Cannabinoid receptor ligand bias: implications in the central nervous system.

 

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“The G protein-coupled cannabinoid receptors CB1, CB2, GPR18, and GPR55 regulate neurotransmission, pain, and inflammation and have been intensively investigated as potential drug targets. Each of these GPCRs is coupled to multiple effector proteins mediating divergent cellular signals. The ligand bias of cannabinoid-targeted compounds is only beginning to be quantified. Research into cannabinoid bias is now revealing correlations between bias in cell culture and functional outcomes in vivo. We present an example study of cannabinoid bias in the context of Huntington disease. In future, an understanding of cannabinoid receptor structure and quantification of ligand bias will optimize drug selection matched to patient population and disease.”

https://www.ncbi.nlm.nih.gov/pubmed/27835801

Cannabinoids and Dementia: A Review of Clinical and Preclinical Data.

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“The endocannabinoid system has been shown to be associated with neurodegenerative diseases and dementia.

We review the preclinical and clinical data on cannabinoids and four neurodegenerative diseases: Alzheimer’s disease (AD), Huntington’s disease (HD), Parkinson’s disease (PD) and vascular dementia (VD).

Numerous studies have demonstrated an involvement of the cannabinoid system in neurotransmission, neuropathology and neurobiology of dementias. In addition, several candidate compounds have demonstrated efficacy in vitro.

However, some of the substances produced inconclusive results in vivo. Therefore, only few trials have aimed to replicate the effects seen in animal studies in patients. Indeed, the literature on cannabinoid administration in patients is scarce.

While preclinical findings suggest causal treatment strategies involving cannabinoids, clinical trials have only assessed the suitability of cannabinoid receptor agonists, antagonists and cannabidiol for the symptomatic treatment of dementia.

Further research is needed, including in vivo models of dementia and human studies.”

https://www.ncbi.nlm.nih.gov/pubmed/27713372

Targeting Cannabinoid CB2 Receptors in the Central Nervous System. Medicinal Chemistry Approaches with Focus on Neurodegenerative Disorders.

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“Endocannabinoids activate two types of specific G-protein-coupled receptors (GPCRs), namely cannabinoid CB1 and CB2. Contrary to the psychotropic actions of agonists of CB1 receptors, and serious side effects of the selective antagonists of this receptor, drugs acting on CB2 receptors appear as promising drugs to combat CNS diseases (Parkinson’s disease, Huntington’s chorea, cerebellar ataxia, amyotrohic lateral sclerosis). Differential localization of CB2 receptors in neural cell types and upregulation in neuroinflammation are keys to understand the therapeutic potential in inter alia diseases that imply progressive neurodegeneration. Medicinal chemistry approaches are now engaged to develop imaging tools to map receptors in the living human brain, to develop more efficacious agonists, and to investigate the possibility to develop allosteric modulators.”

THC (Δ9-Tetrahydrocannabinol) Exerts Neuroprotective Effect in Glutamate-affected Murine Primary Mesencephalic Cultures Through Restoring Mitochondrial Membrane Potential and Anti-apoptosis Involving CB1 Receptor-dependent Mechanism.

Phytotherapy Research

“Aging-related neurodegenerative diseases, such as Parkinson’s disease (PD) or related disorders, are an increasing societal and economic burden worldwide.

Δ9-Tetrahydrocannabinol (THC) is discussed as a neuroprotective agent in several in vitro and in vivo models of brain injury. However, the mechanisms by which THC exhibits neuroprotective properties are not completely understood.

In the present study, we investigated neuroprotective mechanisms of THC in glutamate-induced neurotoxicity in primary murine mesencephalic cultures, as a culture model for PD.

THC protected dopaminergic neurons and other cell types of primary dissociated cultures from glutamate-induced neurotoxicity.

Moreover, THC significantly counteracted the glutamate-induced mitochondrial membrane depolarization and apoptosis.

In conclusion, THC exerts anti-apoptotic and restores mitochondrial membrane potential via a mechanism dependent on CB1 receptor.

It strengthens the fact that THC has a benefit on degenerative cellular processes occurring, among others, in PD and other neurodegenerative diseases by slowing down the progression of neuronal cell death.”

https://www.ncbi.nlm.nih.gov/pubmed/27654887

http://onlinelibrary.wiley.com/wol1/doi/10.1002/ptr.5712/full

Cannabinoids: Glutamatergic Transmission and Kynurenines.

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“The endocannabinoid system (ECS) comprises a complex of receptors, enzymes, and endogenous agonists that are widely distributed in the central nervous system of mammals and participates in a considerable number of neuromodulatory functions, including neurotransmission, immunological control, and cell signaling. In turn, the kynurenine pathway (KP) is the most relevant metabolic route for tryptophan degradation to form the metabolic precursor NAD(+).

Recent studies demonstrate that the control exerted by the pharmacological manipulation of the ECS on the glutamatergic system in the brain may offer key information not only on the development of psychiatric disorders like psychosis and schizophrenia-like symptoms, but it also may constitute a solid basis for the development of therapeutic strategies to combat excitotoxic events occurring in neurological disorders like Huntington’s disease (HD).

Part of the evidence pointing to the last approach is based on experimental protocols demonstrating the efficacy of cannabinoids to prevent the deleterious actions of the endogenous neurotoxin and KP metabolite quinolinic acid (QUIN).

These findings intuitively raise the question about what is the precise role of the ECS in tryptophan metabolism through KP and vice versa. In this chapter, we will review basic concepts on the physiology of both the ECS and the KP to finally describe those recent findings combining the components of these two systems and hypothesize the future course that the research in this emerging field will take in the next years.”

Type-2 Cannabinoid Receptors in Neurodegeneration.

“Based on its wide expression in immune cells, type 2 cannabinoid (CB2) receptors were traditionally thought to act as “peripheral receptors” with an almost exclusively immunomodulatory function. However, their recent identification in mammalian brain areas, as well as in distinct neuronal cells, has opened the way to a re-consideration of CB2 signaling in the context of brain pathophysiology, synaptic plasticity and neuroprotection. To date, accumulated evidence from several independent preclinical studies has offered new perspectives on the possible involvement of CB2signaling in brain and spinal cord traumatic injury, as well as in the most relevant neurodegenerative disorders like Alzheimer’s disease, Parkinson’s disease and Huntington’s chorea. Here, we will review available information on CB2 in these disease conditions, along with data that support also its therapeutic potential to treat them.”

http://www.ncbi.nlm.nih.gov/pubmed/27450295

VCE-003.2, a novel cannabigerol derivative, enhances neuronal progenitor cell survival and alleviates symptomatology in murine models of Huntington’s disease.

“Cannabinoids have shown to exert neuroprotective actions in animal models by acting at different targets including canonical cannabinoid receptors and PPARγ.

We previously showed that VCE-003, a cannabigerol (CBG) quinone derivative, is a novel neuroprotective and anti-inflammatory cannabinoid acting through PPARγ. We have now generated a non-thiophilic VCE-003 derivative named VCE-003.2 that preserves the ability to activate PPARγ and analyzed its neuroprotective activity.

This compound exerted a prosurvival action in progenitor cells during neuronal differentiation, which was prevented by a PPARγ antagonist, without affecting neural progenitor cell proliferation. In addition, VCE-003.2 attenuated quinolinic acid (QA)-induced cell death and caspase-3 activation and also reduced mutant huntingtin aggregates in striatal cells.

The neuroprotective profile of VCE-003.2 was analyzed using in vivo models of striatal neurodegeneration induced by QA and 3-nitropropionic acid (3NP) administration. VCE-003.2 prevented medium spiny DARPP32(+) neuronal loss in these Huntington’s-like disease mice models improving motor deficits, reactive astrogliosis and microglial activation. In the 3NP model VCE-003.2 inhibited the upregulation of proinflammatory markers and improved antioxidant defenses in the brain.

These data lead us to consider VCE-003.2 to have high potential for the treatment of Huntington’s disease (HD) and other neurodegenerative diseases with neuroinflammatory traits.”

http://www.ncbi.nlm.nih.gov/pubmed/27430371

The bright side of psychoactive substances: cannabinoid-based drugs in motor diseases.

“Psychoactive substances are associated with the idea of drugs with high addictive liability, affecting mental states, cognition, emotion and motor behavior. However these substances can modify synaptic transmission and help to disclose some mechanisms underlying alterations in brain processing and pathophysiology of motor disease. Hence, the “bright side” of cannabinoid-based drugs must be thoroughly examined to be identified within the latter framework.

We will analyze the preclinical and clinical evidence of cannabinoid-based drugs, discussing their therapeutic value in basal ganglia motor disorders such as Parkinson’s disease and Huntington disease.

Expert commentary: despite the knowledge acquired in the last years, the therapeutic potential of cannabinoid-based drugs should be further tested by novel routes of investigation. This should be focused on the role of cannabinoid signaling system in mitochondrial function as well as on the physical and functional interaction with other key receptorial targets belonging to this network.”

http://www.ncbi.nlm.nih.gov/pubmed/27373318

Endocannabionoid System in Neurological Disorders.

“Several studies support the evidence that the endocannabinoid system and cannabimimetic drugs might have therapeutic potential in numerous pathologies. These pathologies range from neurological disorders, atherosclerosis, stroke, cancer to obesity/metabolic syndrome and others.

In this paper we review the endocannabinoid system signaling and its alteration in neurodegenerative disorders like multiple sclerosis, Alzheimer’s disease, Parkinson’s disease and Huntington’s disease and discuss the main findings about the use of cannabinoids in the therapy of these pathologies.

Despite different etiologies, neurodegenerative disorders exhibit similar mechanisms like neuro-inflammation, excitotoxicity, deregulation of intercellular communication, mitochondrial dysfunction and disruption of brain tissue homeostasis.

Current treatments ameliorate the symptoms but are not curative.

Interfering with the endocannabinoid signaling might be a valid therapeutic option in neuro-degeneration.

To this aim, pharmacological intervention to modulate the endocannabinoid system and the use of natural and synthetic cannabimimetic drugs have been assessed. CB1 and CB2 receptor signaling contributes to the control of Ca2+ homeostasis, trophic support, mitochondrial activity, and inflammatory conditions.

Several studies and patents suggest that the endocannabinoid system has neuro-protective properties and might be a target in neurodegenerative diseases.”

http://www.ncbi.nlm.nih.gov/pubmed/27364363

Neuroprotection by Cannabinoids in Huntington’s Disease

“A Double Blind, Randomized, Cross Over, Placebo Controlled Phase 2 Clinical Trial to Asses Neuroprotection by Cannabinoids in Huntington’s Disease.”

ClinicalTrials.gov

“Huntington’s disease (HD) is a progressive neurodegenerative disorder, related to an abnormal expansion of CAG triplets in the huntingtin gene, characterized by motor, cognitive and behavioral abnormalities, without known effective symptomatic treatment and without known disease slowing strategy. The most severe neuropathological lesions observed in HD take place in the striatum, one brain area important in motor control and rich in cannabinoid receptors (CBR). CBR are subdivided in two classes: CB1R are located in neurons and play a role in neuronal function; CB2R in brain are located mostly in microglia and modulate neuroinflammation.

CBR disappear early in the course of HD, before there is a massive drop out of cells in the striatum. Cannabinoid transmission is also an early event in brains of animal models of HD. In R6/2 mice, which carry large CAG expansions and develop an early and severe HD phenotype the suppression of the CB1R gene further accelerate the development of a severe clinical syndrome and the characteristic brain inclusions and abnormalities of synaptic density. R6/2 treated mice treated with cannabinoids improve their clinical phenotype, their brain lesions, the synaptic density and the levels of BNDF, a neurotrophic factor which enhances survival and resistance of striatal neurons.

Preliminary studies of cannabinoids in patients with HD have shown that these compounds are safe in these patients.”

https://clinicaltrials.gov/show/NCT01502046