Moderate intake of n-3 fatty acids is associated with stable erythrocyte resistance to oxidative stress in hypertriglyceridemic subjects.

Background The important triacylglycerol-lowering capacity of n-3 fatty acids is counterbalanced by their inherent sensitivity to oxidation. Inconsistent results about the latter have been reported in hypertriglyceridemic individuals. After incorporation into cell membranes, n-3 fatty acids may alter membrane-related functions. In view of the distinct composition of hypertriglyceridemic membranes and the prooxidant status in this condition, it can be surmised that cell enrichment with the oxidizable n-3 fatty acids will be associated with an increased hemolytic process. Objective We sought to evaluate the effect of fish oil consumption on n-3 fatty acid incorporation into erythrocyte membra…

Liver X Receptor Regulates Arachidonic Acid Distribution and Eicosanoid Release in Human Macrophages

Objective— Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are highly expressed in macrophages and regulate lipid homeostasis and inflammation. Among putative LXR target genes, lysophosphatidylcholine acyltransferase 3 (LPCAT3) involved in the Lands cycle controls the fatty acid composition at the sn-2 position of glycerophospholipids and, therefore, the availability of fatty acids, such as arachidonic acid (AA), used for eicosanoid synthesis. The aim of our study was to determine whether LXRs could regulate the Lands cycle in human macrophages, to assess the consequences in terms of lipid composition and inflammatory response, and to work out the relative contribut…

Pro-oxidant effects of 7-hydroperoxycholest-5-en-3β-ol on the copper-initiated oxidation of low density lipoprotein

AbstractIn low density lipoproteins (LDL) supplemented with aged cholesterol and oxidized in the presence of Cu2+, an increase of the lipid oxidation parameters was observed compared with pure cholesterol-enriched LDL. A compound, identified as 7-hydroperoxycholesterol (7HPC), isolated from aged cholesterol and added to LDL, reproduced the above effects. The results indicate that the pro-oxidant effect of 7HPC is dependent on the hydroperoxy group since the corresponding alcohol derivative, 7α-hydroxycholesterol, had no such effect. These data suggest that among the LDL-associated lipid peroxides, cholesterol peroxides may have important implications in the susceptibility of this lipoprotei…

Oxidant stress: the role of nutrients in cell-lipoprotein interactions

Oxidant stress is increasingly becoming an important hypothesis to explain the genesis of several pathologies, including cancer, atherosclerosis and also ageing. Beside a few rare genetic defects, dietary factors are thought to play a key role in the regulation of the production of reactive oxygenated species. An imbalance between nutrients, and in particular those involved in antioxidant status, could explain the onset of an enhanced production of free radicals. We will briefly review information concerning oxidation of lipids and lipoproteins which lead to atherothrombosis. We also present new findings supporting a role for blood platelets in generating oxidant species. New data are also …

Acute methionine load‐induced hyperhomocysteinemia enhances platelet aggregation, thromboxane biosynthesis, and macrophage‐derived tissue factor activity in rats

A moderate elevation of plasma homocysteine is a risk factor for atherosclerosis and arterial and veinous thrombosis. However, the mechanisms leading to vascular disorders are poorly understood because studies that have investigated the potential atherothrombogenicity of hyperhomocysteinemia in vivo are scarce. Using a rat model, we were the first to show that dietary folic acid deficiency, a major cause of basal hyperhomocysteinemia, is associated with enhanced macrophage-derived tissue factor and platelet activities. We proposed that an homocysteine-induced oxidative stress may account for this hypercoagulable state. To determine the true thrombogenicity of moderate hyperhomocysteinemia a…

Differential effects of cysteine and methionine residues in the antioxidant activity of human serum albumin

Antioxidant properties of human serum albumin (HSA) may explain part of its beneficial role in various diseases related to free radical attack. In the present study, the antioxidant role of Cys and Met was studied by copper-mediated oxidation of human low density lipoproteins and by free radical-induced blood hemolysis which essentially assessed metal-chelating and free radical scavenging activities, respectively. Mild conditions were set up to specifically modify Cys and Met residues by N-ethylmaleimide (NEM) and chloramine T treatments, respectively. We found that Met and Cys accounted for 40-80% of total antioxidant activity of HSA. Copper binding to HSA was decreased by about 50% with c…

Effect of fish oil on LDL oxidation and plasma homocysteine concentrations in health.

Oxidation of low-density lipoprotein (LDL) and hyperhomocysteinemia are believed to play a role in therogenesis. Whether n-3 polyunsaturated fatty acids increase LDL susceptibility to oxidation or influence homocysteine (Hcy) metabolism has long been a subject of controversy. In this study, we evaluated the effect of 8 weeks of dietary supplementation with 6 g/day of fish oil (FO; 3 g of n-3 fatty acids) on plasma lipoproteins, in vitro LDL peroxidation, antioxidant status, and plasma Hcy concentrations in 16 normolipidemic subjects. FO rapidly and significantly (P < .01) decreased plasma total and very low density lipoprotein triglyceride concentrations and had no effect on LDL or high-den…

Effect of exercise training on in vitro LDL oxidation and free radical-induced hemolysis: the HERITAGE Family Study.

Oxidant stress and overproduction of reactive oxygen species (ROS) contribute to the development of cardiovascular disease. Oxidative modifications of low-density lipoproteins (LDL) are thought to play an early and critical role in atherogenesis. LDL oxidation can be reproduced in vitro, but results usually show a large interindividual variation not entirely explained by the environment. Free radical-induced hemolysis is also proposed to reveal the overall antioxidant capacity. The roles of genetic factors and exercise on the variability of both measures were investigated. The study was conducted in 146 healthy individuals from 28 families participating in a 20-week exercise-training progra…

Folate deficiencies and cardiovascular pathologies.

Abstract Although folates are widely distributed in foods, folate deficiencies may be more frequent than expected because their true availability may be impaired due to their lability under various food cooking and processing conditions. Folate deficiency is frequently observed in elderly people, smokers, alcoholics and oral contraceptive users. It is also associated with the mutation leading to the thermolabile variant of N5, 10-methylenetetrahydrofolate reductase which is observed in about 10 % of the population. In addition to the essential role of the intracellular pool of polyglutamates in de novo biosynthesis of deoxyribonucleotides which allow cell growth and division, the reduced an…

Enhanced platelet thromboxane synthesis and reduced macrophage-dependent fibrinolytic activity related to oxidative stress in oral contraceptive-treated female rats.

Abstract In previous studies conducted in rats and in women, we have shown that oral contraceptive (OC) administration induced a platelet hyperaggregation simultaneously with an increased platelet lipid biosynthesis which might be related to lipid peroxidation. In the present study, we specifically studied the arachidonic acid and the fibrinolytic pathways in relation to the fatty acid composition in female rats treated for 6 weeks with OC (ethinyl estradiol plus lynestrenol). We found that platelets of treated animals were not only hyper-responsive to thrombin and ADP, but also to sodium arachidonate. In addition, the results of the thrombin-induced release of labeled arachidonic acid pre-…

Déficiences en folates et pathologie cardiovasculaire

Resume Bien que les folates soient largement distribues dans l'alimentation, ils sont sensibles a de nombreuses agressions physicochimiques qui reduisent fortement leur biodisponibilite. Ainsi, contrairement aux idees recues, la deficience en folates concernerait une proportion importante de la population occidentale. La deficience en folates est frequemment observee chez les personnes âgees, les fumeurs et les alcooliques, lors de l'utilisation de certaines medications telles que le methotrexate, les anticonvulsifs et les œstroprogestatifs synthetiques ainsi que lors de la mutation thermolabile de la N 5,10 -methylenetetrahydrofolate reductase. A cote du role majeur du pool intracellulaire…

Role of the cyclic AMP-dependent pathway in free radical-induced cholesterol accumulation in vascular smooth muscle cells.

We have previously reported that free radical-treated vascular smooth muscle cells (SMC) lead to cholesterol accumulation in vitro. In the current study, we investigated the effects of oxidative stress on cyclic AMP concentration and cAMP-dependent enzymes involved in cholesterol homeostasis in A7r5 cells. Under our conditions of a mild oxidative stress, namely with no change in cell viability, we found that free radicals, initiated using azobis-amidinopropane dihydrochloride (AAPH), resulted in a dose-dependent decrease in cellular cAMP which was opposed by vitamin E preincubation. Although the addition of adenylate cyclase activators (carbacyclin and forskolin) increased cAMP levels it di…

Determination of sterols, oxysterols, and fatty acids of phospholipids in cells and lipoproteins: A one-sample method

In addition to fatty acids, especially polyunsaturated species, cholesterol oxidizes and leads to various oxygenated derivatives, named oxysterols. They display a wide range of adverse biological properties. Monitoring oxysterols is important in the evaluation of the potential risks associated with lipid oxidation. In the present study, a quick and reliable method was developed for analysis of oxysterols, sterols, and fatty acid composition of phospholipids in the same biological sample. Total lipid extraction was determined after addition of several internal standards (epicoprostanol for sterols, 19-hydroxy-cholesterol for oxysterol and di-heptadecanoyl-phosphatidylcholine for phospholipid…

Glycated albumin with loss of fatty acid binding capacity contributes to enhanced arachidonate oxygenation and platelet hyperactivity: relevance in patients with type 2 diabetes.

High plasma concentrations of nonesterified fatty acids (NEFAs), transported bound to serum albumin, are associated with type 2 diabetes (T2D). The effects of albumin on platelet function were investigated in vitro. Modifications of albumin, such as those due to glycoxidation, were found in patients with T2D, and the consequences of these modifications on biological mechanisms related to NEFA handling were investigated. Mass spectrometry profiles of albumin from patients with T2D differed from those from healthy control subjects. Diabetic albumin showed impaired NEFA binding capacity, and both structural and functional alterations could be reproduced in vitro by incubating native albumin wi…

Involvement of Oxysterols and Lysophosphatidylcholine in the Oxidized LDL–Induced Impairment of Serum Albumin Synthesis by HEPG2 Cells

Abstract —Oxidized low density lipoproteins (Ox-LDLs) are increasingly thought to be a key element in atherogenesis. We have previously reported that serum albumin has important antioxidant properties and that a reduced synthesis of albumin may represent a crucial point in the overall antioxidant defense. In the present work, we aimed at determining whether Ox-LDL could modulate albumin synthesis in cultured human hepatocytes (HepG2 cells). With the use of enzyme immunoassay and radiolabeled leucine incorporation followed by specific immunoprecipitation, Ox-LDL was found to lead to a dose-dependent decrease in albumin secretion. Moreover, the protein synthesis and mRNA levels were decrease…

Long-term moderate magnesium-deficient diet shows relationships between blood pressure, inflammation and oxidant stress defense in aging rats

International audience; Epidemiological and experimental studies have indicated a relationship among aging, dietary Mg, inflammatory stress, and cardiovascular disease. Our aim in the present study was to investigate possible links between dietary Mg, oxidant stress parameters, and inflammatory status with aging in rats. We designed a long-term study in which rats were fed for 22 months with moderately deficient (150 mg/kg), standard (800 mg/kg), or supplemented (3200 mg/kg) Mg diets. Comparisons were made with young rats fed with the same diets for 1 month. Compared to the standard and supplemented diets, the Mg-deficient diet significantly increased blood pressure, plasma interleukin-6, f…

Impaired cellular cholesterol efflux by oxysterol-enriched high density lipoproteins.

One of the proposed antiatherogenicity role of high-density lipoproteins (HDL) is believed to stimulate removal of cholesterol from the peripheral cells back to the liver for excretion. We have investigated the effects of oxidation-related modifications of HDL on their ability to stimulate cholesterol efflux from cultured cells. Human HDL (HDL3, 1.13 < d < 1.21 g/ml) have been modified either by malondialdehyde or by copper-mediated oxidation (Ox-HDL3). Compared with native HDL3, the modified HDL3 resulted in a significantly reduced efflux of labeled cholesterol from preloaded macrophages (P388D1 cell line). Analysis of lipid composition of Ox-HDL3 by gas chromatography revealed the presenc…

Enhanced susceptibility of cholesteryl sulfate-enriched low density lipoproteins to copper-mediated oxidation

AbstractCholesteryl sulfate (CS) is a minor component of cell membranes, also present in lipoproteins, and its exact function is unknown. Since oxidation of low density lipoproteins (LDL) is thought to be an important determinant of atherogenesis, we investigated the influence of CS enrichment on copper-mediated oxidation of LDL. CS was found to act as a pro-oxidant, as measured by lipid oxidation parameters. The results also suggest that these effects were dependent on the sulfate group since pure cholesterol or cholesteryl acetate did not promote Cu2+-mediated oxidation. Our findings imply that CS may affect the oxidizability and hence the potential atherogenicity of LDL.

Folic Acid Deficiency Enhances Oral Contraceptive-Induced Platelet Hyperactivity

Abstract In previous studies conducted in female rats and in women, oral contraceptives (OC) were found to induce a platelet hyperactivity that was related to an oxidative stress. Because cases of megaloblastic anemia have been reported to occur in women taking OC, these treatments are suspected of depleting folate stores. In the study presented herein, which was conducted in rats, we sought to determine the influence of dietary folic acid deficiency (FD) on the thrombogenicity of OC. Animals were fed for 6 weeks with either a folic acid-deficient diet (250 μg/kg folic acid) or a control diet (750 μg/kg). One-half of the animals in each group were treated with OC (ethinyl estradiol plus ly…

Potential role of oxysterols and lysolecithin in the oxidised LDL-induced decrease in albumin synthesis in HEPG2 cells

Oxidative stress leads to cholesterol accumulation in vascular smooth muscle cells.

The transformation of macrophages and smooth muscle cells into foam cells by modified low-density lipoproteins (LDL) is one of the key events of atherogenesis. Effects of free radicals have mainly been studied in LDL, and other than toxicity, data dealing with direct action of free radicals on cells are scarce. This study focused on the direct effects of free radicals on cholesterol metabolism of smooth muscle cells. A free radical generator, azobis-amidinopropane dihydrochloride, was used, and conditions for a standardized oxidative stress were set up in vascular smooth muscle cells. After free radical action, the cells presented an accumulation of cholesterol that appeared to be the resul…

Altérations du métabolisme de l'homocystéine et maladies cardiovasculaires

Resume L'homocysteine est un produit intermediaire du metabolisme de la methionine. L'augmentation moderee ou intermediaire de la concentration totale en homocysteine circulante, detectee dans les conditions basales ou apres le test de surcharge orale en methionine, est maintenant reconnue comme un facteur de risque important des maladies cardiovasculaires et des thromboses, chez les femmes comme chez les hommes, au meme titre que les facteurs de risques conventionnels. L'hyperhomocysteinemie, qui depend d'une inhibition de la voie de remethylation, d'une inhibition ou d'une saturation de la voie de transsulfuration, resulte d'une alteration de la regulation coordonnee du metabolisme de l'h…

Glucose and free radicals impair the antioxidant properties of serum albumin

Epidemiological data consistently show that reduced levels of serum albumin, which is the most abundant protein in plasma, are associated with an increased mortality risk. Various biological properties evidenced by direct effects of the albumin molecule may explain its beneficial effects. The present work aimed to investigate in vitro whether glycation or free radicals or both factors would affect the antioxidant properties of bovine serum albumin (BSA). Glycation was performed by long-term incubations (60 days) of BSA with increasing concentrations of glucose (up to 500 mmol/l) at 37 degreesC. Minimally oxidized BSA was obtained after controlled incubations of dialyzed BSA samples with a w…

High Serum Cholesteryl Ester Transfer Rates and Small High-Density Lipoproteins Are Associated With Young Age in Patients With Acute Myocardial Infarction

Objectives Our aim was to characterize cholesteryl ester transfer protein (CETP) activity in the early phase of acute myocardial infarction (MI). Background Cholesteryl ester transfer protein catalyzes the transfer of cholesteryl esters from high-density lipoprotein (HDL) donors to apolipoprotein B-containing lipoprotein acceptors. Methods The CETP concentration, lipid profiles, and the rate of cholesteryl ester transfer (CET) from a tracer dose of radiolabeled HDL toward endogenous lipoproteins were determined within 24 h after symptom onset. Results Among 347 patients with first MI, CETP concentration, triglycerides, and non–HDL-cholesterol increased across tertiles of the CET rate, where…

Differential effects of oxidized LDL on apolipoprotein AI and B synthesis in HepG2 cells

Oxidized low-density lipoproteins (Ox-LDL) are key elements in atherogenesis. Apolipoprotein AI (apoAI) is an active component of the antiatherogenic high-density lipoproteins (HDL). In contrast, plasma apolipoprotein B (apoB), the main component of LDL, is highly correlated with coronary risk. Our results, obtained in HepG2 cells, show that Ox-LDL, unlike native LDL, leads to opposite effects on apoB and apoAI, namely a decrease in apoAI and an increase in apoB secretion as evaluated by [(3)H]leucine incorporation and specific immunoprecipitation. Parallel pulse-chase studies show that Ox-LDL impaired apoB degradation, whereas apoAI degradation was increased and mRNA levels were decreased.…

Gas chromatographic analysis of resveratrol in plasma, lipoproteins and cells after in vitro incubations

Resveratrol is a trihydroxystilbene present in certain red wines. It may play a role in the inhibition of lipoprotein oxidation and platelet activity. We have developed the first method to measure resveratrol in animal and human samples and to study its incorporation in vitro. After adding epicoprostanol as an internal standard, samples are subjected to lipid extraction in the presence of antioxidant and under dim light to minimize both denaturation and isomerization of the trans-resveratrol to the cis-form. Extracts were purified by cold acetone precipitation and the resveratrol-containing acetone phase was evaporated under nitrogen. The resveratrol was analyzed as a trimethylsilyl derivat…