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.     

A ferriprotoporphyrin IX-chloroquine complex promotes membrane phospholipid peroxidation. A possible mechanism for antimalarial action

Selenium-dependent glutathione peroxidase activity is documented for the first time in insects. Reduction in glutathione peroxidase activity in the cytosol of adult house flies by lowering selenium in the diet results in significant increases in peroxidative injury. Catalase activity, while higher in low-selenium flies than in selenium-supplemented flies, does not prevent lipid peroxidation. The discovery of glutathione peroxidase activity in insects eliminates an anomaly which partially limited the usefulness of these animals as models for the study of the antioxidant defense system.     

Cytosolic factors which affect microsomal lipid peroxidation in lung and liver

Studies were carried out to determine the effects of lung and liver cytosol on pulmonary and hepatic mierosomal lipid peroxidation, to determine the cytosolic concentrations of various substances which affect lipid peroxidation, and to determine which of these substances is responsible for the effects of the cytosol on lipid peroxidation. Lung cytosol inhibits both enzymatic (NADPH-induced) and nonenzymatic (Fe²⁺-induced) lung microsomal lipid peroxidation. In contrast, liver cytosol stimulates lipid peroxidation in hepatic microsomes during incubation alone, enhances Fe²⁺-stimulated lipid peroxidation, and has no effect on the NADPH-induced response. Substances which are known to be involved in inhibition of lipid peroxidation, including glutathione, glutathione reductase, glutathione peroxidase, and superoxide dismutase, are found in greater concentrations in liver cytosol than in lung cytosol. However, ascorbate is found in approximately equal concentrations in pulmonary and hepatic cytosol. Most of the effects of the cytosol on lipid peroxidation seem to be due to ascorbate and glutathione. For example, ascorbate, in concentrations found in lung cytosol, inhibits lung microsomal lipid peroxidation to about the same extent as the cytosol. The effects of liver cytosol on hepatic microsomal lipid peroxidation can be duplicated by concentrations of ascorbate and glutathione normally found in the cytosol; i.e., ascorbate stimulates and glutathione inhibits lipid peroxidation with the net effect being similar to that of liver cytosol. The results indicate that ascorbate has opposite effects on pulmonary and hepatic microsomal lipid peroxidation and suggest that ascorbate plays a major role in protecting pulmonary tissue against the harmful effects of lipid peroxidation.     

Acetaldehyde-dependent oxidation of glutathione catalyzed by rat liver cytosol

We have identified a novel reaction in which acetaldehyde promotes rat hepatic cytosolic catalysis of O2 consumption coupled with glutathione oxidation without apparent release of activated forms of O2. Acetaldehyde is not consumed in the reaction. The reaction (O2 consumption or oxidized glutathione production) is saturable with respect to varying glutathione (K'm congruent to 20-45 microM) but not at high acetaldehyde concentrations. However, activity in the range of acetaldehyde found in liver from alcohol metabolism (10-100 microM) appeared to be saturable (K'm congruent to 25-50 microM). Since neither acetaldehyde-dependent glutathione loss nor O2 consumption is detectable in guinea pig hepatic cytosol or hepatic cytosol from selenium-deficient rats, we propose that acetaldehyde interacts with glutathione peroxidase, converting the enzyme into a glutathione oxidase.     

Investigation of lipid peroxide and glutathione redox status of chicken concerning on high dietary selenium intake

This study was designed to investigate the effects of excess (24.5 mg Se/kg feed) inorganic and organic dietary selenium supplementation on 3-week-old broilers. The experiments lasted 4 days. Intensity of lipid peroxidation processes (malondialdehyde, MDA) and the amount (reduced glutathione, GSH) and activity (glutathione peroxidase activity, GSHPx) of gluathione redox system were measured in blood plasma, red blood cell hemolysate and liver. Voluntary feed intake in the selenium-treated groups reduced remarkably. Elevated GSH concentration and GSHPx activity were measured in plasma and liver of both selenium-treated groups compared to the untreated control and the 'pair-fed' controls. The lipid peroxidation processes in the liver showed higher intensity than the control due to both selenium treatment. The applied dose of selenite and selenomethionine does not inhibit, but even improves the activity of glutathione redox system in the liver during the early period of selenium exposure.     

Effect of selenium on the system of superoxide anion radical formation and detoxication in hepatocarcinogenesis

It is established that the introduction of selenium in combination with diethylnitrosamine into rat organisms has a preventive influence on the tumour formation. The intensity of superoxide radicals formation by the liver cell microsomes in this case decreases, while the activity of superoxide dismutase, glutathione peroxidase I, glutathione reductase and concentration of selenium in microsomes increases. The anticarcinogenic action of selenium is considered as a result of an increase in the activity of superoxide dismutase, glutathione peroxidase I and glutathione reductase. This increase induces detoxication of superoxide radicals forming in considerable amounts in rat liver cells under the effect of carcinogen.     

Effect of chronic ethanol treatment on the t-butyl hydroperoxide-dependent lipid peroxidation in rat liver

1. The effect of chronic ethanol consumption on the level of the t-butyl hydroperoxide (Bu'OOH)-induced lipid peroxidation in rat liver homogenate and subcellular fractions was measured using chemiluminescence technique and malondialdehyde formation. 2. It was shown that under the action of ethanol the rate of lipid peroxidation was decreased in the whole and "postnuclear" liver homogenates. 3. Ethanol significantly decreased the intensity of lipid peroxidation in microsomes, but did not affect the Bu'OOH-dependent process in mitochondria. 4. The level of lipid peroxidation was reduced after incubation of the total particulate fraction (mitochondria plus microsomes) with the undialysed cytosol from ethanol-treated rat liver. Dialysis of the cytosol prevented depressive effect of ethanol treatment on lipid peroxidation. 5. Reduced glutathione (0.1-1.0 mM) was shown to decrease the rate of lipid peroxidation in rat liver microsomes, but did not affect its level in mitochondria. 6. Pyrazole injections to rats reduced and phenobarbital treatment increased the level of the Bu'OOH-dependent lipid peroxidation in liver microsomes. 7. The data obtained indicate that the Bu'OOH-dependent lipid peroxidation is not an appropriate marker of the ethanol-induced oxidative stress in rat liver cells.     

Changes in peroxidation under conditions of 3,4-benzypyrene-induced carcinogenesis

The activities of enzymatic systems generating and destroying peroxides and the lipid peroxide content in neoplastic rat liver and 3,4-benzpyrene-induced sarcoma were studied. The tumour was characterized by high activity of glutathione peroxidase and low activity of catalase. No urate- and glycolate oxidases or ascorbat dependent peroxidation of lipids and lipid peroxides were found in the tumour. In the liver of neoplastic animals the activities of glutathione peroxidase and NADPH-dependent system of microsomal phospholipid peroxidation and the lipd peroxides content were increased, whereas the activities of catalase and urate oxidase were decreased.     

Characterization of Oxidative Stress in Various Tissues of Diabetic and Galactose-fed Rats

Rats fed a galactose-rich diet have been used for several years as a model for diabetes to study, particularly in the eye, the effects of excess blood hexoses. This study sought to determine the utility of galactosemia as a model for oxidative stress in extraocular tissues by examining biomarkers of oxidative stress in galactose-fed rats and experimentally-induced diabetic rats. Sprague-Dawley rats were divided into four groups: experimental control; streptozotocin-induced diabetic; insulin-treated diabetic; and galactose-fed. The rats were maintained on these regimens for 30 days, at which point the activities of catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as levels of lipid peroxidation and reduced and oxidized glutathione were determined in heart, liver, and kidney. This study indicates that while there are some similarities between galactosemic and diabetic rats in these measured indices of oxidative stress (hepatic catalase activity levels and hepatic and renal levels of oxidized glutathione in both diabetic and galactosemic rats were significantly decreased when compared to normal), overall the galactosemic rat model is not closely parallel to the diabetic rat model in extra-ocular tissues. In addition, several effects of diabetes (increased hepatic glutathione peroxidase activity, increased superoxide dismutase activity in kidney and heart, decreased renal and increased cardiac catalase activity) were not mimicked in galactosemic rats, and glutathione concentration in both liver and heart was affected in opposite ways in diabetic rats and galactose- fed rats. Insulin treatment reversed/prevented the activity changes in renal and cardiac superoxide dismutase, renal and cardiac catalase, and hepatic glutathione peroxidase as well as the hepatic changes in lipid peroxidation and reduced and oxidized glutathione, and the increase in cardiac glutathione. Thus, prudence should be exercised in the use of experimentally galactosemic rats as a model for diabetes until the correspondence of the models has been more fully characterized.     

Role of a partially purified glutathione S-transferase from rat liver nuclei in the inhibition of nuclear lipid peroxidation

Glutathione protects isolated rat liver nuclei against lipid peroxidation by inducing a lag period prior to the onset of peroxidation. This GSH-dependent protection was abolished by exposing isolated nuclei to the glutathione S-transferase inhibitor S-octylglutathione. In incubations containing 0.2 mM S-octylglutathione, the GSH-induced lag period was reduced from 30 to 5 min. S-Octylglutathione (0.2 mM) also completely inhibited nuclear glutathione S-transferase activity and reduced glutathione peroxidase activity by 85%. About 70% of the glutathione S-transferase activity associated with isolated nuclei was solubilized with 0.3% Triton X-100. This solubilized glutathione S-transferase activity was partially purified by utilizing a S-hexylglutathione affinity column. The partially purified nuclear glutathione S-transferase exhibited glutathione peroxidase activity towards lipid hydroperoxides in solution. The data from the present study indicate that a glutathione S-transferase associated with the nucleus may contribute to glutathione-dependent protection of isolated nuclei against lipid peroxidation. Evidence was obtained which indicates that this enzyme is distinct from the microsomal glutathione S-transferase.     

The effect of age and selenium on some biochemical parameters in rat liver

Two age groups, 3 and 15 mo, were used to investigate whether age-associated changes in some parameters related to lipid peroxidation occur in the liver of male Wistar rats and to observe possible effects of dietary selenium supplementation (0.25 and 0.50 ppm) for 12 mo on the same parameters. At these experimental conditions, the most important observation was that peroxidation did not change by aging, at least until 15 mo of age. In addition, the activity of Sedependent glutathione peroxidase (GSH-Px, EC 1.11.1.9) was higher in the liver of the older animals. It is suggested that the enzyme could have a role in the unchanged hepatic peroxidation observed in aged male rats. On the other hand, an effect of dietary selenium supplementation on those parameters was not observed, probably because the selenium levels were still at an adequate plateau.     

Glutathione peroxidase activities during selenium depletion of adult female rats and during selenium repletion of their offspring

The main purpose of the present investigation was to produce young rats with severe selenium deficiency, but with no clinical signs of this deficiency, and to examine their liver and red blood cell (RBC) glutathione peroxidase activities during selenium repletion. To achieve this goal, female breeders were fed a selenium-deficient diet beginning 2 weeks before mating. The liver glutathione peroxidase activity of the dams was significantly lower than the activity of comparable nonpregnant females after 5 and 10 weeks of selenium depletion. This difference arose exclusively during the period of pregnancy. In contrast, the RBC glutathione peroxidase activity was significantly increased during this period. Only traces of liver enzyme activity were found in the offspring, and the RBC enzyme activity was only 2% of that of the selenium-repleted controls. Body weight was retarded in the male offspring. However, no severe signs of clinical selenium deficiency were observed. The glutathione peroxidase activity in the liver and RBCs of the offspring was determined after 0, 2, 4, 7, 14, and approximately 40 days of selenium repletion. The liver enzyme activity increased faster in females than in males, while the opposite was found for the RBCs. After 14 days of selenium repletion, the glutathione peroxidase activity of the liver was essentially restored, and the RBC enzyme activity was about half that of the control values. This type of rat may prove useful in studies in which young selenium-deficient rats are preferable, as well as in studies of selenium functions that might not be directly related to the role of selenium in glutathione peroxidase.     

Effect of selenium on resistance of hemoglobin to photooxidative processes

On an example of a guinea pig it is shown that exogenous selenium (0.5 mg Na2SeO3 per 1 kg of the animal weight) during 2-hour exposition in the animal organism increases the resistance to the photo-induced oxidation of haemoglobin in erythrocyte lysates without additional stimulation of glutathione peroxidase mechanism of haemoglobin protection by exogenous selenium. It is shown that the saturation of haemoglobin fractions by selenium hampers the oxidative modification of haemoglobin. Using pregnancy of women as a natural model of selenium-deficiency condition, it has been shown that physiological debilitation of saturation erythrocytes with selenium, including haemoglobin fractions of lysates erythrocytes caused debilitation of resistance of haemoglobin to photooxidative destruction. Under these conditions not only activity of enzyme glutathione peroxidise in erythrocyte lysates, but also the peroxidase activity of haemoglobin (in the presence of glutathione) were decreased. It is more characteristic of erythrocyte lysates with a less content of selenium, i.e. for the erythrocytes of women on late terms of pregnancy that testifies to the presence of certain relation between haemoglobin saturation with selenium and its peroxidase activity (in the presence of glutathione).     

Selenium and Vitamin E Modulates Radiation-Induced Liver Toxicity in Pregnant and Nonpregnant Rat: Effects of Colemanite and Hematite Shielding

The levels of liver lipid peroxidation, glutathione peroxidase, reduced glutathione, and vitamins A and E were used to follow the level of oxidative damage caused by ionizing radiation in pregnant rats. The possible protective effects of selenium and vitamin E supplemented to rats housed in concrete-protected cages using hematite and colemanite were tested and compared to untreated controls. Ninety-six rats were randomly divided into four main equal groups namely control (A), normal concrete (B), concrete containing colemanite (C), and concrete containing hematite (D). Except group A, all groups exposed to 7 Gy radiation. The four main groups were divided into four subgroups each as follows: subgroups 1 (n?=?6): nonpregnant control rats. Subgroups 2 (n?=?6): selenium and vitamin E combination was intraperitoneally (i.p.) given to the nonpregnant rats for 20 days. Subgroups 3 (n?=?6): pregnant control rats. Subgroups 4 (n?=?6): selenium and vitamin E combination was i.p. given to the pregnant rats for concessive 20 days. Lactate dehydrogenate, alkaline phosphates, and lipid peroxidation values were higher in subgroups 1 and 3 than in no radiation group although glutathione peroxidase and vitamin E levels in liver were lower in radiation group than in no radiation group. Lactate dehydrogenate activity and lipid peroxidation levels were found to be decreased in subgroups 2 and 4 protected with concrete containing hematite and colemanite when compared to subgroup 1 and 3 with normal concrete. The radiation doses in rats housed by concrete without colemanite and hematite exposed radiation clearly showed liver degeneration. In conclusion, selenium and vitamin E supplementations and housing by concrete with colemanite was found to offer protection against gamma-irradiation-induced liver damage and oxidative stress in rats, probably by exerting a protective effect against liver necrosis via its free radical scavenging and membrane stabilizing. Protective effects of colemanite in the liver seem to be more important than in hematite.     

The effects of in vitro lipid peroxidation on the activity of rat liver microsomal glutathione S-transferase from rats supplemented or deficient in antioxidants

Glutathione S-transferases are a group of multifunctional isozymes that play a central role in the detoxification of hydrophobic xenobiotics with electrophilic centers (1). In this study we investigated the effects of in vitro lipid peroxidation on the activity of liver microsomal glutathione S-transferases from rats either supplemented or deficient in both vitamin E and selenium. Increased formation of malondialdehyde (MDA), a by-product of lipid peroxidation, was associated with a decreased activity of rat liver microsomal glutathione S-transferase. The inhibition of glutathione S-transferase occurred rapidly in microsomes from rats fed a diet deficient in both vitamin E and selenium (the B diet) but was delayed for 15 minutes in microsomes from rats fed the same diet but supplemented with these micro-nutrients (B+E+Se diet). Lipid peroxidation inhibits microsomal glutathione S-transferase and this inhibition is modulated by dietary antioxidants.     

Effects of new antioxidant compounds PNU-104067F and PNU-74389G on antioxidant defense in normal and diabetic rats

Diabetes mellitus and its complications are associated with elevated oxidative stress, leading to much interest in antioxidant compounds as possible therapeutic agents. Two new classes of antioxidant compounds, the pyrrolopyrimidines and the 21-aminosteroids, are known to inhibit lipid peroxidation and other biomolecular oxidation. We hypothesized that in the presence of excess oxidants or the impaired antioxidant defense seen in diabetes mellitus, administration of antioxidants such as these may reverse the effects of diabetes on antioxidant parameters. This study measured the effects of subchronic (14 day) treatment with a pyrrolopyrimidine (PNU-104067F) or a 21-aminosteroid (PNU-74389G) in normal and diabetic Sprague-Dawley rats. Activity levels of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, concentrations of oxidized and reduced glutathione, and lipid peroxidation were used as measures of antioxidant defense in liver, kidney, heart, and brain tissue. In normal rats, the only effect was a 43% increase in cardiac lipid peroxidation after treatment with PNU-104067F. In diabetic rats, the only reversals of the effects of diabetes were a 30% decrease in hepatic glutathione peroxidase activity after PNU-74389G treatment and a 33% increase in cardiac glutathione disulfide concentration after PNU-104067F treatment. In contrast to these effects, increased cardiac glutathione peroxidase and catalase activities, increased brain glutathione peroxidase activity, increased hepatic lipid peroxidation, decreased hepatic glutathione content, and decreased hepatic catalase activity were seen in diabetic rats, reflecting an exacerbation of the effects of diabetes.     

Effects of selenium on RNA synthesis and content in rat pancreas.

In order to investigate the effect of selenium supplementation on RNA in the rat pancreas, the rate of in vitro incorporation of [3H]uridine into RNA by pancreas slices derived from two groups of rats fed either a low-selenium diet or a diet supplemented with 0.25 mg/kg selenium as selenite was examined. The RNA and lipid peroxide contents and glutathione peroxidase activity in homogenates from the pancreas were also determined. After feeding for 12-14 weeks, the rates of [3H]uridine incorporation were significantly higher in the pancreatic tissue from the selenium-supplemented diet group. Concomitantly, an increase in glutathione peroxidase activities and RNA content, and a reduction of lipid peroxides, were also found in the pancreatic tissue of the selenium-supplemented group. The results suggest that selenium supplementation at a level of 0.25 mg/kg selenium could promote RNA synthesis with an increase in glutathione peroxidase activity and a decrease of lipid peroxides.     

Purification of a cytosolic enzyme from human liver with phospholipid hydroperoxide glutathione peroxidase activity

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a selenoprotein which inhibits peroxidation ofmicrosomes. The human enzyme, which may play an important role in protecting the cell from oxidative damage, has not been purified or characterized. PHGPx was isolated from human liver using ammonium sulphate fractionation, affinity chromatography on bromosulphophthalein-glutathione-agarose, gel filtration on Sephadex G-50, anion exchange chromatography on Mono Q resin and high resolution gel filtration on Superdex 75. The protein was purified about 112,000-fold, and 12 μg, was obtained from 140 g of human liver with a 9% yield. PHGPx was active on hydrogen peroxide, cumene hydroperoxide, linoleic acid hydroperoxide and phosphatidylcholine hydroperoxide. The molecular weight, as estimated from non-denaturing gel filtration, was 16,100. The turnover number (37°C, pH 7.6) on (β-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl)-γ-palmitoyl)-l-α-phosphatidylcholine was 91 mol mo⁻¹ s⁻¹. As reported for pig PHGPx, activity of the enzyme from human liver on cumene hydroperoxide and on linoleic acid hydroperoxide was inhibited by deoxycholate. In the presence of glutathione, the enzyme was a potent inhibitor of ascorbate/Fe induced lipid peroxidation in microsomes derived from human B lymphoblastic AHH-1 TK ± CHol cells but not from human liver microsomes. Human cell line microsomes contained no detectable PHGPx activity. However, microsomes prepared from human liver contained 0.009 U/mg of endogenous PHGPx activity, which is 4–5 times the activity required for maximum inhibition of lipid peroxidation when pure PHGPx was added back to human lymphoblastic cell microsomes. PHGPx from human liver exhibits similar properties to previously described enzymes with PHGPx activity isolated from pig and rat tissues, but does not inhibit peroxidation of human liver microsomes owing to a high level of PHGPx activity already present in these microsomes.     

Influence of a low-selenium diet on erythrocyte glutathione peroxidase and alkane production in exhaled air of rats as a measure of lipid peroxidation in vivo during growth

Erythrocyte glutathione peroxidase activity and alkane production in exhaled air of growing rats were studied as a measure of lipid peroxidation in vivo. When 4-weeks-old, rats were fed a low-selenium (0.05 mg/kg) refined soy concentrate-based diet but adequate in vitamin E and other nutrients. Rats of control groups were fed the same diet supplemented with varying amounts of selenium as sodium selenite. After 10 weeks, erythrocyte glutathione peroxidase activity in the group fed the low selenium diet had decreased to about 40% of the original level. Feeding this diet for a longer period resulted in a slow increase of the glutathione peroxidase level. After about 37 weeks, this level was equal to the initial level. During the same period of rapid growth, ethane and pentane production in the exhaled air of a group of similar animals on the diet containing 0.05 mg Se per kg was slightly although significantly higher compared with the levels of animals on a supplemented (0.4 mg Se per kg) diet. Differences were highest when glutathione peroxidase activity levels in the erythrocytes were lowest and negligible at the start of the experiment and after the period of rapid growth. These results support the view that the seleno-enzyme glutathione peroxidase is active in the defense mechanism of the cell against lipid proxidation.     

Effects of selenium-deficient diets on the production of prostaglandins and other oxygenated metabolites of arachidonic acid and linoleic acid by rat and rabbit aortae

Selenium is an essential component of glutathione peroxidase, which reduces free and esterified hydroperoxides of polyunsaturated fatty acids. Adequate glutathione peroxidase activity could be important for the maintenance of prostacyclin synthesis by blood vessels, since hydroperoxides can inhibit the formation of this substance. We have investigated the effects of dietary selenium deficiency on glutathione peroxidase activity and the synthesis of 6-oxoprostaglandin F1 alpha and monohydroxy and trihydroxy metabolites of polyunsaturated fatty acids by aorta. The latter products can be formed either by the actions of cyclooxygenase or lipoxygenase or by lipid peroxidation. Aortic glutathione peroxidase activity was reduced by over 80% by feeding rats a selenium-deficient diet for 4 weeks, and to undetectable levels after 6 weeks. There were no appreciable differences in the levels of free and esterified oxygenated metabolites of linoleic acid or arachidonic acid between the control and treated groups after 4 weeks. However, after 6 weeks, there were modest, but statistically significant reductions in the formation of 6-oxoprostaglandin F1 alpha and monohydroxy products formed by cyclooxygenase. On the other hand, the amounts of esterified 18:2 metabolites appeared to be higher in aortae from animals on the selenium-deficient diet, although only the increase in esterified 9-hydroxy-10,12-octadecadienoic acid was statistically significant. These results suggest that selenium deficiency can affect the formation of prostacyclin and other oxygenated metabolites of polyunsaturated fatty acids by aorta, possibly by increasing lipid peroxidation. However, the differences between control and selenium-deficient rats after 6 weeks were not very dramatic, in spite of the fact that glutathione peroxidase activity was undetectable. It would therefore appear that additional mechanisms are also involved in controlling the levels of lipid hydroperoxides in aorta.