The CB1 cannabinoid receptor is coupled to the activation of protein kinase B/Akt

A review of the direct targets of the cannabinoids cannabidiol, Δ9-tetrahydrocannabinol, N-arachidonoylethanolamine and 2-arachidonoylglycerol

Marijuana has been used by humans for thousands of years for both medicinal and recreational purposes. This included the treatment of pain, inflammation, seizures, and nausea. In the 1960s, the structure of the principal psychoactive ingredient Δ9-tetrahydrocannabinol was determined, and over the next few decades, two cannabinoid receptors were characterized along with the human endocannabinoid system and what it affects. This includes metabolism, the cardiovascular and reproductive systems, and it is involved in such conditions as inflammation, cancer, glaucoma, and liver and musculoskeletal disorders. In the central nervous system, the endocannabinoid system has been linked to appetite, learning, memory, and conditions such as depression, anxiety, schizophrenia, stroke, multiple sclerosis, neurodegeneration, addiction, and epilepsy. It was the profound effectiveness of cannabidiol, a non-psychoactive ingredient of marijuana, to relieve the symptoms of Dravet syndrome, a severe form of childhood epilepsy, that recently helped spur marijuana research. This has helped substantially to change society's attitude towards this potential source of useful drugs. However, research has also revealed that the actions of endocannabinoids, such as anandamide and 2-arachidonoylglycerol, and the phytocannabinoids, tetrahydrocannabinol and cannabidiol, were not just due to interactions with the two cannabinoid receptors but by acting directly on many other targets including various G-protein receptors and cation channels, such as the transient receptor potential channels for example. This mini-review attempts to survey the effects of these 4 important cannabinoids on these currently identified targets.

Classical cannabinoid receptors as target in cancer-induced bone pain: a systematic review, meta-analysis and bioinformatics validation

To test the hypothesis that genetic and pharmacological modulation of the classical cannabinoid type 1 (CB1) and 2 (CB2) receptors attenuate cancer-induced bone pain, we searched Medline, Web of Science and Scopus for relevant skeletal and non-skeletal cancer studies from inception to July 28, 2022. We identified 29 animal and 35 human studies. In mice, a meta-analysis of pooled studies showed that treatment of osteolysis-bearing males with the endocannabinoids AEA and 2-AG (mean difference [MD] - 24.83, 95% confidence interval [95%CI] - 34.89, - 14.76, p < 0.00001) or the synthetic cannabinoid (CB) agonists ACPA, WIN55,212-2, CP55,940 (CB1/2-non-selective) and AM1241 (CB2-selective) (MD - 28.73, 95%CI - 45.43, - 12.02, p = 0.0008) are associated with significant reduction in paw withdrawal frequency. Consistently, the synthetic agonists AM1241 and JWH015 (CB2-selective) increased paw withdrawal threshold (MD 0.89, 95%CI 0.79, 0.99, p < 0.00001), and ACEA (CB1-selective), AM1241 and JWH015 (CB2-selective) reduced spontaneous flinches (MD - 4.85, 95%CI - 6.74, - 2.96, p < 0. 00001) in osteolysis-bearing male mice. In rats, significant increase in paw withdrawal threshold is associated with the administration of ACEA and WIN55,212-2 (CB1/2-non-selective), JWH015 and AM1241 (CB2-selective) in osteolysis-bearing females (MD 8.18, 95%CI 6.14, 10.21, p < 0.00001), and treatment with AM1241 (CB2-selective) increased paw withdrawal thermal latency in males (mean difference [MD]: 3.94, 95%CI 2.13, 5.75, p < 0.0001), confirming the analgesic capabilities of CB1/2 ligands in rodents. In human, treatment of cancer patients with medical cannabis (standardized MD - 0.19, 95%CI - 0.35, - 0.02, p = 0.03) and the plant-derived delta-9-THC (20 mg) (MD 3.29, CI 2.24, 4.33, p < 0.00001) or its synthetic derivative NIB (4 mg) (MD 2.55, 95%CI 1.58, 3.51, p < 0.00001) are associated with reduction in pain intensity. Bioinformatics validation of KEGG, GO and MPO pathway, function and process enrichment analysis of mouse, rat and human data revealed that CB1 and CB2 receptors are enriched in a cocktail of nociceptive and sensory perception, inflammatory, immune-modulatory, and cancer pathways. Thus, we cautiously conclude that pharmacological modulators of CB1/2 receptors show promise in the treatment of cancer-induced bone pain, however further assessment of their effects on bone pain in genetically engineered animal models and cancer patients is warranted.

Injury-induced activation of the endocannabinoid system promotes axon regeneration

Regeneration after a peripheral nerve injury still remains a challenge, due to the limited regenerative potential of axons after injury. While the endocannabinoid system (ECS) has been widely studied for its neuroprotective and analgesic effects, its role in axonal regeneration and during the conditioning lesion remains unexplored. In this study, we observed that a peripheral nerve injury induces axonal regeneration through an increase in the endocannabinoid tone. We also enhanced the regenerative capacity of dorsal root ganglia (DRG) neurons through the inhibition of endocannabinoid degradative enzyme MAGL or a CB1R agonist. Our results suggest that the ECS, via CB1R and PI3K-pAkt pathway activation, plays an important role in promoting the intrinsic regenerative capacity of sensory neurons after injury.

The Role of Cannabinoids in CNS Development: Focus on Proliferation and Cell Death

The active principles of Cannabis sativa are potential treatments for several diseases, such as pain, seizures and anorexia. With the increase in the use of cannabis for medicinal purposes, a more careful assessment of the possible impacts on embryonic development becomes necessary. Surveys indicate that approximately 3.9% of pregnant women use cannabis in a recreational and/or medicinal manner. However, although the literature has already described the presence of endocannabinoid system components since the early stages of CNS development, many of their physiological effects during this stage have not yet been established. Moreover, it is still uncertain how the endocannabinoid system can be altered in terms of cell proliferation and cell fate, neural migration, neural differentiation, synaptogenesis and particularly cell death. In relation to cell death in the CNS, knowledge about the effects of cannabinoids is scarce. Thus, the present work aims to review the role of the endocannabinoid system in different aspects of CNS development and discuss possible side effects or even opportunities for treating some conditions in the development of this tissue.

Molecular networks underlying cannabinoid signaling in skeletal muscle plasticity

The cannabinoid system is ubiquitously present and is classically considered to engage in neural and immunity processes. Yet, the role of the cannabinoid system in the whole body and tissue metabolism via central and peripheral mechanisms is increasingly recognized. The present review provides insights in (i) how cannabinoid signaling is regulated via receptor-independent and -dependent mechanisms and (ii) how these signaling cascades (might) affect skeletal muscle plasticity and physiology. Receptor-independent mechanisms include endocannabinoid metabolism to eicosanoids and the regulation of ion channels. Alternatively, endocannabinoids can act as ligands for different classic (cannabinoid receptor 1 [CB₁ ], CB₂ ) and/or alternative (e.g., TRPV1, GPR55) cannabinoid receptors with a unique affinity, specificity, and intracellular signaling cascade (often tissue-specific). Antagonism of CB₁ might hold clues to improve oxidative (mitochondrial) metabolism, insulin sensitivity, satellite cell growth, and muscle anabolism, whereas CB₂ agonism might be a promising way to stimulate muscle metabolism and muscle cell growth. Besides, CB₂ ameliorates muscle regeneration via macrophage polarization toward an anti-inflammatory phenotype, induction of MyoD and myogenin expression and antifibrotic mechanisms. Also TRPV1 and GPR55 contribute to the regulation of muscle growth and metabolism. Future studies should reveal how the cannabinoid system can be targeted to improve muscle quantity and/or quality in conditions such as ageing, disease, disuse, and metabolic dysregulation, taking into account challenges that are inherent to modulation of the cannabinoid system, such as central and peripheral side effects.

Cannabis and Cannabinoids in Reproduction and Fertility: Where We Stand

Although cannabis use is increasing in general population, their prevalence among young adults is remarkably high. In recent years, their medical use gained a renewed interest. However, it can underline the reputation of cannabis being a harmless drug. Between cannabinoids, uniquely found on the cannabis plant, Δ⁹-tetrahydrocannabinol (THC) is the well-studied compound. It is responsible for the psychoactive effects via central cannabinoid receptors. Nevertheless, cannabinoids interact with other chemical signalling systems such as the hypothalamic-pituitary-gonadal axis. THC indirectly decreases gonadotropin-releasing hormone (GnRH) secretion by the hypothalamus. The consequences are diverse, and several key hormones are affected. THC disturbs important reproductive events like folliculogenesis, ovulation and sperm maturation and function. Although generally accepted that cannabinoid consumption impacts male and female fertility, prevailing evidence remains largely on pre-clinical studies. Here, we introduce cannabinoids and the endocannabinoid system, and we review the most prominent clinical evidence about cannabis consumption in reproductive potential and teratogenicity.

Cannabidiol induces autophagy via ERK1/2 activation in neural cells

Autophagy is a lysosomal catabolic process essential to cell homeostasis and is related to the neuroprotection of the central nervous system. Cannabidiol (CBD) is a non-psychotropic phytocannabinoid present in Cannabis sativa. Many therapeutic actions have been linked to this compound, including autophagy activation. However, the precise underlying molecular mechanisms remain unclear, and the downstream functional significance of these actions has yet to be determined. Here, we investigated CBD-evoked effects on autophagy in human neuroblastoma SH-SY5Y and murine astrocyte cell lines. We found that CBD-induced autophagy was substantially reduced in the presence of CB1, CB2 and TRPV1 receptor antagonists, AM 251, AM 630 and capsazepine, respectively. This result strongly indicates that the activation of these receptors mediates the autophagic flux. Additionally, we demonstrated that CBD activates autophagy through ERK1/2 activation and AKT suppression. Interestingly, CBD-mediated autophagy activation is dependent on the autophagy initiator ULK1, but mTORC1 independent. Thus, it is plausible that a non-canonical pathway is involved. Our findings collectively provide evidence that CBD stimulates autophagy signal transduction via crosstalk between the ERK1/2 and AKT kinases, which represent putative regulators of cell proliferation and survival. Furthermore, our study sheds light on potential therapeutic cannabinoid targets that could be developed for treating neurodegenerative disorders.

Medical Cannabis in Oncology: a Valuable Unappreciated Remedy or an Undesirable Risk?

OPINION STATEMENT

The use of the cannabis plant by cancer patients has been rising significantly in the past few years worldwide, primarily driven by public demand. There is an obvious need for more reliable scientific data, pharmacology information, a better understanding of its mode of action, and available clinical evidence supporting its robust use. Physicians must complete a thorough medical assessment, screening for potential drugs, or treatment contraindications before allowing its consumption. In light of the growing popularity of cannabis usage, it is highly essential that, in the near future, the medical community will be able to provide practical recommendations and explicit guidelines, including doses, and that cannabinoid concentrations in the used products are defined regarding its prescription before any medical procedure involving its usage is authorized. Here, we review and describe the favorable outcomes demonstrating the benefits of cannabis as an adjunctive treatment to conventional medicines for chemotherapy-induced nausea, vomiting, and cancer-related pain (primarily refractory chronic or neuropathic pain). Although not yet substantial enough, the treatment of anorexia, insomnia, depression, and anxiety is also seemingly favorable. To date, reports regarding its anti-neoplastic effects or its potent immunosuppressive properties influencing response to immunotherapy are still very conflicting and controversial. Thus, with the current state of evidence, cannabis use is not advisable as initial treatment, as an adjunct or an advanced line of care. In the coming years, we expect that preclinical data and animal models will shift to the clinical arena, and more patients will be recruited for clinical trials, and their reports will advance the field. Thus, physicians should prescribe cannabis only if careful clarification and consideration is provided together with a follow-up response evaluation.

Biased Coupling to β-Arrestin of Two Common Variants of the CB2 Cannabinoid Receptor

β-arrestins are partners of the G protein-coupled receptors (GPCRs), regulating their intracellular trafficking and signaling. Development of biased GPCR agonists, selectively targeting either G protein or β-arrestin pathways, are in the focus of interest due to their therapeutic potential in different pathological conditions. The CB₂ cannabinoid receptor (CB₂R) is a GPCR involved in various functions in the periphery and the central nervous system. Two common occurring variants of CB₂R, harboring Q63R or L133I missense mutations, have been implicated in the development of a diverse set of disorders. To evaluate the effect of these mutations, we characterized the binding profile of these mutant CB₂ receptors to G proteins and β-arrestin2. Although their ability to inhibit cAMP signaling was similar, the Q63R mutant had increased, whereas the L133I mutant receptor had decreased β-arrestin2 binding. In line with these observations, the variants also had altered intracellular trafficking. Our results show that two common variants of the CB₂ receptor have biased signaling properties, which may contribute to the pathogenesis of the associated disorders and may offer CB₂R as a target for further development of biased receptor activation strategies.

Endocannabinoids Produced by White Adipose Tissue Modulate Lipolysis in Lean but Not in Obese Rodent and Human

White adipose tissue (WAT) possesses the endocannabinoid system (ECS) machinery and produces the two major endocannabinoids (ECs), arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). Accumulating evidence indicates that WAT cannabinoid 1 receptors (CB1R) are involved in the regulation of fat storage, tissue remodeling and secretory functions but their role in controlling lipid mobilization is unclear. In the present study, we used different strategies to acutely increase ECS activity in WAT and tested the consequences on glycerol production as a marker of lipolysis. Treating lean mice or rat WAT explants with JLZ195, which inhibits ECs degrading enzymes, induced an increase in 2-AG tissue contents that was associated with a CB1R-dependent decrease in lipolysis. Direct treatment of rat WAT explants with AEA also inhibited glycerol production while mechanistic studies revealed it could result from the stimulation of Akt-signaling pathway. Interestingly, AEA treatment decreased lipolysis both in visceral and subcutaneous WAT collected on lean subjects suggesting that ECS also reduces fat store mobilization in Human. In obese mice, WAT content and secretion rate of ECs were higher than in control while glycerol production was reduced suggesting that over-produced ECs may inhibit lipolysis activating local CB1R. Strikingly, our data also reveal that acute CB1R blockade with Rimonabant did not modify lipolysis in vitro in obese mice and human explants nor in vivo in obese mice. Taken together, these data provide physiological evidence that activation of ECS in WAT, by limiting fat mobilization, may participate in the progressive tissue remodeling that could finally lead to organ dysfunction. The present findings also indicate that acute CB1R blockade is inefficient in regulating lipolysis in obese WAT and raise the possibility of an alteration of CB1R signaling in conditions of obesity.

Hepatocyte cannabinoid 1 receptor nullification alleviates toxin-induced liver damage via NF-κB signaling

Cannabinoid 1 receptor (CB1R) expression is upregulated in the liver with viral hepatitis, cirrhosis, and both alcoholic and non-alcoholic fatty liver disease (FLD), whereas its expression is muted under usual physiological conditions. Inhibiting CB1R has been shown to be beneficial in preserving hepatic function in FLD but it is unclear if inhibiting CB1R during an inflammatory response to an acute hepatic injury, such as toxin-induced injury, would also be beneficial. We found that intrinsic CB1R in hepatocytes regulated liver inflammation-related gene transcription. We tested if nullification of hepatocyte-specific CB1R (hCNR1^−/−) in mice protects against concanavalin A (Con A)-induced liver injury. We looked for evidence of liver damage and markers of inflammation in response to Con A by measuring liver enzyme levels and proinflammatory cytokines (e.g., TNF-α, IL-1β, IL-6, IL-17) in serum collected from hCNR1^−/− and control mice. We observed a shift to the right in the dose-response curve for liver injury and inflammation in hCNR1^−/− mice. We also found less inflammatory cell infiltration and focal necrosis in livers of hCNR1^−/− mice compared to controls, resulting from downregulated apoptotic markers. This anti-apoptotic mechanism results from increased activation of nuclear factor kappa B (NF-κB), especially cAMP-dependent cannabinoid signaling and membrane-bound TNF-α, via downregulated TNF-α receptor 2 (TNFR2) transcription levels. Collectively, these findings provide insight into involvement of CB1R in the pathogenesis of acute liver injury.

Inhibition of striatonigral autophagy as a link between cannabinoid intoxication and impairment of motor coordination

The use of cannabis is rapidly expanding worldwide. Thus, innovative studies aimed to identify, understand and potentially reduce cannabis-evoked harms are warranted. Here, we found that Δ⁹-tetrahydrocannabinol, the psychoactive ingredient of cannabis, disrupts autophagy selectively in the striatum, a brain area that controls motor behavior, both in vitro and in vivo. Boosting autophagy, either pharmacologically (with temsirolimus) or by dietary intervention (with trehalose), rescued the Δ⁹-tetrahydrocannabinol-induced impairment of motor coordination in mice. The combination of conditional knockout mouse models and viral vector-mediated autophagy-modulating strategies in vivo showed that cannabinoid CB₁ receptors located on neurons belonging to the direct (striatonigral) pathway are required for the motor-impairing activity of Δ⁹-tetrahydrocannabinol by inhibiting local autophagy. Taken together, these findings identify inhibition of autophagy as an unprecedented mechanistic link between cannabinoids and motor performance, and suggest that activators of autophagy might be considered as potential therapeutic tools to treat specific cannabinoid-evoked behavioral alterations.

Cannabinoid Receptor 2 (CB2) Signals via G-alpha-s and Induces IL-6 and IL-10 Cytokine Secretion in Human Primary Leukocytes

Cannabinoid receptor 2 (CB₂) is a promising therapeutic target for immunological modulation. There is, however, a deficit of knowledge regarding CB₂ signaling and function in human primary immunocompetent cells. We applied an experimental paradigm which closely models the in situ state of human primary leukocytes (PBMC; peripheral blood mononuclear cells) to characterize activation of a number of signaling pathways in response to a CB₂-selective ligand (HU308). We observed a "lag" phase of unchanged cAMP concentration prior to development of classically expected Gα_i-mediated inhibition of cAMP synthesis. Application of G protein inhibitors revealed that this apparent lag was a result of counteraction of Gα_i effects by concurrent Gα_s activation. Monitoring downstream signaling events showed that activation of p38 was mediated by Gα_i, whereas ERK1/2 and Akt phosphorylation were mediated by Gα_i-coupled βγ. Activation of CREB integrated multiple components; Gα_s and βγ mediated ∼85% of the response, while ∼15% was attributed to Gα_i. Responses to HU308 had an important functional outcome-secretion of interleukins 6 (IL-6) and 10 (IL-10). IL-2, IL-4, IL-12, IL-13, IL-17A, MIP-1α, and TNF-α were unaffected. IL-6/IL-10 induction had a similar G protein coupling profile to CREB activation. All response potencies were consistent with that expected for HU308 acting via CB₂. Additionally, signaling and functional effects were completely blocked by a CB₂-selective inverse agonist, giving additional evidence for CB₂ involvement. This work expands the current paradigm regarding cannabinoid immunomodulation and reinforces the potential utility of CB₂ ligands as immunomodulatory therapeutics.

Unidirectional opioid-cannabinoid cross-tolerance in the modulation of social play behavior in rats

RATIONALE

The endocannabinoid and the endogenous opioid systems interact in the modulation of social play behavior, a highly rewarding social activity abundantly expressed in young mammals. Prolonged exposure to opioid or cannabinoid receptor agonists induces cross-tolerance or cross-sensitization to their acute behavioral effects.

OBJECTIVES AND METHODS

Behavioral and biochemical experiments were performed to investigate whether cross-tolerance or cross-sensitization occurs to the play-enhancing effects of cannabinoid and opioid drugs on social play behavior, and the possible brain substrate involved.

RESULTS

The play-enhancing effects induced by systemic administration of JZL184, which inhibits the hydrolysis of the endocannabinoid 2-AG, were suppressed in animals repeatedly pretreated with the opioid receptor agonist morphine. Conversely, acute morphine administration increased social play in rats pretreated with vehicle or with either JZL184 or the cannabinoid agonist WIN55,212-2. Acute administration of JZL184 increased the activation of both CB1 receptors and their effector Akt in the nucleus accumbens and prefrontal cortex, brain regions important for the expression of social play. These effects were absent in animals pretreated with morphine. Furthermore, only animals repeatedly treated with morphine and acutely administered with JZL184 showed reduced activation of CB1 receptors and Akt in the amygdala.

CONCLUSIONS

The present study demonstrates a dynamic opioid-cannabinoid interaction in the modulation of social play behavior, occurring in limbic brain areas strongly implicated in social play behavior. A better understanding of opioid-cannabinoid interactions in social play contributes to clarify neurobiological aspects of social behavior at young age, which may provide new therapeutic targets for social dysfunctions.

Synthetic Cannabinoids Influence the Invasion of Glioblastoma Cell Lines in a Cell- and Receptor-Dependent Manner

The current treatment of glioblastoma is not sufficient, since they are heterogeneous and often resistant to chemotherapy. Earlier studies demonstrated effects of specific cannabinoid receptor (CB) agonists on the invasiveness of glioblastoma cell lines, but the exact mechanism remained unclear. Three human glioblastoma cell lines were treated with synthetic CB ligands. The effect of cannabinoids on microRNAs (miRs), Akt, and on the expression of proliferation and apoptosis markers were analyzed. Furthermore, in a model of organotypic hippocampal slice cultures cannabinoid mediated changes in the invasiveness were assessed. MicroRNAs and the activation of Akt which are related to cell migration, apoptosis, and proliferation were evaluated and found not to be associated with changes in the invasiveness after treatment with CB ligands. Also proliferation and/or apoptosis were not altered after treatment. The effects of cannabinoids on invasiveness could be blocked by the application of receptor antagonists and are likely mediated via CB₁/CB₂. In conclusion, our results suggest that cannabinoids can influence glioblastoma cell invasion in a receptor and cell type specific manner that is independent of proliferation and apoptosis. Thus, cannabinoids can potentially be used in the future as an addition to current therapy.

Potential Use of Cannabinoids for the Treatment of Pancreatic Cancer

Background: Cannabinoid extracts may have anticancer properties, which can improve cancer treatment outcomes. The aim of this review is to determine the potentially utility of cannabinoids in the treatment of pancreatic cancer.

Methods: A literature review focused on the biological effects of cannabinoids in cancer treatment, with a focus on pancreatic cancer, was conducted. In vitro and in vivo studies that investigated the effects of cannabinoids in pancreatic cancer were identified and potential mechanisms of action were assessed.

Results: Cannabinol receptors have been identified in pancreatic cancer with several studies showing in vitro antiproliferative and proapoptotic effects. The main active substances found in cannabis plants are cannabidiol (CBD) and tetrahydrocannabinol (THC). There effects are predominately mediated through, but not limited to cannabinoid receptor-1, cannabinoid receptor-2, and G-protein-coupled receptor 55 pathways. In vitro studies consistently demonstrated tumor growth-inhibiting effects with CBD, THC, and synthetic derivatives. Synergistic treatment effects have been shown in two studies with the combination of CBD/synthetic cannabinoid receptor ligands and chemotherapy in xenograft and genetically modified spontaneous pancreatic cancer models. There are, however, no clinical studies to date showing treatment benefits in patients with pancreatic cancer.

Conclusions: Cannabinoids may be an effective adjunct for the treatment of pancreatic cancer. Data on the anticancer effectiveness of various cannabinoid formulations, treatment dosing, precise mode of action, and clinical studies are lacking.

The Role of Endogenous Neuroprotective Mechanisms in the Prevention of Retinal Ganglion Cells Degeneration

Retinal neurons are not able to undergo spontaneous regeneration in response to damage. A variety of stressors, i.e., UV radiation, high temperature, ischemia, allergens, and others, induce reactive oxygen species production, resulting in consecutive alteration of stress-response gene expression and finally can lead to cell apoptosis. Neurons have developed their own endogenous cellular protective systems. Some of them are preventing cell death and others are allowing functional recovery after injury. The high efficiency of these mechanisms is crucial for cell survival. In this review we focus on the contribution of the most recently studied endogenous neuroprotective factors involved in retinal ganglion cell (RGC) survival, among which, neurotrophic factors and their signaling pathways, processes regulating the redox status, and different pathways regulating cell death are the most important. Additionally, we summarize currently ongoing clinical trials for therapies for RGC degeneration and optic neuropathies, including glaucoma. Knowledge of the endogenous cellular protective mechanisms may help in the development of effective therapies and potential novel therapeutic targets in order to achieve progress in the treatment of retinal and optic nerve diseases.

Cannabinoid Receptors and the Endocannabinoid System: Signaling and Function in the Central Nervous System

The biological effects of cannabinoids, the major constituents of the ancient medicinal plant Cannabis sativa (marijuana) are mediated by two members of the G-protein coupled receptor family, cannabinoid receptors 1 (CB1R) and 2. The CB1R is the prominent subtype in the central nervous system (CNS) and has drawn great attention as a potential therapeutic avenue in several pathological conditions, including neuropsychological disorders and neurodegenerative diseases. Furthermore, cannabinoids also modulate signal transduction pathways and exert profound effects at peripheral sites. Although cannabinoids have therapeutic potential, their psychoactive effects have largely limited their use in clinical practice. In this review, we briefly summarized our knowledge of cannabinoids and the endocannabinoid system, focusing on the CB1R and the CNS, with emphasis on recent breakthroughs in the field. We aim to define several potential roles of cannabinoid receptors in the modulation of signaling pathways and in association with several pathophysiological conditions. We believe that the therapeutic significance of cannabinoids is masked by the adverse effects and here alternative strategies are discussed to take therapeutic advantage of cannabinoids.

Functional selectivity at G-protein coupled receptors: Advancing cannabinoid receptors as drug targets

The phenomenon of functional selectivity, whereby a ligand preferentially directs the information output of a G-protein coupled receptor (GPCR) along (a) particular effector pathway(s) and away from others, has redefined traditional GPCR signaling paradigms to provide a new approach to structure-based drug design. The two principal cannabinoid receptors (CBRs) 1 and 2 belong to the class-A GPCR subfamily and are considered tenable therapeutic targets for several indications. Yet conventional orthosteric ligands (agonists, antagonists/inverse agonists) for these receptors have had very limited clinical utility due to their propensity to incite on-target adverse events. Chemically distinct classes of cannabinergic ligands exhibit signaling bias at CBRs towards individual subsets of signal transduction pathways. In this review, we discuss the known signaling pathways regulated by CBRs and examine the current evidence for functional selectivity at CBRs in response to endogenous and exogenous cannabinergic ligands as biased agonists. We further discuss the receptor and ligand structural features allowing for selective activation of CBR-dependent functional responses. The design and development of biased ligands may offer a pathway to therapeutic success for novel CBR-targeted drugs.

The Therapeutic Aspects of the Endocannabinoid System (ECS) for Cancer and their Development: From Nature to Laboratory

The endocannabinoid system (ECS) is a group of neuromodulatory lipids and their receptors, which are widely distributed in mammalian tissues. ECS regulates various cardiovascular, nervous, and immune system functions inside cells. In recent years, there has been a growing body of evidence for the use of synthetic and natural cannabinoids as potential anticancer agents. For instance, the CB1 and CB2 receptors are assumed to play an important role inside the endocannabinoid system. These receptors are abundantly expressed in the brain and fatty tissue of the human body. Despite recent developments in molecular biology, there is still a lack of knowledge about the distribution of CB1 and CB2 receptors in the human kidney and their role in kidney cancer. To address this gap, we explore and demonstrate the role of the endocannabinoid system in renal cell carcinoma (RCC). In this brief overview, we elucidate the therapeutic aspects of the endocannabinoid system for various cancers and explain how this system can be used for treating kidney cancer. Overall, this review provides new insights into cannabinoids' mechanisms of action in both in vivo and in vitro models, and focuses on recent discoveries in the field.

Cannabidiol Modulates the Immunophenotype and Inhibits the Activation of the Inflammasome in Human Gingival Mesenchymal Stem Cells

Human Gingival Mesenchymal Stem Cells (hGMSCs) are multipotential cells that can expand and differentiate in culture under specific and standardized conditions. In the present study, we have investigated whether in vitro pre-treatment of hGMSCs with Cannabidiol (CBD) can influence their expression profile, improving the therapeutic potential of this cell culture. Following CBD treatment (5 μM) for 24 h, gene expression analysis through Next Generation Sequencing (NGS) has revealed several genes differentially expressed between CBD-treated hGMSCs (CBD-hGMSCs) and control cells (CTR-hGMSCs) that were linked to inflammation and apoptosis. In particular, we have demonstrated that CBD treatment in hGMSCs prevented the activation of the NALP3-inflammasome pathway by suppressing the levels of NALP3, CASP1, and IL18, and in parallel, inhibited apoptosis, as demonstrated by the suppression of Bax. CBD treatment was also able to modulate the expression of the well-known mesenchymal stem cell markers (CD13, CD29, CD73, CD44, CD90, and CD166), and other surface antigens. Specifically, CBD led to the downregulation of genes codifying for antigens involved in the activation of the immune system (CD109, CD151, CD40, CD46, CD59, CD68, CD81, CD82, CD99), while it led to the upregulation of those implicated in the inhibition of the immune responses (CD47, CD55, CD276). In conclusion, the present study will provide a new simple and reproducible method for preconditioning hGMSCs with CBD, before transplantation, as an interesting strategy for improving the hGMSCs molecular phenotype, reducing the risk of immune or inflammatory reactions in the host, and in parallel, for increasing their survival and thus, their long-term therapeutic efficacy.

Cannabinoids and GI Disorders: Endogenous and Exogenous

OPINION STATEMENT

Despite the political and social controversy affiliated with it, the medical community must come to the realization that cannabinoids exist as a ubiquitous signaling system in many organ systems. Our understanding of cannabinoids and how they relate not only to homeostasis but also in disease states must be furthered through research, both clinically and in the laboratory. The identification of the cannabinoid receptors in the early 1990s have provided us with the perfect target of translational research. Already, much has been done with cannabinoids and the nervous system. Here, we explore the implications it has for the gastrointestinal tract. Most therapeutics currently on the market presently target only one aspect of the cannabinoid system. Our main purpose here is to highlight areas of research and potential avenues of discovery that the cannabinoid system has yet to reveal.

The pharmacology of palmitoylethanolamide and first data on the therapeutic efficacy of some of its new formulations

Palmitoylethanolamide (PEA) has emerged as a potential nutraceutical, because this compound is naturally produced in many plant and animal food sources, as well as in cells and tissues of mammals, and endowed with important neuroprotective, anti-inflammatory and analgesic actions. Several efforts have been made to identify the molecular mechanism of action of PEA and explain its multiple effects both in the central and the peripheral nervous system. Here, we provide an overview of the pharmacology, efficacy and safety of PEA in neurodegenerative disorders, pain perception and inflammatory diseases. The current knowledge of new formulations of PEA with smaller particle size (i.e. micronized and ultra-micronized) when given alone or in combination with antioxidant flavonoids (i.e. luteolin) and stilbenes (i.e. polydatin) is also reviewed.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Cell Type-Specific Tandem Affinity Purification of the Mouse Hippocampal CB1 Receptor-Associated Proteome

G protein coupled receptors (GPCRs) exert their effects through multiprotein signaling complexes. The cannabinoid receptor type 1 (CB1) is among the most abundant GPCRs in the mammalian brain and involved in a plethora of physiological functions. We used a combination of viral-mediated cell type-specific expression of a tagged CB1 fusion protein (CB1-SF), tandem affinity purification (TAP) and proteomics on hippocampal mouse tissue to analyze the composition and differences of CB1 protein complexes in glutamatergic neurons and in GABAergic interneurons. Purified proteins underwent tryptic digestion and were identified using deep-coverage data-independent acquisition with ion mobility separation-enhanced mass spectroscopy, leading to the identification of 951 proteins specifically enriched in glutamatergic and GABAergic CB1-SF TAP samples as compared to controls. Gene Ontology and protein network analyses showed an enrichment of single proteins and functional clusters of proteins involved in already well described domains of CB1 functions. Supported by this consistent data set we could confirm already known CB1 interactors, reveal new potentially interacting proteins and differences in cell type-specific signaling properties of CB1, thereby providing the foundation for further functional studies on differential CB1 signaling.

Orchestrated activation of mGluR5 and CB1 promotes neuroprotection

The metabotropic glutamate receptor 5 (mGluR5) and the cannabinoid receptor 1 (CB₁) exhibit a functional interaction, as CB₁ regulates pre-synaptic glutamate release and mGluR5 activation increases endocannabinoid synthesis at the post-synaptic site. Since both mGluR5 and CB₁ promote neuroprotection, we delineated experiments to investigate a possible link between CB₁ and mGluR5 activation in the induction of neuroprotection using primary cultured corticostriatal neurons. We find that either the pharmacological blockade or the genetic ablation of either mGluR5 or CB₁ can abrogate both CB₁- and mGluR5-mediated neuroprotection against glutamate insult. Interestingly, decreased glutamate release and diminished intracellular Ca²⁺ do not appear to play a role in CB₁ and mGluR5-mediated neuroprotection. Rather, these two receptors work cooperatively to trigger the activation of cell signaling pathways to promote neuronal survival, which involves MEK/ERK1/2 and PI3K/AKT activation. Interestingly, although mGluR5 activation protects postsynaptic terminals and CB₁ the presynaptic site, intact signaling of both receptors is required to effectively promote neuronal survival. In conclusion, mGluR5 and CB₁ act in concert to activate neuroprotective cell signaling pathways and promote neuronal survival.

Acute upregulation of neuronal mitochondrial type-1 cannabinoid receptor and it's role in metabolic defects and neuronal apoptosis after TBI

Metabolic defects and neuronal apoptosis initiated by traumatic brain injury (TBI) contribute to subsequent neurodegeneration. They are all regulated by mechanisms centered around mitochondrion. Type-1 cannabinoid receptor (CB1) is a G-protein coupled receptor (GPCR) enriched on neuronal plasma membrane. Recent evidences point to the substantial presence of CB1 receptors on neuronal mitochondrial outer membranes (mtCB1) and the activation of mtCB1 influences aerobic respiration via inhibiting mitochondrial cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/complex I pathway. The expression and role of neuronal mtCB1 under TBI are unknown. Using TBI models of cultured neurons, wild type and CB1 knockout mice, we found mtCB1 quickly upregulated after TBI. Activation of mtCB1 promoted metabolic defects accompanied with ATP shortage but protected neurons from apoptosis. Selective activation of plasma membrane CB1 showed no effects on neuronal metabolism and apoptosis. Activation of mtCB1 receptors inhibited mitochondrial cAMP/PKA/complex I and resulted in exacerbated metabolic defects accompanied with a higher ratio of ATP reduction to oxygen consumption decrease as well as neuronal apoptosis. Further research found the remarkable accumulation of protein kinase B (AKT) on neuronal mitochondria following TBI and the activation of mtCB1 upregulated mitochondrial AKT/complex V activity. Upregulation of mitochondrial AKT/complex V activity showed anti-apoptosis effects and alleviated ATP shortage in metabolic defects. Taken together, we have identified mtCB1 quickly upregulate after TBI and a dual role the mtCB1 might play in metabolic defects and neuronal apoptosis initiated by TBI: the inhibition of mitochondrial cAMP/PKA/complex I aggravates metabolic defects, energy insufficiency as well as neuronal apoptosis, but the coactivation of mitochondrial AKT/complex V mitigates energy insufficiency and neuronal apoptosis.

Mechanisms of Biased β-Arrestin-Mediated Signaling Downstream from the Cannabinoid 1 Receptor

Activation of G protein-coupled receptors results in multiple waves of signaling that are mediated by heterotrimeric G proteins and the scaffolding proteins β-arrestin 1/2. Ligands can elicit full or subsets of cellular responses, a concept defined as ligand bias or functional selectivity. However, our current understanding of β-arrestin-mediated signaling is still very limited. Here we provide a comprehensive view of β-arrestin-mediated signaling from the cannabinoid 1 receptor (CB1R). By using a signaling biased receptor, we define the cascades, specific receptor kinases, and molecular mechanism underlying β-arrestin-mediated signaling: We identify the interaction kinetics of CB1R and β-arrestin 1 during their endocytic trafficking as directly proportional to its efficacy. Finally, we demonstrate that signaling results in the control of genes clustered around prosurvival and proapoptotic functions among others. Together, these studies constitute a comprehensive description of β-arrestin-mediated signaling from CB1Rs and suggest modulation of receptor endocytic trafficking as a therapeutic approach to control β-arrestin-mediated signaling.

Obesity and Its Potential Effects on Antidepressant Treatment Outcomes in Patients with Depressive Disorders: A Literature Review

Accumulating evidence regarding clinical, neurobiological, genetic, and environmental factors suggests a bidirectional link between obesity and depressive disorders. Although a few studies have investigated the link between obesity/excess body weight and the response to antidepressants in depressive disorders, the effect of weight on treatment response remains poorly understood. In this review, we summarized recent data regarding the relationship between the response to antidepressants and obesity/excess body weight in clinical studies of patients with depressive disorders. Although several studies indicated an association between obesity/excess body weight and poor antidepressant responses, it is difficult to draw definitive conclusions due to the variability of subject composition and methodological differences among studies. Especially, differences in sex, age and menopausal status, depressive symptom subtypes, and antidepressants administered may have caused inconsistencies in the results among studies. The relationship between obesity/excess body weight and antidepressant responses should be investigated further in high-powered studies addressing the differential effects on subject characteristics and treatment. Moreover, future research should focus on the roles of mediating factors, such as inflammatory markers and neurocognitive performance, which may alter the antidepressant treatment outcome in patients with comorbid obesity and depressive disorder.

Endogenous and Synthetic Cannabinoids as Therapeutics in Retinal Disease

The functional significance of cannabinoids in ocular physiology and disease has been reported some decades ago. In the early 1970s, subjects who smoked Cannabis sativa developed lower intraocular pressure (IOP). This led to the isolation of phytocannabinoids from this plant and the study of their therapeutic effects in glaucoma. The main treatment of this disease to date involves the administration of drugs mediating either the decrease of aqueous humour synthesis or the increase of its outflow and thus reduces IOP. However, the reduction of IOP is not sufficient to prevent visual field loss. Retinal diseases, such as glaucoma and diabetic retinopathy, have been defined as neurodegenerative diseases and characterized by ischemia-induced excitotoxicity and loss of retinal neurons. Therefore, new therapeutic strategies must be applied in order to target retinal cell death, reduction of visual acuity, and blindness. The aim of the present review is to address the neuroprotective and therapeutic potential of cannabinoids in retinal disease.

Proapoptotic effect of endocannabinoids in prostate cancer cells

In the early stages, prostate cancer is androgen‑ dependent; therefore, medical castration has shown significant results during the initial stages of this pathology. Despite this early effect, advanced prostate cancer is resilient to such treatment. Recent evidence shows that derivatives of Cannabis sativa and its analogs may exert a protective effect against different types of oncologic pathologies. The purpose of the present study was to detect the presence of cannabinoid receptors (CB1 and CB2) on cancer cells with a prostatic origin and to evaluate the effect of the in vitro use of synthetic analogs. In order to do this, we used a commercial cell line and primary cultures derived from prostate cancer and benign prostatic hyperplasia. The presence of the CB1 and CB2 receptors was determined by immunohistochemistry where we showed a higher expression of these receptors in later stages of the disease (samples with a high Gleason score). Later, treatments were conducted using anandamide, 2-arachidonoyl glycerol and a synthetic analog of anandamide, methanandamide. Using the MTT assay, we proved that the treatments produced a cell growth inhibitory effect on all the different prostate cancer cultures. This effect was demonstrated to be dose-dependent. The use of a specific CB1 receptor blocker (SR141716) confirmed that this effect was produced primarily from the activation of the CB1 receptor. In order to understand the MTT assay results, we determined cell cycle distribution by flow cytometry, which showed no variation at the different cell cycle stages in all the cultures after treatment. Treatment with endocannabinoids resulted in an increase in the percentage of apoptotic cells as determined by Annexin V assays and caused an increase in the levels of activated caspase-3 and a reduction in the levels of Bcl-2 confirming that the reduction in cell viability noted in the MTT assay was caused by the activation of the apoptotic pathway. Finally, we observed that endocannabinoid treatment activated the Erk pathway and at the same time, produced a decrease in the activation levels of the Akt pathway. Based on these results, we suggest that endocannabinoids may be a beneficial option for the treatment of prostate cancer that has become nonresponsive to common therapies.

Functions of the CB1 and CB 2 receptors in neuroprotection at the level of the blood-brain barrier

The cannabinoid (CB) receptors are the main targets of the cannabinoids, which include plant cannabinoids, endocannabinoids and synthetic cannabinoids. Over the last few years, accumulated evidence has suggested a role of the CB receptors in neuroprotection. The blood-brain barrier (BBB) is an important brain structure that is essential for neuroprotection. A link between the CB receptors and the BBB is thus likely, but this possible connection has only recently gained attention. Cannabinoids and the BBB share the same mechanisms of neuroprotection and both protect against excitotoxicity (CB1), cell death (CB1), inflammation (CB2) and oxidative stress (possibly CB independent)-all processes that also damage the BBB. Several examples of CB-mediated protection of the BBB have been found, such as inhibition of leukocyte influx and induction of amyloid beta efflux across the BBB. Moreover, the CB receptors were shown to improve BBB integrity, particularly by restoring the tightness of the tight junctions. This review demonstrated that both CB receptors are able to restore the BBB and neuroprotection, but much uncertainty about the underlying signaling cascades still exists and further investigation is needed.

Antihypertensive and neuroprotective effects of catestatin in spontaneously hypertensive rats: interaction with GABAergic transmission in amygdala and brainstem

The chromogranin A-derived peptide catestatin (CST) exerts sympathoexcitatory and hypertensive effects when microinjected into the rostral ventrolateral medulla (RVLM: excitatory output); it exhibits sympathoinhibitory and antihypertensive effects when microinjected into the caudal ventrolateral medulla (CVLM: inhibitory output) of vagotomized normotensive rats. Here, continuous infusion of CST into the central amygdalar nucleus (CeA) of spontaneously hypertensive rats (SHRs) for 15 days resulted in a marked decrease of blood pressure (BP) in 6-month- (by 37 mm Hg) and 9-month- (by 65 mm Hg)old rats. Whole-cell patch-clamp recordings on pyramidal CeA neurons revealed that CST increased both spontaneous inhibitory postsynaptic current (sIPSC) amplitude plus frequency, along with reductions of sIPSC rise time and decay time. Inhibition of GABAA receptors (GABAARs) by bicuculline completely abolished CST-induced sIPSC, corroborating that CST signals occur through this major neuroreceptor complex. Hypertension is a major risk factor for cerebrovascular diseases, leading to vascular dementia and neurodegeneration. We found a marked neurodegeneration in the amygdala and brainstem of 9-month-old SHRs, while CST and the GABAAR agonist Muscimol provided significant neuroprotection. Enhanced phosphorylation of Akt and ERK accounted for these neuroprotective effects through anti-inflammatory and anti-apoptotic activities. Overall our results point to CST exerting potent antihypertensive and neuroprotective effects plausibly via a GABAergic output, which constitute a novel therapeutic measure to correct defects in blood flow control in disorders such as stroke and Alzheimer's disease.

Cannabinoid-hypocretin cross-talk in the central nervous system: what we know so far

Emerging findings suggest the existence of a cross-talk between hypocretinergic and endocannabinoid systems. Although few studies have examined this relationship, the apparent overlap observed in the neuroanatomical distribution of both systems as well as their putative functions strongly point to the existence of such cross-modulation. In agreement, biochemical and functional studies have revealed the existence of heterodimers between CB1 cannabinoid receptor and hypocretin receptor-1, which modulates the cellular localization and downstream signaling of both receptors. Moreover, the activation of hypocretin receptor-1 stimulates the synthesis of 2-arachidonoyl glycerol culminating in the retrograde inhibition of neighboring cells and suggesting that endocannabinoids could contribute to some hypocretin effects. Pharmacological data indicate that endocannabinoids and hypocretins might have common physiological functions in the regulation of appetite, reward and analgesia. In contrast, these neuromodulatory systems seem to play antagonistic roles in the regulation of sleep/wake cycle and anxiety-like responses. The present review attempts to piece together what is known about this interesting interaction and describes its potential therapeutic implications.

CB1 cannabinoid receptors couple to focal adhesion kinase to control insulin release

Endocannabinoid signaling has been implicated in modulating insulin release from β cells of the endocrine pancreas. β Cells express CB1 cannabinoid receptors (CB1Rs), and the enzymatic machinery regulating anandamide and 2-arachidonoylglycerol bioavailability. However, the molecular cascade coupling agonist-induced cannabinoid receptor activation to insulin release remains unknown. By combining molecular pharmacology and genetic tools in INS-1E cells and in vivo, we show that CB1R activation by endocannabinoids (anandamide and 2-arachidonoylglycerol) or synthetic agonists acutely or after prolonged exposure induces insulin hypersecretion. In doing so, CB1Rs recruit Akt/PKB and extracellular signal-regulated kinases 1/2 to phosphorylate focal adhesion kinase (FAK). FAK activation induces the formation of focal adhesion plaques, multimolecular platforms for second-phase insulin release. Inhibition of endocannabinoid synthesis or FAK activity precluded insulin release. We conclude that FAK downstream from CB1Rs mediates endocannabinoid-induced insulin release by allowing cytoskeletal reorganization that is required for the exocytosis of secretory vesicles. These findings suggest a mechanistic link between increased circulating and tissue endocannabinoid levels and hyperinsulinemia in type 2 diabetes.

Association between cannabinoid CB₁ receptor expression and Akt signalling in prostate cancer

Background

In prostate cancer, tumour expression of cannabinoid CB₁ receptors is associated with a poor prognosis. One explanation for this association comes from experiments with transfected astrocytoma cells, where a high CB receptor expression recruits the Akt signalling survival pathway. In the present study, we have investigated the association between CB₁ receptor expression and the Akt pathway in a well-characterised prostate cancer tissue microarray.

Methodology/Principal Findings

Phosphorylated Akt immunoreactivity (pAkt-IR) scores were available in the database. CB₁ receptor immunoreactivity (CB₁IR) was rescored from previously published data using the same scale as pAkt-IR. There was a highly significant correlation between CB₁IR and pAkt-IR. Further, cases with high expression levels of both biomarkers were much more likely to have a more severe form of the disease at diagnosis than those with low expression levels. The two biomarkers had additive effects, rather than an interaction, upon disease-specific survival.

Conclusions/Significance

The present study provides data that is consistent with the hypothesis that at a high CB₁ receptor expression, the Akt signalling pathway becomes operative.

Equipotent inhibition of fatty acid amide hydrolase and monoacylglycerol lipase - dual targets of the endocannabinoid system to protect against seizure pathology

Advances in the understanding of the endogenous cannabinoid system have led to several therapeutic indications for new classes of compounds that enhance cannabinergic responses. Endocannabinoid levels are elevated during pathogenic conditions, and inhibitors of endocannabinoid inactivation promote such on-demand responses. The endocannabinoids anandamide and 2-arachidonoyl glycerol have been implicated in protective signaling against excitotoxic episodes, including seizures. To better understand modulatory pathways that can exploit such responses, we used the new generation compound AM6701 that blocks both the anandamide-deactivating enzyme fatty acid amide hydrolase (FAAH) and the 2-arachidonoyl glycerol-deactivating enzyme monoacylglycerol lipase (MAGL) with equal potency. Also studied was the structural isomer AM6702 which is 44-fold more potent for inhibiting FAAH versus MAGL. When applied before and during kainic acid (KA) exposure to cultured hippocampal slices, AM6701 protected against the resulting excitotoxic events of calpain-mediated cytoskeletal damage, loss of presynaptic and postsynaptic proteins, and pyknotic changes in neurons. The equipotent inhibitor was more effective than its close relative AM6702 at protecting against the neurodegenerative cascade assessed in the slice model. In vivo, AM6701 was also the more effective compound for reducing the severity of KA-induced seizures and protecting against behavioral deficits linked to seizure damage. Corresponding with the behavioral improvements, cytoskeletal and synaptic protection was elicited by AM6701, as found in the KA-treated hippocampal slice model. It is proposed that the influence of AM6701 on FAAH and MAGL exerts a synergistic action on the endocannabinoid system, thereby promoting the protective nature of cannabinergic signaling to offset excitotoxic brain injury.

Cannabis exposure associated with weight reduction and β-cell protection in an obese rat model

The aim of this study was to investigate the effect of an organic cannabis extract on β-cell secretory function in an in vivo diet-induced obese rat model and determine the associated molecular changes within pancreatic tissue. Diet-induced obese Wistar rats and rats fed on standard pellets were subcutaneously injected with an organic cannabis extract or the vehicle over a 28-day period. The effect of diet and treatment was evaluated using the intraperitoneal glucose tolerance tests (IPGTTs) and qPCR analysis on rat pancreata harvested upon termination of the experiment. The cafeteria diet induced an average weight difference of 32g and an overall increase in body weight in the experimental groups occurred at a significantly slower rate than the control groups, irrespective of diet. Area under the curve for glucose (AUC(g)) in the obese group was significantly lower compared to the lean group (p<0.001), with cannabis treatment significantly reducing the AUC(g) in the lean group (p<0.05), and remained unchanged in the obese group, relative to the obese control group. qPCR analysis showed that the cafeteria diet induced down-regulation of the following genes in the obese control group, relative to lean controls: UCP2, c-MYC and FLIP. Cannabis treatment in the obese group resulted in up-regulation of CB1, GLUT2, UCP2 and PKB, relative to the obese control group, while c-MYC levels were down-regulated, relative to the lean control group. Treatment did not significantly change gene expression in the lean group. These results suggest that the cannabis extract protects pancreatic islets against the negative effects of obesity.

Cannabinoid receptors CB1 and CB2 form functional heteromers in brain

Exploring the role of cannabinoid CB(2) receptors in the brain, we present evidence of CB(2) receptor molecular and functional interaction with cannabinoid CB(1) receptors. Using biophysical and biochemical approaches, we discovered that CB(2) receptors can form heteromers with CB(1) receptors in transfected neuronal cells and in rat brain pineal gland, nucleus accumbens, and globus pallidus. Within CB(1)-CB(2) receptor heteromers expressed in a neuronal cell model, agonist co-activation of CB(1) and CB(2) receptors resulted in a negative cross-talk in Akt phosphorylation and neurite outgrowth. Moreover, one specific characteristic of CB(1)-CB(2) receptor heteromers consists of both the ability of CB(1) receptor antagonists to block the effect of CB(2) receptor agonists and, conversely, the ability of CB(2) receptor antagonists to block the effect of CB(1) receptor agonists, showing a bidirectional cross-antagonism phenomenon. Taken together, these data illuminate the mechanism by which CB(2) receptors can negatively modulate CB(1) receptor function.

Cannabinoids, endocannabinoids, and cancer

The endocannabinoid system consists of an array of endogenously produced bioactive lipids that activate cannabinoid receptors. Although the primary focus of endocannabinoid biology has been on neurological and psychiatric effects, recent work has revealed several important interactions between the endocannabinoid system and cancer. Several different types of cancer have abnormal regulation of the endocannabinoid system that contributes to cancer progression and correlates to clinical outcomes. Modulation of the endocannabinoid system by pharmacological agents in various cancer types reveals that it can mediate antiproliferative and apoptotic effects by both cannabinoid receptor-dependent and -independent pathways. Selective agonists and antagonists of the cannabinoid receptors, inhibitors of endocannabinoid hydrolysis, and cannabinoid analogs have been utilized to probe the pathways involved in the effects of the endocannabinoid system on cancer cell apoptosis, proliferation, migration, adhesion, and invasion. The antiproliferative and apoptotic effects produced by some of these pharmacological probes reveal that the endocannabinoid system is a promising new target for the development of novel chemotherapeutics to treat cancer.

Cannabinoid receptor agonists modulate oligodendrocyte differentiation by activating PI3K/Akt and the mammalian target of rapamycin (mTOR) pathways

BACKGROUND AND PURPOSE

The endogenous cannabinoid system participates in oligodendrocyte progenitor differentiation in vitro. To determine the effect of synthetic cannabinoids on oligodendrocyte differentiation, we exposed differentiating cultures of oligodendrocytes with cannabinoid CB(1), CB(2) and CB(1)/CB(2) receptor agonists and antagonists. The response of the PI3K/Akt and the mammalian target of rapamycin (mTOR) signalling pathways were studied as effectors of cannabinoid activity.

EXPERIMENTAL APPROACH

Purified oligodendrocyte progenitor cells (OPC) obtained from primary mixed glial cell cultures were treated for 48 h with CB(1), CB(2) and CB(1) /CB(2) receptor agonists (ACEA, JWH133 and HU210, respectively) in the presence or absence of the antagonists AM281 (CB(1) receptor) and AM630 (CB(2) receptor). Moreover, inhibitors of the phosphatidylinositol 3-kinase (PI3K)/Akt and mTOR pathways (LY294002 and rapamycin, respectively) were used to study the involvement of these pathways on cannabinoid-induced OPC maturation.

KEY RESULTS

ACEA, JWH133 and HU-210 enhanced OPC differentiation as assessed by the expression of stage specific antigens and myelin basic protein (MBP). Moreover, this effect was blocked by the CB receptor antagonists. ACEA, JWH133 and HU210 induced a time-dependent phosphorylation of Akt and mTOR, whereas the inhibitors of PI3K/Akt (LY294002) or of mTOR (rapamycin) reversed the effects of HU-210 on oligodendrocyte differentiation and kinase activation.

CONCLUSIONS AND IMPLICATIONS

Activation of cannabinoid CB(1) or CB(2) receptors with selective agonists accelerated oligodendrocyte differentiation through the mTOR and Akt signalling pathways.

Omega-3 N-acylethanolamines are endogenously synthesised from omega-3 fatty acids in different human prostate and breast cancer cell lines

Omega-3 (n-3) fatty acids inhibit breast and prostate cancer cell growth. We previously showed that N-acylethanolamine derivatives of n-3 (n-3-NAE) are endocannabinoids, which regulate cancer cell proliferation. These n-3-NAE are synthesised in certain cells/tissues, after supplementing with fatty acids, however, no one has assessed whether and to what extent this occurs in cancer cells. We determined levels of endogenous n-3-NAEs in hormone sensitive and insensitive prostate and breast cancer cells and subsequent effects on other endocannabinoids (anandamide and 2-arachidonoylglycerol), before and after supplementing with DHA and EPA fatty acids, using HPLC tandem mass spectrometry. This is the first study reporting that n-3-NAEs are synthesised from their parent n-3 fatty acids in cancer cells, regardless of tumour type, hormone status or the presence of fatty acid amide hydrolase. This could have important implications for the use of n-3 fatty acids as therapeutic agents in breast and prostate cancers expressing cannabinoid receptors.

The endocannabinoid system and cancer: therapeutic implication

The endocannabinoid system is implicated in a variety of physiological and pathological conditions (inflammation, immunomodulation, analgesia, cancer and others). The main active ingredient of cannabis, Δ(9) -tetrahydrocannabinol (Δ(9) -THC), produces its effects through activation of CB(1) and CB(2) receptors. CB(1) receptors are expressed at high levels in the central nervous system (CNS), whereas CB(2) receptors are concentrated predominantly, although not exclusively, in cells of the immune system. Endocannabinoids are endogenous lipid-signalling molecules that are generated in the cell membrane from phospholipid precursors. The two best characterized endocannabinoids identified to date are anandamide (AEA) and 2-arachidonoylglycerol (2-AG). Here we review the relationship between the endocannabinoid system and anti-tumour actions (inhibition of cell proliferation and migration, induction of apoptosis, reduction of tumour growth) of the cannabinoids in different types of cancer. This review will focus on examining how activation of the endocannabinoid system impacts breast, prostate and bone cancers in both in vitro and in vivo systems. The therapeutic potential of cannabinoids for cancer, as identified in clinical trials, is also discussed. Identification of safe and effective treatments to manage and improve cancer therapy is critical to improve quality of life and reduce unnecessary suffering in cancer patients. In this regard, cannabis-like compounds offer therapeutic potential for the treatment of breast, prostate and bone cancer in patients. Further basic research on anti-cancer properties of cannabinoids as well as clinical trials of cannabinoid therapeutic efficacy in breast, prostate and bone cancer is therefore warranted.

N-arachidonoyl-L-serine is neuroprotective after traumatic brain injury by reducing apoptosis

N-arachidonoyl-L-serine (AraS) is a brain component structurally related to the endocannabinoid family. We investigated the neuroprotective effects of AraS following closed head injury induced by weight drop onto the exposed fronto-parietal skull and the mechanisms involved. A single injection of AraS following injury led to a significant improvement in functional outcome, and to reduced edema and lesion volume compared with vehicle. Specific antagonists to CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) or large conductance calcium-activated potassium (BK) channels reversed these effects. Specific binding assays did not indicate binding of AraS to the GPR55 cannabinoid receptor. N-arachidonoyl-L-serine blocked the attenuation in phosphorylated extracellular-signal-regulated kinase 1/2 (ERK) levels and led to an increase in pAkt in both the ipsilateral and contralateral cortices. Increased levels of the prosurvival factor Bcl-xL were evident 24 hours after injury in AraS-treated mice, followed by a 30% reduction in caspase-3 activity, measured 3 days after injury. Treatment with a CB2 antagonist, but not with a CB1 antagonist, reversed this effect. Our results suggest that administration of AraS leads to neuroprotection via ERK and Akt phosphorylation and induction of their downstream antiapoptotic pathways. These protective effects are related mostly to indirect signaling via the CB2R and TRPV1 channels but not through CB1 or GPR55 receptors.

The anandamide effect on NO/cGMP pathway in human platelets

In this study the effect of the endocannabinoid anandamide on platelet nitric oxide (NO)/cGMP pathway was investigated. Data report that anandamide in a dose-and time-dependent manner increased NO and cGMP levels and stimulated endothelial nitric oxide synthase (eNOS) activity. These parameters were significantly reduced by LY294002, selective inhibitor of PI3K and by MK2206, specific inhibitor of AKT. Moreover anandamide stimulated both eNOSser1177 and AKTser473 phosphorylation. Finally the anandamide effect on NO and cGMP levels, eNOS and AKT phosphorylation/activation were inhibited by SR141716, specific cannabinoid receptor 1 antagonist, supporting the involvement of anandamide binding to this receptor. Overall data of this report indicate that low concentrations of anandamide, through PI3K/AKT pathway activation, stimulates eNOS activity and increases NO levels in human platelets. In such way anandamide contributes to extend platelet survival.

α₂-Adrenoceptors activate noradrenaline-mediated glycogen turnover in chick astrocytes

In the brain, glycogen is primarily stored in astrocytes where it is regulated by several hormones/neurotransmitters, including noradrenaline that controls glycogen breakdown (in the short term) and synthesis. Here, we have examined the adrenoceptor (AR) subtype that mediates the glycogenic effect of noradrenaline in chick primary astrocytes by the measurement of glycogen turnover (total (14) C incorporation of glucose into glycogen) following noradrenergic activation. Noradrenaline and insulin increased glycogen turnover in a concentration-dependent manner. The effect of noradrenaline was mimicked by stimulation of α(2) -ARs (and to a lesser degree by β(3) -ARs), but not by stimulation of α(1) -, β(1) -, or β(2) -ARs, and occurred only in astrocytes and not neurons. In chick astrocytes, studies using RT-PCR and radioligand binding showed that α(2A) - and α(2C) -AR mRNA and protein were present. α(2) -AR- or insulin-mediated glycogen turnover was inhibited by phosphatidylinositol-3 kinase inhibitors, and both insulin and clonidine caused phosphorylation of Akt and glycogen synthase kinase-3 in chick astrocytes. α(2) -AR but not insulin-mediated glycogen turnover was inhibited by pertussis toxin pre-treatment indicating involvement of Gi/o proteins. These results show that the increase in glycogen turnover caused by noradrenaline is because of activation of α(2) -ARs that increase glycogen turnover in astrocytes utilizing a Gi/o-PI3K pathway.