Showing papers on "Hydrogen peroxide published in 1985"

Free-radical chemistry of cigarette smoke and its toxicological implications.

Abstract: Cigarette smoke contains two very different populations of free radicals, one in the tar and one in the gas phase. The tar phase contains several relatively stable free radicals; we have identified the principal radical as a quinone/hydroquinone (Q/QH2) complex held in the tarry matrix. We suggest that this Q/QH2 polymer is an active redox system that is capable of reducing molecular oxygen to produce superoxide, eventually leading to hydrogen peroxide and hydroxyl radicals. In addition, we have shown that the principal radical in tar reacts with DNA in vitro, possibly by covalent binding. The gas phase of cigarette smoke contains small oxygen- and carbon-centered radicals that are much more reactive than are the tar-phase radicals. These gas-phase radicals do not arise in the flame, but rather are produced in a steady state by the oxidation of NO to NO2, which then reacts with reactive species in smoke such as isoprene. We suggest that these radicals and the metastable products derived from these radical reactions may be responsible for the inactivation of alpha 1-proteinase inhibitor by fresh smoke. Cigarette smoke oxidizes thiols to disulfides; we suggest the active oxidants are NO and NO2. The effects of smoke on lipid peroxidation are complex, and this is discussed. We also discuss the toxicological implications for the radicals in smoke in terms of a number of radical-mediated disease processes, including emphysema and cancer.

Topical antimicrobial toxicity.

Abstract: • Three topical antibiotics and four antiseptics (1% povidone-iodine, 0.25% acetic acid, 3% hydrogen peroxide, and 0.5% sodium hypochlorite) were directly applied to cultured human fibroblasts to quantitatively assess their cytotoxicity. The four antiseptics were found to be cytotoxic; all of the cytotoxic agents except hydrogen peroxide were subsequently found to adversely affect wound healing in an animal model. Comparison of bactericidal and cytotoxic effects of serial dilutions of these four topical agents indicated the cellular toxicity of hydrogen peroxide and acetic acid exceeded their bactericidal potency. Bactericidal noncytotoxic dilutions of povidone-iodine and sodium hypochlorite were identified. These experiments provide evidence that 1% povidone-iodine, 3% hydrogen peroxide, 0.5% sodium hypochlorite, and 0.25% acetic acid are unsuitable for use in wound care. This sequence of experiments could be used to identify bactericidal, noncytotoxic agents prior to their clinical use. (Arch Surg1985;120:267-270)

Enzymatic activities of an extracellular, manganese-dependent peroxidase from Phanerochaete chrysosporium

Abstract: An extracellular peroxidase was purified by chromatofocusing column chromatography from the growth medium of ligninolytic cultures of the white-rot fungus Phanerochaete chrysosporium Burds BKM-1767 The enzyme was electrophoretically pure with an Mr of 45 000–47 000 It contained an easily dissociable heme, and required Mn2+ ions for activity In the presence of hydrogen peroxide and Mn2+ it oxidized compounds such as vanillylacetone, 2,6-dimethyloxyphenol, curcumin, syringic acid, guaiacol, syringaldazine, divanillylacetone, and coniferyl alcohol It did not oxidize veratryl alcohol In reactions requiring Mn2+ and O2, but not hydrogen peroxide, the enzyme oxidized glutathione, dithiothreitol, and NADPH with production of hydrogen peroxide The hydrogen peroxide produced could be used as a co-substrate by ligninases such as those that oxidize veratryl alcohol, or by the peroxidase itself to oxidize lignin model compounds

Mammalian cells are not killed by DNA single-strand breaks caused by hydroxyl radicals from hydrogen peroxide.

Abstract: Cell killing by ionizing radiation has been shown to be caused by hydroxyl free radicals formed by water radiolysis We have previously suggested that the killing is not caused by individual OH free radicals but by the interaction of volumes of high radical density with DNA to cause locally multiply damaged sites (LMDS) (J F Ward, Radiat Res 86, 185-195, 1985) Here we test this hypothesis using hydrogen peroxide as an alternate source of OH radicals The route to OH production from H2O2 is expected to cause singly damaged sites rather than LMDS Chinese hamster V79-171 cells were treated with H2O2 at varying concentrations for varying times at 0 degree C DNA damage produced intracellularly was measured by alkaline elution and quantitated in terms of Gray-equivalent damage by comparing the rate of its elution with that of DNA from gamma-irradiated cells The yield of DNA damage produced increases with increasing concentration of H2O2 and with time of exposure H2O2 is efficient in producing single-strand breaks; treatment with 50 microM for 30 min produces damage equivalent to that formed by 10 Gy of gamma irradiation In the presence of a hydroxyl radical scavenger, dimethyl sulfoxide (DMSO), the yield of damage decreases with increasing DMSO concentration consistent with the scavenging of hydroxyl radicals traveling an average of 15 A prior to reacting with the DNA In contrast to DNA damage production, cell killing by H2O2 treatment at 0 degree C is inefficient Concentrations of 5 X 10(-2) M H2O2 for 10 min are required to produce significant cell killing; the DNA damage yield from this treatment can be calculated to be equivalent to 6000 Gy of gamma irradiation The conclusion drawn is that individual DNA damage sites are ineffectual in killing cells Mechanisms are suggested for killing at 0 degree C at high concentrations and for the efficient cell killing by H2O2 at 37 degrees C at much lower concentrations

Studies on the mechanism of alkaline peroxide delignification of agricultural residues.

Abstract: Alkaline solutions of hydrogen peroxide partially delignify wheat straw and other lignocellulosic materials, leaving a cellulosic residue that is highly susceptible to enzymatic digestion by cellulase. The delignification reaction is strongly dependent upon the pH of the reaction mixture, with an optimum at pH 11.5-11.6, pKa for the dissociation H(2)O(2) right harpoon over left harpoon H(+) + HOO(-). The data are consistent with a mechanism in which H(2)O(2) decomposition products such as .OH and O(2) (-)., rather than H(2)O(2) or HOO(-), are the primary lignin oxidizing species. During the course of the delignification reaction, O(2) is evolved from the reaction mixture indicating active H(2)O(2) decomposition. At a given concentration of H(2)O(2), the rate of O(2) evolution is proportional to the amount of lignocellulosic substrate present in the reaction mixture. However, the total amount of O(2) evolved is inversely proportional to the amount of substrate present, indicating that some of the peroxide oxygen becomes incorporated into lignin degradation products. The amount of peroxide oxygen incorporated can range as high as 2 O(2) per lignin C(9) unit, depending upon the initial concentration of lignocellulosic substrate.

Cellular and bacterial toxicities of topical antimicrobials.

Abstract: Cellular and bacterial toxicities of four commonly used topical antimicrobials (1% povidone-iodine, 3% hydrogen peroxide, 0.25% acetic acid, and 0.5% sodium hypochlorite) were assayed in vitro using cultures of human fibroblasts and Staphylococcus aureus. All agents tested at full strength killed 100 percent of exposed fibroblasts. Fibroblast toxicity exceeded bacterial toxicity with serial dilutions of hydrogen peroxide and acetic acid. Dilutions of povidone-iodine (1:1000) and sodium hypochlorite (1:100) were identified where no fibroblast toxicity occurred while full bactericidal activity persisted.

Scavenging of OH Radicals Produced in the Sonolysis of Water

Abstract: SummaryThe yield of hydrogen peroxide in the sonication of argon-saturated water was studied in the presence of various solutes. The efficiency of OH radical scavenging is expressed by the reciprocal value of c½, the solute concentration at which the H2O2 yield is decreased by 50 per cent. c½ ranges over several orders of magnitude. It is not related to the specific reactivity towards OH in homogeneous solution. However, it is correlated to the hydrophobicity of the solutes. The competition of I− and a second solute for OH was also studied. The competition between I− and HCO−2 follows similar kinetics as in homogeneous solution. However, many other solutes compete in the manner which would be expected if radical scavenging occurred in different phases. The effects are explained in terms of OH radical formation in gaseous argon bubbles, combination of OH radicals to form H2O2 in an interfacial area, and enrichment of hydrophobic solutes in the bubbles.

Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium.

Abstract: The addition ofN-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES) to RPMI 1640 medium markedly increases the production of cytotoxic products during exposure of the medium to visible light. The cytotoxicity has been analyzed by measuring uptake of [3H]thymidine by murine thymocytes cultured in preirradiated medium containing 25 mM HEPES. Complete inhibition of thymidine uptake was produced by exposing 50% of the culture medium to light for 3 h before addition of cells. The HEPES-mediated effect requires only that HEPES and riboflavin be exposed to light; other medium constituents are not necessary. Hydrogen peroxide is a principal cytotoxic agent produced in this system. It is demonstrated that most, but not all, of the inhibition of thymidine uptake can be attributed to hydrogen peroxide.

Production of the superoxide adduct of myeloperoxidase (compound III) by stimulated human neutrophils and its reactivity with hydrogen peroxide and chloride.

Abstract: Examination of the spectra of phagocytosing neutrophils and of myeloperoxidase present in the medium of neutrophils stimulated with phorbol myristate acetate has shown that superoxide generated by the cells converts both intravacuolar and exogenous myeloperoxidase into the superoxo-ferric or oxyferrous form (compound III or MPO2). A similar product was observed with myeloperoxidase in the presence of hypoxanthine, xanthine oxidase and Cl-. Both transformations were inhibited by superoxide dismutase. Thus it appears that myeloperoxidase in the neutrophil must function predominantly as this superoxide derivative. MPO2 autoxidized slowly (t 1/2 = 12 min at 25 degrees C) to the ferric enzyme. It did not react directly with H2O2 or Cl-, but did react with compound II (MP2+ X H2O2). MPO2 catalysed hypochlorite formation from H2O2 and Cl- at approximately the same rate as the ferric enzyme, and both reactions showed the same H2O2-dependence. This suggests that MPO2 can enter the main peroxidation pathway, possibly via its reaction with compound II. Both ferric myeloperoxidase and MPO2 showed catalase activity, in the presence or absence of Cl-, which predominated over chlorination at H2O2 concentrations above 200 microM. Thus, although the reaction of neutrophil myeloperoxidase with superoxide does not appear to impair its chlorinating ability, the H2O2 concentration in its environment will determine whether the enzyme acts primarily as a catalase or peroxidase.

Effects of oxygen radicals on cerebral arterioles

Abstract: Xanthine oxidase and xanthine, a combination that produces hydrogen peroxide and superoxide anion radical, applied topically in anesthetized cats equipped with cranial windows caused arteriolar dilation during application, sustained dilation 1 h after washout, and reduced reactivity to the vasoconstrictive effects of arterial hypocapnia, discrete lesions of the endothelium, and morphological abnormalities of the vascular smooth muscle by electron microscopy. Similar effects were seen in small, but not in large, arterioles during topical application of hydrogen peroxide or hydrogen peroxide plus ferrous sulfate, a combination that produces free hydroxyl radical. The functional changes caused by xanthine oxidase plus xanthine were inhibited completely by superoxide dismutase plus catalase. Superoxide dismutase or catalase, each by itself, eliminated the residual effects seen after washout and reduced the dilation during application of xanthine oxidase. The results show that superoxide anion radical and hydrogen peroxide produce reversible arteriolar dilation and that consistent vascular damage is produced in the presence of both superoxide anion radical and hydrogen peroxide.

Metal ions and oxygen radical reactions in human inflammatory joint disease.

Abstract: Activated phagocytic cells produce superoxide (O2-) and hydrogen peroxide (H2O2); their production is important in bacterial killing by neutrophils and has been implicated in tissue damage by activated phagocytes. H2O2 and O2- are poorly reactive in aqueous solution and their damaging actions may be related to formation of more reactive species from them. One such species is hydroxyl radical (OH.), formed from H2O2 in the presence of iron- or copper-ion catalysts. A major determinant of the cytotoxicity of O2- and H2O2 is thus the availability and location of metal-ion catalysts of OH. formation. Hydroxyl radical is an initiator of lipid peroxidation. Iron promoters of OH. production present in vivo include ferritin, and loosely bound iron complexes detectable by the 'bleomycin assay'. The chelating agent Desferal (desferrioxamine B methanesulphonate) prevents iron-dependent formation of OH. and protects against phagocyte-dependent tissue injury in several animal models of human disease. The use of Desferal for human treatment should be approached with caution, because preliminary results upon human rheumatoid patients have revealed side effects. It is proposed that OH. radical is a major damaging agent in the inflamed rheumatoid joint and that its formation is facilitated by the release of iron from transferrin, which can be achieved at the low pH present in the micro-environment created by adherent activated phagocytic cells. It is further proposed that one function of lactoferrin is to protect against iron-dependent radical reactions rather than to act as a catalyst of OH. production.

Detection of hydrogen peroxide produced by microorganisms on an ABTS peroxidase medium.

Abstract: Previously published methods to detect the production of hydrogen peroxide by microorganisms have been of limited usefulness for routine diagnosis because the sensitivity of some of these procedures does not allow the isolation of single H 2 O 2 -producing colonies. The new medium containing 2,2′-azino-di (3-ethyl benzthiazoline-6-sulphonic acid) and horseradish peroxidase is more sensitive and faster than established methods.

Photogeneration of hydrogen peroxide in aqueous TiO2 dispersions

Abstract: Evidence is presented which demonstrates that titanium dioxide does in fact photogenerate H2O2 in the presence of the donor sodium formate. However, this H2O2 has only a transient existence in aque...

Electrochemical sensor having three layer membrane containing immobilized enzymes

Abstract: An electrochemical sensor is formed having a working electrode for detecting hydrogen peroxide surrounded by a cylinder portion, and with an enzymecontaining membrane at its tip. The membrane has a porous layer permeable to hydrogen peroxide between a layer containing an immobilized enzyme capable of decomposing hydrogen peroxide and a layer containing an immobilized enzyme capable of decomposing a substrate to form hydrogen peroxide. The cylinder portion is embedded in the layer containing the hydrogen peroxide decomposing enzyme and surrounds the working electrode such that the electrode is in contact with the porous layer but is not in contact with the layer containing the hydrogen peroxide decomposing enzyme. The layer containing the hydrogen peroxide forming enzyme is on a side of the porous layer opposite the electrode so as not to contact the electrode. Activity of the hydrogen peroxide decomposing enzyme is no more than one-fourth of the activity of the hydrogen peroxide forming enzyme. The electrochemical sensor reduces base line elevation after measurement action has been discontinued and measurement of a next sample is restarted.

Changes in catalase activity and hydrogen peroxide concentration in plants in response to low temperature

Abstract: Taxicity of oxygen species such as free radicals and H2O2 has been invoked to explain a number of degradative processes in plants, most involving photo-oxidation Since catalase is a major protectant against accumulation and toxicity of H2O2, we examined alterations in catalase activity in several plant species (Pisum sativum L cv Greenfeast, Vigna radiata (L) R Wilcz, Cucumis sativus L cv Heinz Pickling, and Passiflora spp) during chilling, and compared this change to change in H2O2 content Catalase activity was reduced in a range of chilling sensitive and tolerant species by exposure to low temperature This reduction in catalase activity correlated better with the onset of visible symptoms than with the treatment itself Visible injury in turn was dependent on light and temperature differences Hydrogen peroxide concentrations invariably decreased with low temperatures Reduction in catalase activity therefore does not necessarily imply accumulation of H2O2 to damaging levels The absence of a clear inverse relationship between catalase activity and H2O2 concentration suggests the continued activity of other reactions that remove H2O2 and these may be important in the tolerance of plants to oxidative attack Loss of catalase activity may result from the inability of damaged peroxisomal membranes to transport catalase precursors into the peroxisome