Oxidative damage in the red cells of vitamin E-deficient rats

Alterations in Ca²⁺ homeostasis and oxidative damage induced by ethion in erythrocytes of Wistar rats: ameliorative effect of vitamin E

Organophosphate (OP) insecticides have been reported to induce oxidative stress due to lipid peroxidation and alteration in defense mechanisms. It is known that calcium content in erythrocytes plays a very important in normal physiology of cells. Erythrocytes are a very convenient model to understand the susceptibility of membrane to oxidative damage induced by various xenobiotic compounds. The aim of present study was to investigate the effects of ethion induced oxidative damage, alterations in membrane bound enzymes and Ca(2+) homeostasis and a possible protective role of vitamin E. Adult male albino rats of Wistar strain were orally administered ethion and vitamin E daily for 28 days. Animals were randomly divided into four groups: control; ethion treated (2.7 mg/kgbw/day); vitamin E treated (50mg/kg of bw/day); ethion+vitamin E treated. The animals were sacrificed after 7, 14, 21 and 28 days. Erythrocyte membranes were prepared and analyzed for protein, lipid peroxidation (LPO) and membrane bound ATPases. Furthermore, Ca(2+) homeostasis as function of time and concentration was evaluated in erythrocytes. The results from the present study show that in vivo administration of ethion resulted in oxidative damage to erythrocyte membranes as evident by increased lipid peroxidation. The increased LPO following ethion intoxication was accompanied by significant decrease in the activities of Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase and disturbed Ca(2+)homeostasis in erythrocytes. Furthermore, vitamin E treatment had a beneficial effect by decreasing lipid peroxidation; partially restoring activities of membrane bound ATPases and Ca(2+) homeostasis. The present study suggests that ethion exerts its toxic effect by increasing LPO, altering the activity of membrane bound enzymes and disturbing Ca(2+) homeostasis. Vitamin E treatment ameliorated the toxic effects of ethion suggesting its role as a potential antioxidant.

Antioxidant therapy attenuates oxidative insult caused by benzonidazole in chronic Chagas' heart disease

Chronic chagasic cardiac patients are exposed to oxidative stress that apparently contributes to disease progression. Benznidazole (BZN) is the main drug used for the treatment of chagasic patients and its action involves the generation of reactive species. 41 patients with Chagas' heart disease were selected and biomarkers of oxidative stress were measured before and after 2 months of BZN treatment (5 mg/kg/day) and the subsequent antioxidant supplementation with vitamin E (800 UI/day) and C (500 mg/day) during 6 months. Patients were classified according to the modified Los Andes clinical hemodynamic classification in groups IA, IB, II and III, and the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR), as well as the contents of reduced glutathione (GSH), thiobarbituric acid reactive species (TBARS), protein carbonyl (PC), vitamin E and C and nitric oxide (NO), myeloperoxidase (MPO) and adenosine deaminase (ADA) activities were measured in their blood. Excepting in group III, after BZN treatment SOD, CAT, GPx and GST activities as well as PC levels were enhanced while vitamin E levels were decreased in these groups. After antioxidant supplementation the activities of SOD, GPx and GR were decreased whereas PC, TBARS, NO, and GSH levels were decreased. In conclusion, BZN treatment promoted an oxidative insult in such patients while the antioxidant supplementation was able to attenuate this effect by increasing vitamin E levels, decreasing PC and TBARS levels, inhibiting SOD, GPx and GR activities as well as inflammatory markers, mainly in stages with less cardiac involvement.

Antioxidant therapy attenuates oxidative stress in chronic cardiopathy associated with Chagas' disease

Oxidative stress is common in inflammatory processes of many diseases, including the Chagas' disease, which is characterized by chronic inflammation. The present study is a sequence of a related publication [Oliveira TB, Pedrosa RC, Wilhelm Filho D. Oxidative stress in chronic cardiopathy associated with Chagas' disease. Int J Cardiol in press.] on the same subjects, which showed an increase in oxidative stress associated with the progression of the severity of the disease. Components of the antioxidant system and oxidative biomarkers present in the blood were measured in the same chronic chagasic patients (n=40), before and after vitamin E (800 IU/day) and vitamin C (500 mg/day) supplementation for 6 months. Antioxidant enzymes and contents of reduced glutathione in erythrocytes and plasma TBARS contents were analyzed in four groups of patients in different stages of chronic Chagas heart disease (n=10 each group, groups I, II, III, and IV) according to the Los Andes classification. After the combined vitamin supplementation, TBARS and protein carbonyl levels were decreased in plasma, whilst red cell GSH contents were increased in group I. The vitamin E contents found in the plasma were inversely related to the severity of the disease. No differences in gamma-glutamiltransferase activities were detected but the myeloperoxidase levels were decreased in patients at the initial stages, whilst seric nitric oxide levels were increased in groups II and III. After the antioxidant supplementation, CAT activity was increased in group II, GPx activity was increased in group I, GR activity was increased in groups I and II, whilst the GST activity was decreased in groups II, III and IV. The results clearly indicate that the antioxidant supplementation was able to counteract the progressive oxidative stress associated with the disease. New perspectives for the treatment of Chagas' disease might include an antioxidant therapy in order to attenuate the consequences of oxidative insult related to this disease.

Effect of genistein supplementation on tissue genistein and lipid peroxidation of serum, liver and low-density lipoprotein in hamsters

The aim of this study was to investigate the effects of genistein supplementation in a vitamin E-deficient diet on the genistein concentrations and the lipid oxidation of serum, liver and low-density lipoprotein (LDL) of hamsters. Thirty-six male hamsters were randomly divided into three groups and fed a vitamin E-deficient semisynthetic diet (AIN-76) containing different levels of genistein, i.e., G0 (control group, genistein-free diet), G50 (50 mg genistein/kg diet) and G200 (200 mg genistein/kg diet) for 5 weeks. The concentrations of genistein in serum and liver significantly increased with the increase of genistein supplementation. The vitamin E contents in LDL were higher in hamsters fed G50 or G200 diets than in hamsters fed genistein-free diet. Genistein supplementation to hamsters significantly reduced the propagation rate during conjugated diene formation of LDL oxidation, and the lag time of LDL oxidation in hamsters fed G200 diets was significantly lower than that of G0 diets. In addition, genistein supplementation significantly raised serum total antioxidant capacity and decreased the thiobarbituric acid-reactive substances (TBARS) of LDL and liver in hamsters. However, no significant differences in TBARS were found in serum, irrespective of genistein addition. On the other hand, the relative contents of polyunsaturated fatty acids in LDL were decreased after genistein supplementation. There was a negative correlation between lag time and P/S ratio, and a positive correlation between lag time and vitamin E contents. These data demonstrate that genistein supplementation markedly increased its concentrations in body tissues and reduced oxidative stress of lipid oxidation of serum, liver and LDL.

The possible role of essential fatty acids in the pathophysiology of malnutrition: a review

Biochemical evidence of essential fatty acid deficiency (EFAD) may exist in protein-energy malnutrition (PEM). EFAD is characterised by low 18:2omega6, often in combination with low 20:4omega6 and 22:6omega3, and high 18:1omega9 and 20:3omega9. Some PEM symptoms, notably skin changes, impaired resistance to infections, impaired growth rate and disturbed development may at least partly be explained by EFAD. One or more of the following factors could induce EFAD in PEM: low EFA intake, poor lipid digestion, absorption, transport, desaturation and increased EFA beta-oxidation and peroxidation. EFAD may perpetuate itself by decreasing lipid absorption and transport, and aggravate PEM by impairing nutrient absorption and dietary calorie utilisation. Micronutrient deficiencies may contribute to the impaired EFA bioavailability and metabolism. Nutritional rehabilitation strategies in PEM may consider adequate intakes of EFA and micronutrients, e.g. by promoting breastfeeding. More research is required to gain detailed insight into the role of EFAD in PEM.

Protective effect of vitamin E in dimethoate and malathion induced oxidative stress in rat erythrocytes

Organophosphate (OP) pesticides such as dimethoate and malathion intoxication has been shown to produce oxidative stress due to the generation of free radicals and alter the antioxidant defense system in erythrocytes. It is possible that vitamin E being present at the cell membrane site may prevent OP-induced oxidative damage. In the present study, rats were pretreated orally with vitamin E (250 mg/kg body wt, twice a week for 6 weeks) prior to oral administration of a single low dose of dimethoate and/or malathion (0.01% LD(50)). The result showed that treatment with OP increased lipid peroxidation (LPO) in erythrocytes, however, vitamin E pretreated rats administered OP's showed decreased LPO in erythrocytes. The increase in the activities of superoxide dismutase (SOD) and catalase (CAT) and total-SH content in erythrocytes from dimethoate and/or malathion treated rats as compared to control appears to be a response towards increased oxidative stress. Vitamin E pretreated animals administered OP's showed a lowering in these parameters as compared to OP treated rats which indicates that vitamin E provide protection against OP-induced oxidative stress. The glutathione-S-transferase (GST) activity in erythrocytes was inhibited in OP intoxicated rats which partially recovered in vitamin E pretreated animals administered OP's. Inhibition in erythrocyte and serum acetylcholinesterase (AChE) activity was not relieved in vitamin E pretreated rats administered OP's probably due to the competitive nature of enzyme inhibition by OP's. The results show that vitamin E may amelierate OP-induced oxidative stress by decreasing LPO and altering antioxidant defense system in erthrocytes.

Cacao liquor polyphenols reduce oxidative stress without maintaining alpha-tocopherol levels in rats fed a vitamin E-deficient diet

The effect of crude polyphenols (CLP) from cacao liquor on vitamin E-deficient rats was examined. The CLP fraction contained 49.8% antioxidative polyphenols such as catechins and their oligomers. Supplementation of the vitamin E-deficient diet with CLP for 7 wk did not prevent the decrease in alpha-tocopherol levels in the liver, kidney, heart, brain, and plasma. The lipid peroxide levels in these tissues increased in the group fed the vitamin E-deficient diet compared with the control group. However, these changes were inhibited in a dose-dependent manner as a result of supplementation of the vitamin E-deficient diet with 0.25, 0.5, or 1.0% CLP. The lipid peroxide levels in plasma increased in the group fed the vitamin E-deficient diet. This change tended to be suppressed as a result of supplementation of the diet with CLP, but the difference was not significant. There was no evidence of absorption and distribution of CLP to the tissues; however, CLP intake resulted in a decrease in oxidative stress without maintaining vitamin E levels in the plasma and the tissues.

alpha-Tocopherol enhances the peroxidase activity of hemoglobin on phospholipid hydroperoxide

We have used direct separation of phospholipid hydroperoxide and phospholipid hydroxide by high performance liquid chromatography to examine the phospholipid hydroperoxide peroxidase activity of hemoglobin (Hb) in the presence of hydrogen donors. Hb exhibits phospholipid hydroperoxide peroxidase activity and rapidly breaks down phospholipid hydroperoxide to thiobarbituric acid-reactive substances. However, in the presence of alpha-tocopherol, some phospholipid hydroperoxide is converted to phospholipid hydroxide, which is more stable than the hydroperoxide and is much less reactive with thiobarbituric acid. Other electron donors such as glutathione and ascorbate are less effective than alpha-tocopherol. Free cysteine also shows some ability to reduce phospholipid hydroperoxides to corresponding hydroxides, but cys-93 beta of Hb did not participate in the reaction, as shown by N-ethylmaleimide modification. Hemin alone catalysed the reaction, in the absence of protein. The results therefore show that Hb catalyses an apparent phospholipid hydroperoxide alpha-tocopherol peroxidase reaction due to bound hemin, and that the reduction depends on the ability of hydrogen donors to react with the intermediate phospholipid alkoxyl radical and does not involve reduction by deprotonated sulfhydryl groups.

Cadmium-induced lipid peroxidation and the antioxidant system in rat erythrocytes: the role of antioxidants

Cadmium (Cd)-induced oxidative damage in erythrocytes causes loss of membrane function by enhancing lipid peroxidation (LPO) and altering the erythrocyte antioxidant system. Vitamin E and/or selenium (Se) was administered to rats, prior to Cd intoxication, in order to prepare the animals to withstand oxidative assault. The treatment with Cd increased LPO in erythrocytes while animals pretreated with vitamin E and/or Se prior to Cd treatment showed decreased LPO as compared with animals given Cd alone. The erythrocyte SOD and CAT activities decreased significantly with Cd treatment. The pretreatment with vitamin E and/or Se prior to Cd administration partially reversed such changes. The erythrocytes showed a marked depletion in glutathione (GSH) content with Cd treatment. The antioxidant treatments before Cd administration helped to maintain the erythrocyte GSH content. The erythrocyte glutathione reductase (GSH-R) activity increased markedly when treatments with vitamin E and Se were applied. The GSH-R activity was not observed to decrease in animals treated with antioxidant prior to Cd intoxication, which may mean that the replenishment of erythrocyte GSH content is via GSH-R. The glutathione-S-transferase (GST) activity increased significantly with Cd intoxication; however, treatment with antioxidants prior to Cd treatment decreased erythrocyte GST activity. The results show that Cd-induced LPO decreased the antioxidant capability of the erythrocytes, causing erythrocyte membrane damage.

Separation of representative lipid compounds of biological membranes and lipid derivatives from peroxidized polyunsaturated fatty acids by reversed phase high-performance liquid chromatography

A complex mixture of different lipid compounds, including phosphatidylcholine, phosphatidylserine, all trans-retinol, 15(S)-hydroperoxyeicosatetraenoic acid, D-alpha-tocopherol, saturated and unsaturated fatty acids can be separated by reversed phase HPLC by using a C-18, 120 mm x 4 mm, 3 microns particle size column and a step gradient from acetonitrile/water (1:1; v:v) to 100% acetonitrile at a flow rate of 0.8 ml/min. By applying this elution condition, separation of various groups of lipid hydroperoxides and lipid derivatives, each one originating from a different in vitro peroxidized polyunsaturated fatty acid, can be obtained. Simultaneous detection is carried out by a diode array detector at a wavelength accumulation range set up between 195 and 400 nm. The possibility of simultaneously having such a large number of measurements renders this chromatographic method particularly suitable in studies concerning lipid peroxidation where, in addition to the detection of free radical-induced lipid hydroperoxides, data on some key antioxidant molecules, i.e. vitamin A and E, as well as that of structural compounds of biological membranes, i.e. phosphatidylcholine and phosphatidylserine, can be achieved.

Red cell vitamin E and oxidative damage: a dual role of reducing agents

The purpose of this study was to determine the role of reducing agents in maintaining the integrity of vitamin E-deficient red cells. Three groups of one-month-old male Wistar rats were fed a basal vitamin E-deficient diet supplemented with either 0, 10 or 100 mg d, 1-alpha-tocopheryl acetate per kg diet for up to 12 weeks. Washed red blood cells (5%) were resuspended in saline-phosphate buffer, pH 7.4, and were incubated at 37 degrees C with or without containing 12.5 mM 2, 2'-azobis (2amino- propane) dihydrochloride (AAPH), 2.8 mM glucose, 1 mM ascorbic acid, 10 mM hydrogen peroxide (H2O2), 250 microM dimethylsulfoxide (DMSO) or 2.8 mM deoxyribose (DR) for up to 20 hours. Addition of either glucose, AAPH, ascorbic acid or H2O2 markedly accelerated the rates of hemolysis and lipid peroxidation in the red cells of vitamin E-deficient rats. On the contrary, both glucose and ascorbic acid were protective against oxidative damage to the red cells of vitamin E-supplemented rats in a dose-dependent manner. Also, vitamin E-supplemented red cells were more resistant to AAPH and H2O2 than the deficient cells. DMSO or. DR had no significant effects on the rates of hemolysis or lipid peroxidation. Glucose, but not others, maintained or slowed down the loss of glutathione (GSH) during incubation. The results obtained suggest a dual role of ascorbic acid and GSH in the function of vitamin E in maintaining red cell integrity: these reducing agents may exert antioxidant function by participating in vitamin E regeneration when certain levels of vitamin E is maintained, but promote oxidative damage by enhancing free radical generation when vitamin E is low or depleted.

Role of antioxidants on the erythrocytes resistance to lipid peroxidation after acute iron overload in rats

Iron overload was developed in rats by ip injection of iron-dextran. Iron concentration in plasma increased 12-fold after 20 h of iron supplementation and unsaturated iron binding capacity (UIBC) drastically decreased in iron overloaded compared to control rats (69 +/- 36 and 177 +/- 19 micrograms/dl, respectively). Lipid peroxidation in plasma increased by 285% and plasma alpha-tocopherol content decreased by 40% after 20 h of iron overload. alpha-Tocopherol supplementation decreased by 30% the measured increase in TBARS content in plasma after iron injection. On the other hand, both iron and TBARS content in erythrocytes were not significantly different in control and iron loaded rats. However, red blood cells from iron treated rats exposed to pro-oxidant conditions showed a significant increase in TBARS content as compared to control erythrocytes. alpha-Tocopherol pretreatment prevented this increase. Moreover, red blood cells from iron loaded rats showed a higher content of TBARS after incubation with plasma from iron-dextran injected rats than after incubation with plasma from control animals. This measured increase was partially prevented by alpha-tocopherol supplementation. Neither the activity of antioxidant enzymes nor the content of alpha-tocopherol in red blood cells were affected by iron overload. Total thiols content was significantly lower (30%) in erythrocytes isolated from iron treated rats. The data presented here suggest that free radical generation catalyzed by metal ions may lead to consumption of thiols. The decrease in thiols content in erythrocytes could afford an appropriate degree of protection and avoid other oxidative damage to these cells.