Xanthine Dehydrogenase Activity Research Articles

Commensal bacteria promote azathioprine therapy failure in inflammatory bowel disease via decreasing 6-mercaptopurine bioavailability

Azathioprine (AZA) therapy failure, though not the primary cause, contributes to disease relapse and progression in inflammatory bowel disease (IBD). However, the role of gut microbiota in AZA therapy failure remains poorly understood. We found a high prevalence of Blautia wexlerae in patients with IBD with AZA therapy failure, associated with shorter disease flare survival time. Colonization of B.wexlerae increased inflammatory macrophages and compromised AZA's therapeutic efficacy in mice with intestinal colitis. B.wexlerae colonization reduced 6-mercaptopurine (6-MP) bioavailability by enhancing selenium-dependent xanthine dehydrogenase (sd-XDH) activity. The enzyme sd-XDH converts 6-MP into its inactive metabolite, 6-thioxanthine (6-TX), thereby impairing its ability to inhibit inflammation in mice. Supplementation with Bacillus (B.) subtilis enriched in hypoxanthine phosphoribosyltransferase (HPRT) effectively mitigated B.wexlerae-induced AZA treatment failure in mice with intestinal colitis. These findings emphasize the need for tailored management strategies based on B.wexlerae levels in patients with IBD.

Population pharmacokinetics, pharmacodynamics and pharmacogenetics modelling of oxypurinol in Hmong adults with gout and/or hyperuricemia.

The aim of this study was to quantify identifiable sources of variability, including key pharmacogenetic variants in oxypurinol pharmacokinetics and their pharmacodynamic effect on serum urate (SU). Hmong participants (n = 34) received 100 mg allopurinol twice daily for 7days followed by 150 mg allopurinol twice daily for 7days. A sequential population pharmacokinetic pharmacodynamics (PKPD) analysis with non-linear mixed effects modelling was performed. Allopurinol maintenance dose to achieve target SU was simulated based on the final PKPD model. A one-compartment model with first-order absorption and elimination best described the oxypurinol concentration-time data. Inhibition of SU by oxypurinol was described with a direct inhibitory Emax model using steady-state oxypurinol concentrations. Fat-free body mass, estimated creatinine clearance and SLC22A12 rs505802 genotype (0.32 per T allele, 95% CI 0.13, 0.55) were found to predict differences in oxypurinol clearance. Oxypurinol concentration required to inhibit 50% of xanthine dehydrogenase activity was affected by PDZK1 rs12129861 genotype (-0.27 per A allele, 95% CI -0.38, -0.13). Most individuals with both PDZK1 rs12129861 AA and SLC22A12 rs505802 CC genotypes achieve target SU (with at least 75% success rate) with allopurinol below the maximum dose, regardless of renal function and body mass. In contrast, individuals with both PDZK1 rs12129861 GG and SLC22A12 rs505802 TT genotypes would require more than the maximum dose, thus requiring selection of alternative medications. The proposed allopurinol dosing guide uses individuals' fat-free mass, renal function and SLC22A12 rs505802 and PDZK1 rs12129861 genotypes to achieve target SU.

Leukocyte Tyrosine Kinase (Ltk) Is the Mendelian Determinant of the Axolotl Melanoid Color Variant.

The great diversity of color patterns observed among amphibians is largely explained by the differentiation of relatively few pigment cell types during development. Mexican axolotls present a variety of color phenotypes that span the continuum from leucistic to highly melanistic. The melanoid axolotl is a Mendelian variant characterized by large numbers of melanophores, proportionally fewer xanthophores, and no iridophores. Early studies of melanoid were influential in developing the single-origin hypothesis of pigment cell development, wherein it has been proposed that all three pigment cell types derive from a common progenitor cell, with pigment metabolites playing potential roles in directing the development of organelles that define different pigment cell types. Specifically, these studies identified xanthine dehydrogenase (XDH) activity as a mechanism for the permissive differentiation of melanophores at the expense of xanthophores and iridophores. We used bulked segregant RNA-Seq to screen the axolotl genome for melanoid candidate genes and identify the associated locus. Dissimilar frequencies of single-nucleotide polymorphisms were identified between pooled RNA samples of wild-type and melanoid siblings for a region on chromosome 14q. This region contains gephyrin (Gphn), an enzyme that catalyzes the synthesis of the molybdenum cofactor that is required for XDH activity, and leukocyte tyrosine kinase (Ltk), a cell surface signaling receptor that is required for iridophore differentiation in zebrafish. Wild-type Ltk crispants present similar pigment phenotypes to melanoid, strongly implicating Ltk as the melanoid locus. In concert with recent findings in zebrafish, our results support the idea of direct fate specification of pigment cells and, more generally, the single-origin hypothesis of pigment cell development.

Xanthine dehydrogenase rewires metabolism and the survival of nutrient deprived lung adenocarcinoma cells by facilitating UPR and autophagic degradation.

Xanthine dehydrogenase (XDH) is the rate-limiting enzyme in purine catabolism by converting hypoxanthine to xanthine and xanthine to uric acid. The altered expression and activity of XDH are associated with the development and prognosis of multiple types of cancer, while its role in lung adenocarcinoma (LUAD) remains unknown. Herein, we demonstrated that XDH was highly expressed in LUAD and was significantly correlated with poor prognosis. Though inhibition of XDH displayed moderate effect on the viability of LUAD cells cultured in the complete medium, it significantly attenuated the survival of starved cells. Similar results were obtained in XDH-knockout cells. Nucleosides supplementation rescued the survival of starved LUAD cells upon XDH inhibition, while inhibition of purine nucleoside phosphorylase abrogated the process, indicating that nucleoside degradation is required for the XDH-mediated survival of LUAD cells. Accordingly, metabolic flux revealed that ribose derived from nucleoside fueled key carbon metabolic pathways to sustain the survival of starved LUAD cells. Mechanistically, down-regulation of XDH suppressed unfolded protein response (UPR) and autophagic flux in starved LUAD cells. Inhibition of XDH decreased the level of amino acids produced by autophagic degradation, which was accompanied with down-regulation of mTORC1 signaling. Supplementation of amino acids including glutamine or glutamate rescued the survival of starved LUAD cells upon knockout or inhibition of XDH. Finally, XDH inhibitors potentiated the anti-cancer activity of 2-deoxy-D-glucose that induced UPR and/or autophagy in vitro and in vivo. In summary, XDH plays a crucial role in the survival of starved LUAD cells and targeting XDH may improve the efficacy of drugs that induce UPR and autophagy in the therapy of LUAD.

AB0138 XANTHINE OXIDOREDUCTASE: BLOOD PROFILE IN SYSTEMIC CONNECTIVE TISSUE DISEASES

BackgroundSystemic lupus erythematosus (SLE) and systemic scleroderma (SSc) are systemic connective tissue diseases. Their development is based on a generalized immune inflammatory process. Deep immunological and metabolic disorders in these diseases have along with general characteristic distinctive features. XOR is a multifunctional enzyme. The reactions catalyzed by XOR are a source of reactive forms of oxygen and nitrogen, nitric oxide, which are of great physiological importance, and are also responsible for the development of many pathophysiological reactions. Analysis of changes in the activity of interconverting forms of XOR (xanthine oxidase (XO), ЕС 1.17.3.2 and xanthine dehydrogenase (XDG), ЕС 1.17.1.4) in plasma and blood cells is of interest.Objectivesto characterize differences of XO and XDG activities profiles in blood of SLE and SSc patients.MethodsThe researcher was carried out in agreement with the WMA Declaration of Helsinki principles. 56 SLE patients and 51 SSc patients were enrolled in this study. Diagnosis of SLE was verified using the SLICC criteria (2012). SSc was verified according to ACR/EULAR criteria (2013). The reference group consisted of 35 healthy controls. XO and XDG activities were measured in plasma, lysed WBC, lysed RBC using spectrophotometric method [1]. Results were expressed as Me (Q25; Q75). The Mann-Whitney U test was used for statistical analysis, differences were considered significant when p<0.05.ResultsMean age of SLE patients was 35 (31; 42) years, mean duration of disease was 8 (5; 11) years. Mean age of SSc patients was 43 (38; 48) years, mean SSc duration was 8 (6; 9) years. The enzyme indices included in the study did not depend on the sex and age of healthy individuals. XO activity was increased in plasma of SLE and SSc patients (p<0.001 for both disease). The activity of XO was higher in SLE (p<0.001). XO activity of lysed WBC was decreased in both diseases (p<0.001). XDG activity was decreased in lysed WBC and lysed RBC of patients with SLE and SSc (all p<0.001). Activity of this enzyme was lower in lysed WBC and higher in lysed RBC in SLE compared with SSc (all p<0.001). In contrast to SLE, accompanied by low levels of plasma XDH activity (p<0.001), SSc was characterized by increased activity of this enzyme (p<0.001). Also, increased XO activity was revealed in lysed RBC of SSc patients (p<0.001). The values of this enzymatic activity did not differ between the group of SLE patients and healthy controls (p=0.977).ConclusionChanges in the activity of oxidase and dehydrogenase forms of XOR were revealed in plasma, lysed WBC, lysed RBC of SLE and SSc patients, which determine characteristic blood profiles in these diseases. Changes in the balance of XOR enzymatic activities can affect the exchange of purine nucleotides, the pool of reactive oxygen and nitrogen species in body tissues, participating in the processes inherent in these diseases.

Ксантиноксидоредуктаза лимфоцитов: зависимость активности от внесуставных проявлений при ревматоидном артрите

Study Objective: To study lymphocyte lysates for the dependence of the activity of xanthine oxidoreductase (XOR) complex: xanthine oxidase (XO) and xanthine dehydrogenase (XDG) — on the presence of extraarticular (systemic) manifestations (EAM) in patients with rheumatoid arthritis (RA). Study Design: Comparative study. Material and Methods. The study included 77 patients with verified RA (study group) and 35 apparently healthy subjects (control group). Lymphocytes were isolated using А. Böyum method in Lymphosep with a density gradient of 1.077–1.079 g/mL. Ferment activity was measured with kinetic methods and expressed in nM/min/mL equivalent to 107 cells per 1 mL. Study Results. XO reference range is 14.11–31.33 nM/min/mL; that of XDG — 18.62–39.64 nM/min/mL. For RA patients as a whole and patients with and without EAMs, lymphocytes demonstrated a significant reduction in the activity of both ferments vs controls (р < 0.001); in RA patients with EAMs, the XO and XDG activity was even lower (р < 0.001). Spearman correlation analysis identified the dependence of XO and XDG activity on the presence of EAMs: direct moderate correlations for XO (ρ = 0.6; p < 0.001) and XDG (ρ = 0.499; p = 0.000041). There is a strong direct correlation between XO and XDG activity, the intensity of which was higher where RA was associated with EAMs: (ρ = 0.72; p = 0.025) and (ρ = 0.87, p = 0.004) for RA only with articular involvement and for RA with EAMs, respectively. Conclusion. In lymphocytes of patients with RA, we found some changes in the XOR enzyme profile, the intensity of which depends on the presence of EAMs in the clinical presentation of the disease. Where XO activity is below 10.86 nM/min/mL and/or with XDG activity below 14.31 nM/min/mL, it is assumed that RA patients have EAMs. It is then recommended that the patient undergoes a comprehensive examination for early EAM identification and therapy adjustment. Keywords: rheumatoid arthritis, lymphocytes, xanthine oxidoreductase, xanthine oxidase, xanthine dehydrogenase.

AB0061 ALTERATIONS OF XANTHINE OXIDOREDUCTASE ACTIVITY IN RED BLOOD CELLS AFTER GLUCOCORTICOID TREATMENT IN RHEUMATOID ARTHRITIS

Background:According to modern concepts, rheumatoid arthritis (RA) refers to severe autoimmune rheumatic diseases. The activation of free radical oxidation processes is essential in the development of this disease [1]. Xanthine oxidoreductase is a significant reactive oxygen species source [2]. Despite the great advances in the treatment of rheumatoid arthritis (RA) associated with the introduction of innovative drugs and especially the improvement of the strategy for their use into clinical practice, glucocorticoids still remain an important component of RA pharmacotherapy in actual clinical practice.Objectives:to evaluate the changes in activities of xanthine oxidoreductase interconvertible forms (xanthine oxidase, ЕС 1.17.3.2 and xanthine dehydrogenase, ЕС 1.17.1.4) in lysed red blood cells of RA patients in relation with glucocorticoid treatment.Methods:47 RA patients with verified RA and 30 healthy controls were enrolled in the study. The diagnosis was verified using the 2010 ACR/EULAR criteria 2010. All patients have moderate DAS28 scores. RA patients were randomized into 2 groups comparable in gender, age and the principal clinical manifestations. Methylprednisolone (Metipred, Orion Corp.), average dose 30 mg/day, and betamethasone (Diprospan, Schering-Plough), single dose7 mg, were administered intramuscularly in the respective groups. Хanthine oxidase (XO) and xanthine dehydrogenase (XDG) activities were measured in lysed red blood cells by spectrophotometric method as previously described [3]. The changes of these enzymes activities were studied in RA patients before and after the injection of glucocorticoids. Statistical comparison tests were selected in according to common guidelines, differences were considered significant when p<0.05. Central tendencies were expressed as means±SEM.Results:Mean age of patients in methylprednisolone group was 41.8±1.05 years, and mean RA duration (± SEM) was 7.9±0.21 years. Mean age of patients in diprospan group was 40.9±1.07 years, and mean RA duration was 8.0±0.33 years. Significant decreases of XO activity and increase of XDG activity were observed in lysed red blood cells of RA patients just after the injection of each glucocorticoid drug. Changes of the enzymatic activities in lysed red blood cells were more pronounced in methylprednisolone group. However enzymatic activity did not reach the level of healthy controls. As described previously, decreased XO activity and increased XDG activity were observed in plasma of RA patients just after the injection of the average therapeutic doses of glucocorticoids, as well as in lysed lymphocytes just after the injection of methylprednisolone [4].Conclusion:Treatment with methylprednisolone and betamethasone can affect the balance of XO/XDG activity and increase the antioxidant potential of the blood. This effect can exert beneficial influence on autoimmune inflammation in RA.

AB0164 ACTIVITIES OF THE OXIDATIVE-RELATED ENZYMES IN SYSTEMIC SCLEROSIS

Background:The oxidative-related enzymes are involved in the pathogenesis of various stages of systemic sclerosis (SSc). SSc is a chronic autoimmune disorder that is intimately associated with vascular damage and therefore with chronic perfusion/reperfusion and oxidative organ injury. Mesenchymal cell activation in SSc is now also considered to be mediated primarily through oxidative burst. Regulation of oxidative stress by specific enzymes including several purine metabolism enzymes is likely to play an important role in SSc progression.Objectives:to characterize interrelationships among circulating xanthine oxidase (XO), xanthine dehydrogenase (XDH), superoxide dismutase (SOD) activities and SSc activity.Methods:The study was performed according to bioethical standards. 51 patients with verified SSc and 30 healthy controls were included in the study. The diagnosis was verified according to ACR/EULAR 2013 criteria. We assessed SSc activity in compliance with the original activity scale that is commonly used in Russia [Guseva N.G., 1993] and by the 2001 European Scleroderma Study Group Activity Index. XO (EC 1.17.3.2), XDH (EC 1.17.1.4), and SOD (EC 1.15.1.1) plasma activities were measured using spectrophotometric techniques as previously described [Dubinina E.E., 1986; Karpova O.V., 2006]. Results are expressed as mean±SD. The Mann-Whitney U test and Spearman’s correlation coefficient were used for statistical analysis.Results:Mean age of patients was 42.8±1.3 years, mean SSc duration was 7.9±0.7 years. Mean enzymatic activities in normal controls were 3.43±0.56 nmol/ml min (for XO), 5.19±0.71 nmol/ml min (for XDH), and 5.40±1.03 units (for SOD). The respective enzymatic activities in SSc group were 3.91±0.62 nmol/ml min, 7.10±0.71 nmol/ml min, and 7.10±2.19 units. All these mean activities were significantly higher in SSc patients comparing to healthy individuals (p<0.001). XO and XDH activities positively correlated with SSc activity (r=0.499, p<0.001, and r=0.741, p<0.001, respectively). The opposite but weaker trend was observed for SOD activity and SSc disease activity (r=-0.190, p=0.188).Conclusion:SSc is characterized by an increase in the intensity of oxidative and antioxidant processes, more pronounced in high disease activity. A close relationship between function of prooxidant/antioxidant enzymes and some of the key SSc pathogenetic mechanisms, especially vascular disease and fibroblast activation, is widely considered. Overall increase of oxidative stress in patients with higher disease activity, as well as depletion of antioxidant capacity can be also linked with disturbance of purine metabolism through XO and XDH modulation. Pathogenetic influence of this imbalance can also be mediated through initial phase of neutrophil extracellular traps (NETs) formation, an eventual source of nucleoprotein containing autoepitopes.Disclosure of Interests:None declared

Enhancing xanthine dehydrogenase activity is an effective way to delay leaf senescence and increase rice yield

Xanthine dehydrogenase (XDH) is an important enzyme in purine metabolism. It is involved in regulation of the normal growth and non-biological stress-induced ageing processes in plants. The present study investigated XDH’s role in regulating rice leaf senescence. We measured physical characteristics, chlorophyll content and fluorescence parameters, active oxygen metabolism, and purine metabolism in wild-type Kitaake rice (Oryza sativa L.), an OsXDH over-expression transgenic line (OE9), and an OsXDH RNA interference line (Ri3) during different growth stages. The expression patterns of the OsXDH gene confirmed that XDH was involved in the regulation of normal and abiotic stress-induced ageing processes in rice. There was no significant difference between the phenotypes of transgenic lines and wild type at the seedling stage, but differences were observed at the full heading and maturation stages. The OE9 plants were taller, with higher chlorophyll content, and their photosystems had stronger light energy absorption, transmission, dissipation, and distribution capacity, which ultimately improved the seed setting rate and 1000-seed weight. The opposite effect was found in the Ri3 plants. The OE9 line had a strong ability to remove reactive oxygen species, with increased accumulation of allantoin and alantoate. Experimental spraying of allantoin on leaves showed that it could alleviate chlorophyll degradation and decrease the content of H2O2 and malonaldehyde (MDA) in rice leaves after the full heading stage. The urate oxidase gene (UO) expression levels in the interference line were significantly lower than those in the over-expression line and wild-type lines. The allantoinase (ALN) and allantoate amidinohydrolase (AAH) genes had significantly higher expression in the Ri3 plants than the in OE9 or wild-type plants, with OE9 plants showing the lowest levels. The senescence-related genes ACD1, WRKY23, WRKY53, SGR, XERO1, and GH27 in Ri3 plants had the highest expression levels, followed by those in the wild-type plants, with OE9 plants showing the lowest levels. These results suggest that enhanced activity of XDH can regulate the synthesis of urea-related substances, improve plant antioxidant capacity, effectively delay the ageing process in rice leaves, and increase rice yield.

Goose astrovirus infection affects uric acid production and excretion in goslings

In 2018, a new goose astrovirus (GAstrV) was reported in China, which causes 2 to 20% deaths in 4- to 16-day-old goslings causing great damages to the livestock industry. Gout is the typical feature of GAstrV infection in goslings. However, the mechanism of gout formation remains unclear. In the present study, 2-day-old goslings were infected intramuscularly with GAstrV for 14 D. One quarter of the infected goslings died, and typical gout pathological changes were found in the dead infected goslings. Pathological changes were observed in the morphology of the kidney and liver, such as degeneration, necrosis, and inflammatory cell infiltration. Accordingly, a high virus load was found in both organs. The serum level of uric acid in the inoculated goslings was higher, whereas no differences were found in levels of creatinine, calcium, and phosphorus. Moreover, the xanthine dehydrogenase (XOD) and adenosine deaminase (ADA) activities and the mRNA levels of xanthine dehydrogenase, adenosine deaminase, phosphoribosyl pyrophosphate amidotransferase, and phosphoribosyl pyrophosphate synthetase 1 in livers increased, wheres the multidrug resistance–associated protein 4 mRNA level and Na-K-ATPase activity in the kidneys decreased. These results showed that GAstrV infection could cause lesions on the liver and kidney and then increase the expression or activity of enzymes related to uric acid production in the liver and decrease renal excretion function, which contribute to hyperuricemia and gout formation.

Turcuron: A standardized bisacurone-rich turmeric rhizome extract for the prevention and treatment of hangover and alcohol-induced liver injury in rats

Objectives: The present work investigated the hepatoprotective effects of Turcuron, a first-of-its-kind extract from Curcuma longa tubers containing 8% bisacurone, with respect to alcohol-induced liver injury in rats. We have further studied its efficacy in improving alcohol metabolism in rats. Materials and Methods: In vitro studies were performed using nitric oxide (NO) scavenging and xanthine dehydrogenase activity. Alcohol-induced liver injury was established in male Sprague Dawley rats by oral administration of 4 g/kg/day of 40% ethanol for 6 weeks. Turcuron (150 and 300 mg/kg) was administered to the rats after 3 weeks of alcohol treatment till the end of the study. In alcohol-induced hangover model, male Wistar rats were administered with single oral dose of 5 ml/kg b.w. of alcohol, 1 h after the treatment with Turcuron (200, 300, and 400 mg/kg). Results: In our preliminary study, Turcuron markedly inhibited the NO production and xanthine dehydrogenase activity in vitro . In the in vivo model rats, Turcuron restored the liver architecture and biochemical parameters and reduced the expression of inflammatory proteins in the liver. Furthermore, Turcuron reduced the blood alcohol and acetaldehyde levels in alcohol hangover model rats. It also increased the activity of Aldehyde dehydrogenase (ALDH) significantly in the liver. Conclusion: Here, we report for the first time, Turcuron-mediated liver protection attributing to the presence of high content of bisacurone in the turmeric extract. Collectively, our data provide valuable evidence for the application of bisacurone-rich turmeric extract as a functional food and/or medicine.

An ancestral variant causing type I xanthinuria in Turkmen and Arab families is predicted to prevail in the Afro-Asian stone-forming belt.

Classical xanthinuria is a rare autosomal recessive metabolic disorder characterized by lack of xanthine dehydrogenase activity that often manifests as xanthine urolithiasis and risk of drug toxicity. Variants in the XDH or HMCS gene underlie classical xanthinuria type I and type II, respectively. Here we present two Israeli Arab families affected by type I xanthinuria in whom a c.2164A>T (Lys722Ter) variant in the XDH gene, previously reported in a Turkish family of Turkmen origin, was identified. Analysis of polymorphic markers surrounding the variant site revealed common haplotypes spanning 0.6 Mbp shared by all three, and 1.7 Mbp shared by two of the studied families. By applying Bayesian methods to a simple model of crossover events through generations in the chromosomes carrying the variant, the most recent common ancestor of these families was found to be 179 (95% credible limit 70) generations old. The estimated antiquity of the variant, the historical genealogy of the affected families and the history and present day dispersion of their people strongly suggest prevalence of this variant in the Afro‐Asian stone‐forming belt. As far as we are aware, this is a first report of an ancient variant causing xanthinuria with potential wide geographical dispersion.

Molecular and biochemical analysis of XDH from Phaseolus vulgaris suggest that uric acid protects the enzyme against the inhibitory effects of nitric oxide in nodules

Xanthine dehydrogenase (XDH) is essential for the assimilation of symbiotically fixed nitrogen in ureidic legumes. Uric acid, produced in the reaction catalyzed by XDH, is the precursor of the ureides, allantoin and allantoate, which are the main N-transporting molecules in these plants. XDH and uric acid have been reported to be involved in the response to stress, both in plants and animals. However, the physiological role of XDH under stressful conditions in ureidic legumes remains largely unexplored. In vitro assays showed that Phaseolus vulgaris XDH (PvXDH) can behave as a dehydrogenase or as an oxidase. Therefore, it could potentially protect against oxidative radicals or, in contrast, it could increase their production. In silico analysis of the upstream genomic region of XDH coding gene from P. vulgaris revealed the presence of several stress-related cis-regulatory elements. PvXDH mRNA and enzymatic activity in plants treated with stress-related phytohormones or subjected to dehydration and stressful temperatures showed several fold induction. However, PvXDH activity was in vivo and in vitro inhibited by nitric oxide in leaves but not in nodules. In extracts from RNAi PvXDH silenced nodules, with lower levels of uric acid, XDH activity was inhibited by SNP which indicates that uric acid produced by XDH in the nodules of this ureidic legume could help to protect XDH against the inhibitory effects of nitric oxide.

Studying the Ameliorative Effect of Bee Venom Against Damage and Inflammation Induced in Gamma-Irradiated Rats

The aim of this study was focused on investigating the possible protective effect of Bee Venom (BV) against gamma radiation induced damage and inflammation in male rats. Gamma-irradiation (6 Gy) resulted in a significant elevation in the level of tumor necrotic factor-alpha (TNF-α) , interleukin-6 (IL-6) , creatinine kinase-MB (CK-MB) and cardiac troponin I (cTnI), lactate dehydrogenase (LDH), creatine phosphokinase (CPK), serum aspartate transaminase (AST) and alanine transaminase (ALT) , serum glucose, malondialdehyde (MDA) concentration and xanthine oxidase activity associated with remarkable decrease in insulin level, glutathione content (GSH) and the activity of xanthine dehydrogenase (XDH), superoxide dismutase (SOD) and catalase (CAT) in heart and liver tissues compared to control group. Injection of BV (5ml/kg b. wt. / day/6weeks) to γ-irradiated rats was found to offer protection against γ-irradiation induced oxidative stress and significantly ameliorated the changes occurred in the above investigated biochemical parameters. It could be concluded that Bee venom clarified a modulatory role against gamma radiation induced oxidative damage and inflammation in the heart and liver tissues.

Protective Effect of Emblica officinalis on Cardiac Dysfunction in Gamma-Irradiated Male Albino Rats

Abstract: Emblica officinalis (EO) is a plant with diverse ethnical medicinal uses. The plant has been explored for diverse pharmacological actions, here it was planned to screen the radio-protective activities of its fruit powder. Experimental Animals and Design: Four groups of male albino rats were used: 1- Control: untreated group. 2- Irradiated: animals exposed to a single dose of whole-body gamma-irradiation (6Gy). 3- Eo group: given daily EO fruit powder dissolved in distalled water at a dose of 750mg/kg b.wt., for 30 days, intragastrically. 4- EO+ Irrad. group: given EO (as group 3), the last dose being 2 hours before irradiation. Blood and heart tissue samples were collected after 2hrs and 2 weeks post irradiation. Parameters Measured: Reduced glutathione (GSH) content and malondialdehyde (MDA) levels were measured in cardiac mitochondrial fraction. Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) activities and the level of advanced oxidation protein products (AOPP) were measured in the cytosolic fraction of heart tissue. Atrial natriuretic peptide (ANP) and creatine phosphokinase (CPK) activity were measured in plasma. Cardiac cytosolic glucose-6-phosphate dehydrogenase (G6PDH) and Lactate dehydrogenase (LDH) activities were determined. Results: EO administration pre-irradiation, improved the disturbances induced in the heart by irradiation.

Exploratory Study of Xanthine Dehydrogenase (XD) Accumulation in Chicks’ Organs: XD Natures and its Inhibitory Activities

Few researches have indicated the availability of xanthine dehydrogenase in some parts of chicks, the enzymatic activity, and the rate of enzyme synthesis during the first few days after hatching. In addition, studies were conducted to examine the relationship between changes in xanthine dehydrogenase in some of these parts and some biomarkers as the excretion of uric acid in chicks fed diets. The developmental changes between xanthine oxidase in these parts and adenosine have also been observed before. However, in the current project, the developmental changes (including organ activity) in xanthine dehydrogenase activity of kidney, liver, pancreas and duodenum are investigated. Unincubated White Leghorn eggs and day-old male chicks were brought. Chicks were fed (Startena) ad libitum and eggs were injected in three sequential days and embryos were gotten on day 19th. Some organs (as liver, kidney, duodenum, and pancreas) tissues of the embryos were isolated and treated with potassium phosphate solution and treated with charcoal and centrifuged. The extracts were let to react with 2-amino-4-hydroxypteridine and NAD in phosphate buffer in order to check the activity using a fluorometer. Specific activities of the xanthine dehydrogenase in organ tissues are listed as micromicromoles of substrate oxidized per minute per milligram protein. Besides, the xanthine dehydrogenase activities in these active tissues were measured from day 17 of incubation to a week after hatching. We reached to a conclusion that the enzyme was formed in the kidney several days prior to hatching and this had stimulated the liver, duodenum, and kidney at hatching in addition, to the central nervous system which resulted in a sensible modification of the pituitary function. Tracking the xanthine dehydrogenase activities in these organs showed no influence on the enzymatic activities except for pancreas which related to dietary situation that clearly refers to a possible interfering agent in the food which opens new arguments. As a result, our study has lucratively discovered 3-types of xanthine dehydrogenases in fledglings.

Inhibitory Effects of Apium graveolens on Xanthine Oxidase Activity and Serum Uric Acid Levels in Hyperuricemic Mice.

Celery (Apium graveolens) is traditionally used to treat rheumatism and cardiovascular disorders. Hyperuricemia is considered as a predisposing factor for gout and is also suggested to be associated with coronary artery disease. In the present study, the effect of hydroalcoholic extracts from A. graveolens (AGE) against potassium oxonate (PO)-induced hyperuricemia was investigated in mice. AGE (250, 500, and 1,000 mg/kg) or allopurinol (5 mg/kg, as positive control) were orally administrated 1 h after PO injection (250 mg/kg, ip) for two weeks. After that, the serum uric acid level and hepatic xanthine dehydrogenase (XDH) and xanthine oxidase (XO) activities were measured. In addition, the antioxidant activity of AGE was determined by assessment of hepatic lipid peroxidation, in vivo and the ferric reducing/antioxidant power assay, in vitro. The extract exhibited good capacity to reduce ferric ion to ferrous ion with mean value of 63.8±8.5 μmol/g. The data also showed that oxonate treatment produced a significant increase in serum uric acid level (4.6 vs. 2.3 mg/ dL, P<0.001), liver XO/XDH activities (P<0.01 and P<0.001, respectively), and hepatic lipid peroxides levels (about two fold, P<0.01), compared to the healthy mice. AGE significantly decreased the serum uric acid level, hepatic XO/XDH activities, and lipid peroxidation, in a dose-dependent manner. Oral administration of 1,000 mg/kg AGE for two weeks reversed the elevated serum uric acid level (2.7 vs. 4.6 mg/dL, P<0.001) and significantly inhibited liver XO/XDH activities (P<0.001) and diminished hepatic lipid peroxidation (0.45 vs. 0.82 nmol/mg protein, P<0.05), compared with hyperuricemic mice. AGE (1,000 mg/kg) per se did not significantly modify these parameters. Our results demonstrated that AGE could reduce the serum uric acid level via inhibition of hepatic XDH/XO and indicated its potential utility as an effective hypouricemic bioactive agent or functional food.

Translucent larval integument and flaccid paralysis caused by genome editing in a gene governing molybdenum cofactor biosynthesis in Bombyx mori

Translucency of the larval integument in Bombyx mori is caused by a lack of uric acid in the epidermis. Hime'nichi translucent (ohi) is a unique mutation causing intermediate translucency of the larval integument and male-specific flaccid paralysis. To determine the gene associated with the ohi mutation, the ohi locus was mapped to a 400-kb region containing 29 predicted genes. Among the genes in this region, we focused on Bombyx homolog of mammalian Gephyrin (BmGphn), which regulates molybdenum cofactor (MoCo) biosynthesis, because MoCo is indispensable for the activity of xanthine dehydrogenase (XDH), a key enzyme in uric acid biosynthesis. The translucent integument of ohi larvae turned opaque after injection of bovine xanthine oxidase, which is a mammalian equivalent to XDH, indicating that XDH activity is defective in ohi larvae. RT-PCR and sequencing analysis showed that (i) in ohi larvae, expression of the BmGphn gene was repressed in the fat body where uric acid is synthesized, and (ii) there was no amino acid substitution in the ohi mutant allele. Finally, we obtained BmGphn knockout alleles (hereafter denoted as BmGphnΔ) by using CRISPR/Cas9. The resulting ohi/BmGphnΔ larvae had translucent integuments, demonstrating that BmGphn is the gene responsible for the ohi phenotype. Our results show that repressed expression of BmGphn is a causative factor for the defective MoCo biosynthesis and XDH activity observed in ohi larvae. Interestingly, all male BmGphnΔ homozygotes died before pupation and showed a flaccid paralysis phenotype. The genetic and physiological mechanisms underlying this flaccid paralysis phenotype are also discussed.

Xanthine Dehydrogenase Involves in the Response of Photosystem and Reactive Oxygen Metabolism to Drought Stress in Rice

Xanthine dehydrogenase (XDH) is a crucial enzyme involved in purine metabolism. Although the essential role of XDH is well studied in leguminous plants and Arabidopsis, the importance of this enzyme remains uncertain in rice. To evaluate how biochemistry indicators respond to XDH down-regulation and up-regulation in rice seedings during drought stress, RNA interference (RNAi) and CDS over-expression were used to generate transgenic lines of Nipponbare (Oryza sativa L.) in which OsXDH, the gene for XDH were silenced and over-expression. When the XDH-suppressed line was subjected to drought stress, the chlorophyll content and chlorophyll fluorescence parameters were markedly reduced in conjunction with significantly O 2 − enhanced production rate and MDA accumulation. This drought-hypersensitive biochemistry indicators was reversed in XDH-intensified line. Meanwhile, the XDH activity and its downstream metabolites were induced by drought stress. These observations support the notion that xanthine dehydrogenase was involved in regulating photosystem and reactive oxygen metabolism in drought stress in rice seedling.

Body mass index is independently associated with xanthine oxidase activity in overweight/obese population

The pathophysiological mechanism of the relationship between xanthine oxidase (XO) activity and obesity has not been completely elucidated. Since inflammation and oxidative stress are regarded as key determinants of enlarged adipose tissue, we aimed to investigate the association between oxidative stress (as measured with XO activity), inflammation [as measured with high-sensitivity C-reactive protein (hsCRP)] and obesity [as measured with body mass index (BMI)]. In addition, we wanted to examine whether hsCRP itself plays an independent role in XO activity increase or it is only mediated through obesity. A total of 118 overweight/obese volunteers (mean age 54.76±15.13years) were included in the current cross-sectional study. Anthropometric, biochemical parameters, and blood pressure were obtained. Significant differences between age, BMI, waist circumference, concentrations of uric acid and hsCRP, as well as xanthine dehydrogenase (XDH) activities were evident among XO tertile groups. Multiple linear regression analysis revealed that BMI (beta = 0.241, p = 0.012) and XDH (beta=-0.489, p < 0.001) are the independent predictors of XO activity (R2-adjusted = 0.333), whereas hsCRP lost its independent role in XO activity prediction. Obesity (as determined with increased BMI) is an independent predictor of high XO activity in overweight/obese population. Level V: cross-sectional descriptive study.