Generation Of Superoxide Ion Research Articles

Activated oxygen species in the oxidation of glutathione A kinetic study

The generation of the superoxide ion in the oxidation of glutathione (GSH) by molecular oxygen has been demonstrated in the absence and in the presence of a catalytic amount of copper ion. An effort has been made to quantify the production of superoxide ion by an NMR method utilising Cu,Zn superoxide dismutase and to correlate it to the reaction mechanism. The oxidation process is first-order with respect to GSH and molecular oxygen, the ratio Δ[GSH]/Δ[O 2] being 4.0 ± 0.1. The rate of superoxide ion generation is independent of the GSH concentration and increases linearly with the O 2 concentration. The addition of Cu 2+ increases the rate of GSH oxidation and of O 2 consumption. Also in this case the oxidation process is first-order with respect to GSH and O 2, while a saturation effect with respect to Cu 2+ is observed. A kinetic scheme involving the formation of a short-living charge-transfer complex between GSH and oxygen is proposed to explain the experimental data.

Defective Leukocyte Fungicidal Activity in End-Organ Resistance to 1,25-Dihydroxyvitamin D

Recent studies have shown 1,25(OH)2D3 receptor-mediated modulation of leukocyte proliferation, differentiation, and function. We examined the phagocytosis and killing of microorganisms by neutrophils and monocytes from five patients of three families with hereditary resistance to 1,25(OH)2D3. Phagocytosis of microorganisms by patients' neutrophils and monocytes was normal. However, defective neutrophil killing activity toward Candida albicans (30-40% of controls) was found in all patients. The killing of Staphylococcus aureus was normal. The neutrophil chemiluminescence, nitroblue tetrazolium (NBT) dye reduction, and the generation of superoxide ions and hydrogen peroxide by neutrophils and monocytes after induction by either soluble stimuli or zymozan particles, did not differ from those in controls. The neutrophil myeloperoxidase activity was also normal. Monocytes obtained from two patients of different families before long-term calcium infusion therapy and after they became normocalcemic, demonstrated a similar impaired fungicidal activity toward Saccharomyces cerevisiae, indicating that hypocalcemia itself was not the cause of the killing defect. However, the addition of the Ca+2 ionophore A23187 (1 microM) to the test medium restored the monocyte fungicidal activity to normal. As patients' neutrophil cytosolic free calcium concentration was similar to that in controls, it is suggested that 1,25-(OH)2D3 exerts its effect on leukocyte function by a putative receptor-mediated regulation of subcellular calcium localization which may be important for fungicidal activity.

Platelet activating factor is a potent stimulant of the production of active oxygen species by human monocyte-derived macrophages

Platelet activating factor (PAF; C16), 1-O-Hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine) stimulated the production of active oxygen species by human monocyte-derived macrophages in culture. An optimal response was observed at a concentration of 13 microM PAF with half-maximal stimulation at 5 microM. The generation of superoxide ion (O2-) and hydrogen peroxide (H2O2) in response to PAF was inhibited specifically by a PAF-antagonist (1-O-Hexadecyl-2-acetyl-sn-glycero-3-phospho (N,N,N,-trimethyl) hexanolamine; such generation varied with the degree of maturation of cultured monocytes into macrophages. Production of active oxygen species increased progressively to reach a maximal level between days 4 to 6 of culture and remained maximal to day 12, after which it decreased progressively. Phorbol 12-myristate-13-acetate (PMA) and opsonized zymosan also stimulated generation of O2- and H2O2. PAF was however distinguished by its potent capacity to stimulate O2- and H2O2 production even at late stages of macrophage maturation (18 days), at which time both PMA and zymosan lacked significant effect. These findings suggest that PAF is a factor of potential relevance to the inflammatory role of the macrophage in atherogenesis.

Ca2+ priming during vitamin D-induced monocytic differentiation of a human leukemia cell line.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) induces monocytic differentiation of the human promyelocytic leukemia line, HL-60, and enhances Ca2+ transport in target cells of the mineral metabolism system. Hence, we determined whether the steroid's maturational effect on HL-60 involves alterations of intracellular calcium [( Ca2+]i). We found that, as detected by indo-1 fluorescence, [Ca2+]i increases in a slow tonic manner from 99 +/- 11 nM in virgin HL-60 to 182 +/- 19 nM (p less than 0.001) in those treated with 1,25-(OH)2D3 for 24 h. The first apparent rise in [Ca2+]i occurs at between 6 and 12 h and parallels expression of alpha-thrombin and N-formyl-methionyl-leucyl-phenylalanine (fMLP) receptors. This increase in [Ca2+]i is derived from extracellular calcium as its reduction abolishes the effect. The increase in [Ca2+]i is associated with an increase in inositol trisphosphate-stimulated Ca2+ flux from intracellular stores. Interestingly, 1,25-(OH)2D3-mediated HL-60 differentiation as manifest by expression of the macrophage-specific antigen, 63D3, is not blocked by low extracellular calcium. In contrast, the fMLP-induced superoxide ion generation is diminished if the increase in [Ca2+]i is prevented. Furthermore, fMLP-stimulated signal transduction is also reduced by limiting the stimulation of [Ca2+]i during 1,25-(OH)2D3 treatment. Thus, although differentiation of HL-60 to the monocytic phenotype by 1,25-(OH)2D3 is Ca2+-independent, expression of response to regulatory stimuli requires priming of cellular Ca2+ stores. The latter appears to be induced by 1,25-(OH)2D3 via stimulated Ca2+ entry through the plasma membrane.

The role of cupric ions in the generation of superoxide in natural waters

Photochemical generation of superoxide ions (O 2 ⊘) in water bodies has been associated with both synthetic and naturally occurring organic compounds. Indirect superoxide measurements are usually made by determining the concentration of hydrogen peroxide (as a product of superoxide dismutation), or by measuring the amount of nitrite produced when superoxide oxidizes hydroxylamine. We have collected evidence that, under alkaline conditions, cupric ions generate superoxide in natural waters by a very sensitive catalytic reaction. This reaction is enhanced by hydroxyl and borate ions. Strong natural and synthetic ligands inhibit the reaction, suggesting that only free or hydrolyzed species are involved. Copper speciation studies were performed using this technique. These results bring a new parameter for evaluating copper toxicity to the aquatic biota, i.e. the toxicity via superoxide ions.

Evidence for the thermal generation of superoxide ions on lanthanum oxide (La2O3)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for the thermal generation of superoxide ions on lanthanum oxide (La2O3)Ji Xiang Wang and Jack H. LunsfordCite this: J. Phys. Chem. 1986, 90, 17, 3890–3891Publication Date (Print):August 1, 1986Publication History Published online1 May 2002Published inissue 1 August 1986https://doi.org/10.1021/j100408a010RIGHTS & PERMISSIONSArticle Views295Altmetric-Citations65LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (278 KB) Get e-Alerts

ChemInform Abstract: Quantitative Generation of Singlet Dioxygen via the Reaction of Tris(bipyridine)ruthenium(III) with Superoxide Ion in Aqueous Solution.

AbstractAuseful photochemical method for the aqueous generation of superoxide ion, the kinetics of its 7 oxidation by Ru(bpy)ä+ as a function of pH, and the quantitative production of ′A802 in the title reaction is described (see scheme, flash photolysis (300‐ns pulse), pH 2‐9, ionic strength 0.1 Mmaintained with LiCl, 23°C).

Increased rate of superoxide ion generation in Fanconi anemia erythrocytes

The rate of generation of superoxide ion, the concentration of Cu, Zn superoxide dismutase and the hematalogical parameters were measured in red blood cells obtained from Fanconi anemia patients and from healthy individuals. No significative difference in the superoxide dismutase concentration was found, while the rate of generation of the superoxide ion doubled in Fanconi anemia patients. The steady-state concentration of the superoxide ion was calculated from these data and was found to be 2.3 times higher in Fanconi anemia erythrocytes than in controls. The possible consequences with respect to the alterations in FA are discussed.

Generation of superoxide ion in human red blood cell lysates.

The generation of superoxide ion in human red blood cell lysates was investigated by an experimental method employing Cu,Zn superoxide dismutase as O2- scavenger and EPR to probe the oxidation state of the enzyme. The average value of the O2- flux in the erythrocytes of 8 normal individuals was (2.02 +/- 0.97) X 10(-8) M S-1. A progressive saturation of the rate of O2- production was found increasing PO2, KM = 1.04 X 10(-4) M, while the autoxidation of oxyhemoglobin did not contribute significantly to the measured O2- production.

Evidence for photochemical generation of superoxide ion in humic waters

On irradiation with visible or near UV light the coloured substances in natural humic waters can undergo several reactions. They may be bleached and partially degraded1–3, perhaps by a cyclic mechanism involving oxidation and reduction of iron4, or they may generate a variety of free radicals5 or serve as sensitizers for the generation of singlet oxygen6–8. They may also bring about the generation of hydrogen peroxide9–11. It has been suggested10,11 that the actual photochemical process may be the generation of superoxide ion, and that hydrogen peroxide is produced by the dismutation of this. We present here more direct evidence for the photochemical generation of superoxide ion, O2·−, in natural waters.

Photochemical generation of superoxide ions from .mu.-superoxo-decacyanodicobalt(III) ions in aqueous solutions

Photochemical generation of superoxide ions from .mu.-superoxo-decacyanodicobalt(III) ions in aqueous solutions

Photochemical generation of superoxide ion (O2-) by rose bengal and Ru(bpy)32+

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemical generation of superoxide ion (O2-) by rose bengal and Ru(bpy)32+Vakula S. Srinivasan, Denise Podolski, Ned J. Westrick, and Douglas C. NeckersCite this: J. Am. Chem. Soc. 1978, 100, 20, 6513–6515Publication Date (Print):September 1, 1978Publication History Published online1 May 2002Published inissue 1 September 1978https://doi.org/10.1021/ja00488a048RIGHTS & PERMISSIONSArticle Views370Altmetric-Citations62LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (375 KB) Get e-Alerts Get e-Alerts

Base-induced generation of superoxide ion and hydroxyl radical from hydrogen peroxide

Base-induced generation of superoxide ion and hydroxyl radical from hydrogen peroxide