51
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Garai S, Kulkarni PM, Schaffer PC, Leo LM, Brandt AL, Zagzoog A, Black T, Lin X, Hurst DP, Janero DR, Abood ME, Zimmowitch A, Straiker A, Pertwee RG, Kelly M, Szczesniak AM, Denovan-Wright EM, Mackie K, Hohmann AG, Reggio PH, Laprairie RB, Thakur GA. Application of Fluorine- and Nitrogen-Walk Approaches: Defining the Structural and Functional Diversity of 2-Phenylindole Class of Cannabinoid 1 Receptor Positive Allosteric Modulators. J Med Chem 2020; 63:542-568. [PMID: 31756109 DOI: 10.1021/acs.jmedchem.9b01142] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cannabinoid 1 receptor (CB1R) allosteric ligands hold a far-reaching therapeutic promise. We report the application of fluoro- and nitrogen-walk approaches to enhance the drug-like properties of GAT211, a prototype CB1R allosteric agonist-positive allosteric modulator (ago-PAM). Several analogs exhibited improved functional potency (cAMP, β-arrestin 2), metabolic stability, and aqueous solubility. Two key analogs, GAT591 (6r) and GAT593 (6s), exhibited augmented allosteric-agonist and PAM activities in neuronal cultures, improved metabolic stability, and enhanced orthosteric agonist binding (CP55,940). Both analogs also exhibited good analgesic potency in the CFA inflammatory-pain model with longer duration of action over GAT211 while being devoid of adverse cannabimimetic effects. Another analog, GAT592 (9j), exhibited moderate ago-PAM potency and improved aqueous solubility with therapeutic reduction of intraocular pressure in murine glaucoma models. The SAR findings and the enhanced allosteric activity in this class of allosteric modulators were accounted for in our recently developed computational model for CB1R allosteric activation and positive allosteric modulation.
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Affiliation(s)
- Sumanta Garai
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Pushkar M Kulkarni
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Peter C Schaffer
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Luciana M Leo
- Center for Substance Abuse Research, Lewis Katz School of Medicine , Temple University , Philadelphia , Pennsylvania 19140 , United States
| | - Asher L Brandt
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Ayat Zagzoog
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Tallan Black
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Xiaoyan Lin
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Dow P Hurst
- Center for Drug Discovery , University of North Carolina Greensboro , Greensboro , North Carolina 27402 , United States
| | - David R Janero
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Department of Chemistry and Chemical Biology, College of Science, and Health Sciences Entrepreneurs , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Mary E Abood
- Center for Substance Abuse Research, Lewis Katz School of Medicine , Temple University , Philadelphia , Pennsylvania 19140 , United States
| | - Anaelle Zimmowitch
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Alex Straiker
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Roger G Pertwee
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences , University of Aberdeen , Aberdeen AB25 2ZD , Scotland, U.K
| | - Melanie Kelly
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Anna-Maria Szczesniak
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Eileen M Denovan-Wright
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Ken Mackie
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Andrea G Hohmann
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Patricia H Reggio
- Center for Drug Discovery , University of North Carolina Greensboro , Greensboro , North Carolina 27402 , United States
| | - Robert B Laprairie
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada.,Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
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52
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Allosteric Modulation of Cannabinoid Receptor 1-Current Challenges and Future Opportunities. Int J Mol Sci 2019; 20:ijms20235874. [PMID: 31771126 PMCID: PMC6928801 DOI: 10.3390/ijms20235874] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 11/19/2019] [Accepted: 11/20/2019] [Indexed: 02/07/2023] Open
Abstract
The cannabinoid receptor type 1 (CB1R), a G protein-coupled receptor (GPCR), plays an essential role in the control of many physiological processes such as hunger, memory loss, gastrointestinal activity, catalepsy, fear, depression, and chronic pain. Therefore, it is an attractive target for drug discovery to manage pain, neurodegenerative disorders, obesity, and substance abuse. However, the psychoactive adverse effects, generated by CB1R activation in the brain, limit the use of the orthosteric CB1R ligands as drugs. The discovery of CB1R allosteric modulators during the last decade provided new tools to target the CB1R. Moreover, application of the site-directed mutagenesis in combination with advanced physical methods, especially X-ray crystallography and computational modeling, has opened new horizons for understanding the complexity of the structure, function, and activity of cannabinoid receptors. In this paper, we present the latest advances in research on the CB1R, its allosteric modulation and allosteric ligands, and their translational potential. We focused on structural essentials of the cannabinoid 1 receptor- ligand (drug) interactions, as well as modes of CB1R signaling regulation.
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53
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Laprairie RB, Mohamed KA, Zagzoog A, Kelly MEM, Stevenson LA, Pertwee R, Denovan-Wright EM, Thakur GA. Indomethacin Enhances Type 1 Cannabinoid Receptor Signaling. Front Mol Neurosci 2019; 12:257. [PMID: 31680861 PMCID: PMC6813218 DOI: 10.3389/fnmol.2019.00257] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/04/2019] [Indexed: 12/19/2022] Open
Abstract
In addition to its known actions as a non-selective cyclooxygenase (COX) 1 and 2 inhibitor, we hypothesized that indomethacin can act as an allosteric modulator of the type 1 cannabinoid receptor (CB1R) because of its shared structural features with the known allosteric modulators of CB1R. Indomethacin enhanced the binding of [3H]CP55940 to hCB1R and enhanced AEA-dependent [35S]GTPγS binding to hCB1R in Chinese hamster ovary (CHO) cell membranes. Indomethacin (1 μM) also enhanced CP55940-dependent βarrestin1 recruitment, cAMP inhibition, ERK1/2 and PLCβ3 phosphorylation in HEK293A cells expressing hCB1R, but not in cells expressing hCB2R. Finally, indomethacin enhanced the magnitude and duration of CP55940-induced hypolocomotion, immobility, hypothermia, and anti-nociception in C57BL/6J mice. Together, these data support the hypothesis that indomethacin acted as a positive allosteric modulator of hCB1R. The identification of structural and functional features shared amongst allosteric modulators of CB1R may lead to the development of novel compounds designed for greater CB1R or COX selectivity and compounds designed to modulate both the prostaglandin and endocannabinoid systems.
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Affiliation(s)
- Robert B Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada.,Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
| | - Kawthar A Mohamed
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
| | - Ayat Zagzoog
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
| | - Melanie E M Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.,Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada
| | - Lesley A Stevenson
- School of Medical Sciences, The Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom
| | - Roger Pertwee
- School of Medical Sciences, The Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom
| | | | - Ganesh A Thakur
- Center for Drug Discovery, Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, United States
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54
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Hurst DP, Garai S, Kulkarni PM, Schaffer PC, Reggio PH, Thakur GA. Identification of CB1 Receptor Allosteric Sites Using Force-Biased MMC Simulated Annealing and Validation by Structure-Activity Relationship Studies. ACS Med Chem Lett 2019; 10:1216-1221. [PMID: 31413808 DOI: 10.1021/acsmedchemlett.9b00256] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 07/10/2019] [Indexed: 02/02/2023] Open
Abstract
Positive allosteric modulation of the cannabinoid 1 receptor (CB1R) has demonstrated distinct therapeutic advantages that address several limitations associated with orthosteric agonism and has opened a promising therapeutic avenue for further drug development. To advance the development of CB1R positive allosteric modulators, it is important to understand the molecular architecture of CB1R allosteric site(s). The goal of this work was to use Force-Biased MMC Simulated Annealing to identify binding sites for GAT228 (R), a partial allosteric agonist, and GAT229 (S), a positive allosteric modulator (PAM) at the CB1R. Our studies suggest that GAT228 binds in an intracellular (IC) TMH1-2-4 exosite that would allow this compound to act as a CB1 allosteric agonist as well as a CB1 PAM. In contrast, GAT229 binds at the extracellular (EC) ends of TMH2/3, just beneath the EC1 loop. At this site, this compound can act as CB1 PAM only. Finally, these results were successfully validated through the synthesis and biochemical evaluation of a focused library of compounds.
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Affiliation(s)
- Dow P. Hurst
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro North Carolina 27412, United States
| | - Sumanta Garai
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Pushkar M. Kulkarni
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Peter C. Schaffer
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Patricia H. Reggio
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro North Carolina 27412, United States
| | - Ganesh A. Thakur
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
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55
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Tseng CC, Baillie G, Donvito G, Mustafa MA, Juola SE, Zanato C, Massarenti C, Dall'Angelo S, Harrison WTA, Lichtman AH, Ross RA, Zanda M, Greig IR. The Trifluoromethyl Group as a Bioisosteric Replacement of the Aliphatic Nitro Group in CB 1 Receptor Positive Allosteric Modulators. J Med Chem 2019; 62:5049-5062. [PMID: 31050898 DOI: 10.1021/acs.jmedchem.9b00252] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The first generation of CB1 positive allosteric modulators (e.g., ZCZ011) featured a 3-nitroalkyl-2-phenyl-indole structure. Although a small number of drugs include the nitro group, it is generally not regarded as being "drug-like", and this is particularly true for aliphatic nitro groups. There are very few case studies where an appropriate bioisostere replaced a nitro group that had a direct role in binding. This may be indicative of the difficulty of replicating its binding interactions. Herein, we report the design and synthesis of ligands targeting the allosteric binding site on the CB1 cannabinoid receptor, in which a CF3 group successfully replaced the aliphatic NO2. In general, the CF3-bearing compounds were more potent than their NO2 equivalents and also showed improved in vitro metabolic stability. The CF3 analogue (1) with the best balance of properties was selected for further pharmacological evaluation. Pilot in vivo studies showed that (±)-1 has similar activity to (±)-ZCZ011, with both showing promising efficacy in a mouse model of neuropathic pain.
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Affiliation(s)
- Chih-Chung Tseng
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K
| | - Gemma Baillie
- Department of Pharmacology & Toxicology , University of Toronto , Toronto M5S 1A8 , Canada
| | | | | | | | - Chiara Zanato
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K
| | - Chiara Massarenti
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K
| | - Sergio Dall'Angelo
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K
| | - William T A Harrison
- Department of Chemistry , University of Aberdeen , Meston Walk, Aberdeen , AB24 3UE Scotland, U.K
| | | | - Ruth A Ross
- Department of Pharmacology & Toxicology , University of Toronto , Toronto M5S 1A8 , Canada
| | - Matteo Zanda
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K.,C.N.R. - I.C.R.M. , via Mancinelli 7 , 20131 Milan , Italy
| | - Iain R Greig
- Kosterlitz Centre for Therapeutics , University of Aberdeen , Foresterhill, Aberdeen , AB25 2ZD Scotland, U.K
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56
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Moreno E, Cavic M, Krivokuca A, Casadó V, Canela E. The Endocannabinoid System as a Target in Cancer Diseases: Are We There Yet? Front Pharmacol 2019; 10:339. [PMID: 31024307 PMCID: PMC6459931 DOI: 10.3389/fphar.2019.00339] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 03/19/2019] [Indexed: 12/15/2022] Open
Abstract
The endocannabinoid system (ECS) has been placed in the anti-cancer spotlight in the last decade. The immense data load published on its dual role in both tumorigenesis and inhibition of tumor growth and metastatic spread has transformed the cannabinoid receptors CB1 (CB1R) and CB2 (CB2R), and other members of the endocannabinoid-like system, into attractive new targets for the treatment of various cancer subtypes. Although the clinical use of cannabinoids has been extensively documented in the palliative setting, clinical trials on their application as anti-cancer drugs are still ongoing. As drug repurposing is significantly faster and more economical than de novo introduction of a new drug into the clinic, there is hope that the existing pharmacokinetic and safety data on the ECS ligands will contribute to their successful translation into oncological healthcare. CB1R and CB2R are members of a large family of membrane proteins called G protein-coupled receptors (GPCR). GPCRs can form homodimers, heterodimers and higher order oligomers with other GPCRs or non-GPCRs. Currently, several CB1R and CB2R-containing heteromers have been reported and, in cancer cells, CB2R form heteromers with the G protein-coupled chemokine receptor CXCR4, the G protein-coupled receptor 55 (GPR55) and the tyrosine kinase receptor (TKR) human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2). These protein complexes possess unique pharmacological and signaling properties, and their modulation might affect the antitumoral activity of the ECS. This review will explore the potential of the endocannabinoid network in the anti-cancer setting as well as the clinical and ethical pitfalls behind it, and will develop on the value of cannabinoid receptor heteromers as potential new targets for anti-cancer therapies and as prognostic biomarkers.
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Affiliation(s)
- Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Milena Cavic
- Department of Experimental Oncology, Institute for Oncology and Radiology of Serbia, Belgrade, Serbia
| | - Ana Krivokuca
- Department of Experimental Oncology, Institute for Oncology and Radiology of Serbia, Belgrade, Serbia
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Enric Canela
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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57
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Scott CE, Tang Y, Alt A, Burford NT, Gerritz SW, Ogawa LM, Zhang L, Kendall DA. Identification and biochemical analyses of selective CB 2 agonists. Eur J Pharmacol 2019; 854:1-8. [PMID: 30951717 DOI: 10.1016/j.ejphar.2019.03.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/19/2019] [Accepted: 03/28/2019] [Indexed: 12/14/2022]
Abstract
Cannabinoid CB1 and CB2 receptors are activated by Δ9-tetrahydrocannabinol, a psychoactive component of marijuana. The cannabinoid CB1 receptor is primarily located in the brain and is responsible for the psychoactive side effects, whereas the cannabinoid CB2 receptor is located in immune cells and is an attractive target for immune-related maladies. We identify small molecules that selectively bind to the cannabinoid CB2 receptor and can be further developed into therapeutics. The affinity of three molecules, ABK5, ABK6, and ABK7, to the cannabinoid CB2 receptor was determined with radioligand competition binding. The potency of G-protein coupling was determined with GTPγS binding. The three compounds bound selectively to the cannabinoid CB2 receptor, and no binding to the cannabinoid CB1 receptor was detected up to 10 μM. Immunoblotting studies show that the amount of ERK1/2 and MEK phosphorylation increased in a Gi/o-dependent manner. Furthermore, an immune cell line (Jurkat cells) was treated with ABK5, and as a result, inhibited cell proliferation. These three compounds are novel cannabinoid CB2 receptor agonists and hold promise to be further developed to treat inflammation and the often-associated pain.
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Affiliation(s)
- Caitlin E Scott
- Department of Pharmaceutical Sciences, University of Connecticut, 69 N Eagleville Rd, Storrs, CT, 06269, USA
| | - Yaliang Tang
- Department of Pharmaceutical Sciences, University of Connecticut, 69 N Eagleville Rd, Storrs, CT, 06269, USA
| | - Andrew Alt
- Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT, 06492, USA
| | - Neil T Burford
- Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT, 06492, USA
| | - Samuel W Gerritz
- Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT, 06492, USA
| | - Lisa M Ogawa
- Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT, 06492, USA
| | - Litao Zhang
- Bristol-Myers Squibb, Research and Development, 5 Research Parkway, Wallingford, CT, 06492, USA
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, 69 N Eagleville Rd, Storrs, CT, 06269, USA.
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58
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Laprairie RB, Bagher AM, Rourke JL, Zrein A, Cairns EA, Kelly MEM, Sinal CJ, Kulkarni PM, Thakur GA, Denovan-Wright EM. Positive allosteric modulation of the type 1 cannabinoid receptor reduces the signs and symptoms of Huntington's disease in the R6/2 mouse model. Neuropharmacology 2019; 151:1-12. [PMID: 30940536 DOI: 10.1016/j.neuropharm.2019.03.033] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 12/18/2022]
Abstract
Huntington's disease (HD) is an inherited progressive neurodegenerative disease characterized by motor, cognitive, and behavioural changes. One of the earliest changes to occur in HD is a reduction in cannabinoid 1 receptor (CB1) levels in the striatum, which is strongly correlated with HD pathogenesis. CB1 positive allosteric modulators (PAM) enhance receptor affinity for, and efficacy of activation by, orthosteric ligands, including the endocannabinoids anandamide and 2-arachidonoylglycerol. The goal of this study was to determine whether the recently characterized CB1 allosteric modulators GAT211 (racemic), GAT228 (R-enantiomer), and GAT229 (S-enantiomer), affected the signs and symptoms of HD. GAT211, GAT228, and GAT229 were evaluated in normal and HD cell models, and in a transgenic mouse model of HD (7-week-old male R6/2 mice, 10 mg/kg/d, 21 d, i.p.). GAT229 was a CB1 PAM that improved cell viability in HD cells and improved motor coordination, delayed symptom onset, and normalized gene expression in R6/2 HD mice. GAT228 was an allosteric agonist that did not enhance endocannabinoid signaling or change symptom progression in R6/2 mice. GAT211 displayed intermediate effects between its enantiomers. The compounds used here are not drugs, but probe compounds used to determine the potential utility of CB1 PAMs in HD. Changes in gene expression, and not protein, were quantified in R6/2 HD mice because HD pathogenesis is associated with dysregulation of mRNA levels. The data presented here provide the first proof of principle for the use of CB1 PAMs to treat the signs and symptoms of HD.
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Affiliation(s)
- Robert B Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, Canada; Department of Pharmacology, Dalhousie University, Canada
| | - Amina M Bagher
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, King AbdulAziz University,Saudi Arabia; Department of Pharmacology, Dalhousie University, Canada
| | - Jillian L Rourke
- Department of Pharmacology, Dalhousie University, Canada; Department of Chemistry & Biochemistry, Mount Allison University, Canada
| | - Adel Zrein
- Department of Pharmacology, Dalhousie University, Canada
| | | | - Melanie E M Kelly
- Department of Pharmacology, Dalhousie University, Canada; Department of Ophthalmology and Visual Sciences, Dalhousie University, Canada
| | | | - Pushkar M Kulkarni
- Center for Drug Discovery, Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, USA
| | - Ganesh A Thakur
- Center for Drug Discovery, Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, USA
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59
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Lu D, Immadi SS, Wu Z, Kendall DA. Translational potential of allosteric modulators targeting the cannabinoid CB 1 receptor. Acta Pharmacol Sin 2019; 40:324-335. [PMID: 30333554 PMCID: PMC6460365 DOI: 10.1038/s41401-018-0164-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 08/27/2018] [Indexed: 12/11/2022] Open
Abstract
The cannabinoid type-1 (CB1) receptor, a G-protein-coupled receptor, is an attractive target for drug discovery due to its involvement in many physiological processes. Historically, drug discovery efforts targeting the CB1 receptor have focused on the development of orthosteric ligands that interact with the active site to which endogenous cannabinoids bind. Research performed over the last several decades has revealed substantial difficulties in translating CB1 orthosteric ligands into druggable candidates. The difficulty is mainly due to the adverse effects associated with orthosteric CB1 ligands. Recent discoveries of allosteric CB1 modulators provide tremendous opportunities to develop CB1 ligands with novel mechanisms of action; these ligands may potentially improve the pharmacological effects and enhance drug safety in treating the disorders by regulating the functions of the CB1 receptor. In this paper, we review and summarize the complex pharmacological profiles of each class of CB1 allosteric modulators, the development of new classes of CB1 allosteric modulators and the results from in vivo assessments of their therapeutic value.
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Affiliation(s)
- Dai Lu
- Rangel College of Pharmacy, Texas A&M University, Kingsville, TX, 78363, USA.
| | - Sri Sujana Immadi
- Rangel College of Pharmacy, Texas A&M University, Kingsville, TX, 78363, USA
| | - Zhixing Wu
- Rangel College of Pharmacy, Texas A&M University, Kingsville, TX, 78363, USA
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT, 06269, USA
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60
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Pandey P, Roy KK, Doerksen RJ. Negative allosteric modulators of cannabinoid receptor 2: protein modeling, binding site identification and molecular dynamics simulations in the presence of an orthosteric agonist. J Biomol Struct Dyn 2019; 38:32-47. [PMID: 30652534 DOI: 10.1080/07391102.2019.1567384] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Selective activation of the cannabinoid receptor subtype 2 (CB2) shows promise for treating pain, inflammation, multiple sclerosis, cancer, ischemic/reperfusion injury and osteoporosis. Target selectivity and off-target side effects are two major limiting factors for orthosteric ligands, and therefore, the search for allosteric modulators (AMs) is a widely used drug discovery approach. To date, only a limited number of negative CB2 AMs have been identified, possessing only micromolar activity at best, and the CB2 receptor's allosteric site(s) are not well characterized. Herein, we used computational approaches including receptor modeling, site mapping, docking, molecular dynamics (MD) simulations and binding free energy calculations to predict, characterize and validate allosteric sites within the complex of the CB2 receptor with bound orthosteric agonist CP55,940. After docking of known negative CB2 allosteric modulators (NAMs), dihydro-gambogic acid (DHGA) and trans-β-caryophyllene (TBC) (note that TBC also shows agonist activity), at the predicted allosteric sites, the best total complex with CB2, CP55,940 and NAM was embedded into a hydrated lipid bilayer and subjected to a 200 ns MD simulation. The presence of an AM affected the CB2-CP55,940 complex, altering the relative positioning of the toggle switch residues and promoting a strong π-π interaction between Phe1173.36 and Trp2586.48. Binding of either TBC or DHGA to a putative allosteric pocket directly adjacent to the orthosteric ligand reduced the binding free energy of CP55,940, which is consistent with the expected effect of a negative AM. The identified allosteric sites present immense scope for the discovery of novel classes of CB2 AMs.
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Affiliation(s)
- Pankaj Pandey
- Department of BioMolecular Sciences, Division of Medicinal Chemistry, School of Pharmacy, The University of Mississippi, University, MS, USA
| | - Kuldeep K Roy
- Department of BioMolecular Sciences, Division of Medicinal Chemistry, School of Pharmacy, The University of Mississippi, University, MS, USA.,National Institute of Pharmaceutical Education and Research (NIPER), Kolkata, India
| | - Robert J Doerksen
- Department of BioMolecular Sciences, Division of Medicinal Chemistry, School of Pharmacy, The University of Mississippi, University, MS, USA.,Research Institute of Pharmaceutical Sciences, School of Pharmacy, The University of Mississippi, University, MS, USA
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Wold EA, Chen J, Cunningham KA, Zhou J. Allosteric Modulation of Class A GPCRs: Targets, Agents, and Emerging Concepts. J Med Chem 2019; 62:88-127. [PMID: 30106578 PMCID: PMC6556150 DOI: 10.1021/acs.jmedchem.8b00875] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
G-protein-coupled receptors (GPCRs) have been tractable drug targets for decades with over one-third of currently marketed drugs targeting GPCRs. Of these, the class A GPCR superfamily is highly represented, and continued drug discovery for this family of receptors may provide novel therapeutics for a vast range of diseases. GPCR allosteric modulation is an innovative targeting approach that broadens the available small molecule toolbox and is proving to be a viable drug discovery strategy, as evidenced by recent FDA approvals and clinical trials. Numerous class A GPCR allosteric modulators have been discovered recently, and emerging trends such as the availability of GPCR crystal structures, diverse functional assays, and structure-based computational approaches are improving optimization and development. This Perspective provides an update on allosterically targeted class A GPCRs and their disease indications and the medicinal chemistry approaches toward novel allosteric modulators and highlights emerging trends and opportunities in the field.
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Affiliation(s)
- Eric A. Wold
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jianping Chen
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Kathryn A. Cunningham
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jia Zhou
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
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62
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Lafreniere J, Kelly M. Potential for endocannabinoid system modulation in ocular pain and inflammation: filling the gaps in current pharmacological options. Neuronal Signal 2018; 2:NS20170144. [PMID: 32714590 PMCID: PMC7373237 DOI: 10.1042/ns20170144] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 02/06/2023] Open
Abstract
Challenges in the management of ocular pain are an underappreciated topic. Currently available therapeutics lack both efficacy and clear guidelines for their use, with many also possessing unacceptable side effects. Promising novel agents would offer analgesic, anti-inflammatory, and possibly neuroprotective actions; have favorable ocular safety profiles; and show potential in managing neuropathic pain. Growing evidence supports a link between the endocannabinoid system (ECS) and a range of physiological and disease processes, notably those involving inflammation and pain. Both preclinical and clinical data suggest analgesic and anti-inflammatory actions of cannabinoids and ECS-modifying drugs in chronic pain conditions, including those of neuropathic origin. This review will examine existing evidence for the anatomical and physiological basis of ocular pain, specifically, ocular surface disease and the development of chronic ocular pain. The mechanism of action, efficacy, and limitations of currently available treatments will be discussed, and current knowledge related to ECS-modulation of ocular pain and inflammatory disease will be summarized. A perspective will be provided on the future directions of ECS research in terms of developing cannabinoid therapeutics for ocular pain.
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Affiliation(s)
| | - Melanie E.M. Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada
- Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
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63
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Slivicki RA, Xu Z, Kulkarni PM, Pertwee RG, Mackie K, Thakur GA, Hohmann AG. Positive Allosteric Modulation of Cannabinoid Receptor Type 1 Suppresses Pathological Pain Without Producing Tolerance or Dependence. Biol Psychiatry 2018; 84:722-733. [PMID: 28823711 PMCID: PMC5758437 DOI: 10.1016/j.biopsych.2017.06.032] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 06/02/2017] [Accepted: 06/22/2017] [Indexed: 11/28/2022]
Abstract
BACKGROUND Activation of cannabinoid CB1 receptors suppresses pathological pain but also produces unwanted central side effects. We hypothesized that a positive allosteric modulator of CB1 signaling would suppress inflammatory and neuropathic pain without producing cannabimimetic effects or physical dependence. We also asked whether a CB1 positive allosteric modulator would synergize with inhibitors of endocannabinoid deactivation and/or an orthosteric cannabinoid agonist. METHODS GAT211, a novel CB1 positive allosteric modulator, was evaluated for antinociceptive efficacy and tolerance in models of neuropathic and/or inflammatory pain. Cardinal signs of direct CB1-receptor activation were evaluated together with the propensity to induce reward or aversion and physical dependence. Comparisons were made with inhibitors of endocannabinoid deactivation (JZL184, URB597) or an orthosteric cannabinoid agonist (WIN55,212-2). All studies used 4 to 11 subjects per group. RESULTS GAT211 suppressed allodynia induced by complete Freund's adjuvant and the chemotherapeutic agent paclitaxel in wild-type but not CB1 knockout mice. GAT211 did not impede paclitaxel-induced tumor cell line toxicity. GAT211 did not produce cardinal signs of direct CB1-receptor activation in the presence or absence of pathological pain. GAT211 produced synergistic antiallodynic effects with fatty acid amide hydrolase and monoacylglycerol lipase inhibitors in paclitaxel-treated mice. Therapeutic efficacy was preserved over 19 days of chronic dosing with GAT211, but it was not preserved with the monoacylglycerol lipase inhibitor JZL184. The CB1 antagonist rimonabant precipitated withdrawal in mice treated chronically with WIN55,212-2 but not in mice treated with GAT211. GAT211 did not induce conditioned place preference or aversion. CONCLUSIONS Positive allosteric modulation of CB1-receptor signaling shows promise as a safe and effective analgesic strategy that lacks tolerance, dependence, and abuse liability.
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Affiliation(s)
- Richard A. Slivicki
- Program in Neuroscience, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts,Psychological and Brain Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts
| | - Zhili Xu
- Psychological and Brain Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts
| | - Pushkar M. Kulkarni
- Department of Pharmaceutical Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts
| | | | - Ken Mackie
- Program in Neuroscience, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts,Psychological and Brain Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts,Gill Center for Biomolecular Science, Bloomington, Indiana
| | - Ganesh A. Thakur
- Department of Pharmaceutical Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts
| | - Andrea G. Hohmann
- Program in Neuroscience, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts,Psychological and Brain Sciences, Center for Drug Discovery, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts,Gill Center for Biomolecular Science, Bloomington, Indiana
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64
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Saleh N, Hucke O, Kramer G, Schmidt E, Montel F, Lipinski R, Ferger B, Clark T, Hildebrand PW, Tautermann CS. Multiple Binding Sites Contribute to the Mechanism of Mixed Agonistic and Positive Allosteric Modulators of the Cannabinoid CB1 Receptor. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201708764] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Noureldin Saleh
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Berlin, and Berlin Institute of Health; Institute of Medical Physics and Biophysics; Charitéplatz 1 10117 Berlin Germany
| | - Oliver Hucke
- Department for Medicinal Chemistry; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Gert Kramer
- Department for CNS research; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Esther Schmidt
- Department for Drug Discovery Sciences; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Florian Montel
- Department for Medicinal Chemistry; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Radoslaw Lipinski
- Department for Medicinal Chemistry; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Boris Ferger
- Department for CNS research; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
| | - Timothy Clark
- Computer-Chemie-Centrum; Friedrich-Alexander-Universität Erlangen-Nürnberg; Nägelsbachstraße 25 91052 Erlangen Germany
| | - Peter W. Hildebrand
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Berlin, and Berlin Institute of Health; Institute of Medical Physics and Biophysics; Charitéplatz 1 10117 Berlin Germany
- Universität Leipzig; Institute of Medical Physics and Biophysics; Härtelstraße 16-18 04107 Leipzig Germany
| | - Christofer S. Tautermann
- Department for Medicinal Chemistry; Boehringer Ingelheim Pharma GmbH & Co KG; Birkendorfer Straße 65 88397 Biberach an der Riss Germany
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65
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Saleh N, Hucke O, Kramer G, Schmidt E, Montel F, Lipinski R, Ferger B, Clark T, Hildebrand PW, Tautermann CS. Multiple Binding Sites Contribute to the Mechanism of Mixed Agonistic and Positive Allosteric Modulators of the Cannabinoid CB1 Receptor. Angew Chem Int Ed Engl 2018; 57:2580-2585. [PMID: 29314474 DOI: 10.1002/anie.201708764] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 12/23/2017] [Indexed: 12/27/2022]
Abstract
The cannabinoid CB1 receptor (CB1R) is an abundant metabotropic G-protein-coupled receptor that has been difficult to address therapeutically because of CNS side effects exerted by orthosteric drug candidates. Recent efforts have focused on developing allosteric modulators that target CB1R. Compounds from the recently discovered class of mixed agonistic and positive allosteric modulators (Ago-PAMs) based on 2-phenylindoles have shown promising functional and binding properties as CB1R ligands. Here, we identify binding modes of both the CP 55,940 agonist and GAT228, a 2-phenylindole allosteric modulator, by using our metadynamics simulation protocol, and quantify their affinity and cooperativity by atomistic simulations. We demonstrate the involvement of multiple adjunct binding sites in the Ago-PAM characteristics of the 2-phenylindole modulators and explain their ability to compete with orthosteric agonists at higher concentrations. We validate these results experimentally by showing the contribution of multiple sites on the allosteric binding of ZCZ011, another homologous member of the class, together with the orthosteric agonist.
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Affiliation(s)
- Noureldin Saleh
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Berlin, and Berlin Institute of Health, Institute of Medical Physics and Biophysics, Charitéplatz 1, 10117, Berlin, Germany
| | - Oliver Hucke
- Department for Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Gert Kramer
- Department for CNS research, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Esther Schmidt
- Department for Drug Discovery Sciences, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Florian Montel
- Department for Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Radoslaw Lipinski
- Department for Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Boris Ferger
- Department for CNS research, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
| | - Timothy Clark
- Computer-Chemie-Centrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße 25, 91052, Erlangen, Germany
| | - Peter W Hildebrand
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Berlin, and Berlin Institute of Health, Institute of Medical Physics and Biophysics, Charitéplatz 1, 10117, Berlin, Germany.,Universität Leipzig, Institute of Medical Physics and Biophysics, Härtelstraße 16-18, 04107, Leipzig, Germany
| | - Christofer S Tautermann
- Department for Medicinal Chemistry, Boehringer Ingelheim Pharma GmbH & Co KG, Birkendorfer Straße 65, 88397, Biberach an der Riss, Germany
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66
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Dopart R, Lu D, Lichtman AH, Kendall DA. Allosteric modulators of cannabinoid receptor 1: developing compounds for improved specificity. Drug Metab Rev 2018; 50:3-13. [PMID: 29355030 PMCID: PMC6134837 DOI: 10.1080/03602532.2018.1428342] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The cannabinoid receptor 1 (CB1) is a G protein-coupled receptor (GPCR) that is located primarily in the central nervous system. CB1 is a therapeutic target which may impact pathways to mediate pain, neurodegenerative disorders, hunger, and drug-seeking behavior. Despite these benefits, development of orthosteric therapeutic compounds, which target the endogenous ligand-binding site of CB1, has been challenging due to detrimental side effects including psychoactivity, depression, and suicidal thoughts. However, CB1 also has an allosteric binding site(s), which is topographically distinct from the orthosteric site. Allosteric modulation of CB1 has a number of potential advantages including providing a mechanism for more precise control of downstream pathways and circumventing these side effects. In this review, we summarize the concept of allosteric modulation and focus on the structure-activity relationship studies of the well-characterized allosteric modulators, ORG27569 and PSNCBAM-1 and their derivatives, and a few other recent modulators. We review studies on the properties of these modulators on CB1 signaling in cells and their effects in vivo. While many current allosteric modulators also produce complex outcomes, they provide new advances for the design of CB1 centered therapeutics.
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Affiliation(s)
- Rachel Dopart
- a Department of Pharmaceutical Sciences , University of Connecticut , Storrs , CT , USA
| | - Dai Lu
- b Rangel College of Pharmacy , Health Science Center, Texas A&M University , Kingsville , TX , USA
| | - Aron H Lichtman
- c Department of Pharmacology and Toxicology , Virginia Commonwealth University , Richmond , VA , USA
| | - Debra A Kendall
- a Department of Pharmaceutical Sciences , University of Connecticut , Storrs , CT , USA
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Abstract
Allosteric modulation of the type 1 cannabinoid receptor (CB1R) holds great therapeutic potential. This is because allosteric modulators do not possess intrinsic efficacy, but instead augment (positive allosteric modulation) or diminish (negative allosteric modulation) the receptor's response to endogenous ligand. Consequently, CB1R allosteric modulators have an effect ceiling which allows for the tempering of CB1R signaling without the desensitization, tolerance, dependence, and psychoactivity associated with orthosteric compounds. Pain, movement disorders, epilepsy, obesity are all potential therapeutic targets for CB1R allosteric modulation. Several challenges exist for the development of CB1R allosteric modulators, such as receptor subtype specificity, translation to in vivo systems, and mixed allosteric/agonist/inverse agonist activity. Despite these challenges, elucidation of crystal structures of CB1R and compound design based on structure-activity relationships will advance the field. In this review, we will cover recent progress for CB1R allosteric modulators and discuss the future promise of this research.
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Affiliation(s)
- Mariam Alaverdashvili
- a College of Pharmacy and Nutrition , University of Saskatchewan , Saskatoon , Canada
| | - Robert B Laprairie
- a College of Pharmacy and Nutrition , University of Saskatchewan , Saskatoon , Canada
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68
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Paronis CA, Chopda GR, Vemuri K, Zakarian AS, Makriyannis A, Bergman J. Long-Lasting In Vivo Effects of the Cannabinoid CB1 Antagonist AM6538. J Pharmacol Exp Ther 2018; 364:485-493. [PMID: 29311110 DOI: 10.1124/jpet.117.245647] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/04/2018] [Indexed: 11/22/2022] Open
Abstract
AM6538 is a cannabinoid antagonist that binds CB1 receptors expressed in HEK-293 cells in a wash-resistant manner. The effects of AM6538 in live animals has not previously been established. We characterized the antagonist effects of AM6538 in male mice, using a warm-water tail-withdrawal assay, and in male squirrel monkeys trained to discriminate the CB1 agonist AM4054 from vehicle. The cannabinoid agonists WIN 55,212, Δ9-tetrahydrocannabinol (THC), and AM4054 all produced 100% maximum possible antinociceptive effects in mice following vehicle pretreatment. One-hour pretreatment with increasing doses of AM6538 (0.1-10 mg/kg) produced first rightward, then downward shifts of the agonist dose-effect functions. Rimonabant, 1-10 mg/kg, produced parallel rightward shifts of the AM4054 dose-effect functions, and baseline effects of AM4054 were nearly recovered within 24 hours following 10 mg/kg of rimonabant. In contrast, in mice treated with 10 mg/kg of AM6538, antagonism of THC or AM4054 lasted up to 7 days. AM6538 also antagonized the discriminative stimulus effects of AM4054 in squirrel monkeys in a dose-related manner, and the effects of 3.2 mg/kg of AM6538 endured for more than 7 days. The effective reduction in CB1 receptor reserve was used to calculate the relative efficacy (tau values) of WIN 55,212, THC, and AM4054 in mice and of AM4054 monkeys, with results indicating that THC has a lower efficacy than WIN 55,212 or AM4054 in mice. These results demonstrate that AM6538 is a long-acting CB antagonist in vivo, and further suggest that differences in CB efficacy can be revealed in behavioral assays following AM6538 treatment.
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Affiliation(s)
- Carol A Paronis
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
| | - Girish R Chopda
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
| | - Kiran Vemuri
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
| | - Ani S Zakarian
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
| | - Alexandros Makriyannis
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
| | - Jack Bergman
- Center for Drug Discovery (C.A.P., K.V., A.M.) and Department of Pharmaceutical Sciences (C.A.P., G.R.C., A.M.), Northeastern University, Boston, Massachusetts; and Preclinical Pharmacology Program, McLean Hospital, Belmont, Massachusetts (C.A.P., A.S.Z., J.B.)
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69
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Enantiomer-specific positive allosteric modulation of CB 1 signaling in autaptic hippocampal neurons. Pharmacol Res 2017; 129:475-481. [PMID: 29158048 DOI: 10.1016/j.phrs.2017.11.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 10/27/2017] [Accepted: 11/16/2017] [Indexed: 11/20/2022]
Abstract
The cannabinoid signaling system is found throughout the CNS and its involvement in several pathological processes makes it an attractive therapeutic target. Because orthosteric CB1 cannabinoid receptor ligands have undesirable adverse effects there has been great interest in the development of allosteric modulators - both negative (NAMs) and positive (PAMs) - of these receptors. NAMs of CB1 appeared first on the scene, followed more recently by PAMs. Because allosteric modulation can vary depending on the orthosteric ligand it is important to study their function in a system that employs endogenous cannabinoids. We have recently surveyed first generation NAMs using cultured autaptic hippocampal neurons. These neurons express depolarization induced suppression of excitation (DSE), a form of synaptic plasticity that is mediated by CB1 and 2-arachidonoyl glycerol (2-AG); they are therefore an excellent neuronal model of endogenous cannabinoid signaling in which to test CB1 modulators. In this study we find that while two related compounds, GAT211 and ZCZ011, each show PAM-like responses in autaptic hippocampal neurons, they also exhibit complex pharmacology. Notably we were able to separate the PAM- and agonist-like responses of GAT211 by examining the enantiomers of this racemic compound: GAT228 and GAT229. We find that GAT229 exhibits PAM-like behavior while GAT228 appears to directly activate the CB1 receptor. Both GAT229 and ZCZ011 represent the first PAMs that we have found to be effective in using this 2-AG utilizing neuronal model system. Because these compounds may exhibit both probe selectivity and biased signaling it will be important to test them with anandamide as well as other signaling pathways.
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Khurana L, Mackie K, Piomelli D, Kendall DA. Modulation of CB1 cannabinoid receptor by allosteric ligands: Pharmacology and therapeutic opportunities. Neuropharmacology 2017; 124:3-12. [PMID: 28527758 PMCID: PMC5540789 DOI: 10.1016/j.neuropharm.2017.05.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/12/2017] [Accepted: 05/16/2017] [Indexed: 02/03/2023]
Abstract
Cannabinoid pharmacology has been intensely studied because of cannabis' pervasive medicinal and non-medicinal uses as well as for the therapeutic potential of cannabinoid-based drugs for the treatment of pain, anxiety, substance abuse, obesity, cancer and neurodegenerative disorders. The identification of allosteric modulators of the cannabinoid receptor 1 (CB1) has given a new direction to the development of cannabinoid-based therapeutics due to the many advantages offered by targeting allosteric site(s). Allosteric receptor modulators hold potential to develop subtype-specific and pathway-specific therapeutics. Here we briefly discuss the first-generation of allosteric modulators of CB1 receptor, their structure-activity relationships, signaling pathways and the allosteric binding site(s) on the CB1 receptor. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".
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Affiliation(s)
- Leepakshi Khurana
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269, United States
| | - Ken Mackie
- Gill Center and Departmental of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, United States
| | - Daniele Piomelli
- Department of Anatomy and Neurobiology, University of California, Irvine, CA 92697, United States; Department of Biological Chemistry, University of California, Irvine, CA 92697, United States
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269, United States.
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Woodhams SG, Chapman V, Finn DP, Hohmann AG, Neugebauer V. The cannabinoid system and pain. Neuropharmacology 2017; 124:105-120. [PMID: 28625720 PMCID: PMC5785108 DOI: 10.1016/j.neuropharm.2017.06.015] [Citation(s) in RCA: 176] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/31/2017] [Accepted: 06/14/2017] [Indexed: 01/20/2023]
Abstract
Chronic pain states are highly prevalent and yet poorly controlled by currently available analgesics, representing an enormous clinical, societal, and economic burden. Existing pain medications have significant limitations and adverse effects including tolerance, dependence, gastrointestinal dysfunction, cognitive impairment, and a narrow therapeutic window, making the search for novel analgesics ever more important. In this article, we review the role of an important endogenous pain control system, the endocannabinoid (EC) system, in the sensory, emotional, and cognitive aspects of pain. Herein, we briefly cover the discovery of the EC system and its role in pain processing pathways, before concentrating on three areas of current major interest in EC pain research; 1. Pharmacological enhancement of endocannabinoid activity (via blockade of EC metabolism or allosteric modulation of CB1receptors); 2. The EC System and stress-induced modulation of pain; and 3. The EC system & medial prefrontal cortex (mPFC) dysfunction in pain states. Whilst we focus predominantly on the preclinical data, we also include extensive discussion of recent clinical failures of endocannabinoid-related therapies, the future potential of these approaches, and important directions for future research on the EC system and pain. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".
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Affiliation(s)
- Stephen G Woodhams
- Arthritis UK Pain Centre, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom.
| | - Victoria Chapman
- Arthritis UK Pain Centre, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - David P Finn
- Pharmacology & Therapeutics, School of Medicine, Galway Neuroscience Centre and Centre for Pain Research, NCBES, National University of Ireland Galway, University Road, Galway, Ireland
| | - Andrea G Hohmann
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA; Program in Neuroscience, Indiana University, Bloomington, IN, USA; Interdisciplinary Biochemistry Graduate Program, Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA; Gill Center for Biomolecular Science, Indiana University, Bloomington, IN, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Zubrzycki M, Janecka A, Liebold A, Ziegler M, Zubrzycka M. Effects of centrally administered endocannabinoids and opioids on orofacial pain perception in rats. Br J Pharmacol 2017; 174:3780-3789. [PMID: 28771697 DOI: 10.1111/bph.13970] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 07/12/2017] [Accepted: 07/27/2017] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Endocannabinoids and opioids play a vital role in mediating pain-induced analgesia. The specific effects of these compounds within the orofacial region are largely unknown. In this study, we tried to determine whether an increase in cannabinoid and opioid concentration in the CSF affects impulse transmission between the motor centres localized in the vicinity of the third and fourth cerebral ventricles. EXPERIMENTAL APPROACH The study objectives were realized on rats using a method that allows the recording of the amplitude of evoked tongue jerks (ETJ) in response to noxious tooth pulp stimulation. The amplitude of ETJ was a measure of the effect of neurotransmitters on neural structures. KEY RESULTS Perfusion of cerebral ventricles with anandamide (AEA), endomorphin-2 (EM-2), URB597, an inhibitor of fatty acid amide hydrolase (FAAH) and JZL195, a dual inhibitor of FAAH and monoacylglycerol lipase (MAGL) reduced the ETJ amplitude. The antinociceptive effect of AEA, EM-2, URB597 and JZL195 was blocked by CB1 receptor antagonist, AM251 and by μ receptor-antagonist, β-funaltrexamine. In contrast to AEA, 2-arachidonoylglycerol alone did not decrease ETJ amplitude. CONCLUSIONS AND IMPLICATIONS We demonstrated that in the orofacial area, analgesic activity is modulated by AEA and that EM-2-induced antinociception was mediated by μ and CB1 receptors. The action of AEA and EM-2 is tightly regulated by FAAH and FAAH/MAGL, by preventing the breakdown of endogenous cannabinoids in regions where they are produced on demand. Therefore, the current findings support the therapeutic potential of FAAH and FAAH/MAGL inhibitors as novel pharmacotherapeutic agents for orofacial pain.
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Affiliation(s)
- Marek Zubrzycki
- Department of Cardiovascular and Thoracic Surgery, University of Ulm, Ulm, Germany
| | - Anna Janecka
- Department of Biomolecular Chemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
| | - Andreas Liebold
- Department of Cardiovascular and Thoracic Surgery, University of Ulm, Ulm, Germany
| | - Mechthild Ziegler
- Department of Cardiac Anesthesiology, University Hospital Ulm, Ulm, Germany
| | - Maria Zubrzycka
- Department of Cardiovascular Physiology, Interdepartmental Chair of Experimental and Clinical Physiology, Medical University of Lodz, Lodz, Poland
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Nguyen T, German N, Decker AM, Langston TL, Gamage TF, Farquhar CE, Li JX, Wiley JL, Thomas BF, Zhang Y. Novel Diarylurea Based Allosteric Modulators of the Cannabinoid CB1 Receptor: Evaluation of Importance of 6-Pyrrolidinylpyridinyl Substitution. J Med Chem 2017; 60:7410-7424. [PMID: 28792219 DOI: 10.1021/acs.jmedchem.7b00707] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Allosteric modulators of the cannabinoid CB1 receptor have recently been reported as an alternative approach to modulate the CB1 receptor for therapeutic benefits. In this study, we report the design and synthesis of a series of diarylureas derived from PSNCBAM-1 (2). Similar to 2, these diarylureas dose-dependently inhibited CP55,940-induced intracellular calcium mobilization and [35S]GTP-γ-S binding while enhancing [3H]CP55,940 binding to the CB1 receptor. Structure-activity relationship studies revealed that the pyridinyl ring of 2 could be replaced by other aromatic rings and the pyrrolidinyl ring is not required for CB1 allosteric modulation. 34 (RTICBM-74) had similar potencies as 2 in all in vitro assays but showed significantly improved metabolic stability to rat liver microsomes. More importantly, 34 was more effective than 2 in attenuating the reinstatement of extinguished cocaine-seeking behavior in rats, demonstrating the potential of this diarylurea series as promising candidates for the development of relapse treatment of cocaine addiction.
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Affiliation(s)
- Thuy Nguyen
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Nadezhda German
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Ann M Decker
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Tiffany L Langston
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Thomas F Gamage
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Charlotte E Farquhar
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, University at Buffalo, the State University of New York , Buffalo, New York 14214, United States
| | - Jenny L Wiley
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Brian F Thomas
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
| | - Yanan Zhang
- Research Triangle Institute , Research Triangle Park, North Carolina 27709, United States
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Cairns EA, Szczesniak AM, Straiker AJ, Kulkarni PM, Pertwee RG, Thakur GA, Baldridge WH, Kelly MEM. The In Vivo Effects of the CB 1-Positive Allosteric Modulator GAT229 on Intraocular Pressure in Ocular Normotensive and Hypertensive Mice. J Ocul Pharmacol Ther 2017; 33:582-590. [PMID: 28719234 DOI: 10.1089/jop.2017.0037] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE Orthosteric cannabinoid receptor 1 (CB1) activation leads to decreases in intraocular pressure (IOP). However, use of orthosteric CB1 agonists chronically has several disadvantages, limiting their usefulness as clinically relevant drugs. Allosteric modulators interact with topographically distinct sites to orthosteric ligands and may be useful to circumvent some of these disadvantages. The purpose of this study was to investigate the effects of the novel CB1-positive allosteric modulator (PAM) GAT229 on IOP. METHODS IOP was measured using rebound tonometry in anesthetized normotensive C57Bl/6 mice and in a genetic model of ocular hypertension [nose, eyes, ears (nee) mice] before drug administration, and at 1, 6, and 12 h thereafter. RESULTS In normotensive mice, topical administration of 5 μL GAT229 alone at either 0.2% or 2% did not reduce IOP. However, a subthreshold dose (0.25%) of the nonselective orthosteric CB1 agonist WIN 55,212-2, when combined with 0.2% GAT229, significantly reduced IOP compared with vehicle at 6 and 12 h. Similarly, combination of subthreshold Δ9-tetrahydrocannabinol (a nonselective orthosteric CB1 agonist; 1 mg/kg) with topical 0.2% GAT229 produced IOP lowering at 6 h. In nee mice, administration of topical 0.2% GAT229 or 10 mg/kg GAT229 alone was sufficient to lower IOP at 6 and 12 h, and 12 h, respectively. CONCLUSIONS The CB1 PAM GAT229 reduces IOP in ocular hypertensive mice and enhanced CB1-mediated IOP reduction when combined with subthreshold CB1 orthosteric ligands in normotensive mice. Administration of CB1 PAMs may provide a novel approach to reduce IOP with fewer of the disadvantages associated with orthosteric CB1 activation.
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Affiliation(s)
- Elizabeth A Cairns
- 1 Department of Pharmacology, Dalhousie University , Halifax, Nova Scotia, Canada
| | | | - Alex J Straiker
- 2 Department of Psychological and Brain Sciences, Indiana University , Bloomington, Indiana
| | - Pushkar M Kulkarni
- 3 Department of Pharmaceutical Sciences School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts
| | - Roger G Pertwee
- 4 School of Medicine, Medical Sciences, and Nutrition, Institute of Medical Sciences, University of Aberdeen , Aberdeen, Scotland
| | - Ganesh A Thakur
- 3 Department of Pharmaceutical Sciences School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts
| | - William H Baldridge
- 5 Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia, Canada .,6 Department of Ophthalmology and Visual Sciences, Dalhousie University , Halifax, Nova Scotia, Canada
| | - Melanie E M Kelly
- 1 Department of Pharmacology, Dalhousie University , Halifax, Nova Scotia, Canada .,6 Department of Ophthalmology and Visual Sciences, Dalhousie University , Halifax, Nova Scotia, Canada
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Kulkarni AR, Garai S, Janero DR, Thakur GA. Design and Synthesis of Cannabinoid 1 Receptor (CB1R) Allosteric Modulators: Drug Discovery Applications. Methods Enzymol 2017; 593:281-315. [PMID: 28750808 DOI: 10.1016/bs.mie.2017.06.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Also expressed in various peripheral tissues, the type-1 cannabinoid receptor (CB1R) is the predominant G protein-coupled receptor (GPCR) in brain, where it is responsible for retrograde control of neurotransmitter release. Cellular signaling mediated by CB1R is involved in numerous physiological processes, and pharmacological CB1R modulation is considered a tenable therapeutic approach for diseases ranging from substance-use disorders and glaucoma to metabolic syndrome. Despite the design and synthesis of a variety of bioactive small molecules targeted to the CB1R orthosteric ligand-binding site, the potential of CB1R as a therapeutic GPCR has been largely unrealized due to adverse events associated with typical orthosteric CB1R agonists and antagonists/inverse agonists. Modulation of CB1R-mediated signal transmission by targeting alternative allosteric ligand-binding site(s) on the receptor has garnered interest as a potentially safer and more effective therapeutic modality. This chapter highlights the design and synthesis of novel, pharmacologically active CB1R allosteric modulators and emphasizes how their molecular properties and the positive and negative allosteric control they exert can lead to improved CB1R-targeted pharmacotherapeutics, as well as designer covalent probes that can be used to map CB1R allosteric binding domains and inform structure-based drug design.
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Affiliation(s)
- Abhijit R Kulkarni
- School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, United States
| | - Sumanta Garai
- School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, United States
| | - David R Janero
- School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, United States; Center for Drug Discovery, Northeastern University, Boston, MA, United States; College of Science, Northeastern University, Boston, MA, United States; Health Sciences Entrepreneurs, Northeastern University, Boston, MA, United States
| | - Ganesh A Thakur
- School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, United States.
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Abstract
G protein-coupled receptors, such as the cannabinoid type 1 receptor (CB1R), have been shown to interact with multiple binding partners to transmit signals. In both transfected cell systems and in endogenously expressing cell lines, CB1R signaling has been described as multifaceted. The question remains as to how this highly widely expressed receptor signals in a given cell at a given time in vivo. The concept of functional selectivity, or biased agonism, describes the ability of an agonist to engage the receptor in a manner that preferentially engages certain signaling interactions (e.g., G proteins) over others (e.g., β-arrestins), presumably by stabilizing certain receptor conformations. There is growing interest in using such properties of ligands to direct signaling downstream of CB1R toward desirable therapeutic outcomes and to avoid adverse side effects. While it is not currently clear what pathways should be engaged and which should be avoided, the development of biased agonist tool compounds will aid in answering these questions. In this chapter, we discuss the approaches and caveats to assessing biased agonism at the CB1R.
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Affiliation(s)
| | - Edward L Stahl
- The Scripps Research Institute, Jupiter, FL, United States
| | - Laura M Bohn
- The Scripps Research Institute, Jupiter, FL, United States.
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Abstract
The cannabinoid CB1 receptor is abundant in the central nervous system and regulates neuronal transmission and other key physiological processes including those leading to pain, inflammation, memory, and feeding behavior. CB1 is activated by the endogenous ligands, arachidonoyl ethanolamine and 2-arachidonoyl glycerol, by various synthetic ligands (e.g., CP55940), and by Δ9-tetrahydrocannabinol, the psychoactive component of Cannabis sativa. These CB1 ligands are orthosteric and transduce downstream signals by binding CB1 and primarily inducing Gi coupling, but Gs and β-arrestin coupling are also possible. Recently, allosteric modulators for CB1 were discovered that bind to topographically distinct sites and can noncompetitively impact the potency and efficacy of orthosteric compounds. These offer the exciting potential for mechanistic analyses and for developing therapeutics. Yet, it is critical to elucidate whether a compound is a positive allosteric modulator or a negative allosteric modulator of orthosteric ligand-induced CB1 profiles to understand pathway specificity and ameliorate diseases. In this chapter, we present equilibrium and kinetic binding analysis to reveal the impact of allosteric modulators on CB1. Also described are activities consistent with CB1 activation (or inactivation) and include cellular internalization of CB1 and downstream signaling patterns. Since many CB1 allosteric modulators do not enhance G protein coupling, it is critical to distinguish CB1 activation and biased signaling patterns via β-arrestin from CB1 inactivation. These strategies can illuminate pathway specificity and are valuable for the fine-tuning of CB1 function.
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