1
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Cui X, Liu J, Uniyal A, Xu Q, Zhang C, Zhu G, Yang F, Sivanesan E, Linderoth B, Raja SN, Guan Y. Enhancing spinal cord stimulation-induced pain inhibition by augmenting endogenous adenosine signalling after nerve injury in rats. Br J Anaesth 2024; 132:746-757. [PMID: 38310069 PMCID: PMC10925891 DOI: 10.1016/j.bja.2024.01.005] [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: 11/28/2023] [Revised: 01/03/2024] [Accepted: 01/05/2024] [Indexed: 02/05/2024] Open
Abstract
BACKGROUND The mechanisms for spinal cord stimulation (SCS) to alleviate chronic pain are only partially known. We aimed to elucidate the roles of adenosine A1 and A3 receptors (A1R, A3R) in the inhibition of spinal nociceptive transmission by SCS, and further explored whether 2'-deoxycoformycin (dCF), an inhibitor of adenosine deaminase, can potentiate SCS-induced analgesia. METHODS We used RNAscope and immunoblotting to examine the distributions of adora1 and adora3 expression, and levels of A1R and A3R proteins in the spinal cord of rats after tibial-spared nerve injury (SNI-t). Electrophysiology recording was conducted to examine how adenosine receptor antagonists, virus-mediated adora3 knockdown, and dCF affect SCS-induced inhibition of C-fibre-evoked spinal local field potential (C-LFP). RESULTS Adora1 was predominantly expressed in neurones, whereas adora3 is highly expressed in microglial cells in the rat spinal cord. Spinal application of antagonists (100 μl) of A1R (8-cyclopentyl-1,3-dipropylxanthine [DPCPX], 50 μM) and A3R (MRS1523, 200 nM) augmented C-LFP in SNI-t rats (DPCPX: 1.39 [0.18] vs vehicle: 0.98 [0.05], P=0.046; MRS1523: 1.21 [0.07] vs vehicle: 0.91 [0.03], P=0.002). Both drugs also blocked inhibition of C-LFP by SCS. Conversely, dCF (0.1 mM) enhanced SCS-induced C-LFP inhibition (dCF: 0.60 [0.04] vs vehicle: 0.85 [0.02], P<0.001). In the behaviour study, dCF (100 nmol 15 μl-1, intrathecal) also enhanced inhibition of mechanical hypersensitivity by SCS in SNI-t rats. CONCLUSIONS Spinal A1R and A3R signalling can exert tonic suppression and also contribute to SCS-induced inhibition of spinal nociceptive transmission after nerve injury. Inhibition of adenosine deaminase may represent a novel adjuvant pharmacotherapy to enhance SCS-induced analgesia.
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Affiliation(s)
- Xiang Cui
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Jing Liu
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Ankit Uniyal
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA; Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Chi Zhang
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Guangwu Zhu
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Fei Yang
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Eellan Sivanesan
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Bengt Linderoth
- Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Srinivasa N Raja
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Yun Guan
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA; Department of Neurological Surgery, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
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2
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Oliva P, Suresh RR, Pasquini S, Salmaso V, Will EJ, Tosh DK, Gao ZG, Liu N, Gavrilova O, Vincenzi F, Varani K, Jacobson KA. 2-Amino-5-arylethynyl-thiophen-3-yl-(phenyl)methanones as A 1 Adenosine Receptor Positive Allosteric Modulators. ACS Med Chem Lett 2023; 14:1640-1646. [PMID: 38116442 PMCID: PMC10726435 DOI: 10.1021/acsmedchemlett.3c00315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/06/2023] [Indexed: 12/21/2023] Open
Abstract
A1 adenosine receptor (A1AR) agonists have cerebroprotective, cardioprotective, antinociceptive, and other pharmaceutical applications. We explored the structure-activity relationship of 5-arylethynyl aminothiophenes as A1AR positive allosteric modulators (PAMs). The derivatives were compared in binding and functional assays at the human A1AR, indicating that some fluoro-substituted analogues have enhanced PAM activity. We identified substitution of the terminal phenyl ring in 12 (2-F-Ph), 15 (3,4-F2-Ph, MRS7935), and 21 (2-CF3-Ph) as particularly enhancing the PAM activity. 15 was also shown to act as an A1 ago-PAM with EC50 ≈ 2 μM, without activity (30 μM) at other ARs. Molecular modeling indicated that both the 5-arylethynyl and the 4-neopentyl groups are located in a region outside the receptor transmembrane helix bundle that is in contact with the phospholipid bilayer, consistent with the preference for nonpolar substitution of the aryl moiety. Although they are hydrophobic, these PAMs could provide potential drug candidate molecules for engaging protective A1ARs.
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Affiliation(s)
- Paola Oliva
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - R. Rama Suresh
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Silvia Pasquini
- Department
of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Via Fossato di Mortara 17-19, 44121 Ferrara, Italy
| | - Veronica Salmaso
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Edward J. Will
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Dilip K. Tosh
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Zhan-Guo Gao
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Naili Liu
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Oksana Gavrilova
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
| | - Fabrizio Vincenzi
- Department
of Translational Medicine, University of
Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Katia Varani
- Department
of Translational Medicine, University of
Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Kenneth A. Jacobson
- Laboratory
of Bioorganic Chemistry and Mouse Metabolism Core, National
Institute of Diabetes and Digestive and Kidney
Disease, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, United States
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3
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Nguyen ATN, Tran QL, Baltos JA, McNeill SM, Nguyen DTN, May LT. Small molecule allosteric modulation of the adenosine A 1 receptor. Front Endocrinol (Lausanne) 2023; 14:1184360. [PMID: 37435481 PMCID: PMC10331460 DOI: 10.3389/fendo.2023.1184360] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 05/23/2023] [Indexed: 07/13/2023] Open
Abstract
G protein-coupled receptors (GPCRs) represent the target for approximately a third of FDA-approved small molecule drugs. The adenosine A1 receptor (A1R), one of four adenosine GPCR subtypes, has important (patho)physiological roles in humans. A1R has well-established roles in the regulation of the cardiovascular and nervous systems, where it has been identified as a potential therapeutic target for a number of conditions, including cardiac ischemia-reperfusion injury, cognition, epilepsy, and neuropathic pain. A1R small molecule drugs, typically orthosteric ligands, have undergone clinical trials. To date, none have progressed into the clinic, predominantly due to dose-limiting unwanted effects. The development of A1R allosteric modulators that target a topographically distinct binding site represent a promising approach to overcome current limitations. Pharmacological parameters of allosteric ligands, including affinity, efficacy and cooperativity, can be optimized to regulate A1R activity with high subtype, spatial and temporal selectivity. This review aims to offer insights into the A1R as a potential therapeutic target and highlight recent advances in the structural understanding of A1R allosteric modulation.
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Affiliation(s)
- Anh T. N. Nguyen
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Quan L. Tran
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Jo-Anne Baltos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Samantha M. McNeill
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Diep T. N. Nguyen
- Department of Information Technology, Faculty of Engineering and Technology, Vietnam National University, Hanoi, Vietnam
| | - Lauren T. May
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
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Pasquini S, Contri C, Cappello M, Borea PA, Varani K, Vincenzi F. Update on the recent development of allosteric modulators for adenosine receptors and their therapeutic applications. Front Pharmacol 2022; 13:1030895. [PMID: 36278183 PMCID: PMC9581118 DOI: 10.3389/fphar.2022.1030895] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/20/2022] [Indexed: 11/13/2022] Open
Abstract
Adenosine receptors (ARs) have been identified as promising therapeutic targets for countless pathological conditions, spanning from inflammatory diseases to central nervous system disorders, from cancer to metabolic diseases, from cardiovascular pathologies to respiratory diseases, and beyond. This extraordinary therapeutic potential is mainly due to the plurality of pathophysiological actions of adenosine and the ubiquitous expression of its receptors. This is, however, a double-edged sword that makes the clinical development of effective ligands with tolerable side effects difficult. Evidence of this is the low number of AR agonists or antagonists that have reached the market. An alternative approach is to target allosteric sites via allosteric modulators, compounds endowed with several advantages over orthosteric ligands. In addition to the typical advantages of allosteric modulators, those acting on ARs could benefit from the fact that adenosine levels are elevated in pathological tissues, thus potentially having negligible effects on normal tissues where adenosine levels are maintained low. Several A1 and various A3AR allosteric modulators have been identified so far, and some of them have been validated in different preclinical settings, achieving promising results. Less fruitful, instead, has been the discovery of A2A and A2BAR allosteric modulators, although the results obtained up to now are encouraging. Collectively, data in the literature suggests that allosteric modulators of ARs could represent valuable pharmacological tools, potentially able to overcome the limitations of orthosteric ligands.
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Affiliation(s)
- Silvia Pasquini
- Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Ferrara, Italy
| | - Chiara Contri
- Department of Translational Medicine, University of Ferrara, Ferrara, Italy
| | - Martina Cappello
- Department of Translational Medicine, University of Ferrara, Ferrara, Italy
| | | | - Katia Varani
- Department of Translational Medicine, University of Ferrara, Ferrara, Italy
- *Correspondence: Katia Varani,
| | - Fabrizio Vincenzi
- Department of Translational Medicine, University of Ferrara, Ferrara, Italy
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5
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Positive allosteric mechanisms of adenosine A 1 receptor-mediated analgesia. Nature 2021; 597:571-576. [PMID: 34497422 PMCID: PMC8711093 DOI: 10.1038/s41586-021-03897-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 08/11/2021] [Indexed: 02/08/2023]
Abstract
The adenosine A1 receptor (A1R) is a promising therapeutic target for non-opioid analgesic agents to treat neuropathic pain1,2. However, development of analgesic orthosteric A1R agonists has failed because of a lack of sufficient on-target selectivity as well as off-tissue adverse effects3. Here we show that [2-amino-4-(3,5-bis(trifluoromethyl)phenyl)thiophen-3-yl)(4-chlorophenyl)methanone] (MIPS521), a positive allosteric modulator of the A1R, exhibits analgesic efficacy in rats in vivo through modulation of the increased levels of endogenous adenosine that occur in the spinal cord of rats with neuropathic pain. We also report the structure of the A1R co-bound to adenosine, MIPS521 and a Gi2 heterotrimer, revealing an extrahelical lipid-detergent-facing allosteric binding pocket that involves transmembrane helixes 1, 6 and 7. Molecular dynamics simulations and ligand kinetic binding experiments support a mechanism whereby MIPS521 stabilizes the adenosine-receptor-G protein complex. This study provides proof of concept for structure-based allosteric drug design of non-opioid analgesic agents that are specific to disease contexts.
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6
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Metzner K, Gross T, Balzulat A, Wack G, Lu R, Schmidtko A. Lack of efficacy of a partial adenosine A1 receptor agonist in neuropathic pain models in mice. Purinergic Signal 2021; 17:503-514. [PMID: 34313915 PMCID: PMC8410902 DOI: 10.1007/s11302-021-09806-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 06/28/2021] [Indexed: 12/25/2022] Open
Abstract
Previous studies suggest that adenosine A1 receptors (A1R) modulate the processing of pain. The aim of this study was to characterize the distribution of A1R in nociceptive tissues and to evaluate whether targeting A1R with the partial agonist capadenoson may reduce neuropathic pain in mice. The cellular distribution of A1R in dorsal root ganglia (DRG) and the spinal cord was analyzed using fluorescent in situ hybridization. In behavioral experiments, neuropathic pain was induced by spared nerve injury or intraperitoneal injection of paclitaxel, and tactile hypersensitivities were determined using a dynamic plantar aesthesiometer. Whole-cell patch-clamp recordings were performed to assess electrophysiological properties of dissociated DRG neurons. We found A1R to be expressed in populations of DRG neurons and dorsal horn neurons involved in the processing of pain. However, administration of capadenoson at established in vivo doses (0.03–1.0 mg/kg) did not alter mechanical hypersensitivity in the spared nerve injury and paclitaxel models of neuropathic pain, whereas the standard analgesic pregabalin significantly inhibited the pain behavior. Moreover, capadenoson failed to affect potassium currents in DRG neurons, in contrast to a full A1R agonist. Despite expression of A1R in nociceptive neurons, our data do not support the hypothesis that pharmacological intervention with partial A1R agonists might be a valuable approach for the treatment of neuropathic pain.
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Affiliation(s)
- Katharina Metzner
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany.
| | - Tilman Gross
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Annika Balzulat
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Gesine Wack
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Ruirui Lu
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Achim Schmidtko
- Institute of Pharmacology and Clinical Pharmacy, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
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7
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Vincenzi F, Pasquini S, Battistello E, Merighi S, Gessi S, Borea PA, Varani K. A 1 Adenosine Receptor Partial Agonists and Allosteric Modulators: Advancing Toward the Clinic? Front Pharmacol 2020; 11:625134. [PMID: 33362567 PMCID: PMC7756085 DOI: 10.3389/fphar.2020.625134] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 11/17/2020] [Indexed: 11/21/2022] Open
Affiliation(s)
- Fabrizio Vincenzi
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
| | - Silvia Pasquini
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
| | - Enrica Battistello
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
| | - Stefania Merighi
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
| | - Stefania Gessi
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
| | | | - Katia Varani
- Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy
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8
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Targeting Adenosine Receptors: A Potential Pharmacological Avenue for Acute and Chronic Pain. Int J Mol Sci 2020; 21:ijms21228710. [PMID: 33218074 PMCID: PMC7698931 DOI: 10.3390/ijms21228710] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 11/17/2020] [Indexed: 12/14/2022] Open
Abstract
Adenosine is a purine nucleoside, responsible for the regulation of multiple physiological and pathological cellular and tissue functions by activation of four G protein-coupled receptors (GPCR), namely A1, A2A, A2B, and A3 adenosine receptors (ARs). In recent years, extensive progress has been made to elucidate the role of adenosine in pain regulation. Most of the antinociceptive effects of adenosine are dependent upon A1AR activation located at peripheral, spinal, and supraspinal sites. The role of A2AAR and A2BAR is more controversial since their activation has both pro- and anti-nociceptive effects. A3AR agonists are emerging as promising candidates for neuropathic pain. Although their therapeutic potential has been demonstrated in diverse preclinical studies, no AR ligands have so far reached the market. To date, novel pharmacological approaches such as adenosine regulating agents and allosteric modulators have been proposed to improve efficacy and limit side effects enhancing the effect of endogenous adenosine. This review aims to provide an overview of the therapeutic potential of ligands interacting with ARs and the adenosinergic system for the treatment of acute and chronic pain.
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9
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Spinal astrocytes in superficial laminae gate brainstem descending control of mechanosensory hypersensitivity. Nat Neurosci 2020; 23:1376-1387. [DOI: 10.1038/s41593-020-00713-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 08/24/2020] [Indexed: 12/16/2022]
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10
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Barczewska M, Juranek J, Wojtkiewicz J. Origins and Neurochemical Characteristics of Porcine Intervertebral Disc Sympathetic Innervation: a Preliminary Report. J Mol Neurosci 2017; 63:50-57. [PMID: 28762133 PMCID: PMC5581820 DOI: 10.1007/s12031-017-0956-3] [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: 05/28/2017] [Accepted: 07/21/2017] [Indexed: 11/28/2022]
Abstract
Intervertebral disc diseases (IVDDs) form a group of a vertebral column disorders affecting a large number of people worldwide. It is estimated that approximately 30% of individuals at the age of 35 and approximately 90% of individuals at the age of 60 and above will have some form of disc-affecting pathological changes leading to disc herniation, prolapse and degeneration as well as discogenic pain. Here, we aimed to establish the origins and neurochemical characteristics of porcine intervertebral disc sympathetic innervation involved in pain signalling in IVDD patients. Pigs were given an injection of the Ominipaque contrast agent and Fast Blue (FB) retrograde tracer into the L4-L5 intervertebral disc and euthanized at 2, 1, and 3 months post injection. Following euthanasia, bilateral sympathetic chain ganglia (SChG) Th13 to C1 were collected. The presence, distribution and neurochemical characteristics of retrogradely labelled SChG neurons were examined. The majority (88.8%) of all FB+ cells were found in the L3-L5 SChG. Most FB+ neurons stained for dopamine beta hydroxylase (DBH); one-third to one-quarter stained for somatostatin (SOM), neuropeptide Y (NPY) or leu-enkephalin (LENK); and only a few stained for galanin (GAL). Compared with the control, the greatest decline in neurochemical immunostaining was observed 2 weeks post injection, and the lowest decline was noticed 1 month post injection. Our study, for the first time, provides insight into the complex patterns of intervertebral disc sympathetic innervation and suggests that the best time for neurochemical balance restoration therapy would be 1 month post-injury, when the neuronal concentration of all studied substances is close to the initial physiological level, thus providing favourable conditions for successful recovery.
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Affiliation(s)
- Monika Barczewska
- Department of Neurology and Neurosurgery, Faculty of Medical Sciences, University of Warmia and Mazury, Olsztyn, Poland
| | - Judyta Juranek
- Department of Pathophysiology, Faculty of Medical Sciences, University of Warmia and Mazury in Olsztyn, Ul. Warszawska 30, 10-082, Olsztyn, Poland
| | - Joanna Wojtkiewicz
- Department of Pathophysiology, Faculty of Medical Sciences, University of Warmia and Mazury in Olsztyn, Ul. Warszawska 30, 10-082, Olsztyn, Poland. .,Laboratory for Regenerative Medicine, Faculty of Medical Sciences, University of Warmia and Mazury, Olsztyn, Poland. .,Foundation for the Nerve Cells Regeneration, Olsztyn, Poland.
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Varani K, Vincenzi F, Merighi S, Gessi S, Borea PA. Biochemical and Pharmacological Role of A1 Adenosine Receptors and Their Modulation as Novel Therapeutic Strategy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1051:193-232. [DOI: 10.1007/5584_2017_61] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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12
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Sakkal LA, Rajkowski KZ, Armen RS. Prediction of consensus binding mode geometries for related chemical series of positive allosteric modulators of adenosine and muscarinic acetylcholine receptors. J Comput Chem 2017; 38:1209-1228. [PMID: 28130813 PMCID: PMC5403616 DOI: 10.1002/jcc.24728] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Revised: 11/29/2016] [Accepted: 12/20/2016] [Indexed: 12/13/2022]
Abstract
Following insights from recent crystal structures of the muscarinic acetylcholine receptor, binding modes of Positive Allosteric Modulators (PAMs) were predicted under the assumption that PAMs should bind to the extracellular surface of the active state. A series of well-characterized PAMs for adenosine (A1 R, A2A R, A3 R) and muscarinic acetylcholine (M1 R, M5 R) receptors were modeled using both rigid and flexible receptor CHARMM-based molecular docking. Studies of adenosine receptors investigated the molecular basis of the probe-dependence of PAM activity by modeling in complex with specific agonist radioligands. Consensus binding modes map common pharmacophore features of several chemical series to specific binding interactions. These models provide a rationalization of how PAM binding slows agonist radioligand dissociation kinetics. M1 R PAMs were predicted to bind in the analogous M2 R PAM LY2119620 binding site. The M5 R NAM (ML-375) was predicted to bind in the PAM (ML-380) binding site with a unique induced-fit receptor conformation. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Leon A. Sakkal
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, 901 Walnut St. Suite 918. Philadelphia, PA 19170
| | - Kyle Z. Rajkowski
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, 901 Walnut St. Suite 918. Philadelphia, PA 19170
| | - Roger S. Armen
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, 901 Walnut St. Suite 918. Philadelphia, PA 19170
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Adenosine receptor targets for pain. Neuroscience 2016; 338:1-18. [DOI: 10.1016/j.neuroscience.2015.10.031] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 09/29/2015] [Accepted: 10/15/2015] [Indexed: 12/21/2022]
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14
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Bravo L, Mico JA, Rey-Brea R, Camarena-Delgado C, Berrocoso E. Effect of DSP4 and desipramine in the sensorial and affective component of neuropathic pain in rats. Prog Neuropsychopharmacol Biol Psychiatry 2016; 70:57-67. [PMID: 27181607 DOI: 10.1016/j.pnpbp.2016.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 05/08/2016] [Accepted: 05/09/2016] [Indexed: 12/13/2022]
Abstract
Previous findings suggest that neuropathic pain induces characteristic changes in the noradrenergic system that may modify the sensorial and affective dimensions of pain. We raise the hypothesis that different drugs that manipulate the noradrenergic system can modify specific domains of pain. In the chronic constriction injury (CCI) model of neuropathic pain, the sensorial (von Frey and acetone tests) and the affective (place escape/avoidance paradigm) domains of pain were evaluated in rats 1 and 2weeks after administering the noradrenergic neurotoxin [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride] (DSP4, 50mg/kg). In other animals, we evaluated the effect of enhancing noradrenergic tone in the 2weeks after injury by administering the antidepressant desipramine (10mg/kg/day, delivered by osmotic minipumps) during this period, a noradrenaline reuptake inhibitor. Moreover, the phosphorylation of the extracellular signal regulated kinases (p-ERK) in the anterior cingulate cortex (ACC) was also assessed. The ACC receives direct inputs from the main noradrenergic nucleus, the locus coeruleus, and ERK activation has been related with the expression of pain-related negative affect. These studies revealed that DSP4 almost depleted noradrenergic axons in the ACC and halved noradrenergic neurons in the locus coeruleus along with a decrease in the affective dimension and an increased of p-ERK in the ACC. However, it did not modify sensorial pain perception. By contrast, desipramine reduced pain hypersensitivity, while completely impeding the reduction of the affective pain dimension and without modifying the amount of p-ERK. Together results suggest that the noradrenergic system may regulate the sensorial and affective sphere of neuropathic pain independently.
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Affiliation(s)
- Lidia Bravo
- Neuropsychopharmacology & Psychobiology Research Group, University of Cádiz, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, 28007 Madrid, Spain; Psychobiology Area, Department of Psychology, University of Cadiz, Spain
| | - Juan A Mico
- Neuropsychopharmacology & Psychobiology Research Group, University of Cádiz, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, 28007 Madrid, Spain; Department of Neuroscience, University of Cádiz, Spain
| | - Raquel Rey-Brea
- Neuropsychopharmacology & Psychobiology Research Group, University of Cádiz, Spain
| | | | - Esther Berrocoso
- Neuropsychopharmacology & Psychobiology Research Group, University of Cádiz, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, 28007 Madrid, Spain; Psychobiology Area, Department of Psychology, University of Cadiz, Spain.
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Kaushal R, Taylor BK, Jamal AB, Zhang L, Ma F, Donahue R, Westlund KN. GABA-A receptor activity in the noradrenergic locus coeruleus drives trigeminal neuropathic pain in the rat; contribution of NAα1 receptors in the medial prefrontal cortex. Neuroscience 2016; 334:148-159. [PMID: 27520081 DOI: 10.1016/j.neuroscience.2016.08.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 07/20/2016] [Accepted: 08/03/2016] [Indexed: 12/24/2022]
Abstract
Trigeminal neuropathic pain is described as constant excruciating facial pain. The study goal was to investigate the role of nucleus locus coeruleus (LC) in a model of chronic orofacial neuropathic pain (CCI-ION). The study examines LC's relationship to both the medullary dorsal horn receiving trigeminal nerve sensory innervation and the medial prefrontal cortex (mPFC). LC is a major source of CNS noradrenaline (NA) and a primary nucleus involved in pain modulation. Although descending inhibition of acute pain by LC is well established, contribution of the LC to facilitation of chronic neuropathic pain is also reported. In the present study, a rat orofacial pain model of trigeminal neuropathy was induced by chronic constrictive injury of the infraorbital nerve (CCI-ION). Orofacial neuropathic pain was indicated by development of whisker pad mechanical hypersensitivity. Hypersensitivity was alleviated by selective elimination of NA neurons, including LC (A6 cell group), with the neurotoxin anti-dopamine-β-hydroxylase saporin (anti-DβH-saporin) microinjected either intracerebroventricularly (i.c.v.) or into trigeminal spinal nucleus caudalis (spVc). The GABAA receptor antagonist, bicuculline, administered directly into LC (week 8) inhibited hypersensitivity. This indicates a valence shift in which increased GABAA signaling ongoing in LC after trigeminal nerve injury paradoxically produces excitatory facilitation of the chronic pain state. Microinjection of NAα1 receptor antagonist, benoxathian, into mPFC attenuated whisker pad hypersensitivity, while NAα2 receptor antagonist, idazoxan, was ineffective. Thus, GABAA-mediated activation of NA neurons during CCI-ION can facilitate hypersensitivity through NAα1 receptors in the mPFC. These data indicate LC is a chronic pain generator.
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Affiliation(s)
- R Kaushal
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - B K Taylor
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - A B Jamal
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - L Zhang
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - F Ma
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - R Donahue
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - K N Westlund
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536-0298, United States.
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16
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Noradrenergic Locus Coeruleus pathways in pain modulation. Neuroscience 2016; 338:93-113. [PMID: 27267247 DOI: 10.1016/j.neuroscience.2016.05.057] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/20/2016] [Accepted: 05/27/2016] [Indexed: 12/30/2022]
Abstract
The noradrenergic system is crucial for several activities in the body, including the modulation of pain. As the major producer of noradrenaline (NA) in the central nervous system (CNS), the Locus Coeruleus (LC) is a nucleus that has been studied in several pain conditions, mostly due to its strategic location. Indeed, apart from a well-known descending LC-spinal pathway that is important for pain control, an ascending pathway passing through this nucleus may be responsible for the noradrenergic inputs to higher centers of the pain processing, such as the limbic system and frontal cortices. Thus, the noradrenergic system appears to modulate different components of the pain experience and accordingly, its manipulation has distinct behavioral outcomes. The main goal of this review is to bring together the data available regarding the noradrenergic system in relation to pain, particularly focusing on the ascending and descending LC projections in different conditions. How such findings influence our understanding of these conditions is also discussed.
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17
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Abstract
Adenosine is an ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A1, A2A, A2B and A3 adenosine receptors (ARs). Allosteric enhancers to A1ARs may represent novel therapeutic agents because they increase the activity of these receptors by mediating a shift to their active form in the A1AR-G protein ternary complex. In this manner, they are able to amplify the action of endogenous adenosine, which is produced in high concentrations under conditions of metabolic stress. A1AR allosteric enhancers could be used as a justifiable alternative to the exogenous agonists that are characterized by receptor desensitization and downregulation. In this review, an analysis of some of the most interesting allosteric modulators of A1ARs has been reported.
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18
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Synthesis and biological evaluation of a new series of 2-amino-3-aroyl thiophene derivatives as agonist allosteric modulators of the A1 adenosine receptor. A position-dependent effect study. Eur J Med Chem 2015; 101:185-204. [PMID: 26141910 DOI: 10.1016/j.ejmech.2015.06.041] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 06/05/2015] [Accepted: 06/22/2015] [Indexed: 11/20/2022]
Abstract
The 2-amino-3-(p-chlorobenzoyl)thiophene scaffold has been widely employed as a pharmacophore for the identification of small molecules acting as allosteric modulators at the adenosine A1 receptor. A new series of 2-amino-3-(p-chlorobenzoyl)-4-benzyl-5-arylthiophene derivatives, characterized by the absence as well as the presence of electron-releasing or electron-withdrawing groups on the phenyl ring at the 4- and 5-positions of the thiophene ring, were identified as positive allosteric enhancers at the adenosine A1 receptor in binding (saturation, competition and dissociation kinetics) and functional assays. To better understand the positional requirements of substituents on the 2-amino-3-(p-chlorobenzoyl)thiophene core, the corresponding regioisomeric 4-aryl-5-benzylthiophene analogues were synthesized and found to possess reduced allosteric enhancer activity.
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19
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Individual differences in acute pain-induced endogenous analgesia predict time to resolution of postoperative pain in the rat. Anesthesiology 2015; 122:895-907. [PMID: 25581910 DOI: 10.1097/aln.0000000000000593] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Chronic postsurgical pain, a significant public health problem, occurs in 10 to 50% of patients undergoing major surgery. Acute pain induces endogenous analgesia termed conditioned pain modulation (CPM), and the strength of CPM preoperatively predicts the likelihood of chronic postsurgical pain. The relation between CPM and recovery from surgery has not been examined in preclinical models. METHODS CPM was assessed in individual rats and correlated with each animal's time course of recovery of hypersensitivity after partial spinal nerve ligation. The role of descending noradrenergic pathways in the spinal cord to mechanisms of CPM and recovery was tested using idazoxan to block noradrenergic receptors or antidopamine β-hydroxylase-conjugated saporin to ablate these pathways. Behavioral hypersensitivity, static weight bearing, and spinal glial activation were measured after partial spinal nerve ligation. RESULTS The strength of CPM varied over two-fold between individuals and was directly correlated with the slope of recovery from hypersensitivity after surgery (P < 0.0001; r = 0.660). CPM induced the release of norepinephrine in the spinal cord and was partially blocked by intrathecal idazoxan or dopamine β-hydroxylase-saporin. Dopamine β-hydroxylase-saporin also slowed recovery and enhanced spinal glial activation after partial spinal nerve ligation surgery. Ongoing activation of these pathways was critical to sustained recovery because intrathecal dopamine β-hydroxylase-saporin given 7 weeks after recovery reinstituted hypersensitivity, while having no effect in animals without previous surgery. CONCLUSION Collectively, these studies provide a clear back-translation from clinical observations of CPM and chronic postsurgical pain and suggest that the ability to engage ongoing descending endogenous noradrenergic signaling may be critical in determining time course of recovery from hypersensitivity after surgery.
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Imlach WL, Bhola RF, May LT, Christopoulos A, Christie MJ. A Positive Allosteric Modulator of the Adenosine A1 Receptor Selectively Inhibits Primary Afferent Synaptic Transmission in a Neuropathic Pain Model. Mol Pharmacol 2015; 88:460-8. [DOI: 10.1124/mol.115.099499] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 06/23/2015] [Indexed: 11/22/2022] Open
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21
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Romagnoli R, Baraldi PG, IJzerman AP, Massink A, Cruz-Lopez O, Lopez-Cara LC, Saponaro G, Preti D, Aghazadeh Tabrizi M, Baraldi S, Moorman AR, Vincenzi F, Borea PA, Varani K. Synthesis and Biological Evaluation of Novel Allosteric Enhancers of the A1 Adenosine Receptor Based on 2-Amino-3-(4′-Chlorobenzoyl)-4-Substituted-5-Arylethynyl Thiophene. J Med Chem 2014; 57:7673-86. [DOI: 10.1021/jm5008853] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Romeo Romagnoli
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Pier Giovanni Baraldi
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Adriaan P. IJzerman
- Leiden Academic
Centre for Drug Research, Division of Medicinal Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Arnault Massink
- Leiden Academic
Centre for Drug Research, Division of Medicinal Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Olga Cruz-Lopez
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Luisa Carlota Lopez-Cara
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Giulia Saponaro
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Delia Preti
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Mojgan Aghazadeh Tabrizi
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Stefania Baraldi
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Fossato
di Mortara 17-19, 44121 Ferrara, Italy
| | - Allan R. Moorman
- King Pharmaceuticals
Inc., Research and Development, 4000
CentreGreen Way, Suite 300, Cary, North Carolina 27513
| | - Fabrizio Vincenzi
- Dipartimento
di Scienze Mediche, Sezione di Farmacologia, Università di Ferrara, Via Savonarola 9, 44121 Ferrara, Italy
| | - Pier Andrea Borea
- Dipartimento
di Scienze Mediche, Sezione di Farmacologia, Università di Ferrara, Via Savonarola 9, 44121 Ferrara, Italy
| | - Katia Varani
- Dipartimento
di Scienze Mediche, Sezione di Farmacologia, Università di Ferrara, Via Savonarola 9, 44121 Ferrara, Italy
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Antonioli L, Csóka B, Fornai M, Colucci R, Kókai E, Blandizzi C, Haskó G. Adenosine and inflammation: what's new on the horizon? Drug Discov Today 2014; 19:1051-68. [DOI: 10.1016/j.drudis.2014.02.010] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/06/2014] [Accepted: 02/25/2014] [Indexed: 12/18/2022]
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23
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Kennedy DP, McRobb FM, Leonhardt SA, Purdy M, Figler H, Marshall MA, Chordia M, Figler R, Linden J, Abagyan R, Yeager M. The second extracellular loop of the adenosine A1 receptor mediates activity of allosteric enhancers. Mol Pharmacol 2014; 85:301-9. [PMID: 24217444 PMCID: PMC3913357 DOI: 10.1124/mol.113.088682] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 11/11/2013] [Indexed: 01/26/2023] Open
Abstract
Allosteric enhancers of the adenosine A1 receptor amplify signaling by orthosteric agonists. Allosteric enhancers are appealing drug candidates because their activity requires that the orthosteric site be occupied by an agonist, thereby conferring specificity to stressed or injured tissues that produce adenosine. To explore the mechanism of allosteric enhancer activity, we examined their action on several A1 receptor constructs, including (1) species variants, (2) species chimeras, (3) alanine scanning mutants, and (4) site-specific mutants. These findings were combined with homology modeling of the A1 receptor and in silico screening of an allosteric enhancer library. The binding modes of known docked allosteric enhancers correlated with the known structure-activity relationship, suggesting that these allosteric enhancers bind to a pocket formed by the second extracellular loop, flanked by residues S150 and M162. We propose a model in which this vestibule controls the entry and efflux of agonists from the orthosteric site and agonist binding elicits a conformational change that enables allosteric enhancer binding. This model provides a mechanism for the observations that allosteric enhancers slow the dissociation of orthosteric agonists but not antagonists.
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Affiliation(s)
- Dylan P Kennedy
- Department of Pharmacology (D.P.K.), Department of Molecular Physiology and Biological Physics (S.A.L., M.P., H.F., M.C., R.F., M.Y.), Cardiovascular Research Center (M.A.M., R.F., M.Y.), Center for Membrane Biology (M.Y.), and Department of Medicine, Division of Cardiovascular Medicine (M.Y.), University of Virginia School of Medicine, Charlottesville, Virginia; the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California (F.M.M., R.A.); and the La Jolla Institute for Allergy and Immunology (J.L.), La Jolla, California
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Vincenzi F, Targa M, Romagnoli R, Merighi S, Gessi S, Baraldi PG, Borea PA, Varani K. TRR469, a potent A(1) adenosine receptor allosteric modulator, exhibits anti-nociceptive properties in acute and neuropathic pain models in mice. Neuropharmacology 2014; 81:6-14. [PMID: 24486382 DOI: 10.1016/j.neuropharm.2014.01.028] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 01/14/2014] [Accepted: 01/20/2014] [Indexed: 01/21/2023]
Abstract
A(1) adenosine receptors (ARs) have been identified as a potential target for the development of anti-nociceptive compounds. The present study explores the analgesic effects of a novel A(1)AR positive allosteric modulator, TRR469, in different models of acute and chronic pain in mice. To evaluate the allosteric enhancement, in vitro binding experiments were performed. The anti-nociceptive properties were investigated in formalin and writhing tests, and in the streptozotocin-induced diabetic neuropathic pain model. Rotarod and catalepsy tests were used to identify potential side effects, while the functional effect of TRR469 was studied using [(3)H]-d-aspartate release from synaptosomes. TRR469 effectively inhibited nociceptive responses in the formalin and writhing tests, with effects comparable to those of the reference analgesic morphine. Isobolographic analysis of the combination of TRR469 and morphine revealed an additive interaction. TRR469 was anti-allodynic in the neuropathic pain model and did not display locomotor or cataleptic side effects. TRR469 enhanced the binding of the agonist radioligand [(3)H]-CCPA and induced a 33-fold increase of adenosine affinity in spinal cord membranes. In mouse spinal cord synaptosomes, TRR469 enhanced the inhibitory effect of A(1)AR activation on [(3)H]-d-aspartate release, a non-metabolizable analogue of glutamate. In conclusion, this research demonstrates the anti-nociceptive effect of the novel compound TRR469, one of the most potent and effective A(1)AR positive allosteric modulators so far synthesized. The use of TRR469 allows for the possibility of exploiting analgesic properties of endogenous adenosine, with a minor potential to develop the various side effects often associated with the use of direct receptor agonists.
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Affiliation(s)
- Fabrizio Vincenzi
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Martina Targa
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Romeo Romagnoli
- Department of Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Stefania Merighi
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Stefania Gessi
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Pier Giovanni Baraldi
- Department of Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Pier Andrea Borea
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy
| | - Katia Varani
- Department of Medical Sciences, Pharmacology Section, University of Ferrara, via Fossato di Mortara 17/19, 44121 Ferrara, Italy.
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Synthesis and biological evaluation of novel 2-amino-3-aroyl-4-neopentyl-5-substituted thiophene derivatives as allosteric enhancers of the A₁ adenosine receptor. Bioorg Med Chem 2013; 22:148-66. [PMID: 24332652 DOI: 10.1016/j.bmc.2013.11.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/21/2013] [Indexed: 11/23/2022]
Abstract
2-Amino-3-benzoyl thiophenes have been widely reported to act as allosteric enhancers at the A1 adenosine receptor. Their activity can be increased considerably by appropriate substitutions at the 4- and 5-positions of the thiophene ring. Substituent size at the thiophene C-4 position seemed to be a factor closely related to activity, with the 4-neopentyl (2,2-dimethylpropyl) substitution showing the greatest enhanced activity. A wide series of 2-amino-3-aroyl-4-neopentylthiophene derivatives with general structure 3, characterized by the presence of different substituents (bromine, aryl and heteroaryl) at the 5-position of the thiophene ring, have been identified as potent AEs at the A1AR. With only one exception, all of the synthesized compounds proved to be superior to the reference compound PD 81,723 in a functional assay. Derivatives 3p, 3u, 3am, 3ap and 3ar were the most active compounds in binding (saturation and competition) and functional cAMP studies, being able to potentiate agonist [(3)H]CCPA binding to the A1 receptor.
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Key Words
- 2-Amino-3-benzoylthiophene
- 2-chloro-N(6)-cyclopentyladenosine
- A(1) adenosine receptor
- AE(s)
- Allosteric modulation
- CCPA
- CHO
- CNS
- CsF
- ERG
- EWG
- G protein-coupled receptors
- GPCRs
- N-bromosuccinimide
- NBS
- PdCl(2)(DPPF)
- [(3)H](4-(2-[7-amino-2-(2-furil)[1,2.4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol)
- [(3)H]1,3-dipropyl-8-cyclopentyl-xanthine
- [(3)H]2-chloro-N(6)-cyclopentyladenosine
- [(3)H]5-N-(4-methoxyphenylcarbamoyl)amino-8-propyl-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine
- [(3)H]CCPA
- [(3)H]DPCPX
- [(3)H]MRE-3008F20
- [(3)H]ZM 241385
- [1,1′-bis(diphenylphosphino)ferrocene] dichloropalladium(II) complex with dichloromethane
- allosteric enhancer(s)
- cAMP
- central nervous system
- cesium fluoride
- chinese hamster ovary
- cyclic adenosine monophosphate
- electron-releasing group
- electron-withdrawing group
- hA(1)AR
- human A(1) adenosine receptor
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Song Z, Ansah O, Meyerson B, Pertovaara A, Linderoth B. Exploration of supraspinal mechanisms in effects of spinal cord stimulation: Role of the locus coeruleus. Neuroscience 2013; 253:426-34. [DOI: 10.1016/j.neuroscience.2013.09.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/29/2013] [Accepted: 09/03/2013] [Indexed: 01/29/2023]
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Ankle joint mobilization affects postoperative pain through peripheral and central adenosine A1 receptors. Phys Ther 2013; 93:401-12. [PMID: 23086409 DOI: 10.2522/ptj.20120226] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND Physical therapists frequently use joint mobilization therapy techniques to treat people with musculoskeletal dysfunction and pain. Several studies suggest that endogenous adenosine may act in an analgesic fashion in various pain states. OBJECTIVE The purpose of this study was to investigate the contribution of the adenosinergic system on the antihyperalgesic effect of ankle joint mobilization (AJM). DESIGN This was a experimental study. METHODS To test the hypothesis that the adrenosinergic system is involved in the antihyperalgesic effect of AJM, mice (25-35 g) submitted to plantar incision surgery were used as a model of acute postoperative pain. The mice were subjected to AJM for 9 minutes. Withdrawal frequency to mechanical stimuli was assessed 24 hours after plantar incision surgery and 30 minutes after AJM, adenosine, clonidine, or morphine treatments. The adenosinergic system was assessed by systemic (intraperitoneal), central (intrathecal), and peripheral (intraplantar) administration of caffeine. The participation of the A1 receptor was investigated using a selective adenosine A1 receptor subtype antagonist. In addition, previous data on the involvement of the serotonergic and noradrenergic systems in the antihyperalgesic effect of AJM were confirmed. RESULTS Ankle joint mobilization decreased mechanical hyperalgesia, and this effect was reversed by pretreatment of the animals with caffeine given by intraperitoneal, intraplantar, and intrathecal routes. In addition, intraplanar and intrathecal administrations of 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, a selective adenosine A1 subtype receptor antagonist) or systemic administration of yohimbine or ρ-chlorophenylalanine methyl ester hydrochloride (PCPA) blocked the antihyperalgesia induced by AJM. LIMITATIONS The results are limited to animal models and cannot be generalized to acute pain in humans. CONCLUSIONS This study demonstrated the involvement of the adenosinergic system in the antihyperalgesic effect of AJM in a rodent model of pain and provides a possible mechanism basis for AJM-induced relief of acute pain.
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Kimatrai-Salvador M, Baraldi PG, Romagnoli R. Allosteric modulation of A1-adenosine receptor: a review. DRUG DISCOVERY TODAY. TECHNOLOGIES 2013; 10:e285-e296. [PMID: 24050280 DOI: 10.1016/j.ddtec.2012.08.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Allosteric modulators of adenosine receptors represent an alternative to direct-acting adenosine agonists and nucleoside uptake blockers, preferably those can selectively modulate the response to adenosine in only those organs or localized areas of a given organ in which production of adenosine is increased. Allosteric enhancers at the adenosine A1 receptor have received attention as anti-arrhythmic cardiac agents, and, more recently, as anti-lipolytic agents. In addition, this class of compounds has therapeutic potential as analgesics and neuroprotective agents.
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Hayashida KI, Peters CM, Gutierrez S, Eisenach JC. Depletion of endogenous noradrenaline does not prevent spinal cord plasticity following peripheral nerve injury. THE JOURNAL OF PAIN 2012; 13:49-57. [PMID: 22155404 PMCID: PMC3381881 DOI: 10.1016/j.jpain.2011.09.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 09/30/2011] [Accepted: 09/30/2011] [Indexed: 01/12/2023]
Abstract
UNLABELLED The present study examined the role of endogenous noradrenaline on glial and neuronal plasticity in the spinal cord in rats after peripheral nerve injury. An intrathecal injection of dopamine-β-hydroxylase antibody conjugated to saporin (DβH-saporin) completely depleted noradrenergic axons in the spinal cord and also reduced noradrenergic neurons in the locus coeruleus (A6) and A5 noradrenergic nucleus in the brainstem and noradrenergic axons in the paraventricular nucleus of the hypothalamus. DβH-saporin treatment itself did not alter mechanical withdrawal threshold, but enhanced mechanical hypersensitivity and intrathecal clonidine analgesia after L5-L6 spinal nerve ligation. In the spinal dorsal horn of spinal nerve ligation rats, DβH-saporin treatment increased choline acetyltransferase immunoreactivity as well as immunoreactivity in microglia of ionized calcium binding adaptor molecule 1[IBA1] and in astrocytes of glial fibrillary acidic protein, and brain-derived nerve growth factor content. DβH-saporin treatment did not, however, alter the fractional release of acetylcholine from terminals by dexmedetomidine after nerve injury. These results suggest that endogenous tone of noradrenergic fibers is not necessary for the plasticity of α2-adrenoceptor analgesia and glial activation after nerve injury, but might play an inhibitory role on glial activation. PERSPECTIVE This study demonstrates that endogenous noradrenaline modulates plasticity of glia and cholinergic neurons in the spinal cord after peripheral nerve injury and hence influences the pathophysiology of spinal cord changes associated with neuropathic pain.
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Affiliation(s)
- Ken-Ichiro Hayashida
- Department of Anesthesiology, Wake Forest University School of Medicine, Winston Salem, North Carolina 27157, USA
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Göblyös A, Ijzerman AP. Allosteric modulation of adenosine receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1309-18. [PMID: 20599682 DOI: 10.1016/j.bbamem.2010.06.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 06/10/2010] [Accepted: 06/10/2010] [Indexed: 10/19/2022]
Abstract
Allosteric ligands for G protein-coupled receptors (GPCRs) may alter receptor conformations induced by an orthosteric ligand. These modulators can thus fine-tune classical pharmacological responses. In this review we will describe efforts to synthesize and characterize allosteric modulators for one particular GPCR subfamily, the adenosine receptors. There are four subtypes of these receptors: A(1), A(2A), A(2B) and A(3). Allosteric enhancers for the adenosine A(1) receptor may have anti-arrythmic and anti-lipolytic activity. They may also act as analgesics and neuroprotective agents. A(3) allosteric enhancers are thought to be beneficial in ischemic conditions or as antitumor agents. We will summarize recent developments regarding the medicinal chemistry of such compounds. Most data have been and are published about the adenosine A(1) and A(3) receptor, whereas limited or no information is available for the A(2A) and A(2B) receptor, respectively. Receptor mutation studies are also discussed, as they may shed light on the localization of the allosteric binding sites. This article is part of a Special Issue entitled: "Adenosine Receptors".
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Affiliation(s)
- Anikó Göblyös
- Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Leiden, The Netherlands
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Retrograde viral vector-mediated inhibition of pontospinal noradrenergic neurons causes hyperalgesia in rats. J Neurosci 2009; 29:12855-64. [PMID: 19828800 DOI: 10.1523/jneurosci.1699-09.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Pontospinal noradrenergic neurons form a component of an endogenous analgesic system and represent a potential therapeutic target. We tested the principle that genetic manipulation of their excitability can alter nociception using an adenoviral vector (AVV-PRS-hKir(2.1)) containing a catecholaminergic-selective promoter (PRS) to retrogradely transduce and inhibit the noradrenergic neurons projecting to the lumbar dorsal horn through the expression of a potassium channel (hKir(2.1)). Expression of hKir(2.1) in catecholaminergic PC12 cells hyperpolarized the membrane potential and produced a barium-sensitive inward rectification. LC neurons transduced by AVV-PRS-hKir(2.1) in slice cultures also showed barium-sensitive inward rectification and reduced spontaneous firing rate (median 0.2 Hz; n = 19 vs control 1.0 Hz; n = 18, p < 0.05). Pontospinal noradrenergic neurons were retrogradely transduced in vivo by injection of AVV into the lumbar dorsal horn (L4-5). Rats transduced with AVV-PRS-hKir(2.1) showed thermal but not mechanical hyperalgesia. Similar selective augmentation of thermal hyperalgesia was seen in the CFA-inflammatory pain model after AVV-PRS-hKir(2.1). In the formalin test, rats transduced with hKir(2.1) showed enhanced nocifensive behaviors (both Phase I and II, p < 0.05, n = 11/group) and increased c-Fos-positive cells in the lumbar dorsal horn. Transduction with AVV-PRS-hKir(2.1) before spared nerve injury produced no change in tactile or cold allodynia. Thus, the selective genetic inhibition of approximately 150 pontospinal noradrenergic neurons produces a modality-specific thermal hyperalgesia, increased nocifensive behaviors, and spinal c-Fos expression in the formalin test, but not in the spared nerve injury model of neuropathic pain, indicating that these neurons exert a selective tonic restraining influence on in vivo nociception.
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Viisanen H, Pertovaara A. Antinociception by motor cortex stimulation in the neuropathic rat: does the locus coeruleus play a role? Exp Brain Res 2009; 201:283-96. [PMID: 19826796 DOI: 10.1007/s00221-009-2038-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 09/24/2009] [Indexed: 11/29/2022]
Abstract
We studied whether stimulation of the primary motor cortex (M1) attenuates pain-related spinal withdrawal responses of neuropathic and healthy control rats, and whether the descending antinociceptive effect is relayed through the noradrenergic locus coeruleus (LC). The assessments of the noxious heat-evoked limb withdrawals reflecting spinal nociception and recordings of single LC units were performed in spinal nerve-ligated neuropathic and sham-operated control rats under light pentobarbital anesthesia. Electric stimulation of M1 produced equally strong spinal antinociception in neuropathic and control rats. Following microinjection into M1, a group I metabotropic glutamate receptor agonist (DHPG; 10 nmol) and a high (25 nmol) but not low (2.5 nmol) dose of glutamate slightly increased on-going discharge rates of LC neurons in neuropathic but not in control animals. Influence of electric stimulation of M1 on LC neurons was studied only in the neuropathic group, in which discharge rates of LC neurons were increased by electric M1 stimulation. Lidocaine block of the LC or block of descending noradrenergic influence by intrathecal administration of a alpha(2)-adrenoceptor antagonist failed to produce a significant attenuation of the spinal antinociceptive effect induced by electric M1 stimulation in the neuropathic or the sham group. The results indicate that stimulation of the rat M1 induces spinal antinociception in neuropathic as well as control conditions. While M1 stimulation may activate the LC, particularly in the neuropathic group, the contribution of coeruleospinal noradrenergic pathways may not be critical for the spinal antinociceptive effect induced by M1 stimulation.
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Affiliation(s)
- Hanna Viisanen
- Biomedicum Helsinki, Institute of Biomedicine/Physiology, POB 63, University of Helsinki, 00014, Helsinki, Finland
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Joo JD, In JH, Jung HS, Kim YS, Kim DW, Choi WY, Shin EY, Jeon YS. Lidocaine attenuates the expression of ERK1/2 and CREB in a neuropathic pain model of rats. Korean J Anesthesiol 2009; 56:319-324. [PMID: 30625743 DOI: 10.4097/kjae.2009.56.3.319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In addition to causing the loss of voluntary sensory and motor function, spinal cord injury (SCI) often creates a state of central neuropathic pain. Rats given SCI display increases in the activated form of transcription factors ERK 1/2, p38 MAPK, and CREB in the spinal cord, which correspond to allodynia in a model of neuropathic pain. The current study was designed to determine if lidocaine had an effect on the development of neuropathic pain in response to SCI. METHODS Male Sprague Dawley rats were anesthetized and then received a L5-L6 spinal nerve ligation (neuropathic rats). The levels of intracellular cell-signaling protein, ERK 1/2 and CREB were then assessed by western blot analysis of samples collected from a sham operated (control) group, a neuropathic pain and normal saline (NP + NS) group, and a neuropathic pain and 5% lidocaine (NP + Lido) group. RESULTS The increased levels of ERK 1/2 and CREB protein that were observed in the neuropathic pain model were reduced by continuous infusion of 5% lidocaine. CONCLUSIONS The current results suggest that lidocaine therapy may be an effective method of preventing and treating central neuropathic pain following SCI, and that these effects may occur via the reduced expression of ERK 1/2 and CREB in the intracellular cell-signaling pathway.
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Affiliation(s)
- Jin Deok Joo
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Jang Hyeok In
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Hong Soo Jung
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Yong Shin Kim
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Dae Woo Kim
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Woo Young Choi
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Eun Young Shin
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
| | - Yeon Soo Jeon
- Department of Anesthesiology and Pain Medicine, St. Vincent Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.
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Brightwell JJ, Taylor BK. Noradrenergic neurons in the locus coeruleus contribute to neuropathic pain. Neuroscience 2009; 160:174-85. [PMID: 19223010 DOI: 10.1016/j.neuroscience.2009.02.023] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 01/20/2009] [Accepted: 02/04/2009] [Indexed: 12/17/2022]
Abstract
Current theories of neuropathic hypersensitivity include an imbalance of supraspinal inhibition and facilitation. Our overall hypothesis is that the locus coeruleus (LC), classically interpreted as a source of pain inhibition, may paradoxically result in facilitation after tibial and common peroneal nerve transection (spared sural nerve injury--SNI). We first tested the hypothesis that non-noxious tactile hind paw stimulation of the spared sural innervation territory increases neuronal activity in the LC in male rats. We observed a bilateral increase in the stimulus-evoked expression of transcription factors Fos and phosphorylated CREB (pCREB) in LC after SNI but not sham surgery; these markers of neuronal activity correlated with the intensity of tactile allodynia. We next tested the hypothesis that noradrenergic neurons contribute to the development of neuropathic pain. To selectively destroy these neurons, we delivered antidopamine-beta-hydroxylase saporin (anti-DbetaH-saporin) into the i.c.v. space 2 weeks before SNI. We found that anti-DbetaH-saporin, but not an IgG-saporin control, reduced behavioral signs of tactile allodynia, mechanical hyperalgesia, and cold allodynia from 3 to 28 days. after SNI. Our final experiment tested the hypothesis that the LC contributes to the maintenance of neuropathic pain. We performed SNI, waited 2 weeks for maximal allodynia and hyperalgesia to develop, and then administered the local anesthetic lidocaine (4%) directly into the LC parenchyma. Lidocaine reduced all behavioral signs of neuropathic pain in a reversible manner, suggesting that the LC contributes to pain facilitation. We conclude that, in addition to its well-known inhibition of acute and inflammatory pain, the LC facilitates the development and maintenance of neuropathic pain in the SNI model. Further studies are needed to determine the facilitatory pathways emanating from the LC.
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Affiliation(s)
- J J Brightwell
- Department of Pharmacology, School of Medicine, Tulane University, New Orleans, LA 70112, USA
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Abstract
Allosteric modulators for adenosine receptors may have potential therapeutic advantage over orthosteric ligands. Allosteric enhancers at the adenosine A1 receptor have been linked to antiarrhythmic and antilipolytic activity. They may also have therapeutic potential as analgesics and neuroprotective agents. A3 allosteric enhancers are postulated to be useful against ischemic conditions or as antitumor agents. In this review, we address recent developments regarding the medicinal chemistry of such compounds. Most efforts have been and are directed toward adenosine A1 and A3 receptors, whereas limited or no information is available for A2A and A2B receptors. We also discuss some findings, mostly receptor mutation studies, regarding localization of the allosteric binding sites on the receptors.
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Bilkei-Gorzo A, Abo-Salem OM, Hayallah AM, Michel K, Müller CE, Zimmer A. Adenosine receptor subtype-selective antagonists in inflammation and hyperalgesia. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:65-76. [PMID: 18188542 DOI: 10.1007/s00210-007-0252-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 12/14/2007] [Indexed: 12/22/2022]
Abstract
In this study, we examined the effects of systemic and local administration of the subtype-selective adenosine receptor antagonists PSB-36, PSB-1115, MSX-3, and PSB-10 on inflammation and inflammatory hyperalgesia. Pharmacological blockade of adenosine receptor subtypes after systemic application of antagonists generally led to a decreased edema formation after formalin injection and, with the exception of A(3) receptor antagonism, also after the carrageenan injection. The selective A(2B) receptor antagonist PSB-1115 showed a biphasic, dose-dependent effect in the carrageenan test, increasing edema formation at lower doses and reducing it at a high dose. A(1) and A(2B) antagonists diminished pain-related behaviors in the first phase of the formalin test, while the second, inflammatory phase was attenuated by A(2B) and A(3) antagonists. The A(2B) antagonist was particularly potent in reducing inflammatory pain dose-dependently reaching the maximum effect at a low dose of 3 mg/kg. Inflammatory hyperalgesia was totally eliminated by the A(2A) antagonist MSX-3 at a dose of 10 mg/kg. In contrast to the A(1) antagonist, the selective antagonists of A(2A), A(2B), and A(3) receptors were also active upon local administration. Our results demonstrate that the blockade of adenosine receptor subtypes can decrease the magnitude of inflammatory responses. Selective A(2A) antagonists may be useful for the treatment of inflammatory hyperalgesia, while A(2B) antagonists have potential as analgesic drugs for the treatment of inflammatory pain.
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Affiliation(s)
- Andras Bilkei-Gorzo
- Institute of Molecular Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany.
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May LT, Sexton PM, Christopoulos A. Effects of urea pretreatment on the binding properties of adenosine A1 receptors. Br J Pharmacol 2006; 146:1119-29. [PMID: 16231004 PMCID: PMC1751243 DOI: 10.1038/sj.bjp.0706419] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The effect of denaturation and/or extraction of nonintegral membrane proteins by 7 M urea on the binding of the antagonist [3H]cyclopentyl-1,3-dipropylxanthine 8 dipropyl-2,3 ([3H]DPCPX), and the agonists adenosine, (-)-N6-(2-phenylisopropyl)-adenosine (R-PIA) and N6-cyclohexyladenosine (CHA), was investigated at human A1 adenosine receptors stably expressed in CHO cells. Pretreatment with urea caused a 56% reduction in membrane proteins. Compared to controls, the use of adenosine deaminase (ADA), 100 microM 5'-guanylylimidodiphosphate (Gpp(NH)p) or urea each caused equivalent increases in specific [3H]DPCPX binding. Neither the binding kinetics nor the affinity of [3H]DPCPX were significantly different in urea-pretreated compared to ADA-pretreated membranes. At 25 degrees C in ADA-pretreated membranes, the competition isotherms for R-PIA and CHA were characterized by two affinity states. Gpp(NH)p (100 microM) reduced, but did not abolish, the value of the high-affinity dissociation constant. Similar results were obtained after treatment with urea for R-PIA, whereas the high-affinity state for CHA was abolished. At 37 degrees C, urea pretreatment, but not 100 microM Gpp(NH)p, abolished high-affinity agonist competition binding. There was no significant effect of any of the treatments on the low-affinity agonist binding state. In urea-pretreated membranes, exogenously added adenosine competed according to a simple mass-action model with a pK(L) of 5.66+/-0.05 (n=3). Compared to the more common approaches of ADA treatment and/or use of guanine nucleotides, our findings suggest that urea pretreatment represents an inexpensive and useful approach for investigating the binding properties of adenosine A1 ligands (including adenosine) to the G protein-uncoupled form of the receptor.
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Affiliation(s)
- Lauren T May
- Molecular Pharmacology Laboratory, Department of Pharmacology, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Patrick M Sexton
- Molecular Pharmacology Laboratory, Department of Pharmacology, The University of Melbourne, Parkville, 3010 Victoria, Australia
- Howard Florey Institute, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Arthur Christopoulos
- Molecular Pharmacology Laboratory, Department of Pharmacology, The University of Melbourne, Parkville, 3010 Victoria, Australia
- Howard Florey Institute, The University of Melbourne, Parkville, 3010 Victoria, Australia
- Author for correspondence:
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Abstract
Allosteric modulation of membrane receptors has been intensively studied in the past three decades and is now considered to be an important indirect mechanism for the control of receptor function. The allosteric site on the GABA(A) receptor is the target for the most widely prescribed sleep medicines, the benzodiazepines. Cinacalcet, an allosteric enhancer of the calcium-sensing receptor, is used to treat secondary hyperparathyroidism. Allosteric ligands might be especially valuable to control receptors for which the design of selective orthosteric agonists or antagonists has been elusive, such as muscarinic acetylcholine receptors.
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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40
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Gao ZG, Kim SK, Ijzerman AP, Jacobson KA. Allosteric modulation of the adenosine family of receptors. Mini Rev Med Chem 2005; 5:545-53. [PMID: 15974932 PMCID: PMC3431557 DOI: 10.2174/1389557054023242] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Allosteric modulators for adenosine receptors (ARs) are of an increasing interest and may have potential therapeutic advantage over orthosteric ligands. Benzoylthiophene derivatives (including PD 81,723), 2-aminothiazolium salts, and related allosteric modulators of the A(1) AR have been studied. The benzoylthiophene derivatives were demonstrated to be selective enhancers for the A(1) AR, with little or no effect on other subtypes of ARs. Allosteric modulation of the A(2A) AR has also been reported. A(3) allosteric enhancers may be predicted to be useful against ischemic conditions. We have recently characterized two classes of A(3) AR allosteric modulators: 3-(2-pyridinyl)isoquinolines (e.g. VUF5455) and 1H-imidazo-[4,5-c]quinolin-4-amines (e.g. DU124183), which selectively decreased the agonist dissociation rate at the human A(3)AR but not at A(1) and A(2A) ARs. DU124183 left-shifted the agonist conc.-response curve for inhibition of forskolin-stimulated cAMP accumulation in intact cells expressing the human A(3)AR with up to 30% potentiation of the maximal efficacy. The increased potency of A(3) agonists was evident only in the presence of an A(3) antagonist, since VUF5455 and DU124183 also antagonized, i.e. displaced binding at the orthosteric site, with K(i) values of 1.68 and 0.82 microM, respectively. A(3)AR mutagenesis studies implicated F182(5.43) and N274(7.45) in the action of the enhancers and was interpreted using a rhodopsin-based A(3)AR molecular model, suggesting multiple binding modes. Amiloride analogues, SCH-202676 (N-(2,3-diphenyl-1,2,4-thiadiazol-5(2H)-ylidene)methanamine), and sodium ions were demonstrated to be common allosteric modulators for at least three subtypes (A(1), A(2A), and A(3)) of ARs.
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MESH Headings
- Animals
- Humans
- Models, Molecular
- Mutagenesis
- Receptor, Adenosine A1/chemistry
- Receptor, Adenosine A1/drug effects
- Receptor, Adenosine A2A/chemistry
- Receptor, Adenosine A2A/drug effects
- Receptor, Adenosine A2B/chemistry
- Receptor, Adenosine A2B/drug effects
- Receptors, Purinergic P1/chemistry
- Receptors, Purinergic P1/drug effects
- Receptors, Purinergic P1/genetics
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Affiliation(s)
- Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Inst. of Health, Bethesda, Maryland 20892-0810, USA.
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Obata H, Conklin D, Eisenach JC. Spinal noradrenaline transporter inhibition by reboxetine and Xen2174 reduces tactile hypersensitivity after surgery in rats. Pain 2005; 113:271-276. [PMID: 15661433 DOI: 10.1016/j.pain.2004.10.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 09/16/2004] [Accepted: 10/18/2004] [Indexed: 11/21/2022]
Abstract
Spinal noradrenaline (NA) released in response to noxious stimuli may play an important role in suppression of nociceptive transmission. Here, we investigated the efficacy of a competitive NA transporter inhibitor (reboxetine) and a noncompetitive NA transporter inhibitor peptide, Xen2174, isolated from the Pacific cone snail, to treat tactile hypersensitivity following paw incisional surgery. Male Sprague-Dawley rats were anesthetized, an incision of the plantar aspect of the hind paw was performed, and withdrawal threshold to von Frey filaments near the surgical site determined. Reboxetine (0.5-5 microg) and Xen2174 (0.3-100 microg) increased withdrawal threshold when injected 24h after paw incision, with a peak effect at 15-60 min, for Xen2174, an ED50 value of 0.64 microg. Administration of Xen2174 (3-30 microg) 15 min before incision also reduced hypersensitivity in a dose-dependent manner. Withdrawal threshold after the single 30 microg dose was greater than vehicle control even at 2, 3, and 5 days after incision. Doses <or=30 microg did not alter spontaneous behavior. The anti-hypersensitivity effect of 10 microg of Xen2174 was totally blocked by the alpha2-adrenoceptor antagonist, idazoxan, and partially blocked by the muscarinic antagonist, atropine. These data suggest that selective NA transporter inhibition suppresses post-incisional hypersensitivity through a different mechanism from that of neuropathic pain, since we previously reported that reversal of hypersensitivity by intrathecal clonidine, an alpha2-adrenoceptor agonist, following spinal nerve ligation is completely blocked by intrathecal atropine. Finally, these data suggest that intrathecal administration of Xen2174 at the time of spinal anesthesia might produce postoperative analgesia in humans.
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Affiliation(s)
- Hideaki Obata
- Department of Anesthesiology and Center for the Pharmacologic Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157 Department of Anesthesiology, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan
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De Vry J, Kuhl E, Franken-Kunkel P, Eckel G. Pharmacological characterization of the chronic constriction injury model of neuropathic pain. Eur J Pharmacol 2004; 491:137-48. [PMID: 15140630 DOI: 10.1016/j.ejphar.2004.03.051] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Revised: 03/01/2004] [Accepted: 03/25/2004] [Indexed: 11/15/2022]
Abstract
The chronic constriction injury model is a rat model of neuropathic pain based on a unilateral loose ligation of the sciatic nerve. The aim of the present study was to test its sensitivity to various clinically validated and experimental drugs. Mechanical allodynia and thermal hyperalgesia developed within one week post-surgery and were reliably present for at least 7 weeks. Mechanical allodynia was strongly attenuated by morphine (minimal effective dose in brackets: 8 mg/kg, p.o.) and the cannabinoids Delta9-tetrahydrocannabinol (3 mg/kg, p.o.) and (-)-cis-3-[2-hydroxy-4(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol (CP 55,940; 0.05 mg/kg, i.p.), and weakly/moderately attenuated by the anticonvulsants gabapentin (50 mg/kg, i.p.) and carbamazepine (32 mg/kg, i.p.), the muscle relaxant baclofen (3 mg/kg, i.p.), and the adenosine kinase inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine (ABT-702; 30 mg/kg, i.p.). Thermal hyperalgesia was strongly attenuated by morphine (16 mg/kg, p.o.), Delta9-tetrahydrocannabinol (6 mg/kg, p.o.), CP 55,940 (0.025 mg/kg, i.p.), carbamazepine (32 mg/kg, i.p.) and the antidepressant amitriptyline (32 mg/kg, p.o.), and weakly/moderately attenuated by gabapentin (50 mg/kg, i.p.), the anti-inflammatory cyclooxygenase-2 inhibitor rofecoxib (30 mg/kg, i.p.) and the adenosine A1 receptor positive allosteric modulator 2-amino-4,5,6,7-tetrahydrobenzo(b)thiophen-3-yl 4-chlorophenylmethanone (T62; 30 mg/kg, i.p.). Both symptoms were hardly or not affected by the nonselective N-methyl-d-aspartate receptor antagonists ketamine and dizocilpine, and the N-methyl-d-aspartate receptor NR2B-selective antagonists ifenprodil and R-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenyl-methyl)-1-piperidine propranol (Ro 25-6981). The finding that mechanical allodynia and/or thermal hyperalgesia are attenuated by various established compounds further supports the validity of the chronic constriction injury model for the study of neuropathic pain and its use for the identification of novel treatments.
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Affiliation(s)
- Jean De Vry
- CNS Research, Bayer HealthCare, Aprather Weg 18a, 42096 Wuppertal, Germany.
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Jasmin L, Tien D, Janni G, Ohara PT. Is noradrenaline a significant factor in the analgesic effect of antidepressants? Pain 2003; 106:3-8. [PMID: 14581104 DOI: 10.1016/j.pain.2003.08.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Luc Jasmin
- Department of Neurological Surgery, University of California San Francisco, Box 0112, 505 Parnassus Avenue, San Francisco, CA 94143, USA.
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Hack SP, Vaughan CW, Christie MJ. Modulation of GABA release during morphine withdrawal in midbrain neurons in vitro. Neuropharmacology 2003; 45:575-84. [PMID: 12941371 DOI: 10.1016/s0028-3908(03)00205-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Chronic treatment with opioids induces adaptations in neurons leading to tolerance and dependence. Studies have implicated the midbrain periaqueductal gray (PAG) in the expression of many signs of withdrawal. Patch-clamp recording techniques were used to examine whether augmentation of adenylyl cyclase signalling produces hyperexcitation in GABAergic nerve terminals within the mouse PAG. Both the rate of mIPSCs and the amplitude of evoked IPSCs during naloxone-precipitated withdrawal was profoundly enhanced in chronically morphine treated mice, compared to vehicle treated controls, in the presence but not the absence an adenosine A(1) receptor antagonist DPCPX. Enhanced GABAergic transmission in the presence of DPCPX was abolished by blocking protein kinase A. Inhibitors of cAMP transport, phosphodiesterase and nucleotide transport mimicked the effect of DPCPX. Coupling efficacy of micro-receptors to presynaptic inhibition of GABA release was increased in dependent mice in the presence of DPCPX. The increased coupling efficacy was abolished by blocking protein kinase A, which unmasked an underlying micro-receptor tolerance. These findings indicate that enhanced adenylyl cyclase signalling following chronic morphine treatment produces (1) GABAergic terminal hyperexcitability during withdrawal that is retarded by a concomitant increase in endogenous adenosine, and (2) enhanced micro-receptor coupling to presynaptic inhibition that overcomes an underlying tolerance.
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Affiliation(s)
- Stephen P Hack
- Department of Pharmacology and Pain Management Research Institute, University of Sydney and Royal North Shore Hospital, St Leonards, NSW 2006, Australia.
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Abstract
Although only recently applied to the study of nociception, 'molecular neurosurgery', producing highly selective neural lesions using targeted cytotoxins, has proven a valuable tool for analysis of nociceptive systems and promises to yield much more information on the role of specific types of neurons in pain perception and possibly new pain therapies. Neuropeptide-toxin conjugates, particularly, substance P-saporin, have proven useful research tools and may find clinical applications. Targeting non-lethal moieties (enzymes, genes, viruses) also may prove useful for research and therapeutic purposes.
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Affiliation(s)
- Ronald G Wiley
- Department of Neurology, Vanderbilt University, Nashville, TN 37212, USA.
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Li X, Conklin D, Pan HL, Eisenach JC. Allosteric adenosine receptor modulation reduces hypersensitivity following peripheral inflammation by a central mechanism. J Pharmacol Exp Ther 2003; 305:950-5. [PMID: 12606636 DOI: 10.1124/jpet.102.047951] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of adenosine A1 receptors by endogenous adenosine or synthetic agonists produces antinociception in animal models of acute pain and also reduces hypersensitivity in models of inflammatory and nerve-injury pain. Allosteric adenosine modulators facilitate and potentiate the action of adenosine agonists at the A1 receptors. The purpose of the current study was to examine the effect and site of action for an allosteric adenosine modulator, T62 [2-amino-3-(4-chlorobenzoyl)-5,6, 7,8-tetrahydrobenzothiophene], in rat models of acute pain and inflammation. Intrathecal (i.t.) T62 did not change the withdrawal latency or threshold of normal rats to acute heat or to acute paw pressure. In contrast, i.t. T62 reversed thermal hypersensitivity in carrageenin-inflamed rats. Subcutaneous (s.c.) injection of T62 into the inflamed paw had no such effect. To investigate a potential site of action on nociceptors, single-unit afferent activity to mechanical stimuli on A delta- and C-fibers was examined in normal or carrageenin-inflamed rats before and after intravenous (i.v.) T62 administration. Intravenous T62, 3 mg/kg, had no significant effect in either normal or inflamed conditions. These results support previous studies to suggest that adenosine receptor modulators lack efficacy to acute nociceptive stimuli in the normal condition, but reduce hypersensitivity during inflammation through a central mechanism.
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Affiliation(s)
- Xinhui Li
- Department of Anesthesiology and Center for the Study of Pharmacologic Plasticity in the Presence of Pain, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1009, USA.
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Abstract
In the central nervous system (CNS), adenosine is an important neuromodulator and regulates neuronal and non-neuronal cellular function (e.g. microglia) by actions on extracellular adenosine A(1), A(2A), A(2B) and A(3) receptors. Extracellular levels of adenosine are regulated by synthesis, metabolism, release and uptake of adenosine. Adenosine also regulates pain transmission in the spinal cord and in the periphery, and a number of agents can alter the extracellular availability of adenosine and subsequently modulate pain transmission, particularly by activation of adenosine A(1) receptors. The use of capsaicin (which activates receptors selectively expressed on C-fibre afferent neurons and produces neurotoxic actions in certain paradigms) allows for an interpretation of C-fibre involvement in such processes. In the spinal cord, adenosine availability/release is enhanced by depolarization (K(+), capsaicin, substance P, N-methyl-D-aspartate (NMDA)), by inhibition of metabolism or uptake (inhibitors of adenosine kinase (AK), adenosine deaminase (AD), equilibrative transporters), and by receptor-operated mechanisms (opioids, 5-hydroxytryptamine (5-HT), noradrenaline (NA)). Some of these agents release adenosine via an equilibrative transporter indicating production of adenosine inside the cell (K(+), morphine), while others release nucleotide which is converted extracellularly to adenosine by ecto-5'-nucleotidase (capsaicin, 5-HT). Release can be capsaicin-sensitive, Ca(2+)-dependent and involve G-proteins, and this suggests that within C-fibres, Ca(2+)-dependent intracellular processes regulate production and release of adenosine. In the periphery, adenosine is released from both neuronal and non-neuronal sources. Neuronal release from capsaicin-sensitive afferents is induced by glutamate and by neurogenic inflammation (capsaicin, low concentration of formalin), while that from sympathetic postganglionic neurons (probably as adenosine 5'-triphosphate (ATP) with NA) occurs following more generalized inflammation. Such release is modified differentially by inhibitors of AK and AD. Following nerve injury, there is an alteration in capsaicin-sensitive adenosine release, as spinal release now is less responsive to opioids, while peripheral release is less responsive to inhibitors of metabolism. Following inflammation, adenosine is released from a variety of cell types in addition to neurons (e.g. endothelial cells, neutrophils, mast cells, fibroblasts). ATP is released both spinally and peripherally following inflammation or injury, and may be converted to adenosine by ecto-5'-nucleotidase contributing an additional source of adenosine. Release of adenosine from both spinal and peripheral compartments has inhibitory effects on pain transmission, as methylxanthine adenosine receptor antagonists reduce analgesia produced by agents which augment extracellular levels of adenosine spinally (morphine, 5-HT, substance P, AK inhibitors) and peripherally (AK inhibitors, AD inhibitors). Increases in extracellular adenosine availability also may contribute to antiinflammatory effects of certain agents (methotrexate, sulfasalazine, salicylates, AK inhibitors), and this could have secondary effects on pain signalling in chronic inflammation. The purpose of the present review is to consider: (a). the factors that regulate the extracellular availability of adenosine in the spinal cord and at peripheral sites; and (b). the extent to which this adenosine affects pain signalling in these two distinct compartments.
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Affiliation(s)
- Jana Sawynok
- Department of Pharmacology, Dalhousie University, Halifax, NS Canada B3H 1X5.
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