Cholesterol ester accumulation in cultured aortic smooth muscle cells. Induction of cholesterol ester retention by chloroquine and low density lipoprotein and its reversion by mixtures of high density apolipoprotein and sphingomyelin.

Accretion of cholesterol ester was studied in rat aortic smooth muscle cells in culture. Confluent multilayers of smooth muscle cells were exposed to human low density lipoprotein (LDL) and chloroquine and this treatment resulted in a very marked increase in cellular cholesterol ester. The degree of enrichment in cholesterol ester was related inversely to the cell density in the petri dish and was maximal in 48 h.

Chloroquine-induced interference with degradation of serum lipoproteins in rat liver, studied in vivo and in vitro.

The effect of chloroquine, an inhibitor of certain lysosomal enzymes including cathepsin B (EC 3.4.22.

Deposition and mobilization of cholesterol ester in cultured human skin fibroblasts.

Human skin fibroblasts in culture served as a model system to study intracellular cholesterol ester deposition in mesenchymal cells. Confluent cultures were exposed to homologous low density lipoprotein alone and together with chloroquine. In the presence of low density lipoprotein alone, even at half circulating serum concentrations, cellular free cholesterol increased no more than 12%, while the increase in cholesterol ester ranged from 13--100% during 48 h of incubation.

Ultrastructural localization of concanavalin A in the perfused rat heart.

Staining of the surface coat of heart capillaries and aorta was achieved by perfusing concanavalin A and phytohemagglutinin coupled to horseradish peroxidase through the rat heart. The binding of these lectins provides evidence for the presence of glycoproteins containing mannose, glucose, and N-acetylgalactosamine residues in the endothelial surface coat of rat aorta and heart capillaries. The binding of concanavalin A to capillary endothelium was further followed with radioautography of 125I-labeled concanavalin A in the in vitro perfused rat heart.

Interaction of concanavalin A with membrane-bound and solubilized lipoprotein lipase of rat heart.

Concanavalin A was used to study the configuration of lipoprotein lipase at the surface of capillary endothelium. Incubation of heart homogenates with increasing concentrations of concanavalin A for 5-60 min resulted in inhibition of up to 50% of enzyme activity. The inhibition was related to the concentration of lectin and the time of incubation and was fully reversible by postincubation with alpha-methyl-D-mannoside.

High density lipoproteins reduce the uptake of low density lipoproteins by human endothelial cells in culture.

Endothelial cells, explanted from human umbilical veins and cultured, maintained morphological characteristics of vascular endothelium. When exposed to human serum lipoproteins, the cells bound and took up low density lipoproteins in preference to high density lipoproteins. High density lipoproteins reduced markedly the uptake of low density lipoproteins and affected surface binding to a lesser extent.

Cholesterol content and sterol synthesis in human skin fibroblasts and rat aortic smooth muscle cells exposed to lipoprotein-depleted serum and high density apolipoprotein/phospholipid mixtures.

Confluent cultures of human skin fibroblasts and rat aortic smooth muscle cells were shown to lose 15-27% of their cellular cholesterol upon replacement of the fetal calf serum with human high density lipoprotein (50 mug cholesterol/ml) or lipoprotein-depleted serum at a concentration equivalent to 40% whole serum. Addition to the latter medium of high density apoliproprotein/phospholipid mixtures resulted in further enhancement of cellular cholesterol loss which was evident by 12 h of incubation. Human skin fibroblasts that had been enriched in cholesterol by previous incubation with low density lipoprotein lost their cholesterol in the presence of a high density apolipoprotein/sphingomyelin mixture as readily as non-enriched cells.

Binding, internalization, and degradation of low density lipoprotein by normal human fibroblasts and by fibroblasts from a case of homozygous familial hypercholesterolemia.

Skin fibroblasts from a patient with homozygous familial hypercholesterolemia (HFH) were compared with normal skin fibroblasts with regard to binding, internalization, and degradation of iodinated human low density lipoprotein (LDL). Like other cell lines from HFH patients, the mutant cells showed no suppression of sterol synthesis by LDL. Surface binding, measured at 0 degrees to eliminate the appreciable internalization that was shown to occur at 37 degrees, was on the average slightly less for HFH cells than normal cells at low LDL concentrations but comparable or even greater at high LDL concentrations (greater than 60 mug of LDL protein per ml).

Radioiodinated lipoproteins: absorption of 125I radioactivity by high density solutions.

Concentrations of potassium bromide commonly used for separation of lipoproteins were shown to cause absorption of 125I and thus reduce the counting efficiency of the labeled lipoproteins. Chloroform was shown to cause a 50% reduction in counting efficiency of lipid from 125I-labeled lipoprotein. No reduction of counting efficiency was observed in the presence of high density solutions when 131I was used as label.

A comparative study on the removal of cellular lipids from Landschütz ascites cells by human plasma apolipoproteins.

The effects of human plasma lipoprotein-proteins on the removal of cellular lipids from Landschütz ascites cells were studied. Cellular lipids were labeled by injecting mice previously injected with ascites with either [3H]cholesterol or [3H]choline. Apoproteins from very low density (apoC-I, C-II, and C-111) and high density (apoA-I and A-II) lipoproteins were used.

Surface binding and interiorization of homologous and heterologous serum lipoproteins by rat aortic smooth muscle cells in culture.

Rat aortic smooth muscle cells in culture were incubated with rat or human iodinated low and high density lipoprotein at 5-50 mug/ml for 3 h. With the homologous lipoproteins, 25-49% of total cellular protein radioactivity was trypsin releasable and was considered as surface-bound radioactivity, while the balance represented cellular uptake. The ratio of surface-bound to cellular label was higher when the cells were incubated with human lipoproteins and was about 9 : 1 with human high density lipoprotein.

Interference with the transport of heparin-releasable lipoprotein lipase in the perfused rat heart by colchicine and vinblastine.

The effect of pretreatment with colchicine or vinblastine on the lipoprotein lipase activity of rat heart was studied. Administration of colchicine or vinblastine 4 h prior to perfusion of the heart caused a very marked reduction in lipoprotein lipase activity released into the perfusate within 1 min of heparin perfusion. At the same time an increase in residual heart lipase occurred so that total lipoprotein lipase content of the heart (heparin releasable plus residual) did not change.

Turnover of phospholipids in rat aortic smooth muscle cells in culture.

Smooth muscle cells derived from rat aortic media were explanted and grown in culture for 14 to 60 days. During that time they formed a confluent multilayer and depostied extracellular material resembling newly formed elastin. The lipid composition of the cells in culture differed slightly from the parent cells in the intact aorta with respect to a higher phospholipid/DNA ratio and a higher lecithin content.

Comparative uptake of rat and human serum low-density and high-density lipoproteins by rat aortic smooth muscle cells in culture.

Rat aortic smooth muscle cells in culture were exposed to rat and human serum (LDL) and high-density (HDL) lipoproteins labeled with 125-I. 125-I-lipid was taken up preferentially from all of the lipoproteins used. 125-I-protein uptake of both rat LDL and HDL was significantly higher than that of the corresponding human lipoproteins, and human LDL was preferred to human HDL.

Colchicine-induced inhibition of plasma lipoprotein lipase release in the intact rat.

The release of plasma lipoprotein lipase by heparin was studied in fed and food-deprived rats pretreated with colchicine and vinblastine. Four hours after the administration of either drug the lipoprotein lipase activity released by heparin was only half of that found in controls. Colchicine affected the release of both protamine-sensitive and protamine-resistant lipoprotein lipase.

The removal of cholesterol from aortic smooth muscle cells in culture and Landschutz ascites cells by fractions of human high-density apolipoprotein.

Ascites cells were labeled by intraperitoneal injection of [3H]cholesterol and aortic smooth muscle cells by addition of [3H]cholesterol to the serum component of the culture medium. The release of cholesterol from cells into a serum-free medium supplemented with the various "acceptors" was studied using ascites cells in suspension and aortic smooth muscle cells in a multilayer culture. Unfractionated human high-density apolipoprotein was somewhat more effective in the removal of labeled cellular free cholesterol, in both cell types, than apolipoprotein derived from rat high-density lipoprotein.