Uric acid, a peroxynitrite scavenger, inhibits CNS inflammation, blood-CNS barrier permeability changes, and tissue damage in a mouse model of multiple sclerosis

Associations between purine metabolites and monoamine neurotransmitters in first-episode psychosis

Schizophrenia (SZ) is a biochemically complex disorder characterized by widespread defects in multiple metabolic pathways whose dynamic interactions, until recently, have been difficult to examine. Rather, evidence for these alterations has been collected piecemeal, limiting the potential to inform our understanding of the interactions amongst relevant biochemical pathways. We herein review perturbations in purine and neurotransmitter metabolism observed in early SZ using a metabolomic approach. Purine catabolism is an underappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. We have observed a homeostatic imbalance of purine catabolism in first-episode neuroleptic-naïve patients with SZ (FENNS). Precursor and product relationships within purine pathways are tightly correlated. Although some of these correlations persist across disease or medication status, others appear to be lost among FENNS suggesting that steady formation of the antioxidant uric acid (UA) via purine catabolism is altered early in the course of illness. As is the case for within-pathway correlations, there are also significant cross-pathway correlations between respective purine and tryptophan (TRP) pathway metabolites. By contrast, purine metabolites show significant cross-pathway correlation only with tyrosine, and not with its metabolites. Furthermore, several purine metabolites (UA, guanosine, or xanthine) are each significantly correlated with 5-hydroxyindoleacetic acid (5-HIAA) in healthy controls, but not in FENNS at baseline or 4-week after antipsychotic treatment. Taken together, the above findings suggest that purine catabolism strongly associates with the TRP pathways leading to serotonin (5-hydroxytryptamine, 5-HT) and kynurenine metabolites. The lack of a significant correlation between purine metabolites and 5-HIAA, suggests alterations in key 5-HT pathways that may both be modified by and contribute to oxidative stress via purine catabolism in FENNS.

Serum uric acid level in patients with relapsing-remitting multiple sclerosis

Uric acid (UA) is a hydrophilic antioxidant product associated with multiple sclerosis (MS). We conducted a randomized case-control study to evaluate the serum level of UA in different phases of MS in comparison with levels in a healthy control population. Serum UA was checked in 130 patients with relapsing-remitting MS (85 patients in remitting and 45 patients in relapsing phase) and 50 age-matched controls using a quantitative enzyme-linked immunosorbent assay (ELISA). The mean concentrations of UA in serum was 6.41(±3.18)mg/dL in patients with remitting MS, 4.76(±1.66)mg/dL in patients with relapsing MS and 6.33(±2.94)mg/dL in controls. There was a significant difference between mean UA concentration in relapsing MS and remitting MS (p<0.001), and between patients with relapsing MS and controls (p=0.002); however, the difference between levels for patients in the remitting phase of MS and the control group was not significant (p=0.87). It seems probable that UA has a role in the prevention of disease activity in MS.

Effect of short-term maximal exercise on biochemical markers of muscle damage, total antioxidant status, and homocysteine levels in football players

Purpose

Prolonged physical exercise results in transient elevations of biochemical markers of muscular damage. This study examined the effect of short-term maximal exercise on these markers, homocysteine levels (Hcy), and total antioxidant status (TAS) in trained subjects.

Methods

Eighteen male football players participated in this study. Blood samples were collected 5-min before and 3-min after a 30-s Wingate test.

Results

The results indicated that plasma biochemical markers of muscle injury increased significantly after the Wingate test (P<0.05). Moreover, significant increase of white blood Cells and their main subpopulations (i.e. monocytes, neutrophiles, and lymphocytes) (P<0.001) has been observed. Likewise, uric acid, total bilirubin, and TAS increased significantly after exercise (P<0.05). However, Hcy levels were unaffected by the Wingate test (for 3-min post-exercise measurement).

Conclusions

Short-term maximal exercise (e.g. 30-s Wingate test) is of sufficient intensity and duration to increase markers of muscle damage, and TAS; but not Hcy levels. Increases in the selected enzymes probably come primarily from muscle damage, rather than liver damage. Moreover, increase of TAS confirms the Wingate test induced oxidative stress.

Down-regulation of Myelin Gene Expression in Human Oligodendrocytes by Nitric Oxide: Implications for Demyelination in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune demyelinating disorder of the central nervous system (CNS) with unknown etiology. Several studies have shown that demyelination in MS is caused by proinflammatory mediators and nitric oxide (NO), which is released by perivascular infiltrates and/or activated glial cells. Both endogenous NO released by microglia and astrocytes; and NO generated from exogenous NO donors are known to induce oligodendrocytes death. However, the molecular mechanism of oligodendroglial death is poorly understood. Here we explore the role of NO in modulating the expression of myelin-specific genes that leads to oligodendroglial death. We investigated the effect of NO on the expression of myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), myelin oligodendrocyte glycoprotein (MOG), and proteolipid protein (PLP) in human primary oligodendrocytes. Combination of IFN-γ and bacterial lipopolysaccharide (LPS) or double stranded RNA in the form of polyIC induced the production of NO and decreased the expression of myelin gene in human fetal mixed glial cultures. Either a scavenger of NO (PTIO) or an inhibitor of inducible nitric oxide synthase (L-NIL) abrogated (LPS+IFN-γ)- and polyIC-mediated suppression of myelin genes in human mixed glial cells. The role of NO was further corroborated by the inhibition of myelin gene expression in purified human oligodendroglia by several NO donors including SNP, NOC-7, SIN-1, and SNAP. This study illustrates a novel biological role of NO in down-regulating the expression of myelin genes preceding the death of oligodendrocytes.

Neurodegenerative evidence in mice brains with cecal ligation and puncture-induced sepsis: preventive effect of the free radical scavenger edaravone

Sepsis is a major clinical challenge and septic encephalopathy is its nasty complication. The pathogenesis and underlying mechanisms of septic encephalopathy are not well understood. This study sought to fully characterize sepsis-associated biochemical and histopathological changes in brains of mice after cecal ligation and puncture, regarded as a highly clinically relevant animal model of polymicrobial sepsis. Real-time PCR analysis showed that gene expression levels of proinflammatory cytokines, including tumor necrosis factor-α and interleukin-1β, were significantly up-regulated in brain tissues from septic mice, but to a much lesser extent when compared with those in peripheral tissues such as lungs. Blood-brain barrier (BBB) permeability was significantly increased in septic mice, as determined by the measurement of sodium fluorescein and Evans blue content. Sepsis resulted in increases in NADPH oxidase activity and expression of p47^phox and p67^phox and up-regulation of inducible nitric oxide (NO) synthase in brains, indicating that superoxide, produced by NADPH oxidase, reacts with NO to form peroxynitrite, that maybe lead to the loss of BBB integrity. Light and electron microscopic examination of septic mouse brain showed serious neuronal degeneration, as indicated by hyperchromatic, shrunken, pyknotic, and electron-dense neurons. These histopathogical changes were prevented by treatment with the free radical scavenger edaravone. Together, these results suggest that sepsis can lead to rapid neurodegenerative changes in brains via free radical species production and possibly subsequent injury to the BBB. We may also provide a potentially useful therapeutic tool for treating septic encephalopathy.

The influence of nutritional factors on the prognosis of multiple sclerosis

The effect of nutrition and dietary supplements on the course of multiple sclerosis (MS) is a topic of great interest to both patients and clinicians. In particular, vitamin D status has been shown to influence both the incidence and the course of MS. High vitamin D levels are probably protective against the development of MS, although the efficacy of vitamin D supplementation in slowing progression of MS remains to be established. The influence of polyunsaturated fatty acids (PUFAs) on the development and course of MS has also long been under investigation. Small clinical trials suggest a modest reduction in the severity and duration of relapses in patients with MS receiving PUFA supplements. Other nutritional factors have been evaluated for their effect on MS disease progression, including milk proteins, gluten, probiotics, antioxidants (uric acid, vitamins A, C and E, lipoic acid), polyphenols, Ginkgo biloba extracts and curcumin. However, further studies are needed to evaluate the effects of these dietary components on the relapse rate and progression of MS. This Review gives an overview of the literature on the nutritional factors most commonly implicated as having an effect on MS and discusses the biological rationale that is thought to underlie their influence.

Modification of γ-secretase by nitrosative stress links neuronal ageing to sporadic Alzheimer's disease

Inherited familial Alzheimer's disease (AD) is characterized by small increases in the ratio of Aβ42 versus Aβ40 peptide which is thought to drive the amyloid plaque formation in the brain of these patients. Little is known however whether ageing, the major risk factor for sporadic AD, affects amyloid beta-peptide (Aβ) generation as well. Here we demonstrate that the secretion of Aβ is enhanced in an in vitro model of neuronal ageing, correlating with an increase in γ-secretase complex formation. Moreover we found that peroxynitrite (ONOO⁻), produced by the reaction of superoxide anion with nitric oxide, promoted the nitrotyrosination of presenilin 1 (PS1), the catalytic subunit of γ-secretase. This was associated with an increased association of the two PS1 fragments, PS1-CTF and PS1-NTF, which constitute the active catalytic centre. Furthermore, we found that peroxynitrite shifted the production of Aβ towards Aβ₄₂ and increased the Aβ₄₂/Aβ₄₀ ratio. Our work identifies nitrosative stress as a potential mechanistic link between ageing and AD.

Metabolomics of cerebrospinal fluid reveals changes in the central nervous system metabolism in a rat model of multiple sclerosis

Experimental Autoimmune Encephalomyelitis (EAE) is the most commonly used animal model for Multiple Sclerosis (MScl). CSF metabolomics in an acute EAE rat model was investigated using targetted LC-MS and GC-MS. Acute EAE in Lewis rats was induced by co-injection of Myelin Basic Protein with Complete Freund's Adjuvant. CSF samples were collected at two time points: 10 days after inoculation, which was during the onset of the disease, and 14 days after inoculation, which was during the peak of the disease. The obtained metabolite profiles from the two time points of EAE development show profound differences between onset and the peak of the disease, suggesting significant changes in CNS metabolism over the course of MBP-induced neuroinflammation. Around the onset of EAE the metabolome profile shows significant decreases in arginine, alanine and branched amino acid levels, relative to controls. At the peak of the disease, significant increases in concentrations of multiple metabolites are observed, including glutamine, O-phosphoethanolamine, branched-chain amino acids and putrescine. Observed changes in metabolite levels suggest profound changes in CNS metabolism over the course of EAE. Affected pathways include nitric oxide synthesis, altered energy metabolism, polyamine synthesis and levels of endogenous antioxidants. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-011-0306-3) contains supplementary material, which is available to authorized users.

iNOS-mediated secondary inflammatory response differs between rat strains following experimental brain contusion

BACKGROUND

Nitric oxide is a key mediator of post-traumatic inflammation in the brain. We examined the expressions of iNOS, nNOS, and eNOS in inbred DA and PVGa rat strains where DA is susceptible to autoimmune neuroinflammation and PVGa-resistant.

METHODS

Parietal contusions using a weight drop model were produced in five rats per genotype. After 24 h, the brains were removed and analyzed using a range of immunohistochemical methods.

RESULTS

PVGa presented significantly increased iNOS expression in infiltrating inflammatory cells in the perilesional area compared to DA (p < 0.05). The amount of w3/13-positive infiltrating inflammatory cells did not differ between strains. eNOS and nNOS expression did not differ between strains. iNOS-positive cells coexpressed neuronal (NeuN), macrophage (ED-1), and leucocyte (w3/13) markers. MnSOD was significantly increased in PVGa (p < 0.05). 3-Nitrotyrosine, a measure of peroxynitrite levels, and fluoro-jade stained neuronal degeneration, did not differ between strains.

CONCLUSIONS

Two inbred rat strains with genetically determined differences in susceptibility to develop autoimmune disease displayed different levels of the inflammatory and anti-inflammatory mediators iNOS and MnSOD, indicating genetic regulation. Interestingly, the increased levels of iNOS did not lead to elevated expression of the neuronal cell-death marker fluoro-jade. The increased iNOS expression was correlated with increased expression of superoxide scavenger MnSOD. Excessive peroxynitrite formation was probably prevented by limitation of available superoxide. Subsequently, the higher expression of potentially deleterious iNOS in PVGa did not result in increased neuronal death.

Diurnal variations of plasma homocysteine, total antioxidant status, and biological markers of muscle injury during repeated sprint: effect on performance and muscle fatigue--a pilot study

The aim of this study was (i) to evaluate whether homocysteine (Hcy), total antioxidant status (TAS), and biological markers of muscle injury would be affected by time of day (TOD) in football players and (ii) to establish a relationship between diurnal variation of these biomarkers and the daytime rhythm of power and muscle fatigue during repeated sprint ability (RSA) exercise. In counterbalanced order, 12 football (soccer) players performed an RSA test (5 x[6 s of maximal cycling sprint + 24 s of rest]) on two different occasions: 07:00-08:30 h and 17:00-18:30 h. Fasting blood samples were collected from a forearm vein before and 3-5 min after each RSA test. Core temperature, rating of perceived exertion, and performances (i.e., Sprint 1, Sprint 2, and power decrease) during the RSA test were significantly higher at 17:00 than 07:00 h (p < .001, p < .05, and p < .05, respectively). The results also showed significant diurnal variation of resting Hcy levels and all biological markers of muscle injury with acrophases (peak times) observed at 17:00 h. These fluctuations persisted after the RSA test. However, biomarkers of antioxidant status' resting levels (i.e., total antioxidant status, uric acid, and total bilirubin) were higher in the morning. This TOD effect was suppressed after exercise for TAS and uric acid. In conclusion, the present study confirms diurnal variation of Hcy, selected biological markers of cellular damage, and antioxidant status in young football players. Also, the higher performances and muscle fatigue showed in the evening during RSA exercise might be due to higher levels of biological markers of muscle injury and lower antioxidant status at this TOD.

Hybrid nanocrystals: University of Kentucky US20060280680A1

This patent application claims an interesting and novel combination of passive accumulation of drug nanocrystals within diseased tissue, in combination with active uptake of the nanocrystals by diseased cells. The patent application further claims the hybrid nanocrystals combining imaging or stabilizing molecules as inclusions in the crystal matrix. There is a focus on cancer chemotherapy and imaging, but the initial claims are not disease specific. In this patent evaluation, the novelty and utility of this application is examined, while the state of the art in nanocrystal formulations and formulation is discussed.

Extra-renal elimination of uric acid via intestinal efflux transporter BCRP/ABCG2

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.

Serum uric acid levels in patients with multiple sclerosis: a meta-analysis

BACKGROUND

Serum uric acid (UA), a natural scavenger of peroxynitrite, has been found to be of lower levels in patients with multiple sclerosis (MS) in some recent preliminary studies.

OBJECTIVE

To evaluate the correlation between serum UA levels and several clinical parameters of MS reliably.

METHODS

We surveyed studies on the serum UA levels and MS patients with comprehensive search and review of the references. A meta-analysis was performed to demonstrate the potential association between serum UA levels in MS patients and their clinical characteristics by random effects models. Results The serum UA levels were lower in patients with MS than in healthy controls (standardized mean difference (SMD) = -0·68; 95% confidence interval (CI): -0·82 to -0·55), as well as in other inflammatory neurological diseases (OINDs) (SMD = -0·45; 95% CI: -0·60 to -0·30). Similarly, the serum UA levels decreased in MS patients with clinical activity when compared to MS with clinical inactivity (SMD = -0·29; 95% CI: -0·48 to -0·10), as well as in relapsing-remitting MS (RRMS) patients with relapse in comparison to RRMS patients with remission (SMD = 0·64; 95% CI: 0·39 to 0·89). However, the results suggested that serum UA levels did not correlate with higher (or lower) expanded disability status scale (SMD = -0·09; 95% CI: -0·10 to 0·27) and magnetic resonance imaging (MRI) activity (SMD = -0·14; 95% CI: -0·13 to 0·41). In the subtypes of MS group, there were significant differences in serum UA levels between secondary progressive MS (SPMS) and RRMS (SMD = -0·34; 95% CI: 0·16 to 0·52), or primary progressive MS (PPMS) (SMD = -0·58; 95% CI: -0·89 to -0·27), but no significant difference between RRMS and PPMS (SMD = -0·18; 95% CI: -0·44 to 0·08).

CONCLUSIONS

Our study suggests that UA is relevant to MS. Future research is needed to determine whether the administration of UA levels by inosine might be considered as a novel treatment strategy for MS.

Multiple sclerosis

Multiple sclerosis (MS) is a chronic, complex neurological disease with a variable clinical course in which several pathophysiological mechanisms such as axonal/ neuronal damage, demyelination, inflammation, gliosis, remyelination and repair, oxidative injury and excitotoxicity, alteration of the immune system as well as biochemical disturbances and disruption of blood-brain barrier are involved.(1,2) Exacerbations of MS symptoms reflect inflammatory episodes, while the neurodegenerative aspects of gliosis and axonal loss result in the progression of disability. The precise aetiology of MS is not yet known, although epidemiological data indicate that it arises from a complex interactions between genetic susceptibility and environmental factors.(3) In this chapter the brain structures and processes involved in immunopathogenesis of MS are presented. Additionally, clinical phenotypes and biomarkers of MS are showed.

A case of hereditary xanthinuria type 1 accompanied by bilateral renal calculi

Hereditary xanthinuria is an extremely rare purine metabolism disorder caused by a genetic abnormality in xanthine dehydrogenase. A new case of hereditary xanthinuria type 1 accompanied by bilateral renal calculi was encountered. We performed an allopurinol loading test and diagnosed classical type 1 xanthinuria. Through genetic diagnosis, we identified a mutation site in the xanthine dehydrogenase gene. Genetic analysis revealed a homozygous deletion of cytosine 2,567 in the xanthine dehydrogenase gene, and as a result, a stop codon was formed at position 928. Renal failure caused by the deposition of xanthine crystals is a known complication because xanthine is poorly soluble in water. With high fluid intake and low purine diet, no significant increase in calculi has been observed in this patient for 2 years.

Antioxidants, redox signaling, and pathophysiology in schizophrenia: an integrative view

Schizophrenia (SZ) is a brain disorder that has been intensively studied for over a century; yet, its etiology and multifactorial pathophysiology remain a puzzle. However, significant advances have been made in identifying numerous abnormalities in key biochemical systems. One among these is the antioxidant defense system (AODS) and redox signaling. This review summarizes the findings to date in human studies. The evidence can be broadly clustered into three major themes: perturbations in AODS, relationships between AODS alterations and other systems (i.e., membrane structure, immune function, and neurotransmission), and clinical implications. These domains of AODS have been examined in samples from both the central nervous system and peripheral tissues. Findings in patients with SZ include decreased nonenzymatic antioxidants, increased lipid peroxides and nitric oxides, and homeostatic imbalance of purine catabolism. Reductions of plasma antioxidant capacity are seen in patients with chronic illness as well as early in the course of SZ. Notably, these data indicate that many AODS alterations are independent of treatment effects. Moreover, there is burgeoning evidence indicating a link among oxidative stress, membrane defects, immune dysfunction, and multineurotransmitter pathologies in SZ. Finally, the body of evidence reviewed herein provides a theoretical rationale for the development of novel treatment approaches.

Oxidative stress and blood-brain barrier dysfunction under particular consideration of matrix metalloproteinases

A cell's "redox" (oxidation and reduction) state is determined by the sum of all redox processes yielding reactive oxygen species (ROS), reactive nitrogen species (RNS), and other reactive intermediates. Low amounts of ROS/RNS are generated by different mechanisms in every cell and are important regulatory mediators in many signaling processes (redox signaling). When the physiological balance between the generation and elimination of ROS/RNS is disrupted, oxidative/nitrosative stress with persistent oxidative damage of the organism occurs. Oxidative stress has been suggested to act as initiator and/or mediator of many human diseases. The cerebral vasculature is particularly susceptible to oxidative stress, which is critical since cerebral endothelial cells play a major role in the creation and maintenance of the blood-brain barrier (BBB). This article will only contain a focused introduction on the biochemical background of redox signaling, since this has been reported already in a series of excellent recent reviews. The goal of this work is to increase the understanding of basic mechanisms underlying ROS/RNS-induced BBB disruption, with a focus on the role of matrix metalloproteinases, which, after all, appear to be a key mediator in the initiation and progression of BBB damage elicited by oxidative stress.

Rabies virus clearance from the central nervous system

Rabies, a neurological disease associated with replication in central nervous system (CNS) tissues of any of a number of rabies viruses endemic in nature, is generally fatal. Prophylactic medical intervention is immune mediated and directed at preventing the spread of the virus from a peripheral site of exposure to the CNS. While individuals rarely develop immune responses capable of clearing the virus from CNS tissues, a variety of laboratory-attenuated rabies viruses are readily cleared from the CNS tissues in animal models. By comparing immune responses to wild-type and attenuated rabies viruses in these models, we have discovered that the latter induce processes required for immune effector infiltration into CNS tissues that are absent from lethal infections. Predominant among these are activities of cells of the neurovascular unit (NVU) that promote an interaction with circulating immune cells. In the absence of this interaction, the specialized barrier function of the NVU remains intact and circulating virus-specific immune effectors are largely excluded from infected CNS tissues. Studies of mixed infections with wild-type and attenuated rabies viruses reveal that wild-type rabies viruses fail to trigger, rather than inhibit, the interactions between immune cells and the NVU required for virus clearance from the CNS. These studies provide insights into how immune effectors with the capacity to clear the virus may be delivered into CNS tissues to contain a wild-type rabies virus infection. However, to apply immunotherapeutic strategies beyond the initial stages of CNS infection, further insights into the fate of the infected cells during virus clearance are needed.

Antiasthmatic drugs targeting the cysteinyl leukotriene receptor 1 alleviate central nervous system inflammatory cell infiltration and pathogenesis of experimental autoimmune encephalomyelitis

Cysteinyl leukotrienes (CysLTs) are potent proinflammatory mediators and are considered to play a key role in inflammatory diseases such as asthma. Antagonists targeting the receptor of CysLTs (CysLT1) are currently used as antiasthmatic drugs. CysLTs have also been implicated in other inflammatory reactions. In this study, we report that in experimental autoimmune encephalomyelitis animals, CysLT1 is upregulated in immune tissue and the spinal cord, and CysLT levels in the blood and cerebrospinal fluid are also higher than in normal mice. Two clinically used antiasthma drugs, montelukast and zafirlukast, both targeting CysLT1, effectively block the CNS infiltration of inflammatory cells and thus reduce the incidence, peak severity, and cumulative clinical scores. Further study indicated that CysLT1 signaling does not affect the differentiation of pathogenic T helper cells. It might affect the pathogenesis of experimental autoimmune encephalomyelitis by increasing the secretion of IL-17 from myelin oligodendrocyte glycoprotein-specific T cells, increasing the permeability of the blood-brain barrier and inducing chemotaxis of T cells. These effects can be blocked by CysLT1 antagonists. Our findings indicate that the antiasthmatic drugs against CysLT1 can also be used to treat multiple sclerosis.

Xanthine oxidoreductase: a journey from purine metabolism to cardiovascular excitation-contraction coupling

Xanthine oxidoreductase (XOR) is a ubiquitous complex cytosolic molybdoflavoprotein which controls the rate limiting step of purine catabolism by converting xanthine to uric acid. It is known that optimum concentrations of uric acid (UA) and reactive oxygen species (ROS) are necessary for normal functioning of the body. The ability of XOR to perform detoxification reactions, and to synthesize UA and reactive oxygen species (ROS) makes it a versatile intra- and extra-cellular protective "housekeeping enzyme". It is also an important component of the innate immune system. The enzyme is a target of drugs against gout and hyperuricemia and the protein is of major interest as it is associated with ischemia reperfusion (I/R) injury, vascular disorders in diabetes, cardiovascular disorders, adipogenesis, metabolic syndrome, cancer, and many other disease conditions. Xanthine oxidoreductase in conjugation with antibodies has been shown to have an anti-tumor effect due to its ability to produce ROS, which in turn reduces the growth of cancer tissues. Apart from this, XOR in association with nitric oxide synthase also participates in myocardial excitation-contraction coupling. Although XOR was discovered over 100 years ago, its physiological and pathophysiological roles are still not clearly elucidated. In this review, various physiological and pathophysiological functional aspects of XOR and its association with various forms of cancer are discussed in detail.

Arachidonyl trifluoromethyl ketone ameliorates experimental autoimmune encephalomyelitis via blocking peroxynitrite formation in mouse spinal cord white matter

Inhibition of phospholipase A(2) (PLA(2)) has recently been found to attenuate the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a commonly used animal model of multiple sclerosis (MS). However, the protective mechanisms that underlie PLA(2) inhibition are still not well understood. In this study, we found that cytosolic PLA(2) (cPLA(2)) was highly expressed in infiltrating lymphocytes and macrophages/microglia in mouse spinal cord white matter. Although cPLA(2) is also expressed in spinal cord neurons and oligodendrocytes, there were no differences observed in these cell types between EAE and control animals. Arachidonyl trifluoromethyl ketone (AACOCF3), a cPLA(2) inhibitor, significantly reduced the clinical symptoms and inhibited the body weight loss typically found in EAE mice. AACOCF3 also attenuated the loss of mature, myelin producing, oligodendrocytes, and axonal damage in the spinal cord white matter. Nitrotyrosine immunoreactivity, an indicator of peroxynitrite formation, was dramatically increased in EAE mice and attenuated by treatment with AACOCF3. These protective effects were not evident when AA861, an inhibitor of lipoxygenase, was used. In primary cultures of microglia, lipopolysaccharide (LPS) induced an upregulation of cPLA(2), inducible nitric oxide synthase (iNOS) and components of the NADPH oxidase complex, p47phox and p67phox. AACOCF3 significantly attenuated iNOS induction, nitric oxide production and the generation of reactive oxygen species in reactive microglia. Similar to the decomposition catalyst of peroxynitrite, AACOCF3 also blocked oligodendrocyte toxicity induced by reactive microglia. These results suggest that AACOCF3 may prevent oligodendrocyte loss in EAE by attenuating peroxynitrite formation in the spinal cord white matter.

Breakdown of the blood-brain barrier during tick-borne encephalitis in mice is not dependent on CD8+ T-cells

Tick-borne encephalitis (TBE) virus causes severe encephalitis with serious sequelae in humans. The disease is characterized by fever and debilitating encephalitis that can progress to chronic illness or fatal infection. In this study, changes in permeability of the blood-brain barrier (BBB) in two susceptible animal models (BALB/c, and C57Bl/6 mice) infected with TBE virus were investigated at various days after infection by measuring fluorescence in brain homogenates after intraperitoneal injection of sodium fluorescein, a compound that is normally excluded from the central nervous system. We demonstrate here that TBE virus infection, in addition to causing fatal encephalitis in mice, induces considerable breakdown of the BBB. The permeability of the BBB increased at later stages of TBE infection when high virus load was present in the brain (i.e., BBB breakdown was not necessary for TBE virus entry into the brain), and at the onset of the first severe clinical symptoms of the disease, which included neurological signs associated with sharp declines in body weight and temperature. The increased BBB permeability was in association with dramatic upregulation of proinflammatory cytokine/chemokine mRNA expression in the brain. Breakdown of the BBB was also observed in mice deficient in CD8⁺ T-cells, indicating that these cells are not necessary for the increase in BBB permeability that occurs during TBE. These novel findings are highly relevant to the development of future therapies designed to control this important human infectious disease.

Distinct role of nitric oxide and peroxynitrite in mediating oligodendrocyte toxicity in culture and in experimental autoimmune encephalomyelitis

Nitric oxide has been implicated in the pathogenesis of multiple sclerosis. However, it is still unclear whether nitric oxide plays a protective role or is deleterious. We have previously shown that peroxynitrite, a reaction product of nitric oxide and superoxide, is toxic to mature oligodendrocytes (OLs). The toxicity is mediated by intracellular zinc release, phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), activation of 12-lipoxygenase (12-LOX) and the formation of reactive oxygen species (ROS). In this study, we found that the donors of nitric oxide, dipropylenetriamine NONOate (DPT NONOate) and diethylenetriamine NONOate (DETA NONOate), protected OLs from peroxynitrite or zinc-induced toxicity. The protective mechanisms appear to be attributable to their inhibition of peroxynitrite- or zinc-induced ERK1/2 phosphorylation and 12-LOX activation. In cultures of mature OLs exposed to lipopolysaccharide (LPS), induction of inducible nitric oxide synthase (iNOS) generated nitric oxide and rendered OLs resistant to peroxynitrite-induced toxicity. The protection was eliminated when 1400W, a specific inhibitor of iNOS, was co-applied with LPS. Using MOG35-55-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, we found that nitrotyrosine immunoreactivity, an indicator of peroxynitrite formation, was increased in the spinal cord white matter, which correlated with the loss of mature OLs. Targeted gene deletion of the NADPH oxidase component gp91phox reduced clinical scores, the formation of nitrotyrosine and the loss of mature OLs. These results suggest that blocking the formation specifically of peroxynitrite, rather than nitric oxide, may be a protective strategy against oxidative stress induced toxicity to OLs.

A reversible form of axon damage in experimental autoimmune encephalomyelitis and multiple sclerosis

In multiple sclerosis, a common inflammatory disease of the central nervous system, immune-mediated axon damage is responsible for permanent neurological deficits. How axon damage is initiated is not known. Here we use in vivo imaging to identify a previously undescribed variant of axon damage in a mouse model of multiple sclerosis. This process, termed 'focal axonal degeneration' (FAD), is characterized by sequential stages, beginning with focal swellings and progressing to axon fragmentation. Notably, most swollen axons persist unchanged for several days, and some recover spontaneously. Early stages of FAD can be observed in axons with intact myelin sheaths. Thus, contrary to the classical view, demyelination-a hallmark of multiple sclerosis-is not a prerequisite for axon damage. Instead, focal intra-axonal mitochondrial pathology is the earliest ultrastructural sign of damage, and it precedes changes in axon morphology. Molecular imaging and pharmacological experiments show that macrophage-derived reactive oxygen and nitrogen species (ROS and RNS) can trigger mitochondrial pathology and initiate FAD. Indeed, neutralization of ROS and RNS rescues axons that have already entered the degenerative process. Finally, axonal changes consistent with FAD can be detected in acute human multiple sclerosis lesions. In summary, our data suggest that inflammatory axon damage might be spontaneously reversible and thus a potential target for therapy.

Therapeutic immune clearance of rabies virus from the CNS

The long-held concept that rabies infection is lethal in humans once the causative rabies virus has reached the CNS has been called into question by the recent survival of a number of patients with clinical rabies. Studies in animal models provide insight into why survival from a rabies virus infection that has spread to the CNS is possible and the immune mechanisms involved. In the CNS, both innate mechanisms capable of inhibiting virus replication and the activity of infiltrating rabies virus-specific T and B cells with the capacity to clear the virus are required. Deficiencies in the induction of either aspect of rabies immunity can lead to lethal consequences but may be overcome by novel approaches to active and passive immunization.

Adenosine A2A receptors and uric acid mediate protective effects of inosine against TNBS-induced colitis in rats

Inflammatory bowel disease comprises chronic recurrent inflammation of gastrointestinal tract. This study was conducted to investigate inosine, a potent immunomodulator, in 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced chronic model of experimental colitis, and contribution of adenosine A(2A) receptors and the metabolite uric acid as possible underlying mechanisms. Experimental colitis was rendered in rats by a single colonic administration of 10 mg of TNBS. Inosine, potassium oxonate (a hepatic uricase inhibitor), SCH-442416 (a selective adenosine A(2A) receptor antagonist), inosine+potassium oxonate, or inosine+SCH-442416 were given twice daily for 7 successive days. At the end of experiment, macroscopic and histopathologic scores, colonic malondialdehyde (MDA), Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-1beta (IL-1β) levels, and myeloperoxidase (MPO) activity were assessed. Plasma uric acid level was measured throughout the experiment. Both macroscopic and histological features of colonic injury were markedly ameliorated by either inosine, oxonate or inosine+oxonate. Likewise, the elevated amounts of MPO and MDA abated as well as those of TNF-α and IL-1β (P<0.05). SCH-442416 partially reversed the effect of inosine on theses markers, while inosine+oxonate showed a higher degree of protection than each treatment alone (P<.0.05). No significant difference was observed between TNBS and SCH-442416 groups. Uric acid levels were significantly higher in inosine or oxonate groups compared to control. Inosine+oxonate resulted in an even more elvelated uric acid level than each treatment alone (P<0.05). Inosine elicits notable anti-inflammatory effects on TNBS-induced colitis in rats. Uric acid and adenosine A(2A) receptors contribute to these salutary properties.

Protein tyrosine nitration in cellular signal transduction pathways

How specificity and reversibility in tyrosine nitration are defined biologically in cellular systems is poorly understood. As more investigations identify proteins involved in cell regulatory pathways in which only a small fraction of that protein pool is modified by nitration to affect cell function, the mechanisms of biological specificity and reversal should come into focus. In this review experimental evidence has been summarized to suggest that tyrosine nitration is a highly selective modification and under certain physiological conditions fulfills the criteria of a physiologically relevant signal. It can be specific, reversible, occurs on a physiological time scale, and, depending on a target, can result in either activation or inhibition.

Different roles of radical scavengers--ascorbate and urate in the cerebrospinal fluid of amyotrophic lateral sclerosis patients

Ferrous iron, released from iron deposits in the motor cortex and other brain regions of amyotrophic lateral sclerosis (ALS) patients, participates in the Fenton reaction in cerebrospinal fluid (CSF) alongside H(2)O(2), which is continuously released by neuronal cells. In vivo, the production of notoriously reactive hydroxyl radicals via this reaction could lead to the progression of the disease. Herein, we have examined the effect of ascorbate and uric acid on the production of hydroxyl radicals in CSF from both sporadic ALS patients and control subjects. Electron paramagnetic resonance spectroscopy identified ascorbyl radicals in CSF from ALS patients whereas it was undetectable in control CSF. The addition of H(2)O(2) to the CSF from ALS patients provoked further formation of ascorbyl radicals and the formation of hydroxyl radicals ex vivo. The hydroxyl addition of uric acid to CSF from ALS patients diminished the production of hydroxyl radicals. In conclusion, there are clear differences between the roles of the two examined radical scavengers in the CSF of ALS patients indicating that the use of ascorbate could have unfavourable effects in ALS patients.

Peroxisomes are oxidative organelles

Peroxisomes are multifunctional organelles with an important role in the generation and decomposition of reactive oxygen species (ROS). In this review, the ROS-producing enzymes, as well as the antioxidative defense system in mammalian peroxisomes, are described. In addition, various conditions leading to disturbances in peroxisomal ROS metabolism, such as abnormal peroxisomal biogenesis, hypocatalasemia, and proliferation of peroxisomes are discussed. We also review the role of mammalian peroxisomes in some physiological and pathological processes involving ROS that lead to mitochondrial abnormalities, defects in cell proliferation, and alterations in the central nervous system, alcoholic cardiomyopathy, and aging. Antioxid.

Uric acid as a CNS antioxidant

Oxidative damage is a consistent finding in a number of central nervous system (CNS) disorders. Uric acid (UA) is a potent hydrophilic antioxidant that is modified by diet and drug. Several lines of evidence suggest that plasma UA may modulate outcomes in neurologic disease, but little attention has been paid to CNS levels of UA. Our objective was to test the hypothesis that cerebrospinal fluid (CSF) UA is determined by plasma UA, modified by blood-brain barrier (BBB) integrity and associated with rate of cognitive decline in Alzheimer's disease (AD). Also, since UA and ascorbic acid may act as antioxidants for one another, we also explored a potential interaction between them in the brain. Thirty-two patients with mild to moderate AD (Mini-Mental Status Exam 19 +/- 5) participated in a longitudinal biomarker study for one year involving standardized clinical assessments. CSF and blood were collected at baseline for UA, ascorbic acid, and albumin. Cognitive measures were collected at baseline and again one year later. CSF UA was independent of age, gender, and AD severity. CSF and plasma UA were positively correlated (r=0.669, p=0.001) and BBB impairment was associated with higher CSF levels of UA (p=0.028). Neither plasma nor CSF UA reached significant association with rates of cognitive decline over 1 year. CSF UA and CSF ascorbic acid were positively correlated (r=0.388, p=0.001). The hypothesis that CSF UA is determined by plasma UA and BBB integrity is supported, as is the hypothesis that UA and ascorbic acid are associated in CSF but not plasma. Adequately powered prospective studies would help assess any role for UA in primary and secondary prevention of AD.

Reactive nitroxidative species and nociceptive processing: determining the roles for nitric oxide, superoxide, and peroxynitrite in pain

Pain is a multidimensional perception and is modified at distinct regions of the neuroaxis. During enhanced pain, neuroplastic changes occur in the spinal and supraspinal nociceptive modulating centers and may result in a hypersensitive state termed central sensitization, which is thought to contribute to chronic pain states. Central sensitization culminates in hyperexcitability of dorsal horn nociceptive neurons resulting in increased nociceptive transmission and pain perception. This state is associated with enhanced nociceptive signaling, spinal glutamate-mediated N-methyl-D: -aspartate receptor activation, neuroimmune activation, nitroxidative stress, and supraspinal descending facilitation. The nitroxidative species considered for their role in nociception and central sensitization include nitric oxide (NO), superoxide ([Formula: see text]), and peroxynitrite (ONOO(-)). Nitroxidative species are implicated during persistent but not normal nociceptive processing. This review examines the role of nitroxidative species in pain through a discussion of their contributions to central sensitization and the underlying mechanisms. Future directions for nitroxidative pain research are also addressed. As more selective pharmacologic agents are developed to target nitroxidative species, the exact role of nitroxidative species in pain states will be better characterized and should offer promising alternatives to available pain management options.

Homeostatic imbalance of purine catabolism in first-episode neuroleptic-naïve patients with schizophrenia

BACKGROUND

Purine catabolism may be an unappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. Accumulating evidence suggests a pivotal role of oxidative stress in schizophrenia pathology.

METHODOLOGY/PRINCIPAL FINDINGS

Using high-pressure liquid chromatography coupled with a coulometric multi-electrode array system, we compared 6 purine metabolites simultaneously in plasma between first-episode neuroleptic-naïve patients with schizophrenia (FENNS, n = 25) and healthy controls (HC, n = 30), as well as between FENNS at baseline (BL) and 4 weeks (4w) after antipsychotic treatment. Significantly higher levels of xanthosine (Xant) and lower levels of guanine (G) were seen in both patient groups compared to HC subjects. Moreover, the ratios of G/guanosine (Gr), uric acid (UA)/Gr, and UA/Xant were significantly lower, whereas the ratio of Xant/G was significantly higher in FENNS-BL than in HC. Such changes remained in FENNS-4w with exception that the ratio of UA/Gr was normalized. All 3 groups had significant correlations between G and UA, and Xan and hypoxanthine (Hx). By contrast, correlations of UA with each of Xan and Hx, and the correlation of Xan with Gr were all quite significant for the HC but not for the FENNS. Finally, correlations of Gr with each of UA and G were significant for both HC and FENNS-BL but not for the FENNS-4w.

CONCLUSIONS/SIGNIFICANCE

During purine catabolism, both conversions of Gr to G and of Xant to Xan are reversible. Decreased ratios of product to precursor suggested a shift favorable to Xant production from Xan, resulting in decreased UA levels in the FENNS. Specifically, the reduced UA/Gr ratio was nearly normalized after 4 weeks of antipsychotic treatment. In addition, there are tightly correlated precursor and product relationships within purine pathways; although some of these correlations persist across disease or medication status, others appear to be lost among FENNS. Taken together, these results suggest that the potential for steady formation of antioxidant UA from purine catabolism is altered early in the course of illness.

Tempol ameliorates murine viral encephalomyelitis by preserving the blood-brain barrier, reducing viral load, and lessening inflammation

Multiple sclerosis (MS) is a progressive inflammatory and/or demyelinating disease of the human central nervous system (CNS). Most of the knowledge about the pathogenesis of MS has been derived from murine models, such as experimental autoimmune encephalomyelitis and viral encephalomyelitis. Here, we infected female C57BL/6 mice with a neurotropic strain of the mouse hepatitis virus (MHV-59A) to evaluate whether treatment with the multifunctional antioxidant tempol (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy) affects the ensuing encephalomyelitis. In untreated animals, neurological symptoms developed quickly: 90% of infected mice died 10 days after virus inoculation and the few survivors presented neurological deficits. Treatment with tempol (24 mg/kg, ip, two doses on the first day and daily doses for 7 days plus 2 mM tempol in the drinking water ad libitum) profoundly altered the disease outcome: neurological symptoms were attenuated, mouse survival increased up to 70%, and half of the survivors behaved as normal mice. Not surprisingly, tempol substantially preserved the integrity of the CNS, including the blood-brain barrier. Furthermore, treatment with tempol decreased CNS viral titers, macrophage and T lymphocyte infiltration, and levels of markers of inflammation, such as expression of inducible nitric oxide synthase, transcription of tumor necrosis factor-alpha and interferon-gamma, and protein nitration. The results indicate that tempol ameliorates murine viral encephalomyelitis by altering the redox status of the infectious environment that contributes to an attenuated CNS inflammatory response. Overall, our study supports the development of therapeutic strategies based on nitroxides to manage neuroinflammatory diseases, including MS.

Effect of uric acid on nephrotoxicity induced by mercuric chloride in rats

Oxidative stress is an important mechanism in mercury poisoning. We studied the effect of uric acid, a natural and potent reactive oxygen species and peroxynitrite scavenger, in HgCl( 2)-induced nephrotoxicity. Rats were injected with a unique dose of HgCl(2) (2.5 mg/kg body weight, subcutaneously) and then vehicle (for 3 days, twice daily) or HgCl(2) (unique dose) and intraperitoneal uric acid suspension (250 mg/kg body weight, twice daily, for 3 days), and then killed at 24, 48 and 72 hours after HgCl(2) administration (n = 5 for each group). At the end of the experimental study, kidneys and blood samples were taken. Tissues were prepared and examined under light microscopy. Uric acid significantly prevented the increase in plasma levels of creatinine and blood urea nitrogen (BUN); it helped maintain systemic nitrate/nitrite concentration and total antioxidant capacity. Uric acid attenuated the increase of renal lipid peroxidation and it markedly diminished nitrotyrosine signal and histopathological changes as early as 24 hours after HgCl(2) administration. Uric acid did not prevent a decrease in beta-actin signal caused by mercuric chloride, but it promoted a faster recovery when compared to the HgCl(2) alone group. Our results indicate that UA could play a beneficial role against HgCl(2) toxicity by preventing systemic and renal oxidative stress and tissue damage.

(–)-Epicatechin 3-O-gallate ameliorates the damages related to peroxynitrite production by mechanisms distinct from those of other free radical inhibitors

This study was carried out to elucidate whether the protective activity of (–)-epicatechin 3-O-gallate (ECg) against excessive peroxynitrite (ONOO−) production, is distinct from the activity of several well-known free radical inhibitors, the ONOO− inhibitors ebselen and uric acid, the superoxide anion (O2−) scavenger copper zinc superoxide dismutase (CuZnSOD) and the selective inducible nitric oxide synthase inhibitor l-N6-(1-iminoethyl)lysine hydrochloride (l-NIL). To generate ONOO−, male Wistar rats (n = 6/group) were subjected to ischaemia–reperfusion process together with lipopolysaccharide (LPS) injection. Although ECg did not scavenge the ONOO− precursors nitric oxide (NO) and O2−, it reduced the 3-nitrotyrosine level, a property similar to that of uric acid, but distinct from l-NIL. In addition, the elevation in myeloperoxidase activity was reversed by the administration of ECg, uric acid and SOD, but not by that of l-NIL. Furthermore, ECg was the more potent scavenger of the ONOO− decomposition product, the hydroxyl radical (·OH), than any other free radical inhibitor tested. The LPS plus ischaemia–reperfusion process resulted in renal dysfunction, estimated by measuring the parameters of renal function – serum urea nitrogen and creatinine levels. However, administration of ECg ameliorated renal dysfunction more than that of the other free radical inhibitors. Moreover, ECg reduced the excessive uric acid level, while the others did not, suggesting a property of ECg distinct from the others. Furthermore, proteinuria, which was demonstrated by the low- and high-molecular weight (LMW and HMW) protein bands of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern, caused by LPS plus ischaemia–reperfusion, was attenuated by administration of ECg and l-NIL, after which the HMW band intensities decreased and LMW protein bands were absent. This study indicates that, in an in-vivo model of ONOO− generation, ECg, l-NIL and uric acid exert stronger protective activity against ONOO−-induced oxidative damage than SOD and ebselen, and that the mechanism whereby ECg protects against ONOO− is distinct from that of l-NIL or uric acid.

Serum uric acid levels and neuromyelitis optica

Uric acid (UA) has been reported to be reduced in the serum of patients with multiple sclerosis (MS) and optic neuritis (ON). However, the relationship between UA and neuromyelitis optica (NMO) was unknown. NMO was claimed to be a distinct nosologic entity from MS. The aim of our study was to investigate the correlation between serum UA level and the clinical characteristics of NMO. The serum UA level was measured in 403 Chinese patients; 69 with NMO, 32 ON, 127 MS, 80 cerebral infarction (CI) patients, and 95 healthy controls (CTL). Serum UA level in NMO was significantly lower than that in CI (249.89 +/- 93.74 vs. 315.42 +/- 85.57 micromol/L, p = 0.004) and CTL (249.89 +/- 93.74 vs. 314.33 +/- 102.05 micromol/L, p < 0.0001). However, no difference was found between NMO and MS (p = 0.496) or NMO and ON (p = 0.858). When the analysis was performed in the female cohort separately, UA level was significantly lower in females than in males in all groups. It was also shown in our study that UA level in patients with NMO was not correlated with disease activity revealed by MRI, disease disability or duration of disease. Our results indicated a reduced serum UA level in patients with NMO.

IL-12 p40 homodimer, the so-called biologically inactive molecule, induces nitric oxide synthase in microglia via IL-12R beta 1

Earlier we have demonstrated that IL-12 p40 homodimer (p40(2)) induces the expression of inducible nitric oxide synthase (iNOS) in microglia. This study was undertaken to investigate underlying mechanisms required for IL-12 p40(2)- and IL-12 p70-induced expression of iNOS in microglia. IL-12 p40(2) alone induced the activation of both extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK). Interestingly, the ERK pathway coupled p40(2) to iNOS expression via C/EBP beta, but not NF-kappaB, whereas the p38 pathway relayed the signal from p40(2) to iNOS expression via both NF-kappaB and C/EBP beta. Furthermore, by using microglia from IL-12R beta 1 (-/-) and IL-12R beta 2 (-/-) mice or siRNA against IL-12R beta 1 and IL-12R beta 2, we demonstrate that p40(2) induced the expression of iNOS in microglia via IL-12R beta 1-(ERK+p38)-(NF-kappaB +C/EBP beta) pathway. In contrast, both IL-12R beta 1 and IL-12R beta 2 were involved for IL-12 p70-induced microglial expression of iNOS. Although IL-12R beta 1 coupled p70 to NF-kappaB and C/EBP beta, IL-12R beta 2 was responsible for p70-mediated activation of GAS. This study delineates a new role of IL-12R beta 1 and IL-12R beta 2 for the expression of iNOS and production of NO in microglia that may participate in the pathogenesis of neuroinflammatory diseases.

Cerebrospinal fluid and serum uric acid levels in patients with multiple sclerosis

BACKGROUND

Peroxynitrite was hypothesized to be involved in the pathogenesis of multiple sclerosis (MS) through its various neurotoxic effects. Uric acid (UA) was shown to be a strong peroxynitrite scavenger.

METHODS

We analyzed cerebrospinal fluid (CSF) and serum UA concentrations in 30 MS patients and 20 controls with non-inflammatory neurological diseases (NIND) and correlated these findings with demographic and clinical characteristics of MS patients. Disease activity was assessed by brain magnetic resonance imaging (MRI) and the CSF/serum albumin quotient as an indicator of the state of blood-brain-barrier (BBB).

RESULTS

Serum UA concentrations were found to be significantly lower in MS patients compared with controls (p=0.019). CSF UA concentrations were lower in MS patients as compared to controls, as well as in patients with active MS (clinical and/or MRI activity) in comparison to patients with inactive MS or controls, but these differences were not statistically significant. Significant correlation was found between CSF and serum UA concentrations (p=0.016) in MS patients, but not in controls; and between CSF UA concentrations and the CSF/serum albumin quotient in MS patients (p=0.043), but not in controls.

CONCLUSIONS

Our results support the significance of UA in the pathogenesis of MS. Decreased serum UA concentrations in MS patients might be due to both intrinsically reduced antioxidant capacity and increased UA consumption in MS. CSF UA concentrations may not be a reliable marker of disease activity in MS since its concentration is dependent on leakage of UA molecules from serum through the damaged BBB and the balance between consumption/production within the central nervous system (CNS).

Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium

N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was observed via in-cell Western. The functionality of the expressed NMDA-R was determined by measuring DiBAC fluorescence in ROS-preexposed cells upon stimulation with the specific agonist NMDA. Finally, the effects on barrier integrity were evaluated using the ECIS system to detect changes in monolayer impedance upon NMDA-R stimulation after exposure to ROS. The expression of NR1 significantly (p<0.001) increased 72 h after 30 min exposure to superoxide (+33.8+/-7.5%), peroxynitrite (+84.9+/-10.7%), or hydrogen peroxide (+92.8+/-7.6%), resulting in increased cellular response to NMDA-R stimulation and diminished monolayer impedance. We conclude that oxidative stress upregulates NMDA-R on cerebrovascular endothelium and thus heightens susceptibility to glutamate-induced BBB disruption.

Effect of uric acid on gentamicin-induced nephrotoxicity in rats - role of matrix metalloproteinases 2 and 9

In this work, we aimed to study the effect of uric acid on gentamicin-induced nephrotoxicity. Male Sprague-Dawley rats were assigned to one of six groups (six rats each) which received intraperitoneal injections for 9 days: (S) saline; (UA) Uric acid alone; (G) Gentamicin alone; (G + UA) Gentamicin + uric acid; (G rec) Gentamicin recovery and (G + UA rec) Gentamicin + uric acid recovery. In (G rec) and (G + UA rec), rats recovered for 7 days after the last injection. Urine and blood samples were taken on day 0 and at the end of every stage. Kidneys were harvested for histological scoring, determination of renal malondialdehyde (MDA), zymography and western blots for matrix metalloprotease (MMP)-2 and MMP-9. Uric acid alone did not provoke changes in biochemical and histological parameters when compared to controls. Gentamicin alone increased significantly plasma creatinine and blood urea nitrogen and caused a moderate histological damage. When combined with uric acid, these conditions worsened. MMP-9 activity and expression was decreased in rats from group G + UA as compared with rats from group G, while activity of MMP-2 was similarly increased in both groups when compared to controls. The increase in renal MDA induced by gentamicin was not altered when it was combined with uric acid. During the recovery stage, all biochemical parameters returned to normal levels, though a trend for delay of tubular damage recovery was observed in group G + UA rec when compared with group G rec. The results indicate that uric acid worsens gentamicin-induced nephrotoxicity. The mechanism is likely to implicate down-regulation of MMP-9.

Endothelial NOS-deficient mice reveal dual roles for nitric oxide during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a demyelinating autoimmune disease characterized by infiltration of T cells into the central nervous system (CNS) after compromise of the blood-brain barrier. A model used to mimic the disease in mice is experimental autoimmune encephalomyelitis (EAE). In this report, we examine the clinical and histopathological course of EAE in eNOS-deficient (eNOS-/-) mice to determine the role of nitric oxide (NO) derived from this enzyme in the disease progression. We find that eNOS-/- mice exhibit a delayed onset of EAE that correlates with delayed BBB breakdown, thus suggesting that NO production by eNOS underlies the T cell infiltration into the CNS. However, the eNOS-/- mice also eventually exhibit more severe EAE and delayed recovery, indicating that NO undertakes dual roles in MS/EAE, one proinflammatory that triggers disease onset, and the other neuroprotective that promotes recovery from disease exacerbation events.

The treatment of multiple sclerosis with inosine

OBJECTIVE

The objective of this study is to evaluate the safety and tolerability of inosine in patients with relapsing-remitting multiple sclerosis (RRMS). The secondary objectives are to assess the effects of inosine administration on serum urate (UA) levels, the progression of neurologic disability, the cumulative number of new, active lesions on magnetic resonance imaging (MRI), and changes in serum levels for markers of inflammation.

DESIGN

Oral administration of inosine was used to raise serum levels of the natural peroxynitrite scavenger UA in 16 patients with RRMS during a 1-year randomized, double-blind trial.

OUTCOME MEASURES

The endpoints studied were relapse rate, disability assessed by the Kurtzke Expanded Disability Status Scale (EDSS), MRI, and analysis of serum levels of nitrotyrosine, and oxidative and pro-inflammatory makers.

RESULTS

Increased serum UA levels correlated with a significant decrease in the number of gadolinium-enhanced lesions and improved EDSS. A number of MRI intensity-based parameters were altered by inosine treatment, in certain cases correlating with changes in serum UA levels. In a patient with low serum UA and high lesion activity, raising UA levels by inosine treatment decreased serum nitrotyrosine while increasing the ratio of Th2 to Th1 cytokines in circulating cells. The only side-effect correlated with inosine treatment was kidney stone formation in 4/16 subjects.

CONCLUSIONS

These data suggest that the use of inosine to raise serum UA levels may have benefits for at least some MS patients. The effect of this treatment is likely to be a consequence of inactivation of peroxynitrite-dependent free radicals. Close monitoring of serum UA levels as well as other measures are required to avoid the potential development of kidney stones.