Tag Archives: CB(1) and CB(2) receptors

The endocannabinoid system: a promising target for the management of type 2 diabetes.

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“Type 2 diabetes is closely related to abdominal obesity and is generally associated with other cardiometabolic risk factors, resulting in a high incidence of cardiovascular complications.

Several animal and human observations suggest that the endocannabinoid (EC) system is overactivated in presence of abdominal obesity and/or diabetes, and contributes to disturbances of energy balance and metabolism.

Not only it regulates the intake of nutrients through central mechanisms located within the hypothalamus and limbic area, but it also intervenes in transport, metabolism and deposit of the nutrients in the digestive tract, liver, adipose tissue, skeletal muscle, and possibly pancreas.

Activation of both central and peripheral CB1 receptors promotes weight gain and associated metabolic changes. Conversely, rimonabant, the first selective CB(1) receptor antagonist in clinical use, has been shown to reduce body weight, waist circumference, triglycerides, blood pressure, insulin resistance and C-reactive protein levels, and to increase HDL cholesterol and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients.

Rimonabant was generally well-tolerated, but with a slightly higher incidence of depressed mood disorders, anxiety, nausea and dizziness compared to placebo. New trials are supposed to confirm the potential role of rimonabant (and other CB1 neutral antagonists or inverse agonists) in overweight/obese patients with type 2 diabetes and high risk cardiovascular disease.”

Modulation of HIVGP120 Antigen-Specific Immune Responses In Vivo by Δ9-Tetrahydrocannabinol.

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“Approximately 25 % of HIV patients use marijuana for its putative therapeutic benefit…

Previously, a surrogate in vitro mouse model was established, which induced CD8+ T cell proliferation and gp120-specific IFNγ production. ∆9-Tetrahydrocannabinol (THC), the predominant psychoactive compound in marijuana, suppressed or enhanced the responses depending on the magnitude of cellular activation.

The purpose of the current study was to investigate whether THC produced similar effects in vivo and therefore a mouse model to induce HIVgp120-specific immune responses was established…

Collectively, our findings demonstrate that under certain conditions, THC enhances HIV antigen-specific immune responses, which occurs through CB1/CB2-dependent and -independent mechanisms.”

http://www.ncbi.nlm.nih.gov/pubmed/25900076

http://www.thctotalhealthcare.com/category/hivaids/

Differential upregulation of the cannabinoid CB2 receptor in neurotoxic and inflammation-driven rat models of Parkinson’s disease.

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“The cannabinoid CB2 receptor has recently emerged as a potential anti-inflammatory target to break the self-sustaining cycle of neuroinflammation and neurodegeneration that is associated with neurodegenerative diseases.

…the aim of this study was to investigate and compare the changes that occur in the endocannabinoid system in neurotoxic and inflammation-driven models of Parkinson’s disease.

…this study has shown that the endocannabinoid system is dysregulated in animal models of Parkinson’s disease, and has also revealed significant differences in the level of dysregulation between the models themselves.

This study indicates that targeting the CB2 receptor may represent a viable target for anti-inflammatory disease modification in Parkinson’s disease.”

 http://www.ncbi.nlm.nih.gov/pubmed/25895887

http://www.thctotalhealthcare.com/category/parkinsons-disease/

Attenuation of morphine antinociceptive tolerance by cannabinoid CB1 and CB2 receptor antagonists.

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“Cannabinoid CB1 and CB2 receptor antagonists may be useful for their potential to increase or prolong opioid analgesia while attenuating the development of opioid tolerance.

The aim of this study was to investigate the effects of AM251 (a selective CB1 antagonist) and JTE907 (a selective CB2 antagonist) on morphine analgesia and tolerance in rats…

In conclusion, we observed that co-injection of AM251 and JTE907 with morphine attenuated expression of tolerance to morphine analgesic effects and decreased the morphine analgesia.”

http://www.ncbi.nlm.nih.gov/pubmed/25894754

Cannabinoids Inhibit T-cells via Cannabinoid Receptor 2 in an in vitro Assay for Graft Rejection, the Mixed Lymphocyte Reaction

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“Cannabinoids are known to have anti-inflammatory and immunomodulatory properties.

Cannabinoid receptor 2 (CB2) is expressed mainly on leukocytes and is the receptor implicated in mediating many of the effects of cannabinoids on immune processes.

This study tested the capacity of Δ9-tetrahydrocannabinol (Δ9-THC) and of two CB2-selective agonists to inhibit the murine Mixed Lymphocyte Reaction (MLR), an in vitro correlate of graft rejection following skin and organ transplantation. Both CB2-selective agonists and Δ9-THC significantly suppressed the MLR in a dose dependent fashion…

Together, these data support the potential of this class of compounds as useful therapies to prolong graft survival in transplant patients.

Cannabinoids were reported to have effects on immune responses as early as the 1970s, but the basis for this activity was not understood until the cannabinoid receptors were cloned

Ideally, the anatomically disparate expression of CB1 and CB2 would allow for the use of compounds selective for CB2, and thus eliminate the unwanted psychoactive effects from CB1 activation, while maintaining the anti-inflammatory and immunosuppressive properties.

CB2-selective cannabinoids have been proposed as possible candidates to block graft rejection.

The results presented in this paper show that Δ9-THC, a mixed CB1/CB2 agonist, and two CB2-selective agonists can inhibit the Mixed Lymphocyte Reaction (MLR), an in vitro correlate of organ and skin graft rejection.”

 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864984/

Endocannabinoids mediate bidirectional striatal spike-timing dependent plasticity.

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“Synaptic plasticity, a main substrate for learning and memory, is commonly assessed with prolonged stimulations. Since learning can arise from few or even a single trial, synaptic strength is expected to adapt rapidly. However, it remains elusive whether synaptic plasticity occurs in response to limited event occurrences. To answer this question, we investigated if a low number of paired stimulations can induce plasticity in a major synaptic learning rule, the spike-timing dependent plasticity (STDP). It is known that 100 pairings induce bidirectional STDP, i.e. spike-timing-dependent potentiation (tLTP) and depression (tLTD) at most central synapses. In rodent striatum, we found that tLTD progressively disappears when the number of paired stimulations is decreased (below 50 pairings) whereas tLTP displays a biphasic profile: tLTP is observed for 75-100 pairings, absent for 25-50 pairings and reemerges for 5-10 pairings. This tLTP, induced by very few pairings (∼5-10), depends on the endocannabinoid (eCB) system. This eCB-tLTP involves postsynaptic endocannabinoid synthesis, requires paired activity (post- and presynaptic) and the activation of type-1 cannabinoidreceptor (CB1R) and transient receptor potential vanilloid type-1 (TRPV1) activation. eCB-tLTP occurs in both striatopallidal and striatonigral MSNs and is dopamine-dependent. Lastly, we show that eCB-LTP and eCB-LTD can be induced sequentially in the same neuron, depending on the cellular conditioning paradigm. Thus, while usually considered as simply depressing synaptic function, endocannabinoids constitute a versatile system underlying bidirectional plasticity. Our results reveal a novel form of synaptic plasticity, eCB-tLTP, which may underlie rapid learning capabilities characterizing behavioral flexibility.”

http://www.ncbi.nlm.nih.gov/pubmed/25873197

A role for GPR55 in human placental venous endothelial cells.

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“Endocannabinoids and their G protein-coupled receptors have been suggested to play a key role in human pregnancy, by regulating important aspects such as implantation, decidualization, placentation and labor.

G protein-coupled receptor 55 (GPR55) was previously postulated to be another cannabinoid receptor, since specific cannabinoids were shown to act independently of the classical cannabinoid receptors CB1 or CB2.

Current knowledge about GPR55 expression and function in human placenta is very limited and motivated us to evaluate human placental GPR55 expression in relation to other human peripheral tissues and to analyze spatiotemporal GPR55 expression in human placenta.

Gene expression analysis revealed low GPR55 levels in human placenta, when compared to spleen and lung, the organs showing highest GPR55 expression.

Moreover, expression analysis showed 5.8 fold increased placental GPR55 expression at term compared to first trimester. Immunohistochemistry located GPR55 solely at the fetal endothelium of first trimester and term placentas. qPCR and immunocytochemistry consistently confirmed GPR55 expression in isolated primary placental arterial and venous endothelial cells. Incubation with L-α-lysophosphatidylinositol (LPI), the specific and functional ligand for GPR55, at a concentration of 1 µM, significantly enhanced migration of venous, but not arterial endothelial cells.

LPI-enhanced migration was inhibited by the GPR55 antagonist O-1918, suggesting a role of the LPI-GPR55 axis in placental venous endothelium function.”

Minireview: From the Bench, Toward the Clinic: Therapeutic Opportunities for Cannabinoid Receptor Modulation.

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The effects of cannabinoids have been known for centuries and over the past several decades two G-protein coupled receptors, CB1 and CB2, have been identified that are responsible for their activity.

Endogenous lipid-derived cannabinergic agents have been found, biosynthetic and catabolic machinery characterized, and synthetic agents have been designed to modulate these receptors.

Selective agents including agonists, antagonists, inverse agonists and novel allosteric modulators targeting either CB1 or CB2 have been developed to inhibit or augment their basal tone.

As a result, the role these receptors play in human physiology and their potential therapeutic applications in disease states are being elucidated.

The CB1 receptor while ubiquitous is densely expressed in the brain and CB2 is largely found on cells of immune origin.

This minireview highlights the role of CB1 in excitotoxic assaults in the brain and its potential to limit addiction liability.

In addition, it will examine the relationship between receptor activity and stimulation of insulin release from pancreatic β-cells, insulin resistance and feeding behavior leading toward obesity.

The role of CB2 in the neuropathology of amyotrophic lateral sclerosis and in the central manifestations of chronic HIV infection potentially converges at inflammatory cell activation thereby providing an opportunity for intervention.

Lastly, CB2 modulation is discussed in the context of an experimental model of post-menopausal osteoporosis.

Achieving exquisite receptor selectivity and elucidating the mechanisms underlying receptor inhibition and activation will be essential for the development of the next generation of cannabinergic-based therapeutic agents.”

Role of the endogenous cannabinoid system in nicotine addiction: novel insights.

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“Several lines of evidence have shown that the endogenous cannabinoids are implicated in several neuropsychiatric diseases. Notably, preclinical and human clinical studies have shown a pivotal role of the cannabinoid system in nicotine addiction.

The CB1 receptor inverse agonist/antagonist rimonabant (also known as SR141716) was effective to decrease nicotine-taking and nicotine-seeking in rodents, as well as the elevation of dopamine induced by nicotine in brain reward area. Rimonabant has been shown to improve the ability of smokers to quit smoking in randomized clinical trials. However, rimonabant was removed from the market due to increased risk of psychiatric side-effects observed in humans.

Recently, other components of the endogenous cannabinoid system have been explored. Here, we present the recent advances on the understanding of the role of the different components of the cannabinoid system on nicotine’s effects.

Those recent findings suggest possible alternative ways of modulating the cannabinoid system that could have implication for nicotine dependence treatment.”

http://www.ncbi.nlm.nih.gov/pubmed/25859226

http://www.thctotalhealthcare.com/category/addiction/

The role of the endocannabinoid system in pain.

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“Preparations of the Cannabis sativa plant have been used to analgesic effect for millenia, but only in recent decades has the endogenous system responsible for these effects been described.

The endocannabinoid (EC) system is now known to be one of the key endogenous systems regulating pain sensation, with modulatory actions at all stages of pain processing pathways.

The EC system is composed of two main cannabinoid receptors (CB1 and CB2) and two main classes of endogenous ligands or endocannabinoids (ECs).

The receptors have distinct expression profiles, with CB1 receptors found at presynaptic sites throughout the peripheral and central nervous systems (PNS and CNS, respectively), whilst CB2 receptor is found principally (but not exclusively) on immune cells.

The endocannabinoid ligands are lipid neurotransmitters belonging to either the N-acyl ethanolamine (NAEs) class, e.g. anandamide (AEA), or the monoacylglycerol class, e.g. 2-arachidonoyl glycerol (2-AG).

Both classes are short-acting transmitter substances, being synthesised on demand and with signalling rapidly terminated by specific enzymes. ECs acting at CB1 negatively regulate neurotransmission throughout the nervous system, whilst those acting at CB2 regulate the activity of CNS immune cells.

Signalling through both of these receptor subtypes has a role in normal nociceptive processing and also in the development resolution of acute pain states.

In this chapter, we describe the general features of the EC system as related to pain and nociception and discuss the wealth of preclinical and clinical data involving targeting the EC system with focus on two areas of particular promise: modulation of 2-AG signalling via specific enzyme inhibitors and the role of spinal CB2 in chronic pain states.”

http://www.ncbi.nlm.nih.gov/pubmed/25846617

http://www.thctotalhealthcare.com/category/pain-2/