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 poly(ADP-ribose) in primary cultures of rabbit synovial fibroblasts after treatment with active oxygen released by xanthine/xanthine oxidase is inhibited by addition of 1 and 10 microM 4-hydroxy-2,3-trans-nonenal (HNE). The endogenous formation of HNE by the xanthine/xanthine oxidase system is not responsible for the inhibitory effect of the aldehyde, owing to the low accumulation rate of the lipid peroxidation product in the system used. HNE is able to inhibit the isolated nuclear enzyme ADP-ribosyltransferase, as shown by an in vitro assay with an Ki of 4 mumol/litre. Therefore the molecular basis of HNE-mediated effects on cell proliferation, differentiation and transformation might be due to the inhibitory effect of poly(ADP-ribos)ylation.
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PMID:Inhibition of poly(ADP-ribose) formation by 4-hydroxynonenal in primary cultures of rabbit synovial fibroblasts. 864 46

Iron catalyzed free radical formation and lipid peroxidation are accepted mechanisms of heme protein-induced acute renal failure. However, the source(s) of those free radicals which trigger lipid peroxidation in proximal tubular cells remains unknown. This study tested the potential involvement of mitochondrial electron transport, xanthine oxidase activity, and arachidonic acid metabolism in the heme-induced peroxidative state. The impact of cytosolic Ca2+ loading also was assessed. Rhabdomyolysis was induced in mice by glycerol injection, and two hours later heme-laden proximal tubular segments (PTS) were isolated for study. PTS from normal mice served as controls. During 30 to 60 minute incubations, heme loaded PTS developed progressive cytotoxicity (LDH release) and iron-dependent lipid peroxidation (malondialdehyde, MDA, generation; inhibited by deferoxamine). Site 2 (antimycin A) or site 3 (cyanide, hypoxia) mitochondrial respiratory chain inhibition completely blocked lipid peroxidation, whereas site 1 inhibition (rotenone) doubled its extent (presumably by shunting NADH through NADH dehydrogenase, a free radical generating system). Conversely, these agents did not substantially alter MDA in normal PTS. Normal and heme loaded PTS developed comparable degrees of LDH release during respiratory blockade irrespective of increased or decreased MDA production (indicating that lipid peroxidation was not a critical determinant of cell death). Neither increasing free arachidonic acid (PLA2 treatment) nor adding cyclooxygenase/lipoxygenase/cytochrome p450 inhibitors conferred a consistent protective effect. Altering free Ca2+ status (chelators; ionophore addition) and xanthine oxidase inhibition had no discernible impacts. Despite mitochondrial free radical production, mitochondrial function, as assessed by the ATP/ADP ratio, seemingly remained intact. In conclusion, (1) the terminal mitochondrial respiratory chain is the dominant source of free radicals which trigger PTS lipid peroxidation; (2) iron is a required secondary factor; (3) although mitochondria fuel lipid peroxidation, they do not appear to be critical targets of the heme-induced oxidant attack.
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PMID:Mitochondrial free radical production induces lipid peroxidation during myohemoglobinuria. 864 15

A biphenyl compound, 3,4,3',4'-tetrahydroxy-5,5'-diisopropyl-2,2'-dimethylbiphenyl (1), and a flavonoid, eriodicytol (2), were isolated as antioxidative components from the leaves of Thymus vulgaris by bioassay-directed fractionation. These compounds inhibited superoxide anion production in the xanthine/xanthine oxidase system. Mitochondrial and microsomal lipid peroxidation induced by Fe(III)-ADP/NADH or Fe(III)-ADP/NADPH were also inhibited by these compounds. Compound 1 is an extremely potent antioxidant; complete inhibition was observed at 1 microM against both microsomal and mitochondrial peroxidation. Furthermore, compound 1 protected red cells against oxidative hemolysis. These phenolic compounds were shown to be effective to protect biological systems against various oxidative stresses.
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PMID:Antiperoxidative components in Thymus vulgaris. 869 32

Two typical systems of lipid peroxidation in egg yolk phosphatidylcholine (egg PC) liposomes were compared: an enzymic system involving superoxide (O2) generated by xanthine (X), xanthine oxidase (XO) and Fe(3+)-chelates (Fe(3+)-ADP and Fe(3+)-EDTA), and a non-enzymic system involving ascorbic acid (ASA) and Fe2+. These two systems exhibited a different pH-dependence: the rate in the enzymic system was maximal at pH 8-8.5, whereas that in the non-enzymic system was high below pH 7.4 and low above pH 7.6. The rates of lipid peroxidation differed with the membrane charge, and this charge-dependent phenomenon differed in the two peroxidation systems: in the Fe(3+)-chelates/X-XO-system, the rate was slow in neutrally charged egg PC liposomes and rapid in egg PC liposomes containing negatively charged dicetylphosphate (DCP) or positively charged stearylamine (SA), whereas in the Fe2+/AsA-system, the rate was rapid in neutral egg PC liposomes but no lipid peroxidation occurred in egg PC liposomes charged with DCP or SA. The decomposition rate of the hydroperoxide of PC (PC-OOH) incorporated into dimyristoyl-phosphatidylcholine (DMPC) liposomes differed depending on the membrane charge in the two systems and this charge-dependence of the rates correlated well with that of the initiation rate of lipid peroxidation dependent on membrane charge. In the Fe2+/AsA-system, lipid peroxidation depended on the endogenous presence of PC-OOH, and the amounts of PC-OOH required for initiation of the reaction differed depending on the membrane charge. However, in the Fe(3+)-chelates/X-XO-system, lipid peroxidation occurred very slowly in the absence of PC-OOH, but rapidly in its presence.
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PMID:Lipid peroxidation in egg phosphatidylcholine liposomes: comparative studies on the induction systems Fe2+/ascorbate and Fe(3+)-chelates/xanthine-xanthine oxidase. 874 72

We investigated the hypothesis that xanthine oxidase (XO) mediates platelet aggregation and cyclic flow variations (CFVs) in stenosed canine coronary arteries. CFVs were produced by an external constrictor placed at the site of the coronary artery with the injured endothelium. The severity of CFVs was evaluated by a pulsed Doppler flow probe. If CFVs developed, dogs intravenously received allopurinol, a specific XO inhibitor. The transcardiac gradient (difference between coronary vein and left atrium) of purine metabolites was determined during CFVs and after allopurinol administration. Allopurinol significantly reduced CFVs (from 8 +/- 1 to 1 +/- 1 cycles/h, P < 0.01, n = 14), whereas saline did not (from 8 +/- 1 to 7 +/- 1 cycles/h, n = 7). In seven dogs with CFVs, the transcardiac gradient of xanthine and uric acid concentrations significantly increased after the establishment of CFVs and significantly decreased after the administration of allopurinol. In vitro platelet studies showed that XO enhanced (from 30.9 +/- 2.0 to 47.6 +/- 1.5%, P < 0.0001, n = 10) and allopurinol inhibited ADP-induced platelet aggregation (from 48.3 +/- 1.3 to 24.8 +/- 1.5%, P < 0.0001, n = 10). Our results indicate that allopurinol inhibits platelet aggregation in vitro and provides a protection against CFVs in vivo. Thus XO may be an important mediator in this model.
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PMID:Xanthine oxidase mediates cyclic flow variations in a canine model of coronary arterial thrombosis. 876 49

Experiments were designed to evaluate endothelium-dependent responses of pulmonary arteries following prolonged exposure to oxygen-derived free radicals. Rings of canine pulmonary arteries with and without endothelium were suspended for measurement of isometric force in organ chambers and incubated with xanthine (10(-4)M) plus xanthine oxidase (0.015 U/ml) for 1 h in the absence and presence of either superoxide dismutase (SOD, 150 U/ml), catalase (1,200 U/ml), deferoxamine (10(-3)M), or a combination of all three scavengers. Xanthine plus xanthine oxidase caused significantly greater contractions of rings without compared with those with endothelium. In rings with endothelium, contractions were reduced by SOD or catalase but not by deferoxamine. Following 1 h of exposure to xanthine plus xanthine oxidase, endothelium-dependent relaxations to ADP were reduced but not those to bradykinin or the calcium ionophore A-23187 (calcimycin). Relaxations to ADP were not corrected by incubation with the antioxidants used singly or in combination during the exposure to xanthine plus xanthine oxidase. These results suggest that oxygen-derived free radicals generated from exogenously applied xanthine plus xanthine oxidase cause contractions of canine pulmonary arteries. In addition, even when contractions of rings with endothelium were prevented by SOD and catalase, subsequent expression of some but not all endothelium-dependent relaxations were reduced. Therefore, scavenging of oxygen-derived free radicals may prevent some but not all of the vascular injury caused by oxygen-derived free radicals.
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PMID:Effects of prolonged exposure to oxygen-derived free radicals in canine pulmonary arteries. 876 72

We investigated the inhibition mechanism of lipid peroxidation by estrogens. Estradiol and 2-hydroxyestradiol showed strong inhibitory activities toward NADPH and ADP-Fe(3+)-dependent lipid peroxidations in the microsomes from rat livers only when the steroids were added to the reaction system before the start of the peroxidation reaction. These steroids also strongly inhibited oxygen uptake only when added before the start of the reaction. These results suggest that estradiol and 2-hydroxyestradiol inhibit the initial stage of microsomal lipid peroxidation. Lipid peroxidation of erythrocyte membranes induced by the systems of xanthine oxidase-hypoxanthine and ascorbate was strongly inhibited by 2-hydroxyestradiol, but not by estradiol. Lipid peroxidation of erythrocyte membranes induced by 2.2'-azobis- (amidinopropane) dihydrochloride was not markedly inhibited by estradiol and 2-hydroxyestradiol, suggesting that the steroids have low reactivity with lipid peroxyl radicals. However, lipid peroxidation induced by t-butyl hydroperoxide-Fe3+ was strongly inhibited only by 2-hydroxyestradiol. It seems that 2-hydroxyestradiol may interact with alkoxyl rather than with peroxyl radicals during lipid peroxidation.
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PMID:Inhibition of lipid peroxidation by estradiol and 2-hydroxyestradiol. 877 1

Treatment of rabbit synovial fibroblasts with active oxygen (AO) released by xanthine/xanthine oxidase resulted in an induction of procollagenase in these cells in concentrations ranging from 12.5 micrograms/ml xanthine plus 0.0025 U/ml xanthine oxidase to 50 micrograms/ml xanthine plus 0.01 U/ml xanthine oxidase. Preceding this there was an accumulation of poly(ADP-ribose) for the same concentration range of xanthine/xanthine oxidase. Furthermore, it was found that AO caused activation of the latent procollagenase to the active enzyme in concentrations ranging from 0.1 micrograms/ml xanthine plus 0.00002 U/ml xanthine oxidase to 1 microgram/ml xanthine plus 0.0002 U/ml xanthine oxidase. It is suggested that poly(ADP-ribosyl)ation participates in the induction of procollagenase by relaxing chromatin. Furthermore, it is proposed that AO activates latent procollagenase under physiological conditions.
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PMID:Induction and activation of procollagenase in rabbit synovial fibroblasts after treatment with active oxygen released by xanthine/xanthine oxidase. 883 93

The impact of in vivo ischaemia and ischaemia-reperfusion (I-R) on mitochondrial respiratory function was investigated in hypertrophied (HP) hearts with aortic constriction compared with control hearts using an open-chest rat surgical model. Moreover, mitochondrial susceptibility to superoxide radicals (O2-.) in vitro was examined in HP and control hearts with or without I-R. With the site I substrates pyruvate-malate, mitochondrial state 4 (basal) respiration and the respiratory control index (RCI) were not affected by either ischaemia alone or I-R in both HP and control hearts. State 3 (ADP-stimulated) respiration was increased with I-R in control hearts, but showed a reduction after I-R in the HP hearts. Exposure of mitochondria to O2-. (20 nM hypoxanthine in the presence of 0.13 unit mL-1 xanthine oxidase) significantly increased state 4 respiration, whereas state 3 respiration and RCI were decreased in all treatment groups. I-R hearts in both HP and control showed greater increases in state 4 respiration with O2-. than either sham or ischaemic hearts. HP hearts exhibited a significantly lesser extent of inhibition in state 3 respiration and RCI by O2-. compared with control hearts. These changes in mitochondrial respiratory properties were not observed with the site II substrate succinate. Myocardial reduced vs. oxidized glutathione ratio was significantly decreased after I-R in both control and HP hearts. Malondialdehyde content showed an increase with I-R, but the increase was significant only in control hearts. These data indicate that short-term in vivo I-R does not impair heart mitochondrial respiratory function, but renders the organelles more vulnerable to imposed oxidative stress. Mitochondria from the HP hearts are more resistant to free radical damage under normal and ischaemic conditions; however, this advantage is severely compromised after reperfusion.
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PMID:Ischaemia-reperfusion induced alterations of mitochondrial function in hypertrophied rat heart. 886 86

The acetone-H2O (9:1) extract from the stem of Cistanche deserticola showed a strong free radical scavenging activity. Nine major phenylethanoid compounds were isolated from this extract. They were identified by NMR as acteoside, isoacteoside, 2'-acetylacteoside, tubuloside B, echinacoside, tubuloside A, syringalide A 3'-alpha-rhamnopyranoside, cistanoside A and cistanoside F. All of these compounds showed stronger free radical scavenging activities than alpha-tocopherol on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and xanthine/xanthine oxidase (XOD) generated superoxide anion radical (O2-.). Among the nine compounds, isoacteoside and tubuloside B, whose caffeoyl moiety is at 6'-position of the glucose, showed an inhibitory effect on XOD. We further studied the effects of these phenylethanoids on the lipid peroxidation in rat liver microsomes induced by enzymatic and non-enzymatic methods. As expected, each of them exhibited significant inhibition on both ascorbic acid/Fe2+ and ADP/NADPH/Fe3+ induced lipid peroxidation in rat liver microsomes, which were more potent than alpha-tocopherol of caffeic acid. The antioxidative effect was found to be potentiated by an increase in the number of phenolic hydroxyl groups in the molecule.
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PMID:Antioxidative effects of phenylethanoids from Cistanche deserticola. 899 43


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