Showing papers on "Oxidative stress published in 1987"

Alterations in Free Radical Tissue-Defense Mechanisms in Streptozocin-Induced Diabetes in Rat: Effects of Insulin Treatment

Abstract: We investigated the possible involvement of reactive oxygen radical-related processes in chronic (12-wk) diabetes induced in rats by streptozocin (STZ). Diabetes was associated with significantly increased activities of catalase (CAT), glutathione reductase (GSSG-RD), and CuZn-superoxide dismutase (SOD) in the pancreas and of CAT and GSSG-RD in the heart. On the other hand, the liver of diabetic rats showed a generalized decrease in CAT, glutathione peroxidase (GSH-PX), and SOD as well as in the levels of reduced glutathione (GSH). Diabetic kidney also showed decreases in CAT and SOD, but the activities of GSH-PX were increased. Insulin treatment (9-12 U/kg body wt) that was started after 8 wk of diabetes and continued for 4 wk reversed all of the foregoing alterations in tissue antioxidant status. Our results suggest the presence of increased oxidative stress in uncontrolled diabetes as manifested by the marked alterations in tissue antioxidant enzyme activities, the magnitude of which increased with the degree of emaciation. The complex patterns of changes observed in the various tissues examined are believed to be the result of compensatory increases in enzyme activities (usually involving enzymes whose activity in control tissues is low) and direct inhibitory effects, possibly resulting from an increased tissue-oxidant activity. Our findings support the view that tissue antioxidant status may be an important factor in the etiology of diabetes and its complications.

Oxidative stress in chemical toxicity.

Abstract: The toxic effects of compounds which undergo redox cycling via enzymatic one-electron reduction are reviewed. First of all, the enzymatic reduction of these compounds leads to reactive intermediates, mainly radicals which react with oxygen, whereby superoxide anion radicals are formed. Further oxygen metabolites are hydrogen peroxide, singlet oxygen and hydroxyl radicals. The role of these oxygen metabolites in toxicity is discussed. The occurrence of lipid peroxidation during redox cycling of quinonoide compounds, e.g., adriamycin, and the possible relationship to their toxicity is critically evaluated. It is shown that iron ions play a crucial role in lipid peroxidation induced by redox cycling compounds. DNA damage by metal chelates, e.g., bleomycin, is discussed on the basis of findings that enzymatic redox cycling of a bleomycin-iron complex has been observed. The involvement of hydroxyl radicals in bleomycin-induced DNA damage occurring during redox cycling in cell nuclei is claimed. Redox cycling of other substances, e.g., aromatic amines, is discussed in relation to carcinogenesis. Other chemical groups, e.g., nitroaromatic compounds, hydroxylamines and azo compounds are included. Other targets for oxygen radical attack, e.g., proteins, are also dealt with. It is concluded that oxygen radical formation by redox cycling may be a critical event in toxic effects of several compounds if the protective mechanisms of cells are overwhelmed.

Free radical mediated cell toxicity by redox cycling chemicals.

Abstract: Free radical formation has been implicated in the toxicity of a wide range of xenobiotics. In recent years, particular interest has been paid to compounds which can undergo a one electron reduction to form a radical species which can then react with oxygen forming superoxide (O2.-) and regenerating the parent molecule. This process, which is called redox cycling, leads to a disproportionate consumption of O2 and cellular reducing equivalents and the formation of active oxygen species, ultimately causing oxidative stress. It has been proposed that cell death results from a loss in control of Ca2+ homeostasis caused by thiol oxidation at critical enzyme sites. Physical properties of redox cycling compounds such as their one electron reduction potentials are important in determining their rate of reduction by cellular reductases and the reactivity of the radicals so formed with oxygen and other molecules. Although redox cycling of many compounds can be clearly demonstrated in vitro, the unequivocal demonstration of this process in vivo and its involvement in in vivo toxicities remains a challenging area for future research.

Improved procedure for determining glutathione in plasma as an index of myocardial oxidative stress.

Abstract: Glutathione plays an important role in the detoxification processes of electrophilic metabolites of xenobiotics and oxygen free radicals, such that release of reduced and oxidized glutathione into the plasma is considered a reliable index of oxidative stress. However, reduced glutathione in plasma undergoes spontaneous autoxidation, with mixed disulfide formation. We developed a new, simple, quick method to overcome this problem by treating the blood, immediately after collection, with thiol reagents. We add 5,5'-dithiobis(2-nitrobenzoic acid) and N-ethylmaleimide to the blood before determination of total and oxidized glutathione, respectively. We find the proposed assay useful for investigating oxidative stress in clinical situations.

Regulation of 5‐lipoxygenase activity by the glutathione status in human polymorphonuclear leukocytes

Abstract: The influence of the glutathione status of human polymorphonuclear leukocytes (PMN) on 5-lipoxygenase activity was studied by treating cells with increasing concentrations of 1-chloro-2,4-dinitrobenzene (Dnp-Cl) or azodicarboxylic acid bis(dimethylamide) (Diamide). Subsequent incubation with arachidonate resulted in an up to tenfold-stimulated formation of 5-hydroxyeicosatetraenoic acid, leukotriene B4, leukotriene B4 isomers and omega-hydroxyleukotriene B4. Higher concentrations of the GSH reagents were inhibitory. At maximal stimulation by Dnp-Cl, 5-hydroperoxyeicosatetraenoic acid started to be built up at the expense of 5-HETE at glutathione levels which were diminished by about 50% compared to resting cells. No increase in cytosolic Ca2+ could be measured under these conditions by the fura-2 method. In PMN homogenates Dnp-Cl and Diamide were without effect and even caused inhibition when 5-lipoxygenase was stimulated by Ca2+ and ATP. 15-Lipoxygenase was either unchanged in the case of Diamide, or even increased after pretreatment with Dnp-Cl. The results allow us to conclude that 5-lipoxygenase activity in intact PMN is regulated not only by Ca2+ but in a complex manner also by the glutathione redox status. Conditions of oxidative stress increase the activity which may reflect the in vivo situation under phagocytosis and oxidative burst.

Relationship among oxidative stress, growth cycle, and sporulation in Bacillus subtilis.

Abstract: The sensitivity of Bacillus subtilis to hydrogen peroxide (oxidative stress) was found to vary with the position of the culture in the growth cycle. The most dramatic change occurred at the stationary phase, when the cells became totally resistant to 10 mM H2O2, in contrast to the loss of 3 to 4 log units of viability when treated at the early log phase. Two of the eight proteins induced by a protective concentration of H2O2 (50 muM) were also induced (in the absence of oxidative stress) on entry into the late log phase of growth. The response of five isogenic spo0 mutants (spo0B, spo0E, spo0F, spo0H, and spo0J) to oxidative stress was identical to that of the wild-type parental strain. In an isogenic spo0A strain, mid-log-phase cells were 100-fold less sensitive to 10 mM H2O2 than was the wild type. Pretreatment with 50 microM H2O2 induced little further protection, suggesting that the response is constitutive in this strain. By comparison of proteins induced by 50 microM H2O2 in the wild-type, spo0A, spo0H, and spo0J strains, four proteins were identified that may be essential for protection against lethal concentrations of H2O2. The presence of multiple copies of the spo0H gene in a spo0A background converted the stress phenotype of the spo0A mutant to that of the wild type but left the sporulation phenotype unaltered.

Involvement of iron and iron-catalyzed free radical production in ethanol metabolism and toxicity.

Abstract: Lipoperoxidation, a degradative process of membranous polyunsaturated fatty acids, has been suggested to represent an important mechanism in the pathogenesis of ethanol toxicity on the liver and possibly also on the brain. Catalysis by transition metals, especially iron, is involved in the biosynthesis of free radicals contributing to lipid peroxidation. Although the exact nature of the redox-active iron implicated in this catalysis is still unknown, it has been well established that lipid peroxidation can be prevented in vitro by iron chelators such as desferrioxamine. Deprivation of redox-active iron through desferrioxamine inhibits by about 50% the microsomal oxidation of ethanol in vitro and reduces very significantly in vivo the overall ethanol elimination rate in rats. Administration of desferrioxamine together with ethanol also reduces the ethanol-induced disturbances in the antioxidant defense mechanisms of the hepatocyte. It also reduces in mice both the severity of physical dependence on ethanol and lethality following the acute administration of a narcotic dose of ethanol. Chronic overloading of rats with iron results, on the opposite, in an increased rate of ethanol elimination, although alcohol dehydrogenase and catalase activities are reduced and cytochrome P-450 depleted in the liver of such iron-overloaded animals. The magnitude of the ethanol-induced increase in lipid peroxidation and decrease in the major membranous antioxidant, alpha-tocopherol, is exacerbated in iron-overloaded rats. Several disturbances of iron metabolism have been reported in human alcoholics. Their contribution to ethanol toxicity appears very likely in the case of hepatic siderosis associated with alcohol abuse. Ethanol could however disturb iron metabolism even in the absence of gross abnormalities of the total iron stores. It is suggested that ethanol intoxication could increase cellular redox-active iron, thus contributing to an enhanced steady-state concentration of reactive-free radicals. This oxidative stress would lead to lipoperoxidative damage and cellular injury.

Hydroxyl radical generation by microsomes after chronic ethanol consumption.

Abstract: The effect of iron and other compounds known to be toxic because of the production of oxygen radicals, e.g., paraquat and menadione on the generation of hydroxyl radicals (.OH) by microsomes from chronic ethanol-fed rats and their pair-fed controls was determined. In the absence of any additions, or in the presence of ferric-chloride, -ADP or -EDTA, microsomes from the ethanol-fed rats showed a 2-fold increase in the production of .OH. Paraquat and menadione increased the generation of .OH by microsomes from the ethanol-fed and the pair-fed controls to an identical extent and thus these promoters of oxidative stress were not any more effective in interacting with microsomes after ethanol treatment. Under all conditions, .OH generation was sensitive to inhibition by catalase, implicating H2O2 as the precursor of .OH, whereas superoxide dismutase was without any significant effect. A working scheme to accommodate aspects of the interaction of iron, menadione and paraquat with microsomes with the subsequent production of .OH is described. The fact that .OH generation by microsomes in the presence of several sources of iron such as unchelated iron or ferric-ADP is elevated after chronic ethanol consumption could contribute to the hepatotoxic effects of ethanol. Studies on iron metabolism by liver cells and the effect of ethanol on the disposition of this critical trace metal are needed to further evaluate the role of oxygen radicals in the actions of ethanol.

Regulation of Redox States of Plasma Proteins by Metabolism and Transport of Glutathione and Related Compounds

Abstract: Glutathione is one of the most abundant naturally occurring thiols in living organisms and is synthesized in its reduced from (GSH). GSH has been known to play a fundamental role in cellular events in different cells and tissues, including protection of organisms against oxidative stress. The two peptide linkages of GSH are sequentially degraded by γ-glutamyltransferase and peptidases that hydrolyze the cysteinylglycine bond; all these enzymes are localized on the outer surface of cell membranes. The turnover of GSH in animals can be understood on the basis of the following three factors: (1) synthesis of GSH occurs exclusively intracellularly, while its degradation occurs predominantly extracellularly; (2) plasma membranes of many tissues and cells have secretory transport systems for GSH and its derivatives; (3) levels of the transferase, a key enzyme for GSH degradation, differ from one tissue to another. Thus, GSH released from tissues with low transferase activity (such as the liver) must be transferred for its rapid turnover to tissues with high enzyme activity (such as the kidney). Further studies on the states of thiol compounds transported via the circulation should be relevant to the understanding of the full scope and physiological significance of the interorgan cooperation of GSH metabolism. Many enzymes and proteins have free SH and disulfide groups within molecules. Function, stability, and in vivo fate of these macromolecules could be affected significantly by their redox state. Although cells and tissues have enzymic defense mechanisms against oxidative stress, the mechanism by which the homeostasis of the redox state of extracellular compartments (such as plasma, urine, bile, etc.) is maintained remains obscure. Plasma mercaptoalbumin (M-Alb) has 17 disulfide bonds and one free cysteinyl residue (Cys-34). This free thiol group can form mixed disulfides with low-molecular weight compounds, such as GSH and cysteine, to generate nonmercaptoalbumin (NM-Alb). Thus, when titrated by several different thiol reagents, less than 1 mole of free SH group (0.4–0.7) was usually detected per mole albumin. The ratio of M-Alb to NM-Alb in plasma samples varies significantly from one sample to another. Many plasma proteins in nonalbumin fractions also formed mixed disulfides with GSH and cysteine. The extent of mixed disulfide formation and the ratio of M-Alb to NM-Alb appeared to change markedly, depending on the redox state of the organisms. The present paper describes the mode of interorgan metabolism and transport of GSH and related compounds, the mechanism by which the redox state of albumin and other plasma proteins is controlled, and their biological significance in healthy and diseased conditions in normal and analbuminemic mutant rats.

Oxidative stress and growth temperature in Bacillus subtilis.

Abstract: Pretreatment of Bacillus subtilis with low concentrations of hydrogen peroxide protected the cells against the lethal effects of higher levels of oxidative stress. During the period of adaptation, eight proteins were induced, as detected by one-dimensional gel electrophoresis. Four of these proteins were the same size as four of the proteins induced by the temperature upshift. The range of proteins synthesized in response to an elevation in temperature depended both on the starting (lower) temperature and on the temperature to which the cells were shifted. Both catalase and superoxide dismutase were present at high levels in B. subtilis, but neither was induced by oxidative stress or temperature upshift. In fact, catalase activity was reduced after the temperature upshift. Images

Prevention by Fructose-1,6-bisphosphate of Cardiac Oxidative Damage Induced in Mice by Subchronic Doxorubicin Treatment

Abstract: An experimental model of mild, subchronic doxorubicin cardiotoxicity in mice was investigated by monitoring changes of biochemical parameters related to cell response against oxidative stress in both liver and heart. A specific increase of the lactate dehydrogenase isoenzyme typical of the heart was observed for doxorubicin-treated mice. Lipid peroxidation, as evaluated by malondialdehyde determination, and catalase activity were greatly increased in heart and unaffected in liver. On the other hand, these changes can be considered as indicative of early heart damage induced by doxorubicin. Glutathione, glutathione peroxidase, and 6-phosphogluconate dehydrogenase values were not significantly altered by the treatment and glucose-6-phosphate dehydrogenase increased in both liver and heart. Administration of fructose-1,6-bisphosphate strongly reduced the increase of plasma lactate dehydrogenase, heart lipid peroxidation, and heart catalase while no effect on the diagnostically irrelevant increase of glucose-6-phosphate dehydrogenase was observed. The inhibitory effect on the onset of biochemical modification typical of early subchronic doxorubicin cardiotoxicity may be related to stimulation of ATP synthesis by fructose-1,6-bisphosphate and is therapeutically promising in view of the lack of toxicity of fructose-1,6-bisphosphate as a drug.

Ethanol-induced oxidative stress in the rat cerebellum.

Abstract: An acute ethanol load (50 mmol/kg, i.p.) produces an increase in lipid peroxidation in the rat cerebellum. The levels of ascorbate and alpha-tocopherol, which represent efficient antioxidants acting synergetically, are decreased. This decrease seems highly indicative of a consumption of the antioxidants in quenching free radicals and suggests that acute ethanol induces an oxidative stress at the cerebellar level. As allopurinol, a xanthine oxidase inhibitor, prevents the decrease in alpha-tocopherol, xanthine oxidase may contribute to this oxidative stress.

Oxidative stress from alcohol in the brain.

Abstract: An acute ethanol load administered to rats results in an enhancement in lipid peroxidation in the cerebellum, a brain area which is particularly sensitive to free radical attack. The ethanol load induces also a decrease in the cerebellar concentration of the three main endogenous anti-oxidant small molecules, i.e. alpha-tocopherol, ascorbate and glutathione. These findings are highly suggestive of a cerebellar oxidative stress due to acute ethanol administration. However this administration does not enhance brain mitochondrial superoxide production as well as cerebellar mitochondrial hydrogen peroxide production. An oxidative stress could also play a role in some effects of chronic alcohol intoxication on the brain. This is particularly suggested by the beneficial effects of the administration of desferrioxamine, an iron-chelator and free radical scavenger, on physical dependence on alcohol in rodents. A speculative synthesis of the mechanisms that might be involved in such an oxidative stress on the central nervous system is presented.

Comparative study on the selenium- and N-acetylcysteine-related effects on the toxic action of hyperoxia, paraquat and the enzyme reaction hypoxanthine-xanthine oxidase in cultured endothelial cells

Abstract: The potential protective effect of N-acetylcysteine against various types of oxidative stress (exposure to hyperoxia, treatment with paraquat, incubation in the presence of the hypoxanthine-xanthine oxidase system) was tested in primary cultures of porcine aortic endothelial cells. It was compared to that of selenomethionine (Se-Met), known to increase glutathione peroxidase activity, when given either alone or in combination with N-acetylcysteine. LDH release,3H-thymidine (TdR) incorporation into DNA and DNA content were measured to assess the cytotoxic effect of the conditions tested. Total and oxidized glutathione content was also determined. Whereas Se-Met had a partial protective effect on all the conditions but paraquat treatment, N-acetylcysteine administration had no effect on the hyperoxia induced changes and significantly worsened the cytotoxic action of paraquat. On the other hand, LDH release following an incubation in the presence of the hypoxanthine-xanthine oxidase was significantly reduced after N-acetylcysteine treatment. No major change in total nor in oxidized glutathione followed N-acetylcysteine treatment in control and experimental conditions. A dose-dependent protective effect of N-acetylcysteine was obtained when this agent was given concomitantly with the xanthine oxidase system. These data suggest that in cultured endothelial cells a N-acetylcysteine-related protective effect, if present, is most likely to result from the direct scavenging action of N-acetylcysteine.

Detection of Free Radical Intermediates in the Oxidative Metabolism of Carcinogenic Hydrazine Derivatives

Abstract: Hydrazine derivatives are widely used in agriculture, in industry, as rocket propellants, and in medicine. Hydrazines also occur naturally in tobacco and mushrooms. Many hydrazines tested in animal studies appear to be carcinogenic and induce tumors in various target tissues in mice, hamsters, and rats. The use of hydrazine derivatives in humans is often complicated by adverse side-effects such as liver injury and rheumatoid arthritis. A number of studies have demonstrated that hydrazine derivatives are activated to reactive intermediates, such as free radicals, through a variety of cellular oxidative metabolic pathways. The aim of this work is to demonstrate the occurrence of free radical intermediates during the metabolic activation of various hydrazine derivatives and to characterize the enzymatic system($ responsible for the activation to free radical species. The hydrazines studied are acetylhydrazine, isoniazid, isopropylhydrazine, iproniazid, methylhydrazine, 1, I-dimethylhydrazine, and 1,2-dimethylhydrazine. The model systems chosen are those of rat liver microsomes and isolated hepatocytes. Free radical intermediates have been demonstrated by the electron spin resonance spectroscopy coupled to spin trapping technique. The activation mechanism has been characterized using inhibitors ofthe mixed function oxidase system and ofthe FAD-dependent oxygenase system. Glutathione was able to scavenge, with high efficiency, the free radicals produced.

Oxidative stress injury studied in isolated intact cells.

Abstract: Oxidative damage produced by oxygen free radicals has been investigated in various mammalian cells in culture. Incubation of these cells with redox cycling quinones resulted in a stimulation of superoxide anion and hydrogen peroxide formation. Further metabolism of H2O2 by glutathione peroxidase caused oxidation and depletion of cellular glutathione followed by oxidation of protein sulfhydryl groups and cytotoxicity. Several targets susceptible to oxidative modification have been identified, including the mitochondrial, endoplasmic reticular, and plasma membrane Ca2+-translocases. As result, a marked and sustained increase in cytosolic free Ca2+ concentration occurred, followed by the activation of some catabolic Ca2+-dependent processes, namely phospholipases, proteases, and endonucleases. In addition, an impairment of the transmembranal signal-transducing system(s) was found. Recent investigations demonstrated that several modifications occur also in the cytoskeleton of oxidative stress-challenged cells. They mainly consist of oxidative actin cross-linking and dissociation of the cytoskeleton from the plasma membrane. All these alterations appear to contribute to the multifactorial process underlying the irreversible cell injury caused by oxidative stress.

Biochemical mechanisms of oxidative liver cell injury.

Abstract: The toxicological implications of the formation of active oxygen species have attracted growing interest in recent years. Under aerobic conditions, oxygen radicals are normal cellular metabolites. However, the production of oxygen radicals may be greatly stimulated in the presence of various redox active compounds. Eventually, the stimulation of oxygen radical production may be so great as to overwhelm the cellular defence systems, create an oxidative stress and bring about toxicity. Recent studies in this laboratory indicate that glutathione and protein thiol depletion play a critical role in the development of oxidative cell injury. This depletion of cellular thiols can result in a disturbance of intracellular calcium ion homeostasis, which seems to be directly related to cell killing.