Xanthine Dehydrogenase Oxidase Research Articles

Multichannel Sensor for Detection of Molybdenum Ions Based on Nitrogen-Doped Carbon Quantum Dot Ensembles

Trace elements such as cobalt (Co), molybdenum (Mo), and zinc (Zn) play necessary roles in different biological functions. Co is a microelement that influences the vascular system. Mo works as an enzymatic cofactor of three enzymes (aldehyde oxidase, sulfite oxidase, and xanthine oxidase dehydrogenase). However, these elements are difficult to detect, since the analytical methods developed have a high cost, which restrict their applicability. In this sense, fluorescent sensors are an alternative for detecting trace elements, such as Mo4+ ions. Herein, a new multichannel trace elements sensor has been proposed to detect Mo entities. In this sense, two different N-CQDs were synthesized and fully characterized. The N-CQDs presented quantum yield values of 25.93% and 6.02% and excellent solubility in water. Also, a mixture of these two carbon-based nanoparticles was used to identify and to quantify Mo in water between seven different trace elements. The method was found to reach 1.28 and 3.88 ppm for limit of detection (LOD) and quantification (LOQ), respectively. To further verify the potential of the detection platform, the multichannel sensor was applied to identify the different concentrations of metal ions (Fe2+, Co2+, Mn2+, Cu2+, Zn2+, Mg2+, and Mo4+) in water. The data matrix was treated using different algorithms, such as K-Means and Discriminant Analysis (DA). The detection strategy has successfully identified the molybdenum ions at 5 ppm. This result shows the potential application of a multichannel sensor toward the detection of Mo entities, since it is comparable with the molybdenum test already available on the market.

ADME, Molecular Targets, Docking, and Dynamic Simulation Studies of Phytoconstituents of Cymbopogon citratus (DC.)

Cymbopogon citratus (DC) Stapf. is utilized in both culinary and medicinal contexts, wherein its extracts demonstrate a range of therapeutic properties, including antidiabetic, antioxidant, and anti-inflammatory activities. This investigation aimed to computationally analyze phytochemicals of C. citratus, evaluating their pharmacokinetics and binding dynamics. The findings revealed a combination of high and low gastrointestinal absorption (GIA) for C. citratus (DC.) phytochemicals, with some exhibiting permeability across the blood-brain barrier (BBB). Xanthine dehydrogenase/oxidase (XDH) emerged as the primary human molecular target of C. citratus phytocompounds, while XDH and matrix metalloproteinase-9 (MMP9) have central connectivity in the protein interaction network. Orientin has best binding affinity with XDH (−9.083 kcal.mol−1) and MMP9 (−9.051 kcal.mol−1). Molecular dynamic simulations indicated the favorable stability and interactions of XDH with orientin and quercetin, respectively. In summary, this investigation underscores the potential of twenty-six (26) phytochemicals in C. citratus extract to combat cancer and neurodegenerative diseases through mechanisms targeting XDH and MMP9.

Toxicity Profiling and Antihyperuricemic Activity of Goubion: A Polyherbal Formulation.

The objective of the present study was to determine the acute and subacute toxicity profile of a polyherbal formulation called "Goubion" in addition to the in vivo antihyperuricemic study using fructose-induced hyperuricemia. Goubion is a combination of Colchicum autumnale (tuber), Tribulus terresteris (fruit), Vitex negundo (leaves), Smilax chinensis (root), Glycyrrhiza glabra (root), and Curcuma amada (rhizome). The acute toxicity study revealed no signs of mortality and morbidity at a single dose of 2000 mg/kg. Similarly, the results of the subacute repeated dose toxicity study exhibited no signs of mortality at any of the doses. However, significant changes in hematological, biochemical, and renal parameters were recorded at the dose of 60 mg/kg. Antihyperuricemic activity was tested at the dose of 15 mg/kg and 20 mg/kg of Goubion, respectively against 5 mg/kg Allopurinol. Based on the antihyperuricemic study, we infer that the Goubion has a significant hypouricemic action, as it remarkably decreased the elevated uric acid levels. The results also suggest the potential inhibitory capability of Goubion on xanthine oxidase dehydrogenase might be the mechanism behind the hypouricemic effect.

Chemical constituents and synergistic anti-gout studies on Eurycoma longifolia and potential mechanisms evaluation based on systemic analysis approach

37 compounds mainly including triterpenoids with the quassinoid skeleton and β-carboline alkaloids have been isolated from the roots of Eurycoma longifolia Jack (EL), which has been used as traditional medicine for a long history. It has been demonstrated that the total extracts from EL could significantly inhibit the joint swelling in MSU-induced acute gout arthritis rat model at middle and high doses (P < 0.05, P < 0.01), as meanwhile, better performance than that of positive control (P < 0.05, P < 0.01) has been observed at the dose of 10 g/kg. Aiming to search potential compounds and probable mechanisms, network pharmacology, molecular docking and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis were adopted, leading to the hypothesis of 17 targets related to different pathogenesis of gout and 5 potential compounds (C36, C107, C124, C125 and C130) among 156 selected compounds, playing synergetic role with multiple targets. Instead of the guiding ideology of “a gene, a drug, a disease”, varieties of compounds but not a single one from EL display holistic performance through multiple pathways with multi-targets. It was noteworthy that Xanthine dehydrogenase/oxidase (XDH), Prostaglandin G/H synthase 2 (PTGS2), Fatty acid-binding protein, liver (FABP1), Purine nucleoside phosphorylase (PNP), and Peroxisome proliferator activated receptor alpha (PPARA) were the key targets with intensely interaction. Furthermore, the functional enrichment analysis indicated that EL probably produced the gout protection effects by synergistic regulation in multiple biological pathways, including Toll-like receptor signaling pathway, MAPK signaling pathway, and NOD-like receptor signaling pathway, etc.

Rs1800796 of the IL6 gene is associated with increased risk for anti-tuberculosis drug-induced hepatotoxicity in Chinese Han children

Previous studies have revealed the important contribution of the immune response and oxidative stress to the development of anti-tuberculosis drug-induced hepatotoxicity (ATDH). To investigate whether single-nucleotide polymorphisms (SNPs) of the cytokine gene interleukin-6 (IL6) and oxidative stress genes xanthine dehydrogenase/oxidase (XO) and inducible nitric oxide synthase (NOS2) were associated with susceptibility to ATDH, we performed a case-control study including 41 ATDH cases and 116 ATDH-free controls in Chinese Han children. Significant difference in the allele distribution of rs1800796 in the IL6 gene was observed between the case and control groups, and the G allele of rs1800796 was associated with an increased risk for ATDH (odds ratio: 2.48, 95%CI: 1.40–4.40, P = 0.002). However, no significant difference was observed in the allele and genotype distributions of the other SNPs of the IL6, XO and NOS2 genes between the case and control groups after Bonferroni correction. In addition, no interaction was found between all selected SNPs. These findings indicate that genetic variants of the IL6 gene might contribute to the development of ATDH in the Chinese Han pediatric population.

Modulation of Xanthine metabolism ameliorates inflammation and accelerates diabetic wound healing

Abstract Wound healing in diabetic patients is impaired because of dysregulated innate immune response that results in a chronic inflammatory state. It has been shown by our group and others that metabolites can contribute to a state of chronic inflammation in diabetic tissues. In a murine model of Type-2 diabetes (diet-induced obese mice; DIO), we assessed role of uric acid in driving macrophage-mediated inflammation and delayed wound healing. Using liquid chromatography-mass spectrometry, we show that macrophages from DIO mice have reduced levels of xanthine, a precursor in the uric acid pathway. Xanthine is converted to uric acid via Xanthine oxidase/dehydrogenase (XOR) encoded by the Xdh gene. DIO macrophages express higher levels of Xdh and increased levels of uric acid, suggesting increased XOR activity. Further, exogenous addition of uric acid led to increased production of IL-1β by macrophages. Importantly, pharmacologic inhibition of XOR with Allopurinol resulted in reduced levels of IL-1β expression by macrophages. In order to examine this in vivo, DIO mice were treated with Allopurinol leading to significantly improved wound healing. In summary, our data suggest that the xanthine metabolic pathway can be targeted therapeutically to accelerate wound healing in diabetic patients.

Nitrite reductase activity of rat and human xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase: evaluation of their contribution to NO formation in vivo.

Nitrite is presently considered a NO "storage form" that can be made available, through its one-electron reduction, to maintain NO formation under hypoxia/anoxia. The molybdoenzymes xanthine oxidase/dehydrogenase (XO/XD) and aldehyde oxidase (AO) are two of the most promising mammalian nitrite reductases, and in this work, we characterized NO formation by rat and human XO/XD and AO. This is the first characterization of human enzymes, and our results support the employment of rat liver enzymes as suitable models of the human counterparts. A comprehensive kinetic characterization of the effect of pH on XO and AO-catalyzed nitrite reduction showed that the enzyme's specificity constant for nitrite increase 8-fold, while the Km(NO2(-)) decrease 6-fold, when the pH decreases from 7.4 to 6.3. These results demonstrate that the ability of XO/AO to trigger NO formation would be greatly enhanced under the acidic conditions characteristic of ischemia. The dioxygen inhibition was quantified, and the Ki(O2) values found (24.3-48.8 μM) suggest that in vivo NO formation would be fine-tuned by dioxygen availability. The potential in vivo relative physiological relevance of XO/XD/AO-dependent pathways of NO formation was evaluated using HepG2 and HMEC cell lines subjected to hypoxia. NO formation by the cells was found to be pH-, nitrite-, and dioxygen-dependent, and the relative contribution of XO/XD plus AO was found to be as high as 50%. Collectively, our results supported the possibility that XO/XD and AO can contribute to NO generation under hypoxia inside a living human cell. Furthermore, the molecular mechanism of XO/AO-catalyzed nitrite reduction was revised.

Identification of cancer mechanisms through computational systems modeling.

Colorectal cancer is one of the most prevalent causes of cancer death. It has been studied extensively for a long time, and numerous genetic and epigenetic events have been associated with the disease. However, its molecular mechanisms are still unclear. High-throughput metabolomics data, combined with customized computational systems modeling, can assist our understanding of some of these mechanisms by revealing connections between alterations in enzymatic activities and their consequences for a person's metabolic profile. Of particular importance in this context is purine metabolism, as it provides the nucleotides needed for cell proliferation. We employ a computational systems approach to infer molecular mechanisms associated with purine metabolism in colorectal carcinoma. The approach uses a dynamic model of purine metabolism as the simulation system and metabolomics data as input. The execution of large-scale Monte Carlo simulations and optimization with the model permits a step-wise reduction in possibly affected enzyme mechanisms, from which likely targets emerge. According to our results, some enzymes in the purine pathway system are very unlikely the targets of colorectal carcinoma. In fact, only three enzymatic steps emerge with statistical confidence as most likely being affected, namely: amidophosphoribosyltransferase (ATASE), 5'-nucleotidase (5NUC), and the xanthine oxidase/dehydrogenase (XD) reactions. The first of these enzymes catalyzes the first committed step of de novo purine biosynthesis, while the other two enzymes are associated with critical purine salvage pathways. The identification of these enzymes is statistically significant and robust. In addition, the results suggest potential secondary targets. The computational method cannot discern whether the inferred mechanisms constitute symptoms of colorectal carcinoma, or whether they might be causative and critical components of the uncontrolled cellular growth in cancer. The inferred molecular mechanisms present testable hypotheses that suggest targeted experiments for future studies of colorectal carcinoma and might eventually lead to improved diagnosis and treatment.

Thiopurine metabolism monitoring: implications in inflammatory bowel diseases

Thiopurines (TP) are widely used in the management of inflammatory bowel diseases. Side effects and inefficacy are a major concern as they lead to withdrawal of the drug. Tools investigating TP metabolism are useful to avoid inadequate cessation of TP therapy. TP metabolism is complex and many enzymes are involved. Among them, Thiopurine methyl transferase is the only one routinely measured by pheno- or genotyping. A decreased TPMT activity results in a potential overdosing of TP drugs leading to myelotoxicity, whereas an ultra-high activity leads to TP ineffectiveness and overproduction of methylated compounds responsible for hepatotoxicity. TPMT determination prior to TP treatment results in an individual adapted dose. Xanthine oxidase/dehydrogenase (XOD), inosine triphosphate pyrophosphatase (ITPA) and glutathion-S-transferase (GST) are other promising enzyme targets that might help to explain TP efficacy or toxicity. ITPA and GST polymorphisms might potentially be related to some TP side effects, while a XOD inhibition by allopurinol could avoid TP-related hepatotoxicity. Utilization of thiopurine metabolites, 6-thioguanine nucleotides and 6-methylmercaptopurine, is discussed, specifically, in case of thiopurine failure and recommendations are given about their interpretation and potential dose optimization. These enzymes and metabolites tests are complementary to the regular monitoring of blood cells count and liver tests which remains mandatory.

Novel pharmacogenetic markers for treatment outcome in azathioprine‐treated inflammatory bowel disease

Azathioprine (AZA) pharmacogenetics are complex and much studied. Genetic polymorphism in TPMT is known to influence treatment outcome. Xanthine oxidase/dehydrogenase (XDH) and aldehyde oxidase (AO) compete with TPMT to inactivate AZA. To assess whether genetic polymorphism in AOX1, XDH and MOCOS (the product of which activates the essential cofactor for AO and XDH) is associated with AZA treatment outcome in IBD. Real-time PCR was conducted for a panel of single nucleotide polymorphism (SNPs) in AOX1, XDH and MOCOS using TaqMan SNP genotyping assays in a prospective cohort of 192 patients receiving AZA for IBD. Single nucleotide polymorphism AOX1 c.3404A > G (Asn1135Ser, rs55754655) predicted lack of AZA response (P = 0.035, OR 2.54, 95%CI 1.06-6.13) and when combined with TPMT activity, this information allowed stratification of a patient's chance of AZA response, ranging from 86% in patients where both markers were favourable to 33% where they were unfavourable (P < 0.0001). We also demonstrated a weak protective effect against adverse drug reactions (ADRs) from SNPs XDH c.837C > T (P = 0.048, OR 0.23, 95% CI 0.05-1.05) and MOCOS c.2107A > C, (P = 0.058 in recessive model, OR 0.64, 95%CI 0.36-1.15), which was stronger where they coincided (P = 0.019). These findings have important implications for clinical practice and our understanding of AZA metabolism.

Influence of xanthine oxidase on thiopurine metabolism in Crohn’s disease

The thiopurines, azathioprine (AZA) and mercaptopurine are extensively used in Crohn's discase (CD). Thiopurine bioactivation can be diverted by either thiopurine methyltransferase (TPMT), or by xanthine oxidase/dehydrogenase (XOD) which forms 6-thiouric acid (6TU). To investigate whether chronic inflammation could influence small intestinal XOD activity using urinary excretion of 6TU as a surrogate marker of XOD activity. 6-Thiouric acid excretion was compared between 32 CD patients and nine dermatology patients (control group), on AZA. Six CD patients were interesting: five with low TPMT activity (one deficient, four intermediate), and one receiving AZA/allopurinol co-therapy. There was no statistical difference in 6TU excretion between the CD and control group. CD location, severity or surgery did not affect excretion. The TPMT-deficient patient excreted 89% of daily AZA dose as 6TU, but excretion by TPMT carriers was essentially normal. Concurrent 5-aminosalicylic acid therapy increased 6TU excretion significantly (median 32.9%), consistent with inhibiting TPMT. 6TU was undetectable in the patient on AZA/allopurinol co-therapy. The results refuted our hypothesis, but fitted a model where most of an oral thiopurine dose effectively escapes first-pass metabolism by gut XOD, but is heavily catabolized by TPMT. Bioavailability of thiopurines may be competitively inhibited by dietary purines.

Upregulation of xanthine oxidase by tobacco smoke condensate in pulmonary endothelial cells

Tobacco smoking has been causally linked to the development of chronic obstructive pulmonary disease. It has been reported that the reactive oxygen species (ROS)- generating enzyme xanthine dehydrogenase/oxidase (XO) is increased in smoking-related stomach ulcers and that gastric mucosal damage caused by tobacco smoke can be blocked by the XO inhibitor allopurinol. In order to test the hypothesis that tobacco may cause the upregulation of XO in the lung, cultured rat pulmonary microvascular endothelial cells were exposed to tobacco smoke condensate (TSC). TSC at a concentration of 20 μg/mL significantly upregulated XO activity after 24 h of exposure. Longer exposure (1 week) to a lower concentration of TSC (2 μg/mL) also caused an increase in XO activity. Unlike hypoxia, TSC treatment did not alter the phosphorylation of XO. However, TSC treatment increased XO mRNA expression and the XO gene promoter activity. Furthermore, actinomycin D blocked the activation of XO by TSC. In conclusion, our results indicate that tobacco smoke condensate causes upregulation of XO transcription and activity.

Role of xanthine dehydrogenase and aging on the innate immune response of Drosophila

It has been proposed that uric acid is an important scavenger of deleterious oxygen species and peroxynitrite in biological systems. The cellular sources responsible for the generation of damage-causing reactive oxygen species (ROS) are widespread. Xanthine dehydrogenase (XDH) / oxidase (XOD) catalyzes the oxidation of xanthine to uric acid. The rosy (ry) gene encodes XDH/XOD in Drosophila melanogaster. XDH codes for uric acid which is a ROS scavenger. XOD however is an enzyme system implicated in ROS production. In this study, we investigated the roles of XDH in the fly's immune defense response to infection and in the aging process. We first compared ROS generation and nitric oxide (NO) level in the whole body and the gut of XDH mutant with those of wild type. Our results suggested that XDH has a protective effect with respect to both ROS and NO generations, particularly in the gut. We also examined the effect of a XDH deletion mutant on the relative sensitivity of the organism against bacterial infection, on the immune inducibility of antimicrobial peptides and on the effect of aging in the defensive response to infection. Our results strongly suggest that XDH plays an important role in the innate immune response and that the age-associated deterioration of the innate immune response might be, at least in part, associated with the loss of XDH activity in the aging process.

Molybdenum Requirement of Female Rats

Sixty 3-wk-old female Sprague-Dawley rats were randomly divided into six groups of 10 animals each. Group 1 was fed for 8 wk purified AIN-76A diet (basal diet) containing 0.025 mg molybdenum/kg diet. Groups 2–6 were fed the same basal diet supplemented with sodium molybdate to provide total dietary Mo of 0.050, 0.100, 0.200, 0.400 and 0.800 mg/kg diet, respectively. Molybdenum concentration in liver and brain increased linearly up to the 0.200 mg Mo/kg diet level. Beyond this level, no further significant increase occurred. Dietary Mo of 0.100 mg/kg elevated the Mo concentration in heart to its maximal level. Supplementation with 0.025 mg Mo/kg to a total of 0.05 mg Mo/kg diet significantly increased Mo concentration in spleen and kidney; higher levels of dietary Mo did not result in further significant responses. Molybdenum supplementation significantly increased the activities of xanthine dehydrogenase/oxidase (XDH), sulfite oxidase and superoxide dismutase in the liver, and of XDH in small intestinal mucosa. Maximal activities were attained at 0.050, 0.050, 0.200 and 0.100 mg Mo/kg diet, respectively. Dietary Mo of 0.200 mg/kg diet was estimated as the Mo requirement of rats fed the AIN-76A diet.

Xanthine oxidase/dehydrogenase in mammary gland of mouse: relationship to mammogenesis and lactogenesisin vivoandin vitro

Xanthine oxidase/dehydrogenase (XO/XDH) increases at mid gestation in mammary gland but not in liver of the mouse and remains elevated until the pups are weaned at 20 d post partum. The increase in enzyme activity is due neither to alteration in activators or inhibitors nor to a production of a variant enzyme with altered catalytic properties. The increase is preceded in vivo by a surge of prolactin-like activity (placental lactogen) in plasma, and prolactin is required for induction of XO/XDH in explant culture in vitro. Induction of XO/XDH in vivo and in vitro precedes the full histological differentiation of the gland. In addition, induction of XO/XDH in vitro occurs more rapidly and at lower concentrations of prolactin than does histological differentiation. Thus although XO/XDH is present in milk, increased XO/XDH activity is an early event in mammogenesis in vivo and in vitro rather than a terminal component of differentiation.

The role of dietary molybdenum on estrous activity, fertility, reproduction and molybdenum and copper enzyme activities of female rats

In this study, we investigated the effect of supplemental molybdenum (Mo) on estrous activity, fertility and reproduction, hepatic xanthine dehydrogenase/oxidase (XDH/OX), sulfite oxidase (SOX) and plasma ceruloplasmin (Cp) in female SD rats. Weanling female rats were assigned to five dietary treatment groups and fed an AIN-76A diet. They were given deionized water containing either no Mo or Mo at 5, 10, 50 and 100 mg/l. Mo significantly prolonged the estrous cycle when fed 10 mg/l or higher. Gestational weight gain was higher for the controls and the 5 mg/l, than for the 10–100 mg/l treatments. Histological data suggested that Mo supplemented at 10 mg/l or higher delayed fetal esophageal development, transfer of fetal hemopoiesis to bone marrow and myelination in the spinal cord. Intrauterine deaths were few, but the rate of fetal resorption increased with supplementation at 10 mg/l or higher. Mean hepatic XDH/XO, SOX and plasma Cu-Cp activity increased with Mo supplementation. This study suggests that supplemental Mo may influence estrous activity and embryogenesis. Hepatic XDH/OX, SOX and plasma ceruloplasmin may be affected differently in gestating and nongestating animals.

HUMAN FETAL XANTHINE OXIDASE

Xanthine oxidase (E.C. 1.2.3.2.) has been implicated in the pathogenesis of perinatal postischemic and hyperoxic tissue injuries through its action on the accumulated substrate, hypoxanthine (Hx), and concomitant oxygen free radical production. We measured the activity of xanthine dehydrogenase/oxidase (XOD), and its apparent Km for the main physiological substrate, hypoxanthine, in human fetal liver, intestine, brain, and myocardium. Autopsy samples from 45 fetuses (10-20 gestational weeks), 9 preterm babies (25-28 weeks), and 15 term babies were included in the study. XOD-activity increases in the liver and decreases in the intestine with gestation. During the last trimester the hepatic activity increases almost twofold to a mean of about 0.5 nmol/mg protein/min, while that in the intestine decreases to a third, a mean of about 0.3 nmol/mg protein/min. The apparent Km for Hx is 4.8-5.5 μM in the intestine throughout gestation and in the liver at term, but higher than 30 μM in the liver during the first half of pregnancy. The activity is below 20 pmol/mg protein/min in the brain, and undetectable in the myocardium. Thus, human fetal liver and intestine have substantial enzymatic capacity to convert Hx and/or xanthine to uric acid throughout a gestation. This is a prerequisite but not proof of the involvement of XOD in the pathogenesis of perinatal ischemia-reperfusion injury.