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)

Endothelial cells control vascular homeostasis by generating paracrine factors that regulate vascular tone, inhibit platelet function, prevent adhesion of leukocytes, and limit proliferation of vascular smooth muscle. The dominant factor responsible for many of those effects is endothelium-derived nitric oxide (NO). Endothelial dysfunction characterized by enhanced inactivation or reduced synthesis of NO, alone or in combination, is seen in conjunction with risk factors for cardiovascular disease. Endothelial dysfunction can promote vasospasm, thrombosis, vascular inflammation, and proliferation of the intima. Vascular oxidative stress and increased production of reactive oxygen species contributes to mechanisms of vascular dysfunction. Oxidative stress is mainly caused by an imbalance between the activity of endogenous pro-oxidative enzymes (such as NADPH oxidase, xanthine oxidase or the mitochondrial respiratory chain) and antioxidant enzymes (such as superoxide dismutase, glutathione peroxidase, heme oxygenase, thioredoxin peroxidase/peroxiredoxin, catalase and paraoxonase). In addition, small-molecular-weight antioxidants might have a role in the defense against oxidative stress. Increased concentrations of reactive oxygen species reduce bioactive NO through chemical inactivation, forming toxic peroxynitrite, which in turn can uncouple endothelial NO synthase to form a dysfunctional superoxide-generating enzyme that contributes further to oxidative stress. The role of oxidative stress in vascular dysfunction and atherogenesis, and strategies for its prevention are discussed.
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PMID:Oxidative stress in vascular disease: causes, defense mechanisms and potential therapies. 1846 Oct 48

Many studies have shown a strong correlation between urate levels and cardiovascular disease. The formation of urate is complex as the same enzyme that produces urate, xanthine oxidase (XO) also catalyzes the formation of reactive oxygen species (ROS). There is some evidence that the urate molecule has free radical scavenging properties in vitro and acute infusions of urate improve endothelial function in at-risk populations. High levels of ROS are clearly linked to worse outcome in a variety of conditions. Allopurinol has been the archetypal XO inhibitor for over 40 years. Small studies have demonstrated its beneficial effects, mainly in heart failure but also in a variety of other cohorts of patients with cardiovascular risk. It is a safe agent, provided suitable patients are chosen and monitored carefully. Newer promising agents like oxypurinol have not shown the expected benefits in larger multicentered studies. This review looks at the biology of urate, its role in cardiovascular disease, the possible mechanisms by which XO inhibitors exert their beneficial effect on endothelial dysfunction, and examines the possible causes for the failure of newer agents to live up to expectations.
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PMID:The role of urate and xanthine oxidase inhibitors in cardiovascular disease. 1846 21

Reactive oxygen species (ROS) are important mediators in vascular biology. Venous function, although relevant to cardiovascular disease, is still understudied. We compared aspects of ROS metabolism between a major artery (the aorta) and a major vein (the vena cava, VC) of the rat, with the hypothesis that venous ROS metabolism would be overall increased compared with its arterial counterpart. Superoxide and hydrogen peroxide (H2O2) release in basal conditions was higher in VC compared with aorta. The antioxidant capacity for H2O2 was also higher in VC than in aorta. Exogenous superoxide induced a higher contraction in VC compared with aorta. Protein expression of three major ROS metabolizing enzymes, xanthine oxidase (XO), CuZn-SOD, and catalase, was higher in VC compared with aorta. Because XO seemed a likely source of the higher VC ROS levels, we examined it further and found higher mRNA expression and activity of XO in VC compared with aorta. We also investigated the impact of XO inhibition by allopurinol on aorta and VC functional responses to norepinephrine, ANG II, ET-1, and ACh. Maximal ET-1-mediated contraction was decreased by allopurinol in VC but not in the aorta. Our results suggest that there are overall differences in ROS metabolism between aorta and VC, with the latter operating normally at a higher set point, releasing but also being able to handle, higher ROS levels. We propose XO to be an important source for these differences. The result of this particular comparison may be reflective of a general arteriovenous contrast.
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PMID:A comparison of reactive oxygen species metabolism in the rat aorta and vena cava: focus on xanthine oxidase. 1866 Apr 42

The endothelium plays a crucial role in the regulation of vascular tone. Recent studies have indicated that endothelial dysfunction develops in the presence of cardiovascular risk factors such as hypertension, diabetes mellitus, hypercholesterolemia and in chronic smokers, as well as in patients with a family history of cardiovascular disease. It has now been established that endothelial dysfunction represents the first indicator of vascular damage. Endothelial function can be assessed in coronary and peripheral conductance and resistance vessels by means of invasive and noninvasive (ultrasound-guided) methods such as intracoronary infusion of acetylcholine, the endothelium-dependent vasodilator. It is interesting that endothelial dysfunction in the presence of cardiovascular risk factors can be almost completely corrected by the acute administration of antioxidants such as vitamin C, pointing to a crucial role of reactive oxygen species in mediating this phenomenon. Superoxide producing enzymes involved in the increased production of reactive oxygen species include NADPH oxidase, nitric oxide synthase in the uncoupled state, mitochondrial superoxide sources, cyclooxygenase and xanthine oxidase. Recent studies indicate that the endothelial dysfunction found in coronary and peripheral conductance and resistance vessels provide prognostic information about future cardiovascular events. The role of endothelial dysfunction in the setting of primary prevention is not yet clear, but is being investigated in the current Gutenberg Heart Study.
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PMID:[Endothelial dysfunction: pathophysiology, diagnosis and prognosis]. 1900 47

The aim of this study was to investigate the effects of a high-cholesterol diet on oxidant/antioxidant status and nitric oxide synthase (NOS) activity in erythrocytes from rats. Sixteen Sprague-Dawley-type albino male rats were used in the study. The rats were randomly divided into 2 groups: the control group (group 1) was fed a standard rat diet, and the treated group (group 2) was fed a high-cholesterol diet (4% cholesterol, 1% cholic acid, and 0.5% thiouracil) in addition to standard pellet rat diet for 3 months. At the end of the study period, blood samples were obtained from the rats under ether anesthesia. Oxidant (malondialdehyde level, sensitivity to oxidation value, and xanthine oxidase [XO] activity) and antioxidant parameters (antioxidant potential value, superoxide dismutase, catalase, and glutathione peroxidase activities) were studied in erythrocyte preparations. Activities of erythrocyte NOS and arginase enzymes and serum total cholesterol levels were also measured. We observed that serum total cholesterol levels, erythrocyte XO activities, and sensitivity to oxidation values significantly increased in group 2 (cholesterol fed) compared with the control group (group 1). Erythrocyte NOS activities were also found to decrease in group 2. In conclusion, our results suggest that cholesterol feeding causes an increase in XO activity and a decrease in NOS activity in the erythrocytes from rats. The increase in XO activity may render the erythrocyte membranes sensitive to oxidant stress, and the decrease in NOS activity in the erythrocytes may increase cardiovascular disease risk via reduced endothelial relaxation.
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PMID:High-cholesterol diet increases xanthine oxidase and decreases nitric oxide synthase activities in erythrocytes from rats. 1908 10

The prevalence of gout has been increasing in epidemic proportions over the last several decades. Hyperuricemia has been shown to be associated with metabolic syndrome and to be an independent risk factor for cardiovascular disease. Associations between hyperuricemia, obesity and aging have provided an impetus in recent years to develop alternative methods of treating hyperuricemia and gout. Febuxostat is a new non-purine xanthine oxidase inhibitor indicated for chronic gout. Febuxostat has been shown to quickly and effectively lower serum urate levels in patients with chronic gout. This manuscript will review febuxostat, its pharmacokinetics and pharmacodynamics, efficacy and adverse events and use in patients with comorbid conditions. The review will also summarize the phase III trials leading up to the drug's approval by both the European Commission in 2008 and the U.S. FDA in 2009. Possible implications the medication may have in the future on gout and hyperuricemia will also be discussed.
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PMID:Febuxostat: a new agent for lowering serum urate. 1949 90

Uric acid (UA) results from xanthine oxidase (XO) catabolism of xanthine and is the final product of purine catabolism in humans. In this species, hyperuricemia is associated with gout, nephropathy, and increased cardiovascular disease risk. Although the effects of hyperuricemia in vascular biology are overall controversial, UA has been described as an antioxidant and as potentially improving endothelial function. Hypertension is associated with endothelial dysfunction. We hypothesized that UA improves the endothelial function of aorta from deoxycorticosterone acetate (DOCA)-salt hypertensive rats. UA (100 microM) in the presence of the uricase inhibitor oxonic acid (10 microM) did not modify relaxation to acetylcholine (ACh) (1 nM-10 microM) in the aorta from nontreated, sham normotensive, and DOCA-salt hypertensive rats [response to 10 microM ACh for UA versus vehicle, respectively: nontreated = 37 +/- 7 versus 48 +/- 7%, sham = 53 +/- 15 versus 57 +/- 20%, DOCA = 81 +/- 4 versus 85 +/- 2% from 20 microM prostaglandin 2alpha (PGF(2alpha))-induced contraction]. Allopurinol (100 microM), a XO inhibitor, did not significantly alter the ACh-induced relaxation of sham and DOCA aortic rings (response to 10 microM ACh for allopurinol versus vehicle, respectively: sham = 61 +/- 5 versus 68 +/- 9%, DOCA = 87 +/- 6 versus 88 +/- 3% from 20 microM PGF(2alpha)-induced contraction). Uricemia, ranging from unmeasurable to 547 microM in sham and to 506 microM in DOCA rats, was not significantly different between these two groups. The expression and activity of XO, as well as the expression of uricase, were not different between sham and DOCA rat aorta. We conclude that, at least in vitro, UA does not affect the ACh-induced relaxation of normotensive and DOCA-salt hypertensive rats.
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PMID:Uric acid does not affect the acetylcholine-induced relaxation of aorta from normotensive and deoxycorticosterone acetate-salt hypertensive rats. 2021 10

Endothelium-derived nitric oxide (NO) is a paracrine factor that controls vascular tone, inhibits platelet function, prevents adhesion of leukocytes, and reduces proliferation of the intima. An enhanced inactivation and/or reduced synthesis of NO is seen in conjunction with risk factors for cardiovascular disease. This condition, referred to as endothelial dysfunction, can promote vasospasm, thrombosis, vascular inflammation, and proliferation of vascular smooth muscle cells. Vascular oxidative stress with an increased production of reactive oxygen species (ROS) contributes to mechanisms of vascular dysfunction. Oxidative stress is mainly caused by an imbalance between the activity of endogenous pro-oxidative enzymes (such as NADPH oxidase, xanthine oxidase, or the mitochondrial respiratory chain) and anti-oxidative enzymes (such as superoxide dismutase, glutathione peroxidase, heme oxygenase, thioredoxin peroxidase/peroxiredoxin, catalase, and paraoxonase) in favor of the former. Also, small molecular weight antioxidants may play a role in the defense against oxidative stress. Increased ROS concentrations reduce the amount of bioactive NO by chemical inactivation to form toxic peroxynitrite. Peroxynitrite-in turn-can "uncouple" endothelial NO synthase to become a dysfunctional superoxide-generating enzyme that contributes to vascular oxidative stress. Oxidative stress and endothelial dysfunction can promote atherogenesis. Therapeutically, drugs in clinical use such as ACE inhibitors, AT(1) receptor blockers, and statins have pleiotropic actions that can improve endothelial function. Also, dietary polyphenolic antioxidants can reduce oxidative stress, whereas clinical trials with antioxidant vitamins C and E failed to show an improved cardiovascular outcome.
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PMID:Nitric oxide and oxidative stress in vascular disease. 2030 72

Over the last two decades, it has become increasingly clear that reactive oxygen species (ROS), including free radicals are involved in cardiovascular disease. In recent years, there has been a growing interest in the clinical implications of these oxidants. The ROS are common by-products of many oxidative biochemical and physiological processes. They can be released by xanthine oxidase, NAD(P)H oxidase, lipoxygenases, mitochondria, or the uncoupling of nitric oxide synthase in vascular cells. ROS mediate various signaling pathways that underlie vascular inflammation in atherogenesis. Various animal models of oxidative stress support that ROS have causal role in atherosclerosis and other cardiovascular diseases. They are too reactive to be tolerated in living tissue, and aerobic organisms use sophisticated defense system, both enzymatic and non-enzymatic for prevention of overload of free radicals. In a number of pathophysiological conditions, the delicate equilibrium between free-radical production and antioxidant capability can be altered in favor of the former, thus leading to oxidative stress and increased tissue injury. This review focuses on the biochemical evidences concerning involvement of ROS in several cardiovascular diseases, namely atherosclerosis, heart failure, hypertension and ischemia/reperfusion injury.
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PMID:Oxidative stress in cardiovascular disease. 2036 6

An abnormal production of reactive oxygen species (ROS) and the subsequent decrease in vascular bioavailability of nitric oxide (NO) have long been proposed to be the common pathogenetic mechanism of the endothelial dysfunction, resulting from diverse cardiovascular risk factors such as hypercholesterolaemia, diabetes mellitus, chronic smoking, metabolic syndrome, and hypertension. Superoxide produced by the nicotinamide dinucleotide phosphate (NADPH) oxidase, mitochondrial sources, or the xanthine oxidase may react with NO, thereby resulting in excessive formation of peroxynitrite, a reactive nitrogen species that has been demonstrated to accelerate the atherosclerotic process by causing direct structural damage and by causing further ROS production. Despite this sound biological rationale and a number of pre-clinical and clinical lines of evidence, studies testing the effects of classical antioxidants such as vitamin C, vitamin E, or folic acid in combination with vitamin E have been disappointing. Rather, substances such as statins, angiotensin-converting enzyme inhibitors, or AT1-receptor blockers, which possess indirect antioxidant properties mediated by the stimulation of NO production and simultaneous inhibition of superoxide production (e.g. from the NADPH oxidase), have been shown to improve vascular function in pre-clinical and clinical studies and to reduce the incidence of cardiovascular events in patients with cardiovascular disease. Today, oxidative stress remains an attractive target for cardiovascular prevention and therapy. However, a deeper understanding of its source, and of its role in vascular pathology, is necessary before new trials are attempted.
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PMID:Is oxidative stress a therapeutic target in cardiovascular disease? 2097 1


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