Category Archives: Parkinson’s Disease

CB1 cannabinoid receptor signalling in Parkinson’s disease.

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Abstract

“Signalling at CB(1) cannabinoid receptors plays a key role in the control of movement in health and disease. In recent years, an increased understanding of the physiological role of transmission at CB(1) receptors throughout the basal ganglia circuitry has led to the identification of novel therapeutic approaches to both the symptoms of Parkinson’s disease and the side effects of current anti-parkinsonian therapies, especially L(3,4) dihydroxyphenylalamine (levodopa)-induced dyskinesia. Thus, because activation of basal ganglia CB(1) receptors can modulate neurotransmission and contribute to synaptic plasticity in a manner similar to that described in other brain regions, it also appears that endocannabinoids might modulate cell-cell signalling via effects on neurotransmitter re-uptake and postsynaptic actions mediating cross talk between multiple receptor types. Recent studies in animal models and in the clinic suggest that CB(1) receptor antagonists could prove useful in the treatment of parkinsonian symptoms and levodopa-induced dyskinesia, whereas CB(1) receptor agonists could have value in reducing levodopa-induced dyskinesia.”

http://www.ncbi.nlm.nih.gov/pubmed/12550742

Depression in Parkinson’s disease is related to a genetic polymorphism of the cannabinoid receptor gene (CNR1).

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Abstract

“Depression is a common symptom in Parkinson’s disease (PD) and it is present in up to 40% of the patients. The cause of depression in PD is thought to be related to disturbance of monoamine neurotransmission. The endogenous cannabinoid system mediates different brain processes that play a role in the control of behaviour and emotions. Cannabinoid function may be altered in neuropsychiatry diseases, directly or through interactions with monoamine, GABA and glutamate systems. For this reason, we have investigated whether there is a genetic risk factor for depression in PD linked to the polymorphisms of CB1 receptor gene. Depression was more frequent in patients with PD than in controls with osteoarthritis. The presence of depression did not correlate with the stage of the disease but it was more frequent in patients with pure akinetic syndrome than in those with tremoric or mixed type PD. The CB1 receptor gene polymorphism (AAT)n is considered to modify the transcription of the gene and, therefore, it may have functional relevance. We analysed the length of the polymorphic triplet (AAT)n of the gene that encodes CB1 (CNR1) receptor in 89 subjects (48 PD patients and 41 controls). In patients with PD, the presence of two long alleles, with more than 16 repeated AAT trinucleotides in the CNR1 gene, was associated with a reduced prevalence of depression (Fisher’s exact test: P=0.003). This association did not reach significant differences in the control group, but the number of control individuals with depression was too small to allow for statistical analysis. Since the alleles with long expansions may have functional impact in cannabinoid neurotransmission, our data suggest that the pharmacological manipulation of cannabinoid neurotransmission could open a new therapeutic approach for the treatment of depression in PD and possibly in other conditions.”

http://www.ncbi.nlm.nih.gov/pubmed/15668727

Cannabinoids reduce levodopa-induced dyskinesia in Parkinson’s disease: a pilot study.

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Abstract

“The lateral segment of the globus pallidus (GPl) is thought to be overactive in levodopa-induced dyskinesia in PD. Stimulation of cannabinoid receptors in the GPl reduces gamma-aminobutyric acid (GABA) reuptake and enhances GABA transmission and may thus alleviate dyskinesia. In a randomized, double-blind, placebo-controlled, crossover trial (n = 7), the authors demonstrate that the cannabinoid receptor agonist nabilone significantly reduces levodopa-induced dyskinesia in PD.”

http://www.ncbi.nlm.nih.gov/pubmed/11739835

Cannabinoids provide neuroprotection against 6-hydroxydopamine toxicity in vivo and in vitro: relevance to Parkinson’s disease.

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Abstract

“Cannabinoids have been reported to provide neuroprotection in acute and chronic neurodegeneration. In this study, we examined whether they are also effective against the toxicity caused by 6-hydroxydopamine, both in vivo and in vitro, which may be relevant to Parkinson’s disease (PD). First, we evaluated whether the administration of cannabinoids in vivo reduces the neurodegeneration produced by a unilateral injection of 6-hydroxydopamine into the medial forebrain bundle. As expected, 2 weeks after the application of this toxin, a significant depletion of dopamine contents and a reduction of tyrosine hydroxylase activity in the lesioned striatum were noted, and were accompanied by a reduction in tyrosine hydroxylase-mRNA levels in the substantia nigra. None of these events occurred in the contralateral structures. Daily administration of delta9-tetrahydrocannabinol (delta9-THC) during these 2 weeks produced a significant waning in the magnitude of these reductions, whereas it failed to affect dopaminergic parameters in the contralateral structures. This effect of delta9-THC appeared to be irreversible since interruption of the daily administration of this cannabinoid after the 2-week period did not lead to the re-initiation of the 6-hydroxydopamine-induced neurodegeneration. In addition, the fact that the same neuroprotective effect was also produced by cannabidiol (CBD), another plant-derived cannabinoid with negligible affinity for cannabinoid CB1 receptors, suggests that the antioxidant properties of both compounds, which are cannabinoid receptor-independent, might be involved in these in vivo effects, although an alternative might be that the neuroprotection exerted by both compounds might be due to their anti-inflammatory potential. As a second objective, we examined whether cannabinoids also provide neuroprotection against the in vitro toxicity of 6-hydroxydopamine. We found that the non-selective cannabinoid agonist HU-210 increased cell survival in cultures of mouse cerebellar granule cells exposed to this toxin. However, this effect was significantly lesser when the cannabinoid was directly added to neuronal cultures than when these cultures were exposed to conditioned medium obtained from mixed glial cell cultures treated with HU-210, suggesting that the cannabinoid exerted its major protective effect by regulating glial influence to neurons. In summary, our results support the view of a potential neuroprotective action of cannabinoids against the in vivo and in vitro toxicity of 6-hydroxydopamine, which might be relevant for PD. Our data indicated that these neuroprotective effects might be due, among others, to the antioxidant properties of certain plant-derived cannabinoids, or exerted through the capability of cannabinoid agonists to modulate glial function, or produced by a combination of both mechanisms.”

http://www.ncbi.nlm.nih.gov/pubmed/15837565

Neuroprotection by Δ9-Tetrahydrocannabinol, the Main Active Compound in Marijuana, against Ouabain-Induced In Vivo Excitotoxicity

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“These results provide evidence that the cannabinoid system can serve to protect the brain against neurodegeneration.”

“In summary, we have shown that in an in vivo model of neurodegeneration Δ9-THC reduces neuronal damage via a CB1-receptor-mediated mechanism. This holds in both the acute and late phase after induction of excitotoxicity. Δ9-THC inhibits astrogliosis via a non-CB1-receptor-controlled mechanism. The results strengthen the concept that the endogenous cannabinoid system may serve to establish a defense system for the brain. This system may be functional in several neurodegenerative diseases in which excitotoxicity is thought to play a role, such as amyotrophic lateral sclerosis, Huntington’s and Parkinson’s diseases, and also in acute neuronal damage as found in stroke and traumatic brain injury. It is conceivable that the endogenous cannabinoid system can be exploited for therapeutic interventions in these types of primarily incurable diseases.”

http://www.jneurosci.org/content/21/17/6475.long

The cannabinoid system and pain: towards new drugs?

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Abstract

“The various components of the endocannabinoid system were discovered in the last twenty years. The cannabinoid system has attracted pharmacologists interest for its potential as therapeutic targets for several diseases ranging from obesity to Parkinson’s disease and from multiple sclerosis to pain. Research initially focused on cannabinoid receptor 1 (CB1), but, due to psychotropic side effects related to its activation, the attempts to develop an agonist drug for this receptor has been so far unsuccessful. Recently the possibility to target CB2 has emerged as an alternative for the treatment of pain. The main advantage of targeting CB2 resides in the possibility to elicit the analgesic effect without the psychotropic side effects. Evidence of the analgesic effect of CB2 selective agonists has been obtained in various models of both inflammatory and neuropathic chronic pain. To explain the mechanism at the basis of this analgesic effect different hypotheses have been proposed: effect on inflammatory cells, reduction of basal NGF tone, induction of beta-endorphin release from keratinocytes, direct action on nociceptors. Evidence in support of this last hypothesis comes from down regulation of capsaicin-induced CGRP release in spinal cord slices and Dorsal Root Ganglia (DRG) neurons in culture after treatment with CB2 selective agonists. CB2 agonists are probably acting through several mechanisms and thus CB2 represents an interesting and promising target in the chronic pain field. Further clarification of the mechanisms at the basis of CB2 analgesic effect would surely be an intriguing and stimulating area of research for the years to come.”

http://www.ncbi.nlm.nih.gov/pubmed/19358815

From cannabis to the endocannabinoid system: refocussing attention on potential clinical benefits.

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Image result for West Indian Med J

“Cannabis sativa is one of the oldest herbal remedies known to man. Over the past four thousand years, it has been used for the treatment of numerous diseases but due to its psychoactive properties, its current medicinal usage is highly restricted. In this review, we seek to highlight advances made over the last forty years in the understanding of the mechanisms responsible for the effects of cannabis on the human body and how these can potentially be utilized in clinical practice. During this time, the primary active ingredients in cannabis have been isolated, specific cannabinoid receptors have been discovered and at least five endogenous cannabinoid neurotransmitters (endocannabinoids) have been identified. Together, these form the framework of a complex endocannabinoid signalling system that has widespread distribution in the body and plays a role in regulating numerous physiological processes within the body. Cannabinoid ligands are therefore thought to display considerable therapeutic potential and the drive to develop compounds that can be targeted to specific neuronal systems at low enough doses so as to eliminate cognitive side effects remains the ‘holy grail’ of endocannabinoid research.”

http://www.ncbi.nlm.nih.gov/pubmed/23155985

Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities.

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Philosophical Transactions of the Royal Society B: Biological Sciences: 367 (1607)

“Human tissues express cannabinoid CB(1) and CB(2) receptors that can be activated by endogenously released ‘endocannabinoids’ or exogenously administered compounds in a manner that reduces the symptoms or opposes the underlying causes of several disorders in need of effective therapy. Three medicines that activate cannabinoid CB(1)/CB(2) receptors are now in the clinic: Cesamet (nabilone), Marinol (dronabinol; Δ(9)-tetrahydrocannabinol (Δ(9)-THC)) and Sativex (Δ(9)-THC with cannabidiol). These can be prescribed for the amelioration of chemotherapy-induced nausea and vomiting (Cesamet and Marinol), stimulation of appetite (Marinol) and symptomatic relief of cancer pain and/or management of neuropathic pain and spasticity in adults with multiple sclerosis (Sativex). This review mentions several possible additional therapeutic targets for cannabinoid receptor agonists. These include other kinds of pain, epilepsy, anxiety, depression, Parkinson’s and Huntington’s diseases, amyotrophic lateral sclerosis, stroke, cancer, drug dependence, glaucoma, autoimmune uveitis, osteoporosis, sepsis, and hepatic, renal, intestinal and cardiovascular disorders. It also describes potential strategies for improving the efficacy and/or benefit-to-risk ratio of these agonists in the clinic. These are strategies that involve (i) targeting cannabinoid receptors located outside the blood-brain barrier, (ii) targeting cannabinoid receptors expressed by a particular tissue, (iii) targeting upregulated cannabinoid receptors, (iv) selectively targeting cannabinoid CB(2) receptors, and/or (v) adjunctive ‘multi-targeting’.”  https://www.ncbi.nlm.nih.gov/pubmed/23108552

“Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities”  http://rstb.royalsocietypublishing.org/content/367/1607/3353.long

Cannabinoid receptor stimulation is anti-inflammatory and improves memory in old rats

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“The number of activated microglia increase during normal aging. Stimulation of endocannabinoid receptors can reduce the number of activated microglia, particularly in the hippocampus, of young rats infused chronically with lipopolysaccharide (LPS). In the current study we demonstrate that endocannabinoid receptor stimulation by administration of WIN-55212-2 (2 mg/kg/day) can reduce the number of activated microglia in hippocampus of aged rats and attenuate the spatial memory impairment in the water pool task. Our results suggest that the action of WIN-55212-2 does not depend upon a direct effect upon microglia or astrocytes but is dependent upon stimulation of neuronal cannabinoid receptors. Aging significantly reduced cannabinoid type 1 receptor binding but had no effect on cannabinoid receptor protein levels. Stimulation of cannabinoid receptors may provide clinical benefits in age-related diseases that are associated with brain inflammation, such as Alzheimer’s disease.”

“Our results are consistent with the hypothesis that CB receptors on hippocampal neurons modulate glutamatergic and GABAergic function and this leads to reduced microglia activation. This mechanism may underlie the neuroprotective effects of cannabinoids”.

“Importantly, the benefits of cannabinoid receptor stimulation occurred at a dose that did not impair performance in a spatial memory task, indeed the performance of aged rats was significantly improved. This finding is particularly relevant for elderly for patients suffering with diseases associated with brain inflammation, e.g. AD, Parkinson’s disease or multiple sclerosis. The current report is the first to our knowledge to demonstrate the anti-inflammatory actions of cannabinoid therapy in aged animals and strongly advocate an cannabinoid-based therapy for neuroinflammation-related diseases, as well as a potential tool to reduce the impairment in memory processes occurring during normal aging.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2586121/

Cannabinoid receptors and endocannabinoids: role in neuroinflammatory and neurodegenerative disorders.

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Abstract

“The G-protein coupled receptors for Δ⁹-tetrahydrocannabinol, the major psychoactive principle of marijuana, are known as cannabinoid receptors of type 1 (CB₁) and 2 (CB₂) and play important functions in degenerative and inflammatory disorders of the central nervous system. Whilst CB₁ receptors are mostly expressed in neurons, where they regulate neurotransmitter release and synaptic strength, CB₂ receptors are found mostly in glial cells and microglia, which become activated and over-express these receptors during disorders such as Alzheimer’s disease, multiple sclerosis, amyotropic lateral sclerosis, Parkinson’s disease, and Huntington’s chorea. The neuromodulatory actions at CB₁ receptors by endogenous agonists (‘endocannabinoids’), of which anandamide and 2-arachidonoylglycerol are the two most studied representatives, allows them to counteract the neurochemical unbalances arising during these disorders. In contrast, the immunomodulatory effects of these lipophilic mediators at CB₂ receptors regulate the activity and function of glia and microglia. Indeed, the level of expression of CB₁ and CB₂ receptors or of enzymes controlling endocannabinoid levels, and hence the concentrations of endocannabinoids, undergo time- and brain region-specific changes during neurodegenerative and neuroinflammatory disorders, with the initial attempt to counteract excitotoxicity and inflammation. Here we discuss this plasticity of the endocannabinoid system during the aforementioned central nervous system disorders, as well as its dysregulation, both of which have opened the way to the use of either direct and indirect activators or blockers of CB₁ and CB₂ receptors for the treatment of the symptoms or progression of these diseases.”

http://www.ncbi.nlm.nih.gov/pubmed/20632970