Die Rolle von LRP1 in der Funktion des NMDA-Rezeptors

Ein funktionelles Zusammenspiel von LRP1, einem Mitglied der LDL-Rezeptorfamilie, mit dem NMDA-Rezeptor, einem Glutamat Rezeptor, wurde durch die Interaktion beider Proteine sowie eine tPa-vermittelte, LRP1-abhängige Signalübertragung durch den NMDA-Rezeptor belegt. Darüber hinaus zeigen Mäuse mit einem konditionellen neuronalen knock-out des Lrp1 Gens Verhaltensänderungen, die mit einer beeinträchtigten Signalübertragung durch NMDA-Rezeptoren assoziiert werden könnten. Die genaue Rolle von LRP1 in der NMDA-Rezeptor-Funktion bleibt allerdings noch unklar. In der vorliegenden Arbeit wurde die Rolle von LRP1 bei der Expression der NR2B-Untereinheit des NMDA-Rezeptors an der Zelloberfläche primärer kortikaler Neurone untersucht. Zu diesem Zweck wurde die knock-in Mauslinie LRP1ΔNPxY2, die sich durch eine Alanin Substitution im NPxY2 Motiv des LRP1 auszeichnet, eingesetzt. rnEs konnte gezeigt werden, dass diese knock-in Mutation in einer erhöhten Expression von LRP1 und der NMDA-Rezeptoruntereinheiten NR1 und NR2B an der Zelloberfläche primärer kortikaler Neurone resultiert. Der Effekt konnte durch eine reduzierte Endozytoserate von LRP1 und der NR1-und NR2B-Untereinheiten in primären LRP1ΔNPxY2 Neuronen erklärt werden. Darüber hinaus wurde ein verändertes Phosphorylierungsmuster der Internalisierungssignale der NR2B-Rezeptoruntereinheit Serin S1480 und Tyrosin Y1472 an der Zelloberfläche primärer LRP1ΔNPxY2 Neurone detektiert. Die verantwortlichen Kinasen Fyn und Kasein-Kinase II sind allerdings in LRP1ΔNPxY2 Neuronen im Vergleich zu den Wildtyp-Kontrollen nicht abweichend reguliert. In den Co-Immunopräzipitationsexperimenten wurde gezeigt, dass die Bindung von LRP1 mit NR2B durch die Phosphorylierung reguliert wird und dieser Regulationsmechanismus in LRP1ΔNPxY2 Neuronen beeinträchtigt ist. Dies resultiert in einer stärkeren Bindung von NR2B-Rezeptoruntereinheit an LRP1. Aufgrund reduzierter Internalisierungsraten von LRP1 in LRP1ΔNPxY2 Neuronen führt dieser Umstand zu einer Akkumulation beider Rezeptorproteine an der Zelloberfläche. Schließlich wurden die NMDA-Rezeptor-assoziierten Verhaltensänderungen wie die Hyperaktivität und die Defizite im direkten und umgekehrten räumlichen Lernvermögen in den LRP1ΔNPxY2 Tieren nachgewiesen. Zusammengefasst, demonstrieren diese Ergebnisse, dass LRP1 eine kritische Rolle in der Regulierung der NR2B-Expression an der Zelloberfläche spielt.

NOVEL THERAPEUTIC TARGETS IDENTIFIED BY HIGH-THROUGHPUT TECHNOLOGIES FOR TRIPLE-NEGATIVE BREAST CANCER

Triple-negative breast cancers (TNBC) are characterized by the lack of or reduced expression of the estrogen and progesterone receptors, and normal expression of the human epidermal growth factor receptor 2. The lack of a well-characterized target for treatment leaves only systemic chemotherapy as the mainstay of treatment. Approximately 60-70% of patients are chemosensitive, while the remaining majority does not respond. Targeted therapies that take advantage of the unique molecular perturbations found in triple-negative breast cancer are needed. The genes that are frequently amplified or overexpressed represent potential therapeutic targets for triple-negative breast cancer. The purpose of this study was to identify and validate novel therapeutic targets for triple-negative breast cancers. 681 genes showed consistent and highly significant overexpression in TNBC compared to receptor-positive cancers in 2 data sets. For two genes, 3 of the 4 siRNAs showed preferential growth inhibition in TNBC cells. These two genes were the low density lipoprotein receptor-related protein 8 (LRP8) and very low-density lipoprotein receptor (VLDLR). Exposure to their cognate ligands, reelin and apolipoprotein E isoform 4 (ApoE4), stimulated the growth of TNBC cells in vitro. Suppression of the expression of either LRP8 or VLDLR or exposure to RAP (an inhibitor of ligand binding to LRP8 and VLDLR) abolished this ligand-induced proliferation. High-throughput protein and metabolic arrays revealed that ApoE4 stimulation rescued TNBC cells from serum-starvation induced up-regulation of genes involved in lipid biosynthesis, increased protein expression of oncogenes involved in the MAPK/ERK and DNA repair pathways, and reduced the serum-starvation induction of biochemicals involved in oxidative stress response and glycolytic metabolism. shLRP8 MDA-MB-231 xenografts had reduced tumor volume, in comparison to parental and shCON xenografts. These results indicate that LRP8-APOE signaling confers survival advantages to TNBC tumors under reduced nutrient conditions and during cellular environmental stress. We revealed that the LRP8-APOE receptor-ligand system is overexpressed in human TNBC. We also demonstrated that this receptor system mediates a strong growth promoting and survival function in TNBC cells in vitro and helps to sustain the growth of MDA-MD-231 xenografts. We propose that inhibitors of LRP8-APOE signaling may be clinically useful therapeutic agents for triple-negative breast cancer.

Effect of neoadjuvant chemotherapy on low-density lipoprotein (LDL) receptor and LDL receptor-related protein 1 (LRP-1) receptor in locally advanced breast cancer

Low-density lipoprotein (LDL) receptors are overexpressed in most neoplastic cell lines and provide a mechanism for the internalization and concentration of drug-laden nanoemulsions that bind to these receptors. The aim of the present study was to determine whether the administration of standard chemotherapeutic schemes can alter the expression of LDL and LDL receptor-related protein 1 (LRP-1) receptors in breast carcinoma. Fragments of tumoral and normal breast tissue from 16 consecutive volunteer women with breast cancer in stage II or III were obtained from biopsies before the beginning of neoadjuvant chemotherapy and after chemotherapy, from fragments excised during mastectomy. Tissues were analyzed by immunohistochemistry for both receptors. Because complete response to treatment was achieved in 4 patients, only the tumors from 12 were analyzed. Before chemotherapy, there was overexpression of LDL receptor in the tumoral tissue compared to normal breast tissue in 8 of these patients. LRP-1 receptor overexpression was observed in tumors of 4 patients. After chemotherapy, expression of both receptors decreased in the tumors of 6 patients, increased in 4 and was unchanged in 2. Nonetheless, even when chemotherapy reduced receptors expression, the expression was still above normal. The fact that chemotherapy does not impair LDL receptors expression supports the use of drug carrier systems that target neoplastic cells by the LDL receptor endocytic pathway in patients on conventional chemotherapy.

Antagonistic effects of oxidized low density lipoprotein and alpha-tocopherol on CD36 scavenger receptor expression in monocytes: involvement of protein kinase B and peroxisome proliferator-activated receptor-gamma

Vitamin E deficiency increases expression of the CD36 scavenger receptor, suggesting specific molecular mechanisms and signaling pathways modulated by alpha-tocopherol. We show here that alpha-tocopherol down-regulated CD36 expression (mRNA and protein) in oxidized low density lipoprotein (oxLDL)-stimulated THP-1 monocytes, but not in unstimulated cells. Furthermore, alpha-tocopherol treatment of monocytes led to reduction of fluorescent oxLDL-3,3'-dioctadecyloxacarbocyanine perchlorate binding and uptake. Protein kinase C (PKC) appears not to be involved because neither activation of PKC by phorbol 12-myristate 13-acetate nor inhibition by PKC412 was affected by alpha-tocopherol. However, alpha-tocopherol could partially prevent CD36 induction after stimulation with a specific agonist of peroxisome proliferator-activated receptor-gamma (PPARgamma; troglitazone), indicating that this pathway is susceptible to alpha-tocopherol action. Phosphorylation of protein kinase B (PKB) at Ser473 was increased by oxLDL, and alpha-tocopherol could prevent this event. Expression of PKB stimulated the CD36 promoter as well as a PPARgamma element-driven reporter gene, whereas an inactive PKB mutant had no effect. Moreover, coexpression of PPARgamma and PKB led to additive induction of CD36 expression. Altogether, our results support the existence of PKB/PPARgamma signaling pathways that mediate CD36 expression in response to oxLDL. The activation of CD36 expression by PKB suggests that both lipid biosynthesis and fatty acid uptake are stimulated by PKB.

Porphyromonas gingivalis lipopolysaccharide alters atherosclerotic-related gene expression in oxidized low-density-lipoprotein-induced macrophages and foam cells

The molecular mechanism between atherosclerosis formation and periodontal pathogens is not clear although positive correlation between periodontal infections and cardiovascular diseases has been reported. Objective: To determine if atherosclerosis related genes were affected in foam cells during and after its formation by P. gingivalis lipopolysaccharide (LPS) stimulation. Methods: Macrophages from human THP-1 monocytes were treated with oxidized low density lipoprotein (oxLDL) to induce the formation of foam cells. P. gingivalis LPS was added to cultures of either oxLDL-induced macrophages or foam cells. The expression of atherosclerosis related genes was assayed by quantitative real time PCR and the protein production of granulocyte-macrophage colony-stimulating factor（GM-CSF）, monocyte chemotactic protein-1 (MCP-1), IL-1β, IL-10 and IL-12 was determined by ELISA. Nuclear translocation of NF-κB P65 was detected by immunocytochemistry and western blot was used to evaluate IKB-α degradation to confirm the NF-κB pathway activation. Results: P. gingivalis LPS stimulated atherosclerosis related gene expression in foam cells and increased oxLDL induced expression of chemokines, adhesion molecules, growth factors, apoptotic genes, and nuclear receptors in macrophages. Transcription of the pro-inflammatory cytokines IL-1β and IL-12 was elevated in response to LPS in both macrophages and foam cells, whereas the anti-inflammatory cytokine IL-10 was not affected. Increased NF-κB pathway activation was also observed in LPS and oxLDL co-stimulated macrophages. Conclusion: P. gingivalis LPS appears to be an important factor in the development of atherosclerosis by stimulation of atherosclerosis related gene expression in both macrophages and foam cells via activation of the NF-κB pathway.

Expression of the peroxisome proliferator-activated receptor γ (PPARγ) in human atherosclerosis and regulation in macrophages by colony stimulating factors and oxidized low density lipoprotein

The peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-dependent transcription factor that has been demonstrated to regulate fat cell development and glucose homeostasis. PPARγ is also expressed in a subset of macrophages and negatively regulates the expression of several proinflammatory genes in response to natural and synthetic ligands. We here demonstrate that PPARγ is expressed in macrophage foam cells of human atherosclerotic lesions, in a pattern that is highly correlated with that of oxidation-specific epitopes. Oxidized low density lipoprotein (oxLDL) and macrophage colony-stimulating factor, which are known to be present in atherosclerotic lesions, stimulated PPARγ expression in primary macrophages and monocytic cell lines. PPARγ mRNA expression was also induced in primary macrophages and THP-1 monocytic leukemia cells by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA). Inhibition of protein kinase C blocked the induction of PPARγ expression by TPA, but not by oxLDL, suggesting that more than one signaling pathway regulates PPARγ expression in macrophages. TPA induced the expression of PPARγ in RAW 264.7 macrophages by increasing transcription from the PPARγ1 and PPARγ3 promoters. In concert, these observations provide insights into the regulation of PPARγ expression in activated macrophages and raise the possibility that PPARγ ligands may influence the progression of atherosclerosis.

Interaction of very-low-density lipoprotein isolated from type I (insulin-dependent) diabetic subjects with human monocyte-derived macrophages

Very-low-density lipoproteins (VLDL) (density less than 1.006 g/mL) were isolated from type I (insulin-dependent) diabetic patients in good to fair glycemic control and from age-, sex-, and race-matched, nondiabetic, control subjects. VLDL were incubated with human, monocyte-derived macrophages obtained from nondiabetic donors, and the rates of cellular cholesteryl ester synthesis and cholesterol accumulation were determined. VLDL isolated from diabetic patients stimulated significantly more cholesteryl ester synthesis than did VLDL isolated from control subjects (4.04 +/- 1.01 v 1.99 +/- 0.39 nmol 14C-cholesteryl oleate synthesized/mg cell protein/20 h; mean +/- SEM, P less than .05). The stimulation of cholesteryl ester synthesis in macrophages incubated with VLDL isolated from diabetic patients was paralleled by a significant increase in intracellular cholesteryl ester accumulation (P less than .05). The increase in cholesteryl ester synthesis and accumulation in macrophages were mediated by a significant increase in the receptor mediated, high affinity degradation (2.55 +/- 0.23 v 2.12 +/- 0.20 micrograms degraded/mg cell protein/20 h) and accumulation (283 +/- 35 v 242 +/- 33 ng/mg cell protein/20 h) of 125I-VLDL isolated from diabetic patients compared with VLDL from control subjects. To determine if changes in VLDL apoprotein composition were responsible for the observed changes in cellular rates of cholesteryl ester synthesis and accumulation, we also examined the apoprotein composition of the VLDL from both groups. There were no significant differences between the apoproteins B, E, and C content of VLDL from both groups. We also determined the chemical composition of VLDL isolated from both groups of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycosylation of low-density lipoprotein enhances cholesteryl ester synthesis in human monocyte-derived macrophages

Glucose can react with the lysine residues of low-density lipoproteins (LDLs) and convert the lipoprotein to a form with a receptor-mediated uptake by cultured cells that is impaired. However, in contrast to other modified lipoproteins taken up by both murine and human macrophages via the scavenger-receptor pathway that may induce the formation of foam cells, glycosylated LDL is not recognized by murine macrophages, and thus far, it has not been shown to lead to marked intracellular accumulation of cholesterol in human macrophages. This study illustrates that glycosylated LDL incubated with human monocyte-derived macrophages, at a concentration of 100 micrograms LDL/ml medium, stimulates significantly more cholesteryl ester (CE) synthesis than does control LDL (10.65 +/- 1.5 vs. 4.8 +/- 0.13 nmol.mg-1 cell protein.20 h-1; P less than .05). At LDL concentrations similar to those of plasma, the rate of CE synthesis in macrophages incubated with glycosylated LDL is more markedly enhanced than that observed in cells incubated with control LDL (3-fold increase). The marked stimulation of CE synthesis in human macrophages exposed to glycosylated LDL is paralleled by a significant increase in CE accumulation in these cells (P less than .001). The increase in CE synthesis and accumulation seem to be mediated by an increase in the degradation of glycosylated LDL by human macrophages. Glycosylated LDL enters the macrophages and is degraded by the classic LDL-receptor pathway in slightly smaller amounts than control LDL, but its degradation by pathways other than the classic LDL receptor or scavenger receptor is markedly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor-mediated endocytosis and intracellular trafficking of insulin and low-density lipoprotein by retinal vascular endothelial cells

PURPOSE: The authors investigated the receptor-mediated endocytosis (RME) and intracellular trafficking of insulin and low-density lipoprotein (LDL) in cultured retinal vascular endothelial cells (RVECs). METHODS: Low-density lipoprotein and insulin were conjugated to 10 nm colloidal gold, and these ligands were added to cultured bovine RVECs for 20 minutes at 4 degrees C. The cultures were then warmed to 37 degrees C and fixed after incubation times between 30 seconds and 1 hour. Control cells were incubated with unconjugated gold colloid at times and concentrations similar to those of the ligands. Additional control cells were exposed to several concentrations of anti-insulin receptor antibody or a saturating solution of unconjugated insulin before incubation with gold insulin. RESULTS: Using transmission electron microscopy, insulin gold and LDL gold were both observed at various stages of RME. Insulin-gold particles were first seen to bind to the apical plasma membrane (PM) before clustering in clathrin-coated pits and internalization in coated vesicles. Gold was later visualized in uncoated cytoplasmic vesicles, corresponding to early endosomes and multivesicular bodies (MVBs) or late endosomes. In several instances, localized regions of the limiting membrane of the MVBs appeared coated, a feature of endosomal membranes not previously described. After RME at the apical PM and passage through the endosomal system, the greater part of both insulin- and LDL-gold conjugates was seen to accumulate in large lysosome-like compartments. However, a small but significant proportion of the internalized ligands was transcytosed and released as discrete membrane-associated quanta at the basal cell surface. The uptake of LDL gold was greatly increased in highly vacuolated, late-passage RVECs. In controls, anti-insulin receptor antibody and excess unconjugated insulin caused up to 89% inhibition in gold-insulin binding and internalization. CONCLUSION: These results illustrate the internalization and intracellular trafficking by RVECs of insulin and LDL through highly efficient RME, and they provide evidence for at least two possible fates for the endocytosed ligands. This study outlines a route by which vital macromolecules may cross the inner blood-retinal barrier.

Anti-oxidized low-density lipoprotein (oxLDL) antibody levels are not related to increasing circulating oxLDL concentrations during the course of pregnancy

To address the question of whether the high levels of oxidative modified low-density lipoproteins (oxLDL) in pregnancy are opposed by an appropriate humoral autoimmune response providing anti-oxLDL autoantibodies in maternal serum of healthy women throughout gestation.

Receptors for oxidized low-density lipoprotein on elicited mouse peritoneal macrophages can recognize both the modified lipid moieties and the modified protein moieties: Implications with respect to macrophage recognition of apoptotic cells

It has been shown previously that the binding of oxidized low-density lipoprotein (OxLDL) to resident mouse peritoneal macrophages can be inhibited (up to 70%) by the apoprotein B (apoB) isolated from OxLDL, suggesting that macrophage recognition of OxLDL is primarily dependent on its modified protein moiety. However, recent experiments have demonstrated that the lipids isolated from OxLDL and reconstituted into a microemulsion can also strongly inhibit uptake of OxLDL (up to 80%). The present studies show that lipid microemulsions prepared from OxLDL bind to thioglycollate-elicited macrophages at 4°C in a saturable fashion and inhibit the binding of intact OxLDL and also of the apoB from OxLDL. Reciprocally, the binding of the OxLDL-lipid microemulsions was strongly inhibited by intact OxLDL. A conjugate of synthetic 1-palmitoyl 2(5-oxovaleroyl) phosphatidylcholine (an oxidation product of 1-palmitoyl 2-arachidonoyl phosphatidylcholine) with serum albumin, shown previously to inhibit macrophage binding of intact OxLDL, also inhibited the binding of both the apoprotein and the lipid microemulsions prepared from OxLDL. Finally, a monoclonal antibody against oxidized phospholipids, one that inhibits binding of intact OxLDL to macrophages, also inhibited the binding of both the resolubilized apoB and the lipid microemulsions prepared from OxLDL. These studies support the conclusions that: (i) at least some of the macrophage receptors for oxidized LDL can recognize both the lipid and the protein moieties; and (ii) oxidized phospholipids, in the lipid phase of the lipoprotein and/or covalently linked to the apoB of OxLDL, likely play a role in that recognition.

Apolipoprotein E competitively inhibits receptor-dependent low density lipoprotein uptake by the liver but has no effect on cholesterol absorption or synthesis in the mouse.

This study examines the question of whether apolipoprotein E (apoE) alters steady-state concentrations of plasma cholesterol carried in low density lipoproteins (LDL-C) by acting as a competitive inhibitor of hepatic LDL uptake or by altering the rate of net cholesterol delivery from the intestinal lumen to the liver. To differentiate between these two possibilities, rates of cholesterol absorption and synthesis and the kinetics of hepatic LDL-C transport were measured in vivo in mice with either normal (apoE+/+) or zero (apoE-/-) levels of circulating apoE. Rates of cholesterol absorption were essentially identical in both genotypes and equaled approximately 44% of the daily dietary load of cholesterol. This finding was consistent with the further observation that the rates of cholesterol synthesis in the liver (approximately 2,000 nmol/h) and extrahepatic tissues (approximately 3,000 nmol/h) were also essentially identical in the two groups of mice. However, the apparent Michaelis constant for receptor-dependent hepatic LDL-C uptake was markedly lower in the apoE-/- mice (44 +/- 4 mg/dl) than in the apoE+/+ animals (329 +/- 77 mg/dl) even though the maximal transport velocity for this uptake process was essentially the same (approximately 400 micrograms/h per g) in the two groups of mice. These studies, therefore, demonstrate that apoE-containing lipoproteins can act as potent competitive inhibitors of hepatic LDL-C transport and so can significantly increase steady-state plasma LDL-C levels. This apolipoprotein plays no role, however, in the regulation of cholesterol absorption, sterol biosynthesis, or hepatic LDL receptor number, at least in the mouse.

The 94- to 97-kDa mouse macrophage membrane protein that recognizes oxidized low density lipoprotein and phosphatidylserine-rich liposomes is identical to macrosialin, the mouse homologue of human CD68.

We have previously reported the partial purification of a 94- to 97-kDa plasma membrane protein from mouse peritoneal macrophages that binds oxidatively modified low density lipoprotein (OxLDL) and phosphatidylserine-rich liposomes. We have now identified that protein as macrosialin, a previously cloned macrophage-restricted membrane protein in the lysosomal-associated membrane protein family (mouse homologue of human CD68). Early in the course of purification of the 94- to 97-kDa protein, a new OxLDL-binding band at 190-200 kDa appeared and copurified with the 94- to 97-kDa protein. The HPLC pattern of tryptic peptides from this higher molecular mass ligand-binding band closely matched that derived from the 94- to 97-kDa band. Specifically, the same three macrosialin-derived tryptic peptides (9, 9, and 15 residues) were present in the purified 94- to 97-kDa band and in the 190- to 200-kDa band and antisera raised against peptide sequences in macrosialin recognized both bands. An antiserum against macrosialin precipitated most of the 94- to 97-kDa OxLDL-binding material. We conclude that the binding of OxLDL to mouse macrophage membranes is in part attributable to macrosialin. Our previous studies show that OxLDL competes with oxidized red blood cells and with apoptotic thymocytes for binding to mouse peritoneal macrophages. Whether macrosialin plays a role in recognition of OxLDL and oxidatively damaged cells by intact macrophages remains uncertain.

Downstream effects on human low density lipoprotein of homocysteine exported from endothelial cells in an in vitro system

A model system is presented using human umbilical vein endothelial cells (HUVECs) to investigate the role of homocysteine (Hcy) in atherosclerosis. HUVECs are shown to export Hcy at a rate determined by the flux through the methionine/Hcy pathway. Additional methionine increases intracellular methionine, decreases intracellular folate, and increases Hcy export, whereas additional folate inhibits export. An inverse relationship exists between intracellular folate and Hcy export. Hcy export may be regulated by intracellular S-adenosyl methionine rather than by Hcy. Human LDLs exposed to HUVECs exporting Hcy undergo time-related lipid oxidation, a process inhibited by the thiol trap dithionitrobenzoate. This is likely to be related to the generation of hydroxyl radicals, which we show are associated with Hcy export. Although Hcy is the major oxidant, cysteine also contributes, as shown by the effect of glutamate. Finally, the LDL oxidized in this system showed a time-dependent increase in uptake by human macrophages, implying an upregulation of the scavenger receptor. These results suggest that continuous export of Hcy from endothelial cells contributes to the generation of extracellular hydroxyl radicals, with associated oxidative modification of LDL and incorporation into macrophages, a key step in atherosclerosis. Factors that regulate intracellular Hcy metabolism modulate these effects. Copyright © 2005 by the American Society for Biochemistry and Molecular Biology, Inc.

Oxidation of protein in human low-density lipoprotein exposed to peroxyl radicals facilitates uptake by monocytes; protection by antioxidants in vitro

Generation of neoepitopes on apolipoprotein B within oxidised low-density lipoprotein (LDL) is important in the unregulated uptake of LDL by monocytic scavenger receptors (CD36, SR-AI, LOX-1). Freshly isolated LDL was oxidised by peroxyl radicals generated from the thermal decomposition of an aqueous azo-compound. We describe that formation of carbonyl groups on the protein component is early as protein oxidation was seen after 90min. This is associated with an increased propensity for LDL uptake by U937 monocytes. Three classes of antioxidants (quercetin, dehydroepiandrosterone (DHEA) and ascorbic acid) have been examined for their capacity to inhibit AAPH-induced protein oxidation, (protein carbonyls, Δ electrophoretic mobility and LDL uptake by U937 monocytes). CD36 expression was assessed by flow cytometry and was seen to be unaltered by oxidised LDL uptake. All three classes were effective antioxidants, quercetin (P<0.01), ascorbic acid (P<0.01), DHEA (P<0.05). As LDL protein is the control point for LDL metabolism, the degree of oxidation and protection by antioxidants is likely to be of great importance for (patho)-physiological uptake of LDL by monocytes. © 2003 Elsevier B.V. All rights reserved.