Showing papers on "Oxidative stress published in 1989"

Is Parkinson's disease a progressive siderosis of substantia nigra resulting in iron and melanin induced neurodegeneration?

Abstract: – Razor sharp and high iron deposits are present in the substantia nigra (SN). Although the function of such high iron content is not known, the homeostatis of brain iron is important for normal brain function. The participation of free tissue iron in oxidative stress (OS), resulting in the formation of cytotoxic hydroxyl radical (·OH) from H2O2 (Fenton reaction) and promotion of membrane lipid peroxides by ·OH can no longer be questioned as a biological phenomenon. The highly selective increase of Fe2+ and Fe3+ and lipid peroxidation observed in parkinsonian SN points to OS in such brains. Lipid peroxidation proceeds with either Fe2+ or Fe3+ provided a mechanism exists to facilitate the interconversion of iron between its redox states. Indeed H2O2 derived from MAO B reaction and autooxidation of dopamine to melanin in the SN can drive the iron dependent Fenton reaction. Furthermore, interaction of iron with melanin may be even more important considering that melanin avidly binds Fe3+ and reduce it to Fe2+, resulting in ·OH generation. Thus, without evoking environmental neurotoxins, the excessive accumulation of free iron in the SN and “melanintrap'’could be the trigger for accelerated cell death and Parkinsonism.

Impairment of glutathione metabolism in erythrocytes from patients with diabetes mellitus

Abstract: The metabolism of glutathione and activities of its related enzymes were studied in erythrocytes from patients with non-insulin-dependent diabetes mellitus (NIDDM). A decrease in the levels of the reduced form of glutathione and an increase in the levels of glutathione disulfide were found in erythrocytes of diabetics. To elucidate these changes in the levels of glutathione, synthetic and degradative processes were studied. The activity of gamma-glutamylcysteine synthetase was significantly lower in diabetics than in normal controls. The activity of glutathione synthetase of each group was the same. The rate of outward transport of glutathione disulfide in diabetics decreased to approximately 70% of that of normal controls. The activity of glutathione reductase decreased in diabetics. These data suggest that the decrease in the levels of reduced form of glutathione in erythrocytes of diabetics is brought about by impaired glutathione synthesis and that the increase in the levels of glutathione disulfide is brought about by the decreased transport activity of glutathione disulfide through the erythrocyte membrane together with a decrease in the activity of glutathione reductase. These data also suggest that the impairment of glutathione metabolism weakens the defense mechanism against oxidative stress in erythrocytes of diabetics.

Formation of 8-hydroxydeoxyguanosine in liver DNA of rats following long-term exposure to a peroxisome proliferator.

Abstract: The mechanism by which nongenotoxic peroxisome proliferators induce hepatocellular carcinomas in rats and mice remains intriguing. The available experimental evidence suggests that the proliferation of peroxisomes and induction of peroxisome-associated enzymes results in oxidative stress which then leads to tumorigenesis. However, so far no direct evidence for oxidative DNA damage in livers of peroxisome proliferator-treated animals has been established. In the present study we have examined the DNA obtained from the livers of rats treated with ciprofibrate, a potent peroxisome proliferator, for variable periods of time for 8-hydroxydeoxyguanosine (8-OH-dG), an adduct that results from the damage of DNA caused by hydroxyl radical. Administration of ciprofibrate in diet at a concentration of 0.025% for 16, 28, 36, or 40 weeks resulted in progressive increases in the levels of 8-OH-dG. At 16, 28, and 40 weeks of ciprofibrate treatment, the 8-OH-dG in the liver DNA was significantly increased as compared to controls. This increase in 8-OH-dG levels is attributed to persistent peroxisome proliferation resulting from chronic ciprofibrate treatment as no increase in 8-OH-dG was found in liver DNA of rats that received a single large dose of ciprofibrate. The results of this study clearly demonstrate, for the first time, that persistent proliferation of peroxisomes leads to specific oxidative DNA damage.

Bacterial adaptation to oxidative stress: implications for pathogenesis and interaction with phagocytic cells.

Abstract: During phagocytosis, phagocytic cells generate superoxide and other reactive oxygen species, which are involved in antibacterial activity. However, many bacteria possess antioxidant defenses that may explain their survival in inflammatory foci. These defenses include antioxidant enzymes such as superoxide dismutase and catalase, DNA repair systems, scavenging substrates, and competition with phagocytes for molecular oxygen. These defenses are probably coordinated, and different responses occur with different reactive oxygen species. Escherichia coli and Salmonella typhimurium mutants have allowed the demonstration of a variety of critical genes for enzymatic defense and DNA repair, as well as an oxyR regulon system. In more complex systems, the conditions found in inflammatory foci, such as decreasing glucose and the production of lactate, enhance bacterial catalase production and resistance to hydrogen peroxide. Resistance and adaptation to phagocyte-derived oxidant stress are critical aspects of bacterial pathogenesis.

Free Radicals and the Regulation of Mammalian Cell Proliferation

Abstract: The question of whether free radicals or free radical-related species play a role in the modulation of mammalian cell proliferation is examined. Although a positive role for free radicals as specific components of mitogenic pathways is not apparent it is clear that certain free radical-derived species can have a significant modulatory influence on components of major growth signal transduction mechanisms. Free radical-derived species are also involved in the production of prostaglandins which themselves can modulate cell growth. Free radicals themselves appear to have a down regulatory effect on cell proliferation inasmuch as protection from oxidative stress enhances cell proliferation. On the other hand, in certain cases low levels of active oxygen species can enhance cell proliferation.

Oxidative DNA damage caused by persistent peroxisome proliferation: its role in hepatocarcinogenesis.

Abstract: Peroxisome proliferations are considered as a novel class of hepatocarcinogenic agents because of their non-mutagenic nature and their ability to cause a significant increase in the levels of hydrogen peroxide generating peroxisomal fatty acid β-oxidation enzyme in the liver. Sustained increase in the number of peroxisomes in liver has been shown to induce oxidative stress in the liver. Increased levels of H 2 O 2 generation, hydroxyl free-radical formation, lipid peroxidation and accumulation of lipofuscin are found in the livers of rats following long-term treatment with peroxisome proliferators. Recent evidence indicates the presence of 8-hydroxydeoxyguanosine in the liver DNA of rats chronically treated with a peroxisome proliferator suggesting that this may be the basis for carcinogenesis by this class of non-mutagenic carcinogens.

Toxicity of aromatic thiols in the human red blood cell

Abstract: Thiophenol and 4-aminothiophenol were used to study levels of toxicity in human red blood cells. Thiophenols caused conversion of oxyhemoglobin to methemoglobin. Reduction of corresponding disulfides by intracellular glutathione caused cyclic reduction/oxidation reactions, resulting in increased oxidative flux. Three levels of oxidative stress were observed in these experiments: the lowest level resulted from incubation with 0.25 mM thiophenol; the intermediate level with 0.50 mM thiophenol or 0.25 mM 4-aminothiophenol; the highest levels with 0.50 mM 4-aminothiophenol. Methemoglobin formation increased with increasing level of oxidative stress. Glycolysis and the hexose monophosphate shunt were inhibited at the intermediate and highest levels of stress, respectively. Above the highest level of stress non-intact hemoglobin was formed and cell lysis occurred. These metabolic responses were reflected in cellular levels of NADH, NADPH and reduced glutathione. At the lowest level of oxidative stress, both glycolysis and hexose monophosphate shunt were increased such that near-normal levels of NADH, NADPH and reduced glutathione were maintained and methemoglobin formation was kept to a minimum. The response of red cells to 0.25 mM thiophenol appears to represent a level of oxidative stress to which the cell is capable of adaptive metabolic response. Glycolysis contributes approximately one-quarter of the total reducing equivalents from glucose metabolism in response to the oxidative challenge by thiophenol. The results suggest that the metabolic response to autoxidation of endogenous thiols is thiol exchange with glutathione and reduction of resulting glutathione disulfide by the hexose monophosphate shunt.

Cell proliferation and oxidative stress.

Abstract: Antioxidants such as mannitol, butylated hydroxytoluene and a-tocopherol enhance the growth of pol-yoma virus transformed and non-transformed BHK-21 cells. In the case of mannitol this is observed even in the absence of added calf serum. In part these effects may operate to protect cellular growth control mechanisms. On the other hand oxidants such as H2O2 and t-butyl hydroperoxide can inhibit growth and overall cellular protein synthesis, through mechanisms that are likely to involve radicals. In the case of H2O2, the inhibitory effects can nevertheless be reduced by 'prestressing' the cells with mild heat or with H2O2 itself.Paradoxically very low concentrations (10−8 M) of H2 02 or t-butyl hydroperoxide can actually stimulate cell growth, even in the absence of serum. These stimulatory effects however do not appear to involve radicals as they are enhanced by inclusion of mannitol or DMSO in the medium.

Oxygen Radicals Acting as Chemical Messengers: A Hypothesis

Abstract: Based on a critical reappraisal of the reactions of radicals in a biological milieu, a hypothesis is proposed according to which superoxide anion radicals act as biological messengers rather than as mediators or precursors of cellular damage under oxidative stress conditions.

Oxidation state of tissue thiol groups and content of protein carbonyl groups in chickens with inherited muscular dystrophy.

Abstract: Indirect evidence suggests that oxidative stress may play a role in the pathogenesis of inherited muscular dystrophy, but the significance and precise extent of this contribution is poorly understood. Compared with normal muscle, significantly higher contents of glutathione, glutathione disulphide, protein-glutathione mixed disulphides and protein carbonyl groups, and significantly lower contents of free protein thiol groups, were found in pectoralis major muscle of genetically dystrophic chickens (the muscle affected by this disease) at 4 weeks of age. Other tissues did not show such marked disease-related differences. Interestingly, the protein pool in normal, but not dystrophic, pectoralis major muscle was relatively less oxidized in relation to the glutathione pool as compared with other tissues studied. The mechanisms by which this unique relationship between the thiol pools is maintained remain unknown. Although the physiological consequences of the increased content of protein carbonyl groups and the altered thiol pools in dystrophic muscle are not clear, the changes evident at such a young age are consistent with the occurrence of oxidative stress and may reflect significant damage to cellular proteins in this disease.

Ingestion of high doses of fish oil increases the susceptibility of cellular membranes to the induction of oxidative stress.

Abstract: Feeding rats with 4 g/kg body weight of sardine oil during 7 or 14 days increases the content of eicosapentaenoic acid and docosahexanoic acid in the erythrocyte and hepatic microsomal membranes by 2 to 6%. These membranes show increased susceptibility to the induction of oxidative stress, expressed as lipid peroxidation, when they are exposed to Fe2+-ascorbate and to NADPH-Fe3+-ADP, respectively. The results indicate that in order to prevent the increased susceptibility to lipid peroxidation, supplementation with larger amounts of antioxidants may be needed than those required to stabilize the oil.

Brain chemiluminescence and oxidative stress in hyperthyroid rats

Abstract: Newborn Wistar rats were made hyperthyroid by injection of tri-iodothyronine and assayed for survival, brain oxygen uptake, brain chemiluminescence and activity of antioxidant enzymes. Brain chemiluminescence was measured (1) by removing the parietal bones or (2) through the translucid parietal bones. Control animals showed a brain chemiluminescence of 130 +/- 12 c.p.s./cm2 and 99 +/- 10 c.p.s./cm2 for procedures (1) and (2) respectively. Hyperthyroid rats showed increases in the spontaneous brain photoemission of 46 and 70% compared with controls, measured by procedures 1 and 2 respectively. The hyperthyroid state did not modify the oxygen-dependent chemiluminescence of brain homogenates. The hyperthyroid animals showed a 30% increase in the oxygen uptake of brain slices and a dramatic shortening of life-span to about 16 weeks. Superoxide dismutase (the Cu-Zn enzyme), catalase and Se-dependent glutathione peroxidase activities of brain homogenates were increased by 18, 36 and 30% respectively in the hyperthyroid animals. Isolated brain mitochondria produced 0.18-0.20 nmol of H2O2/min per mg of protein in state 4 in the presence of succinate as substrate. No difference was observed between control and hyperthyroid animals. It is concluded that hyperthyroidism leads to hypermetabolism and oxidative stress in the brain. The increased levels of oxygen and peroxyl radicals may contribute to premature ageing in these animals.

Dissociation of the accumulation of single-strand breaks in DNA from the killing of cultured hepatocytes by an oxidative stress.

Abstract: The relationship was explored between the accumulation of single-strand breaks in DNA and the killing of cultured hepatocytes by an oxidative stress generated by either tert-butyl hydroperoxide (TBHP), glucose oxidase, or menadione The accumulation of DNA strand breaks was measured fluorometrically by the rate of the alkaline unwinding of DNA In each case, DNA strand breaks were detected before the loss of cell viability DNA damage and cell killing depended on a cellular source of iron Pretreatment of the hepatocytes with the ferric iron chelator deferoxamine prevented both, and the readdition of iron to the medium restored the DNA damage and the cell killing In addition, the radical scavenger keto-methiolbutyric acid reduced the extent of DNA damage and prevented the cell killing By contrast, the antioxidants N,N'-diphenyl-p-phenylenediamine and butylated hydroxytoluene prevented the cell killing but not the DNA single-strand breaks induced by TBHP Similarly, acidification of the culture medium also prevented the cell killing, without any effect on the extent of the DNA damage by TBHP, glucose oxidase, and menadione These data indicate that DNA damage and cell killing produced by an oxidative stress depend upon the iron-catalyzed formation of a potent oxidizing species However, the accumulation of such damage can be dissociated from the mechanisms that lethally injure the cells

Differential effects of hyperoxia and hydrogen peroxide on DNA damage, polyadenosine diphosphate-ribose polymerase activity, and nicotinamide adenine dinucleotide and adenosine triphosphate contents in cultured endothelial cells and fibroblasts

Abstract: The effects of oxidative stress on DNA damage and associated reactions, increased polyadenosine diphosphate-ribose polymerase (PARP) activity and decreased nicotinamide adenine dinucleotide (NAD) and adenosine triphosphate (ATP) contents, have been tested in primary cultures of porcine aortic endothelial cells. The cells were treated with 50-500 microM H2O2 for 20 min or 100 microM paraquat for 3 days or were exposed to 95% O2 for 2 and 5 days. The administration of 250-500 microM H2O2 resulted in a marked increase in PARP activity and a profound depletion of ATP and NAD. Although hyperoxia had no effect on PARP activity and reduced only slightly the ATP and NAD stores, it markedly reduced the ability of endothelial cells to increase PARP activity upon exposure to DNase. Paraquat had a similar effect. Human dermal fibroblasts were also exposed to 50-500 microM H2O2 for 20 min or 95% O2 for 5 days. Their response to H2O2 differed from that of endothelial cells by their ability to maintain the ATP content at a normal level. Fibroblasts were also insensitive to the effect of hyperoxia. These results suggest that the oxidant-related DNA damage is a function of the type of oxidative stress used and may be cell-specific.

Oxidative stress. Biochemistry and human disease.

Abstract: The early involvement of free radicals in the evolution of life may explain their ubiquitous presence and vital physiological role. Imbalance between protection against free radicals and their generation, explains the likely association of various diseases with toxic oxygen species. An elaborate defence system against oxygen-free radicals exists. The effects of oxidative stress are manifold. Direct demonstration of oxygen radicals in intact biological systems is difficult. Frequently, effect-related measurements are used in this respect. The clinical conditions adult respiratory distress syndrome and multiple organ failure, reflex sympathetic dystrophy and sugar cataract are discussed and the role of oxygen radicals in the aetiology of these diseases are described.

Glutathione peroxidase and catalase in liver, kidney, testis and brain regions of rats following cadmium exposure and subsequent withdrawal.

Abstract: Intraperitioneal administration of 0.4 mg/kg Cadmium (Cd) daily for 45 days was found to inhibit the activities of glutathione peroxidase and catalase in liver, kidney, testis and various brain regions at different time intervals. The magnitude of inhibition was increased with the period of exposure. Cd produced significant inhibition of glutathione peroxidase at 15 days in liver, kidney and cerebellum only; however, the enzyme activity was found to be decreased in all the tissues, except corpus striatum, at 30 and 45 days of exposure. Hippocampal glutathione peroxidase remained unaltered throughout the experiment. Catalase was found to be inhibited in all the tissues at different time intervals. The withdrawal of Cd treatment for 15 days after 45 days of exposure did not show significant recovery in the activity of both enzymes of different organs, except kidney and testis where partial and full recoveries respectively were observed. Since these two enzymes constitute an important part of cellular defence mechanism against oxidation, their widespread persistent inhibition may be of great signifi-cance in view of the recent reports showing the possible involvement of oxidative stress in the mechanism of Cd toxicity.

Elevated Superoxide Dismutase in Bloom's Syndrome: A Genetic Condition of Oxidative Stress

Abstract: We have found that Bloom9s syndrome (BS) cells exhibit elevated levels of superoxide dismutase activity. Since SOD activity has been shown to reflect the intracellular superoxide (O2-) content, these results indicate that BS cells exhibit oxidative stress which ultimately results in DNA damage. Elevated sister chromatid exchange, the major cytological characteristic of BS, and superoxide dismutase induction were simulated in normal lymphoblastoid cells by treatment with compounds that increase the steady-state concentration of O2⨪. The sister chromatid exchange response of a BS lymphoid cell line was modulated through the control of the endogenous O2⨪ content. We therefore suggest that a major biochemical defect resulting from this genetic disorder is chronic over-production of the superoxide radical anion. The consequence of high O2⨪ levels concomitant with induced superoxide dismutase activity is the formation of enormous amounts of H2O2 which can apparently inactivate the enzymes responsible for its elimination. The inefficient removal of peroxide can result in high rates of sister chromatid exchange and chromosomal damage in BS cells and in normal cells treated with oxidation-reduction cycling compounds through the formation of highly reactive intermediary forms of active oxygen.

The ratio of oxidized/reduced glutathione as an index of oxidative stress in various experimental models of shock syndrome.

Abstract: Red blood cells are well equipped to handle intracellular oxidative stress, their membranes are permeable to O2- and H2O2, and in this way they are important regulators of oxygen reactions occurring in their surroundings. The protective effect against reduced oxygen species - generated during the endothelial cell injury of various tissues - is attributed mainly to the glutathione metabolism of red blood cells. The blood concentration of reduced (GSH) and oxidized glutathione (GSSG) was determined by a sensitive method using glutathione reductase in experimental shock syndromes induced by paraquat toxicity, tourniquet ligature and endotoxin in rats, by bleeding and reperfusion in dogs and by transient ligature of thoracic aorta in newborn piglets. Under these conditions the concentration of GSSG was elevated and GSH was lowered, resulting in an increase in the redox ratio: [GSSG/(GSH + GSSG)] x 100 (GSSG/GSH); particularly during reperfusion. Determination of the GSSG/GSH seems to be a reliable index to assess the degree of oxidative stress "in vivo".