oxypurinol and Coronary-Disease

Xanthine oxidase (XO), a major source of superoxide, has been implicated in endothelial dysfunction in atherosclerosis. Mechanisms, however, leading to endothelial XO activation remain poorly defined. We tested the effect of angiotensin II (Ang II) on endothelial XO and its relevance for endothelial dysfunction in patients with coronary disease.. XO protein levels and XO-dependent superoxide production were determined in cultured endothelial cells in response to Ang II. In patients with coronary disease, endothelium-bound XO activity as determined by ESR spectroscopy and endothelium-dependent vasodilation were analyzed before and after 4 weeks of treatment with the AT1-receptor blocker losartan, the XO inhibitor allopurinol, or placebo. Ang II substantially increased endothelial XO protein levels and XO-dependent superoxide production in cultured endothelial cells, which was prevented by NAD(P)H-oxidase inhibition. In vivo, endothelium-bound XO activity was reduced by losartan and allopurinol, but not placebo therapy in patients with coronary disease. XO inhibition with oxypurinol improved endothelium-dependent vasodilation before, but not after losartan or allopurinol therapy.. These findings suggest a novel mechanism whereby Ang II promotes endothelial oxidant stress, ie, by redox-sensitive XO activation. In patients with coronary disease, losartan therapy reduces endothelium-bound XO activity likely contributing to improved endothelial function.

Topics: Aged; Allopurinol; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Cattle; Cells, Cultured; Coronary Circulation; Coronary Disease; Endothelial Cells; Endothelium, Vascular; Enzyme Activation; Enzyme Inhibitors; Female; Humans; Losartan; Male; Middle Aged; NADPH Oxidases; Oxypurinol; Superoxides; Vasodilation; Xanthine Oxidase

Rabbit hearts were mounted on a Langendorff apparatus and after measurement of baseline hemodynamic function exposed to 30 minutes normothermic arrest. Hearts were reperfused at 37 degrees C with buffer solution containing oxypurinol in different concentration: group II (0.01 mM), group III (0.1 mM), group IV (1 mM). Group I did not receive active drug and served as control. Each group consisted of eight hearts. After reperfusion, hemodynamic function was again measured and compared to baseline. Groups III and IV showed significantly less deterioration (p less than 0.05) than the control, while group II was better than the control, but in general differences were nonsignificant. We conclude that oxypurinol ameliorates ischemic cardiac damage following normothermic cardiac arrest. The beneficial effect of oxypurinol is most likely due to the drug's scavenging effect of oxygen-free radicals.

Topics: Animals; Blood Pressure; Cardiac Output; Coronary Disease; Heart Arrest, Induced; Hypoxanthine; Hypoxanthines; Inosine; Myocardial Contraction; Myocardial Reperfusion Injury; Oxypurinol; Rabbits; Ventricular Function, Left; Xanthine; Xanthines

We assessed the effect of hypoxia/reoxygenation on 14C-albumin flux across endothelial monolayers. Cultured bovine pulmonary artery endothelial cells were grown to confluence on nitrocellulose filters (pore size 12 microns). The endothelialized filters were mounted in Ussing-type chambers which were filled with cell culture medium (M 199). Equimolar amounts (33 nM) of 14C-labeled and unlabeled albumin were added to the "hot" and "cold" chambers, respectively. The monolayers were then exposed to successive periods (90 min) of normoxia (pO2 145 mmHg), hypoxia (pO2 20 mmHg), and reoxygenation (pO2 145 mmHg). A gas bubbling system was used to control media pO2 and to ensure adequate mixing. Four aliquots of culture media were taken during each period in order to calculate the 14C-albumin permeability across the endothelialized filter. In some experiments, either the xanthine oxidase inhibitor, oxypurinol (10 microM), or superoxide dismutase (600 U/mL), was added to the media immediately prior to the experiments. As compared to the normoxic control period, albumin permeability was 1.5 times higher during hypoxia (p less than 0.01) and 2.3 times higher during reoxygenation (p less than 0.01). The reoxygenation-induced increase in albumin permeability was prevented by either oxypurinol or superoxide dismutase. These data indicate that xanthine oxidase-derived oxygen radicals contribute to the hypoxia/reoxygenation-induced endothelial cell dysfunction. The altered endothelial barrier function induced by hypoxia/reoxygenation is consistent with the microvascular dysfunction observed following reperfusion of ischemic tissues.

Topics: Animals; Biological Transport; Carbon Radioisotopes; Cattle; Cells, Cultured; Coronary Disease; Endothelium; Free Radicals; Oxygen; Oxypurinol; Serum Albumin; Superoxide Dismutase; Xanthine Oxidase

It has been postulated that oxygen-centered free radicals are produced in significant quantities upon reperfusion of ischemic myocardium and could cause the death of myocytes that are still reversibly injured at the end of ischemia ("reperfusion injury"). However, we have shown previously that anti-free radical therapies including superoxide dismutase (SOD) and inhibitors of xanthine oxidase did not limit infarct size after 40 minutes of ischemia and 4 days of reperfusion in dogs. To test whether 40 minutes of ischemia is too brief a period to produce the prerequisite conditions for free radical-mediated necrosis upon reperfusion, we studied infarcts produced by 90 minutes of ischemia followed by reperfusion. Dogs in an SOD-catalase group received a 60-minute infusion of SOD (15,000 units/kg) and catalase (55,000 units/kg) beginning 25 minutes before and ending 35 minutes after reperfusion. A second group of dogs received a single injection of the xanthine oxidase inhibitor oxypurinol (20 mg/kg) 25 minutes before reperfusion. Infarct size was assessed histologically relative to the size of the area at risk and to collateral blood flow to the ischemic region. Infarct size as a percentage of the area at risk was similar in the control group (40.7 +/- 5.5%, n = 11), the SOD-catalase group (38.0 +/- 6.4%; n = 8), and the oxypurinol-treated group (41.4 +/- 6.1%; n = 7) [p = not significant (NS) by analysis of variance]. In controls, there was an inverse relation between infarct size and collateral blood flow; neither of the treatments altered this relation (p = NS by analysis of covariance).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Catalase; Coronary Circulation; Coronary Disease; Dogs; Female; Free Radicals; Hemodynamics; Male; Myocardial Infarction; Oxygen; Oxypurinol; Superoxide Dismutase; Time Factors

Xanthine oxidase (XO) has been hypothesized to be a potential source of oxygen-derived free radicals during reperfusion of ischemic myocardium based on the fact that allopurinol, a XO-inhibitor, can reduce reperfusion injury. In this communication we report that both allopurinol and oxypurinol, the principle metabolite of allopurinol, prevent the reperfusion injury in isolated pig heart. However, we found that neither pig heart nor pig blood contain any XO activity. Our study showed a direct free radical scavenging action of these XO-inhibitors during ischemia and reperfusion, as judged by the reduction of free radical signals when compared using an Electron Paramagnetic Resonance Spectrometer. Using a Luminometer, we also confirmed that both allopurinol and oxypurinol can scavenge ClO2, HOCl, and significantly inhibit free radical signals generated by activated neutrophils. These XO-inhibitors, however, failed to scavenge O2. and OH. radicals. Our results suggest that these XO-inhibitors salvaged the ischemic-reperfused myocardium by scavenging free radicals, and not by inhibiting XO in the pig heart.

Topics: Adenosine Triphosphate; Allopurinol; Animals; Coronary Disease; Female; Free Radicals; Heart; Hydroxides; Hydroxyl Radical; Hypoxanthine; Hypoxanthines; Male; Myocardium; Oxypurinol; Phosphocreatine; Pyrimidines; Swine; Xanthine; Xanthine Oxidase; Xanthines

A Langendorff isolated rat heart preparation was used to determine the effect of oxypurinol, a xanthine oxidase inhibitor, and deferoxamine, an iron binding agent, on the extent of myocardial reperfusion injury after 60 minutes of ischaemia. Thirty rats were divided into three groups of 10, and an isolated heart preparation made from each rat. The isolated hearts were perfused for 15 minutes with a modified Krebs-Henseleit perfusate solution to permit stabilisation of the preparation. Each heart was then subjected to 60 minutes of total ischaemia at 37 degrees C followed by 60 minutes of reperfusion with either saline treated perfusate, oxypurinol treated perfusate (1.3 mmol.litre-1), or deferoxamine treated perfusate (0.61 mmol.litre-1). Reperfusion injury was assessed by the total amount of creatine phosphokinase released into the perfusate, by changes in myocardial vascular resistance, and by morphological examination. The saline treated group released significantly more creatine phosphokinase into the perfusate than either the oxypurinol treated group (p less than 0.05) or the deferoxamine treated group (p less than 0.05). The mean vascular resistance increased for all groups during the 60 minutes of reperfusion compared with that just before ischaemia but was significantly greater in the saline treated group than in the drug treated groups (p less than 0.01). Ultrastructural examination of a randomly selected heart from each group after 60 minutes of reperfusion showed pronounced attenuation of mitochondrial and endoplasmic reticulum swelling, increased maintenance of membrane integrity, and diminished separation of myofilaments in the oxypurinol treated and deferoxamine treated hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Coronary Disease; Creatine Kinase; Deferoxamine; Heart; Male; Microscopy, Electron; Myocardium; Oxypurinol; Pyrimidines; Rats; Rats, Inbred Strains; Vascular Resistance

Recent evidence suggests that postischemic myocardial dysfunction (or myocardial "stunning") may be mediated by oxygen free radicals, but the mechanism for their production remains unknown. To explore the role of xanthine oxidase as a potential source of free radicals, open-chest dogs undergoing a 15-min occlusion of the left anterior descending coronary artery (LAD) followed by 4 h of reperfusion (REP) received intravenously either allopurinol (50 mg/kg 48 h, 20 h, and 30 min before occlusion, 10 mg/kg 1 min before REP, and 6.25 mg X kg-1 X h-1 throughout REP, n = 13) or saline (n = 14). The two groups were similar with respect to occluded bed size (postmortem perfusion) and collateral flow (radioactive microspheres). In controls, the transcardiac difference in plasma uric acid (great cardiac vein - arterial concentration) increased 199 +/- 70% (means +/- SE) during ischemia (P less than 0.02) and remained elevated for 5 min after REP; no increase was observed in treated dogs. Regional myocardial function was assessed by measuring systolic wall thickening with an epicardial Doppler probe. The two groups exhibited comparable systolic thickening under base-line conditions and similar degrees of dyskinesis during ischemia. Following REP, however, recovery of contractile function (expressed as percent of preocclusion values) was considerably greater in allopurinol-treated as compared with control dogs: 57 +/- 14 vs. -22 +/- 16 (P less than 0.01) at 1 h, 70 +/- 13 vs. -15 +/- 15 (P less than 0.001) at 2 h, 65 +/- 14 vs. -28 +/- 13 (P less than 0.001) at 3 h, and 68 +/- 13 vs. -17 +/- 14 (P less than 0.001) at 4 h. These differences could not be ascribed to hemodynamic factors. The results suggest that xanthine oxidase is a source of the oxygen free radicals responsible for myocardial stunning following a brief episode of reversible regional ischemia.

Topics: Allopurinol; Animals; Blood Gas Analysis; Body Temperature; Coronary Circulation; Coronary Disease; Dogs; Half-Life; Hematocrit; Hemodynamics; Kinetics; Myocardium; Oxypurinol; Potassium; Regional Blood Flow; Uric Acid; Xanthine; Xanthine Oxidase; Xanthines