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

Renal ischemia injures the renal tubular cell by disrupting the vital cellular metabolic machinery. Further cell damage is caused by restoration of blood flow when oxygen free radicals are produced. Cellular sources of oxygen free radicals include the electron transport chain, the microsomal electron transport chain, oxidant enzymes (xanthine oxidase, cyclo-oxygenase), phagocytes, and cellular auto-oxidation of Fe2+ and epinephrine. Oxygen radicals cause lipid peroxidation of cell and organelle membranes, disrupting the structural integrity and capacity for cell transport and energy production. Studies in models of acute renal failure have yielded convincing evidence that oxygen free radical production occurs during ischemia/reperfusion. More than a dozen reports have demonstrated the ability of exogenous antioxidants to ameliorate renal injury in vivo. Direct demonstration of increased oxygen free radical production during reoxygenation following hypoxia has been shown in cultured renal epithelial cells. Oxygen free radicals also play a role in toxic acute renal failure. The therapeutic usefulness of free radical scavengers remains to be tested.
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PMID:Oxygen free radicals in acute renal failure. 175 21

The purpose of this study was to better characterize renal adenine nucleotide pool responses to different forms of shock, contrast the changes to those found in other intra-abdominal organs (the liver and small intestine), and assess whether these changes are closely mimicked by those produced by renal arterial occlusion, the usual method used to study ischemic acute renal failure. Rats were subjected to hemorrhagic shock, septic shock, or cardiopulmonary shock of varying severities and durations. The liver consistently had the greatest energy depletion, followed by the kidney, and then the small intestine. However, only the kidney developed clear morphological damage (S3 brush border sloughing). Kidney adenylate pools were better preserved during septic shock and cardiopulmonary shock than during hemorrhagic shock despite comparable blood pressures. Only profound hemorrhagic shock (35-40 mm Hg for 25 minutes) decreased total adenylate pools (ATP + ADP + AMP). However, the degree of renal catabolite (nucleosides plus purine base) accumulation did not correlate with the amount of renal total adenine nucleotide depletion, partially because circulating catabolites contributed to intrarenal catabolite pools. Purine base/uric acid ratios differed among shocked organs, consistent with different degrees of xanthine oxidase activity (small intestine greater than liver greater than kidney). Renal morphological damage decreased during the immediate (0-30 minutes) postshock period, and the extent of this improvement was not altered by xanthine oxidase inhibition (oxypurinol), suggesting that the immediate postshock period is not one of serious oxidative injury. Shock, in comparison with renal arterial occlusion, caused only modest ATP loss/catabolite accumulation, very low purine base/uric acid ratios, and no immediate-reperfusion (0-30 minutes) resynthesis of the total adenylate pool. Thus, ischemia-induced renal adenylate changes may differ considerably, depending on the nature of the ischemic event.
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PMID:Adenine nucleotide changes in kidney, liver, and small intestine during different forms of ischemic injury. 198 61

Transitional metals, particularly iron, markedly potentiate oxidant damage to isolated cell organelles. However, determining the probable importance of iron in damage to intact cells is difficult because of our inability experimentally to increase the cell content of this transition metal. We now report that heme is a uniquely effective iron delivery vehicle, capable of loading large amounts of potentially reactive iron into intact cells. We find that endothelial cells in vitro rapidly incorporate free heme and this heme-loading sensitizes endothelium to oxidant-mediated cytotoxicity caused by hydrogen peroxide, the hypoxanthine/xanthine oxidase system, or phorbol-stimulated PMN. Although the precise mechanism of the heme-aggravated cytotoxicity is not yet known, it closely parallels amplified lipid peroxidation in endothelial cell membranes suggesting the importance of lipid injury. Hemopexin, by complexing heme, protects endothelial cells from activated PMN, but only if added simultaneously. The hydrophobic iron chelator and antioxidant, U74500A, abrogates heme-augmented hydrogen peroxide and PMN-mediated endothelial damage. Such compounds, therefore, may have therapeutic potential in one or more of the listed clinical syndromes. We speculate that exposure of endothelium to free heme may potentiate vascular damage in various clinical syndromes, including acute renal failure after massive intravascular hemolysis, crush injuries, reperfusion after myocardial infarction (perhaps secondary to cardiac myoglobin release), retrolental fibroplasia associated with neonatal hemopexin deficiency, and, perhaps, atherosclerosis involving sites of turbulence that may trigger minor red blood cell lysis.
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PMID:Heme uptake by endothelium synergizes polymorphonuclear granulocyte-mediated damage. 213 29

Uric acid, as the end-product of purine metabolism in humans, presents a clinical problem because of its relative insolubility, particularly in the acid environment of the distal nephron of the kidney. As a result, states of enhanced purine catabolism increase the urate load on the kidney, leading to intrarenal precipitation. Major causes of increased purine metabolism are malignancies with rapid cell turnover, such as leukemias and lymphomas, and the added acceleration of cell lysis that occurs with chemotherapy and radiation. Serum urate levels rise rapidly, and acute renal failure occurs as a consequence of tubular deposition of urate and uric acid. The keys to the diagnosis of acute uric acid nephropathy are the appropriate clinical setting of increased cell lysis, oliguria, marked hyperuricemia, and hyperuricosuria. A urinary uric acid-to-creatinine ratio greater than 1 helps to distinguish acute uric acid nephropathy from other catabolic forms of acute renal failure in which serum urate is elevated. Preventive treatment involves pharmacologic xanthine oxidase inhibition with allopurinol and alkaline diuresis. Occasionally, acute renal failure occurs despite allopurinol because of the tubular precipitation of the precursor metabolites, such as xanthine, which accumulate with xanthine oxidase inhibition. Dialysis therapy may be required both to correct azotemia and to reduce the body burden of urate. Hemodialysis is preferred because it can achieve greater clearance than other dialysis modes.
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PMID:Acute uric acid nephropathy. 219 58

The conversion rates of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) were compared with the time course of in vivo lipid peroxidation (LPO) in an ischemia-reperfusion model of acute renal failure in the rat. LPO, measured as the renal release of malondialdehyde (MDA), was found to be markedly elevated only during the first 5 min of blood reflow following a 45-min interval of ischemia (arteriovenous MDA difference -277.3 +/- 53.5 vs. 3.7 +/- 5.7 nmol/l in controls, n = 14). After 30 min of reperfusion, arteriovenous MDA differences nearly reached control values (9.7 +/- 31.8 nmol/l, n = 7). In contrast to enhanced LPO, no significant conversion of XDH to XO was found (XO activity in controls: 23 +/- 1% of XO plus XDH activity vs. 26 +/- 3% after 45 min of ischemia, n = 7). Therefore XO-derived superoxide anion radicals cannot be considered causative for LPO in the reperfusion interval of experimental ischemic acute renal failure.
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PMID:Xanthine oxidase: evidence against a causative role in renal reperfusion injury. 230 86

Inherited adenine phosphoribosyltransferase (APRT) has a recessive transmission. When it is very important, adenine can't be restored into nucleic acids pool and will changed into 2,8-dihydroxyadenine (2,8-DHA) by xanthine oxidase. To date in all countries but Japan, 2,8-DHA urolithiasis is observed only into homozygotic subjects with complete APRT deficiency Commonly, its onset is observed in childhood often dramatically. The authors report two new pediatric cases into new french families. First a 8 years old boy with spontaneous elimination of two lithiasis after right lumbar pain. Secondly an infant (nineteen months) who has presented an acute renal failure with anuria. Bilateral lithiasis included into pyelourectal junctions have been pulled out by bilateral surgical pyelotomy. In each case, lithiasis were radiolucent and diagnosis made by ultrasonography. The uric acid metabolism was normal and it is the infra red spectrophotometric study of stones that had recognised the 2,8-DHA component. In the second case, bilateral residual lithiasis have been broken by piezoelectric extra-corporeal lithotripsy with good tolerance and favorable result. The two children received preventive treatment. After 36 and 19 months they have no recurrence. In the literature, the frequency of 2,8-DHA lithiasis is very more low than the theoretical of homozygotics in population (1/100,000). The common confusion with uric lithiasis is one possible explanation. So spectrophotometric study of radiolucent stones was meant to be realised when uric metabolism is not disturbed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[2,8-dihydroxyadenine lithiasis. 2 new pediatric cases of an unknown metabolic deficit. The use of extracorporal lithotripsy]. 238

To assess the effects of xanthine oxidase (XO) inhibition on ischemic injury, rats were pretreated with oxypurinol (OXY, 5 mg/kg) and subjected to 30 min of bilateral renal artery occlusion. OXY's effect on adenine nucleotide-nucleoside-purine base concentrations was determined at 10 and 30 min of ischemia and during reperfusion (5 and 30 min). To assess whether XO-mediated oxidant stress influences the severity of ischemic acute renal failure (IARF), the effects of 1) OXY pretreatment and 2) hypoxanthine infusion were assessed. During ischemia OXY inhibited XO activity (more than fourfold rise in hypoxanthine-xanthine ratios) and induced quantitatively trivial but significant increases in ATP and total adenine nucleotide concentrations (by 30 min). Increased OXY dosage (15 mg/kg) or allopurinol (40 mg/kg) had no greater effects. At 5 min of reflow, OXY maintained XO inhibition but did not influence adenine nucleotide levels. By 30 min of reflow, 17-20% increments in ATP-total adenine nucleotides resulted. Nevertheless, OXY did not lessen the severity of IARF (assessed by azotemia-histology at 24 h). Hypoxanthine infusion increased end-ischemic hypoxanthine concentrations by 47%, but it did not change the severity of renal damage. Conclusions include 1) OXY-allopurinol induces intrarenal XO inhibition; 2) XO inhibitors slightly increase late ischemic-reperfusion adenine nucleotide concentrations; and 3) neither XO inhibition nor intrarenal hypoxanthine loading alters the severity of IARF, suggesting that XO-mediated oxidant stress is not a critical, consistent mediator of ischemic renal injury.
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PMID:Effects of xanthine oxidase inhibition on ischemic acute renal failure in the rat. 260 62

Xanthine oxidase (XO) activity and hydroxyl radical (.OH) formation are widely proposed mediators of renal reperfusion injury, potentially altering the severity of, and recovery from, postischemic acute renal failure. The goal of this study was to ascertain whether combination XO inhibitor (oxypurinol) and .OH scavenger (Na benzoate) therapy, given at the time of renal ischemia, alters the extent of: (1) tubular necrosis and filtration failure; (2) DNA fragmentation/apoptosis (assessed in situ by terminal deoxynucleotidyl transferase reactivity); (3) early tubular regenerative responses (proliferating cell nuclear antigen expression; (3H)thymidine incorporation); and (4) the rate and/or degree of functional and morphologic repair. The effects of XO inhibition, .OH scavengers, and "catalytic" iron (FeSO4) on human proximal tubular cell proliferation in vitro were also assessed with a newly established cell line (HK-2). Male Sprague-Dawley rats were subjected to 35 min of bilateral renal arterial occlusion with or without oxypurinol/benzoate therapy. These agents did not alter the extent of tubular necrosis or filtration failure, proliferating cell nuclear antigen expression or thymidine incorporation, or the rate/extent of renal functional/morphologic repair. DNA fragmentation did not precede tubular necrosis, and it was unaffected by antioxidant therapy. By 5 days postischemia, both treatment groups demonstrated regenerating epithelial fronds that protruded into the lumina. These structures contained terminal deoxynucleotidyl transferase-reactive, but morphologically intact, cells, suggesting the presence of apoptosis. Oxypurinol and .OH scavengers (benzoate; dimethylthiourea) suppressed in vitro tubular cell proliferation; conversely, catalytic Fe had a growth-stimulatory effect. These results suggest that: (1) XO inhibition/.OH scavenger therapy has no discernible net effect on postischemic acute renal failure; (2) DNA fragmentation does not precede tubular necrosis, suggesting that it is not a primary mediator of ischemic cell death; and (3) antioxidants can be antiproliferative for human tubular cells, possibly mitigating their potential beneficial effects.
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PMID:An evaluation of antioxidant effects on recovery from postischemic acute renal failure. 791 60

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

Oxidant injury is considered to be an important mechanism in the pathophysiology of acute renal failure. It has been thought that decrease in extracellular and intracellular fluid and endotoxemia seen in obstructive jaundice may cause an increase in production of oxygen free radicals and impairment in antioxidant defense mechanism. This study is designed to investigate the possible role of oxidant injury in renal failure seen in jaundiced patients. In this study, 28 rats were divided into four groups: Control (C)(N = 7); Renal ischemia (RI)(N = 7); Obstructive jaundice+renal ischemia (OJ+RI)(N = 7); Obstructive jaundice (OJ)(N = 7). All groups were compared with each other according to renal failure findings and enzyme activities, such as Xanthine oxidase (XOD), Superoxide Dismutase (SOD) and Catalase in renal cortex and Glutathione Peroxidase (GSH-Px), in blood at 3rd day after ischemia and reperfusion. Renal failure findings monitored by blood urea and creatinine levels, seemed more evident in OJ+RI than RI group (p < 0.05). When compared with RI, in OJ+RI group, increase in XOD activity at 3rd day was statistically significant [0.259 +/- 0.01 U/g (tissue) and 0.362 +/- 0.03 U/g (tissue) respectively] (p < 0.05). SOD and GSH-Px activities of each ischemic group at 3rd day were decreased compared to non-ischemic groups. This fall was significant (p < 0.05). But there was no statistical difference between jaundiced and non-jaundiced groups. Alterations in catalase activities also had no statistical significance. These findings may suggest that the injury induced by oxygen free radicals at re-oxygenation of tissue after ischemia may also play a role in the pathogenesis of acute renal failure developed in obstructive jaundice.
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PMID:The role of oxygen free radicals in acute renal failure complicating obstructive jaundice: an experimental study. 951 37


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