Biomedical subjects

A N Orekhov

Publications and source records attributed to A N Orekhov.

At least 19 recordsLinked to original sources

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↗

PubMed1992

[Atherogenic properties of phenothiazine drugs manifesting in cultured cells of the human aortic intima].

The effects of phenothiazine drugs on the levels of cholesterol in smooth cells of the human aortic intima. Two antiarrhythmics (ethacizin and ethmozine) and two neuroleptics (trifluoperazine and chlorpromazine) were evaluated. The three agents ethacizin, trifluoperazine, and chlorpromazine given in concentrations of 10(-7) to 10(-5) M were ascertained to cause intracellular cholesterol accumulation, whereas ethmozine produced no effects on the intracellular levels of cholesterol. Ethacizin failed to cause cholesterol accumulation when the cells were incubated with ethacizin in the culture medium supplemented with lipid-deficient serum. Ethacizin in a concentration o 10(-5) M was shown to inhibit the synthesis of cholesterol esters and had no action on the intracellular synthesis of steroids.

Anti-Arrhythmia Agents↗

PubMed1992

[Elimination of the atherogenic effect of beta blocker propranolol by papaverine].

Recently, the ability of beta-blockers to stimulate proliferative activity and induce lipid accumulation in cultured human aortic intimal cells has been demonstrated. Moreover, the addition of calcium antagonists completely blocked the increase in proliferative activity and abolished cholesterol accumulation caused by propranolol. In this study blood serum of rabbits treated with 20 mg of propranolol induced 2-fold cholesterol accumulation in mouse peritoneal macrophages. Papaverin did not influence this effect. In case of simultaneous administration of propranolol and papaverin rabbit serum did not exhibit the ability to accumulate intracellular lipids. Propranolol substantially stimulated the formation of myointimal thickening and neutral lipid accumulation in denuded rabbit aorta. Papaverin completely blocked the propranolol-produced atherogenic changes. The data suggest that in vitro and in vivo atherogenic effects of beta-blockers may be prevented by papaverin.

Animals↗

PubMed1992

Multiple-modified desialylated low density lipoproteins that cause intracellular lipid accumulation. Isolation, fractionation and characterization.

BACKGROUND: The basic differences between sialylated (sialic acid rich) and desialylated (sialic acid poor) human low density lipoproteins (LDL) are not fully defined. It is not known whether there are any differences in the LDL composition of coronary atherosclerosis patients and healthy individuals. EXPERIMENTAL DESIGN: Sialylated (45 to 94% of total LDL) and desialylated (6 to 55%) LDL were separated by affinity chromatography on Ricinus communis agglutinin-agarose, and their chemical composition and physical properties were examined. RESULTS: Sialic acid contents in sialylated LDL fractions of healthy subjects and patients were the same and 1.5 to 3-fold higher than in desialylated LDL. Desialylated LDL had smaller sizes and greater electrophoretic mobility than sialylated ones. Desialylated, but not sialylated LDL, induced 1.5- to 4-fold accumulation of neutral lipids in human aortic smooth muscle cells and human blood monocytes. Subfractions of desialylated LDL containing lower amount of sialic acid revealed higher ability to accumulate lipids in cultured cells. Desialylated LDL contained lower amounts of cholesteryl esters, free cholesterol and triglycerides as compared with sialylated LDL. On the other hand, concentration of di-, monoglycerides and free fatty acids in desialylated LDL was 2 to 3-fold higher than in sialylated lipoproteins. Desialylated LDL fraction was characterized by lower levels of phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, but higher content of lysophosphatidylcholine. Freshly isolated sialylated and desialylated LDL contained equal amounts of thiobarbituric acid reactive substances, but oxidation of desialylated LDL was more pronounced in presence of Cu(2+)-ions. Desialylated LDL had higher level of oxysterols and lower amounts of vitamin A and E. Content of free amino groups of lysine in desialylated LDL of patients was 2-fold lower than in sialylated LDL. This difference was partially due to masking of amino groups caused by conformational change in the tertiary structure of apolipoprotein, partially to chemical modification of amino groups. When subfractionated by density gradient ultracentrifugation, desialylated LDL was represented by higher density particles than sialylated LDL. Sialic acid content in desialylated LDL subfractions decreased with rise of lipoprotein density. Higher density desialylated LDL and in less extent sialylated LDL contained smaller amounts of free and esterified cholesterol and phospholipids. Only the densest subfractions of desialylated LDL from healthy subjects caused intracellular lipid accumulation. Ability of patients' desialylated LDL to accumulate cholesterol in cells increased with particle density. CONCLUSIONS: Extensive biochemical and biophysical analysis performed in this study shows that desialylated LDL differ from these sialylated LDL in many respects. The LDL of coronary atherosclerosis patients differ from those in healthy individuals in several parameters.

Adult↗

PubMed1992

Characterization of desialylated low-density lipoproteins which cause intracellular lipid accumulation.

The properties of sialylated (sialic acid rich) and desialylated (sialic acid poor) fractions of low-density lipoproteins (LDL) isolated from blood plasma of healthy subjects and coronary atherosclerosis patients have been investigated. Sialylated (60-90% of total LDL) and desialylated (10-40%) LDL were separated by affinity chromatography on Ricinus communis agglutinin-agarose. Sialic acid contents in sialylated LDL fractions of healthy subjects and patients were found to be the same, and 1.5 to 3-fold higher than in desialylated LDL. Desialylated LDL had smaller sizes and greater electrophoretic mobility than sialylated, ones. Desialylated, but not sialylated, LDL induced 1.5 to 4-fold accumulation of neutral lipids in human aortic smooth-muscle cells. Desialylated LDL contained lower amounts of cholesteryl esters, free cholesterol and triglycerides as compared to sialylated LDL. On the other hand, the concentrations of di-, monoglycerides and free fatty acids in desialylated LDL were 2 to 3-fold higher than in sialylated lipoproteins. The desialylated LDL fraction was characterized by lower levels of phosphatidylcholine, sphingomyelin and phosphatidylethanolamine, but a higher content of lysophosphatidylcholine. Levels of thiobarbituric acid-reactive substances in freshly isolated desialylated and sialylated LDL were the same. Desialylated LDL had a higher level of oxysterols and lower amounts of vitamins A and E. The content of free amino groups of lysine in desialylated LDL of patients was 2-fold lower than in sialylated LDL. The results of this study demonstrate that multiple physico-chemical parameters of desialylated LDL differ from those of sialylated LDL.

Adult↗

PubMed1992

Sialic acid content of human low density lipoproteins affects their interaction with cell receptors and intracellular lipid accumulation.

Low density lipoproteins (LDL) isolated from the plasma of patients with angiographically demonstrable coronary heart disease (CHD) induced accumulation of triglycerides, free cholesterol, and cholesteryl esters in cultured macrophages, smooth muscle cells, and endothelial cells derived from uninvolved intima of human aorta, but not in skin fibroblasts or hepatoma cells. The sialic acid content of LDL from CHD patients was 40-75% lower than that from healthy donors. There was a negative correlation between LDL sialic acid content and the LDL-induced accumulation of total intracellular cholesterol. Neuraminidase treatment of LDL from normal healthy donors produced sialic acid-depleted LDL (Ds-LDL) which was able to stimulate intracellular lipid accumulation. Neuraminidase treatment of LDL from CHD patients further increased its capacity to induce intracellular lipid accumulation. Sialic acid-poor LDL isolated by affinity chromatography of LDL from CHD patients induced a 2- to 4-fold increase of free and esterified cholesterol in human intimal smooth muscle cells. Binding, uptake, and degradation of 125I-labeled Ds-LDL by macrophages and endothelial cells were 1.5- to 2-fold higher than for native LDL. Binding and uptake of Ds-LDL was inhibited 64-93% by the addition of 20-fold excess acetylated LDL (Ac-LDL); in the inverse experiment, the level of inhibition was 35-54%. These data indicate that a sialic acid-poor form of LDL isolated from CHD patients can interact with both native and scavenger LDL receptors. A sialic acid-poor form of LDL may be a naturally occurring ligand that interacts with the scavenger receptor(s) on macrophages and endothelial cells.

Adult↗