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Pedrelli M, Davoodpour P, Degirolamo C, Gomaraschi M, Graham M, Ossoli A, Larsson L, Calabresi L, Gustafsson JÅ, Steffensen KR, Eriksson M, Parini P. Hepatic ACAT2 knock down increases ABCA1 and modifies HDL metabolism in mice. PLoS One 2014; 9:e93552. [PMID: 24695360 PMCID: PMC3973598 DOI: 10.1371/journal.pone.0093552] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 03/06/2014] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVES ACAT2 is the exclusive cholesterol-esterifying enzyme in hepatocytes and enterocytes. Hepatic ABCA1 transfers unesterified cholesterol (UC) to apoAI, thus generating HDL. By changing the hepatic UC pool available for ABCA1, ACAT2 may affect HDL metabolism. The aim of this study was to reveal whether hepatic ACAT2 influences HDL metabolism. DESIGN WT and LXRα/β double knockout (DOKO) mice were fed a western-type diet for 8 weeks. Animals were i.p. injected with an antisense oligonucleotide targeted to hepatic ACAT2 (ASO6), or with an ASO control. Injections started 4 weeks after, or concomitantly with, the beginning of the diet. RESULTS ASO6 reduced liver cholesteryl esters, while not inducing UC accumulation. ASO6 increased hepatic ABCA1 protein independently of the diet conditions. ASO6 affected HDL lipids (increased UC) only in DOKO, while it increased apoE-containing HDL in both genotypes. In WT mice ASO6 led to the appearance of large HDL enriched in apoAI and apoE. CONCLUSIONS The use of ASO6 revealed a new pathway by which the liver may contribute to HDL metabolism in mice. ACAT2 seems to be a hepatic player affecting the cholesterol fluxes fated to VLDL or to HDL, the latter via up-regulation of ABCA1.
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Affiliation(s)
- Matteo Pedrelli
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Molecular Nutrition Unit, Department of Bioscience and Nutrition, Karolinska Institutet, Stockholm, Sweden
| | - Padideh Davoodpour
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Chiara Degirolamo
- Division of Lipid Science, Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Monica Gomaraschi
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Mark Graham
- Cardiovascular Group, Department of Antisense Drug Discovery, Isis Pharmaceuticals, Inc., Carlsbad, California, United States of America
| | - Alice Ossoli
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Lilian Larsson
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Laura Calabresi
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Jan-Åke Gustafsson
- Molecular Nutrition Unit, Department of Bioscience and Nutrition, Karolinska Institutet, Stockholm, Sweden
- Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, Texas, United States of America
| | - Knut R. Steffensen
- Molecular Nutrition Unit, Department of Bioscience and Nutrition, Karolinska Institutet, Stockholm, Sweden
| | - Mats Eriksson
- Molecular Nutrition Unit, Department of Bioscience and Nutrition, Karolinska Institutet, Stockholm, Sweden
- Department of Medicine, Karolinska Institute, Stockholm, Sweden
| | - Paolo Parini
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Molecular Nutrition Unit, Department of Bioscience and Nutrition, Karolinska Institutet, Stockholm, Sweden
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Page K, Lange Y. Cell adhesion to fibronectin regulates membrane lipid biosynthesis through 5'-AMP-activated protein kinase. J Biol Chem 1997; 272:19339-42. [PMID: 9235931 DOI: 10.1074/jbc.272.31.19339] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We have shown that attachment to a fibronectin substrate stimulates two pathways of lipid biosynthesis in cultured human fibroblasts. Detachment of these cells (mechanically, with trypsin, or by RGDS peptides) caused a significant decrease in their 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity and in their incorporation of [3H]acetate into fatty acids. This inhibition was substantially reversed by the reattachment of cells to fibronectin substrates, but not to poly-L-lysine substrates or to fibronectin in solution. Inhibiting phosphoprotein phosphatase activity with okadaic acid blocked the recovery of both biosynthetic activities. Both 3-hydroxy-3-methylglutaryl-coenzyme A reductase and fatty acid biosynthesis are known to be inhibited by the action of 5'-AMP-activated protein kinase, which is activated by an increase in the level of AMP relative to ATP. For example, in our system, sodium azide and 2-deoxy-D-glucose increased the ratio of cellular AMP to ATP and caused a decrease in lipid biosynthesis. We then verified the prediction that detachment of cells from substrates also caused an increase in the AMP/ATP ratio. We therefore conclude that the attachment of cells to fibronectin promotes lipid biosynthesis, presumably in coordination with the cellular growth response evoked by attachment to the extracellular matrix.
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Affiliation(s)
- K Page
- Department of Biochemistry, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612, USA
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Orekhov AN, Tertov VV, Kudryashov SA, Smirnov VN. Triggerlike stimulation of cholesterol accumulation and DNA and extracellular matrix synthesis induced by atherogenic serum or low density lipoprotein in cultured cells. Circ Res 1990; 66:311-20. [PMID: 2297806 DOI: 10.1161/01.res.66.2.311] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A 72-hour incubation of cultured cells with blood sera or plasma of patients suffering from coronary heart disease (CHD) with angiographically assessed coronary atherosclerosis caused a threefold to fourfold elevation of intracellular cholesterol. An elevated cholesterol level in the cells precultured with patients' sera was retained several days after the removal of the examined serum from culture. The accumulation of intracellular cholesterol was accompanied by enhanced synthesis of DNA, total protein, collagen, sulfated glycosaminoglycans, and hyaluronic acid. Enhanced DNA and total protein synthesis was retained for at least 9 days after the serum had been removed from culture. The obtained results suggest that the sera of CHD patients possess an atherogenic potential that manifests itself at the arterial cell level in the stable stimulation of atherosclerotic cellular processes: proliferation, lipidosis, and fibrosis. The examined sera of healthy donors were devoid of such an atherogenic potential. The low density lipoprotein (LDL) fraction (density, 1.030-1.050 g/cm3) obtained from an atherogenic serum had the same atherogenic potential as a whole serum. Atherosclerotic alterations in cultured intimal cells caused by atherogenic LDL were retained for at least 3 days after the removal of the lipoprotein from culture. Preincubation of intimal cells with LDL obtained from healthy donors had no effect on the intracellular cholesterol level or the synthesis of DNA and extracellular matrix. One may assume that the atherogenic potential of CHD patients' sera is related to the presence of LDLs that are qualitatively different from the LDL of healthy subjects.
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Affiliation(s)
- A N Orekhov
- Institute of Experimental Cardiology, USSR Cardiology Research Center, Moscow
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4
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DeLamatre JG, Sarphie TG, Archibold RC, Hornick CA. Metabolism of apoE-free high density lipoproteins in rat hepatoma cells: evidence for a retroendocytic pathway. J Lipid Res 1990. [DOI: 10.1016/s0022-2275(20)43205-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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5
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Tanabe S, Sherman H, Smith L, Yang LA, Fleming R, Hay R. Biogenesis of plasma lipoproteins in rat hepatoma McA-RH7777: importance of diffusion-mediated events during cell growth. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY : JOURNAL OF THE TISSUE CULTURE ASSOCIATION 1989; 25:1129-40. [PMID: 2481672 DOI: 10.1007/bf02621264] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cultured McA-RH7777 rat hepatoma cells actively synthesize and secrete plasma lipoproteins. However, synthesis of [14C]triglyceride declines monotonically throughout the early growth period and remains low in postconfluent cultures; and net secretion of [14C]triglyceride is 10-fold more efficient in logarithmically growing cultures than in postconfluent cultures. Secretion of apolipoproteins associated with very low density and low density lipoproteins is selectively reduced in postconfluent cultures. The temporal reductions in [14C]triglyceride production are related more strongly to increasing cell concentration (cells/cm3 medium) than to increasing cell density (cells/cm2 growth surface). We have allowed cells to grow either retained within small circular corrals or unrestricted in culture dishes. When seeded at equal density (10(4) cells/cm2) but at one-fifth the cell concentration, corralled cells synthesize twice as much [14C]triglyceride per cell after 2 and 4 d, and are 10 times as efficient in [14C]triglyceride secretion by 6 d of growth, as noncorralled cells. When seeded at equal cell concentration (10(5) cells/dish) but at 5 times the cell density, corralled cells are only 20% less efficient at [14C]triglyceride synthesis and secretion than noncorralled cells. Conditioned medium depresses synthesis and secretion efficiency of [14C]triglyceride. Orotic acid exposure also inhibits synthesis of [14C]triglyceride and secretion of certain [35S]apolipoproteins in early cultures, but it has no significant effect on late cultures. We conclude that diffusion-mediated events are important regulators of triglyceride and apolipoprotein production in growing rat hepatoma cells, but that events associated with formation of cell-to-cell contacts play a minor role in regulation of plasma lipoprotein biogenesis.
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Affiliation(s)
- S Tanabe
- Department of Pathology, University of Chicago, Illinois 60637
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6
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Slotte JP, Chait A, Bierman EL. Cholesterol accumulation in aortic smooth muscle cells exposed to low density lipoproteins. Contribution of free cholesterol transfer. ARTERIOSCLEROSIS (DALLAS, TEX.) 1988; 8:750-8. [PMID: 3196219 DOI: 10.1161/01.atv.8.6.750] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Incubation of cultured arterial smooth muscle cells with large concentrations of low density lipoproteins (LDL) resulted in a net increase in cell cholesterol and cholesteryl ester mass that was dependent on LDL concentration and time of incubation. Use of an inhibitor of acyl-CoA:cholesterol acyl-transferase (ACAT) reduced the accumulation of cholesteryl ester mass by 40% (range 25% to 50%), suggesting that a significant proportion of the cholesteryl ester mass that accumulated from LDL did so without being hydrolyzed and re-esterified. Quiescent arterial smooth muscle cells exposed for 48 hours to 0.5 mg/ml of 125I-LDL accumulated 115 nmol total sterol/mg cell protein. However, these cells took up and degraded only 21 micrograms of 125I-LDL protein, which contains 64 nmol total cholesterol. Hence, only about 60% of the increase in cell-associated cholesterol mass was accounted for by LDL particle uptake and degradation. Further, when cells were incubated with 3H cholesteryl linoleyl ether-labeled LDL, the net increase of total cell cholesterol was 81 nmol/mg cell protein. However, only 49 nmol of total cholesterol was taken up by LDL particle uptake, as calculated from the uptake of the 3H cholesteryl linoleyl ether tracer. It thus appears that about 40% of the accumulated cholesterol mass was derived independent of LDL particle uptake, suggesting the possibility of transfer of free cholesterol from the surface of LDL to the cell surface. The occurrence of cholesterol surface transfer was independently verified by the measurement of the uptake and cellular distribution of LDL-derived free 3H-cholesterol. A substantial fraction of the accumulated cell cholesterol mass (approximately 40%) was derived from surface transfer of LDL free cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J P Slotte
- Department of Medicine, University of Washington, Seattle 98195
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7
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Friedman G, Wernette-Hammond ME, Hui DY, Mahley RW, Innerarity TL. Characterization of lipoprotein receptors on rat Fu5AH hepatoma cells. J Lipid Res 1987. [DOI: 10.1016/s0022-2275(20)38573-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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8
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Abstract
The existence of a cholesteryl ester cycle in cultured Fu5AH hepatoma cells was documented and factors affecting the rate of turnover of the cholesteryl ester cycle in this cell line were explored. The influence of the physical state of the lipid inclusion in which the cholesteryl esters are stored could be addressed in this cell line because these cells can be induced to store cholesteryl esters in anisotropic (liquid-crystalline) cytoplasmic inclusions by exposure to free cholesterol-rich phospholipid dispersions or in isotropic (liquid) inclusions by addition of oleic acid to the phospholipid dispersions. To examine the relative rates of turnover of the cholesteryl ester cycle in the cells with the two types of inclusions, the fraction of cholesteryl linolenate, a cholesteryl ester present in low amounts in these inclusions, was examined after cells were exposed to medium containing linolenate. After 12 h, cells with anisotropic inclusions contained 17.5% cholesteryl linolenate and cells with isotropic inclusions contained 29.8% cholesteryl linolenate, suggesting an approximately 2-fold difference in turnover of the cholesteryl ester pool. To determine whether this difference was due to a differential rate of cholesteryl ester hydrolysis, the acyl CoA: cholesterol acyl transferase arm of the cholesteryl ester cycle was blocked using a specific inhibitor, Sandoz 58-035. In the presence of this compound, cholesteryl ester was hydrolysed twice as fast in cells with isotropic inclusions as compared to that in cells with anisotropic inclusions. The difference in rate of turnover of the cholesteryl ester cycle was shown to be related to the rate of hydrolysis of cholesteryl ester which, in turn, is related to the physical state of the stored cholesteryl ester.
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Delplanque B, Jacotot B. Influence of environmental medium on fatty acid composition of human cells: leukocytes and fibroblasts. Lipids 1987; 22:241-9. [PMID: 3600201 DOI: 10.1007/bf02533986] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fibroblasts in culture and leukocytes have been widely used to study fatty acid and lipoprotein cellular metabolism. The present investigations were designed to study the role of nutritional and environmental factors on lipid metabolism in these two types of cells. Leukocytes freshly isolated from human blood and fibroblasts cultured in media enriched in human serum (HS) have relatively similar fatty acid distributions. However, more important differences are observed in fibroblasts cultured in media enriched with HS or with fetal bovine serum (FBS). It is obvious that the quantity and quality of fatty acids are very different in FBS and HS, but intracellular regulation ensures relative homogeneity of saturated (SFA) and monounsaturated fatty acids (MUFA) in the cells, particularly in phospholipids. The first modifications induced by different media (FBS or HS) are detected on cellular growth; the differences seem to be due more to the fatty acid (FA) quantitative supply than to the FA quality of each culture medium. The major modifications in FA composition induced by different culture media concern the polyunsaturated fatty acids (PUFA) of phospholipids, especially the n-6 family. The intracellular linoleic acid level depends on the level in the medium, but intracellular n-6 metabolite levels depend both on the level in the medium and on the growth state of the cells. The n-3 family seems to be less affected by the quality of the medium in our experiment, and the cells maintain a stable docosahexaenoic acid (22:6n-3) level. A higher content of the n-3 family in the medium induces a higher level of eicosa- or docosapentaenoic acid, rather than docosahexaenoic acid itself.(ABSTRACT TRUNCATED AT 250 WORDS)
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10
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DeLamatre J, Wolfbauer G, Phillips MC, Rothblat GH. Role of apolipoproteins in cellular cholesterol efflux. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 875:419-28. [PMID: 3004588 DOI: 10.1016/0005-2760(86)90061-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of serum apolipoproteins, particle size and concentration on the effectiveness of phosphatidylcholine (PC)-containing acceptor particles in causing release of cholesterol from cells growing in culture have been investigated. The acceptor particles were prepared by detergent-dialysis procedures and were either egg PC small unilamellar vesicles (SUV) or discoidal complexes of egg PC with apoproteins from human high-density lipoprotein (HDL). Gel filtration chromatography was employed to isolate particles of defined composition and size. The half-times (t 1/2) for the unidirectional efflux of cholesterol from cells prelabeled with [3H]cholesterol were measured as a function of acceptor PC concentration in the extracellular medium. HDL apolipoprotein-egg PC discoidal complexes at 100 micrograms PC/ml gave the following t 1/2 values when incubated with rat Fu5AH hepatoma, human HepG2 hepatoma, human GM3468 skin fibroblast, L-cell and mouse J774 macrophage-tumor cells: 11 +/- 2, 22 +/- 5, 84 +/- 18, 17 +/- 2 and 32 +/- 6 h, respectively. Equivalent experiments using purified apolipoprotein A-I or the total apolipoprotein C fraction to form the egg PC complexes showed that the t 1/2 values for the hepatoma cells were unaltered. However, with the fibroblasts, L-cells and J774 macrophages, the apolipoprotein C complexes gave significantly longer t 1/2 than complexes of egg PC with either apolipoprotein A-I or HDL apolipoprotein which gave the same t 1/2. An analysis based on the theory of fast coagulation of colloid particles to describe collisions between desorbed cholesterol molecules and acceptor particles predicts that the dependence of t 1/2 for cholesterol efflux from a given cell to different acceptors should be normalized when the extracellular level of acceptors is expressed in terms of the product of the radius of the particle times the number concentration of acceptor particles. The decrease in t 1/2 for cholesterol efflux from fibroblasts when the egg PC acceptor was changed from an SUV to an apolipoprotein HDL discoidal complex is consistent with the above concepts. The primary effect of the apolipoproteins in promoting cellular cholesterol efflux seems to be the solubilization of PC so that the PC is present in the extracellular medium as many small particles.
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11
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12
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van Heusden GP, Souren J, Geelen MJ, Wirtz KW. The synthesis and esterification of cholesterol by hepatocytes and H35 hepatoma cells are independent of the level of nonspecific lipid transfer protein. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 846:21-5. [PMID: 4016155 DOI: 10.1016/0167-4889(85)90105-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The level of the nonspecific lipid transfer protein (i.e., sterol carrier protein 2) is 16-fold lower in the Reuber H35 hepatoma cells as compared to the hepatocytes in culture (49 and 810 ng of protein per mg of 105000 X g supernatant protein, respectively). In order to establish whether there is a relationship between the level of nonspecific transfer protein and intracellular cholesterol metabolism, we have determined the biosynthesis and esterification of cholesterol in these hepatoma cells and hepatocytes. Both types of cells incorporated [3H]mevalonate into cholesterol and cholesterol ester. Incubation of both cell types with [3H]cholesterol in the medium resulted in a time-dependent uptake and subsequent conversion into cholesterol ester. In both instances, the amount of 3H label incorporated into cholesterol per mg of cellular protein was about 2-fold higher for the hepatoma cells. The kinetics of esterification of endogenously synthesized cholesterol were similar for both hepatoma cells and hepatocytes. Esterification of cholesterol derived from the medium proceeded 2-times faster in the hepatoma cells than in the hepatocytes. From the kinetics of cholesterol esterification we conclude that cells do not discriminate between cholesterol synthesized de novo and cholesterol derived from the medium. In addition, the proposition that the nonspecific lipid transfer protein is involved in cholesterol synthesis and esterification is not substantiated by this study.
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Bellini F, Phillips MC, Pickell C, Rothblat GH. Role of the plasma membrane in the mechanism of cholesterol efflux from cells. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 777:209-15. [PMID: 6487625 DOI: 10.1016/0005-2736(84)90422-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In order to investigate the role of the plasma membrane in determining the kinetics of removal of cholesterol from cells, the efflux of [3H]cholesterol from intact cells and plasma membrane vesicles has been compared. The release of cholesterol from cultures of Fu5AH rat hepatoma and WIRL-3C rat liver cells to complexes of egg phosphatidylcholine (1 mg/ml) and human high-density apolipoprotein is first order with respect to concentration of cholesterol in the cells, with half-times (t 1/2) for at least one-third of the cell cholesterol of 3.2 +/- 0.6 and 14.3 +/- 1.5 h, respectively. Plasma membrane vesicles (0.5-5.0 micron diameter) were produced from both cell lines by incubating the cells with 50 mM formaldehyde and 2 mM dithiothreitol for 90 min. The efflux of cholesterol from the isolated vesicles follows the same kinetics as the intact, parent cells: the t 1/2 values for plasma membrane vesicles of Fu5AH and WIRL cells are 3.9 +/- 0.5 and 11.2 +/- 0.7 h, respectively. These t 1/2 values reflect the rate-limiting step in the cholesterol efflux process, which is the desorption of cholesterol molecules from the plasma membrane into the extracellular aqueous phase. The fact that intact cells and isolated plasma membranes release cholesterol at the same rates indicates that variations in the plasma membrane structure account for differences in the kinetics of cholesterol release from different cell types. In order to investigate the role of plasma membrane lipids, the kinetics of cholesterol desorption from small unilamellar vesicles prepared from the total lipid isolated from plasma membrane vesicles of Fu5AH and WIRL cells were measured. Half-times of cholesterol release from plasma membrane lipid vesicles of Fu5AH and WIRL cells were the same, with values of 3.1 +/- 0.1 and 2.9 +/- 0.2 h, respectively. Since bilayers formed from isolated plasma membrane lipids do not reproduce the kinetics of cholesterol efflux observed with the intact plasma membranes, it is likely that the local domain structure, as influenced by membrane proteins, is responsible for the differences in t 1/2 values for cholesterol efflux from these cell lines.
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14
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Cassel DL, Phillips MC, Rostron P, Rothblat GH, Utermann G. The conformation of apolipoprotein E isoforms in phospholipid complexes and their interaction with human Hep G2 cells. Atherosclerosis 1984; 52:203-18. [PMID: 6089844 DOI: 10.1016/0021-9150(84)90119-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The human hepatoma cell line, Hep G2, has been used to compare the metabolism by isolated liver cells of purified isoforms of human apolipoprotein E (apo E). Complexes of [125I]apo E-3/3, 2/2, 3/2 and 4/3 with dimyristoyl phosphatidylcholine (DMPC) were prepared by a detergent-dialysis method: discoidal, bilayer complexes with a stoichiometry of 125 +/- 15 mol DMPC/mol apo E resulted. The predominant phenotype apo E-3/3, and the phenotype apo E-2/2 characteristic of patients with Type III hyperlipoproteinemia, interact similarly with DMPC and adopt the same conformation with 60-70% alpha-helix, as monitored by circular dichroism spectroscopy. The uptake and degradation at 37 degrees C, and binding at 4 degrees C by Hep G2 cells, of [125I]apo E-3/3/DMPC and [125I]apo E-2/2/DMPC complexes were compared. Apo E-3/3 was degraded more rapidly than apo E-2/2 suggesting that the diminished catabolism of the latter phenotype by intact livers is due to lack of recognition by the hepatocytes. The observed degradation of apo E was 3-4 times greater than that which could be attributed to fluid phase endocytosis and low-affinity adsorptive endocytosis. The degradation of [125I]apo A-I by Hep G2 cells can be accounted for by the above endocytotic mechanisms. The distinction between apo E-3/3 and apo E-2/2 isoforms is attributed to the presence of a cell-surface receptor on Hep G2 cells which binds apo E-3/3 with a higher affinity than apo E-2/2.
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16
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Cellular cholesteryl ester clearance. Relationship to the physical state of cholesteryl ester inclusions. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)43931-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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17
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Nervi FO, Del Pozo R, Covarrubias CF, Ronco BO. The effect of progesterone on the regulatory mechanisms of biliary cholesterol secretion in the rat. Hepatology 1983; 3:360-7. [PMID: 6840681 DOI: 10.1002/hep.1840030314] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We tested the hypothesis that progesterone, an inhibitor of cholesterol esterification in liver microsomes, increases biliary cholesterol output by increasing the availability of cholesterol. Initial bile samples of 20 min were obtained from acute bile fistula rats after seven daily doses of progesterone (5 to 55 mg per kg of body weight). Biliary cholesterol output correlated with the doses of progesterone, r = 0.64 (p less than 0.005). A 100% increment in biliary cholesterol output was obtained with progesterone doses of 30 to 55 mg per kg of body weight. Under these conditions, biliary phospholipid output increased 50% (p less than 0.02), but bile salt output remained normal. The relationship between biliary cholesterol and phospholipids as a function of bile salt output was studied after acute depletion of the bile salt pool. A rectangular hyperbola was the best curve fitting for the experimental data in control and progesterone-injected rats. In the physiological range of bile salt output, between 60 and 120 nmoles per gm per min, progesterone-injected rats secreted 100% more biliary cholesterol than did controls. The calculated theoretical maximal cholesterol and phospholipid outputs were significantly increased in progesterone-injected animals. Serum and hepatic cholesterol pool, free and ester fractions, remained normal. The acyl-CoA: cholesterol acyltransferase reaction was 30% inhibited in hepatic microsomes of progesterone-injected rats, (p less than 0.05). The changes in biliary phospholipids and cholesterol output produced by progesterone were rapidly reversed by either 0.5% cholesterol feeding or 2 mg per kg of body weight ethynyl estradiol injection. These manipulations simultaneously produced a 100% increment in the microsomal acyl-CoA: cholesterol acyltransferase activity (p less than 0.005) and increased 4-fold the concentration of hepatic cholesterol esters. This experimental model suggests a functional interrelationship between biliary cholesterol output and the rate at which the liver esterifies cholesterol.
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15 Acyl Coenzyme A: Cholesterol O-Acyltransferase. ACTA ACUST UNITED AC 1983. [DOI: 10.1016/s1874-6047(08)60313-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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Rothblat GH, Phillips MC. Mechanism of cholesterol efflux from cells. Effects of acceptor structure and concentration. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34593-9] [Citation(s) in RCA: 150] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Yau-Young AO, Rothblat GH, Small DM. Mobilization of cholesterol from cholesterol ester-enriched tissue culture cells by phospholipid dispersions. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 710:181-7. [PMID: 7066356 DOI: 10.1016/0005-2760(82)90148-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The accumulation of cholesterol esters in foam cells of the arterial intima is an important characteristic of fatty streak lesions of atherosclerosis. We wished to know if cholesterol ester accumulations in cells could be mobilized by altering their external milieu. Thus, phospholipid dispersions were used to remove cholesterol from a cholesterol ester-enriched cell line. Rat hepatoma cells, Fu5AH, were loaded with cholesterol esters by incubation in medium supplemented with hyperlipemic rabbit serum. After removing the loading medium, we incubated the cells in serum-free medium containing egg phosphatidylcholine dispersions. Unesterified cellular cholesterol level decreased in the first 4 h and then remained at a constant level. The cholesterol esters decreased after a lag time of about 2 h and the triacylglycerol level increased after 3 h. The decrease in cellular cholesterol ester depended on the amount of phospholipid in the medium. Cellular cholesterol ester decreased with increasing concentration of medium phospholipid to 2 mumols/ml and then plateaued. The removed cellular sterols appeared in the medium as free cholesterol. Since there was no measurable cholesterol esterase activity in the medium, the cholesterol ester in the cells was hydrolyzed before it appeared in the medium. The fatty acyl composition of the cellular cholesterol esters remained unchanged after significant reduction, suggesting that the hydrolysis of cholesterol esters was not specific for the acyl chain. Sphingomyelin and dimyristoyl phosphatidylcholine dispersions, though cytotoxic, were also effective in reducing cellular cholesterol esters. These experiments demonstrate that cholesterol ester accumulations in these cells can be reduced when phospholipid dispersions are used as cholesterol acceptors in the extracellular medium.
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Hepatic acylcoenzyme A: cholesterol acyltransferase activity during diet-induced hypercholesterolemia in cynomolgus monkeys. J Lipid Res 1981. [DOI: 10.1016/s0022-2275(20)37376-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Warhurst G, Wynn CH. Subcellular changes associated with culture of Chinese hamster fibroblasts in hyperlipemic medium. Atherosclerosis 1981; 38:383-93. [PMID: 7225177 DOI: 10.1016/0021-9150(81)90054-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Chinese hamster fibroblasts grown in hyperlipemic rabbit serum, enriched 20-fold in total cholesterol, show accumulation of cholesterol ester to 5-6 times the normal level, whereas free cholesterol levels show minimal changes. Changes with serum concentration and time show the uptake to be saturable. Concomitant with accumulation of cholesterol ester, the median density of lysosomes as observed on analytical sub-cellular fractionation decreased markedly, indicating a lysosomal localisation of accumulated sterol. These changes were freely and rapidly reversible on return to normal medium. The implications of these findings and the potential use of the system as a model for investigation of the subcellular consequences of lipid uptake is discussed.
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23
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24
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Alam SS, Solen KA, Layman DL, Riddle MC, Connor WE. The mass uptake of cholesterol ester from low density lipoproteins by cultured smooth muscle and adventitial cells of human aortas. Circ Res 1980; 47:374-83. [PMID: 7408119 DOI: 10.1161/01.res.47.3.374] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cultured human smooth muscle and adventitial cells were incubated with human serum and low density lipoprotein (LDL) to study the uptake and accumulation of cholesterol ester from exogenous LDL. The cellular total cholesterol varied with the amount of LDL cholesterol in the medium. The cholesterol ester content increased 4-fold after 2 hours of incubation. A 6-fold rise occurred by 24 hours and continued to 72 hours. The cholesterol ester of the adventitial cells was markedly depleted by incubation with abetalipoproteinemic serum or with a lipid-depleted plasma fraction. By the use of 14C-labeled LDL free cholesterol in the incubation medium, we calculated that some 70-80% of the total accumulated cholesterol ester after 24 hours of incubation was derived from LDL cholesterol ester, and only 20-30% was synthesized by the cells. These studies demonstrated conclusively that human cells greatly increase their cholesterol ester mass after incubation with LDL.
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25
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Spector AA, Kaduce TL, Dane RW. Effect of dietary fat saturation on acylcoenzyme A:cholesterol acyltransferase activity of rat liver microsomes. J Lipid Res 1980. [DOI: 10.1016/s0022-2275(20)39822-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Bates SR. Source of the cholesterol ester accumulated in monkey arterial smooth muscle cells grown in hyperlipemic serum. Circ Res 1979; 45:821-8. [PMID: 115612 DOI: 10.1161/01.res.45.6.821] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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27
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Smith BP, St Clair RW, Lewis JC. Cholesterol esterification and cholesteryl ester accumulation in cultured pigeon and monkey arterial smooth muscle cells. Exp Mol Pathol 1979; 30:190-208. [PMID: 105930 DOI: 10.1016/0014-4800(79)90053-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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28
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Bates SR. Accumulation and loss of cholesterol esters in monkey arterial smooth muscle cells exposed to normal and hyperlipemic serum lipoproteins. Atherosclerosis 1979; 32:165-76. [PMID: 222304 DOI: 10.1016/0021-9150(79)90081-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The effects of high low and very low density lipoprotein fractions from normal or hyperlipemic rhesus monkey serum on the accumulation or removal of cholesterol esters from rhesus monkey smooth muscle cells in tissue culture were determined. Serum or serum lipoproteins were labeled with [14C] free cholesterol and adjusted to the same free cholesterol level in the incubation medium. Of the two normal lipoproteins examined, the LDL fraction caused more esterification than the HDL. Cells incubated in hyperlipemic serum showed a 2-fold stimulation in esterification as compared to cells in normal serum. This was contributed by hyperlipemic VLDL and LDL and led to a concomitant increase in cellular cholesterol ester content. Both hyperlipemic LDL and HDL stimulated esterification when compared to their normal counterparts. Cholesterol ester removal was examined by incubating the serum or lipoprotein fractions with cells enriched in cholesterol ester through a prior exposure to hyperlipemic serum. The cells incubated in normal or hyperlipemic HDL or lipoprotein-deficient serum had the lowest cholesterol ester content. Thus, the lipoprotein fractions which caused the lowest levels of cholesterol esterification were also the most efficient in the removal of cellular cholesterol esters.
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29
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Spector AA, Mathur SN, Kaduce TL. Role of acylcoenzyme A: cholesterol o-acyltransferase in cholesterol metabolism. Prog Lipid Res 1979; 18:31-53. [PMID: 42927 DOI: 10.1016/0163-7827(79)90003-1] [Citation(s) in RCA: 128] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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30
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St Clair RW, Leight MA. Differential effects of isolated lipoproteins from normal and hypercholesterolemic rhesus monkeys on cholesterol esterification and accumulation in arterial smooth muscle cells in culture. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 530:279-91. [PMID: 208631 DOI: 10.1016/0005-2760(78)90013-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Whole serum obtained from hypercholesterolemic rhesus monkeys was found to stimulate cholesterol esterification and cholesteryl ester accumulation in rhesus monkey arterial smooth muscle cells in culture to a significantly greater extent than normocholesterolemic serum. This was true even when the cholesterol concentration of the culture medium was equalized. Isolation and characterzation of the low density lipoproteins (LDL) from rhesus monkeys indicated that the LDL from hypercholesterolemic animals was 33% larger than LDL from normocholesterolemic animals due principally to an increase in the amount of cholesteryl ester per molecule. As a result, LDL from hypercholesterolemic animals transported over 50% more cholesterol per molecule than did normal LDL. The LDL of altered composition from hypercholesterolemic animals, when added to smooth muscle cells in culture, was nearly twice as effective in stimulating cholesterol esterification and cholesteryl ester accumulation than was LDL of normal composition. Results suggest that at least part of the exaggerated ability of whole hypercholesterolemic serum to stimulate the esterification and accumulation of cholesterol in cells in culture is due to the presence of LDL of altered composition.
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31
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Horwitz AF, Wight A, Ludwig P, Cornell R. Interrelated lipid alterations and their influence on the proliferation and fusion of cultured myogenic cells. J Biophys Biochem Cytol 1978; 77:334-57. [PMID: 565779 PMCID: PMC2110055 DOI: 10.1083/jcb.77.2.334] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We have cultured myogenic cells derived from primary explants and a cell line (L6) in a lipid-depleted medium (LDM) and produced large alterations of the fatty acyl and polar headgroup composition and of the cellular sterol levels. These alterations were produced by altering the composition of the media as follows: removing biotin and providing exogenous fatty acid; removing choline and providing exogenous ethanolamine or choline analogues; and by adding 25-OH cholesterol, an inhibitor of 3-hydroxy-3-methylglutarate (HMG)-CoA reductase. Relatively small, secondary alterations of other lipid classes accompany the large primary alteration. In general, they are not obviously compensatory for the primary alteration by retaining some physical property. We have explored the influence of these lipid alterations on myoblast proliferation and fusion into myotubes. In general, considerable variability appears tolerated, but there also appear to be limits. Long-term cultures grown in media containing a single fatty acid do not proliferate indefinitely, and the fatty acid does not become the sole fatty acyl component of the phospholipids. This phenomenon is also observed for cultures enriched in phosphatidylethanolamine (PE) or phosphatidyldimethylethanolamine (PDME). The influence of the lipid alterations on fusion is particularly interesting. The inclusion of 25-OH cholesterol inhibits fusion. Enrichment of the fatty acyl chains with elaidate or the polar headgroups with PE also inhibits fusion, but in contrast to that by 25-OH cholesterol, a significant fraction of the myoblasts are aligned and interacting with each other. Oleate enrichment enhances the rate of fusion.
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32
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Rothblat GH, Arbogast LY, Ray EK. Stimulation of esterified cholesterol accumulation in tissue culture cells exposed to high density lipoproteins enriched in free cholesterol. J Lipid Res 1978. [DOI: 10.1016/s0022-2275(20)41308-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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33
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Rothblat G. Drug screening in cell cultures. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1978; 109:195-205. [PMID: 364946 DOI: 10.1007/978-1-4684-0967-3_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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34
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Hata Y, Ishii T. The lipids in human atherosclerosis--morphological demonstrations of five forms of atheroma lipids. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1978; 109:129-43. [PMID: 215004 DOI: 10.1007/978-1-4684-0967-3_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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35
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Effect of dietary fat saturation on acylcoenzyme A: cholesterol acyltransferase activity of Ehrlich cell microsomes. J Lipid Res 1977. [DOI: 10.1016/s0022-2275(20)41600-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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36
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Abstract
The fetal calf serum on which two astroblast cell lines were grown was shown to be deficient in essential fatty acids. The fatty acid profiles of lipids of these two cell lines showed very low amounts of polyunsaturated fatty acids. In order to know if this low level of unsaturation was due to the lack of essential fatty acids in serum, or to a lack of desaturase activities in the cells, we have investigated the modifications of the cell lipid fatty acid patterns when serum was enriched in essential fatty acids. Linoleic acid was incorporated in rather high amounts in the cell lipids, while linolenic acid was very poorly incorporated. These two essential fatty acids were converted into polyunsaturated fatty acids only when they were added alone to the serum. Both cell clones exhibited a lack in the delta 4 desaturase activity. No morphological changes of the cells occured after nine days of culture with modified serum.
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37
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Rothblat GH, Rosen JM, Insull W, Yau AO, Small DM. Production of cholesteryl ester-rich, anisotropic inclusions by mammalian cells in culture. Exp Mol Pathol 1977; 26:318-24. [PMID: 192580 DOI: 10.1016/0014-4800(77)90059-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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38
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39
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Rosen JM, Rothblat GH. Origin of fatty acids of cholesteryl ester accumulated by Fu5AH cells in culture. Lipids 1977; 12:222-7. [PMID: 191717 DOI: 10.1007/bf02533298] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The Fu5AH rat hepatoma cell line accumulates cholesteryl ester (CE) upon incubation in medium supplemented with hyperlipemic serum or hyperlipemic serum lipoproteins. This cell line was used to investigate the origin of the fatty acids esterified to cholesterol in intracellular accumulations of CE. The intracellular CE-fatty acid distribution was found to be markedly different from that of the lipoprotein which stimulated the accumulation. Free fatty acids added to the culture medium were found esterified to cholesterol in the cells, demonstrating that cellular esterification contributes to the accumulation of CE. Using a subline of Fu5AH cells containing radioactivity labeled intracellular fatty acids, it was found that about one-third of the fatty acid moiety of CE accumulated by the cells during a 24 hr incubation with hyperlipemic serum was derived from endogenous fatty acids. The drug chloroquine was found to inhibit cellular cholesterol esterification, so that only 4% of CE-fatty acids were derived from endogenous fatty acids. Evidence is presented suggesting a major role for cellular esterification in CE accumulation by Fu5AH cells.
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40
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Warburton MJ, Colin H. W. The uptake of triton WR-1339 and various lipids by liver lysosomes of the syrian hamster (Mesocricetus auratus). ACTA ACUST UNITED AC 1977. [DOI: 10.1016/0020-711x(77)90137-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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41
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McGee R, Brenneman DE, Spector AA. Regulation of fatty acid biosynthesis in Ehrlich cells by ascites tumor plasma lipoproteins. Lipids 1977; 12:66-74. [PMID: 189155 DOI: 10.1007/bf02532975] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Fatty acid biosynthesis in Ehrlich cells in vitro was reduced when very low density lipoproteins (VLDL) isolated from the ascites tumor plasma were added to the incubation medium. The degree of inhibition was dependent on the VLDL concentration. At the VLDL concentrations usually present in the ascites plasma, there was a 30% decrease in biosynthesis as measured by (3)H(2)O incorporation into fatty acids. Analysis of the labeled fatty acids by gas liquid chromatography indicated that this decrease was due to a reduction in fatty acid de novo biosynthesis and that chain elongation actually was increased when VLDL were present. Although ascites plasma low- and high density lipoproteins also produced a concentration-dependent inhibition of fatty acid biosynthesis, their effects were much smaller than those of the VLDL. Studies employing VLDL and radioactive free fatty acids indicated that the cells took up utlilzed fatty acids derived from these lipoproteins. When VLDL were present, labeled free fatty acid incorporation into cell phospholipids, cholesteryl esters, and CO(2) decreased, whereas its incorporation into the cell free fatty acid pool increased. By contrast, the cells incorporated only very small amounts of fatty acid from either low- or high density lipoproteins. This suggests that the VLDL exert their inhibitory effect on fatty acid synthesis by supplying exogenous fatty acids to the cells.
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42
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Bates SR, Wissler RW. Effect of hyperlipemic serum on cholesterol accumulation in monkey aortic medial cells. BIOCHIMICA ET BIOPHYSICA ACTA 1976; 450:78-88. [PMID: 823978 DOI: 10.1016/0005-2760(76)90300-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of hyperlipemic monkey serum on cholesterol ester formation and accumulation in monkey aortic medial cells grown in tissue culture was studied. The cellular incorporation and esterification of free cholesterol was followed using the specific activity of serum labeled with free [14C]cholesterol while the cellular sterol content was analyzed by gas-liquid chromatographic techniqyes. The effects produced by hyperlipemic monkey serum (HMS) and normal monkey serum (NMS) were evaluated at both comparable percentage levels in the media and at equivalent exogenous cholesterol concentrations. When the two sera were adjusted to equal exogenous free cholesterol levels, the incorporation of free cholesterol by the aortic medial cells was related to the free cholesterol concentration of the culture media whether supplied by normal or hyperlipemic serum cholesterol. Under these conditions the total cholesterol content of the HMS-grown cells was 35% greater than that of NMS-grown cells, due to an elevation in free cholesterol of approximately 3 mug/mg cell protein and a 2- to 4-fold increase in esterified cholesterol. At similar percentage levels, the hyperlipemic serum stimulated a greater incorporation of free cholesterol into the monkey medial cells, accompanied by a 2-fold increase in the cellular esterification of this free cholesterol.
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