Low-density Lipoprotein Lipid Peroxidation Research Articles

In vitro evaluation of antiatherogenic potential of Origanum × paniculatum, Lippia alba, Clinopodium nepeta, and Eucalyptus globulus essential oils

IntroductionEssential oils (EOs) are mixtures of secondary plant metabolism compounds with potential lipid-lowering activity and antioxidant properties. They may therefore be considered as add-on therapy for the prevention and treatment of cardiovascular diseases. MethodsEOs of Origanum × paniculatum (OpEO), Lippia alba (chemotype linalool) (LaLEO), Clinopodium nepeta (CnEO) and Eucalyptus globulus (EgEO), were evaluated on THP-1 foam cell macrophages as a cellular model of atherogenesis. Cell viability was determined by the MTT assay, lipid content by thin-layer chromatography, and Oil Red O staining. Antioxidant activity was evaluated by TBARS on low-density lipoprotein lipid peroxidation, and by ABTS•+, DPPH•, and FRAP assays. EOs were characterised by gas chromatography–mass spectrometry and a predictive multivariate data analysis was performed by partial least square regression (PLS) to identify the components related to antiatherogenic potential. ResultsOpEO reduced foam cell viability (IC50 = 45 µl/l) and cholesterol and triacylglycerol content and demonstrated antioxidant activity. In contrast, LaLEO increased lipid content and showed a prooxidant capacity with low reduction of cell viability (IC50 = 340 µl/l). CnEO showed prooxidant activity and reduction of cell viability (IC50 = 130 µl/l) without changes in lipid content. EgEO showed antioxidant activity, lipid increase, and low cytotoxicity (IC50 = 770 µl/l). PLS analysis suggests that cis-sabinene hydrate is responsible for cell viability inhibition, thymol and β-cis-terpineol decrease lipid content and possess antioxidant activity, and linalool increases lipid levels and has prooxidant capacity. ConclusionsOpEO is a promising natural product for therapy against atherosclerosis, with cis-sabinene hydrate, thymol, and β-cis-terpineol as potential active principles.

Protective Effect of Lusianthridin on Hemin-Induced Low-Density Lipoprotein Oxidation.

Oxidation of low-density lipoprotein (LDL) plays a crucial role in the pathogenesis of atherosclerosis. Hemin (iron (III)-protoporphyrin IX) is a degradation product of hemoglobin that can be found in thalassemia patients. Hemin is a strong oxidant that can cause LDL oxidation and contributes to atherosclerosis in thalassemia patients. Lusianthridin from Dendrobium venustrum is a phenolic compound that possesses antioxidant activity. Hence, lusianthridin could be a promising compound to be used against hemin-induced oxidative stress. The major goal of this study is to evaluate the protective effect of lusianthridin on hemin-induced low-density lipoprotein oxidation (he-oxLDL). Here, various concentrations of lusianthridin (0.25, 0.5, 1, and 2 µM) were preincubated with LDL for 30 min, then 5 µM of hemin was added to initiate the oxidation, and oxidative parameters were measured at various times of incubation (0, 1, 3, 6, 12, 24 h). Lipid peroxidation of LDL was measured by thiobarbituric reactive substance (TBARs) assay and relative electrophoretic mobility (REM). The lipid composition of LDL was analyzed by using reverse-phase HPLC. Foam cell formation with he-oxLDL in RAW 264.7 macrophage cells was detected by Oil Red O staining. The results indicated that lusianthridin could inhibit TBARs formation, decrease REM, decrease oxidized lipid products, as well as preserve the level of cholesteryl arachidonate and cholesteryl linoleate. Moreover, He-oxLDL incubated with lusianthridin for 24 h can reduce the foam cell formation in RAW 264.7 macrophage cells. Taken together, lusianthridin could be a potential agent to be used to prevent atherosclerosis in thalassemia patients.

Wide Biological Role of Hydroxytyrosol: Possible Therapeutic and Preventive Properties in Cardiovascular Diseases.

The growing incidence of cardiovascular disease (CVD) has promoted investigations of natural molecules that could prevent and treat CVD. Among these, hydroxytyrosol, a polyphenolic compound of olive oil, is well known for its antioxidant, anti-inflammatory, and anti-atherogenic effects. Its strong antioxidant properties are due to the scavenging of radicals and the stimulation of synthesis and activity of antioxidant enzymes (SOD, CAT, HO-1, NOS, COX-2, GSH), which also limit the lipid peroxidation of low-density lipoprotein (LDL) cholesterol, a hallmark of atherosclerosis. Lowered inflammation and oxidative stress and an improved lipid profile were also demonstrated in healthy subjects as well as in metabolic syndrome patients after hydroxytyrosol (HT) supplementation. These results might open a new therapeutic scenario through personalized supplementation of HT in CVDs. This review is the first attempt to collect together scientific literature on HT in both in vitro and in vivo models, as well as in human clinical studies, describing its potential biological effects for cardiovascular health.

Citrus reticulata peel oil as an antiatherogenic agent: Hypolipogenic effect in hepatic cells, lipid storage decrease in foam cells, and prevention of LDL oxidation

Background and aimsHypercholesterolemia and oxidative stress are two of the most important risk factors for atherosclerosis. The aim of the present work was to evaluate mandarin (Citrus reticulata) peel oil (MPO) in cholesterol metabolism and lipid synthesis, and its antioxidant capacity. Methods and resultsIncubation of hepatic HepG2 cells with MPO (15–60 μL/L) reduced cholesterogenesis and saponifiable lipid synthesis, demonstrated by [14C]acetate radioactivity assays. These effects were associated with a decrease in a post-squalene reaction of the mevalonate pathway. Molecular docking analyses were carried out using three different scoring functions to examine the cholesterol-lowering property of all the components of MPO against lanosterol synthase. Docking simulations proposed that minor components of MPO monoterpenes, like alpha-farnesene and neryl acetate, as well the major component, limonene and its metabolites, could be partly responsible for the inhibitory effects observed in culture assays. MPO also decreased RAW 264.7 foam cell lipid storage and its CD36 expression, and prevented low-density lipoprotein (LDL) lipid peroxidation. ConclusionThese results may imply a potential role of MPO in preventing atherosclerosis by a mechanism involving inhibition of lipid synthesis and storage and the decrease of LDL lipid peroxidation.

The Effects of an Olive Fruit Polyphenol-Enriched Yogurt on Body Composition, Blood Redox Status, Physiological and Metabolic Parameters and Yogurt Microflora.

In the present study we investigated the effects of an olive polyphenol-enriched yogurt on yogurt microflora, as well as hematological, physiological and metabolic parameters, blood redox status and body composition. In a randomized double-blind, crossover design, 16 (6 men, 10 women) nonsmoking volunteers with non-declared pathology consumed either 400 g of olive fruit polyphenol-enriched yogurt with 50 mg of encapsulated olive polyphenols (experimental condition—EC) or 400 g of plain yogurt (control condition—CC) every day for two weeks. Physiological measurements and blood collection were performed before and after two weeks of each condition. The results showed that body weight, body mass index, hip circumference and systolic blood pressure decreased significantly (p < 0.05) following the two-week consumption of yogurt regardless of condition. A tendency towards significance for decreased levels of low density lipoprotein (LDL) cholesterol (p = 0.06) and thiobarbituric acid reactive substances (p < 0.05) following two weeks of polyphenol-enriched yogurt consumption was observed. The population of lactic acid bacteria (LAB) and production of lactate in yogurt were significantly enhanced after addition of olive polyphenols, contrary to the population of yeasts and molds. The results indicate that consumption of the polyphenol-enriched yogurt may help individuals with non-declared pathology reduce body weight, blood pressure, LDL cholesterol levels and lipid peroxidation, and promote growth of beneficial LAB.

High density lipoprotein level is negatively associated with the increase of oxidized low density lipoprotein lipids after a fatty meal.

Recent reports show that a fatty meal can substantially increase the concentration of oxidized lipids in low density lipoprotein (LDL). Knowing the LDL-specific antioxidant effects of high density lipoprotein (HDL), we aimed to investigate whether HDL can modify the postprandial oxidative stress after a fatty meal. Subjects of the study (n = 71) consumed a test meal (a standard hamburger meal) rich in lipid peroxides, and blood samples were taken before, 120, 240, and 360 min after the meal. The study subjects were divided into four subgroups according to the pre-meal HDL cholesterol value (HDL subgroup 1, 0.66-0.91; subgroup 2, 0.93-1.13; subgroup 3, 1.16-1.35; subgroup 4, 1.40-2.65 mmol/L). The test meal induced a marked postprandial increase in the concentration of oxidized LDL lipids in all four subgroups. The pre-meal HDL level was associated with the extent of the postprandial rise in oxidized LDL lipids. From baseline to 6 h after the meal, the concentration of ox-LDL increased by 48, 31, 24, and 16% in the HDL subgroup 1, 2, 3, and 4, respectively, and the increase was higher in subgroup 1 compared to subgroup 3 (p = 0.028) and subgroup 4 (p = 0.0081), respectively. The pre-meal HDL correlated with both the amount and the rate of increase of oxidized LDL lipids. Results of the present study show that HDL is associated with the postprandial appearance of lipid peroxides in LDL. It is therefore likely that the sequestration and transport of atherogenic lipid peroxides is another significant mechanism contributing to cardioprotection by HDL.

Is atherosclerosis an autoimmune disease?

Immunologic research into pathogenic mechanisms operating in autoimmune-mediated atherosclerosis initially focused on adaptive immunity. Current interest is directed to more basic inflammatory mechanisms. Chronic inflammation (innate immunity-associated) may trigger initial events that can lead to atherosclerotic cardiovascular disease. This chronic inflammation may start early in life and be perpetuated by classic atherosclerosis risk factors. Lipid peroxidation of low-density lipoprotein seems to be a key event in the initiation and progression of atherosclerosis. Oxidized low-density lipoprotein triggers inflammatory and immunogenic events that promote endothelial dysfunction and the synthesis and secretion of pro-inflammatory cytokines, leading to an autoimmune response capable of accelerating the intracellular accumulation of lipids within atherosclerotic plaques. Oxidized low-density lipoprotein binds β2-glycoprotein I to form circulating complexes found in both autoimmune and non-autoimmune atherosclerosis. It is likely that β2-glycoprotein I and/or these complexes contribute to early atherogenesis by stimulating pro-inflammatory innate immunity through endogenous sensors and inflammasome/interleukin-1 pathways. We discuss the chronic inflammatory (innate) and autoimmune (adaptive) responses operating in atherosclerosis to discern the role of autoimmunity in atherosclerotic cardiovascular disease.

Onion extract (Allium cepa L.) up-regulates paraoxonase 1 activity with concomitant protection against LDL oxidation in male wistar strain rats subjected to mercuric chloride induced oxidative stress

Onion (Allium cepa L.) is one of the rich sources of flavonoids, consisting mainly of the major flavonols quercetin-3,4'-O-diglucoside (QDG) and quercetin-4'-O-monoglucoside (QMG) with high therapeutic properties. Paraoxonase1 (PON1) protects the oxidative modification of low density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein (HDL). We explored the roles of onion extracts and flavonoids (quercetin & catechin) in the regulation of PON1 expression by measuring its arylesterase activity and correlating with plasma MDA and oxidized LDL levels, as a marker of oxidative stress in wistar strain rats subjected to mercuric chloride (HgCl2) induced oxidative insult. Rats were divided into eight groups. Control, Experimental (HgCl2 treated), Exp + onion extract/catechin/quercetin, Positive control (Normal + onion/catechin/quercetin). Treatment continued for 4 weeks. PON1 activity decreased in rats treated with HgCl2 (HgCl2 treated 23.83 U/ml plasma; control value: 33.20 U/ml plasma) with an increase in susceptibility of LDL for oxidation (values derived after 3000 s; Pearson's r = 0.9970, p< 0.001; control value: Pearson's r = 0.9980, p< 0.001) and plasma MDA level (0.408 nmol/ml plasma; control value: 0.202 nmol/ml plasma). Onion extracts successfully and significantly attenuated the adverse effects of HgCl2 by up regulating PON1 activity (28.10 U/ml plasma) and its protective capacity against LDL oxidation (Pearson's r = 0.9978, p< 0.001) and lipid peroxidation (0.313 nmol/ml plasma). Similar effects were shown by quercetin and catechin with improved oxidative status either by enhancing PON1activities (31.36 & 24.76 U/ml plasma) and antioxidant defenses (0.24 & 0.28 nmol/ml plasma MDA level) or reducing susceptibility to LDL oxidation (Pearson's r = 0.9973 & 0.9984, p < 0.001), when given to oxidatively stressed rats.

Hibiscus sabdariffa leaf polyphenolic extract inhibits LDL oxidation and foam cell formation involving up-regulation of LXRα/ABCA1 pathway

The oxidative modification of low-density lipoprotein (LDL) is involved in the pathogenesis of atherosclerotic lesions through the formation of macrophage-derived foam cells. In the present study, we aimed to investigate the anti-atherosclerotic effect of Hibiscus sabdariffa leaf polyphenolic extract (HLP), which is rich in flavonoid. The inhibitory effect of HLP on oxidation and lipid peroxidation of LDL was defined in vitro. HLP showed potential in reducing foam cell formation and intracellular lipid accumulation in oxidised-LDL (ox-LDL)-induced macrophage J774A.1 cells under non-cytotoxic concentrations. Molecular data showed these influences of HLP might be mediated via liver-X receptor α (LXRα)/ATP-binding cassette transporter A1 (ABCA1) pathway, as demonstrated by the transfection of LXRα siRNA. Our data implied that HLP up-regulated the LXRα/ABCA1 pathway, which in turn led to stimulation of cholesterol removal from macrophages and delay atherosclerosis. These results suggested that HLP potentially could be developed as an anti-atherosclerotic agent.

Characterization of a novel high-density lipoprotein antioxidant capacity assay and its application to high-density lipoprotein fractions

ObjectivesHigh-density lipoprotein (HDL) inhibits low-density lipoprotein (LDL) oxidation therefore it is involved in the prevention of atherogenesis. HDL particles originating from different persons possess different antioxidant activities. Our aim was to establish a method for the measurement of HDL antioxidant capacity, which is suitable for testing the antioxidant activity of HDL samples in a wide range and produces data relevant to in vivo HDL–LDL interactions. Hemin was used as pro-oxidant since its role in the course of LDL oxidation and atherosclerosis is proven. MethodsHemin-induced and hydrogen peroxide catalyzed lipid peroxidation of LDL was performed in the presence and absence of HDL. The time interval required for reaching the maximum reaction velocity (ΔTVmax) was determined and HDL antioxidant capacity was expressed as the ratio of the ΔTVmax with and without HDL. HDL fractions (n=8) isolated by ultracentrifugation from healthy donors were analyzed and their antioxidant capacities were compared. ResultsIn parallel with their increasing density, HDL fractions expressed increasing antioxidant capacity (106.12–194.12%). Within-run and within-laboratory CVs of the method were 1.72–1.87% and 4.09–4.93%, respectively. Alterations of hydrogen peroxide concentration in the range of 50–125μmol/L did not influence the assay results, while the elevation of hemin concentration (between 3 and 9μmol/L) resulted in decreased antioxidant capacity. The values for hemin degradation correlated well with conjugated diene formation. ConclusionsHemin-induced LDL oxidation is a reliable assay system to test the antioxidant capacity of HDL and its subpopulations.

Plasma Lipoproteins as Mediators of the Oxidative Stress Induced by UV Light in Human Skin: A Review of Biochemical and Biophysical Studies on Mechanisms of Apolipoprotein Alteration, Lipid Peroxidation, and Associated Skin Cell Responses

There are numerous studies concerning the effect of UVB light on skin cells but fewer on other skin components such as the interstitial fluid. This review highlights high-density lipoprotein (HDL) and low-density lipoprotein (LDL) as important targets of UVB in interstitial fluid. Tryptophan residues are the sole apolipoprotein residues absorbing solar UVB. The UVB-induced one-electron oxidation of Trp produces •Trp and •O2 − radicals which trigger lipid peroxidation. Immunoblots from buffered solutions or suction blister fluid reveal that propagation of photooxidative damage to other residues such as Tyr or disulfide bonds produces intra- and intermolecular bonds in apolipoproteins A-I, A-II, and B100. Partial repair of phenoxyl tyrosyl radicals (TyrO•) by α-tocopherol is observed with LDL and HDL on millisecond or second time scales, whereas limited repair of α-tocopherol by carotenoids occurs in only HDL. More effective repair of Tyr and α-tocopherol is observed with the flavonoid, quercetin, bound to serum albumin, but quercetin is less potent than new synthetic polyphenols in inhibiting LDL lipid peroxidation or restoring α-tocopherol. The systemic consequences of HDL and LDL oxidation and the activation and/or inhibition of signalling pathways by oxidized LDL and their ability to enhance transcription factor DNA binding activity are also reviewed.

ANTIOXIDATIVE EFFECTS OF TWO NATIVE BERRY SPECIES,EMPETRUM NIGRUMVAR. JAPONICUM K. KOCH ANDRUBUS BUERGERIMIQ., FROM THE JEJU ISLAND OF KOREA

The extracts of two native berries from the Jeju Island of Korea were used to assess polyphenolics and flavonol levels, superoxide dismutase (SOD)-like enzyme activity, free radical scavenging activity, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cell viability, protective effects against H2O2-induced cow pulmonary artery endothelium (CPAE) cell cytotoxicity and inhibition of low density lipoprotein (LDL) peroxidation. The total content of the flavonols and phenolic compounds in the leaves was higher than the fruit for both berries. In the free radical scavenging and SOD-like enzyme assay, all extracts showed strong antioxidative effects. The CPAE viability was greatly reduced and the survival rate was near 37% when the cells were treated with 1.0 mM H2O2 for 24 h. The extracts also inhibited lipid peroxidation in human LDL, measured as reduction in malondialdehyde production. The results showed that the leaf extracts of Empetrum nigrum significantly protected human LDL from Cu2+-induced oxidation. E. nigrum is suggested as an excellent potential source of natural antioxidants. PRACTICAL APPLICATIONS The results of these two Korean native berry species, especially Shiromi species, showed very strong effects on the inhibition of low density lipoprotein (LDL) oxidation and free radical scavenging. The LDL and free radicals have known close relations with coronary artery and cerebrovascular atherosclerosis. The antioxidative effects of these berries were stronger than existing commercial products. From these results, Korean native berry species might be very useful for the development of functional food for antioxidants preventing oxidative stress-related diseases like atherosclerosis. Making a new commercial product with Korean Shiromi berry will have good prospects.

Coincubation of PON1, APO A1, and LCAT increases the time HDL is able to prevent LDL oxidation

The inhibition of low-density lipoprotein (LDL) oxidation by high-density lipoprotein (HDL) is a major antiatherogenic property of this lipoprotein. This activity is due, in part, to HDL associated proteins. However, whether these proteins interact in the antioxidant activity of HDL is unknown. LDL was incubated with apolipoprotein A1 (apo A1), lecithin:cholesterol acyltransferase (LCAT), and paraoxonase-1 (PON1) alone or in combination, in the presence or absence of HDL under oxidizing conditions. LDL lipid peroxide concentrations were determined. Apo A1, LCAT, and PON1 all inhibit LDL oxidation in the absence of HDL and enhance the ability of HDL to inhibit LDL oxidation. Their effect was additive rather than synergistic; the combination of these proteins significantly enhanced the length of time LDL was protected from oxidation. This seemed to be due to the ability of PON1 to prevent the oxidative inactivation of LCAT. Apo A1, LCAT, and PON1 can all contribute to the antioxidant activity of HDL in vitro. The combination of apo A1, LCAT, and PON1 prolongs the time that HDL can prevent LDL oxidation, due, at least in part, to the prevention LCAT inactivation.

Peroxidation of lipoproteins in multiple sclerosis

Human plasma low density lipoproteins (LDL) and high density lipoproteins (HDL) are involved in the transport of lipids, modulate membrane lipid composition and regulate signal transduction. HDL-like lipoproteins have been shown also in human cerebrospinal fluid and it has been hypothesized that they could have a role in lipid transport in central nervous system. After synthesis, lipoproteins are susceptible to lipid peroxidation triggered by reactive oxygen species (ROS and RNS) produced by peripheral and brain cells. Aim of the paper has been to review the scientific literature on the role of lipid peroxidation of LDL and HDL in the molecular mechanisms of multiple sclerosis (MS). Several studies have demonstrated a significant increase in lipid peroxidation products in brain, plasma and cerebrospinal fluid of MS patients. The increase of antibodies against ox-LDL in plasma and the presence of ox-LDL in demyelinating plaques in MS brain suggests that the disease is associated with oxidative damage of lipoproteins. The impairment of antioxidant systems or an increase in the production of ROS and RNS could contribute to lipoprotein peroxidation in MS. Oxidized lipoproteins show several alterations of their functions, they are neurotoxic and have pro-inflammatory properties. Therefore lipoprotein lipid peroxidation products could be involved in demyelination and axonal injury in MS.

Effect of phytosterols on copper lipid peroxidation of human low-density lipoproteins

Objective Phytosterols and stanols have received much attention in the past several years because of their cholesterol-lowering properties, and several studies have shown a protective effect against cardiovascular disease and colon and breast cancer development. A significant decrease of plasma low-density lipoprotein (LDL) cholesterol and apolipoprotein B has been demonstrated in subjects whose diet was supplemented with 2 g/d of plant sterols. Changes in plasma lipoprotein levels were associated with a decrease of oxidized LDL, suggesting that plant sterols could exert an antioxidant effect. The aim of the present study was to further investigate the interaction between the major dietary phytosterols and plasma lipoproteins. Moreover, their antioxidant effect against in vitro–induced lipid peroxidation of human LDL was investigated. Methods Susceptibility to copper-induced lipid peroxidation was investigated in LDLs isolated from plasma of normolipemic subjects. Concentrations of β-sitosterol, campesterol, and stigmasterol ranging from 5 to 50 μM were studied. Analyses of the emission fluorescence spectra of tryptophan and of the probe 6-dodecanoyl-2-dimethyl-aminoaphthalene were used to investigate the effect of phytosterols on apoprotein structure and physicochemical properties of LDL. Results Our results demonstrated that phytosterols exert an inhibitory effect against copper-induced lipid peroxidation of LDLs, as shown by the lowered levels of conjugated dienes in oxidized lipoproteins incubated with different concentrations of plant sterols (5–50 μM). Moreover, analysis of fluorescence emission spectra of tryptophan and 6-dodecanoyl-2-dimethyl-aminoaphthalene demonstrated that phytosterols prevent the alterations of apoprotein structure and physicochemical properties associated with copper-triggered lipid peroxidation of lipoproteins. Conclusion We suggest that the effect exerted by β-sitosterol, stigmasterol, and campesterol against lipid peroxidation of LDL possibly related to phytosterol–lipoprotein interactions could be of physiologic relevance.

The alkyl chain length of 3-alkyl-3′,4′,5,7-tetrahydroxyflavones modulates effective inhibition of oxidative damage in biological systems: Illustration with LDL, red blood cells and human skin keratinocytes

It is shown that the relationship between the alkyl chain length of 3-alkyl-3′,4′,5,7 tetrahydroxyflavones (FnH) bearing alkyl chains of n = 1, 4, 6, 10 carbons and their capacity to counter oxidative damage varies markedly with the nature of the biological system. In Cu 2+-induced lipid peroxidation of low-density lipoprotein (LDL), the less hydrophobic short-chain F1H and F4H are probably located in the outer layer of LDL and parallel the reference flavonoid antioxidant, quercetin (Q) as effective inhibitors of lipid peroxidation. A marked inhibition of haemolysis induced in red blood cells (RBC) suspensions by the membrane-permeant oxidant, tert-butylhydroperoxide (t-BuOOH), is observed with F4H and F6H present at concentration in the micromolar range. However, F10H the most hydrophobic FnH is even more effective than Q against both haemolysis and lipid peroxidation as measured by malondialdehyde (MDA) equivalents. In oxidation of RBC by H 2O 2, at least 50 times more F6H and F10H than by t-BuOOH are required to only partly inhibit haemolysis and MDA production. The F1H, F4H and Q are found rather inactive under these conditions. At concentrations in the micromolar range, a marked protection against the cytotoxic effects of the t-BuOOH-induced oxidative stress in human skin NCTC 2544 keratinocytes is also exhibited by the four FnH antioxidants and is comparable to that of Q. Thus, the four FnH species under study may be considered as potent antioxidants which manifest complementary anti-oxidative actions in biological systems of markedly different complexity.

Acute ingestion of yerba mate infusion (Ilex paraguariensis) inhibits plasma and lipoprotein oxidation

Abstract Yerba mate extract (Ilex paraguariensis) is a source of phenolic compounds that possesses in vitro antioxidant activities and may contribute to a reduction in the risk of cardiovascular disease. In this study we examined the acute effects of the consumption of mate infusion on ex vivo plasma and low-density lipoprotein (LDL) oxidation, plasma antioxidant capacity, and platelet aggregation. Twelve healthy fasted subjects ingested 500 mL of mate infusion and blood samples were collected before and 1 h after mate intake. Lipid peroxidation of plasma and LDL was monitored by the measurement of cholesteryl-ester hydroperoxides (CE-OOH) and cholesterol oxides. The plasma antioxidant capacity was measured as ferric-reducing antioxidant potential (FRAP). Platelet aggregation was evaluated in platelet-rich plasma stimulated with adenosine diphosphate and coagulation was tested in platelet-poor plasma. Ingestion of mate infusion diminished the ex vivo oxidizability of both plasma and LDL particles. After mate intake, the CE-OOH levels were around 50% lower in plasma oxidized with copper or 2,2′-azobis[2-amidine-propane-hydrochloride] (AAPH) and the lag time to plasma oxidation increased 2-fold (P

Antioxidant Actions of Phenolic Compounds Found in Dietary Plants on Low-Density Lipoprotein and Erythrocytes in Vitro

Objective: There is increasing interest in the study of the antioxidant actions of plant phenolic compounds as evidence shows that consumption of plant products rich in these compounds contributes to protection from a number of ailments including cardiovascular diseases. In the present study, the antioxidant effects of selected phenolic compounds from dietary sources, namely barbaloin, 6-gingerol and rhapontin, were investigated.Methods: Low-density lipoprotein (LDL), erythrocytes and erythrocyte membranes were subjected to several in vitro oxidative systems. The antioxidant effects of the phenolic compounds were assessed by their abilities in inhibiting hemolysis and lipid peroxidation of LDL and erythrocyte membranes, and in protecting ATPase activities and protein sulfhydryl groups of erythrocyte membranes.Results: 6-Gingerol and rhapontin were found to exhibit strong inhibition against lipid peroxidation in LDL induced by 2,2′-azobis(2-amidinopropane) hydrochloride (AAPH) and hemin while barbaloin possessed weaker effects. A similar order of antioxidant potencies among the three compounds was observed on the lipid peroxidation of erythrocyte membranes in a tert-butylhydroperoxide (tBHP)/hemin oxidation system. On the other hand, barbaloin and rhapontin were comparatively stronger antioxidants than 6-gingerol in preventing AAPH-induced hemolysis of erythrocytes. Among the three compounds, only barbaloin protected Ca2+-ATPase and protein sulfhydryl groups on erythrocyte membranes against oxidative attack by tBHP/hemin. Interestingly, rhapontin demonstrated protective actions on Na+/K+-ATPase in a sulfhydryl group-independent manner under the same experimental conditions.Conclusions: In view of their protective effects on LDL and erythrocytes against oxidative damage, these phenolic compounds might have potential applications in prooxidant state-related cardiovascular disorders.

17β-Estradiol reverses shear-stress-mediated low density lipoprotein modifications

Within arterial bifurcations or branching points, oscillatory shear stress (OSS) induces oxidative stress mainly via the reduced nicotinamide adenine dinucleodtide phosphate (NADPH) oxidase system. It is unknown whether 17β-estradiol (E 2) can regulate OSS-mediated low-density lipoprotein (LDL) modifications. Bovine aortic endothelial cells were pretreated with E 2 at 5 nmol/L, followed by exposure to OSS (0 ± 3.0 dynes/cm 2 s and 60 cycles/min) in a flow system. E 2 decreased OSS-mediated NADPH oxidase mRNA expression, and E 2-mediated NO production was mitigated by the NO synthase inhibitor N(G)-nitro- l-argenine methyl ester. The rates of O 2 − production in response to OSS increased steadily as determined by superoxide-dismutase-inhibited ferricytochrome c reduction; whereas, pretreatment with E 2 decreased OSS-mediated O 2 − production ( n = 4, p < 0.05). In the presence of native LDL (50 μg/mL), E 2 also significantly reversed OSS-mediated LDL oxidation as determined by high-performance liquid chromatography. In the presence of O 2 − donor, xanthine oxidase (XO), E 2 further reversed XO-induced LDL lipid peroxidation ( n = 3, p < 0.001). Mass spectra acquired in the m/ z 400–1800 range, revealed XO-mediated LDL protein nitration involving tyrosine 2535 in the α-2 domains, whereas pretreatment with E 2 reversed nitration, as supported by the changes in nitrotyrosine intensities. Thus, E 2 plays an indirect antioxidative role. In addition to upregulation of endothelial NO synthase and downregulation of Nox4 expression, E 2 influences LDL modifications via lipid peroxidation and protein nitration.

Hemodialysis reduces inhibitory effect of plasma ultrafiltrate on LDL oxidation and subsequent endothelial reactions

Oxidative modification of low-density lipoprotein (LDL) and its deleterious effect on endothelium is implicated in the pathogenesis of atherosclerosis. Endothelium responds to such an insult by upregulating the synthesis of heme oxygenase-1 (HO-1) and ferritin. Endothelial cell damage and dysfunction have been observed in patients with chronic kidney disease (CKD) on maintenance hemodialysis (HD). We studied the effect of low-molecular-weight components of uremic plasma on LDL oxidation and LDL-oxidation-provoked endothelial cell reactions, such as the induction of cytotoxicity and the upregulation of cell-protective HO-1 and ferritin. Plasma ultrafiltrate (molecular weight<5000 Da) from CKD patients on HD or when treated conservatively exhibited a pronounced inhibition on heme-mediated oxidative modification of LDL. Endothelial cell cytotoxicity provoked by LDL oxidation was also attenuated by plasma ultrafiltrate from CKD patients. During HD treatment, a dramatic drop occurred in the retardation of oxidative reactions, and a loss of endothelial cytoprotection exerted by plasma ultrafiltrate was noted. The upregulation of HO-1 and ferritin in response to oxidative stress of LDL was blunted by uremic plasma ultrafiltrate that was released by the end of HD. The decreased antioxidant capacity of ultrafiltrate after HD occurred as a consequence of the intradialytic removal of L-ascorbic acid, uric acid, bilirubin, 3-indoxyl sulfate, indoxyl-beta-D-glucuronide, p-cresol, and phenol. Intradialytic removal of L-ascorbic acid, uric acid, bilirubin, 3-indoxyl sulfate, indoxyl-beta-D-glucuronide, p-cresol, and phenol increases the risk of LDL oxidation and subsequent endothelial cell damage, which underlines the importance of activation of cytoprotective HO-1 and ferritin in endothelium.