Scavenger Receptors Class A-I/II and CD36 Are the Principal Receptors Responsible for the Uptake of Modified Low Density Lipoprotein Leading to Lipid Loading in Macrophages

Modification of low density lipoprotein (LDL) can result in the avid uptake of these lipoproteins via a family of macrophage transmembrane proteins referred to as scavenger receptors (SRs). The genetic inactivation of either of two SR family members, SR-A or CD36, has been shown previously to reduce oxidized LDL uptakein vitroand atherosclerotic lesions in mice. Several other SRs are reported to bind modified LDL, but their contribution to macrophage lipid accumulation is uncertain. We generated mice lacking both SR-A and CD36 to determine their combined impact on macrophage lipid uptake and to assess the contribution of other SRs to this process. We show that SR-A and CD36 account for 75–90% of degradation of LDL modified by acetylation or oxidation. Cholesteryl ester derived from modified lipoproteins fails to accumulate in macrophages taken from the double null mice, as assessed by histochemistry and gas chromatography-mass spectrometry. These results demonstrate that SR-A and CD36 are responsible for the preponderance of modified LDL uptake in macrophages and that other scavenger receptors do not compensate for their absence.

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Development of Capture Assays for Different Modifications of Human Low-Density Lipoprotein

Clinical and Diagnostic Laboratory Immunology ◽

10.1128/cdli.12.1.68-75.2005 ◽

2005 ◽

Vol 12 (1) ◽

pp. 68-75 ◽

Cited By ~ 27

Author(s):

Gabriel Virella ◽

M. Brooks Derrick ◽

Virginia Pate ◽

Charlyne Chassereau ◽

Suzanne R. Thorpe ◽

...

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Gas Chromatography Mass Spectrometry ◽

Low Density ◽

Modified Ldl ◽

Capture Assay ◽

Carboxymethyl Lysine

ABSTRACT Antibodies to malondialdehyde (MDA)-modified low-density lipoprotein (LDL), copper-oxidized LDL (oxLDL), N ε(carboxymethyl) lysine (CML)-modified LDL, and advanced glycosylation end product (AGE)-modified LDL were obtained by immunization of rabbits with in vitro-modified human LDL preparations. After absorption of apolipoprotein B (ApoB) antibodies, we obtained antibodies specific for each modified lipoprotein with unique patterns of reactivity. MDA-LDL antibodies reacted strongly with MDA-LDL and also with oxLDL. CML-LDL antibodies reacted strongly with CML-LDL and also AGE-LDL. oxLDL antibodies reacted with oxLDL but not with MDA-LDL, and AGE-LDL antibodies reacted with AGE-LDL but not with CML-LDL. Capture assays were set with each antiserum, and we tested their ability to capture ApoB-containing lipoproteins isolated from precipitated immune complexes (IC) and from the supernatants remaining after IC precipitation (free lipoproteins). All antibodies captured lipoproteins contained in IC more effectively than free lipoproteins. Analysis of lipoproteins in IC by gas chromatography-mass spectrometry showed that they contained MDA-LDL and CML-LDL in significantly higher concentrations than free lipoproteins. A significant correlation (r = 0.706, P < 0.019) was obtained between the MDA concentrations determined by chemical analysis and by the capture assay of lipoproteins present in IC. In conclusion, we have developed capture assays for different LDL modifications in human ApoB/E lipoprotein-rich fractions isolated from precipitated IC. This approach obviates the interference of IC in previously reported modified LDL assays and allows determination of the degree of modification of LDL with greater accuracy.

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Gemfibrozil metabolite inhibits in vitro low-density lipoprotein (LDL) oxidation and diminishes cytotoxicity induced by oxidized LDL

Metabolism ◽

10.1016/s0026-0495(00)80012-8 ◽

2000 ◽

Vol 49 (4) ◽

pp. 479-485 ◽

Cited By ~ 4

Author(s):

Mitsunobu Kawamura ◽

Shigeru Miyazaki ◽

Tamio Teramoto ◽

Keiko Ashidate ◽

Hisako Thoda ◽

...

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Ldl Oxidation ◽

Low Density

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Oxidized low density lipoprotein inhibits the migration of aortic endothelial cells in vitro.

The Journal of Cell Biology ◽

10.1083/jcb.120.4.1011 ◽

1993 ◽

Vol 120 (4) ◽

pp. 1011-1019 ◽

Cited By ~ 78

Author(s):

G Murugesan ◽

G M Chisolm ◽

P L Fox

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Lipid Hydroperoxide ◽

Density Lipoprotein ◽

Low Density ◽

Dependent Manner ◽

Oxidized Low Density Lipoprotein ◽

Inhibitor Molecule ◽

Healing Response

Endothelial cell (EC) migration is a critical and initiating event in the formation of new blood vessels and in the repair of injured vessels. Compelling evidence suggests that oxidized low density lipoprotein (LDL) is present in atherosclerotic lesions, but its role in lesion formation has not been defined. We have examined the role of oxidized LDL in regulating the wound-healing response of vascular EC in vitro. Confluent cultures of bovine aortic EC were "wounded" with a razor, and migration was measured after 18 to 24 h as the number of cells moving into the wounded area and the mean distance of cells from the wound edge. Oxidized LDL markedly reduced migration in a concentration- and oxidation-dependent manner. Native LDL or oxidized LDL with a thiobarbituric acid (TBA) reactivity < 5 nmol malondialdehyde equivalents/mg cholesterol was not inhibitory; however, oxidized LDL with a TBA reactivity of 8-12 inhibited migration by 75-100%. Inhibition was half-maximal at 250-300 micrograms cholesterol/ml and nearly complete at 350-400 micrograms/ml. The antimigratory activity was not due to cell death since it was completely reversed 16 h after removal of the lipoprotein. The inhibitor molecule was shown to be a lipid; organic solvent extracts of oxidized LDL inhibited migration to nearly the same extent as the intact particle. When LDL was variably oxidized by dialysis against FeSO4 or CuSO4, or by UV irradiation, the inhibitory activity correlated with TBA reactivity and total lipid peroxides, but not with electrophoretic mobility or fluorescence (360 ex/430 em). This indicates that a lipid hydroperoxide may be the active species. These results suggest the possibility that oxidized LDL may limit the healing response of the endothelium after injury.

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The low-density-lipoprotein pathway of native and chemically modified low-density lipoproteins isolated from plasma incubated in vitro

Biochemical Journal ◽

10.1042/bj2240569 ◽

1984 ◽

Vol 224 (2) ◽

pp. 569-576 ◽

Cited By ~ 16

Author(s):

R Zechner ◽

H Dieplinger ◽

A Roscher ◽

G M Kostner

Keyword(s):

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Fold Increase ◽

Low Density ◽

Apo B ◽

Modified Ldl ◽

Apo E ◽

Lower Extent ◽

Ldl Catabolism

Normal fasting human plasma was incubated for 24 h at 37 degrees C in the presence or absence of lecithin:cholesterol acyltransferase (LCAT) inhibitors. The low-density lipoprotein (LDL) fractions of incubated plasma (control LDL and LCAT-modified LDL) were studied with respect to their chemical and functional properties. LCAT-modified LDL differed from control LDL by a decreased phospholipid and free-cholesterol content, but increased cholesteryl esters. Furthermore, an increase of the relative protein content in LDL by 16-20% was found. Apolipoproteins of LCAT-modified LDL exhibited a 10-fold increase of apo AI, a 4-5-fold increase of apo E, and a 2-fold increase of apo C. All these apolipoproteins resided together with apo B on the same particles. LCAT-modified LDL displayed a higher electrophoretic mobility, a higher hydrated density, a decreased flotation constant and a smaller diameter. Cultured human fibroblasts bound and internalized LCAT-modified LDL to a lower extent than control LDL. The degradation, however, was faster. Modified LDL suppressed 3-hydroxy-3-methylglutaryl-CoA reductase activity to a lower extent than did control LDL. Our results demonstrate that LCAT action, together with lipid transfer and exchange processes, markedly alters the chemical and physiochemical properties of LDL. This in turn significantly influences LDL catabolism in vitro.

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Decomposition of lipid hydroperoxides enhances the uptake of low density lipoprotein by macrophages.

Acta Biochimica Polonica ◽

10.18388/abp.1999_4181 ◽

1999 ◽

Vol 46 (1) ◽

pp. 31-42 ◽

Cited By ~ 3

Author(s):

A V Babiy ◽

J M Gebicki

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Lipid Hydroperoxide ◽

Significant Proportion ◽

Density Lipoprotein ◽

Scavenger Receptors ◽

Lipid Hydroperoxides ◽

Strictly Anaerobic ◽

Low Density ◽

Apo B

This study examined the roles of low-density lipoprotein (LDL) lipid oxidation and peroxide breakdown in its conversion to a form rapidly taken up by mouse peritoneal macrophages. Oxidation of the LDL without decomposition of the hydroperoxide groups was performed by exposure to gamma radiation in air-saturated solutions. Virtually complete decomposition of the hydroperoxides was achieved by treatment of the irradiated LDL with Cu2+ under strictly anaerobic conditions. No uncontrolled LDL uptake by macrophages occurred when the lipoprotein contained less than 150 hydroperoxide groups per particle. More extensively oxidized LDL was taken up and degraded by mouse macrophages significantly faster than the native lipoprotein. The uptake was greatly enhanced by treatment of the oxidized LDL with Cu2+. A significant proportion of the LDL containing intact or copper-decomposed LDL hydroperoxide groups accumulated within the macrophages without further degradation. Treatment of the radiation-oxidized LDL with Cu2+ was accompanied by aggregation of the particles. Competition studies showed that the oxidized LDL was taken up by macrophages via both the LDL and the scavenger receptors, whereas the copper-treated lipoprotein entered the cells only by the scavenger pathway. Phagocytosis also played an important role in the metabolism of all forms of the extensively modified LDL. Our results suggest that minimally-oxidized LDL is not recognized by the macrophage scavenger receptors unless the lipid hydroperoxide groups are decomposed to products able to derivatize the apo B protein.

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Quantification of malondialdehyde and 4-hydroxynonenal adducts to lysine residues in native and oxidized human low-density lipoprotein

Biochemical Journal ◽

10.1042/bj3220317 ◽

1997 ◽

Vol 322 (1) ◽

pp. 317-325 ◽

Cited By ~ 192

Author(s):

Jesús R. REQUENA ◽

Min Xin FU ◽

Mahtab U. AHMED ◽

Alicia J. JENKINS ◽

Timothy J. LYONS ◽

...

Keyword(s):

Oxidative Stress ◽

Gas Chromatography ◽

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Thiobarbituric Acid ◽

Low Density ◽

Lysine Residues

Malondialdehyde (MDA) and 4-hydroxynonenal (HNE) are major end-products of oxidation of polyunsaturated fatty acids, and are frequently measured as indicators of lipid peroxidation and oxidative stress in vivo. MDA forms Schiff-base adducts with lysine residues and cross-links proteins in vitro; HNE also reacts with lysines, primarily via a Michael addition reaction. We have developed methods using NaBH4 reduction to stabilize these adducts to conditions used for acid hydrolysis of protein, and have prepared reduced forms of lysine-MDA [3-(Nε-lysino)propan-1-ol (LM)], the lysine-MDA-lysine iminopropene cross-link [1,3-di(Nε-lysino)propane (LML)] and lysine-HNE [3-(Nε-lysino)-4-hydroxynonan-1-ol (LHNE)]. Gas chromatography/MS assays have been developed for quantification of the reduced compounds in protein. RNase incubated with MDA or HNE was used as a model for quantification of the adducts by gas chromatography/MS. There was excellent agreement between measurement of MDA bound to RNase as LM and LML, and as thiobarbituric acid-MDA adducts measured by HPLC; these adducts accounted for 70Ő80% of total lysine loss during the reaction with MDA. LM and LML (0.002Ő0.12mmol/mol of lysine) were also found in freshly isolated low-density lipoprotein (LDL) from healthy subjects. LHNE was measured in RNase treated with HNE, but was not detectable in native LDL. LM, LML and LHNE increased in concert with the formation of conjugated dienes during the copper-catalysed oxidation of LDL, but accounted for modification of < 1% of lysine residues in oxidized LDL. These results are the first report of direct chemical measurement of MDA and HNE adducts to lysine residues in LDL. LM, LML and LHNE should be useful as biomarkers of lipid peroxidative modification of protein and of oxidative stress in vitro and in vivo.

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Production of oxidized lipids during modification of low-density lipoprotein by macrophages or copper

Biochemical Journal ◽

10.1042/bj3040625 ◽

1994 ◽

Vol 304 (2) ◽

pp. 625-633 ◽

Cited By ~ 72

Author(s):

K L Carpenter ◽

G M Wilkins ◽

B Fussell ◽

J A Ballantine ◽

S E Taylor ◽

...

Keyword(s):

Gas Chromatography ◽

Electrophoretic Mobility ◽

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Maximum Level ◽

Gas Chromatography Mass Spectrometry ◽

Oxidized Lipids ◽

Low Density ◽

Catalysed Oxidation

The oxidation of low-density lipoprotein (LDL) is implicated in atherosclerosis. Lipids and oxidized lipids were analysed by gas chromatography and gas chromatography-mass spectrometry in human LDL incubated with mouse peritoneal macrophages (MPM) or copper (II) sulphate in Ham's F-10 medium or medium alone (control). MPM-modification and copper-catalysed oxidation of LDL resulted in the formation of oxysterols, mainly cholest-5-en-3 beta,7 beta-diol (7 beta-OH-CHOL); 7%-19% of the initial cholesterol was converted to 7 beta-OH-CHOL in 24 h. 7 beta-OH-CHOL levels in control LDL were very low. The increase in 7 beta-OH-CHOL in MPM and copper-oxidized LDL was accompanied by decreases in linoleate and arachidonate and increases in the electrophoretic mobility and degradation of LDL protein by ‘target’ macrophages. The concerted occurrence of these processes and their similarity in both MPM-modification and copper-catalysed oxidation of LDL were suggested by the highly significant cross-correlations. The fall in polyunsaturated fatty acid (PUFA) was accompanied by a directly proportional increase in electrophoretic mobility of the LDL. Production of 7 beta-OH-CHOL and protein degradation by macrophages showed modest elevations during the initial steep fall in PUFA, and showed their greatest increases as the levels of PUFA slowly approached zero. The levels of 7 beta-OH-CHOL and the degradation of LDL by macrophages were directly proportional. The degradation of LDL by macrophages increased rapidly as the electrophoretic mobility of LDL was slowly approaching its maximum level.

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Non-oxidative modification of native low-density lipoprotein by oxidized low-density lipoprotein

Biochemical Journal ◽

10.1042/bj3160377 ◽

1996 ◽

Vol 316 (2) ◽

pp. 377-380 ◽

Cited By ~ 6

Author(s):

Min YANG ◽

David S. LEAKE ◽

Catherine A. RICE-EVANS

Keyword(s):

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Oxidative Modification ◽

Low Density ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Process Studies

The oxidative modification of low-density lipoprotein (LDL) has been implicated in the pathogenesis of atherosclerosis, although little is known as yet about the precise mechanism of oxidation in vivo. The studies presented here demonstrate that, in the absence of cells or transition metals, oxidized LDL can modify native LDL through co-incubation in vitro such as to increase its net negative charge, in a concentration-dependent manner. The interaction is not inhibited by peroxyl radical scavengers or metal chelators, precluding the possibility that the modification of native LDL by oxidized LDL is through an oxidative process. Studies with radioiodinated oxidized LDL showed no transfer of radioactivity to the native LDL, demonstrating that fragmentation of protein and the transfer of some of the fragments does not account for the modified charge on the native LDL particle. The adjacency of native to oxidized LDL in the arterial wall may be a potential mechanism by which the altered recognition properties of the apolipoprotein B-100 may arise rapidly without oxidation or extensive modification of the native LDL lipid itself.

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Bisphenol a Exposure Causes Increased Oxidation of Low Density Lipoprotein (LDL) and Its Abduct in Rats

Asian Journal of Research in Biochemistry ◽

10.9734/ajrb/2021/v9i230195 ◽

2021 ◽

pp. 1-10

Author(s):

Chinenye E. Oguazu ◽

Francis C. Ezeonu ◽

Charles C. Dike ◽

Charles G. Ikimi

Keyword(s):

Bisphenol A ◽

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Diagnostic Procedures ◽

Female Rats ◽

Control Group ◽

Low Density ◽

Modified Ldl ◽

Low Exposure

Background and Objectives: Living organisms are exposed to oxidant agents constantly from both endogenous and exogenous sources. One of such oxidant agent is Bisphenol A (BPA) and its exposure is capable to modify biomolecules and induce damages. Bisphenol A (BPA) is a contaminant with increasing exposure. It exerts toxic effects on cells. This study investigates the possibility of BPA exposure on Low Density Lipoprotein (LDL) perturbations at prevailing low exposure doses in female albino Wistar rats, following exposure for the period of three (3) month. Materials and Methods: Total 12 groups were formed; out of which 11 experimental groups, each containing 10non-pregnant female rats were administered; 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mg of BPA/kgbw/day. To the 12th control group was given water. Blood was collected from animals at the end of every week of the study and serum sample specimens analyzed by routine diagnostic procedures for oxidized LDL such as malondialdehyde modified- LDL (MDA-LDL), oxidized phospholipids LDL (OX-PL LDL), N (epsilon) (carboxymethyl) lysine-modified-LDL (CML LDL) and 4-hydroxynonenal-LDL (HNE-LDL) using Autochemical Analyzer. Results: Significantly increased concentrations of serum oxidized LDL such as MDA-LDL, OX-PL LDL, CML LDL and HNE-LDL were observed at all concentrations of BPA exposure. Conclusion: Bisphenol A alters oxidized LDL such as MDA-LDL, OX-PL LDL, CML LDL and HNE-LDL balance and causes disturbance of internal oxidative statues.

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