Assessing food choice in school children: reliability and construct validity of a method stacking food photographs

Cigarette smoke of which the major component is nicotine plays an important role in the development of cardiovascular diseases. To study the effect of in vitro incubation of LDL with nicotine and its metabolite, cotinine on a copper-induced peroxidation, we monitored the formation of conjugated dienes, hydroperoxides and thiobarbituric acid-reactive substances production. The LDL studied were taken from six non-smokers (aged 41.5 years) and six smokers who consumed at least ten cigarettes per day (40.7 years). LDL oxidation with CuSO4 showed that cigarette smoking promotes LDL susceptibility to peroxidative modification. During the peroxidation of LDL with nicotine (O to 5 mmol/1) and CuSO4 (5 micromol/l), the formation of hydroperoxides decreased when nicotine concentrations increased and the production of TBARS increased in a concomitant manner. The results showed that the presence of nicotine destabilized the production of hydroperoxides in LDL and increased the formation of secondary oxidation products. On the other hand, cotinine had no effect on LDL oxidative susceptibility in smokers and non-smokers.     

Human lung cancer antigens recognized by autologous antibodies: definition of a novel cDNA derived from the tumor suppressor gene locus on chromosome 3p21.3

Supplementation with high doses of alpha-tocopherol has increased the oxidation resistance of LDL in many clinical trials. There have been only a few placebo-controlled trials in healthy persons of alpha-tocopherol doses usually contained in dietary supplements. We carried out a single-blind, placebo-controlled, randomized trial to examine the effect of 200 mg RRR-alpha-tocopheryl acetate/d on the oxidation resistance of atherogenic lipoproteins (VLDL+LDL including intermediate-density lipoproteins) in 40 smoking men. VLDL+LDL oxidation resistance was assessed as conjugated dienes after copper induction and hemin degradation after hydrogen peroxide induction. Also, the LDL total peroxyl-radical trapping antioxidant parameter (LDL TRAP) and plasma malondialdehyde were measured at baseline and after 2 mo of supplementation. Plasma RRR-alpha-tocopherol concentrations were measured at 2-h intervals for 12 h at baseline and after 2 mo of supplementation. Compared with placebo, 200-mg RRR-alpha-tocopheryl acetate supplementation elevated plasma and VLDL+LDL alpha-tocopherol concentrations, LDL TRAP, and oxidation resistance of VLDL+LDL. Plasma alpha-tocopherol increased by 88% (P < 0.0001), VLDL+LDL alpha-tocopherol increased by 90% (P < 0.0001), and LDL TRAP by 58% (P < 0.0001). The time to the start of oxidation (lag time) was prolonged by 34% when assessed with a copper-induced method and by 109% when assessed with a hemin + hydrogen peroxide-induced method; the time to maximal oxidation was prolonged by 21% (copper-induced method) in the vitamin E-supplemented group. Changes in plasma alpha-tocopherol, lipid-standardized alpha-tocopherol, and VLDL+LDL alpha-tocopherol correlated significantly with changes in LDL TRAP, lag time, and time to maximal oxidation. Differences in changes between groups in the area under the curve for plasma alpha-tocopherol were significant (P < 0.009). Our results suggest that 200 mg oral RRR-alpha-tocopheryl acetate/d had a clear effect on the in vitro oxidation of VLDL+LDL in smoking men.     

Dietary flavonoids reduce lipid peroxidation in rats fed polyunsaturated or monounsaturated fat diets

We investigated the influence of dietary flavonoids on alpha-tocopherol status and LDL peroxidation in rats fed diets enriched in either polyunsaturated fatty acids (PUFA) or monounsaturated fatty acids (MUFA). Diets equalized for alpha-tocopherol concentrations were or were not supplemented with 8 g/kg diet of flavonoids (quercetin + catechin, 2:1). After 4 wk of feeding, plasma lipid concentrations were lower in rats fed PUFA than in those fed MUFA with a significant correlation between plasma alpha-tocopherol and cholesterol concentrations, r = 0.94, P < 0. 0001). Dietary lipids influenced the fatty acid composition of VLDL + LDL more than that of HDL or microsomes. The resistance of VLDL + LDL to copper-induced oxidation was higher in rats fed MUFA than in those fed PUFA as assessed by the lower production of conjugated dienes and thiobarbituric acid reactive substances (TBARS) and by the >100% longer lag time for dienes production. (P < 0.0001). Dietary flavonoids significantly reduced by 22% the amounts of dienes produced during 12 h of oxidation in rats fed diets rich in PUFA and lengthened lag time 43% in those fed MUFA. Microsomes of rats fed MUFA produced approximately 50% less TBARS than those of rats fed PUFA (P < 0.0001) and they contained more alpha-tocopherol in rats fed MUFA than in those fed PUFA with higher values (P < 0. 0001) in both groups supplemented with flavonoids (P < 0.0001). Our findings suggest that the intake of dietary flavonoids is beneficial not only when diets are rich in PUFA but also when they are rich in MUFA. It seems likely that these substances contribute to the antioxidant defense and reduce the consumption of alpha-tocopherol in both lipoproteins and membranes.     

Characteristics of ten charge-differing subfractions isolated from human native low-density lipoproteins (LDL). No evidence of peroxidative modifications

Native plasma low-density lipoproteins (LDL) were fractionated into ten subfractions with increasingly negative charges (LDL-1, the least electronegative, to LDL-10) using an anion-exchange column coupled to a fast protein-liquid chromatography system. Prior to fractionation, contaminating Lp(a) and apo A-I-containing lipoproteins were removed from LDL preparations by immunoaffinity chromatography. No significant difference in thiobarbituric acid-reactive substances, vitamin E or free aminogroup was found among subfractions, and no peptide with a higher molecular weight than apo B was observed on SDS-PAGE. We observed a gradual increase in cholesterol esters and a concomitant decrease in triglycerides from LDL-1 to LDL-7, and a reverse tendency from LDL-8 to LDL-10 (P < 0.01). Free cholesterol increased linearly from LDL-1 to LDL-10 (P < 0.01). LDL-1 to -3 had a homogeneous density profile, while other more electronegative subfractions showed a bimodal distribution with a second, minor peak of slightly higher density. A gradual increase in apolipoprotein C-III content related to LDL electronegativity was observed (P < 0.001). Apolipoprotein E content was also increased in the last two subfractions (P < 0.01). LDL subfractions displayed a similar binding fate on human fibroblasts, with the exception of the most electronegative subfractions [LDL-(9 + 10)], which bound more actively to apo B/E receptors (P < 0.05). This study shows that charge heterogeneity of native LDL is not related to lipid peroxidation or derivatization of free aminogroups of apolipoprotein B. In contrast, the enrichment of LDL in apolipoproteins other than apo B may explain, in part, the difference in their particle charge.     

Sacrococcygeal chordoma simulating pilonidal cyst

Tocotrienols from palm oil showed significant ability to inhibit oxidative damage induced by ascorbate-Fe2+ and photosensitization, involving different mechanisms, in rat liver microsomes. The tocotrienol-rich fraction from palm oil (TRF), being tried as a more economical and efficient substitute for alpha-tocopherol, showed time- and concentration-dependent inhibition of protein oxidation as well as lipid peroxidation. It was more effective against protein oxidation. The extent of inhibition by TRF varied with different peroxidation products such as conjugated dienes, lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS). Among the constituents of TRF, gamma-tocotrienol was the most effective followed by its alpha- and delta-isomers. In general, at a low concentration of 5 microM, TRF was able to prevent oxidative damage to significant extent (37% inhibition of protein oxidation and 27-30% of lipid peroxidation at 1 h of incubation). The protective ability of TRF (30.1% at 5 microM with TBARS formation) was significantly higher than that of the dominant form of vitamin E, alpha-tocopherol (16.5% under same conditions). Hence our studies indicate that this fraction from palm oil can be considered as an effective natural antioxidant supplement capable of protecting cellular membranes against oxidative damage.     

Role of apolipoprotein B-derived radical and alpha-tocopheroxyl radical in peroxidase-dependent oxidation of low density lipoprotein

The peroxidation of low density lipoprotein (LDL) may play an important role in the modification of the lipoprotein to an atherogenic form. The oxidation of LDL by peroxidases has recently been suggested as a model for in vivo transition metal ion-independent oxidation of LDL (Wieland, E., S. Parthasarathy, and D. Steinberg. 1993. Proc. Natl. Acad. Sci. USA. 90: 5929-5933). It is possible that in vivo the peroxidase activities of proteins, such as prostaglandin synthase and myeloperoxidase, promote LDL oxidation. We have used horseradish peroxidase (HRP) and H2O2 as a model of peroxidase-dependent oxidation of LDL and we observed the following during HRP/H2O2-initiated LDL oxidation. i) The oxidation of alpha-tocopherol occurred with the concomitant formation of alpha-tocopheroxyl radical. This was followed by the production of an apolipoprotein B (apoB)-derived radical. The apoB radical and the alpha-tocopheroxyl radical were formed under both aerobic and anaerobic conditions. ii) Inclusion of N-t-butyl-alpha-phenylnitrone (PBN) did not inhibit alpha-tocopheroxyl radical formation. The ESR spectrum of a PBN/LDL-lipid derived adduct was observed after prolonged incubation. iii) There was formation of conjugated dienes, lipid hydroperoxides and thiobarbituric acid reactive substances. Our data indicate that HRP/H2O2 oxidizes both alpha-tocopherol and apoB to the corresponding radicals and concomitantly initiates lipid peroxidation.     

Impact of LDL carotenoid and alpha-tocopherol content on LDL oxidation by endothelial cells in culture

Carotenoids and alpha-tocopherol are dietary, lipophilic antioxidants that may protect plasma lipoproteins from oxidation, a process believed to contribute to atherogenesis. Previous work demonstrated that after the Cu(II)-initiated oxidation of human low density lipoprotein (LDL) in vitro, carotenoids and alpha-tocopherol were destroyed before significant lipid peroxidation took place, and that alpha-tocopherol was destroyed at a much faster rate than were the carotenoids. Additionally, in vitro enrichment of LDL with beta-carotene, but not with lutein or lycopene, inhibited LDL oxidation. In the present studies the impact of LDL carotenoid and alpha-tocopherol content on LDL oxidation by human endothelial cells (EaHy-1) in culture was assessed. LDL isolated from 11 individual donors was incubated at 0.25 mg protein/mL with EaHy-1 cells in Ham's F-10 medium for up to 48 h. Formation of lipid hydroperoxides was assessed by chemical analysis and the contents of lutein, beta-cryptoxanthin, lycopene, beta-carotene and alpha-tocopherol were determined by high performance liquid chromatography. The extent of lipid peroxidation correlated with the endogenous alpha-tocopherol content of the LDL but not with its content of carotenoids. As in the Cu(II)-initiated system, carotenoids and alpha-tocopherol were destroyed before significant peroxidation took place, but, in the cell-mediated system, alpha-tocopherol and the carotenoids were destroyed at comparable rates. Also, like the Cu(II)-initiated oxidation, enrichment of the LDL with beta-carotene protected it from oxidation by the endothelial cells. However, enrichment with either lutein or lycopene actually enhanced the cell-mediated oxidation of the LDL. Thus, the specific content of carotenoids in low density lipoprotein (LDL) clearly modulates its susceptibility to oxidation, but individual carotenoids may either inhibit or promote LDL oxidation.     

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

BACKGROUND: Peroxidatively modified low-density lipoprotein (LDL) may contribute to the atherosclerotic process; therefore, protecting LDL against peroxidation may reduce or retard the progression of atherosclerosis. We evaluated the effect of alpha-tocopherol on copper-catalyzed LDL peroxidative modification. METHODS: The protective effects of alpha-tocopherol on copper-catalyzed LDL peroxidative modification were examined by measurement of the concentration of lipid hydroperoxides in LDL and by the provision of LDL cholesterol to lymphocytes via the LDL receptor-mediated pathway. RESULTS: The measurement of concentration of lipid hydroperoxides in LDL showed that alpha-tocopherol inhibited the peroxidative modification of LDL. Also, alpha-tocopherol preserved the ability of LDL to be recognized by LDL receptors in peripheral blood lymphocytes to the same extent as native LDL. CONCLUSION: These findings indicate that alpha-tocopherol may protect LDL against peroxidative modification, maintaining its ability to act as a ligand for LDL receptors in vivo.     

Oxidative susceptibility of low density lipoprotein subfractions is related to their ubiquinol-10 and alpha-tocopherol content

The conjugated polyene fatty acid parinaric acid (PnA) undergoes a stoichiometric loss in fluorescence upon oxidation and can be used to directly monitor peroxidative stress within lipid environments. We evaluated the course of potentially atherogenic oxidative changes in low density lipoproteins (LDL) by monitoring the oxidation of PnA following its incorporation into buoyant (p = 1.026-1.032 g/ml) and dense (p = 1.040-1.054 g/ml) LDL subfractions. Copper-induced oxidation of LDL-associated PnA exhibited an initial lag phase followed by an increased rate of loss until depletion. Increased PnA oxidation occurred immediately after the antioxidants ubiquinol-10 and alpha-tocopherol were consumed but before there were marked elevations in conjugated dienes. Despite differences in sensitivity to early oxidation events, PnA oxidation and conjugated diene lag times were correlated (r = 0.582; P = 0.03), and both indicated a greater susceptibility of dense than buoyant LDL in accordance with previous reports. The greater susceptibility of PnA in dense LDL was attributed to reduced levels of ubiquinol-10 and alpha-tocopherol, which were approximately 50% lower than in buoyant LDL (mol of antioxidant/mol of LDL) and together accounted for 80% of the variation in PnA oxidation lag times. These results suggest that PnA is a useful probe of LDL oxidative susceptibility and may be superior to conjugated dienes for monitoring the initial stages of LDL lipid peroxidation. Differences in oxidative susceptibility among LDL density subfractions are detected by the PnA assay and are due in large part to differences in their antioxidant content.     

Oxidative modification of low-density lipoprotein and atherogenetic risk in beta-thalassemia

We investigated the oxidative state of low-density lipoprotein (LDL) in patients with beta-thalassemia to determine whether there was an association with atherogenesis. Conjugated diene lipid hydroperoxides (CD) and the level of major lipid antioxidants in LDL, as well as modified LDL protein, were evaluated in 35 beta-thalassemia intermedia patients, aged 10 to 60, and compared with age-matched healthy controls. Vitamin E and beta-carotene levels in LDL from patients were 45% and 24% of that observed in healthy controls, respectively. In contrast, the mean amount of LDL-CD was threefold higher and lysil residues of apo B-100 were decreased by 17%. LDL-CD in thalassemia patients showed a strong inverse correlation with LDL vitamin E (r = -0.784; P <.0001), while a negative trend was observed with LDL-beta-carotene (r = -0.443; P =.149). In the plasma of thalassemia patients, malondialdehyde (MDA), a byproduct of lipid peroxidation, was increased by about twofold, while vitamin E showed a 52% decrease versus healthy controls. LDL-CD were inversely correlated with plasma vitamin E (r = -0.659; P <.0001) and correlated positively with plasma MDA (r = 0.621; P <. 0001). Plasma ferritin was positively correlated with LDL-CD (r = 0.583; P =.0002). No correlation was found between the age of the patients and plasma MDA or LDL-CD. The LDL from thalassemia patients was cytotoxic to cultured human fibroblasts and cytotoxicity increased with the content of lipid peroxidation products. Clinical evidence of mild to severe vascular complications in nine of the patients was then matched with levels of LDL-CD, which were 36% to 118% higher than the mean levels of the patients. Our results could account for the incidence of atherogenic vascular diseases often reported in beta-thalassemia patients. We suggest that the level of plasma MDA in beta-thalassemia patients may represent a sensitive index of the oxidative status of LDL in vivo and of its potential atherogenicity.     

Early destruction of tryptophan residues of apolipoprotein B is a vitamin E-independent process during copper-mediated oxidation of LDL

The decrease of the tryptophan fluorescence (Ex/Em = 282/331 nm) was used to monitor the kinetics of copper-mediated LDL oxidation. Cu2+ causes a concentration-dependent quenching of the LDL Trp-fluorescence, the maximum of about 22% suggests that 8-9 Trp residues (out of a total of 37) are accessible for Cu2+ ions. Decomposition of LDL tryptophan commences immediately after addition of Cu2+ and proceeds in two stages with quite different rates. At a molar ratio of Cu2+/LDL = 33:1 the LDL particle looses 1 Trp every 13.5 min in the initial slow phase and every 4.1 min in the subsequent rapid The second, stage temporarily coincides with the propagating lipid peroxidation. In the initial phase loss of Trp proceeds with a constant rate for up to 200 min depending on the copper concentration. Whereas lipid peroxidation accelerates after consumption of vitamin E, rate of Trp loss does not increase. Loading of LDL with vitamin E has also no effect on the initial rate of Trp loss. During the initial phase a loss of one Trp residue/LDL is accompanied by the loss of two alpha-tocopherols and the generation of two conjugated lipid hydroperoxides. The results suggest Trp residues play a role in initiating the lipid peroxidation process in the LDL particle. In such kinetic studies, precautions must be taken to avoid photodecomposition of LDL-Trp. The LDL vitamin E fluorescence (Ex/Em = 290/323 nm) does not interfere with the Trp fluorescence even at high concentrations.     

Measurement of lipid peroxidation

Lipid peroxidation results in the formation of conjugated dienes, lipid hydroperoxides and degradation products such as alkanes, aldehydes and isoprostanes. The approach to the quantitative assessment of lipid peroxidation depends on whether the samples involve complex biological material obtained in vivo, or whether the samples involve relatively simple mixtures obtained in vitro. Samples obtained in vivo contain a large number of products which themselves may undergo metabolism. The measurement of conjugated diene formation is generally applied as a dynamic quantitation e.g. during the oxidation of LDL, and is not generally applied to samples obtained in vivo. Lipid hydroperoxides readily decompose, but can be measured directly and indirectly by a variety of techniques. The measurement of MDA by the TBAR assay is non-specific, and is generally poor when applied to biological samples. More recent assays based on the measurement of MDA or HNE-lysine adducts are likely to be more applicable to biological samples, since adducts of these reactive aldehydes are relatively stable. The discovery of the isoprostanes as lipid peroxidation products which can be measured by gas chromatography mass spectrometry or immunoassay has opened a new avenue by which to quantify lipid peroxidation in vivo, and will be discussed in detail.     

Atherosclerosis, with special reference to vitamin E

The relationship between atherosclerosis and fat soluble vitamin, especially vitamin E is reviewed on the basis of oxidised modification of low density lipoprotein (LDL). Data now support the notion that the oxidised LDL is present in the blood and arterial wall and antioxidant drugs such as probucol and vitamin E, beta-carotene, may prevent the progression of atherosclerosis. LDL alpha-tocopherol levels are generally correlated to the plasma concentrations and supplementation with alpha-tocopherol increases its content in LDL. There is a significant correlation between the LDL alpha-tocopherol level and the resistance to oxidative modification. Epidemiological data also shows the relation between low levels of plasma vitamin E and the increased incidence of coronary heart disease. Clinical application of vitamin E should be clarified in detail to inhibit the progression of atherosclerosis.     

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.     

Cosupplementation with coenzyme Q prevents the prooxidant effect of alpha-tocopherol and increases the resistance of LDL to transition metal-dependent oxidation initiation

There is considerable interest in the ability of antioxidant supplementation, in particular with vitamin E, to attenuate LDL oxidation, a process implicated in atherogenesis. Since vitamin E can also promote LDL lipid peroxidation, we investigated the effects of supplementation with vitamin E alone or in combination with coenzyme Q on the early stages of the oxidation of isolated LDL. Isolated LDL was obtained from healthy subjects before and after in vitro enrichment with vitamin E (D-alpha-tocopherol, alpha-TOH) or dietary supplementation with D-alpha-TOH (1 g/d) and/or coenzyme Q (100 mg/d). LDL oxidation initiation was assessed by measurement of the consumption of alpha-TOH and cholesteryl esters containing polyunsaturated fatty acids and the accumulation of cholesteryl ester hydroperoxides during incubation of LDL in the transition metal-containing Ham's F-10 medium in the absence and presence of human monocyte-derived macrophages (MDMs). Native LDL contained 8.5 +/- 2 molecules of alpha-TOH and 0.5 to 0.8 molecules of ubiquinol-10 (CoQ10H2, the reduced form of coenzyme Q) per lipoprotein particle. Incubation of this LDL in Ham's F-10 medium resulted in a time-dependent loss of alpha-TOH with concomitant stoichiometric conversion of the major cholesteryl esters to their respective hydroperoxides. MDMs enhanced this process. LDL lipid peroxidation occurred via a radical chain reaction in the presence of alpha-TOH, and the rate of this oxidation decreased on alpha-TOH depletion. In vitro enrichment of LDL with alpha-TOH resulted in an LDL particle containing sixfold to sevenfold more alpha-TOH, and such enriched LDL was more readily oxidized in the absence and presence of MDMs compared with native LDL. In vivo alpha-TOH-deficient LDL, isolated from a patient with familial isolated vitamin E deficiency, was highly resistant to Ham's F-10-initiated oxidation, whereas dietary supplementation with vitamin E restored the oxidizability of the patient's LDL. Oral supplementation of healthy individuals for 5 days with either alpha-TOH or coenzyme Q increased the LDL levels of alpha-TOH and CoQ10H2 by two to three or three to four times, respectively. alpha-TOH-supplemented LDL was significantly more prone to oxidation, whereas CoQ10H2-enriched LDL was more resistant to oxidation initiation by Ham's F-10 medium than native LDL. Cosupplementation with both alpha-TOH and coenzyme Q resulted in LDL with increased levels of alpha-TOH and CoQ10H2, and such LDL was markedly more resistant to initiation of oxidation than native or alpha-TOH-enriched LDL. These results demonstrate that oral supplementation with alpha-TOH alone results in LDL that is more prone to oxidation initiation, whereas cosupplementation with coenzyme Q not only prevents this prooxidant activity of vitamin E but also provides the lipoprotein with increased resistance to oxidation.     

Cerebral metabolic monitoring experience in critical neurological patients

The effects of vitamin E on lipid peroxidation, intracellular free Ca2+ concentration ([Ca2+]i), and cell death were investigated in the postischemic immature cerebellum. Deprivation of oxygen and glucose for 10-min in a suspension of freshly dissociated granule cells from the cerebellum of 9-day-old male rat pups resulted in a recovery-induced consumption of cell nonenzymatic antioxidants (ascorbic acid, glutathione, and alpha-tocopherol) and development of membrane lipid peroxidation as measured by the thiobarbituric acid method. The rate of lipid peroxidation of the postischemic cells was stimulated, not reduced, by treatment of the cells with vitamin E (5-30 microM alpha-tocopherol phosphate). In flow-cytometric studies a 10-min period of ischemia resulted in a small increase in intracellular calcium concentration, lipid peroxidation products and cell death, but in the presence of alpha-tocopherol the same treatment caused a dramatic increase in cell death, accompanied by a large increase in [Ca2+]i and lipid peroxidation products. Pretreatment of the cells with a mixture of three antioxidants (vitamin C/rutin/ubiquinol-10, 10/5/1) or nickel (Ni2+) reduced the alpha-tocopherol-induced increases in [Ca2+]i, and cell death. Hydrogen peroxide (1 mM) and the water-soluble analogue of vitamin E, trolox (50 microM), mimicked the effect of vitamin E on lipid peroxidation in the postischemic cells. Pretreatment of the cells with the intracellular Ca2+ chelator BAPTA-AM, reduced both the alpha-tocopherol-induced increase in [Ca2+]i and cell death. The effect of vitamin E on [Ca2+]i was age dependent and decreased abruptly during maturation of the cerebellum between the first and second weeks of life. Results of in vitro treatment of the immature cerebellar cells with the water-soluble form of vitamin E (alpha-tocopherol phosphate) suggest that, after consumption of cellular co-antioxidants, vitamin E may be converted to an alpha-tocopheroxyl radical, which act as a toxic prooxidant as cellular bioenergetics deteriorate.     

Antioxidant properties of butein isolated from Dalbergia odorifera

The antioxidant properties of butein, isolated from Dalbergia odorifera T. Chen, were investigated in this study. Butein inhibited iron-induced lipid peroxidation in rat brain homogenate in a concentration-dependent manner with an IC50, 3.3+/-0.4 microM. It was as potent as alpha-tocopherol in reducing the stable free radical diphenyl-2-picrylhydrazyl (DPPH) with an IC0.200, 9.2+/-1.8 microM. It also inhibited the activity of xanthine oxidase with an IC50, 5.9+/-0.3 microM. Besides, butein scavenged the peroxyl radical derived from 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH) in aqueous phase, but not that from 2,2-azobis(2, 4-dimethylvaleronitrile) (AMVN) in hexane. Furthermore, butein inhibited copper-catalyzed oxidation of human low-density lipoprotein (LDL), as measured by conjugated dienes and thiobarbituric acid-reactive substance (TBARS) formations, and electrophoretic mobility in a concentration-dependent manner. Spectral analysis revealed that butein was a chelator of ferrous and copper ions. It is proposed that butein serves as a powerful antioxidant against lipid and LDL peroxidation by its versatile free radical scavenging actions and metal ion chelation.     

High-dose vitamin E supplementation has no effect on ethanol-induced pathological liver injury

The effect of alpha-tocopherol (alpha-T) supplementation on ethanol-induced liver damage was studied. The intragastric feeding rat model was used in this study. Both normal and alpha-T supplemented animals (3125 IU/kg body weight) were fed liquid diet and ethanol for 1 mo. In pair-fed animals, ethanol was isocalorically replaced by dextrose. The blood ethanol level in the ethanol-fed groups was between 150 to 350 mg/dl. Lipid peroxidation was assessed by measuring liver thiobarbituric acid reactive substances (TBARS) and conjugated dienes. Liver damage was assessed by light microscopy. Overall, chronic ethanol treatment resulted in increase in TBARS and conjugated dienes in both normal (60% and 35%, P < .01, respectively) and alpha-T-supplemented groups (50% and 47%, P < .01, respectively). In animals receiving either dextrose or ethanol and regular diet, there was a significant inverse correlation between liver alpha-T and TBARS (r = 0.88, P < 0.01) and conjugated dienes (r = -0.75, P < .05). In contrast, in the vitamin E-supplemented rats, a significant positive correlation was observed between liver alpha-T, TBARS (r = 0.78, P < .01) and conjugated dienes (r = 0.87, P < .01). Of major significance is that alpha-T supplementation had no effect on ethanol-induced pathological changes in the liver. In conclusion, these results show that in the intragastric feeding model, alpha-T supplementation had no protective effect on ethanol-induced liver damage.     

Catecholamine regulation of the prefrontal cortex

In order to contribute to the understanding of the biological properties of nafazatrom, an antithrombotic agent (NAP), we studied its effects on peroxidation of low density lipoproteins (LDL), lipid liposomes, heart homopgenate, and its interaction with alpha-tocopherol radical. NAP decreased the FeSO4 and H202-induced peroxidation of phosphatidylcholine liposomes and heart homogenate, and it decreased peroxidation of LDL induced by CuSO4 or 2,2'-azobis(2-amidinopropane). The antioxidant effect of NAF was about 3 times less potent than that of alpha-tocopherol (alpha-TOC) in phosphatidylcholine liposomes, and NAF was about 2-4 times more efficient to decrease peroxidation of LDL than alpha-TOC. Possible interaction of NAF with alpha-tocopherol radical (alpha-TR) was studied by EPR spectroscopy. NAF decreased the concentration of alpha-TR, but it was about 100-times less efficient than vitamin C. This may indicate that NAF does not interfere with alpha-TR formation and/or reduction of alpha-TR in biological system. The obtained results may help the explanation of biological effects of NAF.     

Methacrylonitrile induced oxidative stress in rat liver

MeAN administration (40mg/kg body wt/day (i.e. 1/5 of LD50) resulted in increased levels of lipid peroxidation products, conjugated dienes and lipofuscin-like substances in rat liver. Significant decrease in GSH and a decreased activity of hepatic SOD, CAT and GPx were observed. There was also an increase in glutathione S-transferase and G6PD activities, decreased plasma ceruloplasmin and vitamin C implying oxidative stress caused by MeAN.