Progress in Brain Cannabinoid CB2 Receptor Research: From Genes to Behavior.

Neuroscience & Biobehavioral Reviews

“The type 2 cannabinoid receptor (CB2R) was initially regarded as a peripheral cannabinoid receptor. However, recent technological advances in gene detection, alongside the availability of transgenic mouse lines, indicate that CB2Rs are expressed in both neurons and glial cells in the brain under physiological and pathological conditions, and are involved in multiple functions at cellular and behavioral levels. Brain CB2Rs are inducible and neuroprotective via up-regulation in response to various insults, but display species differences in gene and receptor structures, CB2R expression, and receptor responses to various CB2R ligands. CB2R transcripts also differ between the brain and spleen. In the brain, CB2A is the major transcript isoform, while CB2A and CB2B transcripts are present at higher levels in the spleen. These new findings regarding brain versus spleen CB2R isoforms may in part explain why early studies failed to detect brain CB2R gene expression. Here, we review evidence supporting the expression and function of brain CB2R from gene and receptor levels to cellular functioning, neural circuitry, and animal behavior.”

https://www.ncbi.nlm.nih.gov/pubmed/30611802

https://www.sciencedirect.com/science/article/pii/S0149763418308297?via%3Dihub

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Cannabinoid Receptor Type 1 Agonist ACEA Improves Cognitive Deficit on STZ-Induced Neurotoxicity Through Apoptosis Pathway and NO Modulation.

“The cannabinoid system has the ability to modulate cellular and molecular mechanisms, including excitotoxicity, oxidative stress, apoptosis, and inflammation, acting as a neuroprotective agent, by its relationship with signaling pathways associated to the control of cell proliferation, differentiation, and survival. Recent reports have raised new perspectives on the possible role of cannabinoid system in neurodegenerative diseases like Alzheimer disease’s (AD).

Our study has demonstrated a participation of the cannabinoid system in cellular survival, involving the CB1 receptor, which occurs by positive regulation of the anti-apoptotic proteins, suggesting the participation of this system in neurodegenerative processes. Our data suggest that the cannabinoid system is an interesting therapeutic target for the treatment of neurodegenerative diseases.”

https://www.ncbi.nlm.nih.gov/pubmed/30607903

https://link.springer.com/article/10.1007%2Fs12640-018-9991-2

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Attenuation Effect of Cannabinoid Type 1 Receptor Activation on Methamphetamine-Induced Neurodegeneration and Locomotion Impairments among Male Rats.

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“A number of neuroimaging studies on human addicts have revealed that abuse of Methamphetamine (METH) can induce neurodegenerative changes in various brain regions like the cerebral cortex and cerebellum. Although the underlying mechanisms of METH-induced neurotoxicity have been studied, the cellular and molecular mechanisms of METH-induced neurotoxicity remain to be clarified.

Previous studies implicated that cannabinoid type 1 receptors (CB1Rs) exert neuroprotective effects on several models of cerebral toxicity, but their role in METH-induced neurotoxicity has been rarely investigated. Moreover, the cerebellum was considered as a potential target to evaluate the effects of cannabinoids on locomotion activity as the CB1Rs are most widely distributed in the molecular layer of cerebellum. Therefore, the present study was carried out to evaluate whether neurodegeneration induced in the cerebellum tissue implicated in locomotion deficit induced by METH.

FINDINGS:

The results of the present study demonstrated that repeated exposure to METH increased cerebellar degeneration level as compared to the saline and dimethyl sulfoxide (DMSO) groups. In addition, METH-treated rats showed hyperactivity as compared to the saline and DMSO groups. Pretreatment with WIN significantly attenuated neurodegeneration and hyperactivity induced by METH.

CONCLUSION:

The findings of this study provided evidence that CB1Rs may serve as a therapeutic strategy for attenuation of METH-induced locomotor deficits.”

https://www.ncbi.nlm.nih.gov/pubmed/30574283

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294485/

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Hemp (Cannabis sativa L.) Seed Phenylpropionamides Composition and Effects on Memory Dysfunction and Biomarkers of Neuroinflammation Induced by Lipopolysaccharide in Mice.

ACS Omega

“Hempseed has achieved a growing popularity in human nutrition, particularly regarding essential amino acids and fatty acids. The multiple positive attributes of hempseed have led to the further study of its constituents.

In this study, hempseed extract containing phenylpropionamides (TPA) was obtained and its chemical profile and content were obtained using high-performance liquid chromatography technology based on previous study.

The anti-neuroinflammatory effect of TPA extract was evaluated using a lipopolysaccharide (LPS)-induced mouse model. Fourteen phenylpropionamides (TPA) were identified in the obtained extract with a total content of 233.52 ± 2.50 μg/mg extract.

In mice, TPA prevented the learning and spatial memory damage induced by LPS. Increased brain levels of IL-1β, IL-6, and TNF-α in the LPS-induced mice were reduced by TPA treatment. Furthermore, TPA attenuated LPS-induced hippocampal neuronal damage in mice.

This study demonstrates the nutraceutical potential of hempseed from a neuroprotective perspective.”

https://www.ncbi.nlm.nih.gov/pubmed/30556022

https://pubs.acs.org/doi/10.1021/acsomega.8b02250

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An Analysis of Endocannabinoid Concentrations and Mood Following Singing and Exercise in Healthy Volunteers.

Image result for frontiers in behavioral neuroscience “The euphoric feeling described after running is, at least in part, due to increased circulating endocannabinoids (eCBs). eCBs are lipid signaling molecules involved in reward, appetite, mood, memory and neuroprotection.

The aim of this study was to investigate whether activities other than running can increase circulating eCBs.

Nine healthy female volunteers (mean 61 years) were recruited from a local choir. Circulating eCBs, haemodynamics, mood and hunger ratings were measured before and immediately after 30 min of dance, reading, singing or cycling in a fasted state.

Singing increased plasma levels of anandamide (AEA) by 42% (P < 0.05), palmitoylethanolamine (PEA) by 53% (P < 0.01) and oleoylethanolamine (OEA) by 34% (P < 0.05) and improved positive mood and emotions (P < 0.01), without affecting hunger scores.

Dancing did not affect eCB levels or hunger ratings, but decreased negative mood and emotions (P < 0.01).

Cycling increased OEA levels by 26% (P < 0.05) and tended to decrease how hungry volunteers felt, without affecting mood.

Reading increased OEA levels by 28% (P < 0.01) and increased the desire to eat.

Plasma AEA levels were positively correlated with how full participants felt (P < 0.05). Plasma OEA levels were positively correlated with positive mood and emotions (P < 0.01). All three ethanolamines were positively correlated with heart rate (HR; P < 0.0001).

These data suggest that activities other than running can increase plasma eCBs associated with changes in mood or appetite. Increases in eCBs may underlie the rewarding and pleasurable effects of singing and exercise and ultimately some of the long-term beneficial effects on mental health, cognition and memory.”

https://www.ncbi.nlm.nih.gov/pubmed/30534062

https://www.frontiersin.org/articles/10.3389/fnbeh.2018.00269/full

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Beta-caryophyllene alleviates diet-induced neurobehavioral changes in rats: The role of CB2 and PPAR-γ receptors.

Biomedicine & Pharmacotherapy

“Insulin resistance (IR) and obesity predispose diseases such as diabetes, cardiovascular and neurodegenerative disorders.

Beta-caryophyllene (BCP), a natural sesquiterpene, exerts neuroprotective, anxiolytic and antidepressant effects via its selective agonism to cannabinoid receptor 2 (CB2R). BCP was shown to have an anti-diabetic effect, however, the implication of CB2R is yet to be elucidated. A link between CB2R agonism and PPAR-γ activation has been discussed, but the exact mechanism is not well-defined.

This study was designed to examine the role of BCP in improving diet-induced metabolic (insulin resistance), neurobehavioral (anxiety, depression and memory deficit), and neurochemical (oxidative, inflammatory and neurotrophic factor) alterations in the prefrontal cortex of obese rats’ brain. The involvement of CB2R and/or PPAR-γ dependent activity was also investigated.

KEY RESULTS:

Beta-caryophyllene alleviated HFFD-induced IR, oxidative-stress, neuroinflammation and behavioral changes. The anxiolytic, anti-oxidant and anti-inflammatory effects of BCP were mediated by both PPAR-γ and CB2R. The effects of BCP on glycemic parameters seem to be CB2R-dependent with the non-significant role of PPAR-γ. Furthermore, BCP-evoked antidepressant and memory improvement are likely mediated only via CB2R, mainly by upregulation of PGC-1α and BDNF.

CONCLUSION:

This study suggests the potential effect of BCP in treating HFFD-induced metabolic and neurobehavioral alterations. BCP seems to activate PPAR-γ in a ligand-independent manner, via upregulation and activation of PGC-1α. The BCP activation of PPAR–γ seems to be CB2R-dependent.”

https://www.ncbi.nlm.nih.gov/pubmed/30469079

https://www.sciencedirect.com/science/article/pii/S0753332218370033?via%3Dihub

“β-caryophyllene (BCP) is a common constitute of the essential oils of numerous spice, food plants and major component in Cannabis.”   http://www.ncbi.nlm.nih.gov/pubmed/23138934

“Beta-caryophyllene is a dietary cannabinoid.”  https://www.ncbi.nlm.nih.gov/pubmed/18574142

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Activation of GPR55 induces neuroprotection of hippocampal neurogenesis and immune responses of neural stem cells following chronic, systemic inflammation.

Brain, Behavior, and Immunity

“New neurons are continuously produced by neural stem cells (NSCs) within the adult hippocampus. Numerous diseases, including major depressive disorder and HIV-1 associated neurocognitive disorder, are associated with decreased rates of adult neurogenesis. A hallmark of these conditions is a chronic release of neuroinflammatory mediators by activated resident glia.

Recent studies have shown a neuroprotective role on NSCs of cannabinoid receptor activation. Yet, little is known about the effects of GPR55, a candidate cannabinoid receptor, activation on reductions of neurogenesis in response to inflammatory insult.

In the present study, we examined NSCs exposed to IL-1β in vitro to assess inflammation-caused effects on NSC differentiation and the ability of GPR55 agonists to attenuate NSC injury.

Taken together, these results suggest a neuroprotective role of GPR55 activation on NSCs in vitro and in vivo and that GPR55 provides a novel therapeutic target against negative regulation of hippocampal neurogenesis by inflammatory insult.”

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Neuroprotection by cannabidiol and hypothermia in a piglet model of newborn hypoxic-ischemic brain damage.

Neuropharmacology

“Hypothermia, the gold standard after a hypoxic-ischemic insult, is not beneficial in all treated newborns.

Cannabidiol is neuroprotective in animal models of newborn hypoxic-ischemic encephalopathy.

This study compared the relative efficacies of cannabidiol and hypothermia in newborn hypoxic-ischemic piglets and assessed whether addition of cannabidiol augments hypothermic neuroprotection.

RESULTS:

HI led to sustained depressed brain activity and increased microglial activation, which was significantly improved by cannabidiol alone or with hypothermia but not by hypothermia alone. Hypoxic-ischemic-induced increases in Lac/NAA, Glu/NAA, TNFα or apoptosis were not reversed by either hypothermia or cannabidiol alone, but combination of the therapies did. No treatment modified the effects of HI on oxidative stress or astroglial activation. Cannabidiol treatment was well tolerated.

CONCLUSIONS:

cannabidiol administration after hypoxia-ischemia in piglets offers some neuroprotective effects but the combination of cannabidiol and hypothermia shows some additive effect leading to more complete neuroprotection than cannabidiol or hypothermia alone.”

https://www.ncbi.nlm.nih.gov/pubmed/30468796

https://www.sciencedirect.com/science/article/pii/S0028390818308554?via%3Dihub

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Cannabinoid receptor agonists reduce the short-term mitochondrial dysfunction and oxidative stress linked to excitotoxicity in the rat brain.

Neuroscience

“The endocannabinoid system (ECS) is involved in a considerable number of physiological processes in the Central Nervous System.

Recently, a modulatory role of cannabinoid receptors (CBr) and CBr agonists on the reduction of the N-methyl-d-aspartate receptor (NMDAr) activation has been demonstrated. Quinolinic acid (QUIN), an endogenous analog of glutamate and excitotoxic metabolite produced in the kynurenine pathway (KP), selectively activates NMDAr and has been shown to participate in different neurodegenerative disorders.

Since the early pattern of toxicity exerted by this metabolite is relevant to explain the extent of damage that it can produce in the brain, in this work we investigated the effects of the synthetic CBr agonist WIN 55,212-2 (WIN) and other agonists (anandamide or AEA, and CP 55,940 or CP) on early markers of QUIN-induced toxicity in rat striatal cultured cells and rat brain synaptosomes.

WIN, AEA and CP exerted protective effects on the QUIN-induced loss of cell viability. WIN also preserved the immunofluorescent signals for neurons and CBr labeling that were decreased by QUIN. The QUIN-induced early mitochondrial dysfunction, lipid peroxidation and reactive oxygen species (ROS) formation were also partially or completely prevented by WIN pretreatment, but not when this CBr agonist was added simultaneously with QUIN to brain synaptosomes.

These findings support a neuroprotective and modulatory role of cannabinoids in the early toxic events elicited by agents inducing excitotoxic processes.”

https://www.ncbi.nlm.nih.gov/pubmed/25446347

https://www.sciencedirect.com/science/article/abs/pii/S0306452214009737?via%3Dihub

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Effects of Cannabidiol on Diabetes Outcomes and Chronic Cerebral Hypoperfusion Comorbidities in Middle-Aged Rats.

“Diabetes and aging are risk factors for cognitive impairments after chronic cerebral hypoperfusion (CCH).

Cannabidiol (CBD) is a phytocannabinoid present in the Cannabis sativa plant. It has beneficial effects on both cerebral ischemic diseases and diabetes.

We have recently reported that diabetes interacted synergistically with aging to increase neuroinflammation and memory deficits in rats subjected to CCH.

The present study investigated whether CBD would alleviate cognitive decline and affect markers of inflammation and neuroplasticity in the hippocampus in middle-aged diabetic rats submitted to CCH.

These results suggest that the neuroprotective effects of CBD in middle-aged diabetic rats subjected to CCH are related to a reduction in neuroinflammation. However, they seemed to occur independently of hippocampal neuroplasticity changes.”

https://www.ncbi.nlm.nih.gov/pubmed/30430393

https://link.springer.com/article/10.1007%2Fs12640-018-9972-5

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