scholarly journals Macrophage cholesteryl ester hydrolases and hormone-sensitive lipase prefer specifically oxidized cholesteryl esters as substrates over their non-oxidized counterparts

2000 ◽  
Vol 352 (1) ◽  
pp. 125-133 ◽  
Author(s):  
Jutta BELKNER ◽  
Hannelore STENDER ◽  
Hermann-Georg HOLZHÜTTER ◽  
Cecilia HOLM ◽  
Hartmut KÜHN
Keyword(s):  
Cholesteryl Ester ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Oxidative Modification ◽  
Hormone Sensitive Lipase ◽  
Cholesteryl Esters ◽  
Uptake Mechanism ◽  
Hormone Sensitive

The oxidative modification of low-density lipoprotein (LDL) has been implicated as a pro-atherogenic process in the pathogenesis of atherosclerosis. Macrophages rapidly take up oxidized LDL via scavenger-receptor-mediated pathways and thereby develop into lipid-laden foam cells. The uptake mechanism has been studied extensively and several types of scavenger receptors have been identified. In contrast, the intracellular fate of oxidized LDL lipids is less well investigated. We studied the degradation of specifically oxidized cholesteryl esters by murine macrophages using an HPLC-based assay, and found that oxidized substrates are hydrolysed preferentially from a 1:1 molar mixture of oxidized and non-oxidized cholesteryl esters. This effect was observed at both neutral and acidic pH. Similar results were obtained with lysates of human monocytes and with pure recombinant human hormone-sensitive lipase. These data suggest that the intracellular oxidation of cholesteryl esters may facilitate intracellular cholesteryl ester hydrolysis, and thus may represent an anti-atherogenic process.

The LDL receptor is not necessary for acute adrenal steroidogenesis in mouse adrenocortical cells

2007 ◽  
Vol 292 (2) ◽  
pp. E408-E412 ◽  
Author(s):  
Fredric B. Kraemer ◽  
Wen-Jun Shen ◽  
Shailja Patel ◽  
Jun-ichi Osuga ◽  
Shun Ishibashi ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Vital Role ◽  
Hormone Sensitive Lipase ◽  
Cholesteryl Esters ◽  
Selective Uptake ◽  
Adrenal Cells ◽  
Adrenal Steroidogenesis ◽  
Hormone Sensitive

Steroid hormones are synthesized using cholesterol as precursor. To determine the functional importance of the low density lipoprotein (LDL) receptor and hormone-sensitive lipase (HSL) in adrenal steroidogenesis, adrenal cells were isolated from control, HSL−/−, LDLR−/−, and double LDLR/HSL−/− mice. The endocytic and selective uptake of apolipoprotein E-free human high density lipoprotein (HDL)-derived cholesteryl esters did not differ among the mice, with selective uptake accounting for >97% of uptake. In contrast, endocytic uptake of either human LDL- or rat HDL-derived cholesteryl esters was reduced 80–85% in LDLR−/− and double- LDLR/HSL−/− mice. There were no differences in the selective uptake of either human LDL- or rat HDL-derived cholesteryl esters among the mice. Maximum corticosterone production induced by ACTH or dibutyryl cyclic AMP and lipoproteins was not altered in LDLR−/− mice but was reduced 80–90% in HSL−/− mice. Maximum corticosterone production was identical in HSL−/− and double- LDLR/HSL−/− mice. These findings suggest that, although the LDL receptor is responsible for endocytic delivery of cholesteryl esters from LDL and rat HDL to mouse adrenal cells, it appears to play a negligible role in the delivery of cholesterol for acute adrenal steroidogenesis in the mouse. In contrast, HSL occupies a vital role in adrenal steroidogenesis because of its link to utilization of selectively delivered cholesteryl esters from lipoproteins.

scholarly journals Morphological characterization of the cholesteryl ester cycle in cultured mouse macrophage foam cells.

1983 ◽  
Vol 97 (4) ◽  
pp. 1156-1168 ◽  
Author(s):  
D J McGookey ◽  
R G Anderson
Keyword(s):  
Cholesteryl Ester ◽  
Lipase Activity ◽  
Lipid Droplets ◽  
Free Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
The Body ◽  
Cyclic Process ◽  
Low Density ◽  
Cholesteryl Esters

Mouse peritoneal macrophages can be induced to accumulate cholesteryl esters by incubating them in the presence of acetylated low density lipoprotein. The cholesteryl esters are sequestered in neutral lipid droplets that remain in the cell even when the acetylated low density lipoprotein is removed from the culture media. Previous biochemical studies have determined that the cholesterol component of cholesteryl ester droplets constantly turns over with a half time of 24 h by a cyclic process of de-esterification and re-esterification. We have used morphologic techniques to determine the spatial relationship of cholesteryl ester, free cholesterol, and lipase activity during normal turnover and when turnover is disrupted. Lipid droplets were surrounded by numerous 7.5-10.0-nm filaments; moreover, at focal sites on the margin of each droplet there were whorles of concentrically arranged membrane that penetrated the matrix. Histochemically detectable lipase activity was associated with these stacks of membrane. Using filipin as a light and electron microscopic probe for free cholesterol, we determined that a pool of free cholesterol was associated with each lipid droplet. Following incubation in the presence of the exogenous cholesterol acceptor, high density lipoprotein, the cholesteryl ester droplets disappeared and were replaced with lipid droplets of a different lipid composition. Inhibition of cholesterol esterification caused cholesteryl ester droplets to disappear and free cholesterol to accumulate in numerous myelin-like structures in the body of the cell.

scholarly journals Treatment of macrophages with oxidized low-density lipoprotein increases their intracellular glutathione content

1991 ◽  
Vol 278 (2) ◽  
pp. 429-434 ◽  
Author(s):  
V M Darley-Usmar ◽  
A Severn ◽  
V J O'Leary ◽  
M Rogers
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Human Monocyte ◽  
Cell Types ◽  
Oxidative Modification ◽  
Glutathione Depletion ◽  
Lipid Phase ◽  
Low Density ◽  
Oxidized Low Density Lipoprotein

Macrophages derived from the human monocyte cell line THP-1 or isolated from the peritoneum of C3H/HEJ mice were incubated with oxidized low-density lipoprotein (LDL) and the total glutathione content (oxidized plus reduced) was measured. An initial depletion of glutathione was followed by an increase, such that after a period of 24 h the glutathione content has approximately doubled. This response required the oxidation of the lipid phase of the LDL molecule, since both native LDL and acetylated LDL had little effect on glutathione levels. The response of the cells to oxidized LDL was dependent on the extent of oxidative modification of the protein. It was also found that 4-hydroxynonenal had a similar effect on THP-1 cells, and we suggest that this or other aldehydes present in oxidized LDL causes the induction of glutathione synthesis in response to an initial oxidative stress and consequent glutathione depletion. In addition, we found that both cell types possess transferases and peroxidases capable of detoxifying aldehydes and peroxides. However, treatment of cells with oxidized LDL or 4-hydroxynonenal for a period of 24 h had no effect on the activities of these enzymes.

The human breast carcinoma cell line HBL-100 acquires exogenous cholesterol from high-density lipoprotein via CLA-1 (CD-36 and LIMPII analogous 1)-mediated selective cholesteryl ester uptake

2000 ◽  
Vol 349 (2) ◽  
pp. 559-566 ◽  
Author(s):  
Pirkko J. PUSSINEN ◽  
Barbara KARTEN ◽  
Andrea WINTERSPERGER ◽  
Helga REICHER ◽  
Mark MCLEAN ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
High Density Lipoprotein ◽  
Cholesteryl Ester ◽  
Density Lipoprotein ◽  
High Density ◽  
Hormone Sensitive Lipase ◽  
Potential Candidate ◽  
Selective Uptake ◽  
Exogenous Cholesterol ◽  
Hormone Sensitive

Aberrant cell proliferation is one of the hallmarks of carcinogenesis, and cholesterol is thought to play an important role during cell proliferation and cancer progression. In the present study we examined the pathways that could contribute to enhanced proliferation rates of HBL-100 cells in the presence of apolipoprotein E-depleted high-density lipoprotein subclass 3 (HDL3). When HBL-100 cells were cultivated in the presence of HDL3 (up to 200 μg/ml HDL3 protein), the growth rates and cellular cholesterol content were directly related to the concentrations of HDL3 in the culture medium. In principle, two pathways can contribute to cholesterol/cholesteryl ester (CE) uptake from HDL3, (i) holoparticle- and (ii) scavenger-receptor BI (SR-BI)-mediated selective uptake of HDL3-associated CEs. Northern- and Western-blot analyses revealed the expression of CLA-1 (CD-36 and LIMPII analogous 1), the human homologue of the rodent HDL receptor SR-BI. In line with CLA-1 expression, selective uptake of HDL3-CEs exceeded HDL3-holoparticle uptake between 12- and 58-fold. Competition experiments demonstrated that CLA-1 ligands (oxidized HDL, oxidized and acetylated low-density lipoprotein and phosphatidylserine) inhibited selective HDL3-CE uptake. In line with the ligand-binding specificity of CLA-1, phosphatidylcholine did not compete for selective HDL3-CE uptake. Selective uptake was regulated by the availability of exogenous cholesterol and PMA, but not by adrenocorticotropic hormone. HPLC analysis revealed that a substantial part of HDL3-CE, which was taken up selectively, was subjected to intracellular hydrolysis. A potential candidate facilitating extralysosomal hydrolysis of HDL3-CE is hormone-sensitive lipase, an enzyme which was identified in HBL-100 cells by Western blots. Our findings demonstrate that HBL-100 cells are able to acquire HDL-CEs via selective uptake. Subsequent partial hydrolysis by hormone-sensitive lipase could provide ‘free’ cholesterol that is available for the synthesis of cellular membranes during proliferation of cancer cells.

scholarly journals Endogenously produced lipoprotein lipase enhances the binding and cell association of native, mildly oxidized and moderately oxidized low-density lipoprotein in mouse peritoneal macrophages

1999 ◽  
Vol 343 (2) ◽  
pp. 347-353 ◽  
Author(s):  
Xiaosong WANG ◽  
Joachim GREILBERGER ◽  
Sanja LEVAK-FRANK ◽  
Robert ZIMMERMANN ◽  
Rudolf ZECHNER ◽  
...  
Keyword(s):  
Lipoprotein Lipase ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Relative Proportion ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Peritoneal Macrophages ◽  
Low Density ◽  
Cell Binding ◽  
Mouse Peritoneal Macrophages

It has been well established that purified lipoprotein lipase (LPL) can facilitate the cellular uptake of various native and modified lipoproteins when added exogenously to macrophages. Because activated macrophages express LPL endogenously, it was the aim of this study to investigate the effect of macrophage-produced LPL on the uptake of native low-density lipoprotein (LDL) and LDL that has been modified to various degrees by Cu2+-mediated oxidation. Cell binding and uptake of Eu3+-labelled native and oxidized LDL was determined in mouse peritoneal macrophages (MPM) from normal mice and induced mutant mice that lack LPL expression in MPM. We found that LPL expressed by MPM was able to increase cell binding and association of native LDL (by 121% and 101% respectively), mildly oxidized LDL (by 47% and 43%) and moderately oxidized LDL (by 30% and 22%). With increased levels of lipoprotein oxidation, the relative proportion of LPL-mediated LDL uptake decreased. This decrease was not due to weakened binding of LPL to oxidized LDL. The drastically increased uptake of highly oxidized LDL in MPM by scavenger-receptor-mediated pathways might dominate the simultaneous exogenous or endogenous LPL-mediated uptake of this lipoprotein. Competition experiments with positively charged poly(amino acids) furthermore suggested that histidine, arginine and lysine residues in LPL are important for the interaction between LDL and LPL. Our results imply that physiological levels of LPL produced by macrophages facilitate the uptake of native LDL as well as mildly and moderately oxidized LDL. This process might, in the micro-environment of arteries, contribute to the accumulation of macrophage lipids and the formation of foam cells.

scholarly journals 3-Nitrotyrosine in the proteins of human plasma determined by an ELISA method

1998 ◽  
Vol 330 (2) ◽  
pp. 795-801 ◽  
Author(s):  
Jamshad KHAN ◽  
M. David BRENNAN ◽  
Nicholas BRADLEY ◽  
Beirong GAO ◽  
Richard BRUCKDORFER ◽  
...  
Keyword(s):  
Plasma Proteins ◽  
Biological Fluids ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Oxidative Modification ◽  
Elisa Method ◽  
Tyrosine Residues ◽  
Inflammatory Conditions ◽  
Ic50 Values

The modification of tyrosine residues in proteins to 3-nitrotyrosine by peroxynitrite or other potential nitrating agents has been detected in biological systems that are subject to oxidative stress. A convenient semi-quantitative method has been developed to assay nitrated proteins in biological fluids and homogenates using a competitive ELISA developed in our laboratory. This assay selectivity detected 3-nitro-L-tyrosine residues in a variety of peroxynitrite-treated proteins (BSA, human serum albumin (HSA), α1-antiprotease inhibitor, pepsinogen and fibrinogen) and also in a nitrated peptide, but had a low affinity for free 3-nitro-L-tyrosine and 3-chloro-L-tyrosine. The IC50 values for the inhibition of antibody binding by different nitrated proteins were in the range 5-100 nM, suggesting that the antibody discriminated between nitrotyrosine residues in different environments. The presence of nitrotyrosine in plasma proteins was detected by Western blot analysis and quantified by the ELISA. A concentration of 0.12±0.01 μM nitro-BSA equivalents was measured in the proteins of normal plasma which was increased in peroxynitrite-treated plasma and was elevated in inflammatory conditions. HSA and low-density lipoprotein (LDL) isolated from plasma contained 0.085±0.04 and 0.03±0.006 nmol nitro-BSA equivalents/mg protein, respectively. Comparison of the level of nitration in peroxynitrite-treated HSA and LDL in the presence and absence of plasma indicates that nitration and presumably oxidation is inhibited by plasma antioxidants. The presence of nitrotyrosine in LDL is consistent with previous reports implicating peroxynitrite in the oxidative modification of lipoproteins and the presence of a low concentration of oxidized LDL in the blood.

Acute and long-term effects of low-density lipoprotein (LDL)-apheresis on oxidative damage to LDL and reducing capacity of erythrocytes in patients with severe familial hypercholesterolaemia

2001 ◽  
Vol 100 (2) ◽  
pp. 191-198 ◽  
Author(s):  
C. STEFANUTTI ◽  
S. DI GIACOMO ◽  
A. VIVENZIO ◽  
G. C. ISACCHI ◽  
R. MASELLA ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Fatty Acid Content ◽  
Density Lipoprotein ◽  
Acute Effect ◽  
Oxidative Modification ◽  
Conjugate Diene ◽  
Ldl Apheresis ◽  
Conjugate Diene Formation

Several studies have suggested that the oxidative modification of low-density lipoprotein (LDL) could play a key role in the early stages of atherosclerosis. The susceptibility of LDL to oxidation has been found to be greater in patients with coronary heart disease. Familial hypercholesterolaemia (FH) is a powerful clinical model in which to study the predictive role of LDL in atherogenesis. LDL-apheresis is a treatment that is able to decrease lipid levels in plasma. This study was aimed at investigating the reducing capacity of erythrocytes and the in vitro susceptibility to oxidation of LDL isolated from patients with homozygous, heterozygous and double-heterozygous FH, who were treated fortnightly with LDL-apheresis or left untreated. In 14 FH patients, at baseline and after a cycle of treatment, the susceptibility of LDL to oxidative modification was analysed by studying the kinetics of conjugate diene formation. Plasma hydroperoxides, polyunsaturated fatty acid content, LDL electrophoretic mobility on agarose, the titre of auto-antibodies against oxidized LDL and serum paraoxonase activity were also measured. Furthermore, in order to evaluate a potential relationship between LDL oxidation and redox status, erythrocyte GSH and ATP levels were determined in FH patients treated regularly or never treated previously by LDL-apheresis. Unlike in the control group, the oxidative status of LDL in all FH patients was modified by LDL-apheresis, as revealed by the higher negative charge and the increase in levels of hydroperoxides and antibodies against oxidized LDL in the plasma. Our findings suggest both an acute effect and a long-term effect of LDL-apheresis in FH patients treated with dextran sulphate cellulose apheresis. The acute effect of LDL-apheresis on the susceptibility to oxidation of plasma and LDL was demonstrated by significant decreases in plasma hydroperoxide content, total LDL concentration and polyunsaturated fatty acid content. The increased resistance of LDL to oxidation was shown by prolongation of the lag time (P < 0.05) in samples after a single cycle of treatment. The long-term effect of LDL-apheresis was demonstrated by the comparable values for lag phases (obtained from the kinetics of conjugate diene formation) in patients under active treatment and controls. Compared with healthy controls and untreated patients, the erythrocyte GSH content was significantly higher (P⩽ 0.001) in the treated group, suggesting the activation of reducing mechanisms.

scholarly journals GLYCATED LOW-DENSITY LIPOPROTEIN IN DIABETIC AND NON-DIABETIC PATIENTS

2019 ◽  
pp. 123-126
Author(s):  
OMAR ABDULWAHID AL-ANI ◽  
ABDURRAHMAN AL-BAZZAZ
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Oxidative Modification ◽  
Diabetic Group ◽  
Enzyme Linked Immunosorbent Assay ◽  
Diabetic Patients ◽  
Low Density ◽  
Serum Samples ◽  
Diabetes Center

Objective: The importance of measuring the blood level of modified low-density lipoprotein (LDL) molecules is an effective method of identifying people at risk of coronary atherosclerosis; this is because, in the early stages of atherosclerosis, lipolysis and oxidative modification have a role in promoting the uptake of these lipids through macrophages; therefore, this research aims to measure the level of glycated LDL (Gly-LDL) in the blood and its association with metabolic parameters of diabetic patients (diabetes mellitus) and non-diabetic (hyperlipidemia). Methods: At a University Diabetes Center in Riyadh, we using routine automatic analysis methods, fasting serum samples were analyzed for 31 patients with Type-2 diabetes and 31 non-diabetic patients for LDL, high-density lipoprotein (HDL), total cholesterol, glycated hemoglobin, glucose, and triglycerides (TG), and using enzyme-linked immunosorbent assay to analyze Gly-LDL for the same sample. Results: The level of serum Gly-LDL in non-diabetic was higher than in diabetic patients (p=0.037). Gly-LDL level correlated significantly with LDL in the diabetic group (p=0.035) and was insignificant with other parameters; moreover, it is significantly correlated with HDL (p=0.048), TG (p=0.035), and very LDL (p=0.03) in the non-diabetic group and insignificant with other parameters. Conclusion: Measuring rates of Gly-LDL can be used in the early detection of cardiovascular disease, especially in people with diabetes, as they are more susceptible to modified and oxidized LDL.

scholarly journals Pro-oxidant and cytotoxic effects of circulating heme

Blood ◽  
2002 ◽  
Vol 100 (3) ◽  
pp. 879-887 ◽  
Author(s):  
Viktória Jeney ◽  
József Balla ◽  
Akihiro Yachie ◽  
Zsuzsa Varga ◽  
Gregory M. Vercellotti ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Oxidative Modification ◽  
Heme Oxygenase 1 ◽  
Lipid Hydroperoxides ◽  
Human Patient ◽  
Free Heme ◽  
The Central Nervous System ◽  
Deficient Child

Abstract Numerous pathologies may involve toxic side effects of free heme and heme-derived iron. Deficiency of the heme-catabolizing enzyme, heme oxygenase-1 (HO-1), in both a human patient and transgenic knockout mice leads to an abundance of circulating heme and damage to vascular endothelium. Although heme can be directly cytotoxic, the present investigations examine the possibility that hemoglobin-derived heme and iron might be indirectly toxic through the generation of oxidized forms of low-density lipoprotein (LDL). In support, hemoglobin in plasma, when oxidized to methemoglobin by oxidants such as leukocyte-derived reactive oxygen, causes oxidative modification of LDL. Heme, released from methemoglobin, catalyzes the oxidation of LDL, which in turn induces endothelial cytolysis primarily caused by lipid hydroperoxides. Exposure of endothelium to sublethal concentrations of this oxidized LDL leads to induction of both HO-1 and ferritin. Similar endothelial cytotoxicity was caused by LDL isolated from plasma of an HO-1–deficient child. Spectral analysis of the child's plasma revealed a substantial oxidation of plasma hemoglobin to methemoglobin. Iron accumulated in the HO-1–deficient child's LDL and several independent assays revealed oxidative modification of the LDL. We conclude that hemoglobin, when oxidized in plasma, can be indirectly cytotoxic through the generation of oxidized LDL by released heme and that, in response, the intracellular defense—HO-1 and ferritin—is induced. These results may be relevant to a variety of disorders—such as renal failure associated with intravascular hemolysis, hemorrhagic injury to the central nervous system, and, perhaps, atherogenesis—in which hemoglobin-derived heme may promote the formation of fatty acid hydroperoxides.

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