“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/]]>
Tag Archives: G-Protein coupled receptors
Anti-inflammatory role of cannabidiol and O-1602 in cerulein-induced acute pancreatitis in mice.
“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]]>GPR55: a new promising target for metabolism?
“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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Potential of GPCRs to modulate MAPK and mTOR pathways in Alzheimer's disease.
“Despite efforts to understand the mechanism of neuronal cell death, finding effective therapies for neurodegenerative diseases is still a challenge. Cognitive deficits are often associated with neurodegenerative diseases. Remarkably, in the absence of consensus biomarkers, diagnosis of diseases such as Alzheimer’s still relies on cognitive tests. Unfortunately, all efforts to translate findings in animal models to the patients have been unsuccessful. Alzheimer’s disease may be addressed from two different points of view, neuroprotection or cognitive enhancement. Based on recent data, the mammalian target of rapamycin (mTOR) pathway arises as a versatile player whose modulation may impact on mechanisms of both neuroprotection and cognition. Whereas direct targeting of mTOR does not seem to constitute a convenient approach in drug discovery, its indirect modulation by other signaling pathways seems promising. In fact, G-protein-coupled receptors (GPCRs) remain the most common ‘druggable’ targets and as such pharmacological manipulation of GPCRs with selective ligands may modulate phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), mitogen-activated protein (MAP) kinase and mTOR signaling pathways. Thus, GPCRs become important targets for potential drug treatments in different neurodegenerative disorders including, but not limited to, Alzheimer’s disease. GPCR-mediated modulation of mTOR may take advantage of different GPRCs coupled to different G-dependent and G-independent signal transduction routes, of functional selectivity and/or of biased agonism. Signals mediated by GPCRs may act as coincidence detectors to achieve different benefits in different stages of the neurodegenerative disease.” https://www.ncbi.nlm.nih.gov/pubmed/28189739]]>
Potential of GPCRs to modulate MAPK and mTOR pathways in Alzheimer’s disease.
“Despite efforts to understand the mechanism of neuronal cell death, finding effective therapies for neurodegenerative diseases is still a challenge. Cognitive deficits are often associated with neurodegenerative diseases.
Remarkably, in the absence of consensus biomarkers, diagnosis of diseases such as Alzheimer’s still relies on cognitive tests. Unfortunately, all efforts to translate findings in animal models to the patients have been unsuccessful. Alzheimer’s disease may be addressed from two different points of view, neuroprotection or cognitive enhancement.
Based on recent data, the mammalian target of rapamycin (mTOR) pathway arises as a versatile player whose modulation may impact on mechanisms of both neuroprotection and cognition. Whereas direct targeting of mTOR does not seem to constitute a convenient approach in drug discovery, its indirect modulation by other signaling pathways seems promising.
In fact, G-protein-coupled receptors (GPCRs) remain the most common ‘druggable’ targets and as such pharmacological manipulation of GPCRs with selective ligands may modulate phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), mitogen-activated protein (MAP) kinase and mTOR signaling pathways.
Thus, GPCRs become important targets for potential drug treatments in different neurodegenerative disorders including, but not limited to, Alzheimer’s disease. GPCR-mediated modulation of mTOR may take advantage of different GPRCs coupled to different G-dependent and G-independent signal transduction routes, of functional selectivity and/or of biased agonism. Signals mediated by GPCRs may act as coincidence detectors to achieve different benefits in different stages of the neurodegenerative disease.”
Pharmacology of cannabinoids in the treatment of epilepsy.
“The use of cannabis products in the treatment of epilepsy has long been of interest to researchers and clinicians alike; however, until recently very little published data were available to support its use. This article summarizes the available scientific data of pharmacology from human and animal studies on the major cannabinoids which have been of interest in the treatment of epilepsy, including ∆9-tetrahydrocannabinol (∆9-THC), cannabidiol (CBD), ∆9-tetrahydrocannabivarin (∆9-THCV), cannabidivarin (CBDV), and ∆9-tetrahydrocannabinolic acid (Δ9-THCA). It has long been known that ∆9-THC has partial agonist activity at the endocannabinoid receptors CB1 and CB2, though it also binds to other targets which may modulate neuronal excitability and neuroinflammation. The actions of Δ9-THCV and Δ9-THCA are less well understood. In contrast to ∆9-THC, CBD has low affinity for CB1 and CB2 receptors and other targets have been investigated to explain its anticonvulsant properties including TRPV1, voltage gated potassium and sodium channels, and GPR55, among others. We describe the absorption, distribution, metabolism, and excretion of each of the above mentioned compounds. Cannabinoids as a whole are very lipophilic, resulting in decreased bioavailability, which presents challenges in optimal drug delivery. Finally, we discuss the limited drug-drug interaction data available on THC and CBD. As cannabinoids and cannabis-based products are studied for efficacy as anticonvulsants, more investigation is needed regarding the specific targets of action, optimal drug delivery, and potential drug-drug interactions.” https://www.ncbi.nlm.nih.gov/pubmed/28087250]]>
Two Janus cannabinoids that are both CB2 agonists and CB1 antagonists.
“The cannabinoid signaling system includes two G protein coupled receptors, CB1 and CB2. These receptors are widely distributed throughout the body and have each been implicated in many physiologically important processes.
Though the cannabinoid signaling system has therapeutic potential, a persistent hurdle has remained the development of receptor-selective ligands. Because CB1 and CB2 are involved in diverse processes, it would be advantageous develop ligands that differentially engaging CB1 and CB2.
In summary we have determined that GW405833 and AM1710 are not only CB2 agonists but also CB1 antagonists, with distinctive and complex signaling properties. Thus experiments using these compounds must take into account their potential activity at CB1 receptors.”
Decreased CB receptor binding and cannabinoid signaling in three brain regions of a rat model of schizophrenia.
“Schizophrenia is a serious mental health disorder characterized by several behavioral and biochemicel abnormalities.
In a previous study we have shown that mu-opioid (MOP) receptor signaling is impaired in specific brain regions of our three-hit animal model of schizophrenia. Since the cannabinoid system is significantly influenced in schizophrenic patients, in the present work we investigated cannabinoid (CB) receptor binding and G-protein activation in cortical, subcortical and cerebellar regions of control and ‘schizophrenic’ rats.
Taken together, in all three brain areas of model rats both cannabinoid receptor binding and cannabinoid agonist-mediated G-protein activation were regularly decreased.
Our results revealed that besides the opioids, the endocannabinoid – cannabis receptor system also shows impairment in our rat model, increasing its face validity and translational utility.”
Evidence for a GPR18 Role in Diurnal Regulation of Intraocular Pressure.
“The diurnal cycling of intraocular pressure (IOP) was first described in humans more than a century ago. This cycling is preserved in other species. The physiologic underpinning of this diurnal variation in IOP remains a mystery, even though elevated pressure is indicated in most forms of glaucoma, a common cause of blindness. Once identified, the system that underlies diurnal variation would represent a natural target for therapeutic intervention.
We now report that NAPE-PLD and FAAH mice do not exhibit a diurnal cycling of IOP. These enzymes produce and break down acylethanolamines, including the endogenous cannabinoid anandamide. The diurnal lipid profile in mice shows that levels of most N-acyl ethanolamines and, intriguingly, N-arachidonoyl glycine (NAGly), decline at night: NAGly is a metabolite of arachidonoyl ethanolamine and a potent agonist at GPR18 that lowers intraocular pressure. The GPR18 blocker O1918 raises IOP during the day when pressure is low, but not at night. Quantitative PCR analysis shows that FAAH mRNA levels rise with pressure, suggesting that FAAH mediates the changes in pressure.
CONCLUSIONS:
Our results support FAAH-dependent NAGly action at GPR18 as the physiologic basis of the diurnal variation of intraocular pressure in mice.”
Functional selectivity at G-protein coupled receptors: Advancing cannabinoid receptors as drug targets.
“The phenomenon of functional selectivity, whereby a ligand preferentially directs the information output of a G-protein coupled receptor (GPCR) along (a) particular effector pathway(s) and away from others, has redefined traditional GPCR signaling paradigms to provide a new approach to structure-based drug design.
The two principal cannabinoid receptors (CBRs) 1 and 2 belong to the class-A GPCR subfamily and are considered tenable therapeutic targets for several indications. Yet conventional orthosteric ligands (agonists, antagonists/inverse agonists) for these receptors have had very limited clinical utility due to their propensity to incite on-target adverse events. Chemically distinct classes of cannabinergic ligands exhibit signaling bias at CBRs toward individual subsets of signal transduction pathways.
In this review, we discuss the known signaling pathways regulated by CBRs and examine the current evidence for functional selectivity at CBRs in response to endogenous and exogenous cannabinergic ligands as biased agonists. We further discuss the receptor and ligand structural features allowing for selective activation of CBR-dependent functional responses. The design and development of biased ligands may offer a pathway to therapeutic success for novel CBR-targeted drugs.”