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)

Effect of nafamostat mesilate (FUT-175), a serine protease inhibitor, having anti-inflammatory effects was studied on superoxide (O2-) production in rat polymorphonuclear leucocytes (PMN) and compared with those of other serine protease inhibitors and typical anti-inflammatory agents. 1) O2- productions in rat PMN stimulated with concanavalin A (Con A) and cytochalasin B (Cyt B) were too weak to observe. With NADH, however, strong O2- production was induced by Con A and Cyt B. 2) FUT-175 at 10(-6) and 10(-5) M inhibited O2- production in rat PMN induced by Con A and Cyt B with NADH in a concentration-dependent manner. 3) The serine protease inhibitor L-tosylamido-2-phenylethyl-chloromethyl ketone (TPCK) and soybean trypsin inhibitor (SBTI) inhibited O2- production at 10(-5) M and 10(-4) M, respectively, while aprotinin, chymostatin and leupeptin did not. 4) Neither indomethacin nor dexamethasone, typical anti-inflammatory agents, inhibited O2- production. Mepacrine, a phospholipase A2 inhibitor, strongly inhibited it. 5) O2- production in PMN prepared from the rat administered FUT-175, 200 mg/kg, p.o., was significantly decreased in comparison with that of the control rat. 6) FUT-175 had no effect on O2- production by hypoxanthine-xanthine oxidase. These results showed FUT-175 had a strong inhibitory effect on O2- production in rat PMN which other typical anti-inflammatory agents did not have.
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PMID:[Inhibitory effect of nafamostat mesilate (FUT-175) on O2- production in rat polymorphonuclear leucocytes]. 301 53

The neuroexcitotoxin kainate has been used as a selective lesioning agent to model the etiology of a number of neurodegenerative disorders. Although excitotoxins cause susceptible neurons to undergo prolonged or repeated depolarization, the proximate metabolic pathology responsible for neuronal necrosis has remained elusive. We report here that kainate-induced death of cerebellar neurons in culture is prevented by inhibiting the enzyme xanthine oxidase, a cellular source of cytotoxic superoxide radicals (O2-.). Moreover, neurons are also protected from excitotoxin-induced death by the addition to the culture medium of either superoxide dismutase or mannitol, which scavenge superoxide and hydroxyl radicals, respectively, or serine protease inhibitor, which forestalls formation of xanthine oxidase. These findings indicate that excitotoxin-induced neuronal degeneration is mediated by superoxide radicals generated by xanthine oxidase, a mechanism partially analogous to that proposed for tissue damage seen upon reperfusion of ischemic tissues.
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PMID:Mechanism of kainate toxicity to cerebellar neurons in vitro is analogous to reperfusion tissue injury. 304 Sep 9

This study was conducted with rats to assess the involvement of leukocytes in a model of CO-mediated brain injury. Myeloperoxidase activity, measured as an index of leukocyte sequestration, was found to be increased 10-fold in brain microvessel segments prepared from rats immediately or 90 min after exposure to CO. Fluorescence and light microscopic examinations revealed leukocytes in microvessels taken from CO-poisoned rats, but not in that from control rats. Studies were then conducted with rats that had been made leukopenic or treated with monoclonal anti-CD-18 F(ab')2 fragments to inhibit leukocyte adherence to the vasculature. Neither of these groups of animals exhibited the biochemical changes observed in the brains of sham-treated rats: conversion of xanthine dehydrogenase (XD) to sulfhydryl-irreversible xanthine oxidase (XO), and lipid peroxidation, at 90 min following CO poisoning. Treatment with a synthetic serine protease inhibitor, gabexate mesylate, also prevented these biochemical changes if administered immediately after CO poisoning, but the agent did not inhibit leukocyte sequestration. Rats depleted of XD and XO by a tungsten diet, and those treated with allopurinol to inhibit XD and XO, also exhibited at least a 10-fold increase in myeloperoxidase activity in microvessels immediately after CO poisoning, but only a 5-fold increase at 90 min. In vitro studies demonstrated that B2 integrin-dependent polymorphonuclear leukocyte adherence was impaired immediately following CO poisoning although the adherence molecules were expressed on the membrane surface. Adherence function normalized by 45 min. The results suggest that leukocytes are responsible for the development of biochemical changes in brain following CO poisoning, and the sequence of events is as follows: leukocyte sequestration in the microvasculature, B2 integrin-dependent adherence, protease-mediated conversion of XD to XO, O2 radical-dependent lipid peroxidation.
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PMID:Leukocytes in carbon monoxide-mediated brain oxidative injury. 824 31

Four models of acute pancreatitis have been previously developed that use the ex vivo perfused isolated canine pancreas preparation. The four models include the intraarterial infusion of oleic acid (FFA) that mimics hyperlipemic pancreatitis, partial obstruction of the pancreatic duct with secretin stimulation (POSS) that mimics gallstone pancreatitis, a 2-hour period of ischemia before perfusion (ISCH 2) that mimics shock pancreatitis, and the infusion of cerulein at supramaximal stimulatory doses (CER), which lacks an obvious clinical counterpart. In the FFA, POSS, and ISCH 2 pancreatitis, but not in the CER pancreatitis, toxic oxygen metabolites, generated by the enzyme xanthine oxidase (XO), have been shown to be important mediators in the early pathogenesis. Ordinarily XO primarily occurs as xanthine dehydrogenase (XD) but can be converted to XO, which is the form that generates toxic oxygen metabolites. This conversion of XD to XO may take place either reversibly by way of sulfhydryl group oxidation or irreversibly by means of proteolytic cleavage of XD. This study was undertaken to investigate the mechanism of conversion of XD to XO in the FFA-, POSS-, and ISCH 2-induced pancreatitis models. CER pancreatitis was studied for comparison. After 4 hours of perfusion, pancreatitis was manifest by edema, weight gain, and hyperamylasemia in all four models. Dithiothreitol, a sulfhydryl group protector, ameliorated the weight gain in the FFA (40 +/- 14 gm to 18 +/- 13 gm; p < 0.05), POSS (28 +/- 10 gm to 9 +/- 3 gm; p < 0.05), and ISCH 2 pancreatitis (30 +/- 13 gm to 15 +/- 3 gm; p < 0.05), and ameliorated the hyperamylasemia in the POSS pancreatitis (12,062 +/- 4304 units/dl to 5877 +/- 2659 units/dl; p < 0.05). The CER pancreatitis was not ameliorated with dithiothreitol. A serine protease inhibitor of low molecular weight, phenylmethylsulfonyl fluoride, ameliorated only the CER pancreatitis (weight gain from 28 +/- 10 gm to 17 +/- 10 gm, p < 0.05; amylase activity from 38,116 +/- 6491 units/dl to 23,372 +/- 11,654 units/dl, p < 0.05), and not the FFA, POSS, or ISCH 2 pancreatitis. We conclude that in the three models of pancreatitis (FFA, POSS, and ISCH 2) that are mediated by toxic oxygen metabolites, XD is converted to XO reversibly by way of sulfhydryl group oxidation rather than irreversibly by way of proteolysis. In the CER pancreatitis, where XO does not play a role in the pathogenesis, proteolytic enzymes may be important mediators in the injury.
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PMID:The mechanism of conversion of xanthine dehydrogenase to xanthine oxidase in acute pancreatitis in the canine isolated pancreas preparation. 841 95

In rats subjected to water immersion restraint (WIR) stress for 1, 3, and 6 h, gastric mucosal lesions developed time-dependently with an increase in lipid peroxide (LPO) levels and a decrease in nonprotein sulfhydryl levels in the gastric mucosa. The gastric mucosal xanthine oxidase (XO) activity significantly increased with the conversion of xanthine dehydrogenase (XD) to XO at 6 h of WIR (3.2-fold that of the control group without WIR). A significant increase in myeloperoxidase (MPO) activity, an index of neutrophil infiltration, occurred in the gastric mucosa at 3 and 6 h of the WIR (2.2- and 3.3-fold that of the control group without WIR, respectively). In contrast, superoxide dismutase, catalase, and glutathione peroxidase activities in the gastric mucosa did not change during the WIR period. Pretreatment with either allopurinol (AP), an inhibitor of XO, or soybean trypsin inhibitor (STI), a serine protease inhibitor, attenuated the lesion development at 6 h of WIR, but not at 3 h. In the gastric mucosa of rats pretreated with AP, enhancements of LPO formation, sulfhydryl oxidation, and XO activity found at 6 h of WIR were prevented with inhibition of XD plus XO activity, while in the gastric mucosa of rats pretreated with STI, these enhancements were prevented with inhibition of the conversion of XD to XO. In the gastric mucosa of rats pretreated with anti-polymorphonuclear leukocyte antiserum, the lesion development and enhanced LPO formation and sulfhydryl oxidation found at 3 and 6 h of WIR were prevented with a decrease in increased MPO activity. These results indicate that in the gastric mucosa of rats with WIR stress, the progression of lesions is mainly related to enhanced LPO formation and sulfhydryl oxidation which depend on an increased generation of oxygen free radicals via the xanthine-XO system and neutrophils rather than the change in the oxygen free radical-scavenging activity of antioxidant enzymes. The present results also suggest that increased gastric mucosal LPO formation and sulfhydryl oxidation found at 3 h of WIR could be mainly due to neutrophil-derived oxygen free radicals, while enhanced gastric mucosal LPO formation and sulfhydryl oxidation found at 6 h of WIR could be due to both neutrophil- and XO-derived oxygen free radicals.
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PMID:Involvement of the xanthine-xanthine oxidase system and neutrophils in the development of acute gastric mucosal lesions in rats with water immersion restraint stress. 932 61

It has been shown that erythrocyte membrane proteins become susceptible to degradation by membrane-bound serine protease activity after oxidative modification of the membranes (M. Beppu, M. Inoue, T. Ishikawa, K. Kikugawa, Biochim. Biophys. Acta 1196 (1994) 81-87). The aim of the present study was to clarify the presence of the serine protease in oxidized erythrocyte membranes and to characterize the selectivity of the enzyme to oxidized proteins. Human erythrocytes were oxidized in vitro with xanthine/xanthine oxidase/Fe(III) and oxidized membranes isolated. Proteolytic activity of the membranes toward spectrin obtained from oxidized membranes and bovine serum albumin oxidized with H2O2/horseradish peroxidase was increased by membrane oxidation, and the degradability of the substrates was increased by substrate oxidation. The proteolytic activity was inhibited by the serine protease inhibitor diisopropyl fluorophosphate (DFP). The 72 kDa and 80 kDa proteins in the membranes were labeled by [3H]DFP when detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions and subsequent fluorography. The 72 kDa protein was found to be a serine enzyme, acetylcholine esterase. The 80 kDa protein appeared to be responsible for the degradation of oxidatively damaged proteins. The 80 kDa protein was loosely bound to membranes and readily solubilized into a 0.1% NP-40 detergent solution. The presence of the same 80 kDa protease in intact erythrocyte cytosol was suggested. The increased serine protease activity in oxidized membranes can result from the increased adherence of the cytosolic 80 kDa serine protease to the membranes due to oxidation.
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PMID:Characterization of membrane-bound serine protease related to degradation of oxidatively damaged erythrocyte membrane proteins. 981 51

The widely distributed xanthine oxidoreductase (XOR) system has been shown to be modulated upon exposure of animals to ionizing radiation through the conversion of xanthine dehydrogenase (XDH) into xanthine oxidase (XO). In the present work, radiomodification of the XOR system by phenylmethylsulfonyl fluoride (PMSF) and dithiothreitol (DTT) was examined using female Swiss albino mice which were irradiated with gamma rays at a dose rate 0.023 Gy s(-1). PMSF, a serine protease inhibitor, and DTT, the sulfhydryl reagent, were administered intraperitoneally prior to irradiation. The specific activities of XDH and XO as well as the XDH/XO ratio and the total activity (XDH+XO) were determined in the liver of the mice. The inhibition of XO activity, restoration of XDH activity, and increase in the XDH/XO ratio upon administration of PMSF were suggestive of irreversible conversion of XDH into XO mediated through serine proteases. The biochemical events required for the conversion were probably initiated during the early phase of irradiation, as the treatment with PMSF immediately after irradiation did not have a modulatory effect. Interestingly, DTT was not effective in modulating radiation-induced changes in the XOR system or oxidative damage in the liver of mice. The DTT treatment resulted in inhibition of the release of lactate dehydrogenase. However, the protection appears to be unrelated to the formation of TBARS. On the other hand, the presence of PMSF during irradiation inhibited radiation-induced oxidative damage and radiation-induced increases in the specific activity of lactate dehydrogenase. These findings suggest that a major effect of ionizing radiation is irreversible conversion of xanthine to xanthine oxidase.
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PMID:Radiomodfication of xanthine oxidoreductase system in the liver of mice by phenylmethylsulfonyl fluoride and dithiothreitol. 1085 70

Alpha(1)-proteinase inhibitor (alpha(1)-PI) is a natural serine protease inhibitor. Although mainly thought to protect the airways from neutrophil elastase, alpha(1)-PI may also regulate the development of airway hyperresponsiveness (AHR), as indicated by our previous findings of an inverse relationship between lung alpha(1)-PI activity and the severity of antigen-induced AHR. Because allergic stimulation of the airways causes release of elastase, tissue kallikrein, and reactive oxygen species (ROS), all of which can reduce alpha(1)-PI activity and contribute to AHR, we hypothesized that administration of exogenous alpha(1)-PI should protect against pathophysiological airway responses caused by these agents. In untreated allergic sheep, airway challenge with elastase, xanthine/xanthine oxidase (which generates ROS), high-molecular-weight kininogen, the substrate for tissue kallikrein, and antigen resulted in bronchoconstriction. ROS and antigen also induced AHR to inhaled carbachol. Treatment with 10 mg of recombinant alpha(1)-PI (ralpha(1)-PI) blocked the bronchoconstriction caused by elastase, high-molecular-weight kininogen, and ROS, and the AHR induced by ROS and antigen. One milligram of ralpha(1)-PI was ineffective. These are the first in vivo data demonstrating the effects of ralpha(1)-PI. Our results are consistent with and extend findings obtained with human plasma-derived alpha(1)-PI and suggest that alpha(1)-PI may be important in the regulation of airway responsiveness.
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PMID:Recombinant alpha 1-proteinase inhibitor blocks antigen- and mediator-induced airway responses in sheep. 1243 33

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