Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 formation of carbon centered free radicals, identified as methylcarbonyl species, was observed using ESR spectroscopy and the spin trapping agent 4-pyridyl-1-oxide-N-t-butyl nitrone (4-POBN) during the oxidation of acetaldehyde by xanthine oxidase. The reaction was dependent upon the presence of OH. radicals and was inhibited by the addition of superoxide dismutase, catalase or OH. radical scavengers. The generation of methylcarbonyl radicals was associated with a doubling of stable acetaldehyde adducts with serum albumin, and 4-POBN or superoxide dismutase and catalase, completely blocked this effect. Thus, methylcarbonyl radicals contributed to acetaldehyde-mediated protein alkylation which is involved in causing toxic as well as immunological reactions ascribed to acetaldehyde.
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PMID:Free radical activation of acetaldehyde and its role in protein alkylation. 802 86

One of the current theories of cardiovascular disease is that it may begin with oxygen radical-induced damages. Extensive studies have been made in different laboratories to elucidate the mechanism of oxidative damages in the presence of added iron salts. However, those in vitro studies are unlikely to be relevant to the in vivo situation, where in the normal physiological condition most of the iron remains bound with proteins. In the present study we have demonstrated that an in vitro system containing desferrioxamine, a strong iron chelator, superoxide generated by the action of xanthine oxidase on acetaldehyde initiates lipid peroxidation and protein changes in the guinea pig cardiac microsomes. We have further demonstrated that superoxide-initiated lipid peroxidation and protein changes are completely prevented by ascorbic acid. SOD also prevents but catalase, alpha-tocopherol, glutathione, uric acid, thiourea, mannitol and histidine are without effect. When NADPH is used instead of generated superoxide, the lipid peroxidation and protein changes are exclusively inhibited by ascorbic acid. SOD, catalase and other antioxidants are ineffective. The results obtained with guinea pigs may be extrapolated to humans, because like guinea pigs humans are also incapable of synthesizing ascorbic acid.
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PMID:Protective effect of ascorbic acid against lipid peroxidation and oxidative damage in cardiac microsomes. 810 91

When Escherichia coli was incubated with xanthine oxidase and acetaldehyde, the killing of E. coli was accelerated by iron-EDTA but inhibited by hematin or hemoglobin. On the other hand, when E. coli was incubated with human neutrophils in the presence of phorbol myristate acetate (PMA), all of these iron species at concentrations of a few micromolar accelerated the inactivation of neutrophils and in so doing protected the E. coli from being killed by the neutrophils. The inactivation of the neutrophils was accompanied by an increase in lipid peroxidation and by a decrease in viability measured with trypan blue. This inactivation was inhibited by scavengers such as deoxyribose, mannitol, or thiourea. Desferrioxamine B and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) both inhibited the inactivation mediated by iron-EDTA, but had no effect on the hematin- or hemoglobin-mediated inactivation. Vanadium (vanadyl ion), an effective Fenton reagent, behaved in the same way as iron-EDTA relative to the effects of DMPO on neutrophil inactivation. These results led us to conclude that neutrophils were inactivated during PMA stimulation by OH radicals in the presence of iron-EDTA and by some other oxidizing species when hematin or Hb is present. Ascorbate enhanced the inactivation of neutrophils mediated by these iron species. Catalase was very effective in inhibiting neutrophil inactivation. Superoxide dismutase was not as effective but the combination with catalase was most effective.
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PMID:The effect of hemoglobin, hematin, and iron on neutrophil inactivation in superoxide generating systems. 813 43

Lipid peroxidation (LPO) is the oxidative deterioration of polyunsaturated fatty acids (PUFA) with the production of lipid hydroperoxides, cyclic peroxides, cyclic endoperoxides, and finally fragmentation to ketones and aldehydes (including malonaldehyde, MDA). Estimation of LPO through MDA formation measured by assaying thiobarbituric acid (TBA) reactive products remains the method of choice to study the development of oxidative stress in tissues. However, MDA estimation by TBA reactive products is non-specific and often gives erroneous results. In this report we describe a method using high-performance liquid chromatographic separation to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), acetone, and propionaldehyde (PDA), the degradation products of oxygen-derived free radicals (ODFR) and PUFA, as presumptive markers for LPO. Oxidative stress was induced in the tissue by perfusing an isolated rat heart with hydroxyl radical generating system (xanthine + xanthine oxidase + FeCl3 + EDTA). The coronary effluents were collected, derivatized with 2,4-dinitrophenylhydrazine (DNPH), and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected onto a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v), measured at three different wavelengths (307, 325 and 356 nm) using a Waters M-490 multichannel UV detector and collected for gas chromatography-mass spectrometry (GC-MS) analysis. The peaks were identified by cochromatography with DNPH derivatives of authentic standards, peak addition, UV pattern of absorption at the three wavelengths, and by GC-MS. The retention items of MDA, FDA, ADA, acetone, and PDA were 5.3, 6.6, 10.3, 16.5, and 20.5 min, respectively. The results of our study indicated progressive increase of all five lipid metabolites as a function of the duration of ODFR perfusion. Hydroxyl radical scavengers, superoxide dismutase plus catalase, completely inhibited the formation of these lipid metabolites, demonstrating that the release of lipid metabolites from the isolated heart was indeed in response to oxidative stress. Since MDA, FDA, ADA, acetone, and PDA are the products of ODFR-PUFA interactions, this method allows proper estimation of LPO which monitors the oxidative stress developed during the reperfusion of ischemic myocardium.
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PMID:High-performance liquid chromatographic method for the simultaneous detection of malonaldehyde, acetaldehyde, formaldehyde, acetone and propionaldehyde to monitor the oxidative stress in heart. 813 6

Sera of patients with various inflammatory and autoimmune rheumatic diseases were screened for the presence of xanthine oxidase (XOD) and compared to sera from healthy donors and patients with nonrheumatic diseases including AIDS, internal diseases, and different carcinomas. Up to 50-fold higher levels of XOD were detected in rheumatic sera (P < 0.001). In addition, serum sulfhydryls (SH) were determined as sensitive markers of oxidative stress. The SH status in rheumatic patients was diminished by 45-75% (P < 0.001) and inversely correlated to the concentration of serum XOD (R = 0.73), suggesting a causal interrelation. The depletion of serum sulfhydryls by the oxyradical-producing XOD/acetaldehyde system was mimicked successfully ex vivo in human serum from healthy donors. Cortisone treatment of patients suffering from systemic lupus erythematosus and rheumatoid arthritis impressively normalized elevated XOD concentrations in rheumatic sera to those of healthy controls. The participation of xanthine oxidase in the depletion of serum antioxidants in rheumatic patients is discussed in the light of substrate availability and Km values.
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PMID:Elevated levels of xanthine oxidase in serum of patients with inflammatory and autoimmune rheumatic diseases. 822 62

The extracellular production of singlet oxygen (O2(1 delta g)) by stimulated macrophages was measured using a modification of our quantitative method initially developed to measure the intracellular production of O2(1 delta g) by neutrophils (Steinbeck, M. J., Khan, A. U., and Karnovsky, M. J. (1992) J. Biol. Chem. 267, 13425-13433). Glass coverslips were coated with the specific chemical trap for O2(1 delta g), 9,10-diphenylanthracene (DPA) and perylene, which is an internal standard, in a methylene chloride solution containing 0.3 mg/ml polystyrene. On evaporation, the polystyrene formed an even coating of DPA and perylene over the surface of a glass coverslip (PDP film). Unstimulated macrophages or macrophages stimulated with 4 beta-phorbol 12-myristate 13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP) were then added to the PDP film in a darkened room and incubated at 37 degrees C for 30 min in a humidified 5% CO2 atmosphere. Both unstimulated and stimulated cells adhered to the PDP film in approximately equivalent numbers. Only stimulated cells produced measurable amounts of O2(1 delta g) in a dose-dependent response to either PMA or fMLP. The production of O2(1 delta g) by macrophages stimulated with PMA was maximal in response to 25 ng, 17.8 +/- 1.3 nmol of O2(1 delta g)/approximately 1.00 x 10(6) cells. The maximal response for fMLP was at a concentration of 1 microM, 18.4 +/- 1.0 nmol of O2(1 delta g)/approximately 1.00 x 10(6) cells. The specific detection of O2(1 delta g) by this method was confirmed by thermally releasing O2(1 delta g) from the DPA-O2(1 delta g) reaction product, DPA-endoperoxide, regenerating the original DPA compound. Production of O2(1 delta g) by the stimulated cells was inhibited 80-89% by the addition of 60-120 micrograms of superoxide dismutase, an enzyme that converts superoxide to hydrogen peroxide and ground state molecular oxygen or 79-84% with the addition of 2 mM histidine, an avid quencher of O2(1 delta g). Neither of these additions interfered with adhesion of the cells to the PDP film. The ability of superoxide dismutase to inhibit the production of O2(1 delta g) suggested that O2(1 delta g) was produced via a superoxide-dependent route. The ability of an oxidase to produce O2(1 delta g) secondary to superoxide production was substantiated further using a xanthine oxidase-acetaldehyde system. Purified xanthine oxidase produced both superoxide and O2(1 delta g), and their production was inhibited by the addition of superoxide dismutase.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Extracellular production of singlet oxygen by stimulated macrophages quantified using 9,10-diphenylanthracene and perylene in a polystyrene film. 834 Mar 89

Oxygen free radicals may be generated during ethanol metabolization by cytochrome P450, or due to the formation of xanthine oxidase by ethanol effect on xanthine dehydrogenase. After transformation into acetaldehyde, the metabolism of this compound by xanthine oxidase or by aldehyde oxidase also generates oxygen radicals. We present the hypothesis of a vicious cycle during ethanol metabolization by aldehyde oxidase, which would amplify the process and be responsible for an increased degree of lipid peroxidation.
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PMID:[Alcohol and free oxygen radicals]. 839 65

--2-(Dimethylamino) fluorene (1a) and 5-benzoyloxy-2,3,7,8,12,13,17,18-octaethylporphyrin (4) react with superoxide anion radical (generated from KO2/18-crown-6 polyether) in aprotic media. Yet, when incorporated into the lipid bilayer of dimyristoyl phosphatidylcholine liposomes, these two substrates are inert to superoxide, generated enzymatically (xanthine oxidase/acetaldehyde) or radiolytically (60Co or 137Cs source/formate solution). On the other hand, 7-acetoxy-4-methylcoumarin (6), which reacts with superoxide in aprotic media yielding the corresponding 4-methylumbelliferone (7), also gives the same product when incorporated within the liposomal bilayer and reacted with radiolytically or enzymatically generated superoxide. In the latter case, the reaction is inhibited by SOD. NMR studies indicate that in contradistinction to the highly lipophilic 1a and 4, which presumably lie well within the lipid bilayer, 7 lies in a highly polar region of the bilayer. These results suggest that superoxide anion does not penetrate deep into the liposomal bilayer; nevertheless, superoxide reactions can, indeed, be observed, provided the active site of the substrate lies at or near the lipid-water interface.
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PMID:Can superoxide organic chemistry be observed within the liposomal bilayer? 872 33

Reactive oxygen species are involved in luminol chemiexcitation induced in biological systems, but the contribution of nitrogen-derived oxidants in the process still remains unclear. Herein, we report that luminol chemiluminescence (LCL) induced by a superoxide (O2.-)- and hydrogen peroxide (H2O2)-generating system (2-25 mU/ml xanthine oxidase plus acetaldehyde and oxygen) was markedly inhibited by nitric oxide (.NO) added either as bolus (0-10 microM) or a continuous flow (0-10 microM/min). However, the inhibition of LCL was followed by an overshoot in light emission after most .NO was consumed or the infusion stopped and was due to reactions of remaining peroxynitrite, the product of the reaction between O2.- and .NO, with luminol. Nitric oxide also inhibited peroxynitrite- and glucose oxidase-induced LCL, but no overshoot was observed. On the other hand, a continuous flux of pure peroxynitrite, at 2 to 10 microM/min, induced LCL with quantum yields close to those obtained by identical micromolar fluxes of O2.-, while peroxynitrite formed from the decomposition of the sydnonimine SIN-1 yielded 76% of the chemiluminescence obtained with authentic peroxynitrite. Peroxynitrite-induced LCL was 80 and 55% inhibitable by SOD and catalase, respectively, showing that there were O2.- and H2O2-dependent routes of chemiexcitation. The hydroxyl radical scavengers dimethyl sulfoxide, mannitol, and ethanol and the metal chelator diethylenetriaminepentaacetic acid did not inhibit peroxynitrite-induced LCL while desferrioxamine was an efficient inhibitor of light emission by reaction with an activated state of peroxynitrous acid which is responsible of performing the initial one-electron oxidation of luminol. Our results are consistent with a dual role of .NO in O2.(-)-induced LCL: (I) formation of peroxynitrite which in turn promotes the light-emitting route and (II) reaction with luminol radical intermediates directing the system toward a dark pathway. These considerations are of critical importance when analyzing cell- and tissue-derived LCL in .NO-, O2.(-)-, and peroxynitrite-producing systems.
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PMID:Modulatory role of nitric oxide on superoxide-dependent luminol chemiluminescence. 880 69

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.
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PMID:Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases. 889 26


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