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

Prolonged oral cannabinoid administration prevents neuroinflammation, lowers β-amyloid levels and improves cognitive performance in Tg APP 2576 mice

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“Background

Alzheimer’s disease (AD) brain shows an ongoing inflammatory condition and non-steroidal anti-inflammatories diminish the risk of suffering the neurologic disease. Cannabinoids are neuroprotective and anti-inflammatory agents with therapeutic potential.”

“… we have shown that chronically administered cannabinoid showed marked beneficial effects concomitant with inflammation reduction and increased Aβ clearance.”

“Cannabinoids, whether plant derived, synthetic or endocannabinoids, interact with two well characterized cannabinoid receptors, CB1 and CB2 . In addition, some cannabinoids may interact with other receptors, such as the TRPV1 receptor or the orphan receptor GPR55. The CB1 receptor is widely distributed, with a particularly high expression in brain, which contrasts with the limited expression of the CB2 receptor, which is characteristic of immune organs and cells. In fact, while CB1 receptors are expressed by all types of cells in the brain (neurons and glial cells), CB2 are mainly localized in microglial cells, the resident immune cell of the brain.”

“We and others have proposed cannabinoids as preventive treatment for AD, based on their neuroprotective and anti-inflammatory effects. Indeed, cannabinoids are able to decrease the release of cytokines and nitric oxide in cultured microglial cells induced by lipopolysacharide and Aβ addition. In several in vitro studies cannabidiol (CBD), the major non-psychotropic constituent of cannabis, has shown to be neuroprotective against β-amyloid (Aβ) addition to cultured cells.”

“Conclusions

In summary, cannabinoid agonists, in particular CB2 selective agonists, interfere with several interconnected events of importance in the pathophysiology of AD. These compounds by directly interacting with cannabinoid receptors, in particular CB2, decrease microglial activation thereby reducing inflammation and its consequences (eg cognitive deficits). At the same time they may indirectly have beneficial effects on microglial activation (eg decrease cytokine release) by lowering brain Aβ levels.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292807/

Cannabinoids as novel anti-inflammatory drugs

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Figure 1

“Cannabinoids are a group of compounds that mediate their effects through cannabinoid receptors. The discovery of Δ9-tetrahydrocannabinol (THC) as the major psychoactive principle in marijuana, as well as the identification of cannabinoid receptors and their endogenous ligands, has led to a significant growth in research aimed at understanding the physiological functions of cannabinoids. Cannabinoid receptors include CB1, which is predominantly expressed in the brain, and CB2, which is primarily found on the cells of the immune system. The fact that both CB1 and CB2 receptors have been found on immune cells suggests that cannabinoids play an important role in the regulation of the immune system. Recent studies demonstrated that administration of THC into mice triggered marked apoptosis in T cells and dendritic cells, resulting in immunosuppression. In addition, several studies showed that cannabinoids downregulate cytokine and chemokine production and, in some models, upregulate T-regulatory cells (Tregs) as a mechanism to suppress inflammatory responses. The endocannabinoid system is also involved in immunoregulation. For example, administration of endocannabinoids or use of inhibitors of enzymes that break down the endocannabinoids, led to immunosuppression and recovery from immune-mediated injury to organs such as the liver. Manipulation of endocannabinoids and/or use of exogenous cannabinoids in vivo can constitute a potent treatment modality against inflammatory disorders. This review will focus on the potential use of cannabinoids as a new class of anti-inflammatory agents against a number of inflammatory and autoimmune diseases that are primarily triggered by activated T cells or other cellular immune components.”

“Cannabis, commonly known as marijuana, is a product of the Cannabis sativa plant and the active compounds from this plant are collectively referred to as cannabinoids. For several centuries, marijuana has been used as an alternative medicine in many cultures and, recently, its beneficial effects have been shown in: the treatment of nausea and vomiting associated with cancer chemotherapy; anorexia and cachexia seen in HIV/AIDS patients; and in neuropathic pain and spasticity in multiple sclerosis. Cannabinoid pharmacology has made important advances in recent years after the discovery of the cannabinoid receptors (CB1 and CB2). Cannabinoid receptors and their endogenous ligands have provided an excellent platform for the investigation of the therapeutic effects of cannabinoids. It is well known that CB1 and CB2 are heterotrimeric Gi/o-protein-coupled receptors and that they are both expressed in the periphery and the CNS. However, CB1 expression is predominant in the CNS, especially on presynaptic nerves, and CB2 is primarily expressed on immune cells.”

“Cannabinoids are potent anti-inflammatory agents and they exert their effects through induction of apoptosis, inhibition of cell proliferation, suppression of cytokine production and induction of T-regulatory cells (Tregs).”

“Executive summary

  • Cannabinoids, the active components of Cannabis sativa, and endogenous cannabinoids mediate their effects through activation of specific cannabinoid receptors known as cannabinoid receptor 1 and 2 (CB1 and CB2).
  • The cannabinoid system has been shown both in vivo and in vitro to be involved in regulating the immune system through its immunomodulatory properties.
  • Cannabinoids suppress inflammatory response and subsequently attenuate disease symptoms. This property of cannabinoids is mediated through multiple pathways such as induction of apoptosis in activated immune cells, suppression of cytokines and chemokines at inflammatory sites and upregulation of FoxP3+ regulatory T cells.
  • Cannabinoids have been tested in several experimental models of autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, colitis and hepatitis and have been shown to protect the host from the pathogenesis through induction of multiple anti-inflammatory pathways.
  • Cannabinoids may also be beneficial in certain types of cancers that are triggered by chronic inflammation. In such instances, cannabinoids can either directly inhibit tumor growth or suppress inflammation and tumor angiogenesis.”                      http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2828614/

Cannabidiol for neurodegenerative disorders: important new clinical applications for this phytocannabinoid?

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Abstract

“Cannabidiol (CBD) is a phytocannabinoid with therapeutic properties for numerous disorders exerted through molecular mechanisms that are yet to be completely identified. CBD acts in some experimental models as an anti-inflammatory, anticonvulsant, antioxidant, antiemetic, anxiolytic and antipsychotic agent, and is therefore a potential medicine for the treatment of neuroinflammation, epilepsy, oxidative injury, vomiting and nausea, anxiety and schizophrenia, respectively. The neuroprotective potential of CBD, based on the combination of its anti-inflammatory and antioxidant properties, is of particular interest and is presently under intense preclinical research in numerous neurodegenerative disorders. In fact, CBD combined with Δ(9) -tetrahydrocannabinol is already under clinical evaluation in patients with Huntington’s disease to determine its potential as a disease-modifying therapy. The neuroprotective properties of CBD do not appear to be exerted by the activation of key targets within the endocannabinoid system for plant-derived cannabinoids like Δ(9) -tetrahydrocannabinol, i.e. CB(1) and CB(2) receptors, as CBD has negligible activity at these cannabinoid receptors, although certain activity at the CB(2) receptor has been documented in specific pathological conditions (i.e. damage of immature brain). Within the endocannabinoid system, CBD has been shown to have an inhibitory effect on the inactivation of endocannabinoids (i.e. inhibition of FAAH enzyme), thereby enhancing the action of these endogenous molecules on cannabinoid receptors, which is also noted in certain pathological conditions. CBD acts not only through the endocannabinoid system, but also causes direct or indirect activation of metabotropic receptors for serotonin or adenosine, and can target nuclear receptors of the PPAR family and also ion channels.”

http://www.ncbi.nlm.nih.gov/pubmed/22625422

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

Cannabinoids as Therapeutic Agents for Ablating Neuroinflammatory Disease

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“Cannabinoids have been reported to alter the activities of immune cells in vitro and in vivo. These compounds may serve as ideal agents for adjunct treatment of pathological processes that have a neuroinflammatory component. As highly lipophilic molecules, they readily access the brain. Furthermore, they have relatively low toxicity and can be engineered to selectively target cannabinoid receptors. To date, two cannabinoid receptors have been identified, characterized and designated CB1 and CB2. CB1 appears to be constitutively expressed within the CNS while CB2 apparently is induced during inflammation. The inducible nature of CB2 extends to microglia, the resident macrophages of the brain that play a critical role during early stages of inflammation in that compartment. Thus, the cannabinoid-cannabinoid receptor system may prove therapeutically manageable in ablating neuropathogenic disorders such as Alzheimer’s disease, multiple sclerosis, amyotrophic.”

“The marijuana plant, Cannabis sativa, has been consumed therapeutically and recreationally for centuries because of its medicinal and psychotropic attributes. Cannabis contains a complex array of substances, including a group of terpenoid-like, highly lipophilic compounds referred to as cannabinoids. To date, over 60 cannabinoids have been identified from the marijuana plant. Cannabinoids account for the majority of the effects attributed to marijuana that users experience, including euphoria, impaired perception and memory, and mild sedation. While cannabinoids have been used to abolish loss of appetite and to ablate nausea and pain in patients suffering from severe medical disorders, these compounds also possess immune modulatory properties that may prove detrimental to human health. However, accumulating evidence suggests that cannabinoids also may serve as therapeutic agents in neuropathogenic diseases, pathologically hallmarked by elicitation of pro-inflammatory factors by cells of the central nervous system (CNS) and infiltrated peripheral immunocytes. Cannabinoids have the potential to be ideal therapeutic candidates in abolishing inflammatory neuropathies in that they can readily penetrate the blood brain barrier (BBB) to access the brain, have low levels of toxicity, and can specifically exert their effects through cannabinoid receptors. The major cannabinoid receptor type that appears to be targeted in neuroinflammation is cannabinoid receptor 2 (CB2). This receptor has been identified in select cells of the CNS, can be induced on demand during early inflammatory events, and has been shown to attenuate pro-inflammatory cytokine production by microglia, the resident macrophages of the brain that play a central role in many neuropathological processes.”

“In the present review the immune modulatory properties of cannabinoids, including their relation to interaction with cannabinoid receptors as linked to inflammatory neuropathies will be discussed. Included in this review will be an overview of the signal transduction cascades associated with cannabinoid receptors, and the effects of cannabinoid receptor signaling on immune cell function and immunity, and more importantly in the CNS. These discussions will lay the groundwork for the critical element of this review, in which we explore the potential of cannabinoid receptors to serve as therapeutic targets to attenuate the elicitation of pro-inflammatory mediators during neuropathogenic diseases and disorders such as Alzheimer’s disease (AD), Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), HIV Encephalitis (HIVE), Closed Head Injury (CHI) and Granulomatous Amebic Encephalitis (GAE).”

“It is apparent that therapeutic intervention at an early stage of neuroinflammation is critical. The recognition that microglia express CB2 and that its activation results in ablation of untoward immune responses indicates that this receptor may serve as an ideal therapeutic target. Cannabinoids, as highly lipophilic compounds, can readily penetrate the BBB and access the brain. Furthermore, these compounds can be designed to have low toxicity, minimal psychotropic properties, and to selectively target cells that express the CB2, particularly microglia that serve as endogenous immune cells of the CNS and that play a prominent role in neuroinflammatory processes.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2750822/

Nonpsychotropic Cannabinoid Receptors Regulate Microglial Cell Migration

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“During neuroinflammation, activated microglial cells migrate toward dying neurons, where they exacerbate local cell damage. The signaling molecules that trigger microglial cell migration are poorly understood. In this paper, we show that pathological overstimulation of neurons by glutamate plus carbachol dramatically increases the production of the endocannabinoid 2-arachidonylglycerol (2-AG) but only slightly increases the production of anandamide and does not affect the production of two putative endocannabinoids, homo-γ-linolenylethanolamide and docosatetraenylethanolamide. We further show that pathological stimulation of microglial cells with ATP also increases the production of 2-AG without affecting the amount of other endocannabinoids. Using a Boyden chamber assay, we provide evidence that 2-AG triggers microglial cell migration. This effect of 2-AG occurs through CB2 and abnormal-cannabidiol-sensitive receptors, with subsequent activation of the extracellular signal-regulated kinase 1/2 signal transduction pathway. It is important to note that cannabinol and cannabidiol, two nonpsychotropic ingredients present in the marijuana plant, prevent the 2-AG-induced cell migration by antagonizing the CB2 and abnormal-cannabidiol-sensitive receptors, respectively. Finally, we show that microglial cells express CB2 receptors at the leading edge of lamellipodia, which is consistent with the involvement of microglial cells in cell migration. Our study identifies a cannabinoid signaling system regulating microglial cell migration. Because this signaling system is likely to be involved in recruiting microglial cells toward dying neurons, we propose that cannabinol and cannabidiol are promising nonpsychotropic therapeutics to prevent the recruitment of these cells at neuroinflammatory lesion sites.”

“Because marijuana produces remarkable beneficial effects, patients with multiple sclerosis, for example, commonly use this plant as a therapeutic agent; however, we still lack essential information on the mechanistic basis of these beneficial effects.”

“The marijuana plant, Cannabis sativa, contains >60 cannabinoid compounds, the best known being Δ9-tetrahydrocannabinol (THC), cannabinol (CBN), and cannabidiol (CBD) (for review, see. Cannabinoid compounds produce their biological effects by acting through at least three cannabinoid receptors (see Table1). These include the cloned cannabinoid CB1 receptors, which are expressed predominately in the CNS, the cloned cannabinoid CB2 receptors, which are expressed predominately by immune cells, and the abnormal-cannabidiol-sensitive receptors (hereafter referred to as abn-CBD receptors). The latter receptors have not been cloned yet, but they have been pinpointed pharmacologically in mice lacking CB1 and CB2 receptors and are also known as anandamide (AEA) receptors.”

“We also show that CBN and CBD, two nonpsychotropic bioactive compounds of marijuana, may antagonize the 2-AG-induced recruitment of microglial cells. This is in agreement with the fact that nabilone, a synthetic analog of THC, produces minimal palliative effects against multiple sclerosis symptoms, whereas smoking cannabis is reported to be beneficial. Therefore, our results suggest that bioactive cannabinoids present in the marijuana plant, such as CBN and CBD, are likely to underlie the increased efficacy of cannabis versus nabilone and therefore hold promise as nonpsychotropic therapeutics to treat neuroinflammation.”

http://www.jneurosci.org/content/23/4/1398.long

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

Inflammation and aging: can endocannabinoids help?

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“Aging often leads to cognitive decline due to neurodegenerative process in the brain. As people live longer, a growing concern exist linked to long-term, slowly debilitating diseases that have not yet found a cure, such as Alzheimer’s disease. Recently, the role of neuroinflammation has attracted attention due to its slow onset, chronic nature and its possible role in the development of many different neurodegenerative diseases. In the future, treatment of chronic neuroinflammation may help counteract aspects of neurodegenerative disease. Our recent studies have focused upon the endocannabinoid system for its unique effects on the expression of neuroinflammation. The basis for the manipulation of the endocannabinoid system in the brain in combination with existing treatments for Alzheimer’s disease will be discussed in this review.”

“Endocannabinoids

Cannabinoid refers to naturally occurring or synthetic molecules mimicking the activity of plant-derived cannabinoids from Cannabis Sativa. Two types of cannabinoid receptors have been so far identified in the body, named CB1 and CB2. Discovery of cannabinoid receptors (CBr) lead to the finding of endogenous agonists for these receptors called endocannabinoids (EC). EC are derived from arachidonic acid, arachidonoylethanolamide (anandamide), and 2-arachidonoyl glycerol (2-AG), synthesized on-demand post-synaptically and released in response to the entry of calcium ions. These EC in combination with the two known CBr constitute the endocannabinoid system (ECS). In the central nervous system (CNS), CB1 is overwhelmingly represented over CB2 and particularly abundant in cortical regions, the hippocampus, cerebellum and basal ganglia while CB2 may be restricted to microglia or neurons in the brainstem  and cerebellum. Deactivation of the EC is due to a rapid enzymatic degradation in the synaptic cleft or after membrane transport. The ECS is thought to be a neuromodulator and an immunomodulator. In the CNS, the ECS can influence food intake, endocrine release, motor control, cognitive processes, emotions and perception. Cannabinoids treatment has been shown to be neuroprotective under many experimental conditions. Drugs that manipulate the ECS are currently evaluated in various diseases ranging from cancer to AIDS for their peripheral analgesic and immunosuppressive properties. Their anti-inflammatory actions may make them useful in the treatment of multiple sclerosis, Parkinson’s disease and AD. Very little in vivo evidence to support the use of EC receptor agonists has been reported, although in vitro studies have found evidence for their anti-inflammatory effectiveness. Our recent work demonstrated the anti-inflammatory effect of a chronic treatment of a low dose of the CBr agonist WIN-55,212-2 (without psychoactive effects) on the consequences of chronic neuroinflammation induced by the infusion of LPS into the 4th ventricle of young rats. Moreover, that same anti-inflammatory effect was found using a non-psychoactive dose given by slow subcutaneous infusion of WIN-55,212-2 to healthy aged rats; these rats also demonstrated improved spatial memory. Our ongoing work in aged rats has shown that treatment with the CBr agonist WIN-55,212-2 increases neurogenesis in the hippocampus. Our preliminary data suggest that the neurogenic and anti-inflammatory effects in aged rats are due to the agonist/antagonist properties of WIN-55,212-2 at multiple receptors.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2408719/

Cannabinoids attenuate the effects of aging upon neuroinflammation and neurogenesis.

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Abstract

“WIN-55,212-2 (WIN-2) can elicit anti-inflammatory and cognitive-enhancing effect in aged rats. The current study was designed to determine the differential role of the endocannabinoid receptor sub-types 1 (CB1) and 2 (CB2) and transient receptor potential vanilloid 1 receptor (TRPV1) in the reduction of age-associated brain inflammation and their effects on neurogenesis in the dentate gyrus of aged rats. Our results demonstrate that 1) the antagonist actions of WIN-2 at the TRPV1 receptor are responsible for the reduction in microglial activation and 2) the agonist actions of WIN-2 at CB1/2 receptors can trigger neurogenesis in the hippocampus of aged rats. Chronic treatment with WIN-2 established an anti-inflammatory cytokine profile within the hippocampus. Our results provide insight into the role of the endocannabinoid and vanilloid systems upon two different and detrimental aspects of normal and pathological aging, chronic neuroinflammation and decline in neurogenesis.”

http://www.ncbi.nlm.nih.gov/pubmed/19385063

Role of endocannabinoids and cannabinoid CB1 receptors in alcohol-related behaviors.

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Abstract

“This review presents the remarkable research during the past several years indicating that some of the pharmacological and behavioral effects of alcohol, including alcohol drinking and alcohol-preferring behavior, are mediated through one of the most abundant neurochemical systems in the central nervous system, the endocannabinoid signaling system. The advances, with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the mammalian system and brain, have helped in understanding the neurobiological basis for drugs of abuse, including alcoholism. The cDNA and genomic sequences encoding G-protein-coupled cannabinoid receptors (CB1 and CB2) from several species have now been cloned. This has facilitated discoveries of endogenous ligands (endocannabinoids). To date, two fatty acid derivatives characterized to be arachidonylethanolamide and 2-arachidonylglycerol have been isolated from both nervous and peripheral tissues. Both these compounds have been shown to mimic the pharmacological and behavioral effects of Delta9-tetrahydrocannabinol, the psychoactive component of marijuana. The involvement of the endocannabinoid signaling system in tolerance development to drugs of abuse, including alcohol, were unknown until recently. Studies from our laboratory demonstrated for the first time the downregulation of CB1 receptor function and its signal transduction by chronic alcohol. The observed downregulation of CB1 receptor binding and its signal transduction results from the persistent stimulation of receptors by the endogenous CB1 receptor agonists arachidonylethanolamide and 2-arachidonylglycerol, the synthesis of which is increased by chronic alcohol treatment. The deletion of CB1 receptor has recently been shown to block voluntary alcohol intake in mice, which is consistent with our previous findings where the DBA/2 mice known to avoid alcohol intake had significantly reduced brain CB1 receptor function. These findings suggest a role for the CB1 receptor gene in excessive alcohol drinking behavior and development of alcoholism. Ongoing investigations may lead to the development of potential therapeutic agents to modulate the endocannabinoid signaling system, which will be helpful for the treatment of alcoholism.”

http://www.ncbi.nlm.nih.gov/pubmed/15542757