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Korsmo HW, Ekperikpe US, Daehn IS. Emerging Roles of Xanthine Oxidoreductase in Chronic Kidney Disease. Antioxidants (Basel) 2024; 13:712. [PMID: 38929151 PMCID: PMC11200862 DOI: 10.3390/antiox13060712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 06/09/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
Xanthine Oxidoreductase (XOR) is a ubiquitous, essential enzyme responsible for the terminal steps of purine catabolism, ultimately producing uric acid that is eliminated by the kidneys. XOR is also a physiological source of superoxide ion, hydrogen peroxide, and nitric oxide, which can function as second messengers in the activation of various physiological pathways, as well as contribute to the development and the progression of chronic conditions including kidney diseases, which are increasing in prevalence worldwide. XOR activity can promote oxidative distress, endothelial dysfunction, and inflammation through the biological effects of reactive oxygen species; nitric oxide and uric acid are the major products of XOR activity. However, the complex relationship of these reactions in disease settings has long been debated, and the environmental influences and genetics remain largely unknown. In this review, we give an overview of the biochemistry, biology, environmental, and current clinical impact of XOR in the kidney. Finally, we highlight recent genetic studies linking XOR and risk for kidney disease, igniting enthusiasm for future biomarker development and novel therapeutic approaches targeting XOR.
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Affiliation(s)
| | | | - Ilse S. Daehn
- Department of Medicine, Division of Nephrology, The Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, Box 1243, New York, NY 10029, USA
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2
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Pimviriyakul P, Sucharitakul J, Maenpuen S. Mechanistic insights into iron-sulfur clusters and flavin oxidation of a novel xanthine oxidoreductase from Sulfobacillus acidophilus TPY. FEBS J 2024; 291:527-546. [PMID: 37899720 DOI: 10.1111/febs.16987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 10/04/2023] [Accepted: 10/24/2023] [Indexed: 10/31/2023]
Abstract
Xanthine oxidoreductase (XOR) catalyzes the oxidation of purines (hypoxanthine and xanthine) to uric acid. XOR is widely used in various therapeutic and biotechnological applications. In this study, we characterized the biophysical and mechanistic properties of a novel bacterial XOR from Sulfobacillus acidophilus TPY (SaXOR). Our results showed that SaXOR is a heterotrimer consisting of three subunits, namely XoA, XoB, and XoC, which denote the molybdenum cofactor (Moco), 2Fe-2S, and FAD-binding domains, respectively. XoC was found to be stable when co-expressed with XoB, forming an XoBC complex. Furthermore, we prepared a fusion of XoB and XoC via a flexible linker (fusXoBC) and evaluated its function in comparison to that of XoBC. Spectroscopic analysis revealed that XoB harbors two 2Fe-2S clusters, whereas XoC bears a single-bound FAD cofactor. Electron transfer from reduced forms of XoC, XoBC, and fusXoBC to molecular oxygen (O2 ) during oxidative half-reaction yielded no flavin semiquinones, implying ultrafast single-electron transfer from 2Fe-2Sred to FAD. In the presence of XoA, XoBC and fusXoBC exhibited comparable XoA affinity and exploited a shared overall mechanism. Nonetheless, the linkage may accelerate the two-step, single-electron transfer cascade from 2Fe-2Sred to FAD while augmenting protein stability. Collectively, our findings provide novel insights into SaXOR properties and oxidation mechanisms divergent from prior mammalian and bacterial XOR paradigms.
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Affiliation(s)
- Panu Pimviriyakul
- Department of Biochemistry, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Jeerus Sucharitakul
- Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
- Skeletal Disorders Research Unit, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Somchart Maenpuen
- Department of Biochemistry, Faculty of Science, Burapha University, Chonburi, Thailand
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3
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Matsuoka M, Yamaguchi J, Kinoshita K. Clinical Significance of Elevated Xanthine Dehydrogenase Levels and Hyperuricemia in Patients with Sepsis. Int J Mol Sci 2023; 24:13857. [PMID: 37762160 PMCID: PMC10530551 DOI: 10.3390/ijms241813857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
Patient outcomes for severe sepsis and septic shock remain poor. Excessive oxidative stress accelerates organ dysfunction in severe acute illnesses. Uric acid (UA) is the most abundant antioxidant. We hypothesized that UA and related molecules, which play a critical role in antioxidant activity, might be markers of oxidative stress in sepsis. The study aimed to clarify the clinical significance of UA and the relationship between UA, molecules related to UA, and outcomes by measuring blood UA, xanthine dehydrogenase (XDH), and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels over time. Blood UA levels in septic patients were correlated with the SOFA score (ρ = 0.36, p < 0.0001) and blood XDH levels (ρ = 0.27, p < 0.0001). Blood XDH levels were correlated with the SOFA score (ρ = 0.59, p < 0.0001) and blood 8-OHdG levels (ρ = -0.32, p < 0.0001). Blood XDH levels were persistently high in fatal cases. Blood XDH level (OR 8.84, 95% CI: 1.42-91.2, p = 0.018) was an independent factor of poor outcomes. The cutoff of blood XDH level was 1.38 ng/mL (sensitivity 92.8%, specificity 61.9%), and those 1.38 ng/mL or higher were associated with a significantly reduced survival rate (blood XDH level > 1.38 ng/mL: 23.7%, blood XDH level < 1.38 ng/mL: 96.3%, respectively, p = 0.0007). Elevated UA levels due to elevated blood XDH levels in sepsis cases may reduce oxidative stress. Countermeasures against increased oxidative stress in sepsis may provide new therapeutic strategies.
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Affiliation(s)
| | - Junko Yamaguchi
- Division of Emergency and Critical Care Medicine, Department of Acute Medicine, Nihon University School of Medicine, 30-1, Oyaguchi Kami-cho, Itabashi-ku, Tokyo 173-8610, Japan; (M.M.); (K.K.)
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4
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Rullo R, Cerchia C, Nasso R, Romanelli V, Vendittis ED, Masullo M, Lavecchia A. Novel Reversible Inhibitors of Xanthine Oxidase Targeting the Active Site of the Enzyme. Antioxidants (Basel) 2023; 12:antiox12040825. [PMID: 37107199 PMCID: PMC10135315 DOI: 10.3390/antiox12040825] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023] Open
Abstract
Xanthine oxidase (XO) is a flavoprotein catalysing the oxidation of hypoxanthine to xanthine and then to uric acid, while simultaneously producing reactive oxygen species. Altered functions of XO may lead to severe pathological diseases, including gout-causing hyperuricemia and oxidative damage of tissues. These findings prompted research studies aimed at targeting the activity of this crucial enzyme. During the course of a virtual screening study aimed at the discovery of novel inhibitors targeting another oxidoreductase, superoxide dismutase, we identified four compounds with non-purine-like structures, namely ALS-1, -8, -15 and -28, that were capable of causing direct inhibition of XO. The kinetic studies of their inhibition mechanism allowed a definition of these compounds as competitive inhibitors of XO. The most potent molecule was ALS-28 (Ki 2.7 ± 1.5 µM), followed by ALS-8 (Ki 4.5 ± 1.5 µM) and by the less potent ALS-15 (Ki 23 ± 9 µM) and ALS-1 (Ki 41 ± 14 µM). Docking studies shed light on the molecular basis of the inhibitory activity of ALS-28, which hinders the enzyme cavity channel for substrate entry consistently with the competitive mechanism observed in kinetic studies. Moreover, the structural features emerging from the docked poses of ALS-8, -15 and -1 may explain the lower inhibition power with respect to ALS-28. All these structurally unrelated compounds represent valuable candidates for further elaboration into promising lead compounds.
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5
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Wen Y, Xu J, Pan D, Wang C. Removal of substrate inhibition of Acinetobacter baumannii xanthine oxidase by point mutation at Gln-201 enables efficient reduction of purine content in fish sauce. Food Chem X 2023; 17:100593. [PMID: 36845495 PMCID: PMC9944496 DOI: 10.1016/j.fochx.2023.100593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 02/02/2023] [Accepted: 02/02/2023] [Indexed: 02/09/2023] Open
Abstract
Xanthine oxidase is an oxidase that has a molybdopterin structure with substrate inhibition. Here, we show that a single point mutation (Q201) in the Acinetobacter baumannii xanthine oxidase (AbXOD) obtained mutant Q201E (k cat =799.44 s-1, no inhibition) with high enzyme activity and decrease of substrate inhibition in 5 mmol/L high substrate model, and which cause two loops structure change at active center, characterized by complete loss of substrate inhibition without reduction of enzymatic activity. Molecular docking results showed that the change of flexible loop increased the affinity between substrate and enzyme, and the formation of a π-π bond and two hydrogen bonds made the substrate more stable in the active center. Ultimately, Q201E can still maintain better enzyme activity under high purine content (an approximately 7-fold improvement over the wild-type), indicating a broader application prospect in the manufacture of low-purine food.
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Affiliation(s)
| | | | | | - Chenghua Wang
- Corresponding author at: College of Light Industry and Food Engineering, 100 Daxue East Road, Nanning 530004, People’s Republic of China.
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6
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Kusano T, Nishino T, Okamoto K, Hille R, Nishino T. The mechanism and significance of the conversion of xanthine dehydrogenase to xanthine oxidase in mammalian secretory gland cells. Redox Biol 2022; 59:102573. [PMID: 36525890 PMCID: PMC9760657 DOI: 10.1016/j.redox.2022.102573] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/03/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
The conversion of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) occurs only in mammalian species. In fresh bovine milk, the enzyme exists predominantly as the oxidase form, in contrast to various normal organs where it is found primarily as the dehydrogenase: the mechanism of conversion to the oxidase in milk remains obscure. A systematic search for the essential factors for conversion from XDH to XO has been performed within fresh bovine milk using the highly purified dehydrogenase form after removal endogenous oxidase form by fractionation analysis. We find that conversion to the oxidase form requires four components under air: lactoperoxidase (LPO), XDH, SCN-, and substrate hypoxanthine or xanthine; the contribution of sulfhydryl oxidase appears to be minor. Disulfide bond formation between Cys-535 and Cys-995 is principally involved in the conversion, consistent with the result obtained from previous work with transgenic mice. In vitro reconstitution of LPO and SCN- results in synergistic conversion of the dehydrogenase to the oxidase the presence of xanthine, indicating the conversion is autocatalytic. Milk from an LPO knockout mouse contains a significantly greater proportion of the dehydrogenase form of the enzyme, although some oxidase form is also present, indicating that LPO contributes principally to the conversion, but that sulfhydryl oxidase (SO) may also be involved to a minor extent. All the components XDH/LPO/SCN- are necessary to inhibit bacterial growth in the presence of xanthine through disulfide bond formation in bacterial protein(s) required for replication, as part of an innate immunity system in mammals. Human GTEx Data suggest that mRNA of XDH and LPO are highly co-expressed in the salivary gland, mammary gland, mucosa of the airway and lung alveoli, and we have confirmed these human GTEx Data experimentally in mice. We discuss the possible roles of these components in the propagation of SARS-CoV-2 in these human cell types.
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Affiliation(s)
- Teruo Kusano
- Department of Biochemistry and Molecular Biology, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-Ku, Tokyo, Japan
| | - Tomoko Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-Ku, Tokyo, Japan
| | - Ken Okamoto
- Department of Biochemistry and Molecular Biology, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-Ku, Tokyo, Japan
| | - Russ Hille
- Department of Biochemistry, University of California, Riverside, USA
| | - Takeshi Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-Ku, Tokyo, Japan.
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7
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Skeletal muscle as a reservoir for nitrate and nitrite: The role of xanthine oxidase reductase (XOR). Nitric Oxide 2022; 129:102-109. [DOI: 10.1016/j.niox.2022.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 09/16/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
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8
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Dogan SA, Giacchin G, Zito E, Viscomi C. Redox Signaling and Stress in Inherited Myopathies. Antioxid Redox Signal 2022; 37:301-323. [PMID: 35081731 DOI: 10.1089/ars.2021.0266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Significance: Reactive oxygen species (ROS) are highly reactive compounds that behave like a double-edged sword; they damage cellular structures and act as second messengers in signal transduction. Mitochondria and endoplasmic reticulum (ER) are interconnected organelles with a central role in ROS production, detoxification, and oxidative stress response. Skeletal muscle is the most abundant tissue in mammals and one of the most metabolically active ones and thus relies mainly on oxidative phosphorylation (OxPhos) to synthesize adenosine triphosphate. The impairment of OxPhos leads to myopathy and increased ROS production, thus affecting both redox poise and signaling. In addition, ROS enter the ER and trigger ER stress and its maladaptive response, which also lead to a myopathic phenotype with mitochondrial involvement. Here, we review the role of ROS signaling in myopathies due to either mitochondrial or ER dysfunction. Recent Advances: Relevant advances have been evolving over the last 10 years on the intricate ROS-dependent pathways that act as modifiers of the disease course in several myopathies. To this end, pathways related to mitochondrial biogenesis, satellite cell differentiation, and ER stress have been studied extensively in myopathies. Critical Issues: The analysis of the chemistry and the exact quantitation, as well as the localization of ROS, are still challenging due to the intrinsic labile nature of ROS and the technical limitations of their sensors. Future Directions: The mechanistic studies of the pathogenesis of mitochondrial and ER-related myopathies offer a unique possibility to discover novel ROS-dependent pathways. Antioxid. Redox Signal. 37, 301-323.
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Affiliation(s)
- Sukru Anil Dogan
- Department of Molecular Biology and Genetics, Center for Life Sciences and Technologies, Bogazici University, Istanbul, Turkey
| | - Giacomo Giacchin
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ester Zito
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy.,Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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9
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Čėnas N, Nemeikaitė-Čėnienė A, Kosychova L. Single- and Two-Electron Reduction of Nitroaromatic Compounds by Flavoenzymes: Mechanisms and Implications for Cytotoxicity. Int J Mol Sci 2021; 22:ijms22168534. [PMID: 34445240 PMCID: PMC8395237 DOI: 10.3390/ijms22168534] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 07/30/2021] [Accepted: 08/04/2021] [Indexed: 12/14/2022] Open
Abstract
Nitroaromatic compounds (ArNO2) maintain their importance in relation to industrial processes, environmental pollution, and pharmaceutical application. The manifestation of toxicity/therapeutic action of nitroaromatics may involve their single- or two-electron reduction performed by various flavoenzymes and/or their physiological redox partners, metalloproteins. The pivotal and still incompletely resolved questions in this area are the identification and characterization of the specific enzymes that are involved in the bioreduction of ArNO2 and the establishment of their contribution to cytotoxic/therapeutic action of nitroaromatics. This review addresses the following topics: (i) the intrinsic redox properties of ArNO2, in particular, the energetics of their single- and two-electron reduction in aqueous medium; (ii) the mechanisms and structure-activity relationships of reduction in ArNO2 by flavoenzymes of different groups, dehydrogenases-electrontransferases (NADPH:cytochrome P-450 reductase, ferredoxin:NADP(H) oxidoreductase and their analogs), mammalian NAD(P)H:quinone oxidoreductase, bacterial nitroreductases, and disulfide reductases of different origin (glutathione, trypanothione, and thioredoxin reductases, lipoamide dehydrogenase), and (iii) the relationships between the enzymatic reactivity of compounds and their activity in mammalian cells, bacteria, and parasites.
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Affiliation(s)
- Narimantas Čėnas
- Institute of Biochemistry of Vilnius University, Saulėtekio 7, LT-10257 Vilnius, Lithuania;
- Correspondence: ; Tel.: +370-5-223-4392
| | - Aušra Nemeikaitė-Čėnienė
- State Research Institute Center for Innovative Medicine, Santariškių St. 5, LT-08406 Vilnius, Lithuania;
| | - Lidija Kosychova
- Institute of Biochemistry of Vilnius University, Saulėtekio 7, LT-10257 Vilnius, Lithuania;
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10
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Xanthine Oxidase-Induced Inflammatory Responses in Respiratory Epithelial Cells: A Review in Immunopathology of COVID-19. Int J Inflam 2021; 2021:1653392. [PMID: 34367545 PMCID: PMC8346299 DOI: 10.1155/2021/1653392] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/09/2021] [Accepted: 07/19/2021] [Indexed: 01/16/2023] Open
Abstract
Xanthine oxidase (XO) is an enzyme that catalyzes the production of uric acid and superoxide radicals from purine bases: hypoxanthine and xanthine and is also expressed in respiratory epithelial cells. Uric acid, which is also considered a danger associated molecule pattern (DAMP), could trigger a series of inflammatory responses by activating the inflammasome complex path and NF-κB within the endothelial cells and by inducing proinflammatory cytokine release. Concurrently, XO also converts the superoxide radicals into hydroxyl radicals that further induce inflammatory responses. These conditions will ultimately sum up a hyperinflammation condition commonly dubbed as cytokine storm syndrome (CSS). The expression of proinflammatory cytokines and neutrophil chemokines may be reduced by XO inhibitor, as observed in human respiratory syncytial virus (HRSV)-infected A549 cells. Our review emphasizes that XO may have an essential role as an anti-inflammation therapy for respiratory viral infection, including coronavirus disease 2019 (COVID-19).
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11
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Xu L, Yang Y, Chen J. The role of reactive oxygen species in cognitive impairment associated with sleep apnea. Exp Ther Med 2020; 20:4. [PMID: 32934669 PMCID: PMC7471880 DOI: 10.3892/etm.2020.9132] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 02/07/2020] [Indexed: 02/07/2023] Open
Abstract
Obstructive sleep apnea (OSA), a common breathing and sleeping disorder, is associated with a broad range of neurocognitive difficulties. Intermittent hypoxia (IH), one major characteristic of OSA, has been shown to impair learning and memory due to increased levels of reactive oxygen species (ROS). Under normal conditions, ROS are produced in low concentrations and act as signaling molecules in different processes. However, IH treatment leads to elevated ROS production via multiple pathways, including mitochondrial electron transport chain dysfunction and in particular complex I dysfunction, and induces oxidative tissue damage. Moreover, elevated ROS results in the accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) and increased activity of peroxisomes, such as NADPH oxidase, xanthine oxidase and phospholipase A2. Furthermore, oxidative tissue damage has been found in regions of the brains of patients with OSA, including the cortex and hippocampus, which are associated with memory and executive function. Furthermore, increased ROS levels in these regions of the brain induce damage via inflammation, apoptosis, ER stress and neuronal activity disturbance. The present review focuses on the mechanism of excessive ROS production in an OSA model and the relationship between ROS and cognitive impairment.
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Affiliation(s)
- Linhao Xu
- Department of Cardiology, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310006, P.R. China.,Department of Pathology, School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, P.R. China.,Translational Medicine Research Center, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310006, P.R. China
| | - Yibo Yang
- College of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 201424, P.R. China
| | - Jian Chen
- Department of Pathology, School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, P.R. China
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12
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Nishikawa T, Nagata N, Shimakami T, Shirakura T, Matsui C, Ni Y, Zhuge F, Xu L, Chen G, Nagashimada M, Yamashita T, Sakai Y, Yamashita T, Mizukoshi E, Honda M, Kaneko S, Ota T. Xanthine oxidase inhibition attenuates insulin resistance and diet-induced steatohepatitis in mice. Sci Rep 2020; 10:815. [PMID: 31965018 PMCID: PMC6972756 DOI: 10.1038/s41598-020-57784-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 01/07/2020] [Indexed: 12/19/2022] Open
Abstract
Hyperuricemia drives the development of nonalcoholic fatty liver disease (NAFLD). Pharmacological inhibition of xanthine oxidase (XO), a rate-limiting enzyme for uric acid (UA) production, has been demonstrated to improve hepatic steatosis in diet-induced obese mice. However, it remains unclear whether inhibition of XO improves nonalcoholic steatohepatitis (NASH), a more advanced form of NAFLD, in terms of both liver inflammation and fibrosis. Here, we investigated the effects of febuxostat and allopurinol, two XO inhibitors clinically used for gout, on a mouse model of NASH. Furthermore, we conducted a single-arm, open-label intervention study with febuxostat for NAFLD patients with hyperuricemia. Despite a similar hypouricemic effect of the XO inhibitors on blood UA level, febuxostat, but not allopurinol, significantly decreased hepatic XO activity and UA levels in the NASH model mice. These reductions in hepatic XO activity and UA levels were accompanied by attenuation of insulin resistance, lipid peroxidation, and classically activated M1-like macrophage accumulation in the liver. Furthermore, in NAFLD patients with hyperuricemia, treatment with febuxostat for 24 weeks decreased the serum UA level, accompanied by reductions in the serum levels of liver enzymes, alanine aminotransferase and aspartate aminotransferase. XO may represent a promising therapeutic target in NAFLD/NASH, especially in patients with hyperuricemia.
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Affiliation(s)
- Tomoki Nishikawa
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Naoto Nagata
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.,Department of Cellular and Molecular Function Analysis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Tetsuro Shimakami
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Takashi Shirakura
- Pharmaceutical Development Research Laboratories, Teijin Institute for Bio-Medical Research, Teijin Pharma Limited, Hino, Japan
| | - Chieko Matsui
- Pharmaceutical Development Research Laboratories, Teijin Institute for Bio-Medical Research, Teijin Pharma Limited, Hino, Japan
| | - Yinhua Ni
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Fen Zhuge
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Liang Xu
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Guanliang Chen
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Mayumi Nagashimada
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Taro Yamashita
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Yoshio Sakai
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Tatsuya Yamashita
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.,Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Eishiro Mizukoshi
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Masao Honda
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Shuichi Kaneko
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Tsuguhito Ota
- Department of Cell Metabolism and Nutrition, Advanced Preventive Medical Sciences Research Center, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan. .,Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Asahikawa, Japan.
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13
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ROS Generation and Antioxidant Defense Systems in Normal and Malignant Cells. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:6175804. [PMID: 31467634 PMCID: PMC6701375 DOI: 10.1155/2019/6175804] [Citation(s) in RCA: 408] [Impact Index Per Article: 81.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 06/24/2019] [Indexed: 02/08/2023]
Abstract
Reactive oxygen species (ROS) are by-products of normal cell activity. They are produced in many cellular compartments and play a major role in signaling pathways. Overproduction of ROS is associated with the development of various human diseases (including cancer, cardiovascular, neurodegenerative, and metabolic disorders), inflammation, and aging. Tumors continuously generate ROS at increased levels that have a dual role in their development. Oxidative stress can promote tumor initiation, progression, and resistance to therapy through DNA damage, leading to the accumulation of mutations and genome instability, as well as reprogramming cell metabolism and signaling. On the contrary, elevated ROS levels can induce tumor cell death. This review covers the current data on the mechanisms of ROS generation and existing antioxidant systems balancing the redox state in mammalian cells that can also be related to tumors.
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14
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Lv Y, Gao X, Luo Y, Fan W, Shen T, Ding C, Yao M, Song S, Yan L. Apigenin ameliorates HFD-induced NAFLD through regulation of the XO/NLRP3 pathways. J Nutr Biochem 2019; 71:110-121. [PMID: 31325892 DOI: 10.1016/j.jnutbio.2019.05.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/21/2019] [Accepted: 05/21/2019] [Indexed: 12/25/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is the most common cause of liver-related morbidity and mortality disease in the world. However, no effective pharmacological treatment for NAFLD has been found. In this study, we used a high fat diet (HFD)-induced NAFLD model to investigate hepatoprotective effect of apigenin (API) against NAFLD and further explored its potential mechanism. Our results demonstrated that gavage administration of API could mitigate HFD-induced liver injury, enhance insulin sensitivity and markedly reduce lipid accumulation in HFD-fed mice livers. In addition, histological analysis showed that hepatic steatosis and macrophages recruitment in the API treatment group were recovered compared with mice fed with HFD alone. Importantly, API could reverse the HFD-induced activation of the NLRP3 inflammasome, further reduced inflammatory cytokines IL-1β and IL-18 release, accompanied with the inhibition of xanthine oxidase (XO) activity and the reduction of uric acid and reactive oxygen species (ROS) production. The pharmacological role of API was further confirmed using free fatty acid (FFA) induced cell NAFLD model. Taking together, our results demonstrated that API could protect against HFD-induced NAFLD by ameliorating hepatic lipid accumulation and inflammation. These protective effects may be partially attributed to the regulation of XO by API, which further modulated NLRP3 inflammasome activation and inflammatory cytokines IL-1β and IL-18 release. Therefore API is a potential therapeutic agent for the prevention of NAFLD.
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Affiliation(s)
- Yanan Lv
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Xiaona Gao
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Yan Luo
- Administration for Market Regulation of GuangDong Province Key Laboratory of Supervision for Edible Agricultural Products, Shenzhen Centre of Inspection and Testing for Agricultural Products, Shenzhen 518000, GuangDong Province, China
| | - Wentao Fan
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Tongtong Shen
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Chenchen Ding
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Ming Yao
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China
| | - Suquan Song
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China.
| | - Liping Yan
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China; Jiangsu Engineering Laboratory of Animal Immunology, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, Jiangsu Province, China.
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15
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Kelley EE. Diminishing Inflammation by Reducing Oxidant Generation: Nitrated Fatty Acid-Mediated Inactivation of Xanthine Oxidoreductase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1127:59-65. [PMID: 31140171 DOI: 10.1007/978-3-030-11488-6_4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Inhibition of xanthine oxidoreductase (XOR) has proven beneficial in a plethora of inflammatory disease processes due to a net reduction in pro-inflammatory oxidants and secondary nitrating species. Electrophilic nitrated fatty acid derivatives, such as nitro-oleic acid (OA-NO2) are also noted to display a broad spectrum of anti-inflammatory effects via interaction with critical signaling pathways. An alternative process in which nitrated fatty acids may extend anti-inflammatory actions is via inactivation of XOR, a process that is more effective than allo/oxypurinol-mediated inhibition. Herein, we describe the molecular aspects of nitrated fatty acid-associated inactivation of XOR, identify specificity via structure function relationships and discuss XOR as a crucial component of the anti-inflammatory portfolio of nitrated fatty acids.
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Affiliation(s)
- Eric E Kelley
- Department of Physiology and Pharmacology, West Virginia University, Morgantown, WV, USA.
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16
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Fais A, Era B, Asthana S, Sogos V, Medda R, Santana L, Uriarte E, Matos MJ, Delogu F, Kumar A. Coumarin derivatives as promising xanthine oxidase inhibitors. Int J Biol Macromol 2018; 120:1286-1293. [DOI: 10.1016/j.ijbiomac.2018.09.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/31/2018] [Accepted: 09/01/2018] [Indexed: 01/01/2023]
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17
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Bender D, Schwarz G. Nitrite-dependent nitric oxide synthesis by molybdenum enzymes. FEBS Lett 2018; 592:2126-2139. [DOI: 10.1002/1873-3468.13089] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 05/02/2018] [Indexed: 01/07/2023]
Affiliation(s)
- Daniel Bender
- Department of Chemistry; Institute for Biochemistry; University of Cologne; Germany
- Center for Molecular Medicine Cologne (CMMC); University of Cologne; Germany
| | - Guenter Schwarz
- Department of Chemistry; Institute for Biochemistry; University of Cologne; Germany
- Center for Molecular Medicine Cologne (CMMC); University of Cologne; Germany
- Cologne Cluster of Excellence in Cellular Stress Responses in Aging-associated Diseases (CECAD); University of Cologne; Germany
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18
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Kanemitsu T, Tsurudome Y, Kusunose N, Oda M, Matsunaga N, Koyanagi S, Ohdo S. Periodic variation in bile acids controls circadian changes in uric acid via regulation of xanthine oxidase by the orphan nuclear receptor PPARα. J Biol Chem 2017; 292:21397-21406. [PMID: 29101234 DOI: 10.1074/jbc.m117.791285] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 11/01/2017] [Indexed: 12/16/2022] Open
Abstract
Xanthine oxidase (XOD), also known as xanthine dehydrogenase, is a rate-limiting enzyme in purine nucleotide degradation, which produces uric acid. Uric acid concentrations in the blood and liver exhibit circadian oscillations in both humans and rodents; however, the underlying mechanisms remain unclear. Here, we demonstrate that XOD expression and enzymatic activity exhibit circadian oscillations in the mouse liver. We found that the orphan nuclear receptor peroxisome proliferator-activated receptor-α (PPARα) transcriptionally activated the mouse XOD gene and that bile acids suppressed XOD transactivation. The synthesis of bile acids is known to be under the control of the circadian clock, and we observed that the time-dependent accumulation of bile acids in hepatic cells interfered with the recruitment of the co-transcriptional activator p300 to PPARα, thereby repressing XOD expression. This time-dependent suppression of PPARα-mediated transactivation by bile acids caused an oscillation in the hepatic expression of XOD, which, in turn, led to circadian alterations in uric acid production. Finally, we also demonstrated that the anti-hyperuricemic effect of the XOD inhibitor febuxostat was enhanced by administering it at the time of day before hepatic XOD activity increased. These results suggest an underlying mechanism for the circadian alterations in uric acid production and also underscore the importance of selecting an appropriate time of day for administering XOD inhibitors.
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Affiliation(s)
| | | | | | | | - Naoya Matsunaga
- From the Departments of Pharmaceutics and.,Glocal Healthcare Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Satoru Koyanagi
- From the Departments of Pharmaceutics and.,Glocal Healthcare Science, Kyushu University, Fukuoka 812-8582, Japan
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19
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Li W, Yang S. Targeting oxidative stress for the treatment of ischemic stroke: Upstream and downstream therapeutic strategies. Brain Circ 2016; 2:153-163. [PMID: 30276293 PMCID: PMC6126224 DOI: 10.4103/2394-8108.195279] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/04/2016] [Accepted: 07/13/2016] [Indexed: 12/27/2022] Open
Abstract
Excessive oxygen and its chemical derivatives, namely reactive oxygen species (ROS), produce oxidative stress that has been known to lead to cell injury in ischemic stroke. ROS can damage macromolecules such as proteins and lipids and leads to cell autophagy, apoptosis, and necrosis to the cells. This review describes studies on the generation of ROS, its role in the pathogenesis of ischemic stroke, and recent development in therapeutic strategies in reducing oxidative stress after ischemic stroke.
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Affiliation(s)
- Wenjun Li
- Center for Neuroscience Discovery, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Shaohua Yang
- Center for Neuroscience Discovery, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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20
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Simultaneous Determination of Uric Acid, Xanthine and Hypoxanthine in Human Plasma and Serum by HPLC–UV: Uric Acid Metabolism Tracking. Chromatographia 2016. [DOI: 10.1007/s10337-016-3208-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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21
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Kelley EE. A new paradigm for XOR-catalyzed reactive species generation in the endothelium. Pharmacol Rep 2015; 67:669-74. [PMID: 26321266 DOI: 10.1016/j.pharep.2015.05.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 05/06/2015] [Accepted: 05/08/2015] [Indexed: 01/14/2023]
Abstract
A plethora of vascular pathology is associated with inflammation, hypoxia and elevated rates of reactive species generation. A critical source of these reactive species is the purine catabolizing enzyme xanthine oxidoreductase (XOR) as numerous reports over the past 30 years have demonstrated XOR inhibition to be salutary. Despite this long standing association between increased vascular XOR activity and negative clinical outcomes, recent reports reveal a new paradigm whereby the enzymatic activity of XOR mediates beneficial outcomes by catalyzing the one electron reduction of nitrite (NO2(-)) to nitric oxide (NO) when NO2(-) and/or nitrate (NO3(-)) levels are enhanced either via dietary or pharmacologic means. These observations seemingly countervail numerous reports of improved outcomes in similar models upon XOR inhibition in the absence of NO2(-) treatment affirming the need for a more clear understanding of the mechanisms underpinning the product identity of XOR. To establish the micro-environmental conditions requisite for in vivo XOR-catalyzed oxidant and NO production, this review assesses the impact of pH, O2 tension, enzyme-endothelial interactions, substrate concentrations and catalytic differences between xanthine oxidase (XO) and xanthine dehydrogenase (XDH). As such, it reveals critical information necessary to distinguish if pursuit of NO2(-) supplementation will afford greater benefit than inhibition strategies and thus enhance the efficacy of current approaches to treat vascular pathology.
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Affiliation(s)
- Eric E Kelley
- University of Pittsburgh, School of Medicine, Department of Anesthesiology and Vascular Medicine Institute, Pittsburgh, USA.
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22
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Kelley EE. Dispelling dogma and misconceptions regarding the most pharmacologically targetable source of reactive species in inflammatory disease, xanthine oxidoreductase. Arch Toxicol 2015; 89:1193-207. [PMID: 25995007 DOI: 10.1007/s00204-015-1523-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 04/27/2015] [Indexed: 01/04/2023]
Abstract
Xanthine oxidoreductase (XOR), the molybdoflavin enzyme responsible for the terminal steps of purine degradation in humans, is also recognized as a significant source of reactive species contributory to inflammatory disease. In animal models and clinical studies, inhibition of XOR has resulted in diminution of symptoms and enhancement of function in a number of pathologies including heart failure, diabetes, sickle cell anemia, hypertension and ischemia-reperfusion injury. For decades, XOR involvement in pathologic processes has been established by salutary outcomes attained from treatment with the XOR inhibitor allopurinol. This has served to frame a working dogma that elevation of XOR-specific activity is associated with enhanced rates of reactive species generation that mediate negative outcomes. While adherence to this narrowly focused practice of designating elevated XOR activity to be "bad" has produced some benefit, it has also led to significant underdevelopment of the processes mediating XOR regulation, identification of alternative reactants and products as well as micro-environmental factors that alter enzymatic activity. This is exemplified by recent reports: (1) identifying XOR as a nitrite reductase and thus a source of beneficial nitric oxide ((•)NO) under in vivo conditions similar to those where XOR inhibition has been assumed an optimal treatment choice, (2) describing XOR-derived uric acid (UA) as a critical pro-inflammatory mediator in vascular and metabolic disease and (3) ascribing an antioxidant/protective role for XOR-derived UA. When taken together, these proposed and countervailing functions of XOR affirm the need for a more comprehensive evaluation of product formation as well as the factors that govern product identity. As such, this review will critically evaluate XOR-catalyzed oxidant, (•)NO and UA formation as well as identify factors that mediate their production, inhibition and the resultant impact on inflammatory disease.
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Affiliation(s)
- Eric E Kelley
- Department of Anesthesiology and Vascular Medicine Institute, School of Medicine, University of Pittsburgh, W1357 BST, 200 Lothrop Street, Pittsburgh, PA, 15213, USA,
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23
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Nitrite reduction by molybdoenzymes: a new class of nitric oxide-forming nitrite reductases. J Biol Inorg Chem 2015; 20:403-33. [DOI: 10.1007/s00775-014-1234-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/14/2014] [Indexed: 02/07/2023]
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24
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Affiliation(s)
- Luisa B. Maia
- REQUIMTE/CQFB, Departamento
de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - José J. G. Moura
- REQUIMTE/CQFB, Departamento
de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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25
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Structural and functional insights into the catalytic inactivity of the major fraction of buffalo milk xanthine oxidoreductase. PLoS One 2014; 9:e87618. [PMID: 24498153 PMCID: PMC3909206 DOI: 10.1371/journal.pone.0087618] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 12/26/2013] [Indexed: 12/13/2022] Open
Abstract
Background Xanthine oxidoreductase (XOR) existing in two interconvertible forms, xanthine dehydrogenase (XDH) and xanthine oxidase (XO), catabolises xanthine to uric acid that is further broken down to antioxidative agent allantoin. XOR also produces free radicals serving as second messenger and microbicidal agent. Large variation in the XO activity has been observed among various species. Both hypo and hyper activity of XOR leads to pathophysiological conditions. Given the important nutritional role of buffalo milk in human health especially in south Asia, it is crucial to understand the functional properties of buffalo XOR and the underlying structural basis of variations in comparison to other species. Methods and Findings Buffalo XO activity of 0.75 U/mg was almost half of cattle XO activity. Enzymatic efficiency (kcat/Km) of 0.11 sec−1 µM−1 of buffalo XO was 8–10 times smaller than that of cattle XO. Buffalo XOR also showed lower antibacterial activity than cattle XOR. A CD value (Δε430 nm) of 46,000 M−1 cm−1 suggested occupancy of 77.4% at Fe/S I centre. Buffalo XOR contained 0.31 molybdenum atom/subunit of which 48% existed in active sulfo form. The active form of XO in buffalo was only 16% in comparison to ∼30% in cattle. Sequencing revealed 97.4% similarity between buffalo and cattle XOR. FAD domain was least conserved, while metal binding domains (Fe/S and Molybdenum) were highly conserved. Homology modelling of buffalo XOR showed several variations occurring in clusters, especially close to FAD binding pocket which could affect NAD+ entry in the FAD centre. The difference in XO activity seems to be originating from cofactor deficiency, especially molybdenum. Conclusion A major fraction of buffalo milk XOR exists in a catalytically inactive form due to high content of demolybdo and desulfo forms. Lower Fe/S content and structural factors might be contributing to lower enzymatic efficiency of buffalo XOR in a minor way.
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26
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Xanthine oxidoreductase-catalyzed reactive species generation: A process in critical need of reevaluation. Redox Biol 2013; 1:353-8. [PMID: 24024171 PMCID: PMC3757702 DOI: 10.1016/j.redox.2013.05.002] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 05/19/2013] [Indexed: 12/13/2022] Open
Abstract
Nearly 30 years have passed since the discovery of xanthine oxidoreductase (XOR) as a critical source of reactive species in ischemia/reperfusion injury. Since then, numerous inflammatory disease processes have been associated with elevated XOR activity and allied reactive species formation solidifying the ideology that enhancement of XOR activity equates to negative clinical outcomes. However, recent evidence may shatter this paradigm by describing a nitrate/nitrite reductase capacity for XOR whereby XOR may be considered a crucial source of beneficial (•)NO under ischemic/hypoxic/acidic conditions; settings similar to those that limit the functional capacity of nitric oxide synthase. Herein, we review XOR-catalyzed reactive species generation and identify key microenvironmental factors whose interplay impacts the identity of the reactive species (oxidants vs. (•)NO) produced. In doing so, we redefine existing dogma and shed new light on an enzyme that has weathered the evolutionary process not as gadfly but a crucial component in the maintenance of homeostasis.
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Key Words
- Free radicals
- GAGs, glycosaminoglycans
- H2O2, hydrogen peroxide
- Hypoxia
- I/R, ischemia/reperfusion
- Inflammation
- NOS, nitric oxide synthase
- Nitric oxide
- Nitrite
- O2•−, superoxide
- Oxygen tension
- ROS, reactive oxygen species
- XDH, xanthine dehydrogenase
- XO, xanthine oxidase
- XOR, xanthine oxidoreductase)
- Xanthine oxidoreductase
- •NO, nitric oxide
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27
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Bueno M, Wang J, Mora AL, Gladwin MT. Nitrite signaling in pulmonary hypertension: mechanisms of bioactivation, signaling, and therapeutics. Antioxid Redox Signal 2013; 18:1797-809. [PMID: 22871207 PMCID: PMC3619206 DOI: 10.1089/ars.2012.4833] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
SIGNIFICANCE Pulmonary arterial hypertension (PAH) is a disorder characterized by increased pulmonary vascular resistance and mean pulmonary artery pressure leading to impaired function of the right ventricle, reduced cardiac output, and death. An imbalance between vasoconstrictors and vasodilators plays an important role in the pathobiology of PAH. RECENT ADVANCES Nitric oxide (NO) is a potent vasodilator in the lung, whose bioavailability and signaling pathway are impaired in PAH. It is now appreciated that the oxidative product of NO metabolism, the inorganic anion nitrite (NO(2)(-)), functions as an intravascular endocrine reservoir of NO bioactivity that can be reduced back to NO under physiological and pathological hypoxia. CRITICAL ISSUES The conversion of nitrite to NO is controlled by coupled electron and proton transfer reactions between heme- and molybdenum-containing proteins, such as hemoglobin and xanthine oxidase, and by simple protonation and disproportionation, and possibly by catalyzed disproportionation. The two major sources of nitrite (and nitrate) are the endogenous L-arginine-NO pathway, by oxidation of NO, and the diet, with conversion of nitrate from diet into nitrite by oral commensal bacteria. In the current article, we review the enzymatic formation of nitrite and the available data regarding its use as a therapy for PAH and other cardiovascular diseases. FUTURE DIRECTIONS The successful efficacy demonstrated in several animal models and safety in early clinical trials suggest that nitrite may represent a promising new therapy for PAH.
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Affiliation(s)
- Marta Bueno
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA 15213, USA
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28
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Cantu-Medellin N, Kelley EE. Xanthine oxidoreductase-catalyzed reduction of nitrite to nitric oxide: insights regarding where, when and how. Nitric Oxide 2013; 34:19-26. [PMID: 23454592 DOI: 10.1016/j.niox.2013.02.081] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 02/13/2013] [Accepted: 02/19/2013] [Indexed: 01/13/2023]
Abstract
Numerous inflammatory disorders are associated with elevated levels of xanthine oxidoreductase (XOR) and allied enhancement of reactive species formation contributory to systemic pathology. Despite a long standing association between increased XOR activity and negative clinical outcomes, recent reports describe a paradigm shift where XOR mediates beneficial actions by catalyzing the reduction of NO2(-) to NO. While provocative, these observations contradict reports of improved outcomes in similar models upon XOR inhibition as well as reports revealing strict anoxia as a requisite for XOR-mediated NO formation. To garner a more clear understanding of conditions necessary for in vivo XOR-catalyzed NO production, this review critically analyzes the impact of O2 tension, pH, substrate concentrations, glycoaminoglycan docking and inhibition strategies on the nitrite reductase activity of XOR and reveals a hypoxic milieu where this process may be operative. As such, information herein serves to link recent reports in which XOR activity has been identified as mediating the beneficial outcomes resulting from nitrite supplementation to a microenvironmental setting where XOR can serve as substantial source of NO.
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Affiliation(s)
- Nadiezhda Cantu-Medellin
- University of Pittsburgh, Department of Anesthesiology and Vascular Medicine Institute, United States
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29
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Tabima DM, Frizzell S, Gladwin MT. Reactive oxygen and nitrogen species in pulmonary hypertension. Free Radic Biol Med 2012; 52:1970-86. [PMID: 22401856 PMCID: PMC3856647 DOI: 10.1016/j.freeradbiomed.2012.02.041] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 02/23/2012] [Accepted: 02/25/2012] [Indexed: 02/07/2023]
Abstract
Pulmonary vascular disease can be defined as either a disease affecting the pulmonary capillaries and pulmonary arterioles, termed pulmonary arterial hypertension, or a disease affecting the left ventricle, called pulmonary venous hypertension. Pulmonary arterial hypertension (PAH) is a disorder of the pulmonary circulation characterized by endothelial dysfunction, as well as intimal and smooth muscle proliferation. Progressive increases in pulmonary vascular resistance and pressure impair the performance of the right ventricle, resulting in declining cardiac output, reduced exercise capacity, right-heart failure, and ultimately death. While the primary and heritable forms of the disease are thought to affect over 5000 patients in the United States, the disease can occur secondary to congenital heart disease, most advanced lung diseases, and many systemic diseases. Multiple studies implicate oxidative stress in the development of PAH. Further, this oxidative stress has been shown to be associated with alterations in reactive oxygen species (ROS), reactive nitrogen species (RNS), and nitric oxide (NO) signaling pathways, whereby bioavailable NO is decreased and ROS and RNS production are increased. Many canonical ROS and NO signaling pathways are simultaneously disrupted in PAH, with increased expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and xanthine oxidoreductase, uncoupling of endothelial NO synthase (eNOS), and reduction in mitochondrial number, as well as impaired mitochondrial function. Upstream dysregulation of ROS/NO redox homeostasis impairs vascular tone and contributes to the pathological activation of antiapoptotic and mitogenic pathways, leading to cell proliferation and obliteration of the vasculature. This paper will review the available data regarding the role of oxidative and nitrosative stress and endothelial dysfunction in the pathophysiology of pulmonary hypertension, and provide a description of targeted therapies for this disease.
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Affiliation(s)
- Diana M. Tabima
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, 15213
| | - Sheila Frizzell
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, 15213
| | - Mark T. Gladwin
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, 15213
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213
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30
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Kelley EE, Khoo NK, Hundley NJ, Malik UZ, Freeman BA, Tarpey MM. Hydrogen peroxide is the major oxidant product of xanthine oxidase. Free Radic Biol Med 2010; 48:493-8. [PMID: 19941951 PMCID: PMC2848256 DOI: 10.1016/j.freeradbiomed.2009.11.012] [Citation(s) in RCA: 282] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2009] [Revised: 11/06/2009] [Accepted: 11/15/2009] [Indexed: 02/07/2023]
Abstract
Xanthine oxidase (XO) is a critical source of reactive oxygen species (ROS) in inflammatory disease. Focus, however, has centered almost exclusively on XO-derived superoxide (O(2)(*-)), whereas direct H(2)O(2) production from XO has been less well investigated. Therefore, we examined the relative quantities of O(2)(*-) and H(2)O(2) produced by XO under a range (1-21%) of O(2) tensions. At O(2) concentrations between 10 and 21%, H(2)O(2) accounted for approximately 75% of ROS production. As O(2) concentrations were lowered, there was a concentration-dependent increase in H(2)O(2) formation, accounting for 90% of ROS production at 1% O(2). Alterations in pH between 5.5 and 7.4 did not affect the relative proportions of H(2)O(2) and O(2)(*-) formation. Immobilization of XO, by binding to heparin-Sepharose, further enhanced relative H(2)O(2) production by approximately 30%, under both normoxic and hypoxic conditions. Furthermore, XO bound to glycosaminoglycans on the apical surface of bovine aortic endothelial cells demonstrated a similar ROS production profile. These data establish H(2)O(2) as the dominant (70-95%) reactive product produced by XO under clinically relevant conditions and emphasize the importance of H(2)O(2) as a critical factor when examining the contributory roles of XO-catalyzed ROS in inflammatory processes as well as cellular signaling.
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Affiliation(s)
- Eric E. Kelley
- Department of Anesthesiology, University of Pittsburgh, School of Medicine
- Address correspondence to: Eric E. Kelley, Ph.D., University of Pittsburgh, School of Medicine, Department of Anesthesiology, W-1357 Biomedical Sciences Tower, 200 Lothrop Street, Pittsburgh, PA, 15213, Phone: 412-648-9683, Fax: 412-648-9587, , Margaret M. Tarpey, M.D., University of Pittsburgh, School of Medicine, Department of Anesthesiology, W-1358 Biomedical Sciences Tower, 200 Lothrop Street, Pittsburgh, PA, 15213, Phone: 412-648-9684, Fax: 412-648-9587, mtarpey+@pitt.edu
| | - Nicholas K.H. Khoo
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine
| | | | - Umair Z. Malik
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine
| | - Bruce A. Freeman
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine
| | - Margaret M. Tarpey
- Department of Anesthesiology, University of Pittsburgh, School of Medicine
- Pittsburgh VA Medical Center
- Address correspondence to: Eric E. Kelley, Ph.D., University of Pittsburgh, School of Medicine, Department of Anesthesiology, W-1357 Biomedical Sciences Tower, 200 Lothrop Street, Pittsburgh, PA, 15213, Phone: 412-648-9683, Fax: 412-648-9587, , Margaret M. Tarpey, M.D., University of Pittsburgh, School of Medicine, Department of Anesthesiology, W-1358 Biomedical Sciences Tower, 200 Lothrop Street, Pittsburgh, PA, 15213, Phone: 412-648-9684, Fax: 412-648-9587, mtarpey+@pitt.edu
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Jiao M, Zhou YL, Li HT, Zhang DL, Chen J, Liang Y. Structural and functional alterations of two multidomain oxidoreductases induced by guanidine hydrochloride. Acta Biochim Biophys Sin (Shanghai) 2010; 42:30-8. [PMID: 20043044 DOI: 10.1093/abbs/gmp107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The unfolding and refolding of two multidomain oxidoreductases, bovine liver catalase and flavoprotein bovine milk xanthine oxidase (XO), have been analyzed by fluorescence spectroscopy, circular dichroism, and activity measurements. Two intermediates, a partially folded active dimer disassembled from the native tetramer and a partially folded inactivated monomer, are found to exist in the conformational changes of catalase induced by guanidine hydrochloride (GdnHCl). Similarly, two intermediates, an active, compacted intermediate bound by flavin adenine dinucleotide (FAD) partially and an inactive flexible intermediate with FAD completely dissociated, exist in the conformational changes of XO induced by GdnHCl. The activity regains completely and an enhancement in activity compared with the native catalase or native XO is observed by dilution of catalase or XO incubated with GdnHCl at concentrations not >0.5 or 1.8 M into the refolding buffer, but the yield of reactivation for catalase or XO is zero when the concentration of GdnHCl is >1.5 or 3.0 M. The addition of FAD provides a remarkable protection against the inactivation of XO by GdnHCl under mild denaturing conditions, and the conformational change of XO is irreversible after FAD has been removed in the presence of a strong denaturing agent. These findings provide impetus for exploring the influences of cofactors such as FAD on the structure-function relationship of xanthine oxidoreductases.
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Affiliation(s)
- Ming Jiao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
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Leopold JA, Loscalzo J. Oxidative risk for atherothrombotic cardiovascular disease. Free Radic Biol Med 2009; 47:1673-706. [PMID: 19751821 PMCID: PMC2797369 DOI: 10.1016/j.freeradbiomed.2009.09.009] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Revised: 08/31/2009] [Accepted: 09/06/2009] [Indexed: 02/07/2023]
Abstract
In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.
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Affiliation(s)
- Jane A Leopold
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Nishino T, Okamoto K, Eger BT, Pai EF, Nishino T. Mammalian xanthine oxidoreductase - mechanism of transition from xanthine dehydrogenase to xanthine oxidase. FEBS J 2008; 275:3278-89. [PMID: 18513323 DOI: 10.1111/j.1742-4658.2008.06489.x] [Citation(s) in RCA: 249] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Reactive oxygen species are generated by various biological systems, including NADPH oxidases, xanthine oxidoreductase, and mitochondrial respiratory enzymes, and contribute to many physiological and pathological phenomena. Mammalian xanthine dehydrogenase (XDH) can be converted to xanthine oxidase (XO), which produces both superoxide anion and hydrogen peroxide. Recent X-ray crystallographic and site-directed mutagenesis studies have revealed a highly sophisticated mechanism of conversion from XDH to XO, suggesting that the conversion is not a simple artefact, but rather has a function in mammalian organisms. Furthermore, this transition seems to involve a thermodynamic equilibrium between XDH and XO; disulfide bond formation or proteolysis can then lock the enzyme in the XO form. In this review, we focus on recent advances in our understanding of the mechanism of conversion from XDH to XO.
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Affiliation(s)
- Tomoko Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan
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34
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Atmani D, Baghiani A, Harrison R, Benboubetra M. NADH oxidation and superoxide production by caprine milk xanthine oxidoreductase. Int Dairy J 2005. [DOI: 10.1016/j.idairyj.2004.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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35
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Yesbergenova Z, Yang G, Oron E, Soffer D, Fluhr R, Sagi M. The plant Mo-hydroxylases aldehyde oxidase and xanthine dehydrogenase have distinct reactive oxygen species signatures and are induced by drought and abscisic acid. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:862-76. [PMID: 15941399 DOI: 10.1111/j.1365-313x.2005.02422.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The plant molybdenum-cofactor (Moco) and flavin-containing enzymes, xanthine dehydrogenase (XDH; EC 1.2.1.37) and aldehyde oxidase (AO; EC 1.2.3.1) are thought to play important metabolic roles in purine metabolism and hormone biosynthesis, respectively. Their animal counterparts contribute to reactive oxygen species (ROS) production in numerous pathologies and here we examined these enzymes as potential sources of ROS in plants. Novel in-gel assay techniques and Moco sulfurase mutants, lacking a sulfur ligand in their Moco active center, were employed to demonstrate that the native tomato and Arabidopsis XDHs are capable of producing O, but not H2O2, while the animal counterpart was shown to produce both, O and H2O2. Superoxide production was dependent on Moco sulfuration when using hypoxanthine/xanthine but not NADH as substrates. The activity was inhibited by diphenylene iodonium (DPI), a suicide inhibitor of FAD containing enzymes. Analysis of XDH in an Arabidopsis Atxdh1 T-DNA insertion mutant and RNA interference lines revealed loss of O activity, providing direct molecular evidence that plant XDH generates superoxides. Contrary to XDH, AO activity produced only H2O2 dissimilar to native animal AO, that can produce O as well. Surprisingly, H2O2 accumulation was not sensitive to DPI. Plant ROS production and transcript levels of AO and XDH were rapidly upregulated by application of abscisic acid and in water-stressed leaves and roots. These results, supported by in vivo measurement of ROS accumulation, indicate that plant AO and XDH are possible novel sources for ROS increase during water stress.
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Affiliation(s)
- Zhazira Yesbergenova
- The Albert Katz Department of Dryland Biotechnologies, The Jacob Blaustein Institute for Desert Research, Ben-Gurion University, PO Box 653, Beer Sheva 84105, Israel
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36
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Berry CE, Hare JM. Xanthine oxidoreductase and cardiovascular disease: molecular mechanisms and pathophysiological implications. J Physiol 2003; 555:589-606. [PMID: 14694147 PMCID: PMC1664875 DOI: 10.1113/jphysiol.2003.055913] [Citation(s) in RCA: 618] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
There is substantial evidence that oxidative stress participates in the pathophysiology of cardiovascular disease. Biochemical, molecular and pharmacological studies further implicate xanthine oxidoreductase (XOR) as a source of reactive oxygen species in the cardiovascular system. XOR is a member of the molybdoenzyme family and is best known for its catalytic role in purine degradation, metabolizing hypoxanthine and xanthine to uric acid with concomitant generation of superoxide. Gene expression of XOR is regulated by oxygen tension, cytokines and glucocorticoids. XOR requires molybdopterin, iron-sulphur centres, and FAD as cofactors and has two interconvertible forms, xanthine oxidase and xanthine dehydrogenase, which transfer electrons from xanthine to oxygen and NAD(+), respectively, yielding superoxide, hydrogen peroxide and NADH. Additionally, XOR can generate superoxide via NADH oxidase activity and can produce nitric oxide via nitrate and nitrite reductase activities. While a role for XOR beyond purine metabolism was first suggested in ischaemia-reperfusion injury, there is growing awareness that it also participates in endothelial dysfunction, hypertension and heart failure. Importantly, the XOR inhibitors allopurinol and oxypurinol attenuate dysfunction caused by XOR in these disease states. Attention to the broader range of XOR bioactivity in the cardiovascular system has prompted initiation of several randomised clinical outcome trials, particularly for congestive heart failure. Here we review XOR gene structure and regulation, protein structure, enzymology, tissue distribution and pathophysiological role in cardiovascular disease with an emphasis on heart failure.
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Affiliation(s)
- Cristine E Berry
- The Johns Hopkins Hospital School of Medicine, Cardiology Division, 600 N Wolfe Street, Carnegie 568, Baltimore, MD 21287, USA
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Garattini E, Mendel R, Romão MJ, Wright R, Terao M. Mammalian molybdo-flavoenzymes, an expanding family of proteins: structure, genetics, regulation, function and pathophysiology. Biochem J 2003; 372:15-32. [PMID: 12578558 PMCID: PMC1223366 DOI: 10.1042/bj20030121] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2003] [Revised: 02/04/2003] [Accepted: 02/10/2003] [Indexed: 12/11/2022]
Abstract
The molybdo-flavoenzymes are structurally related proteins that require a molybdopterin cofactor and FAD for their catalytic activity. In mammals, four enzymes are known: xanthine oxidoreductase, aldehyde oxidase and two recently described mouse proteins known as aldehyde oxidase homologue 1 and aldehyde oxidase homologue 2. The present review article summarizes current knowledge on the structure, enzymology, genetics, regulation and pathophysiology of mammalian molybdo-flavoenzymes. Molybdo-flavoenzymes are structurally complex oxidoreductases with an equally complex mechanism of catalysis. Our knowledge has greatly increased due to the recent crystallization of two xanthine oxidoreductases and the determination of the amino acid sequences of many members of the family. The evolution of molybdo-flavoenzymes can now be traced, given the availability of the structures of the corresponding genes in many organisms. The genes coding for molybdo-flavoenzymes are expressed in a cell-specific fashion and are controlled by endogenous and exogenous stimuli. The recent cloning of the genes involved in the biosynthesis of the molybdenum cofactor has increased our knowledge on the assembly of the apo-forms of molybdo-flavoproteins into the corresponding holo-forms. Xanthine oxidoreductase is the key enzyme in the catabolism of purines, although recent data suggest that the physiological function of this enzyme is more complex than previously assumed. The enzyme has been implicated in such diverse pathological situations as organ ischaemia, inflammation and infection. At present, very little is known about the pathophysiological relevance of aldehyde oxidase, aldehyde oxidase homologue 1 and aldehyde oxidase homologue 2, which do not as yet have an accepted endogenous substrate.
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Affiliation(s)
- Enrico Garattini
- Laboratory of Molecular Biology, Istituto di Ricerche Farmacologiche Mario Negri, via Eritrea 62, 20157 Milan, Italy.
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Metzler DE, Metzler CM, Sauke DJ. Transition Metals in Catalysis and Electron Transport. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50019-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Harris CM, Sanders SA, Massey V. Role of the flavin midpoint potential and NAD binding in determining NAD versus oxygen reactivity of xanthine oxidoreductase. J Biol Chem 1999; 274:4561-9. [PMID: 9988690 DOI: 10.1074/jbc.274.8.4561] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Xanthine oxidoreductase from bovine milk can be prepared in two interconvertible forms, xanthine oxidase (XO) and xanthine dehydrogenase (XDH), depending on the number of protein cysteines versus cystines. Enzyme forms differ in respect to their oxidizing substrates; XDH prefers NAD to molecular oxygen, whereas XO only reacts significantly with oxygen. The preference for oxidizing substrate is partially explained by thermodynamics. Unlike XDH, the midpoint potential of the FAD, the center at which oxygen and NAD react, is too high in XO to efficiently reduce NAD (Hunt, J., Massey, V., Dunham, W.R., and Sands, R.H. (1993) J. Biol. Chem. 268, 18685-18691). To distinguish between changes in thermodynamics and in substrate binding, samples of both XO and XDH have been prepared in which the native FAD has been replaced with an FAD analog of different redox potential, 1-deaza-FAD or 8-CN-FAD. Reductive titrations indicate that both 1-deaza-XO and 1-deaza-XDH have a flavin midpoint potential similar to native XDH and that 8-CN-XO and 8-CN-XDH each have a flavin potential higher than XO. Both the low potential 1-deaza-XO and the high potential 8-CN-XDH contain essentially no xanthine/NAD activity. However, 1-deaza-XDH does exhibit xanthine/NAD activity, and 8-CN-XO has normal xanthine/oxygen activity. The binding of NAD to oxidized XO and XDH was investigated by ultrafiltration and isothermal titration calorimetry. The Kd for the binding of NAD to XDH was determined to be 280 +/- 145 microM by ultrafiltration and 160 +/- 40 microM by isothermal titration calorimetry. No evidence for the binding of NAD to XO by either method could be obtained. A low flavin midpoint potential is necessary but not sufficient for dehydrogenase activity.
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Affiliation(s)
- C M Harris
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606, USA
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