Time-course studies by synchrotron X-ray solution scattering of the structure of human low-density lipoprotein during Cu(2+)-induced oxidation in relation to changes in lipid composition

The effects of oxidative stress on the development of atherosclerosis

Atherosclerosis is a cardiovascular disease (CVD) known widely world wide. Several hypothesizes are suggested to be involved in the narrowing of arteries during process of atherogenesis. The oxidative modification hypothesis is related to oxidative and anti-oxidative imbalance and is the most investigated. The aim of this study was to review the role of oxidative stress in atherosclerosis. Furthermore, it describes the roles of oxidative/anti-oxidative enzymes and compounds in the macromolecular and lipoprotein modifications and in triggering inflammatory events. The reactive oxygen (ROS) and reactive nitrogen species (RNS) are the most important endogenous sources produced by non-enzymatic and enzymatic [myeloperoxidase (MPO), nicotinamide adenine dinucleotide phosphate (NADH) oxidase and lipoxygenase (LO)] reactions that may be balanced with anti-oxidative compounds [glutathione (GSH), polyphenols and vitamins] and enzymes [glutathione peroxidase (Gpx), peroxiredoxins (Prdx), superoxide dismutase (SOD) and paraoxonase (PON)]. However, the oxidative and anti-oxidative imbalance causes the involvement of cellular proliferation and migration signaling pathways and macrophage polarization leads to the formation of atherogenic plaques. On the other hand, the immune occurrences and the changes in extra cellular matrix remodeling can develop atherosclerosis process.

High Hydrostatic Pressure Induces a Lipid Phase Transition and Molecular Rearrangements in Low-Density Lipoprotein Nanoparticles

Low-density lipoproteins (LDL) are natural lipid transporter in human plasma whose chemically modified forms contribute to the progression of atherosclerosis and cardiovascular diseases accounting for a vast majority of deaths in westernized civilizations. For the development of new treatment strategies, it is important to have a detailed picture of LDL nanoparticles on a molecular basis. Through the combination of X-ray and neutron small-angle scattering (SAS) techniques with high hydrostatic pressure (HHP) this study describes structural features of normolipidemic, triglyceride-rich and oxidized forms of LDL. Due to the different scattering contrasts for X-rays and neutrons, information on the effects of HHP on the internal structure determined by lipid rearrangements and changes in particle shape becomes accessible. Independent pressure and temperature variations provoke a phase transition in the lipid core domain. With increasing pressure an inter-related anisotropic deformation and flattening of the particle are induced. All LDL nanoparticles maintain their structural integrity even at 3000 bar and show a reversible response toward pressure variations. The present work depicts the complementarity of pressure and temperature as independent thermodynamic parameters and introduces HHP as a tool to study molecular assembling and interaction processes in distinct lipoprotein particles in a nondestructive manner.

Aggregation and fusion of low-density lipoproteins in vivo and in vitro

Low-density lipoproteins (LDLs, also known as 'bad cholesterol') are the major carriers of circulating cholesterol and the main causative risk factor of atherosclerosis. Plasma LDLs are 20- to 25-nm nanoparticles containing a core of cholesterol esters surrounded by a phospholipid monolayer and a single copy of apolipoprotein B (550 kDa). An early sign of atherosclerosis is the accumulation of LDL-derived lipid droplets in the arterial wall. According to the widely accepted 'response-to-retention hypothesis', LDL binding to the extracellular matrix proteoglycans in the arterial intima induces hydrolytic and oxidative modifications that promote LDL aggregation and fusion. This enhances LDL uptake by the arterial macrophages and triggers a cascade of pathogenic responses that culminate in the development of atherosclerotic lesions. Hence, LDL aggregation, fusion, and lipid droplet formation are important early steps in atherogenesis. In vitro, a variety of enzymatic and nonenzymatic modifications of LDL can induce these reactions and thereby provide useful models for their detailed analysis. Here, we summarize current knowledge of the in vivo and in vitro modifications of LDLs leading to their aggregation, fusion, and lipid droplet formation; outline the techniques used to study these reactions; and propose a molecular mechanism that underlies these pro-atherogenic processes. Such knowledge is essential in identifying endogenous and exogenous factors that can promote or prevent LDL aggregation and fusion in vivo and to help establish new potential therapeutic targets to decelerate or even block these pathogenic reactions.

Effect of oxidation on the structure of human low- and high-density lipoproteins

This work presents a controlled study of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) structural changes due to in vitro oxidation with copper ions. The changes were studied by small-angle x-ray scattering (SAXS) and dynamic light scattering (DLS) techniques in the case of LDL and by SAXS, DLS, and Z-scan (ZS) techniques in the case of HDL. SAXS data were analyzed with a to our knowledge new deconvolution method. This method provides the electron density profile of the samples directly from the intensity scattering of the monomers. Results show that LDL particles oxidized for 18 h show significant structural changes when compared to nonoxidized particles. Changes were observed in the electrical density profile, in size polydispersity, and in the degree of flexibility of the APO-B protein on the particle. HDL optical results obtained with the ZS technique showed a decrease of the amplitude of the nonlinear optical signal as a function of oxidation time. In contrast to LDL results reported in the literature, the HDL ZS signal does not lead to a complete loss of nonlinear optical signal after 18 h of copper oxidation. Also, the SAXS results did not indicate significant structural changes due to oxidation of HDL particles, and DLS results showed that a small number of oligomers formed in the sample oxidized for 18 h. All experimental results for the HDL samples indicate that this lipoprotein is more resistant to the oxidation process than are LDL particles.

Simultaneous binding of the anti-cancer IgM monoclonal antibody PAT-SM6 to low density lipoproteins and GRP78

The tumour-derived monoclonal IgM antibody PAT-SM6 specifically kills malignant cells by an apoptotic mechanism linked to the excessive uptake of plasma lipids. The mechanism is postulated to occur via the multi-point attachment of PAT-SM6 to the unfolded protein response regulator GRP78, located on the surface of tumour cells, coupled to the simultaneous binding of plasma low density lipoprotein (LDL). We prepared and characterised LDL and oxidized LDL using sedimentation velocity and small-angle X-ray scattering (SAXS) analysis. Enzyme-linked immunosorbent (ELISA) techniques indicated apparent dissociation constants of approximately 20 nM for the binding of LDL or oxidized LDL to PAT-SM6. ELISA experiments showed cross competition with LDL inhibiting PAT-SM6 binding to immobilised GRP78, while, in the reverse experiment, GRP78 inhibited PAT-SM6 binding to immobilized LDL. In contrast to the results of the ELISA experiments, sedimentation velocity experiments indicated relatively weak interactions between LDL and PAT-SM6, suggesting immunoabsorbance to the microtiter plate is driven by an avidity-based binding mechanism. The importance of avidity and the multipoint attachment of antigens to PAT-SM6 was further investigated using antigen-coated polystyrene beads. Absorption of GRP78 or LDL to polystyrene microspheres led to an increase in the inhibition of PAT-SM6 binding to microtiter plates coated with GRP78 or LDL, respectively. These results support the hypothesis that the biological action of PAT-SM6 in tumour cell apoptosis depends on the multivalent nature of PAT-SM6 and the ability to interact simultaneously with LDL and multiple GRP78 molecules clustered on the tumour cell surface.

Efficacy of fentanyl and/or lidocaine on total antioxidants and total oxidants during craniotomy

OBJECTIVE

The aim of this study was to investigate the oxidative, hemodynamic, and analgesic effects of local lidocaine infiltration, or intravenous (IV) fentanyl injection, or a combination of lidocaine and IV fentanyl during head fixation in a 3-pin headrest in patients undergoing elective craniotomy.

DESIGN

Double-blind, randomized, placebo-controlled study.

SETTING

Gaziantep University Medical Faculty, Department of Anesthesiology and Reanimation.

METHODS

Eighty patients were randomly assigned to one of four groups. Five minutes before pin fixation, patients in group L received 1 mg/kg of lidocaine 2% for scalp infiltration (n=20), group F received 1 μg/kg of IV fentanyl (n=20), group FL received 1 mg/kg of lidocaine 2% and 1 μg/kg of fentanyl (n=20), and group P received a placebo (n=20). Following standard anesthesia, basal, pre- and post-fixational hemodynamic data were recorded. Blood samples were taken for evaluation of oxidant and antioxidant levels before and after pin fixation.

RESULTS

The total antioxidant levels after pin fixation were highest in group FL followed by group F, then group L and finally group P (ie, FL>F>L>P) (P<0.05). The mean arterial blood pressure (MAP) after pin fixation was higher than the MAP before pin fixation in groups L and P (P<0.05), but was lower in groups F and FL (P<0.05).

CONCLUSION

The combination of fentanyl and lidocaine before pin fixation is useful in preventing severe hemodynamic response to pain stimuli, such as pin fixation, and in increasing total antioxidant levels in the post-fixational period during craniotomy in adults.

1H NMR at 800MHz facilitates detailed phospholipid follow-up during atherogenic modifications in low density lipoproteins

The structure of low density lipoprotein (LDL) particles and, particularly, the enzymatic and oxidative modifications of their surface is crucial in the initiation of atherosclerosis. Due to the structural complexity of LDL, there is a lack of suitable methods for dynamic follow-up studies of the molecular mechanisms in native and modified particles in physiological conditions. Here, we report that phosphatidylcholine (PC), lysophosphatidylcholine (lyso-PC), and sphingomyelin (SM) can all be identified and quantified in LDL particles by (1)H NMR spectroscopy at 800 MHz. The signal assignment for the lyso-PC is novel and we illustrate the applicability of the methodology in the case of lipid peroxidation that is generally considered as one of the key proatherogenic modifications of LDL. It was found, somewhat surprisingly, that the LDL-associated phospholipase A(2) is activated in the very beginning of the formation of PC-hydroperoxides. The (patho)physiological rationale of the resulting lyso-PC generation is also briefly discussed.

Untangling the role of amyloid in atherosclerosis

PURPOSE OF REVIEW

Amyloid deposits are a defining feature of several age-related and debilitating diseases. Their widespread presence in atherosclerotic plaques suggests a potential role in lesion development. This review discusses the proteins known to accumulate in atheroma and examines the evidence that amyloid-like structures activate macrophage signaling pathways linked to inflammation and prothrombotic potential.

RECENT FINDINGS

Numerous proteins that accumulate in atherosclerotic plaques form amyloid fibrils in vivo, including apolipoproteins, beta-amyloid, and alpha1-antitrypsin. In addition, oxidation or enzymatic modification of low-density lipoproteins induces a structural reorganization of the particle, including the acquisition of amyloid-like properties. Similarly, glycation of serum albumin, as observed in diabetes, is accompanied by the formation of aggregates with all the hallmarks of amyloid. Several receptors implicated in atherogenesis modulate the fate of amyloid fibrils by mediating their clearance (scavenger receptors A and B-I), activating inflammatory signaling cascades (receptor for advanced glycation endproducts), or both (CD36). Finally, recent studies indicate that amyloid deposition accelerates diet-induced atherosclerosis in mice.

SUMMARY

Given the substantial evidence that amyloid fibrils or preamyloidogenic species are cytotoxic, the aberrant deposition of amyloid in the intima may be pathologically important in vascular inflammation and the promotion of atherosclerosis.

Oxidation of low-density lipoproteins induces amyloid-like structures that are recognized by macrophages

The macrophage scavenger receptor CD36 plays a key role in the initiation of atherosclerosis through its ability to bind to and internalize oxidized low-density lipoproteins (oxLDL). Prompted by recent findings that the CD36 receptor also recognizes amyloid fibrils formed by beta-amyloid and apolipoprotein C-II, we investigated whether the oxidation of low-density lipoproteins (LDL) generates characteristic amyloid-like structures and whether these structures serve as CD36 ligands. Our studies demonstrate that LDL oxidized by copper ions, 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH), or ozone react with the diagnostic amyloid dyes thioflavin T and Congo Red and bind to serum amyloid P component (SAP), a universal constituent of physiological amyloid deposits. X-ray powder diffraction patterns for native LDL show a diffuse powder diffraction ring with maximum intensity corresponding to an atomic spacing of approximately 4.7 A, consistent with the spacing between beta-strands in a beta-sheet. Ozone treatment of LDL generates an additional diffuse powder diffraction ring with maximum intensity indicating a spacing of approximately 9.8 A. This distance is consistent with the presence of cross-beta-structure, a defining characteristic of amyloid. Evidence that these cross-beta-amyloid structures in oxLDL are recognized by macrophages is provided by the observation that SAP strongly inhibits the association and internalization of (125)I-labeled copper-oxidized LDL by peritoneal macrophages. The ability of SAP to bind to amyloid-like structures in oxLDL and prevent lipid uptake by macrophages highlights the potential importance of these structures and suggests an important preventative role for SAP in foam cell formation and early-stage atherosclerosis.

Characterization of native and oxidized human low-density lipoproteins by the Z-scan technique

The nonlinear optical response of human normal and oxidized by Cu2+ low-density lipoproteins particles (LDL), were investigated by the Z-scan technique as a function of temperature and concentration of LDL particles. The Z-scan signals increase linearly with concentration of normal LDL particles, following the usual Beer-Lambert law in a broad range of concentrations. The oxidized LDL particles do not show nonlinear optical response. On the other hand, normal LDL increases its nonlinear optical response as a function of temperature. These behaviors can be attributed to an absorbing element that is modified by the oxidative process. Contrarily, changes in the physical state of the cores and conformation of the ApoB100 protein due to an increase in temperature seems to enhance their nonlinear optical properties. This tendency is not due to aggregation of particles. The main contribution to the nonlinear optical response of normal LDL particles comes from the phospholipid fraction of the particles.

Lysophosphatidylcholine and 7-oxocholesterol modulate Ca2+ signals and inhibit the phosphorylation of endothelial NO synthase and cytosolic phospholipase A2

The oxidation of plasma LDLs (low-density lipoproteins) is a key event in the pathogenesis of atherosclerosis. LPC (lysophosphatidylcholine) and oxysterols are major lipid constitutents of oxidized LDLs. In particular, 7-oxocholesterol has been found in plasma from cardiac patients and atherosclerotic plaque. In the present study, we investigated the ability of 7-oxocholesterol and LPC to regulate the activation of eNOS (endothelial nitric oxide synthase) and cPLA2 (cytosolic phospholipase A2) that synthesize two essential factors for vascular wall integrity, NO (nitric oxide) and arachidonic acid. In endothelial cells from human umbilical vein cords, both 7-oxocholesterol (150 microM) and LPC (20 microM) decreased histamine-induced NO release, but not the release activated by thapsigargin. The two lipids decreased NO release through a PI3K (phosphoinositide 3-kinase)-dependent pathway, and decreased eNOS phosphorylation. Their mechanisms of action were, however, different. The NO release reduction was dependent on superoxide anions in LPC-treated cells and not in 7-oxocholesterol-treated ones. The Ca2+ signals induced by histamine were abolished by LPC, but not by 7-oxocholesterol. The oxysterol also inhibited (i) the histamine- and thapsigargin-induced arachidonic acid release, and (ii) the phosphorylation of both cPLA2 and ERK1/2 (extracellular-signal-regulated kinases 1/2). The results show that 7-oxocholesterol inhibits eNOS and cPLA2 activation by altering a Ca2+-independent upstream step of PI3K and ERK1/2 cascades, whereas LPC desensitizes eNOS by interfering with receptor-activated signalling pathways. This suggests that 7-oxocholesterol and LPC generate signals which cross-talk with heterologous receptors, effects which could appear at early stage of atherosclerosis.

Structural changes of low density lipoproteins with Cu2+and glucose induced oxidation

The compositional and structural changes of lipids and apolipoproteins during in vitro oxidation of low density lipoprotein (LDL) are investigated in this study by IR spectroscopy. For comparison, LDL samples containing either copper or glucose at physiological or pathological concentrations are considered in order to know the separate affects of these chemical factors on LDL oxidation. The results show that the initial steps of lipid oxidation proceed through hydrogen atom loss from methylene groups, as well as loss of cholesteryl ester molecules, and later a recovering of carbonyl compounds resulting from aldehyde formation that generally occurs in autooxidation processes. Lipid oxidation is induced by copper ions, and glucose enhances metal ion induced LDL oxidation as determined by conjugated diene formation. As to the protein conformational changes, IR spectroscopy reveals for the first time that LDL oxidation involves formation of beta-sheet structures, these being more abundant in LDL samples with pathological concentrations of glucose or copper. Consequently, the LDL structural changes may contribute to the recognition of oxidized LDL particles by scavenger receptors.

One site on the apoB-100 specifically binds 17-beta-estradiol and regulates the overall structure of LDL

The major protein component (apoB-100) of low-density lipoprotein (LDL) is known as a multipotential molecule the several functional regions of which can all be affected by key structural modifications driven by specific domains. Based on our previous report on structural and conformational modifications of apoB-100 in the presence of 17-beta-estradiol (E2), we characterized the interaction between E2 and the apoB-100 and further explored the induced alterations in terms of the structural arrangement of the whole LDL particle. We report evidence for the existence on apoB-100 of a single specific and saturable binding site for E2, the occupancy of which modifies the overall structure of the protein, inducing an increase in the alpha-helix fraction. As a consequence, the structure of the LDL particle is deeply perturbed, with a change in the arrangement of both the outer shell and lipid core and an overall volume shrinkage. The evidence of a regulation of apoB-100 structure by a physiological ligand opens new perspectives in the study of the biological addressing of the LDL particle and suggests a novel rationale in the search for mechanisms underlying the beneficial role of E2 in decreasing the risk of early lesions in atherosclerosis.

Cholesteryl ester oxidation products in atherosclerosis

Lipid oxidation products are formed at sites of increased oxidant stress and have been shown to accumulate in atherosclerotic lesions. Although recent studies have focused on the formation and metabolism of oxidized lipids, very little is known about their biological activities and possible (patho)physiological functions. Oxidation of cholesteryl esters containing unsaturated fatty acids leads to the formation of hydroperoxides that are either reduced to alcohols or degrade into biologically active "core-aldehydes". In this review, the mechanisms of formation and metabolic fate of oxidized cholesteryl esters, their occurrence, as well as possible biological activities are discussed. Based on the current knowledge, cholesteryl ester oxidation leads to the formation of biologically active substances, which could actively contribute to the progression of atherosclerotic lesions and their resulting complications.

Smoking has no effect on the amino acid composition of apolipoprotein B100 of LDL while directly influencing the antioxidant status

Previous studies have demonstrated increased plasma levels of oxidised low-density lipoprotein (oxLDL) in chronic smokers, which has been associated with the extent of endothelial dysfunction. In this study we examine the relationship between the amino acid composition of apolipoprotein B100 (apo B) of low-density lipoprotein (LDL), by reverse phase HPLC after precolumn derivatisation, between smokers (> or =40 cigarettes/day) and nonsmokers in relation to their plasma and LDL antioxidant status. While there was a significant difference in the levels of plasma vitamin C and alpha-tocopherol between female smokers and nonsmokers, as well as in the levels of LDL alpha-tocopherol, there was no significant difference in the amino acid composition of apo B between the two groups.

Antioxidant enzymes and human diseases

OBJECTIVES

To describe the importance of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase working together in human cells against toxic reactive oxygen species, their relationship with several pathophysiologic processes and their possible therapeutic implications.

CONCLUSIONS

Reactive oxygen species (ROS) are involved in the cell growth, differentiation, progression, and death. Low concentrations of ROS may be beneficial or even indispensable in processes such as intracellular signaling and defense against micro-organisms. Nevertheless, higher amounts of ROS play a role in the aging process as well as in a number of human disease states, including cancer, ischemia, and failures in immunity and endocrine functions. As a safeguard against the accumulation of ROS, several nonenzymatic and enzymatic antioxidant activities exist. Therefore, when oxidative stress arises as a consequence of a pathologic event, a defense system promotes the regulation and expression of these enzymes.

Inhibition of peroxyl radical-mediated lipid oxidation by plasmalogen phospholipids and alpha-tocopherol

The recently discovered peroxyl radical scavenging properties of plasmalogen phospholipids led us to evaluate their potential interactions with alpha-tocopherol. The oxidative decay of plasmalogen phospholipids and of polyunsaturated fatty acids as induced by peroxyl radicals (generated from 2,2'-azobis-2-amidinopropane hydrochloride; AAPH) was studied in micelles using 1H-NMR and chemical analyses. In comparison with alpha-tocopherol, a 20- to 25-fold higher concentration of plasmalogen phospholipids was needed to induce a similar inhibition of peroxyl radical-mediated oxidation of polyunsaturated fatty acids. Plasmalogen phospholipids and alpha-tocopherol protected each other from oxidative degradation. In low-density lipoproteins (LDL) and micelles supplemented with plasmalogen phospholipids plus alpha-tocopherol, the peroxyl radical-promoted oxidation was additively diminished. The differences in the capacities to inhibit oxidation processes induced by peroxyl radicals between the plasmalogen phospholipids and alpha-tocopherol were less pronounced in the LDL particles than in the micelles. In conclusion, plasmalogen phospholipids and alpha-tocopherol apparently compete for the interaction with the peroxyl radicals. Oxidation processes induced by peroxyl radicals are inhibited in an additive manner in the presence of the two radical scavengers. The contribution of the plasmalogen phospholipids to the protection against peroxyl radical promoted oxidation in vivo is expected to be at least as important as that of alpha-tocopherol.

Role of plasmalogens in the enhanced resistance of LDL to copper-induced oxidation after LDL apheresis

Extracorporeal reduction of plasma low density lipoproteins (LDLs) by LDL apheresis was shown to attenuate the proatherogenic influences of LDL, such as impairment of vasodilation and increased monocyte adhesion to the endothelium. In 16 patients with familial hypercholesterolemia, we analyzed whether LDL apheresis by the heparin precipitation procedure affected the oxidative resistance of LDL. Plasma LDL cholesterol concentrations were reduced by 65% after the apheresis. The lag time of copper-mediated LDL oxidation was increased from 103 to 117 minutes (P<0.0005). The LDL contents of alpha-tocopherol and beta-carotene, as well as the ratio of monounsaturated to polyunsaturated fatty acids in LDL, were not altered. However, the LDL apheresis induced a 15% increase in the LDL contents of plasmalogen phospholipids (P<0.0005), a class of ether phospholipids that were recently shown to prevent lipid oxidation. The phosphatidylcholine (PC) to lysoPC ratio was elevated by 16% after the apheresis (P<0.0005). The percent increase in LDL plasmalogen phospholipids showed a close association with the increased lag time after apheresis (P<0.0005). The LDL plasmalogen contents of the blood samples from patients and from normolipidemic donors were also positively related to the lag time (P<0.005). In vitro loading of LDL with plasmalogen phospholipids resulted in a prolongation of the lag time and an increase in the PC/lysoPC ratio. In conclusion, the rapid rise in LDL contents of plasmalogen phospholipids most probably causes the increase in lag time after LDL apheresis. Plasmalogens appear to play an important role in the oxidation resistance of LDL in vivo.

Comparison of the inhibitory effects of ApoB100 and tissue factor pathway inhibitor on tissue factor and the influence of lipoprotein oxidation

The procoagulant activity of tissue factor is regulated by circulating inhibitors such as tissue factor pathway inhibitor (TFPI) and LDL. These 2 inhibitors also readily associate making the distinction between their activities difficult. We have examined the relative contributions of intact and C-terminal truncated TFPI and ApoB100. By following the inhibitory potential of the preparations, over a period of 120 minutes, it was demonstrated that TFPI and LDL-resembling particles inhibited tissue factor at different rates. TFPI was found to be a short, fast-acting inhibitor, whereas the action of LDL-resembling particles was more prolonged but slower. The oxidation of LDL has been closely associated with the development of cardiovascular disease, including atherosclerosis and thrombosis. Positively charged amino acids, particularly lysine residues, are prone to alterations via the formation of adducts by lipid peroxidation products. These residues are important in the inhibition of tissue factor activity by ApoB100. They also play an important role in the inhibitory Kunitz domains of TFPI. We have shown that the decline in the ability of LDL to inhibit tissue factor was as a result of modifications in LDL arising from oxidation. By examining the effects of oxidation on full-length and C-terminal truncated TFPI bound to LDL-resembling particles, we found that TFPI is only affected when in close association with ApoB100. C-terminal truncated TFPI was not affected significantly by oxidation. Finally, chemical modification of lysine and arginine residues reduced the overall inhibition of tissue factor by TFPI. We propose that TFPI and LDL act separately to inhibit tissue factor in vivo. However, the oxidation of LDL can alter both the endogenous activity of ApoB100 and reduce that of closely associated TFPI, compromising normal hemostasis.

Contribution of copper binding to the inhibition of lipid oxidation by plasmalogen phospholipids

The role of plasmalogen phospholipids for copper-induced lipid oxidation was evaluated. Using 1H-NMR we observed that the copper (CuSO4)-promoted oxidative degradation of polyunsaturated fatty acids in micellar solution was dose-dependently attenuated by the plasmalogen lysoplasmenylethanolamine from bovine brain (lysoBP-PtdEtn). This was due to a direct interaction of copper ions with the plasmalogen-specific enol ether double bond. The enol ether methine 1H signal decreased on the addition of copper, saturation being reached at a molar ratio of lysoBP-PtdEtn to copper of 1:1. The original 1H signal was recovered almost completely after the addition of EDTA. Enrichment of micelles and low-density lipoproteins (LDLs) with plasmalogen phospholipids led to a decrease in the Cu(II) concentration in the aqueous media. After loading of LDLs in vitro with BP-PtdEtn, the LDL-dependent formation of Cu(I) was decreased, in particular in particles experimentally supplemented with alpha-tocopherol. The suppression of copper-promoted lipid oxidation that was observed in the presence of plasmalogen phospholipids plus alpha-tocopherol was greater than the sum of the protective effects elicited by the two substances alone. In conclusion, the formation of a complex between copper ions and the plasmalogens accounts partly for their inhibition of copper-induced lipid oxidation.