Copper can promote oxidation of LDL by markedly different mechanisms

Interactions between CuO NPs and PS: The release of copper ions and oxidative damage

Copper oxide nanoparticles (CuO NPs) can adversely affect lung health possibly by inducing oxidative damage through the release of copper ions. However, the migration and transformation processes of CuO NPs in lung lining fluid is still unclear, and there are still conflicting reports of redox reactions involving copper ions. To address this, we examined the release of copper ions from CuO NPs in simulated lung fluid supplemented with pulmonary surfactant (PS), and further analyzed the mechanisms of PS-CuO NPs interactions and the health hazards. The results showed that the phospholipid of PS was adsorbed on the particle surface, which not only induced aggregation of the particles but also provided a reaction environment for the interaction of PS with CuO NPs. PS was able to promote the release of ions from CuO NPs, of which the protein was a key component. Lipid peroxidation, protein destabilization, and disruption of the interfacial chemistry also occurred in the PS-CuO NPs interactions, during which copper ions were present only as divalent cations. Meanwhile, the contribution of the particle surface cannot be neglected in the oxidative damage to the lung caused by CuO NPs. Through reacting with biomolecules, CuO NPs accomplished ion release and induced oxidative damage associated with PS. This research was the first to reveal the mechanism of CuO NPs releasing copper ions and inducing lipid oxidative damage in the presence of PS, which provides a new idea of transition metal-induced health risk in human body.

A national cross-sectional analysis of dietary copper intake and abdominal aortic calcification in the US adults: NHANES 2013-2014

BACKGROUND AND AIMS

Copper is an essential dietary element with a crucial role in physiological regulation. However, the relationship between dietary copper intake and abdominal aortic calcification (AAC) remains uncertain.

METHODS AND RESULTS

This study encompassed a cohort of 2535 adults aged over 40 years, derived from the National Health and Nutrition Examination Survey 2013-2014. Dietary copper intake from both food sources and supplements was assessed through two 24-h dietary recall interviews. AAC was measured by dual-energy X-ray absorptiometry and classified into 3 groups using the Kauppila score system. Multivariable logistic regression models were constructed to evaluate the association between dietary copper intake and AAC. Among the participants, a total of 771 individuals (30.4%) were diagnosed with AAC, of which 239 (9.4%) exhibited severe AAC. Higher dietary copper intake was significantly associated with a lower incidence of severe AAC. Specifically, for each 1 mg/day increase in dietary copper intake, the incidence of severe AAC decreased by 38% (odds ratios [OR] 0.62, 95% confidence intervals [CI] 0.39-0.98) after adjustment for relevant covariates. Moreover, individuals in the third tertile of copper intake had a 37% lower incidence of AAC compared to those in the first tertile [OR 0.63, 95% CI (0.43-0.95)]. However, no significant associations were found between supplemental copper intake or serum copper levels and AAC.

CONCLUSIONS

This study demonstrates that lower dietary copper intake, rather than serum copper levels or supplement copper intake, is significantly associated with a higher prevalence of AAC in adults ≥40 years old in the United States.

Copper homeostasis and cuproptosis in health and disease

As an essential micronutrient, copper is required for a wide range of physiological processes in virtually all cell types. Because the accumulation of intracellular copper can induce oxidative stress and perturbing cellular function, copper homeostasis is tightly regulated. Recent studies identified a novel copper-dependent form of cell death called cuproptosis, which is distinct from all other known pathways underlying cell death. Cuproptosis occurs via copper binding to lipoylated enzymes in the tricarboxylic acid (TCA) cycle, which leads to subsequent protein aggregation, proteotoxic stress, and ultimately cell death. Here, we summarize our current knowledge regarding copper metabolism, copper-related disease, the characteristics of cuproptosis, and the mechanisms that regulate cuproptosis. In addition, we discuss the implications of cuproptosis in the pathogenesis of various disease conditions, including Wilson's disease, neurodegenerative diseases, and cancer, and we discuss the therapeutic potential of targeting cuproptosis.

Azocompounds as generators of defined radical species: Contributions and challenges for free radical research

Peroxyl radicals participate in multiple processes involved in critical changes to cells, tissues, pharmacueticals and foods. Some of these reactions explain their association with degenerative pathologies, including cardiovascular and neurological diseases, as well as cancer development. Azocompounds, and particularly AAPH (2,2'-Azobis(2-methylpropionamidine) dihydrochloride), a cationic water-soluble derivative, have been employed extensively as sources of model peroxyl radicals. A considerable number of studies have reported mechanistic data on the oxidation of biologically-relevant targets, the scavenging activity of foods and natural products, and the reactions with, and responses of, cultured cells. However, despite the (supposed) experimental simplicity of using azocompounds, the chemistry of peroxyl radical production and subsequent reactions is complicated, and not always considered in sufficient depth when analyzing experimental data. The present work discusses the chemical aspects of azocompounds as generators of peroxyl (and other) radicals, together with their contribution to our understanding of biochemistry, pharmaceutical and food chemistry research. The evidence supporting a role for the formation of alkoxyl (RO•) and other radicals during thermal and photochemical decomposition of azocompounds is assessed, together with the potential influence of such species on the reactions under study.

Molecular Characterization, Protein-Protein Interaction Network, and Evolution of Four Glutathione Peroxidases from Tetrahymena thermophila

Glutathione peroxidases (GPxs) form a broad family of antioxidant proteins essential for maintaining redox homeostasis in eukaryotic cells. In this study, we used an integrative approach that combines bioinformatics, molecular biology, and biochemistry to investigate the role of GPxs in reactive oxygen species detoxification in the unicellular eukaryotic model organism Tetrahymena thermophila. Both phylogenetic and mechanistic empirical model analyses provided indications about the evolutionary relationships among the GPXs of Tetrahymena and the orthologous enzymes of phylogenetically related species. In-silico gene characterization and text mining were used to predict the functional relationships between GPxs and other physiologically-relevant processes. The GPx genes contain conserved transcriptional regulatory elements in the promoter region, which suggest that transcription is under tight control of specialized signaling pathways. The bioinformatic findings were next experimentally validated by studying the time course of gene transcription and enzymatic activity after copper (Cu) exposure. Results emphasize the role of GPxs in the detoxification pathways that, by complex regulation of GPx gene expression, enable Tethraymena to survive in high Cu concentrations and the associated redox environment.

Dapsone protects brain microvascular integrity from high-fat diet induced LDL oxidation

Atherosclerosis was considered to induce many vascular-related complications, such as acute myocardial infarction and stroke. Abnormal lipid metabolism and its peroxidation inducing blood–brain barrier (BBB) leakage were associated with the pre-clinical stage of stroke. Dapsone (DDS), an anti-inflammation and anti-oxidation drug, has been found to have protective effects on vascular. However, whether DDS has a protective role on brain microvessels during lipid oxidation had yet to be elucidated. We investigated brain microvascular integrity in a high-fat diet (HFD) mouse model. We designed this study to explore whether DDS had protective effects on brain microvessels under lipid oxidation and tried to explain the underlying mechanism. In our live optical study, we found that DDS significantly attenuated brain microvascular leakage through reducing serum oxidized low-density lipoprotein (oxLDL) in HFD mice (p < 0.001), and DDS significantly inhibited LDL oxidation in vitro (p < 0.001). Our study showed that DDS protected tight junction proteins: ZO-1 (p < 0.001), occludin (p < 0.01), claudin-5 (p < 0.05) of microvascular endothelial cells in vivo and in vitro. DDS reversed LAMP1 aggregation in cytoplasm, and decreased the destruction of tight junction protein: ZO-1 in vitro. We first revealed that DDS had a protective role on cerebral microvessels through preventing tight junction ZO-1 from abnormal degradation by autophagy and reducing lysosome accumulation. Our findings suggested the significance of DDS in protecting brain microvessels under lipid metabolic disorders, which revealed a novel potential therapeutic strategy in brain microvascular-related diseases.

Identification and molecular characterization of two Cu/Zn-SODs and Mn-SOD in the marine ciliate Euplotes crassus: Modulation of enzyme activity and transcripts in response to copper and cadmium

The superoxide dismutase (SOD) family is a first line antioxidant enzyme group involved in transformation of the superoxide anion (O₂^-) into hydrogen peroxide (H₂O₂) and O₂. SOD gene expression patterns and enzyme activities therefore have a role as molecular biomarkers in evaluating the oxidative stress status of aquatic organisms. However, antioxidant enzyme systems are yet to be fully explored in the marine ciliates. In this study, we identified and characterized two types of Cu/Zn SODs (Ec-Cu/ZnSOD1 and Ec-Cu/ZnSOD2) and Ec-Mn SOD in the marine ciliate Euplotes crassus. Subsequently, SOD activity and transcriptional modulation of the relevant genes were investigated after the exposure to Cd and Cu for 8 h. All Ec-SODs showed conserved domains and metal binding sites on their active sites. Total SOD activity was induced at 1 h after exposure to Cd (125 and 1000 μg/L), and showed a marginal increase at 1-h exposure to Cu (10 and 100 μg/L). However, SOD activity was maintained at a steady level under Cd and decreased under Cu exposure conditions at 3 h and 8 h. mRNA expression of both the Ec-Cu/Zn-SODs and Mn-SOD were remarkably elevated after the exposure to Cd (250-1000 μg/L, maximum 4-fold, p < 0.05) and, in particular, Cu (25-100 μg/L, maximum > 20-fold, p < 0.05), in a concentration - dependent manner. These findings suggest that Ec-SODs may be actively involved in cellular protection against metal - mediated oxidative stress. This study is therefore helpful in understanding the molecular responses for metal toxicity in the ciliates.

Ethyl pyruvate inhibits oxidation of LDL in vitro and attenuates oxLDL toxicity in EA.hy926 cells

Background

Ethyl pyruvate (EP) exerts anti-inflammatory and anti-oxidative properties. The aim of our study was to investigate whether EP is capable of inhibiting the oxidation of LDL, a crucial step in atherogenesis. Additionally, we examined whether EP attenuates the cytotoxic effects of highly oxidized LDL in the human vascular endothelial cell line EA.hy926.

Methods

Native LDL (nLDL) was oxidized using Cu²⁺ ions in the presence of increasing amounts of EP. The degree of LDL oxidation was quantified by measuring lipid hydroperoxide (LPO) and malondialdehyde (MDA) concentrations, relative electrophoretic mobilities (REMs), and oxidation-specific immune epitopes. The cytotoxicity of these oxLDLs on EA.hy926 cells was assessed by measuring cell viability and superoxide levels. Furthermore, the cytotoxicity of highly oxidized LDL on EA.hy926 cells under increasing concentrations of EP in the media was assessed including measurements of high energy phosphates (ATP).

Results

Oxidation of nLDL using Cu²⁺ ions was remarkably inhibited by EP in a concentration-dependent manner, reflected by decreased levels of LPO, MDA, REM, oxidation-specific epitopes, and diminished cytotoxicity of the obtained oxLDLs in EA.hy926 cells. Furthermore, the cytotoxicity of highly oxidized LDL on EA.hy926 cells was remarkably attenuated by EP added to the media in a concentration-dependent manner reflected by a decrease in superoxide and an increase in viability and ATP levels.

Conclusions

EP has the potential for an anti-atherosclerotic drug by attenuating both, the oxidation of LDL and the cytotoxic effect of (already formed) oxLDL in EA.hy926 cells. Chronic administration of EP might be beneficial to impede the development of atherosclerotic lesions.

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Thiol oxidase ability of copper ion is specifically retained upon chelation by aldose reductase

Bovine lens aldose reductase is susceptible to a copper-mediated oxidation, leading to the generation of a disulfide bridge with the concomitant incorporation of two equivalents of the metal and inactivation of the enzyme. The metal complexed by the protein remains redox active, being able to catalyse the oxidation of different physiological thiol compounds. The thiol oxidase activity displayed by the enzymatic form carrying one equivalent of copper ion (Cu₁-AR) has been characterized. The efficacy of Cu₁-AR in catalysing thiol oxidation is essentially comparable to the free copper in terms of both thiol concentration and pH effect. On the contrary, the two catalysts are differently affected by temperature. The specificity of the AR-bound copper towards thiols is highlighted with Cu₁-AR being completely ineffective in promoting the oxidation of both low-density lipoprotein and ascorbic acid.

Atheroprotective action of a modified organoselenium compound: in vitro evidence

ABSTRACT Oxidation of low-density lipoprotein (LDL) has been strongly suggested to play a significant role in the pathogenesis of atherosclerosis. Thus, reducing LDL oxidation is a potential approach to decrease the risk of the atherosclerosis. Organoselenium compounds have demonstrated promising atheroprotective properties in experimental models. Herein, we tested the in vitro atheroprotective capability of a modified organoselenium compound, Compound HBD, in protecting isolated LDL from oxidation as well as foam cells formation. Moreover, the glutathione peroxidase (GPx)-like activity of Compound HBD was analyzed in order to explore the mechanisms related to the above-mentioned protective effects. The Compound HBD in a concentration-dependent manner reduced the Cu2+-induced formation of conjugated dienes. The protein portion from LDL were also protected from Cu2+-induced oxidation. Furthermore, the Compound HBD efficiently decreased the foam cell formation in J774 macrophage cells exposed to oxidized LDL. We found that the atheroprotective effects of this compound can be, at least in part, related to its GPx-like activity. Our findings demonstrated an impressive effect of Compound HBD against LDL-induced toxicity, a further in vivo study to investigate in more detail the antioxidant and antiatherogenic effects of this compound could be considered.

Evaluation of serum zinc level in patients with newly diagnosed and resistant alopecia areata

BACKGROUND

Alopecia areata (AA) is a non-scarring, autoimmune, inflammatory hair loss disease. Zinc is a trace element involved in important functional activities of hair follicles.

PURPOSE

To evaluate serum zinc levels in patients with newly diagnosed and resistant lesions of AA in comparison to age- and sex-matched healthy controls.

METHODS

The present study included 100 subjects: 50 patients with AA divided into two equally distributed subgroups (25 patients with recent onset AA [subgroup 1] and 25 patients with resistant AA [subgroup 2]) and 50 age- and sex-matched healthy controls. Serum zinc levels were assessed in all subjects. Comparison of mean serum zinc levels was done between all patients and controls, between patients' subgroups as well as between patient's subgroup and controls. Correlations between serum zinc level and extent of AA and its duration were also done in all patients and each patient's subgroup.

RESULTS

A significantly lower serum zinc level was found in patients with AA compared with controls and was significantly lower in patients with resistant AA compared to patients with newly diagnosed AA. Significant inverse correlations existed between serum zinc level, severity of AA, and disease duration in all patients as well as in patients with resistant AA.

CONCLUSION

Lower serum zinc level existed in patients with AA and correlated inversely with disease duration, severity of AA, and its resistance to therapies. Therefore, assessment of serum zinc level in patients with AA appears useful as a marker of severity, disease duration, and resistance to therapies. Accordingly, zinc supplements may provide a therapeutic benefit.

Absence of an effect of vitamin E on protein and lipid radical formation during lipoperoxidation of LDL by lipoxygenase

Low-density lipoprotein (LDL) oxidation is the primary event in atherosclerosis, and LDL lipoperoxidation leads to modifications in apolipoprotein B-100 (apo B-100) and lipids. Intermediate species of lipoperoxidation are known to be able to generate amino acid-centered radicals. Thus, we hypothesized that lipoperoxidation intermediates induce protein-derived free radical formation during LDL oxidation. Using DMPO and immuno-spin trapping, we detected the formation of protein free radicals on LDL incubated with Cu(2+) or the soybean lipoxidase (LPOx)/phospholipase A2 (PLA2). With low concentrations of DMPO (1mM), Cu(2+) dose-dependently induced oxidation of LDL and easily detected apo B-100 radicals. Protein radical formation in LDL incubated with Cu(2+) showed maximum yields after 30 min. In contrast, the yields of apo B-100 radicals formed by LPOx/PLA2 followed a typical enzyme-catalyzed kinetics that was unaffected by DMPO concentrations of up to 50mM. Furthermore, when we analyzed the effect of antioxidants on protein radical formation during LDL oxidation, we found that ascorbate, urate, and Trolox dose-dependently reduced apo B-100 free radical formation in LDL exposed to Cu(2+). In contrast, Trolox was the only antioxidant that even partially protected LDL from LPOx/PLA2. We also examined the kinetics of lipid radical formation and protein radical formation induced by Cu(2+) or LPOx/PLA2 for LDL supplemented with α-tocopherol. In contrast to the potent antioxidant effect of α-tocopherol on the delay of LDL oxidation induced by Cu(2+), when we used the oxidizing system LPOx/PLA2, no significant protection was detected. The lack of protection of α-tocopherol on the apo B-100 and lipid free radical formation by LPOx may explain the failure of vitamin E as a cardiovascular protective agent for humans.

Absence of clinical relationship between oxidized low density lipoproteins and diabetic peripheral neuropathy: a case control study

Background

The pathophysiology of diabetic peripheral neuropathy (DPN) is complex and uncertain. A potential comorbidity in diabetes mellitus (DM) that may contribute to greater severity of DPN is a lipid disorder, such as with elevated cholesterol, low density lipoproteins or triglycerides. Oxidized low density lipoprotein (oxLDL) is a form of cholesterol that exerts direct toxic effects and contributes to pathogenicity through ligating a receptor called lectin-like receptor (LOX-1).

Methods

We examined plasma oxLDL levels in cohorts of patients with DPN with neuropathic pain (NeP), DPN patients without NeP, DM patients without DPN, patients with idiopathic peripheral neuropathy, and control subjects without DM or neuropathy. Our outcome measure was extent of oxLDL elevation, measured as fasting with Enzyme-Linked ImmunoSorbant Assay (ELISA) studies. Severity of diabetes was assessed using hemoglobin A1C measurements. Neuropathic severity was measured with the Utah Early Neuropathy Score (UENS). We hypothesized that DPN presence would be associated with oxLDL elevations.

Results

A total of 115 subjects (47 with DPN and NeP, 23 with DPN without NeP, 12 with diabetes only, 13 with idiopathic peripheral neuropathy, and 20 control subjects without diabetes or neuropathy) were studied. Duration of diabetes and diabetic glycemic measures were similar between populations with DM. Severity of DPN was similar between cohorts with DPN and NeP and DPN without NeP. Plasma oxLDL levels were similar between all cohorts, without any elevation in the presence of DM noted in any cohort with DM.

Conclusions

oxLDL levels are not different in patients with DPN, and their lack of greater presence suggests that any pathogenic role in human DPN is likely limited.

Human scavenger protein AIM increases foam cell formation and CD36-mediated oxLDL uptake

AIM is expressed by macrophages in response to agonists of the nuclear receptors LXR/RXR. In mice, it acts as an atherogenic factor by protecting macrophages from the apoptotic effects of oxidized lipids. In humans, it is detected in atherosclerotic lesions, but no role related to atherosclerosis has been reported. This study aimed to investigate whether the role of hAIM extends beyond inhibiting oxidized lipid-induced apoptosis. To accomplish this goal, functional analysis with human monocytic THP1 cells and macrophages differentiated from peripheral blood monocytes were performed. It was found that hAIM reduced oxLDL-induced macrophage apoptosis and increased macrophage adhesion to endothelial ICAM-1 by enhancing LFA-1 expression. Furthermore, hAIM increased foam cell formation, as shown by Oil Red O and Nile Red staining, as well as quantification of cholesterol content. This was not a result of decreased reverse cholesterol transport, as hAIM did not affect the efflux significantly from [(3)H] Cholesterol-laden macrophages driven by plasma, apoA-I, or HDL2 acceptors. Rather, flow cytometry studies indicated that hAIM increased macrophage endocytosis of fluorescent oxLDL, which correlated with an increase in the expression of the oxLDLR CD36. Moreover, hAIM bound to oxLDL in ELISA and enhanced the capacity of HEK-293 cells expressing CD36 to endocytose oxLDL, as studied using immunofluorescence microscopy, suggesting that hAIM serves to facilitate CD36-mediated uptake of oxLDL. Our data represent the first evidence that hAIM is involved in macrophage survival, adhesion, and foam cell formation and suggest a significant contribution to atherosclerosis-related mechanisms in the macrophage.

Kinetic modeling of low density lipoprotein oxidation in arterial wall and its application in atherosclerotic lesions prediction

Oxidation of low-density lipoprotein (LDL) is one of the major factors in atherogenic process. Trapped oxidized LDL (Ox-LDL) in the subendothelial matrix is taken up by macrophage and leads to foam cell generation creating the first step in atherosclerosis development. Many researchers have studied LDL oxidation using in vitro cell-induced LDL oxidation model. The present study provides a kinetic model for LDL oxidation in intima layer that can be used in modeling of atherosclerotic lesions development. This is accomplished by considering lipid peroxidation kinetic in LDL through a system of elementary reactions. In comparison, characteristics of our proposed kinetic model are consistent with the results of previous experimental models from other researches. Furthermore, our proposed LDL oxidation model is added to the mass transfer equation in order to predict the LDL concentration distribution in intima layer which is usually difficult to measure experimentally. According to the results, LDL oxidation kinetic constant is an important parameter that affects LDL concentration in intima layer so that existence of antioxidants that is responsible for the reduction of initiating rates and prevention of radical formations, have increased the concentration of LDL in intima by reducing the LDL oxidation rate.

Interaction and reactivity of urocanic acid towards peroxyl radicals

The capacity of urocanic acid to interact with peroxyl radicals has been evaluated in several systems: oxidation in the presence of a free radical source (2,2'-azobis(2-amidinopropane; AAPH), protection of phycocyanin bleaching elicited by peroxyl radicals, and Cu(II)- and AAPH-promoted LDL oxidation. The results indicate that both isomers (cis and trans) are mild peroxyl radical scavengers. For example, trans-urocanic acid is nearly 400 times less efficient than Trolox in the protection of the peroxyl radical promoted bleaching of phycocyanin. Regarding the removal of urocanic acid by peroxyl radicals, nearly 100 muM trans-urocanic acid is required to trap half of the produced radicals under the employed conditions (10 mM AAPH, 37 degrees C). Competitive experiments show that the cis-isomer traps peroxyl radicals 30% less efficiently than the trans-isomer. Given the high concentrations that trans-urocanic acid reaches in skin, its capacity to trap peroxyl radicals could contribute to the protection of the tissue towards ROS-mediated processes. Furthermore, both isomers, and particularly the cis-isomer, protect LDL from Cu(II)-induced oxidation.

The antioxidant activity of copper(II) (3,5-diisopropyl salicylate)4 and its protective effect against streptozotocin-induced diabetes mellitus in rats

Oxidative stress has been suggested as a potential contributor to the development of diabetic complications. In this study, we investigated the protective effect of a strong antioxidant copper complex against streptozotocin (STZ)-induced diabetes in animals. Out of four copper complexes used, copper(II) (3,5-diisopropyl salicylate)4 (Cu(II)DIPS) was found to be the most potent antioxidant-copper complex. Pretreatment with Cu(II)DIPS (5 mg/kg) twice a week prior to the injection of streptozotocin (50 mg/kg) has reduced the level of hyperglycemia by 34 % and the mortality rate by 29 %. Injection of the same dosage of the ligand 3,5-diisopropyl salicylate has no effect on streptozotocin-induced hyperglycemia. The same copper complex has neither hypoglycemic activity when injected in normal rats nor antidiabetic activity when injected in STZ-induced diabetic rats. The protective effect of Cu(II)DIPS could be related to its strong antioxidant activity compared to other copper complexes median effective concentration (MEC) = 23.84 μg/ml and to Trolox MEC = 29.30 μg/ml. In addition, it reduced serum 8-hydroxy-2'-deoxyguanosine, a biomarker of oxidative DNA damage, by 29 %. This effect may explain why it was not effective against diabetic rats, when β Langerhans cells were already destroyed. Similar protective activities were reported by other antioxidants like Trolox.

Carbon monoxide promotes respiratory hemoproteins iron reduction using peroxides as electron donors

The physiological role of the respiratory hemoproteins (RH), hemoglobin and myoglobin, is to deliver O(2) via its binding to their ferrous (Fe(II)) heme-iron. Under variety of pathological conditions RH proteins leak to blood plasma and oxidized to ferric (Fe(III), met) forms becoming the source of oxidative vascular damage. However, recent studies have indicated that both metRH and peroxides induce Heme Oxygenase (HO) enzyme producing carbon monoxide (CO). The gas has an extremely high affinity for the ferrous heme-iron and is known to reduce ferric hemoproteins in the presence of suitable electron donors. We hypothesized that under in vivo plasma conditions, peroxides at low concentration can assist the reduction of metRH in presence of CO. The effect of CO on interaction of metRH with hydrophilic or hydrophobic peroxides was analyzed by following Soret and visible light absorption changes in reaction mixtures. It was found that under anaerobic conditions and low concentrations of RH and peroxides mimicking plasma conditions, peroxides served as electron donors and RH were reduced to their ferrous carboxy forms. The reaction rates were dependent on CO as well as peroxide concentrations. These results demonstrate that oxidative activity of acellular ferric RH and peroxides may be amended by CO turning on the reducing potential of peroxides and facilitating the formation of redox-inactive carboxyRH. Our data suggest the possible role of HO/CO in protection of vascular system from oxidative damage.

Iron-catalyzed oxidation of Trp residues in low-density lipoprotein

The mechanisms of oxidation of low-density lipoproteins (LDLs) are not well defined, but epidemiological and experimental studies suggest that iron-catalyzed processes may contribute to atherogenesis. The aim of this study was to test the hypothesis that iron-catalyzed oxidations of LDLs in vitro produce diagnostic biomarkers of oxidation of the apolipoprotein that could be applied to studies in vivo. LDLs were oxidized in the presence of Fe2+, EDTA, and ascorbic acid for up to 40 h. Following delipidation and trypsin digestion, the peptides were separated by HPLC, with four peaks detected at 365 nm, whereas none were observed in peptides from unoxidized LDLs. The peptides were identified by MALDI-QTOF mass spectrometry as IVQILP(W+4) EQNEQVK, IYSL(W+4)EHSTK, FEGLQE(W+4)EGK, and YH(W+4)EHTGLTLR, with (W+4) rather than the W residues of the unoxidized protein. The mass gains (+4 increase in m/z in tryptophan, W) and absorbance at 365 nm indicate kynurenines, which were trypsin-releasable peptides that are on the surface of LDL particles. All four peptides thus characterized share the sequence of WE. The preferential oxidation of W residues in WE sequences suggest contributions from the C-proximate glutamate residues in chelation of the iron species, thereby influencing site selectivities of oxidation. These kynurenine-containing peptides might serve as biomarkers of iron-mediated oxidations in vivo.

Age- and gender-based studies of trace metal levels and various enzymes associated with myocardial infarction

The present investigation deals with the determination of various serum enzymes known to be elevated during myocardial infarction (MI) and estimation of selected metals like Cu, Cr, Co, Fe, Pb, and Mg by flame atomic absorption spectrophotometry. The data obtained thereby were processed for the determination of correlation coefficient matrix among the cardiac enzymes and the serum metals. The study evidenced the accumulation of Pb during MI and reduction in the level of Fe. A significant negative correlation was observed between Cu and creatine kinase-MB. The data were also segregated into various groups to study the influence of age and gender on the levels of selected parameters. In both the genders, the age of the patients was found to be correlated significantly with various cardiac enzymes. In case of male patients, the most significant correlation was observed between age and blood sugar at random. The other significant correlations among the male patients included Cr-CPK, Cr-creatine kinase-MB, Fe-age, and others. In female patients, the pairs of studied parameters that exhibited significant correlations included age-lactic dehydrogenase, creatine phosphokinase isoenzyme-aspartate aminotransferase, lactic dehydrogenase-creatine phosphokinase isoenzymes, Pb-Fe, and Cu-Co in addition to others.

Copper and myeloperoxidase-modified LDLs activate Nrf2 through different pathways of ROS production in macrophages

Low-density lipoprotein (LDL) oxidation is a key step in atherogenesis, promoting the formation of lipid-laden macrophages. Here, we compared the effects of copper-oxidized LDLs (OxLDLs) and of the more physiologically relevant myeloperoxidase-oxidized LDLs (MoxLDLs) in murine RAW264.7 macrophages and in human peripheral blood monocyte-derived macrophages. Both oxidized LDLs, contrary to native LDLs, induced foam cell formation and an intracellular accumulation of reactive oxygen species (ROS). This oxidative stress was responsible for the activation of the NF-E2-related factor 2 (Nrf2) transcription factor, and the subsequent Nrf2-dependent overexpression of the antioxidant genes, Gclm and HO-1, as evidenced by the invalidation of Nrf2 by RNAi. MoxLDLs always induced a stronger response than OxLDLs. These differences could be partly explained by specific ROS-producing mechanisms differing between OxLDLs and MoxLDLs. Whereas both types of oxidized LDLs caused ROS production partly by NADPH oxidase, only MoxLDLs-induced ROS production was dependent on cytosolic PLA2. This study highlights that OxLDLs and MoxLDLs induce an oxidative stress, through distinct ROS-producing mechanisms, which is responsible for the differential activation of the Nrf2 pathway. These data clearly suggest that results obtained until now with copper oxidized-LDLs should be carefully reevaluated, taking into consideration physiologically more relevant oxidized LDLs.

Protective activity of plicatin B against human LDL oxidation induced in metal ion-dependent and -independent processes. Experimental and theoretical studies

Oxidation of low-density lipoproteins (LDL) is thought to be a major factor in the pathophysiology of atherosclerosis. Natural antioxidants have been shown to protect LDL from oxidation and to inhibit atherogenic developments in animals. Structurally related prenylated pterocarpans, erybraedin C and bitucarpin A, and the prenylchalcone plicatin B were examined for their ability to inhibit LDL oxidation in vitro. The kinetic profile of peroxidation is characterized by the lag time of oxidation (t(lag)), the maximal rate of oxidation (V(max)) and the maximal accumulation of oxidation products (OD(max)). Specific variation of the set of kinetic parameters by antioxidants may provide important information about the mechanism of inhibitory action of a given compound. At equimolar concentrations (1 microM) the prenylated derivatives tested were found to inhibit 1 microM copper sulphate-induced oxidation of LDL (50 microg protein/ml) in accordance with the following order of activity: plicatin B>erybraedin Cbitucarpin A. Structural aspects, such as hydrogen-donating substituents, their number and arrangement in the aromatic ring moieties, and the prenyl and methoxy substituents, were investigated in order to explain the findings obtained. It is well known that the antioxidant activity of flavonoids is believed to be caused by a combination of transition metal chelation and free-radical-scavenging activities. To investigate these differences we comparatively studied the protective mechanism of plicatin B in copper-dependent or -independent LDL oxidation. The latter was mediated by 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (ABAP). We measured the formation of conjugated dienes (OD(234 nm)). Plicatin B (0.2-1.5 microM) delayed the Cu(2+) (1 microM) promoted oxidation as conjugate diene formation (t(lag)) of the LDL by 45.2-123.5 min and reduced V(max) by 0.46-0.29 microM/min. In the ABAP (0.2mM) promoted LDL oxidation t(lag) increased by 67.2-110.2 min through plicatin B (0.5-2.5 microM). In experiments in which Cu(2+) concentrations increased (0.5 - 3 microM) and the amount of plicatin B (1 microM) was maintained constant, a significant decrease in t(lag) and an increase in V(max) was observed. In this study plicatin B appeared to exhibit a mixed mechanism, interfering with the formation of the radicals by chelating copper involved in the initiation/propagation reaction, but also by scavenging free hydroperoxyl radicals resulting from ABAP thermolysis. In addition, theoretical analysis indicated that plicatin B preferentially established the chelating complex with Cu(2+), because its affinity value is notably higher (by a factor of 5) than that for Cu(+).

Properties of Quercetin Conjugates: Modulation of LDL Oxidation and Binding to Human Serum Albumin

Quercetin is an important dietary flavonoid with in vitro antioxidant activity. However, it is found in human plasma as conjugates with glucuronic acid, sulfate or methyl groups, with no significant amounts of free quercetin present. The antioxidant properties of the conjugates found in vivo and their binding to serum albumin are unknown, but essential for understanding possible actions of quercetin in vivo. We, therefore, tested the most abundant human plasma quercetin conjugates, quercetin-3-glucuronide, quercetin-3'-sulfate and isorhamnetin-3-glucuronide, for their ability to inhibit Cu(II)-induced oxidation of human low density lipoprotein and to bind to human albumin, in comparison to free flavonoids and other quercetin conjugates. LDL oxidation lag time was increased by up to four times by low (<2 microM) concentrations of quercetin-3-glucuronide, but was unaffected by equivalent concentrations of quercetin-3'-sulfate and isorhamnetin-3-glucuronide. In general, the compounds under study prolonged the lag time of copper-induced LDL oxidation in the order: quercetin-7-glucuronide > quercetin > quercetin-3-glucuronide = quercetin-3-glucoside > catechin > quercetin-4'-glucuronide > isorhamnetin-3-glucuronide > quercetin-3'-sulfate. Thus the proposed products of small intestine metabolism (quercetin-7-glucuronide, quercetin-3-glucuronide) are more efficient antioxidants than subsequent liver metabolites (isorhamnetin-3-glucuronide, quercetin-3'-sulfate). Albumin-bound conjugates retained their property of protecting LDL from oxidation, although the order of efficacy was altered (quercetin-3'-sulfate > quercetin-7-glucuronide > quercetin-3-glucuronide > quercetin-4'-glucuronide = isorahmnetin-3-glucuronide). Kq values (concentration required to achieve 50% quenching) for albumin binding, as assessed by fluorescence quenching of Trp214, were as follows: quercetin-3'-sulfate (approximately 4 microM)= quercetin > or = quercetin-7-glucuronide > quercetin-3-glucuronide = quercetin-3-glucoside > isorhamnetin-3-glucuronide > quercetin-4'-glucuronide (approximately 20 microM). The data show that flavonoid intestinal and hepatic metabolism have profound effects on ability to inhibit LDL oxidation and a lesser but significant effect on binding to serum albumin.

Lipid Peroxidation in the Presence of Albumin, Inhibitory and Prooxidative Effects

Oxidative modifications of LDL are involved in atherogenesis. Previously we have developed a simple assay to evaluate the susceptibility of lipids to copper-induced peroxidation in the relatively natural milieu of unfractionated serum in the presence of excess citrate. Based on our previous results we have proposed that the inducer of peroxidation in our optimized assay is a copper-citrate complex. Recent investigations indicate that under certain conditions a copper-albumin complex may induce peroxidation of ascorbate. Two different complexes may be formed in albumin-containing systems (e.g. serum) namely 1:1 and 2:1 copper-albumin complexes. The aim of the present work was to evaluate the possibility that at least one of these complexes may be responsible for the induction of peroxidation of lipids in lipidic systems containing copper and albumin, including our optimized assay. Towards this end, we have investigated the dependence of copper-induced peroxidation on the concentration of added albumin in lipidic systems in the absence and presence of citrate. In all the systems investigated in this study (PLPC liposomes, LDL, HDL and mixtures of HDL and LDL) we found that at low concentrations of free copper (e.g. in the presence of excess citrate) the 2:1 copper-albumin complex is redox-active and that this complex is the major contributor to the initiation of lipid peroxidation in these systems and in our optimized assay. The possible relevance of the induction of peroxidation in vivo by the latter complex has yet to be studied.

Diphenyl diselenide, a simple glutathione peroxidase mimetic, inhibits human LDL oxidation in vitro

Oxidative modification of low-density lipoprotein (LDL) represents an important factor in atherogenesis. In the present study, we have investigated the antioxidant capability of diphenyl diselenide (PhSe)(2), a simple organoseleno compound, against copper (Cu2+) and peroxyl radical-induced human LDL oxidation in vitro. In initial studies using human serum, (PhSe)(2) caused a dose-dependent inhibition of Cu(2+)-induced lipid peroxidation, which was correlated to thiol consumption. (PhSe)(2) increased lipid peroxidation lag phase and decreased lipid peroxidation rate in isolated human LDL, evaluated by measuring both conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) levels. Consistent with these observations, (PhSe)(2) showed a marked inhibitory effect on 2,2-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced oxidation of LDL or parinaric acid (PnA) incorporated into LDL. (PhSe)(2) also displayed a dose-dependent protective effect against Cu(2+)-induced lipid peroxidation in rat aortic slices. Interestingly, besides the antioxidant effects of (PhSe)(2) toward the lipid moieties of LDL, which was related to its thiol-peroxidase activity, protein moieties from human isolated LDL were also protected against Cu(2+)-induced oxidation. The results presented herein are the first to show that (i) (PhSe)(2) inhibits lipid peroxidation in human isolated LDL in vitro, (ii) this phenomenon is related to its thiol-peroxidase activity, and (iii) this chalcogen also prevents the oxidation of protein moieties of human LDL. Taken together, such data render (PhSe)(2) a promising molecule for pharmacological studies with respect to the atherogenic process.

Advanced but not localized prostate cancer is associated with increased oxidative stress

PURPOSE

Oxidative damage has been linked to prostate carcinogenesis but its role in disease development and progression remains elusive. We investigated associations between indexes of oxidative stress with localized and advanced prostate cancer. Specifically we assessed the susceptibility of serum lipids to copper induced peroxidation (oxidizability).

MATERIALS AND METHODS

Serum oxidizability, and levels of alpha-tocopherol, malonyldialdehyde and uric acid were assessed in samples from 79 patients with prostate cancer, including 42 with localized and 37 with metastatic disease receiving androgen deprivation therapy, and 25 control subjects. Oxidizability was assayed by continuous spectroscopic monitoring of the accumulation of peroxidation products. The lag preceding oxidation, that is the delay between the induction and propagation of the reaction, served as a measure of the resistance of serum lipids to oxidation.

RESULTS

Compared to control subjects patients with localized prostate cancer had no difference in oxidative stress indexes, whereas those with metastatic disease had a shorter lag preceding oxidation and increased malonyldialdehyde (p <0.05), each reflecting a state of high oxidative stress. In patients with prostate cancer the probability of disease progression from localized to advanced state increased with a shorter lag preceding oxidation (p <0.001), increased malonyldialdehyde (p <0.03) and decreased uric acid (p <0.04). Localized and metastatic disease was associated with increased rather than decreased alpha-tocopherol (p <0.008 and <0.005, respectively).

CONCLUSIONS

Patients with advanced prostate cancer are subject to high oxidative stress, as determined by increased susceptibility of serum lipids to peroxidation. This association was not detected in patients with localized cancer and it is not attributable to altered levels of alpha-tocopherol.

Antioxidative and antiproliferative properties of selected barley (Hordeum vulgarae L.) cultivars and their potential for inhibition of low-density lipoprotein (LDL) cholesterol oxidation

Aqueous methanolic extracts of whole kernels from six different barley cultivars, namely, Falcon, AC Metcalfe, Tyto, Tercel, Phoenix, and Peregrine, were examined for their total phenolic content (TPC), oxygen radical scavenging capacity (ORACFL), hydroxyl radical scavenging capacity (HORACFL), potency in prevention of lipid oxidation using the Rancimat method, efficacy in inhibition of Cu(II)-induced human LDL cholesterol oxidation, and antiproliferative activities using Caco-2 colorectal adenocarcinoma cell line. Total phenolic content as measured by Folin-Ciocalteu's method ranged from 0.68 to 1.19 mg of ferulic acid equiv/g of defatted material, whereas ORACFL and HORACFL values were 11.28-19.10 and 9.06-12.99 micromol of Trolox equiv/g of defatted material, respectively. Protection factor (PF), a measure of the effect of extracts on the prevention of oxidation of stripped corn oil as measured by Rancimat, ranged from 0.97 to 1.59. Furthermore, barley extracts showed 19.64-33.93% inhibition against Cu(II)-induced human LDL cholesterol oxidation at a final concentration of 0.02 mg/mL. The proliferation of Caco-2 colon cancer cells was significantly (p < 0.05) inhibited in a dose-dependent fashion in the presence of all barley extracts tested at the end of the day 4 of incubation. At the end of day 4, barley extracts rendered 29.3-51.2 and 9.3-15.9% inhibition of cell proliferation at 0.5 and 0.05 mg/mL, respectively. Phenolic extracts from whole barley kernel tested possessed high antioxidant, antiradical, and antiproliferative potentials. Therefore, inclusion of whole barley into the daily diet may render beneficial health benefits.

Common variants of apolipoprotein A-IV differ in their ability to inhibit low density lipoprotein oxidation

Apolipoprotein A-IV (apoA-IV) inhibits lipid peroxidation, thus demonstrating potential anti-atherogenic properties. The aim of this study was to investigate how the inhibition of low density lipoprotein (LDL) oxidation was influenced by common apoA-IV isoforms. Recombinant wild type apoA-IV (100 microg/ml) significantly inhibited the oxidation of LDL (50 microg protein/ml) by 5 microM CuSO(4) (P<0.005), but not by 100 microM CuSO(4), suggesting that it may act by binding copper ions. ApoA-IV also inhibited the oxidation of LDL by the water-soluble free-radical generator 2,2'-azobis(amidinopropane) dihydrochloride (AAPH; 1 mM), as shown by the two-fold increase in the time for half maximal conjugated diene formation (T(1/2); P<0.05) suggesting it can also scavenge free radicals in the aqueous phase. Compared to wild type apoA-IV, apoA-IV-S347 decreased T(1/2) by 15% (P=0.036) and apoA-IV-H360 increased T(1/2) by 18% (P=0.046). All apoA-IV isoforms increased the relative electrophoretic mobility of native LDL, suggesting apoA-IV can bind to LDL and acts as a site-specific antioxidant. The reduced inhibition of LDL oxidation by apoA-IV-S347 compared to wild type apoA-IV may account for the previous association of the APOA4 S347 variant with increased CHD risk and oxidative stress.

A Comparative Study of the Metal Ion Uptake and Antioxidant Enzyme Activities ofFusarium equisetiandFusarium acuminatumas a Function of External Magnesium Concentration

The increase of Mg2+, from 1.3 to 3 microM, in growth medium of F. equiseti and F. acuminatum increased intracellular magnesium levels from 0.83 and 0.81 microM to 1.75 and 1.42 microM on the 12th day, respectively. Intracellular magnesium levels also elevated depending upon the number of incubation days. The maximum manganese levels of F. equiseti and F. acuminatum obtained in 1.6 microM Mg2+ culture medium were 0.67 and 1.23 microM, while maximum iron levels were determined to be 1.3 microM Mg2+ as 0.51 and 0.29 microM, respectively. The maximum intracellular iron and manganese levels were decreased significantly with increasing Mg2+ concentration in the culture medium and were increased depending upon the incubation period. However, intracellular zinc levels of these strains didn't change with Mg2+ concentration and incubation period. The maximum superoxide dismutase (MnSOD) activities of F. equiseti and F. acuminatum, related to increased intracellular manganese levels up to 1.6 microM Mg2+ in growth medium, were determined to be 78 and 110 IU/mg, respectively. CAT activity variations showed agreement with SOD activity and reached a maximum at 320 and 225 IU/mg under the same conditions. The minimum LPO levels of the Fusarium strains with the maximum MnSOD and CAT activities were determined as 1.2 and 0.9 nmol MDA/g., wet weight. The higher LPO level of F. equiseti grown at the same condition, in spite of 1.42-fold higher CAT activity due to the 1.41-fold lower SOD activity, as well as a 2.0-fold higher iron level, indicated increases in the generation of reactive oxygen species via the Fenton reaction.

Measurement of plasma oxidized low-density lipoprotein and its clinical implications

Oxidized low-density lipoprotein (OxLDL) has been shown to exist in human circulating plasma. Several groups including ours have developed methods for immunologically measuring OxLDL, which have been applied to several clinical, both cross-sectional and prospective, studies. These data clearly show that OxLDL levels correlate well with the severity of cardiovascular diseases. In particular, recent observations suggest that plasma OxLDL levels could be a useful marker for predicting future cardiovascular events; however, substantial differences exist among the different methods of OxLDL measurement. To evaluate the clinical data on circulating OxLDL, a proper understanding of the similarity, differences, and limitation of the methods is needed. This paper summarizes the characteristics of the methods used and recent clinical findings.

High density lipoprotein subfractions: isolation, composition, and their duplicitous role in oxidation

The plasma HDLs represent a major class of cholesterol-transporting lipoprotein that can be divided into two distinct subfractions, HDL(2) and HDL(3), by ultracentrifugation. Existing methods for the subfractionation of HDL requires lengthy ultracentrifugations, making them unappealing for large-scale studies. We describe a method that subfractionates HDL from plasma in only 6 h, representing a substantial decrease in total isolation time. The subfractions so isolated were assessed for a variety of lipid and protein components, in addition to their susceptibility to oxidation, both alone and in combination with VLDL and LDL. We report for the first time a prooxidant role for HDL during VLDL oxidation, in which HDL donates preformed hydroperoxides to VLDL in a cholesteryl ester transfer protein (CETP)-dependent process. Examination of the participation of HDL in LDL oxidation has reinforced its classic role as a potent antioxidant. Furthermore, we have also implicated the second major HDL-associated enzyme, LCAT, in these processes, whereby it acts as a potent prooxidant during VLDL oxidation but as an antioxidant during LDL oxidation. Thus, we have identified a potentially duplicitous role for HDL in the pathogenesis of atherosclerosis, attributable to both CETP and LCAT.

Serum lipid oxidizibility in term premature rupture of the membranes

OBJECTIVE

In our previous studies we have shown that the process of term labor is associated with oxidative stress, as indicated by increased susceptibility of maternal serum lipids to copper induced peroxidation. In order to continue evaluating the role of oxidative stress in the labor process, we next tested whether term premature rupture of the membranes (PROM) is also associated with increased susceptibility of maternal serum lipids to copper induced peroxidation.

DESIGN

A controlled prospective study.

SETTING

Tertiary care centre.

POPULATION

31 healthy women with term PROM and 19 healthy pregnant women with intact membranes. The women were matched for maternal and gestational age.

METHODS

Venous blood was drawn from the women (up to 6h after rupture of the membranes and prior to labor in the PROM group), and the kinetics of copper-induced oxidation of serum lipids ex vivo were monitored spectroscopically at 37 degrees C by continuous recording of absorbance at 245 nm.

RESULTS

The lag phase, reflecting resistance of serum lipids to oxidation, was similar in the PROM group when compared to the control group (43.7+/-3.2 versus 41.9+/-1.6 min, P=0.61). However, the maximal rate of oxidation (V(max)) and the maximal accumulation of absorbing products (OD(max)) were shorter in the PROM group when compared to the control group (5.14+/-0.26 versus 6.29+/-0.4010(-3) OD(245) nm/min, P=0.016; 0.61+/-0.03 versus 0.71+/-0.04 OD(245) nm, P=0.07).

CONCLUSION

As opposed to term labor, term PROM is not associated with increased maternal systemic oxidative stress when compared to normal pregnant women. The role for oxidative stress in preterm PROM warrants further studies.

Protection of mitochondria during cold storage of liver and following transplantation: comparison of the two solutions, University of Wisconsin and Eurocollins

Injury to allografts during ischaemia/reperfusion contribute to the development of graft failure following transplantation with significant morbidity and mortality to patients. The development of University of Wisconsin solution has significantly improved the quality of graft preservation and transplant outcome relative to formerly used solutions such as Eurocollins. The aim of this study was to further characterize mitochondrial structural and functional alterations occurring in rat livers following cold storage and transplantation. Mitochondrial impairment after prolonged storage in Eurocollins included decreased cyt. c+c1, cyt. b and cyt. a+a3 concentration and dramatic falls in the activities of the respiratory chain enzymes ubiquinol-cyt. c oxidoreductase and cytochrome oxidase. Under the same conditions the highest hydroperoxide but lowest vitamin E concentrations were also found. Although both the Eurocollins and University of Wisconsin preservation solutions have limitations in preventing oxidative injuries following cold storage and reperfusion, our data indicate that mitochondrial impairment was higher in Eurocollins- than in University of Wisconsin-stored livers. Further improvements are necessary in maintaining the stability of mitochondria in order to optimize preservations solutions used in transplantations.

Antioxidant Effects of Quinoline Alkaloids and 2,4-Di-tert-butylphenol Isolated from Scolopendra subspinipes

The oxidized low-density lipoprotein (ox-LDL) plays a critical role at the early stages of atherosclerosis. Thus, the prevention of LDL-oxidation by antioxidants may arrest the progression of atherosclerosis. Two quinoline alkaloids, 3,8-dihydroxyquinoline (1) and 2,8-dihydroxy-3,4-dimethoxyquinoline (3), and 2,4-di-tert-butylphenol (2) were isolated from the dried body of Scolopendra subspinipes. Compounds 1-3 exhibited antioxidant activities on copper-mediated (1: IC50=2.6 microM, 2: IC50=8.2 microM, 3: IC50=63.0 microM), AAPH-mediated oxidation (1: IC50=3.9 microM, 2: IC50=9.9 microM, 3: IC50=71.8 microM), and SIN-1-mediated oxidation (1: 70%, 2: 52%, 3: 29% at 5.0 microM) in the TBARS assay. The antioxidant activities of compounds 1-3 were tested with respect to other parameters, such as the lag time of conjugated diene fromation, relative electrophoretic mobility (REM) of ox-LDL, and apoB-100 fragmentation on copper-mediated LDL-oxidation. In addition, compounds 1-3 showed 1,1-diphenyl-2-picrylhydrasyl (DPPH) radical scavenging activity and compound 1 also exhibited metal chelating activity.

Arterial endothelial dysfunction in baboons fed a high-cholesterol, high-fat diet

BACKGROUND

Endothelial dysfunction signals the initiation and progression of atherosclerosis. Elevated LDL-cholesterol concentrations have been suggested to induce endothelial dysfunction, but direct in vivo evidence for the relation is still lacking.

OBJECTIVE

We examined the hypothesis that a high-cholesterol, high-fat (HCHF) diet can directly cause endothelial dysfunction in vivo.

DESIGN

We measured inflammatory and endothelial dysfunctional markers in circulating blood and directly in endothelial cells, which were collected by femoral artery biopsies, in 10 baboons before and after a 7-wk HCHF dietary challenge.

RESULTS

We found that the HCHF diet induced a high inflammatory status, as indicated by increased concentrations of interleukin 6, tumor necrosis factor alpha (TNF-alpha), and monocyte chemoattractant protein 1. Although the concentrations of endothelial dysfunctional markers, such as soluble vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1, were not increased by the HCHF diet, membrane-bound VCAM-1 and membrane-bound E-selectin on endothelial cells were highly increased after 7 wk of the HCHF diet (P < 0.01). In contrast, the concentrations of endothelial nitric oxide synthase in endothelial cells were significantly reduced by the 7-wk HCHF diet (P < 0.01). Furthermore, the dietary challenge attenuated endothelial cell responses to TNF-alpha, lipopolysaccharide, native LDL cholesterol, and oxidized LDL-cholesterol stimulation.

CONCLUSIONS

Our results show that an HCHF diet can directly induce inflammation and endothelial dysfunction. Prior in vivo exposure to an HCHF diet attenuates the in vitro responses of endothelial cells to atherogenic risk factors. This preconditioning phenomenon may have significant clinical relevance.

Increased plasma concentrations of Palmitoylethanolamide, an endogenous fatty acid amide, affect oxidative damage of human low-density lipoproteins: An in vitro study

Fatty acid ethanolamides (NAEs) are naturally occurring hydrophobic molecules usually present in a very small amount in many mammalian tissues and cells. Moreover, these compounds have been isolated in mammalian biological fluids, such as blood. Palmitoylethanolamide (C16:0) (PEA) is a fully saturated NAE, which presents some possible pharmaceutical activities, such as anti-inflammatory and antinociceptive effects. PEA is physiologically present in the mammalian blood at concentrations ranging from 9.4 to 16.7 pmol/ml. Since increasing evidence indicates that oxidative modification of low-density lipoproteins (LDL) is an important determinant in atherogenesis, the aim of this study was to evaluate the effect of physiologically relevant concentrations of PEA on Cu2+-induced LDL oxidation (measured as conjugated dienes formation). Our experiments indicate both anti-oxidative and slightly pro-oxidative effects of PEA. The anti-oxidative effect is obtained at low PEA concentrations (0.01 and 0.1 microM), while the pro-oxidative effect is obtained at a higher PEA concentration (1 microM). Fluorescence and circular dichroism data indicate that the effect of PEA occurs mainly by affecting the conformational features of ApoB-100.

Oxidative stress in the fetal circulation does not depend on mode of delivery

OBJECTIVE

We tested whether neonates are subject to oxidative stress by comparing the susceptibility of umbilical blood lipids with copper-induced peroxidation.

STUDY DESIGN

Umbilical arterial and venous blood samples were drawn from 32 pregnant women who delivered by elective cesarean section (CS) and from 32 pregnant women who delivered by spontaneous vaginal delivery (SVD) in a tertiary care center. Oxidative stress was evaluated by spectrophotometric monitoring of copper-induced peroxidation of serum samples.

RESULTS

The lag preceding lipid peroxidation in umbilical arterial blood was shorter than the lag in umbilical venous blood, irrespective of mode of delivery (14.0+/-1.8 vs 50.6+/-8.25 min, P=.0004 in SVD group; 17.7+/-1.6 vs 39.2+/-7.6 min, P=.006 in CS group).

CONCLUSION

Umbilical arterial lipids are more susceptible to peroxidation than umbilical venous lipids, indicating high oxidative stress in the fetal circulation irrespective of mode of delivery.

Potential anti-atherogenic cell action of the naturally occurring 4-O-methyl derivative of gallic acid on Ang II-treated macrophages

We have recently established that the blood concentrations of gallic acid (GA), a polyphenolic component naturally found in food, and its O-methyl derivatives are very low (practically < or = 1 microM) in physiological (postprandial) condition. Using acellular oxidant systems and macrophage-differentiated promonocytes (MDPs) THP-1, we show here that the direct and indirect (through depressing effect on the superoxide cell production) antioxidant properties of these components were not effective at these concentrations. In contrast, 4-O-methyl GA was the most efficient component to depress AT1R and CD36 mRNA expression in Ang II-treated MDPs, suggesting a strong inhibition of Ang II-triggered pro-atherogenic mechanisms of foam cell formation.