Showing papers on "Xanthine published in 2020"
TL;DR: New insights into purine metabolism including the role of XOR activity are discussed in this review, indicating differential regulation of hypoxanthine and xanthine in a general population.
Abstract: Xanthine oxidoreductase (XOR) consists of two different forms, xanthine dehydrogenase and xanthine oxidase (XO), and is a rate-limiting enzyme of uric acid production from hypoxanthine and xanthine. Uric acid is the end product of purine metabolism in humans and has a powerful antioxidant effect. The lack of ascorbic acid, known as vitamin C, in hominoids has been thought to cause a compensatory increase in uric acid as an antioxidant by unfunctional gene mutation of uricase to a pseudogene. Because XO is involved in an increase in reactive oxygen species (ROS) by generating superoxide and hydrogen peroxide, inadequate activation of XOR promotes oxidative stress-related tissue injury. Plasma XOR activity is associated with obesity, smoking, liver dysfunction, hyperuricemia, dyslipidemia, insulin resistance, and adipokines, indicating a novel biomarker of metabolic disorders. However, XOR activity in adipose tissue is low in humans unlike in rodents, and hypoxanthine is secreted from human adipose tissue. The concentration of hypoxanthine, but not xanthine, is independently associated with obesity in a general population, indicating differential regulation of hypoxanthine and xanthine. Treatment with an XOR inhibitor can decrease uric acid for preventing gout, reduce production of XO-related ROS, and promote reutilization of hypoxanthine and ATP production through the salvage pathway. It has recently been suggested that discontinuation of an XOR inhibitor causes adverse cardiovascular outcomes as XOR inhibitor withdrawal syndrome, possibly due to cardiac disturbance of conduction and contraction by reduced ATP production. New insights into purine metabolism, including the role of XOR activity in the past 5 yr, are mainly discussed in this review.
101 citations
TL;DR: In this article, a ratiometric fluorescent and colorimetric dual-signal sensor for H2O2 and xanthine was developed, which has high sensitivity and excellent selectivity.
34 citations
TL;DR: A colorimetric and fluorimetric dual-channel optical probe for H 2 O 2 is obtained due to the glucose/xanthine transformations under formation of H 2O 2 by the relevant oxidase catalysis, the probe can be applied for detection of glucose and xanthine.
Abstract: The multifunctional hemin@carbon dot hybrid nanozymes (hemin@CD) with simultaneous peroxidase-like activity and fluorescence signalling property was prepared for the first time. Based on these properties, hemin@CD was applied to develop a dual-channel fluorescent probe for H2O2 and H2O2-based biocatalytic systems. By virtue of the peroxidase-like activity, hemin@CD can catalyze the oxidative coupling of 4-aminoantipyrine with phenol in the presence of H2O2 to form a pink-red quinoneimine dye with a maximum absorbance at 505 nm. Under the excitation wavelength of 480 nm, the green fluorescence of hemin@CD peaks at 540 nm and is quenched by the generated quinoneimine dye due to an inner filter effect, and also by H2O2 because of dynamic quenching. Thus, a colorimetric and fluorimetric dual-channel optical probe for H2O2 is obtained. Due to the glucose/xanthine transformations under formation of H2O2 by the relevant oxidase catalysis, the probe can be applied for detection of glucose and xanthine. The colorimetric detection limits for H2O2, glucose and xanthine are 0.11, 0.15, 0.11 μM, and the and fluorimetric detection limits are 0.15, 0.15, 0.12 μM, respectively.
34 citations
TL;DR: Uric acid is synthesized by oxidation of hypoxanthine and xanthine using a catalyzing enzyme, XOR, which can be a source of reactive oxygen species and a metabolic biomarker associated with obesity, hyperuricemia, liver dysfunction and insulin resistance.
Abstract: Aims/introduction Uric acid is synthesized by oxidation of hypoxanthine and xanthine using a catalyzing enzyme, xanthine oxidoreductase (XOR), which can be a source of reactive oxygen species. Plasma XOR activity is a metabolic biomarker associated with obesity, hyperuricemia, liver dysfunction and insulin resistance. However, it has recently been reported that XOR activity in fat tissue is low in humans, unlike in rodents, and that hypoxanthine is secreted from human fat tissue. Materials and methods The associations of obesity with hypoxanthine, xanthine and plasma XOR activity were investigated in 484 participants (men/women: 224/260) of the Tanno-Sobetsu Study. Results Levels of hypoxanthine, xanthine and plasma XOR activity were significantly higher in men than in women. In 59 participants with hyperuricemia, 11 (men/women: 11/0) participants were being treated with an XOR inhibitor and had a significantly higher level of xanthine, but not hypoxanthine, than that in participants without treatment. In all of the participants, hypoxanthine concentration in smokers was significantly higher than that in non-smokers. Stepwise and multivariate regression analyses showed that body mass index, smoking habit and xanthine were independent predictors of hypoxanthine after adjustment of age, sex and use of antihyperuricemic drugs. Whereas, alanine transaminase, hypoxanthine and plasma XOR activity were independent predictors for xanthine, and alanine transaminase, triglycerides and xanthine were independent predictors for plasma XOR activity. Conclusions The concentration of hypoxanthine, but not that of xanthine, is independently associated with obesity and smoking habit, indicating differential regulation of hypoxanthine and xanthine in a general population.
30 citations
TL;DR: First evidence of biodegradation of GO in the gastrointestinal tract using zebrafish as a model is provided and inhibition of the degradation of GO resulted in increased neutrophil infiltration into theintestinal tract, indicative of inflammation.
Abstract: Understanding the biological fate of graphene-based materials such as graphene oxide (GO) is crucial to assess adverse effects following intentional or inadvertent exposure. Here we provide first evidence of biodegradation of GO in the gastrointestinal tract using zebrafish as a model. Raman mapping was deployed to assess biodegradation. The degradation was blocked upon knockdown of nos2a encoding the inducible nitric oxide synthase (iNOS) or by pharmacological inhibition of NOS using L-NAME, demonstrating that the process was nitric oxide (NO)-dependent. NO-dependent degradation of GO was further confirmed in vitro by combining a superoxide-generating system, xanthine/xanthine oxidase (X/XO), with an NO donor (PAPA NONOate), or by simultaneously producing superoxide and NO by decomposition of SIN-1. Finally, by using the transgenic strain Tg(mpx:eGFP) to visualize the movement of neutrophils, we could show that inhibition of the degradation of GO resulted in increased neutrophil infiltration into the gastrointestinal tract, indicative of inflammation.
22 citations
21 citations
TL;DR: Overall, MWCNT-AuNP-CCE exhibited a promising platform for the future development of sensitive electrochemical sensors for the detection of purine derivatives in real samples.
20 citations
TL;DR: It is demonstrated that EGCG has obvious anti-hyperuricemia effects in vitro and in vivo via the inhibition of XOD activity and GLUT9 expression and the promotion of OAT1 expression.
Abstract: Background: This study investigates the effect of epigallocatechin gallate (EGCG) from tea leaves on hyperuricemia and explores the underlying mechanisms in vitro and in vivo .
Methods: The effects of EGCG on proliferation of BRL 3A rat liver cells were evaluated by CCK8 and after stimulation by xanthine the uric acid and xanthine oxidase (XOD) levels were evaluated by a kit; In an in vivo experiment, rats were treated with oxonic acid potassium salt combined with ethylamine pyrimidine to induce high uric acid hematic disease (7 days), The serum uric acid levels and XOD levels were evaluated by a kit, The expressions of OTA1 and GLUT9 were detected by RT-qPCR and Immunohistochemical. Results: EGCG had no effect on proliferation, and significantly reduced serum uric acid levels and inhibited XOD activity (P mOAT1 expression in the kidney tissues and reduced mGLUT9 expression (P Conclusions: These results demonstrate that EGCG has obvious anti-hyperuricemia effects in vitro and in vivo via the inhibition of XOD activity and GLUT9 expression and the promotion of OAT1 expression.
19 citations
TL;DR: This work set out to investigate whether caffeine levels correlated with alterations of energy and redox metabolism in stored red blood cells.
17 citations
TL;DR: Examination of the interactions of flavonoid aglycones and some of their conjugates with XO-catalyzed xanthine and 6-mercaptopurine oxidation in vitro found many flavonoids showed similar or stronger inhibition of XO than the positive control allopurinol.
Abstract: Flavonoids are natural phenolic compounds, which are the active ingredients in several dietary supplements. It is well-known that some flavonoid aglycones are potent inhibitors of the xanthine oxidase (XO)-catalyzed uric acid formation in vitro. However, the effects of conjugated flavonoid metabolites are poorly characterized. Furthermore, the inhibition of XO-catalyzed 6-mercaptopurine oxidation is an important reaction in the pharmacokinetics of this antitumor drug. The inhibitory effects of some compounds on xanthine vs. 6-mercaptopurine oxidation showed large differences. Nevertheless, we have only limited information regarding the impact of flavonoids on 6-mercaptopurine oxidation. In this study, we examined the interactions of flavonoid aglycones and some of their conjugates with XO-catalyzed xanthine and 6-mercaptopurine oxidation in vitro. Diosmetin was the strongest inhibitor of uric acid formation, while apigenin showed the highest effect on 6-thiouric acid production. Kaempferol, fisetin, geraldol, luteolin, diosmetin, and chrysoeriol proved to be similarly strong inhibitors of xanthine and 6-mercaptopurine oxidation. While apigenin, chrysin, and chrysin-7-sulfate were more potent inhibitors of 6-mercaptopurine than xanthine oxidation. Many flavonoids showed similar or stronger (even 5- to 40-fold) inhibition of XO than the positive control allopurinol. Based on these observations, the extremely high intake of flavonoids may interfere with the elimination of 6-mercaptopurine.
17 citations
TL;DR: In this paper, an improved electrochemical analysis of clinical samples in bodily fluids was designed, which allows reliable identification of several coexisting substances (tryptophan, uric acid, xanthine and hypoxanthine) present on different physiological levels.
TL;DR: This chapter discusses these properties and their relevance to human pathophysiology with a focus on Allopurinol as well as newer xanthine oxidase inhibitors such as Febuxostat and Topiroxostat.
Abstract: Xanthine oxidase inhibitors are primarily used in the clinical prevention and treatment of gout associated with hyperuricemia. The archetypal xanthine oxidase inhibitor, Allopurinol has been shown to have other beneficial effects such as a reduction in vascular reactive oxygen species and mechano-energetic uncoupling. This chapter discusses these properties and their relevance to human pathophysiology with a focus on Allopurinol as well as newer xanthine oxidase inhibitors such as Febuxostat and Topiroxostat. Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) are collectively referred to as xanthine oxidoreductase (XOR). XDH is initially synthesised as a 150-kDa protein from which XO is derived, e.g. under conditions of ischemia/hypoxia either reversibly by conformational changes (calcium or SH oxidation) or irreversibly by proteolysis, the latter leading to formation of a 130-kDa form of XO. Both, XO and XDH, catalyse the conversion of hypoxanthine via xanthine to uric acid, the former by using oxygen forming superoxide and hydrogen peroxide and the latter NAD+. However, XDH is in principle also able to generate ROS.
TL;DR: It is demonstrated that individual methylxanthines like caffeine mediate unique or inverse expression patterns, which suggests that the replacement of single methylXanthines by others could result in unexpected effects, which could not be anticipated by the comparison to other substances in this substance class.
Abstract: Methylxanthines are a group of substances derived from the purine base xanthine with a methyl group at the nitrogen on position 3 and different residues at the nitrogen on position 1 and 7. They are widely consumed in nutrition and used as pharmaceuticals. Here we investigate the transcriptional regulation of 83 genes linked to Alzheimer’s disease in the presence of five methylxanthines, including the most prominent naturally occurring methylxanthines—caffeine, theophylline and theobromine—and the synthetic methylxanthines pentoxifylline and propentofylline. Methylxanthine-regulated genes were found in pathways involved in processes including oxidative stress, lipid homeostasis, signal transduction, transcriptional regulation, as well as pathways involved in neuronal function. Interestingly, multivariate analysis revealed different or inverse effects on gene regulation for caffeine compared to the other methylxanthines, which was further substantiated by multiple comparison analysis, pointing out a distinct role for caffeine in gene regulation. Our results not only underline the beneficial effects of methylxanthines in the regulation of genes in neuroblastoma wild-type cells linked to neurodegenerative diseases in general, but also demonstrate that individual methylxanthines like caffeine mediate unique or inverse expression patterns. This suggests that the replacement of single methylxanthines by others could result in unexpected effects, which could not be anticipated by the comparison to other substances in this substance class.
TL;DR: A series of novel 1,2,3-triazole based xanthine derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) activity and showed excellent inhibitory activity of DPP-4.
Abstract: Inhibitors of dipeptidyl peptidase-4 (DPP4) have been shown to be effective treatments for type 2 diabetes. A series of novel 1,2,3-triazole based xanthine derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) activity. Among them, the representative compounds 7b, 7e, 7g and 6e showed excellent inhibitory activity of DPP-4 with IC50 values ranging from 87.41 to 16.34 nM, respectively. The SAR of these xanthine derivatives have been discussed, which would be useful for developing novel DPP-4 inhibitors as treating type 2 diabetes. 1,2,3-triazole based xanthine derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) activity. The SAR of these xanthine derivatives had been discussed, which would be useful for developing novel DPP-4 inhibitors as treating type 2 diabetes.
TL;DR: The purpose of this study is identify and isolate theophylline-degrading fungi and investigate their application in production of methylxanthines with theophyLLine as feedstock through microbial conversion, and biologically produce 3-methylxanthine and xanthine efficiently from theophylla efficiently through a new microbial synthesis platform.
Abstract: Caffeine, theobromine and theophylline are main purine alkaloid in tea. Theophylline is the downstream metabolite and it remains at a very low level in Camellia sinensis. In our previous study, Aspergillus sydowii could convert caffeine into theophylline in solid-state fermentation of pu-erh tea through N-demethylation. In this study, tea-derived fungi caused theophylline degradation in the solid-state fermentation. The purpose of this study is identify and isolate theophylline-degrading fungi and investigate their application in production of methylxanthines with theophylline as feedstock through microbial conversion. Seven tea-derived fungi were collected and identified by ITS, β-tubulin and calmodulin gene sequences, Aspergillus ustus, Aspergillus tamarii, Aspergillus niger and A. sydowii associated with solid-state fermentation of pu-erh tea have shown ability to degrade theophylline in liquid culture. Particularly, A. ustus and A. tamarii could degrade theophylline highly significantly (p < 0.01). 1,3-dimethyluric acid, 3-methylxanthine, 3-methyluric acid, xanthine and uric acid were detected consecutively by HPLC in A. ustus and A. tamarii, respectively. The data from absolute quantification analysis suggested that 3-methylxanthine and xanthine were the main degraded metabolites in A. ustus and A. tamarii, respectively. 129.48 ± 5.81 mg/L of 3-methylxanthine and 159.11 ± 10.8 mg/L of xanthine were produced by A. ustus and A. tamarii in 300 mg/L of theophylline liquid medium, respectively. For the first time, we confirmed that isolated A. ustus, A. tamarii degrade theophylline through N-demethylation and oxidation. We were able to biologically produce 3-methylxanthine and xanthine efficiently from theophylline through a new microbial synthesis platform with A. ustus and A. tamarii as appropriate starter strains.
TL;DR: Overall, guanine deaminase upregulation increased UV-induced keratinocyte senescence in SK, via uric acid mediated by reactive oxygen species followed by DNA damage.
Abstract: DNA damage and oxidative stress play a critical role in photoageing. Seborrhoeic keratosis (SK) affects sunlight-exposed sites in aged individuals. This study examined the mechanism of photoageing in SK. The guanine deaminase gene, which is involved in purine metabolism, was upregulated with uric acid levels and p21 in SK. Guanine deaminase was detectable in keratinocytes. Repeated exposure to ultraviolet (UV) increased levels of guanine deaminase, together with DNA damage, such as γ-H2AX and cyclobutane pyrimidine dimer formation, generation of reactive oxygen species, and keratinocyte senescence, which were reversed by guanine deaminase knockdown. However, guanine deaminase overexpression and H2O2 formed γ-H2AX, but not cyclobutane pyrimidine dimer. Loss-of-function guanine deaminase mutants reduced the metabolic end-product uric acid, which was increased by exposure to exogenous xanthine. Repeated exposure to UV increased levels of uric acid. Exogenous uric acid increased cellular senescence, reactive oxygen species, and γ-H2AX, similar to guanine deaminase. Overall, guanine deaminase upregulation increased UV-induced keratinocyte senescence in SK, via uric acid mediated by reactive oxygen species followed by DNA damage.
TL;DR: Plasma XOR activity was found to be positively associated with serum uric acid level independent of other known confounding factors affecting that level, including gender difference, eGFR, adiponectin level, VFA, and HOMA-IR.
Abstract: Background We developed a novel high-sensitive assay for plasma xanthine oxidoreductase (XOR) activity that is not affected by the original serum uric acid level. However, the association of plasma XOR activity with that level has not been fully examined. Methods This cross-sectional study included 191 subjects (91 males, 100 females) registered in the MedCity21 health examination registry. Plasma XOR activity was determined using our assay for plasma XOR activity with [13C2,15N2] xanthine and liquid chromatography/triple quadrupole mass spectrometry. Serum levels of uric acid and adiponectin, and visceral fat area (VFA) obtained by computed tomography were measured, and insulin resistance was determined based on the homeostasis model assessment (HOMA-IR) index. Results The median values for uric acid and plasma XOR activity were 333 μmol/L and 26.1 pmol/h/mL, respectively. Multivariable linear regression analysis showed a significant and positive association of serum uric acid level (coefficient: 26.503; 95% confidence interval: 2.06, 50.945; p = 0.035) with plasma XOR activity independent of VFA and HOMA-IR, and also age, gender, alcohol drinking habit, systolic blood pressure, estimated glomerular filtration rate (eGFR), glycated hemoglobin A1c, triglyceride, and adiponectin levels. The "gender*XOR activity" interaction was not significant (p = 0.91), providing no evidence that gender modifies the relationship between plasma XOR activity and serum uric acid level. Conclusions Plasma XOR activity was found to be positively associated with serum uric acid level independent of other known confounding factors affecting that level, including gender difference, eGFR, adiponectin level, VFA, and HOMA-IR.
TL;DR: An on-line capillary electrophoresis (CE) based XOD immobilized enzyme microreactor (IMER) was developed for the enzyme kinetics assays and inhibitor screening, which indicated that dihydroquercetin, quercet in, biochanin A and epicatechin had significant inhibitory effect on XOD.
Abstract: Xanthine oxidase (XOD) is a key enzyme in the human body to produce uric acid, and its inhibitor can be used for the treatment of hyperuricemia and gout. In this study, an online CE-based XOD immobilized enzyme microreactor (IMER) was developed for the enzyme kinetics assays and inhibitor screening. After 30 consecutive runs, the XOD activity remained about 95.6% of the initial immobilized activity. The Michaelis-Menten constant (Km ) of the immobilized XOD was determined as 0.39 mM using xanthine as substrate. The half-maximal inhibitory concentration and inhibition constant of the known inhibitor 4-aminopyrazolo[3,4-d]pyrimidine on XOD were determined as 11.9 and 5.2 μM, respectively. Then, the developed method was applied to evaluate the XOD inhibitory activity of 10 flavonoids, which indicated that dihydroquercetin, quercetin, biochanin A, and epicatechin had significant inhibitory effect on XOD. In addition, molecular docking results verified that the binding energy of the flavonoids with enzyme were in line with their inhibitory activity determined by XOD-IMER. Therefore, the developed XOD-IMER is a potential tool for the primary screening of XOD inhibitors from natural products.
TL;DR: The results from animal experiments demonstrate that TF1 is effective in reducing serum uric acid in mice and suggest that theaflavin may be a potential drug candidate for the treatment of hyperuricaemia.
13 May 2020
TL;DR: Uric acid might be the potential biomarker for OTLF and play an important role within the detailed pathway and XDH could affect purine metabolism by suppressing the expression of hypoxanthine and xanthine leading to low serum levels of uric acid in OTLf.
Abstract: To establish a metabolite fingerprint of ossification of the thoracic ligamentum flavum (OTLF) patients using liquid chromatography-mass spectrometry (LC-MS) in combination with transcriptomic data and explore the potential molecular mechanism of pathogenesis. The study cohort was composed of 25 patients with OTLF and 23 healthy volunteers as a control group. Thirty-seven metabolites were identified out by UPLC-MS including uric acid and hypoxanthine. Nine metabolites, including uric acid and hypoxanthine, were found with a Variable Importance in Projection (VIP) score over 1 (p < 0.05). Pathway enrichment indicated that purine metabolism pathways and the other four metabolism pathways were enriched. Transcriptomic data revealed that purine metabolism have a substantial change in gene expression of OTLF and that xanthine dehydrogenase (XDH) is the key regulatory factor. Receiver operating characteristic (ROC) analysis indicated that 17 metabolites, including uric acid, were found with an AUC value of over 0.7. Uric acid might be the potential biomarker for OTLF and play an important role within the detailed pathway. XDH could affect purine metabolism by suppressing the expression of hypoxanthine and xanthine leading to low serum levels of uric acid in OTLF, which could be a focal point in developing new therapeutic methods for OTLF.
TL;DR: The data show a different modulation of adenosine metabolism participants in the cerebral cortex of these animal models, which suggest that adenosinergic metabolism is involved in the neurodegeneration of AD.
Abstract: Adenosine is a neuromodulator that has been involved in aging and neurodegenerative diseases as Alzheimer's disease (AD). In the present work, we analyzed the possible modulation of purine metabolites, 5'nucleotidase (5'NT) and adenosine deaminase (ADA) activities, and adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its phosphorylated form during aging in the cerebral cortex. Three murine models were used: senescence-accelerated mouse-resistant 1 (SAMR1, normal senescence), senescence-accelerated mouse-prone 8 (SAMP8, a model of AD), and the wild-type C57BL/6J (model of aging) mice strains. Glutamate and excitatory amino acid transporter 2 (EAAT2) levels were also measured in these animals. HPLC, Western blotting, and enzymatic activity evaluation were performed to this aim. 5'-Nucleotidase (5'NT) activity was decreased at six months and recovered at 12 months in SAMP8 while opposite effects were observed in SAMR1 at the same age, and no changes in C57BL/6J mice. ADA activity significantly decreased from 3 to 12 months in the SAMR1 mice strain, while a significant decrease from 6 to 12 months was observed in the SAMP8 mice strain. Regarding purine metabolites, xanthine and guanosine levels were increased at six months in SAMR1 without significant differences in SAMP8 mice. In C57BL/6J mice, inosine and xanthine were increased, while adenosine decreased, from 4 to 24 months. The AMPK level was decreased at six months in SAMP8 without significant changes nor in SAMR1 or C57BL/6J strains. Glutamate and EAAT2 levels were also modulated during aging. Our data show a different modulation of adenosine metabolism participants in the cerebral cortex of these animal models. Interestingly, the main differences between SAMR1 and SAMP8 mice were found at six months of age, SAMP8 being the most affected strain. As SAMP8 is an AD model, results suggest that adenosinergic metabolism is involved in the neurodegeneration of AD.
TL;DR: The feasibility of large-scale hypoxanthine production by engineered E. coli strain Q2973 is demonstrated, and provides a reference for subsequent studies on purine analogs and nucleosides.
Abstract: Nucleosides and purine analogues have multiple functions in cell physiology, food additives, and pharmaceuticals, and some are produced on a large scale using different microorganisms. However, biosynthesis of purines is still lacking. In the present study, we engineered the de novo purine biosynthesis pathway, branched pathways, and a global regulator to ensure highly efficient hypoxanthine production by Escherichia coli. The engineered strain Q2973 produced 1243 mg/L hypoxanthine in fed-batch fermentation, accompanied by an extremely low accumulation of byproducts such as acetate and xanthine. We also performed global gene expression analysis to illustrate the mechanism for improving hypoxanthine production. This study demonstrated the feasibility of large-scale hypoxanthine production byan engineered E. coli strain, and provides a reference for subsequent studies on purine analogues and nucleosides.
08 Dec 2020
TL;DR: Diazirine-containing photoaffinity probes, based on the potent and selective TRPC1/4/5 channel inhibitor Pico145, allowed the development of an assay to probe cellular interactions between TRPC5 protein and xanthine-based TRPC 5 channel modulators.
Abstract: TRPC1/4/5 cation channels are emerging drug targets for the treatment of, amongst others, central nervous system (CNS) disorders, kidney disease, and cardiovascular and metabolic disease. Various small-molecule TRPC1/4/5 modulators have been reported, including highly potent xanthine derivatives that distinguish between specific TRPC1/4/5 tetramers. However, tools to profile ligand engagement by TRPC1/4/5 channels in live cells are lacking. Here, we report a set of potent xanthine-based photoaffinity probes that functionally mimic the xanthines Pico145 and AM237. Using these probes, we have developed a photoaffinity labelling protocol for TRPC5 channels, providing the first method for the quantitative assessment of binding interactions of TRPC5 with small molecules in cells. This method could be important for drug discovery efforts targeting the xanthine/lipid binding site of TRPC1/4/5 channels.
TL;DR: In this paper, Syringic acid derivatives were designed and synthesized with alcohol and amines to form ester and amide linkage with the help of molecular docking, and the synthesized compounds were evaluated for their antioxidant and xanthine oxidase inhibitory potential.
Abstract: Background Xanthine oxidase (XO; EC 1.17.3.2) has been considered as a potent drug target for the cure and management of pathological conditions prevailing due to high levels of uric acid in the bloodstream. The role of xanthine oxidase has been well established in the generation of hyperuricemia and gout due to its important role in catalytic oxidative hydroxylation of hypoxanthine to xanthine and further catalyses of xanthine to generate uric acid. In this research, syringic acid, a bioactive phenolic acid was explored to determine the capability of itself and its derivatives to inhibit xanthine oxidase. Objective The study aimed to develop new xanthine oxidase inhibitors from natural constituents along with the antioxidant potential. Methods In this report, we designed and synthesized syringic acid derivatives hybridized with alcohol and amines to form ester and amide linkage with the help of molecular docking. The synthesized compounds were evaluated for their antioxidant and xanthine oxidase inhibitory potential. Results Results of the study revealed that SY3 produces very good xanthine oxidase inhibitory activity. All the compounds showed very good antioxidant activity. The enzyme kinetic studies performed on syringic acid derivatives showed a potential inhibitory effect on XO ability in a competitive manner with IC50 value ranging from 07.18μM-15.60μM and SY3 was revealed as the most active derivative. Molecular simulation revealed that new syringic acid derivatives interacted with the amino acid residues SER1080, PHE798, GLN1194, ARG912, GLN 767, ALA1078 and MET1038 positioned inside the binding site of XO. Results of antioxidant activity revealed that all the derivatives showed very good antioxidant potential. Conclusion Molecular docking proved to be an effective and selective tool in the design of new syringic acid derivatives .This hybridization of two natural constituents could lead to desirable xanthine oxidase inhibitors with improved activity.
TL;DR: This study is the first to confirm that A. sydowii PT-2 and A. tamarii PT-7 degrade theobromine through N-demethylation and oxidation, respectively, and showed the potential application in 3-methylxanthine production with theobromaine as feedstock through the N- Demethylation at N-7 position.
Abstract: Methylxanthines, including caffeine, theobromine and theophylline, are natural and synthetic compounds in tea, which could be metabolized by certain kinds of bacteria and fungi. Previous studies confirmed that several microbial isolates from Pu-erh tea could degrade and convert caffeine and theophylline. We speculated that these candidate isolates also could degrade and convert theobromine through N-demethylation and oxidation. In this study, seven tea-derived fungal strains were inoculated into various theobromine agar medias and theobromine liquid mediums to assess their capacity in theobromine utilization. Related metabolites with theobromine degradation were detected by using HPLC in the liquid culture to investigate their potential application in the production of 3-methylxanthine. Based on theobromine utilization capacity, Aspergillus niger PT-1, Aspergillus sydowii PT-2, Aspergillus ustus PT-6 and Aspergillus tamarii PT-7 have demonstrated the potential for theobromine biodegradation. Particularly, A. sydowii PT-2 and A. tamarii PT-7 could degrade theobromine significantly (p < 0.05) in all given liquid mediums. 3,7-Dimethyluric acid, 3-methylxanthine, 7-methylxanthine, 3-methyluric acid, xanthine, and uric acid were detected in A. sydowii PT-2 and A. tamarii PT-7 culture, respectively, which confirmed the existence of N-demethylation and oxidation in theobromine catabolism. 3-Methylxanthine was common and main demethylated metabolite of theobromine in the liquid culture. 3-Methylxanthine in A. sydowii PT-2 culture showed a linear relation with initial theobromine concentrations that 177.12 ± 14.06 mg/L 3-methylxanthine was accumulated in TLM-S with 300 mg/L theobromine. Additionally, pH at 5 and metal ion of Fe2+ promoted 3-methylxanthine production significantly (p < 0.05). This study is the first to confirm that A. sydowii PT-2 and A. tamarii PT-7 degrade theobromine through N-demethylation and oxidation, respectively. A. sydowii PT-2 showed the potential application in 3-methylxanthine production with theobromine as feedstock through the N-demethylation at N-7 position.
TL;DR: Interestingly, the analysis of data collected demonstrated that molecules from natural sources or their mimetics and semisynthetic derivatives constitute the majority of compounds being explored at the moment by means of in vitro and in vivo animal studies and several of these molecules can be useful as lead compounds and some of them can even have the potential to be considered in the future clinical candidates for the treatment of hyperuricemia.
Abstract: Hyperuricemia is characterized by elevated uric acid (UA) levels on blood, which can lead to gout, a common pathology. These high UA levels are associated with increased purine ingestion and metabolization and/or its decreased excretion. In this field, xanthine oxidase (XO), by converting hypoxanthine and xanthine to UA, plays an important role in hyperuricemia control. Based on limitations and adverse effects associated with the use of allopurinol and febuxostat, the most known approved drugs with XO inhibitory effect, the search for new molecules with XO activity is growing. However, despite the high number of studies, it was found that the majority of tested products with relevant XO inhibition were left out, and no further pharmacological evaluation was performed. Thus, in the present review, available information published in the past six years concerning isolated molecules with in vitro XO inhibition complemented with cytotoxicity evaluation as well as other relevant studies, including in vivo hypouricemic effect, and pharmacokinetic/pharmacodynamic profile was compiled. Interestingly, the analysis of data collected demonstrated that molecules from natural sources or their mimetics and semisynthetic derivatives constitute the majority of compounds being explored at the moment by means of in vitro and in vivo animal studies. Therefore, several of these molecules can be useful as lead compounds and some of them can even have the potential to be considered in the future clinical candidates for the treatment of hyperuricemia.
TL;DR: Seven new compounds including three pairs of enantiomeric xanthine analogues (1-3), a pair of enantomeric hypoxanthine analogue (4), and three pairsof enantiomersic N-acetyldopamine dimers (6-8), together with a known one (5) were isolated from the insect Cyclopelta parva.
TL;DR: It is expected that treatment with XOR and URAT1 inhibitors will effectively decrease purine pools in the body and prevent cell injury due to ROS generated during XOR-mediated reactions.
Abstract: Xanthine and hypoxanthine are intermediate metabolites of uric acid and a source of reactive oxidative species (ROS) by xanthine oxidoreductase (XOR), suggesting that facilitating their elimination is beneficial. Since they are reabsorbed in renal proximal tubules, we investigated their reabsorption mechanism by focusing on the renal uric acid transporters URAT1 and GLUT9, and examined the effect of clinically used URAT1 inhibitor on their renal clearance when their plasma concentration is increased by XOR inhibitor. Uptake study for [3H]xanthine and [3H]hypoxanthine was performed using URAT1- and GLUT9-expressing Xenopus oocytes. Transcellular transport study for [3H]xanthine was carried out using Madin-Darby canine kidney (MDCK)II cells co-expressing URAT1 and GLUT9. In in vivo pharmacokinetic study, renal clearance of xanthine was estimated based on plasma concentration and urinary recovery. Uptake by URAT1- and GLUT9-expressing oocytes demonstrated that xanthine is a substrate of URAT1 and GLUT9, while hypoxanthine is not. Transcellular transport of xanthine in MDCKII cells co-expressing URAT1 and GLUT9 was significantly higher than those in mock cells and cells expressing URAT1 or GLUT9 alone. Furthermore, dotinurad, a URAT1 inhibitor, increased renal clearance of xanthine in rats treated with topiroxostat to inhibit XOR. It was suggested that xanthine is reabsorbed in the same manner as uric acid through URAT1 and GLUT9, while hypoxanthine is not. Accordingly, it is expected that treatment with XOR and URAT1 inhibitors will effectively decrease purine pools in the body and prevent cell injury due to ROS generated during XOR-mediated reactions.
TL;DR: A new method using hydroethidine as a fluorescent probe coupled with high-performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for simultaneously screening xanthine oxidase inhibitors and superoxide anion scavengers from natural product libraries.
Abstract: Excess reactive oxygen species can cause cellular damage, and are involved in many pathological processes such as inflammation, atherosclerosis and cancer. Reactive oxygen species can be generated by several mechanisms, one of which involves the reaction of xanthine oxidase with xanthine to generate a superoxide anion and uric acid. In this study, a new method using hydroethidine as a fluorescent probe coupled with high-performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for simultaneously screening xanthine oxidase inhibitors and superoxide anion scavengers. This method was validated using the known superoxide anion radical scavenger L-ascorbic acid and the xanthine oxidase inhibitor febuxostat. As a result, six compounds, including salvianolic acid C, quercetin, apigenin, α-tocopherol, formononetin and aloin, were successfully screened by this method. Compared with traditional colorimetric methods, the developed method was sensitive, accurate and fast. This work demonstrated that the developed fluorescent probe coupled with HPLC-MS method was effective for simultaneously screening xanthine oxidase inhibitors and superoxide anion radical scavengers from natural product libraries.
TL;DR: The present example supports the nascent knowledge concerning protein conjugation to nanoparticle as a means for the modulation of biological activity in immobilized enzymes.
Abstract: Generally, enzyme immobilization on nanoparticles leads to nano-conjugates presenting partially preserved, or even absent, biological properties. Notwithstanding, recent research demonstrated that the coupling to nanomaterials can improve the activity of immobilized enzymes. Herein, xanthine oxidase (XO) was immobilized by self-assembly on peculiar naked iron oxide nanoparticles (surface active maghemite nanoparticles, SAMNs). The catalytic activity of the nanostructured conjugate (SAMN@XO) was assessed by optical spectroscopy and compared to the parent enzyme. SAMN@XO revealed improved catalytic features with respect to the parent enzyme and was applied for the electrochemical studies of xanthine. The present example supports the nascent knowledge concerning protein conjugation to nanoparticle as a means for the modulation of biological activity.