Molybdoenzyme Participation In Plant Biochemical Processes

Molybdenum is a key microelement in plant vital functioning. The microelement can be absorbed by the plants only in the form of molybdate-anion. The Molybdenum deficiency affects negatively to the most important agricultural growing. As molybdenum takes part in such vital mechanisms as nitrogen and sulfur metabolism, plant hormone biosynthesis, and purine banding catabolism. Molybdenum is included in enzyme content which is called molybdoenzyms. Having bonded with molybdopterin it creates molybdenum co-factor (Moco) and gets oxidation-reduction properties. Moco is included in active site of molybdoenzymes. They take part in sulfur and nitrogen metabolism, and detrimental compound detoxication. Molybdenum deficiency is characterized by the slow plant growth, low amount of chlorophyll ascorbic acid capacity.It was noticed that plants suffering from the molybdenum deficiency can be saved, sodium molibdate can be used, it can be put directly in the soil or plant leaves can sprayed with the solution. There are five plant molibdoenzymes which are currently known: sulfite oxidase (SO), xanthine dehydrogenase (XD), nitrate reductase (NR), aldehyde oxidase (AO) and mitochondrial amidoxim-regenerative component. Nitrate reductase catalyzes the first stage of nitrate assimilation, eucariotic organisms contain three isoforms of the molybdoezimes: A NADH, A NAD(P)H и NADPH. Xanthine dehydrogenase regulates purine metabolism. XD increases plant antioxidant ability and slows down leaves aging. Molybdoenzymess are involved in the process of the stress adaptation, defining of the mechanisms and their reaction to environmental stress conditions is important for plant stress resistance.

Xanthine dehydrogenase as a prognostic biomarker related to tumor immunology in hepatocellular carcinoma

Background Xanthine dehydrogenase (XDH) is a critical enzyme involved in the oxidative metabolism of purines, pterin and aldehydes and a central component of the innate immune system. However, the prognostic value of XDH in predicting tumor-infiltrating lymphocyte abundance, the immune response, and survival in different cancers, including hepatocellular carcinoma (HCC), is still unclear. Methods XDH expression was analyzed in multiple databases, including Oncomine, the Tumor Immune Estimation Resource (TIMER), the Kaplan–Meier plotter database, the Gene Expression Profiling Interactive Analysis (GEPIA) database, and The Cancer Genome Atlas (TCGA). XDH-associated transcriptional profiles were detected with an mRNA array, and the levels of infiltrating immune cells were validated by immunohistochemistry (IHC) of HCC tissues. A predictive signature containing multiple XDH-associated immune genes was established using the Cox regression model. Results Decreased XDH mRNA expression was detected in human cancers originating from the liver, bladder, breast, colon, bile duct, kidney, and hematolymphoid system. The prognostic potential of XDH mRNA expression was also significant in certain other cancers, including HCC, breast cancer, kidney or bladder carcinoma, gastric cancer, mesothelioma, lung cancer, and ovarian cancer. In HCC, a low XDH mRNA level predicted poorer overall survival, disease-specific survival, disease-free survival, and progression-free survival. The prognostic value of XDH was independent of the clinical features of HCC patients. Indeed, XDH expression in HCC activated several immune-related pathways, including the T cell receptor, PI3K-AKT, and MAPK signaling pathways, which induced a cytotoxic immune response. Importantly, the microenvironment of XDHhigh HCC tumors contained abundant infiltrating CD8 + T cells but not exhausted T cells. A risk prediction signature based on multiple XDH-associated immune genes was revealed as an independent predictor in the TCGA liver cancer cohort. Conclusion These findings suggest that XDH is a valuable prognostic biomarker in HCC and other cancers and indicate that it may function in tumor immunology. Loss of XDH expression may be an immune evasion mechanism for HCC.

Identification of a new mutation in the human xanthine dehydrogenase responsible for xanthinuria type I

Objectives Hereditary xanthinuria is a rare, autosomal and recessive disorder characterized by severe hypouricemia and increased xanthine excretion, caused by a deficiency of xanthine dehydrogenase/oxidase (XDH/XO, EC: 1.17.1.4/1.17.3.2) in type I, or by a deficiency of XDH/XO and aldehyde oxidase (AOX, EC: 1.2.3.1) in type II. Case presentation We describe a novel point mutation in the XDH gene in homozygosis found in a patient with very low serum and urine levels of uric acid, together with xanthinuria. He was asymptomatic but renal calculi were discovered during imaging. Additional cases were found in his family and dietary recommendations were made in order to prevent further complications. Conclusions Hereditary xanthinuria is an underdiagnosed pathology, often found in a routine analysis that shows hypouricemia. It is important for Laboratory Medicine to acknowledge how to guide clinicians in the diagnosis.

AB0049 RELATIONSHIP OF RHEUMATOID FACTOR AND XANTHINE OXIDOREDUCTASE ENZYMATIC CONSTITUENTS IN SEVERAL BLOOD COMPARTMENTS OF RHEUMATOID ARTHRITIC PATIENTS

Background:Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by the presence of rheumatoid factor (RF) and anticitrulline autoantibodies. Recent evidences suggest that impairment of neutrophil extracellular traps (NETs) could exert substantial influence on RA pathogenesis. The production of NETs depends heavily on the ROS generation. One of its mechanisms is xanthine oxidoreductase (XOR) mediated degradation of purine metabolites. Analysis of pro-oxidant activity of the enzymatic complex XOR and its constituents, xanthine oxidase (XO) and xanthine dehydrogenase (XDG), is an issue of considerable interest in this context.Objectives:Evaluation of XO and XDG activities in RF-positive and RF-negative RA using both plasma and lysed lymphocyte samples.Methods:The research was carried out in agreement with the WMA Declaration of Helsinki principles. Diagnosis of RA had been verified using ACR/EULAR 2010 criteria. Enzymatic activities in plasma and lymphocytes were measured spectrophotometrically and expressed as nmol/min/ml. Enzymatic activities in lymphocytes were also normalized to 1×107 cells/ml. Statististical tests were selected in line with common guidelines. Differences were considered significant when p<0.05. Reference ranges were calculated as means ±2SD.Results:75 adult RA patients (52 females and 23 males, mean age 43.9±0.97 years, mean disease duration 8.5±0.3 years) from the rheumatology unit of Volgograd Clinical Emergency Hospital #25 as well as 35 healthy controls were included in the study. RF-positive RA and RF-negative RA were observed in 49 (65.3%) and 26 (34.7%) patients, respectively. Reference ranges for plasma and lymphocyte XO activities were 2.60-3.96 and 14.2-27.8 nmol/min/ml, respectively. Similar ranges for XDG activities were 4.49-5.93 and 22.5-40.7 nmol/min/ml, respectively. Enzymatic profile of RA patients is characterized by significantly increased XO activity in plasma and decreased XO and XDG activities in lymphocytes (р<0.001). XO activity is increased (p<0.001), XDG activity is decreased (p<0.001) in blood plasma of patients with RF-negative RA, while the activity of both enzymes is decreased in lymphocytes (p<0.001). XO activity (p<0.001) and XDG activity (p<0.05) is increased in blood plasma, XO activity and XDG activity are decreased (p<0.001) in lymphocytes of patients with RF-positive RA. Plasma XO and XDG activities are also higher, and lymphocyte XO and XDG activities are lower in patients with RF-positive RA than in patients with RF-negative RA (р<0.001).Conclusion:Our study revealed the relationship between enzyme parameters and rheumatoid factor presence. More pronounced changes in the enzyme activities were observed in patients with RF-positive RA. These results demonstrate that activation of the xanthine oxidase/xanthine dehydrogenase enzyme complex is an substantial factor of induction and continuation of the autoimmune rheumatoid inflammation.Disclosure of Interests:None declared

AB0841 ALTERED XANTHINE OXIDASE AND XANTHINE DEHYDROGENASE ACTIVITIES IN RED BLOOD CELLS AS A CONTRIBUTION TO AUTOIMMUNE ANEMIA APPEARANCE IN RHEUMATOID ARTHRITIS

Background:Rheumatoid arthritis (RA) is severe autoimmune joint disease, accompanied by a wide variety of extra-articular manifestations. Anemia is one of the most common organ involvements in RA, being diagnosed in 36-65% patients. Iron metabolism alterations, shortened RBC lifespan, and impaired erythropoiesis in bone marrow are believed to play a leading role in RA-related anemia development. These processes in RA can be mediated by increased effect of proinflammatory cytokines, including IFNγ and TNFα, and similar mechanisms could contribute to high xanthine oxidoreductase (XOR) expression. This enzyme makes multiple pathophysiological effects, some of which can be related to the development of anemia in RA. Reactive oxygen species generated by XOR are capable, in particular, of damaging cell membranes, exerting influence on iron mobilization from ferritin in liver, and inducing changes in intestinal iron absorption.Objectives:Evaluation of changes in XOR interconvertible forms (xanthine oxidase and xanthine dehydrogenase) activities in RBC of RA patients.Methods:The research was carried out in agreement with the WMA Declaration of Helsinki principles. 75 RA patients with verified RA were enrolled in the study. The diagnosis was verified using the ACR/EULAR criteria (2010). The reference group consisted of 35 healthy individuals. Хanthine oxidase (XO, ЕС 1.17.3.2) and xanthine dehydrogenase (XDG, ЕС 1.17.1.4) activities were measured in lysed red blood cells by spectrophotometric method as previously described [1]. The enzymatic activities were expressed as nmol/min/ml and normalized to 1×109 cells/ml. Statistical comparison tests were selected in according to common guidelines. Central tendencies were expressed as means±SEM. Differences were considered significant when p<0.05.Results:Mean age of RA patients was 43.9±0.97 years, and mean RA duration was 8.5±0.3 years. Extra-articular manifestations were diagnosed in 32 (42.7%) RA patients and 17 (53.1%) of them had anemia. We revealed substantial changes in XO and XDG activities in lysed RBC of RA patients with anemia. Increased XO activity and decreased XDG activity were observed in comparison with healthy controls (р<0.001 for both enzymes). In parallel with the increase in DAS28 index, significant growth of XOD/XDG coefficient was observed, which was caused by both XOD activity elevation and XDG activity reduction in lysed RBC (p<0.001 for both enzymes). Enzymatic activities depended also on the extra-articular RA manifestations. Mean XO activity was higher and mean XDG activity were lower in patients with extra-articular manifestations (p<0.05 for both enzymes), but the extent of changes was substantially less comparing to anemia.Conclusion:Autoimmune inflammation in RA is accompanied by changes in enzymatic activities of XOR interconvertible forms and their ratio. Transformation of XDG into КО ultimately leads to significant increase in the generation of reactive oxygen species that have a damaging effect on lipids, proteins and other cellular components, and specifically in RBC. This fact may be one of the reasons for their premature damage and development of anemia in RA.References:[1]Zborovskaya I.A., et al. Influence of analgetics on plasma and lymphocytic activity of the purine metabolism enzymes in rheumatoid arthritis patients. Russian Journal of Pain 2018;3:47Disclosure of Interests:None declared

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.References:[1]Mateen S., et al. Increased reactive oxygen species formation and oxidative stress in rheumatoid arthritis. PLoS ONE 2016;11(4):e0152925.[2]Çimen M.Y., et al. Oxidant/antioxidant status of the erythrocytes from patients with rheumatoid arthritis. Clin Rheumatol 2000;19(4):275-277.[3]Zborovskaya I.A., et al. Influence of analgetics on plasma and lymphocytic activity of the purine metabolism enzymes in rheumatoid arthritis patients. Russian Journal of Pain 2018;3:47.[4]Mozgovaya E.E., et al. Xanthinoxidase and xanthine dehydrogenase activities in rheumatoid arthritis after glucocorticoid treatment. Osteoporosis International 2019;30(2):S433-434.Disclosure of Interests:None declared

Similar solutions to a common challenge: Regulation of genes encoding Ralstonia solanacearum xanthine dehydrogenase

The stringent response involves accumulation of (p)ppGpp, and it ensures that survival is prioritized. Production of (p)ppGpp requires purine synthesis, and upregulation of an operon that encodes the purine salvage enzyme xanthine dehydrogenase (Xdh) has been observed during stringent response in some bacterial species, where direct binding of ppGpp to a TetR-family transcription factor is responsible for increased xdh gene expression. We show here that the plant pathogen Ralstonia solanacearum has a regulatory system in which the LysR-family transcription factor XanR controls expression of the xan operon; this operon encodes Xdh as well as other enzymes involved in purine salvage, which favor accumulation of xanthine. XanR bound upstream of the xan operon, a binding that was attenuated on addition of either ppGpp or cyclic di-guanosine monophosphate (c-di-GMP). Using a reporter in which enhanced green fluorescent protein (EGFP) is expressed under control of a modified xan promoter, XanR was shown to repress EGFP production. Our data suggest that R. solanacearum features a regulatory mechanism in which expression of genes encoding purine salvage enzymes is controlled by a transcription factor that belongs to a different protein family, yet performs similar regulatory functions.