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PubMed1987

Oxidants and human disease: some new concepts.

Oxidant species such as superoxide radical (O.2-), hydrogen peroxide (H2O2), hydroxyl radical (HO.), and lipid peroxides (LOOH) are becoming increasingly implicated in human disease. However, the question of whether such oxidants are a major cause of tissue injury in human disease or are merely produced during such injury has been difficult to answer because of inadequate experimental techniques, and possibly because of an overemphasis on lipid peroxidation as a mechanism of oxidant injury. Recent developments in methodology, in our understanding of the primary mechanism of oxidant toxicity to cells, and in concepts of antioxidant protection are reviewed. Good evidence now exists for some role of oxidant damage to tissues in the pathology of several human diseases, including rheumatoid arthritis, reperfusion injury, immune injury to lung and kidney, and cerebral trauma or ischemia. These have led to promising suggestions for new therapeutic approaches.

Antioxidants↗
PubMed1985

Inhibition of neutrophil function by hydrogen peroxide. Effect of SH-group-containing compounds.

Stimulated neutrophils generate appreciable amounts of hydrogen peroxide (H2O2) which may be responsible for auto-oxidative injury and damage to adjacent cells. In the present study we describe inhibitory effects of H2O2 on neutrophil phagocytosis, bactericidal activity and associated metabolic processes as well as the effect of non-protein SH-compounds on H2O2-treated cells. Preincubation of neutrophils with low concentrations of H2O2 (1 mumoles/5 X 10(6) cell) results in delayed phagocytosis of Escherichia coli, which returns to normal levels in the later stages of incubation, while the activity of the HMPS and the production of O-2 and H2O2 remain unaffected. Bactericidal activity of the cells was more sensitive to peroxide treatment and even at low concentrations H2O2 induced some inhibition (12.2%) of neutrophils' capacity to kill E. coli. Increasing the concentrations of H2O2 in the preincubation mixtures resulted in a progressive decline in the neutrophils phagocytic and killing capacity for E. coli and was accompanied by inhibition of HMPS activity and the release of granule enzymes but not of O-2 or H2O2. The H2O2/O-2 molar ratio of peroxide-treated cells was elevated by up to 26.7% and this was followed closely by the reduction in the intracellular levels of reduced glutathione (GSH). Incubation of H2O2-treated neutrophils with all five SH-compounds used in the study resulted in the improvement of the phagocytic capacity of the cells. Improvement of the bactericidal capacity and degranulation responses of H2O2-treated neutrophils was achieved by incubation with cysteine, penicillamine, alpha-MPG and MMPC but not GSH. Stimulus-dependent H2O2 production by H2O2-treated cells, the H2O2/O-2 molar ratio and the intracellular levels of GSH remained unaltered after treatment with SH-compounds. The data shows that SH-compounds, in addition to their antiinflammatory properties, also have the ability to reverse the oxidant-induced inhibition of neutrophil function, a property of potential therapeutic significance.

Blood Bactericidal Activity↗
PubMed1991

Hydrogen peroxide-induced oxidative stress to the mammalian heart-muscle cell (cardiomyocyte): lethal peroxidative membrane injury.

Oxidative stress induced by hydrogen peroxide (H2O2) may contribute to the pathogenesis of ischemic-reperfusion injury in the heart. For the purpose of investigating directly the injury potential of H2O2 on heart muscle, a cellular model of H2O2-induced myocardial oxidative stress was developed. This model employed primary monolayer cultures of intact, beating neonatal-rat cardiomyocytes and discrete concentrations of reagent H2O2 in defined, supplement-free culture medium. Cardiomyocytes challenged with H2O2 readily metabolized it such that the culture content of H2O2 diminished over time, but was not depleted. The consequent H2O2-induced oxidative stress caused lethal sarcolemmal disruption (as measured by lactate dehydrogenase release), and cardiomyocyte integrity could be preserved by catalase. During oxidative stress, a spectrum of cellular derangements developed, including membrane phospholipid peroxidation, thiol oxidation, consumption of the major chain-breaking membrane antiperoxidant (alpha-tocopherol), and ATP loss. No net change in the protein or phospholipid contents of cardiomyocyte membranes accompanied H2O2-induced oxidative stress, but an increased turnover of these membrane constituents occurred in response to H2O2. Development of lethal cardiomyocyte injury during H2O2-induced oxidative stress did not require the presence of H2O2 itself; a brief "pulse" exposure of the cardiomyocytes to H2O2 was sufficient to incite the pathogenic mechanism leading to cell disruption. Cardiomyocyte disruption was dependent upon an intracellular source of redox-active iron and the iron-dependent transformation of internalized H2O2 into products (e.g., the hydroxyl radical) capable of initiating lipid peroxidation, since iron chelators and hydroxyl-radical scavengers were cytoprotective. The accelerated turnover of cardiomyocyte-membrane protein and phospholipid was inhibited by antiperoxidants, suggesting that the turnover reflected molecular repair of oxidized membrane constitutents. Likewise, the consumption of alpha-tocopherol and the oxidation of cellular thiols appeared to be epiphenomena of peroxidation. Antiperoxidant interventions coordinately abolished both H2O2-induced lipid peroxidation and sarcolemmal disruption, demonstrating that an intimate pathogenic relationship exists between sarcolemmal peroxidation and lethal compromise of cardiomyocyte integrity in response to H2O2-induced oxidative stress. Although sarcolemmal peroxidation was causally related to cardiomyocyte disruption during H2O2-induced oxidative stress, a nonperoxidative route of H2O2 cytotoxicity was also identified, which was expressed in the complete absence of cardiomyocyte-membrane peroxidation. The latter mode of H2O2-induced cardiomyocyte injury involved ATP loss such that membrane peroxidation and cardiomyocyte disruption on the one hand and cellular de-energization on the other could be completely dissociated.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1989

Pervanadate [peroxide(s) of vanadate] mimics insulin action in rat adipocytes via activation of the insulin receptor tyrosine kinase.

Both vanadate and hydrogen peroxide (H2O2) are known to have insulin-mimetic effects. We previously reported that the mixture of vanadate plus H2O2 results in the generation of a peroxide(s) of vanadate, which strongly enhances IGF-II binding to rat adipocytes (Kadota et al., 1987b). We now report that pervanadate mimics insulin in isolated rat adipocytes to (1) stimulate lipogenesis, (2) inhibit epinephrine-stimulated lipolysis, and (3) stimulate protein synthesis. The efficacy of pervanadate is comparable to that of insulin. However, it is 10(2)-10(3) times more potent than vanadate alone. Exposure of intact rat adipocytes to pervanadate was found to activate the WGA-purified insulin receptor tyrosine kinase assayed with the exogenous substrate poly(Glu80/Tyr20) in a dose-dependent manner to a maximum of 1464% of control at 10(-3) M compared with a maximum insulin effect of 1046% at 10(-6) M. In contrast, in vitro assayed autophosphorylation of the WGA-purified extract was increased 3-fold after exposure of intact cells to insulin but not significantly increased after pervanadate. Furthermore, high concentrations of pervanadate (10(-5) M) inhibited subsequent in vitro added insulin-stimulated autophosphorylation. In vitro addition of pervanadate to WGA-purified receptors could not stimulate autophosphorylation or exogenous tyrosine kinase activity and did not inhibit insulin-stimulated autophosphorylation. Labeling of intact adipocytes with [32P]orthophosphate followed by exposure to 10(-4) M pervanadate increased insulin receptor beta-subunit phosphorylation (7.9 +/- 3.0)-fold, while 10(-7) M insulin and 10(-4) vanadate increased labeling (5.3 +/- 1.8)- and (1.1 +/- 0.2)-fold, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1989

[Peroxidative antimalaria mechanism of sodium artesunate].

Peroxidative antimalaria action of sodium artesunate was studied in vitro. Under alkaline conditions, sodium artesunate could produce active oxygen species, including the superoxide anion (O2-) and hydrogen peroxide (H2O2), but no O2- or H2O2 was produced by the drug at pH 7.4. However, sodium artesunate could increase the concentration of O2- and H2O2 in erythrocytes by increasing membrane lipid peroxidation, with this action being more marked in infected than in normal erythrocytes.

Animals↗
PubMed1990

Intracellular iron mediates the enhancing effect of histidine on the cellular killing and clastogenicity induced by H2O2.

The enhancing effect of L-histidine on the hydrogen peroxide (H2O2) induction of micronuclei and of sister-chromatid exchanges (SCEs) as well as on its killing effect was investigated using Chinese hamster fibroblasts. L-Histidine increased cellular killing and the frequency of micronuclei but not SCEs induced by H2O2. Superoxide dismutase and mannitol did not decrease the killing effect whereas mannitol completely prevented the formation of micronuclei and of SCEs induced by H2O2 or by H2O2 plus L-histidine. When the iron-complexing agents EDTA or o-phenanthroline were present, only o-phenanthroline inhibited the killing and clastogenic effects of H2O2 or of H2O2 plus L-histidine. D-Histidine had the same effect as L-histidine, but histamine and L-urocanic acid did not. These results indicated that both the amino and the carboxylic groups of histidine are required for the enhancing effect and suggested that it depends on the formation of an intracellular histidine-iron complex able to react with H2O2 generating reactive oxygen species.

Analysis of Variance↗
PubMed1991

Purification of cytochrome c peroxidase for monitoring H2O2 production.

One of the most precise methods of determining hydrogen peroxide (H2O2) formation by biological systems is based on measuring the rate of enzyme-substrate complex formation between H2O2 and cytochrome c peroxidase (CCP). The main problem with this method is that CCP is not commercially available and has to be prepared in the laboratory. We have modified some currently available methods for purifying a highly active preparation of CCP in about 4 d. It includes a batch extraction of protein using DEAE-sepharose followed by concentration either by lyophilization or by passing the extract through a small DEAE-sepharose column instead of by ultrafiltration. The concentrated preparation is passed through a Sephadex G-75 column and the final CCP crystallized against water. The final preparations had a purity index (PI, ratio of absorbance at 408 nm/280 nm, equivalent to heme/protein ratio) above 1.2. These changes make the overall procedure very simple, preserving enzyme activity and spectral properties. In addition, we point out that special care has to be taken to eliminate cytochrome c from crude CCP extracts. Cytochrome c not only introduces an artifact when determining PI, but is also may act as a hydrogen donor for CCP when monitoring H2O2 formation, thus decreasing the sensitivity of this method.

Cytochrome-c Peroxidase↗
PubMed1987

Halothane anesthesia decreases human monocyte hydrogen peroxide generation. Protection of monocytes by activation with gamma interferon.

In an effort to determine the impact of halothane anesthesia on certain human cell-mediated immune functions, normal, purified human monocytes and lymphocytes were exposed to halothane in vitro at varying concentrations for up to 8 hours. Subsequently, these human effector cells were analyzed for their ability to function in several cell-mediated immunologic assays. Natural killer cell activity against K-562 was unaffected by halothane in most of the donors tested. Similarly, the ability of purified monocytes to inhibit MBL-2 tumor cell growth was unchanged. Halothane appeared to decrease the proliferative response of lymphocytes to phytohemagglutinin (PHA) in approximately 50% of the normal donors tested. In contrast, the ability of monocytes to lyse antibody-coated red cell targets (ADCC) was unaffected by even maximal exposure to halothane. Of interest was the finding that human monocytes exposed to as low as 2% halothane anesthesia for 4 hours displayed a dramatic down-regulation of hydrogen peroxide (H2O2) release. Since it is known that hydrogen peroxide and other incompletely reduced forms of oxygen secreted by monocytes can play a major role in the antimicrobial, antitumor, and inflammatory functions of these cells, this finding may help explain the enhanced susceptibility of post-operative patients to infections.

Adult↗
PubMed1985

A common pathway for protection of bacteria against damage by solar UVA (334 nm, 365 nm) and an oxidising agent (H2O2).

Pre-exposure of growing bacterial populations to low concentrations of hydrogen peroxide (H2O2) protects a repair-proficient strain of Escherichia coli (AB1157) very strongly and a rec A strain (AB2463) to a lesser extent from the lethal action of subsequent exposure to 5 mM H2O2 in buffer. The conditioning procedure also protects AB1157 and AB2463 from the toxic effects of UVA (334 nm, 365 nm) radiation but not UVB (313 nm) or UVC (254 nm) radiations. Pretreatment of growing AB1157 with low fluences of UVA (365 nm) radiation leads to the induction of resistance to H2O2, an effect which apparently requires protein synthesis. As in a previous report, the treatment of growing populations with low concentrations of H2O2 enhanced the resistance of such populations to H2O2 challenge in the growth medium. However, when H2O2 (+ Cu2+)-treated bacteriophage were subsequently infected into AB1157 under optimal inducing conditions, their resistance was not enhanced relative to infection into untreated bacteria. We conclude that the primary mechanism for the inducible effects observed could be the induction of H2O2 scavenging activity by low concentrations of H2O2 either introduced into the growth medium directly or produced by low fluences of UVA irradiation.

Bacteriophage lambda↗
PubMed1986

Superoxide generation during cardiopulmonary bypass: is there a role for vitamin E?

The cytotoxic metabolites of oxygen [superoxide (O-2), hydrogen peroxide (H2O2), and hydroxyl (OH.)] have been demonstrated to be involved in the peroxidation of membrane lipids consequently altering membrane composition, morphology, and function. Of all the lines of defense adopted by living organisms against toxic oxygen free radicals, vitamin E is most effective in the prevention of membrane damage. Cardiopulmonary bypass (CPB) has been shown to activate complement and cause sequestration of leukocytes which can recruit, adhere, and stimulate release of cytotoxic oxygen radicals. A prospective study of 30 patients evaluated the effects of CPB with and without an exogenous free radical scavenger (Group I, N = 20, control) and (Group II, N = 10, vitamin E) on H2O2 (a marker of oxygen free radicals) malonaldehyde (a marker of lipid peroxidation), transpulmonary leukosequestration, and plasma levels of vitamins E and C. Group I showed a progressive increase in H2O2 during CPB from 65 +/- 6 to 130 +/- 11 micron/ml (P less than 0.0001); plasma vitamin E decreased from 15 +/- 3 to 6 +/- 1 mg/liter (P less than 0.0001) while vitamin C increased from 1.6 +/- .3 to 2.3 +/- .3 mg/dl (P less than 0.0001). Group II showed no significant increase in H2O2 (from 78 +/- 8 to 93 +/- 5 microns/ml) during CPB and a significant reduction in H2O2 levels compared to Group I (P less than 0.001); plasma vitamins E and C did not change significantly in Group II.(ABSTRACT TRUNCATED AT 250 WORDS)

Ascorbic Acid↗
PubMed1985

Initiation of membranal lipid peroxidation by activated metmyoglobin and methemoglobin.

The interaction of hydrogen peroxide (H2O2) with metmyoglobin (MetMb) led very rapidly to the generation of an active species which could initiate lipid peroxidation. The activity of this prooxidant decreased rapidly during the first minutes, but 50% of its activity remained stable for more than 30 min. In this model system, it was found that small amounts of H2O2 (1-10 microM) could activate MetMb for significant lipid peroxidation. The incubation of the sarcosomal lipids with activated MetMb caused oxygen absorption. No absorption of oxygen was determined in the presence of membrane with MetMb or H2O2 alone. Methemoglobin (MetHb) was also found to be activated by H2O2 and to initiate lipid peroxidation. Membranal lipid peroxidation initiated by activated MetMb was inhibited by several reducing compounds and antioxidants. However, several hydroxyl radical scavengers and catalase failed to inhibit this reaction.

Animals↗
PubMed1988

Stable H2O2-resistant variants of Chinese hamster fibroblasts demonstrate increases in catalase activity.

Hydrogen peroxide (H2O2)-resistant variants of the Chinese hamster ovary HA-1 line have been derived by culturing cells in progressively higher concentrations of H2O2 (greater than 200 days, in 50-800 microM H2O2). The H2O2-resistant phenotype has been stable for over 60 passages (240 days) following removal from the H2O2 stress. The resistant cells demonstrate both increased capacity to deplete exogenously added H2O2 from the growth medium and increased catalase activity. H2O2 resistance correlates well with catalase activity. An increase in chromosome number occurred in the cells adapted to 200-800 microM H2O2, but increases in aneuploidy and tetraploidy were not necessary for resistance. These results suggest that adaptation to chronic oxidative stress mediated by H2O2 in mammalian cells is accompanied by a stable heritable change in expression of catalase activity.

Animals↗
PubMedDate not supplied

Mechanism of acetaminophen-stimulated NADPH oxidation catalyzed by the peroxidase-H2O2 system.

The oxidation of NADPH catalyzed by horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) is markedly increased by the presence of acetaminophen in a concentration-dependent manner. The oxidation follows pseudo-first order kinetics with respect to acetaminophen concentration. The product of the oxidation is enzymatically active NADP+. The stoichiometry of the reaction shows that 1.4 mol of NADPH are oxidized per mole of H2O2 added, and the addition of superoxide dismutase to the reaction mixture increases the ratio of NADPH oxidized:H2O2 consumed, which suggests formation of superoxide as a product. Monitoring cytochrome c reduction in the presence and absence of superoxide dismutase further suggests formation of superoxide. These results indicate that the HRP-H2O2 system oxidizes acetaminophen to the phenoxyl radical, N-acetyl-p-benzosemiquinone imime, which undergoes a rapid electron transfer reaction with NADPH. The NADP thus formed reacts with molecular oxygen to produce superoxide.

Acetaminophen↗
PubMed1991

Thiol modification in H2O2- and thromboxane-induced vaso- and bronchoconstriction in rat perfused lung.

Hydrogen peroxide (H2O2), arachidonic acid (AA), and U-44069, a thromboxane analogue, all induced vaso- and bronchoconstriction in the isolated perfused rat lung. The role of protein sulfhydryl modifications in these processes was investigated. The thiol oxidizing agent diamide inhibited both vaso- and bronchoconstriction induced by H2O2, AA, or U-44069. Diamide had only a marginal effect on glutathione and protein thiol levels and no effect on lung mechanics. The diamide inhibition was reversible, and H2O2-induced vaso- and bronchoconstriction was almost maximal after 10 min of perfusion with buffer. The recovery was more rapid if dithiothreitol, a thiol reducing agent, was used in the buffer. H2O2- and AA-induced vaso- and bronchoconstriction is caused by thromboxane release. Diamide did not influence H2O2- or AA-dependent thromboxane formation, indicating that neither AA release nor AA metabolism to thromboxane is sensitive to thiol oxidation. Thus our results indicate that the site of diamide-induced thiol oxidation is the thromboxane receptor or its signal transduction.

Animals↗
PubMed1990

Hydrogen peroxide production during experimental protein glycation.

The accumulation of hydrogen peroxide (H2O2) during incubations of protein with glucose (experimental glycation) has previously been too low for direct measurement although it is suggested to be the precursor of protein-damaging hydroxylating agents. We have thus developed a simple H2O2-measuring technique which relies upon the rapid peroxide-mediated oxidation of Fe2+ to Fe3+ (catalysed by sorbitol) under acidic conditions followed by reaction of the latter cation with the dye, xylenol orange. We have used the method to demonstrate that incubation mixtures of protein and glucose generates nanomolar levels of hydrogen peroxide in the presence of protein under physiological conditions of pH and temperature.

Chemical Phenomena↗
PubMed1987

Reversible oxidation of glyceraldehyde 3-phosphate dehydrogenase thiols in human lung carcinoma cells by hydrogen peroxide.

Human lung carcinoma cells (A549) were oxidatively stressed with mildly-toxic or non-toxic amounts of hydrogen peroxide (H2O2, 0.1 mM to 120 mM) for 5 min. Hydrogen peroxide exposure resulted in a dose dependent inhibition of binding (pH 7) of the thiol reagent iodoacetic acid (IAA) to a 38 kDa cell protein. Incubation of cells in saline for 60 min following H2O2 removal restored the ability of IAA to bind to the protein. Treatment with 20 mM dithiothreitol or 2 M urea also restored IAA binding, but 10% Triton X102 or 1 mM Brij 58 had no effect. Increasing to pH 11 during the IAA binding also increased thiol availability. Glyceraldehyde 3-phosphate dehydrogenase (EC 1.2.1.12) has been identified as the protein undergoing thiol/disulfide redox status and enzymic activity changes.

Catalase↗
PubMed1989

Effects of free radicals on the fluidity of myocardial membranes.

Free radicals, including superoxide anions (O2.-), hydroxyl radical (HO.), and hypohalite radical (OCl.), as well as oxidants such as hydrogen peroxide (H2O2) and hypochlorous acid (HOCl), have been indicated in the pathogenesis of myocardial ischemic and reperfusion injury. In this report, we compared the integrity of the myocardial membrane when exposed to these free radicals/oxidants. Isolated rat heart membrane preparations were exposed to chemically generated free radicals with or without their respective scavengers. Membrane fluidity was monitored by fluorescence polarization using the diphenylhexatriene probe, as well as by electron spin resonance (ESR) spectroscopy using 2,2,6,6-tetramethyl piperidine-n-oxyl as the spin labeling agent. HO., H2O2, and OCl. + HOCl increased the fluorescence polarization (FP) and microviscosity significantly by 1.7-fold, 1.8-fold, and 1.7-fold, respectively, as compared to an only 1.2-fold increase in FP by O2.-. O2.- did not alter the fatty acid profiles of the membrane phospholipids. However, HO. and H2O2 reduced the arachidonic acid contents in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). These radicals also stimulated the lipid peroxidation by several-fold, while that by O2.- was only insignificant. These results suggest that HO. and H2O2 decreased the membrane fluidity and induced lipid peroxidation by releasing the arachidonic acid from PC, PE, and PI.

Animals↗
PubMed1987

Hyperoxia increases H2O2 production by brain in vivo.

Hyperoxia and hyperbaric hyperoxia increased the rate of cerebral hydrogen peroxide (H2O2) production in unanesthetized rats in vivo, as measured by the H2O2-mediated inactivation of endogenous catalase activity following injection of 3-amino-1,2,4-triazole. Brain catalase activity in rats breathing air (0.2 ATA O2) decreased to 75, 61, and 40% of controls due to endogenous H2O2 production at 30, 60, and 120 min, respectively, after intraperitoneal injection of 3-amino-1,2,4-triazole. The rate of catalase inactivation increased linearly in rats exposed to 0.6 ATA O2 (3 ATA air), 1.0 ATA O2 (normobaric 100% O2) and 3.0 ATA O2 (3 ATA 100% O2) compared with 0.2 ATA O2 (room air). Catalase inactivation was prevented by pretreatment of rats with ethanol (4 g/kg), a competitive substrate for the reactive catalase-H2O2 intermediate, compound I. This confirmed that catalase inactivation by 3-amino-1,2,4-triazole was due to formation of the catalase-H2O2 intermediate, compound I. The linear rate of catalase inactivation allows estimates of the average steady-state H2O2 concentration within brain peroxisomes to be calculated from the formula: [H2O2] = 6.6 pM + 5.6 ATA-1 X pM X [O2], where [O2] is the concentration of oxygen in ATA that the rats are breathing. Thus the H2O2 concentration in brains of rats exposed to room air is calculated to be about 7.7 pM, rises 60% when O2 tension is increased to 100% O2, and increases 300% at 3 ATA 100% O2, where symptoms of central nervous system toxicity first become apparent. These studies support the concept that H2O2 is an important mediator of O2-induced injury to the central nervous system.

Amitrole↗