Effect of vitamin E on human aortic endothelial cell production of chemokines and adhesion to monocytes

Vitamin E, oxidative stress, and inflammation

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the Western world. Its incidence has also been increasing lately in developing countries. Several lines of evidence support a role for oxidative stress and inflammation in atherogenesis. Oxidation of lipoproteins is a hallmark in atherosclerosis. Oxidized low-density lipoprotein induces inflammation as it induces adhesion and influx of monocytes and influences cytokine release by monocytes. A number of proinflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) modulate monocyte adhesion to endothelium. C-reactive protein (CRP), a prototypic marker of inflammation, is a risk marker for CVD and it could contribute to atherosclerosis. Hence, dietary micronutrients having anti-inflammatory and antioxidant properties may have a potential beneficial effect with regard to cardiovascular disease. Vitamin E is a potent antioxidant with anti-inflammatory properties. Several lines of evidence suggest that among different forms of vitamin E, alpha-tocopherol (AT) has potential beneficial effects with regard to cardiovascular disease. AT supplementation in human subjects and animal models has been shown to decrease lipid peroxidation, superoxide (O2-) production by impairing the assembly of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase as well as by decreasing the expression of scavenger receptors (SR-A and CD36), particularly important in the formation of foam cells. AT therapy, especially at high doses, has been shown to decrease the release of proinflammatory cytokines, the chemokine IL-8 and plasminogen activator inhibitor-1 (PAI-1) levels as well as decrease adhesion of monocytes to endothelium. In addition, AT has been shown to decrease CRP levels, in patients with CVD and in those with risk factors for CVD. The mechanisms that account for nonantioxidant effects of AT include the inhibition of protein kinase C, 5-lipoxygenase, tyrosine-kinase as well as cyclooxygenase-2. Based on its antioxidant and anti-inflammatory activities, AT (at the appropriate dose and form) could have beneficial effects on cardiovascular disease in a high-risk population.

Protocatechuic aldehyde suppresses TNF-alpha-induced ICAM-1 and VCAM-1 expression in human umbilical vein endothelial cells

Adhesion molecules, which play a crucial role in the development of atherogenesis, are produced by endothelial cells following stimulation with various inflammatory cytokines. The current studies examined the effect of a potent water-soluble antioxidant, protocatechuic aldehyde (derived from the Chinese herb, Salvia miltiorrhiza), on the expression of adhesion molecules in human umbilical vein endothelial cells (HUVECs) stimulated with tumor necrosis factor-alpha (TNF-alpha). Protocatechuic aldehyde appeared to specifically downregulate the TNF-alpha-induced cell surface expression of vascular adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1) on HUVECs as well as the release of soluble VCAM-1and ICAM-1 from HUVECs in a dose-response manner at pharmacologically relevant concentrations (0.15-1.35 mM). We also observed a dose-dependent lowering of mRNA expression of VCAM-1 and ICAM-1 in the presence of protocatechuic aldehyde. Furthermore, protocatechuic aldehyde (0.15, 0.45, and 1.35 mM) notably inhibited TNF-alpha-induced upregulation of U937 cell adhesion to HUVECs to 83.7%, 60.9%, and 40.8%, respectively. A gel shift assay further showed that protocatechuic aldehyde inhibited the TNF-alpha-activated NF-kappaB and AP-1 DNA binding activities in a dose-dependent manner. Collectively, these results indicate that protocatechuic aldehyde inhibits TNF-alpha-stimulated VCAM-1 and ICAM-1expression in HUVECs through a mechanism that involves NF-kappaB and AP-1.

Vitamin E increases production of vasodilator prostanoids in human aortic endothelial cells through opposing effects on cyclooxygenase-2 and phospholipase A2

Impairment of endothelium-dependent vasodilation is associated with the initiation and development of atherosclerosis. Vasodilator prostanoids constitute a protective mechanism in maintaining normal vasomotor function. In the current study, we determined the effect of in vitro vitamin E supplementation at physiologically relevant concentrations (10-60 micromol/L) on the production of the vasodilator prostanoids prostaglandin I(2) (PGI(2); prostacyclin) and prostaglandin E(2)(PGE(2)) by human aortic endothelial cells (HAECs) as well as its underlying mechanism. Results showed that vitamin E dose dependently (10-40 micromol/L) increased the production of both prostanoids by HAECs. This was associated with a dose-dependent (10-40 micromol/L) upregulation of cytosolic phospholipase A(2) (cPLA(2)) expression and arachidonic acid release. In contrast, vitamin E dose dependently (10-60 micromol/L) inhibited cyclooxygenase (COX) activity but did not affect the expression of either COX-1 or COX-2, indicating that the effect of vitamin E on COX activity was post-translational. Thus, vitamin E had opposing effects on the 2 key enzymes in prostanoid biosynthesis; at the concentrations used in this study, this resulted in a net increase in the production of vasodilator prostanoids. The vitamin E-induced increase in PGI(2) and PGE(2) production may contribute to its suggested beneficial effect in preserving endothelial function.

Cholinergic stimulation blocks endothelial cell activation and leukocyte recruitment during inflammation

Endothelial cell activation plays a critical role in regulating leukocyte recruitment during inflammation and infection. Based on recent studies showing that acetylcholine and other cholinergic mediators suppress the production of proinflammatory cytokines via the α7 nicotinic acetylcholine receptor (α7 nAChR) expressed by macrophages and our observations that human microvascular endothelial cells express the α7 nAChR, we examined the effect of cholinergic stimulation on endothelial cell activation in vitro and in vivo. Using the Shwartzman reaction, we observed that nicotine (2 mg/kg) and the novel cholinergic agent CAP55 (12 mg/kg) inhibit endothelial cell adhesion molecule expression. Using endothelial cell cultures, we observed the direct inhibitory effects of acetylcholine and cholinergic agents on tumor necrosis factor (TNF)-induced endothelial cell activation. Mecamylamine, an nAChR antagonist, reversed the inhibition of endothelial cell activation by both cholinergic agonists, confirming the antiinflammatory role of the nAChR cholinergic pathway. In vitro mechanistic studies revealed that nicotine blocked TNF-induced nuclear factor–κB nuclear entry in an inhibitor κB (IκB)α- and IκBɛ-dependent manner. Finally, with the carrageenan air pouch model, both vagus nerve stimulation and cholinergic agonists significantly blocked leukocyte migration in vivo. These findings identify the endothelium, a key regulator of leukocyte trafficking during inflammation, as a target of anti-inflammatory cholinergic mediators.

Polystyrene surface coated with vitamin E modulates human granulocyte adhesion and MMP-9 release

Vitamin E (Vit.E, alpha-tocopherol) is a natural biological antioxidant and antinflammatory agent, which protects cells from the effects of free radicals and inhibits inflammation. For such properties Vit.E has been used to improve the biocompatibility of materials such as cellulose membrane for hemodialysis. In this study granulocytes adhesion and activation have been studied after contact with normal cell culture grade polystyrene (PS) and Vit.E-coated polystyrene (Vit.E 0.1 and 0.3% (v/v)) using optical microscopy, flow cytometry and substrate zymography. Vit.E increased the number of adherent granulocytes both at 0.1% (11470 +/- 1064 cells/cm(2), P < 0.01) and 0.3% ( 13706 +/-818) cells/cm(2), P < 0.001) concentration compared to normal PS (5529+/-692 cells/cm(2)). The morphology of granulocytes adherent to Vit.E-PS appeared lightly altered and no differences have been observed in their respiratory burst compared to control granulocyte, while matrix metalloproteinase 9 or gelatinase B (MMP-9) release and activation were increased compared to the normal PS samples. Our data indicate that Vit.E-coated surface induced an increase in granulocytes adhesion and MMP-9 release in the absence of the typical oxidative stress, hallmark of granulocytes activation. A possible explanation of the phenomenon is that Vit.E modifies the surface protein adsorption thus increasing cell adhesion and in turn MMP-9 releasing.

Effect of vitamin E addition to poly(D,L)-lactic acid on surface properties and osteoblast behaviour

Vitamin E (Vit.E, alpha-tocoferol) is a natural agent with anti-oxidative and anti-inflammatory properties and it has been suggested that it could act as a stimulating factor for osteoblast proliferation and maturation. We produced poly(D,L)-lactic acid films enriched with Vit.E (1, 5 and 10% w/w) and investigated their surface properties using the FTIR analysis, sessile measure of wettability and serum protein adsorption, and evaluated attachment and spreading of MC-3T3 E1 murine osteoblast cells. FTIR analysis showed the presence of Vit.E on the polymer surface and Vit.E increased the polymer wettability in a concentration-dependent manner. The serum total protein adsorption increased significantly onto the 10% Vit.E P(D,L)-LA and the main protein adsorbed was albumin. The presence of albumin, considered as an anti-adhesive protein, on the surface of Vit.E enriched P(D,L)-LA films (especially 5 and 10% Vit.E) could explain, at least in part, the behaviour of MC-3T3 osteoblast cells seeded onto the polymers. Cell adhesion and spreading were strongly decreased by Vit.E (5 and 10%) in spite of the increased wettability. This reaction could be cell type-specific, independent by the surface wettability and linked to cell-specific characteristics (membrane phospholipid composition, integrins expression). Moreover a direct effect of Vit.E on cell adhesion and spreading cannot be completely excluded.

Vitamin E supplementation suppresses macrophage accumulation and endothelial cell expression of adhesion molecules in the aorta of hypercholesterolemic rabbits

Suppression of cell adhesion molecule expression and macrophage accumulation by the endothelium is believed to play an important role in preventing the development of atherosclerosis. Earlier, we have shown that in vitro supplementation of human aortic endothelial cells with Vitamin E dose-dependently reduced expression of adhesion molecules and monocyte adhesion. Here, we report the in vivo down-regulation of endothelial cell adhesion molecules expression and macrophage accumulation in the aortas of hypercholesterolemic rabbits supplemented with Vitamin E. To this end, New Zealand White rabbits were fed a semi-purified diet containing 30 (control) or 1000 IU/kg Vitamin E. After 4 weeks, both groups' diets were switched to an atherogenic diet (0.3% cholesterol, 9% hydrogenated coconut oil, and 1% corn oil) containing the respective levels of Vitamin E and fed for 2, 4, and 6 weeks. Vitamin E supplemented rabbits had significantly higher levels of Vitamin E in their plasma and aortas. Frozen aorta sections were fixed and stained by an avidin-biotin complex method using Rb2/3 and Rb1/9 monoclonal antibodies against rabbit ICAM-1 and VCAM-1, respectively, and with RAM-11 for macrophage and von Willebrand factor for endothelial cells, followed by staining with secondary antibodies and counterstaining and evaluation under the microscope. At 6 weeks on atherogenic diet treatment, a trend (P = 0.08) toward a lower score of ICAM-1 expression by endothelial cells was observed in the aorta of Vitamin E treated rabbits compared to the control. However, a decrease in the score of VCAM-1 expression by endothelial cells in Vitamin E treated rabbits did not reach to a statistical significance. At 4 and 6 weeks on atherogenic diet, Vitamin E supplementation also significantly (P = 0.003) inhibited the accumulation of macrophages in the aorta. These results support the concept that down-regulation of adhesion molecule expression and suppression of monocyte/macrophage activation by Vitamin E in vivo is one of the potential mechanisms by which Vitamin E may suppress the development of aortic lesions in a rabbit model of atherosclerosis.

Ethanol blocks leukocyte recruitment and endothelial cell activation in vivo and in vitro

Immune system impairment and increased susceptibility to infection among alcohol abusers is a significant but not well-understood problem. We hypothesized that acute ethanol administration would inhibit leukocyte recruitment and endothelial cell activation during inflammation and infection. Using LPS and carrageenan air pouch models in mice, we found that physiological concentrations of ethanol (1-5 g/kg) significantly blocked leukocyte recruitment (50-90%). Because endothelial cell activation and immune cell-endothelial cell interactions are critical regulators of leukocyte recruitment, we analyzed the effect of acute ethanol exposure on endothelial cell activation in vivo using the localized Shwartzman reaction model. In this model, ethanol markedly suppressed leukocyte accumulation and endothelial cell adhesion molecule expression in a dose-dependent manner. Finally, we examined the direct effects of ethanol on endothelial cell activation and leukocyte-endothelial cell interactions in vitro. Ethanol, at concentrations within the range found in human blood after acute exposure and below the levels that induce cytotoxicity (0.1-0.5%), did not induce endothelial cell activation, but significantly inhibited TNF-mediated endothelial cell activation, as measured by adhesion molecule (E-selectin, ICAM-1, VCAM-1) expression and chemokine (IL-8, MCP-1, RANTES) production and leukocyte adhesion in vitro. Studies exploring the potential mechanism by which ethanol suppresses endothelial cell activation revealed that ethanol blocked NF-kappaB nuclear entry in an IkappaBalpha-dependent manner. These findings support the hypothesis that acute ethanol overexposure may increase the risk of infection and inhibit the host inflammatory response, in part, by blocking endothelial cell activation and subsequent immune cell-endothelial cell interactions required for efficient immune cell recruitment.

Vitamin E Modulation of Cardiovascular Disease

Endothelium in the vascular system is an important modulator of vasomotor tone and coagulation, and it plays a crucial role in the inhibition of adhesion and activation of platelets and leukocytes. Evidence indicates that dietary antioxidants may modulate these endothelium-dependent vascular functions through several mechanisms and may contribute to the prevention of vascular diseases such as atherosclerosis. Several cell cultures as well as animal and human clinical and observational studies have tested the efficacy of vitamin E on vascular function and the prevention of atherosclerosis. Our cell culture studies have indicated that vitamin E (alpha-tocopherol) inhibits the activation of endothelial cells stimulated by high levels of low-density lipoprotein cholesterol and pro-inflammatory cytokines. This inhibition is associated with the suppression of chemokines, the expression of cell surface adhesion molecules, and the adhesion of leukocytes to endothelial cells, all of which contribute to the development of lesions in the arterial wall. The molecular mechanisms by which alpha-tocopherol and other tocopherols modulate endothelial cells and smooth muscle functions have been delineated. We, and others, have also demonstrated a positive effect of dietary vitamin E on endothelium and vascular function in animal models of atherosclerosis. Several human clinical trials have also shown an improvement in the surrogate markers of atherosclerosis and vascular function by vitamin E supplementation. However, these findings have been contradicted by several vitamin E supplementation trials for the prevention of secondary cardiovascular events showing null effect. Intervention at a relatively late stage of disease and the single use of vitamin E rather than in combination with other antioxidants might have contributed to these contradictory findings. Evidence from cell cultures, as well as animal and human clinical and observational studies, strongly supports the contribution of dietary vitamin E to the maintenance of vascular function and health, in particular when it is used in combination with other dietary antioxidants, which are found in fruits, vegetables, and nuts.

The antiatherogenic potential of oat phenolic compounds

Avenanthramides are phenolic antioxidants, which are present in oats. Avenanthramides A, B, and C are the major constituents of the total soluble antioxidant phenolic compounds in oats. We tested the potential antiatherogenic activity of partially purified avenanthramides from oats by examining their effects on adhesion of monocytes to human aortic endothelial cell (HAEC) monolayers, expression of adhesion molecules, and production of proinflammatory cytokines and chemokines by HAEC. The oat avenanthramides mixture was prepared and partially purified by column chromatography. This avenanthramide-enriched mixture (AEM) had no toxicity to HAEC as tested up to 40 ng/ml. The pre-incubation of HAEC with 4, 20, and 40ng/ml AEM for 24h significantly decreased adhesion of U937 monocytic cells to interleukin (IL)-1beta-stimulated HAEC in a concentration-dependent manner. Pre-incubation of HAEC with AEM at 20 and 40 microg/ml, but not at 4 microg/ml, for 24h significantly suppressed IL-1beta-stimulated expressions of intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin and the secretion of proinflammatory cytokines IL-6, chemokines IL-8 and monocyte chemoattractant protein (MCP)-1. These data provide evidence for the potential anti-inflammatory and antiatherogenic effects of antioxidant avenanthramides present in oats.

Antioxidant supplementation and nasal inflammatory responses among young asthmatics exposed to high levels of ozone

The inflammatory response to ozone in atopic asthma suggests that soluble mediators of inflammation are released in response to oxidant stress. Antioxidants may alleviate additional oxidative stress associated with photochemical oxidant pollution. This study investigates the impact of antioxidant supplementation on the nasal inflammatory response to ozone exposure in atopic asthmatic children. We conducted a randomized trial using a double-blinded design. Children with asthma (n = 117), residents of Mexico City, were given randomly a daily supplement of vitamins (50 mg/day of vitamin E and 250 mg/day of vitamin C) or placebo. Nasal lavages were performed three times during the 4-month follow-up and analysed for content of interleukin-6 (IL-6), IL-8, uric acid and glutathione (GSx). IL-6 levels in the nasal lavage were increased significantly in the placebo group after ozone exposure while no increase was observed in the supplement group. The difference in response to ozone exposure between the two groups was significant (P = 0.02). Results were similar for IL-8, but with no significant difference between the groups (P = 0.12). GSx decreased significantly in both groups. Uric acid decreased slightly in the placebo group. Our data suggest that vitamin C and E supplementation above the minimum dietary requirement in asthmatic children with a low intake of vitamin E might provide some protection against the nasal acute inflammatory response to ozone.

Serum carotenoids and vitamins in relation to markers of endothelial

BACKGROUND

Endothelial cell dysfunction may be related to an increase in cellular oxidative stress. Carotenoids and vitamins could have an antioxidant-mediated tempering influence on endothelial function and inflammation, thereby reducing the risk of atherosclerosis.

METHODS

We measured serum carotenoids, alpha-tocopherol and Vitamin C concentrations in 379 subjects sampled from the general population. High-sensitive C-reactive protein (CRP), fibrinogen (Fbg) and leukocytes were measured as markers of inflammation. Furthermore, soluble intercellular adhesion molecule-1 (sICAM-1) and flow-mediated vasodilation (FMD; n= 165) were measured as markers of endothelial function. Relationships between serum carotenoids and vitamins and markers of endothelial function and inflammation were analysed after adjustment for confounding.

RESULTS

In the total study group, lutein and lycopene were inversely related to sICAM-1 with regression-coefficients of -0.38+/-0.19 (p = 0.04) and -0.16+/-0.08 (p = 0.04) per 1 micromol/l, respectively. beta-Carotene was inverse related to leukocytes (-0.23+/-0.07; p = 0.007) and CRP (-1.09+/-0.30; p = 0.0003) per 1 micromol/l. Vitamin C was inverse related to CRP (-0.01+/-0.005; p = 0.04) per 1 micromol/l, whereas alpha-tocopherol was positively related to CRP (0.03+/-0.01; p = 0.02) per 1 micro/l. Zeaxanthin was inversely related to FMD (31.2+/-15.3; p = 0.04) per 1 micromol/l.

CONCLUSION

The inverse relations between carotenoids, Vitamin C and sICAM-1, CRP and leukocytes may help to explain the possible protective effect of carotenoids and Vitamin C on atherosclerosis through an influence on inflammatory processes and endothelial function.

Effects of benidipine, a dihydropyridine-Ca2+ channel blocker, on expression of cytokine-induced adhesion molecules and chemoattractants in human aortic endothelial cells

Benidipine hydrochloride (benidipine) is a dihydropyridine-Ca2+ channel blocker with antioxidant properties. We examined the effects of benidipine on cytokine-induced expression of adhesion molecules and chemokines, which play important roles in the adhesion of monocytes to endothelium. Pretreatment of human aortic endothelial cells (HAECs) with benidipine (0.3-10 micromol/l) for 24 h significantly suppressed cytokine-induced vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1) mRNA and protein expression, resulting in reduced adhesion of THP-1 monocytes. Benidipine also suppressed induction of monocyte chemoattractant protein (MCP)-1 and interleukin-8. Benidipine inhibited redox-sensitive transcriptional nuclear factor-kappaB (NF-kappaB) pathway, as determined by Western blotting of inhibitory kappaB (IkappaB) phosphorylation and luciferase reporter assay. Results of analysis using optical isomers of benidipine and antioxidants suggested that these inhibitory effects were dependent on pharmacological effects other than Ca2+ antagonism such as antioxidant effects. Benidipine may thus have anti-inflammatory properties and benefits for in the treatment of atherosclerosis.

Anti-atherosclerotic effects of vitamin E--myth or reality?

Atherosclerosis and its complications such as coronary heart disease, myocardial infarction and stroke are the leading causes of death in the developed world. High blood pressure, diabetes, smoking and a diet high in cholesterol and lipids clearly increase the likelihood of premature atherosclerosis, albeit other factors, such as the individual genetic makeup, may play an additional role. Several epidemiological studies and intervention trials have been performed with vitamin E, and some of them showed that it prevents atherosclerosis. For a long time, vitamin E was assumed to act by decreasing the oxidation of LDL, a key step in atherosclerosis initiation. However, at the cellular level, vitamin E acts by inhibition of smooth muscle cell proliferation, platelet aggregation, monocyte adhesion, oxLDL uptake and cytokine production, all reactions implied in the progression of atherosclerosis. Recent research revealed that these effects are not the result of the antioxidant activity of vitamin E, but rather of precise molecular actions of this compound. It is assumed that specific interactions of vitamin E with enzymes and proteins are at the basis of its non-antioxidant effects. Vitamin E influences the activity of several enzymes (e.g. PKC, PP2A, COX-2, 5-lipooxygenase, nitric oxide synthase, NADPH-oxidase, superoxide dismutase, phopholipase A2) and modulates the expression of genes that are involved in atherosclerosis (e.g. scavenger receptors, integrins, selectins, cytokines, cyclins). These interactions promise to reveal the biological properties of vitamin E and allow designing better strategies for the protection against atherosclerosis progression.

The effects of long-term vitamin E treatment on gene expression and oxidative stress damage in the aging Brown Norway rat epididymis

The male reproductive tract of the Brown Norway rat is profoundly affected by aging. In the epididymis, the site of sperm maturation and storage, aging results in histological and biochemical changes that are suggestive of oxidative stress. Vitamin E is a potent lipid-soluble antioxidant that ameliorates the oxidative stress load associated with some chronic disease conditions. To determine the effects of long-term (18-mo) vitamin E deficiency and supplementation on aging in the epididymis, we assessed gene expression changes using cDNA microarrays and lipid peroxidation using immunohistochemical detection of 4-hydroxynonenal (4-HNE) in 24-mo-old rats. Plasma vitamin E levels were significantly lower in vitamin E-deficient animals and higher in vitamin E-supplemented animals compared with age-matched controls. Vitamin E deficiency resulted in increased expression of oxidative stress-related transcripts along the epididymis. This effect was most marked in the corpus epididymidis, where expression of glutathione S-transferases pi, 8, and mu, as well as superoxide dismutase, increased by over 50%. The effect of vitamin E supplementation on the expression of oxidative stress-related transcripts was primarily decreased expression; however, the magnitude of the gene expression changes was smaller than that observed for vitamin E deficiency. 4-HNE immunostaining was present throughout the epididymis in control animals. Vitamin E deficiency both increased the intensity and altered the distribution of 4-HNE staining, while vitamin E supplementation had no observable effect. In summary, we found that long-term vitamin E treatment alters the expression of oxidative stress-related transcripts. Moreover, long-term vitamin E deficiency exacerbates the effects of age on the accumulation of oxidative stress damage in the epididymis.

Vitamin E modulation of C-reactive protein in smokers with acute coronary syndromes

Acute coronary syndromes are characterized by the expression of proinflammatory cytokines such as C-reactive protein (CRP). Sustained upregulation of inflammatory markers is associated with an adverse prognosis. Vitamin E is known to have significant anti-inflammatory properties and has been associated with a reduction in cardiovascular events in some studies of high-risk patients. The mechanism of benefit remains controversial. We conducted a randomized, double-blind placebo controlled trial of vitamin E 400 IU daily for 6 months in 110 patients with acute coronary syndromes. Serum samples were collected at enrollment and at 2, 4, and 6 months. CRP, interleukin-6 and the soluble cell adhesion molecules were measured. Vitamin E levels increased significantly in the treatment group (from 31 micromol/l at baseline to 51 micromol/l, p <.0001) and were unchanged in the placebo group (32 micromol/l at baseline to 34 micromol/l, p = NS). CRP levels fell in both the vitamin E group and the placebo group over the treatment period (from 17.2 +/- 2.9 to 6.1 +/- 0.8 mg/l and from 21.5 +/- 4.9 to 5.9 +/- 0.9 mg/l, p = NS for the difference between active and placebo groups). However, vitamin E treatment was associated with significantly lower 6 month CRP levels in smokers versus smokers on placebo (4.7 +/- 0.71 mg/l vs. 8.26 +/- 1.5 mg/l, p =.02). Vitamin E reduces CRP levels in smokers with acute coronary syndromes for up to 6 months after hospitalization.

Vitamin E inhibits anti-Fas-induced phosphatidylserine oxidation but does not affect its externalization during apoptosis in Jurkat T cells and their phagocytosis by J774A.1 macrophages

Apoptosis and phagocytosis of apoptotic cells provide for effective and harmless clearance of unwanted or damaged cells in the body. Preferential oxidation of one particular class of phospholipids, phosphatidylserine (PS), is a typical trait of both oxidant- and nonoxidant-induced apoptosis. PS oxidation is likely to play an important role in phagocytosis either by affecting PS externalization acting as an "eat me" signal or by more effective recognition of apoptotic cells by macrophage receptors. This implies that antioxidants effective in inhibiting PS oxidation may affect PS externalization and/or effective removal of apoptotic cells. Therefore, it is essential to determine whether vitamin E, the major lipid-soluble antioxidant of membranes, inhibits PS oxidation, and hence blocks apoptosis/phagocytosis. To test this, we studied the effects of vitamin E on PS oxidation and signaling using a model of anti-Fas-triggered apoptosis in Jurkat T cells. We found that incubation of cells with vitamin E (0.25-50 micro M) resulted in its integration into cells to reach physiologically relevant concentrations. Using labeling of cell phospholipids with oxidation-sensitive and fluorescent cis-parinaric acid (PnA), we found that anti-Fas exposure caused significant and selective oxidation of PnA-PS in Jurkat T cells (22 +/- 2.1% of its content in nonexposed cells). Vitamin E protected PnA-PS against oxidation in a concentration-dependent way such that at 25 micro M and 50 micro M, a complete inhibition of anti-Fas-induced PS oxidation was achieved. At all concentrations used, vitamin E had no effect on either biomarkers of anti-Fas-induced apoptosis (PS externalization, nuclear fragmentation) or phagocytosis of anti-Fas-induced apoptotic cells by J774A.1 macrophages. We conclude that vitamin E does not significantly interfere with extrinsic (death receptor-triggered) pathways of apoptosis and does not affect phagocytosis of anti-Fas-triggered apoptotic cells.

Vitamins in human arteriosclerosis with emphasis on vitamin C and vitamin E

INTRODUCTION

This review focuses on the process of arteriosclerosis arising from oxidative stress on lipoproteins and the general failure of randomized human trials using vitamins to retard this process.

REVIEW

As well as clinical trials, the paper reviews the mechanisms by which a variety of oxidants act. Antioxidants are discussed, emphasizing interactions of vitamins C and E with transition metals that can lead to prooxidation. There is a focus on interactions between supplemental or co-antioxidants that counterbalance prooxidant effects of one another.

CONCLUSIONS

It is concluded that normal cellular supplementation mechanisms are poorly accessible in the arteriosclerotic plaque leading to a prooxidant environment in which the haphazard introduction of vitamins could potentially be hazardous. Continued investigations into basic and clinical redox interactions of the kind discussed in this review using new measuring techniques may lead to approaches whereby antioxidants can be introduced into tissue in controlled ways for reducing arteriosclerosis.

Homologous metabolic and gene activating routes for vitamins E and K

Vitamins E and K share structurally related side chains and are degraded to similar final products. For vitamin E the mechanism has been elucidated as initial omega-hydroxylation and subsequent beta-oxidation. For vitamin K the same mechanism can be suggested analogously. omega-Hydroxylation of vitamin E is catalyzed by cytochrome p450 enzymes, which often are induced by their substrates themselves via the activation of the nuclear receptor PXR. Vitamin E is able to induce CYP3A-forms and to activate a PXR-driven reporter gene. It is shown here that K-type vitamins are also able to activate PXR. A ranking showed that compounds with an unsaturated side chain were most effective, as are tocotrienols and menaquinone-4 (vitamin K(2)), which activated the reporter gene 8-10-fold. Vitamers with a saturated side chain, like tocopherols and phylloquinone were less active (2-5-fold activation). From the fact that CYPs commonly responsible for the elimination of xenobiotics are involved in the metabolism of fat-soluble vitamins and the ability of the vitamins to activate PXR it can be concluded that supranutritional amounts of these vitamins might be considered as foreign.

Intercellular adhesion molecule-1 and vascular endothelial growth factor expression kinetics in macrophage-derived foam cells

Macrophage-derived foam cells seem to play an important role during inflammatory response of atherosclerosis, in which the overexpression of intercellular adhesion molecule-1 (ICAM-1) and vascular endothelial growth factor (VEGF) are associated with the early and later pathological changes in foam cell formation. In this study, we investigated the expression kinetics of ICAM-1 and VEGF in macrophage-derived foam cells. The foam cell model was established through incubating the human monocyte line (U937 cells) with oxidized-low density lipoprotein (ox-LDL). Up-regulated expressions of ICAM-1 and VEGF were analyzed in protein and mRNA levels in U937 foam cells by flow cytometry, ELISA, and Northern blot. Kinetic studies showed the deferent kinds of expression curves in dose response and time course. The expression dose-kinetics demonstrated that the ICAM-1 showed the peak expression induced by ox-LDL 50 mg/L, while VEGF levels increased in a dose-dependent manner with the maximum level induced by ox-LDL 200 mg/L. Time-kinetic studies revealed that the ICAM-1 levels showed the peak expression in 12 h while VEGF expression increased in a time-dependent manner with the maximum level in 48 h. These results proved that both ICAM-1 and VEGF expressions were enhanced in the macrophage-derived foam cells, but ICAM-1 expression increased earlier than the up-regulation of VEGF; low dose of ox-LDL mainly up regulated ICAM-1 expression, while high dose mainly increased the VEGF expression.

Monocyte chemoattractant protein-1 involvement in the alpha-tocopherol-induced reduction of atherosclerotic lesions in apolipoprotein E knockout mice

We studied the effects of alpha-tocopheryl acetate supplementation on the development of fatty streaks and its ability to modulate the expression of monocyte chemoattractant protein (MCP)-1 in aortic lesions of apolipoprotein E knockout mice. For this purpose, 16-week-old apolipoprotein E knockout mice received alpha-tocopherol supplementation (800 mg)/kg diet) for 6 weeks. After this time, total and lipoprotein cholesterol in the serum, hepatic tocopherol, aortic lesion area and MCP-1 (protein and mRNA) expression were analysed. Our present results showed that the dietary supplementation with alpha-tocopherol did not reduce serum cholesterol nor change lipoprotein profile, but it reduced the area of the aortic lesion by 55 %. The reduction in the lesion size was correlated with the reduced expression of MCP-1 mRNA and protein, as detected by real-time quantitative polymerase chain reaction and immunohistochemistry respectively. In conclusion, the results obtained here are relevant to the study of atherosclerosis, as they correlate the effectiveness of vitamin E supplementation in inhibiting the plaque formation with diminished expression of MCP-1 at the aortic lesion.

Ascorbic acid blocks the growth inhibitory effect of tumor necrosis factor-alpha on endothelial cells

Impaired endothelial cell proliferation has been proposed to be an early, critical defect contributing to the development of atherosclerosis. Recent studies show that high plasma tumor necrosis factor (TNF)-alpha levels and low serum ascorbic acid (AA) levels correlate with atherosclerosis severity. Additionally, AA has been reported to have potential beneficial effects in preventing atherosclerosis. Based on these studies, we investigated the role of AA (< or =1mM) on TNF-alpha-mediated vascular endothelial cell growth inhibition in vitro. In accordance with previous reports, we found that TNF-alpha alone inhibited endothelial cell proliferation. Further studies revealed that AA alone enhanced endothelial cell proliferation and that AA blocked endothelial cell growth inhibition induced by TNF-alpha. By contrast, we observed no effect of AA on endothelial cell activation or nuclear entry of nuclear factor-kappaB in response to TNF-alpha. The protective effect of AA on endothelial cell proliferation was not simply the result of its antioxidant activity but did correlate with collagen IV expression by endothelial cells. AA pre-treatment of proliferating endothelial cells promoted retinoblastoma protein (Rb) phosphorylation and decreased p53 levels when compared to untreated cells. Furthermore, the addition of AA to TNF-alpha-treated proliferating endothelial cells blocked both the inhibition of retinoblastoma protein phosphorylation and enhanced p53 expression induced by TNF-alpha. Consistent with these results, we found that AA protects endothelial cells against TNF-alpha-induced apoptosis. These studies highlight the potential therapeutic role of AA in promoting endothelial cell proliferation during inflammatory conditions, such as atherosclerosis and cardiovascular disease.

Increased vascular endothelial cell production of interleukin-6 in severe preeclampsia

OBJECTIVE

The purpose of this study was to determine whether plasma from women with severe preeclampsia stimulates the production of endothelial cell interleukin-6 production and whether vitamin E could inhibit this process.

STUDY DESIGN

Human umbilical vein endothelial cells were cultured in the presence of 5% plasma from women with severe preeclampsia (n = 12) or healthy pregnant women at term (n = 12), with or without 50 micromol/L vitamin E. Levels of interleukin-6 in plasma and human umbilical vein endothelial cell-conditioned media were measured by enzyme-linked immunosorbent assay.

RESULTS

Interleukin-6 levels were elevated 5-fold in preeclamptic plasma compared with normal pregnant plasma (P <.05). Human umbilical vein endothelial cell interleukin-6 production was increased 25% by preeclamptic plasma compared with normal pregnant plasma (P <.005), and increased interleukin-6 production by preeclamptic plasma was inhibited by vitamin E.

CONCLUSION

Endothelial cell activation by preeclamptic plasma stimulates interleukin-6 production, which is inhibited by vitamin E. These findings provide a potential cellular mechanism for the beneficial effects of antioxidant therapy in preeclampsia.

Expression of interleukin-1 beta and interleukin-1 receptor antagonist in oxLDL-treated human aortic smooth muscle cells and in the neointima of cholesterol-fed endothelia-denuded rabbits

The migration of vascular smooth muscle cells (VSMCs) from the media to the intima and the proliferation of intimal VSMCs are key events in restenotic lesion development. These events, which are preceded and accompanied by inflammation, are modulated by the proinflammatory cytokine, interleukin-1 beta (IL-1 beta), which induces vascular smooth muscle cells to express adhesion molecules and to proliferate. IL-1 beta action is complex and regulated, in part, by its naturally occurring inhibitor, the IL-1 receptor antagonist (IL-1ra). Whether there was a temporal and spatial correlation between IL-1 beta and IL-1ra expression in, and release by, oxidized low density lipoproteins (oxLDL)-stimulated human aortic smooth muscle cells (HASMCs) was determined by using ELISA and Western blot. In addition, IL-1 beta and IL-1ra expression was detected in the neointima of endothelia-denuded cholesterol-fed New Zealand white rabbits by immunohistochemistry and Western blot. In HASMCs, oxLDL induced IL-beta and IL-1ra expression and release in a dose- and time-dependent manner. Treatment with 20 microg/ml oxLDL resulted in increased IL-1 beta release after 6 h, which peaked at 24 h, and in increased IL-1ra release, first seen after 12 h, but continuing to increase for at least 48 h. In the cells, IL-beta expression showed a similar pattern to release, whereas IL-1ra expression was seen in unstimulated cells and was not increased by oxLDL treatment. Confocal microscopy showed colocalization of IL-beta and IL-1ra expression in oxLDL-stimulated HASMCs. oxLDL caused significant induction of nuclear factor kappa B and activator protein-1 DNA binding activity in HASMCs (6.6- and 3.3-fold, respectively). In cholesterol-fed endothelia-denuded rabbits, the notably thickened intima showed significant IL-1 beta and IL-1ra expression. These results provide further support for the role of IL-1 system in the pathogenesis of restenosis. This is the first demonstration of IL-1 beta and IL-1ra expression and secretion of oxLDL-treated HASMCs and their expression in the rabbit neointima, suggesting that the smooth muscle cells of the intima are an important source of these factors.

Inflammatory response in the elderly

PURPOSE OF REVIEW

During ageing there may be the onset of a chronic inflammatory state. This review examines the underlying causes of this phenomenon and the role that genotype plays in its intensity.

RECENT FINDINGS

There are predisposing factors for the chronic inflammation that occurs during ageing. These include increased oxidative stress, a decrease in ovarian function, a decrease in stress-induced glucocorticoid sensitivity of pro-inflammatory cytokine production in men, and an increased incidence of asymptomatic bacteriuria. Obesity induces chronic inflammation. Inflammation is a key factor in the progressive loss of lean tissue and impaired immune function observed in ageing. Polymorphisms in the promoter regions of pro- and anti-inflammatory cytokine genes influence the level of cytokine production and the ageing process. Thus, a genotype for high pro-inflammatory cytokine production results in high cytokine production and may accelerate the rate of tissue loss. Conversely, polymorphisms in the genes for anti-inflammatory cytokines may result in a slowing of tissue loss. In the healthy aged male population, the former polymorphisms are under-represented and the latter over-represented, indicating a genetically determined survival advantage in maintaining inflammation at a low level. Nutrients with anti-inflammatory properties, such as vitamin E and n-3 polyunsaturated fatty acid, may reduce the level of chronic inflammation and thereby ameliorate tissue and functional loss during ageing. New evidence suggests that, for the latter nutrient, gene-nutrient interactions occur that alter the effectiveness of dietary therapy.

SUMMARY

Ageing is associated with increased levels of chronic inflammation. This plays a major role in the decline in immune function and lean body mass. Anti-inflammatory nutrient therapy may slow the rate of decline. The pro- and anti-inflammatory cytokine genotype is linked negatively and positively, respectively, with life-span, because of its influence on inflammation.

The European perspective on vitamin E: current knowledge and future research

Vitamin E is indispensible for reproduction in female rats. In humans, vitamin E deficiency primarily causes neurologic dysfunctions, but the underlying molecular mechanisms are unclear. Because of its antioxidative properties, vitamin E is believed to help prevent diseases associated with oxidative stress, such as cardiovascular disease, cancer, chronic inflammation, and neurologic disorders. However, recent clinical trials undertaken to prove this hypothesis failed to verify a consistent benefit. Given these findings, a group of European scientists met to analyze the most recent knowledge of vitamin E function and metabolism. An overview of their discussions is presented in this article, which includes considerations of the mechanisms of absorption, distribution, and metabolism of different forms of vitamin E, including the alpha-tocopherol transfer protein and alpha-tocopherol-associated proteins; the mechanism of tocopherol side-chain degradation and its putative interaction with drug metabolism; the usefulness of tocopherol metabolites as biomarkers; and the novel mechanisms of the antiatherosclerotic and anticarcinogenic properties of vitamin E, which involve modulation of cellular signaling, transcriptional regulation, and induction of apoptosis. Clinical trials were analyzed on the basis of the selection of subjects, the stage of disease, and the mode of intake, dosage, and chemical form of vitamin E. In addition, the scarce knowledge on the role of vitamin E in reproduction was summarized. In conclusion, the scientists agreed that the functions of vitamin E were underestimated if one considered only its antioxidative properties. Future research on this essential vitamin should focus on what makes it essential for humans, why the body apparently utilizes alpha-tocopherol preferentially, and what functions other forms of vitamin E have.

Relationship of glycation, antioxidant status and oxidative stress to vascular endothelial damage in diabetes

AIMS

To examine the inter-relationships of various microvascular pathogenic mechanisms in diabetic patients.

METHODS

Patients with diabetes (n = 18) and non-diabetic subjects (n = 18) were studied.

RESULTS

Blood markers of glycaemic control and glycation differed between the two groups (glucose 10.9 +/- 7.6 vs. 4.7 +/- 0.63 mmol/l, p < 0.01; HbA1c 7.0 +/- 1.3 vs. 4.5 +/- 0.3%, p < 0.001; glycated LDL 8.8 +/- 2.5 vs. 6.1 +/- 1.2%, p < 0.001) but plasma antioxidant status did not. LDL oxidation resistance, measured as lag time to maximum oxidation initiated by copper ions, was decreased in diabetes (58. +/- 14.3 vs. 76.3 +/- 21.5 min, p < 0.01). Both soluble intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), markers of endothelial dysfunction, were significantly higher in diabetes (ICAM 491 +/- 128 vs. 403 +/- 131 micro g/l, p < 0.05; VCAM 546 +/- 157 vs. 393 +/- 106 micro g/l, p < 0.01). Linear correlations were significant between HbA1c and lag time of LDL oxidation (r = -0.39, p < 0.05), ICAM (r = 0.40, p < 0.05) and VCAM (r = 0.38, p < 0.05). LDL oxidizability correlated with vitamin C (r = 0.51, p < 0.01) but not any adhesion molecule. In multivariate analysis, both ICAM and VCAM correlated with HbA1c only (r(2) = 0.16, F = 6.3, p < 0.01; r(2) = 0.14, F = 5.4, p < 0.01 respectively).

CONCLUSION

In diabetes, glycation, tissue oxidation and endothelial function are all abnormal and predisposing to microvascular complications but interrelationships are complex with glycation appearing most direct.

Non-antioxidant molecular functions of alpha-tocopherol (vitamin E)

alpha-Tocopherol (the major vitamin E component) regulates key cellular events by mechanisms unrelated with its antioxidant function. Inhibition of protein kinase C (PKC) activity and vascular smooth muscle cell growth by alpha-tocopherol was first described by our group. Later, alpha-tocopherol was shown to inhibit PKC in various cell types with consequent inhibition of aggregation in platelets, of nitric oxide production in endothelial cells and of superoxide production in neutrophils and macrophages. alpha-Tocopherol diminishes adhesion molecule, collagenase and scavenger receptor (SR-A and CD36) expression and increases connective tissue growth factor expression.

The Boyd Orr lecture. Nutrition interventions in aging and age-associated disease

Aging is a complex biological process, which usually is accompanied by changes in socio-economic status, which may have a great impact on the physical and nutritional status of the elderly. Decreased food intake and a sedentary lifestyle in the growing numbers of the elderly increase their risk for malnutrition, decline of bodily functions and developing chronic diseases. Oxidative stress is believed to be an important factor in aging and many age-associated degenerative diseases. Modulation of oxidative stress by energy restriction in animals has been shown to be one of the mechanisms for retarding the aging process. Dietary antioxidants are regarded as being important in modulating oxidative stress of aging and age-associated diseases. Supplementation of the elderly with vitamin E has been shown to enhance immune response, delay onset of Alzheimer's disease, and increase resistance to oxidative injury associated with exercise. Vitamin E, in comparison with other antioxidants, is also effective in reducing viral titres, but not the longevity of middle-aged mice. Our studies have indicated that polyphenols or vitamin E may assist in preventing cardiovascular disease, in part by decreasing expression by endothelial cells of proinflammatory cytokines, adhesion molecules, and monocyte adhesion. Most recently, we have found that some of these antioxidants may prevent tumour growth by inhibiting angiogenesis via suppression of interleukin 8 and modulation of the cell junction molecule, VE-cadherin. These findings provide further support for the consumption of fruit and vegetables, which contain several forms of phytochemicals with antioxidant activity, in order to reduce the risk of cardiovascular disease and cancer, the leading causes of morbidity and mortality among the elderly.

Regulation of chemokine expression in atherosclerosis

(1) Chemokines play a central role in the pathogenesis of atherosclerosis, contributing to leukocyte recruitment, angiogenesis and also proliferation and migration of smooth muscle cells into atherosclerotic plaques. (2) Leukocytes and endothelial cells are an important source of chemokines, and many of the risk factors associated with atherosclerosis increase chemokine expression. There is now a body of evidence to suggest that interactions between cells such as leukocytes and endothelial cells amplify chemokine release, and this may contribute to sustained chemokine generation in inflammatory conditions. (3) This article summarises, briefly, what is currently known about chemokines release. A number of important pharmacological strategies used in the treatment of atherosclerosis inhibit chemokine release and the extent to which this may contribute to their therapeutic effect will be discussed. Understanding the mechanisms controlling chemokine expression is essential for the design of specific therapeutic interventions in atherosclerosis.

The 80th anniversary of vitamin E: beyond its antioxidant properties

Molecules provided with an antioxidant function may have additional properties, the latter being sometimes of greater importance than the former. In the last ten years, alpha-tocopherol has revealed precise cellular functions, some of which are independent of its antioxidant/radical scavenging ability. At the posttranslational level, alpha-tocopherol inhibits protein kinase C and 5-lipoxygenase and activates protein phosphatase 2A and diacylglycerol kinase. Some genes (CD36, alpha-TTP, alpha-tropomyosin, and collagenase) are affected by alpha-tocopherol at the transcriptional level. alpha-Tocopherol also induces inhibition of cell proliferation, platelet aggregation and monocyte adhesion. These effects are unrelated to the antioxidant activity of vitamin E, but rather are believed to be a result of specific interactions of vitamin E with components of the cell, e. g. proteins, enzymes and membranes. This review focuses on novel non-antioxidant functions of alpha-tocopherol and discusses the possibility that many of the effects previously attributed to the antioxidant functions can also be explained by non-antioxidant mechanisms.

Matrix metalloproteinase-19 is expressed in myeloid cells in an adhesion-dependent manner and associates with the cell surface

We have previously reported the isolation of the human matrix metalloproteinase (MMP)-19 (also referred to as RASI) from a synovium of a patient suffering from rheumatoid arthritis and its expression at the cell surface of activated PBMC. In this study, we have analyzed the regulation and cell surface expression of human MMP-19 in several human cell lines and blood-derived cells. Among the cell lines analyzed, MMP-19 is largely expressed by lung fibroblasts as well as by myeloid cell lines THP-1 and HL-60. After fractionating PBMC into CD14- and CD14+ populations we found that only the latter one expresses MMP-19. Although the myeloid cell lines as well as CD14+ cells express MMP-19 without stimulation, its production can be up-regulated by phorbol esters (PMA) or by adhesion. The adhesion-dependent expression was down-regulated or even abrogated by blockade of adhesion or interfering with adhesion-controlling signaling using alpha-tocopherol. We have shown that MMP-19 associates with the cell surface of myeloid cells. This cell surface association was not affected by phospholipase C. However, acidic treatment of the THP-1-derived cell membranes abolished the immunoprecipitation of MMP-19 thereof. Moreover, a high salt treatment of THP-1 cells diminished the MMP-19 detection on the cell surface. This implicates a noncovalent attachment of MMP-19 to the cell surface. Because a truncated form of the MMP-19, in which the hemopexin-like domain was deleted (Delta(hp)MMP-19), does not associate with the surface, the hemopexin-like domain appears to be critical for the cell surface attachment of human MMP-19.

Tocotrienol is the most effective vitamin E for reducing endothelial expression of adhesion molecules and adhesion to monocytes

Alpha-tocopherol and its esterified derivatives have been shown to be effective in reducing monocytic-endothelial cell adhesion. However, the effect of alpha-tocotrienol (alpha-T3) has not been characterized. In the present study, using human umbilical vein endothelial cells (HUVEC) as the model system, we examined the relative inhibitory effects of alpha-T3 and other vitamin E derivatives on cell surface adhesion molecule expression under TNF-alpha stimulation. Using enzyme-linked immunosorbent assay, we demonstrated that alpha-T3 markedly inhibited the surface expression of vascular cell adhesion molecule-1 in TNF-alpha activated HUVEC in a dose- and time-dependent manner. The optimal inhibition was observed at 25 micromol/l alpha-T3 within 24 h (77+/-5%) without cytotoxicity. In addition, the surface expression of intercellular adhesion molecule-1 and E-selectin were also reduced by 40+/-7 and 42+/-5%, respectively. In order to further evaluate the effects of alpha-T3 on the vascular endothelium, we investigated the ability of monocytes to adhere to endothelial cells. Interestingly, a 63+/-3% decrease in monocytic cell adherence was observed. Compared to alpha-tocopherol and alpha-tocopheryl succinate, alpha-T3 displayed a more profound inhibitory effect on adhesion molecule expression and monocytic cell adherence. This inhibitory action by alpha-T3 on TNF-alpha-induced monocyte adhesion was shown to be NF-kappaB dependent and was interestingly reversed with co-incubation with farnesol and geranylgeraniol, suggesting a role for prenylated proteins in the regulation of adhesion molecule expression. In summary, the above results suggest that alpha-T3 is a potent and effective agent in the reduction of cellular adhesion molecule expression and monocytic cell adherence.

Vitamin E: protective role of a Janus molecule

Since the discovery of vitamin E in 1922, its deficiency has been associated with various disorders, particularly atherosclerosis, ischemic heart disease, and the development of different types of cancer. A neurological syndrome associated with vitamin E deficiency resembling Friedreich ataxia has also been described. Whereas epidemiological studies have indicated the role of vitamin E in preventing the progression of atherosclerosis and cancer, intervention trials have produced contradictory results, indicating strong protection in some cases and no significant effect in others. Although it is commonly believed that phenolic compounds like vitamin E exert only a protective role against free radical damage, antioxidant molecules can exert other biological functions. For instance, the antioxidant activity of 17-beta-estradiol is not related to its role in determining secondary sexual characters, and the antioxidant capacity of all-trans-retinal is distinguished from its role in rhodopsin and vision. Thus, it is not unusual that alpha-tocopherol (the most active form of vitamin E) has properties independent of its antioxidant/radical scavenging ability. The Roman god Janus, shown in ancient coins as having two faces in one body, inspired the designation of 'Janus molecules' for these substances. The new biochemical face of vitamin E was first described in 1991, with an inhibitory effect on cell proliferation and protein kinase C activity. After a decade, this nonantioxidant role of vitamin E is well established, as confirmed by authoritative studies of signal transduction and gene regulation. More recently, a tocopherol binding protein with possible receptor function has been discovered. Despite such important developments in understanding the molecular mechanism and the targets of vitamin E, its new Janus face is not fully elucidated. Greater knowledge of the molecular events related to vitamin E will help in selecting the parameters for clinical intervention studies such as population type, dose response effects, and possible synergism with other compounds.

Alpha-tocopherol (vitamin E) and beta-carotene supplementation does not affect the risk for large abdominal aortic aneurysm in a controlled trial

Antioxidants may retard atherogenesis and limit inflammatory processes involved in aneurysm formation. We evaluated effects of alpha-tocopherol and beta-carotene supplementation on incidence of large abdominal aortic aneurysm (AAA) in a randomised, double-blind, placebo-controlled trial. Subjects (n=29133) were 50-69-years-old male smokers, participants in the Finnish alpha-Tocopherol, beta-Carotene Cancer Prevention (ATBC) Study. They were randomised to receive either 50 mg/day of alpha-tocopherol, or 20 mg/day of beta-carotene, or both, or placebo in a 2x2 design. Incidence of AAA was evaluated from mortality and hospital registers. During 5.8 years of follow-up, 181 men were diagnosed with either ruptured AAA (n=77) or nonruptured large AAA treated with aneurysmectomy (n=104). Relative risk (RR) for AAA was 0.83 (95% confidence interval [CI] 0.62-1.11) among men receiving alpha-tocopherol compared with those who did not, and 0.93 (95% CI 0.69-1.24) among men receiving beta-carotene compared with those who did not. A modest though nonsignificant decrease in risk for nonruptured AAA was observed among alpha-tocopherol supplemented men (RR 0.71, 95% CI 0.48-1.04) compared with men not receiving alpha-tocopherol. For beta-carotene, RR for nonruptured AAA was 0.86 (95% CI 0.59-1.27) compared with men not receiving beta-carotene. Neither antioxidant affected risk for ruptured AAA. In conclusion, long-term supplementation with alpha-tocopherol or beta-carotene had no preventive effect on large AAA among male smokers.

Effects of alpha-tocopherol on superoxide production and plasma intercellular adhesion molecule-1 and antibodies to oxidized LDL in chronic smokers

Antioxidants have been postulated to exert beneficial effects in atherosclerosis. Atherosclerosis is associated with raised plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1) and autoantibodies against oxidized low-density lipoprotein (oxLDL). It is not known whether antioxidants affect these plasma factors in chronic smokers. In a randomized double-blind placebo-controlled study involving 128 male normolipidemic chronic smokers the effect of a 2-year alpha-tocopherol treatment (400 IU dL-alpha-tocopherol daily) on plasma levels of sICAM-1 and autoantibodies against oxLDL was evaluated. In addition, we monitored production of superoxide by leukocytes ex vivo. It was found that compared to nonsmokers (n = 33) plasma levels of IgG but not IgM autoantibodies against oxLDL and concentrations of sICAM-1 in smokers were significantly elevated (30 and 42%, respectively). After supplementation with alpha-tocopherol concentration of TBARS in plasma and in vitro oxidizability of LDL had decreased, but autoantibodies and sICAM-1 had not changed. Production of superoxide was not different between alpha-tocopherol- and placebo-treated smokers. It is concluded that in chronic smokers, long-term treatment with alpha-tocopherol does not normalize the raised levels of sICAM-1 and autoantibodies against oxLDL, both risk factors for initiation or progression of cardiovascular disease, despite a decrease in in vitro oxidizability of LDL.

Nutrition interventions in aging and age-associated disease

The nutritional status and needs of elderly people are associated with age-related biological and often socioeconomic changes. Decreased food intake, a sedentary lifestyle, and reduced energy expenditure in older adults altogether become critical risk factors for malnutrition, especially protein and micronutrients. Surveys indicate that the elderly are particularly at risk for marginal deficiency of vitamins and trace elements. Changes in bodily functions, together with the malnutrition associated with advancing age, increase the risk of developing a number of age-related diseases. Chronic conditions pose difficulties for the elderly in carrying out the activities of daily living and may increase the requirements for certain nutrients due to changes in absorptive and metabolic capacity. Free radicals and oxidative stress have been recognized as important factors in the biology of aging and of many age-associated degenerative diseases. In this regard, modulation of oxidative stress by calorie restriction, as demonstrated in animal models, is suggested as one mechanism to slow the aging process and the decline of body functions. Therefore, dietary components with antioxidant activity have received particular attention because of their potential role in modulating oxidative stress associated with aging and chronic conditions. Several studies have indicated potential roles for dietary antioxidants in the reduction of degenerative disease such as vascular dementia, cardiovascular disease, and cancer. In support of epidemiological studies, our recent studies indicate that the antioxidant properties of vitamin E and polyphenols present in green tea may contribute to reducing the risk of cardiovascular disease, in part by reducing the susceptibility of low density lipoproteins to oxidation, decreasing the vascular endothelial cell expression of pro-inflammatory cytokines, and decreasing the expression of adhesion molecules and monocyte adhesion. Recently, we also demonstrated that these dietary antioxidants may have a preventive role in cancer, potentially through the suppression of angiogenesis by inhibiting interleukin-8 production and the cell junction molecule VE-cadherin. These findings concur with epidemiologic, clinical, and animal studies suggesting that the consumption of green tea and vitamin E is associated with a reduced risk of cardiovascular disease and cancer, the leading causes of morbidity and mortality among the elderly.

Dietary modulation of endothelial function: implications for cardiovascular disease

The vascular endothelium is the primary site of dysfunction in many diseases, particularly cardiovascular disease. A variety of risk factors, including smoking, hypercholesterolemia, hyperhomocysteinemia, hypertension, and diabetes mellitus, adversely affect endothelial function. Emerging evidence suggests an important role of dietary factors in modulating endothelial function. In particular, n-3 fatty acids, antioxidant vitamins (especially vitamins E and C), folic acid, and L-arginine appear to have beneficial effects on vascular endothelial function, either by decreasing endothelial activation or by improving endothelium-dependent vasodilation in patients at high risk of cardiovascular disease as well as in healthy subjects. These effects may serve as one potential mechanism through which these nutrients reduce the risk of cardiovascular disease, as observed in epidemiologic studies and several clinical trials. This article reviews clinical and experimental evidence regarding the role of these nutrients in modulating endothelial function and their potential to prevent cardiovascular disease.

High-Energy Diets, Fatty Acids and Endothelial Cell Function: Implications for Atherosclerosis

Diets high in fat and/or calories can lead to hypertriglyceridemia and postprandial lipemia and thus are considered a risk factor for the development of atherosclerosis. Plasma chylomicron levels are elevated in humans after consuming a high-fat meal, and hepatic synthesis of VLDL is increased when caloric intake is in excess of body needs. High lipoprotein lipase activity and subsequent hydrolysis of triglyceride-rich lipoproteins may be an important source of elevated concentrations of fatty acid anions in the proximity to the endothelium and hence a major risk factor for atherosclerosis. We have shown that selected fatty acids, as well as lipoprotein lipase-derived remnants of lipoproteins isolated from hypertriglyceridemic subjects, can activate vascular endothelial cells and disrupt endothelial integrity. Our studies suggest that omega-6 fatty acids, and especially linoleic acid, cause endothelial cell dysfunction most markedly as well as can potentiate TNF-mediated endothelial cell injury. We propose that high-energy diets, and especially diets rich in linoleic acid, are atherogenic by contributing to an imbalance in cellular oxidative stress/antioxidant status of the endothelium, which can lead to activation of oxidative stress-responsive transcription factors, inflammatory cytokine production and the expression of adhesion molecules. Our data also suggest that nutrients, which have antioxidant and/or membrane stabilizing properties, can protect endothelial cells. These findings contribute to the understanding of the interactive role of high fat/calorie diets and subsequent hypertriglyceridemia with inflammatory components and nutrients that exhibit antiatherogenic properties in the development of atherosclerosis. Moreover, results from our research further support the concept that high-fat/calorie diets and associated postprandial hypertriglyceridemia are significant risk factors for atherosclerosis.

Nonantioxidant functions of alpha-tocopherol in smooth muscle cells

Most tocopherols and tocotrienols, with the exception of alpha-tocopherol, are not retained by humans. This suggests that alpha-tocopherol is recognized uniquely; therefore, it may exert an exclusive function. alpha-Tocopherol possesses distinct properties that are independent of its prooxidant, antioxidant or radical-scavenging ability. alpha-Tocopherol specifically inhibits protein kinase C, the growth of certain cells and the transcription of the CD36 and collagenase genes. Activation events have also been seen on the protein phosphatase 2A (PP(2)A) and on the expression of other genes (alpha-tropomyosin and connective tissue growth factor). Neither ss-tocopherol nor probucol possessed the same specialty functions as alpha-tocopherol. Recently, we isolated a new ubiquitous cytosolic alpha-tocopherol binding protein (TAP). Its motifs suggest that it is a member of the hydrophobic ligand-binding protein family (CRAL-TRIO). TAP may also be involved in the regulation of cellular alpha-tocopherol concentration and alpha-tocopherol-mediated signaling.

Vitamin E and atherosclerosis: beyond prevention of LDL oxidation

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Observational and experimental studies indicate that dietary vitamin E supplementation is associated with reduced risk of atherosclerosis. Evidence indicates that vitamin E, in addition to inhibition of oxidative modification of LDL, may inhibit atherogenesis through several other mechanisms at the molecular and cellular levels, which also include its nonantioxidant functions.

Is there a potential therapeutic role for vitamin E or other antioxidants in atherosclerosis?

In-vitro studies and animal model studies provide an ever-growing body of evidence, direct and indirect, that oxidation of low-density lipoprotein and/or related oxidative mechanisms play a role in atherogenesis. However, two recent, very large, carefully conducted clinical intervention trials using adequate doses of vitamin E demonstrated no effect on a composite end-point of non-fatal infarction, stroke or death from cardiovascular causes. Why the unexpected negative results? Possibly because the animal intervention evidence on which these trials were based deals primarily with very early lesions (fatty streaks). That evidence does not necessarily provide a basis for predicting what antioxidant intervention will do in patients with advanced lesions, particularly when the end-points used relate to unstable plaques and fatal thrombosis, events for which we have no adequate animal models. Nor does it necessarily follow that the same antioxidants used successfully in animals will be effective in humans. The strength of the evidence for the oxidative modification hypothesis is such that negative clinical trials with one particular antioxidant, in patients with very advanced coronary heart disease and lasting only 3-5 years, should not be taken as refutation of the hypothesis. Perhaps different kinds of human trials are needed, trials in which the development of new lesions is measured, in order to test whether antioxidants can decrease the rate of initiation and early progression of atherosclerosis as they do in animals. The answer to the title query is 'Probably, but it is too soon to say'.

Vitamin E and prevention of heart disease in high-risk patients

Several observational studies have suggested that high intake of vitamin E may slow the development and progression of atherosclerosis. Some clinical trials also reported beneficial effects of vitamin E supplementation in the secondary prevention of cardiovascular events. However, results of recent large, multicenter clinical trials reported that vitamin E supplementation was not effective in reducing the incidence of cardiovascular events in high-risk patients.

A novel human tocopherol-associated protein: cloning, in vitro expression, and characterization

Vitamin E (alpha-tocopherol) is an essential dietary nutrient for humans and animals. The mechanisms involved in cellular regulation as well as in the preferential cellular and tissue accumulation of alpha-tocopherol are not yet well established. We previously reported (Stocker, A., Zimmer, S., Spycher, S. E., and Azzi, A. (1999) IUBMB Life 48, 49-55) the identification of a novel 46-kDa tocopherol-associated protein (TAP) in the cytosol of bovine liver. Here, we describe the identification, the molecular cloning into Escherichia coli, and the in vitro expression of the human homologue of bovine TAP, hTAP. This protein appears to belong to a family of hydrophobic ligand binding proteins, which have the CRAL (cis-retinal binding motif) sequence in common. By using a biotinylated alpha-tocopherol derivative and the IASys resonant mirror biosensor, the purified recombinant protein was shown to bind tocopherol at a specific binding site with K(d) 4.6 x 10(-7) m. Northern analyses showed that hTAP mRNA has a size of approximately 2800 base pairs and is ubiquitously expressed. The highest amounts of hTAP message are found in liver, brain, and prostate. In conclusion, hTAP has sequence homology to proteins containing the CRAL_TRIO structural motif. TAP binds to alpha-tocopherol and biotinylated tocopherol, suggesting the existence of a hydrophobic pocket, possibly analogous to that of SEC14.

Selective inhibition by alpha-tocopherol of vascular cell adhesion molecule-1 expression in human vascular endothelial cells

An early event in atherogenesis is the adhesion of monocytes to endothelium via adhesion molecules such as VCAM-1 and intracellular adhesion molecule-1 (ICAM-1). It has been suggested that VCAM-1 plays a very important role in recruitment of monocytes in atherosclerosis. Several studies suggest that vitamin E has antiatherosclerotic properties. However, the mechanism of its antiatherogenic effect awaits elucidation. The aim of our study was to evaluate whether alpha-tocopherol can influence expression of endothelial cell adhesion molecules and endothelial adhesiveness. The study was performed on cultured human umbilical vein endothelial cells (HUVEC). HUVEC were pretreated with alpha-tocopherol (50 micromol/l) in different times before stimulation with TNFalpha (100 U/ml) or IL-1beta (100 U/ml). Protein expression of VCAM-1 and ICAM-1 was measured by flow cytometry. mRNA expression of VCAM-1 was measured by reverse transcription polymerase chain reaction (RT-PCR). alpha-Tocopherol time dependently reduced agonist-induced VCAM-1 in both surface protein (about 40%, 48 h) and mRNA (about 35%, 48 h) expression in HUVEC but not ICAM-1 surface protein expression. Inhibitory effect of alpha-tocopherol was dependent on culture condition of HUVEC. Decreased VCAM-1 expression was associated with reduction (about 40%) of adherence between cytokine-stimulated HUVEC and peripheral blood mononuclear leukocytes (PBMC). Our results suggest that the antiatherogenic effect of alpha-tocopherol may in part be due to a downregulation of VCAM-1 expression.