Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of sulfhydryls in the protection of human polymorphonuclear neutrophils against extracellular oxidant attack was investigated by simultaneously exposing polymorphonuclear neutrophils to the thiol-oxidizing agent diamide and the oxidant-generating system xanthine-xanthine oxidase. Neither diamide nor the oxidants generated by the xanthine-xanthine oxidase system alone impaired the burst in chemiluminescence, hexose monophosphate shunt activity or formate oxidation normally seen during polymorphonuclear neutrophil phagocytosis. Incubation of the polymorphonuclear neutrophils simultaneously with diamide and xanthine-xanthine oxidase markedly impaired polymorphonuclear neutrophil phagocytosis, hexose monophosphate shunt activity, chemiluminescence and formate oxidation. Although the polymorphonuclear neutrophils exposed to diamide and xanthine-xanthine oxidase did not respond to a variety of phagocytizable stimuli, trypan blue exclusion was normal and hexose monophosphate shunt activity could be stimulated by diamide. The damaging effect of the diamide xanthine-xamthine oxidase system could be blocked by the addition of superoxide dismutase or catalase, but not by hydroxyl radical or singlet oxygen scavengers. We hypothesize that an unidentified population of thiols may play a role in protecting the polymorphonuclear neutrophil from endogenously derived oxidants.
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PMID:The effect of oxidant stress on diamide-treated human granulocytes. 46 44

To investigate the possibility that human polymorphonuclear leukocytes (PMN) elaborate sufficient amounts of hydrogen peroxide (H2O2) and other radicals of reduced oxygen to be autotoxic and retard directed cell movement and phagocytosis, the rate of ingestion of opsonized lipopolysaccharide-paraffin oil particles and movement through Nuclepore filters were studied. Ingestion rates were increased under anaerobic conditions and in normal aerobic conditions in the presence of extracellular catalase but not superoxide dismutase (SOD) or scavengers of singlet oxygen or hydroxyl radicals. Conversely, ingestion rates were decreased when cells were exposed to H2O2 or a superoxide anion (O2-)-H2O2 generating system of xanthine-xanthine oxidase. Catalase, but not SOD, prevented the effect and also enhanced the directed movement of PMN in normal aerobic conditions. PMN from volunteers administered 1600 U/day of the membrane lipid antioxidant alpha-tocopherol were hyperphagocytic but killed Staphylococcus aureus 502A less effectively than controls, suggesting that less H2O2 was available to damage PMN or kill bacteria. H2O2-dependent stimulation of the hexose monophosphate shunt, H2O2 release from phaogytizing PMN, and fluoresceinated concanavalin A cap formation promoted by H2O2 damage to microtubules were all diminished, but the release of O2- from phagocytizing PMN was not diminished in the vitamin E group. These results support the hypothesis that directed movement and phagocytosis by PMN are attenuated by autooxidative damage to the cell membrane by endogenously derived H2O2 and that the administration in vivo of vitamin E may prevent this damage by scavenging H2O2.
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PMID:Autooxidation as a basis for altered function by polymorphonuclear leukocytes. 87 28

Preexposure to hypoxia increased survival and lung reduced glutathione-to-oxidized glutathione ratios (GSH/GSSG) and decreased pleural effusions in rats subsequently exposed to continuous hyperoxia. In addition, lungs from hypoxia-preexposed rats developed less acute edematous injury (decreased lung weight gains and lung lavage albumin concentrations) than lungs from normoxia-preexposed rats when isolated and perfused with hydrogen peroxide (H2O2) generated by xanthine oxidase (XO) or glucose oxidase (GO). In contrast, when perfused with elastase or exposed to a hydrostatic left atrial pressure challenge, lungs isolated from hypoxia-preexposed rats developed the same acute edematous injury as lungs from normoxia-preexposed rats. The mechanism by which hypoxia preexposure conferred protection against H2O2 appeared to depend on hexose monophosphate shunt (HMPS)-dependent increases in lung glutathione redox cycle activity. First, before perfusion with GO, lungs from hypoxia-preexposed rats had increased glutathione peroxidase and glucose 6-phosphate dehydrogenase (but not catalase or glutathione reductase) activities compared with lungs from normoxia-preexposed rats. Second, after perfusion with GO, lungs from hypoxia-preexposed rats had increased H2O2 reducing equivalents, as reflected by increased GSH/GSSG and NADPH/NADPH+, compared with lungs from normoxia-preexposed rats. Third, pretreatment of rats with an HMPS inhibitor, (6-aminonicotinamide) or a glutathione reductase inhibitor, [1,3-bis(2-chloroethyl)-1-nitrosourea] prevented hypoxia-conferred protection against H2O2-mediated acute edematous injury in isolated lungs. These findings suggest that increased detoxification of H2O2 by glutathione redox cycle and HMPS-dependent mechanisms contributes to tolerance to hyperoxia and resistance to H2O2 of lungs from hypoxia-preexposed rats.
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PMID:Hypoxia increases glutathione redox cycle and protects rat lungs against oxidants. 321 62

The effects of tetrandrine, a benzylisoquinoline alkaloid useful in the treatment of silicosis, on a broad range of human neutrophil activities was examined in vitro. Random movement, chemotaxis and phagocytosis were significantly suppressed. There was minimal but significant inhibition of lysosomal enzyme secretion from specific (secondary) but not azurophil (primary) granules. The same concentration of tetrandrine (10 micrograms/ml) caused marked depression of hexose-monophosphate shunt activity and hydrogen peroxide production, but inhibition of superoxide anion generation was observed even at a concentration of 0.1 microgram/ml. This discrepancy was attributed to the capacity of tetrandrine to scavenge oxygen radicals, as shown by experiments using hypoxanthine-xanthine oxidase to generate superoxide. These potent antiphagocytic and antioxidant properties of tetrandrine may account for some of its remarkable anti-inflammatory effects.
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PMID:Antiphagocytic and antioxidant properties of plant alkaloid tetrandrine. 335 73

The antibody-dependent cell-mediated cytoxicity (ADCC) by human monocytes and neutrophils was investigated by measuring the release of 51chromate from prelabeled erythrocytes coated with immunoglobulin G. ADCC was found to be positively correlated to phagocytosis of 51Cr-labeled erythrocytes and to the postphagocytic events of the effector cells, activation of the hexose monophosphate shunt, and degranulation. Exclusion of oxygen from the incubation media halved the ADCC by both cell types without affectijg phagocytosis or degranulation. Likewise, ADCC by cells from patients suffering from chronic granulomatous disease (CGD) was only half the intensity of ADCC by cells from normals. Inhibitors of mitochondrial respiration were without depressing effect of ADCC. Azide, which in addition to its blocking action on oxydative phosphorylation also inhibits catalase and myeloperoxidase, resulted in a approximately equal to 40% stimulation of ADCC by cells from normals but was without effect of ADCC by cells from CGD patients. The hydroxyl radical scavenger, mannitol, significantly depressed ADCC by cells from normals (P < 0.01) but was without effect on cells from CGD patients. Azide and mannitol also were without effect on ADCC by normal cells when oxygen was excluded. In a xanthine-xanthine oxidase system, erythrocytes were effectively lysed. This lysis was inhibited by catalase, superoxide dismutase, and mannitol. When comparable concentrations of glucose oxidase were used no lysis was observed. H2O2 either alone or in combination with azide did not lyse erythrocytes. It is suggested that ADCC by both monocytes and neutrophils is partly dependent on the generation of hydroxyl radicals by the effector cells.
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PMID:Role of oxygen in antibody-dependent cytotoxicity mediated by monocytes and neutrophils. 625 48

The effects of the beta-receptor blockading agents, metoprolol and sotalol on neutrophil random motility, chemotaxis, post-phagocytic glycolysis, superoxide production, hexose monophosphate shunt activity, myeloperoxidase (MPO) mediated protein iodination and hydrogen peroxide production were assessed in vitro. The concentration range investigated was 10(-8)--10(-2) M for each drug. Both agents caused significant stimulation of neutrophil motility at concentrations of more than 10(-4) M. Increased migration was not associated with increased glycolysis or significant cyclic nucleotide fluctuations, but was inversely related to inhibition of superoxide and hydrogen peroxide generation and MPO mediated iodination with both drugs. In a further series of experiments to determine the relationship between the drug induced inhibition of H2O2 production and MPO mediated protein iodination to stimulation of motility it was found that concentrations of sotalol and metoprolol that caused these effects prevented HRP/H2O2/I- induced inactivation of the leucoattractant and inhibition of neutrophil chemotactic responsiveness. Neither drug inhibited the activity of MPO per se nor the reduction of ferricytochrome c by superoxide generated by the xanthine: xanthine oxidase system in vitro. It is suggested that enhanced neutrophil motility is not related to beta-receptor blockade but rather to restricting the availability of hydrogen peroxide and reactive products of the MPO/H2O2/halide system.
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PMID:In vitro stimulation of neutrophil motility by metoprolol and sotalol related to inhibition of both H2O2 production and peroxidase mediated iodination of the cell and leucoattractant. 625 68

The effects of dapsone on polymorphonuclear leukocyte functions and lymphocyte mitogen-induced transformation were assessed in vitro and in vivo in normal individuals and in newly diagnosed untreated patients with lepromatous leprosy. The effects of dapsone on the cell-free generation of superoxide by the xanthine: xanthine oxidase system and iodination of bovine serum albumin by horseradish peroxidase were also investigated. In normal individuals dapsone mediated stimulation of polymorphonuclear leukocyte migration in vitro and vivo. Dapsone had no effect on postphagocytic hexose monophosphate shunt activity in vivo. Similar effects were found in patients with lepromatous leprosy. Dapsone also decreased the inhibitory activity of serum from patients with lepromatous leprosy on normal polymorphonuclear leukocyte migration in vitro. Progressive loss of serum-mediated inhibition of migration was observed after ingestion of dapsone by the patients. Further experiments showed that stimulation of polymorphonuclear leukocyte motility was related to inhibition of lymphocyte transformation at high concentrations in vitro, but had slight stimulatory activity on phytohemagglutinin-induced transformation in controls and patients in vivo.
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PMID:In vitro and in vivo effects of dapsone on neutrophil and lymphocyte functions in normal individuals and patients with lepromatous leprosy. 626 48

A continuous cloned murine macrophage-like cell line, clone 16 derived from J774, has been found upon appropriate stimulation to be capable of oxidizing glucose by the hexose monophosphate shunt and producing O2- and H2O2. A variant in oxidative metabolism, clone C3C, was selected from this cell line which under similar conditions is unable to produce significant amounts of O2- and H2O2. When cells of the parental clone 16 were infected with epimastigotes of Trypanosoma cruzi, there was significant killing or growth inhibition of the parasites at 3 to 4 days after infection. In contrast, the parasites grew in the oxidative variant, clone C3C. Trypomastigote forms of T. cruzi were found to be only partially killed in the parental clone 16 but grew abundantly in the oxidative variant. Infection of the parental clone, but not the variant, was sufficient to stimulate oxygen metabolism as demonstrated by the increased reduction of nitro blue tetrazolium. Studies on the killing of T. cruzi epimastigotes in cell-free suspension by xanthine-xanthine oxidase indicated that 90% of the killing was catalase sensitive and due to H2O2, with at most 7 to 8% killing which could be inhibited by scavengers of . OH and singlet oxygen (1O2). In the in vitro experiment with H2O2 produced by glucose and glucose oxidase, the 50% lethal doses of epimastigotes and trypomastigotes were 6.0 and 8.7 nmol of H2O2 per min per ml, respectively, indicating that trypomastigotes were more resistant to killing by H2O2 than epimastigotes were. A reconstitution experiment of trypanocidal activity in clone C3C by ingestion of zymosan particles coupled with glucose oxidase showed that H2O2 was essential for this cytocidal process in the macrophage cell line. These results provide clear evidence for killing of an intracellular parasite by a continuous macrophage-like cell line and suggest the importance of the oxidative cytocidal mechanism in this process.
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PMID:Growth of Trypanosoma cruzi in a cloned macrophage cell line and in a variant defective in oxygen metabolism. 635 Jan 85

We have developed a quantitative assay to monitor the oxidative burst (H2O2 production) of polymorphonuclear leukocytes (PMNL) using single cell analysis by flow cytometry, and have examined whether PMNL respond to membrane stimulation with an all-or-none oxidative burst. During incubation with normal neutrophils, dichlorofluorescin diacetate diffused into the cells, was hydrolyzed to 2',7'-dichlorofluorescin (DCFH) and was thereby trapped within the cells. The intracellular DCFH, a nonfluorescent fluorescein analogue, was oxidized to highly fluorescent 2',7'-dichlorofluorescein (DCF) by PMNL stimulated by phorbol myristate acetate (PMA). That the oxidative product was DCF was shown by excitation/emission spectra and by mass spectrometry of the product from PMA-stimulated PMNL. Normal resting and PMA-stimulated PMNL oxidized 6.9 +/- 0.7 and 160 +/- 13 attomoles DCF per cell, respectively, in 15 min. Absence of calcium and magnesium ions and/or addition of 2 mM EDTA did not inhibit DCF formation by PMNL stimulated by 100 ng/ml PMA. Since EDTA prevented aggregation of PMNL (even when stimulated by 100 ng/ml PMA), which would prevent accurate flow cytometric analysis, further experiments were performed with EDTA in the medium. A close correlation between average DCFH oxidation and hexose monophosphate shunt stimulation was demonstrated using cells from patients whose PMNL had oxidative metabolic defects of varying severity. Intracellular DCFH was also oxidized by reagent H2O2 or oxygen derivatives generated by glucose oxidase + glucose or by xanthine oxidase + acetaldehyde; DCFH oxidation by these systems was inhibited by catalase but unchanged by superoxide dismutase. The data indicate that the DCFH oxidation assay is quantitatively related to the oxidative metabolic burst of PMNL, and they strongly suggest that the reaction is mediated by H2O2 generated by the PMNL. Incubation of PMNL with varying concentrations of PMA caused graded responses by all PMNL present; i.e., 1 ng/ml PMA caused a mean response of 34% maximal with a single population of responding PMNL (rather than 66% resting and 34% fully stimulated as predicted by the all-or-none hypothesis). Thus, with these assay conditions, oxidative product formation by PMNL occurs as a graded response to membrane stimulation by PMA.
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PMID:Flow cytometric studies of oxidative product formation by neutrophils: a graded response to membrane stimulation. 683 55

We have characterized the effects of phorbol myristate acetate (PMA) on human monocyte and neutrophil oxidative metabolism and antibody-dependent cytotoxicity toward anti-D sensitized human erythrocytes (RBC) and a human lymphoblastoid cell line (CEM). Hexose monophosphate shunt activity was measured by [1-(14)C]glucose oxidation and target lysis by (51)Cr release. PMA produced a dose-dependent stimulation of hexose monophosphate shunt activity. Neutrophils responded with higher hexose monophosphate shunt activity and at a lower PMA concentration than did monocytes. PMA increased monocyte lysis of antibody-sensitized RBC by two-thirds, but did not affect lysis of CEM targets. Neutrophils were unable to lyse either antibody-sensitized or nonsensitized RBC without the addition of PMA. When PMA was added, lysis of both targets increased markedly. Neutrophils without PMA were able to lyse a small number of both antibody-sensitized and nonsensitized CEM targets. PMA also increased neutrophil lysis of these targets. Target lysis by neutrophils from a patient with chronic granulomatous disease, cells unable to produce reactive oxygen species, was not increased by PMA. Chronic granulomatous disease monocytes, however, responded to PMA by more than doubling lysis of antibody-sensitized RBC. Hypoxia inhibited PMA augmentation of antibody-sensitized RBC lysis by neutrophils, but not by monocytes. Generation of reactive oxygen species by the xanthine-xanthine oxidase system inhibited CEM growth, but did not cause lysis, indicating that in some cases oxidative injury may be nonlytic. We suggest that PMA augments neutrophil cytotoxicity to tumor and RBC targets by stimulating reactive oxygen species-mediated lysis, but in monocytes augmentation of lysis is due to activation of a nonoxidative mechanism of lysis.
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PMID:Activation of monocyte and granulocyte antibody-dependent cytotoxicity by phorbol myristate acetate. 706 17


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