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Shi C, Chang L, Wang J, Dai J, Xu W, Tang J, Mei W, Zhang C, Wang Z, Liao Y, Zhang X, Jiang W, Zhang G, Zhao Z, Xu Y, Zhu L, Li H. Discovery of Novel Non-Nucleoside Inhibitors Interacting with Dizinc Ions of CD73. J Med Chem 2024; 67:9686-9708. [PMID: 38809692 DOI: 10.1021/acs.jmedchem.4c00825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2024]
Abstract
High extracellular concentrations of adenosine triphosphate (ATP) in the tumor microenvironment generate adenosine by sequential dephosphorylation of CD39 and CD73, resulting in potent immunosuppression to inhibit T cell and natural killer (NK) cell function. CD73, as the determining enzyme for adenosine production, has been shown to correlate with poor clinical tumor prognosis. Conventional inhibitors as analogues of adenosine 5'-monophosphate (AMP) may have a risk of further metabolism to adenosine analogues. Here, we report a new series of malonic acid non-nucleoside inhibitors coordinating with zinc ions of CD73. Compound 12f was found to be a superior CD73 inhibitor (IC50 = 60 nM) by structural optimization, and its pharmacokinetic properties were investigated. In mouse tumor models, compound 12f showed excellent efficacy and reversal of immunosuppression in combination with chemotherapeutic agents or checkpoint inhibitors, suggesting that it deserves further development as a novel CD73 inhibitor.
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Affiliation(s)
- Cunjian Shi
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Longfeng Chang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Jie Wang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Jingqi Dai
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Wenyue Xu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Jiangyang Tang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Wenyi Mei
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Chen Zhang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Zedong Wang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Yichen Liao
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Xingsen Zhang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Wenzhe Jiang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Guozhen Zhang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Zhenjiang Zhao
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Yufang Xu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Lili Zhu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Honglin Li
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
- Innovation Center for AI and Drug Discovery, East China Normal University, Shanghai 200062, China
- Lingang Laboratory, Shanghai 200031, China
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Schädlich IS, Winzer R, Stabernack J, Tolosa E, Magnus T, Rissiek B. The role of the ATP-adenosine axis in ischemic stroke. Semin Immunopathol 2023:10.1007/s00281-023-00987-3. [PMID: 36917241 DOI: 10.1007/s00281-023-00987-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 01/25/2023] [Indexed: 03/16/2023]
Abstract
In ischemic stroke, the primary neuronal injury caused by the disruption of energy supply is further exacerbated by secondary sterile inflammation. The inflammatory cascade is largely initiated by the purine adenosine triphosphate (ATP) which is extensively released to the interstitial space during brain ischemia and functions as an extracellular danger signaling molecule. By engaging P2 receptors, extracellular ATP activates microglia leading to cytokine and chemokine production and subsequent immune cell recruitment from the periphery which further amplifies post-stroke inflammation. The ectonucleotidases CD39 and CD73 shape and balance the inflammatory environment by stepwise degrading extracellular ATP to adenosine which itself has neuroprotective and anti-inflammatory signaling properties. The neuroprotective effects of adenosine are mainly mediated through A1 receptors and inhibition of glutamatergic excitotoxicity, while the anti-inflammatory capacities of adenosine have been primarily attributed to A2A receptor activation on infiltrating immune cells in the subacute phase after stroke. In this review, we summarize the current state of knowledge on the ATP-adenosine axis in ischemic stroke, discuss contradictory results, and point out potential pitfalls towards translating therapeutic approaches from rodent stroke models to human patients.
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Affiliation(s)
- Ines Sophie Schädlich
- Department of Neurology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Riekje Winzer
- Institute of Immunology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Joschi Stabernack
- Department of Neurology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Eva Tolosa
- Institute of Immunology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
| | - Tim Magnus
- Department of Neurology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany.
| | - Björn Rissiek
- Department of Neurology, University Medical Centre Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany
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3
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Scaletti E, Huschmann FU, Mueller U, Weiss MS, Sträter N. Substrate binding modes of purine and pyrimidine nucleotides to human ecto-5'-nucleotidase (CD73) and inhibition by their bisphosphonic acid derivatives. Purinergic Signal 2021; 17:693-704. [PMID: 34403084 PMCID: PMC8677862 DOI: 10.1007/s11302-021-09802-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 06/07/2021] [Indexed: 12/20/2022] Open
Abstract
Human ecto-5-nucleotidase (CD73) is involved in purinergic signalling, which influences a diverse range of biological processes. CD73 hydrolyses AMP and is the major control point for the levels of extracellular adenosine. Inhibitors of CD73 thus block the immunosuppressive action of adenosine, a promising approach for cancer immunotherapy. Interestingly, ADP and ATP are competitive inhibitors of CD73, with the most potent small-molecule inhibitors to date being non-hydrolysable ADP analogues. While AMP is the major substrate of the enzyme, CD73 has been reported to hydrolyse other 5′-nucleoside monophosphates. Based on a fragment screening campaign at the BESSY II synchrotron, we present the binding modes of various deoxyribo- and ribonucleoside monophosphates and of four additional fragments binding to the nucleoside binding site of the open form of the enzyme. Kinetic analysis of monophosphate hydrolysis shows that ribonucleotide substrates are favoured over their deoxyribose equivalents with AMP being the best substrate. We characterised the initial step of AMP hydrolysis, the binding mode of AMP to the open conformation of CD73 and compared that to other monophosphate substrates. In addition, the inhibitory activity of various bisphosphonic acid derivatives of nucleoside diphosphates was determined. Although AMPCP remains the most potent inhibitor, replacement of the adenine base with other purines or with pyrimidines increases the Ki value only between twofold and sixfold. On the other hand, these nucleobases offer new opportunities to attach substituents for improved pharmacological properties.
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Affiliation(s)
- Emma Scaletti
- Institute of Bioanalytical Chemistry, Centre for Biotechnology and Biomedicine, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany
| | - Franziska U Huschmann
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Uwe Mueller
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Manfred S Weiss
- Helmholtz-Zentrum Berlin Für Materialien Und Energie, BESSY II, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | - Norbert Sträter
- Institute of Bioanalytical Chemistry, Centre for Biotechnology and Biomedicine, Leipzig University, Deutscher Platz 5, 04103, Leipzig, Germany.
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4
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Jeffrey JL, Lawson KV, Powers JP. Targeting Metabolism of Extracellular Nucleotides via Inhibition of Ectonucleotidases CD73 and CD39. J Med Chem 2020; 63:13444-13465. [PMID: 32786396 DOI: 10.1021/acs.jmedchem.0c01044] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In the tumor microenvironment, unusually high concentrations of extracellular adenosine promote tumor proliferation through various immunosuppressive mechanisms. Blocking adenosine production by inhibiting nucleotide-metabolizing enzymes, such as ectonucleotidases CD73 and CD39, represents a promising therapeutic strategy that may synergize with other immuno-oncology mechanisms and chemotherapies. Emerging small-molecule ectonucleotidase inhibitors have recently entered clinical trials. This Perspective will outline challenges, strategies, and recent advancements in targeting this class with small-molecule inhibitors, including AB680, the first small-molecule CD73 inhibitor to enter clinical development. Specific case studies, including structure-based drug design and lead optimization, will be outlined. Preclinical data on these molecules and their ability to enhance antitumor immunity will be discussed.
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Affiliation(s)
- Jenna L Jeffrey
- Arcus Biosciences, 3928 Point Eden Way, Hayward, California 94545, United States
| | - Kenneth V Lawson
- Arcus Biosciences, 3928 Point Eden Way, Hayward, California 94545, United States
| | - Jay P Powers
- Arcus Biosciences, 3928 Point Eden Way, Hayward, California 94545, United States
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Nedeljkovic N. Complex regulation of ecto-5'-nucleotidase/CD73 and A 2AR-mediated adenosine signaling at neurovascular unit: A link between acute and chronic neuroinflammation. Pharmacol Res 2019; 144:99-115. [PMID: 30954629 DOI: 10.1016/j.phrs.2019.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 04/01/2019] [Accepted: 04/03/2019] [Indexed: 12/20/2022]
Abstract
The review summarizes available data regarding the complex regulation of CD73 at the neurovascular unit (NVU) during neuroinflammation. Based on available data we propose the biphasic pattern of CD73 regulation at NVU, with an early attenuation and a postponed up-regulation of CD73 activity. Transient attenuation of CD73 activity on leukocyte/vascular endothelium and leukocyte/astrocyte surface, required for the initiation of a neuroinflammatory response, may be effectuated either by catalytic inhibition of CD73 and/or by shedding of the CD73 molecule from the cell surface, while postponed induction of CD73 is effectuated by transcriptional up-regulation of Nt5e and posttranslational modifications. Neuroinflammatory conditions are also associated with significant enhancement and gain-of-function of A2AR-mediated adenosine signaling. However, in contrast to the temporary prevalence of A2AR over A1R signaling during an acute inflammatory response, prolonged induction of A2AR and resulting perpetual CD73/A2AR coupling may be a contributing factors in the transition between acute and chronic neuroinflammation. Thus, pharmacological targeting of the CD73/A2AR axis may attenuate inflammatory response and ameliorate neurological deficits in chronic neuroinflammatory conditions.
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Affiliation(s)
- Nadezda Nedeljkovic
- Department of General Physiology and Biophysics, Faculty of Biology University of Belgrade, Studentski trg 3, Belgrade 11001, Serbia.
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6
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Guarracino JF, Cinalli AR, Veggetti MI, Losavio AS. Endogenous purines modulate K + -evoked ACh secretion at the mouse neuromuscular junction. J Neurosci Res 2018; 96:1066-1079. [PMID: 29436006 DOI: 10.1002/jnr.24223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/19/2018] [Accepted: 01/26/2018] [Indexed: 11/11/2022]
Abstract
At the mouse neuromuscular junction, adenosine triphosphate (ATP) is co-released with the neurotransmitter acetylcholine (ACh), and once in the synaptic cleft, it is hydrolyzed to adenosine. Both ATP/adenosine diphosphate (ADP) and adenosine modulate ACh secretion by activating presynaptic P2Y13 and A1 , A2A , and A3 receptors, respectively. To elucidate the action of endogenous purines on K+ -dependent ACh release, we studied the effect of purinergic receptor antagonists on miniature end-plate potential (MEPP) frequency in phrenic diaphragm preparations. At 10 mM K+ , the P2Y13 antagonist N-[2-(methylthio)ethyl]-2-[3,3,3-trifluoropropyl]thio-5'-adenylic acid, monoanhydride with (dichloromethylene)bis[phosphonic acid], tetrasodium salt (AR-C69931MX) increased asynchronous ACh secretion while the A1 , A3 , and A2A antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), (3-Ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1, 4-(±)-dihydropyridine-3,5-, dicarboxylate (MRS-1191), and 2-(2-Furanyl)-7-(2-phenylethyl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine (SCH-58261) did not modify neurosecretion. The inhibition of equilibrative adenosine transporters by S-(p-nitrobenzyl)-6-thioinosine provoked a reduction of 10 mM K+ -evoked ACh release, suggesting that the adenosine generated from ATP is being removed from the synaptic space by the transporters. At 15 and 20 mM K+ , endogenous ATP/ADP and adenosine bind to inhibitory P2Y13 and A1 and A3 receptors since AR-C69931MX, DPCPX, and MRS-1191 increased MEPP frequency. Similar results were obtained when the generation of adenosine was prevented by using the ecto-5'-nucleotidase inhibitor α,β-methyleneadenosine 5'-diphosphate sodium salt. SCH-58261 only reduced neurosecretion at 20 mM K+ , suggesting that more adenosine is needed to activate excitatory A2A receptors. At high K+ concentration, the equilibrative transporters appear to be saturated allowing the accumulation of adenosine in the synaptic cleft. In conclusion, when motor nerve terminals are depolarized by increasing K+ concentrations, the ATP/ADP and adenosine endogenously generated are able to modulate ACh secretion by sequential activation of different purinergic receptors.
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Affiliation(s)
- Juan F Guarracino
- Laboratorio de Neurofisiología, Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Alejandro R Cinalli
- Laboratorio de Neurofisiología, Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Mariela I Veggetti
- Laboratorio de Neurofisiología, Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Adriana S Losavio
- Laboratorio de Neurofisiología, Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autónoma de Buenos Aires, Argentina
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7
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Cardoso AM, Schetinger MRC, Correia-de-Sá P, Sévigny J. Impact of ectonucleotidases in autonomic nervous functions. Auton Neurosci 2015; 191:25-38. [PMID: 26008223 DOI: 10.1016/j.autneu.2015.04.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 01/05/2023]
Abstract
Adenine and uracil nucleotides play key functions in the autonomic nervous system (ANS). For instance, ATP acts as a neurotransmitter, co-transmitter and neuromodulator in the ANS. The purinergic system encompasses (1) receptors that respond to extracellular purines, which are designated as P1 and P2 purinoceptors, (2) purine release and uptake, and (3) a cascade of enzymes that regulate the concentration of purines near the cell surface. Ectonucleotidases and adenosine deaminase (ADA) are enzymes responsible for the hydrolysis of ATP (and other nucleotides such as ADP, UTP, UDP, AMP) and adenosine, respectively. Accordingly, these enzymes are expected to play an important role in the control of neuro-effector transmission in tissues innervated by both the sympathetic and parasympathetic divisions of the ANS. Indeed, ectonucleotidases have the ability to either terminate P2 receptor responses initiated by nucleoside triphosphates (ATP and UTP), and/or to favor the activation of ADP (e.g. P2Y1,12,13) and UDP (e.g. P2Y6) and/or adenosine (P1) specific receptors. In addition, ectonucleotidases can also importantly protect some P2 receptors from desensitization (e.g. P2X1, P2Y1). In this review, we present the (putative) roles of ectonucleotidases and ADA in the ANS with a focus on their regulatory activity at neuro-effector junctions in the following tissues: heart, vas deferens, urinary bladder, salivary glands, blood vessels and the intestine. We also present their implication in nociceptive transmission.
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Affiliation(s)
- Andréia Machado Cardoso
- Post-Graduation Program in Toxicological Biochemistry, Department of Biochemistry and Molecular Biology of the Center of Natural and Exact Sciences of the Federal University of Santa Maria, Santa Maria Rio Grande do Sul, Brazil; Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec City, Québec G1V 0A6, Canada; Centre de Recherche du CHU de Québec - Université Laval, Québec G1V 4G2, Canada.
| | - Maria Rosa Chitolina Schetinger
- Post-Graduation Program in Toxicological Biochemistry, Department of Biochemistry and Molecular Biology of the Center of Natural and Exact Sciences of the Federal University of Santa Maria, Santa Maria Rio Grande do Sul, Brazil
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia e Neurobiologia, MedInUP, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), 4050-313 Porto, Portugal
| | - Jean Sévigny
- Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec City, Québec G1V 0A6, Canada; Centre de Recherche du CHU de Québec - Université Laval, Québec G1V 4G2, Canada.
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8
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Hinze AV, Mayer P, Harst A, von Kügelgen I. P2X1 receptor-mediated inhibition of the proliferation of human coronary smooth muscle cells involving the transcription factor NR4A1. Purinergic Signal 2013; 9:677-86. [PMID: 23873636 PMCID: PMC3889386 DOI: 10.1007/s11302-013-9380-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 07/03/2013] [Indexed: 01/28/2023] Open
Abstract
Adenine nucleotides acting at P2X1 receptors are potent vasoconstrictors. Recently, we demonstrated that activation of adenosine A2B receptors on human coronary smooth muscle cells inhibits cell proliferation by the induction of the nuclear receptor subfamily 4, group A, member 1 (NR4A1; alternative notation Nur77). In the present study, we searched for long-term effects mediated by P2X1 receptors by analyzing receptor-mediated changes in cell proliferation and in the expression of NR4A1. Cultured human coronary smooth muscle cells were treated with selective receptor ligands. Effects on proliferation were determined by counting cells and measuring changes in impedance. The induction of transcription factors was assessed by qPCR. The P2X receptor agonist α,β-methylene-ATP and its analog β,γ-methylene-ATP inhibited cell proliferation by about 50 % after 5 days in culture with half-maximal concentrations of 0.3 and 0.08 μM, respectively. The effects were abolished or markedly attenuated by the P2X1 receptor antagonist NF449 (carbonylbis-imino-benzene-triylbis-(carbonylimino)tetrakis-benzene-1,3-disulfonic acid; 100 nM and 1 μM). α,β-methylene-ATP and β,γ-methylene-ATP applied for 30 min to 4 h increased the expression of NR4A1; NF449 blocked or attenuated this effect. Small interfering RNA directed against NR4A1 diminished the antiproliferative effects of α,β-methylene-ATP and β,γ-methylene-ATP. α,β-methylene-ATP (0.1 to 30 μM) decreased migration of cultured human coronary smooth muscle cells in a chamber measuring changes in impedance; NF449 blocked the effect. In conclusion, our results demonstrate for the first time that adenine nucleotides acting at P2X1 receptors inhibit the proliferation of human coronary smooth muscle cells via the induction of the early gene NR4A1.
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Affiliation(s)
- Annette Viktoria Hinze
- />Federal Institute for Drugs and Medical Devices, Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
- />Department of Pharmacology and Toxicology, University of Bonn, 53105 Bonn, Germany
- />Department of Clinical Chemistry and Clinical Pharmacology, University of Bonn, 53105 Bonn, Germany
| | - Peter Mayer
- />Federal Institute for Drugs and Medical Devices, Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Anja Harst
- />Federal Institute for Drugs and Medical Devices, Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Ivar von Kügelgen
- />Department of Pharmacology and Toxicology, University of Bonn, 53105 Bonn, Germany
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9
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Jackson EK, Cheng D, Mi Z, Verrier JD, Janesko-Feldman K, Kochanek PM. Role of CD73 in Renal Sympathetic Neurotransmission in the Mouse Kidney. Physiol Rep 2013; 1. [PMID: 24066228 PMCID: PMC3779432 DOI: 10.1002/phy2.57] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Adenosine formed during renal sympathetic nerve stimulation (RSNS) enhances, by activating A1 receptors, the postjunctional effects of released norepinephrine and participates in renal sympathetic neurotransmission. Because in many cell types CD73 (ecto-5'-nucleotidase) is important for the conversion of 5'-AMP to adenosine, we investigated whether CD73 is necessary for normal renal sympathetic neurotransmission. In isolated kidneys from CD73 wild-type mice (CD73 +/+; n=17) perfused at a constant rate with Tyrode's solution, RSNS increased perfusion pressure by 17±4, 36±8 and 44±10 mm Hg at 3, 5 and 7 Hz, respectively. Similar responses were elicited from kidneys isolated from CD73 knockout mice (CD73 -/-; n=13; 28±11, 43±10 and 44±10 mm Hg at 3, 5 and 7 Hz, respectively); and a high concentration (100 μmol/L) of α,β-methyleneadenosine 5'-diphosphate (CD73 inhibitor) did not alter responses to RSNS in C57BL/6 mouse kidneys (n=5; 21±5, 36±8 and 43±9 at 3, 5 and 7 Hz, respectively). Measurements of renal venous adenosine and inosine (adenosine metabolite) by liquid chromatography-tandem mass spectrometry demonstrated that the metabolism of exogenous 5'-AMP to adenosine and inosine was similar in CD73 -/- versus CD73 +/+ kidneys. A1 receptor mRNA expression was increased in CD73 -/- kidneys, and 2-chloro-N6-cyclopentyladenosine (0.1 μmol/L; A1 receptor agonist) enhanced renovascular responses to norepinephrine more in CD73 -/- versus CD73 +/+ kidneys. We conclude that CD73 is not essential for renal sympathetic neurotransmission because in the absence of renal CD73 other enzymes metabolize 5'-AMP to adenosine and because of compensatory upregulation of postjunctional coincident signaling between norepinephrine and adenosine.
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Affiliation(s)
- Edwin K Jackson
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15219
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10
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Sakowicz-Burkiewicz M, Grden M, Maciejewska I, Szutowicz A, Pawelczyk T. High glucose impairs ATP formation on the surface of human peripheral blood B lymphocytes. Int J Biochem Cell Biol 2013; 45:1246-54. [PMID: 23523697 DOI: 10.1016/j.biocel.2013.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/05/2013] [Accepted: 03/11/2013] [Indexed: 12/20/2022]
Abstract
Diabetes-associated lymphocyte dysfunction may be attributed to the direct effect of hyperglycemia, but the impact of glucose concentration on B cell functionality is not fully resolved. Since, adenosine 5'-triphosphate (ATP) and its metabolite adenosine are the core constituents of the purinergic signaling network involved in regulation of immune response we aimed to investigate the impact of high glucose concentration on ATP outflow and metabolism on B cell surface. Purified human peripheral blood B cells cultured at high glucose (25 mM) concentration released significantly less ATP (~60%) comparing to cells cultured in low glucose (5mM) concentration. We observed that high glucose altered ATP hydrolysis on B cell surface due to increased activity of nucleoside triphosphate diphosphohydrolase-1 (NTPDase-1/CD39). In the presence of 10 μM [(3)H]AMP and 100 μM ATP significant quantities of [(3)H]ADP and [(3)H]ATP were generated, although the AMP to ADP phosphorylation potential of B cells cultured in high glucose decreased significantly. The flow cytometry analysis revealed that the level of ecto-adenylate kinase 1β (AK1β) on surface of B cells cultured in high glucose decreased significantly. Inhibition of NTPDase1/CD39 activity with 100 μM ARL67156 resulted in decreased cell viability, although significantly more viable cells retained in the culture media containing low glucose compared to high glucose media. Selective inhibition of P2X7 purinergic receptor irrespective of glucose concentration completely protected B cells against the ARL 67156-induced cell death. We assume that high glucose-induced alteration of ATP handling on B cell surface might contribute to impaired functionality of B cells in diabetes.
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11
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Pajski ML, Venton BJ. The mechanism of electrically stimulated adenosine release varies by brain region. Purinergic Signal 2012. [PMID: 23192278 DOI: 10.1007/s11302-012-9343-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Adenosine plays an important role in neuromodulation and neuroprotection. Recent identification of transient changes in adenosine concentration suggests adenosine may have a rapid modulatory role; however, the extent of these changes throughout the brain is not well understood. In this report, transient changes in adenosine evoked by one second, 60 Hz electrical stimulation trains were compared in the caudate-putamen, nucleus accumbens, hippocampus, and cortex. The concentration of evoked adenosine varies between brain regions, but there is less variation in the duration of signaling. The highest concentration of adenosine was evoked in the dorsal caudate-putamen (0.34 ± 0.08 μM), while the lowest concentration was in the secondary motor cortex (0.06 ± 0.02 μM). In all brain regions, adenosine release was activity-dependent. In the nucleus accumbens, hippocampus, and prefrontal cortex, this release was partly due to extracellular ATP breakdown. However, in the caudate-putamen, release was not due to ATP metabolism but was ionotropic glutamate receptor-dependent. The results demonstrate that transient, activity-dependent adenosine can be evoked in many brain regions but that the mechanism of formation and release varies by region.
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Affiliation(s)
- Megan L Pajski
- Chemistry Department, University of Virginia, Charlottesville, VA 22904, USA
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12
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Korboukh I, Hull-Ryde EA, Rittiner JE, Randhawa AS, Coleman J, Fitzpatrick BJ, Setola V, Janzen WP, Frye SV, Zylka MJ, Jin J. Orally active adenosine A(1) receptor agonists with antinociceptive effects in mice. J Med Chem 2012; 55:6467-77. [PMID: 22738238 DOI: 10.1021/jm3004834] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Adenosine A(1) receptor (A(1)AR) agonists have antinociceptive effects in multiple preclinical models of acute and chronic pain. Although numerous A(1)AR agonists have been developed, clinical applications of these agents have been hampered by their cardiovascular side effects. Herein we report a series of novel A(1)AR agonists, some of which are structurally related to adenosine 5'-monophosphate (5'-AMP), a naturally occurring nucleotide that itself activates A(1)AR. These novel compounds potently activate A(1)AR in several orthogonal in vitro assays and are subtype selective for A(1)AR over A(2A)AR, A(2B)AR, and A(3)AR. Among them, UNC32A (3a) is orally active and has dose-dependent antinociceptive effects in wild-type mice. The antinociceptive effects of 3a were completely abolished in A(1)AR knockout mice, revealing a strict dependence on A(1)AR for activity. The apparent lack of cardiovascular side effects when administered orally and high affinity (K(i) of 36 nM for the human A(1)AR) make this compound potentially suitable as a therapeutic.
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Affiliation(s)
- Ilia Korboukh
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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13
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Fausther M, Lecka J, Soliman E, Kauffenstein G, Pelletier J, Sheung N, Dranoff JA, Sévigny J. Coexpression of ecto-5'-nucleotidase/CD73 with specific NTPDases differentially regulates adenosine formation in the rat liver. Am J Physiol Gastrointest Liver Physiol 2012; 302:G447-59. [PMID: 22135310 PMCID: PMC3287391 DOI: 10.1152/ajpgi.00165.2011] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ectonucleotidases modulate purinergic signaling by hydrolyzing ATP to adenosine. Here we characterized the impact of the cellular distribution of hepatic ectonucleotidases, namely nucleoside triphosphate diphosphohydrolase (NTPDase)1/CD39, NTPDase2/CD39L1, NTPDase8, and ecto-5'-nucleotidase/CD73, and of their specific biochemical properties, on the levels of P1 and P2 receptor agonists, with an emphasis on adenosine-producing CD73. Immunostaining and enzyme histochemistry showed that the distribution of CD73 (protein and AMPase activity) overlaps partially with those of NTPDase1, -2, and -8 (protein levels and ATPase and ADPase activities) in normal rat liver. CD73 is expressed in fibroblastic cells located underneath vascular endothelial cells and smooth muscle cells, which both express NTPDase1, in portal spaces in a distinct fibroblast population next to NTPDase2-positive portal fibroblasts, and in bile canaliculi, together with NTPDase8. In fibrotic rat livers, CD73 protein expression and activity are redistributed but still overlap with the NTPDases mentioned. The ability of the observed combinations of ectonucleotidases to generate adenosine over time was evaluated by reverse-phase HPLC with the recombinant rat enzymes at high "inflammatory" (500 μM) and low "physiological" (1 μM) ATP concentrations. Overall, ATP was rapidly converted to adenosine by the NTPDase1+CD73 combination, but not by the NTPDase2+CD73 combination. In the presence of NTPDase8 and CD73, ATP was sequentially dephosphorylated to the CD73 inhibitor ADP, and then to AMP, thus resulting in a delayed formation of adenosine. In conclusion, the specific cellular cocompartmentalization of CD73 with hepatic NTPDases is not redundant and may lead to the differential activation of P1 and P2 receptors, under normal and fibrotic conditions.
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Affiliation(s)
- Michel Fausther
- 1Centre de recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec (pavillon CHUL), Québec and Département de microbiologie-infectiologie et d'immunologie, Faculté de médecine, Université Laval, Québec, QC, Canada; ,2Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut; and ,3Division of Gastroenterology and Hepatology, Department of Internal Medicine, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Joanna Lecka
- 1Centre de recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec (pavillon CHUL), Québec and Département de microbiologie-infectiologie et d'immunologie, Faculté de médecine, Université Laval, Québec, QC, Canada;
| | - Elwy Soliman
- 2Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut; and
| | - Gilles Kauffenstein
- 1Centre de recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec (pavillon CHUL), Québec and Département de microbiologie-infectiologie et d'immunologie, Faculté de médecine, Université Laval, Québec, QC, Canada;
| | - Julie Pelletier
- 1Centre de recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec (pavillon CHUL), Québec and Département de microbiologie-infectiologie et d'immunologie, Faculté de médecine, Université Laval, Québec, QC, Canada;
| | - Nina Sheung
- 2Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut; and
| | - Jonathan A. Dranoff
- 2Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut; and ,3Division of Gastroenterology and Hepatology, Department of Internal Medicine, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Jean Sévigny
- 1Centre de recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec (pavillon CHUL), Québec and Département de microbiologie-infectiologie et d'immunologie, Faculté de médecine, Université Laval, Québec, QC, Canada;
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14
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Rittiner JE, Korboukh I, Hull-Ryde EA, Jin J, Janzen WP, Frye SV, Zylka MJ. AMP is an adenosine A1 receptor agonist. J Biol Chem 2012; 287:5301-9. [PMID: 22215671 DOI: 10.1074/jbc.m111.291666] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5'-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5'-monophosphonate, ACP) directly activated the adenosine A(1) receptor (A(1)R). In contrast, AMP only activated the adenosine A(2B) receptor (A(2B)R) after hydrolysis to adenosine by ecto-5'-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A(1)R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A(1)R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A(1)R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A(1)R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine.
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Affiliation(s)
- Joseph E Rittiner
- Department of Cell and Molecular Physiology, University of North Carolina Neuroscience Center, Chapel Hill, North Carolina 27599, USA
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15
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Costa MA, Barbosa A, Neto E, Sá-e-Sousa A, Freitas R, Neves JM, Magalhães-Cardoso T, Ferreirinha F, Correia-de-Sá P. On the role of subtype selective adenosine receptor agonists during proliferation and osteogenic differentiation of human primary bone marrow stromal cells. J Cell Physiol 2011; 226:1353-66. [PMID: 20945394 DOI: 10.1002/jcp.22458] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Purines are important modulators of bone cell biology. ATP is metabolized into adenosine by human primary osteoblast cells (HPOC); due to very low activity of adenosine deaminase, the nucleoside is the end product of the ecto-nucleotidase cascade. We, therefore, investigated the expression and function of adenosine receptor subtypes (A(1) , A(2A) , A(2B) , and A(3) ) during proliferation and osteogenic differentiation of HPOC. Adenosine A(1) (CPA), A(2A) (CGS21680C), A(2B) (NECA), and A(3) (2-Cl-IB-MECA) receptor agonists concentration-dependently increased HPOC proliferation. Agonist-induced HPOC proliferation was prevented by their selective antagonists, DPCPX, SCH442416, PSB603, and MRS1191. CPA and NECA facilitated osteogenic differentiation measured by increases in alkaline phosphatase (ALP) activity. This contrasts with the effect of CGS21680C which delayed HPOC differentiation; 2-Cl-IB-MECA was devoid of effect. Blockade of the A(2B) receptor with PSB603 prevented osteogenic differentiation by NECA. In the presence of the A(1) antagonist, DPCPX, CPA reduced ALP activity at 21 and 28 days in culture. At the same time points, blockade of A(2A) receptors with SCH442416 transformed the inhibitory effect of CGS21680C into facilitation. Inhibition of adenosine uptake with dipyridamole caused a net increase in osteogenic differentiation. The presence of all subtypes of adenosine receptors on HPOC was confirmed by immunocytochemistry. Data show that adenosine is an important regulator of osteogenic cell differentiation through the activation of subtype-specific receptors. The most abundant A(2B) receptor seems to have a consistent role in cell differentiation, which may be balanced through the relative strengths of A(1) or A(2A) receptors determining whether osteoblasts are driven into proliferation or differentiation.
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Affiliation(s)
- M Adelina Costa
- Laboratório de Farmacologia e Neurobiologia, UMIB, Instituto de Ciências Biomédicas Abel Salazar - Universidade do Porto (ICBAS-UP), Portugal
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16
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Oses JP, Batassini C, Pochmann D, Böhmer AE, Vuaden FC, Silvestrin RB, Oliveira A, Bonan CD, Bogo MR, Souza DO, Portela LVC, Sarkis JJDF, Mello e Souza T. The hydrolysis of striatal adenine- and guanine-based purines in a 6-hydroxydopamine rat model of Parkinson's disease. Neurochem Res 2010; 36:215-22. [PMID: 21046237 DOI: 10.1007/s11064-010-0305-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2010] [Indexed: 01/08/2023]
Abstract
Parkinson's disease (PD) is characterized by a progressive neurodegeneration in the substantia nigra and a striatal dopamine decrease. Striatal extracellular adenosine and ATP modulate the dopaminergic neurotransmission whereas guanosine has a protective role in the brain. Therefore, the regulation of their levels by enzymatic activity may be relevant to the clinical feature of PD. Here it was evaluated the extracellular nucleotide hydrolysis from striatal slices 4 weeks after a unilateral infusion with 6-OHDA into the medial forebrain bundle. This infusion increased ADP, AMP, and GTP hydrolysis by 15, 25, and 41%, respectively, and decreased GDP hydrolysis by 60%. There was no change in NTPDases1, 2, 3, 5, 6, and 5'-nucleotidase transcription. Dopamine depletion changes nucleotide hydrolysis and, therefore, alters the regulation of striatal nucleotide levels. These changes observed in 6-OHDA-lesioned animals may contribute to the symptoms observed in the model and provide evidence to indicate that extracellular purine hydrolysis is a key factor in understanding PD, giving hints for new therapies.
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Affiliation(s)
- Jean Pierre Oses
- Departamento de Bioquímica, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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17
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Pajski ML, Venton BJ. Adenosine Release Evoked by Short Electrical Stimulations in Striatal Brain Slices is Primarily Activity Dependent. ACS Chem Neurosci 2010; 1:775-787. [PMID: 21218131 DOI: 10.1021/cn100037d] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Adenosine is an important neuromodulator in the brain. Traditionally, adenosine is thought to arise in the extracellular space by either an extracellular mechanism, where it is formed outside the cell by the breakdown of released ATP, or an intracellular mechanism, where adenosine made inside the cell is transported out. Recently, a proposed third mechanism of activity dependent adenosine release has also been proposed. Here, we used fast-scan cyclic voltammetry to compare the time course and mechanism of adenosine formation evoked by either low- or high-frequency stimulations in striatal rat brain slices. Low-frequency stimulations (5 pulses at 10 Hz) resulted in an average adenosine efflux of 0.22 ± 0.02 μM, while high-frequency stimulations (5 pulses, 60 Hz) evoked 0.36 ± 0.04 μM. Blocking intracellular formation by inhibiting adenosine transporters with S-(4-nitrobenzyl)-6-thioinosine (NBTI) or propentofylline did not decrease release for either frequency, indicating that the release was not due to the intracellular mechanism. Blocking extracellular formation with ARL-67156 reduced low-frequency release about 60%, but did not affect high-frequency release. Both low- and high-frequency stimulated release were almost completely blocked by removal of calcium, indicating activity dependence. Reducing dopamine efflux did not affect adenosine release but inhibiting ionotropic glutamate receptors did, indicating that adenosine release is dependent on downstream effects of glutamate. Therefore, adenosine release after short, high-frequency physiological stimulations is independent of transporter activity or ATP metabolism, and may be due to direct release of adenosine after glutamate receptor activation.
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Affiliation(s)
- Megan L. Pajski
- Chemistry Department, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - B. Jill Venton
- Chemistry Department, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904, United States
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18
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Genzen JR, Yang D, Ravid K, Bordey A. Activation of adenosine A2B receptors enhances ciliary beat frequency in mouse lateral ventricle ependymal cells. Cerebrospinal Fluid Res 2009; 6:15. [PMID: 19922651 PMCID: PMC2791093 DOI: 10.1186/1743-8454-6-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 11/18/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ependymal cells form a protective monolayer between the brain parenchyma and cerebrospinal fluid (CSF). They possess motile cilia important for directing the flow of CSF through the ventricular system. While ciliary beat frequency in airway epithelia has been extensively studied, fewer reports have looked at the mechanisms involved in regulating ciliary beat frequency in ependyma. Prior studies have demonstrated that ependymal cells express at least one purinergic receptor (P2X7). An understanding of the full range of purinergic receptors expressed by ependymal cells, however, is not yet complete. The objective of this study was to identify purinergic receptors which may be involved in regulating ciliary beat frequency in lateral ventricle ependymal cells. METHODS High-speed video analysis of ciliary movement in the presence and absence of purinergic agents was performed using differential interference contrast microscopy in slices of mouse brain (total number of animals = 67). Receptor identification by this pharmacological approach was corroborated by immunocytochemistry, calcium imaging experiments, and the use of two separate lines of knockout mice. RESULTS Ciliary beat frequency was enhanced by application of a commonly used P2X7 agonist. Subsequent experiments, however, demonstrated that this enhancement was observed in both P2X7+/+ and P2X7-/- mice and was reduced by pre-incubation with an ecto-5'-nucleotidase inhibitor. This suggested that enhancement was primarily due to a metabolic breakdown product acting on another purinergic receptor subtype. Further studies revealed that ciliary beat frequency enhancement was also induced by adenosine receptor agonists, and pharmacological studies revealed that ciliary beat frequency enhancement was primarily due to A2B receptor activation. A2B expression by ependymal cells was subsequently confirmed using A2B-/-/beta-galactosidase reporter gene knock-in mice. CONCLUSION This study demonstrates that A2B receptor activation enhances ciliary beat frequency in lateral ventricle ependymal cells. Ependymal cell ciliary beat frequency regulation may play an important role in cerebral fluid balance and cerebrospinal fluid dynamics.
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Affiliation(s)
- Jonathan R Genzen
- Departments of Neurosurgery & Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8082, USA
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19
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Costa G, Pereira T, Neto AM, Cristóvão AJ, Ambrósio AF, Santos PF. High glucose changes extracellular adenosine triphosphate levels in rat retinal cultures. J Neurosci Res 2009; 87:1375-80. [PMID: 19084903 DOI: 10.1002/jnr.21956] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Diabetic retinopathy (DR) is the leading cause of blindness in adults. In diabetes, there is activation of microglial cells and a concomitant release of inflammatory mediators. However, it remains unclear how diabetes triggers an inflammatory response in the retina. Activation of P2 purinergic receptors by adenosine triphosphate (ATP) may contribute to the inflammatory response in the retina, insofar as it has been shown to be associated with microglial activation and cytokine release. In this work, we evaluated how high glucose, used as a model of hyperglycemia, considered the main factor in the development of DR, affects the extracellular levels of ATP in retinal cell cultures. We found that basal extracellular ATP levels were not affected by high glucose or mannitol, but the extracellular elevation of ATP, after a depolarizing stimulus, was significantly higher in retinal cells cultured in high glucose compared with control or mannitol-treated cells. The increase in the extracellular ATP was prevented by application of botulinum neurotoxin A or by removal of extracellular calcium. In addition, degradation of exogenously added ATP was significantly lower in high-glucose-treated cells. It was also observed that, in retinal cells cultured under high-glucose conditions, the changes in the intracellular calcium concentrations were greater than those in control or mannitol-treated cells. In conclusion, in this work we have shown that high glucose alters the purinergic signaling system in the retina, by increasing the exocytotic release of ATP and decreasing its extracellular degradation. The resulting high levels of extracellular ATP may lead to inflammation involved in the pathogenesis of DR.
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Affiliation(s)
- G Costa
- Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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20
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Duarte-Araújo M, Nascimento C, Timóteo MA, Magalhães-Cardoso MT, Correia-de-Sá P. Relative contribution of ecto-ATPase and ecto-ATPDase pathways to the biphasic effect of ATP on acetylcholine release from myenteric motoneurons. Br J Pharmacol 2009; 156:519-33. [PMID: 19154428 DOI: 10.1111/j.1476-5381.2008.00058.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE The relative contribution of distinct ecto-nucleotidases to the modulation of purinergic signalling may depend on differential tissue distribution and substrate preference. EXPERIMENTAL APPROACH Extracellular ATP catabolism (assessed by high-performance liquid chromatography) and its influence on [(3)H]acetylcholine ([(3)H]ACh) release were investigated in the myenteric plexus of rat ileum in vitro. KEY RESULTS ATP was primarily metabolized via ecto-ATPDase (adenosine 5'-triphosphate diphosphohydrolase) into AMP, which was then dephosphorylated into adenosine by ecto-5'-nucleotidase. Alternative conversion of ATP into ADP by ecto-ATPase (adenosine 5'-triphosphatase) was more relevant at high ATP concentrations. ATP transiently increased basal [(3)H]ACh outflow in a 2',3'-O-(2,4,6-trinitrophenyl)adenosine-5'-triphosphate (TNP-ATP)-dependent, tetrodotoxin-independent manner. ATP and ATPgammaS (adenosine 5'-[gamma-thio]triphosphate), but not alpha,beta-methyleneATP, decreased [(3)H]ACh release induced by electrical stimulation. ADP and ADPbetaS (adenosine 5'[beta-thio]diphosphate) only decreased evoked [(3)H]ACh release. Inhibition by ADPbetaS was prevented by MRS 2179 (2'-deoxy-N(6)-methyl adenosine 3',5'-diphosphate diammonium salt, a selective P2Y(1) antagonist); blockade of ADP inhibition required co-application of MRS 2179 plus adenosine deaminase (which inactivates endogenous adenosine). Blockade of adenosine A(1) receptors with 1,3-dipropyl-8-cyclopentyl xanthine enhanced ADPbetaS inhibition, indicating that P2Y(1) stimulation is cut short by tonic adenosine A(1) receptor activation. MRS 2179 facilitated evoked [(3)H]ACh release, an effect reversed by the ecto-ATPase inhibitor, ARL67156, which delayed ATP conversion into ADP without affecting adenosine levels. CONCLUSIONS AND IMPLICATIONS ATP transiently facilitated [(3)H]ACh release from non-stimulated nerve terminals via prejunctional P2X (probably P2X(2)) receptors. Hydrolysis of ATP directly into AMP by ecto-ATPDase and subsequent formation of adenosine by ecto-5'-nucleotidase reduced [(3)H]ACh release via inhibitory adenosine A(1) receptors. Stimulation of inhibitory P2Y(1) receptors by ADP generated alternatively via ecto-ATPase might be relevant in restraining ACh exocytosis when ATP saturates ecto-ATPDase activity.
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Affiliation(s)
- M Duarte-Araújo
- Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Portugal
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Early temporal changes in ecto-nucleotidase activity after cortical stab injury in rat. Neurochem Res 2007; 33:873-9. [PMID: 17992570 DOI: 10.1007/s11064-007-9529-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 10/11/2007] [Indexed: 01/19/2023]
Abstract
During a variety of insults to the brain adenine nucleotides are released in large quantities from damaged cells, triggering multiple cellular responses to injury. Here, we evaluated changes in extracellular ATP, ADP and AMP hydrolysis at different times (0-24 hours) after unilateral cortical stab injury (CSI) in adult rats. Results demonstrated that 24 hours following CSI, ATP and ADP hydrolyzing activities were not significantly altered in injured cortex. Based on calculated V (ATP)/V (ADP) ratio it was concluded that ATP/ADP hydrolysis was primarily catalyzed by NTPDase1 enzyme form. In contrast, AMP hydrolysis, catalyzed by 5'-nucleotidase, was significantly reduced at least 4 hours following CSI. Kinetic analysis and Lineweaver-Burk transformation of the enzyme velocities obtained over the range of AMP concentrations (0.05-1.50 mM) revealed that inhibition of 5'-nucleotidase activity after CSI was of the uncompetitive type. Taken together our data suggest that injured tissue has reduced potential for extracellular metabolism of adenine nucleotides in early stages after CSI.
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Modrak-Wójcik A, Kirilenko A, Shugar D, Kierdaszuk B. Role of ionization of the phosphate cosubstrate on phosphorolysis by purine nucleoside phosphorylase (PNP) of bacterial (E. coli) and mammalian (human) origin. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 37:153-64. [PMID: 17639373 DOI: 10.1007/s00249-007-0205-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Revised: 05/31/2007] [Accepted: 06/12/2007] [Indexed: 10/23/2022]
Abstract
Kinetics of the reactions of purine nucleoside phosphorylases (PNP) from E. coli (PNP-I, the product of the deoD gene) and human erythrocytes with their natural substrates guanosine (Guo), inosine (Ino), a substrate analogue N(7)-methylguanosine (m(7)Guo), and orthophosphate (P(i), natural cosubstrate) and its thiophosphate analogue (SP(i)), found to be a weak cosubstrate, have been studied in the pH range 5-8. In this pH range Guo and Ino exist predominantly in the neutral forms (pK(a) 9.2 and 8.8); m(7)Guo consists of an equilibrium mixture of the cationic and zwitterionic forms (pK(a) 7.0); and P(i) and SP(i) exhibit equilibria between monoanionic and dianionic forms (pK(a) 6.7 and 5.4, respectively). The phosphorolysis of m(7)Guo (at saturated concentration) with both enzymes exhibits Michaelis kinetics with SP(i), independently of pH. With P(i), the human enzyme shows Michaelis kinetics only at pH approximately 5. However, in the pH range 5-8 for the bacterial enzyme, and 6-8 for the human enzyme, enzyme kinetics with P(i) are best described by a model with high- and low-affinity states of the enzymes, denoted as enzyme-substrate complexes with one or two active sites occupied by P(i), characterized by two sets of enzyme-substrate dissociation constants (apparent Michaelis constants, K (m1) and K (m2)) and apparent maximal velocities (V (max1) and V (max2)). Their values, obtained from non-linear least-squares fittings of the Adair equation, were typical for negative cooperativity of both substrate binding (K (m1) < K (m2)) and enzyme kinetics (V (max1)/K (m1) > V (max2)/K (m2)). Comparison of the pH-dependence of the substrate properties of P(i) versus SP(i) points to both monoanionic and dianionic forms of P(i) as substrates, with a marked preference for the dianionic species in the pH range 5-8, where the population of the P(i) dianion varies from 2 to 95%, reflected by enzyme efficiency three orders of magnitude higher at pH 8 than that at pH 5. This is accompanied by an increase in negative cooperativity, characterized by a decrease in the Hill coefficient from n (H) approximately 1 to n (H) approximately 0.7 for Guo with the human enzyme, and to n (H) approximately 0.7 and 0.5 for m(7)Guo with the E. coli and human enzymes, respectively. Possible mechanisms of cooperativity are proposed. Attention is drawn to the substrate properties of SP(i) in relation to its structure.
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Affiliation(s)
- Anna Modrak-Wójcik
- Department of Biophysics, Institute of Experimental Physics, University of Warsaw, Warsaw, Poland
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Stimulation of an alpha1-adrenergic receptor downregulates ecto-5' nucleotidase activity on the apical membrane of RPE cells. Purinergic Signal 2006; 2:499-507. [PMID: 18404487 PMCID: PMC2104005 DOI: 10.1007/s11302-005-3980-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Accepted: 09/13/2005] [Indexed: 12/11/2022] Open
Abstract
The purines ATP and adenosine play an important role in the communication between the photoreceptors and the retinal pigment epithelium (RPE). While the RPE is known to release ATP into subretinal space, the source of extracellular adenosine is unclear. In other tissues, ecto-nucleotidases mediate the consecutive dephosphorylation of ATP to AMP, and AMP is converted to adenosine by ecto-5' nucleotidase (CD73). This study identifies ecto-5' nucleotidase on RPE cells and investigates modulation of enzyme activity. The RPE was the most active site of 5'AMP dephosphorylation in the posterior rat eye. The ecto-5' nucleotidase inhibitor alphabetamADP prevented the production adenosine by the apical membrane of the bovine RPE. Cultured human ARPE-19 cells expressed mRNA and protein for ecto-5' nucleotidase. The production of phosphate from 5'AMP by ARPE-19 cells was inhibited by alphabetamADP, but the ecto-alkaline phosphatase inhibitor levamisole had no effect. Degradation of 5'AMP was blocked by norepinephrine, epinephrine and phenylephrine, with inhibition by antagonists prazosin and corynanthine implicating the alpha1 adrenergic receptor. The block of enzyme activity by norepinephrine was rapid, occurring within 1 min, and was similar at both 4 and 37 degrees C, consistent with cleavage of the enzyme from its GPI anchor. HPLC measurements indicated norepinephrine reduced levels of adenosine in the bath. In the apical face of the bovine-RPE eyecup, norepinephrine reduced the production of phosphate from 5'AMP, suggesting that both receptor and enzyme face sub-retinal space. In conclusion, RPE cells express ecto-5' nucleotidase, with activity on the apical membrane, and stimulation of alpha-1 adrenergic receptors downregulates activity. As epinephrine is released at light onset, and adenosine can inhibit phagocytosis, the corresponding decrease in subretinal adenosine levels may contribute to the enhanced the phagocytosis of rod outer segments that occurs at this time.
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Barreto-Chaves MLM, Carneiro-Ramos MS, Cotomacci G, Júnior MBC, Sarkis JJF. E-NTPDase 3 (ATP diphosphohydrolase) from cardiomyocytes, activity and expression are modulated by thyroid hormone. Mol Cell Endocrinol 2006; 251:49-55. [PMID: 16584835 DOI: 10.1016/j.mce.2006.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 01/12/2006] [Accepted: 02/20/2006] [Indexed: 11/19/2022]
Abstract
Degradation of adenine nucleotides by myocardial cells occurs, in part, by a cascade of surface-located enzymes converting ATP into adenosine that has important implications for the regulation of the nucleotide/nucleoside ratio modulating the cardiac functions. Thyroid hormones have profound effects on cardiovascular system, as observed in hypo- and hyperthyroidism. Combined biochemical parameters and gene expression analysis approaches were used to investigate the influence of tri-iodothyronine (T3) on ATP and ADP hydrolysis by isolated myocytes. Cultures of cardiomyocytes were submitted to increasing doses of T3 for 24h. Enzymatic activity and expression were evaluated. T3 (0.1 nM) caused an increase in ATP and ADP hydrolysis. Experiments with specific inhibitors suggest the involvement of an NTPDase, which was confirmed by an increase in NTPDase 3 messenger RNA (mRNA) levels. Since T3 promotes an increase in the contractile protein, leading to cardiac hypertrophy, it is tempting to postulate that the increase in ATP hydrolysis and the decrease in the extracellular levels signify an important factor for prevention of excessive contractility.
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Affiliation(s)
- Maria Luiza M Barreto-Chaves
- Laboratory of Cellular Biology and Functional Anatomy, Department of Anatomy, Biomedical Sciences Institute, University of São Paulo, Av. Prof. Lineu Prestes 2415, Cidade Universitária, São Paulo, SP 05508-900, Brazil.
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Murata T, Suzuki S, Takeuchi T, Takeshita T. Relation between plasma adenosine and serum TSH levels in women with hyperemesis gravidarum. Arch Gynecol Obstet 2005; 273:331-6. [PMID: 16292579 DOI: 10.1007/s00404-005-0091-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Accepted: 09/30/2005] [Indexed: 10/25/2022]
Abstract
INTRODUCTION This study investigated the relation between adenosine and thyroid function associated with hyperemesis gravidarum. METHODS We examined 84 Japanese singleton pregnant women with an average age of 33.0+/-5.8 years at 9-12 weeks gestation being managed at our hospital. The patients were divided into three groups according to the severity of emesis: (1) those with hyperemesis gravidarum (nausea and vomiting with weight loss >5%, n=13), (2) those with emesis (nausea and vomiting with weight loss <5%, n=31), and (3) those with no symptoms as a control (n=40). RESULTS The average serum TSH levels in the emesis and hyperemesis groups were significantly higher than that in the control group (P<0.05). The average plasma adenosine level in the hyperemesis group was significantly higher than those in the control pregnant and emesis groups (P<0.05). There were no significant differences in plasma adenosine levels between the control pregnant and emesis groups. The serum TSH level showed significant correlations with weight loss (%) and plasma adenosine levels (P<0.05). CONCLUSIONS Our findings support the possible role of adenosine in counteracting the further progression of hyperemesis gravidarum associated with gestational thyrotoxicosis.
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Affiliation(s)
- Tomoaki Murata
- Department of Obstetrics and Gynecology, Tokyo Rinkai Hospital, 1-4-2 Rinkai-cho, Edogawa-ku, 134-0086 Tokyo, Japan
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Hunsucker SA, Mitchell BS, Spychala J. The 5'-nucleotidases as regulators of nucleotide and drug metabolism. Pharmacol Ther 2005; 107:1-30. [PMID: 15963349 DOI: 10.1016/j.pharmthera.2005.01.003] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2005] [Indexed: 11/19/2022]
Abstract
The 5'-nucleotidases are a family of enzymes that catalyze the dephosphorylation of nucleoside monophosphates and regulate cellular nucleotide and nucleoside levels. While the nucleoside kinases responsible for the initial phosphorylation of salvaged nucleosides have been well studied, many of the catabolic nucleotidases have only recently been cloned and characterized. Aside from maintaining balanced ribo- and deoxyribonucleotide pools, substrate cycles that are formed with kinase and nucleotidase activities are also likely to regulate the activation of nucleoside analogues, a class of anticancer and antiviral agents that rely on the nucleoside kinases for phosphorylation to their active forms. Both clinical and in vitro studies suggest that an increase in nucleotidase activity can inhibit nucleoside analogue activation and result in drug resistance. The physiological role of the 5'-nucleotidases will be covered in this review, as will the evidence that these enzymes can mediate resistance to nucleoside analogues.
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Affiliation(s)
- Sally Anne Hunsucker
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Pawelczyk T, Grden M, Rzepko R, Sakowicz M, Szutowicz A. Region-specific alterations of adenosine receptors expression level in kidney of diabetic rat. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 167:315-25. [PMID: 16049319 PMCID: PMC1603567 DOI: 10.1016/s0002-9440(10)62977-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pathological alterations of renal function in insulin-dependent diabetes have been attributed to numerous factors, including adenosine. This study examined the expression levels of adenosine receptors (ARs) in the kidney of the streptozotocin-induced diabetic rat. In the diabetic kidney A1-AR mRNA levels increased 1.7- and 2.8-fold in cortex and medulla, respectively. This was accompanied by increased A1-AR protein levels in membranes of kidney cortex (1.5-fold) and medulla (threefold). A1-AR immunoreactivity increased strongly along medullar tubules especially in the collecting duct. The levels of A2a-AR mRNA increased twofold in diabetic kidney cortex but remained unchanged in medulla; however, A2a-AR protein levels increased more than threefold in cortex. Immunohistochemistry showed increased A2a-AR immunoreactivity in luminal membranes of cortical collecting ducts and in epithelial cells of preglomerular vessels. There were no significant changes in A2b-AR expression in diabetic kidney except in medullar membranes, where the receptor protein content decreased by 60%. A3-AR mRNA levels in diabetic kidney remained unchanged, but membrane-associated A3-AR protein levels increased by 70% in diabetic kidney cortex and decreased by 80% in medulla. These changes in ARs genes expression, receptor protein content, and cellular and tissue distribution, correspond to abnormalities characteristic of the diabetic kidney, suggesting involvement in pathogenesis of diabetic nephropathy.
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Affiliation(s)
- Tadeusz Pawelczyk
- Department of Molecular Medicine, Medical University of Gdansk, ul. Debinki 7, paw. 29, 80-211 Gdansk, Poland.
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Carneiro-Ramos MS, da Silva VB, Coutinho MB, Battastini AMO, Sarkis JJF, Barreto-Chaves MLM. Thyroid hormone stimulates 5'-ecto-nucleotidase of neonatal rat ventricular myocytes. Mol Cell Biochem 2005; 265:195-201. [PMID: 15543949 DOI: 10.1023/b:mcbi.0000044396.31443.a8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Degradation of adenine nucleotides in myocardial cells has important physiological implications associated with the regulation of the high-energy phosphate precursor pool and the production of adenosine. Adenosine may be released as from cells or, following adenine nucleotides release, they may be metabolized and rapidly converted to adenosine via the action of an ectoenzyme cascade formed by an ATP diphosphohydrolase and a 5'-nucleotidase. Thyroid hormones are known to have profound effects on the cardiovascular system, as demonstrated by the changes accompanying both hypothyroidism and hyperthyroidism. We previously reported that thyroid hormone significantly increases the ecto-5'-nucleotidase (CD73) activity and expression in C6 glioma cells culture. The object of the present study was to evaluate the extracellular adenosine production from AMP in cardiomyocytes and also the effect of (T3) on activity and expression of the enzyme, CD73. Primary cultures of rat ventricular neonatal cardiac myocytes were submitted to increasing doses of T3 for 24 h. Cell viability and purity were estimated by measuring the release of lactate dehydrogenase (LDH) activity and immunofluorescence cell staining, respectively. CD73 activity was measurement using a malachite green method and RT-PCR was used to analyze enzyme expression. T3 stimulated CD73 activity and expression of the cells, suggesting that this effect could promote an increase in adenosine formation and, therefore, has an important modulatory role in the elicitation of responses that serve to restore the tissue oxygen supply-to-demand ratio back to normal.
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Duarte-Araújo M, Nascimento C, Alexandrina Timóteo M, Magalhães-Cardoso T, Correia-de-Sá P. Dual effects of adenosine on acetylcholine release from myenteric motoneurons are mediated by junctional facilitatory A(2A) and extrajunctional inhibitory A(1) receptors. Br J Pharmacol 2004; 141:925-34. [PMID: 14993098 PMCID: PMC1574269 DOI: 10.1038/sj.bjp.0705697] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2003] [Revised: 11/30/2003] [Accepted: 01/13/2004] [Indexed: 11/08/2022] Open
Abstract
1. The coexistence of both inhibitory A(1) and facilitatory A(2) adenosine receptors in the rat myenteric plexus prompted the question of how adenosine activates each receptor subtype to regulate cholinergic neurotransmission. 2. Exogenously applied adenosine (0.3-300 microm) decreased electrically evoked [(3)H]acetylcholine ([(3)H]ACh) release. Blocking A(1) receptors with 1,3-dipropyl-8-cyclopentylxanthine (10 nm) transformed the inhibitory action of adenosine into a facilitatory effect. Adenosine-induced inhibition was mimicked by the A(1) receptor agonist R-N(6)-phenylisopropyladenosine (0.3 microm), but the A(2A) agonist CGS 21680C (0.003 microm) produced a contrasting facilitatory effect. 3. Increasing endogenous adenosine levels, by the addition of (1) the adenosine precursor AMP (30-100 microm), (2) the adenosine kinase inhibitor 5'-iodotubercidin (10 microm) or (3) inhibitors of adenosine uptake (dipyridamole, 0.5 microm) and of deamination (erythro-9(2-hydroxy-3-nonyl)adenine, 50 microm), enhanced electrically evoked [(3)H]ACh release (5 Hz for 40 s). Release facilitation was prevented by adenosine deaminase (ADA, 0.5 U ml(-1)) and by the A(2A) receptor antagonist ZM 241385 (50 nm); these compounds decreased [(3)H]ACh release by 31+/-6% (n=7) and 37+/-10% (n=6), respectively. 4. Although inhibition of ecto-5'-nucleotidase by alpha,beta-methylene ADP (200 microm) or by concanavalin A (0.1 mg ml(-1)) attenuated endogenous adenosine formation from AMP, analysed by HPLC, the corresponding reduction in [(3)H]ACh release only became evident when stimulation of the myenteric plexus was prolonged to over 250 s. 5. In summary, we found that endogenously generated adenosine plays a predominantly tonic facilitatory effect mediated by prejunctional A(2A) receptors. Extracellular deamination and cellular uptake may restrict endogenous adenosine actions to the neuro-effector region near the release/production sites.
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Affiliation(s)
- Margarida Duarte-Araújo
- Laboratório de Farmacologia/UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal
| | - Carlos Nascimento
- Laboratório de Farmacologia/UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal
| | - M Alexandrina Timóteo
- Laboratório de Farmacologia/UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal
| | - Teresa Magalhães-Cardoso
- Laboratório de Farmacologia/UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia/UMIB, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto, L. Prof. Abel Salazar, 2, 4099-003 Porto, Portugal
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Magalhães-Cardoso MT, Pereira MF, Oliveira L, Ribeiro JA, Cunha RA, Correia-de-Sá P. Ecto-AMP deaminase blunts the ATP-derived adenosine A2A receptor facilitation of acetylcholine release at rat motor nerve endings. J Physiol 2003; 549:399-408. [PMID: 12679375 PMCID: PMC2342942 DOI: 10.1113/jphysiol.2003.040410] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
At synapses, ATP is released and metabolised through ecto-nucleotidases forming adenosine, which modulates neurotransmitter release through inhibitory A1 or facilitatory A2A receptors, according to the amounts of extracellular adenosine. Neuromuscular junctions possess an ecto-AMP deaminase that can dissociate extracellular ATP catabolism from adenosine formation. In this study we have investigated the pattern of ATP release and its conversion into adenosine, to probe the role of ecto-AMP deaminase in controlling acetylcholine release from rat phrenic nerve terminals. Nerve-evoked ATP release was 28 +/- 12 pmol (mg tissue)-1 at 1 Hz, 54 +/- 3 pmol (mg tissue)-1 at 5 Hz and disproportionally higher at 50 Hz (324 +/- 23 pmol (mg tissue)-1). Extracellular ATP (30 microM) was metabolised with a half time of 8 +/- 2 min, being converted into ADP then into AMP. AMP was either dephosphorylated into adenosine by ecto-5'-nucleotidase (inhibited by ATP and blocked by 200 microM alpha,beta-methylene ADP) or deaminated into IMP by ecto-AMP deaminase (inhibited by 200 microM deoxycoformycin, which increased adenosine formation). Dephosphorylation and deamination pathways also catabolised endogenously released adenine nucleotides, since the nerve-evoked extracellular AMP accumulation was increased by either alpha,beta-methylene ADP (200 microM) or deoxycoformycin (200 microM). In the presence of nitrobenzylthioinosine (30 microM) to inhibit adenosine transport, deoxycoformycin (200 microM) facilitated nerve-evoked [3H]acetylcholine release by 77 +/- 9 %, an effect prevented by the A2A receptor antagonist, ZM 241385 (10 nM). It is concluded that, while ecto-5'-nucleotidase is inhibited by released ATP, ecto-AMP deaminase activity transiently blunts adenosine formation, which would otherwise reach levels high enough to activate facilitatory A2A receptors on motor nerve terminals.
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Affiliation(s)
- M Teresa Magalhães-Cardoso
- Laboratório de Farmacologia-UMIB, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Portugal
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Walker JP, Barbato JC, Koch LG. Cardiac adenosine production in rat genetic models of low and high exercise capacity. Am J Physiol Regul Integr Comp Physiol 2002; 283:R168-73. [PMID: 12069942 DOI: 10.1152/ajpregu.00621.2001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously demonstrated that Copenhagen (COP) and DA inbred rat strains show a wide difference in a test for aerobic treadmill running that correlated positively with isolated cardiac function. The purpose of this study was to test adenosine production as a candidate intermediate phenotype that may explain part of the difference in running and cardiac performance in these genetic models for low and high aerobic capacity. Adenosine production was measured as the activity of soluble 5'-nucleotidase and membrane-bound ecto-5'-nucleotidase in the membrane pellet and supernatant fractions of left and right ventricular muscle and gracilis muscle taken from 10 DA and 10 COP rats. Ecto-5'-nucleotidase activity in the membrane pellet of hearts from both DA and COP accounted for the vast majority of the total tissue adenosine production (>90% in the left ventricle and >80% in the right ventricle). Ecto-5'-nucleotidase activity in the pellet fraction was significantly higher in the left (22.4%) and right (46.1%) ventricles of DA rats compared with COP rats, with no differences in total protein content. There were no significant differences between the strains for 5'-nucleotidase activity in the cardiac supernatant, the gracilis pellet, or the gracilis supernatant. These data support the hypothesis that an increase in cardiac adenosine production may contribute to the greater aerobic running capacity of the DA rats.
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Affiliation(s)
- Jon P Walker
- Functional Genomics Laboratory, Medical College of Ohio, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA
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Depreter M, Walker T, De Smet K, Beken S, Kerckaert I, Rogiers V, Roels F. Hepatocyte polarity and the peroxisomal compartment: a comparative study. THE HISTOCHEMICAL JOURNAL 2002; 34:139-51. [PMID: 12495220 DOI: 10.1023/a:1020990414190] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In search of factors that regulate the phenotype of the peroxisomal compartment in wild-type liver parenchymal cells, we compared hepatocyte polarity to peroxisome differentiation, using adult liver as the standard. Differentiation parameters were evaluated in a three-dimensional culture model (spheroid), in 'sandwich' and monolayer primary hepatocyte cultures, and in 15.5 and 18.5-day-old foetal rat liver. Peroxisomes, studied by immunohistochemistry, enzyme histochemistry, and catalase specific activity, were better differentiated depending on foetal age (day 18.5 > day 15.5) and culture type (spheroid > sandwich > monolayer). The hepatocyte polarity markers ATP-, ADP-, and AMP-hydrolysing activities were, in all models, mislocalized at the lateral plasma membrane, whereas in contrast the multidrug resistance-associated protein 2 (mrp2) antigen was always correctly immunolocalized at the apical membrane domain. In cultures, the correct secretion of fluorescein (mrp2-mediated) into bile canaliculi was observed. Bile canaliculi (branching, ultrastructure and immunolocalization of the tight-junction associated protein ZO-1), were better differentiated in 18.5 than in 15.5-day-old foetal liver and in spheroid > sandwich > monolayer cultures. Our results show a parallelism between changes of the peroxisomal compartment and bile canalicular structure together with mrp2-mediated secretory function. Distinct polarization characteristics do not necessarily change simultaneously, suggesting different regulatory mechanisms.
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Affiliation(s)
- Marianne Depreter
- Department of Human Anatomy, Embryology, Histology, and Medical Physics, Ghent University, Godshuizenlaan 4, B-9000 Gent, Belgium
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García-Ayllón MS, Campoy FJ, Vidal CJ, Muñoz-Delgado E. Identification of inactive ecto-5'-nucleotidase in normal mouse muscle and its increased activity in dystrophic Lama2(dy) mice. J Neurosci Res 2001; 66:656-65. [PMID: 11746385 DOI: 10.1002/jnr.10014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ecto-5'-nucleotidase (eNT) activity and protein in normal (NM) and merosin-deficient dystrophic (DM) Lama2(dy) mice muscle were studied. eNT activity in DM was three- to four-fold that in NM. eNT in NM and DM displayed the same kinetic properties. Slot and Western blotting revealed that the immunoreactive protein was two to three times more abundant in control muscle, when NM and DM samples with the same eNT activity were compared, indicating that mouse muscle contains catalytically inactive eNT components. eNT activity and protein peaks coincided in sedimentation analyses, revealing that inactive eNT occurs as dimers. Most eNT activity and protein of NM bound to Lens culinaris (LCA) or Ricinus communis (RCA) agglutinins, but half of the activity and one-third of the protein bound to wheat germ agglutinin (WGA). Although WGA interaction did not permit full separation of inactive eNT, the results suggest that similar proportions of active species with and without WGA reactivity occur in mouse muscle, whereas a great fraction of the inactive eNT variants lack WGA reactivity. Because the level of eNT protein was little modified in DM, the higher eNT activity in dystrophic than in control muscle may result from misregulation in the synthesis of active and inactive eNT species or from conversion of inactive into active components.
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Affiliation(s)
- M S García-Ayllón
- Departamento de Bioquímica y Biología Molecular-A, Universidad de Murcia, Espinardo, Murcia, Spain
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Abstract
Ecto-nucleotidases play a pivotal role in terminating the signalling via ATP and in producing adenosine, a neuromodulator in the nervous system. We have now investigated the pattern of adenosine formation with different concentrations of extracellular ATP in rat hippocampal nerve terminals. It was found that adenosine formation is delayed with increasing concentrations of ATP. Also, the rate of adenosine formation increased sharply when the extracellular concentrations of ATP + ADP decrease below 5 microM, indicating that ATP/ADP feed-forwardly inhibit ecto-5'-nucleotidase allowing a burst-like formation of adenosine possibly designed to activate facilitatory A2A receptors. Initial rate measurements of ecto-5'-nucleotidase in hippocampal nerve terminals, using IMP as substrate, showed that ATP and ADP are competitive inhibitors (apparent Ki of 14 and 4 microM). In contrast, in hippocampal immunopurified cholinergic nerve terminals, a burst-like formation of adenosine is not apparent, suggesting that channelling processes may overcome the feed-forward inhibition of ecto-5'-nucleotidase, thus favouring A1 receptor activation.
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Affiliation(s)
- R A Cunha
- Department of Chemistry & Biochemistry, Faculty of Sciences, University of Lisbon, Portugal.
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Koziolkiewicz M, Gendaszewska E, Maszewska M, Stein CA, Stec WJ. The mononucleotide-dependent, nonantisense mechanism of action of phosphodiester and phosphorothioate oligonucleotides depends upon the activity of an ecto-5'-nucleotidase. Blood 2001; 98:995-1002. [PMID: 11493444 DOI: 10.1182/blood.v98.4.995] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many reports indicate different nonantisense yet sequence-specific effects of antisense phosphorothioate oligonucleotides. Products of enzymatic degradation of the oligonucleotides can also influence cell proliferation. The cytotoxic effects of deoxyribonucleoside-5'-phosphates (dNMPs) and their 5'-phosphorothioate analogs, deoxyribonucleoside-5'-monophosphorothioates (dNMPSs) on 4 human cell types (HeLa, HL-60, K-562, and endothelial cells) were examined, and the effects were correlated with the catabolism of these compounds. The results indicate that differences in cytotoxicity of dNMPs or dNMPSs in these cells depend upon different activity of an ecto-5'-nucleotidase. It has also been found that dNMPSs stimulate proliferation of human umbilical vein endothelial cells and HL-60 cells in a concentration-dependent manner. This stimulation might be caused by the binding of deoxynucleoside-5'-phosphorothioates to as-yet unidentified nucleotide receptor(s) at the cell surface. (Blood. 2001;98:995-1002)
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Affiliation(s)
- M Koziolkiewicz
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Łódz,
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Cunha RA. Adenosine as a neuromodulator and as a homeostatic regulator in the nervous system: different roles, different sources and different receptors. Neurochem Int 2001; 38:107-25. [PMID: 11137880 DOI: 10.1016/s0197-0186(00)00034-6] [Citation(s) in RCA: 461] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Adenosine exerts two parallel modulatory roles in the CNS, acting as a homeostatic modulator and also as a neuromodulator at the synaptic level. We will present evidence to suggest that these two different modulatory roles are fulfilled by extracellular adenosine originated from different metabolic sources, and involve receptors with different sub-cellular localisation. It is widely accepted that adenosine is an inhibitory modulator in the CNS, a notion that stems from the preponderant role of inhibitory adenosine A(1) receptors in defining the homeostatic modulatory role of adenosine. However, we will review recent data that suggests that the synaptically localised neuromodulatory role of adenosine depend on a balanced activation of inhibitory A(1) receptors and mostly facilitatory A(2A) receptors. This balanced activation of A(1) and A(2A) adenosine receptors depends not only on the transient levels of extracellular adenosine, but also on the direct interaction between A(1) and A(2A) receptors, which control each other's action.
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Affiliation(s)
- R A Cunha
- Laboratory of Neurosciences, Faculty of Medicine, University of Lisbon, Portugal.
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Contribution of ecto-5′-nucleotidase to the inhibition of platelet aggregation by human endothelial cells. Blood 2000. [DOI: 10.1182/blood.v96.6.2157] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
We studied the role of adenosine (Ado), which is generated from adenine nucleotides via the activity of ecto-5′-nucleotidase (ecto-5′-NT), in the inhibition of platelet aggregation by endothelial cells (ECs). The enzymatic activity of nucleotidases on human umbilical vein endothelial cells (HUVECs) was examined with regard to (1) the inhibition of adenosine diphosphate (ADP)–induced platelet aggregation and (2) the liberation of inorganic phosphate from adenine nucleotides. Adenosine 5′-monophosphate (AMP) preincubated with HUVECs significantly inhibited ADP-induced platelet aggregation. This was completely blocked by the treatment of HUVECs with a specific inhibitor of ecto-5′-NT, 5′-[αβ-methylene] diphosphate (APCP), or by the addition of an A2a receptor antagonist. Neither nitric oxide nor prostacyclin was involved in this inhibitory activity, suggesting that Ado generated in the incubation medium by the activity of 5′-NT on HUVECs inhibited platelet aggregation. When ADP was incubated on HUVECs, it lost most of its agonistic activity for platelets. Pretreatment of HUVECs with APCP at a concentration that abolished ecto-5′-NT activity partially restored ADP-induced platelet aggregation. Ecto-5′-NT contributes to EC function by inhibiting platelet aggregation in cooperation with ATP diphosphohydrolase, which degrades ADP to AMP.
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Abstract
We studied the role of adenosine (Ado), which is generated from adenine nucleotides via the activity of ecto-5′-nucleotidase (ecto-5′-NT), in the inhibition of platelet aggregation by endothelial cells (ECs). The enzymatic activity of nucleotidases on human umbilical vein endothelial cells (HUVECs) was examined with regard to (1) the inhibition of adenosine diphosphate (ADP)–induced platelet aggregation and (2) the liberation of inorganic phosphate from adenine nucleotides. Adenosine 5′-monophosphate (AMP) preincubated with HUVECs significantly inhibited ADP-induced platelet aggregation. This was completely blocked by the treatment of HUVECs with a specific inhibitor of ecto-5′-NT, 5′-[αβ-methylene] diphosphate (APCP), or by the addition of an A2a receptor antagonist. Neither nitric oxide nor prostacyclin was involved in this inhibitory activity, suggesting that Ado generated in the incubation medium by the activity of 5′-NT on HUVECs inhibited platelet aggregation. When ADP was incubated on HUVECs, it lost most of its agonistic activity for platelets. Pretreatment of HUVECs with APCP at a concentration that abolished ecto-5′-NT activity partially restored ADP-induced platelet aggregation. Ecto-5′-NT contributes to EC function by inhibiting platelet aggregation in cooperation with ATP diphosphohydrolase, which degrades ADP to AMP.
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Santos PF, Caramelo OL, Carvalho AP, Duarte CB. Characterization of ATP release from cultures enriched in cholinergic amacrine-like neurons. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-4695(19991115)41:3<340::aid-neu3>3.0.co;2-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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40
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Garvey EP, Prus KL. A specific inhibitor of heart cytosolic 5'-nucleotidase I attenuates hydrolysis of adenosine 5'-monophosphate in primary rat myocytes. Arch Biochem Biophys 1999; 364:235-40. [PMID: 10190979 DOI: 10.1006/abbi.1999.1133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ATP breakdown was triggered in primary rat myocytes in the presence of coformycin to force the catabolism of AMP through hydrolysis to adenosine. Selective inhibitors of the cytosolic 5'-nucleotidase I (c-N-I) from myocardium were used to measure the intracellular contribution of this enzyme to AMP hydrolysis under these conditions. The selective inhibitor 5-ethynyl-2',3'-dideoxyuridine inhibited the hydrolysis of AMP to adenosine in a concentration-dependent manner with an IC50 value of 20 microM. Maximal inhibition prevented 76% of the conversion of AMP to adenosine, indicating that under these conditions the majority of AMP hydrolysis in rat myocytes occurs through this enzyme. When ATP breakdown was triggered in the presence of thymidine 5'-phosphonate, a more potent inhibitor of the purified cytosolic 5'-nucleotidase, less inhibition of AMP hydrolysis occurred and only after prolonged preincubation of the myocytes with the inhibitor. These data demonstrate that the selective nucleoside inhibitors of c-N-I can effectively block the hydrolysis of AMP inside myocytes. Thus, these inhibitors may be useful tools in identifying the role of c-N-I during ATP catabolism in whole tissue and animal experiments.
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Affiliation(s)
- E P Garvey
- Division of Biochemistry, Glaxo Wellcome, Research Triangle Park, North Carolina, 27709, USA.
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41
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Kuzmin AI, Lakomkin VL, Kapelko VI, Vassort G. Interstitial ATP level and degradation in control and postmyocardial infarcted rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C766-71. [PMID: 9730960 DOI: 10.1152/ajpcell.1998.275.3.c766] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
With the aim of estimating interstitial levels and the breakdown process of ATP, cardiac microdialysis was performed in the left ventricular wall of in situ control and postinfarcted as well as of isolated, Langendorff-perfused rat hearts. With the use of a bioluminescence technique for dialysate ATP measurement, the baseline interstitial fluid ATP concentration in in situ hearts was estimated to be 38 +/- 8 nM. Regional ischemia induced an early peak increase in interstitial fluid ATP to 373 +/- 73 nM that correlates with the maximal incidence of ventricular arrhythmias. During continuous infusion of individual adenine nucleotides (50 microM ATP, ADP, or AMP), the dialysate samples were analyzed for adenine nucleotides, nucleosides, and bases using HPLC with ultraviolet detection. The patterns of catabolites were consistent with the major pathway of metabolism, that is, sequential dephosphorylation catalyzed by a chain of separate ecto-nucleotidases. In in situ postinfarcted hearts as well as in perfused hearts, a reduced catabolism rate of extracellular adenine nucleotides was observed. In conclusion, in in situ rat hearts, ATP can be released in substantial amounts in the interstitium where it readily undergoes enzymatic degradation. Dephosphorylation occurs sequentially and faster in in situ control hearts than in in situ postinfarcted or in perfused hearts.
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Affiliation(s)
- A I Kuzmin
- Institute of Experimental Cardiology, National Cardiology Research Center, Moscow 121 552, Russia
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42
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Rosi F, Agostinho AB, Carlucci F, Zanoni L, Porcelli B, Marinello E, Galieni P, Tabucchi A. Behaviour of human lymphocytic isoenzymes of 5'-nucleotidase. Life Sci 1998; 62:2257-66. [PMID: 9651114 DOI: 10.1016/s0024-3205(98)00206-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The behaviour of 5'-nucleotidase isoenzymes (ecto-5'-nucleotidase, e-Ns and c-N-II soluble 5'-nucleotidases) was studied in lymphocytes from patients with B-cell chronic lymphocytic leukemia. A strong reduction in ecto- and soluble activities was observed, although the pattern of the three 5'-nucleotidases did not always strictly overlap. A significant decrease (p<0.05) in ecto-5'-nucleotidase, e-Ns and c-N-II was found in B and T populations (B lymphocytes: 1.13, 0.88 and 1.26 nmol/h/10(6) cells versus 95.96, 9.64 and 13.73 nmol/h/10(6) cells in controls; T lymphocytes: 1.31, 0.23 and 0.06 nmol/h/10(6) cells versus 9.25, 1.31 and 2.10 nmol/h/10(6) cells in healthy subjects). The percentage of ecto-5'-nucleotidase-positive cells (CD73+) was reduced in leukemia patients, indicating a lower number of active molecules on the cell surface. The results of RT-PCR analysis showed that the ecto-5'-nucleotidase mRNA of leukemia patients was not defective.
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Affiliation(s)
- F Rosi
- Institute of Biochemistry and Enzymology, University of Siena, Italy
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Sansum AJ, Chessell IP, Hicks GA, Trezise DJ, Humphrey PP. Evidence that P2X purinoceptors mediate the excitatory effects of alphabetamethylene-ADP in rat locus coeruleus neurones. Neuropharmacology 1998; 37:875-85. [PMID: 9776383 DOI: 10.1016/s0028-3908(98)00095-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Extracellular and whole-cell patch clamp recordings were used to study the excitatory responses elicited by purine nucleotides in pontine slices of the rat brain containing the locus coeruleus (LC). The P2 purinoceptor agonists, alphabeta-methyleneadenosine 5'-triphosphate (alphabetameATP) and adenosine 5'-O-(2-thiodiphosphate) (ADPalphabetaS), and a novel purinoceptor agonist, alphabeta-methyleneadenosine 5'-diphosphate (alphabetameADP), elicited concentration-dependent increases in the spontaneous firing rate over the concentration range (1-300 microM). On vagus nerve or dorsal root preparations alphabetameADP (100 microM) had no agonist activity. In the presence of both alphabetameATP (300 microM), ADPbetaS (300 microM) elicited a further and significant increase in the firing rate of the LC neurones, whilst neither alphabetameATP nor alphabetameADP (300 microM) elicited a further response. The P2 purinoceptor antagonists, suramin (100 microM) and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 30 microM), markedly attenuated responses to all three agonists. Whole-cell recording of membrane current showed that, at - 60 mV, alphabetameATP and alphabetameADP (both 100 microM) elicited inward currents of a similar magnitude, whilst the inward currents elicited by a lower concentration of ADPbetaS (30 microM) were larger and faded in the presence of this agonist. In the presence of tetrodotoxin and a combination of other neurotransmission blockers, both alphabetameATP and alphabetameADP still produced inward currents. Based on the known selectivity of the agonists used in this study, there appear to be two distinct P2 purinoceptor types present on neurones in the LC, which correspond to the P2X and P2Y types. The responses elicited by alphabetameADP appear to be mediated through a putative P2X purinoceptor, although further work is required to determine which P2X receptor subtype(s) are involved.
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Affiliation(s)
- A J Sansum
- Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, UK.
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Menezes de Oliveira E, Oliveira Battastini AM, Meirelles MN, Menezes Moreira C, Dutra Dias R, Freitas Sarkis JJ. Characterization and localization of an ATP diphosphohydrolase activity (EC 3.6.1.5) in sarcolemmal membrane from rat heart. Mol Cell Biochem 1997; 170:115-23. [PMID: 9144325 DOI: 10.1023/a:1006848701467] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In the present report we describe an ATP diphosphohydrolase (apyrase EC 3.6.1.5) in rat cardiac sarcolemma. It is Ca2+ dependent and is insensitive to ouabain, orthovanadate, N-ethylmaleimide (NEM), lanthanum, and oligomycin that are classical ATPase inhibitors. Sodium azide that is a mitochondrial inhibitor at low concentrations, did not affect the enzyme activity at 5.0 mM or below. In contrast, at high concentrations (> 10 mM) sodium azide inhibited the enzyme. Levamisole, a specific inhibitor of alkaline phosphatase and P1, P5-di(adenosine 5'-)pentaphosphate (Ap5A), a specific inhibitor of adenylate kinase did not inhibit the enzyme. Mercury chloride showed a parallel inhibition of the hydrolysis of both substrates of apyrase. Similar inhibition profiles are powerful evidence for a common catalytic site for the hydrolysis of both substrates. The enzyme has an optimum pH range of 7.5-8.0 and catalyzes the hydrolysis of triphospho- and diphosphonucleosides other than ATP or ADP. The apparent Km (Michaelis constant) and Vmax (maximal velocity) are 62.1 +/- 5.2 microM and 1255.7 +/- 178 micromol inorganic phosphate liberated/min/mg with ATP and 59.4 +/- 4.3 microM and 269.2 +/- 39 micromol inorganic phosphate liberated/min/mg with ADP. Enzyme markers indicated that this apyrase is associated with the plasma membrane. A deposition of lead phosphate granules on the outer surface of the sarcolemmal vesicles was observed by electron microscopy in the presence of either ATP or ADP as substrate. It is suggested that the ATP diphosphohydrolase could regulate the concentration of extracellular adenosine, and thus is important in the control of vascular tone and coronary flow.
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Affiliation(s)
- E Menezes de Oliveira
- University Hospital of Santa Maria, Center of Health Sciences, Federal University of Santa Maria, RS, Brazil
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Cunha RA, Correia-de-Sá P, Sebastião AM, Ribeiro JA. Preferential activation of excitatory adenosine receptors at rat hippocampal and neuromuscular synapses by adenosine formed from released adenine nucleotides. Br J Pharmacol 1996; 119:253-60. [PMID: 8886406 PMCID: PMC1915871 DOI: 10.1111/j.1476-5381.1996.tb15979.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. In the present work, we investigated the action of adenosine originating from extracellular catabolism of adenine nucleotides, in two preparations where synaptic transmission is modulated by both inhibitory A1 and excitatory A(2a)-adenosine receptors, the rat hippocampal Schaffer fibres/CA1 pyramid synapses and the rat innervated hemidiaphragm. 2. Endogenous adenosine tonically inhibited synaptic transmission, since 0.5-2 u ml-1 of adenosine deaminase increased both the population spike amplitude (30 +/- 4%) and field excitatory post-synaptic potential (f.e.p.s.p.) slope (27 +/- 4%) recorded from hippocampal slices and the evoked [3H]-acetylcholine ([3H]-ACh) release from the motor nerve terminals (25 +/- 2%). 3. alpha, beta-Methylene adenosine diphosphate (AOPCP) in concentrations (100-200 microM) that almost completely inhibited the formation of adenosine from the extracellular catabolism of AMP, decreased population spike amplitude by 39 +/- 5% and f.e.p.s.p. slope by 32 +/- 3% in hippocampal slices and [3H]-ACh release from motor nerve terminals by 27 +/- 3%. 4. Addition of exogenous 5'-nucleotidase (5 u ml-1) prevented the inhibitory effect of AOPCP on population spike amplitude and f.e.p.s.p. slope by 43-57%, whereas the P2 antagonist, suramin (100 microM), did not modify the effect of AOPCP. 5. In both preparations, the effect of AOPCP resulted from prevention of adenosine formation since it was no longer evident when accumulation of extracellular adenosine was hindered by adenosine deaminase (0.5-2 u ml-1). The inhibitory effect of AOPCP was still evident when A1 receptors were blocked by 1,3-dipropyl-8-cyclopentylxanthine (2.5-5 nM), but was abolished by the A2 antagonist, 3,7-dimethyl-1-propargylxanthine (10 microM). 6. These results suggest that adenosine originating from catabolism of released adenine nucleotides preferentially activates excitatory A2 receptors in hippocampal CAI pyramid synapses and in phrenic motor nerve endings.
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Affiliation(s)
- R A Cunha
- Laboratory of Pharmacology, Gulbenkian Institute of Science, Oeiras, Portugal
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Mallet RT, Sun J, Fan WL, Kang YH, Bünger R. Magnesium activated adenosine formation in intact perfused heart: predominance of ecto 5'-nucleotidase during hypermagnesemia. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1290:165-76. [PMID: 8645720 DOI: 10.1016/0304-4165(96)00016-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Magnesium ion is an allosteric effector of 5'-nucleotidase and thus activates adenosine production from AMP. Two distinct 5'-nucleotidase systems, the membrane-bound ecto and the soluble cytosolic isoforms, exist in mammalian myocardium. The aim of this study was to delineate the contributions of the ecto vs. cytosolic isoforms to Mg2+-stimulated cardiac purine nucleoside formation and release. Isolated guinea pig hearts were retrogradely perfused at their physiological aortic pressure with Krebs-Henseleit bicarbonate buffer fortified with 10 mM glucose. AMP and the adenylate degradatives adenosine and inosine were measured in coronary venous effluent and in epicardial transudate, which was sampled to estimate concentrations of adenylate degradatives in the interstitium. When perfusate Mg2+ was increased from 0.6 to 6 mM, coronary vascular resistance and spontaneous heart rate fell, and steady-state coronary venous release of adenosine + inosine rose severalfold. Cytosolic free magnesium, as estimated by 31P-NMR after 15 min of perfusion with 6 mM Mg2+ or from chemically measured indicator metabolites after 30 min, rose 60 and 144% respectively (P < 0.05). Excess Mg2+ stimulated purine nucleoside release nearly threefold in coronary venous effluent and four- to sevenfold in epicardial transudate. 50 microM, alpha,beta-methylene adenosine 5'-diphosphate (AOPCP), a selective inhibitor of ecto 5'-nucleotidase, elevated interstitial AMP concentration tenfold, did not attenuate basal nucleoside release, but completely inhibited Mg2+-stimulated coronary venous purine nucleoside release and blunted Mg2+-stimulated interstitial purine nucleoside formation by 69%. During perfusion with exogenous 1 microM [8-14C]AMP, excess perfusate MgCl2 increased [14C]adenosine release by 63% in coronary effluent and 133% in epicardial transudate. AOPCP decreased baseline [14C]adenosine release in coronary effluent and epicardial transudate by 85-90%, caused equilibration of arterial and epicardial AMP, and attenuated MgCl2 activation of p[14C]adenosine formation by approx. 75%, in both the vascular and interstitial compartments. Intramyocytic concentrations of allosteric regulators of the cytosolic 5'-nucleotidases were evaluated in stop-frozen myocardium. Excess magnesium did not appreciably alter intracellular pH and ATP concentration, but lowered free cytosolic ADP and AMP concentrations by 50 and 70%, respectively. A simplified model of compartmentalized adenosine metabolism is proposed in which magnesium ion-activated cardiac purine release originates predominantly from the ecto 5'-nucleotidase; magnesium ion stimulation of metabolic flux through the cytosolic isoforms was constrained by concomitant reductions in intracellular AMP substrate and allosteric activator ADP. Magnesium ion-enhanced adenosine formation by 5'-nucleotidase could contribute to the known cardioprotective effects of this clinically used cation.
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Affiliation(s)
- R T Mallet
- Department of Physiology, University of North Texas Health Science Center, Fort Worth 76107-2699, USA
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Minamino T, Kitakaze M, Komamura K, Node K, Takeda H, Inoue M, Hori M, Kamada T. Activation of protein kinase C increases adenosine production in the hypoxic canine coronary artery through the extracellular pathway. Arterioscler Thromb Vasc Biol 1995; 15:2298-304. [PMID: 7489256 DOI: 10.1161/01.atv.15.12.2298] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Both ischemia and hypoxia increase adenosine production in the heart. This study tested whether hypoxia increases adenosine production in the coronary artery via ecto-5'-nucleotidase and the role of protein kinase C in this condition. Canine left circumflex coronary artery was rapidly removed and incubated in 10 mL Krebs-Henseleit solution for 30 minutes. The Krebs-Henseleit solution contained 5'-iodotubercidin and 2'-deoxycoformycin, which inhibit adenosine kinase and adenosine deaminase, respectively. Adenosine production was measured in intact coronary arteries under normoxic conditions (16.2 +/- 1.2 pmol/mg protein). Adenosine production was reduced by 27% after removal of endothelium. Ecto-5'-nucleotidase activity of coronary arteries with and without endothelium was 51 +/- 6 and 41 +/- 4 nmol/mg protein per minute under normoxic conditions. Hypoxia increased adenosine production to 27.0 +/- 2.3 and 20.0 +/- 0.8 pmol/mg protein with and without endothelium. Hypoxia also increased ecto-5'-nucleotidase activity of coronary arteries with and without endothelium (74 +/- 8 and 53 +/- 5 nmol/mg protein per minute; P < .05). Increases in adenosine production under hypoxic conditions were blunted by both an inhibitor of ecto-5'-nucleotidase and inhibitors of protein kinase C. Activation of ecto-5'-nucleotidase was blunted by an inhibitor of protein kinase C. These results indicate that hypoxia increased extracellular adenosine production and activated ecto-5'-nucleotidase via activation of protein kinase C in coronary arterial smooth muscle and endothelial cells. Increased adenosine production in coronary arteries during hypoxia may contribute to coronary vasodilation and cardioprotection against ischemic injury.
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Affiliation(s)
- T Minamino
- First Department of Medicine, Osaka University School of Medicine, Suita, Japan
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Michel AD, Chau NM, Fan TP, Frost EE, Humphrey PP. Evidence that [3H]-alpha,beta-methylene ATP may label an endothelial-derived cell line 5'-nucleotidase with high affinity. Br J Pharmacol 1995; 115:767-74. [PMID: 8548175 PMCID: PMC1908513 DOI: 10.1111/j.1476-5381.1995.tb14999.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
1. In membranes prepared from a permanent cell line of endothelial origin (WEC cells), [3H]-alpha, beta-methylene ATP ([3H]-alpha, beta-meATP) labelled high (pKd = 9.5; Bmax = 3.75 pmol mg-1 protein) and low (pKd = 7.2; Bmax = 23.3 pmol mg-1 protein) affinity binding sites. The high affinity [3H]-alpha, beta-meATP binding sites in the WEC cell membranes could be selectively labelled with a low concentration of the radioligand (1 nM). In competition studies performed at a radioligand concentration of 1 nM, 88.6% of the sites possessed high affinity (pIC50 = 8.26) for alpha, beta-meATP. 2. The high affinity [3H]-alpha, beta-meATP binding sites appeared heterogeneous since in competition studies a number of nucleotide analogues (alpha, beta-meADP, ATP, ADP, AMP, GTP, GppNHp, GMP) and adenosine identified two populations of the sites labelled by 1 nM [3H]-alpha, beta-meATP. The proportion of sites with high affinity for these compounds was found to vary between 42 and 69%. 3. Approximately 60-69% of the binding sites labelled with 1 nM [3H]-alpha, beta-meATP possessed high affinity for alpha, beta-meADP (pIC50 = 8.87), AMP (pIC50 = 7.12), GMP (pIC50 = 7.34), UTP (pIC50 = 6.12), GTP (pIC50 = 7.59), GppNHp (pIC50 = 7.35) and adenosine (pIC50 = 5.45). The sites at which these compounds possessed high affinity were probably the same, since, in the presence of GMP at a concentration (10 microM) sufficient to inhibit selectively the binding of [3H]-alpha,beta-meATP, the [3H]-alpha,beta-meATP binding sites with high affinity for AMP, UTP, alpha, beta-meADP, GTP, GppNHp and adenosine were also occluded.4. WEC cell membranes were able to metabolize a trace concentration (6 nM) of [3H]-AMP to [3H]-adenosine under the conditions of the binding assay. The pIC50 values of adenosine (5.99), GMP (7.55)and the substrate AMP (7.19) for inhibiting this [3H]-AMPase activity were almost identical to their high affinity pIC50 estimates obtained in the binding assay. Although alpha, beta-meADP, alpha, beta-meATP, beta,upsilon-meATP,ATP, ADP and GppNHp identified heterogeneity in the [3H]-AMPase activity of the WEC cells, theirpIC50 values for inhibiting the major portion of the [3H]-AMPase activity were similar to their respective high affinity pIC50 values in the binding assay. It thus seems likely that WEC cells express a form of 5'-nucleotidase that possesses high affinity for both alpha,beta-meADP and alpha,beta-meATP and that this enzyme can be labelled by [3H]-alpha,beta-meATP.5. In the presence of 10 microM GMP, the affinity estimates for alpha,beta-meADP, AMP, GMP, GTP, GppNHp,ADP and adenosine at the high affinity [3H]-alpha,beta4-meATP binding sites that remained available, were lowa nd similar to their affinity estimates at the high affinity [3H]-alpha,beta-meATP binding sites of rat vas deferens. Since the high affinity [3H]-alpha,beta-meATP binding sites in rat vas deferens are thought to be P2x purinoceptors it is possible that the high affinity [3H]-alpha,beta-meATP binding sites in the WEC which possess low affinity for alpha,beta-meADP are also P2x purinoceptors.
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Affiliation(s)
- A D Michel
- Glaxo Institute of Applied Pharmacology, University of Cambridge
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Cunha RA, Ribeiro JA, Sebastião AM. Purinergic modulation of the evoked release of [3H]acetylcholine from the hippocampus and cerebral cortex of the rat: role of the ectonucleotidases. Eur J Neurosci 1994; 6:33-42. [PMID: 8130931 DOI: 10.1111/j.1460-9568.1994.tb00245.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Modulation by exogenous and endogenous adenine nucleotides and adenosine of [3H]acetylcholine release evoked by veratridine (10 microM) was compared in synaptosomal fractions from the hippocampus and the cerebral cortex of the rat. In both brain areas, exogenously added ATP or adenosine (10-100 microM) inhibited the evoked tritium release. In the hippocampus, ATP gamma S, an ATP analogue more resistant to catabolism than ATP, was virtually devoid of effect on tritium release, and the effect of ATP was prevented by the ecto-5'-nucleotidase inhibitor alpha,beta-methylene ADP (100 microM), by adenosine deaminase (2 U/ml) and by the A1 adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 20 nM). In contrast, in the cerebral cortex, the effect of ATP on tritium release was not prevented by either alpha,beta-methylene ADP (100 microM) or adenosine deaminase (2 U/ml), and several ATP analogues (30 microM) inhibited release. The order of intensity of the inhibitory effects of the ATP analogues was: ATP gamma S > ATP > beta,gamma-imido ATP > beta,gamma-methylene ATP >> 2-methyl-S-ATP, alpha,beta-methylene ATP. The effect of ATP gamma S in the cerebral cortex was prevented by DPCPX (20 nM) and was not affected by the P2 purinoceptor antagonist suramin (100 microM). In the hippocampus, alpha,beta-methylene ADP (100 microM) increased the evoked release of tritium, and adenosine deaminase (2 U/ml) produced an even greater increase; when adenosine deaminase was added in the presence of alpha,beta-methylene ADP, adenosine deaminase still increased the evoked release of tritium. In the cerebral cortex, DPCPX (20 nM) and adenosine deaminase (2 U/ml) increased the evoked tritium release by a similar magnitude, but the effect of adenosine deaminase was smaller than in the hippocampus. It is concluded that in the cerebral cortex ATP as such presynaptically inhibits acetylcholine release, whereas in the hippocampus the role of adenine nucleotides is as a source of endogenous extracellular adenosine that tonically inhibits acetylcholine release. The results also show that besides formation of adenosine from adenine nucleotides, released adenosine as such contributes in nearly equal amounts to the pool of endogenous adenosine that presynaptically inhibits acetylcholine release in the hippocampus.
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Affiliation(s)
- R A Cunha
- Laboratory of Pharmacology, Gulbenkian Institute of Science, Portugal
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Baiocchi C, Pesi R, Turriani M, Tozzi MG, Camici M, Ipata PL. Membrane-bound 5'-nucleotidase/nucleoside phosphotransferase from Bacillus cereus. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1993; 25:1625-9. [PMID: 8288031 DOI: 10.1016/0020-711x(93)90521-f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
1. A search for nucleoside phosphotransferase activity in Bacillus cereus led to the following results: (i) The phosphotransferase activity was associated with a membrane bound 5'-nucleotidase. (ii) The enzyme phosphorylates both purine and pyrimidine nucleosides as well as 2',3'-dideoxyinosine. (iii) The enzyme was inhibited by adenylic nucleotide di- and triphosphates, and its nucleotidase activity was increased in the presence of inosine as phosphate acceptor. 2. Bacterial and vertebrate 5'-nucleotidases with phosphotransferase activity differ for several characteristics, such as cellular location, substrate specificity, magnesium requirement and regulation.
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Affiliation(s)
- C Baiocchi
- Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy
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