GPR55 – a putative “type 3” cannabinoid receptor in inflammation.

“G protein-coupled receptor 55 (GPR55) shares numerous cannabinoid ligands with CB1 and CB2 receptors despite low homology with those classical cannabinoid receptors. The pharmacology of GPR55 is not yet fully elucidated; however, GPR55 utilizes a different signaling system and downstream cascade associated with the receptor. Therefore, GPR55 has emerged as a putative “type 3” cannabinoid receptor, establishing a novel class of cannabinoid receptor. Furthermore, the recent evidence of GPR55-CB1 and GPR55-CB2 heteromerization along with its broad distribution from central nervous system to peripheries suggests the importance of GPR55 in various cellular processes and pathologies and as a potential therapeutic target in inflammation.”

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GPR55 G protein-coupled receptor 55 [ Homo sapiens (human) ]

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“This gene belongs to the G-protein-coupled receptor superfamily. The encoded integral membrane protein is a likely cannabinoid receptor. It may be involved in several physiological and pathological processes by activating a variety of signal transduction pathways. ” https://www.ncbi.nlm.nih.gov/gene/9290

“The orphan receptor GPR55 is a novel cannabinoid receptor”  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095107/

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The orphan receptor GPR55 is a novel cannabinoid receptor

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“Preparations of Cannabis sativa have been used for medicinal and recreational purposes for at least 4000 years and extracts of C. sativa contain over 60 different pharmacologically active components the most prominent being Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol

Ligands such as cannabidiol and abnormal cannabidiol which exhibit no CB1or CB2 activity and are believed to function at a novel cannabinoid receptor, also showed activity at GPR55.

These data suggest that GPR55 is a novel cannabinoid receptor, and its ligand profile with respect to CB1and CB2 described here will permit delineation of its physiological function(s).”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095107/

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GPR55: A therapeutic target for Parkinson’s disease?

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“The GPR55 receptor is expressed abundantly in the brain, especially in the striatum, suggesting it might fulfill a role in motor function. Indeed, motor behavior is impaired in mice lacking GPR55, which also display dampened inflammatory responses.

Abnormal-cannabidiol (Abn-CBD), a synthetic cannabidiol (CBD) isomer, is a GPR55 agonist that may serve as a therapeutic agent in the treatment of inflammatory diseases.

In this study, we explored whether modulating GPR55 could also represent a therapeutic approach for the treatment of Parkinson’s disease (PD).

These results demonstrate for the first time that activation of GPR55 might be beneficial in combating PD.”

https://www.ncbi.nlm.nih.gov/pubmed/28807673

http://www.sciencedirect.com/science/article/pii/S0028390817303842

“The orphan receptor GPR55 is a novel cannabinoid receptor”  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095107/

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The novel cannabinoid receptor GPR55 mediates anxiolytic-like effects in the medial orbital cortex of mice with acute stress.

Biomed Central

“The G protein-coupled receptor 55 (GPR55) is a novel cannabinoid receptor, whose exact role in anxiety remains unknown. The present study was conducted to explore the possible mechanisms by which GPR55 regulates anxiety and to evaluate the effectiveness of O-1602 in the treatment of anxiety-like symptoms. Mice were exposed to two types of acute stressors: restraint and forced swimming. Anxiety behavior was evaluated using the elevated plus maze and the open field test. We found that O-1602 alleviated anxiety-like behavior in acutely stressed mice. We used lentiviral shRNA to selective ly knockdown GPR55 in the medial orbital cortex and found that knockdown of GPR55 abolished the anxiolytic effect of O-1602. We also used Y-27632, a specific inhibitor of ROCK, and U73122, an inhibitor of PLC, and found that both inhibitors attenuated the effectiveness of O-1602. Western blot analysis revealed that O-1602 downregulated the expression of GluA1 and GluN2A in mice. Taken together, these results suggest that GPR55 plays an important role in anxiety and O-1602 may have therapeutic potential in treating anxiety-like symptoms.”

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GPR55 and the regulation of glucose homeostasis.

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“Pathophysiological conditions such as obesity and type 2 diabetes (T2D) are reportedly associated to over-activation of the endocannabinoid system (ECS). Therefore, modulation of the ECS offers potential therapeutic benefits on those diseases. GPR55, the receptor for L-α-lysophosphatidylinositol (LPI) that has also affinity for various cannabinoid ligands, is distributed at the central and peripheral level and it is involved in several physiological processes. This review summarizes the localization and role of GPR55 in tissues that are crucial for the regulation of glucose metabolism, and provides an update on its contribution in obesity and insulin resistance. The therapeutic potential of targeting the GPR55 receptor is also discussed.”

https://www.ncbi.nlm.nih.gov/pubmed/28457969

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Antihyperalgesic Activities of Endocannabinoids in a Mouse Model of Antiretroviral-Induced Neuropathic Pain.

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“Nucleoside reverse transcriptase inhibitors (NRTIs) are the cornerstone of the antiretroviral therapy for human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). However, their use is sometimes limited by the development of a painful sensory neuropathy, which does not respond well to drugs.

Smoked cannabis has been reported in clinical trials to have efficacy in relieving painful HIV-associated sensory neuropathy.

The aim of this study was to evaluate whether the expression of endocannabinoid system molecules is altered during NRTI-induced painful neuropathy, and also whether endocannabinoids can attenuate NRTI-induced painful neuropathy.

Conclusion: These data show that ddC induces thermal hyperalgesia, which is associated with dysregulation of the mRNA expression of some endocannabinoid system molecules. The endocannabinoids AEA and 2-AG have antihyperalgesic activity, which is dependent on cannabinoid receptor and GPR55 activation. Thus, agonists of cannabinoid receptors and GPR55 could be useful therapeutic agents for the management of NRTI-induced painful sensory neuropathy.”

https://www.ncbi.nlm.nih.gov/pubmed/28373843

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Anti-inflammatory role of cannabidiol and O-1602 in cerulein-induced acute pancreatitis in mice.

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“The anti-inflammatory effects of O-1602 and cannabidiol (CBD), the ligands of G protein-coupled receptor 55 (GPR55), on experimental acute pancreatitis (AP) were investigated.

Cannabidiol or O-1602 treatment significantly improved the pathological changes of mice with AP and decreased the enzyme activities, IL-6 and tumor necrosis factor α; levels, and the myeloperoxidase activities in plasma and in the organ tissues.

G protein-coupled receptor 55 mRNA and protein expressed in the pancreatic tissue, and the expressions were decreased in the mice with AP, and either CBD or O-1602 attenuated these changes to a certain extent.

CONCLUSION:

Cannabidiol and O-1602 showed anti-inflammatory effects in mice with AP and improved the expression of GPR55 in the pancreatic tissue as well.”

https://www.ncbi.nlm.nih.gov/pubmed/22850623

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GPR55: a new promising target for metabolism?

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“GPR55 is a G-protein coupled receptor (GPCR) that has been identified as a new cannabinoid receptor. Given the wide localization of GPR55 in brain and peripheral tissues, this receptor has emerged as a regulator of multiple biological actions. Lysophosphatidylinositol (LPI) is generally accepted as the endogenous ligand of GPR55. In this review, we will focus on the role of GPR55 in energy balance and glucose metabolism. We will summarize its actions on feeding, nutrient partitioning, gastrointestinal motility and insulin secretion in preclinical models and the scarce data available in humans. The potential of GPR55 to become a new pharmaceutical target to treat obesity and type 2 diabetes, as well as the foreseeing difficulties are also discussed.”  https://www.ncbi.nlm.nih.gov/pubmed/28196832

 “GPR55 – a putative “type 3” cannabinoid receptor in inflammation.”  https://www.ncbi.nlm.nih.gov/pubmed/26669245
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Metabolism of endocannabinoids.

“Endocannabinoids belong to a group of ester, ether and amide derivatives of fatty acids, which are endogenous ligands of receptors CB1, CB2, TRPV1 and GPR55 that are included in the endocannabinoid system of the animal organism. The best known endocannabinoids are: N-arachidonylethanolamide called anandamide (AEA) and 2-arachidonoylglycerol (2-AG). They occur in all organisms, and their highest level is observed in the brain. In this review the mechanisms of synthesis and degradation of both AEA and 2-AG are shown. Endocannabinoids are synthesized from phospholipids (mainly phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol) located in the cell membrane. As a result of arachidonic acid transfer from phosphatidylcholine to phosphatidylethanolamine, N-arachidonoyl phosphatidylethanolamine is formed, which is hydrolyzed to AEA by phospholipase D, C and A2. However, 2-AG is formed during the hydrolysis of phosphatidylinositol catalyzed mainly by DAGL. The primary role of endocannabinoids is the activation of cannabinoid receptors. Both AEA and 2-AG are primarily agonists of the CB1 receptor and to a lower degree CB2 and TRPV1r eceptors, but 2-AG has stronger affinity for these receptors. Through activation of receptors, endocannabinoids affect cellular metabolism and participate in the metabolic processes by receptor-independent pathways. Endocannabinoids which are not bound to the receptors are degraded. The main enzymes responsible for the hydrolysis of AEA and 2-AG are FAAH and MAGL, respectively. Apart from hydrolytic degradation, endocannabinoids may also be oxidized by cyclooxygenase-2, lipoxygenases, and cytochrome P450. It has been shown that the metabolites of both endocannabinoids also have biological significance.”

http://www.ncbi.nlm.nih.gov/pubmed/27516570

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