholesterol more than 200 mg/dl), which is able to cause accumulation of intracellular cholesterol in cultured cells has been recently shown to be directly related to the level of total cholesterol and LDL cholesterol. The study was undertaken to examine how a lovastatin-induced decrease in LDL levels affects serum atherogenicity in patients with CHD and hypercholesterolemia. It was shown that the therapy of 22 patients with CHD and hypercholesterolemia led to a reduction in total and LDL cholesterol levels on an average by 24% and 32%, respectively. There were 3- and 1.5-2-fold decreases in circulatory immune complexes and the atherogenic potential, respectively. The findings suggest that the significant reduction in serum LDL cholesterol levels in patients with CHD concurrent with hypercholesterolemia who take hypolipidemic therapy is followed by a decrease in the atherogenic potential.

Animals↗