CB1 Cannabinoid Receptors Increase Neuronal Precursor Proliferation through AKT/Glycogen Synthase Kinase-3��/��-Catenin Signaling

The endocannabinoid system is involved in the regulation of many physiological effects in the central and peripheral nervous system. Recent findings have demonstrated the presence of a functional endocannabinoid system within neuronal progenitors located in the hippocampus and ventricular/subventricular zone that participates in the regulation of cell proliferation. It is presently unknown whether the endocannabinoid system exerts a widespread effect on neuronal precursors from different neurogenic regions, and very little is known about the signaling by which it regulates neuronal precursor proliferation. Herein, we demonstrate the presence of cannabinoid CB₁ receptors in granule cell precursors (GCPs) during early cerebellar development. Activation of CB₁ receptors by HU-210 promoted GCP proliferation in vitro, an effect that was prevented by a selective CB₁ antagonist. Accordingly, in vivo experiments showed that GCP proliferation was increased by chronic HU-210 treatment and that in CB₁-deficient mice cell proliferation was significantly lower than in wild-type littermates, indicating that the endocannabinoid system is physiologically involved in regulation of GCP proliferation. The pro-proliferative effect of cannabinoids in GCPs was mediated through the CB₁/AKT/glycogen synthase kinase-3β/β-catenin pathway. Involvement of this pathway was also observed in cultures of neuronal precursors from the subventricular zone, suggesting that this pathway may be a general mechanism by which endocannabinoids regulate proliferation of neuronal precursors. These observations suggest that endocannabinoids constitute a new family of lipid signaling cues that may exert a widespread effect on neuronal precursor proliferation during brain development.     

Is lipid signaling through cannabinoid 2 receptors part of a protective system?

The mammalian body has a highly developed immune system which guards against continuous invading protein attacks and aims at preventing, attenuating or repairing the inflicted damage. It is conceivable that through evolution analogous biological protective systems have been evolved against non-protein attacks. There is emerging evidence that lipid endocannabinoid signaling through cannabinoid 2 (CB₂) receptors may represent an example/part of such a protective system/armamentarium. Inflammation/tissue injury triggers rapid elevations in local endocannabinoid levels, which in turn regulate signaling responses in immune and other cells modulating their critical functions. Changes in endocannabinoid levels and/or CB₂ receptor expressions have been reported in almost all diseases affecting humans, ranging from cardiovascular, gastrointestinal, liver, kidney, neurodegenerative, psychiatric, bone, skin, autoimmune, lung disorders to pain and cancer, and modulating CB₂ receptor activity holds tremendous therapeutic potential in these pathologies. While CB₂ receptor activation in general mediates immunosuppressive effects, which limit inflammation and associated tissue injury in large number of pathological conditions, in some disease states activation of the CB₂ receptor may enhance or even trigger tissue damage, which will also be discussed alongside the protective actions of the CB₂ receptor stimulation with endocannabinoids or synthetic agonists, and the possible biological mechanisms involved in these effects.     

Enhancement of endocannabinoid signaling by fatty acid amide hydrolase inhibition: A neuroprotective therapeutic modality

AimsThis review posits that fatty acid amide hydrolase (FAAH) inhibition has therapeutic potential against neuropathological states including traumatic brain injury; Alzheimer's, Huntington's, and Parkinson's diseases; and stroke.Main methodsThis proposition is supported by data from numerous in vitro and in vivo experiments establishing metabolic and pharmacological contexts for the neuroprotective role of the endogenous cannabinoid (“endocannabinoid”) system and selective FAAH inhibitors.Key findingsThe systems biology of endocannabinoid signaling involves two main cannabinoid receptors, the principal endocannabinoid lipid mediators N-arachidonoylethanolamine (“anandamide”) (AEA) and 2-arachidonoyl glycerol (2-AG), related metabolites, and the proteins involved in endocannabinoid biosynthesis, biotransformation, and transit. The endocannabinoid system is capable of activating distinct signaling pathways on-demand in response to pathogenic events or stimuli, thereby enhancing cell survival and promoting tissue repair. Accumulating data suggest that endocannabinoid system modulation at discrete targets is a promising pharmacotherapeutic strategy for treating various medical conditions. In particular, neuronal injury activates cannabinoid signaling in the central nervous system as an intrinsic neuroprotective response. Indirect potentiation of this salutary response through pharmacological inhibition of FAAH, an endocannabinoid-deactivating enzyme, and consequent activation of signaling pathways downstream from cannabinoid receptors have been shown to promote neuronal maintenance and function.SignificanceThis therapeutic modality has the potential to offer site- and event-specific neuroprotection under conditions where endocannabinoids are being produced as part of a physiological protective mechanism. In contrast, direct application of cannabinoid receptor agonists to the central nervous system may activate CB receptors indiscriminately and invite unwanted psychotrophic effects.     

Type-1 (CB1) Cannabinoid Receptor Promotes Neuronal Differentiation and Maturation of Neural Stem Cells

Neural stem cells (NSCs) are self-renewing cells that can differentiate into multiple neural lineages and repopulate regions of the brain after injury. We have investigated the role of endocannabinoids (eCBs), endogenous cues that modulate neuronal functions including neurogenesis, and their receptors CB₁ and CB₂ in mouse NSCs. Real-time PCR and Western blot analyses indicated that CB₁ is present at higher levels than CB₂ in NSCs. The eCB anandamide (AEA) or the CB₁-specific agonist ACEA enhanced NSC differentiation into neurons, but not astrocytes and oligodendrocytes, whereas the CB₂-specific agonist JWH133 was ineffective. Conversely, the effect of AEA was inhibited by CB₁, but not CB₂, antagonist, corroborating the specificity of the response. CB₁ activation also enhanced maturation of neurons, as indicated by morphometric analysis of neurites. CB₁ stimulation caused long-term inhibition of the ERK1/2 pathway. Consistently, pharmacological inhibition of the ERK1/2 pathway recapitulated the effects exerted by CB₁ activation on neuronal differentiation and maturation. Lastly, gene array profiling showed that CB₁ activation augmented the expression of genes involved in neuronal differentiation while decreasing that of stemness genes. These results highlight the role of CB₁ in the regulation of NSC fate and suggest that its activation may represent a pro-neuronal differentiation signal.     

The evolution and comparative neurobiology of endocannabinoid signalling

CB₁- and CB₂-type cannabinoid receptors mediate effects of the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide in mammals. In canonical endocannabinoid-mediated synaptic plasticity, 2-AG is generated postsynaptically by diacylglycerol lipase alpha and acts via presynaptic CB₁-type cannabinoid receptors to inhibit neurotransmitter release. Electrophysiological studies on lampreys indicate that this retrograde signalling mechanism occurs throughout the vertebrates, whereas system-level studies point to conserved roles for endocannabinoid signalling in neural mechanisms of learning and control of locomotor activity and feeding. CB₁/CB₂-type receptors originated in a common ancestor of extant chordates, and in the sea squirt Ciona intestinalis a CB₁/CB₂-type receptor is targeted to axons, indicative of an ancient role for cannabinoid receptors as axonal regulators of neuronal signalling. Although CB₁/CB₂-type receptors are unique to chordates, enzymes involved in biosynthesis/inactivation of endocannabinoids occur throughout the animal kingdom. Accordingly, non-CB₁/CB₂-mediated mechanisms of endocannabinoid signalling have been postulated. For example, there is evidence that 2-AG mediates retrograde signalling at synapses in the nervous system of the leech Hirudo medicinalis by activating presynaptic transient receptor potential vanilloid-type ion channels. Thus, postsynaptic synthesis of 2-AG or anandamide may be a phylogenetically widespread phenomenon, and a variety of proteins may have evolved as presynaptic (or postsynaptic) receptors for endocannabinoids.     

Cannabinoid receptor signaling in progenitor/stem cell proliferation and differentiation

Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries, much earlier than the discovery and characterization of their substrate of action, the endocannabinoid system (ECS). The latter is an ensemble of endogenous lipids, their receptors [in particular type-1 (CB₁) and type-2 (CB₂) cannabinoid receptors] and metabolic enzymes. Cannabinoid signaling regulates cell proliferation, differentiation and survival, with different outcomes depending on the molecular targets and cellular context involved. Cannabinoid receptors are expressed and functional from the very early developmental stages, when they regulate embryonic and trophoblast stem cell survival and differentiation, and thus may affect the formation of manifold adult specialized tissues derived from the three different germ layers (ectoderm, mesoderm and endoderm). In the ectoderm-derived nervous system, both CB₁ and CB₂ receptors are present in neural progenitor/stem cells and control their self-renewal, proliferation and differentiation. CB₁ and CB₂ show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of mesoderm-derived hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. Here, we will review these new findings, which unveil the involvement of eCB signaling in the regulation of progenitor/stem cell fate in the nervous system and in the periphery. The developmental regulation of cannabinoid receptor expression and cellular/subcellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease.     

In vivo pharmacology of endocannabinoids and their metabolic inhibitors: Therapeutic implications in Parkinson's disease and abuse liability

This review focuses on the behavioral pharmacology of endogenous cannabinoids (endocannabinoids) and indirect-acting cannabinoid agonists that elevate endocannabinoid tone by inhibiting the activity of metabolic enzymes. Similarities and differences between prototype cannabinoid agonists, endocannabinoids and inhibitors of endocannabinoid metabolism are discussed in the context of endocannabinoid pharmacokinetics in vivo. The distribution and function of cannabinoid and non-CB₁/CB₂ receptors are also covered, with emphasis on their role in disorders characterized by dopamine dysfunction, such as drug abuse and Parkinson's disease. Finally, evidence is presented to suggest that FAAH inhibitors lack the abuse liability associated with CB₁ agonists, although they may modify the addictive properties of other drugs, such as alcohol.     

Cannabidiol as an emergent therapeutic strategy for lessening the impact of inflammation on oxidative stress

Oxidative stress with reactive oxygen species generation is a key weapon in the arsenal of the immune system for fighting invading pathogens and initiating tissue repair. If excessive or unresolved, however, immune-related oxidative stress can initiate further increasing levels of oxidative stress that cause organ damage and dysfunction. Targeting oxidative stress in various diseases therapeutically has proven more problematic than first anticipated given the complexities and perversity of both the underlying disease and the immune response. However, growing evidence suggests that the endocannabinoid system, which includes the CB₁ and CB₂ G-protein-coupled receptors and their endogenous lipid ligands, may be an area that is ripe for therapeutic exploitation. In this context, the related nonpsychotropic cannabinoid cannabidiol, which may interact with the endocannabinoid system but has actions that are distinct, offers promise as a prototype for anti-inflammatory drug development. This review discusses recent studies suggesting that cannabidiol may have utility in treating a number of human diseases and disorders now known to involve activation of the immune system and associated oxidative stress, as a contributor to their etiology and progression. These include rheumatoid arthritis, types 1 and 2 diabetes, atherosclerosis, Alzheimer disease, hypertension, the metabolic syndrome, ischemia-reperfusion injury, depression, and neuropathic pain.     

Negative Regulation of Leptin-induced Reactive Oxygen Species (ROS) Formation by Cannabinoid CB1 Receptor Activation in Hypothalamic Neurons

The adipocyte-derived, anorectic hormone leptin was recently shown to owe part of its regulatory effects on appetite-regulating hypothalamic neuropeptides to the elevation of reactive oxygen species (ROS) levels in arcuate nucleus (ARC) neurons. Leptin is also known to exert a negative regulation on hypothalamic endocannabinoid levels and hence on cannabinoid CB₁ receptor activity. Here we investigated the possibility of a negative regulation by CB₁ receptors of leptin-mediated ROS formation in the ARC. Through pharmacological and molecular biology experiments we report data showing that leptin-induced ROS accumulation is 1) blunted by arachidonyl-2′-chloroethylamide (ACEA) in a CB₁-dependent manner in both the mouse hypothalamic cell line mHypoE-N41 and ARC neuron primary cultures, 2) likewise blocked by a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, troglitazone, in a manner inhibited by T0070907, a PPAR-γ antagonist that also inhibited the ACEA effect on leptin, 3) blunted under conditions of increased endocannabinoid tone due to either pharmacological or genetic inhibition of endocannabinoid degradation in mHypoE-N41 and primary ARC neuronal cultures from MAGL^−/− mice, respectively, and 4) associated with reduction of both PPAR-γ and catalase activity, which are reversed by both ACEA and troglitazone. We conclude that CB₁ activation reverses leptin-induced ROS formation and hence possibly some of the ROS-mediated effects of the hormone by preventing PPAR-γ inhibition by leptin, with subsequent increase of catalase activity. This mechanism might underlie in part CB1 orexigenic actions under physiopathological conditions accompanied by elevated hypothalamic endocannabinoid levels.     

Cannabinoid CB<Subscript>2</Subscript> Receptor-Mediated Anti-nociception in Models of Acute and Chronic Pain

The endocannabinoid system consists of cannabinoid CB₁ and CB₂ receptors, endogenous ligands and their synthesising/metabolising enzymes. Cannabinoid receptors are present at key sites involved in the relay and modulation of nociceptive information. The analgesic effects of cannabinoids have been well documented. The usefulness of nonselective cannabinoid agonists can, however, be limited by psychoactive side effects associated with activation of CB₁ receptors. Following the recent evidence for CB₂ receptors existing in the nervous system and reports of their up-regulation in chronic pain states and neurodegenerative diseases, much research is now aimed at shedding light on the role of the CB₂ receptor in human disease. Recent studies have demonstrated anti-nociceptive effects of selective CB₂ receptor agonists in animal models of pain in the absence of CNS side effects. This review focuses on the analgesic potential of CB₂ receptor agonists for inflammatory, post-operative and neuropathic pain states and discusses their possible sites and mechanisms of action. Jhaveri and Sagar joint first author.     

Ketogenic diet is antiepileptogenic in pentylenetetrazole kindled mice and decrease levels of N-acylethanolamines in hippocampus

The ketogenic diet (KD) is used for the treatment of refractory epilepsy in children, however, the mechanism(s) remains largely unknown. Also, the antiepileptogenic potential in animal models of epilepsy has been poorly addressed. Activation of cannabinoid type-1 receptor (CB₁-R) upon seizure activity may mediate neuroprotection as may several N-acylethanolamines. It is unknown how the KD interfere with the endocannabinoid system.We investigated the antiepileptogenic potential of the KD in the pentylenetetrazole kindling model in young mice and measured the hippocampal levels of CB₁-R by Western blot and of endocannabinoids and N-acylethanolamines by mass spectrometry.The KD significantly decreased incidence and severity of seizures, and significantly increased the latency to clonic convulsions. There were no changes in levels of endocannabinoids or CB₁-R expression by either seizure activity or type of diet. The level of oleoylethanolamide as well as the sum of N-acylethanolamines were significantly decreased by the KD, but were unaffected by seizure activity.The study shows that the KD had clear antiepileptogenic properties in the pentylenetetrazole kindling model and does not support a role of endocannabinoids in this model. The significance of the decreased hippocampal level of oleoylethanolamide awaits further studies.     

Mechanisms underlying in vivo neuroprotection by the endocannabinoid anandamide and the cannabinoid/vanilloid receptor agonist,arvanil

The endocannabinoid anandamide (AEA) and some of its oxidative metabolites are putative ligands for the vanilloid receptor (VR₁). AEA affords protection against excitotoxicity induced in vivo by ouabain, a Na⁺/K⁺‐ATPase inhibitor. This effect is only partly dependent of the cannabinoid CB₁ receptor. Here, we assessed whether VR₁ is involved in neuroprotection by AEA and arvanil, which is a hydrolysis‐stable ligand for both VR₁ and CB₁. Using magnetic resonance imaging we show that: (i) modulation of VR₁, by the agonists arvanil and capsaicin and the antagonist capsazepine, leads to neuroprotective effects in the late but not acute phase after i.c. ouabain‐injection; (ii) arvanil is a potent neuroprotectant, acting at both CB₁ and VR₁; and (iii) the neuroprotective effects of AEA are mediated by CB₁ but not by lipoxygenase metabolites or VR₁.     

Receptor heteromerization expands the repertoire of cannabinoid signaling in rodent neurons

A fundamental question in G protein coupled receptor biology is how a single ligand acting at a specific receptor is able to induce a range of signaling that results in a variety of physiological responses. We focused on Type 1 cannabinoid receptor (CB₁R) as a model GPCR involved in a variety of processes spanning from analgesia and euphoria to neuronal development, survival and differentiation. We examined receptor dimerization as a possible mechanism underlying expanded signaling responses by a single ligand and focused on interactions between CB₁R and delta opioid receptor (DOR). Using co-immunoprecipitation assays as well as analysis of changes in receptor subcellular localization upon co-expression, we show that CB₁R and DOR form receptor heteromers. We find that heteromerization affects receptor signaling since the potency of the CB₁R ligand to stimulate G-protein activity is increased in the absence of DOR, suggesting that the decrease in CB₁R activity in the presence of DOR could, at least in part, be due to heteromerization. We also find that the decrease in activity is associated with enhanced PLC-dependent recruitment of arrestin3 to the CB₁R-DOR complex, suggesting that interaction with DOR enhances arrestin-mediated CB₁R desensitization. Additionally, presence of DOR facilitates signaling via a new CB₁R-mediated anti-apoptotic pathway leading to enhanced neuronal survival. Taken together, these results support a role for CB₁R-DOR heteromerization in diversification of endocannabinoid signaling and highlight the importance of heteromer-directed signal trafficking in enhancing the repertoire of GPCR signaling.     

Anandamide Suppresses Proliferation and Cytokine Release from Primary Human T-Lymphocytes Mainly via CB2 Receptors

Background

Anandamide (AEA) is an endogenous lipid mediator that exerts several effects in the brain as well as in peripheral tissues. These effects are mediated mainly by two types of cannabinoid receptors, named CB₁R and CB₂R, making AEA a prominent member of the “endocannabinoid” family. Also immune cells express CB₁ and CB₂ receptors, and possess the whole machinery responsible for endocannabinoid metabolism. Not surprisingly, evidence has been accumulated showing manifold roles of endocannabinoids in the modulation of the immune system. However, details of such a modulation have not yet been disclosed in primary human T-cells.

Methodology/Significance

In this investigation we used flow cytometry and ELISA tests, in order to show that AEA suppresses proliferation and release of cytokines like IL-2, TNF-α and INF-γ from activated human peripheral T-lymphocytes. However, AEA did not exert any cytotoxic effect on T-cells. The immunosuppression induced by AEA was mainly dependent on CB₂R, since it could be mimicked by the CB₂R selective agonist JWH-015, and could be blocked by the specific CB₂R antagonist SR144528. Instead the selective CB₁R agonist ACEA, or the selective CB₁R antagonist SR141716, were ineffective. Furthermore, we demonstrated an unprecedented immunosuppressive effect of AEA on IL-17 production, a typical cytokine that is released from the unique CD4+ T-cell subset T-helper 17.

Conclusions/Significance

Overall, our study investigates for the first time the effects of the endocannabinoid AEA on primary human T-lymphocytes, demonstrating that it is a powerful modulator of immune cell functions. In particular, not only we clarify that CB₂R mediates the immunosuppressive activity of AEA, but we are the first to describe such an immunosuppressive effect on the newly identified Th-17 cells. These findings might be of crucial importance for the rational design of new endocannabinoid-based immunotherapeutic approaches.     

The role of fatty acid amide hydrolase inhibition in nicotine reward and dependence

The endogenous cannabinoid anandamide (AEA) exerts the majority of its effects at CB₁ and CB₂ receptors and is degraded by fatty acid amide hydrolase (FAAH). FAAH KO mice and animals treated with FAAH inhibitors are impaired in their ability to hydrolyze AEA and other non-cannabinoid lipid signaling molecules, such as oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). AEA and these other substrates activate non-cannabinoid receptor systems, including TRPV1 and PPAR-α receptors. In this mini review, we describe the functional consequences of FAAH inhibition on nicotine reward and dependence as well as the underlying endocannabinoid and non-cannabinoid receptor systems mediating these effects. Interestingly, FAAH inhibition seems to mediate nicotine dependence differently in mice and rats. Indeed, pharmacological and genetic FAAH disruption in mice enhances nicotine reward and withdrawal. However, in rats, pharmacological blockade of FAAH significantly inhibits nicotine reward and has no effect in nicotine withdrawal. Studies suggest that non-cannabinoid mechanisms may play a role in these species differences.     

Cannabinoid-2 receptor limits inflammation,oxidative/nitrosative stress,and cell death in nephropathy

Cisplatin is an important chemotherapeutic agent; however, its nephrotoxicity limits its clinical use. Enhanced inflammatory response and oxidative/nitrosative stress seem to play a key role in the development of cisplatin-induced nephropathy. Activation of cannabinoid-2 (CB₂) receptors with selective agonists exerts anti-inflammatory and tissue-protective effects in various disease models. We have investigated the role of CB₂ receptors in cisplatin-induced nephrotoxicity using the selective CB₂ receptor agonist HU-308 and CB₂ knockout mice. Cisplatin significantly increased inflammation (leukocyte infiltration, CXCL1/2, MCP-1, TNFα, and IL-1β levels) and expression of adhesion molecule ICAM-1 and superoxide-generating enzymes NOX2, NOX4, and NOX1 and enhanced ROS generation, iNOS expression, nitrotyrosine formation, and apoptotic and poly(ADP-ribose) polymerase-dependent cell death in the kidneys of mice, associated with marked histopathological damage and impaired renal function (elevated serum BUN and creatinine levels) 3 days after the administration of the drug. CB₂ agonist attenuated the cisplatin-induced inflammatory response, oxidative/nitrosative stress, and cell death in the kidney and improved renal function, whereas CB₂ knockouts developed enhanced inflammation and tissue injury. Thus, the endocannabinoid system, through CB₂ receptors, protects against cisplatin-induced kidney damage by attenuating inflammation and oxidative/nitrosative stress, and selective CB₂ agonists may represent a promising novel approach to preventing this devastating complication of chemotherapy.     

The CB₁ receptor-mediated endocannabinoid signaling and NGF: the novel targets of curcumin

Increasing interest has recently been attracted towards the identification of natural compounds including those with antidepressant properties. Curcumin has shown promising antidepressant effect, however, its molecular target(s) have not been well defined. Based on the interaction between the neurotrophins and endocannabinoid system as well as their contribution to the emotional reactivity and antidepressant action, here we show that 4-week treatment with curcumin, similar to the classical antidepressant amitriptyline, results in the sustained elevation of brain nerve growth factor (NGF) and endocannabinoids in dose-dependent and brain region-specific fashion. Pretreatment with cannabinoid CB₁ receptor neutral antagonist AM4113, but not the CB₂ antagonist SR144528, prevents the enhancement of brain NGF contents. AM4113 exerts no effect by itself. Our findings by presenting the CB₁ receptor-mediated endocannabinoid signaling and NGF as novel targets for curcumin, suggest that more attention should be focused on the therapeutic potential of herbal medicines including curcumin.     

The Endocannabinoid/Endovanilloid N-Arachidonoyl Dopamine (NADA) and Synthetic Cannabinoid WIN55,212-2 Abate the Inflammatory Activation of Human Endothelial Cells

Although cannabinoids, such as Δ⁹-tetrahydrocannabinol, have been studied extensively for their psychoactive effects, it has become apparent that certain cannabinoids possess immunomodulatory activity. Endothelial cells (ECs) are centrally involved in the pathogenesis of organ injury in acute inflammatory disorders, such as sepsis, because they express cytokines and chemokines, which facilitate the trafficking of leukocytes to organs, and they modulate vascular barrier function. In this study, we find that primary human ECs from multiple organs express the cannabinoid receptors CB₁R, GPR18, and GPR55, as well as the ion channel transient receptor potential cation channel vanilloid type 1. In contrast to leukocytes, CB₂R is only minimally expressed in some EC populations. Furthermore, we show that ECs express all of the known endocannabinoid (eCB) metabolic enzymes. Examining a panel of cannabinoids, we demonstrate that the synthetic cannabinoid WIN55,212-2 and the eCB N-arachidonoyl dopamine (NADA), but neither anandamide nor 2-arachidonoylglycerol, reduce EC inflammatory responses induced by bacterial lipopeptide, LPS, and TNFα. We find that endothelial CB₁R/CB₂R are necessary for the effects of NADA, but not those of WIN55,212-2. Furthermore, transient receptor potential cation channel vanilloid type 1 appears to counter the anti-inflammatory properties of WIN55,212-2 and NADA, but conversely, in the absence of these cannabinoids, its inhibition exacerbates the inflammatory response in ECs activated with LPS. These data indicate that the eCB system can modulate inflammatory activation of the endothelium and may have important implications for a variety of acute inflammatory disorders that are characterized by EC activation.     

Ulcerative Colitis Induces Changes on the Expression of the Endocannabinoid System in the Human Colonic Tissue

Background

Recent studies suggest potential roles of the endocannabinoid system in gastrointestinal inflammation. Although cannabinoid CB₂ receptor expression is increased in inflammatory disorders, the presence and function of the remaining proteins of the endocannabinoid system in the colonic tissue is not well characterized.

Methodology

Cannabinoid CB₁ and CB₂ receptors, the enzymes for endocannabinoid biosynthesis DAGLα, DAGLβ and NAPE-PLD, and the endocannabinoid-degradating enzymes FAAH and MAGL were analysed in both acute untreated active ulcerative pancolitis and treated quiescent patients in comparison with healthy human colonic tissue by immunocytochemistry. Analyses were carried out according to clinical criteria, taking into account the severity at onset and treatment received.

Principal Findings

Western blot and immunocytochemistry indicated that the endocannabinoid system is present in the colonic tissue, but it shows a differential distribution in epithelium, lamina propria, smooth muscle and enteric plexi. Quantification of epithelial immunoreactivity showed an increase of CB₂ receptor, DAGLα and MAGL expression, mainly in mild and moderate pancolitis patients. In contrast, NAPE-PLD expression decreased in moderate and severe pancolitis patients. During quiescent pancolitis, CB₁, CB₂ and DAGLα expression dropped, while NAPE-PLD expression rose, mainly in patients treated with 5-ASA or 5-ASA+corticosteroids. The number of immune cells containing MAGL and FAAH in the lamina propria increased in acute pancolitis patients, but dropped after treatment.

Conclusions

Endocannabinoids signaling pathway, through CB₂ receptor, may reduce colitis-associated inflammation suggesting a potential drugable target for the treatment of inflammatory bowel diseases.     

Cannabinoid signaling system: Does it play a function in cell proliferation and migration,neuritic elongation and guidance and synaptogenesis during brain ontogenesis?

The cannabinoid signaling system is located during brain development in a position concordant with playing a modulatory function in the regulation of neuronal and glial cell proliferation and migration, survival of neural progenitors, axonal elongation and synaptogenesis and differentiation of oligodendrocytes and formation of myelin. This assumption is based on the fact that CB₁ receptors and their ligands emerge early in brain development and are transiently expressed in certain brain regions that play key roles in these processes. We have recently proposed that this modulatory action might be exerted through regulating L1 and other cell adhesion molecules, that are also key elements for those processes. The present commentary will address these two questions trying to summarize all the available evidence and to suggest the future directions for research.Key words: cannabinoid signaling system, CB₁ receptors, brain development, neural cell proliferation, migration and differentiation, cell adhesion moleculesThe study of the molecular mechanisms underlying the psychoactive effects of Cannabis sativa led to the discovery of the “endogenous cannabinoid system”, an intercellular signaling system that plays modulatory functions in brain synapses and also in the periphery. It consists of multiple endocannabinoid ligands, their membrane receptors (CB₁, CB₂ and others), anabolic and catabolic enzymes, as well as a membrane-transport mechanism. The function(s) of this system has (have) been extensively studied in adult mammals pointing to an important role in the regulation of numerous neurobiological processes. Studies conducted during the last decade, which addressed the ontogeny of this system in the brain, led to the assumption that the endocannabinoid system might also play relevant modulatory functions during brain development. This assumption derived from certain particularities found in the ontogenic pattern of the endocannabinoid system, which mimicked similar results found for neurotransmitters having a neurotrophic function.¹ Thus, the endo cannabinoid signaling system, in particular the CB₁ receptors: (1) emerge early in brain development,^1–5 (2) are particularly abundant in forebrain subventricular zones and cortical structures,^1,4 which play a key role in cell proliferation and migration, respectively, and (3) and are transiently located, during restricted ontogenic periods, in forebrain white matter structures, in particular transverse commissural tracts,^1,2,4 which are essential for cell migration and axonal elongation. The fact that this “atypical” distribution of the CB₁ receptor disappears coinciding with the conclusion of the establishement of synaptic communication and postsynaptic target selection^1,6 is highly suggestive of a specific role of the cannabinoid signaling in these processes.