Accumulation Of Cellular Cholesterol Esters Research Articles

Metabolic reprogramming of the myeloid lineage by Schistosoma mansoni infection persists independently of antigen exposure.

Macrophages have a defined role in the pathogenesis of metabolic disease and cholesterol metabolism where alternative activation of macrophages is thought to be beneficial to both glucose and cholesterol metabolism during high fat diet induced disease. It is well established that helminth infection protects from metabolic disease, but the mechanisms underlying protection are not well understood. Here, we investigated the effects of Schistosoma mansoni infection and cytokine activation in the metabolic signatures of bone marrow derived macrophages using an approach that integrated transcriptomics, metabolomics, and lipidomics in a metabolic disease prone mouse model. We demonstrate that bone marrow derived macrophages (BMDM) from S. mansoni infected male ApoE-/- mice have dramatically increased mitochondrial respiration compared to those from uninfected mice. This change is associated with increased glucose and palmitate shuttling into TCA cycle intermediates, increased accumulation of free fatty acids, and decreased accumulation of cellular cholesterol esters, tri and diglycerides, and is dependent on mgll activity. Systemic injection of IL-4 complexes is unable to recapitulate either reductions in systemic glucose AUC or the re-programing of BMDM mitochondrial respiration seen in infected males. Importantly, the metabolic reprogramming of male myeloid cells is transferrable via bone marrow transplantation to an uninfected host, indicating maintenance of reprogramming in the absence of sustained antigen exposure. Finally, schistosome induced metabolic and bone marrow modulation is sex-dependent, with infection protecting male, but not female mice from glucose intolerance and obesity. Our findings identify a transferable, long-lasting sex-dependent reprograming of the metabolic signature of macrophages by helminth infection, providing key mechanistic insight into the factors regulating the beneficial roles of helminth infection in metabolic disease.

Uptake of dexamethasone incorporated into liposomes by macrophages and foam cells and its inhibitory effect on cellular cholesterol ester accumulation

To confirm the efficacy of dexamethasone incorporated into liposomes in the treatment of atherosclerosis, the uptake of dexamethasone-liposomes by macrophages and foam cells and its inhibitory effect on cellular cholesterol ester accumulation in these cells were investigated in-vitro. Dexamethasone-liposomes were prepared with egg yolk phosphatidylcholine, cholesterol and dicetylphosphate in a lipid molar ratio of 7/2/1 by the hydration method. This was adjusted to three different particle sizes to clarify the influence of particle size on the uptake by the macrophages and foam cells, and the inhibitory effect on cellular cholesterol ester accumulation. The distribution of particle sizes of dexamethasone-liposomes were 518.7+/-49.5 nm (L500), 202.2+/-23.1 nm (L200), and 68.6+/-6.5 nm (L70), respectively. For each size, dexamethasone concentration and dexamethasone/lipid molar ratio in dexamethasone-liposome suspension were 1 mg dexamethasone mL-1 and 0.134 mol dexamethasone mol-1 total lipids, respectively. The zeta potential was approximately -70 mV for all sizes. Dexamethasone-liposomes or free dexamethasone were added to the macrophages in the presence of oxidized low density lipoprotein (oxLDL) and foam cells, and then incubated at 37 degrees C. The uptake amount of dexamethasone by the macrophages and foam cells after a 24-h incubation was L500>L200>free dexamethasone>L70. The macrophages in the presence of oxLDL and foam cells were incubated with dexamethasone-liposomes or free dexamethasone for 24 h at 37 degrees C to evaluate the inhibitory effect on the cellular cholesterol ester accumulation. The cellular cholesterol ester level in the macrophages treated with oxLDL was significantly increased compared with that in macrophages without additives. L500, L200 and free dexamethasone significantly inhibited this cholesterol ester accumulation. L500, L200 and free dexamethasone also significantly reduced cellular cholesterol ester accumulation in foam cells. In addition, the relationship between the area under the uptake amount of dexamethasone-time curve (AUC) and the inhibition rate of cholesterol ester accumulation in macrophages and foam cells was evaluated. The inhibition rate of cholesterol ester accumulation (%) was related to the AUC in both types of cell. These results suggested that dexamethasone-liposomes would be a useful approach to the development of a novel drug delivery system for atherosclerotic therapy. Furthermore, the prediction of the inhibitory effect of dexamethasone on cellular cholesterol ester accumulation may become possible by using the results of this study.

2-Aminopurine Inhibits Lipid Accumulation Induced by Apolipoprotein E-Deficient Lipoprotein in Macrophages: Potential Role of Eukaryotic Initiation Factor-2α Phosphorylation in Foam Cell Formation

We previously reported that apolipoprotein (Apo) E-deficient, ApoB48-containing (E^–/B48) lipoproteins inhibited expression of lysosomal hydrolase and transformed mouse peritoneal macrophages (MPMs) into foam cells. The present study examined the effect of 2-aminopurine (2-AP), an inhibitor of eukaryotic initiation factor (eIF)-2α phosphorylation, on E^–/B48 lipoprotein-induced changes in gene expression and foam cell formation. Our data demonstrated that E^–/B48 lipoproteins enhanced phosphorylation of eIF-2α in macrophages. Incubation of MPMs with E^–/B48 lipoproteins inhibited the translation efficiency of mRNAs encoding lysosomal acid lipase, cathepsin B, and cation-dependent mannose 6 phosphate receptor, with a parallel reduction in the level of these proteins. Addition of 2-AP to the culture media alleviated the suppressive effect of E^–/B48 lipoproteins on lysosomal hydrolase mRNA translation, increased macrophage degradation of E^–/B48 lipoproteins, and inhibited foam cell formation. Transfection of MPMs with a nonphosphorylatable eIF-2α mutant also attenuated the suppressive effect of E^–/B48 lipoproteins on expression of lysosomal acid lipase, associated with a reduced accumulation of cellular cholesterol esters. This is the first demonstration that ApoE-deficient lipoproteins inhibit lysosomal hydrolase synthesis and transform macrophages into foam cells through induction of eIF-2α phosphorylation.

Stable overexpression of human macrophage cholesteryl ester hydrolase results in enhanced free cholesterol efflux from human THP1 macrophages

Reduction of the lipid burden of atherosclerotic lesion-associated macrophage foam cells is a logical strategy to reduce the plaque volume. Since extracellular cholesterol acceptor-mediated cholesterol efflux is the only recognized mechanism of cholesterol removal from foam cells and this process is rate limited at the level of intracellular cholesterol ester hydrolysis, a reaction catalyzed by neutral cholesteryl ester hydrolase (CEH), we examined the hypothesis that CEH overexpression in the human macrophage monocyte/macrophage cell line THP1 results in increased cholesterol efflux, as well as decreased cellular cholesterol ester accumulation. We generated THP1-CEH cells with stable integration of human macrophage CEH cDNA driven by the cytomegalovirus promoter. Compared with wild-type THP1 cells (THP1-WT), THP1-CEH cells showed increased CEH mRNA expression and increased CEH activity. Efflux of free or unesterified cholesterol by acetylated LDL-loaded THP1-CEH cells to ApoA-I by an ABCA1-dependent pathway or to HDL by an ABCG1-dependent pathway was significantly higher than that in THP1-WT cells. In addition, THP1-CEH cells accumulated significantly lower amount of esterified cholesterol. CEH overexpression, therefore, not only enhances cholesterol efflux but also reduces cellular accumulation of cholesteryl esters. Taken together, these data provide evidence for evaluating CEH expression in human macrophages as a potential target for attenuation of foam cell formation and regression of atherosclerotic plaques.

Aortic drug delivery of dexamethasone palmitate incorporated into lipid microspheres and its antiatherosclerotic effect in atherogenic mice

In order to confirm the efficacy of dexamethasone (DXM) palmitate incorporated into lipid microspheres (d-lipo) on atherosclerosis, the aortic drug delivery by d-lipo and its antiatherosclerotic effect were investigated. In an in vitro uptake experiment, d-lipo or DXM was added to macrophages and foam cells, and then incubated for 1, 4, 8 and 24 h at 37°C. The uptake of drug by these cells after addition of d-lipo was higher than that of DXM at each time point. In an in vitro pharmacological experiment, the macrophages and foam cells were incubated with d-lipo or DXM for 24 h at 37°C. The inhibitory effect of d-lipo on cellular cholesterol ester (CE) accumulation in these cells was significantly more potent than that of DXM. In an in vivo pharmacokinetic experiment, d-lipo or DXM was intravenously administered to atherogenic mice, and then aorta was collected at 1, 8, and 24 h after administration. The aortic drug concentration after administration of d-lipo to atherogenic mice was higher than that of DXM at each time point. In an in vivo pharmacological experiment, d-lipo or DXM was intravenously administered to atherogenic mice once a week for 7 weeks. The inhibitory effect of d-lipo on the aortic CE accumulation in atherogenic mice was significantly more potent than that of DXM. These findings suggest that efficient drug delivery to the atherosclerotic lesions by d-lipo produces an excellent antiatherosclerotic effect at a lower dose. Therefore, d-lipo may be useful for the development of drug delivery systems for atherosclerotic therapy.

Analysis of cholesterol ester accumulation in macrophages by the use of digital imaging fluorescence microscopy

Low density lipoprotein (LDL) induced accumulation of cholesterol esters was analyzed by the digital imaging fluorescence microscopy (DIFM) in murine tumor macrophages. To analyze cholesterol ester accumulation, P388D 1 macrophages were incubated with increasing quantities of unmodified or acetylated human LDL, washed, and live stained with a lipophylic fluorescent dye Nile Red. The increase in fluorescence intensity was quantitatively determined by the interactive laser cytometer (ACAS 470) and compared with the accumulation of cellular cholesterol esters determined by the gas liquid chromatography. Correlation between the two methods was highly significant ( r > 0.9, P < 0.001). A good agreement between the two methods was also found in terms of sensitivity and reproducibility. With the use of 589 nm narrowband interference filter in the light path of emitted light the intensity of fluorescence correlated well with cellular cholesterol ester content even in the presence of relatively high concentrations of triglycerides. Therefore, digital imaging fluorescence microscopy appears to be a reliable method for quantification of cholesterol ester accumulation at the single cell level offering new possibilities of studying interactions between cells and cholesterol ester rich lipoproteins.

Hyperlipoproteinaemia and xanthomatosis as a model of cholesterol ester accumulation.

AbstractA local event which occurs after damage of a blood vessel can be the start of cellular cholesterol ester accumulation. Thrombocytes and macrophages will adhere to the endothelial wall. Subsequently lipoproteins and macrophages permeate this endothelial wall. The perivascularly arranged macrophages will internalize the “modified lipoproteins” and eventually cholesterol ester accumulation will take place. This cholesterol ester accumulation can also occur in smooth muscle cells. The reversibility of the accumulation depends on the lipoprotein levels and on the physico‐chemical characteristics of the accumulated cholesterol (esters). This phenomenon takes place in the formation of xanthomas as well as in atherogenesis.

Prevention of the hyperlipidemic serum or LDL-induced cellular cholesterol ester accumulation by 22-hydroxycholesterol and its analogue

Incubation of monkey arterial smooth muscle cells with hyperlipidemic serum or low-density lipoproteins (LDL) produces intracellular cholesterol ester accumulation. Increased esterification of free cholesterol within the cell may account for this effect. To examine such a possibility, oxygenated sterols were used to block cholesterol esterification. The increased esterification of free cholesterol by smooth muscle cells and human skin fibroblasts, through their exposure to hyperlipidemic lipoproteins, was inhibited by 22-hydroxycholesterol and its analogue, SC-32561 (22-hydroxy-25-fluorocholesterol). The hyperlipidemic LDL-stimulated elevation in the cholesterol ester content of the smooth muscle cells was also prevented by these sterols. This reduction in cellular cholesterol ester did not coincide with an increase in free cholesterol. 22-Hydroxycholesterol also blocked the stimulation of the esterification of cholesterol due to 25-hydroxycholesterol. In the absence of lipoproteins, 22-hydroxycholesterol and SC-32561 had a minor effect on the incorporation of [ 14C]oleate into cholesterol esters, and efficiently reduced sterol synthesis in fibroblasts and smooth muscle cells. 22-Hydroxycholesterol and SC-32561 had the additional effect of lowering the number of cellurface LDL receptors to a greater extent than did hyperlipidemic LDL. The presence of 22-hydroxycholesterol did not alter the interaction of normal LDL with the receptor. Oxygenated sterols recovered in the cell represented 4–21% of the total sterol content. The level of intracellular oxygenated sterols was significantly reduced by the presence of lipoproteins in the culture media. Due to the multiple effects of the oxysterols, they were not effective as tools in determining the contribution of acyl-coenzyme A:cholesterol acyltransferase enzyme activity to the intracellular pool of cholesterol esters. These results indicated that 22-hydroxycholesterol and SC-32561 effectively blocked the hyperlipidemic LDL-stimulated increase in smooth muscle cell cholesterol ester content by lowering cholesterol esterification, reducing cholesterol synthesis and down-regulating LDL cell-surface receptors.

Interaction of low density lipoproteins from normal and hyperlipemic rhesus monkeys with arterial smooth muscle cells in culture

Monkey arterial smooth muscle cell binding, incorporation and degradation of low density lipoproteins (LDL) from normal or hyperlipemic rhesus monkey plasma were examined by labeling lipoproteins with 125I. Specific and nonspecific binding of both lipoproteins occurred. Although the dissociation constant for the normal LDL was twice as high as for hyperlipemic LDL, indicating a higher binding affinity for hyperlipemic LDL, the maximal binding capacity of the smooth muscle cells for normal [ 125I]LDL was 2-fold higher than for hyperlipemic [ 125I]LDL. In competition experiments where the two types of LDL competed with normal [ 125I]LDL for binding to smooth muscle cells, LDL isolated from hyperlipemic plasma was a more effective competitor than normal LDL. Receptors for normal LDL were reduced to a greater extent by preincubation with hyperlipemic LDL than by the same protein concentration of normal LDL. Under conditions where nonspecific uptake of lipoproteins would occur predominantly, the cells showed higher incorporation and degradation of normal LDL than hyperlipemic LDL. The corresponding cellular cholesterol ester levels showed an inverse pattern, with higher accumulation of cholesterol ester in the cells grown in hyperlipemic LDL. The results suggest that binding and incorporation of LDL by specific receptors or through the nonspecific pathway play a role in the changes of cellular cholesterol content but cannot totally account for the enhanced accumulation of cellular cholesterol esters produced by hyperlipemic monkey LDL.

Source of the cholesterol ester accumulated in monkey arterial smooth muscle cells grown in hyperlipemic serum.

HomeCirculation ResearchVol. 45, No. 6Source of the cholesterol ester accumulated in monkey arterial smooth muscle cells grown in hyperlipemic serum. Free AccessAbstractPDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessAbstractPDF/EPUBSource of the cholesterol ester accumulated in monkey arterial smooth muscle cells grown in hyperlipemic serum. S R Bates S R BatesS R Bates Search for more papers by this author Originally published1 Dec 1979https://doi.org/10.1161/01.RES.45.6.821Circulation Research. 1979;45:821–828 Previous Back to top Next FiguresReferencesRelatedDetailsCited By Minor L, Mahlberg F, Gray Jerome W, Lewis J, Rothblat G and Glick J (1991) Lysosomal hydrolysis of lipids in a cell culture model of smooth muscle foam cells, Experimental and Molecular Pathology, 10.1016/0014-4800(91)90028-V, 54:2, (159-171), Online publication date: 1-Apr-1991. Orekhov A, Tertov V, Kudryashov S and Smirnov V (1990) Triggerlike stimulation of cholesterol accumulation and DNA and extracellular matrix synthesis induced by atherogenic serum or low density lipoprotein in cultured cells., Circulation Research, 66:2, (311-320), Online publication date: 1-Feb-1990.Slotte J, Chait A and Bierman E (1988) Cholesterol accumulation in aortic smooth muscle cells exposed to low density lipoproteins. Contribution of free cholesterol transfer., Arteriosclerosis: An Official Journal of the American Heart Association, Inc., 8:6, (750-758), Online publication date: 1-Nov-1988.Stein O, Halperin G and Stein Y (1987) Long-term effects of verapamil on aortic smooth muscle cells cultured in the presence of hypercholesterolemic serum., Arteriosclerosis: An Official Journal of the American Heart Association, Inc., 7:6, (585-592), Online publication date: 1-Nov-1987. Davis H, Glagov S and Zarins C (1985) Role of acid lipase in cholesteryl ester accumulation during atherogenesis, Atherosclerosis, 10.1016/0021-9150(85)90099-1, 55:2, (205-215), Online publication date: 1-May-1985. Bates S, Jett C and Miller J (1983) Prevention of the hyperlipidemic serum or LDL-induced cellular cholesterol ester accumulation by 22-hydroxycholesterol and its analogue, Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 10.1016/0005-2760(83)90050-4, 753:3, (281-293), Online publication date: 1-Oct-1983. Fielding C and Fielding P (1982) Cholesterol Transport Between Cells and Body Fluids: Role of Plasma Lipoproteins and the Plasma Cholesterol Esterification System, Medical Clinics of North America, 10.1016/S0025-7125(16)31425-0, 66:2, (363-373), Online publication date: 1-Mar-1982. Wissler R, Fischer-Dzoga K, Bates S and Chen R (1981) Arterial Smooth Muscle Cells in Tissue Culture Structure and Function of the Circulation, 10.1007/978-1-4615-7927-4_8, (427-474), . December 1, 1979Vol 45, Issue 6 Advertisement Article InformationMetrics Copyright © 1979 by American Heart Associationhttps://doi.org/10.1161/01.RES.45.6.821 Originally publishedDecember 1, 1979 PDF download Advertisement

Cellular cholesterol ester accumulation induced by free cholesterol-rich lipid dispersions.

The influence of lipoprotein composition on free cholesterol (RC) esterification and accumulation of esterified cholesterol (EC) was studied in cells of Fu5AH rat hepatoma exposed to culture media supplemented with (FC/P) ranging from 0.6 to 2.8. In the presence of normal human serum, FC-lecithin dispersions witb a FC/P greater than one stimulated both the esterification of FC and the accumulation of cellular EC. Conversely, dispersions with FC/P values of approximately one had no effect on either FC esterification or the accumulation of EC when compared to cells grown in the absence of lipid dispersions. No stimulation of cellular response was obtained when FC-rich dispersions were added to cells in the absence of serum; however, stimulation was observed when cells were exposed to isolated human serum lipoproteins (very low density, low density, and high density). With each lipoprotein, FC-lecithin dispersions with FC/P values less than one inhibited cholesteryl ester accumulation, FC-rich dispersions stimulated, and dispersions with FC/P values of approximately one had an effect equivalent to that of isolated lipproteins alone. These studies extablish that cellular FC esterification and EC content are not influenced solely by the FC concentration of medium, but rather respond to the ratio of FC to phospholipidl These studies also suggest that serum lipoproteins participate in the transfer of FC carried by FC-rich lecithin dispersions to cells.