Administration Of Uric Acid Research Articles

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Introduction: High oxypyrines level in blood and, may be, in cerebrospinal fluid (CSF), is a strong risk factor for brain ischaemia and stroke. It is known that exogenous administration of uric acid, shows obvious antiradical, antioxidant and neuroprotective effects whereas endogenous increased its

Neuroprotection by urate on 6‐OHDA‐lesioned rat model of Parkinson's disease: linking to Akt/GSK3β signaling pathway

Higher plasma urate level is reported to be associated with a reduced risk and slower progression of Parkinson's disease (PD). In this study, we explored the effects of urate on dopaminergic neurons in nigrostriatal pathway in the 6-hydroxydopamine (6-OHDA) unilaterally lesioned rats. Uric acid (UA), when given twice daily at 200 mg/kg intraperitoneally for 10 consecutive days, elevated urate (the anionic form of UA) in plasma and striatum by 55% and 36.8%, respectively, as compared with vehicle group. This regimen of UA was found to ameliorate the behavioral deficits, dopaminergic neuron loss as well as dopamine depletion in the nigrostriatal system. Moreover, UA administration was capable of increasing glutathione level and superoxide dismutase activity while decreasing malondialdehyde accumulation in striatum. In addition, the phosphorylation of both protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK3β) in the lesioned striata of 6-OHDA-lesioned rats was dramatically reduced as compared with sham-operated rats. This reduction was attenuated in the Parkinsonian rats receiving UA treatment. Similarly, in vitro findings showed that UA alleviated the decrease in Akt activation and the increase in GSK3β activity caused by 6-OHDA. Furthermore, neuroprotection by urate and its regulation on GSK3β phosphorylation at Ser9 was found to be abolished in the presence of PI3K inhibitor. Therefore, our findings demonstrated that urate was able to protect dopaminergic neurons in rat nigrostriatal pathway against the neurotoxicity of 6-OHDA, and showed that its beneficial effects may be related to its regulation on Akt/GSK3β signaling.

The effects of allopurinol, uric acid, and inosine administration on xanthine oxidoreductase activity and uric acid concentrations in broilers

The purpose of these studies was to determine the effects of uric acid (UA) and inosine administration on xanthine oxidoreductase activity in broilers. In experiment one, 25 broilers were assigned to 5 treatment groups: control, AL (25 mg of allopurinol/kg of body mass), AR (AL for 2 wk followed by allopurinol withdrawal over wk 3), UAF (AL plus 6.25 g of UA sodium salt/kg of feed), and UAI (AL plus 120 mg of UA sodium salt injected daily). The UA administration had no effect on plasma concentration of UA (P > 0.05), and all allopurinol-treated birds had lower (P < 0.05) UA levels than controls. The UA concentrations were restored in both plasma and kidney of AR birds at wk 3, but liver UA concentrations remained lower. Whereas xanthine oxidoreductase (XOR) activity in the liver (LXOR) was reduced (P < 0.05) by allopurinol treatment, XOR activity in the kidney (KXOR) was not affected (P = 0.05). In experiment two, 3 groups of 5 birds each were fed 0 (control), 0.6 M inosine/kg of feed (INO), or INO plus 50 mg of allopurinol/kg of body mass (INOAL). The INOAL birds showed lower total LXOR activity, but KXOR activity was not affected. Both INO and INOAL birds had higher plasma and kidney UA concentrations than controls. The results suggest that regulation of UA production is tissue dependent.

Low antioxidant status of serum uric acid, bilirubin and albumin in patients with neuromyelitis optica

Oxidative stress plays a central role in neuropathology of multiple sclerosis (MS). The patients with MS have low antioxidant status. Antioxidant therapy may represent an attractive treatment of MS. However, the relationship between neuromyelitis optica (NMO), a distinct nosologic entity or a form of MS, and antioxidant status has not fully been investigated. To investigate the correlation between NMO and serum antioxidant status of uric acid (UA), bilirubin and albumin. The serum levels of antioxidant molecules UA, bilirubin (Tbil and Ibil) and albumin were measured in 236 individuals comprising healthy subjects and patients with NMO or MS. We found that serum levels of UA, Tbil, Ibil and albumin in patients with NMO were significantly lower than those in healthy control group. Moreover, these results were also observed when the male and female cohorts were investigated separately. Likewise, the serum levels of UA, Tbil, Ibil and albumin in patients with NMO were also lower than those of patients with MS. In all groups, women had lower serum UA, Tbil, Ibil and albumin levels than men. In UA groups, women had significantly lower serum UA levels than men. We concluded that there were reducing serum levels of UA, bilirubin and albumin in patients with NMO. The study showed patients with NMO had low antioxidant status. As a replacement therapy to patients, administration of albumin, bilirubin and UA or theirs precursors, such as inosine of UA precursor, may be beneficial to the patients with NMO.

Is there a trigger role of peroxynitrite in the anti-arrhythmic effect of ischaemic preconditioning and peroxynitrite infusion?

This study has examined whether peroxynitrite (PN), generated during the preconditioning (PC) procedure or administered by brief intracoronary infusions, plays a trigger role in the anti-arrhythmic effects of preconditioning and peroxynitrite in anaesthetized dogs. To achieve this we infused the peroxynitrite scavenger uric acid (UA; 0.2 mg/kg/min, i.v.) over a 30 min period, just prior to a 25 min occlusion of the left anterior descending coronary artery, in preconditioned (UA + PC, n = 8), peroxynitrite-treated (UA + PN, n = 8) and in control (UAC; n = 9) dogs. The effects were compared to those obtained from groups (PC, n = 10; PN, n = 10; C1, n = 14) without uric acid administration. Severities of ischaemia (ST-segment elevation, inhomogeneity of electrical activation) and ventricular arrhythmias (VPBs, VT, VF), plasma nitrate/nitrite levels, as well as myocardial superoxide and nitrotyrosine productions were determined. Both preconditioning and the infusion of peroxynitrite increased nitrotyrosine formation which was abolished by the simultaneous administration of urate. Despite this, the protective effects of preconditioning (i.e. reductions in arrhythmias, superoxide and nitrotyrosine productions, as well as the increase in nitric oxide availability), occurring during the prolonged period of occlusion and reperfusion were still present. In contrast, urate completely abolished the protection resulted from peroxynitrite administration. This effect is most probably due to the fact that urate has already scavenged peroxynitrite during the infusion. Interestingly, urate itself, given prior to ischaemia and reperfusion, was also protective. We conclude that peroxynitrite in nanomolar concentrations can induce an anti-arrhythmic effect but peroxynitrite, generated during the preconditioning stimulus, is not necessary for the preconditioning-induced anti-arrhythmic protection.

Uric Acid Levels Are Relevant in Patients With Stroke Treated With Thrombolysis

Uric acid (UA) is a neuroprotective antioxidant that improves the benefits of alteplase in experimental ischemia. However, it is unknown whether endogenous UA also influences the response to thrombolysis in patients with stroke. A total of 317 consecutive patients treated with thrombolysis were included in a prospective stroke registry. Demographics, laboratory data, neurological course, and infarction volume were prospectively collected. Excellent outcome was defined as achieving a modified Rankin Scale score <2 at 90 days. Binary and ordinal logistic regression models were used to analyze modified Rankin Scale score at 90 days. UA levels were significantly higher in patients with an excellent outcome than in patients with a poor outcome (5.82 [1.39] versus 5.42 [1.81], P=0.029). In multivariate models, increased UA levels (OR, 1.23; 95% CI, 1.03 to 1.49; P=0.025) were associated with an excellent outcome and with an increased risk of shifting to a better category across the modified Rankin Scale (OR, 1.19; 95% CI, 1.04 to 1.38; P=0.014) independently of the effect of confounders. The levels of UA and the volume of final infarction were inversely correlated (r=-0.216, P<0.001) and the inverse correlation remained after adjustment for age, sex, and baseline National Institutes of Health Stroke Scale score (t value=-2.54, P=0.01). Significantly lower UA levels were found in patients with malignant middle cerebral artery infarction and parenchymal hemorrhage post-thrombolysis. Increased UA serum levels are associated with better outcome in patients with stroke treated with reperfusion therapies. These results support the assessment of the potential neuroprotective role of the exogenous administration of UA in patients with stroke treated with thrombolysis.

The Urico-Ictus Study, a Phase 3 Study of Combined Treatment with Uric Acid and rtPA Administered Intravenously in Acute Ischaemic Stroke Patients within the First 4.5 H of Onset of Symptoms

Oxidative stress is a major contributor to brain damage in patients with ischaemic stroke. Uric acid (UA) is a potent endogenous antioxidant molecule. In experimental ischaemia in rats, the exogenous administration of uric acid is neuroprotective and enhances the effect of rtPA. Moreover, in acute stroke patients receiving rtPA within 3 h of stroke onset, the intravenous administration of uric acid is safe, prevents an early decline in uric acid levels and reduces an early increase in oxidative stress markers and in active matrix metalloproteinase nine levels. To determine whether the combined treatment with uric acid and rtPA is superior to rtPA alone in terms of clinical efficacy in acute ischaemic stroke patients treated within the first 4.5 h of onset of symptoms. Multicentre, interventional, randomised, double-blind and vehicle-controlled efficacy study with parallel assignment (1 : 1). Estimated enrolment: 420 patients over 3 years, starting in January 2010. Treatment arms included patients will receive a single intravenous infusion of 1 g of UA dissolved in a vehicle (500 ml of 0.1% lithium carbonate and 5% mannitol) (n=210) or vehicle alone (n=210). the study will include patients older than 18 years, treated with rtPA within the first 4.5 h of clinical onset and with a baseline National Institute of Health Stroke Scale score >6 and <25 and a modified Rankin Scale score < or =2 before the ischaemic event. Patients with renal insufficiency, gout or asymptomatic hiperuricaemia treated with allopurinol will be excluded. The primary outcome measure is the proportion of patients achieving an modified Rankin Scale of 0 to 1 at 3 months after treatment or two in those patients with a prior qualifying modified Rankin Scale of 2. Secondary outcome measures include the final infarction volume measured at 72 h and the proportion of patients with symptomatic intracranial haemorrhage (> or =4 points of increase in the National Institute of Health Stroke Scale score).

Effects of hyperbaric oxygen on uric acid and arachidonic acid: a metabolomic study in rats and humans

Hyperoxia is routinely used to prevent or treat hypoxemia and acute respiratory failure, and sustain aerobic life in military and commercial operations. However, breathing oxygen acutely at high pressures and for long durations is toxic. The present study aimed to investigate effects of hyperbaric oxygen (HBO) exposure on plasma metabolite profiles. We applied a liquid chromatography-mass spectrometry based metabolomic approach to analyze metabolites from plasma of both rats and humans under HBO conditions to explore the possible effects of HBO on the body. Uric acid (UA) and arachidonic acid concentrations were changed significantly in both rat and human plasma, and some precursor metabolites of UA in the UA pathway were also changed. For acute and chronic HBO exposures on plasma UA after exogenous UA injection, the results indicated exogenous administration of UA significantly increased plasma UA and ascorbic acid levels. However, these returned to normal levels 48 h after HBO exposure. These findings suggest HBO exposure can combat the harmful effects of increased UA from exposure to elevated partial pressure of oxygen. Furthermore, exogenous administration of UA not only does not disturb its metabolism, but also increases its anti-oxidative capacity (increase ascorbic acid). These findings suggest that the use of antioxidants might be necessary under HBO exposure, especially under extreme HBO exposure.

Tyrosine Nitration of PA700 Activates the 26S Proteasome to Induce Endothelial Dysfunction in Mice With Angiotensin II–Induced Hypertension

The ubiquitin-proteasome system has been implicated in oxidative stress-induced endothelial dysfunction in cardiovascular diseases. However, the mechanism by which oxidative stress alters the ubiquitin-proteasome system is poorly defined. The present study was conducted to determine whether oxidative modifications of PA700, a 26S proteasome regulatory subunit, contributes to angiotensin II (Ang II)-induced endothelial dysfunction. Exposure of human umbilical vein endothelial cells to low concentrations of Ang II, but not vehicle, for 6 hours significantly decreased the levels of tetrahydro-l-biopterin (BH4), an essential cofactor of endothelial NO synthase, which was accompanied by a decrease in GTP cyclohydrolase I, the rate-limiting enzyme for de novo BH4 synthesis. In addition, Ang II increased both tyrosine nitration of PA700 and the 26S proteasome activity, which were paralleled by increased coimmunoprecipitation of PA700 and the 20S proteasome. Genetic inhibition of NAD(P)H oxidase or administration of uric acid (a peroxynitrite scavenger) or N(G)-nitro-l-arginine methyl ester (nonselective NO synthase inhibitor) significantly attenuated Ang II-induced PA700 nitration, 26S proteasome activation, and reduction of GTP cyclohydrolase I and BH4. Finally, Ang II infusion in mice decreased the levels of both BH4 and GTP cyclohydrolase I and impaired endothelial-dependent relaxation in isolated aortas, and all of these effects were prevented by the administration of MG132, a potent inhibitor for 26S proteasome. We conclude that Ang II increases tyrosine nitration of PA700 resulting in accelerated GTP cyclohydrolase I degradation, BH4 deficiency, and consequent endothelial dysfunction in hypertension.

Course of matrix metalloproteinase-9 isoforms after the administration of uric acid in patients with acute stroke

Oxidative stress as well as expression and activity of matrix metalloproteinase 9 (MMP-9) are rapidly enhanced after cerebral ischemia. The magnitude of these effects is related to stroke outcome. In human stroke, the extent of oxidative stress correlates well with increased MMP-9 expression. The aim of this study was to evaluate whether treatment with the antioxidant molecule uric acid (UA) decreased the levels of MMP-9 in stroke patients treated with rtPA. The patients were part of a pilot, double-blind, randomized, vehicle-controlled study of patients with acute stroke treated with rtPA (< 3 h) and randomized to receive an intravenous infusion of UA (n = 16) or vehicle (n = 8). Total matrix metalloproteinase (tMMP)-9 and active (aMMP-9) levels were measured in serum at baseline (< 3 h), at the end of study treatment infusion (< 5.5 h), and at 48 hours. Total MMP-9 and aMMP-9 increased very early after stroke onset in patients allocated vehicle after rtPA therapy. Lower increments of aMMP-9 were associated with better outcome at 3 months. UA treatment was associated with reduced levels of aMMP-9 at T1 (p < 0.02) in multivariate models adjusted for age, NIHSS score, and baseline aMMP-9 levels. The decline of aMMP-9 attained after UA administration supports further clinical assessment of UA therapy in patients with acute stroke.

Effect of acute gouty arthritis on sleep patterns: A preclinical study

Background It has been demonstrated that the interrelation between pain and sleep produces changes in sleep patterns and pain perception. Although some evidences suggest that sleep and pain may interact in a complex way, polysomnographic studies in animals with acute nociception are limited in number. Aims This study was carried out in order to evaluate the effect of intra-articular knee injection of uric acid on sleep-wake patterns. Methods Surgical electrode implantation was performed in seven anesthetized Wistar rats to carry out 10 h polysomnographic recordings. Acute nociception was induced by the intra-articular administration of 30% uric acid crystals into the knee joint of the right hind limb. Two recordings before and after intra-articular drug administration were obtained. Sleep-wake parameters were classified as (i) wakefulness (W), (ii) slow wave sleep (SWS), and (iii) rapid eye movement (REM) sleep. Frequency and duration from each parameter were evaluated under the two above-mentioned conditions. Results Intra-articular administration of uric acid induced: (i) an increased duration of wakefulness ( p = 0.014), (ii) a decrement in the duration ( p = 0.001) and number of events ( p = 0.027) in REM sleep, and (iii) a decrement in the total sleep time ( p = 0.001). SWS did not present statistical differences between groups. Conclusions These data suggest that a nociceptive stimulus, induced by the intra-articular administration of uric acid, alters the sleep-wake equilibrium with REM sleep being particularly altered. However, further research concerning pain–sleep interaction is needed.

The influence of uric acid treatments on liver glutathione system prevent oxidative damages in experimental autoimmune encephalomyelitis mice

Recently we reported that antioxidant system in brain and spinal cord in experimental autoimmune encephalomyelitis (EAE) mice is mainly affected at early stages of the disease [M. Zargari, A. Allameh, M.H. Sanati, T. Tiraihi, S.H. Lavasani, O. Emadyan, Relationship between the clinical scoring and demyelination in central nervous system with total antioxidant capacity of plasma during experimental autoimmune encephalomyelitis development in mice, Neurosci. Lett. 412 (2007), 24-28]. The aim of the present study was to investigate the role of uric acid (UA) on antioxidant system in liver and plasma of EAE mice. EAE was induced in C57/BL6 mice (n=60), followed by i.p. administration of UA (10mg/kg BW) in 30 mice at three distinct clinical stages (A: prior to onset, B: after onset, C: after development of EAE). Livers were removed and processed for measurement of lipid peroxidation products, reduced glutathione (GSH), and glutathione S-transferase (GST) and total antioxidant capacity of plasma (FRAP). The results showed that lipid peroxidation products in liver of EAE mice was increased significantly ( approximately 85%) as compared to normal. UA administration to EAE mice caused a significant suppression of liver lipid peroxidation products ( approximately 45%) at early stages (A and B). There was an inverse relationship between lipid peroxidation and cellular GSH in liver. GSH was significantly depleted in mice liver during the EAE progression, but it was recovered ( approximately 29%) when UA was injected before the onset of the disease (groups A and B). Plasma total antioxidant capacity was significantly decreased during the development of EAE, however it was subsided in mice treated with UA as compared to the corresponding controls (21%) in groups A and B. Elevated liver GST as a result of EAE induction was reversed in mice treated with UA particularly in groups A and B. These results indicate that hepatic glutathione system, particularly GST plays a major role in modulation of oxidative damages to central nervous system (CNS) during EAE induction. The positive response of antioxidant system to UA administration in EAE mice was corroborated with improvement of clinical manifestation of the animals.

Uric acid administration in patients with acute stroke: a novel approach to neuroprotection

Uric acid (UA) is the end product of purine catabolism in humans and is a powerful antioxidant whose generation is increased under ischemic conditions. However, both clinical and experimental studies reveal a gradual exhaustion of the antioxidant capacity after transient cerebral ischemia, and the magnitude of this consumption seems to be correlated with the extent of brain tissue injury, growth of the infarction, severity of neurological impairment in the acute phase, and long-term functional outcome. Growing evidence supports the neuroprotective effect of UA administration after brain ischemia. In experimental conditions, the administration of UA is neuroprotective both in mechanical models of brain ischemia (transient or permanent intraluminal occlusion of the middle cerebral artery) and in thromboembolic models of autologous clot injection. The administration of UA is feasible and safe in healthy volunteers. In acute stroke patients treated with recombinant tissue plasminogen activator (rt-PA), co-administration of UA has proven to reduce lipid peroxidation and to prevent the fall in UA blood levels that occur very early after stroke onset. Currently, a multicentric Phase III clinical trial is testing whether the administration of UA increases the clinical benefits of rt-PA, which represents the only approved therapy in patients with acute ischemic stroke. This review summarizes the available information justifying such a novel therapeutic approach in this devastating clinical condition.

Reactive Oxygen Species Modulate Anopheles gambiae Immunity against Bacteria and Plasmodium

The involvement of reactive oxygen species (ROS) in mosquito immunity against bacteria and Plasmodium was investigated in the malaria vector Anopheles gambiae. Strains of An. gambiae with higher systemic levels of ROS survive a bacterial challenge better, whereas reduction of ROS by dietary administration of antioxidants significantly decreases survival, indicating that ROS are required to mount effective antibacterial responses. Expression of several ROS detoxification enzymes increases in the midgut and fat body after a blood meal. Furthermore, expression of several of these enzymes increases to even higher levels when mosquitoes are fed a Plasmodium berghei-infected meal, indicating that the oxidative stress after a blood meal is exacerbated by Plasmodium infection. Paradoxically, a complete lack of induction of catalase mRNA and lower catalase activity were observed in P. berghei-infected midguts. This suppression of midgut catalase expression is a specific response to ookinete midgut invasion and is expected to lead to higher local levels of hydrogen peroxide. Further reduction of catalase expression by double-stranded RNA-mediated gene silencing promoted parasite clearance by a lytic mechanism and reduced infection significantly. High mosquito mortality is often observed after P. berghei infection. Death appears to result in part from excess production of ROS, as mortality can be decreased by oral administration of uric acid, a strong antioxidant. We conclude that ROS modulate An. gambiae immunity and that the mosquito response to P. berghei involves a local reduction of detoxification of hydrogen peroxide in the midgut that contributes to limit Plasmodium infection through a lytic mechanism.

Response to Letter by Dawson et al

HomeStrokeVol. 39, No. 1Response to Letter by Dawson et al Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBResponse to Letter by Dawson et al Sergio Amaro, Víctor Obach and Álvaro Cervera Anna M. Planas Ángel Chamorro Sergio AmaroSergio Amaro Institute of Neurosciences, IDIBAPS, Hospital Clinic Barcelona, Barcelona, Spain Search for more papers by this author , Víctor ObachVíctor Obach Institute of Neurosciences, IDIBAPS, Hospital Clinic Barcelona, Barcelona, Spain Search for more papers by this author and Álvaro CerveraÁlvaro Cervera Institute of Neurosciences, IDIBAPS, Hospital Clinic Barcelona, Barcelona, Spain Search for more papers by this author Anna M. PlanasAnna M. Planas Institute for Biomedical Research (IIBB)-Spanish Research Council (CSIC), IDIBAPS, Barcelona, Spain Search for more papers by this author Ángel ChamorroÁngel Chamorro Institute of Neurosciences, IDIBAPS, Hospital Clinic Barcelona, Barcelona, Spain Search for more papers by this author Originally published29 Nov 2007https://doi.org/10.1161/STROKEAHA.107.503532Stroke. 2008;39:e10Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: November 29, 2007: Previous Version 1 Response:We appreciate the interest generated by our recent report describing that the dual treatment with tPA and uric acid (UA) is feasible, safe and able to decrease lipid peroxidation in patients with acute ischemic stroke.1 In our view, this research effort complies well with the thorough and thoughtful debate requested by Dawson and colleagues, although these investigators reproduce previous worries expressed in this section of the journal.2 Our current encouraging results, together with the experimental data that we have gathered in the ischemic rat brain,3 pave the way to further clinical evaluation in a larger efficacy trial, as we have supported.4 Our methods adhere to current recommendations on good experimental research and clinical trial design. However, only further study will unveil whether the transient elevation of UA levels is harmful5 or beneficial in patients with acute stroke.6 As we have cautioned,7 this approach is independent of the (unsettled) potential relationship between chronic elevation of UA and cardiovascular disease.DisclosuresNone.1 Amaro S, Soy D, Obach V, Cervera A, Planas AM, Chamorro A. A pilot study of dual treatment with recombinant tissue plasminogen activator and uric acid in acute ischemic stroke. Stroke. 2007; 38: 2173–2175.LinkGoogle Scholar2 Weir CJ, Muir SW, Walters MR, Lees KR. Yin and Yang of uric acid in patients with stroke. Stroke. 2004; 35: e11–e20.LinkGoogle Scholar3 Romanos E, Planas AM, Amaro S, Chamorro A. Uric acid reduces brain damage and improves the benefits of rt-PA in a rat model of thromboembolic stroke. J Cereb Blood Flow Metab. 2007; 27: 14–20.CrossrefMedlineGoogle Scholar4 Chamorro A, Planas AM, Muner DS, Deulofeu R. Uric acid administration for neuroprotection in patients with acute brain ischemia. Med Hypotheses. 2004; 62: 173–176.CrossrefMedlineGoogle Scholar5 Weir CJ, Muir SW, Walters MR, Lees KR. Serum urate as an independent predictor of poor outcome and vascular events after acute stroke. Stroke. 2003; 34: 1951–1957.LinkGoogle Scholar6 Chamorro A, Obach V, Cervera A, Revilla M, Deulofeu R, Aponte JH. Prognostic significance of uric acid serum concentration in patients with acute ischaemic stroke. Stroke. 2002; 33: 1048–1052.CrossrefMedlineGoogle Scholar7 Chamorro A, Planas AM. Yin and yang of uric acid in patients with stroke. Response. Stroke. 2004; 35: e11–e12.LinkGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails January 2008Vol 39, Issue 1 Advertisement Article InformationMetrics https://doi.org/10.1161/STROKEAHA.107.503532 Originally publishedNovember 29, 2007 PDF download Advertisement

A Pilot Study of Dual Treatment With Recombinant Tissue Plasminogen Activator and Uric Acid in Acute Ischemic Stroke

Uric acid (UA) increases the neuroprotective effects of recombinant tissue plasminogen activator (rt-PA) in experimental ischemia. In patients with stroke, increased UA levels have been linked to better stroke recovery, but the clinical safety of dual administration of UA and rt-PA is unknown. Using a double-blind design, we assessed the safety of exogenous UA in patients with acute stroke treated with rt-PA. Patients were randomized to an intravenous solution of 500 mL of 5% mannitol/0.1% lithium carbonate (vehicle group, n=8) or 500 or 1000 mg of UA (n=16). Safety end points at day 90, lipid peroxidation (serum malondialdehyde), and serum kinetics of UA were established. Twenty-four patients with stroke were treated with rt-PA within mean (SD) 133 (35) minutes of clinical onset (admission National Institutes of Health Stroke Scale score mean [SD] 11 [7], age 71 [10.6] years, 71% males). Levels of UA decreased in the vehicle group and increased for approximately 24 hours in the high dose of UA group, which also had lower levels of malondialdehyde at day 5. Mortality (12.5%), symptomatic central nervous system bleeding (0%), and outcome at day 90 were similar in the 3 treatment arms; one patient in the high-dose group had a mild gouty episode. The administration of UA appears to be safe, decreases lipid peroxidation, and prevents an early fall of UA in serum in patients treated with rt-PA within 3 hours of stroke onset. The clinical efficacy of dual administration of exogenous UA and rt-PA deserves further investigation in a larger acute stroke trial.

Neutrophils-derived peroxynitrite contributes to acute hyperalgesia and cell influx in zymosan arthritis

We investigated the contribution of neutrophils to joint hyperalgesia and peroxynitrite formation in zymosan arthritis. Rats received 1 mg zymosan intra-articular, and joint hyperalgesia was measured using the rat knee-joint articular incapacitation test. After 6 h, joint exudates were collected by aspiration for the assessment of cell influx, myeloperoxidase activity, and nitrite (as an index of nitric oxide formation) levels. Nitrotyrosine content, used as an index of peroxynitrite formation, was measured in joint exudates, using enzyme-linked immunosorbent assay. A group of rats was rendered neutropenic through the administration of a rabbit anti-rat neutrophil antibody (2 ml kg(-1), i.p.) 30 min before injection of 1 mg zymosan intra-articular. Other groups received uric acid (100 or 250 mg kg(-1), i.p.), the peroxynitrite scavenger, 30 min before 1 mg zymosan intra-articular. Controls received the vehicle. The significant inhibition of joint hyperalgesia in neutropenic animals was associated to significantly decreased cell influx, myeloperoxidase activity, nitric oxide, and nitrotyrosine levels in the joint exudates, as compared to naive rats. Uric acid administration inhibited both hyperalgesia and cell influx, as compared to controls. Neutrophils are involved in both nitric oxide and peroxynitrite formation in zymosan arthritis, thereby contributing to acute joint hyperalgesia. Scavenging of reactive nitrogen species (e.g. peroxynitrite) inhibits neutrophil migration and joint hyperalgesia in the acute phase of zymosan arthritis in rats.

Uric Acid Restores Endothelial Function in Patients With Type 1 Diabetes and Regular Smokers

Endothelial dysfunction is a characteristic finding in both patients with type 1 diabetes and in regular smokers and is an important precursor to atherosclerosis. The urate molecule has antioxidant properties, which could influence endothelial function. The impact of acutely raising uric acid concentrations on endothelial function was studied in eight men with type 1 diabetes, eight healthy regular smokers, and eight age-matched healthy control subjects in a randomized, four-way, double-blind, placebo-controlled study. Subjects received 1,000 mg uric acid i.v. in vehicle, 1,000 mg vitamin C as a control antioxidant, vehicle alone, or 0.9% saline on separate occasions over 1 h. Forearm blood flow responses to intrabrachial acetylcholine and sodium nitroprusside were assessed using venous occlusion plethysmography. Responses to acetylcholine, but not sodium nitroprusside, were impaired in patients with diabetes (P < 0.001) and in smokers (P < 0.005) compared with control subjects. Administration of uric acid and vitamin C selectively improved acetylcholine responses in patients with type 1 diabetes (P < 0.01) and in regular smokers (P < 0.05). Uric acid administration improved endothelial function in the forearm vascular bed of patients with type 1 diabetes and smokers, suggesting that high uric acid concentrations in vivo might serve a protective role in these and other conditions associated with increased cardiovascular risk.

Uric acid protects against secondary damage after spinal cord injury

Peroxynitrite contributes to the pathogenesis of various neurodegenerative disorders through multiple mechanisms and is thought to mediate secondary neuronal cell death after spinal cord injury (SCI). Here we establish that physiologically relevant levels of uric acid (UA), a selective inhibitor of certain peroxynitrite-mediated reactions, block the toxic effects of peroxynitrite on primary spinal cord neurons in vitro. Furthermore, administration of UA at the onset of SCI in a mouse model inhibits several pathological changes in the spinal cord including general tissue damage, nitrotyrosine formation, lipid peroxidation, activation of poly(ADP-ribose) polymerase, and neutrophil invasion. More importantly, UA treatment improves functional recovery from the injury. Taken together, our findings support the concept that peroxynitrite contributes to the pathophysiology of secondary damage after SCI. They also raise the possibility that elevating UA levels may provide a therapeutic approach for the treatment of SCI as well as other neurological diseases with a peroxynitrite-mediated pathological component.

Gout

In most cases gout is the clinical manifestation of familial hyperuricemia. Pathogenesis of hyperuricemia, clinical manifestations, diagnosis and differential diagnosis of hyperuricemia and gout are described. Treatment of hyperuricemia consists of dietary measurements and administration of uric acid lowering drugs, such as allopurinol or uricosuric agents. Nonsteroidal antiinflammatory drugs, colchicine and glucocorticosteroids are the treatment of choice for the acute gout attack. Prophylaxis of acute uric acid nephropathy consists of hydration, urine alkalinization and administration of allopurinol or rasburicase. For treatment of acute uric acid nephropathy rasburicase is the drug of choice.