1
|
Ford AC, Vanner S, Kashyap PC, Nasser Y. Chronic Visceral Pain: New Peripheral Mechanistic Insights and Resulting Treatments. Gastroenterology 2024; 166:976-994. [PMID: 38325759 PMCID: PMC11102851 DOI: 10.1053/j.gastro.2024.01.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 11/15/2023] [Accepted: 01/05/2024] [Indexed: 02/09/2024]
Abstract
Chronic visceral pain is one of the most common reasons for patients with gastrointestinal disorders, such as inflammatory bowel disease or disorders of brain-gut interaction, to seek medical attention. It represents a substantial burden to patients and is associated with anxiety, depression, reductions in quality of life, and impaired social functioning, as well as increased direct and indirect health care costs to society. Unfortunately, the diagnosis and treatment of chronic visceral pain is difficult, in part because our understanding of the underlying pathophysiologic basis is incomplete. In this review, we highlight recent advances in peripheral pain signaling and specific physiologic and pathophysiologic preclinical mechanisms that result in the sensitization of peripheral pain pathways. We focus on preclinical mechanisms that have been translated into treatment approaches and summarize the current evidence base for directing treatment toward these mechanisms of chronic visceral pain derived from clinical trials. The effective management of chronic visceral pain remains of critical importance for the quality of life of suffers. A deeper understanding of peripheral pain mechanisms is necessary and may provide the basis for novel therapeutic interventions.
Collapse
Affiliation(s)
- Alexander C Ford
- Leeds Institute of Medical Research at St. James's, University of |Leeds, Leeds, United Kingdom; Leeds Gastroenterology Institute, Leeds Teaching Hospitals National Health Service Trust, Leeds, United Kingdom
| | - Stephen Vanner
- Gastrointestinal Diseases Research Unit, Kingston General Hospital, Queen's University, Kingston, Ontario, Canada
| | - Purna C Kashyap
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, Minnesota
| | - Yasmin Nasser
- Snyder Institute for Chronic Diseases, Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
| |
Collapse
|
2
|
Brierley SM, Greenwood-Van Meerveld B, Sarnelli G, Sharkey KA, Storr M, Tack J. Targeting the endocannabinoid system for the treatment of abdominal pain in irritable bowel syndrome. Nat Rev Gastroenterol Hepatol 2023; 20:5-25. [PMID: 36168049 DOI: 10.1038/s41575-022-00682-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/16/2022] [Indexed: 12/27/2022]
Abstract
The management of visceral pain in patients with disorders of gut-brain interaction, notably irritable bowel syndrome, presents a considerable clinical challenge, with few available treatment options. Patients are increasingly using cannabis and cannabinoids to control abdominal pain. Cannabis acts on receptors of the endocannabinoid system, an endogenous system of lipid mediators that regulates gastrointestinal function and pain processing pathways in health and disease. The endocannabinoid system represents a logical molecular therapeutic target for the treatment of pain in irritable bowel syndrome. Here, we review the physiological and pathophysiological functions of the endocannabinoid system with a focus on the peripheral and central regulation of gastrointestinal function and visceral nociception. We address the use of cannabinoids in pain management, comparing them to other treatment modalities, including opioids and neuromodulators. Finally, we discuss emerging therapeutic candidates targeting the endocannabinoid system for the treatment of pain in irritable bowel syndrome.
Collapse
Affiliation(s)
- Stuart M Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Bedford Park, South Australia, Australia.,Hopwood Centre for Neurobiology, Lifelong Health, South Australian Health and Medical Research Institute, North Terrace, Adelaide, South Australia, Australia
| | | | - Giovanni Sarnelli
- Department of Clinical Medicine and Surgery, University of Naples "Federico II", Naples, Italy
| | - Keith A Sharkey
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. .,Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. .,Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
| | - Martin Storr
- Department of Medicine, Ludwig-Maximilians University, Munich, Germany.,Zentrum für Endoskopie, Starnberg, Germany
| | - Jan Tack
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| |
Collapse
|
3
|
Burillo-Putze G, Richards JR, Rodríguez-Jiménez C, Sanchez-Agüera A. Pharmacological management of cannabinoid hyperemesis syndrome: an update of the clinical literature. Expert Opin Pharmacother 2022; 23:693-702. [DOI: 10.1080/14656566.2022.2049237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | - John R. Richards
- Department of Emergency Medicine, University of California, Davis Medical Center, Sacramento, CA, USA
| | - Consuelo Rodríguez-Jiménez
- Facultad de Ciencias de la Salud, Universidad Europea de Canarias, Tenerife, Spain
- Clinical Pharmacology Department, Hospital Universitario de Canarias, Tenerife, Spain
| | | |
Collapse
|
4
|
Castro J, Garcia-Caraballo S, Maddern J, Schober G, Lumsden A, Harrington A, Schmiel S, Lindstrom B, Adams J, Brierley SM. Olorinab (APD371), a peripherally acting, highly selective, full agonist of the cannabinoid receptor 2, reduces colitis-induced acute and chronic visceral hypersensitivity in rodents. Pain 2022; 163:e72-e86. [PMID: 33863856 PMCID: PMC8675055 DOI: 10.1097/j.pain.0000000000002314] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 03/12/2021] [Accepted: 04/02/2021] [Indexed: 11/25/2022]
Abstract
ABSTRACT Abdominal pain is a key symptom of inflammatory bowel disease and irritable bowel syndrome, for which there are inadequate therapeutic options. We tested whether olorinab-a highly selective, full agonist of the cannabinoid receptor 2 (CB2)-reduced visceral hypersensitivity in models of colitis and chronic visceral hypersensitivity (CVH). In rodents, colitis was induced by intrarectal administration of nitrobenzene sulfonic acid derivatives. Control or colitis animals were administered vehicle or olorinab (3 or 30 mg/kg) twice daily by oral gavage for 5 days, starting 1 day before colitis induction. Chronic visceral hypersensitivity mice were administered olorinab (1, 3, 10, or 30 mg/kg) twice daily by oral gavage for 5 days, starting 24 days after colitis induction. Visceral mechanosensitivity was assessed in vivo by quantifying visceromotor responses (VMRs) to colorectal distension. Ex vivo afferent recordings determined colonic nociceptor firing evoked by mechanical stimuli. Colitis and CVH animals displayed significantly elevated VMRs to colorectal distension and colonic nociceptor hypersensitivity. Olorinab treatment significantly reduced VMRs to control levels in colitis and CVH animals. In addition, olorinab reduced nociceptor hypersensitivity in colitis and CVH states in a concentration- and CB2-dependent manner. By contrast, olorinab did not alter VMRs nor nociceptor responsiveness in control animals. Cannabinoid receptor 2 mRNA was detected in colonic tissue, particularly within epithelial cells, and dorsal root ganglia, with no significant differences between healthy, colitis, and CVH states. These results demonstrate that olorinab reduces visceral hypersensitivity through CB2 agonism in animal models, suggesting that olorinab may provide a novel therapy for inflammatory bowel disease- and irritable bowel syndrome-associated abdominal pain.
Collapse
Affiliation(s)
- Joel Castro
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| | - Sonia Garcia-Caraballo
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| | - Jessica Maddern
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| | - Gudrun Schober
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| | - Amanda Lumsden
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Andrea Harrington
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| | - Shirdi Schmiel
- Arena Pharmaceuticals, Inc, San Diego, CA, United States
| | | | - John Adams
- Arena Pharmaceuticals, Inc, San Diego, CA, United States
| | - Stuart M. Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute (FHMRI), Flinders University, Bedford Park, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
- Discipline of Medicine, University of Adelaide, North Terrace, Adelaide, South Australia, Australia
| |
Collapse
|
5
|
Christie S, Brookes S, Zagorodnyuk V. Endocannabinoids in Bladder Sensory Mechanisms in Health and Diseases. Front Pharmacol 2021; 12:708989. [PMID: 34290614 PMCID: PMC8287826 DOI: 10.3389/fphar.2021.708989] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 06/23/2021] [Indexed: 01/23/2023] Open
Abstract
The recent surge in research on cannabinoids may have been fueled by changes in legislation in several jurisdictions, and by approval for the use of cannabinoids for treatment of some chronic diseases. Endocannabinoids act largely, but not exclusively on cannabinoid receptors 1 and 2 (CBR1 and CBR2) which are expressed in the bladder mainly by the urothelium and the axons and endings of motor and sensory neurons. A growing body of evidence suggests that endocannabinoid system constitutively downregulates sensory bladder function during urine storage and micturition, under normal physiological conditions. Similarly, exogenous cannabinoid agonists have potent modulatory effects, as do inhibitors of endocannabinoid inactivation. Results suggest a high potential of cannabinoids to therapeutically ameliorate lower urinary tract symptoms in overactive bladder and painful bladder syndromes. At least part of this may be mediated via effects on sensory nerves, although actions on efferent nerves complicate interpretation. The sensory innervation of bladder is complex with at least eight classes identified. There is a large gap in our knowledge of the effects of endocannabinoids and synthetic agonists on different classes of bladder sensory neurons. Future studies are needed to reveal the action of selective cannabinoid receptor 2 agonists and/or peripherally restricted synthetic cannabinoid receptor 1 agonists on bladder sensory neurons in animal models of bladder diseases. There is significant potential for these novel therapeutics which are devoid of central nervous system psychotropic actions, and which may avoid many of the side effects of current treatments for overactive bladder and painful bladder syndromes.
Collapse
Affiliation(s)
- Stewart Christie
- Discipline of Human Physiology, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, SA, Australia
| | - Simon Brookes
- Discipline of Human Physiology, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, SA, Australia
| | - Vladimir Zagorodnyuk
- Discipline of Human Physiology, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, Adelaide, SA, Australia
| |
Collapse
|
6
|
Yacyshyn BR, Hanauer S, Klassen P, English BA, Stauber K, Barish CF, Gilder K, Turner S, Higgins PDR. Safety, Pharmacokinetics, and Efficacy of Olorinab, a Peripherally Acting, Highly Selective, Full Agonist of the Cannabinoid Receptor 2, in a Phase 2a Study of Patients With Chronic Abdominal Pain Associated With Crohn's Disease. CROHN'S & COLITIS 360 2020; 3:otaa089. [PMID: 36777064 PMCID: PMC9802051 DOI: 10.1093/crocol/otaa089] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Indexed: 11/14/2022] Open
Abstract
Background This randomized, open-label phase 2a study investigated the safety/tolerability, pharmacokinetics, and efficacy of olorinab-a highly selective, peripherally acting, full agonist of the cannabinoid receptor 2-in patients with Crohn's disease (CD) experiencing abdominal pain. Methods Eligible subjects 18-80 years of age with quiescent to mildly active CD were randomized to receive olorinab 25 or 100 mg three times daily for 8 weeks. The primary objective was to assess safety/tolerability. Results Fourteen subjects received olorinab 25 mg (N = 6) or 100 mg (N = 8). Ten subjects [4 (67%) in the 25-mg group and 6 (75%) in the 100-mg group] reported a total of 34 treatment-emergent adverse events (TEAEs; 32 grade 1/2, not serious events; 2 grade 3, serious, not treatment-related events). No dose reductions or discontinuations due to TEAEs or deaths were reported. Dose-proportional increases in olorinab exposure from 25 to 100 mg were observed, with minimal accumulation at both doses. At week 8, the mean (SD) change from baseline in average abdominal pain score at peak olorinab plasma concentrations was -4.61 (1.77) in the 25-mg group (P = 0.0043) and -4.57 (2.17) in the 100-mg group (P = 0.0036). The change from baseline at week 8 in the mean (SD) number of pain-free days per week was +1.60 (2.61) in the 25-mg group and +2.33 (3.62) in the 100-mg group. No subject required pain medication on study. Conclusions Patients with quiescent to mildly active CD receiving olorinab experienced mild-to-moderate adverse events and an improvement in abdominal pain scores in this study.
Collapse
Affiliation(s)
- Bruce R Yacyshyn
- Department of Gastroenterology, University of Cincinnati, Cincinnati, Ohio, USA,Address correspondence to: Bruce R. Yacyshyn, MD, University of Louisville College of Medicine, CTR Building, Room 506, 505 East Hancock Street, Louisville, KY 40202 ()
| | - Stephen Hanauer
- Department of Gastroenterology and Hepatology, Northwestern University, Chicago, Illinois, USA
| | - Preston Klassen
- Arena Pharmaceuticals Inc., Research and Development, San Diego, California, USA
| | - Brett A English
- Arena Pharmaceuticals Inc., Clinical Development, San Diego, California, USA
| | - Kathe Stauber
- Arena Pharmaceuticals Inc., Nonclinical Development and Clinical Pharmacology, San Diego, California, USA
| | - Charles F Barish
- Department of Gastroenterology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Kye Gilder
- Arena Pharmaceuticals Inc., Biostatistics and Data Management, San Diego, California, USA
| | - Stewart Turner
- Arena Pharmaceuticals Inc., Olorinab Global Program Lead, San Diego, California, USA
| | - Peter D R Higgins
- Department of Gastroenterology, University of Michigan, Ann Arbor, Michigan, USA
| |
Collapse
|
7
|
Dothel G, Chang L, Shih W, Barbaro MR, Cremon C, Stanghellini V, De Ponti F, Mayer EA, Barbara G, Sternini C. µ-opioid receptor, β-endorphin, and cannabinoid receptor-2 are increased in the colonic mucosa of irritable bowel syndrome patients. Neurogastroenterol Motil 2019; 31:e13688. [PMID: 31336406 PMCID: PMC6791736 DOI: 10.1111/nmo.13688] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 07/04/2019] [Accepted: 07/11/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND AND AIMS The gut immune, cannabinoid, and opioid systems constitute an integrated network contributing to visceral sensation and pain modulation. We aimed to assess the expression of the µ-opioid receptor (MOR), its ligand β-endorphin (β-END), and cannabinoid receptor-2 (CB2 ) in patients with irritable bowel syndrome (IBS) and asymptomatic controls (AC) and their correlation with sex and symptom perception. METHODS Mucosal biopsies were obtained from the left colon of 31 IBS patients (45% women) with predominant constipation (IBS-C, 9) or diarrhea (IBS-D, 10) or with mixed bowel habits (IBS-M, 12) and 32 AC (44% women) and processed for qRT-PCR, Western blotting, and immunohistochemistry. KEY RESULTS µ-opioid receptor and CB2 mRNA and protein expression and β-END protein levels were increased in patients with IBS compared to AC (all Ps=0.021). A significant sex by IBS interaction was found in relation to CB2 mRNA expression (P = .003) with women showing a markedly higher expression to men (P = .035). In contrast, in AC, men had higher expression than women (P = .033). β-END, MOR, and CB2 immunoreactivities (IR) were localized to CD4+T cells including EMR-1+ eosinophils and CD31+ T cells but not to mast cells. CONCLUSIONS The increased expression of MOR, β-END, and CB2 in the mucosa of IBS patients, where they are localized to immune cells, suggests that opioid and cannabinoid systems play an immune-related compensatory role in visceral pain in IBS patients. Further work is necessary to support this hypothesis.
Collapse
Affiliation(s)
- G Dothel
- CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, USA
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - L Chang
- CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, USA
- G. Oppenheimer Family Center for Neurobiology of Stress and Resilience, University of California Los Angeles, USA
| | - W Shih
- Department of Biostatistics, David Geffen School of Medicine, University of California Los Angeles, USA
| | - MR Barbaro
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - C Cremon
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - V Stanghellini
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - F De Ponti
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - EA Mayer
- CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, USA
- Department of Biostatistics, David Geffen School of Medicine, University of California Los Angeles, USA
| | - G Barbara
- Department of Medical and Surgical Sciences, University of Bologna, Italy
| | - C Sternini
- CURE: Digestive Diseases Research Center, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, USA
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, USA
| |
Collapse
|
8
|
The endocannabinoid system: Novel targets for treating cancer induced bone pain. Biomed Pharmacother 2019; 120:109504. [PMID: 31627091 DOI: 10.1016/j.biopha.2019.109504] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 09/16/2019] [Accepted: 09/26/2019] [Indexed: 02/08/2023] Open
Abstract
Treating Cancer-induced bone pain (CIBP) continues to be a major clinical challenge and underlying mechanisms of CIBP remain unclear. Recently, emerging body of evidence suggested the endocannabinoid system (ECS) may play essential roles in CIBP. Here, we summarized the current understanding of the antinociceptive mechanisms of endocannabinoids in CIBP and discussed the beneficial effects of endocannabinoid for CIBP treatment. Targeting non-selective cannabinoid 1 receptors or selective cannabinoid 2 receptors, and modulation of peripheral AEA and 2-AG, as well as the inhibition the function of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) have produced analgesic effects in animal models of CIBP. Management of ECS therefore appears to be a promising way for the treatment of CIBP in terms of efficacy and safety. Further clinical studies are encouraged to confirm the possible translation to humans of the very promising results already obtained in the preclinical studies.
Collapse
|
9
|
Galligan JJ. Cannabinoid-induced relief of hypermotility in a rat model of the irritable bowel syndrome. Neurogastroenterol Motil 2019; 31:e13613. [PMID: 31094052 DOI: 10.1111/nmo.13613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 04/16/2019] [Indexed: 02/08/2023]
Abstract
Cannabinoid-2 receptor agonists may be useful in treating intestinal motility disorders.
Collapse
Affiliation(s)
- James J Galligan
- Neuroscience Program and the Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| |
Collapse
|
10
|
Guerrero-Alba R, Barragán-Iglesias P, González-Hernández A, Valdez-Moráles EE, Granados-Soto V, Condés-Lara M, Rodríguez MG, Marichal-Cancino BA. Some Prospective Alternatives for Treating Pain: The Endocannabinoid System and Its Putative Receptors GPR18 and GPR55. Front Pharmacol 2019; 9:1496. [PMID: 30670965 PMCID: PMC6331465 DOI: 10.3389/fphar.2018.01496] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/07/2018] [Indexed: 12/12/2022] Open
Abstract
Background: Marijuana extracts (cannabinoids) have been used for several millennia for pain treatment. Regarding the site of action, cannabinoids are highly promiscuous molecules, but only two cannabinoid receptors (CB1 and CB2) have been deeply studied and classified. Thus, therapeutic actions, side effects and pharmacological targets for cannabinoids have been explained based on the pharmacology of cannabinoid CB1/CB2 receptors. However, the accumulation of confusing and sometimes contradictory results suggests the existence of other cannabinoid receptors. Different orphan proteins (e.g., GPR18, GPR55, GPR119, etc.) have been proposed as putative cannabinoid receptors. According to their expression, GPR18 and GPR55 could be involved in sensory transmission and pain integration. Methods: This article reviews select relevant information about the potential role of GPR18 and GPR55 in the pathophysiology of pain. Results: This work summarized novel data supporting that, besides cannabinoid CB1 and CB2 receptors, GPR18 and GPR55 may be useful for pain treatment. Conclusion: There is evidence to support an antinociceptive role for GPR18 and GPR55.
Collapse
Affiliation(s)
- Raquel Guerrero-Alba
- Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Paulino Barragán-Iglesias
- School of Behavioral and Brain Sciences and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX, United States
| | - Abimael González-Hernández
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Santiago de Querétaro, Mexico
| | - Eduardo E Valdez-Moráles
- Cátedras CONACYT, Departamento de Cirugía, Centro de Ciencias Biomédicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Vinicio Granados-Soto
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, Mexico City, Mexico
| | - Miguel Condés-Lara
- Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Santiago de Querétaro, Mexico
| | - Martín G Rodríguez
- Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | - Bruno A Marichal-Cancino
- Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| |
Collapse
|
11
|
Zielińska A, Sałaga M, Włodarczyk M, Fichna J. Chronic abdominal pain in irritable bowel syndrome - current and future therapies. Expert Rev Clin Pharmacol 2018; 11:729-739. [PMID: 29957084 DOI: 10.1080/17512433.2018.1494571] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Irritable bowel syndrome (IBS) is a functional gut disorder that typically manifests in early adult years. One of the two major symptoms of the disease is chronic, visceral pain. The patients report pain as the most distressing symptom with the greatest impact on quality of life, challenging both to patients and healthcare providers. Areas covered: This review focuses on the pathophysiology of abdominal pain in IBS and describes current treatment possibilities. It also covers latest findings that may lead to novel pharmacological options in IBS pain management. Expert commentary: Pain is the main contributor to severity in IBS. Seeking pain alleviation is the most common reason that IBS sufferers consult with their physicians. Not all patients report being satisfied with available treatments for pain in IBS and there is a pressing need to find new, more efficient therapies for this syndrome.
Collapse
Affiliation(s)
- Anna Zielińska
- a Department of Biochemistry, Faculty of Medicine , Medical University of Lodz , Lodz , Poland
| | - Maciej Sałaga
- a Department of Biochemistry, Faculty of Medicine , Medical University of Lodz , Lodz , Poland
| | - Marcin Włodarczyk
- a Department of Biochemistry, Faculty of Medicine , Medical University of Lodz , Lodz , Poland.,b Department of General and Colorectal Surgery, Faculty of Military Medicine , Medical University of Lodz , Lodz , Poland
| | - Jakub Fichna
- a Department of Biochemistry, Faculty of Medicine , Medical University of Lodz , Lodz , Poland
| |
Collapse
|
12
|
Pesce M, D'Alessandro A, Borrelli O, Gigli S, Seguella L, Cuomo R, Esposito G, Sarnelli G. Endocannabinoid-related compounds in gastrointestinal diseases. J Cell Mol Med 2017; 22:706-715. [PMID: 28990365 PMCID: PMC5783846 DOI: 10.1111/jcmm.13359] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 07/23/2017] [Indexed: 12/14/2022] Open
Abstract
The endocannabinoid system (ECS) is an endogenous signalling pathway involved in the control of several gastrointestinal (GI) functions at both peripheral and central levels. In recent years, it has become apparent that the ECS is pivotal in the regulation of GI motility, secretion and sensitivity, but endocannabinoids (ECs) are also involved in the regulation of intestinal inflammation and mucosal barrier permeability, suggesting their role in the pathophysiology of both functional and organic GI disorders. Genetic studies in patients with irritable bowel syndrome (IBS) or inflammatory bowel disease have indeed shown significant associations with polymorphisms or mutation in genes encoding for cannabinoid receptor or enzyme responsible for their catabolism, respectively. Furthermore, ongoing clinical trials are testing EC agonists/antagonists in the achievement of symptomatic relief from a number of GI symptoms. Despite this evidence, there is a lack of supportive RCTs and relevant data in human beings, and hence, the possible therapeutic application of these compounds is raising ethical, political and economic concerns. More recently, the identification of several EC-like compounds able to modulate ECS function without the typical central side effects of cannabino-mimetics has paved the way for emerging peripherally acting drugs. This review summarizes the possible mechanisms linking the ECS to GI disorders and describes the most recent advances in the manipulation of the ECS in the treatment of GI diseases.
Collapse
Affiliation(s)
- Marcella Pesce
- Department of Clinical Medicine and Surgery, 'Federico II' University of Naples, Naples, Italy.,Division of Neurogastroenterology & Motility, Great Ormond Street Hospital and University of College (UCL), London, UK
| | - Alessandra D'Alessandro
- Department of Clinical Medicine and Surgery, 'Federico II' University of Naples, Naples, Italy
| | - Osvaldo Borrelli
- Division of Neurogastroenterology & Motility, Great Ormond Street Hospital and University of College (UCL), London, UK
| | - Stefano Gigli
- Department of Physiology and Pharmacology 'Vittorio Erspamer', La Sapienza University of Rome, Rome, Italy
| | - Luisa Seguella
- Department of Physiology and Pharmacology 'Vittorio Erspamer', La Sapienza University of Rome, Rome, Italy
| | - Rosario Cuomo
- Department of Clinical Medicine and Surgery, 'Federico II' University of Naples, Naples, Italy
| | - Giuseppe Esposito
- Department of Physiology and Pharmacology 'Vittorio Erspamer', La Sapienza University of Rome, Rome, Italy
| | - Giovanni Sarnelli
- Department of Clinical Medicine and Surgery, 'Federico II' University of Naples, Naples, Italy
| |
Collapse
|
13
|
Abstract
Inflammatory bowel diseases (IBDs) often take a chronic debilitating course. Given the chronicity of IBD, the limitations of the available medications, their potential side effects, and the impact of the disease on patients' quality of life, it is not surprising IBD patients are ranked among the highest users of complementary and alternative medicine (CAM). Since CAM has become very popular in real-life practice of Western Communities, caregivers must gain more knowledge about these therapies, their mechanism of action, benefits, and risks. This article reviews and discusses up-to-date scientific and clinical data regarding the most prevalent herbal CAM therapies.
Collapse
|
14
|
Gyires K, Zádori ZS. Role of Cannabinoids in Gastrointestinal Mucosal Defense and Inflammation. Curr Neuropharmacol 2017; 14:935-951. [PMID: 26935536 PMCID: PMC5333598 DOI: 10.2174/1570159x14666160303110150] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 12/14/2015] [Accepted: 02/26/2016] [Indexed: 02/06/2023] Open
Abstract
Modulating the activity of the endocannabinoid system influences various gastrointestinal physiological and pathophysiological processes, and cannabinoid receptors as well as regulatory enzymes responsible for the synthesis or degradation of endocannabinoids representing potential targets to reduce the development of gastrointestinal mucosal lesions, hemorrhage and inflammation. Direct activation of CB1 receptors by plant-derived, endogenous or synthetic cannabinoids effectively reduces both gastric acid secretion and gastric motor activity, and decreases the formation of gastric mucosal lesions induced by stress, pylorus ligation, nonsteroidal anti-inflammatory drugs (NSAIDs) or alcohol, partly by peripheral, partly by central mechanisms. Similarly, indirect activation of cannabinoid receptors through elevation of endocannabinoid levels by globally acting or peripherally restricted inhibitors of their metabolizing enzymes (FAAH, MAGL) or by inhibitors of their cellular uptake reduces the gastric mucosal lesions induced by NSAIDs in a CB1 receptor-dependent fashion. Dual inhibition of FAAH and cyclooxygenase enzymes induces protection against both NSAID-induced gastrointestinal damage and intestinal inflammation. Moreover, in intestinal inflammation direct or indirect activation of CB1 and CB2 receptors exerts also multiple beneficial effects. Namely, activation of both CB receptors was shown to ameliorate intestinal inflammation in various murine colitis models, to decrease visceral hypersensitivity and abdominal pain, as well as to reduce colitis-associated hypermotility and diarrhea. In addition, CB1 receptors suppress secretory processes and also modulate intestinal epithelial barrier functions. Thus, experimental data suggest that the endocannabinoid system represents a promising target in the treatment of inflammatory bowel diseases, and this assumption is also confirmed by preliminary clinical studies.
Collapse
Affiliation(s)
- Klára Gyires
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvarad ter 4., 1089, Budapest, Hungary
| | | |
Collapse
|
15
|
Romero-Sandoval EA, Asbill S, Paige CA, Byrd-Glover K. Peripherally Restricted Cannabinoids for the Treatment of Pain. Pharmacotherapy 2016; 35:917-25. [PMID: 26497478 DOI: 10.1002/phar.1642] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The use of cannabinoids for the treatment of chronic diseases has increased in the United States, with 23 states having legalized the use of marijuana. Although currently available cannabinoid compounds have shown effectiveness in relieving symptoms associated with numerous diseases, the use of cannabis or cannabinoids is still controversial mostly due to their psychotropic effects (e.g., euphoria, laughter) or central nervous system (CNS)-related undesired effects (e.g., tolerance, dependence). A potential strategy to use cannabinoids for medical conditions without inducing psychotropic or CNS-related undesired effects is to avoid their actions in the CNS. This approach could be beneficial for conditions with prominent peripheral pathophysiologic mechanisms (e.g., painful diabetic neuropathy, chemotherapy-induced neuropathy). In this article, we discuss the scientific evidence to target the peripheral cannabinoid system as an alternative to cannabis use for medical purposes, and we review the available literature to determine the pros and cons of potential strategies that can be used to this end.
Collapse
Affiliation(s)
- E Alfonso Romero-Sandoval
- Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, South Carolina
| | - Scott Asbill
- Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, South Carolina
| | - Candler A Paige
- Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, South Carolina
| | - Kiara Byrd-Glover
- Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, South Carolina
| |
Collapse
|
16
|
Abstract
The marijuana plant Cannabis sativa has been used for centuries as a treatment for a variety of ailments. It contains over 60 different cannabinoid compounds. Studies have revealed that the endocannabinoid system is involved in almost all major immune events. Cannabinoids may, therefore, be beneficial in inflammatory disorders. In murine colitis, cannabinoids decrease histologic and microscopic inflammation. In humans, cannabis has been used to treat a plethora of gastrointestinal problems, including anorexia, emesis, abdominal pain, diarrhea, and diabetic gastroparesis. Despite anecdotal reports on medical cannabis in inflammatory bowel disease (IBD), there are few controlled studies. In an observational study in 30 patients with Crohn's disease (CD), we found that medical cannabis was associated with improvement in disease activity and reduction in the use of other medications. In a more recent placebo-controlled study in 21 chronic CD patients, we showed a decrease in the CD activity index >100 in 10 of 11 subjects on cannabis compared to 4 of 10 on placebo. Complete remission was achieved in 5 of 11 subjects in the cannabis group and 1 of 10 in the placebo group. Yet, in an additional study, low-dose cannabidiol did not have an effect on CD activity. In summary, evidence is gathering that manipulating the endocannabinoid system can have beneficial effects in IBD, but further research is required to declare cannabinoids a medicine. We need to establish the specific cannabinoids, as well as appropriate medical conditions, optimal dose, and mode of administration, to maximize the beneficial effects while avoiding any potential harmful effects of cannabinoid use.
Collapse
Affiliation(s)
- Timna Naftali
- Institute of Gastroenterology and Hepatology, Meir Medical Center, Kfar Saba, Israel
| | | | | | | |
Collapse
|
17
|
Petho G, Reeh PW. Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors. Physiol Rev 2013; 92:1699-775. [PMID: 23073630 DOI: 10.1152/physrev.00048.2010] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.
Collapse
Affiliation(s)
- Gábor Petho
- Pharmacodynamics Unit, Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, Pécs, Hungary
| | | |
Collapse
|
18
|
Schicho R, Storr M. Targeting the endocannabinoid system for gastrointestinal diseases: future therapeutic strategies. Expert Rev Clin Pharmacol 2012; 3:193-207. [PMID: 22111567 DOI: 10.1586/ecp.09.62] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cannabinoids extracted from the marijuana plant (Cannabis sativa) and synthetic cannabinoids have numerous effects on gastrointestinal (GI) functions. Recent experimental data support an important role for cannabinoids in GI diseases. Genetic studies in humans have proven that defects in endocannabinoid metabolism underlie functional GI disorders. Mammalian cells have machinery, the so-called endocannabinoid system (ECS), to produce and metabolize their own cannabinoids in order to control homeostasis of the gut in a rapidly adapting manner. Pharmacological manipulation of the ECS by cannabinoids, or by drugs that raise the levels of endogenous cannabinoids, have shown beneficial effects on GI pathophysiology. This review gives an introduction into the functions of the ECS in the GI tract, highlights the role of the ECS in GI diseases and addresses its potential pharmacological exploitation.
Collapse
Affiliation(s)
- Rudolf Schicho
- Division of Gastroenterology, Department of Medicine, University of Calgary, 6D25, TRW Building, 3280 Hospital Drive NW, Calgary T2N 4N1, AB, Canada.
| | | |
Collapse
|
19
|
Abstract
BACKGROUND Endocannabinoids influence immune function and nociceptive signaling. This study examines cannabinoid modulation of sensory signaling from the GI tract following an acute inflammatory response triggered by systemic administration of bacterial lipopolysaccharide (LPS). METHODS A segment of proximal jejunum was intubated, to measure intraluminal pressure, in anesthetized rats. Afferent impulse traffic was recorded from a single isolated paravascular nerve bundle supplying the jejunal loop. Drugs and LPS were administered intravenously and changes in afferent firing were determined. KEY RESULTS The non-selective cannabinoid agonist, WIN55,212-2 (1 mg kg(-1) i.v.) and the anandamide transport inhibitor, VDM11 (1 mg kg(-1) i.v.) but not the fatty acid amide hydrolase (FAAH) inhibitor, URB597 (0.3 mg kg(-1)) caused a significant increase in afferent activity. The WIN55,212-2-induced afferent response was mediated by activation of CB(1) receptors whereas the VDM11 response was mediated by both CB(1) and CB(2) receptor mechanisms. LPS (10 mg kg(-1)) evoked an increase in afferent activity which was significantly reduced in the presence of WIN55,212-2 and VDM11 but not URB597. The inhibitory effect of WIN55,212-2 was prevented by CB(1) but not CB(2) receptor antagonism. In contrast, the inhibitory effect of VDM11 remained unaltered after CB(1) or CB(2) receptor blockade. CONCLUSIONS & INFERENCES Endocannabinoids play a role in modulating afferent signaling and may represent a target for the treatment of visceral hypersensitivity. In contrast to the effects of blocking endocannabinoid uptake (VDM11), inhibiting breakdown of endocannabinoids (URB597) had no effect on baseline or LPS induced afferent firing. Therefore, uptake of cannabinoids rather than breakdown via FAAH terminates their action in the GI tract.
Collapse
Affiliation(s)
- J Donovan
- University of Sheffield, Department of Biomedical Sciences, Sheffield, UK.
| | | |
Collapse
|
20
|
Donovan J, Grundy D. The differential effect of CB1 receptors on the discharge of afferent and efferent fibres supplying the rat jejunum. Neurogastroenterol Motil 2011; 23:567-e209. [PMID: 21414102 DOI: 10.1111/j.1365-2982.2011.01693.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND The cannabinoid receptor (CB(1) ) is expressed on GI sensory neurons and is suggested to play a role in food intake, inflammation and nociception. Expression of CB(1) in the nodose is influenced by nutritional status. Our aim was to determine the functional response of afferent and efferent fibres supplying the proximal jejunum to the CB(1) agonist docosatetraenylethanolamide (DEA) in fed and fasted animals. METHODS Experiments were performed on anesthetized rats, either fed ad libitum or fasted for 24 h. Blood pressure was recorded via the carotid artery and the proximal jejunum intubated to measure intraluminal pressure. A single paravascular nerve bundle was isolated and attached to an electrode for recording either afferent or efferent impulse traffic. KEY RESULTS Docosatetraenylethanolamide (1 mg kg(-1) , i.v.) had a depressor effect on blood pressure but surprisingly had little effect on afferent nerve activity in fed animals. In fasted animals the afferent response to DEA was augmented, however, the blood pressure effect was attenuated. In contrast, DEA caused a significant and prolonged increase in efferent firing, which was diminished in fasted animals. Bilateral cervical vagotomy had no effect on the DEA-mediated efferent response, however, hexamethonium (10 mg kg(-1) ) abolished excitation and unmasked an inhibitory effect of DEA. CONCLUSIONS & INFERENCES Docosatetraenylethanolamide has only a modest effect on intestinal afferent firing but a profound effect on efferent function, which is modulated by changes in nutritional status. The persistent response after vagotomy and block by hexamethonium suggests DEA is acting centrally, although there may be an inhibitory effect at the level of the postganglionic sympathetic neuron.
Collapse
Affiliation(s)
- J Donovan
- Department of Biomedical Sciences, University of Sheffield, Sheffield, UK.
| | | |
Collapse
|
21
|
Walczak JS, Cervero F. Local activation of cannabinoid CB₁ receptors in the urinary bladder reduces the inflammation-induced sensitization of bladder afferents. Mol Pain 2011; 7:31. [PMID: 21554718 PMCID: PMC3115893 DOI: 10.1186/1744-8069-7-31] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 05/09/2011] [Indexed: 12/17/2022] Open
Abstract
Background Systemic administration of cannabinoid agonists is known to reduce pain induced by bladder inflammation and to modulate cystometric parameters in vivo. We have previously reported that intravesical administration of a cannabinoid agonist reduces the electrical activity of bladder afferents under normal conditions. However, the effects of local activation of bladder cannabinoid receptors on afferent activity during inflammation are unknown. This study was aimed to assess the effects of intravesical administration of a cannabinoid agonist on the discharges of afferent fibers in inflamed bladders ex vivo. We also characterized the expression of CB1 receptors in the bladder and their localization and co-expression with TRPV1, a marker of nociceptive afferents. Results Compared to untreated animals, afferent fiber activity in inflamed bladders was increased for intravesical pressures between 10 and 40 mmHg. Local treatment with a non selective cannabinoid agonist (AZ12646915) significantly reduced the afferent activity at intravesical pressures above 20 mmHg. This effect was blocked by AM251 but not by AM630 (selective for CB1 and CB2 respectively). Finally, CB1 was co-expressed with TRPV1 in control and inflamed bladders. Conclusion These results demonstrate that sensitization of bladder afferents induced by inflammation is partly suppressed by intravesical activation of cannabinoid receptors, an effect that appears to be mediated by CB1 receptors. Also, TRPV1 positive fibers were found to co-express CB1, supporting the hypothesis of a direct action of the cannabinoid agonist on nociceptive afferents. Taken together, these results indicate a peripheral modulation by the cannabinoid system of bladder hypersensitivity during inflammation.
Collapse
Affiliation(s)
- Jean-Sébastien Walczak
- McGill University, Anesthesia Research Unit, Faculty of Medicine, Faculty of Dentistry and Alan Edwards Center for Research on Pain, Montréal, Québec, Canada.
| | | |
Collapse
|
22
|
Abstract
Stemming from the centuries-old and well known effects of Cannabis on intestinal motility and secretion, research on the role of the endocannabinoid system in gut function and dysfunction has received ever increasing attention since the discovery of the cannabinoid receptors and their endogenous ligands, the endocannabinoids. In this article, some of the most recent developments in this field are discussed, with particular emphasis on new data, most of which are published in Neurogastroenterology & Motility, on the potential tonic endocannabinoid control of intestinal motility, the function of cannabinoid type-1 (CB1) receptors in gastric function, visceral pain, inflammation and sepsis, the emerging role of cannabinoid type-2 (CB2) receptors in the gut, and the pharmacology of endocannabinoid-related molecules and plant cannabinoids not necessarily acting via cannabinoid CB1 and CB2 receptors. These novel data highlight the multi-faceted aspects of endocannabinoid function in the GI tract, support the feasibility of the future therapeutic exploitation of this signaling system for the treatment of GI disorders, and leave space for some intriguing new hypotheses on the role of endocannabinoids in the gut.
Collapse
Affiliation(s)
- V Di Marzo
- Endocannabinoid Research Group, Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Pozzuoli, Italy.
| | | |
Collapse
|
23
|
Atwood BK, Mackie K. CB2: a cannabinoid receptor with an identity crisis. Br J Pharmacol 2010. [PMID: 20590558 DOI: 10.1111/j.1476-5381] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
CB(2) was first considered to be the 'peripheral cannabinoid receptor'. This title was bestowed based on its abundant expression in the immune system and presumed absence from the central nervous system. However, multiple recent reports question the absence of CB(2) from the central nervous system. For example, it is now well accepted that CB(2) is expressed in brain microglia during neuroinflammation. However, the extent of CB(2) expression in neurons has remained controversial. There have been studies claiming either extreme-its complete absence to its widespread expression-as well as everything in between. This review will discuss the reported tissue distribution of CB(2) with a focus on CB(2) in neurons, particularly those in the central nervous system as well as the implications of that presence. As CB(2) is an attractive therapeutic target for pain management and immune system modulation without overt psychoactivity, defining the extent of its presence in neurons will have a significant impact on drug discovery. Our recommendation is to encourage cautious interpretation of data that have been presented for and against CB(2)'s presence in neurons and to encourage continued rigorous study.
Collapse
Affiliation(s)
- Brady K Atwood
- The Gill Center and the Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | | |
Collapse
|
24
|
Abstract
CB(2) was first considered to be the 'peripheral cannabinoid receptor'. This title was bestowed based on its abundant expression in the immune system and presumed absence from the central nervous system. However, multiple recent reports question the absence of CB(2) from the central nervous system. For example, it is now well accepted that CB(2) is expressed in brain microglia during neuroinflammation. However, the extent of CB(2) expression in neurons has remained controversial. There have been studies claiming either extreme-its complete absence to its widespread expression-as well as everything in between. This review will discuss the reported tissue distribution of CB(2) with a focus on CB(2) in neurons, particularly those in the central nervous system as well as the implications of that presence. As CB(2) is an attractive therapeutic target for pain management and immune system modulation without overt psychoactivity, defining the extent of its presence in neurons will have a significant impact on drug discovery. Our recommendation is to encourage cautious interpretation of data that have been presented for and against CB(2)'s presence in neurons and to encourage continued rigorous study.
Collapse
Affiliation(s)
- Brady K Atwood
- The Gill Center and the Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | | |
Collapse
|
25
|
Darmani NA. Mechanisms of Broad-Spectrum Antiemetic Efficacy of Cannabinoids against Chemotherapy-Induced Acute and Delayed Vomiting. Pharmaceuticals (Basel) 2010; 3:2930-2955. [PMID: 27713384 PMCID: PMC4034105 DOI: 10.3390/ph3092930] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/26/2010] [Accepted: 08/30/2010] [Indexed: 01/02/2023] Open
Abstract
Chemotherapy-induced nausea and vomiting (CINV) is a complex pathophysiological condition and consists of two phases. The conventional CINV neurotransmitter hypothesis suggests that the immediate phase is mainly due to release of serotonin (5-HT) from the enterochromaffin cells in the gastrointestinal tract (GIT), while the delayed phase is a consequence of release of substance P (SP) in the brainstem. However, more recent findings argue against this simplistic neurotransmitter and anatomical view of CINV. Revision of the hypothesis advocates a more complex, differential and overlapping involvement of several emetic neurotransmitters/modulators (e.g. dopamine, serotonin, substance P, prostaglandins and related arachidonic acid derived metabolites) in both phases of emesis occurring concomitantly in the brainstem and in the GIT enteric nervous system (ENS) [1]. No single antiemetic is currently available to completely prevent both phases of CINV. The standard antiemetic regimens include a 5-HT₃ antagonist plus dexamethasone for the prevention of acute emetic phase, combined with an NK1 receptor antagonist (e.g. aprepitant) for the delayed phase. Although NK1 antagonists behave in animals as broad-spectrum antiemetics against different emetogens including cisplatin-induced acute and delayed vomiting, by themselves they are not very effective against CINV in cancer patients. Cannabinoids such as D⁸-THC also behave as broad-spectrum antiemetics against diverse emetic stimuli as well as being effective against both phases of CINV in animals and patients. Potential side effects may limit the clinical utility of direct-acting cannabinoid agonists which could be avoided by the use of corresponding indirect-acting agonists. Cannabinoids (both phyto-derived and synthetic) behave as agonist antiemetics via the activation of cannabinoid CB₁ receptors in both the brainstem and the ENS emetic loci. An endocannabinoid antiemetic tone may exist since inverse CB₁ agonists (but not the corresponding silent antagonists) cause nausea and vomiting.
Collapse
Affiliation(s)
- Nissar A Darmani
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA, USA.
| |
Collapse
|
26
|
Experimental models of visceral pain. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2010; 617:115-54. [PMID: 20336418 DOI: 10.1007/978-1-60327-323-7_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Visceral pain models are used to study afferent nerve traffic during noxious stimulation at the level of the visceral organ. This chapter provides details on several in vitro and in vivo models of organs in the gastrointestinal and genitourinary tract that use electrophysiological recordings of afferent nerve fibres in order to directly characterize stimulus-response relationships. These models can also be used to investigate stimulus-response patterns during physiological (nonpainful) stimulation of the visceral organs or during exposure to pathological stimuli, such as inflammatory mediators during inflammation of the visceral organ.
Collapse
|
27
|
Izzo AA, Sharkey KA. Cannabinoids and the gut: new developments and emerging concepts. Pharmacol Ther 2010; 126:21-38. [PMID: 20117132 DOI: 10.1016/j.pharmthera.2009.12.005] [Citation(s) in RCA: 301] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 12/24/2009] [Indexed: 12/11/2022]
Abstract
Cannabis has been used to treat gastrointestinal (GI) conditions that range from enteric infections and inflammatory conditions to disorders of motility, emesis and abdominal pain. The mechanistic basis of these treatments emerged after the discovery of Delta(9)-tetrahydrocannabinol as the major constituent of Cannabis. Further progress was made when the receptors for Delta(9)-tetrahydrocannabinol were identified as part of an endocannabinoid system, that consists of specific cannabinoid receptors, endogenous ligands and their biosynthetic and degradative enzymes. Anatomical, physiological and pharmacological studies have shown that the endocannabinoid system is widely distributed throughout the gut, with regional variation and organ-specific actions. It is involved in the regulation of food intake, nausea and emesis, gastric secretion and gastroprotection, GI motility, ion transport, visceral sensation, intestinal inflammation and cell proliferation in the gut. Cellular targets have been defined that include the enteric nervous system, epithelial and immune cells. Molecular targets of the endocannabinoid system include, in addition to the cannabinoid receptors, transient receptor potential vanilloid 1 receptors, peroxisome proliferator-activated receptor alpha receptors and the orphan G-protein coupled receptors, GPR55 and GPR119. Pharmacological agents that act on these targets have been shown in preclinical models to have therapeutic potential. Here, we discuss cannabinoid receptors and their localization in the gut, the proteins involved in endocannabinoid synthesis and degradation and the presence of endocannabinoids in the gut in health and disease. We focus on the pharmacological actions of cannabinoids in relation to GI disorders, highlighting recent data on genetic mutations in the endocannabinoid system in GI disease.
Collapse
Affiliation(s)
- Angelo A Izzo
- Department of Experimental Pharmacology, University of Naples Federico II and Endocannabinoid Research Group, Naples, Italy.
| | | |
Collapse
|
28
|
Darmani NA, Ray AP. Evidence for a re-evaluation of the neurochemical and anatomical bases of chemotherapy-induced vomiting. Chem Rev 2009; 109:3158-99. [PMID: 19522506 DOI: 10.1021/cr900117p] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Nissar A Darmani
- Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, California 91766-1854, USA.
| | | |
Collapse
|
29
|
Mode of action of cannabinoids on nociceptive nerve endings. Exp Brain Res 2009; 196:79-88. [PMID: 19306092 DOI: 10.1007/s00221-009-1762-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 02/27/2009] [Indexed: 12/22/2022]
Abstract
In recent years, cannabinoids have emerged as attractive alternatives or supplements to therapy for chronic pain states. However, in humans the activation of cannabinoid receptors in neurons of the central nervous system is associated with psychotropic side effects, temporary memory impairment and dependence, which arise via the effects of cannabinoids on forebrain circuits. For clinical exploitation of the analgesic properties of cannabinoids, a major challenge is to devise strategies that reduce or abolish their adverse effects on cognitive, affective and motor functions without attenuating their analgesic effects. The cannabinoid receptor family currently includes two cloned metabotropic receptors: CB1, CB2 and possibly GPR55 which are distributed widely across many key loci in pain-modulating pathways, including the peripheral terminals of primary afferents. Modulation of transducer ion channels expressed at nociceptive terminals occurs upon activation of metabotropic cannabinoid receptors, but direct cannabinoid action on ion channels involved in sensory transduction or regulation of neuron excitability likely contributes to the peripheral cannabinoid effects.
Collapse
|
30
|
Márquez L, Abanades S, Andreu M. [Endocannabinoid system and bowel inflammation]. Med Clin (Barc) 2009; 131:513-7. [PMID: 19007582 DOI: 10.1157/13127285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The endocannabinoid system is an important regulatory system of multiple functions of the body in all vertebrates. There are 2 specific receptors, CB1 and CB2, through which the cannabinoids exert their effect. CB1-receptors mainly express themselves in myenteric plexuses and submucosal epithelium of the gastrointestinal tract, suggesting their implication in the inhibition of the peristalsis and gastrointestinal contraction. CB2-receptors are expressed in the tissue and immune cells, such as T and B-lymphocytes, monocytes and polymorphonuclear neutrophils, exerting an immunomodulator effect. The role of the endocannabinoid system is not completely known, but there is enough evidence that confirms an important role in the decrease of inflammation through the reduction of the release of pro-inflammatory cytokines. Therefore, it may exert a protective role in many of the points where the homeostasis breaks in inflammatory bowel disease. Research about the mechanisms and effects of the endocannabinoid system in the gastrointestinal tract will allow advancing in the therapy of this illness.
Collapse
Affiliation(s)
- Lucía Márquez
- Servei d'Aparell Digestiu, Hospital del Mar, Universidad Autónoma de Barcelona, Barcelona, Spain
| | | | | |
Collapse
|
31
|
Pethő G, Reeh PW. Effects of Bradykinin on Nociceptors. NEUROGENIC INFLAMMATION IN HEALTH AND DISEASE 2009. [DOI: 10.1016/s1567-7443(08)10407-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
|
32
|
Storr MA, Yüce B, Andrews CN, Sharkey KA. The role of the endocannabinoid system in the pathophysiology and treatment of irritable bowel syndrome. Neurogastroenterol Motil 2008; 20:857-68. [PMID: 18710476 DOI: 10.1111/j.1365-2982.2008.01175.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Irritable bowel syndrome (IBS) is a spectrum of disorders characterized by abdominal discomfort and pain, associated with altered bowel habits. Though gut motility, secretion and sensation may be altered in patients with IBS, the pathophysiology of this condition remains to be fully understood. The endocannabinoid system is involved in the regulation of numerous gastrointestinal functions including motility, sensation and secretion under both physiological and pathophysiological conditions. Activation of cannabinoid (CB)(1) and CB(2) receptors under various circumstances reduces motility, limits secretion and decreases hypersensitivity in the gut. Drugs that alter the levels of endocannabinoids in the gut also reduce motility and attenuate inflammation. In this review, we discuss the role of the endocannabinoid system in gastrointestinal physiology. We go on to consider the involvement of the endocannabinoid system in the context of symptoms associated with IBS and a possible role of this system in the pathophysiology and treatment of IBS.
Collapse
Affiliation(s)
- M A Storr
- Division of Gastroenterology, Department of Medicine, Snyder Institute of Infection, Immunity and Inflammation, University Calgary, Calgary, AB, Canada.
| | | | | | | |
Collapse
|
33
|
Smid SD. Gastrointestinal endocannabinoid system: multifaceted roles in the healthy and inflamed intestine. Clin Exp Pharmacol Physiol 2008; 35:1383-7. [PMID: 18671715 DOI: 10.1111/j.1440-1681.2008.05016.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. The endogenous cannabinoid (endocannabinoid) system is emerging as a key modulator of intestinal physiology, influencing motility, secretion, epithelial integrity and immune function in the gut, in addition to influencing satiety and emesis. 2. Accumulating evidence suggests that the endocannabinoid system may play a pivotal role in the pathophysiology of gastrointestinal disease, particularly in the light of recent studies demonstrating an effect of endocannabinoids on the development of experimental inflammation and linkages with functional clinical disorders characterized by altered motility. 3. The predominant endocannabinoids, anandamide and 2-arachidonoylglycerol, not only mediate their effects via two recognized cannabinoid receptor subtypes, namely CB(1) and CB(2), but emerging evidence now shows they are also substrates for cyclo-oxygenase (COX)-2, generating a distinct and novel class of prostaglandin ethanolamides (prostamides) and prostaglandin glycerol esters. These compounds are bioactive and may mediate an array of biological effects distinct to those of conventional prostanoids. 4. The effects of prostamides on gastrointestinal motility, secretion, sensation and immune function have not been characterized extensively. Prostamides may play an important role in gastrointestinal inflammation, particularly given the enhanced expression of both COX-2 and endocannabinoids that occurs in the inflamed gut. 5. Further preclinical studies are needed to determine the therapeutic potential of drugs targeting the endocannabinoid system in functional and inflammatory gut disorders, to assist with the determination of feasibility for clinical translation.
Collapse
Affiliation(s)
- Scott D Smid
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Health Sciences, The University of Adelaide, Adelaide, South Australia, Australia.
| |
Collapse
|
34
|
Fioramonti J, Bueno L. Role of cannabinoid receptors in the control of gastrointestinal motility and perception. Expert Rev Gastroenterol Hepatol 2008; 2:385-97. [PMID: 19072387 DOI: 10.1586/17474124.2.3.385] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The identification of endocannabinoids and cannabinoid CB1 receptors in key areas of the intestinal wall, such as cholinergic neurons, supports a role for cannabinoids in the control of gastrointestinal motility. Activation of CB1 receptors inhibits the peristaltic reflex and slows down gastrointestinal and colonic transit. Endocannabinoids play an important inhibitory role in the control of the occurrence of transient lower esophageal sphincter relaxations. Cannabinoid receptor agonists inhibit gastric emptying and intestinal motility in humans. There is strong anatomical support for a role of CB1 receptors in the control of gastrointestinal perception, since these receptors have been identified in key sites of the neuronal circuitry involved in the transmission of visceral pain. Experimental data indicate a visceral antinociceptive action of cannabinoid receptor agonists, which remains to be confirmed in humans.
Collapse
Affiliation(s)
- Jean Fioramonti
- Neurogastroenterology and Nutrition Unit, INRA, 180 Chemin de Tournefeuille, BP 3, F-31931 Toulouse Cedex 9, France.
| | | |
Collapse
|
35
|
Kikuchi A, Ohashi K, Sugie Y, Sugimoto H, Omura H. Pharmacological evaluation of a novel cannabinoid 2 (CB2) ligand, PF-03550096, in vitro and in vivo by using a rat model of visceral hypersensitivity. J Pharmacol Sci 2008; 106:219-24. [PMID: 18270474 DOI: 10.1254/jphs.fp0071599] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Previous studies have shown that cannabinoid 2 (CB(2))-receptor agonists might have analgesic effects on visceral hypersensitivity. To extend these results, we have determined the pharmacological characteristics of a newly designed CB(2) ligand, N-[(1S)-1-(aminocarbonyl)-2,2-dimethylpropyl]-3-(3-hydroxy-3-methylbutyl)-2-oxo-2,3-dihydro-1H-benzimidazole-1-carboxamide (PF-03550096), in vitro and in vivo. PF-03550096 showed high affinity to human (K(i) = 7.9 +/- 1.7 nM) and rat CB(2) receptors (K(i) = 47 +/- 5.6 nM). In a cell-based functional assay, PF-03550096 behaved as a full agonist and showed high selectivity for human CB(2) receptors. Orally administered PF-03550096 (3, 10 mg/kg) inhibited the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced decrease in colonic pain threshold with statistical significance. The inhibitory effect of PF-03550096 (10 mg/kg) was significantly reversed by a selective CB(2) antagonist, N-(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl-5-(4-chloro-3-methylphenyl)-1(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528), while SR144528 itself did not modify colonic pain threshold. These results indicate that PF-03550096 is a potent CB(2) agonist and possesses efficacy in a rat model of visceral hypersensitivity.
Collapse
Affiliation(s)
- Akira Kikuchi
- Discovery Research, Pfizer Global Research & Development, Nagoya Laboratories, Pfizer Inc., Chita-gun, Aichi, Japan.
| | | | | | | | | |
Collapse
|
36
|
Storr MA, Sharkey KA. The endocannabinoid system and gut–brain signalling. Curr Opin Pharmacol 2007; 7:575-82. [PMID: 17904903 DOI: 10.1016/j.coph.2007.08.008] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 08/22/2007] [Accepted: 08/23/2007] [Indexed: 11/30/2022]
Abstract
The endocannabinoid system (ECS) consists of cannabinoid receptors, endogenous ligands and the biosynthetic and metabolic enzymes for their formation and degradation. Within the gastrointestinal (GI) tract, the ECS is involved in the regulation of motility, secretion, sensation, emesis, satiety and inflammation. Recent studies examining the ECS in the gut-brain axis have shed new light on this system and reveal many facets of regulation that are amenable to targeting by pharmacological interventions that may prove valuable for the treatment of GI disorders. In particular, it has been shown that endocannabinoid levels in the brain and gut vary according to states of satiety, and in conditions of diarrhea, emesis and inflammation. The expression of cannabinoid (CB)(1) receptors on vagal afferents is controlled by the states of satiety and by gut peptides such as cholecystokinin and ghrelin. Vagal control of gut motor function and emesis is regulated by endocannabinoids in the brainstem acting on CB(1), CB(2) and transient receptor potential vanilloid (TRPV)-1 receptors. The ECS is involved in the modulation of visceral sensation and likely contributes to effects of stress on GI function. This review examines recent developments in our understanding of the ECS in gut-brain signalling.
Collapse
Affiliation(s)
- Martin A Storr
- Department of Medicine, Hotchkiss Brain Institute and Institute of Infection, Immunity and Inflammation, University of Calgary, 3330 Hospital Drive N.W., Calgary, Alberta, Canada
| | | |
Collapse
|
37
|
Wright KL, Duncan M, Sharkey KA. Cannabinoid CB2 receptors in the gastrointestinal tract: a regulatory system in states of inflammation. Br J Pharmacol 2007; 153:263-70. [PMID: 17906675 PMCID: PMC2219529 DOI: 10.1038/sj.bjp.0707486] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The emerging potential for the cannabinoid (CB) system in modulating gastrointestinal inflammation has gained momentum over the last few years. Traditional and anecdotal use of marijuana for gastrointestinal disorders, such as diarrhoea and abdominal cramps is recognized, but the therapeutic benefit of cannabinoids in the 21st century is overshadowed by the psychoactive problems associated with CB1 receptor activation. However, the presence and function of the CB2 receptor in the GI tract, whilst not yet well characterized, holds great promise due to its immunomodulatory roles in inflammatory systems and its lack of psychotropic effects. This review of our current knowledge of CB2 receptors in the gastrointestinal tract highlights its role in regulating abnormal motility, modulating intestinal inflammation and limiting visceral sensitivity and pain. CB2 receptors represent a braking system and a pathophysiological mechanism for the resolution of inflammation and many of its symptoms. CB2 receptor activation therefore represents a very promising therapeutic target in gastrointestinal inflammatory states where there is immune activation and motility dysfunction.
Collapse
Affiliation(s)
- K L Wright
- Department of Pharmacy and Pharmacology, University of Bath Bath, UK
| | - M Duncan
- Institute of Infection, Immunity and Inflammation, Department of Physiology and Biophysics, University of Calgary Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary Calgary, Alberta, Canada
| | - K A Sharkey
- Institute of Infection, Immunity and Inflammation, Department of Physiology and Biophysics, University of Calgary Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary Calgary, Alberta, Canada
- Author for correspondence:
| |
Collapse
|