Increase in heart glutathione redox ratio and total antioxidant capacity and decrease in lipid peroxidation after vitamin E dietary supplementation in guinea pigs

How Robust is the Evidence for a Role of Oxidative Stress in Autism Spectrum Disorders and Intellectual Disabilities?

Growing interest in the pathogenesis of autism spectrum disorders (ASDs) and other intellectual and developmental disabilities (IDD) has led to emerging evidence implicating a role for oxidative stress. However, understanding the strength of this association is made challenging by the use of a variety of purported biomarkers of oxidative stress, many of which have either uncertain specificity or flawed methods of analysis. This review aims to address this issue, which is widespread in the ASD and IDD literature, by providing readers with information concerning the strengths and limitations of the choice and analysis of biomarkers of oxidative stress. We highlight that biomarkers and assays should be specific, sensitive, reproducible, precise, robust, and chosen with careful consideration. Future studies should be sufficiently powered and address sample collection, processing, and storage which are, additionally, poorly considered, sources of bad practice, and potential errors. Only with these issues considered, will the data lead to conclusions as to the precise role of oxidative stress in ASDs and IDD.

Subacute oral toxicity of BDE-15, CDE-15, and HODE-15 in ICR male mice: assessing effects on hepatic oxidative stress and metals status and ascertaining the protective role of vitamin E

The present study examined the effects of oral exposure of 4,4'-dibromodiphenyl ether (BDE-15), 4,4'-dichlorodiphenyl ether (CDE-15), and 4,4'-dihydroxydiphenyl ether (HODE-15) on hepatic oxidative stress (OS) and metal status in Institute of Cancer Research (ICR) male mice. Furthermore, the role of vitamin E in ameliorating potential OS caused by BDE-15, CDE-15, and HODE-15 was investigated. Three groups of mice were exposed to 1.20 mg/kg(body weight)/day of each of the three toxicants for 28 days. Results showed that none of the three toxicants altered growth rates of mice, but significantly increased (P<0.05) relative liver weights and decreased relative kidney weights. Pathological changes including cell swelling, inflammation and vacuolization, and hepatocellular hypertrophy in livers were observed. Significant decreases (P<0.05 and P<0.01) in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activity, and glutathione (GSH) levels, together with increases in malondialdehyde (MDA) content were recorded in all toxicant-treated groups. Hepatic copper levels increased in all toxicant-treated groups. Hepatic zinc levels decreased in the liver of BDE-15-treated mice, whereas they increased in the livers of CDE-15-treated and HODE-15-treated mice. In conclusion, daily exposure to the three toxicants perturbed metal homeostasis and increased OS in mouse liver. Experimental data indicated the hepatic oxidative toxicity of the three toxicants followed the order BDE-15<HODE-15<CDE-15. Moreover, the study proved that daily supplementation of 50 mg/kg vitamin E is effective to ameliorate the hepatic OS status and metal disturbance in mice.

Effects of alpha-tocopheryl acetate and beta-carotene dietary supplementation on the antioxidant enzymes, TBARS and sensory attributes of turkey meat

1. The aim of the study was to evaluate the effects of alpha-tocopheryl acetate (50 mg/kg) and beta-carotene (15 mg/kg) dietary supplementation on the oxidative status of raw turkey breast and leg muscles assessed by thiobarbituric acid test values, the vitamin E levels and the antioxidant enzyme activities. In parallel, a quantitative descriptive sensory analysis was carried out on cooked, stored and reheated samples. 2. Vitamin E was present in sufficient quantity to reduce oxidation, since iron-induced reactive substances (TBARS) were significantly lower in antioxidant-supplemented treatments. The results suggested that the presence of beta-carotene in the diet limits the accumulation of alpha-tocopherol in turkey muscles. 3. In the present study, there was no conclusive relationship between dietary antioxidant supplementation and endogenous antioxidant enzyme activities. 4. Sensory evaluation showed that a longer supplementation time and dose may be necessary in turkeys to prevent meat from rancidity and warmed-over flavour (WOF). Leg pastiness and stringiness were modified by dietary antioxidant supplementation, indicating the possible synergism between antioxidants and cysteine proteinases in the perception of meat quality. 5. Given the modern trends that lead consumers to increase their consumption of poultry meat, it would be interesting to evaluate the commercial potential and cost effectiveness of routine dietary antioxidant supplementation.

Influence of enrofloxacin administration and alpha-tocopheryl acetate supplemented diets on oxidative stability of broiler tissues

The objective of this study was to assess the oxidative stability and presence of antibiotic residues in tissues of broilers fed diets supplemented with alpha-tocopheryl acetate and treated with enrofloxacin. The activities of antioxidant enzymes and antibiotic concentrations in chicken breast, leg, and liver were determined. Iron-induced TBA-reactive substances (TBARS) and vitamin E were evaluated in muscles. The antioxidant effectiveness of vitamin E was reflected by TBARS values being lower in antioxidant-supplemented treatments than in the other dietary groups. On the other hand, antioxidant enzyme activities were not substantially affected by dietary treatments. The concentration of enrofloxacin in tissues was considerable, even after withdrawal 12 d before slaughter. Contrary to the findings in previous studies, enrofloxacin was not extensively metabolized to ciprofloxacin. Supplementation of the diet with 100 mg/kg of alpha-tocopheryl acetate did not have a significant effect on the level of antibiotic found in breast muscle samples. When comparing treatments without antibiotic withdrawal time, alpha-tocopheryl acetate supplementation led to a significant decrease in enrofloxacin level in leg and liver samples. These results showed that mutual interactions between different molecules could modify the drug residues in the tissue, which should be taken into account when considering the drug administration and the establishment of a correct withdrawal time.

Single-sample preparation for simultaneous cellular redox and energy state determination

A simple and reliable method for the preparation of biological samples for the evaluation of biochemical parameters representative of the redox and energy states, such as glutathione (GSH), oxidized glutathione (GSSG), oxidized nicotinamide adenine dinucleotide (NAD+), reduced nicotinamide adenine dinucleotide (NADH), oxidized nicotinamide adenine dinucleotide phosphate (NADP+), reduced nicotinamide adenine dinucleotide phosphate (NADPH), coenzyme A (CoASH), oxidized CoASH, ascorbate, malondialdehyde, oxypurines, nucleosides, and energy metabolites, is presented. Fast deproteinization under nonoxidizing conditions is obtained by tissue homogenization in ice-cold, nitrogen-saturated CH3CN + 10 mM KH2PO4 (3:1; v:v), pH 7.40. After sample centrifugation to pellet precipitated proteins, organic solvent removal is performed on clear supernatants by three washings with large volumes of high-performance liquid chromatography (HPLC)-grade chloroform. The remaining aqueous phase, free of solvent and any lipid-soluble substances that may interfere with the further metabolite analysis, is used for the simultaneous ion-pairing HPLC determination of 39 compounds by means of a Kromasil C-18, 250 x 4.6-mm, 5-microm-particle-size column with tetrabutylammonium hydroxide as the pairing reagent. Results obtained by using the present method to prepare different rat tissue extracts demonstrate that it is possible to perform a single tissue preparation only for monitoring, in the same sample, compounds representative of the redox state (through the direct determination of GSH, GSSG, NAD+, NADH, NADP+, NADPH, CoASH, and oxidized CoASH) and of the cell energy state (by the analysis of oxypurines, nucleosides, and energy metabolites). Applicability of this sample processing procedure to quantify variations of the aforementioned compounds under pathological conditions was effected in rats subjected to moderate closed-head trauma.

Regional accumulation of aluminium in the rat brain is affected by dietary vitamin E

The regional accumulation of aluminium in the brain of male albino Wistar rats was investigated following 4 weeks of administration by intraperitoneal injection of aluminium lactate (10mg aluminium/kg body weight). The consequences of concomitant dietary vitamin E (5, 15, or 20 mg vitamin E/g of food) were also studied. Rat brains were dissected into functional regions, for the measurement of aluminium and markers of oxidative stress. Plasma aluminium levels were increased in all groups of animals receiving aluminium lactate (p < 0.01), and these levels were significantly reduced in rats receiving concomitant vitamin E (p < 0.05). In the group of rats receiving aluminium alone, levels of brain tissue aluminium were increased in all regions of brain examined (p< 0.01). Brain tissue aluminium levels were reduced by concomitant dietary vitamin E. Catalase and reduced glutathione levels were both reduced in several regions of brain in animals treated with aluminium (p < 0.05). Aluminium treatment was not associated with a significant increase in reactive oxygen species (ROS) generation (p > 0.05), although ROS production was attenuated by dietary vitamin E (p < 0.05) in some regions.

Exposure to the fern Onychium contiguum causes increase in lipid peroxidation and alters antioxidant status in urinary bladder

The status of lipid peroxidation, glutathione, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, superoxide dismutase, catalase, ascorbic acid, and alpha-tocopherol was studied in the urinary bladder of guinea pigs exposed to the carcinogenic fern Onychium contiguum. There was significant increase in the preformed lipid peroxides in the urinary bladders from fern exposed animals. The amount of lipid peroxides produced on incubation of urinary bladder homogenates with or without catalyst was significantly higher in the fern exposed animals. The concentrations of glutathione and alpha-tocopherol and the activities of glutathione reductase and catalase were elevated in the urinary bladders of the animals exposed to the fern. No effect was observed on the concentration of ascorbic acid and the activities of glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase. It is summarized that the fern toxins increased oxidative stress in the urinary bladder and antioxidant status was altered. However, the altered antioxidant status did not provide protection from the toxin induced injury. Histopathology of the urinary bladder in the fern exposed animals revealed oedema, haemorrhages, and congestion. This is the first study to show increase in lipid peroxidation along with altered antioxidant status in the urinary bladder of fern exposed animals.

The effect of vitamin E treatment on oxidative stress generated in trained rats

The aim of this study was to investigate the effect of vitamin E treatment on increased oxidative stress in rats exposed to a swimming exercise protocol. In order to examine the effects of physical swimming training on the antioxidant defences of tissues and on their susceptibility to damage induced by exercise, the levels of glutathione (GSH) and thiobarbituric acid reacting substances (TBARS) levels, on indicator of lipid peroxidation in various tissues, have been determined. In this study, four groups of female rats were used while the rats were trained to swim for 30 minutes a day and five days a week which lasted eight weeks and vitamin E (vit. E) supplementation (30 mg/kg/day) has been carried out for five days a week. TBARS levels are significantly found lower in both trained and sedentary vit. E supplemented groups, since vit. E is the most important antioxidant in an earlier line of defence in lipid peroxidation. Also, in vit. E supplemented trained rats, the glutathione response is observed to be significantly higher, supporting with the TBARS levels and in accordance with the literature. But in the sedentary group without vit. E supplementation, the GSH levels of the liver and the heart tissues were significantly lower than both vit. E supplemented sedentary and trained groups. These results evaluate that vit. E confers protection to GSH levels in these tissues where the GSH levels were found significantly lower in the groups not supplemented with vit. E.

Antioxidant enzyme activities and mitochondrial fatty acids in pulmonary hypertension syndrome (PHS) in broilers

Major objectives of this study were to assess antioxidant protection and fatty acid profile in lung mitochondria and whole liver in broilers with pulmonary hypertension syndrome [(PHS; with and without high dietary vitamin E (VE)] (Experiment 1) and in broilers that did not develop PHS but were genetically selected (S) or not selected (NS) for resistance to PHS (Experiment 2). In Experiment 1, lung mitochondrial glutathione peroxidase (GSH-Px) activity was elevated in broilers with PHS compared to controls, broilers fed high VE, and broilers fed high VE with PHS (VE-PHS), but there were no differences in GSH reductase (GSH-Rd) among groups. In liver tissue, GSH-Px was also elevated by PHS but was lower in VE and VE-PHS groups than in controls. There were no differences in liver GSH-Rd, superoxide dismutase (SOD), or gamma-glutamylcysteine synthetase (gamma-GCS) activities with the exception that gamma-GCS was higher in the VE-PHS group than in the other groups. In Experiment 2, S lung mitochondria exhibited lower GSH-Px and higher GSH-Rd compared to NS broilers. In the liver, there were no differences in GSH-Px, GSH-Rd, or gamma-GCS, but SOD was lower in S compared to the NS broilers. High VE increased the percentage of saturated fatty acids and decreased the percentage of unsaturated fatty acids in lung mitochondria in Experiment 1; there were no differences in fatty acid content between S and NS mitochondria in Experiment 2. Thus, it appears that GSH recycling enzyme activities are affected by PHS and high VE presumably in response to differences in oxidative stress and that genetic resistance to PHS is associated with an inherently better capability to metabolize oxidants in lung mitochondria. The increase in saturation of lung mitochondrial fatty acids with high dietary VE would presumably make them more resistant to oxidative stress and, thus, reduce the level of PHS-induced oxidative stress.

Enhanced heme oxygenase activity increases the antioxidant defense capacity of guinea pig liver upon acute cobalt chloride loading: comparison with rat liver

Changes in the activity of so-called oxidative stress defensive enzymes, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and heme oxygenase, as well as changes in lipid peroxidation and reduced glutathione levels, were measured in guinea pig and rat liver after acute cobalt loading. Cobalt chloride administration produced a much higher degree of lipid peroxidation in guinea pig than in rat liver compared with the control animals. The intrahepatic reduced glutathione content in control guinea pig was higher than that in rat, but was equally decreased in both species after cobalt administration. The enzymatic scavengers of free radicals, superoxide dismutase, catalase and glutathione peroxidase, were significantly decreased in rat liver after acute cobalt loading, and as a compensatory reaction, the heme oxygenase activity was increased (seven-fold). In guinea pig liver, only superoxide dismutase activity was depleted in response to cobalt-induced oxidative stress, while catalase and glutathione peroxidase were highly activated and the heme oxygenase activity was dramatically increased (13-fold). It is assumed that enhanced heme oxygenase activity may have important antioxidant significance by increasing the liver oxidative-stress defense capacity.

Effect of vitamin E and selenium on resistance to oxidative stress in chicken superficial pectoralis muscle

One-day-old chicks were reared using diets that differed in their vitamin E and/or selenium content. In chicks depleted of both selenium and vitamin E, signs of exudative diathesis on the superficial pectoralis muscle were observed. The purpose of this research was to determine the defective points of the antioxidant defense system, which made this tissue highly susceptible to nutritionally-induced oxidative stress. Vitamin E, and selenium in lower magnitude, were the factors that strikingly affected the course of mitochondrial lipid peroxidation. Animals fed diets deficient in vitamin E and selenium displayed the lowest reduced glutathione level and glutathione peroxidase activity. The decreased levels of reduced glutathione were not due to a defective activity of glutathione reductase, which was increased in both mitochondria and cytosol. The absence of vitamin E was linked to lowering of mitochondrial thiol levels. The Glutathione peroxidase/Cu,Zn-superoxide dismutase ratio was 2.8 in animals fed selenium and vitamin E, and decreased to 0.13 in animals deficient in both nutrients. This change was indicative of oxidant-induced damage mediated by hydrogen peroxide. Catalase activity increased in an attempt to counteract the decrease in glutathione peroxidase activity. The results obtained showed that alpha-tocopherol and Se deficiencies caused multiple alterations in the antioxidant system and adversely affected the redox state of chicken superficial pectoralis muscle.

Differential alterations in antioxidant capacity in cells from Alzheimer patients

Oxidative stress occurs in brains of Alzheimer's disease (AD) patients. A major question in AD research is whether the oxidative stress is just secondary to neurodegeneration. To test whether oxidative stress is an inherent property of AD tissues, the ability of cultured fibroblasts bearing the AD Presenilin-1 246 Ala-->Glu mutation to handle reactive oxygen species (ROS) was compared to controls. Although ROS in cells from AD subjects were only slightly less than cells from controls under basal conditions (-10%) or after exposure to H(2)O(2) (-16%), treatment with antioxidants revealed clear differences. Pretreatment with DMSO, a hydroxyl radical scavenger, reduced basal and H(2)O(2)-induced ROS levels significantly more in cells from controls (-22%, -22%) than in those from AD subjects (-4%, +14%). On the other hand, pretreatment with Trolox diminished H(2)O(2)-induced ROS significantly more in cells from AD (-60%) than control subjects (-39%). In summary, cells from AD patients have greater Trolox sensitive ROS and less DMSO sensitive ROS than controls. The results demonstrate that fibroblasts bearing this PS-1 mutation have altered means of handling oxidative stress and appear useful for determining the mechanism underlying the altered redox metabolism.

The importance of lipid solubility in antioxidants and free radical generating systems for determining lipoprotein proxidation

The oxidative modification of low-density lipoprotein (LDL) plays an important role in atherosclerosis. Protecting LDL from oxidation has been shown to reduce the risk of coronary heart disease. In this study, we compared the protective effects of two lipophilic antioxidants (vitamin E and lazaroid) with two hydrophilic antioxidants (trolox and vitamin C) in the presence of several different free radical generating systems. Vitamin E (IC50 = 5.9 microM) and lazaroid (IC50 = 5.0 microM) were more effective in inhibiting lipid peroxidation caused by a Fe-ADP free radical generating system than vitamin C (IC50 = 5.2 x 10(3) microM) and trolox (IC5 = 1.2 x 10(3) microM). Preincubation of lipoproteins with a lipophilic antioxidant increased the protective effect against various free radicals. Preincubation with hydrophilic antioxidants did not have an effect. We also tested the efficacy of the antioxidants when the free radicals were generated within the lipid or the aqueous environment surrounding the LDL. For this purpose, we used the peroxyl generating azo-compounds AMVN (2,2'-azobis(2,4-dimethylvaleronitrile)) and AAPH (2,2'azobis(2-amidinopropane) dihydrochloride). All of the antioxidants tested were more effective against free radicals generated in a water soluble medium than they were against free radicals generated in a lipid environment. In conclusion, our data demonstrate that lipid solubility is an important factor for both the antioxidant and the free radical generating systems in determining the extent of lipid peroxidation in LDL. Our data also demonstrate that antioxidant efficacy in one set of experimental conditions may not necessarily translate into a similar degree of protection in another set of conditions where lipophilicity is a variable.

Resveratrol, melatonin, vitamin E, and PBN protect against renal oxidative DNA damage induced by the kidney carcinogen KBrO3

Free radical scavengers can protect against the genotoxicity induced by chemical carcinogens by decreasing oxidative damage. The protective effect of the antioxidants melatonin, resveratrol, vitamin E, butylated hydroxytoluene and 2-mercaptoethylamine, and the spin-trapping compound alpha-phenyl-N-tert-butyl nitrone (PBN) against oxidative DNA damage was studied in the kidney of rats treated with the kidney-specific carcinogen potassium bromate (KBrO3). KBrO3 was given to rats previously treated with melatonin, resveratrol, PBN, vitamin E, butylated hydroxytoluene, or 2-mercaptoethylamine. Oxidative damage to kidney DNA was estimated 6 hours afterwards by measuring 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG) referred to deoxyguanosine (dG) by means of high performance liquid chromatography with electrochemical-coulometric and ultraviolet detection. Levels of oxo8dG in the renal genomic DNA significantly increased by more than 100% after the KBrO3 treatment. This increase was completely abolished by the treatment with resveratrol and was partially prevented by melatonin, PBN and vitamin E. Resveratrol and PBN also prevented the increase in relative kidney weight induced by KBrO3. These results show that various different antioxidants and a free radical trap, working in either the water-soluble or the lipid-soluble compartments, can prevent the oxidative DNA damage induced in the kidney by the carcinogen KBrO3.

Do vitamin E supplements in diets for laboratory animals jeopardize findings in animal models of disease?

Vitamin E has been supplemented to the diets of farm animals to improve fertility, health, growth rates and quality of animal products. Because of the positive experience obtained in farm animals, vitamin E has been added in increasing amounts to the diets of laboratory animals. Today, vitamin E levels in standard rodent maintenance diets range from 30 mg/kg (France, United States), 90-120 mg/kg (Netherlands, United Kingdom) to as much as 200 mg/kg (Germany). While increasing fertility and health of laboratory animals, these vitamin E supplements affect diverse pathophysiological conditions and thus the outcome of animal models of disease. Because of the large variability of vitamin E levels between laboratories within and between different countries, results obtained in established animal models may no longer be comparable and/or reproducible. Researchers should be aware of these vitamin E supplements and carefully control for potential effects in their respective animal models that involve--or may involve--the generation of reactive oxygen species.

Effect of dietary vitamin E on antioxidant status and antioxidant enzyme activities in Sprague-Dawley rats

The effect of dietary vitamin E on plasma, red blood cells (RBC), hepatic antioxidant status, and antioxidant enzyme activities was investigated. Three groups of six Sprague-Dawley rats were fed 0, 100, or 1,500 ppm vitamin E for eight weeks. Plasma alpha-tocopherol level was increased significantly by increasing dietary vitamin E (p < 0.05). Plasma lipid peroxidation (thiobarbituric acid-reactive substances) stimulation by 1 mM t-butyl hydroperoxide was correlated with dietary vitamin E level and was significantly greater in rats fed no vitamin E than in rats fed 100 or 1,500 ppm vitamin E (p < 0.05). RBC reduced glutathione (GSH) level was positively correlated with dietary vitamin E and was significantly greater in rats fed 1,500 ppm vitamin E than in rats fed 0 or 100 ppm vitamin E (p < 0.05). RBC oxidized glutathione was negatively correlated with dietary vitamin E. GSH redox status was expressed as the GSH-to-total GSH ratio; the ratio was also positively correlated with dietary vitamin E and was significantly greater in rats fed 1,500 ppm vitamin E than in rats fed no vitamin E (p < 0.05). For antioxidant enzymes, superoxide dismutase activity in hepatic cytosolic fraction was significantly greater in rats fed 1,500 ppm vitamin E than in rats fed 100 ppm vitamin E. Hepatic GSH reductase activity was significantly greater in rats fed 100 ppm vitamin E than in rats fed no vitamin E (p < 0.05). Dietary vitamin E had no effect on plasma vitamin C and protein thiol levels. In the systems studied, results indicated that dietary vitamin E selectively influences plasma vitamin E level, RBC GSH status, and hepatic cytosolic superoxide dismutase and GSH reductase activities.

Influence of dietary fat and vitamin E on antioxidant status of muscles of turkey

The aim of this study was to better understand the effects of more or less unsaturated fat source (tallow/soy oil/rapeseed oil) and/or vitamin E dietary supplementation (200 ppm) on the antioxidant status (at day 1 post-mortem) of turkey muscles [pectoralis major (Pm) and sartorius (S)]. More particularly, when turkeys were fed tallow, supplementation was sufficient to improve significantly the vitamin E status. Feeding rapeseed oil increased the antioxidant enzyme (AOE) activities (catalase, superoxide dismutase, glutathion reductase), glutathione concentration, and value from the benzoic acid test. Dietary soy oil increased glutathione peroxidase activity, compared to other dietary fat sources. With tallow, most of AOE activities were lower than with rapeseed or soy oil. Whatever the feeding mode, vitamin E supplementation did not affect the AOE activities, glutathione concentration, or values from the benzoic acid test. AOE activities were always higher in the oxidative S muscle than in the glycolytic Pm muscle. After feeding tallow, 9 days of storage increased TBA-RS and carbonyl contents, whereas the activity of many antioxidant enzymes and the total antioxidant activity (TEAC test and benzoic acid test) decreased.

Dietary antioxidant supplementation reverses age-related neuronal changes

Evidence suggests that reactive oxygen species in brain may play a role in the development of age-related neuronal impairments, and that the increase in the concentration of the proinflammatory cytokine, interleukin-1beta (IL-1beta), in aged brain tissue, may also be a contributory factor. In this study, we have analyzed changes in enzymatic and nonenzymatic antioxidant levels, in parallel with interleukin-1beta concentration, in cortical tissue prepared from young and aged rats. We report that there was an age-related increase in the activity of superoxide dismutase without concomitant changes in the activity of catalase or glutathione peroxidase and an age-related decrease in the concentrations of alpha-tocopherol and ascorbate. These observations, coupled with age-related increases in lipid peroxidation and interleukin-1beta concentration, are consistent with a compromised antioxidant defense in cortex of aged rats, a proposal supported by the finding that these changes were not observed in cortical tissue prepared from rats fed on a diet supplemented with alpha-tocopherol and ascorbate for 12 weeks.

Endotoxin increases oxidative injury to proteins in guinea pig liver: protection by dietary vitamin C

Current information suggests that oxidative damage plays a key role in septic shock induced by endotoxin. This raises the possibility that dietary antioxidant vitamins could protect against endotoxin damage. In this study, the effects of endotoxin administration on protein and lipid oxidative damage and endogenous antioxidants were studied in the liver of guinea pigs previously supplemented with marginal or optimum levels of dietary vitamin C, vitamin E or both. Vitamins C and E inhibited in vitro lipid peroxidation in endotoxin-treated animals. Endotoxin significantly increased oxidative damage to liver proteins in animals receiving low doses of both vitamins, a result described here for the first time. This increase was totally prevented in guinea pigs supplemented with vitamin C alone or in combination with vitamin E, a treatment which strongly increased liver ascorbate. Vitamin C caused small significant increases in superoxide dismutase and glutathione, increased uric acid, and synergically increased alpha-tocopherol levels in vitamin E-supplemented animals treated with endotoxin. The results show that dietary vitamin C protects against endotoxin-induced oxidative damage to proteins in the guinea pig liver. This seems mainly due to a direct protective effect of the increased hepatic ascorbate levels present in vitamin C-supplemented animals.

ADP-regulation of mitochondrial free radical production is different with complex I- or complex II-linked substrates: implications for the exercise paradox and brain hypermetabolism

In agreement with classic studies, succinate-supplemented rat and pigeon heart and nonsynaptic brain mitochondrial free radical production is stopped by ADP additions causing the stimulation of respiration from State 4 to State 3. Nevertheless, with Complex I-linked substrates, mitochondria produce free radicals in State 3 at rates similar or somewhat higher than during resting respiration. The absence of sharp increases in free radical production during intense respiration is possible due to strong decreases of free radical leak in State 3. The results indicate that Complex I is the main mitochondrial free radical generator in State 3, adding to its already known important generation of active oxygen species in State 4. The observed rate of mitochondrial free radical production with Complex I-linked substrates in the active State 3 can help to explain two paradoxes: (a) the lack of massive muscle oxidative damage and shortening of life span due to exercise, in spite of up to 23-fold increases of oxygen consumption together with the very low levels of antioxidants present in heart, skeletal muscle, and brain; (b) the presence of some degree of oxidative stress during exercise and hyperactivity in spite of the stop of mitochondrial free radical production by ADP with succinate as substrate.