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Lee N, Choi JY, Ryu YH. The development status of PET radiotracers for evaluating neuroinflammation. Nucl Med Mol Imaging 2024; 58:160-176. [PMID: 38932754 PMCID: PMC11196502 DOI: 10.1007/s13139-023-00831-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/16/2023] [Accepted: 12/05/2023] [Indexed: 06/28/2024] Open
Abstract
Neuroinflammation is associated with the pathophysiologies of neurodegenerative and psychiatric disorders. Evaluating neuroinflammation using positron emission tomography (PET) plays an important role in the early diagnosis and determination of proper treatment of brain diseases. To quantify neuroinflammatory responses in vivo, many PET tracers have been developed using translocator proteins, imidazole-2 binding site, cyclooxygenase, monoamine oxidase-B, adenosine, cannabinoid, purinergic P2X7, and CSF-1 receptors as biomarkers. In this review, we introduce the latest developments in PET tracers that can image neuroinflammation, focusing on clinical trials, and further consider their current implications.
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Affiliation(s)
- Namhun Lee
- Division of Applied RI, Korea Institute of Radiological & Medical Sciences, 75 Nowon-ro, Nowon-gu, Seoul, 01812 Korea
| | - Jae Yong Choi
- Division of Applied RI, Korea Institute of Radiological & Medical Sciences, 75 Nowon-ro, Nowon-gu, Seoul, 01812 Korea
- Radiological and Medico-Oncological Sciences, University of Science and Technology (UST), Seoul, Korea
| | - Young Hoon Ryu
- Department of Nuclear Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
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Pizarro-Galleguillos BM, Kunert L, Brüggemann N, Prasuhn J. Neuroinflammation and Mitochondrial Dysfunction in Parkinson's Disease: Connecting Neuroimaging with Pathophysiology. Antioxidants (Basel) 2023; 12:1411. [PMID: 37507950 PMCID: PMC10375976 DOI: 10.3390/antiox12071411] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/07/2023] [Accepted: 07/10/2023] [Indexed: 07/30/2023] Open
Abstract
There is a pressing need for disease-modifying therapies in patients suffering from neurodegenerative diseases, including Parkinson's disease (PD). However, these disorders face unique challenges in clinical trial designs to assess the neuroprotective properties of potential drug candidates. One of these challenges relates to the often unknown individual disease mechanisms that would, however, be relevant for targeted treatment strategies. Neuroinflammation and mitochondrial dysfunction are two proposed pathophysiological hallmarks and are considered to be highly interconnected in PD. Innovative neuroimaging methods can potentially help to gain deeper insights into one's predominant disease mechanisms, can facilitate patient stratification in clinical trials, and could potentially map treatment responses. This review aims to highlight the role of neuroinflammation and mitochondrial dysfunction in patients with PD (PwPD). We will specifically introduce different neuroimaging modalities, their respective technical hurdles and challenges, and their implementation into clinical practice. We will gather preliminary evidence for their potential use in PD research and discuss opportunities for future clinical trials.
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Affiliation(s)
- Benjamin Matís Pizarro-Galleguillos
- Facultad de Medicina, Universidad de Chile, Santiago 8380453, Chile
- Department of Neurology, University Medical Center Schleswig-Holstein, Campus Lübeck, 23562 Lübeck, Germany
- Institute of Neurogenetics, University of Lübeck, 23562 Lübeck, Germany
- Center for Brain, Behavior, and Metabolism, University of Lübeck, 23562 Lübeck, Germany
| | - Liesa Kunert
- Department of Neurology, University Medical Center Schleswig-Holstein, Campus Lübeck, 23562 Lübeck, Germany
- Institute of Neurogenetics, University of Lübeck, 23562 Lübeck, Germany
- Center for Brain, Behavior, and Metabolism, University of Lübeck, 23562 Lübeck, Germany
| | - Norbert Brüggemann
- Department of Neurology, University Medical Center Schleswig-Holstein, Campus Lübeck, 23562 Lübeck, Germany
- Center for Brain, Behavior, and Metabolism, University of Lübeck, 23562 Lübeck, Germany
| | - Jannik Prasuhn
- Department of Neurology, University Medical Center Schleswig-Holstein, Campus Lübeck, 23562 Lübeck, Germany
- Institute of Neurogenetics, University of Lübeck, 23562 Lübeck, Germany
- Center for Brain, Behavior, and Metabolism, University of Lübeck, 23562 Lübeck, Germany
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD 21287, USA
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Franco R, Navarro G, Martínez-Pinilla E. The adenosine A 2A receptor in the basal ganglia: Expression, heteromerization, functional selectivity and signalling. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 170:49-71. [PMID: 37741696 DOI: 10.1016/bs.irn.2023.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/25/2023]
Abstract
Adenosine is a neuroregulatory nucleoside that acts through four G protein-coupled receptors (GPCRs), A1, A2A, A2B and A3, which are widely expressed in cells of the nervous system. The A2A receptor (A2AR), the GPCR with the highest expression in the striatum, has a similar role to that of receptors for dopamine, one of the main neurotransmitters. Neuronal and glial A2ARs participate in the modulation of dopaminergic transmission and act in almost any action in which the basal ganglia is involved. This chapter revisits the expression of the A2AR in the basal ganglia in health and disease, and describes the diversity of signalling depending on whether the receptors are expressed as monomer or as heteromer. The A2AR can interact with other receptors as adenosine A1, dopamine D2, or cannabinoid CB1 to form heteromers with relevant functions in the basal ganglia. Heteromerization, with these and other GPCRs, provides diversity to A2AR-mediated signalling and to the modulation of neurotransmission. Thus, selective A2AR antagonists have neuroprotective potential acting directly on neurons, but also through modulation of glial cell activation, for example, by decreasing neuroinflammatory events that accompany neurodegenerative diseases. In fact, A2AR antagonists are safe and their potential in the therapy of Parkinson's disease has already led to the approval of one of them, istradefylline, in Japan and United States. The receptor also has a key role in reward circuits and, again, heteromers with dopamine receptors, but also with cannabinoid CB1 receptors, participate in the events triggered by drugs of abuse.
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Affiliation(s)
- Rafael Franco
- Molecular Neurobiology laboratory, Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain; CiberNed, Network Center for Neurodegenerative diseases, National Spanish Health Institute Carlos III, Madrid, Spain; School of Chemistry, Universitat de Barcelona, Barcelona, Spain.
| | - Gemma Navarro
- CiberNed, Network Center for Neurodegenerative diseases, National Spanish Health Institute Carlos III, Madrid, Spain; Department of Biochemistry and Physiology, School of Pharmacy and Food Science Universitat de Barcelona, Barcelona, Spain; Institute of Neurosciences, Universitat de Barcelona, Barcelona, Spain
| | - Eva Martínez-Pinilla
- Department of Morphology and Cell Biology, Faculty of Medicine, University of Oviedo, Asturias, Spain; Instituto de Neurociencias del Principado de Asturias (INEUROPA), Asturias, Spain; Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Asturias, Spain
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Waggan I, Rissanen E, Tuisku J, Joutsa J, Helin S, Parkkola R, Rinne JO, Airas L. Adenosine A 2A receptor availability in patients with early- and moderate-stage Parkinson's disease. J Neurol 2023; 270:300-310. [PMID: 36053386 DOI: 10.1007/s00415-022-11342-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 08/06/2022] [Accepted: 08/17/2022] [Indexed: 01/07/2023]
Abstract
INTRODUCTION Adenosine 2A (A2A) receptors co-localize with dopamine D2 receptors in striatopallidal medium spiny neurons of the indirect pathway. A2A receptor activation in the striatum or pallidum decreases D2 signaling. In contrast, A2A receptor antagonism may help potentiate it. Furthermore, previous PET studies have shown increased A2A receptor availability in striatum of late-stage PD patients with dyskinesia. However, human in vivo evidence for striatal A2A receptor availability in early-stage PD is limited. This study aimed to investigate possible differences in A2A receptor availability in the striatum and pallidum of early- and moderate-stage PD patients without dyskinesias. METHODS Brain MRI and PET with [11C]TMSX radioligand, targeting A2A receptors, was performed in 9 patients with early- and 9 with moderate-stage PD without dyskinesia and in 6 healthy controls. Distribution volume ratios (DVR) were calculated to assess specific [11C]TMSX binding in caudate, putamen and pallidum. RESULTS A2A receptor availability (DVR) was decreased in the bilateral caudate of early-stage PD patients when compared with healthy controls (P = 0.02). Conversely, DVR was increased bilaterally in the pallidum of moderate-stage PD patients compared to healthy controls (P = 0.03). Increased mean striatal DVR correlated with higher motor symptom severity ([Formula: see text] = 0.47, P = 0.02). CONCLUSION Our results imply regional and disease stage-dependent changes in A2A receptor signaling in PD pathophysiology and in response to dopaminergic medication.
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Affiliation(s)
- Imran Waggan
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland.
| | - Eero Rissanen
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
| | - Jouni Tuisku
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
| | - Juho Joutsa
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
| | - Semi Helin
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
| | - Riitta Parkkola
- Department of Radiology, Turku University Hospital and University of Turku, Turku, Finland
| | - Juha O Rinne
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
| | - Laura Airas
- Turku PET Centre, University of Turku, Itäinen Pitkäkatu 4A, 6th floor, 6007, 20520, Turku, Finland
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
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Trinh PNH, Baltos JA, Hellyer SD, May LT, Gregory KJ. Adenosine receptor signalling in Alzheimer’s disease. Purinergic Signal 2022; 18:359-381. [PMID: 35870032 PMCID: PMC9391555 DOI: 10.1007/s11302-022-09883-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/02/2022] [Indexed: 12/11/2022] Open
Abstract
Alzheimer’s disease (AD) is the most common dementia in the elderly and its increasing prevalence presents treatment challenges. Despite a better understanding of the disease, the current mainstay of treatment cannot modify pathogenesis or effectively address the associated cognitive and memory deficits. Emerging evidence suggests adenosine G protein-coupled receptors (GPCRs) are promising therapeutic targets for Alzheimer’s disease. The adenosine A1 and A2A receptors are expressed in the human brain and have a proposed involvement in the pathogenesis of dementia. Targeting these receptors preclinically can mitigate pathogenic β-amyloid and tau neurotoxicity whilst improving cognition and memory. In this review, we provide an accessible summary of the literature on Alzheimer’s disease and the therapeutic potential of A1 and A2A receptors. Although there are no available medicines targeting these receptors approved for treating dementia, we provide insights into some novel strategies, including allosterism and the targeting of oligomers, which may increase drug discovery success and enhance the therapeutic response.
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Affiliation(s)
- Phuc N. H. Trinh
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052 Australia
- Department of Pharmacology, Monash University, Parkville, VIC 3052 Australia
| | - Jo-Anne Baltos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052 Australia
- Department of Pharmacology, Monash University, Parkville, VIC 3052 Australia
| | - Shane D. Hellyer
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052 Australia
| | - Lauren T. May
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052 Australia
- Department of Pharmacology, Monash University, Parkville, VIC 3052 Australia
| | - Karen J. Gregory
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052 Australia
- Department of Pharmacology, Monash University, Parkville, VIC 3052 Australia
- ARC Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Parkville, 3052 Australia
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Hauser RA, Hattori N, Fernandez H, Isaacson SH, Mochizuki H, Rascol O, Stocchi F, Li J, Mori A, Nakajima Y, Ristuccia R, LeWitt P. Efficacy of Istradefylline, an Adenosine A2A Receptor Antagonist, as Adjunctive Therapy to Levodopa in Parkinson's Disease: A Pooled Analysis of 8 Phase 2b/3 Trials. JOURNAL OF PARKINSONS DISEASE 2021; 11:1663-1675. [PMID: 34486986 PMCID: PMC8609697 DOI: 10.3233/jpd-212672] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Istradefylline is a selective adenosine A2A receptor antagonist for the treatment of patients with Parkinson's disease (PD) experiencing OFF episodes while on levodopa/decarboxylase inhibitor. OBJECTIVE This pooled analysis of eight randomized, placebo-controlled, double-blind phase 2b/3 studies evaluated the efficacy and safety of istradefylline. METHODS Istradefylline was evaluated in PD patients receiving levodopa with carbidopa/benserazide and experiencing motor fluctuations. Eight 12- or 16-week trials were conducted (n = 3,245); four of these studies were the basis for istradefylline's FDA approval. Change in OFF time as assessed in patient-completed 24-h PD diaries at Week 12 was the primary endpoint. All studies were designed with common methodology, thereby permitting pooling of data. Pooled analysis results from once-daily oral istradefylline (20 and 40 mg/day) and placebo were evaluated using a mixed-model repeated-measures approach including study as a factor. RESULTS Among 2,719 patients (placebo, n = 992; 20 mg/day, n = 848; 40 mg/day, n = 879), OFF hours/day were reduced at Week 12 at istradefylline dosages of 20 mg/day (least-squares mean difference [LSMD] from placebo in reduction from baseline [95%CI], -0.38 h [-0.61, -0.15]) and 40 mg/day (-0.45 h [-0.68, -0.22], p < 0.0001); ON time without troublesome dyskinesia (ON-WoTD) significantly increased. Similar results were found in the four-study pool (OFF hours/day, 20 mg/day, -0.75 h [-1.10, -0.40]; 40 mg/day, -0.82 h [-1.17, -0.47]). Istradefylline was generally well-tolerated; the average study completion rate among istradefylline-treated patients across all studies was 89.2%. Dyskinesia was the most frequent adverse event (placebo, 9.6%; 20 mg/day, 16.1%; 40 mg/day, 17.7%). CONCLUSION In this pooled analysis, istradefylline significantly improved OFF time and ON-WoTD relative to placebo and was well-tolerated.
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Affiliation(s)
- Robert A Hauser
- Parkinson's Disease and Movement Disorders Center, Department of Neurology, University of South Florida, Tampa, FL, USA
| | - Nobutaka Hattori
- Department of Neurology, Juntendo University School of Medicine, Tokyo, Japan
| | - Hubert Fernandez
- Center for Neuro-Restoration, Cleveland Clinic, Cleveland, OH, USA
| | - Stuart H Isaacson
- Parkinson's Disease and Movement Disorders Center of Boca Raton, Boca Raton, FL, USA
| | - Hideki Mochizuki
- Department of Neurology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Olivier Rascol
- Clinical Investigation Center CIC1436, Departments of Neurosciences and Clinical Pharmacology, Parkinson Expert Center, NS-Park/FCRIN Network and NeuroToul COEN Center, CHU de Toulouse, INSERM and University of Toulouse 3, Toulouse, France
| | | | - June Li
- Kyowa Kirin, Inc., Princeton, NJ, USA
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Lai TH, Toussaint M, Teodoro R, Dukić-Stefanović S, Gündel D, Ludwig FA, Wenzel B, Schröder S, Sattler B, Moldovan RP, Falkenburger BH, Sabri O, Deuther-Conrad W, Brust P. Improved in vivo PET imaging of the adenosine A 2A receptor in the brain using [ 18F]FLUDA, a deuterated radiotracer with high metabolic stability. Eur J Nucl Med Mol Imaging 2021; 48:2727-2736. [PMID: 33532910 PMCID: PMC8263428 DOI: 10.1007/s00259-020-05164-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/13/2020] [Indexed: 02/07/2023]
Abstract
PURPOSE The adenosine A2A receptor has emerged as a therapeutic target for multiple diseases, and thus the non-invasive imaging of the expression or occupancy of the A2A receptor has potential to contribute to diagnosis and drug development. We aimed at the development of a metabolically stable A2A receptor radiotracer and report herein the preclinical evaluation of [18F]FLUDA, a deuterated isotopologue of [18F]FESCH. METHODS [18F]FLUDA was synthesized by a two-step one-pot approach and evaluated in vitro by autoradiographic studies as well as in vivo by metabolism and dynamic PET/MRI studies in mice and piglets under baseline and blocking conditions. A single-dose toxicity study was performed in rats. RESULTS [18F]FLUDA was obtained with a radiochemical yield of 19% and molar activities of 72-180 GBq/μmol. Autoradiography proved A2A receptor-specific accumulation of [18F]FLUDA in the striatum of a mouse and pig brain. In vivo evaluation in mice revealed improved stability of [18F]FLUDA compared to that of [18F]FESCH, resulting in the absence of brain-penetrant radiometabolites. Furthermore, the radiometabolites detected in piglets are expected to have a low tendency for brain penetration. PET/MRI studies confirmed high specific binding of [18F]FLUDA towards striatal A2A receptor with a maximum specific-to-non-specific binding ratio in mice of 8.3. The toxicity study revealed no adverse effects of FLUDA up to 30 μg/kg, ~ 4000-fold the dose applied in human PET studies using [18F]FLUDA. CONCLUSIONS The new radiotracer [18F]FLUDA is suitable to detect the availability of the A2A receptor in the brain with high target specificity. It is regarded ready for human application.
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Affiliation(s)
- Thu Hang Lai
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany.
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden, Germany.
| | - Magali Toussaint
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany.
| | - Rodrigo Teodoro
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Sladjana Dukić-Stefanović
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Daniel Gündel
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Friedrich-Alexander Ludwig
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Barbara Wenzel
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Susann Schröder
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden, Germany
| | - Bernhard Sattler
- Department of Nuclear Medicine, University Hospital Leipzig, Leipzig, Germany
| | - Rareş-Petru Moldovan
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | | | - Osama Sabri
- Department of Nuclear Medicine, University Hospital Leipzig, Leipzig, Germany
| | - Winnie Deuther-Conrad
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Peter Brust
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
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Zarrinmayeh H, Territo PR. Purinergic Receptors of the Central Nervous System: Biology, PET Ligands, and Their Applications. Mol Imaging 2021; 19:1536012120927609. [PMID: 32539522 PMCID: PMC7297484 DOI: 10.1177/1536012120927609] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Purinergic receptors play important roles in central nervous system (CNS). These receptors are involved in cellular neuroinflammatory responses that regulate functions of neurons, microglial and astrocytes. Based on their endogenous ligands, purinergic receptors are classified into P1 or adenosine, P2X and P2Y receptors. During brain injury or under pathological conditions, rapid diffusion of extracellular adenosine triphosphate (ATP) or uridine triphosphate (UTP) from the damaged cells, promote microglial activation that result in the changes in expression of several of these receptors in the brain. Imaging of the purinergic receptors with selective Positron Emission Tomography (PET) radioligands has advanced our understanding of the functional roles of some of these receptors in healthy and diseased brains. In this review, we have accumulated a list of currently available PET radioligands of the purinergic receptors that are used to elucidate the receptor functions and participations in CNS disorders. We have also reviewed receptors lacking radiotracer, laying the foundation for future discoveries of novel PET radioligands to reveal these receptors roles in CNS disorders.
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Affiliation(s)
- Hamideh Zarrinmayeh
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Paul R Territo
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA
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Yang X, Heitman LH, IJzerman AP, van der Es D. Molecular probes for the human adenosine receptors. Purinergic Signal 2021; 17:85-108. [PMID: 33313997 PMCID: PMC7954947 DOI: 10.1007/s11302-020-09753-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 11/01/2020] [Indexed: 11/29/2022] Open
Abstract
Adenosine receptors, G protein-coupled receptors (GPCRs) that are activated by the endogenous ligand adenosine, have been considered potential therapeutic targets in several disorders. To date however, only very few adenosine receptor modulators have made it to the market. Increased understanding of these receptors is required to improve the success rate of adenosine receptor drug discovery. To improve our understanding of receptor structure and function, over the past decades, a diverse array of molecular probes has been developed and applied. These probes, including radioactive or fluorescent moieties, have proven invaluable in GPCR research in general. Specifically for adenosine receptors, the development and application of covalent or reversible probes, whether radiolabeled or fluorescent, have been instrumental in the discovery of new chemical entities, the characterization and interrogation of adenosine receptor subtypes, and the study of adenosine receptor behavior in physiological and pathophysiological conditions. This review summarizes these applications, and also serves as an invitation to walk another mile to further improve probe characteristics and develop additional tags that allow the investigation of adenosine receptors and other GPCRs in even finer detail.
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Affiliation(s)
- Xue Yang
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Laura H. Heitman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Adriaan P. IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Daan van der Es
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Prasad K, de Vries EFJ, Elsinga PH, Dierckx RAJO, van Waarde A. Allosteric Interactions between Adenosine A 2A and Dopamine D 2 Receptors in Heteromeric Complexes: Biochemical and Pharmacological Characteristics, and Opportunities for PET Imaging. Int J Mol Sci 2021; 22:ijms22041719. [PMID: 33572077 PMCID: PMC7915359 DOI: 10.3390/ijms22041719] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/17/2022] Open
Abstract
Adenosine and dopamine interact antagonistically in living mammals. These interactions are mediated via adenosine A2A and dopamine D2 receptors (R). Stimulation of A2AR inhibits and blockade of A2AR enhances D2R-mediated locomotor activation and goal-directed behavior in rodents. In striatal membrane preparations, adenosine decreases both the affinity and the signal transduction of D2R via its interaction with A2AR. Reciprocal A2AR/D2R interactions occur mainly in striatopallidal GABAergic medium spiny neurons (MSNs) of the indirect pathway that are involved in motor control, and in striatal astrocytes. In the nucleus accumbens, they also take place in MSNs involved in reward-related behavior. A2AR and D2R co-aggregate, co-internalize, and co-desensitize. They are at very close distance in biomembranes and form heteromers. Antagonistic interactions between adenosine and dopamine are (at least partially) caused by allosteric receptor–receptor interactions within A2AR/D2R heteromeric complexes. Such interactions may be exploited in novel strategies for the treatment of Parkinson’s disease, schizophrenia, substance abuse, and perhaps also attention deficit-hyperactivity disorder. Little is known about shifting A2AR/D2R heteromer/homodimer equilibria in the brain. Positron emission tomography with suitable ligands may provide in vivo information about receptor crosstalk in the living organism. Some experimental approaches, and strategies for the design of novel imaging agents (e.g., heterobivalent ligands) are proposed in this review.
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Affiliation(s)
- Kavya Prasad
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
| | - Erik F. J. de Vries
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Philip H. Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Rudi A. J. O. Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Department of Diagnostic Sciences, Ghent University Faculty of Medicine and Health Sciences, C.Heymanslaan 10, 9000 Gent, Belgium
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
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11
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Gonçalves MCB, Glaser T, Oliveira SLBD, Ulrich H. Adenosinergic-Dopaminergic Signaling in Mood Disorders: A Mini-Review. J Caffeine Adenosine Res 2020. [DOI: 10.1089/caff.2020.0009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Talita Glaser
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | | | - Henning Ulrich
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil
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12
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Tracers for non-invasive radionuclide imaging of immune checkpoint expression in cancer. EJNMMI Radiopharm Chem 2019; 4:29. [PMID: 31696402 PMCID: PMC6834817 DOI: 10.1186/s41181-019-0078-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 09/21/2019] [Indexed: 12/11/2022] Open
Abstract
Abstract Immunotherapy with checkpoint inhibitors demonstrates impressive improvements in the treatment of several types of cancer. Unfortunately, not all patients respond to therapy while severe immune-related adverse effects are prevalent. Currently, patient stratification is based on immunotherapy marker expression through immunohistochemical analysis on biopsied material. However, expression can be heterogeneous within and between tumor lesions, amplifying the sampling limitations of biopsies. Analysis of immunotherapy target expression by non-invasive quantitative molecular imaging with PET or SPECT may overcome this issue. In this review, an overview of tracers that have been developed for preclinical and clinical imaging of key immunotherapy targets, such as programmed cell death-1, programmed cell death ligand-1, IDO1 and cytotoxic T lymphocyte-associated antigen-4 is presented. We discuss important aspects to consider when developing such tracers and outline the future perspectives of molecular imaging of immunotherapy markers. Graphical abstract Current techniques in immune checkpoint imaging and its potential for future applications ![]()
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13
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Li J, Hong X, Li G, Conti PS, Zhang X, Chen K. PET Imaging of Adenosine Receptors in Diseases. Curr Top Med Chem 2019; 19:1445-1463. [PMID: 31284861 DOI: 10.2174/1568026619666190708163407] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/26/2019] [Accepted: 02/02/2019] [Indexed: 01/08/2023]
Abstract
Adenosine receptors (ARs) are a class of purinergic G-protein-coupled receptors (GPCRs). Extracellular adenosine is a pivotal regulation molecule that adjusts physiological function through the interaction with four ARs: A1R, A2AR, A2BR, and A3R. Alterations of ARs function and expression have been studied in neurological diseases (epilepsy, Alzheimer's disease, and Parkinson's disease), cardiovascular diseases, cancer, and inflammation and autoimmune diseases. A series of Positron Emission Tomography (PET) probes for imaging ARs have been developed. The PET imaging probes have provided valuable information for diagnosis and therapy of diseases related to alterations of ARs expression. This review presents a concise overview of various ARs-targeted radioligands for PET imaging in diseases. The most recent advances in PET imaging studies by using ARs-targeted probes are briefly summarized.
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Affiliation(s)
- Jindian Li
- Department of Radiology, Molecular Imaging Center, Keck School of Medicine, University of Southern California, 2250 Alcazar Street, CSC103, Los Angeles, CA 90033, United States.,State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361102, China
| | - Xingfang Hong
- Laboratory of Pathogen Biology, School of Basic Medical Sciences, Dali University, Dali 671000, China
| | - Guoquan Li
- Department of Radiology, Molecular Imaging Center, Keck School of Medicine, University of Southern California, 2250 Alcazar Street, CSC103, Los Angeles, CA 90033, United States
| | - Peter S Conti
- Department of Radiology, Molecular Imaging Center, Keck School of Medicine, University of Southern California, 2250 Alcazar Street, CSC103, Los Angeles, CA 90033, United States
| | - Xianzhong Zhang
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361102, China
| | - Kai Chen
- Department of Radiology, Molecular Imaging Center, Keck School of Medicine, University of Southern California, 2250 Alcazar Street, CSC103, Los Angeles, CA 90033, United States
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14
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Nagayama H, Kano O, Murakami H, Ono K, Hamada M, Toda T, Sengoku R, Shimo Y, Hattori N. Effect of istradefylline on mood disorders in Parkinson's disease. J Neurol Sci 2019; 396:78-83. [DOI: 10.1016/j.jns.2018.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/11/2018] [Accepted: 11/04/2018] [Indexed: 01/21/2023]
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15
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Palomero-Gallagher N, Zilles K. Cyto- and receptor architectonic mapping of the human brain. HANDBOOK OF CLINICAL NEUROLOGY 2018; 150:355-387. [PMID: 29496153 DOI: 10.1016/b978-0-444-63639-3.00024-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mapping of the human brain is more than the generation of an atlas-based parcellation of brain regions using histologic or histochemical criteria. It is the attempt to provide a topographically informed model of the structural and functional organization of the brain. To achieve this goal a multimodal atlas of the detailed microscopic and neurochemical structure of the brain must be registered to a stereotaxic reference space or brain, which also serves as reference for topographic assignment of functional data, e.g., functional magnet resonance imaging, electroencephalography, or magnetoencephalography, as well as metabolic imaging, e.g., positron emission tomography. Although classic maps remain pioneering steps, they do not match recent concepts of the functional organization in many regions, and suffer from methodic drawbacks. This chapter provides a summary of the recent status of human brain mapping, which is based on multimodal approaches integrating results of quantitative cyto- and receptor architectonic studies with focus on the cerebral cortex in a widely used reference brain. Descriptions of the methods for observer-independent and statistically testable cytoarchitectonic parcellations, quantitative multireceptor mapping, and registration to the reference brain, including the concept of probability maps and a toolbox for using the maps in functional neuroimaging studies, are provided.
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Affiliation(s)
- Nicola Palomero-Gallagher
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany; Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH, Aachen, Germany
| | - Karl Zilles
- Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany; Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH, Aachen, Germany; JARA-BRAIN, Jülich-Aachen Research Alliance, Jülich, Germany.
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16
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Lahesmaa M, Oikonen V, Helin S, Luoto P, U Din M, Pfeifer A, Nuutila P, Virtanen KA. Regulation of human brown adipose tissue by adenosine and A 2A receptors - studies with [ 15O]H 2O and [ 11C]TMSX PET/CT. Eur J Nucl Med Mol Imaging 2018; 46:743-750. [PMID: 30105585 PMCID: PMC6351510 DOI: 10.1007/s00259-018-4120-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 08/01/2018] [Indexed: 12/16/2022]
Abstract
PURPOSE Brown adipose tissue (BAT) has emerged as a potential target to combat obesity and diabetes, but novel strategies to activate BAT are needed. Adenosine and A2A receptor (A2AR) agonism activate BAT in rodents, and endogenous adenosine is released locally in BAT as a by-product of noradrenaline, but physiological data from humans is lacking. The purpose of this pilot study was to investigate the effects of exogenous adenosine on human BAT perfusion, and to determine the density of A2ARs in human BAT in vivo for the first time, using PET/CT imaging. METHODS Healthy, lean men (n = 10) participated in PET/CT imaging with two radioligands. Perfusion of BAT, white adipose tissue (WAT) and muscle was quantified with [15O]H2O at baseline, during cold exposure and during intravenous administration of adenosine. A2AR density of the tissues was quantified with [11C]TMSX at baseline and during cold exposure. RESULTS Adenosine increased the perfusion of BAT even more than cold exposure (baseline 8.3 ± 4.5, cold 19.6 ± 9.3, adenosine 28.6 ± 7.9 ml/100 g/min, p < 0.01). Distribution volume of [11C]TMSX in BAT was significantly lower during cold exposure compared to baseline. In cold, low [11C]TMSX binding coincided with high concentrations of noradrenaline. CONCLUSIONS Adenosine administration caused a maximal perfusion effect in human supraclavicular BAT, indicating increased oxidative metabolism. Cold exposure increased noradrenaline concentrations and decreased the density of A2AR available for radioligand binding in BAT, suggesting augmented release of endogenous adenosine. Our results show that adenosine and A2AR are relevant for activation of human BAT, and A2AR provides a future target for enhancing BAT metabolism.
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Affiliation(s)
- Minna Lahesmaa
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
- Turku PET Centre, Turku University Hospital, Turku, Finland
| | - Vesa Oikonen
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
| | - Semi Helin
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
| | - Pauliina Luoto
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
| | - Mueez U Din
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
- Turku PET Centre, Turku University Hospital, Turku, Finland
| | - Alexander Pfeifer
- Institute of Pharmacology and Toxicology, University of Bonn, Bonn, Germany
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland
- Department of Endocrinology, Turku University Hospital, Turku, Finland
| | - Kirsi A Virtanen
- Turku PET Centre, University of Turku, P.O. Box 52, FI-20520, Turku, Finland.
- Turku PET Centre, Turku University Hospital, Turku, Finland.
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17
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Mishina M, Kimura Y, Sakata M, Ishii K, Oda K, Toyohara J, Kimura K, Ishiwata K. Age-Related Decrease in Male Extra-Striatal Adenosine A 1 Receptors Measured Using11C-MPDX PET. Front Pharmacol 2017; 8:903. [PMID: 29326588 PMCID: PMC5741655 DOI: 10.3389/fphar.2017.00903] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/28/2017] [Indexed: 11/15/2022] Open
Abstract
Adenosine A1 receptors (A1Rs) are widely distributed throughout the entire human brain, while adenosine A2A receptors (A2ARs) are present in dopamine-rich areas of the brain, such as the basal ganglia. A past study using autoradiography reported a reduced binding ability of A1R in the striatum of old rats. We developed positron emission tomography (PET) ligands for mapping the adenosine receptors and we successfully visualized the A1Rs using 8-dicyclopropylmethyl-1-11C-methyl-3-propylxanthine (11C-MPDX). We previously reported that the density of A1Rs decreased with age in the human striatum, although we could not observe an age-related change in A2ARs. The aim of this study was to investigate the age-related change of the density of A1Rs in the thalamus and cerebral cortices of healthy participants using 11C-MPDX PET. We recruited eight young (22.0 ± 1.7 years) and nine elderly healthy male volunteers (65.7 ± 8.0 years). A dynamic series of decay-corrected PET scans was performed for 60 min starting with the injection of 11C-MPDX. We placed the circular regions of interest of 10 mm in diameter in 11C-MPDX PET images. The values for the binding potential (BPND) of 11C-MPDX in the thalamus, and frontal, temporal, occipital, and parietal cortices were calculated using a graphical analysis, wherein the reference region was the cerebellum. BPND of 11C-MPDX was significantly lower in elderly participants than young participants in the thalamus, and frontal, temporal, occipital, and parietal cortices. In the human brain, we could observe the age-related decrease in the distribution of A1Rs.
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Affiliation(s)
- Masahiro Mishina
- Department of Neuro-pathophysiological Imaging, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan.,Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.,Department of Neurological Science, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Yuichi Kimura
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.,Department of Computational Systems Biology, Faculty of Biology-Oriented Science and Technology, Kindai University, Kinokawa, Japan
| | - Muneyuki Sakata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Kenji Ishii
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Keiichi Oda
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.,Department of Radiological Technology, Faculty of Health Sciences, Hokkaido University of Science, Sapporo, Japan
| | - Jun Toyohara
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Kazumi Kimura
- Department of Neurological Science, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Kiichi Ishiwata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.,Institute of Cyclotron and Drug Discovery Research, Southern TOHOKU Research Institute for Neuroscience, Koriyama, Japan.,Department of Biofunctional Imaging, Fukushima Medical University, Fukushima, Japan
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18
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In Vivo PET Imaging of Adenosine 2A Receptors in Neuroinflammatory and Neurodegenerative Disease. CONTRAST MEDIA & MOLECULAR IMAGING 2017; 2017:6975841. [PMID: 29348737 PMCID: PMC5733838 DOI: 10.1155/2017/6975841] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/18/2017] [Indexed: 01/01/2023]
Abstract
Adenosine receptors are G-protein coupled P1 purinergic receptors that are broadly expressed in the peripheral immune system, vasculature, and the central nervous system (CNS). Within the immune system, adenosine 2A (A2A) receptor-mediated signaling exerts a suppressive effect on ongoing inflammation. In healthy CNS, A2A receptors are expressed mainly within the neurons of the basal ganglia. Alterations in A2A receptor function and expression have been noted in movement disorders, and in Parkinson's disease pharmacological A2A receptor antagonism leads to diminished motor symptoms. Although A2A receptors are expressed only at a low level in the healthy CNS outside striatum, pathological challenge or inflammation has been shown to lead to upregulation of A2A receptors in extrastriatal CNS tissue, and this has been successfully quantitated using in vivo positron emission tomography (PET) imaging and A2A receptor-binding radioligands. Several radioligands for PET imaging of A2A receptors have been developed in recent years, and A2A receptor-targeting PET imaging may thus provide a potential additional tool to evaluate various aspects of neuroinflammation in vivo. This review article provides a brief overview of A2A receptors in healthy brain and in a selection of most important neurological diseases and describes the recent advances in A2A receptor-targeting PET imaging studies.
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19
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Abstract
Purpose of Review To review the current status of positron emission tomography (PET) molecular imaging research of levodopa-induced dyskinesias (LIDs) in Parkinson’s disease (PD). Recent Findings Recent PET studies have provided robust evidence that LIDs in PD are associated with elevated and fluctuating striatal dopamine synaptic levels, which is a consequence of the imbalance between dopaminergic and serotonergic terminals, with the latter playing a key role in mishandling presynaptic dopamine release. Long-term exposure to levodopa is no longer believed to solely induce LIDs, as studies have highlighted that PD patients who go on to develop LIDs exhibit elevated putaminal dopamine release before the initiation of levodopa treatment, suggesting the involvement of other mechanisms, including altered neuronal firing and abnormal levels of phosphodiesterase 10A. Summary Dopaminergic, serotonergic, glutamatergic, adenosinergic and opioid systems and phosphodiesterase 10A levels have been shown to be implicated in the development of LIDs in PD. However, no system may be considered sufficient on its own for the development of LIDs, and the mechanisms underlying LIDs in PD may have a multisystem origin. In line with this notion, future studies should use multimodal PET molecular imaging in the same individuals to shed further light on the different mechanisms underlying the development of LIDs in PD.
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20
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Sakata M, Ishibashi K, Imai M, Wagatsuma K, Ishii K, Zhou X, de Vries EF, Elsinga PH, Ishiwata K, Toyohara J. Initial Evaluation of an Adenosine A2A Receptor Ligand, 11C-Preladenant, in Healthy Human Subjects. J Nucl Med 2017; 58:1464-1470. [DOI: 10.2967/jnumed.116.188474] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 02/13/2017] [Indexed: 12/15/2022] Open
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21
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Zhou X, Khanapur S, de Jong JR, Willemsen AT, Dierckx RA, Elsinga PH, de Vries EF. In vivo evaluation of [ 11C]preladenant positron emission tomography for quantification of adenosine A 2A receptors in the rat brain. J Cereb Blood Flow Metab 2017; 37:577-589. [PMID: 26917190 PMCID: PMC5381452 DOI: 10.1177/0271678x16634714] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
[11C]Preladenant was developed as a novel adenosine A2A receptor positron emission tomography radioligand. The present study aims to evaluate the suitability of [11C]preladenant positron emission tomography for the quantification of striatal A2A receptor density and the assessment of striatal A2A receptor occupancy by KW-6002. Sixty- or ninety-minute dynamic positron emission tomography imaging was performed on rats. Tracer kinetics was quantified by the two-tissue compartment model, Logan graphical analysis and several reference tissue-based models. Test-retest reproducibility was assessed by repeated imaging on two consecutive days. Two-tissue compartment model and Logan plot estimated comparable distribution volume ( VT) values of ∼10 in the A2A receptor-rich striatum and substantially lower values in all extra-striatal regions (∼1.5-2.5). The simplified reference tissue model with midbrain or occipital cortex as the reference region proved to be the best non-invasive model for quantification of A2A receptor, showing a striatal binding potential ( BPND) value of ∼5.5, and a test-retest variability of ∼5.5%. The brain metabolite analysis showed that at 60-min post injection, 17% of the radioactivity in the brain was due to radioactive metabolites. The ED50 of KW-6002 in rat striatum for i.p. injection was 0.044-0.062 mg/kg. The study demonstrates that [11C]preladenant is a suitable tracer to quantify striatal A2A receptor density and assess A2A receptor occupancy by A2A receptor-targeting molecules.
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Affiliation(s)
- Xiaoyun Zhou
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Shivashankar Khanapur
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Johan R de Jong
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Antoon Tm Willemsen
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Rudi Ajo Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Philip H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Erik Fj de Vries
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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22
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Zhou X, Boellaard R, Ishiwata K, Sakata M, Dierckx RAJO, de Jong JR, Nishiyama S, Ohba H, Tsukada H, de Vries EFJ, Elsinga PH. In Vivo Evaluation of 11C-Preladenant for PET Imaging of Adenosine A 2A Receptors in the Conscious Monkey. J Nucl Med 2017; 58:762-767. [PMID: 28062599 DOI: 10.2967/jnumed.116.182410] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 11/10/2016] [Indexed: 12/22/2022] Open
Abstract
11C-preladenant was developed as a novel PET ligand for the adenosine A2A receptors (A2ARs). The present study aimed to evaluate the suitability of 11C-preladenant PET for the quantification of striatal A2ARs and the assessment of A2AR occupancy in the conscious monkey brain. Methods:11C-preladenant was intravenously injected into conscious monkeys (n = 4, 18 PET scans), and a 91-min dynamic scan was started. Arterial blood samples in combination with metabolite analysis were obtained during the scan to provide the input function for kinetic modeling. The distribution volume (VT) was obtained by kinetic modeling with a 2-tissue-compartment model. The simplified reference tissue model (SRTM) with selected reference regions (cerebellum, cingulate, parietal cortex, and occipital cortex) was tested to estimate the binding potential (BPND) in A2AR-rich regions. BPND obtained from the SRTM was compared with distribution volume ratio (DVR)-1. The effects of blood volume, blood delay, and scan duration on BPND and DVR-1 were investigated. VT and BPND were also obtained after preblocking with unlabeled preladenant (1 mg/kg), A2AR-selective KW-6002 (0.5-1 mg/kg), and nonselective adenosine receptor antagonist caffeine (2.5-10 mg/kg). A2AR occupancy was studied with caffeine blockade. Results: Regional uptake of 11C-preladenant was consistent with the distribution of A2ARs in the monkey brain, with the highest uptake in the putamen, followed by the caudate, and the lowest uptake in the cerebellum. Tracer kinetics were well described by the 2-tissue-compartment model with a lower constraint on k4 to stabilize fits. The highest VT was observed in A2AR-rich regions (∼5.8-7.4) and lowest value in the cerebellum (∼1.3). BPND values estimated from the SRTM with different scan durations were comparable and were in agreement with DVR-1 (∼4.3-5.3 in A2AR-rich regions). Preladenant preinjection decreased the tracer uptake in A2AR-rich regions to the level of the reference regions. Caffeine pretreatment reduced the tracer uptake in the striatum in a dose-dependent manner. Conclusion:11C-preladenant PET is suitable for noninvasive quantification of A2ARs and assessment of A2AR occupancy in A2AR-rich regions in the monkey brain. SRTM using the cerebellum as the reference tissue is the applicable model for A2AR quantification.
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Affiliation(s)
- Xiaoyun Zhou
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Ronald Boellaard
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Kiichi Ishiwata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.,Institute of Cyclotron and Drug Discovery Research, Southern TOHOKU Research Institute for Neuroscience, Koriyama, Japan.,Department of Biofunctional Imaging, Fukushima Medical University, Fukushima, Japan; and
| | - Muneyuki Sakata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
| | - Rudi A J O Dierckx
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Johan R de Jong
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Shingo Nishiyama
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu, Japan
| | - Hiroyuki Ohba
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu, Japan
| | - Hideo Tsukada
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu, Japan
| | - Erik F J de Vries
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Philip H Elsinga
- University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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23
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Khanapur S, van Waarde A, Dierckx RAJO, Elsinga PH, Koole MJB. Preclinical Evaluation and Quantification of 18F-Fluoroethyl and 18F-Fluoropropyl Analogs of SCH442416 as Radioligands for PET Imaging of the Adenosine A 2A Receptor in Rat Brain. J Nucl Med 2016; 58:466-472. [PMID: 27789720 DOI: 10.2967/jnumed.116.178103] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 10/02/2016] [Indexed: 11/16/2022] Open
Abstract
The cerebral adenosine A2A receptor is an attractive therapeutic target for neuropsychiatric disorders. 18F-fluoroethyl and 18F-fluoropropyl analogs of 18F-labeled pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH442416) (18F-FESCH and 18F-FPSCH, respectively) were developed as A2A receptor-specific PET ligands. Our aim was to determine an appropriate compartmental model for tracer kinetics, evaluate a reference tissue approach, and select the most suitable PET ligand. Methods: A 90-min dynamic PET scan with arterial blood sampling and metabolite analysis was acquired for 22 healthy male Wistar rats starting at the time of 18F-FESCH (n = 12) and 18F-FPSCH (n = 10) injection. For each tracer, half the animals were vehicle-treated whereas the other half were pretreated with the A2A receptor-selective antagonist KW-6002, inducing full blocking. Regional tissue total volume of distribution (VT) was estimated by 1- and 2-tissue-compartment modeling (1TCM and 2TCM, respectively) and Logan graphical analysis. Midbrain, cerebellum, and hippocampus were evaluated as the reference region by comparing baseline VT with VT under full blocking conditions and comparing striatal nondisplaceable binding potential (BPND) using a simplified reference tissue model (SRTM) with distribution volume ratio minus 1 (DVR - 1) for 60- and 90-min scans. Results: On the basis of the Akaike information criterion, 1TCM and 2TCM were the most appropriate models for 18F-FPSCH (baseline striatal VT, 3.7 ± 1.1) and 18F-FESCH (baseline striatal VT, 5.0 ± 2.0), respectively. Baseline striatal VT did not significantly differ between tracers. After pretreatment, striatal VT was reduced significantly, with no significant decrease in hippocampus, midbrain, or cerebellum VT Baseline striatal SRTM BPND did not differ significantly from DVR - 1 except for 18F-FPSCH when using a 60-min scan and midbrain as the reference region, whereas Bland-Altman analysis found a smaller bias for 18F-FESCH and a 60-min scan. After pretreatment, striatal SRTM BPND did not significantly differ from zero except for 18F-FPSCH when using hippocampus as the reference region. Striatal SRTM BPND using midbrain or cerebellum as the reference region was significantly lower for 18F-FPSCH (range, 1.41-2.62) than for 18F-FESCH (range, 1.64-3.36). Conclusion: Dynamic PET imaging under baseline and blocking conditions determined 18F-FESCH to be the most suitable PET ligand for quantifying A2A receptor expression in the rat brain. Accurate quantification is achieved by a 60-min dynamic PET scan and the use of either cerebellum or midbrain as the reference region.
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Affiliation(s)
- Shivashankar Khanapur
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and
| | - Rudi A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and
| | - Philip H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and
| | - Michel J B Koole
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; and .,Department of Nuclear Medicine and Molecular Imaging, KU Leuven, Leuven, Belgium
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Vala C, Morley TJ, Zhang X, Papin C, Tavares AAS, Lee HS, Constantinescu C, Barret O, Carroll VM, Baldwin RM, Tamagnan GD, Alagille D. Synthesis and in vivo Evaluation of Fluorine-18 and Iodine-123 Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine Derivatives as PET and SPECT Radiotracers for Mapping A2A Receptors. ChemMedChem 2016; 11:1936-43. [PMID: 27407017 DOI: 10.1002/cmdc.201600219] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 06/15/2016] [Indexed: 11/06/2022]
Abstract
Imaging agents that target adenosine type 2A (A2A ) receptors play an important role in evaluating new pharmaceuticals targeting these receptors, such as those currently being developed for the treatment of movement disorders like Parkinson's disease. They are also useful for monitoring progression and treatment efficacy by providing a noninvasive tool to map changes in A2A receptor density and function in neurodegenerative diseases. We previously described the successful evaluation of two A2A -specific radiotracers in both nonhuman primates and in subsequent human clinical trials: [(123) I]MNI-420 and [(18) F]MNI-444. Herein we describe the development of both of these radiotracers by selection from a series of A2A ligands, based on the pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine core of preladenant. Each of this series of 16 ligands was found to bind to recombinant human A2A receptor in the low nanomolar range, and of these 16, six were radiolabeled with either fluorine-18 or iodine-123 and evaluated in nonhuman primates. These initial in vivo results resulted in the identification of 7-(2-(4-(4-(2-[(18) F]fluoroethoxy)phenyl)piperazin-1-yl)ethyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine ([(18) F]MNI-444) and 7-(2-(4-(2-fluoro-4-[(123) I]iodophenyl)piperazin-1-yl)ethyl)-2-(furan-2-yl)-7H-imidazo[1,2-c]pyrazolo[4,3-e]pyrimidin-5-amine ([(123) I]MNI-420) as PET and SPECT radiopharmaceuticals for mapping A2A receptors in brain.
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Affiliation(s)
- Christine Vala
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Thomas J Morley
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA.
| | - Xuechun Zhang
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Caroline Papin
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | | | - H Sharon Lee
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Cristian Constantinescu
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Olivier Barret
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Vincent M Carroll
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Ronald M Baldwin
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - Gilles D Tamagnan
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
| | - David Alagille
- Molecular NeuroImaging, a division of inviCRO, 60 Temple Street, Suite 8B, New Haven, CT, 06510, USA
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Jazayeri A, Andrews SP, Marshall FH. Structurally Enabled Discovery of Adenosine A 2A Receptor Antagonists. Chem Rev 2016; 117:21-37. [PMID: 27333206 DOI: 10.1021/acs.chemrev.6b00119] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Over the past decade there has been a revolution in the field of G protein-coupled receptor (GPCR) structural biology. Many years of innovative research from different areas have come together to fuel this significant change in the fortunes of this field, which for many years was characterized by the paucity of high-resolution structures. The determination to succeed has been in part due to the recognized importance of these proteins as drug targets, and although the pharmaceutical industry has been focusing on these receptors, it can be justifiably argued and demonstrated that many of the approved and commercially successful GPCR drugs can be significantly improved to increase efficacy and/or reduce undesired side effects. In addition, many validated targets in this class remain to be drugged. It is widely recognized that application of structure-based drug design approaches can help medicinal chemists a long way toward discovering better drugs. The achievement of structural biologists in providing high-resolution insight is beginning to transform drug discovery efforts, and there are a number of GPCR drugs that have been discovered by use of structural information that are in clinical development. This review aims to highlight the key developments that have brought success to GPCR structure resolution efforts and exemplify the practical application of structural information for the discovery of adenosine A2A receptor antagonists that have potential to treat multiple conditions.
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Affiliation(s)
- Ali Jazayeri
- Heptares Therapeutics Limited , BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, United Kingdom
| | - Stephen P Andrews
- Heptares Therapeutics Limited , BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, United Kingdom
| | - Fiona H Marshall
- Heptares Therapeutics Limited , BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, United Kingdom
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Zheng S, Bai YY, Liu Y, Gao X, Li Y, Changyi Y, Wang Y, Chang D, Ju S, Li C. Salvaging brain ischemia by increasing neuroprotectant uptake via nanoagonist mediated blood brain barrier permeability enhancement. Biomaterials 2015; 66:9-20. [PMID: 26188608 DOI: 10.1016/j.biomaterials.2015.07.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 07/03/2015] [Accepted: 07/09/2015] [Indexed: 12/28/2022]
Abstract
Ischemic stroke is a leading cause of adult disability and cognitive impairment worldwide. Neuroprotective therapy aims to save neurons by impeding the deleterious ischemic insults. However, the low efficiency of the neuroprotectants crossing blood brain barrier (BBB) prevents their clinical translation. In this work, a nanoagonist (NA) was developed to enhance neuroprotectant uptake by specifically increasing BBB permeability in brain ischemia. This NA first targeted ischemic brain vasculatures, temporarily opened local BBB by activating adenosine 2A receptors, and up-regulated the neuroprotectant uptake in brain ischemia. This NA significantly increased the delivery of superoxide dismutase (SOD), a free radical scavenger, into mouse brain ischemia. The combined treatment of NA/SOD achieved a five-fold ischemic volume reduction rate compared to the animal models treated with SOD alone. Non-invasive magnetic resonance imaging (MRI) confirmed the ischemia targeted BBB opening, increased brain drug delivery efficiency and up-regulated therapeutic response during the combined NA/SOD treatment. Since the inefficient brain drug delivery is a general problem for the treatment of central nervous system (CNS) diseases, this work provides a novel strategy to deliver therapeutics by crossing BBB with high efficiency and targeting specificity.
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Affiliation(s)
- Shuyan Zheng
- Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Rd., Shanghai 201203, China
| | - Ying-Ying Bai
- Jiangsu Key Laboratory of Molecular and Functional Imaging Department of Radiology, Zhongda Hospital, Medical School of Southeast University, 87 Dingjiaqiao Rd., Nanjing 210009, China
| | - Yikang Liu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Xihui Gao
- Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Rd., Shanghai 201203, China
| | - Yan Li
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Rd., Shenyang 110016, China
| | - Yinzhi Changyi
- Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Rd., Shanghai 201203, China
| | - Yuancheng Wang
- Jiangsu Key Laboratory of Molecular and Functional Imaging Department of Radiology, Zhongda Hospital, Medical School of Southeast University, 87 Dingjiaqiao Rd., Nanjing 210009, China
| | - Di Chang
- Jiangsu Key Laboratory of Molecular and Functional Imaging Department of Radiology, Zhongda Hospital, Medical School of Southeast University, 87 Dingjiaqiao Rd., Nanjing 210009, China
| | - Shenghong Ju
- Jiangsu Key Laboratory of Molecular and Functional Imaging Department of Radiology, Zhongda Hospital, Medical School of Southeast University, 87 Dingjiaqiao Rd., Nanjing 210009, China.
| | - Cong Li
- Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Rd., Shanghai 201203, China.
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Minor TR, Hanff TC. Adenosine signaling in reserpine-induced depression in rats. Behav Brain Res 2015; 286:184-91. [DOI: 10.1016/j.bbr.2015.02.032] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 02/11/2015] [Accepted: 02/16/2015] [Indexed: 02/05/2023]
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Xu F, Liu P, Pekar JJ, Lu H. Does acute caffeine ingestion alter brain metabolism in young adults? Neuroimage 2015; 110:39-47. [PMID: 25644657 DOI: 10.1016/j.neuroimage.2015.01.046] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Revised: 12/16/2014] [Accepted: 01/26/2015] [Indexed: 12/23/2022] Open
Abstract
Caffeine, as the most commonly used stimulant drug, improves vigilance and, in some cases, cognition. However, the exact effect of caffeine on brain activity has not been fully elucidated. Because caffeine has a pronounced vascular effect which is independent of any neural effects, many hemodynamics-based methods such as fMRI cannot be readily applied without a proper calibration. The scope of the present work is two-fold. In Study 1, we used a recently developed MRI technique to examine the time-dependent changes in whole-brain cerebral metabolic rate of oxygen (CMRO2) following the ingestion of 200mg caffeine. It was found that, despite a pronounced decrease in CBF (p<0.001), global CMRO2 did not change significantly. Instead, the oxygen extraction fraction (OEF) was significantly elevated (p=0.002) to fully compensate for the reduced blood supply. Using the whole-brain finding as a reference, we aim to investigate whether there are any regional differences in the brain's response to caffeine. Therefore, in Study 2, we examined regional heterogeneities in CBF changes following the same amount of caffeine ingestion. We found that posterior brain regions such as posterior cingulate cortex and superior temporal regions manifested a slower CBF reduction, whereas anterior brain regions including dorsolateral prefrontal cortex and medial frontal cortex showed a faster rate of decline. These findings have a few possible explanations. One is that caffeine may result in a region-dependent increase or decrease in brain activity, resulting in an unaltered average brain metabolic rate. The other is that caffeine's effect on vasculature may be region-specific. Plausibility of these explanations is discussed in the context of spatial distribution of the adenosine receptors.
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Affiliation(s)
- Feng Xu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA; The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University, 601 North Caroline Street, MD 21287, USA; F. M Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N Broadway, Baltimore, MD 21205, USA
| | - Peiying Liu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA; The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University, 601 North Caroline Street, MD 21287, USA; Department of Psychiatry, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA
| | - James J Pekar
- The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University, 601 North Caroline Street, MD 21287, USA; F. M Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, 707 N Broadway, Baltimore, MD 21205, USA
| | - Hanzhang Lu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA; The Russell H. Morgan Department of Radiology & Radiological Science, Johns Hopkins University, 601 North Caroline Street, MD 21287, USA; Department of Psychiatry, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.
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Automated reference region extraction and population-based input function for brain [(11)C]TMSX PET image analyses. J Cereb Blood Flow Metab 2015; 35:157-65. [PMID: 25370856 PMCID: PMC4294409 DOI: 10.1038/jcbfm.2014.194] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 10/13/2014] [Accepted: 10/15/2014] [Indexed: 02/07/2023]
Abstract
[(11)C]TMSX ([7-N-methyl-(11)C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine) is a selective adenosine A2A receptor (A2AR) radioligand. In the central nervous system (CNS), A2AR are linked to dopamine D2 receptor function in striatum, but they are also important modulators of inflammation. The golden standard for kinetic modeling of brain [(11)C]TMSX positron emission tomography (PET) is to obtain arterial input function via arterial blood sampling. However, this method is laborious, prone to errors and unpleasant for study subjects. The aim of this work was to evaluate alternative input function acquisition methods for brain [(11)C]TMSX PET imaging. First, a noninvasive, automated method for the extraction of gray matter reference region using supervised clustering (SCgm) was developed. Second, a method for obtaining a population-based arterial input function (PBIF) was implemented. These methods were created using data from 28 study subjects (7 healthy controls, 12 multiple sclerosis patients, and 9 patients with Parkinson's disease). The results with PBIF correlated well with original plasma input, and the SCgm yielded similar results compared with cerebellum as a reference region. The clustering method for extracting reference region and the population-based approach for acquiring input for dynamic [(11)C]TMSX brain PET image analyses appear to be feasible and robust methods, that can be applied in patients with CNS pathology.
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Naganawa M, Mishina M, Sakata M, Oda K, Hiura M, Ishii K, Ishiwata K. Test-retest variability of adenosine A2A binding in the human brain with (11)C-TMSX and PET. EJNMMI Res 2014; 4:76. [PMID: 25621197 PMCID: PMC4293456 DOI: 10.1186/s13550-014-0076-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 12/10/2014] [Indexed: 11/23/2022] Open
Abstract
Background The goal of the present study was to evaluate the reproducibility of cerebral adenosine A2A receptor (A2AR) quantification using 11C-TMSX and PET in a test-retest study. Methods Five healthy volunteers were studied twice. The test-retest variability was assessed for distribution volume (VT) and binding potential relative to non-displaceable uptake (BPND) based on either metabolite-corrected arterial blood sampling or a reference region. The cerebral cortex and centrum semiovale were used as candidate reference regions. Results Test-retest variability of VT was good in all regions (6% to 13%). In the putamen, BPND using the centrum semiovale displayed a lower test-retest variability (3%) than that of BPND using the cerebral cortex as a reference region (5%). The noninvasive method showed a higher or similar level of test-retest reproducibility compared to the invasive method. Conclusions Binding reproducibility is sufficient to use 11C-TMSX as a tool to measure the change in A2AR in the human brain. Electronic supplementary material The online version of this article (doi:10.1186/s13550-014-0076-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mika Naganawa
- PET Center, Yale University School of Medicine, 801 Howard Avenue, PO Box 208048, New Haven, CT 06520-8048 USA ; Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan
| | - Masahiro Mishina
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan ; Department of Neurological Science, Graduate School of Medicine, Nippon Medical School, Tokyo, 113-0022 Japan
| | - Muneyuki Sakata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan
| | - Keiichi Oda
- Department of Radiological Technology, Faculty of Health Sciences, Hokkaido University of Science, Hokkaido, 006-8585 Japan
| | - Mikio Hiura
- Faculty of Sports and Health Studies, Hosei University, Tokyo, 194-0298 Japan
| | - Kenji Ishii
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan
| | - Kiichi Ishiwata
- Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan
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Wu WC, Lien SH, Chang JH, Yang SC. Caffeine alters resting-state functional connectivity measured by blood oxygenation level-dependent MRI. NMR IN BIOMEDICINE 2014; 27:444-52. [PMID: 24478235 PMCID: PMC4260672 DOI: 10.1002/nbm.3080] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 12/26/2013] [Accepted: 01/02/2014] [Indexed: 06/03/2023]
Abstract
This study aimed to investigate the pharmacological effect of caffeine on functional connectivity measured by resting-state blood oxygenation level-dependent (BOLD) MRI in the motor cortex, visual cortex and default mode network (DMN). The protocols and procedures of the study were reviewed and approved by the Institutional Review Board of our institution. On a 3-T clinical MR system, 20 healthy volunteers underwent imaging before and after oral ingestion of a 200-mg over-the-counter caffeine pill (data from three individuals were excluded from further analysis because of excessive motion). The demographics of the remaining participants were as follows: female/male, 8/9; age, 21-35 years; non-habitual caffeine consumers over the past 6 months. Functional connectivity was calculated using the general linear model, assessed in terms of connected area (voxels) and statistical significance (Student t-values), and correlated with changes in regional cerebral blood flow as measured by arterial spin labeling MRI. Per-subject data analysis showed that caffeine decreased functional connectivity in the motor/visual cortices, but its effects on DMN varied among subjects. Correlation analysis of the changes in functional connectivity and regional blood flow suggested that the effect of caffeine on BOLD functional connectivity was predominantly neural (motor/visual cortices) and partly vascular (DMN). Group analysis showed that, after caffeine ingestion, DMN involved more attentional networks, and more extrastriate areas were integrated into the functional connectivity of the visual cortex, which may be associated with the known pharmacological effect of caffeine in elevating alertness. Caffeine consumption should thus be considered in the experimental design and data interpretation of functional connectivity studies using resting-state BOLD MRI.
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Affiliation(s)
- Wen-Chau Wu
- Graduate Institute of Oncology, National Taiwan UniversityTaipei, Taiwan
- Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan UniversityTaipei, Taiwan
- Graduate Institute of Clinical Medicine, National Taiwan UniversityTaipei, Taiwan
- Department of Medical Imaging, National Taiwan University HospitalTaipei, Taiwan
| | - Shu-Hua Lien
- Department of Medical Imaging, National Taiwan University HospitalTaipei, Taiwan
| | - Jia-Horng Chang
- Department of Medical Imaging, National Taiwan University HospitalTaipei, Taiwan
| | - Shun-Chung Yang
- Department of Medical Imaging, National Taiwan University HospitalTaipei, Taiwan
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Lee CF, Chern Y. Adenosine receptors and Huntington's disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 119:195-232. [PMID: 25175968 DOI: 10.1016/b978-0-12-801022-8.00010-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Adenosine regulates important pathophysiological functions via four distinct adenosine receptor subtypes (A1, A2A, A2B, and A3). The A1 and A2A adenosine receptors (A1R and A2AR) are major targets of caffeine and have been extensively investigated. Huntington's disease (HD) is a dominant neurodegenerative disease caused by an abnormal CAG expansion in the Huntingtin gene. Since the first genetic HD model was created almost two decades ago, tremendous progress regarding the function of the adenosine receptors in HD has been made. Chronic intake of caffeine was recently shown to be positively associated with the disease onset of HD. Moreover, genetic polymorphism of A2AR is believed to impact the age of onset. Given the importance of adenosine receptors as drug targets for human diseases, this review highlights the recent findings that delineate the roles of adenosine receptors in HD and discusses their potential for serving as drug targets and/or biomarkers for HD. Adenosine is a purine nucleoside that regulates important physiological functions via four different adenosine receptors (A1, A2A, A2B, and A3). These adenosine receptors have seven transmembrane domains and belong to the G protein-coupled receptor family. The functions of the A1 adenosine receptor (A1R) and A2A adenosine receptor (A2AR) have been investigated relative to HD. In this review, we summarize the recent findings regarding the role of adenosine receptors in HD and discuss the potential application of adenosine receptors as drug targets and biomarkers for HD.
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Affiliation(s)
- Chien-fei Lee
- Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yijuang Chern
- Division of Neuroscience, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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Mishina M, Ishiwata K. Adenosine Receptor PET Imaging in Human Brain. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 119:51-69. [DOI: 10.1016/b978-0-12-801022-8.00002-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Kadowaki Horita T, Kobayashi M, Mori A, Jenner P, Kanda T. Effects of the adenosine A2A antagonist istradefylline on cognitive performance in rats with a 6-OHDA lesion in prefrontal cortex. Psychopharmacology (Berl) 2013; 230:345-52. [PMID: 23748382 DOI: 10.1007/s00213-013-3158-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 05/20/2013] [Indexed: 12/20/2022]
Abstract
RATIONALE Altered cognitive function is a common feature of both the early and later stages of Parkinson's disease (PD) that involves alterations in cortical dopamine content. Adenosine A2A antagonists, such as istradefylline, improve motor function in PD, but their effect on cognitive impairment has not been determined. OBJECTIVE The present study investigated whether impairment of working memory due to the loss of dopaminergic input into the prefrontal cortex (PFC) is reversed by administration of istradefylline. We also evaluated whether A2A antagonist administration modulates dopamine levels in the PFC. METHODS Bilateral lesions of the dopaminergic input to the PFC were produced in rats using 6-hydroxydopamine (6-OHDA). Cognitive performance was evaluated using an object recognition task and delayed alternation task. The effects of istradefylline, donepezil and methamphetamine on cognitive performance were examined. In addition, the effect of istradefylline on extracellular dopamine levels in the PFC was studied. RESULTS PFC dopamine levels and cognitive performance were significantly reduced by 6-OHDA lesioning. Istradefylline, donepezil and methamphetamine improved cognitive performance of PFC-lesioned rats. Istradefylline increased dopamine levels in the PFC in both normal and PFC-lesioned rats. CONCLUSIONS PFC dopaminergic input plays an important role in working memory performance. Blockade of A2A receptors using istradefylline reverses the changes in cognitive function, and this may be due to an increase in PFC dopamine content. Adenosine A2A receptor antagonists not only improve motor performance in PD but may also lead to improved cognition.
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Affiliation(s)
- Takako Kadowaki Horita
- Pharmacological Research Laboratories, Research Division, Kyowa Hakko Kirin Co., Ltd, 1188 Shimotogari, Nagaizumi-cho, Sunto-gun, Shizuoka, 411-8731, Japan
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de Lera Ruiz M, Lim YH, Zheng J. Adenosine A2A Receptor as a Drug Discovery Target. J Med Chem 2013; 57:3623-50. [DOI: 10.1021/jm4011669] [Citation(s) in RCA: 204] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Manuel de Lera Ruiz
- Department
of Chemical Research, Merck Research Laboratories, 770 Sumneytown Pike, West Point, Pennsylvania 19486, United States
| | - Yeon-Hee Lim
- Department
of Chemical Research, Merck Research Laboratories, 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Junying Zheng
- Department
of Chemical Research, Merck Research Laboratories, 126 E. Lincoln Avenue, Rahway, New Jersey 07065, United States
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Rissanen E, Virta JR, Paavilainen T, Tuisku J, Helin S, Luoto P, Parkkola R, Rinne JO, Airas L. Adenosine A2A receptors in secondary progressive multiple sclerosis: a [(11)C]TMSX brain PET study. J Cereb Blood Flow Metab 2013; 33:1394-401. [PMID: 23695433 PMCID: PMC3764386 DOI: 10.1038/jcbfm.2013.85] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 04/07/2013] [Accepted: 05/02/2013] [Indexed: 11/09/2022]
Abstract
In this study, positron emission tomography (PET) imaging with a radioligand to adenosine A2A receptors (A2AR)-a potent regulator of inflammation-was used to gain insight into the molecular alterations in normal-appearing white matter (NAWM) and gray matter (GM) in secondary progressive multiple sclerosis (SPMS). Normal-appearing white matter and GM, despite seeming normal in conventional magnetic resonance imaging (MRI), are important loci of widespread inflammation, neuronal damage, and source of progressive disability in multiple sclerosis (MS). Dynamic PET imaging using A2AR-specific [(11)C]TMSX and brain MRI with diffusion tensor imaging were performed to eight SPMS patients and seven healthy controls. Distribution volumes (VT) of [(11)C]TMSX were analyzed from 13 regions of interest using Logan plot with arterial plasma input. The SPMS patients had significantly increased [(11)C]TMSX-VT in NAWM compared with controls (mean (s.d.): 0.55 (±0.08) vs. 0.45 (±0.05); P=0.036). Both the increased VT and the decreased fractional anisotropy (FA) in NAWM were associated with higher expanded disability status scale (EDSS) scores (P=0.030 and P=0.012, respectively), whereas the T2-lesion load of SPMS patients did not correlate with EDSS. This study shows, that A2ARs are increased in the brain of SPMS patients, and that [(11)C]TMSX-PET provides a novel approach to learn about central nervous system pathology in SPMS in vivo.
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Affiliation(s)
- Eero Rissanen
- Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland.
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Tavares AAS, Batis JC, Papin C, Jennings D, Alagille D, Russell DS, Vala C, Lee H, Baldwin RM, Zubal IG, Marek KL, Seibyl JP, Barret O, Tamagnan GD. Kinetic modeling, test-retest, and dosimetry of 123I-MNI-420 in humans. J Nucl Med 2013; 54:1760-7. [PMID: 23970369 DOI: 10.2967/jnumed.113.119933] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED In vivo imaging of adenosine 2A receptors (A2A) in the brain has attracted significant interest from the scientific community, because studies have shown that dysregulation of these receptors is implicated in a variety of neurodegenerative and psychiatric disorders, including Parkinson and Huntington diseases. This work aimed to describe the kinetic properties, test-retest results, and dosimetry estimates of (123)I-MNI-420, a SPECT radiotracer for the in vivo imaging of A2A in the brain. METHODS Nine healthy human subjects were enrolled in this study; 7 completed (123)I-MNI-420 brain SPECT studies, and 2 participated in whole-body planar imaging evaluating (123)I-MNI-420 biodistribution and dosimetry. For 3 of the brain SPECT studies, arterial blood was collected for invasive modeling. Noninvasive models were also explored, including Logan graphical analysis and simplified reference tissue models. Test-retest reliability was assessed in 4 subjects. To evaluate radiotracer biodistribution and dosimetry, serial whole-body images were acquired immediately after injection and at selected time points after injection. Urine samples were collected over a period of 21 h to calculate urinary excretion. RESULTS (123)I-MNI-420 rapidly entered the human brain and displayed uptake consistent with known A2A densities. At pseudoequilibrium (reached at 90 min after radiotracer injection), stable target-to-cerebellum ratios of around 1.4-2.0 were determined. Binding potentials around 0.8-1.2 were estimated using different kinetic models and the cerebellum as the reference region. Average test-retest variability in the striatum was 4.8%, 3.5%, and 6.5% for the simplified reference tissue model, Logan graphical analysis, and standardized uptake value ratio methods, respectively. The estimated radiation effective dose determined from whole-body studies was 0.036 mSv/MBq. CONCLUSION The data indicate that (123)I-MNI-420 is a useful SPECT radiotracer for imaging A2A in the brain and has radiation doses that would allow for multiple scans in the same research subject each year. The availability of (123)I-MNI-420 offers the possibility of investigating A2A activity in specific conditions and evaluating drug occupancy for A2A candidate therapeutics.
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Seibyl J, Russell D, Jennings D, Marek K. Neuroimaging over the course of Parkinson's disease: from early detection of the at-risk patient to improving pharmacotherapy of later-stage disease. Semin Nucl Med 2013; 42:406-14. [PMID: 23026362 DOI: 10.1053/j.semnuclmed.2012.06.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Brain imaging of striatal dopamine terminal degeneration serves an important role in the clinical management of Parkinson's disease (PD). Imaging biomarkers for interrogating dopaminergic systems are used for clarifying diagnosis when only subtle motor symptoms are present. However, motor dysfunction is not the earliest symptom of PD. There is increasing interest in identifying premotor PD patients, particularly because potential disease-modifying therapies are developed and the clinical imperative becomes early and accurate diagnosis. On the other end of the spectrum of the disease course, during later stages of PD, significant clinical challenges like levo-dopa-induced dyskinesias and medication on-off phenomenon become more prevalent. In this instance, better understanding of altered PD motor pathways suggests the potential utility of novel treatments targeting neuronal systems that are impacted by degenerating dopamine neurons and chronic dopamine replacement treatment. Molecular neuroimaging serves unique roles in both very early PD and later-stage disease, in the former, potentially pushing back the time of diagnosis, and in the latter, elucidating pathology relevant to new drug development.
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Affiliation(s)
- John Seibyl
- Institute for Neurodegenerative Disorders, New Haven, CT, USA.
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Tavares AADS, Batis J, Barret O, Alagille D, Vala C, Kudej G, Koren A, Cosgrove KP, Nice K, Kordower JH, Seibyl J, Tamagnan GD. In vivo evaluation of [(123)I]MNI-420: a novel single photon emission computed tomography radiotracer for imaging of adenosine 2A receptors in brain. Nucl Med Biol 2013; 40:403-9. [PMID: 23332393 DOI: 10.1016/j.nucmedbio.2012.12.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/24/2012] [Accepted: 12/03/2012] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Dysregulation of adenosine 2A (A2A) receptor function in brain has been implicated in multiple psychiatric and neurodegenerative disorders, including schizophrenia and Parkinson's disease, making the development of an imaging agent to study A2A receptors in both healthy brain and disease states desirable. In this study, [(123)I]MNI-420 was evaluated as a potential single photon emission computed tomography (SPECT) radiotracer for imaging A2A receptors in brain. METHODS Two adult male monkeys (Macaca fascicularis) and three adult female baboons (Papio anubis) were anesthetized and imaged on Neurofocus SPECT cameras. Baboons underwent baseline and displacement studies using varying doses of caffeine (2.0-20mg/kg). Baseline and pre-blocking experiments with multiple doses of preladenant (0.01-1.2mg/kg), a highly selective A2A antagonist, were performed in cynomolgus monkeys. RESULTS Following bolus intravenous (i.v.) injection, [(123)I]MNI-420 rapidly entered the non-human primate brain. The regional brain accumulation of [(123)I]MNI-420 matched the known distribution of A2A receptors in brain (highest in the striatum). Striatum to cerebellum ratios and binding potentials of around 3.0-3.5 and 2.0-2.5, respectively, were measured in monkey and baboon brain. A dose-dependent occupancy was observed following i.v. injection of caffeine at pseudo-equilibrium conditions during displacement experiments. Pre-treatment with preladenant blocked specific binding in A2A rich regions in a dose-dependent fashion. CONCLUSIONS The data indicate that [(123)I]MNI-420 holds promise as a SPECT radiotracer for imaging A2A receptors in brain and further evaluation is warranted, in order to determine its utility as a SPECT radiotracer for imaging of A2A in brain.
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Bogenpohl JW, Ritter SL, Hall RA, Smith Y. Adenosine A2A receptor in the monkey basal ganglia: ultrastructural localization and colocalization with the metabotropic glutamate receptor 5 in the striatum. J Comp Neurol 2012; 520:570-89. [PMID: 21858817 DOI: 10.1002/cne.22751] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The adenosine A(2A) receptor (A(2A) R) is a potential drug target for the treatment of Parkinson's disease and other neurological disorders. In rodents, the therapeutic efficacy of A(2A) R modulation is improved by concomitant modulation of the metabotropic glutamate receptor 5 (mGluR5). To elucidate the anatomical substrate(s) through which these therapeutic benefits could be mediated, pre-embedding electron microscopy immunohistochemistry was used to conduct a detailed, quantitative ultrastructural analysis of A(2A) R localization in the primate basal ganglia and to assess the degree of A(2A) R/mGluR5 colocalization in the striatum. A(2A) R immunoreactivity was found at the highest levels in the striatum and external globus pallidus (GPe). However, the monkey, but not the rat, substantia nigra pars reticulata (SNr) also harbored a significant level of neuropil A(2A) R immunoreactivity. At the electron microscopic level, striatal A(2A) R labeling was most commonly localized in postsynaptic elements (58% ± 3% of labeled elements), whereas, in the GPe and SNr, the labeling was mainly presynaptic (71% ± 5%) or glial (27% ± 6%). In both striatal and pallidal structures, putative inhibitory and excitatory terminals displayed A(2A) R immunoreactivity. Striatal A(2A) R/mGluR5 colocalization was commonly found; 60-70% of A(2A) R-immunoreactive dendrites or spines in the monkey striatum coexpress mGluR5. These findings provide the first detailed account of the ultrastructural localization of A(2A) R in the primate basal ganglia and demonstrate that A(2A) R and mGluR5 are located to interact functionally in dendrites and spines of striatal neurons. Together, these data foster a deeper understanding of the substrates through which A(2A) R could regulate primate basal ganglia function and potentially mediate its therapeutic effects in parkinsonism.
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Affiliation(s)
- James W Bogenpohl
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329, USA
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Mishina M, Kimura Y, Naganawa M, Ishii K, Oda K, Sakata M, Toyohara J, Kobayashi S, Katayama Y, Ishiwata K. Differential effects of age on human striatal adenosine A₁ and A(2A) receptors. Synapse 2012; 66:832-9. [PMID: 22623181 DOI: 10.1002/syn.21573] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/01/2012] [Accepted: 05/14/2012] [Indexed: 01/19/2023]
Abstract
The aim of this study was to investigate the effect of age on the distribution of adenosine A₁ receptors (A₁Rs) and adenosine A(2A) receptors (A(2A)Rs) in the striatum of healthy subjects using PET imaging with 8-dicyclopropylmethyl-1-[¹¹C]methyl-3-propylxanthine ([¹¹C]MPDX) and [7-methyl-¹¹C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([¹¹C]TMSX), respectively. We recruited 8 young (22.0 ± 1.7 years) and 10 elderly (65.4 ± 7.6 years) volunteers to undergo [¹¹C]MPDX PET scanning, and 11 young (22.7 ± 2.7 years) and six elderly (60.7 ± 8.5 years) volunteers to undergo [¹¹C]TMSX PET scanning. A dynamic series of decay-corrected PET scans was performed for 60 min following injection of [¹¹C]MPDX or [¹¹C]TMSX. We calculated the binding potential (BP(ND) ) of [¹¹C]MPDX and distribution volume ratio (DVR) of [¹¹C]TMSX in the striatum. The BP(ND) of [¹¹C]MPDX was significantly lower in elderly than in young subjects, both in the putamen and head of the caudate nucleus. The BP(ND) was negatively correlated with age in both the putamen and the head of the caudate nucleus. However, no difference was found between the DVR of [¹¹C]TMSX in the striata of young and elderly subjects, nor was there a correlation between age and the DVR of [¹¹C]TMSX. The effect of age on the distribution of A₁Rs in the human striatum described herein is similar to previous reports of age-related decreases in dopamine D₁ and D₂ receptors. Unlike A₁Rs, however, this study suggests that the distribution of A(2A) Rs does not change with age.
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Affiliation(s)
- Masahiro Mishina
- The Second Department of Internal Medicine, Nippon Medical School, Bunkyo-Ku, Tokyo, Japan; Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Itabashi-Ku, Tokyo, Japan.
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Morelli M, Blandini F, Simola N, Hauser RA. A(2A) Receptor Antagonism and Dyskinesia in Parkinson's Disease. PARKINSON'S DISEASE 2012; 2012:489853. [PMID: 22754707 PMCID: PMC3382949 DOI: 10.1155/2012/489853] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 04/26/2012] [Indexed: 01/13/2023]
Abstract
Dyskinesia, a major complication of treatment of Parkinson's disease (PD), involves two phases: induction, which is responsible for dyskinesia onset, and expression, which underlies its clinical manifestation. The unique cellular and regional distribution of adenosine A(2A) receptors in basal ganglia areas that are richly innervated by dopamine, and their antagonistic role towards dopamine receptor stimulation, have positioned A(2A) receptor antagonists as an attractive nondopaminergic target to improve the motor deficits that characterize PD. In this paper, we describe the biochemical characteristics of A(2A) receptors and the effects of adenosine A(2A) antagonists in rodent and primate models of PD on L-DOPA-induced dyskinesia, together with relevant biomarker studies. We also review clinical trials of A(2A) antagonists as adjuncts to L-DOPA in PD patients with motor fluctuations. These studies have generally demonstrated that the addition of an A(2A) antagonist to a stable L-DOPA regimen reduces OFF time and mildly increases dyskinesia. However, limited clinical data suggest that the addition of an A(2A) antagonist along with a reduction of L-DOPA might maintain anti-Parkinsonian benefit and reduce dyskinesia. Whether A(2A) antagonists might reduce the development of dyskinesia has not yet been tested clinically.
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Affiliation(s)
- Micaela Morelli
- Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy
- CNR Institute of Neuroscience, 09042 Cagliari, Italy
| | - Fabio Blandini
- Interdepartmental Research Center for Parkinson's Disease, National Neurological Institute C. Mondino, 27100 Pavia, Italy
| | - Nicola Simola
- Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy
| | - Robert A. Hauser
- Department of Neurology, University of South Florida, Tampa, FL 33613, USA
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Bhattacharjee AK, Lang L, Jacobson O, Shinkre B, Ma Y, Niu G, Trenkle WC, Jacobson KA, Chen X, Kiesewetter DO. Striatal adenosine A(2A) receptor-mediated positron emission tomographic imaging in 6-hydroxydopamine-lesioned rats using [(18)F]-MRS5425. Nucl Med Biol 2011; 38:897-906. [PMID: 21843786 PMCID: PMC3157043 DOI: 10.1016/j.nucmedbio.2011.01.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/25/2011] [Accepted: 01/30/2011] [Indexed: 10/18/2022]
Abstract
INTRODUCTION A(2A) receptors are expressed in the basal ganglia, specifically in striatopallidal GABAergic neurons in the striatum (caudate-putamen). This brain region undergoes degeneration of presynaptic dopamine projections and depletion of dopamine in Parkinson's disease. We developed an (18)F-labeled A(2A) analog radiotracer ([(18)F]-MRS5425) for A(2A) receptor imaging using positron emission tomography (PET). We hypothesized that this tracer could image A(2A) receptor changes in the rat model for Parkinson's disease, which is created following unilateral injection of the monoaminergic toxin 6-hydroxydopamine (6-OHDA) into the substantia nigra. METHODS [(18)F]-MRS5425 was injected intravenously in anesthetized rats, and PET imaging data were collected. Image-derived percentage injected doses per gram (%ID/g) in regions of interest was measured in the striatum of normal rats and in rats unilaterally lesioned with 6-OHDA after intravenous administration of saline (baseline), D(2) agonist quinpirole (1.0 mg/kg) or D(2) antagonist raclopride (6.0 mg/kg). RESULTS Baseline %ID/g reached a maximum at 90 s and maintained plateau for 3.5 min, and then declined slowly thereafter. In 6-OHDA-lesioned rats, %ID/g was significantly higher in the lesioned side compared to the intact side, and the baseline total %ID/g (data from both hemispheres were combined) was significantly higher compared to quinpirole stimulation starting from 4.5 min until the end of acquisition at 30 min. Raclopride did not produce any change in uptake compared to baseline or between the hemispheres. CONCLUSION Thus, increase of A(2A) receptor-mediated uptake of radioactive MRS5425 could be a superior molecular target for Parkinson's imaging.
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Affiliation(s)
- Abesh Kumar Bhattacharjee
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
| | - Lixin Lang
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
| | - Orit Jacobson
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
| | - Bidhan Shinkre
- Chemical Biology Unit, Laboratory of Cell Biochemistry & Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Ying Ma
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
| | - Gang Niu
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
- Department of Radiology and Imaging Sciences, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD, 20892
| | - William C. Trenkle
- Chemical Biology Unit, Laboratory of Cell Biochemistry & Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Xiaoyuan Chen
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
| | - Dale O. Kiesewetter
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892
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Adenosine A(2A) receptors measured with [C]TMSX PET in the striata of Parkinson's disease patients. PLoS One 2011; 6:e17338. [PMID: 21386999 PMCID: PMC3046146 DOI: 10.1371/journal.pone.0017338] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 01/29/2011] [Indexed: 12/04/2022] Open
Abstract
Adenosine A2A receptors (A2ARs) are thought to interact negatively with the dopamine D2 receptor (D2R), so selective A2AR antagonists have attracted attention as novel treatments for Parkinson's disease (PD). However, no information about the receptor in living patients with PD is available. The purpose of this study was to investigate the relationship between A2ARs and the dopaminergic system in the striata of drug-naïve PD patients and PD patients with dyskinesia, and alteration of these receptors after antiparkinsonian therapy. We measured binding ability of striatal A2ARs using positron emission tomography (PET) with [7-methyl-11C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([11C]TMSX) in nine drug-naïve patients with PD, seven PD patients with mild dyskinesia and six elderly control subjects using PET. The patients and eight normal control subjects were also examined for binding ability of dopamine transporters and D2Rs. Seven of the drug-naïve patients underwent a second series of PET scans following therapy. We found that the distribution volume ratio of A2ARs in the putamen were larger in the dyskinesic patients than in the control subjects (p<0.05, Tukey-Kramer post hoc test). In the drug-naïve patients, the binding ability of the A2ARs in the putamen, but not in the head of caudate nucleus, was significantly lower on the more affected side than on the less affected side (p<0.05, paired t-test). In addition, the A2ARs were significantly increased after antiparkinsonian therapy in the bilateral putamen of the drug-naïve patients (p<0.05, paired t-test) but not in the bilateral head of caudate nucleus. Our study demonstrated that the A2ARs in the putamen were increased in the PD patients with dyskinesia, and also suggest that the A2ARs in the putamen compensate for the asymmetrical decrease of dopamine in drug-naïve PD patients and that antiparkinsonian therapy increases the A2ARs in the putamen. The A2ARs may play an important role in regulation of parkinsonism in PD.
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Abstract
The natural plant alkaloids caffeine and theophylline were the first adenosine receptor (AR) antagonists described in the literature. They exhibit micromolar affinities and are non-selective. A large number of derivatives and analogues were subsequently synthesized and evaluated as AR antagonists. Very potent antagonists have thus been developed with selectivity for each of the four AR subtypes.
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Affiliation(s)
- Christa Müller
- PharmaCenter Bonn, Pharmaceutical Sciences Bonn (PSB), University of Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, An der Immenburg 4, D-53121 Bonn, Germany, Phone +49-228-73-2301, Fax +49-228-73-2567
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 8A, Rm. B1A-19, NIH, NIDDK, LBC, Bethesda, MD 20892, United States of America, Phone +1-301-496-9024, Fax +1-301-480-8422
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Ishiwata K, Kimura Y, Oda K, Ishii K, Sakata M, Kawasaki K, Nariai T, Suzuki Y, Ishibashi K, Mishina M, Hashimoto M, Ishikawa M, Toyohara J. Development of PET radiopharmaceuticals and their clinical applications at the Positron Medical Center. Geriatr Gerontol Int 2010; 10 Suppl 1:S180-96. [PMID: 20590833 DOI: 10.1111/j.1447-0594.2010.00594.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Positron Medical Center has developed a large number of radiopharmaceuticals and 36 radiopharmaceuticals have been approved for clinical use for studying aging and geriatric diseases, especially brain functions. Positron emission tomography (PET) has been used to provide a highly advanced PET-based diagnosis. The current status of the development of radiopharmaceuticals, and representative clinical and methodological results are reviewed.
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Affiliation(s)
- Kiichi Ishiwata
- Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
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Bird MK, Lawrence AJ. The promiscuous mGlu5 receptor--a range of partners for therapeutic possibilities? Trends Pharmacol Sci 2009; 30:617-23. [PMID: 19892412 DOI: 10.1016/j.tips.2009.09.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 09/23/2009] [Accepted: 09/23/2009] [Indexed: 01/20/2023]
Abstract
The issue of non-specific effects for potential therapeutics is particularly salient in neurological/psychiatric disorders, where adverse drug reactions could impair critical brain functions. The issue of specificity is not limited to candidate molecules, as receptor targets themselves often influence physiological as well as pathological outcomes. Metabotropic glutamate receptor 5 (mGlu5) is an example of a "promiscuous" receptor target that has been implicated in addiction, but also many other processes. However, if receptor modulation could be restricted to specific pathways/brain regions, mGlu5 may still prove to be a viable therapeutic target for various indications. Using this premise, a number of possible methods to refine drug development strategy are discussed, including exploiting specific interactions of mGlu5 with other receptors to narrow the influence of pharmacological agents, and also the use of RNA interference targeted to specific cells/regions of the brain.
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Affiliation(s)
- Michael K Bird
- Florey Neuroscience Institutes, University of Melbourne, Parkville, Victoria, 3010, Australia
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Abstract
The adenosine receptors (ARs) in the nervous system act as a kind of "go-between" to regulate the release of neurotransmitters (this includes all known neurotransmitters) and the action of neuromodulators (e.g., neuropeptides, neurotrophic factors). Receptor-receptor interactions and AR-transporter interplay occur as part of the adenosine's attempt to control synaptic transmission. A(2A)ARs are more abundant in the striatum and A(1)ARs in the hippocampus, but both receptors interfere with the efficiency and plasticity-regulated synaptic transmission in most brain areas. The omnipresence of adenosine and A(2A) and A(1) ARs in all nervous system cells (neurons and glia), together with the intensive release of adenosine following insults, makes adenosine a kind of "maestro" of the tripartite synapse in the homeostatic coordination of the brain function. Under physiological conditions, both A(2A) and A(1) ARs play an important role in sleep and arousal, cognition, memory and learning, whereas under pathological conditions (e.g., Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, stroke, epilepsy, drug addiction, pain, schizophrenia, depression), ARs operate a time/circumstance window where in some circumstances A(1)AR agonists may predominate as early neuroprotectors, and in other circumstances A(2A)AR antagonists may alter the outcomes of some of the pathological deficiencies. In some circumstances, and depending on the therapeutic window, the use of A(2A)AR agonists may be initially beneficial; however, at later time points, the use of A(2A)AR antagonists proved beneficial in several pathologies. Since selective ligands for A(1) and A(2A) ARs are now entering clinical trials, the time has come to determine the role of these receptors in neurological and psychiatric diseases and identify therapies that will alter the outcomes of these diseases, therefore providing a hopeful future for the patients who suffer from these diseases.
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Affiliation(s)
- Ana M Sebastião
- Institute of Pharmacology and Neurosciences, Institute of Molecular Medicine, University of Lisbon, 1649-028 Lisbon, Portugal.
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Abstract
Advances in radiotracer chemistry have resulted in the development of novel molecular imaging probes for adenosine receptors (ARs). With the availability of these molecules, the function of ARs in human pathophysiology as well as the safety and efficacy of approaches to the different AR targets can now be determined. Molecular imaging is a rapidly growing field of research that allows the identification of molecular targets and functional processes in vivo. It is therefore gaining increasing interest as a tool in drug development because it permits the process of evaluating promising therapeutic targets to be stratified. Further, molecular imaging has the potential to evolve into a useful diagnostic tool, particularly for neurological and psychiatric disorders. This chapter focuses on currently available AR ligands that are suitable for molecular neuroimaging and describes first applications in healthy subjects and patients using positron emission tomography (PET).
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Affiliation(s)
- Andreas Bauer
- Institute of Neuroscience and Biophysics (INB-3), Research Center Jülich, 52425 Jülich, Germany.
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Abstract
The development of potent and selective agonists and antagonists of adenosine receptors (ARs) has been a target of medicinal chemistry research for several decades, and recently the US Food and Drug Administration has approved Lexiscan, an adenosine derivative substituted at the 2 position, for use as a pharmacologic stress agent in radionuclide myocardial perfusion imaging. Currently, some other adenosine A(2A) receptor (A(2A)AR) agonists and antagonists are undergoing preclinical testing and clinical trials. While agonists are potent antiinflammatory agents also showing hypotensive effects, antagonists are being developed for the treatment of Parkinson's disease.However, since there are still major problems in this field, including side effects, low brain penetration (for the targeting of CNS diseases), short half-life, or lack of in vivo effects, the design and development of new AR ligands is a hot research topic.This review presents an update on the medicinal chemistry of A(2A)AR agonists and antagonists, and stresses the strong need for more selective ligands at the human A(2A)AR subtype, in particular in the case of agonists.
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Affiliation(s)
- Gloria Cristalli
- Dipartimento di Scienze Chimiche, Università di Camerino, 62032 Camerino (MC), Italy.
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