Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously demonstrated that pulmonary vasodilation in response to isoproterenol is attenuated in conscious dogs after left lung autotransplantation (LLA). Our present goal was to identify the cellular mechanism responsible for this dysfunction. Size- and position-matched pulmonary arterial rings were isolated from the right (control) and left (LLA) lungs of 23 dogs 1-14 mo post-LLA. The rings were suspended for isometric tension recording and precontracted, and the vasorelaxant responses to activators of the beta-adrenoreceptor signaling pathway were examined. With the endothelium intact the maximal pulmonary vasorelaxant response to isoproterenol was reduced (P < 0.02) to 57 +/- 9% in LLA rings, compared with 87 +/- 3% in control rings. Responses to the Gs protein activator cholera toxin were also attenuated post-LLA, with the concentration-effect curve shifted to the right (P < 0.01) and no change in the maximal response. In contrast, the vasorelaxant responses to forskolin (adenylyl cyclase activator) or dibutyryl cAMP were similar in endothelium-intact control and LLA rings. In endothelium-denuded rings the maximal vasorelaxant responses to isoproterenol were reduced (P < 0.01) to approximately 25% in both control and LLA rings. In denuded rings cholera toxin, forskolin, and dibutyryl cAMP caused 100% vasorelaxation, and the IC50 values for these agonists were similar in control and LLA rings. Isoproterenol increased (P < 0.05) tissue cAMP to the same extent in control and LLA rings with or without endothelium. In contrast, isoproterenol increased (P < 0.05) tissue cGMP only in endothelium-intact rings, and this effect was reduced (P < 0.05) approximately 50% in LLA rings compared with control. Oxypurinol (endothelial xanthine oxidase inhibitor) restored the pulmonary vasorelaxant response to isoproterenol in endothelium-intact LLA rings. Our results provide the first evidence that activation of the beta-adrenoreceptor signaling pathway in endothelium-intact pulmonary arterial rings results in an increase in cGMP. Moreover, the attenuation in beta-adrenoreceptor-mediated pulmonary vasorelaxation post-LLA is due to inactivation of nitric oxide by endothelium-derived superoxide anion.
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PMID:Endothelial defect mediates attenuated vasorelaxant response to isoproterenol after lung transplantation. 988 29

The purpose of the present study was to determine whether it is possible to alter the development of fatigue and ablate free radical-mediated lipid peroxidation of the diaphragm during loaded breathing by administering oxypurinol, a xanthine oxidase inhibitor. We studied 1) room-air-breathing decerebrate, unanesthetized rats given either saline or oxypurinol (50 mg/kg) and loaded with a large inspiratory resistance until airway pressure had fallen by 50% and 2) unloaded saline- and oxypurinol-treated room-air-breathing control animals. Additional sets of studies were performed with animals breathing 100% oxygen. Animals were killed at the conclusion of loading, and diaphragmatic samples were obtained for determination of thiobarbituric acid-reactive substances and assessment of in vitro force generation. We found that loading of saline-treated animals resulted in significant diaphragmatic fatigue and thiobarbituric acid-reactive substances formation (P < 0.01). Oxypurinol administration, however, failed to increase load trial time, reduce fatigue development, or prevent lipid peroxidation in either room-air-breathing or oxygen-breathing animals. These data suggest that xanthine oxidase-dependent pathways do not generate physiologically significant levels of free radicals during the type of inspiratory resistive loading examined in this study.
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PMID:Oxypurinol administration fails to prevent free radical-mediated lipid peroxidation during loaded breathing. 1048 86

1. Hypercholesterolaemia is associated with abnormal endothelium-related vasodilator function, possibly due to increased destruction .NO by superoxide anions (.O2-). Oxypurinol, a xanthine oxidase (XO) inhibitor with anti-oxidant properties and the active metabolite of the commonly used drug allopurinol, reduces .NO quenching in vitro and has been reported to acutely improve endothelial function in hypercholesterolaemic subjects. 2. The purpose of the present study was to determine whether oral allopurinol improves .NO dilator function in hypercholesterolaemic subjects. 3. A randomized double-blind, placebo-controlled cross-over design evaluated the effect of allopurinol (300 mg daily for 4 weeks) on forearm blood flow (FBF) responses to intrabrachial infusion of acetylcholine (ACh), sodium nitroprusside (SNP) and NG-monomethyl-L-arginine (L-NMMA) in nine hypercholesterolaemic subjects. 4. Endothelium-dependent vascular responses to ACh and L-NMMA were not significantly altered by allopurinol. The endothelium-independent vasodilator response to SNP was similarly unchanged. 5. These results indicate that allopurinol does not influence basal or stimulated activity of the .NO dilator system in hypercholesterolaemic subjects. If intracellular .O2- inactivation .NO is responsible for endothelial dysfunction in hypercholesterolaemia, the source may be other than XO dependent. However, generation of .O2- during the conversion of allopurinol to oxypurinol could offer an alternative, and probably more likely, explanation for the ineffectiveness of allopurinol in vivo.
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PMID:Nitric oxide-dependent endothelial function is unaffected by allopurinol in hypercholesterolaemic subjects. 1054 1

The aim of this work was to evaluate the systemic Hsp72 expression in rat lung and liver in vivo in a model of acute pancreatitis and investigate the possible involvement of xanthine oxidase and neutrophils in this process. Pancreatitis was induced by intraductal administration of 5% sodium taurocholate and samples of lung and liver were obtained 1 and 3 h later. In some groups of rats circulating xanthine oxidase was inhibited with oxypurinol, and neutrophil recruitment was blocked with a monoclonal antibody against P-selectin. Hsp72 expression was assessed by means of Western blot and immunohistochemistry. Results showed Hsp72 induction in lung, but not in liver, shortly after pancreatitis. Hsp72-induced expression was located in bronchial epithelium, alveolar macrophages, infiltrating neutrophils, and blood vessels. Oxypurinol and the antibody against P-selectin prevented pancreatitis-induced lung Hsp72 overexpression suggesting that Hsp72 induction is mediated by neutrophil infiltration into the lungs.
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PMID:Pancreatitis induces HSP72 in the lung: role of neutrophils and xanthine oxidase. 1089 74

We investigated the role of xanthine oxidase-derived oxygen radicals in the development of endothelin-1-induced gastric ulcer. Mucosal lipid peroxidation showed a peak 24 h after injection, while gastric mucosal haemodynamics were fully restored 26 h after endothelin-1 injection. Allopurinol and oxypurinol, but not superoxide dismutase or catalase, protected the gastric mucosa 24 h after endothelin-1 injection. Oxypurinol antagonized both the vasoconstrictor effect of endothelin-1 and the decrease in gastric ATP. All treatments on the second day after endothelin-1 injection significantly reduced gastric mucosal damage. Xanthine oxidase-derived oxygen radicals contributed largely to the exacerbation but they did not mediate the onset of endothelin-1-induced gastric ulcer. Pretreatment with probucol (500 mg/kg, p.o.) also protected the gastric mucosa from endothelin-1-induced mucosal injury by its antioxidant activity. Oxypurinol was gastroprotective through its vasoactive and energy saving actions. The haemodynamic background of endothelin-1-induced gastric ulcer consists of long lasting ischaemia and subsequent "reperfusion" which may be responsible for the late burst of oxygen radicals.
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PMID:Oxygen radicals mediate the final exacerbation of endothelin-1-induced gastric ulcer in rat. 1117 71

Alloxanthine-inhibited xanthine oxidase (XOD) was found to be photoreactivated by irradiation of light of wavelengths in the range of 340-430 nm. The enzyme activity can be fully controlled to be on or off by many dark-light cycles. Electron spin resonance measurement shows the appearance of the molybdenum (V) ion and the reduced form of flavin adenine dinucleotide (FADH.) radical signals after irradiation of the alloxanthine-XOD complex. Electronic-absorption spectrum also shows the bleaching of Fe/S and flavin adenine dinucleotide chromophores at 375 and 450 nm as well as broad-band absorption of FADH. in the range of 500-700 nm. The quantum yield of photoreactivation of the enzyme activity is approximately 0.06. A photoinduced intraenzyme electron-transfer model is proposed to rationalize the photoreactivation process.
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PMID:Photoreactivation of alloxanthine-inhibited xanthine oxidase. 1133 41

The purpose of the present study was to determine whether oxypurinol, a xanthine oxidase inhibitor, reduces free radicals and brain injury in the rat pup hypoxic-ischemia (HI) model. Seven-day-old rat pups had right carotid arteries ligated followed by 2.5h of hypoxia (8% oxygen). Oxypurinol or vehicle was administered by i.p. injection at 5 min after reoxygenation and once daily for 3 days. Brain damage was evaluated by weight deficit of the right hemisphere at 22 days following hypoxia. Oxypurinol treatments did not reduce weight loss in the right hemisphere. Brain weight loss in the right hemisphere were -26.2+/-3.6, -15.2+/-6.9, -21.7+/-4.4, -15.8+/-5.1, and -16.7+/-3.4% in vehicle (n=33), 10 (n=17), 20 (n=16), 40 (n=15), and 135 mg/kg (n=13) oxypurinol-treated groups (p>0.05), respectively. Brain thiobarbituric acid-reacting substances (TBARS) were assessed 3 and 6h after reoxygenation. Concentrations of TBARS rose 1.5-fold due to HI. Oxypurinol did not significantly reduce an HI-induced increase in brain TBARS. Thus, xanthine oxidase may not be the primary source of oxy-radicals in pup brain and as such oxypurinol does not prevent free radical-mediated lipid peroxidation or protect against brain injury in the neonatal rat HI model.
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PMID:Oxypurinol administration fails to prevent hypoxic-ischemic brain injury in neonatal rats. 1257 42

Oscillatory shear stress occurs at sites of the circulation that are vulnerable to atherosclerosis. Because oxidative stress contributes to atherosclerosis, we sought to determine whether oscillatory shear stress increases endothelial production of reactive oxygen species and to define the enzymes responsible for this phenomenon. Bovine aortic endothelial cells were exposed to static, laminar (15 dyn/cm2), and oscillatory shear stress (+/-15 dyn/cm2). Oscillatory shear increased superoxide (O2.-) production by more than threefold over static and laminar conditions as detected using electron spin resonance (ESR). This increase in O2*- was inhibited by oxypurinol and culture of endothelial cells with tungsten but not by inhibitors of other enzymatic sources. Oxypurinol also prevented H2O2 production in response to oscillatory shear stress as measured by dichlorofluorescin diacetate and Amplex Red fluorescence. Xanthine-dependent O2*- production was increased in homogenates of endothelial cells exposed to oscillatory shear stress. This was associated with decreased xanthine dehydrogenase (XDH) protein levels and enzymatic activity resulting in an elevated ratio of xanthine oxidase (XO) to XDH. We also studied endothelial cells lacking the p47phox subunit of the NAD(P)H oxidase. These cells exhibited dramatically depressed O2*- production and had minimal XO protein and activity. Transfection of these cells with p47phox restored XO protein levels. Finally, in bovine aortic endothelial cells, prolonged inhibition of the NAD(P)H oxidase with apocynin decreased XO protein levels and prevented endothelial cell stimulation of O2*- production in response to oscillatory shear stress. These data suggest that the NAD(P)H oxidase maintains endothelial cell XO levels and that XO is responsible for increased reactive oxygen species production in response to oscillatory shear stress.
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PMID:Role of xanthine oxidoreductase and NAD(P)H oxidase in endothelial superoxide production in response to oscillatory shear stress. 1295 34

Oxipurinol [alloxanthine, Oxyprim, oxypurinol] is the active metabolite of the only commercially available xanthine oxidase inhibitor, allopurinol. Oxipurinol is also a xanthine oxidase inhibitor. Oxipurinol is currently being developed by Cardiome Pharma. It is waiting for approval in the US for the treatment of allopurinol-intolerant hyperuricaemia (gout) and is in phase III trials for the treatment of congestive heart failure. Allopurinol is indicated for the treatment of symptomatic hyperuricaemia, or gout. Approximately 3-5% of patients receiving allopurinol develop intolerance to the drug. Oxipurinol was originally developed by Burroughs Wellcome (later GlaxoSmithKline), and has been available on a compassionate-use basis since 1967 for use in allopurinol-intolerant patients. The licensee company ILEX Oncology has stated that oxipurinol does not have patent protection. Oxipurinol's potential for treatment of congestive heart failure is based on the possibility that xanthine oxidase inhibitors may improve myocardial work efficiency by sensitising cardiac muscle cells to calcium ions, which are a key determinant of cardiac muscle function. This results in more efficient contraction of cardiac muscle cells, without the same increase in oxygen demand. At the second annual BioPartnering North America conference (BPN-2004) [February 2004, Vancouver, Canada], Cardiome Pharma stated that it was seeking a commercialisation partner to market and distribute oxipurinol in the US for the treatment of allopurinol-intolerant hyperuricaemia. In 1995, ILEX Oncology obtained an exclusive licence to oxipurinol from Burroughs Wellcome. Burroughs Wellcome later became part of Glaxo Wellcome, which merged with SmithKline Beecham in December 2000 to form GlaxoSmithKline. ILEX's licence agreement is now with GlaxoSmithKline and The Wellcome Foundation. In December 2001, ILEX granted Paralex, a privately held New York-based company, an exclusive sublicence to all of ILEX's rights to oxipurinol for the treatment of hyperuricaemia in allopurinol-intolerant patients. Paralex additionally gained the right to develop and commercialise oxipurinol in all fields, under data and technology owned by ILEX. Furthermore, Paralex had licensed certain intellectual property rights from The John Hopkins University relating to cardiovascular applications of xanthine oxidase inhibitors. Paralex was acquired by Cardiome Pharma in March 2002. Cardiome Pharma announced early in May 2002 that it had exercised its option to acquire from ILEX Oncology Inc. rights to clinical trial data for oxypurinol for the treatment of gout in allopurinol-intolerant patients. ILEX completed its open-label phase II clinical study of Oxyprim in allopurinol-intolerant gout patients, and the trial data were transferred to Cardiome. Cardiome stated in May 2002 that it intended to commence a further phase II trial of oxypurinol in gout. Phase III trials were in progress in 2003 in this indication. In 1995, ILEX Oncology continued the compassionate use distribution of oxipurinol while establishing a US FDA-approved registration plan for the agent. In November 1998, ILEX received Orphan Drug status for the use of oxipurinol in patients with symptomatic hyperuricaemia. ILEX Oncology's Development Pipeline for 1998 stated that oxipurinol had entered phase II clinical trials for the treatment of hyperuricaemia. In 2001, the clinical trials listing service CenterWatch stated that oxipurinol was in a phase II clinical trial with ILEX Oncology for the treatment of symptomatic hyperuricaemia in patients who are intolerant to allopurinol. The trial appeared to be taking place in the US, and was a multicentre, open-label, 14-week study in 90 patients. In February 2003, Cardiome confirmed beginning patient enrollment in three smaller phase II studies, with the first trial (EXOTIC) now completed. These three smaller proof-of-concept studies will observe surrogate endpoints such as cardiac output and exercise tolerance. The second proof-of-concept study in patients with CHF of ischemic aetiology (IV), known as EXOTIC-EF (Evaluation of XanThine Oxidase Inhibition on Cardiac Ejection Fraction), will assess the effects of oxypurinol on left ventricular performance. The EXOTIC-EF trial will start in the first quarter of 2004 and be completed by the second quarter of 2004. The third, LA PLATA, proof-of-concept study will explore the effects of 1 month of oral oxypurinol therapy on exercise capacity and left ventricular performance. It is projected that the LA PLATA study will start in the first quarter of 2004 and be completed by the third quarter of 2004. During the Heart Failure Society of America's meeting on 21 September 2003, Cardiome presented clinical data from its first proof-of-concept EXOTIC (European Xanthine Oxidase Inhibitors Trial In Cardiac Disease) study. Cardiome intends to conduct a second trial, at the Eppendorf Clinic at the University of Hamburg, to determine the effect of oxypurinol on left ventricular performance in patients with CHF of ischaemic aetiology. This study will be an extension of the original proof-of-concept study. According to the 1st Annual BioPartnering conference held in Vancouver, Canada, in February 2003, Cardiome is seeking co-development partners for oxipurinol in the treatment of congestive heart failure. In July 2003, the US Patent and Trademark Office issued a new patent providing additional protection to Cardiome's programme focused on treatment of congestive heart failure with oxypurinol. The patent, No. 6,569,862, was the second issued to the Johns Hopkins University (JHU) in this field. The key claims in the new patent cover use of the entire family of drugs known as xanthine oxidase inhibitors applied to contractile disorders of the heart, including congestive heart failure. An earlier patent issued to JHU contained provisions relating to a specific mechanism of action and to specific forms of heart disease. Both patents and related intellectual property are licensed exclusively to Cardiome.
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PMID:Oxipurinol: alloxanthine, Oxyprim, oxypurinol. 1513 81

Oxypurinol, the active metabolite of allopurinol and a potent xanthine oxidase inhibitor (XOI), is under evaluation as a novel agent for the treatment of congestive heart failure (HF). Several lines of evidence provide the rationale for the hypothesis that XOIs will improve clinical outcomes in patients with HF. First, XOIs have unique positive inotropic effects, improving myocardial contraction and performance while simultaneously improving myocardial energy metabolism. Second, XOIs ameliorate endothelial dysfunction in humans with HF. Finally, XO activity is upregulated in the heart and vasculature of subjects with HF, which may in turn contribute to oxidative stress and/or increased uric acid levels. Together these findings form the rationale for the Controlled Efficacy and Safety Study of Oxypurinol Added to Standard Therapy in Patients with New York Heart Association (NYHA) class III - IV Congestive Heart Failure (OPT-CHF) trial (Food and Drug Administration IND 65,125), a Phase II - III prospective, randomised, double-blind, placebo-controlled trial, which will include patients with stable symptomatic HF in NYHA class III - IV congestive HF who are deemed clinically stable on a standard and appropriately maximised heart failure therapy regimen. The efficacy end point for OPT-CHF is a composite that incorporates measures of patient outcome and well-being.
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PMID:Rationale, design and organisation of an efficacy and safety study of oxypurinol added to standard therapy in patients with NYHA class III - IV congestive heart failure. 1550 Mar 98


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