Enhanced binding of phospholipase-A2-modified low density lipoprotein by human adipocytes

1990 ◽  
Vol 68 (11) ◽  
pp. 1243-1249 ◽  
Author(s):  
Madhu K. Natarajan ◽  
Bessie S. Fong ◽  
Aubie Angel
Keyword(s):  
Membrane Protein ◽  
Plasma Membranes ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Low Density ◽  
Human Adipocytes ◽  
Binding Studies ◽  
Modified Ldl ◽  
Isolated Adipocytes ◽  
Adipocyte Plasma Membranes

Recognition of low density lipoprotein (LDL) by human adipocytes is not dependent on the classical LDL (apoprotein B–E) receptor. To assess whether LDL phospholipids have a role in adipocyte-LDL interactions, binding studies were carried out with human LDL modified with cobra venom phospholipase A2 (PLA2) and freshly isolated adipocytes and purified adipocyte plasma membranes prepared from surgical biopsies. LDL incubated with PLA2 showed increased monoacylphospholipid content, decreased diacylphospholipid content, and increased anodic migration on agarose gel electrophoresis. LDL cholesterol, triglyceride, and protein content remained unchanged. Typically, modification of 16 and 47% of LDL phospholipids enhanced specific binding of 125I-labelled LDL to plasma membranes progressively from 3.1 μg LDL bound/mg membrane protein (control) to 5.8 and 28.2 μg LDL bound/mg membrane protein, respectively. Nonspecific binding was not altered significantly. Excess unlabelled native LDL and high density lipoprotein (HDL3) effectively inhibited binding of PLA2-modified LDL. Freshly isolated adipocytes also showed enhanced binding and uptake of PLA2-modified LDL (0.1 vs. 0.9 μg LDL/(106 cells∙2 h), control vs. modified). The results demonstrate that alterations of LDL phospholipids significantly enhance LDL binding and suggest a regulatory role for phospholipids in lipoprotein–cell interaction. Furthermore, the results support the view that human adipose tissue may be involved in the metabolism of modified lipoproteins, in vivo.Key words: low density lipoprotein, adipocyte, phospholipase, lipoprotein receptors.

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

2005 ◽  
Vol 12 (1) ◽  
pp. 68-75 ◽  
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.

Immunohistochemical Localization of Apolipoprotein B-100 (ApoB-100) and Expression of Glutathione Peroxidase (GSH-PO) in Canine Atherosclerotic Lesions

1998 ◽  
Vol 35 (3) ◽  
pp. 227-229 ◽  
Author(s):  
Y. Kagawa ◽  
E. Uchida ◽  
H. Yokota ◽  
M. Yamaguchi ◽  
H. Taniyama
Keyword(s):  
Glutathione Peroxidase ◽  
Apolipoprotein B ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Immunohistochemical Localization ◽  
Low Density ◽  
Modified Ldl ◽  
Atherosclerotic Lesions ◽  
Foamy Cytoplasm ◽  
Tunica Intima

We used immunohistochemistry to localize canine Apolipoprotein B-100 (CApoB-100) and glutathione peroxidase (GSH-PO) in canine atherosclerotic lesions. CApoB-100 was deposited in the tunica intima and cytoplasms of infiltrating macrophages in early atherosclerotic lesions. In advanced atherosclerotic lesions, the cystic space of the lesions contained a large amount of CApoB-100 immunoreaetive material. Expression of GSH-PO was recognized in the foamy cytoplasm of macrophages and smooth muscle cells in the early and advanced atherosclerotic lesions. These results indicate that expression of GSH-PO is closely associated with the deposition of CApoB-100. In addition, they suggest that, as in human atheromas, low-density lipoprotein (LDL) is peroxidized and changed into modified LDL. Deposition of modified LDL (oxidized or acetylated) may be a critical step in the formation of canine atherosclerotic lesions.

Characterization of high-density lipoprotein binding to rat adipocytes and adipocyte plasma membranes

1988 ◽  
Vol 66 (9) ◽  
pp. 986-997 ◽  
Author(s):  
Eva Zsigmond ◽  
Bessie Fong ◽  
Aubie Angel
Keyword(s):  
Adipose Tissue ◽  
Plasma Membranes ◽  
Density Lipoprotein ◽  
Membrane System ◽  
Rat Plasma ◽  
High Density ◽  
High Density Lipoproteins ◽  
Binding Characteristics ◽  
Isolated Adipocytes ◽  
Adipocyte Plasma Membranes

The interaction of high-density lipoproteins (HDL) with adipocytes is important in the regulation of cellular cholesterol flux. To study the mechanisms of HDL binding and cellular processing, we incubated adipocytes isolated from epididymal and perirenal adipose tissue of male Wistar rats (300 g) with HDL1 (1.07–1.10 g/mL) and HDL2 (1.10–1.14 g/mL) fractions separated from rat plasma by gradient ultracentrifugation. Freshly isolated adipocytes were incubated with 125I-labeled HDL for 2 h at 37 °C to determine cell-associated uptake and degradation. Adipocytes from both fat regions showed significant cell-associated HDL1 and HDL2 uptake and very high medium degradation (2- to 6-fold higher than uptake). To assess 125I-labeled HDL binding independent of cellular metabolism, we purified adipocyte plasma membranes from isolated adipocytes and used them in binding assays. Binding of HDL1 and HDL2 in the membrane system was 85–95% specific, sensitive to high NaCl concentrations, and abolished by pronase treatment. In contrast to HDL2 binding, the maximum HDL1 binding to perirenal plasma membranes was significantly higher than its binding to epididymal membranes (7.2 ± 1.3 vs. 4.4 ± 0.2 μg/mg, n = 6, p < 0.05). This increment in HDL1 binding to perirenal membranes represented an EDTA- sensitive, calcium-dependent component. These results indicate that HDL binding to adipocyte plasma membranes depends on both adipose tissue region and HDL subtype. The membrane binding characteristics, taken together with the cellular uptake results, suggest that adipocytes bind and metabolize HDL and that this interaction may involve a protein receptor.

scholarly journals 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

2002 ◽  
Vol 277 (51) ◽  
pp. 49982-49988 ◽  
Author(s):  
Vidya V. Kunjathoor ◽  
Maria Febbraio ◽  
Eugene A. Podrez ◽  
Kathryn J. Moore ◽  
Lorna Andersson ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Gas Chromatography Mass Spectrometry ◽  
Scavenger Receptors ◽  
Low Density ◽  
Lipid Uptake ◽  
Modified Ldl ◽  
Ldl Uptake

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.

Sign in / Sign up

Export Citation Format

Share Document