Showing papers on "Oxidative stress published in 1985"

Free radicals in biology and medicine

Abstract: 1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?

Oxidative stress: damage to intact cells and organs

Abstract: Oxidative cell damage can be monitored by detection of (a) photoemission of singlet molecular oxygen formed from radical interactions (so-called low-chemical chemiluminescence), (b) end products of lipid peroxidation, such as ethane, and (c) glutathione disulphide release. These methods, preferably used in a complementary fashion, provide insight into the pro-oxidant-antioxidant balance in the intact cell or organ. Recent work from this laboratory on the metabolism of hydroperoxides and aldehydes as well as on redox cycling of the quinone menadione is presented. The comparison of GSSG transport systems in liver and heart reveals a limitation of capacity in the latter, thus making GSSG export potentially critical in the heart. As part of an inter-organ feedback system between extrahepatic tissues and liver, the newly described hormone stimulation of GSH release from liver is also presented.

Effect of hydrogen peroxide on prostaglandin production and cellular integrity in cultured porcine aortic endothelial cells.

Abstract: Oxidative damage to the vascular endothelium may play an important role in the pathogenesis of atherosclerosis and aging, and may account in part for reduced vascular prostacyclin (PGI2) synthesis associated with both conditions. Using H2O2 to induce injury, we investigated the effects of oxidative damage on PGI2 synthesis in cultured endothelial cells (EC). Preincubation of EC with H2O2 produced a dose-dependent inhibition (inhibitory concentration [IC50] = 35 microM) of PGI2 formation from arachidonate. The maximum dose-related effect occurred within 1 min after exposure although appreciable H2O2 remained after 30 min (30% of original). In addition, H2O2 produced both a time- and dose-dependent injury leading to cell disruption, lactate dehydrogenase release, and 51Cr release from prelabeled cells. However, in dramatic contrast to H2O2 effects on PGI2 synthesis, loss of cellular integrity required doses in excess of 0.5 mM and incubation times in excess of 1 h. The superoxide-generating system, xanthine plus xanthine oxidase, produced a similar inhibition of PGI2 formation. Such inhibition was dependent on the generation of H2O2 but not superoxide in that catalase was completely protective whereas superoxide dismutase was not. H2O2 (50 microM) also effectively inhibited basal and ionophore A23187 (0.5 microM)-stimulated PGI2 formation. However, H2O2 had no effect on phospholipase A2 activity, because ionophore A23187-induced arachidonate release was unimpaired. To determine the effects on cyclooxygenase and PGI2 synthase, prostaglandin products from cells prelabeled with [3H]arachidonate and stimulated with ionophore A23187, or products formed from exogenous arachidonate were examined. Inhibition of cyclooxygenase but not PGI2 synthase was observed. Incubation of H2O2-treated cells with prostaglandin cyclic endoperoxide indicated no inhibition of PGI2 synthase. Thus, in EC low doses of H2O2 potently inhibit cyclooxygenase after brief exposure whereas larger doses and prolonged exposure are required for classical cytolytic effects. Surprisingly, PGI2 synthase, which is known to be extremely sensitive to a variety of lipid peroxides, is not inhibited by H2O2. Lipid solubility, enzyme location within the EC membrane, or the local availability of reducing factors may explain these results, and may be important determinants of the response of EC to oxidative stress.

Decreased hepatic glutathione levels in septic shock. Predisposition of hepatocytes to oxidative stress: an experimental approach.

Abstract: • Intracellular metabolite glutathione, existing in either its reduced (GSH) or oxidized states, is crucial for the protection of any cell against an oxidative stress or injury. Significant depletion of intracellular levels of GSH predisposes cells to an oxidative injury. We have investigated the level of hepatic GSH during the early course of sepsis in a physiologically well-characterized septic-sheep model. Following six hours of sepsis, which was characterized by hypotension, hypoxemia, and granulocytopenia, the level of intrahepatic GSH was significantly reduced compared with baseline levels. There was no reduction after two hours of sepsis. Hepatic GSH levels in control animals were unchanged compared with baseline levels. These findings suggest that the liver may be more susceptible to an oxidative stress in septic patients. ( Arch Surg 1985;120:941-945)

Genetic differences in oxygen toxicity are correlated with cytochrome P-450 inducibility.

Abstract: Susceptibility to oxygen toxicity was studied in three inbred and two hybrid strains of mice. Because in vitro studies have shown that the cytochrome P-450 enzymes can produce oxygen radicals and H2O2, we tested the hypothesis that inducibility of these enzymes might play a role in oxygen toxicity. Mice responsive to hepatic microsomal enzyme induction by aromatic hydrocarbons [C3H/HeJ, C3H/HeN, C3H/HeJ X DBA/2J (designated C3D2F1/J), C3H/HeN X DBA/2J (designated C3D2F1/N)] were more sensitive to the toxic effects of 100% oxygen exposure than were genetically unresponsive mice (DBA/2J). DBA/2J mice survived significantly longer exposure periods with less lung damage. Lung and liver cytochrome P-450 levels increased 2-to 3-fold in C3H and F1 mice during 100% oxygen exposure (maximum levels at 72-96 hr) and subsequently fell prior to death. No increases were seen in cytochrome P-450 levels in DBA/2J mice. Metabolic pathways involving cytochrome P-450 enzymes may initiate or modulate oxidative damage due to oxygen radicals. The difference in responsiveness of mice to microsomal enzyme induction may imply genetic differences in susceptibility to oxidative stress, may help to explain species differences in susceptibility, and may have long-term implications in therapeutics and patient care if similar inherited differences exist in humans.

Oxidative stress studied in intact mammalian cells.

Abstract: Exposure of isolated rat hepatocytes to toxic doses of menadione (2-methyl-1,4-naphthoquinone) results in enhanced formation of active oxygen species, depletion of cellular glutathione and protein thiols, and perturbation of intracellular calcium ion homeostasis. An increase in cytosolic Ca2+ concentration, resulting from inhibition of the plasma membrane Ca2+ translocase by menadione metabolism, appears to be critically involved in the development of cytotoxicity.

Glutathione depletion and oxidative stress: study with perfused bovine eye.

Abstract: A bovine eye perfusion system was developed for detoxification studies. The viability of the system was examined by two criteria: the permeability of the aqueous-blood barrier to protein, ...

Depletion of Cellular Glutathione by Exogenous Spermine in V79 Cells: Implications for Spermine-induced Hyperthermic Sensitization

Abstract: The relationship between spermine-induced thermosensitization and modulation in the cellular redox state as measured by glutathione levels was studied using Chinese hamster V79 cells. Marked cellular glutathione depletion was observed for cells treated with exogenous 1 mm spermine at 37°C or 43°C. Glutathione depletion and thermal sensitization by spermine were found to be cell density dependent with maximum depletion and sensitization observed at low cell densities. These findings are discussed in the context that treatment of cells with exogenous polyamines such as spermine can result in cellular oxidative stress which may in part contribute to spermine-induced thermal sensitization.

Formation of activated oxygen in the hypoxic rat liver.

Abstract: The biliary GSSG efflux rate of normoxic perfused rat liver was 1.5 +/- 0.2 nmol/min/g liver wet weight. The GSSG efflux rate as indicator for the flux through the glutathione peroxidase reaction and, therefore, for an oxidative loading increased with the extent of hypoxia. 2.6 +/- 0.5 nmol/min/g were released from the severely hypoxic liver. The hydroxyl radical scavenger formate as well as the xanthine oxidase inhibitor allopurinol reduced the efflux rate of GSSG. GSH was released from the perfused liver at a rate of 15.5 nmol/min/g which was nearly unchanged in severe hypoxia. The high rate of glucose liberation from the hypoxic liver declined to almost that of the normoxic organ in the presence of formate. There is an 'oxidative stress' during hypoxic liver perfusion which probably originates from increased generation of activated oxygen species in the degradation of purine nucleotides.

Role of oxygen in myocardial ischaemic and reperfusion damage: effect of alpha-tocopherol.

Abstract: There is evidence that oxygen-derived free radicals may play a role in myocardial ischaemic and reperfusion injury. Major sources of O2 free radicals formation during ischaemia and reperfusion are: the enzyme xanthine oxidase, activated neutrophils and the myocardial mitochondria. However, in the heart there are defense mechanisms against the toxic oxygen metabolites. They include the enzyme superoxide dismutase, catalase and glutathione peroxidase plus endogenous antioxidants like vitamin E, ascorbic acid and cysteine. We have investigated in the isolated rabbit hearts the effects of ischaemia and reperfusion on these defence mechanisms. 90 min of ischaemia and/or hypoxia induced a significant reduction of mitochondrial superoxide dismutase, and of reduced glutathione/oxidized glutathione ratio which was further declined after reperfusion indicating that an oxidative stress has occurred. These alterations are associated with massive tissue and mitochondrial calcium accumulation, loss of mitochondrial function and severe membrane damage. The effects of vitamin E on these parameters have been investigated. Administration of 1.1 mg of dl-alpha-tocopherol acetate showed a protective effect on mitochondrial function but it failed to improve the recovery of mechanical function during reperfusion.

Erythrocyte (Ca+2 + Mg+2)-ATPase activity: increased sensitivity to oxidative stress in glucose-6-phosphate dehydrogenase deficiency.

Abstract: The effect of the thiol-oxidizing agent diamide on erythrocyte (Ca+2 + Mg+2)-ATPase activity was measured in normal and glucose-6-phosphate-dehydrogenase-deficient (G6PD-) cells. Although the enzyme activity before the oxidative stress was similar in both groups, diamide induced a markedly greater inhibition in the enzyme activity in the G6PD- cells than in the normal controls. These data indicate dependence of erythrocyte (Ca+2 + Mg+2)-ATPase, in part, on the redox status of the cell. The increased vulnerability of (Ca+2 + Mg+2)-ATPase to oxidative stress in G6PD- may be of pathophysiological relevance to their premature destruction in oxidant-induced hemolysis.

Oxidative effects of iron on erythrocytes.

Abstract: In this work we have investigated the effects of iron-induced free radical formation in normal human erythrocytes in vitro, as a model system for studying iron damage, and in erythrocytes from patients with beta-thalassaemia major. The resulting oxidative effects were measured in terms of methaemoglobin formation and reduced glutathione loss. The effects of desferrioxamine, an iron-chelating agent, were also investigated. The results show that the increased methaemoglobin formation after iron-induced oxidative stress is consistent with a decline in the intracellular glutathione levels and that this process is inhibited by desferrioxamine. Similar treatment of red cell haemolysates produces less methaemoglobin. This suggests that, on exposure of intact erythrocytes to iron-induced free radical effects, the red cell membrane exacerbates the breakdown of the antioxidant defences of the cell and the oxidation of haemoglobin.

Antioxidant adaptation: a unified disease theory

Abstract: Free radical-mediated oxidative stress to cells and tissues can generate activated oxygen species and lipid peroxides, which mediate inflammatory/immune symptomatologies and are associated with degenerative disease states and possibly with environmental illness (Levine and Reinhardt, 1983. J. Orthomol. Psychiatry 12,166-183). Rats and mice experimentally exposed to high doses of chemical oxidant stressors can become tolerant as a consequence of antioxidant adaptation. Tolerance is characterized by increased activity of glutathione peroxidase (GP), a key antioxidant enzyme which detoxifies peroxide species, subject to adequate availability of its metal cofactor (selenium) and its cosubstrate (reduced glutathione). Increases in other enzymes of the glutathione pathway (glutathione reductase and glucose-6-phosphate dehydrogenase, among others) also are essential. Humans also may adapt biochemically to oxidative stress. In those inherited disease states characterized by abnormally elevated endogenous oxidative stress, peroxide production is enhanced in selected tissues and GP activity is correspondingly increased. GP activity is also abnormally altered (increased or decreased) in other disease states characterized by increased tissue lipid peroxide levels. The price of continued adaptation for humans, as for laboratory animals, may be premature progression to degenerative disease. Herein we hypothesize a "four-stage" clinical progression to degenerative disease, in individuals subject to sustained oxidative stress. This trend may be interrupted or reversed by the cessation of oxidative stress and dietary replenishment of essential antioxidant factors. We suggest that glutathione peroxidase activity (along with other biochemical indicators of oxidative stress) appears to be a valuable marker enzyme for monitoring the clinical response to nutritional antioxidant therapy. In this article we review the evidence that laboratory animals and humans can adapt to acute oxidative stress, by augmenting . Director of Research Allergy Research Group 400 Preda St. San Leandro, CA 94577 . Director, Biocurrents Division, Allergy Research Group

The effects of ascorbic acid on copper‐induced oxidative changes in human erythrocytes: Example of a biphasic dose‐response relationship

Abstract: In an in vitro study, ascorbic acid reduced the occurrence of copper acetate‐induced oxidative stress in human erythrocytes at biologically relevant concentrations (0.06 ‐ 0.25 mM) while enhancing oxidative changes [i.e., changes in methemoglobin (METHB) and reduced glutathione (GSH)] at higher levels of exposure (> 1.0 mM).