Showing papers on "Xanthine published in 2009"
TL;DR: Data indicate that Nox, but not xanthine oxidase, plays a critical role in generation of the oxidative stress that leads to cone cell death in RP and inhibition of Nox provides a new treatment strategy.
Abstract: Retinitis pigmentosa (RP) is a collection of diseases in which rod photoreceptors die from a variety of mutations. After rods die, the level of tissue oxygen in the outer retina becomes elevated and there is progressive oxidative damage to cones that ultimately triggers apoptosis. In this study, we investigated the hypothesis that NADPH oxidase (Nox) and/or xanthine oxidase serve as critical intermediaries between increased tissue oxygen and the generation of excessive reactive oxygen species that cause oxidative damage to cones. Apocynin, a blocker of Nox, but not allopurinol, a blocker of xanthine oxidase, markedly reduced the superoxide radicals visualized by hydroethidine in the outer retina in the retinal degeneration-1 (rd1(+/+)) model of RP. Compared to rd1(+/+) mice treated with vehicle, those treated with apocynin, but not those treated with allopurinol, had significantly less oxidative damage in the retina measured by ELISA for carbonyl adducts. Apocynin-treated, but not allopurinol-treated, rd1(+/+) mice had preservation of cone cell density, increased mRNA levels for m- and s-cone opsin, and increased mean photopic b-wave amplitude. In Q344ter mice, a model of dominant RP in which mutant rhodopsin is expressed, apocynin treatment preserved photopic electroretinogram b-wave amplitude compared to vehicle-treated controls. These data indicate that Nox, but not xanthine oxidase, plays a critical role in generation of the oxidative stress that leads to cone cell death in RP and inhibition of Nox provides a new treatment strategy.
127 citations
TL;DR: It is found that luteolin and quercetin are competitive inhibitors and that silibinin is a mixed-type inhibitor of the enzyme in vitro, and, unlike allopurinol, the inhibition is not time-dependent.
Abstract: Xanthine oxidoreductase (XOR) is a molybdenum-containing enzyme that under physiological conditions catalyzes the final two steps in purine catabolism, ultimately generating uric acid for excretion. Here we have investigated four naturally occurring compounds that have been reported to be inhibitors of XOR in order to examine the nature of their inhibition utilizing in vitro steady-state kinetic studies. We find that luteolin and quercetin are competitive inhibitors and that silibinin is a mixed-type inhibitor of the enzyme in vitro, and, unlike allopurinol, the inhibition is not time-dependent. These three natural products also decrease the production of superoxide by the enzyme. In contrast, and contrary to previous reports in the literature based on in vivo and other nonmechanistic studies, we find that curcumin did not inhibit the activity of purified XO nor its superoxide production in vitro.
109 citations
TL;DR: It is demonstrated that all purine compounds, including uric acid, are elevated in biological fluids of MS patients, corroborating the notion of sustained purine catabolism, possibly due to imbalance in ATP homeostasis, under these pathological conditions.
96 citations
TL;DR: Crystal structures of as-isolated, functional xanthine oxidase in the course of reaction with the pterin substrate lumazine at 2.2 Å resolution and of the nonfunctional desulfo form of the enzyme in complex withxanthine at 2-6 A̋ resolution are reported.
91 citations
TL;DR: To the authors' knowledge, this is the first report of theophylline N demethylation and coexpression of distinct pathways for caffeine and theophyLLine degradation in bacteria.
Abstract: Pseudomonas putida CBB5 was isolated from soil by enrichment on caffeine. This strain used not only caffeine, theobromine, paraxanthine, and 7-methylxanthine as sole carbon and nitrogen sources but also theophylline and 3-methylxanthine. Analyses of metabolites in spent media and resting cell suspensions confirmed that CBB5 initially N demethylated theophylline via a hitherto unreported pathway to 1- and 3-methylxanthines. NAD(P)H-dependent conversion of theophylline to 1- and 3-methylxanthines was also detected in the crude cell extracts of theophylline-grown CBB5. 1-Methylxanthine and 3-methylxanthine were subsequently N demethylated to xanthine. CBB5 also oxidized theophylline and 1- and 3-methylxanthines to 1,3-dimethyluric acid and 1- and 3-methyluric acids, respectively. However, these methyluric acids were not metabolized further. A broad-substrate-range xanthine-oxidizing enzyme was responsible for the formation of these methyluric acids. In contrast, CBB5 metabolized caffeine to theobromine (major metabolite) and paraxanthine (minor metabolite). These dimethylxanthines were further N demethylated to xanthine via 7-methylxanthine. Theobromine-, paraxanthine-, and 7-methylxanthine-grown cells also metabolized all of the methylxanthines mentioned above via the same pathway. Thus, the theophylline and caffeine N-demethylation pathways converged at xanthine via different methylxanthine intermediates. Xanthine was eventually oxidized to uric acid. Enzymes involved in theophylline and caffeine degradation were coexpressed when CBB5 was grown on theophylline or on caffeine or its metabolites. However, 3-methylxanthine-grown CBB5 cells did not metabolize caffeine, whereas theophylline was metabolized at much reduced levels to only methyluric acids. To our knowledge, this is the first report of theophylline N demethylation and coexpression of distinct pathways for caffeine and theophylline degradation in bacteria.
91 citations
TL;DR: Using calcium carbonate nanoparticles as enzyme immobilization matrix, the developments of xanthine biosensor were achieved by both electrooxidation and electroreduction of the enzymatic-generated hydrogen peroxide based on XnOx and horseradish peroxidase (HRP).
Abstract: Using calcium carbonate nanoparticles as enzyme immobilization matrix, the developments of xanthine biosensor were achieved by both electrooxidation and electroreduction of the enzymatic-generated hydrogen peroxide based on xanthine oxidase (XnOx) and horseradish peroxidase (HRP). Amperometric detection of xanthine was evaluated by holding the modified electrode at 0.55 and −0.05 V (versus SCE), for XnOx/Nano-CaCO 3 and XnOx/HRP/Nano-CaCO 3 , respectively. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 2 × 10 −6 to 2.5 × 10 −4 M and 4 × 10 −7 to 5 × 10 −5 M, respectively. The detection limits were determined to be of 2 × 10 −6 and 1 × 10 −7 M with anodic and cathodic processes, respectively. At lower working potential, XnOx/HRP/Nano-CaCO 3 /GCE bienzymatic system exhibited excellent selectivity; the bienzyme electrode was inert towards ascorbic and uric acid present. Moreover, the permeability of enzyme/Nano-CaCO 3 was evaluated by the use of rotating disk electrode voltammetry.
81 citations
TL;DR: The results suggest that the use of Erythrina stricta for the treatment of gout could be attributed to its xanthine oxidase inhibitory activity.
80 citations
TL;DR: Quantum mechanical/molecular mechanical methods were used to investigate the conversion of xanthine to uric acid in xanthines oxidase, providing detailed insight into the essential mechanistic role of the active-site residues.
Abstract: Quantum mechanical/molecular mechanical (QM/MM) methods were used to investigate the conversion of xanthine to uric acid in xanthine oxidase. Seven mechanistic variants were considered with different tautomeric forms of xanthine, different protonation states of the active-site residues, and different substrate orientations. The most favorable pathway (setup G) has a B3LYP/MM barrier of about 14 kcal mol−1, consistent with the available experimental data. This multistep mechanism starts with Glu1261 deprotonating the xanthine at the N3 position followed by a proton transfer from the cofactor to the N9 atom of xanthine; the thus activated cofactor and substrate then react to form a tetrahedral intermediate, and a subsequent rate-limiting hydride transfer generates the product. The substrate orientation that has commonly been assumed in the literature leads to the most stable reactant complex, but the opposite orientation (“upside down”) is computed to be the most favorable one during the reaction (setup G)....
78 citations
TL;DR: Alterations in the methylation processes in the serotonin pathways and purine metabolism seem to be associated with chronic exposure to cocaine.
Abstract: Mapping metabolic “signatures” can provide new insights into addictive mechanisms and potentially identify biomarkers and therapeutic targets. We examined the differences in metabolites related to the tyrosine, tryptophan, purine, and oxidative stress pathways between cocaine-dependent subjects and healthy controls. Several of these metabolites serve as biological indices underlying the mechanisms of reinforcement, toxicity, and oxidative stress. Metabolomic analysis was performed in 18 DSM-IV-diagnosed cocaine-dependent individuals with at least 2 weeks of abstinence and ten drug-free controls. Plasma concentrations of 37 known metabolites were analyzed and compared using a liquid chromatography electrochemical array platform. Multivariate analyses were used to study the relationship between severity of drug use [Addiction Severity Index (ASI) scores] and biological measures. Cocaine subjects showed significantly higher levels of n-methylserotonin (p < 0.0017) and guanine (p < 0.0031) and lower concentrations of hypoxanthine (p < 0.0002), anthranilate (p < 0.0024), and xanthine (p < 0.012), compared to controls. Multivariate analyses showed that a combination of n-methylserotonin and xanthine contributed to 73% of the variance in predicting the ASI scores (p < 0.0001). Logistic regression showed that a model combining n-methylserotonin, xanthine, xanthosine, and guanine differentiated cocaine and control groups with no overlap. Alterations in the methylation processes in the serotonin pathways and purine metabolism seem to be associated with chronic exposure to cocaine. Given the preliminary nature and cross-sectional design of the study, the findings need to be confirmed in larger samples of cocaine-dependent subjects, preferably in a longitudinal design.
74 citations
TL;DR: Increased system xc− activity in Müller cells subjected to conditions associated with diabetic retinopathy may be beneficial, as this exchanger is important for the synthesis of the antioxidant glutathione.
Abstract: Elevated glutamate levels have been reported in humans with diabetic retinopathy. Retinal Muller glial cells regulate glutamate levels via the GLAST transporter and system x(c)(-) (cystine-glutamate exchanger). We have investigated whether transporter function and gene and/or protein expression are altered in mouse Muller cells cultured under conditions of hyperglycemia or oxidative stress (two factors implicated in diabetic retinopathy). Cells were subjected to hyperglycemic conditions (35 mM glucose) over an 8-day period or to oxidative stress conditions (induced by exposure to various concentrations of xanthine:xanthine oxidase) for 6 h. The Na(+)-dependent and -independent uptake of [(3)H] glutamate was assessed as a measure of GLAST and system x(c)(-) function, respectively. Hyperglycemia did not alter the uptake of [(3)H] glutamate by GLAST or system x(c)(-); neither gene nor protein expression decreased. Oxidative stress (70:14 or 100:20 microM xanthine:mU/ml xanthine oxidase) decreased GLAST activity by approximately 10% but increased system x(c)(-) activity by 43% and 89%, respectively. Kinetic analysis showed an oxidative-stress-induced change in V(max), but not K(m). Oxidative stress caused a 2.4-fold increase in mRNA encoding xCT, the unique component of system x(c)(-). Of the two isoforms of xCT (40 and 50 kDa), oxidative stress induced a 3.6-fold increase in the 40-kDa form localized to the plasma membrane. This is the first report of the differential expression and localization of xCT isoforms as caused by cellular stress. Increased system x(c)(-) activity in Muller cells subjected to conditions associated with diabetic retinopathy may be beneficial, as this exchanger is important for the synthesis of the antioxidant glutathione.
69 citations
TL;DR: HWA 285 was a much more potent inhibitor of adenosine uptake into human erythrocytes than pentoxifylline and other examined xanthines including thiocaffeine, 8-p-sulphophenyltheophylline, theophyllines, caffeine and enprofylline.
Abstract: The effect of two closely related xanthine derivatives, pentoxifylline and HWA 285, on cyclic AMP accumulation in rat hippocampal slices and on adenosine uptake in erythrocytes was examined. Pentoxifylline was a weak competitive antagonist of adenosine effects on cyclic AMP accumulation. HWA 285, by contrast, had a small stimulatory effect per se and also potentiated the effect of adenosine (10-30 microM). Neither pentoxifylline nor HWA 285 significantly affected the cyclic AMP accumulation induced by the stable adenosine analogue NECA or by alpha- or beta-adrenoceptor activation. HWA 285 was a much more potent inhibitor of adenosine uptake into human erythrocytes than pentoxifylline and other examined xanthines including thiocaffeine, 8-p-sulphophenyltheophylline, theophylline, caffeine and enprofylline. It is suggested that HWA 285 may potentiate, rather than antagonize, the effects of endogenous as well as exogenous adenosine, partly as a consequence of adenosine uptake inhibition.
TL;DR: A comparative in vivo study between the known caffeine derived silver carbene SCC1 and SCC8 demonstrated the ability of both complexes to improve the survival rates of mice in a pneumonia model utilizing the clinically isolated infectious strain of Pseudomonas aeruginosa PA M57-15.
Abstract: The increasing incidence of multidrug-resistant (MDR) pulmonary infections in the cystic fibrosis (CF) population has prompted the investigation of innovative silver based therapeutics. The functionalization of the naturally occurring xanthine theobromine at the N1 nitrogen atom with an ethanol substituent followed by the methylation of the N9 nitrogen atom gives the N-heterocyclic carbene precursor 1-(2-hydroxyethyl)-3,7,9-trimethylxanthinium iodide. The reaction of this xanthinium salt with silver acetate produces the highly hydrophilic silver carbene complex SCC8. The in vitro antimicrobial efficacy of this newly synthesized complex was evaluated with excellent results on a variety of virulent and MDR pathogens isolated from CF patients. A comparative in vivo study between the known caffeine derived silver carbene SCC1 and SCC8 demonstrated the ability of both complexes to improve the survival rates of mice in a pneumonia model utilizing the clinically isolated infectious strain of Pseudomonas aeruginosa PA M57-15.
TL;DR: The ability of C.rotundus to inhibit the enzyme xanthine oxidase (XO), the lipid peroxidation and to exert apoptotic effect, may explain possible mechanisms by which C. rotundus exhibits its health benefits.
TL;DR: The results suggest that XOR gene disruption induced the depletion of uric acid and the accumulation of triglyceride-rich substances, xanthine, and hypoxanthine in the renal tubules, ultimately resulting in renal failure through increased renal interstitial fibrosis.
Abstract: Xanthine oxidoreductase (XOR) is an enzyme responsible for purine degradation, reactive oxygen species production, and adipogenesis. XOR gene-disrupted (XOR(-/-)) mice demonstrate renal failure and early death within several months. The aim of this study was to elucidate the mechanism of renal damage in XOR(-/-) mice and to determine the physiological role of XOR in the kidney. Histological analysis revealed that renal tubular damage in XOR(-/-) mice was accompanied by deposition of crystals and lipid-rich substances. Triglyceride content in renal homogenates was significantly increased in XOR(-/-) mice. The level of lipogenesis-related gene expression was comparable in XOR(+/+) and XOR(-/-) mice, whereas the expression of adipogenesis-related gene expression was significantly elevated in XOR(-/-) mice. Urinary excretions of xanthine and hypoxanthine were markedly elevated in XOR(-/-) mice. Immunohistochemical analysis, Western blotting, and real time RT-PCR revealed that various markers of fibrosis, inflammation, ischemia, and oxidative stress were increased in XOR(-/-) mice. Finally, we demonstrate that primary renal epithelial cells from XOR(-/-) mice are more readily transformed to myofibroblasts, which is a marker of increased epithelial mesenchymal transition. These results suggest that XOR gene disruption induced the depletion of uric acid and the accumulation of triglyceride-rich substances, xanthine, and hypoxanthine in the renal tubules. We believe that these changes contribute to a complex cellular milieu characterized by inflammation, tissue hypoxia, and reactive oxygen species production, ultimately resulting in renal failure through increased renal interstitial fibrosis.
TL;DR: The experimental results indicated that inhibitory effect could be achieved by allopurinol with a quasi-reversible competitive type, and this XnOx/LDHs-modified electrode exhibited a developed analytical performance.
TL;DR: P perturbations of neurotransmitter‐related pathways in opioid dependence are examined, which influences mechanisms and indices of oxidative stress, such as antioxidant compounds and purine metabolism.
Abstract: Objective
More must be learned about metabolic and biochemical alterations that contribute to the development and expression of drug dependence. Experimental opioid administration influences mechanisms and indices of oxidative stress, such as antioxidant compounds and purine metabolism. We examined perturbations of neurotransmitter-related pathways in opioid dependence (OD).
Methods
In this preliminary study, we used a targeted metabolomics platform to explore whether biochemical changes were associated with OD by comparing OD individuals (n = 14) and non-drug users (n = 10).
Results
OD patients undergoing short-term methadone detoxification showed altered oxidation–reduction activity, as confirmed by higher plasma levels of α- and γ- tocopherol and increased GSH/GSSG ratio. OD individuals had also altered purine metabolism, showing increased concentration of guanine and xanthosine, with decreased guanosine, hypoxanthine and hypoxanthine/xanthine and xanthine/xanthosine ratios. Other drug use in addition to opioids was associated with partly different biochemical changes.
Conclusions
This is a preliminary investigation using metabolomics and showing multiple peripheral alterations of metabolic pathways in OD. Further studies should explore the metabolic profile of conditions of opioid abuse, withdrawal and long-term abstinence in relation to agonist and antagonist treatment and investigate biochemical signatures of opioid substances and medications. Copyright © 2009 John Wiley & Sons, Ltd.
TL;DR: The levels of adenosine, inosine, uric acid and xanthine may be useful for monitoring the progression of DM and evaluating the treatment.
TL;DR: In this article, the authors solved crystal structures of R. capsulatus XDH in the presence of its substrates hypoxanthine, xanthine and the inhibitor pterin-6-aldehyde using either the inactive desulfo form of the enzyme or an active site mutant (EB232Q).
TL;DR: The results show that antagonism of adenosine analogue-induced antilipolytic effects is a convenient assay forAdenosine antagonistic potency of drugs, except for drugs with a high potency as phosphodiesterase inhibitors.
Abstract: Cyclic AMP accumulation and glycerol release were studied in isolated rat fat cells. Both processes were inhibited by R-site specific adenosine analogues (L-PIA greater than NECA greater than 2-chloro-adenosine greater than D-PIA), but poorly or not at all by the P-site selective analogue SQ 22,536. The effect of a series of xanthine derivatives and of some structurally unrelated phosphodiesterase inhibitors as inhibitors of 2-chloro-adenosine induced inhibition of NA stimulated cyclic AMP accumulation and lipolysis was subsequently examined. The 2-chloroadenosine effect on cyclic AMP accumulation was antagonized by the xanthines with the following order of potency: DPX greater than 8-phenyl-theophylline greater than 8-p-sulpho-phenyl-theophylline greater than verrophylline greater than IBMX greater than theophylline greater than HWA 285 greater than pentoxiphylline greater than caffeine greater than 7-benzyl IBMX greater than theobromine greater than enprofylline greater greater than ZK 62,711. The rank order potency of xanthines against the antilipolytic effect of 2-chloro-adenosine was the same with two notable exceptions: the two potent phosphodiesterase inhibitors 7-benzyl-IBMX and ZK 62,711 were more than 20 times more potent as inhibitors of the antilipolytic effect of 2-chloro-adenosine. The results show that antagonism of adenosine analogue-induced antilipolytic effects is a convenient assay for adenosine antagonistic potency of drugs, except for drugs with a high potency as phosphodiesterase inhibitors. The lipolytic potency of the xanthine derivatives was also studied. The ability of the xanthines to stimulate basal and noradrenaline stimulated lipolysis was generally in agreement with their potency as adenosine antagonists. Adenosine deaminase induced lipolysis was stimulated by potent phosphodiesterase inhibitors.
TL;DR: In this work, colloidal laponite nanoparticles were further expanded into the design of the third-generation biosensor and displayed an excellent electrocatalytic performance to both the oxidation of xanthine and the reduction of nitrate.
TL;DR: In this paper, the first usage of a double walled carbon nanotube (DWCNT) modified carbon paste electrode as biosensor transducer was described, and Xanthine was chosen as a substrate for evaluation of the electrode performance.
Abstract: We describe the first usage of a double walled carbon nanotube (DWCNT) modified carbon paste electrode as biosensor transducer. Xanthine was chosen as a substrate for evaluation of the electrode performance. Proper amount of DWCNT and xanthine oxidase enzyme were mixed with proper amount of graphite and mineral oil for attaining the xanthine biosensor. Results were compared with previous work that includes multi-walled carbon nanotube and single-wall carbon nanotube based carbon paste electrode xanthine biosensors. A linearity was obtained in the concentration range between 2–50 μM xanthine under the response time of 150 s with the equation of y = 0.0441x + 0.2013 and RSD value of 4.20%. This system was applied to the determination of xanthine in canned tuna fish samples and recovery was calculated as 99.20% ± 0.07.
TL;DR: The results of these studies suggest that nitrite can be reduced to vasoactive NO in the systemic vascular bed of the rat by xanthine oxidoreductase and mitochondrial aldehyde dehydrogenase and that the 2 pathways of nitrite activation act in a parallel manner.
Abstract: Sodium nitrite has been shown to have vasodilator activity in experimental animals and in human subjects. However, the mechanism by which nitrite anion is converted to vasoactive nitric oxide (NO) is uncertain. It has been hypothesized that deoxyhemoglobin, xanthine oxidoreductase, mitochondrial aldehyde dehydrogenase, and other heme proteins can reduce nitrite to NO, but studies in the literature have not identified the mechanism in the intact rat, and several studies report no effect of inhibitors of xanthine oxidoreductase. In the present study, the effects of the xanthine oxidoreductase inhibitor allopurinol and the mitochondrial aldehyde dehydrogenase inhibitor cyanamide on decreases in mean systemic arterial pressure in response to i.v. sodium nitrite administration were investigated in the rat. The decreases in mean systemic arterial pressure in response to i.v. administration of sodium nitrite were inhibited in a selective manner after administration of allopurinol in a dose of 25 mg/kg i.v. A sec...
TL;DR: In this study, effects of various flavonoids on aldehyde oxidase (AO) activity were evaluated in vitro and myricetin and quercetin were the most potent inhibitors of both AO and XO.
Abstract: Flavonoids are an important group of natural compounds that can interfere with the activity of some enzymes. In this study, effects of various flavonoids on aldehyde oxidase (AO) activity were evaluated in vitro. AO was partially purified from guinea pig liver. The effects of 12 flavonoids from three subclasses of flavon-3-ol, flavan-3-ol and flavanone on the oxidation of vanillin and phenanthridine as substrates of AO and xanthine as a substrate of xanthine oxidase (XO) were investigated spectrophotometrically. Among the 12 flavonoids, myricetin and quercetin were the most potent inhibitors of both AO and XO. In general, the oxidation of vanillin was more inhibited by flavonoids than that of phenanthridine. Almost all of the flavonoids inhibited AO activity more potently than XO, which was more evident with non-planner flavanols. A planner structure seems to be essential for a potent inhibitory effect and any substitution by sugar moieties reduces the inhibitory effects. This study could provide a new insight into AO natural inhibitors with potential to lead to some food-drug interactions.
TL;DR: A 23-gene cluster is identified that encodes the enzymes for utilizing purines as the sole nitrogen source in the enterobacterium Klebsiella oxytoca, and functions for the products of these genes are revealed.
Abstract: The enterobacterium Klebsiella oxytoca uses a variety of inorganic and organic nitrogen sources, including purines, nitrogen-rich compounds that are widespread in the biosphere. We have identified a 23-gene cluster that encodes the enzymes for utilizing purines as the sole nitrogen source. Growth and complementation tests with insertion mutants, combined with sequence comparisons, reveal functions for the products of these genes. Here, we report our characterization of 12 genes, one encoding guanine deaminase and the others encoding enzymes for converting (hypo)xanthine to allantoate. Conventionally, xanthine dehydrogenase, a broadly distributed molybdoflavoenzyme, catalyzes sequential hydroxylation reactions to convert hypoxanthine via xanthine to urate. Our results show that these reactions in K. oxytoca are catalyzed by a two-component oxygenase (HpxE-HpxD enzyme) homologous to Rieske nonheme iron aromatic-ring-hydroxylating systems, such as phthalate dioxygenase. Our results also reveal previously undescribed enzymes involved in urate oxidation to allantoin, catalyzed by a flavoprotein monooxygenase (HpxO enzyme), and in allantoin conversion to allantoate, which involves allantoin racemase (HpxA enzyme). The pathway also includes the recently described PuuE allantoinase (HpxB enzyme). The HpxE-HpxD and HpxO enzymes were discovered independently by de la Riva et al. (L. de la Riva, J. Badia, J. Aguilar, R. A. Bender, and L. Baldoma, J. Bacteriol. 190:7892-7903, 2008). Thus, several enzymes in this K. oxytoca purine utilization pathway differ from those in other microorganisms. Isofunctional homologs of these enzymes apparently are encoded by other species, including Acinetobacter, Burkholderia, Pseudomonas, Saccharomyces, and Xanthomonas.
TL;DR: Evidence is provided that magnesium lithospermate B exhibits direct superoxide radicals scavenging and xanthine oxidase inhibitory activity and the hypouricemic activity in vivo against potassium oxonate-induced hyperuricaemia in mice is found.
Abstract: In this study we investigated the superoxide radicals scavenging effect and xanthine oxidase inhibitory activity by magnesium lithospermate B, which was originally isolated from the roots of Salvia miltiorrhiza (also named Danshen or Dansham), an important herb in Oriental medicine. Superoxide radicals were generated both in beta-NADH/PMS system and xanthine/ xanthine oxidase system. Magnesium lithospermate B significantly inhibited the reduction of NBT induced by superoxide radicals with an IC(50) of 29.8 microg/mL and 4.06 microg/mL respectively in the two systems. Further study suggested that magnesium lithospermate B can directly inhibit xanthine oxidase and exhibits competitive inhibition. Magnesium lithospermate B was also found to have the hypouricemic activity in vivo against potassium oxonate-induced hyperuricaemia in mice. After oral administration of magnesium lithospermate B at doses of 10, 20 and 30 mg/kg, there was a significant decrease in the serum urate level when compared to the hyperuricemia control. In addition, magnesium lithospermate B significantly protected HL-60 cells from superoxide radicals-induced apoptosis in the xanthine/ xanthine oxidase reactions. This study provided evidence that magnesium lithospermate B exhibits direct superoxide radicals scavenging and xanthine oxidase inhibitory activity.
TL;DR: A number of novel purine nucleosides were tentatively identified via critical interpretation of the combined mass spectrometric data including N3-methyladenosine, N7-methyladenine, 5'-dehydro-2'-deoxyinosine,N3- methylguanine, O6-methylguanosines, N1,N2,N7-trimethylguanosine and N1-methyl-N2-ethylguanoine.
Abstract: Urinary-modified nucleosides have a potential role as cancer biomarkers for a number of malignant diseases. High performance liquid chromatography (HPLC) was combined with full-scan mass spectrometry, MS/MS analysis and accurate mass measurements in order to identify purine nucleosides purified from urine. Potential purine nucleosides were assessed by their evident UV absorbance in the HPLC chromatogram and then further examined by the mass spectrometric techniques. In this manner, numerous modified purine nucleosides were identified in the urine samples from cancer patients including xanthine, adenosine, N1-methyladenosine, 5'-deoxy-5'-methylthioadenosine, 2-methyladenosine, N6-threonylcarbamoyladenosine, inosine, N1-methylinosine, guanosine, N1-methylguanosine, N7-methylguanine, N2-methylguanosine, N2,N2-dimethyguanosine, N2,N2,N7-trimethylguanosine. Furthermore, a number of novel purine nucleosides were tentatively identified via critical interpretation of the combined mass spectrometric data including N3-methyladenosine, N7-methyladenine, 5'-dehydro-2'-deoxyinosine, N3-methylguanine, O6-methylguanosine, N1,N2,N7-trimethylguanosine, N1-methyl-N2-ethylguanosine and N7-methyl-N1-ethylguanosine.
TL;DR: LmaNT4 is an acid-activated purine nucleobase transporter that functions optimally under the physiological conditions the parasite is exposed to in the macrophage phagolysosome, whereas LmaNT3 functions optimALLY at neutral pH.
TL;DR: In this paper, copper's ability to alter XO activity and structure was investigated in vitro after pre-incubation of the enzyme with increasing Cu(2+) concentrations for various periods of time.
Abstract: Xanthine oxidase (XO), a key enzyme in purine metabolism, produces reactive oxygen species causing vascular injuries and chronic heart failure. Here, copper's ability to alter XO activity and structure was investigated in vitro after pre-incubation of the enzyme with increasing Cu(2+) concentrations for various periods of time. The enzymatic activity was measured by following XO-catalyzed xanthine oxidation to uric acid under steady-state kinetics conditions. Structural alterations were assessed by electronic absorption, fluorescence, and circular dichroism spectroscopy. Results showed that Cu(2+) either stimulated or inhibited XO activity, depending on metal concentration and pre-incubation length, the latter also determining the inhibition type. Cu(2+)-XO complex formation was characterized by modifications in XO electronic absorption bands, intrinsic fluorescence, and alpha-helical and beta-sheet content. Apparent dissociation constant values implied high- and low-affinity Cu(2+) binding sites in the vicinity of the enzyme's reactive centers. Data indicated that Cu(2+) binding to high-affinity sites caused alterations around XO molybdenum and flavin adenine dinucleotide centers, changes in secondary structure, and moderate activity inhibition; binding to low affinity sites caused alterations around all XO reactive centers including FeS, changes in tertiary structure as reflected by alterations in spectral properties, and drastic activity inhibition. Stimulation was attributed to transient stabilization of XO optimal conformation. Results also emphasized the potential role of copper in the regulation of XO activity stemming from its binding properties.