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Abstract
Adenosine is a purine ribonucleoside with important roles in various physiological processes. A number of studies have indicated the importance of adenosine in cardiovascular diseases including syncope; however, the accurate determination of adenosine in human blood is challenging due to the molecule’s instability. In the present study, we report a simple method for the pre-treatment of blood samples and the development of a fast and efficient hydrophilic interaction chromatographic tandem mass spectrometry method for the analysis of adenosine in patient blood. During collection, samples were mixed directly with a solvent mixture containing 95% acetonitrile and 10 mM ammonium formate in a Vacutainer tube, resulting in successful prevention of adenosine metabolic processes and direct blood sample deproteinization. The method was validated according to bioanalytical industry guidelines and found to be accurate, repeatable, specific and sensitive with LLOQ 0.005 μg/mL, thus allowing its application in the analysis of real clinical samples.
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Methot JL, Zhou H, McGowan MA, Anthony NJ, Christopher M, Garcia Y, Achab A, Lipford K, Trotter BW, Altman MD, Fradera X, Lesburg CA, Li C, Alves S, Chappell CP, Jain R, Mangado R, Pinheiro E, Williams SMG, Goldenblatt P, Hill A, Shaffer L, Chen D, Tong V, McLeod RL, Lee HH, Yu H, Shah S, Katz JD. Projected Dose Optimization of Amino- and Hydroxypyrrolidine Purine PI3Kδ Immunomodulators. J Med Chem 2021; 64:5137-5156. [PMID: 33797901 DOI: 10.1021/acs.jmedchem.1c00237] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The approvals of idelalisib and duvelisib have validated PI3Kδ inhibitors for the treatment for hematological malignancies driven by the PI3K/AKT pathway. Our program led to the identification of structurally distinct heterocycloalkyl purine inhibitors with excellent isoform and kinome selectivity; however, they had high projected human doses. Improved ligand contacts gave potency enhancements, while replacement of metabolic liabilities led to extended half-lives in preclinical species, affording PI3Kδ inhibitors with low once-daily predicted human doses. Treatment of C57BL/6-Foxp3-GDL reporter mice with 30 and 100 mg/kg/day of 3c (MSD-496486311) led to a 70% reduction in Foxp3-expressing regulatory T cells as observed through bioluminescence imaging with luciferin, consistent with the role of PI3K/AKT signaling in Treg cell proliferation. As a model for allergic rhinitis and asthma, treatment of ovalbumin-challenged Brown Norway rats with 0.3 to 30 mg/kg/day of 3c gave a dose-dependent reduction in pulmonary bronchoalveolar lavage inflammation eosinophil cell count.
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Affiliation(s)
- Joey L Methot
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Hua Zhou
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Meredeth A McGowan
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Neville John Anthony
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Matthew Christopher
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Yudith Garcia
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Abdelghani Achab
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Kathryn Lipford
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Benjamin Wesley Trotter
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Michael D Altman
- Computational and Structural Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Xavier Fradera
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Charles A Lesburg
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Chaomin Li
- Process Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Stephen Alves
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Craig P Chappell
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Renu Jain
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Ruban Mangado
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Elaine Pinheiro
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Sybill M G Williams
- Discovery Biology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Peter Goldenblatt
- In Vitro Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Armetta Hill
- In Vitro Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Lynsey Shaffer
- In Vitro Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Dapeng Chen
- Preclinical Pharmacokinetics and Drug Metabolism, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Vincent Tong
- Preclinical Pharmacokinetics and Drug Metabolism, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Robbie L McLeod
- In Vivo Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Hyun-Hee Lee
- In Vivo Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Hongshi Yu
- Discovery Pharmaceutical Sciences, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Sanjiv Shah
- In Vitro Pharmacology, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
| | - Jason D Katz
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115 United States
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3
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Methot JL, Achab A, Christopher M, Zhou H, McGowan MA, Trotter BW, Fradera X, Lesburg CA, Goldenblatt P, Hill A, Chen D, Otte KM, Augustin M, Shah S, Katz JD. Optimization of Versatile Oxindoles as Selective PI3Kδ Inhibitors. ACS Med Chem Lett 2020; 11:2461-2469. [PMID: 33335668 PMCID: PMC7734802 DOI: 10.1021/acsmedchemlett.0c00441] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/17/2020] [Indexed: 12/11/2022] Open
Abstract
The 3,3-disubstituted oxindole moiety is a versatile and rigid three-dimensionally shaped scaffold. When engineered with a purine hinge-binding core, exceptionally selective PI3Kδ kinase inhibitors were discovered by exploiting small differences in isoform selectivity pockets. Crystal structures of early lead 2f bound to PI3Kδ and PI3Kα helped rationalize the high selectivity observed with 2f. By attenuating the lypophilicity and metabolic liabilities of an oxindole moiety, we improved the preclinical species PK and solubility and reduced adenosine uptake activity. The excellent potency and kinome selectivity of 7-azaoxindole 4d and spirooxindole 5d, together with a low plasma clearance and good half-life in rat and dog, supported a low once-daily predicted human dose.
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Affiliation(s)
- Joey L. Methot
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Abdelghani Achab
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Matthew Christopher
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Hua Zhou
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Meredeth A. McGowan
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - B. Wesley Trotter
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Xavier Fradera
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Charles A. Lesburg
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Peter Goldenblatt
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Armetta Hill
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Dapeng Chen
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Karin M. Otte
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | | | - Sanjiv Shah
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
| | - Jason D. Katz
- Discovery Chemistry, Computational and Structural Chemistry, In Vitro Pharmacology, Pharmacokinetics,
Pharmacodynamics and Drug Metabolism, Merck
& Co., Inc., Boston, Massachusetts 02115, United States
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Methot JL, Zhou H, Kattar SD, McGowan MA, Wilson K, Garcia Y, Deng Y, Altman M, Fradera X, Lesburg C, Fischmann T, Li C, Alves S, Shah S, Fernandez R, Goldenblatt P, Hill A, Shaffer L, Chen D, Tong V, McLeod RL, Yu H, Bass A, Kemper R, Gatto NT, LaFranco-Scheuch L, Trotter BW, Guzi T, Katz JD. Structure Overhaul Affords a Potent Purine PI3Kδ Inhibitor with Improved Tolerability. J Med Chem 2019; 62:4370-4382. [DOI: 10.1021/acs.jmedchem.8b01818] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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5
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Accurate measurement of endogenous adenosine in human blood. PLoS One 2018; 13:e0205707. [PMID: 30359421 PMCID: PMC6201894 DOI: 10.1371/journal.pone.0205707] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/25/2018] [Indexed: 02/07/2023] Open
Abstract
Accurate determination of in vivo circulating concentrations of extracellular adenosine in blood samples is challenging due to the rapid formation and rapid clearance of adenosine in blood. A blood collection protocol was developed based on direct sampling of venous blood into, and instant mixing with, a STOP solution developed to conserve in vivo adenosine concentrations by completely preventing both its formation and clearance in collected blood. Stable isotope labeled AMP and adenosine spiked into blood ex vivo were used in combination with mass spectrometry to evaluate conservation of adenosine and prevention of its formation. A number of approved drugs, including the P2Y12 antagonist ticagrelor, have been described to increase extracellular adenosine. This may contribute to its clinical profile, highlighting the importance of accurate measurement of in vivo adenosine concentrations.A high sensitive ultra performance liquid chromatography–tandem- mass spectrometry (UPLC-tandem-MS) analytical method for plasma adenosine was developed and validated with a lower limit of quantification of 2 nmol/L. The method demonstrated plasma adenosine stability during sample processing and analytical method performance relevant to human blood samples. The final STOP solution proved able to conserve exogenous adenosine and to prevent adenosine formation from exogenous AMP added in vitro to human blood over 15 minutes. The mean endogenous adenosine concentration in plasma prepared from venous blood collected from 10 healthy volunteers was 13 ± 7 nmol/L. Finally, the method was used to demonstrate the previously described concentration-dependent ability of ticagrelor to conserve extracellular adenosine at clinically relevant exposures. In conclusion, we report an optimized sampling protocol and a validated analytical method for accurate measurement of in vivo circulating adenosine concentrations in human blood, suitable for use in clinical trials.
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Kiguti LRA, Borges CS, Mueller A, Silva KP, Polo CM, Rosa JL, Silva PV, Missassi G, Valencise L, Kempinas WG, Pupo AS. Gender-specific impairment of in vitro sinoatrial node chronotropic responses and of myocardial ischemia tolerance in rats exposed prenatally to betamethasone. Toxicol Appl Pharmacol 2017; 334:66-74. [PMID: 28887130 DOI: 10.1016/j.taap.2017.09.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 08/01/2017] [Accepted: 09/04/2017] [Indexed: 01/28/2023]
Abstract
Excessive fetal glucocorticoid exposure has been linked to increased susceptibility to hypertension and cardiac diseases in the adult life, a process called fetal programming. The cardiac contribution to the hypertensive phenotype of glucocorticoid-programmed progeny is less known, therefore, we investigated in vitro cardiac functional parameters from rats exposed in utero to betamethasone. Pregnant Wistar rats received vehicle (VEH) or betamethasone (BET, 0.1mg/kg, i.m.) at gestational days 12, 13, 18 and 19. Male and female offspring were killed at post-natal day 30 and the right atrium (RA) was isolated to in vitro evaluation of drug-induced chronotropic responses. Additionally, whole hearts were retrograde-perfused in a Langendorff apparatus and infarct size in response to in vitro ischemia/reperfusion (I/R) protocol was evaluated. Male and female progeny from BET-exposed pregnant rats had reduced birth weight, a hallmark of fetal programming. Male BET-progeny had increased basal RA rate, impaired chronotropic responses to noradrenaline and adenosine, and increased myocardial damage to I/R. Though a 12-fold reduction in the negative chronotropic responses to adenosine, the effects of non-metabolisable adenosine receptor agonists 5'-(N-ethylcarboxamido)adenosine or 2-Chloro-adenosine were not different between VEH- and BET-exposed male rats. BET-exposed female offspring presented no cardiac dysfunction. Prenatal BET exposure engenders male-specific impairment of sinoatrial node function and on myocardial ischemia tolerance resulting, at least in part, from an increased adenosine metabolism in the heart. In light of the importance of adenosine in the cardiac physiology our results suggest a link between reduced adenosinergic signaling and the cardiac dysfunctions observed in glucocorticoid-induced fetal programming.
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Affiliation(s)
- L R A Kiguti
- Department of Pharmacology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil.
| | - C S Borges
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - A Mueller
- Department of Pharmacology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil; Instituto de Ciências da Saúde, Federal University of Mato Grosso, Sinop, MT, Brazil
| | - K P Silva
- Department of Pharmacology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - C M Polo
- Department of Physiology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - J L Rosa
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - P V Silva
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - G Missassi
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - L Valencise
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - W G Kempinas
- Department of Morphology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
| | - A S Pupo
- Department of Pharmacology, São Paulo State University (UNESP), Institute of Biosciences, Campus of Botucatu, Distrito de Rubião Junior s/n°, 18618-689 Botucatu, SP, Brazil
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Balakumar P, WitnessKoe WE, Gan YS, JemayPuah SM, Kuganesswari S, Prajapati SK, Varatharajan R, Jayachristy SA, Sundram K, Bahari MB. Effects of pre and post-treatments with dipyridamole in gentamicin-induced acute nephrotoxicity in the rat. Regul Toxicol Pharmacol 2017; 84:35-44. [DOI: 10.1016/j.yrtph.2016.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/05/2016] [Accepted: 12/15/2016] [Indexed: 01/14/2023]
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González-Fernández E, Sánchez-Gómez MV, Pérez-Samartín A, Arellano RO, Matute C. A3 Adenosine receptors mediate oligodendrocyte death and ischemic damage to optic nerve. Glia 2013; 62:199-216. [PMID: 24311446 DOI: 10.1002/glia.22599] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 10/28/2013] [Accepted: 10/28/2013] [Indexed: 11/07/2022]
Abstract
Adenosine receptor activation is involved in myelination and in apoptotic pathways linked to neurodegenerative diseases. In this study, we investigated the effects of adenosine receptor activation in the viability of oligodendrocytes of the rat optic nerve. Selective activation of A3 receptors in pure cultures of oligodendrocytes caused concentration-dependent apoptotic and necrotic death which was preceded by oxidative stress and mitochondrial membrane depolarization. Oligodendrocyte apoptosis induced by A3 receptor activation was caspase-dependent and caspase-independent. In addition to dissociated cultures, incubation of optic nerves ex vivo with adenosine and the A3 receptor agonist 2-CI-IB-MECA(1-[2-Chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-1-deoxy-N-methyl-b-D-ribofuranuronamide)-induced caspase-3 activation, oligodendrocyte damage, and myelin loss, effects which were prevented by the presence of caffeine and the A3 receptor antagonist MRS 1220 (N-[9-Chloro-2-(2-furanyl)[1,2,4]-triazolo [1,5-c]quinazolin-5-yl]benzene acetamide). Finally, ischemia-induced injury and functional loss to the optic nerve was attenuated by blocking A3 receptors. Together, these results indicate that adenosine may trigger oligodendrocyte death via activation of A3 receptors and suggest that this mechanism contributes to optic nerve and white matter ischemic damage.
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Affiliation(s)
- Estíbaliz González-Fernández
- CIBERNED, Achucarro Basque Center for Neuroscience and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), E-48940, Leioa, Spain
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Yip KH, Lau HYA, Wise H. Reciprocal modulation of anti-IgE induced histamine release from human mast cells by A₁ and A(2B) adenosine receptors. Br J Pharmacol 2012; 164:807-19. [PMID: 21506953 DOI: 10.1111/j.1476-5381.2011.01446.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Adenosine is believed to participate in the pathological development of asthma through a mast cell-dependent mechanism. Our study aimed to pharmacologically characterize the functions of adenosine receptor (AR) subtypes (A₁, A(2A) , A(2B) and A₃) in primary human cultured mast cells (HCMC). EXPERIMENTAL APPROACH HCMC were derived from progenitor stem cells in buffy coat and the effects of adenosine receptor ligands on basal and IgE-dependent histamine release were evaluated. KEY RESULTS Adenosine and analogues alone did not induce HCMC degranulation. When HCMC were activated by anti-IgE after 10 min pre-incubation with adenosine, a biphasic effect on histamine release was observed with enhancement of HCMC activation at low concentrations of adenosine (10⁻⁹-10⁻⁷ mol·L⁻¹) and inhibition at higher concentrations (10⁻⁶-10⁻⁴ mol·L⁻¹). The potentiating action was mimicked by A₁ AR agonists CCPA and 2'MeCCPA, and inhibited by the A₁ AR antagonist PSB36. In contrast, the inhibitory action of adenosine was mimicked by the non-specific A₂ AR agonist CV1808 and attenuated by A(2B) AR antagonists PSB1115 and MRS1760. The non-selective AR antagonist CGS15943 attenuated both the potentiating and inhibitory actions. CONCLUSIONS AND IMPLICATIONS We have defined for the first time the contribution of A₁ and A(2B) ARs, respectively, to the potentiating and inhibitory action of adenosine on human mast cell activation. With reference to the current trend of developing novel anti-asthmatic agents from AR ligands, our results suggest that inhibition of human mast cell activation would be a mechanism for A₁ AR antagonists, but not A(2B) AR antagonists.
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Affiliation(s)
- K H Yip
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China
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Guillén-Gómez E, Pinilla-Macua I, Pérez-Torras S, Choi DS, Arce Y, Ballarín JA, Pastor-Anglada M, Díaz-Encarnación MM. New role of the human equilibrative nucleoside transporter 1 (hENT1) in epithelial-to-mesenchymal transition in renal tubular cells. J Cell Physiol 2012; 227:1521-8. [PMID: 21678404 DOI: 10.1002/jcp.22869] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Epithelial-to-mesenchymal transition (EMT) is an important pro-fibrotic event in which tubular epithelial cells are transformed into myofibroblasts. Nucleoside transporters (NT) are regulated by many factors and processes, some of which are involved in fibrosis, such as cytokines, inflammation, and proliferation. Equilibrative nucleoside transporter 1 (ENT1) has been proved to be the most widely expressed adenosine transporter. In that sense, ENT1 may be a key player in cell damage signaling. Here we analyze the role of human ENT1 (hENT1) in the EMT process in proximal tubular cells. Addition of the main inducer of EMT, the transforming growth factor-β1, to HK-2 cells increased hENT1 mRNA and protein level expression. ENT1-mediated adenosine uptake was also enhanced. When cells were incubated with dipyridamole to evaluate the potential contribution of ENT1 to EMT by blocking its transport activity, EMT was induced. Moreover, the knock down of hENT1 with siRNA induced EMT and collagen production in HK-2 cells. Kidneys isolated from ENT1 knockout mice showed higher levels of interstitial collagen and α-SMA positive cells than wild-type mice. Our results point to a new potential role of hENT1 as a modulator of EMT in proximal tubular cells. In this sense, hENT1 could be involved in renal protection processes, and the loss or reduced expression of hENT1 would lead to an increased vulnerability of cells to the onset and/or progression of renal fibrosis.
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Affiliation(s)
- Elena Guillén-Gómez
- Laboratori de Biologia Molecular, Universitat Autònoma de Barcelona, Fundació Puigvert, REDinREN, Institut Investigació Biosanitaria Sant Pau, Barcelona, Catalonia, Spain.
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Equilibrative nucleoside transporter 2 regulates associative learning and synaptic function in Drosophila. J Neurosci 2010; 30:5047-57. [PMID: 20371825 DOI: 10.1523/jneurosci.6241-09.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Nucleoside transporters are evolutionarily conserved proteins that are essential for normal cellular function. In the present study, we examined the role of equilibrative nucleoside transporter 2 (ent2) in Drosophila. Null mutants of ent2 are lethal during late larval/early pupal stages, indicating that ent2 is essential for normal development. Hypomorphic mutant alleles of ent2, however, are viable and exhibit reduced associative learning. We additionally used RNA interference to knock down ent2 expression in specific regions of the CNS and show that ent2 is required in the alpha/beta lobes of the mushroom bodies and the antennal lobes. To determine whether the observed behavioral defects are attributable to defects in synaptic transmission, we examined transmitter release at the larval neuromuscular junction (NMJ). Excitatory junction potentials were significantly elevated in ent2 mutants, whereas paired-pulse plasticity was reduced. We also observed an increase in stimulus dependent calcium influx in the presynaptic terminal. The defects observed in calcium influx and transmitter release probability at the NMJ were rescued by introducing an adenosine receptor mutant allele (AdoR(1)) into the ent2 mutant background. The results of the present study provide the first evidence of a role for ent2 function in Drosophila and suggest that the observed defects in associative learning and synaptic function may be attributable to changes in adenosine receptor activation.
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Extracellular adenosine induces apoptosis in Caco-2 human colonic cancer cells by activating caspase-9/-3 via A(2a) adenosine receptors. J Gastroenterol 2009; 44:56-65. [PMID: 19159073 DOI: 10.1007/s00535-008-2273-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Accepted: 08/04/2008] [Indexed: 02/06/2023]
Abstract
BACKGROUND Extracellular adenosine has been shown to induce apoptosis in a variety of cells via an intrinsic pathway linked to adenosine uptake into cells and the ensuing signaling cascades and an extrinsic pathway linked to adenosine receptors. The present study was designed to understand the mechanism underlying adenosine-induced apoptosis of Caco-2 human colonic cancer cells. METHODS To observe cell viability, an MTT assay was carried out in Caco-2 cells untransfected or transfected with the A(2a) adenosine receptor pcDNA3.1. Apoptotic cell death was assessed with flow cytometry using propidium iodide and annexin V and internucleosomal DNA fragmentation analysis. Activities of caspase-3, -8, and -9 were measured using a caspase fluorometric assay kit. Mitochondrial membrane potentials were monitored using a DePsipher kit. Expression of adenosine receptors was examined with the reverse transcription-polymerase chain reaction (RT-PCR) method. RESULTS Extracellular adenosine induced Caco-2 cell apoptosis in a concentration-dependent (1-20 mM) and treatment time-dependent (24-72 h) manner. The adenosine effect was inhibited by DMPX, an inhibitor of A(2a) adenosine receptors and SQ22536, an inhibitor of adenylate cyclase. CGS21680, an agonist of A(2a) adenosine receptors, and forskolin, an adenylate cyclase activator, mimicked the adenosine action. Caco-2 cell death was still induced by overexpressing A(2a) adenosine receptors, and adenosine further promoted the cell death. Adenosine disrupted mitochondrial membrane potentials and activated caspase-9 and -3, but not caspase-8. CONCLUSIONS Extracellular adenosine induces apoptosis in Caco-2 cells by activating caspase-9 and the downstream effector caspase caspase-3 in association with mitochondrial damage via A(2a) adenosine receptors.
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13
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Young JD, Yao SYM, Sun L, Cass CE, Baldwin SA. Human equilibrative nucleoside transporter (ENT) family of nucleoside and nucleobase transporter proteins. Xenobiotica 2008; 38:995-1021. [PMID: 18668437 DOI: 10.1080/00498250801927427] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. The human (h) SLC29 family of integral membrane proteins is represented by four members, designated equilibrative nucleoside transporters (ENTs) because of the properties of the first-characterized family member, hENT1. They belong to the widely distributed eukaryotic ENT family of equilibrative and concentrative nucleoside/nucleobase transporter proteins. 2. A predicted topology of eleven transmembrane helices has been experimentally confirmed for hENT1. The best-characterized members of the family, hENT1 and hENT2, possess similar broad permeant selectivities for purine and pyrimidine nucleosides, but hENT2 also efficiently transports nucleobases. hENT3 has a similar broad permeant selectivity for nucleosides and nucleobases and appears to function in intracellular membranes, including lysosomes. 3. hENT4 is uniquely selective for adenosine, and also transports a variety of organic cations. hENT3 and hENT4 are pH sensitive, and optimally active under acidic conditions. ENTs, including those in parasitic protozoa, function in nucleoside and nucleobase uptake for salvage pathways of nucleotide synthesis and, in humans, are also responsible for the cellular uptake of nucleoside analogues used in the treatment of cancers and viral diseases. 4. By regulating the concentration of adenosine available to cell surface receptors, mammalian ENTs additionally influence physiological processes ranging from cardiovascular activity to neurotransmission.
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Affiliation(s)
- J D Young
- Membrane Protein Research Group, Department of Physiology and Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.
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Barnes K, Dobrzynski H, Foppolo S, Beal PR, Ismat F, Scullion ER, Sun L, Tellez J, Ritzel MWL, Claycomb WC, Cass CE, Young JD, Billeter-Clark R, Boyett MR, Baldwin SA. Distribution and functional characterization of equilibrative nucleoside transporter-4, a novel cardiac adenosine transporter activated at acidic pH. Circ Res 2006; 99:510-9. [PMID: 16873718 DOI: 10.1161/01.res.0000238359.18495.42] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Adenosine plays multiple roles in the efficient functioning of the heart by regulating coronary blood flow, cardiac pacemaking, and contractility. Previous studies have implicated the equilibrative nucleoside transporter family member equilibrative nucleoside transporter-1 (ENT1) in the regulation of cardiac adenosine levels. We report here that a second member of this family, ENT4, is also abundant in the heart, in particular in the plasma membranes of ventricular myocytes and vascular endothelial cells but, unlike ENT1, is virtually absent from the sinoatrial and atrioventricular nodes. Originally described as a monoamine/organic cation transporter, we found that both human and mouse ENT4 exhibited a novel, pH-dependent adenosine transport activity optimal at acidic pH (apparent K(m) values 0.78 and 0.13 mmol/L, respectively, at pH 5.5) and absent at pH 7.4. In contrast, serotonin transport by ENT4 was relatively insensitive to pH. ENT4-mediated nucleoside transport was adenosine selective, sodium independent and only weakly inhibited by the classical inhibitors of equilibrative nucleoside transport, dipyridamole, dilazep, and nitrobenzylthioinosine. We hypothesize that ENT4, in addition to playing roles in cardiac serotonin transport, contributes to the regulation of extracellular adenosine concentrations, in particular under the acidotic conditions associated with ischemia.
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Affiliation(s)
- Kay Barnes
- Institute of Membrane and Systems Biology, University of Leeds, UK.
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King AE, Ackley MA, Cass CE, Young JD, Baldwin SA. Nucleoside transporters: from scavengers to novel therapeutic targets. Trends Pharmacol Sci 2006; 27:416-25. [PMID: 16820221 DOI: 10.1016/j.tips.2006.06.004] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 04/18/2006] [Accepted: 06/19/2006] [Indexed: 11/26/2022]
Abstract
Hydrophilic purine and pyrimidine nucleosides rely on specialized carrier proteins for their membrane translocation. The recent identification of two gene families encoding equilibrative and concentrative nucleoside transporters in mammals and other organisms has provided the essential breakthrough to a more complete understanding of the biological significance of nucleoside transport. Although nucleoside salvage is a primary function of these proteins, recent data indicate functions beyond metabolic recycling. In brain and spinal cord, for example, nucleoside transporters have the potential to regulate synaptic levels of neuroactive purines such as adenosine and, thereby, indirectly modulate physiological processes through G-protein-coupled purine P1 receptors. As described in this review, recent research indicates novel putative functions for CNS nucleoside transporters in sleep, arousal, drug and alcohol addiction, nociception and analgesia. The therapeutic use of nucleoside analogue drugs and nucleoside transporter inhibitors in viral, neoplastic, cardiovascular and infectious disease is also described.
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Affiliation(s)
- Anne E King
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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Nagase K, Tomi M, Tachikawa M, Hosoya KI. Functional and molecular characterization of adenosine transport at the rat inner blood–retinal barrier. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:13-9. [PMID: 16487924 DOI: 10.1016/j.bbamem.2006.01.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 12/06/2005] [Accepted: 01/11/2006] [Indexed: 10/25/2022]
Abstract
The purpose of the present study was to characterize the adenosine transport system(s) at the inner blood-retinal barrier (inner BRB). A conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2), used as an in vitro model of the inner BRB, expresses equilibrative nucleoside transporter 1 (ENT1), ENT2, concentrative nucleoside transporter 2 (CNT2), and CNT3 mRNAs. TR-iBRB2 cells exhibited an Na+-independent and concentration-dependent [3H]adenosine uptake with a Michaelis-Menten constant of 28.5 microM and a maximum uptake rate of 814 pmol/(min mg protein). [3H]Adenosine uptake by TR-iBRB2 cells was strongly inhibited by 2 mM adenosine, inosine, uridine, and thymidine. On the other hand, this process was not inhibited by 100 nM nitrobenzylmercaptopurine riboside and dipyridamole. These uptake studies suggest that ENT2 is involved in [3H]adenosine uptake by TR-iBRB2 cells. Quantitative real-time PCR revealed that the expression of ENT2 mRNA is 5.5-fold greater than that of ENT1 mRNA. An in vivo study suggested that [3H]adenosine is transported from the blood to the retina and significantly inhibited by adenosine and thymidine. The results of this study show that ENT2 most likely mediates adenosine transport at the inner BRB and is expected to play an important role in regulating the adenosine concentration in the retina.
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Affiliation(s)
- Katsuhiko Nagase
- Faculty of Pharmaceutical Sciences, University of Toyama, 2630, Sugitani, Toyama 930-0194, Japan
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Saitoh M, Nagai K, Nakagawa K, Yamamura T, Yamamoto S, Nishizaki T. Adenosine induces apoptosis in the human gastric cancer cells via an intrinsic pathway relevant to activation of AMP-activated protein kinase. Biochem Pharmacol 2004; 67:2005-11. [PMID: 15130776 DOI: 10.1016/j.bcp.2004.01.020] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Accepted: 01/20/2004] [Indexed: 11/29/2022]
Abstract
Extracellular adenosine significantly reduced cell viability in a dose (0.1-20mM)- and treatment time (24-72h)-dependent manner in GT3-TKB cells, a human gastric cancer cell line. Nuclei of cells were reactive to Hoechst 33342, a marker of apoptosis, and an anti-single-stranded DNA. Adenosine-induced GT3-TKB cell death was significantly inhibited by dipyridamole, an inhibitor of adenosine transporter, and 5'-amino-5'-deoxyadenosine, an inhibitor of adenosine kinase, but the effect was not affected by theophylline, a broad inhibitor of adenosine receptors, 8-cyclopentyltheophylline, an inhibitor of A(1) adenosine receptors or 3,7-dimethyl-1-propargylxanthine, an inhibitor of A(2a) adenosine receptors. Adenosine had no effect on mitochondrial membrane potentials. The effect of adenosine on GT3-TKB cell death was not inhibited by a pancaspase inhibitor or inhibitors of caspase-1,-3,-4,-8, and -9. 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR), an activator of AMP-activated protein kinase (AMPK), significantly reduced GT3-TKB cell viability, but the AICAR action was not reinforced in the presence of adenosine. The results of the present study, thus, suggest that extracellular adenosine induces apoptosis in GT3-TKB cells by its uptake into cells and conversion to AMP followed by activation of AMPK, regardless of caspase activation linked to the mitochondria and the endoplasmic reticulum.
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Affiliation(s)
- Masaru Saitoh
- Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan
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Baldwin SA, Beal PR, Yao SYM, King AE, Cass CE, Young JD. The equilibrative nucleoside transporter family, SLC29. Pflugers Arch 2004; 447:735-43. [PMID: 12838422 DOI: 10.1007/s00424-003-1103-2] [Citation(s) in RCA: 489] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 04/28/2003] [Indexed: 11/24/2022]
Abstract
The human SLC29 family of proteins contains four members, designated equilibrative nucleoside transporters (ENTs) because of the properties of the first-characterised family member, hENT1. They belong to the widely-distributed eukaryotic ENT family of equilibrative and concentrative nucleoside/nucleobase transporters and are distantly related to a lysosomal membrane protein, CLN3, mutations in which cause neuronal ceroid lipofuscinosis. A predicted topology of 11 transmembrane helices with a cytoplasmic N-terminus and an extracellular C-terminus has been experimentally confirmed for hENT1. The best-characterised members of the family, hENT1 and hENT2, possess similar broad substrate specificities for purine and pyrimidine nucleosides, but hENT2 in addition efficiently transports nucleobases. The ENT3 and ENT4 isoforms have more recently also been shown to be genuine nucleoside transporters. All four isoforms are widely distributed in mammalian tissues, although their relative abundance varies: ENT2 is particularly abundant in skeletal muscle. In polarised cells ENT1 and ENT2 are found in the basolateral membrane and, in tandem with concentrative transporters of the SLC28 family, may play a role in transepithelial nucleoside transport. The transporters play key roles in nucleoside and nucleobase uptake for salvage pathways of nucleotide synthesis, and are also responsible for the cellular uptake of nucleoside analogues used in the treatment of cancers and viral diseases. In addition, by regulating the concentration of adenosine available to cell surface receptors, they influence many physiological processes ranging from cardiovascular activity to neurotransmission.
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Affiliation(s)
- Stephen A Baldwin
- School of Biochemistry and Molecular Biology, University of Leeds, LS2 9JT, Leeds, UK.
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Kombian SB, Ananthalakshmi KVV, Parvathy SS, Matowe WC. Dopamine and adenosine mediate substance P-induced depression of evoked IPSCs in the rat nucleus accumbens in vitro. Eur J Neurosci 2003; 18:303-11. [PMID: 12887412 DOI: 10.1046/j.1460-9568.2003.02753.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The major projection cells of the nucleus accumbens (NAc) are under a strong inhibitory influence from GABAergic afferents and depend on afferent excitation to produce their output. We have earlier reported that substance P (SP), a peptide which is colocalized with GABA in these neurons, depresses excitatory synaptic transmission in this nucleus (Kombian, S.B., Ananthalakshmi, K.V.V., Parvathy, S.S. & Matowe, W.C. (2003) J. Neurophysiol., 89, 728-738). In order to better understand the role of this peptide in the synaptic physiology of the NAc, it is important to determine its effects on inhibitory synaptic responses. Using whole-cell recording in rat forebrain slices, we show here that SP also depresses evoked inhibitory postsynaptic currents (IPSCs) in the NAc via intermediate neuromodulators. SP caused a partially reversible, dose-dependent decrease in evoked IPSC amplitude. This effect was present without measurable changes in the holding current, input resistance of recorded cells or decay rate (tau) of IPSCs. It was mimicked by a neurokinin-1 (NK1) receptor-selective agonist, [Sar9, Met (O2)11]-SP, and blocked by an NK1 receptor-selective antagonist, L 732 138. The SP-induced IPSC depression was prevented by SCH23390, a dopamine D1-like receptor antagonist and by 8-cyclopentyltheophylline, an adenosine A1 receptor blocker. Furthermore, the SP effect was also markedly attenuated by exogenous adenosine, dipyridamole, rolipram and barium. These data show that SP, acting on NK1 receptors, depresses inhibitory synaptic transmission indirectly by enhancing extracellular dopamine and adenosine levels. SP therefore acts in the NAc to modulate both excitatory and inhibitory afferent inputs using the same mechanism(s).
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Affiliation(s)
- Samuel B Kombian
- Department of Applied Therapeutics, Faculty of Pharmacy, Health Science Center, Kuwait University, PO Box 24923, Safat 13110, Kuwait.
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Begg M, Dale N, Llaudet E, Molleman A, Parsons ME. Modulation of the release of endogenous adenosine by cannabinoids in the myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum. Br J Pharmacol 2002; 137:1298-304. [PMID: 12466239 PMCID: PMC1573610 DOI: 10.1038/sj.bjp.0704985] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2002] [Revised: 08/14/2002] [Accepted: 09/13/2002] [Indexed: 11/09/2022] Open
Abstract
1. Interactions between the cannabinoid system and the adenosine system were investigated in the myenteric plexus-longitudinal muscle (MPLM) of the guinea-pig ileum. 2. Electrically-evoked contractions of the MPLM were inhibited in a concentration dependent manner by exogenous adenosine and the adenosine receptor agonist 2-chloroadenosine. These inhibitory effects were reversed by the selective A(1) receptor antagonist DPCPX (20 nM). 3. Preincubation of the MPLM with the cannabinoid receptor agonist CP55,940 (1 nM) or the endogenous cannabinoid ligand anandamide caused a significant leftward shift in the concentration-effect curves to adenosine and 2-chloroadenosine. 4. Electrically-evoked contractions of the MPLM were inhibited in a concentration dependent manner by the adenosine uptake inhibitor dipyridamole. This inhibition was reversed by DPCPX (20 nM). 5. Pretreatment with CP55,940 (1 nM) or anandamide (10 microM) significantly reduced the inhibition produced by dipyridamole, an effect which was completely reversed by the selective CB(1) receptor ligand SR141716 (100 nM). 6. Electrically evoked adenosine release, measured in real time by means of adenosine-specific biosensors, was inhibited by CP55,940 (10 nM). This inhibition was blocked when CP55,940 was applied in the presence of SR141716 (100 nM). 7. These results confirm the presence of presynaptic CB(1) and A(1) receptors in the guinea-pig MPLM, and suggest that CB(1) receptor stimulation reduces electrically-evoked adenosine release. Overall the data raise the possibility that the cannabinoid system plays a role in the modulation of adenosine transmission in the MPLM.
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Affiliation(s)
- M Begg
- Department of Biosciences, University of Hertfordshire, C.P. Snow Building, College Lane, Hatfield, Herts. AL10 9AB, U.K
| | - N Dale
- Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, U.K
| | - E Llaudet
- Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, U.K
| | - A Molleman
- Department of Biosciences, University of Hertfordshire, C.P. Snow Building, College Lane, Hatfield, Herts. AL10 9AB, U.K
| | - M E Parsons
- Department of Biosciences, University of Hertfordshire, C.P. Snow Building, College Lane, Hatfield, Herts. AL10 9AB, U.K
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Musa H, Dobrzynski H, Berry Z, Abidi F, Cass CE, Young JD, Baldwin SA, Boyett MR. Immunocytochemical demonstration of the equilibrative nucleoside transporter rENT1 in rat sinoatrial node. J Histochem Cytochem 2002; 50:305-9. [PMID: 11850433 DOI: 10.1177/002215540205000302] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Adenosine exerts multiple receptor-mediated effects in the heart, including a negative chronotropic effect on the sinoatrial node. The aim of this study was to investigate the distribution of the equilibrative nucleoside transporter rENT1 in rat sinoatrial node and atrial muscle. Immunocytochemistry and/or immunoblotting revealed abundant expression of this protein in plasma membranes of sinoatrial node and in atrial and ventricular cells. Because rENT1-mediated transport is likely to regulate the local concentrations of adenosine in the sinoatrial node and other parts of the heart, it represents a potential pharmacological target that might be exploited to ameliorate ischemic damage during heart surgery.
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Affiliation(s)
- H Musa
- School of Biomedical Sciences, University of Leeds, United Kingdom
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Usta CK, Adan G, Ozdem SS. The effects of adenosine on isolated right atrial preparations from streptozotocin-diabetic rats. JOURNAL OF AUTONOMIC PHARMACOLOGY 2001; 21:191-5. [PMID: 11952874 DOI: 10.1046/j.1365-2680.2001.00225.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The aim of the present study was to investigate the inhibitory effects of adenosine on the contractile force and chronotropic action of isolated right atrial preparations from streptozotocin (STZ)-diabetic rats. 2. The rats were anaesthetized with diethyl ether and STZ (65 mg kg(-1)) was injected intravenously via the tail vein. 3. Adenosine produced concentration-dependent decreases in the force of contraction and a negative chronotropic action of atria both in control and diabetic groups. The inhibition responses to adenosine were significantly higher in diabetic rat atria than control. 4. Dypiridamole incubation caused a significant potentiation of the inhibitory effect of adenosine on contractile force and chronotropic action of atria in the control group, but not in the diabetic group. In the presence of dipyridamole, the inhibitory effects of adenosine on measured parameters in diabetic rats were not significantly different from those in control rats. 5. These results suggested that atria from 6 weeks STZ-diabetic rats exhibited a supersensitivity to the negative inotropic and chronotropic effects of adenosine compared with atria from control rats because of an impairment in adenosine uptake mechanism. Altered sensitivity to effects of adenosine might reflect relatively early changes in the course of diabetes.
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Affiliation(s)
- C K Usta
- Department of Pharmacology, Akdeniz University Faculty of Medicine, Dekanlik binasi, 07070 Arapsuyu, Antalya, Turkey
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Lee JJ, Talubmook C, Parsons ME. Activation of presynaptic A1-receptors by endogenous adenosine inhibits acetylcholine release in the guinea-pig ileum. JOURNAL OF AUTONOMIC PHARMACOLOGY 2001; 21:29-38. [PMID: 11422576 DOI: 10.1046/j.1365-2680.2001.00201.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. It is well established that presynaptic adenosine A1-receptor activation inhibits acetylcholine (ACh) release in the guinea-pig ileum. The present study extends this observation and examines a possible role for endogenous adenosine in modulating cholinergic nerve function. 2. The actions of the adenosine uptake blocker, dipyridamole, the adenosine deaminase inhibitor, erythro-9(2-hydroxy-3-nonyl)adenine (EHNA) and the A1-receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) were examined on electrically evoked neurogenic, cholinergic twitch contractions of the guinea-pig ileum. Some additional studies measuring [3H]-ACh release were also performed. 3. Adenosine and the selective A1-receptor agonist, 2-chloroadenosine (2-CA), inhibited electrically evoked contractions and, in the case of 2-CA, [3H]-ACh release. The actions were antagonized by DPCPX. At low concentrations, dipyridamole and EHNA enhanced the effect of adenosine causing a leftward shift of the concentration-response curve. In contrast, inhibition induced by 2-CA was unaffected by either dipyridamole or EHNA. 4. When applied alone at higher concentrations, EHNA and dipyridamole produced a concentration-dependent suppression of cholinergic neurotransmission. In both cases, the effect could be reversed by DPCPX. At the same concentration, DPCPX alone produced a small but consistent increase in twitch height and [3H]-ACh release. 5. The data confirm the existence of inhibitory presynaptic adenosine A1-receptors modulating cholinergic nerve function in the guinea-pig ileum and suggests that these receptors can be activated by endogenous adenosine released either as adenosine itself or as an ATP metabolite.
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Affiliation(s)
- J J Lee
- Biosciences Division, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK
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Meester BJ, Shankley NP, Welsh NJ, Wood J, Meijler FL, Black JW. Pharmacological classification of adenosine receptors in the sinoatrial and atrioventricular nodes of the guinea-pig. Br J Pharmacol 1998; 124:685-92. [PMID: 9690860 PMCID: PMC1565446 DOI: 10.1038/sj.bjp.0701891] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
1. The effects of seven agonist and three antagonist adenosine receptor ligands were compared on the guinea-pig sinoatrial (SA) node (isolated right atrium) and atrioventricular (AV) node (perfused whole heart). Single agonist concentration-effect curves were obtained to 5'-N-ethylcarboxamidoadenosine (NECA), R(-)-N6-(2-phenylisopropyl)adenosine (R-PIA), N6-cyclohexyladenosine (CHA), 2-chloroadenosine (CADO),),S(+)-N6-(2-phenylisopropyl)adenosine (L-PIA), 2-phenylaminoadenosine (CV 1808) and N6-aminoadenosine (MeAdo). Adenosine and/or NECA curves were obtained in the absence and presence of the antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), 9-chloro-2 (2-furanyl)-5,6-dihydro-1,2,4-triazolo[1,5-c]quinazolin-5-imine (CGS15943) and N6-(endonorbornan-2-yl)-9-methyladenine (N-0861). 2. A formal comparison of the agonist and antagonist potency data was made by fitting the data to a straight line using a least squares procedure based on principal components analysis to account for the variance on both axes. The antagonist affinity estimates made on the two assays did not deviate significantly from the line of identity. 3. The agonist p[A]50 data obtained on the two assays did not deviate from the line of identity, indicating that there were no significant differences in potencies between the two assays. The p[A]50 ratio of R-PIA and S-PIA was 1.24+/-0.09 in the SA node and 1.36+/-0.11 in the AV node, indicating no difference in the stereoselectivity of the PIA isomers between the two tissues. 4. The agonist potency and antagonist affinity data obtained are consistent with previous findings showing that the AV and SA node data are pharmacologically indistinguishable and belong to the adenosine A1-receptor class. No evidence for the reported A3-receptor was found.
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Affiliation(s)
- B J Meester
- Analytical Pharmacology, Rayne Institute, King's College School of Medicine & Dentistry, London, UK
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