Molecular mechanism of alpha-tocopherol action

Ascorbate and α-tocopherol differentially modulate reactive oxygen species generation by neutrophils in response to FcγR and TLR agonists

Periodontitis, a ubiquitous chronic inflammatory disease, is associated with reduced antioxidant defences and neutrophil hyperactivity in terms of reactive oxygen species (ROS) generation. Its phenotype is thus characterized by oxidative stress. We have determined the effect of antioxidant micronutrients ascorbate and α-tocopherol on neutrophil ROS generation. Peripheral neutrophils from periodontally-healthy individuals ( n = 20) were challenged with phorbol myristate acetate, IgG-opsonised Staphylococcus aureus, Fusobacterium nucleatum or PBS in the presence and absence of micronutrients (50 µM). Total and extracellular ROS were measured by luminol and isoluminol chemiluminescence respectively. Total and extracellular unstimulated, baseline ROS generation was unaffected by α-tocopherol, but inhibited by ascorbate and a combination of both micronutrients. Fcγ-receptor (Fcγ-R)-stimulated total or extracellular ROS generation was not affected by the presence of individual micronutrients. However, the combination significantly reduced extracellular FcγR-stimulated ROS release. Neither micronutrient inhibited TLR-stimulated total ROS, but the combination caused inhibition. Ascorbate and the micronutrient combination, but not α-tocopherol, inhibited extracellular ROS release by TLR-stimulated cells. Such micronutrient effects in vivo could be beneficial in reducing collateral tissue damage in chronic inflammatory diseases, such as periodontitis, while retaining immune-mediated neutrophil function.

Vitamin E-derived copolymers continue the challenge to hemodialysis biomaterials

Improving material biocompatibility has been a continuous effort and remains a major goal of dialysis therapy. In this respect, vitamin E-modified copolymers have been used to produce a generation of biomaterials that has offered new clinical challenges and the chance of further improving the quality of synthetic hemodialyser membranes. This mini review article describes the evolution of these copolymers that only recently have been adopted to develop new vitamin E-modified polysulfone hemodialysers. Biomaterial characteristics and clinical aspects of these membranes are discussed, starting from the most recent contributions that have appeared in the literature that are of interest for the community of nephrology and dialysis specialists, as well as biomaterial scientists.

Serum Levels of Vitamin E Are Associated With Early Recurrence of Atrial Fibrillation After Electric Cardioversion

Background—

Oxidative stress is suggested to play a role in favoring the occurrence of atrial fibrillation (AF). We analyzed whether vitamin E, a known antioxidant, or markers of oxidative stress are associated with AF recurrence in patients undergoing electric cardioversion.

Methods and Results—

A total of 144 patients (83 men; mean age, 71.1±5.4 years) underwent successful biphasic electric cardioversion of nonvalvular persistent AF. At baseline, urinary 8-isoprostaglandin F2α and serum soluble NOX2-derived peptide (sNOX2-dp), high-sensitivity C-reactive protein (hs-CRP), and vitamin E levels were measured in each patient. All patients underwent 3 months of clinical follow-up, including an office visit with ECG every week or in cases of symptom recurrence. During the follow-up, 94 patients maintained sinus rhythm, whereas 50 experienced AF recurrence. In unadjusted analysis, left atrial diameter and levels of urinary isoprostanes and serum sNOX2-dp and hs-CRP were significantly higher and serum vitamin E lower in patients with AF recurrence. In multivariable Cox analysis, serum vitamin E (hazard ratio, 0.734; 95% CI, 0.605–0.891; P <0.001) and, to a lesser extent, hs-CRP ( P =0.047) remained significantly associated with AF recurrence. Urinary isoprostanes and serum sNOX2-dp levels were inversely correlated with serum vitamin E level ( r =−0.626, P <0.001, and r =−0.460, P <0.001, respectively).

Conclusions—

The study shows that low serum vitamin E levels are associated with AF recurrence in patients who underwent cardioversion. Because vitamin E inversely correlated with oxidative stress, the findings reinforce the hypothesis of an interplay between oxidative stress and AF.

α-Tocopheryl phosphate--an activated form of vitamin E important for angiogenesis and vasculogenesis?

Vitamin E was originally discovered as a dietary factor essential for reproduction in rats. Since then, vitamin E has revealed many important molecular properties such as the scavenging of reactive oxygen and nitrogen species or the modulation of signal transduction and gene expression in antioxidant and nonantioxidant manners. A congenital disease, ataxia with vitamin E deficiency, which is characterized by impaired enrichment of α-tocopherol (αT) in plasma due to mutations in the α-tocopherol transfer protein gene, has been discovered. An effect of vitamin E on angiogenesis and vasculogenesis has been observed in several studies, and recently, it has been demonstrated in the placenta of pregnant ewes, possibly involving the stimulation of vascular endothelial growth factor (VEGF) expression. We recently observed that the phosphorylated form of αT, α-tocopheryl phosphate (αTP), increases the expression of VEGF. We propose that the stimulatory effect of αT on angiogenesis and vasculogenesis is potentiated by phosphorylation to αTP, which may act as a cofactor or active lipid mediator increasing VEGF expression. Increased VEGF expression and consequent enhanced angiogenesis and vasculogenesis induced by αTP may explain not only the essential roles of vitamin E on reproduction, but also its beneficial effects against pre-eclampsia, ischemia/reperfusion injury, and during wound healing. It may also serve as a survival factor for brain and muscle cells. The finding that αTP may regulate vasculogenesis may indicate potential, important pathophysiological implications.

Additive antinociceptive effects of a combination of vitamin C and vitamin E after peripheral nerve injury

Accumulating evidence indicates that increased generation of reactive oxygen species (ROS) contributes to the development of exaggerated pain hypersensitivity during persistent pain. In the present study, we investigated the antinociceptive efficacy of the antioxidants vitamin C and vitamin E in mouse models of inflammatory and neuropathic pain. We show that systemic administration of a combination of vitamins C and E inhibited the early behavioral responses to formalin injection and the neuropathic pain behavior after peripheral nerve injury, but not the inflammatory pain behavior induced by Complete Freund's Adjuvant. In contrast, vitamin C or vitamin E given alone failed to affect the nociceptive behavior in all tested models. The attenuated neuropathic pain behavior induced by the vitamin C and E combination was paralleled by a reduced p38 phosphorylation in the spinal cord and in dorsal root ganglia, and was also observed after intrathecal injection of the vitamins. Moreover, the vitamin C and E combination ameliorated the allodynia induced by an intrathecally delivered ROS donor. Our results suggest that administration of vitamins C and E in combination may exert synergistic antinociceptive effects, and further indicate that ROS essentially contribute to nociceptive processing in special pain states.

Vitamin E, signalosomes and gene expression in T cells

CD4+T cells from aged humans or mice show significant reductions in IL-2 production upon activation. The resulting decreased proliferation is linked to higher risks of infection in the elderly. Several lines of evidence indicate that intrinsic defects preferentially affecting the naïve subset of CD4+T cells contribute to this reduced IL-2 production. Comparison of the biochemical pathways that transduce activation signals from the T cell receptor to the IL-2 promoter in young and old CD4+T cells has demonstrated age-related impairments at initial molecular events, in particular the phosphorylation of kinases and adapter proteins involved in the formation of signalosomes - complex multiprotein assemblies that provide the framework for effective signal transduction. Confocal microscopy has demonstrated a series of age-related impairments in effective immune synapse formation. Vitamin E can reverse many of these CD4+T cell age-associated defects, including reduced levels of phosphorylation of critical signaling/adapter proteins as well as defective immune synapse formation. Vitamin E also enhances IL-2 production, expression of several cell cycle control proteins, and proliferation. Although the precise mechanisms underlying this effect are not understood, it is possible that this antioxidant lipophilic vitamin can prevent the propagation of polyunsaturated fatty acid peroxidation in the cell membrane, influence the biochemical characteristics of specific lipid bilayer microdomains involved in signal transduction, modulate the activity of kinases/phosphatases, or interact with intracellular receptors.

Alpha-tocopherol prevents intrauterine undernutrition-induced oligonephronia in rats

The role of α-tocopherol during nephrogenesis was investigated in rats subjected to maternal undernutrition, which reduces the number of nephrons. α-tocopherol (350 mg/kg, p.o.) was administered daily to well-nourished or malnourished Wistar dams during pregnancy, or to prenatal undernourished rats during lactation. The kidneys of 1- and 25-day-old offspring were removed to evaluate expression of angiotensin II (Ang II) and to correlate this with expression of proliferating cell nuclear antigen, α-smooth muscle actin, fibronectin and vimentin in the glomeruli and tubulointerstitial space. One-day-old prenatally undernourished rats had reduced expression of Ang II and of kidney development markers, and presented with an enlarged nephrogenic zone. Maternal administration of α-tocopherol restored the features of normal kidney development in undernourished rats. Twenty-five-day-old prenatally undernourished progeny had fewer glomeruli than the control group. Conversely, animals from mothers that received α-tocopherol during lactation presented with the same number of glomeruli and the same glomerular morphometrical profile as the control group. Analyzing the levels of thiobarbituric acid reactive substances in the liver in conjunction with kidney development markers, it is plausible that α-tocopherol had antioxidant and non-antioxidant actions. This study provides evidence that α-tocopherol treatment restored Ang II expression, and subsequently restored renal structural development.

α-tocopherol and α-tocopheryl phosphate interact with the cannabinoid system in the rodent hippocampus

α-Tocopherol (α-TOH), a dietary component of vitamin E, is well known for its antioxidant capacity. Nevertheless, recent studies have pointed out non-anti-radical properties including cellular and genomic actions. Decreased levels of α-tocopherol in the brain are associated with neuronal dysfunctions ranging from mood disorders to neurodegeneration. All these behavioral effects of α-tocopherol deficiency probably do not rely simply on its anti-radical properties, but could also be reminiscent of a not-yet characterized neuromodulatory action. We have thus measured the direct actions of α-tocopherol and of its natural phosphate derivative, α-tocopheryl phosphate (α-TP), on synaptic transmission in rodent hippocampus. These compounds had opposite actions on both glutamatergic and GABAergic transmission: whereas α-TOH potentiated these transmissions, α-TP inhibited them. Interestingly, these effects were both mediated by cannabinoid receptors (CB1Rs), because they were blocked by the CB1R antagonist AM251. Although α-tocopherol and α-tocopheryl phosphate did not directly bind CB1R, both α-TP and CB1R agonists inhibited forskolin-evoked Erk1/2 phosphorylation in a nonadditive manner. Furthermore, both α-tocopherol and α-tocopheryl phosphate attenuated depolarization-induced suppression of excitation and CB1R agonist-mediated hypothermia. Therefore, we identify α-tocopherol as new lipid modulator of the cannabinoid system in the rodent hippocampus, i.e., a novel "non-anti-radical" action of vitamin E, which may have some preeminent impact in neuronal disorders associated with vitamin E deficiency.

Nutrition-based health: cell-based bioassays for food antioxidant activity evaluation

Food science has progressively evolved and now there are wide evidences that foods have biological activities that are beyond their classical nutritional value. In this field, the antioxidant activity of pure compounds, food, feed, and dietary supplements has been extensively studied and numerous analytical approaches and assay models have been developed, involving various systems from simple chemical assays to animal models and human studies. This article is an overview of different cell-based models that have been used for testing the antioxidant properties of food, feed, and dietary supplements. Advantages, drawbacks, and technical problems to develop and validate suitable, robust, and high-throughput cell-based bioassays for screening food antioxidant activity will be discussed.

Light and moderate doses of ethanol in chemical carcinogenesis of the colon in rats

The aberrant crypt foci (ACF), cyclooxygenase 2 (COX-2), and the proliferating cell nuclear antigen (PCNA) are putative biomarkers for colon cancer. To study the association between light (1 g of ethanol/kg bw) and moderate (3 g of ethanol/kg bw) doses of ethanol with the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), Wistar rats were divided into 6 groups. The colon fragments were collected for histochemical and immunohistochemical analyses, and the liver samples were collected for oxidative stress analysis, with products of lipid peroxidation (malondialdehyde), antioxidant enzymes (glutathione), and vitamin E. The association of light and moderate doses of ethanol with MNNG did not present differences in the oxidative parameters. However, a reduction in vitamin E levels in the carcinogen groups was observed. The association induced a reduction of the COX-2 and PCNA expression. The number of ACF in the group that received a light dose of ethanol had lower rates, while the group that received a moderate dose had the highest rates compared to the control MNNG, demonstrating that the light dose of ethanol could have a protective effect, while the moderate dose could represent a risk during chemical carcinogenesis in rats.

Accumulation of γ- rather than α-tocopherol alters ethylene signaling gene expression in the vte4 mutant of Arabidopsis thaliana

Tocopherols are antioxidants found in chloroplasts of leaves, and it is a matter of current debate whether or not they can affect signaling and gene expression in plant cells. For insight into the possible effects of altered tocopherol composition in chloroplasts on gene expression in the nucleus, the expression of ethylene biosynthesis, perception and signaling genes was investigated in vte1 and vte4 Arabidopsis thaliana mutants, which are impaired in tocopherol (vitamin E) biosynthesis. Changes in gene expression were measured in plants exposed to either salt or water stress, and in young and mature leaves of vte1 and vte4 mutants, which lack tocopherol cyclase and γ-tocopherol methyltransferase, respectively. While transcript levels of ethylene signaling genes in the vte1 mutant and the wild type were similar in all tested conditions, major changes in gene expression occurred in the vte4 mutant, particularly in mature leaves (compared with young leaves) and under salt stress. Accumulation of γ- instead of α-tocopherol in this mutant led to elevated transcript levels of ethylene signaling pathway genes (particularly CTR1, EIN2, EIN3 and ERF1) in mature leaves of control plants. However, with salt treatment, transcript levels of most of these genes remained constant or dropped in the vte4 mutant, while they were dramatically induced in the wild type and the vte1 mutant. Furthermore, under salt stress, leaf age-induced jasmonic acid accumulated in both the vte1 mutant and the wild type, but not in the vte4 mutant. It is concluded that jasmonic acid and ethylene signaling pathways are down-regulated in mature leaves of salt-stressed vte4 plants.

An (1)O2 route to γ-hydroxyalkenal phospholipids by vitamin E-induced fragmentation of hydroperoxydiene-derived endoperoxides

Biologically active phospholipids that incorporate an oxidatively truncated acyl chain terminated by a γ-hydroxyalkenal are generated in vivo. The γ-hydroxyalkenal moiety protrudes from lipid bilayers like whiskers that serve as ligands for the scavenger receptor CD36, fostering endocytosis, e.g., of oxidatively damaged photoreceptor cell outer segments by retinal pigmented endothelial cells. They also covalently modify proteins generating carboxyalkyl pyrroles incorporating the ε-amino group of protein lysyl residues. We postulated that γ-hydroxyalkenals could be generated, e.g., in the eye, through fragmentation of hydroperoxy endoperoxides produced in the retina through reactions of singlet molecular oxygen with polyunsaturated phospholipids. Since phospholipid esters are far more abundant in the retina than free fatty acids, we examined the influence of a membrane environment on the fate of hydroperoxy endoperoxides. We now report that linoleate hydroperoxy endoperoxides in thin films and their phospholipid esters in biomimetic membranes fragment to γ-hydroxyalkenals, and fragmentation is stoichiometrically induced by vitamin E. The product distribution from fragmentation of the free acid in the homogeneous environment of a thin film is remarkably different from that from the corresponding phospholipid in a membrane. In the membrane, further oxidation of the initially formed γ-hydroxyalkenal to a butenolide is disfavored. A conformational preference for the γ-hydroxyalkenal, to protrude from the membrane into the aqueous phase, may protect it from oxidation induced by lipid hydroperoxides that remain buried in the lipophilic membrane core.

No effect of antioxidant supplementation on muscle performance and blood redox status adaptations to eccentric training

BACKGROUND

It was recently reported that antioxidant supplementation decreases training efficiency and prevents cellular adaptations to chronic exercise.

OBJECTIVE

This study aimed to investigate the effects of vitamin C and vitamin E supplementation on muscle performance, blood and muscle redox status biomarkers, and hemolysis in trained and untrained men after acute and chronic exercise. A specific type of exercise was applied (eccentric) to produce long-lasting and extensive changes in redox status biomarkers and to examine more easily the potential effects of antioxidant supplementation.

DESIGN

In a double-blinded fashion, men received either a daily oral supplement of vitamin C and vitamin E (n = 14) or placebo (n = 14) for 11 wk (started 4 wk before the pretraining exercise testing and continued until the posttraining exercise testing). After baseline testing, the subjects performed an eccentric exercise session 2 times/wk for 4 wk. Before and after the chronic eccentric exercise, the subjects underwent one session of acute eccentric exercise, physiologic measurements were performed, and blood samples and muscle biopsy samples (from 4 men) were collected.

RESULTS

The results failed to support any effect of antioxidant supplementation. Eccentric exercise similarly modified muscle damage and performance, blood redox status biomarkers, and hemolysis in both the supplemented and nonsupplemented groups. This occurred despite the fact that eccentric exercise induced marked changes in muscle damage and performance and in redox status after exercise.

CONCLUSION

The complete lack of any effect on the physiologic and biochemical outcome measures used raises questions about the validity of using oral antioxidant supplementation as a redox modulator of muscle and redox status in healthy humans.

A comparative transcriptomic study of vitamin E and an algae-based antioxidant as antioxidative agents: investigation of replacing vitamin E with the algae-based antioxidant in broiler diets

Previous study indicated that inclusion of an algae-based antioxidant as an antioxidative agent [EconomasE, Alltech, Nicholasville, KY; EcoE] significantly reduced the amount of vitamin E (VE) required in broiler diets without compromising performance and meat quality. To assess the mechanisms related to the VE-saving activity of EcoE, as well as other potential functions related to EcoE and VE supplementation, we analyzed gene expression profiles of breast muscle from broilers fed a control diet, the control diet + 50 IU of VE/kg, the control diet + 100 IU of VE/kg, or the control diet + 200 g of EcoE/ton. Evaluation of the serum antioxidant capacity indicated that dietary supplementation of either a high level of VE (50 or 100 IU of VE/kg) or EcoE significantly improved bird antioxidant status. Analysis of gene expression profiles indicated that expression of 542 genes of the breast muscle were altered (P < 0.05, fold change >1.2) by dietary treatments, of which a significant part were commonly regulated by EcoE and VE (especially the control diet + 50 IU of VE/kg). In addition to the process of cellular oxidation, gene ontology analysis indicated the involvement of EcoE and VE on cell morphology, skeletal and muscular system development and function, immune response, and multiple metabolic processes, including lipid, carbohydrate, and drug metabolism. Results of this experiment indicate that the biological roles of high VE, including its activity as an antioxidant, can be greatly mimicked at the transcriptional level by EcoE, and they suggest a relationship of functional redundancy between VE and EcoE in the broiler diets.

A nutrient approach to prostate cancer prevention: The Selenium and Vitamin E Cancer Prevention Trial (SELECT)

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) randomized 35,533 healthy men, >55 yr old (>50 yr if African American), with normal digital rectal exams and prostate specific antigens <4 ng/ml to 1) 200 μg/day l-selenomethionine, 2) 400 IU/day all-rac-alpha-tocopheryl acetate (vitamin E), 3) both supplements, or 4) placebo for 7 to 12 yr. The hypotheses underlying SELECT, that selenium and vitamin E individually and together decrease prostate cancer incidence, derived from epidemiologic and laboratory evidence and significant secondary endpoints in the Nutritional Prevention of Cancer (selenium) and Alpha-Tocopherol Beta-Carotene (vitamin E) trials. In SELECT, prostate cancer incidence did not differ among the 4 arms: hazard ratios [99% confidence intervals (CIs)] for prostate cancer were 1.13 (99% CI = 0.95-1.35, P = 0.06; n = 473) for vitamin E, 1.04 (99% CI = 0.87-1.24, P = 0.62; n = 432) for selenium, and 1.05 (99% CI = 0.88-1.25, P = 0.52; n = 437) for selenium + vitamin E vs. 1.00 (n = 416) for placebo. Statistically nonsignificant increased risks of prostate cancer with vitamin E alone [relative risk (RR) = 1.13, P = 0.06) and newly diagnosed Type 2 diabetes mellitus with selenium alone (RR = 1.07, P = 0.16) were observed. SELECT data show that neither selenium nor vitamin E, alone or together, in the doses and formulations used, prevented prostate cancer in this heterogeneous population of healthy men.

Cytoprotective effects of vitamin E homologues against glutamate-induced cell death in immature primary cortical neuron cultures: Tocopherols and tocotrienols exert similar effects by antioxidant function

Glutamate plays a critical role in pathological cell death within the nervous system. Vitamin E is known to protect cells from glutamate cytotoxicity, either by direct antioxidant action or by indirect nonantioxidant action. Further, α-tocotrienol (α-T3) has been reported to be more effective against glutamate-induced cytotoxicity than α-tocopherol (α-T). To shed more light on the function of vitamin E against glutamate toxicity, the protective effects of eight vitamin E homologues and related compounds, 2,2,5,7,8-pentamethyl-6-chromanol (PMC) and 2-carboxy-2,5,7,8-pentamethyl-6-chromanol (Trolox), against glutamate-induced cytotoxicity on immature primary cortical neurons were examined using different protocols. Glutamate induced the depletion of glutathione and generation of reactive oxygen species and lipid hydroperoxides, leading to cell death. α-, β-, γ-, and δ-T and -T3; PMC; and Trolox all exerted cytoprotective effects against glutamate-induced cytotoxicity, and a longer preincubation time increased both the cellular content and the cytoprotective effects of T more significantly than those of T3, the effect of preincubation being relatively small for T3 and PMC. The protective effect of Trolox was less potent than that of PMC. The cytoprotective effects of α-T and α-T3 corresponded to their intracellular content. Further, lipid peroxidation products were measured after reduction with triphenylphosphine followed by saponification with potassium hydroxide. It was found that glutamate treatment increased the formation of hydroxyeicosatetraenoic acid, hydroxyoctadecadienoic acid, and 8-F(2)-isoprostane 2α, which was suppressed by α-T. This study shows that vitamin E protects cells from glutamate-induced toxicity primarily by direct antioxidant action and that the apparent higher capacity of T3 compared to T is ascribed to the faster uptake of T3 compared to T into the cells. It is suggested that, considering the bioavailability, α-T should be more effective than α-T3 against glutamate toxicity in vivo.

Grape seed extract ameliorates tumor necrosis factor-α-induced inflammatory status of human umbilical vein endothelial cells

BACKGROUND

Inflammation has played a key role in the causation of atherosclerosis. However, the effects of grape seed extract (GSE) on the pro-inflammatory intracellular signaling, enzyme activity, and inflammatory mediators of endothelial cells have not been sufficiently studied, and less information exists on the comparison between GSE and vitamin C, a well-known antioxidant compound, on their anti-inflammatory properties.

PURPOSE

We investigated the effects of GSE and vitamin C on the cell viability, oxidative stress, monocyte adhesion, the expression of nuclear factor-κB inhibitor (IκB), intercellular adhesion molecule-1 (ICAM-1) and cyclooxygenase-2 (COX-2), and the production of prostaglandin E(2) (PG E(2)) in TNF-α-treated human umbilical vein endothelial cells (HUVECs).

METHODS

Cell viability was measured by MTT assay. The adhesion of THP-1 to HUVECs was evaluated by cell adhesion assay. The oxidized nucleoside 8-hydroxydeoxyguanosine (8-OHdG) (an indicator of oxidative damage to DNA), ICAM-1, and PG E(2) were measured by ELISA. IκB and COX-2 expression were evaluated by western blot analysis.

RESULTS

TNF-α (10, 20, and 50 ng/mL), GSE (50 and 200 μg/mL), or vitamin C (100 μM) did not affect cell viability. GSE (50-100 μg/mL) attenuated TNF-α (20 ng/mL)-induced 8-OHdG production, THP-1 adhesion, the expression of IκB degradation, ICAM-1 and COX-2, and the production of PGE(2) in a dose-dependent manner. Vitamin C (100 μM) also showed significant antioxidative and anti-inflammatory effects.

CONCLUSIONS

GSE effectively ameliorates TNF-α-induced inflammatory status of HUVECs. The findings of the present study suggest that consumption of GSE may be beneficial to inflammatory atherosclerosis.

Vitamin E and neurological function

The clinical, neuropathological and electrophysiological evidence that vitamin E (alpha-tocopherol) is essential for normal neurological function will be reviewed. The possible reasons why neural tissues should be particularly affected by a deficiency of this fat-soluble vitamin and the mechanism(s) involved will be considered.

Vitamin E transport, membrane incorporation and cell metabolism: Is alpha-tocopherol in lipid rafts an oar in the lifeboat?

Vitamin E is composed of closely related compounds, including tocopherols and tocotrienols. Studies of the last decade provide strong support for a specific role of alpha-tocopherol in cell signalling and the regulation of gene expression. It produces significant effects on inflammation, cell proliferation and apoptosis that are not shared by other vitamin E isomers with similar antioxidant properties. The different behaviours of vitamin E isomers might relate, at least in part, to the specific effects they exert at the plasma membrane. alpha-Tocopherol is not randomly distributed throughout the phospholipid bilayer of biological membranes, and as compared with other isomers, it shows a propensity to associate with lipid rafts. Distinct aspects of vitamin E transport and metabolism is discussed with emphasis on the interaction between alpha-tocopherol and lipid rafts and the consequences of these interactions on cell metabolism.

alpha-Tocopheryl phosphate--an active lipid mediator?

The vitamin E (alpha-tocopherol, alphaT) derivative, alpha-tocopheryl phosphate (alphaTP), is detectable in small amounts in plasma, tissues, and cultured cells. Studies done in vitro and in vivo suggest that alphaT can become phosphorylated and alphaTP dephosphorylated, suggesting the existence of enzyme(s) with alphaT kinase or alphaTP phosphatase activity, respectively. As a supplement in animal studies, alphaTP can reach plasma concentrations similar to alphaT and only a part is dephosphorylated; thus, alphaTP may act both as pro-vitamin E, but also as phosphorylated form of vitamin E with possibly novel regulatory activities. Many effects of alphaTP have been described: in the test tube alphaTP modulates the activity of several enzymes; in cell culture alphaTP affects proliferation, apoptosis, signal transduction, and gene expression; in animal studies alphaTP prevents atherosclerosis, ischemia/reperfusion injury, and induces hippocampal long-term potentiation. At the molecular level, alphaTP may act as a cofactor for enzymes, as an active lipid mediator similar to other phosphorylated lipids, or indirectly by altering membrane characteristics such as lipid rafts, fluidity, and curvature. In this review, the molecular and cellular activities of alphaTP are examined and the possible functions of alphaTP as a natural compound, cofactor and active lipid mediator involved in signal transduction and gene expression discussed.

Oral vitamin C and E combination modulates blood lipid peroxidation and antioxidant vitamin levels in maximal exercising basketball players

Oxidative stress occurs during maximal exercise, perhaps as a result of increased consumption of oxygen. Vitamins C and E can overcome the effects of antioxidants in exercise. We investigated the effects of supplementation with a combination of vitamin C and E (VCE) on blood lipid peroxidation (LP) and antioxidant levels following maximal training in basketball players.Blood samples were taken from 14 players (group A) and divided into two subgroups namely maximal training (group B) and maximal training plus VCE groups (group C). Group B maximally exercised for 35 days. VCE was supplemented to group C for 35 days and blood samples were taken from group B and C. Plasma and hemolyzed erythrocyte samples were obtained from the players.Erythrocyte glutathione peroxidase (GSH-Px) activity and plasma vitamin E concentration were lower in group B than in group A, whereas plasma and erythrocyte LP levels were higher in group B than in group A. Plasma vitamin A, vitamin E, erythrocyte GSH-Px, and reduced glutathione (GSH) values were higher in group C than in groups A and B although LP levels in plasma and erythrocytes were lower in group C than in group A and B. beta-Carotene values did not change in the three groups.In conclusion, VCE supplementation in maximal exercising basketball players may strengthen the antioxidant defense system by decreasing reactive oxygen species (ROS).

Accumulation of health promoting phytochemicals in wild relatives of tomato and their contribution to in vitro antioxidant activity

Harnessing natural variation is an important aspect of modern marker assisted breeding. Traditionally breeding programmes have focused on increased yield and resistance to biotic and abiotic pressures. However, consumer demands for improved quality have lead to increased effort into the breeding of nutritional quality traits in crop plants. In the present study, health-related phytochemicals (carotenoids, tocopherols and phenolics) present in green, yellow and red wild relatives of tomato have been analyzed during fruit development and ripening. This study shows that the differences in the final colour of the fruits were due to a distinct accumulation of carotenoids mainly related to the expression of the phytoene synthase-1 gene (Psy-1). In ripe red-fruited tomatoes, the different deposition of pigments gave rise in some cases to colour differences visually discernible by the consumer. Important quantitative differences between and across taxa were noticed for the in vitro antioxidant activity (AA) of the samples.

Alpha-tocopherol counteracts the cytotoxicity induced by ochratoxin a in primary porcine fibroblasts

The aims of the current study were to determine the half-lethal concentration of ochratoxin A (OTA) as well as the levels of lactate dehydrogenase release and DNA fragmentation induced by OTA in primary porcine fibroblasts, and to examine the role of α-tocopherol in counteracting its toxicity. Cells showed a dose-, time- and origin-dependent (ear vs. embryo) sensitivity to ochratoxin A. Pre-incubation for 3 h with 1 nM α-tocopherol significantly (P < 0.01) reduced OTA cytotoxicity, lactate dehydrogenase release and DNA damage in both fibroblast cultures. These findings indicate that α-tocopherol supplementation may counteract short-term OTA toxicity, supporting its defensive role in the cell membrane.

Vitamin E regulates adipocytokine expression in a rat model of dietary-induced obesity

The aim of this study was to determine the effect of the antioxidant vitamin E (VE) on adiponectin and leptin expression in obese rats. Thirty weaning male Sprague-Dawley rats were divided into three groups as follows: (1) a control group, fed with normal chow; (2) a diet-induced obesity group (DIO), fed with a high-fat diet and (3) an intervention group, fed with a high-fat diet supplemented with VE (350 mg/kg). After 10 weeks of being fed according to these group assignments, rats were weighed and euthanized. Blood and adipose tissues were then immediately collected; mRNA and protein levels of leptin and adiponectin were measured by realtime reverse transcription-polymerase chain reaction and Western blotting. Biomarkers of oxidative stress, including serum levels of 8-epi-prostaglandin-F(2)alpha (8-epi-PGF(2)alpha) and glutathione peroxidase activity, were also examined. Adiponectin and leptin levels were lower in the DIO group than in the control group. VE intervention increased the expression of both leptin and adiponectin (P values < 0.05). Association analysis showed that serum leptin levels correlated positively with body fat mass (r = 0.601, P < 0.05). Both serum leptin and adiponectin levels were associated with the presence of serum 8-epi-PGF2 alpha (leptin, r = 0.513, P < 0.05; adiponectin, r = -0.422, P < 0.05). Administration of VE decreases leptin and adiponectin expression in obese rats. This finding is consistent with the view that antioxidants can play an important role in the treatment of obesity-related diseases.

Influence of the cyanotoxin microcystin-LR on tocopherol in Alfalfa seedlings (Medicago sativa)

Spray irrigation of crop plants can represent a risk if the water is contaminated with cyanotoxins. These secondary metabolites produced by many cyanobacteria can have adverse effects on organisms, among others the induction of excess oxygen radicals, so-called oxidative stress. Thereby tocopherol as a lipid antioxidant is essential to maintain membrane integrity. In this study the effects of the cyanotoxin microcystin-LR (MC-LR), and a Microcystis crude extract (Mic-CE) containing MC-LR on tocopherol content and gene expression of Homogentisate phytyltransferase (HPT), involved in tocopherol synthesis, were investigated in seedlings of the crop plant Medicago sativa. Exposures to environmental relevant concentrations showed that Mic-CE affects the tocopherols at a lower concentration than the pure toxin. Changes during a 3-day exposure using 0.5mug L(-1) MC-LR and Mic-CE revealed strong increases of alpha- and beta-tocopherol content, whereas the influence on beta-tocopherol was far stronger than on alpha-tocopherol. The HPT mRNA was elevated after 24 and 72h exposure to MC-LR. These results show that also low concentrations of cyanobacterial toxins in the water have strong influence on tocopherol in M. sativa seedlings and therefore represent a stress for the plants.