Lipoproteins secreted by cultured rat hepatocytes contain the antioxidant 1-alk-1-enyl-2-acylglycerophosphoethanolamine

Chromatographic methods for the analyses of 2-halofatty aldehydes and chlorohydrin molecular species of lysophosphatidylcholine

Plasmalogens are targeted by hypohalous acids resulting in the production of 2-chlorofatty aldehydes, 2-bromofatty aldehydes and chlorohydrin species of lysophosphatidylcholine. These novel lipids may have important roles in the pathophysiological sequelae of cardiovascular diseases as well as serve as biomarkers of cardiovascular disease. Accordingly, the discovery of these new lipid species have required the development of techniques for their purification and quantification. Thin layer chromatography, high performance liquid chromatography (LC) and gas chromatography (GC) of these lipids and their derivatives have provided a battery of tools for their analyses. These lipids have been quantified using flame ionization detection (FID) and mass spectrometry (MS).

Identification of lysophosphatidylcholine-chlorohydrin in human atherosclerotic lesions

Lysophosphatidylcholine (LysoPtdCho) levels are elevated in sera in patients with atherosclerosis and in atherosclerotic tissue. Previous studies have shown that reactive chlorinating species attack plasmalogens in human coronary artery endothelial cells (HCAEC), forming lysoPtdCho and lysoPtdCho-chlorohydrin (lysoPtdCho-ClOH). The results herein demonstrate for the first time that lysoPtdCho-ClOH is elevated over 60-fold in human atherosclerotic lesions. In cultured HCAEC, 18:0 lysoPtdCho-ClOH led to a statistically significant increase in P-selectin cell-surface expression, but unlike 18:1 lysoPtdCho did not lead to cyclooxygenase-2 protein expression. These data show that 18:0 lysoPtdCho-ClOH is elevated in atherosclerotic tissue and may have unique pro-atherogenic properties compared to lysoPtdCho.

Plasmalogens in Human Serum Positively Correlate with High- Density Lipoprotein and Decrease with Aging

AIM

The objective of the present study was to propose plasmalogens as a beneficial factor in human plasma by showing a highly positive correlation with high-density lipoprotein (HDL) and a significant reduction with aging.

METHODS

For 148 elderly subjects suspected of coronary artery disease (CAD), clinical characteristics such as coronary stenosis, hyperlipidemia, abnormal glucose tolerance, and hypertension were investigated, and serum biochemical markers including plasmalogens were determined.

RESULTS

Serum plasmalogens levels tended to fall in significant coronary stenosis and abnormal glucose tolerance. Correlative analyses among serum biochemical markers revealed that plasmalogens positively correlate with HDL-related values, particularly apolipoprotein A-I (apo A-I), and that the molar ratio of choline plasmalogen (ChoPlas) to ethanolamine plasmalogen (EtnPlas) correlates positively with low-density lipoprotein (LDL) particle size, and negatively with apo A-II and fasting triglyceride (TG) levels. Comparison of plasmalogens in elderly subjects with those of 119 healthy young subjects showed a marked decrease in serum plasmalogens levels by aging.

CONCLUSION

These results suggest that serum plasmalogens, antioxidant phospholipids, function as a beneficial factor as well as HDL, and that the measurement of serum plasmalogens is useful in clinical diagnosis.

Selective plasmenylcholine oxidation by hypochlorous acid: formation of lysophosphatidylcholine chlorohydrins

The plasmalogen sn-1 vinyl ether bond is targeted by hypochlorous acid (HOCl) produced by activated phagocytes. In the present study, the attack of the plasmalogen sn-1 vinyl ether bond by HOCl is shown to be preferred compared to the attack of double bonds present in the sn-2 position aliphatic chain (sn-2 alkenes) of both plasmenylcholine and phosphatidylcholine. Lysophosphatidylcholine (LPC) is a product from the initial HOCl attack of plasmenylcholine and the sn-2 alkene bonds present in this LPC product are secondary targets of HOCl leading to the production of LPC-chlorohydrins (ClOH). The aliphatic ClOH was demonstrated in both the positive and negative ion mode using collisionally-activated dissociation (CAD) of the molecular ion of LPC-ClOH. Furthermore, HOCl treatment of endothelial cells led to the preferential attack of plasmalogens in comparison to that of diacyl choline glycerophospholipids. Taken together, plasmenylcholine is oxidized preferentially over phosphatidylcholine and leads to the production of LPC-ClOH.

In situ hybridization of dihydroxyacetone phosphate acyltransferase, the regulating enzyme involved in plasmalogen biosynthesis

In situ hybridization can be carried out using different methods. The experimenter has to choose various parameters: the type of tissue fixation, the time of incubation, and the duration of the exposure time. All these parameters are determinant for the sensitivity and the resolution of this technique. This publication of technical aspects described different experiments performed for in situ hybridization on liver tissue. We may conclude on the parameters to optimize each step of the hybridization procedure. Moreover, this technique could be transposed to the brain and applied to little structures with a light expression of DHAP-AT.

Therapeutic uses of antioxidant liposomes

This review will focus on the therapeutic uses of antioxidant liposomes. Antioxidant liposomes have a unique ability to deliver both lipid- and water-soluble antioxidants to tissues. This review will detail the varieties of antioxidants which have been incorporated into liposomes, their modes of administration, and the clinical conditions in which antioxidant liposomes could play an important therapeutic role. Antioxidant liposomes should be particularly useful for treating diseases or conditions in which oxidative stress plays a significant pathophysiological role because this technology has been shown to suppress oxidative stress. These diseases and conditions include cancer, trauma, irradiation, retinotherapy or prematurity, respiratory distress syndrome, chemical weapon exposure, and pulmonary infections.

Identification of α-Chloro Fatty Aldehydes and Unsaturated Lysophosphatidylcholine Molecular Species in Human Atherosclerotic Lesions

Background— A role for myeloperoxidase (MPO) as a mediator of coronary artery disease and acute coronary syndromes has recently received considerable attention. Although active MPO and hypochlorite-modified proteins and peptides have been detected in human atherosclerotic lesions, detection of novel chlorinated oxidized lipid species with proatherogenic properties in vivo has not yet been reported. In this study we show that MPO-generated reactive chlorinating species promote selective oxidative cleavage of plasmalogens, liberating α-chloro fatty aldehydes and unsaturated lysophosphatidylcholine in human atherosclerotic lesions.

Methods and Results— Stable isotope dilution gas chromatography–mass spectrometry methods were used to identify and quantitate the α-chloro fatty aldehyde, 2-chlorohexadecanal, in atherosclerotic versus normal human aorta. Compared with normal aorta, 2-chlorohexadecanal levels were elevated more than 1400-fold in atherosclerotic tissues. Parallel electrospray ionization mass spectrometry studies confirmed 34- and 20-fold increases in the plasmalogen cooxidation products, unsaturated lysophosphatidylcholine molecular species containing linoleic and arachidonic acid, respectively, within atherosclerotic compared with normal aorta. Unsaturated lysophosphatidylcholine containing docosahexaenoic acid was also detected in atherosclerotic but not in normal aorta. Exposure of primary human coronary artery endothelial cells to plasmalogen-derived lysophosphatidylcholine molecular species produced marked increases in P-selectin surface expression.

Conclusions— The present studies demonstrate that plasmalogens are attacked by MPO-derived reactive chlorinating species within human atheroma. The resultant species formed, α-chloro fatty aldehydes and unsaturated lysophospholipids, possess proatherogenic properties, as shown by induction of P-selectin surface expression in primary human coronary artery endothelial cells.

Ethanolamine plasmalogens prevent the oxidation of cholesterol by reducing the oxidizability of cholesterol in phospholipid bilayers

The aims of the present study are to establish an appropriate system for assessing the oxidizability of cholesterol (CH) in phospholipid (PL) bilayers, and to explore the effect of ethanolamine plasmalogens on the oxidizability of CH with the system, through comparing with those of choline plasmalogens, phosphatidylethanolamine, and antioxidant alpha-tocopherol (Toc). Investigation of the effects of oxidants, vesicle lamellar forms, saturation level, and constituent ratio of PLs in vesicles on CH oxidation revealed the suitability of a system comprising unilamellar vesicles and the water-soluble radical initiator 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH). As CH oxidation in the system was found to follow the rate law for autoxidation without significant interference from oxidizable PLs, the oxidizability of CH in PL bilayers could be experimentally determined from the equation: k (p)/(2k (t))(1/2)=R (p)/[LH]R(i)(1/2) by measuring the rate of CH oxidation. It was found with this system that bovine brain ethanolamine plasmalogen (BBEP), bovine heart choline plasmalogen, and egg yolk phosphatidylethanolamine lower the oxidizability of CH in bilayers. Comparison of the dose-dependent effects of each PL demonstrated the greatest ability of BBEP to reduce the oxidizability. A time course study of CH oxidation suggested a novel mechanism of BBEP for lowering the oxidizability of CH besides the action of scavenging radicals.

Therapeutic uses of antioxidant liposomes

This chapter focuses on the use of antioxidant liposomes in the general area of free radical biology and medicine. The term antioxidant liposome is relatively new and refers to liposomes containing lipid-soluble chemical antioxidants, water-soluble chemical antioxidants, enzymatic antioxidants, or combinations of these various antioxidants. The role of antioxidants in health and disease has been extensively discussed, and many excellent reviews and books are available (1–3). Antioxidant liposomes hold great promise in the treatment of many diseases in which oxidative stress plays a prominent role. Oxidative stress is a physiological condition in which the production of damaging free radicals exceeds the in vivo capacity of antioxidant protection mechanisms to prevent pathophysiology. Free radicals are molecules with unpaired electrons, often highly reactive and damaging to biological systems. The biological membranes of subcellular organelles are a major site of free radical damage but proteins and DNA are also significant targets. Moreover, free radicals can alter cellular signal transduction pathways and stimulate the synthesis of inflammatory cytokines. Oxygen radicals and other reactive oxygen species (ROS) arise from the single electron reductions of oxygen.

Plasmalogen levels in serum from patients with impaired carbohydrate or lipid metabolism and in elderly subjects with normal metabolic values

The precise role played by plasmalogen phospholipids (PL) of lipoproteins and cell membranes is not well understood. However, they might act as endogenous antioxidants in defending cell membranes and lipoproteins from reactive oxygen species. A decline of plasmalogen concentrations has been observed in some tissues in normal aging and in some pathologic conditions. For healthy adults, we had reported negative correlations of age with serum plasmalogen PL derived heaxadecanal dimethylacetal (16:0DMA) or octadecanal dimethylacetal (18:0DMA) values. To mark off these age associated changes from disturbances in glucose or lipid metabolism, this study compares the 16:0DMA and 18:0DMA data of serum PL from 118 elderly subjects, aged 57-94 years, and grouped according to the disturbance of glucose or lipid metabolism. Using a new synthetic test mixture of 16:0DMA with oleic acid butylester as a quality control in gas chromatography, the highest 16:0DMA values were found in hypercholesterolemic subjects. However, related to the bulk of serum PL, were the plasmalogens possibly act as antioxidants, the highest values of 16:0DMA/PL were found in controls. A negative correlation of serum triglycerides (TG) with 16:0DMA was detected (n=118). The data suggest a closer association of low DMA values with elevated TG levels as compared to elevated plasma glucose or other serum lipid levels.

Fatty acid composition of choline and ethanolamine glycerophospholipid subclasses in heart tissue of mammals and migratory and demersal fish

The distribution and fatty acid composition of cardiac choline and ethanolamine glycerophospholipids in both migratory and demersal fish and bovine and pig were determined. Phospholipid contents (mg/g heart) were 4.7-9.4 in demersal fish, 14.0-16.5 in migratory fish, and 16.8-20.6 in mammals. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the major components in the phospholipid fraction. Diacyl forms represented 50.2-88.1% of PC in all animals, while plasmalogens comprised 47.0% in bovine, 8.2% in pig and 6.2-7.2% in four species of fish. In PE, plasmalogens varied from 45.0% in bovine and 57.9% in pig to 26.1-29.7% in fish. This glycerophospholipid subclass was identified as containing higher proportions of polyunsaturated fatty acids (PUFAs; 20:4, 20:5, and 22:6) than found in alkylacyl- and diacyl-glycerophospholipids. Qualitative and quantitative differences were found in PE-plasmalogen between land mammals and fish, especially with regard to n-3 fatty acid composition, but no significant difference was noted between migratory and demersal fish.

Analysis of stable oxidized molecular species of glycerophospholipids following treatment of red blood cell ghosts with t-butylhydroperoxide

A model of lipid peroxidation was employed to investigate the formation of oxidized phospholipids in red blood cell membranes after treatment with t-butylhydroperoxide (tBuOOH). On-line normal-phase HPLC/mass spectrometry (LC/MS) with electrospray ionization was used to separate phospholipid classes and analyze the distribution of the major poly-unsaturated fatty acyl groups and corresponding oxidation products. Arachidonic acid was observed primarily in plasmalogen glycerophosphoethanolamine (GPE), whereas linoleic acid was equally distributed in 1,2-diacyl-GPE and glycero-phosphocholine (GPC) lipids. The additions of one and two oxygen atoms to poly-unsaturated phospholipid molecular species were observed as the major, stable products after incubation with tBuOOH. Tandem mass spectrometry was utilized to further structurally characterize the oxidized fatty acyl groups which were identified as 5-, 8-, 9-, 11-, 12-, and 15-hydroxy-eicosatetraenoate (HETE) and 5-, 12-, and 15-hydroperoxyeicosatetraenoate (HpETE) in addition to 9- and 13-hydroxyoctadecadienoate (HODE) and 9- and 13-hydroperoxyoctadecadienoate (HpODE). Although 18:0p/20:4-GPE was the predominate phospholipid species containing arachidonic acid, the major species containing HETE and HpETE were the 1,2-diacyl-GPE with hexadecanoate as the sn-1 substituent. This result would be consistent with a differential pathway of oxidative degradation of arachidonoyl plasmalogen GPE suggesting a unique role for this plasmalogen molecular species glycerophospholipid.

Ether lipid biosynthesis: isolation and molecular characterization of human dihydroxyacetonephosphate acyltransferase

In this paper we describe isolation and molecular characterization of human dihydroxyacetonephosphate acyltransferase (DAP-AT). The enzyme was extracted from rabbit Harderian gland peroxisomes and isolated as a trimeric complex by sucrose density gradient centrifugation. From peptide sequences matching EST-clones were obtained which allowed cloning and sequencing of the cDNA from a human cDNA library. The nucleotide-derived amino acid sequence revealed a protein consisting of 680 amino acid residues of molecular mass 77187 containing a C-terminal type 1 peroxisomal targeting signal. Monospecific antibodies raised against this polypeptide efficiently immunoprecipitated DAP-AT activity from solubilized peroxisomal preparations, thus demonstrating that the cloned cDNA codes for DAP-AT.

Changes in glycerophospholipid profile in experimental nephrotic syndrome

We investigated changes in the glycerophospholipids in kidney tissue and its various intracellular fractions in rats with nephrotic syndrome induced by puromycin aminonucleoside. The ethanolamine plasmalogen, 1-O-alk-1'-enyl-2-acyl-GPE (EP), was increased in kidney tissue obtained from the puromycin-treated animals. A similar increase was found in the mitochondria and endoplasmic reticulum (microsomes) of this tissue. These increases were not found in the liver. Since platelet-activating factor (PAF) is known to be produced in increased amounts in inflammatory disorders, it is suggested that the higher plasmalogen found in rat kidneys during experimental nephrotic syndrome might be derived from increased levels of this autacoid. The increase in PAF may also result in the elevation of plasma PAF-acetylhydrolase (AH) activity observed in these animals.

Marked enrichment of the alkenylacyl subclass of plasma ethanolamine glycerophospholipid with eicosapentaenoic acid in human subjects consuming a fish oil concentrate

Alteration in human platelet fatty acid levels with the consumption of fish oils containing eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have been well documented, but changes in the fatty acid composition of plasma plasmalogenic phospholipid under similar circumstances have not been delineated. In the present study, subjects consumed the fish oil concentrate (MaxEPA) for 6 wk followed immediately by a 6-wk recovery period with no fish oil ingestion. Plasma total choline glycerophospholipid (GPC) and ethanolamine glycerophospholipid (GPE) subclasses isolated from blood samples obtained at 0, 3, 6, 9 and 12 wk of the experimental period were analyzed for fatty acid composition via thin-layer and gas-liquid chromatographic techniques. Consumption of fish oil for 3 or 6 wk significantly elevated the content of n-3 fatty acids while concomitantly decreasing n-6 fatty acid levels in plasma total GPC and in diacyl and alkenylacyl (plasmalogen) GPE. Alkenylacyl GPE exhibited the greatest alteration of both n-3 and n-6 fatty acid levels. Following 6 wk of supplementation with fish oil, EPA rose by 24.6 mol% in alkenylacyl GPE compared to increases of 6.7 and 7.1 mol% in diacyl GPE and total GPC, respectively. The increase in EPA (from 5.0 to 29.6 mol%) in plasma alkenylacyl GPE represents amongst the highest enrichment of EPA in any lipid yet reported in human subjects. DHA also rose by 8.0, 4.8, and 3.1 mol% in alkenylacyl GPE, diacyl GPE, and total GPC, respectively. Alkenylacyl GPE exhibited the greatest mol% decline (by 18.7 mol%) in arachidonic acid (AA, 20:4n-6) following 6 wk of fish oil supplementation. The corresponding decreases of AA in diacyl GPE and total GPC were 8.7 and 1.8 mol%, respectively. Following the 6 wk recovery period, n-3 and n-6 fatty acid levels had returned to pre-supplementation values. The marked enrichment of alkenylacyl GPE in n-3 fatty acids, especially EPA, may be of significance with respect to a unique role for this plasma phospholipid subclass in attenuating certain lipoprotein-mediated cardiovascular effects as observed with fish/fish oil consumption.

Delay of copper-catalyzed oxidation of low density lipoprotein by in vitro enrichment with choline or ethanolamine plasmalogens

Low density lipoprotein (LDL) isolated from human serum of different donors was enriched with plasmalogens and their diacyl analogs in order to investigate a possible effect of these phospholipids on the rate of lipid peroxidation in this lipoprotein. LDL was incubated with either vesicles of choline plasmalogen or phosphatidylcholine in presence of lipoprotein- deficient serum, or with liposomes of ethanolamine plasmalogen or phosphatidylethanolamine together with the non-specific phospholipid transfer protein isolated from beef liver. After re-isolation of LDL by ultracentrifugation, a dose-dependent incorporation of the exogenous phospholipids was obtained. Enrichment of LDL with choline plasmalogen resulted in a delay of the copper-catalyzed oxidation of LDL from five different donors. LDL from two donors was also enriched with diacylglycerophosphocholine which led to a delay of oxidation, but the protective effect was smaller than with choline plasmalogen. Enrichment of LDL from two additional donors with ethanolamine plasmalogen resulted in the strongest protection against oxidation, whereas, diacylglycerophospho-ethanolamine had little effect. The delay of the copper-catalyzed LDL oxidation may be due to a direct antioxidative action of the plasmalogens, which are partially degraded during the lag phase of oxidation, or to an indirect effect caused by alteration of the LDL surface in the presence of an excess of glycerophospholipids.

Plasmalogen oxidation in human serum lipoproteins

The content of plasmalogens in lipoproteins--very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)--in human serum was determined and compared with that after oxidation of the lipoproteins. Similarly, the content of alpha-hydroxyaldehydes produced from plasmalogens via their epoxids during lipidperoxidation (LPO) was studied. Incubation with Fe+ +/ascorbate results in a dramatic decrease in plasmalogens that correlates with an appropriate increase in alpha-hydroxyaldehydes. VLDL and LDL plasmalogens were oxidized to a greater extend (99% decrease) compared to HDL plasmalogens (35%). This finding is discussed with respect to atherogenesis and the recently postulated protective qualities of plasmalogens.

Radical solutions and cultural problems: could free oxygen radicals be responsible for the impaired development of preimplantation mammalian embryos in vitro?

A major obstacle to the study of mammalian development, and to the practical application of knowledge gained from it in the clinic during therapeutic in vitro fertilisation and embryo transfer (IVF-ET), is the propensity of embryos to become retarded or arrested during their culture in vitro. The precise developmental cell cycle in which embryos arrest or delay is characteristic for the species and coincides with the earliest period of embryonic gene expression. Much evidence reviewed here implicates free oxygen radicals (FORs) in the process of arrest. Thus, studies on the development of mouse preimplantation embryos in vitro have shown that (i) FORs are elevated in vitro, but not in vivo, at the time at which embryos become arrested or delayed, (ii) systems for removing reactive oxygen species to limit the formation of hydroxy radicals are present, although they have not yet been assessed quantitatively and may differ qualitatively from those in adult cells, (iii) metabolic and possibly genetic adaptations to oxidative damage are evident, (iv) published procedures for overcoming in vitro arrest are explicable in terms of FOR-mediated damage or responses and (v) the arrest or delay of most embryos in vitro can be reduced or prevented experimentally by addition of metal chelators to limit hydroxy radical formation and lipid hydroperoxidation.

Changes of membrane phospholipid composition of human erythrocytes in hyperlipidemias. I. Increased phosphatidylcholine and reduced sphingomyelin in patients with elevated levels of triacylglycerol-rich lipoproteins

The composition of red blood cell membrane and plasma phospholipids has been analyzed in patients with hyperlipidemias. In red cells of patients with elevated levels of triacylglycerol-rich lipoproteins, phosphatidylcholine (PC) was raised and sphingomyelin (SM) reduced, resulting in a 20% increase of the membrane PC/SM ratio. In plasma phospholipids of these patients PC and SM levels were also higher and lower, respectively and the plasma PC/SM ratio was elevated by more than 50%. Close positive correlations between plasma and membrane phospholipids were obtained for PC, SM and the PC/SM ratio in normolipidemic and hyperlipidemic donors. Plasmalogen phosphatidylethanolamine (PE), a supposed endogenous protector against lipid oxidation, was reduced by about 20% in red cell membrane lipids in hyperlipidemic patients. Also plasmalogen-PE in plasma tended to be reduced in hyperlipidemic donors. Plasma HDL levels were positively related to the content of plasmalogen PE in the red cell membrane. In conclusion, there are closely related increases in PC/SM ratios in plasma and the red cell membrane in patients with elevated levels of triacylglycerol-rich lipoproteins. It is speculated that decreases in red cell membrane plasmalogen-PE in hyperlipidemic patients could be related to impaired antioxidant protection, possibly as a consequence of reductions in plasma HDL levels.

The role of lipid peroxidation and antioxidants in oxidative modification of LDL

The purpose of this study is to provide a comprehensive survey on the compositional properties of LDL (e.g., lipid classes, fatty acids, antioxidants) relevant for its susceptibility to oxidation, on the mechanism and kinetics of LDL oxidation, and on the chemical and physico-chemical properties of LDL oxidized by exposure to copper ions. Studies on the occurrence of oxidized LDL in plasma, arteries, and plaques of humans and experimental animals are discussed with particular focus on the use of poly- and monoclonal antibodies for immunochemical demonstration of apolipoprotein B modifications characteristic for lipid peroxidation. Apart from uptake of oxidized LDL by macrophages, studies describing biological effects of heavily or minimally oxidized LDL are only briefly addressed, since several reviews dealing with this subject were recently published. This article is concluded with a section on the role of natural and synthetic antioxidants in protecting LDL against oxidation, as well as some previously unpublished material from our laboratories.

Subcellular fractionation evidence for a putative peroxisome-mitochondrion attachment in the liver of normal and genetically obese (ob/ob and db/db) mice

1. Liver post-nuclear supernatants (PNS) from several mouse strains were fractionated by zonal centrifugation and fractions analysed by marker-enzyme estimations+electron microscopy. 2. Rate-dependent banding of PNS yielded peroxisome-enriched (PER) and mitochondrion-enriched (MER) regions. 3. Density-dependent banding of PER yielded peroxisomes (approximately 1.22 g/ml) well separated from mitochondria (approximately 1.8 g/ml). 4. Density-dependent banding of MER yielded peroxisomes that co-distributed with mitochondria and electron microscopy revealed close proximity of the two organelles. 5. Experiments demonstrated that co-distribution was not due to weak binding of proteins or to agglutination of organelles. 6. The results indicate in vivo attachment of some mitochondria and peroxisomes.

Therapeutic potential of vitamin E in the pathogenesis of spontaneous atherosclerosis

Spontaneous atherosclerosis is largely an occlusive disease of medium-size arteries whose progression in a hyperlipidemic environment reflects chronic interactions among injury stimuli to the vessel wall and "responses to injury" by vascular tissue and certain blood components. Development of vessel lesions in animal models of spontaneous atherosclerosis and (at least in principle) in man largely reflects responses of three major cell types (vascular endothelial cells, vascular smooth muscle cells, monocytes-macrophages) as well as the content and distribution of lipids among various lipoprotein subclasses and the increased atherogenicity of modified (e.g., oxidized) lipoproteins. The severe clinical complications associated with spontaneous atherosclerosis, along with its rather common incidence in man, have focused attention on the prevention and therapy of this vascular disease state. Some pharmacological studies in animal models of spontaneous atherosclerosis and some retrospective epidemiological studies in man suggest that vitamin E, the principal (if not sole) lipid-soluble chain-breaking tissue antioxidant, might have therapeutic benefit as an antiatherosclerotic agent. This suggestion gains support from a variety of compelling in vitro evidence demonstrating direct influences of vitamin E on cells and lipoproteins likely involved in the pathogenesis of spontaneous atherosclerosis. Biochemical and cellular data indicate that the potential antiatherogenic activity of vitamin E could reflect its activities as a regulator of endothelial, smooth muscle, or monocyte-macrophage function, an inhibitor of endothelial membrane lipid peroxidation, a modulator of plasma lipid levels and lipid distribution among circulating lipoproteins, and a preventor of lipoprotein oxidative modification. On the other hand, there is a comparative lack of conclusive evidence from animal models regarding: (a) the importance to atherogenesis of vascular and cellular processes modulated by vitamin E; (b) the influence of vitamin E on these processes in vivo and, consequently, on the initiation/progression of spontaneous atherosclerosis. Therefore, pharmacologic investigation of vitamin E (and synthetic, vitamin E-like antioxidants) in nutritional and hyperlipidemic animal models of spontaneous atherosclerosis is required to establish whether any atherosclerotic impact is associated with vitamin E and, if so, what the mechanistic basis of the therapeutic benefit is. Such a line of experimental inquiry should also increase our understanding of the pathogenesis of atherosclerotic vessel disease per se.