Tag Archives: G-Protein coupled receptors

GPR3 and GPR6, novel molecular targets for cannabidiol.

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“GPR3 and GPR6 are members of a family of constitutively active, Gs protein-coupled receptors. Previously, it has been reported that GPR3 is involved in Alzheimer’s disease whereas GPR6 plays potential roles in Parkinson’s disease.

GPR3 and GPR6 are considered orphan receptors because there are no confirmed endogenous agonists for them. However, GPR3 and GPR6 are phylogenetically related to the cannabinoid receptors.

In this study, the activities of endocannabinoids and phytocannabinoids were tested on GPR3 and GPR6 using a β-arrestin2 recruitment assay. Among the variety of cannabinoids tested, cannabidiol (CBD), the major non-psychoactive component of marijuana, significantly reduced β-arrestin2 recruitment to both GPR3 and GPR6. In addition, the inhibitory effects of CBD on β-arrestin2 recruitment were concentration-dependent for both GPR3 and GPR6, with a higher potency for GPR6.

These data show that CBD acts as an inverse agonist at both GPR3 and GPR6 receptors. These results demonstrate for the first time that both GPR3 and GPR6 are novel molecular targets for CBD.

Our discovery that CBD acts as a novel inverse agonist on both GPR3 and GPR6 indicates that some of the potential therapeutic effects of CBD (e.g. treatment of Alzheimer’s disease and Parkinson’s disease) may be mediated through these important receptors.”

https://www.ncbi.nlm.nih.gov/pubmed/28571738

http://www.sciencedirect.com/science/article/pii/S0006291X17310744

A chronic low dose of Δ9-tetrahydrocannabinol (THC) restores cognitive function in old mice

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“The balance between detrimental, pro-aging, often stochastic processes and counteracting homeostatic mechanisms largely determines the progression of aging. There is substantial evidence suggesting that the endocannabinoid system (ECS) is part of the latter system because it modulates the physiological processes underlying aging.

The activity of the ECS declines during aging, as CB1 receptor expression and coupling to G proteins are reduced in the brain tissues of older animals and the levels of the major endocannabinoid 2-arachidonoylglycerol (2-AG) are lower. However, a direct link between endocannabinoid tone and aging symptoms has not been demonstrated.

Here we show that a low dose of Δ9-tetrahydrocannabinol (THC) reversed the age-related decline in cognitive performance of mice aged 12 and 18 months. This behavioral effect was accompanied by enhanced expression of synaptic marker proteins and increased hippocampal spine density.

THC treatment restored hippocampal gene transcription patterns such that the expression profiles of THC-treated mice aged 12 months closely resembled those of THC-free animals aged 2 months. The transcriptional effects of THC were critically dependent on glutamatergic CB1 receptors and histone acetylation, as their inhibition blocked the beneficial effects of THC.

Thus, restoration of CB1 signaling in old individuals could be an effective strategy to treat age-related cognitive impairments.”

https://www.ncbi.nlm.nih.gov/pubmed/28481360

https://www.nature.com/nm/journal/vaop/ncurrent/full/nm.4311.html

“CAN MARIJUANA RESTORE MEMORY? NEW STUDY SHOWS CANNABIS CAN REVERSE COGNITIVE DECLINE IN MICE” http://www.newsweek.com/cannabis-marijuana-restores-memory-learning-cognitive-decline-596160

“A little cannabis every day might keep brain ageing at bay” https://www.newscientist.com/article/2130257-a-little-cannabis-every-day-might-keep-brain-ageing-at-bay/

“Low-dose cannabinoid THC restores memory and learning in old mice”  http://www.medicalnewstoday.com/articles/317342.php

“Daily Dose Of Cannabis May Protect And Heal The Brain From Effects Of Aging”  https://www.forbes.com/sites/janetwburns/2017/05/08/daily-dose-of-cannabis-may-protect-and-heal-the-brain-from-effects-of-aging/#70ef658f2e44

“Cannabis reverses aging processes in the brain”  https://medicalxpress.com/news/2017-05-cannabis-reverses-aging-brain.html

“Future dementia cure – Chemical in cannabis could REVERSE the ageing process” http://www.express.co.uk/life-style/health/801827/dementia-cure-cannabis-THC-chemical-memory

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

Cannabinoids as Modulators of Cell Death: Clinical Applications and Future Directions.

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“Endocannabinoids are bioactive lipids that modulate various physiological processes through G-protein-coupled receptors (CB1 and CB2) and other putative targets. By sharing the activation of the same receptors, some phytocannabinoids and a multitude of synthetic cannabinoids mimic the effects of endocannabinoids.

In recent years, a growing interest has been dedicated to the study of cannabinoids properties for their analgesic, antioxidant, anti-inflammatory and neuroprotective effects. In addition to these well-recognized effects, various studies suggest that cannabinoids may affect cell survival, cell proliferation or cell death. These observations indicate that cannabinoids may play an important role in the regulation of cellular homeostasis and, thus, may contribute to tissue remodelling and cancer treatment.

For a long time, the study of cannabinoid receptor signalling has been focused on the classical adenylyl cyclase/cyclic AMP/protein kinase A (PKA) pathway. However, this pathway does not totally explain the wide array of biological responses to cannabinoids. In addition, the diversity of receptors and signalling pathways that endocannabinoids modulate offers an interesting opportunity for the development of specific molecules to disturb selectively the endogenous system.

Moreover, emerging evidences suggest that cannabinoids ability to limit cell proliferation and to induce tumour-selective cell death may offer a novel strategy in cancer treatment.

This review describes the main properties of cannabinoids in cell death and attempts to clarify the different pathways triggered by these compounds that may help to understand the complexity of respective molecular mechanisms and explore the potential clinical benefit of cannabinoids use in cancer therapies.”

https://www.ncbi.nlm.nih.gov/pubmed/28425013

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

Binding Site Characterization of AM1336, a Novel Covalent Inverse Agonist at Human Cannabinoid 2 Receptor, Using Mass Spectrometric Analysis.

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“Cannabinoid 2 receptor (CB2R), a Class A G-protein coupled receptor (GPCR), is a promising drug target in a wide array of pathological conditions. Rational drug design has been hindered due to our poor understanding of the structural features involved in ligand binding. Binding of a high-affinity biarylpyrazole inverse agonist AM1336 to a library of the human CB2 receptor (hCB2R) cysteine-substituted mutants provided indirect evidence that two cysteines in transmembrane helix-7 (H7) were critical for the covalent attachment. Here, we used proteomics analysis of the hCB2R with bound AM1336 to directly identify peptides with covalently attached ligand and applied in-silico modeling for visualization of the ligand-receptor interactions. The hCB2R, with affinity tags (FlaghCB2His6), was produced in a baculovirus-insect cell expression system and purified as a functional receptor using immunoaffinity chromatography. Using mass spectrometry-based bottom-up proteomic analysis of the hCB2R-AM1336 we identified a peptide with AM1336 attached to the cysteine C284(7.38) in H7. The hCB2R homology model in lipid bilayer accommodated covalent attachment of AM1336 to C284(7.38), supporting both biochemical and mass spectrometric data. This work consolidates proteomics data and in-silico modeling, and integrates with our ligand-assisted protein structure (LAPS) experimental paradigm to assist in structure-based design of cannabinoid antagonist/inverse agonists.”

https://www.ncbi.nlm.nih.gov/pubmed/28374590

Cell-Autonomous Excitation of Midbrain Dopamine Neurons by Endocannabinoid-Dependent Lipid Signaling.

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“The major endocannabinoid in the mammalian brain is the bioactive lipid 2-arachidonoylglycerol (2-AG). The best-known effects of 2-AG are mediated by G-protein-coupled cannabinoid receptors. In principle, 2-AG could modify neuronal excitability by acting directly on ion channels, but such mechanisms are poorly understood.

Using a preparation of dissociated mouse midbrain dopamine neurons to isolate effects on intrinsic excitability, we found that 100 nM 2-AG accelerated pacemaking and steepened the frequency-current relationship for burst-like firing. In voltage-clamp experiments, 2-AG reduced A-type potassium current (IA) through a cannabinoid receptor-independent mechanism mimicked by arachidonic acid, which has no activity on cannabinoid receptors. Activation of orexin, neurotensin, and metabotropic glutamate Gq/11-linked receptors mimicked the effects of exogenous 2-AG and their actions were prevented by inhibiting the 2-AG-synthesizing enzyme diacylglycerol lipase α.

The results show that 2-AG and related lipid signaling molecules can directly tune neuronal excitability in a cell-autonomous manner by modulating IA.”

https://www.ncbi.nlm.nih.gov/pubmed/28262417

Cannabinoid HU210 Protects Isolated Rat Stomach against Impairment Caused by Serum of Rats with Experimental Acute Pancreatitis

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“Acute pancreatitis (AP), especially severe AP, is a potentially lethal inflammatory disease of pancreas which often leads to extra-pancreatic complications, even multiple systemic organ dysfunctions. It has been reported that 52% of patients with acute pancreatitis develop acute gastrointestinal mucosal lesion (AGML) or stress ulcer.

For centuries, Cannabis plant and its extracts have been used to alleviate symptoms of gastrointestinal inflammatory diseases.

It has been established that D9-tetrahydrocannabinol, the major psychoactive component of Cannabis, exerts its primary cellular actions though two G protein-coupled receptors, cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptors.

Since then, these two receptors have been recognized as the major regulators of physiological and pathological processes. Cannabinoids can reduce gastrointestinal secretion, and the activation of CB1 receptor exhibits protective role against stress-induced AGML, but the mechanisms of their action remain elusive.

The results from this study prove that the inflammatory responses and the imbalance of the gastric secretion during the development of AP are responsible for the pathogenesis of AGML, and suggest the therapeutic potential of HU210 for AGML associated with acute pancreatitis.

Therefore, our experimental results suggest a novel mechanism in the onset of AGML and new therapeutic values of cannabinoids as supplement of anti-inflammatory therapy in acute pancreatitis.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3532296/

Cannabinoid receptor subtype 2 (CB2R) agonist, GW405833 reduces agonist-induced Ca2+ oscillations in mouse pancreatic acinar cells

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“Acute pancreatitis is an inflammatory disease, which has several causes and symptoms and requires immediate medical attention.

The cannabinoid receptor type 2 (CB2R) is a G protein-coupled receptor that, in humans, is encoded by the CNR2 gene. CB2Rs are predominantly expressed in the periphery, especially in immune cells, suggesting that CB2R mediates the effects of cannabinoids mainly in the immune system.

Emerging evidence demonstrates that the blockade of intracellular Ca2+ signals may protect pancreatic acinar cells against Ca2+ overload, intracellular protease activation, and necrosis.

The activation of cannabinoid receptor subtype 2 (CB2R) prevents acinar cell pathogenesis in animal models of acute pancreatitis.

Collectively, we provide novel evidence that activation of CB2Rs eliminates ACh-induced Ca2+ oscillations and L-arginine-induced enhancement of Ca2+ signaling in mouse pancreatic acinar cells, which suggests a potential cellular mechanism of CB2R-mediated protection in acute pancreatitis.

These results suggest that a CB2R agonist may serve as a novel therapeutic strategy to prevent and/or treat acute pancreatitis. This conclusion is consistent with previous report that a CB2R agonist exhibits a protective effect on pathogenesis in an acute pancreatitis animal model. Our data showing a reduction of intracellular Ca2+ signaling by GW also provide a new target to interpret the role of CB2R agonists in treating acute pancreatitis in addition to CB2R-mediated anti-inflammation.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4949433/

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