Category Archives: Endocannabinoid System

Adolescent ethanol intake alters cannabinoid type-1 receptor localization in astrocytes of the adult mouse hippocampus.

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Addiction Biology

“Cannabinoid type-1 (CB1 ) receptors are widely distributed in the brain and play important roles in astrocyte function and the modulation of neuronal synaptic transmission and plasticity. However, it is currently unknown how CB1 receptor expression in astrocytes is affected by long-term exposure to stressors.

Here we examined CB1 receptors in astrocytes of ethanol (EtOH)-exposed adolescent mice to determine its effect on CB1 receptor localization and density in adult brain.

Our results revealed a significant reduction in CB1 receptor immunoparticles in astrocytic processes of EtOH-exposed mice when compared with controls (positive astrocyte elements: 21.50 ± 2.80 percent versus 37.22 ± 3.12 percent, respectively), as well as a reduction in particle density (0.24 ± 0.02 versus 0.35 ± 0.02 particles/μm).

Altogether, the decrease in the CB1 receptor expression in hippocampal astrocytes of adult mice exposed to EtOH during adolescence reveals a long lasting effect of EtOH on astrocytic CB1 receptors. This deficiency may also have negative consequences for synaptic function.”

https://www.ncbi.nlm.nih.gov/pubmed/29168269

http://onlinelibrary.wiley.com/doi/10.1111/adb.12585/abstract?systemMessage=Wiley+Online+Library+usage+report+download+page+will+be+unavailable+on+Friday+24th+November+2017+at+21%3A00+EST+%2F+02.00+GMT+%2F+10%3A00+SGT+%28Saturday+25th+Nov+for+SGT+

Acetaminophen Relieves Inflammatory Pain Through CB1 Cannabinoid Receptors in the Rostral Ventromedial Medulla.

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Journal of Neuroscience

“Acetaminophen (paracetamol) is a widely used analgesic and antipyretic drug with only incompletely understood mechanisms of action.

Previous work, using models of acute nociceptive pain, indicated that analgesia by acetaminophen involves an indirect activation of CB1 receptors by the acetaminophen metabolite and endocannabinoid re-uptake inhibitor AM 404.  However, the contribution of the cannabinoid system to anti-hyperalgesia against inflammatory pain, the main indication of acetaminophen, and the precise site of the relevant CB1 receptors have remained elusive.

Here, we analyzed acetaminophen analgesia in mice of either sex with inflammatory pain and found that acetaminophen exerted a dose-dependent anti-hyperalgesic action, which was mimicked by intrathecally injected AM 404. Both compounds lost their anti-hyperalgesic activity in CB1-/- mice confirming the involvement of the cannabinoid system.

Our results indicate that the cannabinoid system contributes not only to acetaminophen analgesia against acute pain but also against inflammatory pain, and suggest that the relevant CB1 receptors reside in the RVM.

SIGNIFICANCE STATEMENT: Acetaminophen is a widely used analgesic drug with multiple but only incompletely understood mechanisms of action including a facilitation of endogenous cannabinoid signaling via one of its metabolites. Our present data indicate that enhanced cannabinoid signaling is also responsible for the analgesic effects of acetaminophen against inflammatory pain. Local injections of the acetaminophen metabolite AM 404 and of cannabinoid receptor antagonists as well as data from tissue specific CB1 receptor deficient mice suggest the rostral ventromedial medulla as an important site of the cannabinoid-mediated analgesia by acetaminophen.”

https://www.ncbi.nlm.nih.gov/pubmed/29167401

http://www.jneurosci.org/content/early/2017/11/22/JNEUROSCI.1945-17.2017

Inhibition of monoacylglycerol lipase terminates diazepam-resistant status epilepticus in mice and its effects are potentiated by a ketogenic diet.

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Epilepsia

“Status epilepticus (SE) is a life-threatening and commonly drug-refractory condition. Novel therapies are needed to rapidly terminate seizures to prevent mortality and morbidity.

Monoacylglycerol lipase (MAGL) is the key enzyme responsible for the hydrolysis of the endocannabinoid 2-arachidonoylglycerol (2-AG) and a major contributor to the brain pool of arachidonic acid (AA). Inhibiting of monoacylglycerol lipase modulates synaptic activity and neuroinflammation, 2 mediators of excessive neuronal activation underlying seizures.

We studied the effect of a potent and selective irreversible MAGL inhibitor, CPD-4645, on SE that was refractory to diazepam, its neuropathologic sequelae, and the mechanism underlying the drug’s effects.

SIGNIFICANCE:

MAGL represents a novel therapeutic target for treating status epilepticus and improving its sequelae. CPD-4645 therapeutic effects appear to be predominantly mediated by modulation of neuroinflammation.”

https://www.ncbi.nlm.nih.gov/pubmed/29171003

http://onlinelibrary.wiley.com/doi/10.1111/epi.13950/abstract?systemMessage=Wiley+Online+Library+usage+report+download+page+will+be+unavailable+on+Friday+24th+November+2017+at+21%3A00+EST+%2F+02.00+GMT+%2F+10%3A00+SGT+%28Saturday+25th+Nov+for+SGT+

Regulation of noradrenergic and serotonergic systems by cannabinoids: relevance to cannabinoid-induced effects.

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“The cannabinoid system is composed of Gi/o protein-coupled cannabinoid type 1 receptor (CB1) and cannabinoid type 2 (CB2) receptor and endogenous compounds. The CB1 receptor is widely distributed in the central nervous system (CNS) and it is involved in the regulation of common physiological functions. At the neuronal level, the CB1 receptor is mainly placed at GABAergic and glutamatergic axon terminals, where it modulates excitatory and inhibitory synapses. To date, the involvement of CB2 receptor in the regulation of neurotransmission in the CNS has not been clearly shown. The majority of noradrenergic (NA) cells in mammalian tissues are located in the locus coeruleus (LC) while serotonergic (5-HT) cells are mainly distributed in the raphe nuclei including the dorsal raphe nucleus (DRN). In the CNS, NA and 5-HT systems play a crucial role in the control of pain, mood, arousal, sleep-wake cycle, learning/memory, anxiety, and rewarding behaviour. This review summarizes the electrophysiological, neurochemical and behavioural evidences for modulation of the NA/5-HT systems by cannabinoids and the CB1 receptor. Cannabinoids regulate the neuronal activity of NA and 5-HT cells and the release of NA and 5-HT by direct and indirect mechanisms. The interaction between cannabinoid and NA/5-HT systems may underlie several behavioural changes induced by cannabis such as anxiolytic and antidepressant effects or side effects (e.g. disruption of attention). Further research is needed to better understand different aspects of NA and 5-HT systems regulation by cannabinoids, which would be relevant for their use in therapeutics.”

https://www.ncbi.nlm.nih.gov/pubmed/29169951

http://www.sciencedirect.com/science/article/pii/S0024320517306069”

Synthesis of Photoswitchable Δ9-Tetrahydrocannabinol Derivatives Enables Optical Control of Cannabinoid Receptor 1 Signaling.

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Journal of the American Chemical Society

“The cannabinoid receptor 1 (CB1) is an inhibitory G protein-coupled receptor abundantly expressed in the central nerv-ous system. It has rich pharmacology and largely accounts for the recreational use of cannabis. We describe efficient asymmetric syntheses of four photoswitchable Δ9-tetrahydrocannabinol derivatives (azo-THCs) from a central building block 3-Br-THC. Using electrophysiology and a FRET-based cAMP assay, two compounds are identified as potent CB1 agonists that change their effect upon illumination. As such, azo-THCs enable CB1-mediated optical control of inwardly-rectifying potassium channels, as well as adenylyl cyclase.”

https://www.ncbi.nlm.nih.gov/pubmed/29161035

http://pubs.acs.org/doi/10.1021/jacs.7b06456

Current evidence of cannabinoid-based analgesia obtained in preclinical and human experimental settings.

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European Journal of Pain

“Cannabinoids have a long record of recreational and medical use and become increasingly approved for pain therapy. This development is based on preclinical and human experimental research summarized in this review.

Cannabinoid CB1 receptors are widely expressed throughout the nociceptive system. Their activation by endogenous or exogenous cannabinoids modulates the release of neurotransmitters. This is reflected in antinociceptive effects of cannabinoids in preclinical models of inflammatory, cancer and neuropathic pain, and by nociceptive hypersensitivity of cannabinoid receptor-deficient mice.

Cannabis-based medications available for humans mainly comprise Δ9 -tetrahydrocannabinol (THC), cannabidiol (CBD) and nabilone.

During the last 10 years, six controlled studies assessing analgesic effects of cannabinoid-based drugs in human experimental settings were reported. An effect on nociceptive processing could be translated to the human setting in functional magnetic resonance imaging studies that pointed at a reduced connectivity within the pain matrix of the brain. However, cannabinoid-based drugs heterogeneously influenced the perception of experimentally induced pain including a reduction in only the affective but not the sensory perception of pain, only moderate analgesic effects, or occasional hyperalgesic effects. This extends to the clinical setting.

While controlled studies showed a lack of robust analgesic effects, cannabis was nearly always associated with analgesia in open-label or retrospective reports, possibly indicating an effect on well-being or mood, rather than on sensory pain. Thus, while preclinical evidence supports cannabinoid-based analgesics, human evidence presently provides only reluctant support for a broad clinical use of cannabinoid-based medications in pain therapy.

SIGNIFICANCE:

Cannabinoids consistently produced antinociceptive effects in preclinical models, whereas they heterogeneously influenced the perception of experimentally induced pain in humans and did not provide robust clinical analgesia, which jeopardizes the translation of preclinical research on cannabinoid-mediated antinociception into the human setting.”

https://www.ncbi.nlm.nih.gov/pubmed/29160600

http://onlinelibrary.wiley.com/doi/10.1002/ejp.1148/abstract?systemMessage=Wiley+Online+Library+usage+report+download+page+will+be+unavailable+on+Friday+24th+November+2017+at+21%3A00+EST+%2F+02.00+GMT+%2F+10%3A00+SGT+%28Saturday+25th+Nov+for+SGT+

Effects of chronic Δ9-tetrahydrocannabinol treatment on Rho/Rho-kinase signalization pathway in mouse brain.

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Saudi Pharmaceutical Journal

“Δ9-Tetrahydrocannabinol (Δ9-THC) shows its effects by activating cannabinoid receptors which are on some tissues and neurons. Cannabinoid systems have role on cell proliferation and development of neurons. Furthermore, it is interesting that cannabinoidsystem and rho/rho-kinase signalization pathway, which have important role on cell development and proliferation, may have role on neuron proliferation and development together. Thus, a study is planned to investigate rhoA and rho-kinase enzyme expressions and their activities in the brain of chronic Δ9-THC treated mice. One group of mice are treated with Δ9-THC once to see effects of acute treatment. Another group of mice are treated with Δ9-THC three times per day for one month. After this period, rhoA and rho-kinase enzyme expressions and their activities in mice brains are analyzed by ELISA method. Chronic administration of Δ9-THC decreased the expression of rhoA while acute treatment has no meaningful effect on it. Administration of Δ9-THC did not affect expression of rho-kinase on both chronic and acute treatment. Administration of Δ9-THC increased rho-kinase activity on both chronic and acute treatment, however, chronic treatment decreased its activity with respect to acute treatment. This study showed that chronic Δ9-THC treatment down-regulated rhoA expression and did not change the expression level of rho-kinase which is downstream effector of rhoA. However, it elevated the rho-kinase activity. Δ9-THC induced down-regulation of rhoA may cause elevation of cypin expression and may have benefit on cypin related diseases. Furthermore, use of rho-kinase inhibitors and Δ9-THC together can be useful on rho-kinase related diseases.”

https://www.ncbi.nlm.nih.gov/pubmed/29158718
http://www.sciencedirect.com/science/article/pii/S1319016417301081?via%3Dihub

Modulating the endocannabinoid pathway as treatment for peripheral neuropathic pain: a selected review of preclinical studies.

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“Chemotherapy-induced neuropathic pain is a distressing and commonly occurring side effect of many commonly used chemotherapeutic agents, which in some cases may prevent cancer patients from being able to complete their treatment.

Cannabinoid based therapies have the potential to manage or even prevent pain associated with this syndrome.

Pre-clinical animal studies that investigate the modulation of the endocannabinoid system (endogenous cannabinoid pathway) are being conducted to better understand the mechanisms behind this phenomenon.

Five recent pre-clinical studies identified from Medline published between 2013 and 2016 were selected for review. All studies evaluated the effect of small-molecule agonists or antagonists on components of the endocannabinoid system in rats or mice, using cisplatin or paclitax-el-induced allodynia as a model of chemotherapy-induced neuropathic pain. Activation of the cannabinoid receptor-2 (CB-2) receptor by AM1710 blocked paclitaxel-induced mechanical and cold allodynia in one study.

Four studies investigating the activation of both cannabinoid receptor-1 (CB-1) and CB-2 receptors by dual-agonists (WIN55,21 and CP55,940), or by the introduction of inhibitors of endocannabinoid metabolisers (URB597, URB937, JZL184, and SA-57) showed reduction of chemotherapy-induced al-lodynia. In addition, their results suggest that anti-allodynic effects may also be mediated by additional receptors, including TRPV1 and 5-hydroxytryptamine (5-HT1A).

Pre-clinical studies demon-strate that the activation of endocannabinoid CB-1 or CB-2 receptors produces physiological effects in animal models, namely the reduction of chemotherapy-induced allodynia. These studies also provide in-sight into the biological mechanism behind the therapeutic utility of cannabis compounds in managing chemotherapy-induced neuropathic pain, and provide a basis for the conduct of future clinical studies in patients of this population.”

https://www.ncbi.nlm.nih.gov/pubmed/29156899
http://apm.amegroups.com/article/view/16320

Cannabinoid Receptor Type 1 Agonist ACEA Protects Neurons from Death and Attenuates Endoplasmic Reticulum Stress-Related Apoptotic Pathway Signaling.

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Neurotoxicity Research

“Neurodegeneration is the result of progressive destruction of neurons in the central nervous system, with unknown causes and pathological mechanisms not yet fully elucidated. Several factors contribute to neurodegenerative processes, including neuroinflammation, accumulation of neurotoxic factors, and misfolded proteins in the lumen of the endoplasmic reticulum (ER).

Endocannabinoid signaling has been pointed out as an important modulatory system in several neurodegeneration-related processes, inhibiting the inflammatory response and increasing neuronal survival. Thus, we investigated the presumptive protective effect of the selective cannabinoid type 1 (CB1) receptor agonist) against inflammatory (lipopolysaccharide, LPS) and ER stress (tunicamycin) stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells). Cell viability analysis revealed that ACEA was able to protect against cell death induced by LPS and tunicamycin.

This neuroprotective effect occurs via the CB1 receptor in the inflammation process and via the transient receptor potential of vanilloid type-1 (TRPV1) channel in ER stress. Furthermore, the immunoblotting analyses indicated that the neuroprotective effect of ACEA seems to involve the modulation of eukaryotic initiation factor 2 (eIF2α), transcription factor C/EBP homologous protein (CHOP), and caspase 12, as well as the survival/death p44/42 MAPK, ERK1/2-related signaling pathways.

Together, these data suggest that the endocannabinoid system is a potential therapeutic target in neurodegenerative processes, especially in ER-related neurodegenerative diseases.”

https://www.ncbi.nlm.nih.gov/pubmed/29134561

https://link.springer.com/article/10.1007%2Fs12640-017-9839-1

Involvement of cannabinoid receptor type 2 in light-induced degeneration of cells from mouse retinal cell line in vitro and mouse photoreceptors in vivo.

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Experimental Eye Research

“Earlier studies showed that the expressions of the agonists of the cannabinoid receptors are reduced in the vitreous humor of patients with age-related macular degeneration (AMD), and the cannabinoid type 2 receptor is present in the retinas of rats and monkeys. The purpose of this study was to determine whether the cannabinoid type 2 receptor is involved in the light-induced death of cultured 661W cells, an immortalized murine retinal cell line, and in the light-induced retinal degeneration in mice.

Time-dependent changes in the expression and location of retinal cannabinoid type 2 receptor were determined by Western blot and immunostaining. The cannabinoid type 2 receptor was down-regulated in murine retinae and cone cells. In the in vitro studies, HU-308, a cannabinoidtype 2 receptor agonist, had a protective effect on the light-induced death of 661W cells, and this effect was attenuated by SR144528, a cannabinoid type 2 receptor antagonist.

Because the cannabinoid type 2 receptor is a G-protein coupled receptor and is coupled with Gi/o protein, we investigated the effects of the cAMP-dependent protein kinase (PKA). HU-308 and H89, a PKA inhibitor, deactivated PKA in retinal cone cells, and H89 also suppressed light-induced cell death. For the in vivo studies, a cannabinoid type 2 receptor agonist, HU-308, or an antagonist, SR144528, was injected intravitreally into mouse eyes before the light exposure. Electroretinography was used to determine the physiological status of the retinas. Injection of HU-308 improved the a- and b-waves of the ERGs and also the thickness of the outer nuclear layer of the murine retina after light exposure.

These findings indicate that the cannabinoid type 2 receptor is involved in the light-induced retinal damage through PKA signaling. Thus, activation of cannabinoidtype 2 receptor may be a therapeutic approach for light-associated retinal diseases.”

https://www.ncbi.nlm.nih.gov/pubmed/29133122

http://www.sciencedirect.com/science/article/pii/S0014483516304456?via%3Dihub