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 in vitro antioxidant capacity of sulfasalazine (SASP), its metabolites (SP, 5-ASA), and olsalazine (OAZ), was studied by evaluating their effects on superoxide (O2-.) production. Assay systems were the xanthine-xanthine oxidase (X/XOD) reaction and phorbol myristate acetate (PMA)-activated polymorphonuclear leukocytes (PMNs), using the cytochrome c (cyt-c) reduction assay and a luminol-dependent chemiluminescence method. 5-ASA, SASP, and OAZ showed a dose-dependent scavenger effect in both O2-. generating systems, 5-ASA being the most powerful (greater than 50% of inhibition in the PMNs system and greater than 70% in the X/XOD system at 10 microM concentration). SP had an inhibitory effect only in the PMNs system but did not modify the activity of xanthine oxidase, thus excluding a scavenger action. These data suggest that the scavenger effect of 5-ASA, SASP, and OAZ may be an important mechanism of action.
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PMID:Scavenger effect of sulfasalazine, 5-aminosalicylic acid, and olsalazine on superoxide radical generation. 167 Oct 10

The relative in vitro anti-oxidant efficacy of sulphasalazine (salicylazosulphapyridine, SASP) and its metabolites (5-aminosalicylic acid, 5-ASA; sulphapyridine, SP) was examined by studying their effects on the generation of reactive oxygen species (ROS) using zymosan-stimulated polymorphonuclear leucocytes (PMNs) and a cell free, xanthine-xanthine oxidase system. Salicylazosulphapyridine, 5-ASA, and SP showed anti-oxidant effects to the various degrees. In particular, production of OH, which is one of the most potent reactive oxygen species, was remarkably suppressed by 5-ASA dose relatedly. These findings suggest that SASP and its metabolites play an important role in the inhibition of respiratory bursts. As the potent products of the respiratory burst by polymorphonuclear leucocytes are thought to be important inflammatory mediators, suppression of toxic reactive oxygen species generation by these agents may partly explain the therapeutic efficacy of SASP in ulcerative colitis, which is characterised by an acute mucosal inflammation dominated by polymorphonuclear leucocytes accumulation.
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PMID:Effect of sulphasalazine and its metabolites on the generation of reactive oxygen species. 288 49

Although salicylates have been used for centuries as treatment of inflammatory diseases, the mechanism of action of these drugs is still not clear. Aspirin (acetylsalicylic acid) and other nonsteroidal anti-inflammatory drugs (NSAID) inhibit prostaglandin biosynthesis, a property that appears to explain part of their anti-inflammatory activity. However, this mechanism does not appear to explain the anti-inflammatory properties of salicylic acid, which is a major metabolite of ASA in vivo. Results of prior studies in our laboratory have established that benzoic acid, the parent compound of the salicylate group of drugs, is decarboxylated and hydroxylated by the hydroxyl free radical (OH.) produced by stimulated granulocytes. These observations suggested that salicylates might be similarly metabolized by granulocytes. If so, the capacity of salicylates to rapidly react with OH. might relate directly to their known anti-inflammatory properties. Preliminary experiments established that salicylic acid and aspirin were decarboxylated by the hydroxyl free radical generated by the enzyme system xanthine-xanthine oxidase. We then studied the metabolism of salicylates by human granulocytes. Unstimulated granulocyte suspensions did not oxidize ASA or salicylic acid. However, suspensions stimulated by opsonized zymosan particles rapidly oxidized both substrates in pharmacological concentrations. The rate of oxidation of salicylic acid was 16-fold higher than benzoic acid, whereas the rate of oxidation of ASA was four-fold higher. The reaction was oxygen dependent and could be inhibited by known hydroxyl scavengers, particularly dimethylthiourea. The reaction could also be inhibited by superoxide dismutase and azide, indicating that O-2 and heme or an iron-dependent enzyme were required for the reaction. The reaction was not impaired by compounds known to react with the HOCL and the chloramines generated by stimulated PMN. Furthermore, salicylic acid in high concentrations did not impair the HMPS pathway, the production of O-2 or the production of H2O2 by granulocytes. These data provide evidence that salicylates are rapidly oxidized by the hydroxyl free radical produced by granulocytes and not O-2, H2O2, or HOCL. This capacity of salicylates to react rapidly and selectively react with OH. may directly relate to their anti-inflammatory properties. In addition, results of our experiments indicate that stimulated granulocytes acquire the capacity to metabolize these drugs. Therefore, several metabolites of salicylates may be produced at a site of inflammation, all of which may have altered biological activity compared with the parent compound.
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PMID:Oxidation of salicylates by stimulated granulocytes: evidence that these drugs act as free radical scavengers in biological systems. 303 Nov 58

The effects of aspirin on N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide (FANFT) -induced urinary bladder lesions, endogenous bladder prostaglandin E2 synthesis, and the metabolism of FANFT by bladder epithelial microsomes were examined. Rats were fed 0.5% aspirin and/or a diet containing 0.1% or 0.2% FANFT. Bladder lesions were observed with light and scanning electron microscopy, and the prostaglandin E2 content of rat bladder was measured by radioimmunoassay. Metabolism of FANFT was measured by decreased absorbance at 400 nm. Aspirin inhibited the appearance of hyperplastic lesions induced by feeding 0.1% or 0.2% FANFT for 6 or 12 weeks. Aspirin reduced bladder prostaglandin E2 content at 1, 2, 6, and 13 weeks compared to corresponding control values. Rat and rabbit microsomal metabolism of FANFT were dependent upon specific fatty acid substrate and prevented by specific inhibitors (including aspirin) of prostaglandin endoperoxide synthetase. Other inhibitor and substrate specificity studies suggest that FANFT was not metabolized by xanthine oxidase, lipoxygenase, lipid peroxidation, or mixed-function oxidases. These results suggest that the metabolism of FANFT by prostaglandin endoperoxide synthetase may be involved in the metabolic activation of FANFT necessary for the induction of bladder cancer in rats.
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PMID:Aspirin inhibition of N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide-induced lesions of the urinary bladder correlated with inhibition of metabolism by bladder prostaglandin endoperoxide synthetase. 679 Jan 63

5-[4-(2-Carboxyethylcarbamoyl)phenylazo]salicylic acid disodium salt dihydrate (CAS 80573-04-2, BX661A) is developed as a therapeutic agent for ulcerative colitis. To clarify its mechanism of action, the effects of BX661A and its metabolites 5-aminosalicylic acid (5-ASA) and 4-aminobenzoyl-beta-alanine (4-ABA) on reactive oxygen species: superoxide radicals (O2-) generated by hypoxanthine and xanthine oxidase, hydrogen peroxide (H2O2), hypochlorite radicals (OCl-) and hydroxyl radicals (OH.), were investigated and compared with the effects of 2-hydroxy-5-[[4-[(2-pyridinylamino)sulfonyl]phenyl]azo]-benzoic acid (CAS 599-79-1, salazosulfapyridine, SASP) and its metabolite 4-amino-N-2-pyridinyl-benzenesulfonamide (CAS 144-83-2, sulfapyridine, SP). 1. BX661A, SASP and 5-ASA inhibited O2- radical production in a concentration-dependent manner (IC50 = 0.14, 0.13 and 0.19 mmol/l, respectively). The effects of 4-ABA and SP on O2- radical production were weak (IC50 = > 10 and > 3 mmol/l, respectively). In contrast, superoxide dismutase inhibited O2- radical production in a concentration-dependent manner (IC50 = 1.7 U/ml). 2. BX661A, SASP, 4-ABA and SP had no H2O2 scavenging effects. 5-ASA scavenged H2O2, but its maximal scavenging action was 51.3%. In contrast, catalase scavenged H2O2 in a concentration-dependent manner (IC50 = 0.47 U/ml). 3. BX661A, SASP and 5-ASA scavenged OCl- radicals in a concentration-dependent manner (IC50 = 69.5, 73.8 and 21.7 mumol/l, respectively). 4-ABA and SP had no OCl- radical scavenging effects. In contrast, nordihydroguaiaretic acid (NDGA) scavenged OCl- radicals in a concentration-dependent manner (IC50 = 8.7 mumol/l). 4. BX661A and SASP scavenged OH. radicals in a concentration-dependent manner; the maximal scavenging values were 39.5 (10 mmol/l) and 48.6% (3 mmol/l), respectively. 4-ABA and SP had no OH. radical scavenging effects. In contrast, 5-ASA scavenged OH. radical in a concentration-dependent manner (IC50 = 1.46 mmol/l). These results suggest that BX661A has O2- and OCl- radical scavenging effects and that 5-ASA has O2-, OCl- and OH. radical scavenging effects. Therefore, these effects may be partially involved in the therapeutic effects of BX661A on ulcerative colitis.
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PMID:Effects of BX661A, a new therapeutic agent for ulcerative colitis, on reactive oxygen species in comparison with salazosulfapyridine and its metabolite sulfapyridine. 982 18

Antioxidant components in Aloe vera were examined for lipid peroxidation using rat liver microsomal and mitochondrial enzymes. Among the aloesin derivatives examined, isorabaichromone showed a potent antioxidative activity. The DPPH radical and superoxide anion scavenging activities were determined. As one of the most potent components, isorabaichromone together with feruloylaloesin and p-coumaroylaloesin showed potent DPPH radical and superoxide anion scavenging activities. Electron spin resonance (ESR) using the spin trapping method suggested that the potent superoxide anion scavenging activity of isorabaichromone may have been due to its caffeoyl group. As A. vera has long been used to promote wound healing, the inhibitory effects of aloesin derivatives for cyclooxygenase (Cox)-2 and thromboxane (Tx) A 2 synthase were examined and the participation of p-coumaroyl and feruloyl ester groups in the aloesin skeleton was demonstrated. These findings may explain, at least in part, the wound healing effects of A.vera. Abbreviations. ADP:adenosine diphosphate ASA:ascorbic acid BHT:butylated hydroxytoluene BSA:bovine serum albumin DMPO:5,5-dimethyl-1-pyrroline N-oxide DPPH:1,1-diphenyl-2-picrylhydrazyl EDTA:edetic acid HEPES: N-(2-hydroxyethyl)-piperazine- N-2'-ethane-sulfonic acid NADH:reduced nicotinamide adenine dinucleotide NADPH:reduced nicotinamide adenine dinucleotide phosphate NBT:nitroblue tetrazolium Pg:prostaglandin SOD:superoxide dismutase TBA:thiobarbituric acid TCA:trichloroacetic acid XOD:xanthine oxidase
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PMID:Antioxidant, free radical scavenging and anti-inflammatory effects of aloesin derivatives in Aloe vera. 1245 82

Chemopreventive agents generate oxidative stress, which culminates in cell death and may be part of a general mechanism of chemoprevention. The redox-responsive cyclooxygenase (COX)-2, overexpressed during carcinogenesis, has been a target for cancer prevention. To assess the potential link between chemopreventive agents, oxidative stress and COX-2, we studied the chemopreventive sulindac and nitric oxide-donating aspirin (NO-ASA). Both generated oxidative stress and induced COX-2 in various cell lines, more prominently in dying cells. Two antioxidants and an inhibitor of NADPH oxidase abrogated the induction of COX-2 and cell death. Exogenous xanthine/xanthine oxidase, which produce O(2)(-)., had the same effect. Inhibition of caspases and cox-2 knockdown showed that COX-2 did not participate in reactive oxygen species (ROS) generation or cell death induction in response to NO-ASA. Our results support three potentially useful ideas: (i) the concept that ROS are a critical component of the action of chemopreventive agents; (ii) the notion that COX-2 may not be an ideal target for chemoprevention and (iii) the possibility that COX-2 may be overexpressed in cancer cells due to their state of oxidative stress. It is conceivable that, if further substantiated, these findings may inform the rational design of chemotherapeutic strategies, in particular the choice of agents in combination approaches.
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PMID:Chemopreventive agents induce oxidative stress in cancer cells leading to COX-2 overexpression and COX-2-independent cell death. 1895 95

Acetylsalicylic acid (ASA) causes adverse haemorrhagic reactions in the upper gastrointestinal (GI) tract, and previous results have suggested that combination therapy with 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris) could provide protection in this scenario. Based on this hypothesis, our aim was to develop a new compound from ASA and Tris precursors and to characterize the biological effects of ASA-Tris and the derivatives ASA-bis- and mono-hydroxymethyl-aminomethane (ASA-Bis, ASA-Mono, respectively) using in vivo and in vitro test systems. ASA or ASA conjugates (0.55mmol/kg, each) were administered intragastrically to Sprague-Dawley rats. Changes in the mucosal structure and in the serosal microcirculation were detected by in vivo imaging techniques, the plasma TNF-alpha, tissue xanthine oxidoreductase and myeloperoxidase activities, and liver cytochrome c changes were also determined. In two separate series, platelet aggregation and carrageenan arthritis-induced inflammatory pain were measured in control, ASA and ASA-Tris-treated groups. Severe mucosal injury and a significant decrease in serosal red blood cell velocity developed in the ASA-treated group and an ~2-fold elevation in proinflammatory mediator levels evolved. ASA-Tris did not cause bleeding, microcirculatory dysfunction, mucosal injury or an elevation in proinflammatory markers. The ASA-Mono and ASA-Bis conjugates did not cause macroscopic bleeding, but the inflammatory activation was apparent. ASA-Tris did not influence the cyclooxygenase-induced platelet aggregation significantly, but the inflammatory pain was reduced as effectively as in the case of equimolar ASA doses. ASA-Tris conjugation is an effective approach through which the GI side-effects of ASA are controlled by decreasing the cytokine-mediated progression of pro-inflammatory events.
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PMID:Reduced mucosal side-effects of acetylsalicylic acid after conjugation with tris-hydroxymethyl-aminomethane. Synthesis and biological evaluation of a new anti-inflammatory compound. 2707 40

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