Therapeutic action of cannabinoids in a murine model of multiple sclerosis

The biology that underpins the therapeutic potential of cannabis-based medicines for the control of spasticity in multiple sclerosis

Cannabis-based medicines have recently been approved for the treatment of pain and spasticity in multiple sclerosis (MS). This supports the original perceptions of people with MS, who were using illegal street cannabis for symptom control and pre-clinical testing in animal models of MS. This activity is supported both by the biology of the disease and the biology of the cannabis plant and the endocannabinoid system. MS results from disease that impairs neurotransmission and this is controlled by cannabinoid receptors and endogenous cannabinoid ligands. This can limit spasticity and may also influence the processes that drive the accumulation of progressive disability.

Treatment of rat spinal cord injury with the neurotrophic factor albumin-oleic acid: translational application for paralysis, spasticity and pain

Sensorimotor dysfunction following incomplete spinal cord injury (iSCI) is often characterized by the debilitating symptoms of paralysis, spasticity and pain, which require treatment with novel pleiotropic pharmacological agents. Previous in vitro studies suggest that Albumin (Alb) and Oleic Acid (OA) may play a role together as an endogenous neurotrophic factor. Although Alb can promote basic recovery of motor function after iSCI, the therapeutic effect of OA or Alb-OA on a known translational measure of SCI associated with symptoms of spasticity and change in nociception has not been studied. Following T9 spinal contusion injury in Wistar rats, intrathecal treatment with: i) Saline, ii) Alb (0.4 nanomoles), iii) OA (80 nanomoles), iv) Alb-Elaidic acid (0.4/80 nanomoles), or v) Alb-OA (0.4/80 nanomoles) were evaluated on basic motor function, temporal summation of noxious reflex activity, and with a new test of descending modulation of spinal activity below the SCI up to one month after injury. Albumin, OA and Alb-OA treatment inhibited nociceptive Tibialis Anterior (TA) reflex activity. Moreover Alb-OA synergistically promoted early recovery of locomotor activity to 50 ± 10% of control and promoted de novo phasic descending inhibition of TA noxious reflex activity to 47 ± 5% following non-invasive electrical conditioning stimulation applied above the iSCI. Spinal L4-L5 immunohistochemistry demonstrated a unique increase in serotonin fibre innervation up to 4.2 ± 1.1 and 2.3 ± 0.3 fold within the dorsal and ventral horn respectively with Alb-OA treatment when compared to uninjured tissue, in addition to a reduction in NR1 NMDA receptor phosphorylation and microglia reactivity. Early recovery of voluntary motor function accompanied with tonic and de novo phasic descending inhibition of nociceptive TA flexor reflex activity following Alb-OA treatment, mediated via known endogenous spinal mechanisms of action, suggests a clinical application of this novel neurotrophic factor for the treatment of paralysis, spasticity and pain.

Phytocannabinoids as novel therapeutic agents in CNS disorders

The Cannabis sativa herb contains over 100 phytocannabinoid (pCB) compounds and has been used for thousands of years for both recreational and medicinal purposes. In the past two decades, characterisation of the body's endogenous cannabinoid (CB) (endocannabinoid, eCB) system (ECS) has highlighted activation of central CB(1) receptors by the major pCB, Δ(9)-tetrahydrocannabinol (Δ(9)-THC) as the primary mediator of the psychoactive, hyperphagic and some of the potentially therapeutic properties of ingested cannabis. Whilst Δ(9)-THC is the most prevalent and widely studied pCB, it is also the predominant psychotropic component of cannabis, a property that likely limits its widespread therapeutic use as an isolated agent. In this regard, research focus has recently widened to include other pCBs including cannabidiol (CBD), cannabigerol (CBG), Δ(9)tetrahydrocannabivarin (Δ(9)-THCV) and cannabidivarin (CBDV), some of which show potential as therapeutic agents in preclinical models of CNS disease. Moreover, it is becoming evident that these non-Δ(9)-THC pCBs act at a wide range of pharmacological targets, not solely limited to CB receptors. Disorders that could be targeted include epilepsy, neurodegenerative diseases, affective disorders and the central modulation of feeding behaviour. Here, we review pCB effects in preclinical models of CNS disease and, where available, clinical trial data that support therapeutic effects. Such developments may soon yield the first non-Δ(9)-THC pCB-based medicines.

Anandamide inhibits Theiler's virus induced VCAM-1 in brain endothelial cells and reduces leukocyte transmigration in a model of blood brain barrier by activation of CB(1) receptors

Background

VCAM-1 represents one of the most important adhesion molecule involved in the transmigration of blood leukocytes across the blood-brain barrier (BBB) that is an essential step in the pathogenesis of MS. Several evidences have suggested the potential therapeutic value of cannabinoids (CBs) in the treatment of MS and their experimental models. However, the effects of endocannabinoids on VCAM-1 regulation are poorly understood. In the present study we investigated the effects of anandamide (AEA) in the regulation of VCAM-1 expression induced by Theiler's virus (TMEV) infection of brain endothelial cells using in vitro and in vivo approaches.

Methods

i) in vitro: VCAM-1 was measured by ELISA in supernatants of brain endothelial cells infected with TMEV and subjected to AEA and/or cannabinoid receptors antagonist treatment. To evaluate the functional effect of VCAM-1 modulation we developed a blood brain barrier model based on a system of astrocytes and brain endothelial cells co-culture. ii) in vivo: CB₁ receptor deficient mice (Cnr1^-/-) infected with TMEV were treated with the AEA uptake inhibitor UCM-707 for three days. VCAM-1 expression and microglial reactivity were evaluated by immunohistochemistry.

Results

Anandamide-induced inhibition of VCAM-1 expression in brain endothelial cell cultures was mediated by activation of CB₁ receptors. The study of leukocyte transmigration confirmed the functional relevance of VCAM-1 inhibition by AEA. In vivo approaches also showed that the inhibition of AEA uptake reduced the expression of brain VCAM-1 in response to TMEV infection. Although a decreased expression of VCAM-1 by UCM-707 was observed in both, wild type and CB₁ receptor deficient mice (Cnr1^-/-), the magnitude of VCAM-1 inhibition was significantly higher in the wild type mice. Interestingly, Cnr1^-/- mice showed enhanced microglial reactivity and VCAM-1 expression following TMEV infection, indicating that the lack of CB₁ receptor exacerbated neuroinflammation.

Conclusions

Our results suggest that CB₁ receptor dependent VCAM-1 inhibition is a novel mechanism for AEA-reduced leukocyte transmigration and contribute to a better understanding of the mechanisms underlying the beneficial role of endocannabinoid system in the Theiler's virus model of MS.

Cannabidiol inhibits pathogenic T cells, decreases spinal microglial activation and ameliorates multiple sclerosis-like disease in C57BL/6 mice

BACKGROUND AND PURPOSE

Cannabis extracts and several cannabinoids have been shown to exert broad anti-inflammatory activities in experimental models of inflammatory CNS degenerative diseases. Clinical use of many cannabinoids is limited by their psychotropic effects. However, phytocannabinoids like cannabidiol (CBD), devoid of psychoactive activity, are, potentially, safe and effective alternatives for alleviating neuroinflammation and neurodegeneration.

EXPERIMENTAL APPROACH

We used experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein (MOG) in C57BL/6 mice, as a model of multiple sclerosis. Using immunocytochemistry and cell proliferation assays we evaluated the effects of CBD on microglial activation in MOG-immunized animals and on MOG-specific T-cell proliferation.

KEY RESULTS

Treatment with CBD during disease onset ameliorated the severity of the clinical signs of EAE. This effect of CBD was accompanied by diminished axonal damage and inflammation as well as microglial activation and T-cell recruitment in the spinal cord of MOG-injected mice. Moreover, CBD inhibited MOG-induced T-cell proliferation in vitro at both low and high concentrations of the myelin antigen. This effect was not mediated via the known cannabinoid CB(1) and CB(2) receptors.

CONCLUSIONS AND IMPLICATIONS

CBD, a non-psychoactive cannabinoid, ameliorates clinical signs of EAE in mice, immunized against MOG. Suppression of microglial activity and T-cell proliferation by CBD appeared to contribute to these beneficial effects.

Cannabinoid CB1 receptors regulate neuronal TNF-α effects in experimental autoimmune encephalomyelitis

Cannabinoid CB1 receptors (CB1Rs) regulate the neurodegenerative damage of experimental autoimmune encephalomyelitis (EAE) and of multiple sclerosis (MS). The mechanism by which CB1R stimulation exerts protective effects is still unclear. Here we show that pharmacological activation of CB1Rs dampens the tumor necrosis factor α (TNFα)-mediated potentiation of striatal spontaneous glutamate-mediated excitatory postsynaptic currents (EPSCs), which is believed to cogently contribute to the inflammation-induced neurodegenerative damage observed in EAE mice. Furthermore, mice lacking CB1Rs showed a more severe clinical course and, in parallel, exacerbated alterations of sEPSC duration after induction of EAE, indicating that endogenous cannabinoids activate CB1Rs and mitigate the synaptotoxic action of TNFα in EAE. Consistently, we found that mice lacking the fatty acid amide hydrolase (FAAH), and thus expressing abnormally high brain levels of the endocannabinoid anandamide, developed a less severe EAE associated with preserved TNFα-induced sEPSC alterations. CB1Rs are important modulators of EAE pathophysiology, and might play a mechanistic role in the neurodegenerative damage of MS patients.

Cannabinoids as novel anti-inflammatory drugs

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

Lasting impacts of prenatal cannabis exposure and the role of endogenous cannabinoids in the developing brain

Cannabis is the most commonly used illicit substance among pregnant women. Human epidemiological and animal studies have found that prenatal cannabis exposure influences brain development and can have long-lasting impacts on cognitive functions. Exploration of the therapeutic potential of cannabis-based medicines and synthetic cannabinoid compounds has given us much insight into the physiological roles of endogenous ligands (endocannabinoids) and their receptors. In this article, we examine human longitudinal cohort studies that document the long-term influence of prenatal exposure to cannabis, followed by an overview of the molecular composition of the endocannabinoid system and the temporal and spatial changes in their expression during brain development. How endocannabinoid signaling modulates fundamental developmental processes such as cell proliferation, neurogenesis, migration and axonal pathfinding are also summarized.

Changes in interleukin-1 signal modulators induced by 3,4-methylenedioxymethamphetamine (MDMA): regulation by CB2 receptors and implications for neurotoxicity

BACKGROUND

3,4-Methylenedioxymethamphetamine (MDMA) produces a neuroinflammatory reaction in rat brain characterized by an increase in interleukin-1 beta (IL-1β) and microglial activation. The CB2 receptor agonist JWH-015 reduces both these changes and partially protects against MDMA-induced neurotoxicity. We have examined MDMA-induced changes in IL-1 receptor antagonist (IL-1ra) levels and IL-1 receptor type I (IL-1RI) expression and the effects of JWH-015. The cellular location of IL-1β and IL-1RI was also examined. MDMA-treated animals were given the soluble form of IL-1RI (sIL-1RI) and neurotoxic effects examined.

METHODS

Dark Agouti rats received MDMA (12.5 mg/kg, i.p.) and levels of IL-1ra and expression of IL-1RI measured 1 h, 3 h or 6 h later. JWH-015 (2.4 mg/kg, i.p.) was injected 48 h, 24 h and 0.5 h before MDMA and IL-1ra and IL-1RI measured. For localization studies, animals were sacrificed 1 h or 3 h following MDMA and stained for IL-1β or IL-1RI in combination with neuronal and microglial markers. sIL-1RI (3 μg/animal; i.c.v.) was administered 5 min before MDMA and 3 h later. 5-HT transporter density was determined 7 days after MDMA injection.

RESULTS

MDMA produced an increase in IL-ra levels and a decrease in IL-1RI expression in hypothalamus which was prevented by CB2 receptor activation. IL-1RI expression was localized on neuronal cell bodies while IL-1β expression was observed in microglial cells following MDMA. sIL-1RI potentiated MDMA-induced neurotoxicity. MDMA also increased IgG immunostaining indicating that blood brain-barrier permeability was compromised.

CONCLUSIONS

In summary, MDMA produces changes in IL-1 signal modulators which are modified by CB2 receptor activation. These results indicate that IL-1β may play a partial role in MDMA-induced neurotoxicity.

The endocannabinoid anandamide downregulates IL-23 and IL-12 subunits in a viral model of multiple sclerosis: evidence for a cross-talk between IL-12p70/IL-23 axis and IL-10 in microglial cells

Theiler's virus (TMEV) infection of the central nervous system (CNS) induces an immune-mediated demyelinating disease in susceptible mouse strains and serves as a relevant infection model for human multiple sclerosis (MS). The endocannabinoid system represents a novel therapeutic target for autoimmune and chronic inflammatory diseases due to its anti-inflammatory properties by regulating cytokine network. IL-12p70 and IL-23 are functionally related heterodimeric cytokines that play a crucial role in the pathogenesis of MS. In the present study we showed that the endocannabinoid anandamide (AEA) downregulated the gene expression of IL-12p70 and IL-23 forming subunits mRNAs in the spinal cord of TMEV-infected mice and ameliorated motor disturbances. This was accompanied by significant decreases on the serological levels of IL-12p70/IL-23 and more interestingly, of IL-17A. In contrast, serum levels of IL-10 resulted elevated. In addition, we studied the signalling pathways involved in the regulation of IL-12p70/IL-23 and IL-10 expression in TMEV-infected microglia and addressed the possible interactions of AEA with these pathways. AEA acted through the ERK1/2 and JNK pathways to downregulate IL-12p70 and IL-23 while upregulating IL-10. These effects were partially mediated by CB2 receptor activation. We also described an autocrine circuit of cross-talk between IL-12p70/IL-23 and IL-10, since endogenously produced IL-10 negatively regulates IL-12p70 and IL-23 cytokines in TMEV-infected microglia. This suggests that by altering the cytokine network, AEA could indirectly modify the type of immune responses within the CNS. Accordingly, pharmacological modulation of endocannabinoids might be a useful tool for treating neuroinflammatory diseases.

Role of cannabinoids in multiple sclerosis

Although extracts from the cannabis plant have been used medicinally for thousands of years, it is only within the last 2 decades that our understanding of cannabinoid physiology and the provision of evidence for therapeutic benefit of cannabinoids has begun to accumulate. This review provides a background to advances in our understanding of cannabinoid receptors and the endocannabinoid system, and then considers how cannabinoids may help in the management of multiple sclerosis (MS). The relative paucity of treatments for MS-related symptoms has led to experimentation by patients with MS in a number of areas including the use of cannabis extracts. An increasing amount of evidence is now emerging to confirm anecdotal reports of symptomatic improvement, particularly for muscle stiffness and spasms, neuropathic pain and sleep and bladder disturbance, in patients with MS treated with cannabinoids. Trials evaluating a role in treating other symptoms such as tremor and nystagmus have not demonstrated any beneficial effects of cannabinoids. Safety profiles of cannabinoids seem acceptable, although a slow prolonged period of titration improves tolerability. No serious safety concerns have emerged. Methodological issues in trial design and treatment delivery are now being addressed. In addition, recent experimental evidence is beginning to suggest an effect of cannabinoids on more fundamental processes important in MS, with evidence of anti-inflammation, encouragement of remyelination and neuroprotection. Trials are currently under way to test whether cannabinoids may have a longer term role in reducing disability and progression in MS, in addition to symptom amelioration, where indications are being established.

Regulatory role of cannabinoid receptor 1 in stress-induced excitotoxicity and neuroinflammation

Exposure to stress elicits excitoxicity and neuroinflammation in the brain, contributing to cell death and damage in stress-related neurological and neuropsychiatric diseases. The endocannabinoid system is present in stress-responsive neural circuits and has been proposed as an endogenous neuroprotective system activated in some neuropathological scenarios to restore homeostasis. To elucidate the possible regulatory role of cannabinoid receptor 1 (CB1) in stress-induced excitotoxicity and neuroinflammation, both genetic and pharmacological approaches were used alternatively: (1) wild-type (WT) and CB1 knockout mice (CB1-KO) were exposed to immobilization/acoustic stress (2 h/day for 4 days) and (2) to specifically activate CB1, the selective CB1 agonist Arachidonyl-2'-chloroethylamide (ACEA) (2.5 mg/kg) was intraperitoneally administered daily to some groups of animals. Stress exposure increased CB1 mRNA and protein expression in the prefrontal cortex of WT mice in a mechanism related to N-methyl-D-aspartate glutamate receptor activation. Daily ACEA pretreatment prevented stress-induced: (1) upregulation of CB1 mRNA and protein, (2) decrease in glutamate uptake and glutamate astroglial transporter excitatory amino acid transporter 2 expression, (3) increase in consecutive proinflammatory molecules, such as cytokines (tumor necrosis factor-α and MCP-1), nuclear factor kappa B, and enzymatic sources, such as inducible nitric oxide synthase (NOS-2) and cyclooxygenase-2 (COX-2), (4) increase in lipid peroxidation; although having no effect on plasma corticosterone. Interestingly, a possible related mechanism could be the positive ACEA modulation of the antiinflammatory pathway deoxyprostaglandin/peroxisome proliferator-activated receptor γ (15d-PGJ(2)/PPARγ). Conversely, KO animal experiments indicated that a lack of CB1 produces hypothalamic/pituitary/adrenal (HPA) axis dysregulation and exacerbates stress-induced excitotoxic/neuroinflammatory responses. These multifaceted neuroprotective effects suggest that CB1 activation could be a new therapeutic strategy against neurological/neuropsychiatric pathologies with HPA axis dysregulation and an excitotoxic/neuroinflammatory component in their pathophysiology.

Inverse agonism of cannabinoid CB1 receptor blocks the adhesion of encephalitogenic T cells in inflamed brain venules by a protein kinase A-dependent mechanism

It is well known that the cannabinoid system has a significant role in the regulation of the immune responses. Cannabinoid receptors CB1 and CB2 are expressed on T lymphocytes and mediate the immunomodulatory effects of cannabinoids on T cell functions. Here we show that the treatment of proteolipid protein (PLP)139-151-specific T cells with SR141716A, a CB1 inverse agonist and prototype of the diarylpyrazoles series, induced a strong inhibition of firm adhesion in inflamed brain venules in intravital microscopy experiments. In contrast, SR144528, a potent CB2 inverse agonist, had no significant effect on both rolling and arrest of activated T cells. In addition, two analogs of SR141716A and CB1 inverse agonists, AM251 and AM281 inhibited encephalitogenic T cell adhesion suggesting that selective CB1 inverse agonism interfere with lymphocyte trafficking in the CNS. Flow cytometry experiments showed that CB1 inverse agonists have no effect on adhesion molecule expression suggesting that CB1 blockade interferes with signal transduction pathways controlling T cell adhesion in inflamed brain venules. In addition, integrin clustering was not altered after treatment with CB1 inverse agonists suggesting that adhesion blockade is not due to the modulation of integrin valency. Notably, the inhibitory effect exerted by AM251 and AM281 on the adhesive interactions was completely reverted in the presence of protein kinase A (PKA) inhibitor H89, suggesting that cAMP and PKA activation play a key role in the adhesion blockade mediated by CB1 inverse agonists. To further strengthen these results and unveil a previously unknown inhibitory role of cAMP on activated T cell adhesion in vivo in the context of CNS inflammation, we showed that intracellular increase of cAMP induced by treatment with Bt2cAMP, a permeable analog of cAMP, and phosphodiesterase (PDE) inhibitor theophylline efficiently blocked the arrest of encephalitogenic T cells in inflamed brain venules. Our data show that modulation of CB1 function has anti-inflammatory effects and suggests that inverse agonism of CB1 block signal transduction mechanisms controlling encephalitogenic T cells adhesion in inflamed brain venules by a PKA-dependent mechanism.

The constitutive production of the endocannabinoid 2-arachidonoylglycerol participates in oligodendrocyte differentiation

Endocannabinoids have recently emerged as instructive cues in the developing central nervous system, and, based on the expression of their receptors, we identified oligodendrocytes as potential targets of these molecules. Here, we show that the enzymes responsible for the synthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG), diacylglycerol lipase alpha (DAGLα) and beta (DAGLβ), and degradation, monoacylglycerol lipase (MAGL), can be found in oligodendrocytes at different developmental stages. Moreover, cultured oligodendrocyte progenitor cells (OPCs) express DAGLα and β abundantly, resulting in the stronger production of 2-AG than in differentiated oligodendrocytes. The opposite is observed with MAGL. CB1 and CB2 receptor antagonists (SR141716 and AM630) impaired OPC differentiation into mature oligodendrocytes and likewise, inhibiting DAGL activity with RHC-80267 or tetrahydrolipstatin also blocked oligodendrocyte maturation, an effect reversed by the addition of exogenous 2-AG. Likewise, 2-AG synthesis disruption using specific siRNAs against DAGLα and DAGLβ significantly reduced myelin protein expression in vitro, whereas a pharmacological gain-of-function approach by using cannabinoid agonists or MAGL inhibition had the opposite effects. ERK/MAPK pathway is implicated in oligodendrocyte differentiation because PD98059, an inhibitor of MEK1, abrogated oligodendrocyte maturation. The cannabinoid receptor antagonists and RHC-80267 all diminished basal ERK1/2 phosphorylation, effects that were partially reversed by the addition of 2-AG. Overall, our data suggest a novel role of endocannabinoids in oligodendrocyte differentiation such that constitutive release of 2-AG activates cannabinoid receptors in an autocrine/paracrine way in OPCs, stimulating the ERK/MAPK signaling pathway.

The (AAT)n repeat of the cannabinoid CB1 receptor gene influences disease progression in relapsing multiple sclerosis

Background: Genetic and pharmacological inactivation of cannabinoid CB1 receptors (CB1Rs) exacerbates disease course in experimental autoimmune encephalomyelitis, suggesting that CB1Rs might play a role in the neurodegenerative damage associated with multiple sclerosis (MS).

Objectives: To see whether CNR1 gene polymorphism could influence disease progression in relapsing–remitting MS.

Methods: The genotype of 350 patients for the number of AAT repeats was characterized and correlation studies were performed with measures of disease severity and progression.

Results: MS patients with the homozygous genotype for long AAT repeats in the CNR1 gene had more severe disease and higher risk of progression. These subjects had significantly higher scores on both the progression index and the MS severity scale. Furthermore, the percentage of patients with MS functional composite score progression or Bayesian Risk Estimate for MS (BREMS) score ≥2 (considered at very high risk of secondary progression) was significantly higher in the AAT long group than in the short group, while the frequency of patients with BREMS score ≤−0.63 (very likely to remain progression-free) was not significantly different between the two groups, although lower in the long group. Finally, the frequency of patients prescribed a second-line treatment was significantly higher among subjects of the AAT long group, providing a further, indirect indication of higher disease severity.

Conclusions: The results of the present investigation point to CB1R as an important modulator of disease severity in relapsing MS subjects.

Targeted drug delivery to lymphocytes: a route to site-specific immunomodulation?

Lymphocytes are central to the progression of autoimmune disease, transplant rejection, leukemia, lymphoma and lymphocyte-resident viral diseases such as HIV/AIDs. Strategies to target drug treatments to lymphocytes, therefore, represent an opportunity to enhance therapeutic outcomes in disease states where many current treatment regimes are incompletely effective and promote significant toxicities. Here we demonstrate that highly lipophilic drug candidates that preferentially access the intestinal lymphatics after oral administration show significantly enhanced access to lymphocytes leading to improved immunomodulatory activity. When coadministered with such drugs, lipids enhance lymphocyte targeting via a three tiered action: promotion of drug absorption from the gastrointestinal tract, enhancement of lymphatic drug transport and stimulation of lymphocyte recruitment into the lymphatics. This strategy has been exemplified using a highly lipophilic immunosuppressant (JWH015) where coadministration with selected lipids led to significant increases in lymphatic transport, lymphocyte targeting and IL-4 and IL-10 expression in CD4+ and CD8+ lymphocytes after ex vivo mitogen stimulation. In contrast, administration of a 2.5-fold higher dose of JWH015 in a formulation that did not stimulate lymph transport had no effect on antiinflammatory cytokine levels, in spite of equivalent drug exposure in the blood. The current data suggest that complementary drug design and delivery strategies that combine highly lipophilic, lymphotropic drug candidates with lymph-directing formulations provide enhanced selectivity, potency and therapeutic potential for drug candidates with lymphocyte associated targets.

A synthetic cannabinoid agonist promotes oligodendrogliogenesis during viral encephalitis in rats

Chronic CNS infection by several families of viruses can produce deficits in prefrontal cortex (PFC) and striatal function. Cannabinoid drugs have been long known for their anti-inflammatory properties and their ability to modulate adult neuro and gliogenesis. Therefore, we explored the effects of systemic administration of the cannabinoid agonist WIN55,212-2(WIN) on prefrontal cortex (PFC) and striatal cytogenesis in a viral model of CNS injury and inflammation based on Borna Disease (BD) virus encephalitis. Active BrdU(+) progenitor populations were significantly decreased 1 week after BrdU labeling in BD rats [p<0.001 compared to uninfected (NL) controls] while less than 5% of BrdU(+) cells colabeled for BDV protein. Systemic WIN (1mg/kg i.p. twice daily×7 days) increased the survival of BrdU(+) cells in striatum (p<0.001) and PFC of BD rats, with differential regulation of labeled oligodendroglia precursors vs microglia/macrophages. WIN increased the percentage of BrdU(+) oligodendrocyte precursor cells and decreased BrdU(+) ED-1-labeled phagocytic cells, without producing pro- or antiviral effects. BDV infection decreased the levels of the endocannabinoid anandamide (AEA) in striatum (p<0.05 compared to NL rats), whereas 2-AG levels were unchanged. Our findings indicate that: 1) viral infection is accompanied by alterations of AEA transmission in the striatum, but new cell protection by WIN appears independent of its effect on endocannabinoid levels; and 2) chronic WIN treatment alters the gliogenic cascades associated with CNS injury, promoting oligodendrocyte survival. Limiting reactive gliogenesis and macrophage activity in favor of oliogodendroglia development has significance for demyelinating diseases. Moreover, the ability of cannabinoids to promote the development of biologically supportive or symbiotic oligodendroglia may generalize to other microglia-driven neurodegenerative syndromes including NeuroAIDS and diseases of aging.

Cannabinoid receptor stimulation impairs mitochondrial biogenesis in mouse white adipose tissue, muscle, and liver: the role of eNOS, p38 MAPK, and AMPK pathways

OBJECTIVE

Cannabinoid type 1 (CB1) receptor is involved in whole-body and cellular energy metabolism. We asked whether CB1 receptor stimulation was able to decrease mitochondrial biogenesis in different metabolically active tissues of obese high-fat diet (HFD)-fed mice.

RESEARCH DESIGN AND METHODS

The effects of selective CB1 agonist arachidonyl-2-chloroethanolamide (ACEA) and endocannabinoids anandamide and 2-arachidonoylglycerol on endothelial nitric oxide synthase (eNOS) expression were examined, as were mitochondrial DNA amount and mitochondrial biogenesis parameters in cultured mouse and human white adipocytes. These parameters were also investigated in white adipose tissue (WAT), muscle, and liver of mice chronically treated with ACEA. Moreover, p38 mitogen-activated protein kinase (MAPK) phosphorylation was investigated in WAT and isolated mature adipocytes from eNOS(-/-) and wild-type mice. eNOS, p38 MAPK, adenosine monophosphate-activated protein kinase (AMPK), and mitochondrial biogenesis were investigated in WAT, muscle, and liver of HFD mice chronically treated with ACEA.

RESULTS

ACEA decreased mitochondrial biogenesis and eNOS expression, activated p38 MAPK, and reduced AMPK phosphorylation in white adipocytes. The ACEA effects on mitochondria were antagonized by nitric oxide donors and by p38 MAPK silencing. White adipocytes from eNOS(-/-) mice displayed higher p38 MAPK phosphorylation than wild-type animals under basal conditions, and ACEA was ineffective in cells lacking eNOS. Moreover, mitochondrial biogenesis was downregulated, while p38 MAPK phosphorylation was increased and AMPK phosphorylation was decreased in WAT, muscle, and liver of ACEA-treated mice on a HFD.

CONCLUSIONS

CB1 receptor stimulation decreases mitochondrial biogenesis in white adipocytes, through eNOS downregulation and p38 MAPK activation, and impairs mitochondrial function in metabolically active tissues of dietary obese mice.

The endocannabinoid system as a target for the treatment of neurodegenerative disease

The Cannabis sativa plant has been exploited for medicinal, agricultural and spiritual purposes in diverse cultures over thousands of years. Cannabis has been used recreationally for its psychotropic properties, while effects such as stimulation of appetite, analgesia and anti-emesis have lead to the medicinal application of cannabis. Indeed, reports of medicinal efficacy of cannabis can been traced back as far as 2700 BC, and even at that time reports also suggested a neuroprotective effect of the cultivar. The discovery of the psychoactive component of cannabis resin, Delta(9)-tetrahydrocannabinol (Delta(9)-THC) occurred long before the serendipitous identification of a G-protein coupled receptor at which Delta(9)-THC is active in the brain. The subsequent finding of endogenous cannabinoid compounds, the synthesis of which is directed by neuronal excitability and which in turn served to regulate that excitability, further widened the range of potential drug targets through which the endocannabinoid system can be manipulated. As a result of this, alterations in the endocannabinoid system have been extensively investigated in a range of neurodegenerative disorders. In this review we examine the evidence implicating the endocannabinoid system in the cause, symptomatology or treatment of neurodegenerative disease. We examine data from human patients and compare and contrast this with evidence from animal models of these diseases. On the basis of this evidence we discuss the likely efficacy of endocannabinoid-based therapies in each disease context.

Dendritic Cell Regulation by Cannabinoid-Based Drugs

Cannabinoid pharmacology has made important advances in recent years after the cannabinoid system was discovered. Studies in experimental models and in humans have produced promising results using cannabinoid-based drugs for the treatment of obesity and cancer, as well as neuroinflammatory and chronic inflammatory diseases. Moreover, as we discuss here, additional studies also indicates that these drugs have immunosuppressive and anti-inflammatory properties including modulation of immune cell function. Thus, manipulation of the endocannabinoid system in vivo may provide novel therapeutic strategies against inflammatory disorders. At least two types of cannabinoid receptors, cannabinoid 1 and cannabinoid 2 receptors are expressed on immune cells such as dendritic cells (DC). Dendritic cells are recognized for their critical role in initiating and maintaining immune responses. Therefore, DC are potential targets for cannabinoid-mediated modulation. Here, we review the effects of cannabinoids on DC and provide some perspective concerning the therapeutic potential of cannabinoids for the treatment of human diseases involving aberrant inflammatory processes.

Targeting the cannabinoid pathway limits the development of fibrosis and autoimmunity in a mouse model of systemic sclerosis

Our aim was to evaluate the roles of the cannabinoid pathway in the induction and propagation of systemic sclerosis (SSc) in a mouse model of diffuse SSc induced by hypochlorite injections. BALB/c mice injected subcutaneously every day for 6 weeks with PBS or hypochlorite were treated intraperitoneally with either WIN-55,212, an agonist of the cannabinoid receptors 1 (CB1) and receptors 2 (CB2), with JWH-133, a selective agonist of CB2, or with PBS. Skin and lung fibrosis were then assessed by histological and biochemical methods, and the proliferation of fibroblasts purified from diseased skin was assessed by thymidine incorporation. Autoantibodies were detected by ELISA, and spleen cell populations were analyzed by flow cytometry. Experiments were also performed in mice deficient for CB2 receptors (Cnr2(-/-)). Injections of hypochlorite induced cutaneous and lung fibrosis as well as increased the proliferation rate of fibroblasts isolated from fibrotic skin, splenic B cell counts, and levels of anti-DNA topoisomerase-1 autoantibodies. Treatment with WIN-55,212 or with the selective CB2 agonist JWH-133 prevented the development of skin and lung fibrosis as well as reduced fibroblast proliferation and the development of autoantibodies. Experiments performed in CB2-deficient mice confirmed the influence of CB2 in the development of systemic fibrosis and autoimmunity. Therefore, we demonstrate that the CB2 receptor is a potential target for the treatment of SSc because it controls both skin fibroblast proliferation and the autoimmune reaction.

R-flurbiprofen reduces neuropathic pain in rodents by restoring endogenous cannabinoids

Background

R-flurbiprofen, one of the enantiomers of flurbiprofen racemate, is inactive with respect to cyclooxygenase inhibition, but shows analgesic properties without relevant toxicity. Its mode of action is still unclear.

Methodology/Principal Findings

We show that R-flurbiprofen reduces glutamate release in the dorsal horn of the spinal cord evoked by sciatic nerve injury and thereby alleviates pain in sciatic nerve injury models of neuropathic pain in rats and mice. This is mediated by restoring the balance of endocannabinoids (eCB), which is disturbed following peripheral nerve injury in the DRGs, spinal cord and forebrain. The imbalance results from transcriptional adaptations of fatty acid amide hydrolase (FAAH) and NAPE-phospholipase D, i.e. the major enzymes involved in anandamide metabolism and synthesis, respectively. R-flurbiprofen inhibits FAAH activity and normalizes NAPE-PLD expression. As a consequence, R-Flurbiprofen improves endogenous cannabinoid mediated effects, indicated by the reduction of glutamate release, increased activity of the anti-inflammatory transcription factor PPARγ and attenuation of microglia activation. Antinociceptive effects are lost by combined inhibition of CB1 and CB2 receptors and partially abolished in CB1 receptor deficient mice. R-flurbiprofen does however not cause changes of core body temperature which is a typical indicator of central effects of cannabinoid-1 receptor agonists.

Conclusion

Our results suggest that R-flurbiprofen improves the endogenous mechanisms to regain stability after axonal injury and to fend off chronic neuropathic pain by modulating the endocannabinoid system and thus constitutes an attractive, novel therapeutic agent in the treatment of chronic, intractable pain.

Detailed characterisation of CB2 receptor protein expression in peripheral blood immune cells from healthy human volunteers using flow cytometry

It is commonly accepted from gene expression studies that the CB2 receptor is expressed by most cell types of the rodent and human immune system. However, the exact identity of cells expressing CB2 receptor protein in human blood or the abundance of receptors expressed by each immune subset is not well characterised. We conducted a detailed analysis of CB2 protein levels expressed by blood-derived immune cells from healthy human donors. Flow-cytometry was conducted using 4 commercially available anti-CB2 polyclonal antibodies in conjunction with a selection of immune cell specific markers. Across multiple healthy subjects we observed that NK cells, B-lymphocytes and monocytes expressed a higher level of CB2 receptor than CD4+ or CD8+ T-lymphocytes. Neutrophils also expressed a low level of CB2 receptor. NK cells had the greatest variation in CB2 expression levels, whereas for each of the other cell types CB2 levels were relatively similar between subjects. In contrast to other methods, the high sensitivity of flow-cytometry revealed that CB2 receptors are present on resting T-lymphocytes at low abundance in some healthy subjects. These data provide the first detailed analysis of CB2 protein levels in blood leukocyte subsets from healthy donors and identifies the cell types which could be targeted with CB-mimetic drugs in humans.

Anandamide enhances IL-10 production in activated microglia by targeting CB(2) receptors: roles of ERK1/2, JNK, and NF-kappaB

The endocannabinoid system exhibits anti-inflammatory properties by regulating cytokine production. Anandamide (AEA) down-regulates proinflammatory cytokines in a viral model of multiple sclerosis (MS). However, little is known about the mechanisms by which AEA exerts these effects. Microglial cells are the main source of cytokines within the brain and the first barrier of defense against pathogens by acting as antigen presenting cells. IL-10 is a key physiological negative regulator of microglial activation. In this study we show that AEA enhances LPS/IFNgamma-induced IL-10 production in microglia by targeting CB(2) receptors through the activation of ERK1/2 and JNK MAPKs. AEA also inhibits NF-kappaB activation by interfering with the phosphorylation of IkappaBalpha, which may result in an increase of IL-10 production. Moreover, endogenously produced IL-10 negatively regulates IL-12 and IL-23 cytokines, which in its turn modify the pattern of expression of transcription factors involved in Th commitment of splenocytes. This suggests that by altering the cytokine network, AEA could indirectly modify the type of immune responses within the central nervous system (CNS). Accordingly, pharmacological modulation of AEA uptake and degradation might be a useful tool for treating neuroinflammatory diseases.

The endocannabinoid 2-arachidonoylglycerol reduces lesion expansion and white matter damage after spinal cord injury

A series of pathological events secondary to spinal cord injury (SCI) contribute to the spread of the damage, which aggravates neurological deficits. Here we report that a single dose of the neuroprotective endocannabinoid 2-arachidonoyl glycerol (2-AG) administered early after SCI reduces lesion expansion, which was prevented by simultaneous blockade of both CB1 and CB2 receptors but not by blockade of either receptor alone. Treatment with 2-AG also preserves the white matter around the epicenter of the injury. Moreover, in the preserved white matter, 2-AG protects myelin from damage and reduces oligodendrocyte loss. In addition to these protective actions at the epicenter region, 2-AG also inhibits the myelin damage and delayed oligodendrocyte loss induced at 10mm from the epicenter. Interestingly, the early protective action of 2-AG is maintained 28 days after injury, when the lesion size is still smaller and the preservation of white matter is better in 2-AG-treated animals. Therefore, our results show that 2-AG protects from the expansion of the lesion and white matter damage, which suggest that this endogenous cannabinoid may be useful as a protective treatment for acute SCI.

Evidence that MDMA ('ecstasy') increases cannabinoid CB2 receptor expression in microglial cells: role in the neuroinflammatory response in rat brain

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') produces selective long-lasting serotonergic neurotoxicity in rats. The drug also produces acute hyperthermia which modulates the severity of the neurotoxic response. In addition, MDMA produces signs of neuroinflammation reflected as microglial activation and an increase in the release of interleukin-1beta, the latter of which appears to be a consequence of the hyperthermic response and to be implicated in the neurotoxicity induced by the drug. Over-expression of the cannabinoid CB2 receptor in microglia during non-immune and immune pathological conditions is thought to be aimed at controlling the production of neurotoxic factors such as proinflammatory cytokines. Our objective was to study the pattern of CB2 receptor expression following MDMA and to examine the effect of JWH-015 (a CB2 agonist) on the MDMA-induced neuroinflammatory response as well as 5-hydroxytryptamine (5-HT) neurotoxicity. Adult Dark Agouti rats were given MDMA (12.5 mg/kg, i.p.) and killed 3 h or 24 h later for the determination of CB2 receptor expression. JWH-015 was given 48 h, 24 h and 0.5 h before MDMA and 1 h and/or 6 h later and animals were killed for the determination of microglial activation (3 h and 24 h) and 5-HT neurotoxicity (7 days). MDMA increased CB2 receptor expression shortly after administration and these receptors were found in microglia. JWH-015 decreased MDMA-induced microglial activation and interleukin-1beta release and slightly decreased MDMA-induced 5-HT neurotoxicity. In conclusion, CB2 receptor activation reduces the neuroinflammatory response following MDMA and provides partial neuroprotection against the drug.

An endocannabinoid tone limits excitotoxicity in vitro and in a model of multiple sclerosis

The aim of this study was to evaluate how endocannabinoids interact with excitotoxic processes both in vitro, using primary neural cell cultures, and in vivo, in the TMEV-IDD model of multiple sclerosis. First, we observed that neuronal cells respond to excitotoxic challenges by the production of endocannabinoid molecules which in turn exerted neuroprotective effects against excitotoxicity. The inhibitor of endocannabinoid uptake, UCM707, protected specifically against AMPA-induced excitotoxicity, by activating CB(1) and CB(2) cannabinoid receptors, as well as the nuclear factor, PPARgamma. This neuroprotective effect was reverted by blocking the glial glutamate transporter, GLT-1. Mice subjected to the model of multiple sclerosis showed a decrease in the expression of GLT-1. UCM707 reversed this loss of GLT-1 and induced a therapeutic effect. Our data indicate that the enhancement of the endocannabinoid tone leads to neuroprotection against AMPA-induced excitotoxicity and provides therapeutic effects in this model of multiple sclerosis.

Cannabinoid CB2 receptor agonists protect the striatum against malonate toxicity: relevance for Huntington's disease

Cannabinoid agonists might serve as neuroprotective agents in neurodegenerative disorders. Here, we examined this hypothesis in a rat model of Huntington's disease (HD) generated by intrastriatal injection of the mitochondrial complex II inhibitor malonate. Our results showed that only compounds able to activate CB2 receptors were capable of protecting striatal projection neurons from malonate-induced death. That CB2 receptor agonists are neuroprotective was confirmed by using the selective CB2 receptor antagonist, SR144528, and by the observation that mice deficient in CB2 receptor were more sensitive to malonate than wild-type animals. CB2 receptors are scarce in the striatum in healthy conditions, but they are markedly upregulated after the lesion with malonate. Studies of double immunostaining revealed a significant presence of CB2 receptors in cells labeled with the marker of reactive microglia OX-42, and also in cells labeled with GFAP (a marker of astrocytes). We further showed that the activation of CB2 receptors significantly reduced the levels of tumor necrosis factor-alpha (TNF-alpha) that had been increased by the lesion with malonate. In summary, our results demonstrate that stimulation of CB2 receptors protect the striatum against malonate toxicity, likely through a mechanism involving glial cells, in particular reactive microglial cells in which CB2 receptors would be upregulated in response to the lesion. Activation of these receptors would reduce the generation of proinflammatory molecules like TNF-alpha. Altogether, our results support the hypothesis that CB2 receptors could constitute a therapeutic target to slowdown neurodegeneration in HD.

Exercise attenuates the clinical, synaptic and dendritic abnormalities of experimental autoimmune encephalomyelitis

Voluntary exercise is beneficial in models of primarily neurodegenerative disorders. Whether exercise also affects inflammatory neurodegeneration is unknown. In the present study, we evaluated the clinical, synaptic and neuropathological effects of voluntary wheel running in mice with myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. Exercising EAE mice exhibited less severe neurological deficits compared to control EAE animals. The sensitivity of striatal GABA synapses to the stimulation of cannabinoid CB1 receptors was dramatically downregulated following EAE induction, and was rescued by exercise in EAE mice with access to a running wheel. Finally, we found that exercise was able to contrast dendritic spine loss induced by EAE in striatal neurons, although the degree of inflammatory response was similar in the two experimental groups. Our work suggests that life style and experiences can impact the clinical course of inflammatory neurodegenerative diseases by affecting their synaptic bases.

WIN55,212-2, a cannabinoid receptor agonist, protects against nigrostriatal cell loss in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease

Parkinson's disease (PD) is characterized by the progressive loss of nigrostriatal dopamine neurons leading to motor disturbances and cognitive impairment. Current pharmacotherapies relieve PD symptoms temporarily but fail to prevent or slow down the disease progression. In this study, we investigated the molecular mechanisms by which the non-selective cannabinoid receptor agonist WIN55,212-2 (WIN) protects mouse nigrostriatal neurons from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity and neuroinflammation. Stereological analyses showed that chronic treatment with WIN (4 mg/kg, intraperitoneal), initiated 24 h after MPTP administration, protected against MPTP-induced loss of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta independently of CB1 cannabinoid receptor activation. The neuroprotective effect of WIN was accompanied by increased dopamine and 3,4-dihydroxyphenylacetic acid levels in the substantia nigra pars compacta and dorsal striatum of MPTP-treated mice. At 3 days post-MPTP, we found significant microglial activation and up-regulation of CB2 cannabinoid receptors in the ventral midbrain. Treatment with WIN or the CB2 receptor agonist JWH015 (4 mg/kg, intraperitoneal) reduced MPTP-induced microglial activation, whereas genetic ablation of CB2 receptors exacerbated MPTP systemic toxicity. Furthermore, chronic WIN reversed MPTP-associated motor deficits, as revealed by the analysis of forepaw step width and percentage of faults using the inverted grid test. In conclusion, our data indicate that agonism at CB2 cannabinoid receptors protects against MPTP-induced nigrostriatal degeneration by inhibiting microglial activation/infiltration and suggest that CB2 receptors represent a new therapeutic target to slow the degenerative process occurring in PD.

Targeting CB2 receptors and the endocannabinoid system for the treatment of pain

The endocannabinoid system consists of the cannabinoid (CB) receptors, CB(1) and CB(2), the endogenous ligands anandamide (AEA, arachidonoylethanolamide) and 2-arachidonoylglycerol (2-AG), and their synthetic and metabolic machinery. The use of cannabis has been described in classical and recent literature for the treatment of pain, but the potential for psychotropic effects as a result of the activation of central CB(1) receptors places a limitation upon its use. There are, however, a number of modern approaches being undertaken to circumvent this problem, and this review represents a concise summary of these approaches, with a particular emphasis upon CB(2) receptor agonists. Selective CB(2) agonists and peripherally restricted CB(1) or CB(1)/CB(2) dual agonists are being developed for the treatment of inflammatory and neuropathic pain, as they demonstrate efficacy in a range of pain models. CB(2) receptors were originally described as being restricted to cells of immune origin, but there is evidence for their expression in human primary sensory neurons, and increased levels of CB(2) receptors reported in human peripheral nerves have been seen after injury, particularly in painful neuromas. CB(2) receptor agonists produce antinociceptive effects in models of inflammatory and nociceptive pain, and in some cases these effects involve activation of the opioid system. In addition, CB receptor agonists enhance the effect of mu-opioid receptor agonists in a variety of models of analgesia, and combinations of cannabinoids and opioids may produce synergistic effects. Antinociceptive effects of compounds blocking the metabolism of anandamide have been reported, particularly in models of inflammatory pain. There is also evidence that such compounds increase the analgesic effect of non-steroidal anti-inflammatory drugs (NSAIDs), raising the possibility that a combination of suitable agents could, by reducing the NSAID dose needed, provide an efficacious treatment strategy, while minimizing the potential for NSAID-induced gastrointestinal and cardiovascular disturbances. Other potential "partners" for endocannabinoid modulatory agents include alpha(2)-adrenoceptor modulators, peroxisome proliferator-activated receptor alpha agonists and TRPV1 antagonists. An extension of the polypharmacological approach is to combine the desired pharmacological properties of the treatment within a single molecule. Hopefully, these approaches will yield novel analgesics that do not produce the psychotropic effects that limit the medicinal use of cannabis.

Emerging role of the cannabinoid receptor CB2 in immune regulation: therapeutic prospects for neuroinflammation

There is now a large body of data indicating that the cannabinoid receptor type 2 (CB2) is linked to a variety of immune events. This functional relevance appears to be most salient in the course of inflammation, a process during which there is an increased number of receptors that are available for activation. Studies aimed at elucidating signal transduction events resulting from CB2 interaction with its native ligands, and of the role of exogenous cannabinoids in modulating this process, are providing novel insights into the role of CB2 in maintaining a homeostatic immune balance within the host. Furthermore, these studies suggest that the CB2 may serve as a selective molecular target for therapeutic manipulation of untoward immune responses, including those associated with a variety of neuropathies that exhibit a hyperinflammatory component.

The endocannabinoid anandamide from immunomodulation to neuroprotection. Implications for multiple sclerosis

Over the last decade, the endocannabinoid system (ECS) has emerged as a potential target for multiple sclerosis (MS) management. A growing amount of evidence suggests that cannabinoids may be neuroprotective during CNS inflammation. Advances in the understanding of the physiology and pharmacology of the ECS have potentiated the interest of several components of this system as useful biological targets for disease management. Alterations of the ECS have been recently implicated in a number of neuroinflammatory and neurodegenerative conditions, so that the pharmacological modulation of cannabinoid (CB) receptors and/or of the enzymes controlling synthesis, transport, and degradation of these lipid mediators is considered an option to treat several neurological diseases. This chapter focuses on our current understanding of the function of anandamide (AEA), its biological and therapeutic implications, as well as a description of its effects on neuroimmune modulation.

A cannabinoid agonist interferes with the progression of a chronic model of multiple sclerosis by downregulating adhesion molecules

Adhesion molecules are critical players in the regulation of transmigration of blood leukocytes across the blood-brain barrier in multiple sclerosis (MS). Cannabinoids (CBs) are potential therapeutic agents in the treatment of MS, but the mechanisms involved are only partially known. Using a viral model of MS we observed that the cannabinoid agonist WIN55,212-2 administered at the time of virus infection suppresses intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in brain endothelium, together with a reduction in perivascular CD4+ T lymphocytes infiltrates and microglial responses. WIN55,212-2 also interferes with later progression of the disease by reducing symptomatology and neuroinflammation. In vitro data from brain endothelial cell cultures, provide the first evidence of a role of peroxisome proliferator-activated receptors gamma (PPARgamma) in WIN55,212-2-induced downregulation of VCAM-1. This study highlights that inhibition of brain adhesion molecules by WIN55,212-2 might underline its therapeutic effects in MS models by targeting PPAR-gamma receptors.

Cannabis use in Spanish patients with multiple sclerosis: fulfilment of patients' expectations?

OBJECTIVE

Medicinal use of cannabis in chronic neurological diseases is a controversial topic of medical research and the subject of intense public debate. The aim of the study was to evaluate the prevalence of cannabis use, related factors, and degree of satisfaction in Spanish patients with multiple sclerosis (MS) prior to the establishment of medically supervised use.

METHODS

Cross-sectional, questionnaire-based survey provided during routine medical visits to consecutive patients in two university-based neurology clinics.

RESULTS

The questionnaire was returned by 175 MS patients (94.1% response rate). The prevalence of ever-use and medicinal cannabis use were 43% and 17.1%, respectively. At the time of the survey, cannabis was being used by 12.5% (5/45) of recreational and 56.7% (17/30) of medical users (p<0.001). First cannabis consumption was after MS onset in 15 (50%) medicinal users. Clinical improvement was reported by 14 (46.7%) medicinal users. Smoking use, awareness of cannabis potential benefits, pain, higher disability, and lower age were independently associated with the medicinal use of cannabis. Most patients would support a future legalisation of cannabis for the control of their symptoms and were willing to receive cannabis under medical control once legalised (83.4% of never-users, 94.5% of ever-users, p<0.05).

CONCLUSION

Almost half of our MS patients had tried cannabis at some time. However, medicinal use was low and clinical improvement after cannabis use was only reported by a subset of patients. Overall, MS patients were highly motivated for a future medically controlled use.

Endocannabinoid signaling in microglial cells

The endocannabinoid signaling system (eCBSS) is composed of cannabinoid (CB) receptors, their endogenous ligands (the endocannabinoids, eCB) and the enzymes that produce and inactivate these ligands. Neurons use this signaling system to communicate with each other and Delta9-tetrahydrocannabinol (THC), the main psychotropic ingredient of Cannabis sativa, induces profound behavioral effects by impinging on this communication. Evidence now shows that microglia, the macrophages of the brain, also express a functional eCBSS and that activation of CB receptors expressed by activated microglia controls their immune-related functions. This review summarizes this evidence, discusses how microglia might use the eCBSS to communicate with each other and neighboring cells, and argues that compounds selectively targeting the eCBSS expressed by microglia constitute valuable therapeutics to manage acute and chronic neuroinflammation, without inducing the psychotropic effects and underlying addictive properties commonly associated with THC.

Neuroimmune interactions and pain: focus on glial-modulating targets

Chronic pain is the most difficult type of pain to treat. Previously, the development of analgesics has focused on neuronal targets; however, current analgesics are only modestly effective, have significant side effects and do not provide universal efficacy. New strategies are needed for the development of more effective analgesics. Glial cells have integral roles in CNS homeostasis, and chronic pain etiology and progression. In this review, the role of glia in neuropathic pain and opioid administration is described, as well as the potential superior efficacy and wider therapeutic indices provided by drugs that modulate specific glial function via novel targets.

A diacylglycerol lipase-CB2 cannabinoid pathway regulates adult subventricular zone neurogenesis in an age-dependent manner

The subventricular zone (SVZ) is a major site of neurogenesis in the adult. We now show that ependymal and proliferating cells in the adult mouse SVZ express diacylglycerol lipases (DAGLs), enzymes that synthesise a CB1/CB2 cannabinoid receptor ligand. DAGL and CB2 antagonists inhibit the proliferation of cultured neural stem cells, and the proliferation of progenitor cells in young animals. Furthermore, CB2 agonists stimulate progenitor cell proliferation in vivo, with this effect being more pronounced in older animals. A similar response was seen with a fatty acid amide hydrolase (FAAH) inhibitor that limits degradation of endocannabinoids. The effects on proliferation were mirrored in changes in the number of neuroblasts migrating from the SVZ to the olfactory bulb (OB). In this context, CB2 antagonists reduced the number of newborn neurons appearing in the OB in the young adult animals while CB2 agonists stimulated this in older animals. These data identify CB2 receptor agonists and FAAH inhibitors as agents that can counteract the naturally observed decline in adult neurogenesis that is associated with ageing.

Role of CB2 receptors in neuroprotective effects of cannabinoids

CB2 receptors, the so-called peripheral cannabinoid receptor type, were first described in the immune system, but they have been recently identified in the brain in healthy conditions and, in particular, after several types of cytotoxic stimuli. Specifically, CB2 receptors were identified in microglial cells, astrocytes and, to a lesser extent, in certain subpopulations of neurons. Given the lack of psychoactivity demonstrated by selective CB2 receptor agonists, this receptor becomes an interesting target for the treatment of neurological diseases, in particular, the case of certain neurodegenerative disorders in which induction/up-regulation of CB2 receptors has been already demonstrated. These disorders include Alzheimer's disease, Huntington's chorea, amyotrophic lateral sclerosis and others. Interestingly, in experimental models of these disorders, the activation of CB2 receptors has been related to a delayed progression of neurodegenerative events, in particular, those related to the toxic influence of microglial cells on neuronal homeostasis. The present article will review the evidence supporting that CB2 receptors might represent a key element in the endogenous response against different types of cytotoxic events, and that this receptor type may be a clinically promising target for the control of brain damage in neurodegenerative disorders.