CANNABINOID RECEPTORS AS THERAPEUTIC TARGETS

Versatile solid-phase synthesis of chromenes resembling classical cannabinoids

A novel solid-phase approach toward classical cannabinoids is described. The desired tricyclic natural product analogues are assembled in only four atom economic steps: domino oxa-Michael-aldol condensation, Wittig reaction/enol-ether formation, Diels-Alder cycloaddition and cleavage. The synthesis is designed to allow combinatorial chemistry at several stages of the sequence. The variation of commercially available reagents at three of the reactions (enals/enones, Wittig salts, and dienophiles) allows the introduction of various diversity points. As proof of concept, a small library of 20 members has been synthesized with overall yields ranging from 10% to 60%.

Cloning and pharmacological characterization of the dog cannabinoid CB₂receptor

Comparison of human, rat and mouse cannabinoid CB(2) receptor primary sequences has shown significant divergence at the mRNA and protein sequence level, raising the possibility of species specific pharmacological properties. Additionally, given the importance of the dog as a non-rodent species for predicting human safety during the drug development process, we cloned the dog CB(2) receptor gene and characterized its in-vitro pharmacological properties in a recombinant expression system. A 1.1 kb dog peripheral cannabinoid receptor (dCB(2)) fragment encoding a 360 amino acid protein was cloned from dog spleen cDNA. Analysis of the cloned dCB(2) polypeptide sequence revealed that it shares between 76 and 82% homology with rat, mouse, human and predicted chimpanzee cannabinoid CB(2) receptors. The dog CB(2) receptor expressed in CHO cells displayed similar binding affinities for various synthetic and endogenous cannabinoids as compared to those measured for the human and rat cannabinoid CB(2) receptors. However, these ligands exhibited altered functional potencies and efficacies for the dog cannabinoid CB(2) receptor, which was also found to be negatively coupled to adenylate cyclase activity. These complex pharmacological differences observed across species for the cannabinoid CB(2) receptor suggest that caution should be exerted when analyzing the outcome of animal efficacy and safety studies, notably those involving cannabinoid CB(2) receptor targeting molecules tested in the dog.

Marijuana-based drugs: innovative therapeutics or designer drugs of abuse?

The principal psychoactive component of marijuana, Δ(9)-tetrahydrocannabinol (THC), activates CB1 cannabinoid receptors (CB1Rs). Unfortunately, pharmacological research into the design of effective THC analogs has been hampered by psychiatric side effects. THC-based drug design of a less academic nature, however, has led to the marketing of "synthetic marijuana," labeled as K2 or "Spice," among other terms, which elicits psychotropic actions via CB1R activation. Because of structural dissimilarity to THC, the active ingredients of K2/Spice preparations are widely unregulated. The K2/Spice "phenomenon" provides a context for considering whether marijuana-based drugs will truly provide innovative therapeutics or merely perpetuate drug abuse.

A combined preclinical therapy of cannabinoids and temozolomide against glioma

Glioblastoma multiforme (GBM) is highly resistant to current anticancer treatments, which makes it crucial to find new therapeutic strategies aimed at improving the poor prognosis of patients suffering from this disease. Δ(9)-Tetrahydrocannabinol (THC), the major active ingredient of marijuana, and other cannabinoid receptor agonists inhibit tumor growth in animal models of cancer, including glioma, an effect that relies, at least in part, on the stimulation of autophagy-mediated apoptosis in tumor cells. Here, we show that the combined administration of THC and temozolomide (TMZ; the benchmark agent for the management of GBM) exerts a strong antitumoral action in glioma xenografts, an effect that is also observed in tumors that are resistant to TMZ treatment. Combined administration of THC and TMZ enhanced autophagy, whereas pharmacologic or genetic inhibition of this process prevented TMZ + THC-induced cell death, supporting that activation of autophagy plays a crucial role on the mechanism of action of this drug combination. Administration of submaximal doses of THC and cannabidiol (CBD; another plant-derived cannabinoid that also induces glioma cell death through a mechanism of action different from that of THC) remarkably reduces the growth of glioma xenografts. Moreover, treatment with TMZ and submaximal doses of THC and CBD produced a strong antitumoral action in both TMZ-sensitive and TMZ-resistant tumors. Altogether, our findings support that the combined administration of TMZ and cannabinoids could be therapeutically exploited for the management of GBM.

Acetaminophen inhibits status epilepticus in cultured hippocampal neurons

Status epilepticus (SE) is a major neurological disorder and SE survivors often develop acquired epilepsy and cognitive deficits. Thus, it is important to stop SE and limit brain damage. However, rapid pharmacoresistance develops to anticonvulsants as seizure duration lengthens. Recently, acetaminophen was reported to increase endocannabinoid levels by its conversion to AM 404. Further, cannabinoids are potent anticonvulsants. Here we investigated whether acetaminophen would block SE-like activity in hippocampal neurons. Exposure of cultured hippocampal neurons to a low Mg2+ medium elicits high-frequency epileptiform discharges that exceed 3 Hz (in-vitro SE). Acetaminophen (500 μM) blocks the SE-like activity. CB1 receptor antagonist SR 141716A (1 μM) blocked this inhibitory effect of acetaminophen on SE, indicating that acetaminophen was mediating its anticonvulsant effects through CB1 receptors.

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.

Central and peripheral sites of action for CB₂ receptor mediated analgesic activity in chronic inflammatory and neuropathic pain models in rats

BACKGROUND AND PURPOSE

Cannabinoid CB₂ receptor activation by selective agonists has been shown to produce analgesic effects in preclinical models of inflammatory and neuropathic pain. However, mechanisms underlying CB₂-mediated analgesic effects remain largely unknown. The present study was conducted to elucidate the CB₂ receptor expression in 'pain relevant' tissues and the potential sites of action of CB₂ agonism in rats.

EXPERIMENTAL APPROACH

Expression of cannabinoid receptor mRNA was evaluated by quantitative RT-PCR in dorsal root ganglia (DRGs), spinal cords, paws and several brain regions of sham, chronic inflammatory pain (CFA) and neuropathic pain (spinal nerve ligation, SNL) rats. The sites of CB₂ mediated antinociception were evaluated in vivo following intra-DRG, intrathecal (i.t.) or intraplantar (i.paw) administration of potent CB₂-selective agonists A-836339 and AM1241.

KEY RESULTS

CB₂ receptor gene expression was significantly up-regulated in DRGs (SNL and CFA), spinal cords (SNL) or paws (CFA) ipsilateral to injury under inflammatory and neuropathic pain conditions. Systemic A-836339 and AM1241 produced dose-dependent efficacy in both inflammatory and neuropathic pain models. Local administration of CB₂ agonists also produced significant analgesic effects in SNL (intra-DRG and i.t.) and CFA (intra-DRG) pain models. In contrast to A-836339, i.paw administration of AM-1241 dose-relatedly reversed the CFA-induced thermal hyperalgesia, suggesting that different mechanisms may be contributing to its in vivo properties.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that both DRG and spinal cord are important sites contributing to CB₂ receptor-mediated analgesia and that the changes in CB₂ receptor expression play a crucial role for the sites of action in regulating pain perception.

Targeting cannabinoid receptors as a novel approach in the treatment of graft-versus-host disease: evidence from an experimental murine model

Allogeneic hematopoietic cell transplantation (HCT) is widely used to treat patients with life-threatening malignant and nonmalignant hematological diseases. However, allogeneic HCT often is accompanied by severe and lethal complications from graft-versus-host disease (GVHD), in which activated donor T cells recognize histocompatibility antigenic mismatches and cause significant toxicity in the recipient. In the current study, we tested the hypothesis that activation of cannabinoid receptors on donor-derived T cells may prevent GVHD. We tested the effect of Δ(9)-tetrahydrocannabinol (THC) in an acute model of GVHD that was induced by transferring parental C57BL/6 (B6) spleen cells into (C57BL/6 × DBA/2) F(1)(BDF1) mice. Transfer of B6 cells into BDF1 mice produced severe acute GVHD in the recipient, characterized by lymphoid hyperplasia, weight loss, T helper l cytokine production and mortality. THC administration led to early recovery from body weight loss, reduced tissue injury in the liver and intestine, as well as complete survival. THC treatment reduced the expansion of donor-derived effector T cells and blocked the killing of host-derived immune cells while promoting Foxp3(+) regulatory T cells. Impaired hematopoiesis seen during GVHD was rescued by treatment with THC. The ability of THC to reduce the clinical GVHD was reversed, at least in part, by administration of cannabinoid receptor (CB) 1 and CB2 antagonists, thereby demonstrating that THC-mediated amelioration of GVHD was cannabinoid receptor-dependent. Our results demonstrate for the first time that targeting cannabinoid receptors may constitute a novel treatment modality against acute GVHD.

Analysis of in vitro bioactivity data extracted from drug discovery literature and patents: Ranking 1654 human protein targets by assayed compounds and molecular scaffolds

Background

Since the classic Hopkins and Groom druggable genome review in 2002, there have been a number of publications updating both the hypothetical and successful human drug target statistics. However, listings of research targets that define the area between these two extremes are sparse because of the challenges of collating published information at the necessary scale. We have addressed this by interrogating databases, populated by expert curation, of bioactivity data extracted from patents and journal papers over the last 30 years.

Results

From a subset of just over 27,000 documents we have extracted a set of compound-to-target relationships for biochemical in vitro binding-type assay data for 1,736 human proteins and 1,654 gene identifiers. These are linked to 1,671,951 compound records derived from 823,179 unique chemical structures. The distribution showed a compounds-per-target average of 964 with a maximum of 42,869 (Factor Xa). The list includes non-targets, failed targets and cross-screening targets. The top-278 most actively pursued targets cover 90% of the compounds. We further investigated target ranking by determining the number of molecular frameworks and scaffolds. These were compared to the compound counts as alternative measures of chemical diversity on a per-target basis.

Conclusions

The compounds-per-protein listing generated in this work (provided as a supplementary file) represents the major proportion of the human drug target landscape defined by published data. We supplemented the simple ranking by the number of compounds assayed with additional rankings by molecular topology. These showed significant differences and provide complementary assessments of chemical tractability.

Development and characterization of immobilized cannabinoid receptor (CB1/CB2) open tubular column for on-line screening

Cannabinoid receptors, CB1 and CB2, are therapeutic targets in the treatment of anxiety, obesity, movement disorders, glaucoma, and pain. We have developed an on-line screening method for CB1 and CB2 ligands, where cellular membrane fragments of a chronic myelogenous leukemia cell line, KU-812, were immobilized onto the surface of an open tubular (OT) capillary to create a CB1/CB2-OT column. The binding activities of the immobilized CB1/CB2 receptors were established using frontal affinity chromatographic techniques. This is the first report that confirms the presence of functional CB1 and CB2 receptors on KU-812 cells. The data from this study confirm that the CB1/CB2-OT column can be used to determine the binding affinities (K(i) values) for a single compound and to screen individual compounds or a mixture of multiple compounds. The CB1/CB2-OT column was also used to screen a botanical matrix, Zanthoxylum clava-herculis, where preliminary results suggest the presence of a high-affinity phytocannabinoid.

Inhibition of endocannabinoid catabolic enzymes elicits anxiolytic-like effects in the marble burying assay

Cannabinoids have long been shown to have a range of potential therapeutic effects, including antiemetic actions, analgesia, and anxiolysis. However, psychomimetic and memory disruptive side effects, as well as the potential for abuse and dependence, have restricted their clinical development. Endogenous cannabinoids (i.e., endocannabinoids; eCBs), such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are produced throughout the limbic system and other brain regions associated with emotionality and are believed to modulate behavioral responses to stress-related conditions. AEA and 2-AG are rapidly metabolized by the respective enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Accordingly, inhibition of each enzyme increases brain levels of the appropriate eCB. Although FAAH inhibition has been established to decrease anxiety-like behavior, the role of 2-AG has been difficult to ascertain until the recent synthesis of JZL184, a potent and selective MAGL inhibitor. In the present study, we investigated the effects of inhibiting FAAH or MAGL on anxiety-like behavior in marble burying, a model of repetitive, compulsive behaviors germane to anxiety disorders such as obsessive-compulsive disorder. The FAAH inhibitor PF-3845, the MAGL inhibitor JZL184, and the benzodiazepine diazepam decreased marble burying at doses that did not affect locomotor activity. In contrast, Δ9-tetrahydrocannabinol (THC), the primary psychoactive constituent of marijuana, did not consistently reduce marble burying without also eliciting profound decreases in locomotor behavior. The CB1 cannabinoid receptor antagonist rimonabant blocked the reduction in marble burying caused by FAAH and MAGL inhibitors, but not by diazepam, indicating a CB1 receptor mechanism of action. These data indicate that elevation of AEA or 2-AG reduces marble burying behavior and suggest that their catabolic enzymes represent potential targets for the development of new classes of pharmacotherapeutics to treat anxiety-related disorders.

Identification of potent, noncovalent fatty acid amide hydrolase (FAAH) inhibitors

Starting from a series of ureas that were determined to be mechanism-based inhibitors of FAAH, several spirocyclic ureas and lactams were designed and synthesized. These efforts identified a series of novel, noncovalent FAAH inhibitors with in vitro potency comparable to known covalent FAAH inhibitors. The mechanism of action for these compounds was determined through a combination of SAR and co-crystallography with rat FAAH.

The “New” Marijuana

Synthetic cannabinoid-induced toxicity is increasing in frequency across the US, with more than 1057 reported cases as of August 2010. There is a paucity of literature on synthetic cannabinoid toxicity; however, there are various reports of adverse effects including tachycardia, hypertension, tachypnea, chest pain, heart palpitations, hallucinations, racing thoughts, and seizures. While reports suggest that toxic symptoms last no longer than 3-4 hours, with no residual adverse effects in many cases, there is concern about serious acute and long-term toxicities. This article reviews the development, abuse, toxicity, treatment, and legal status of synthetic cannabinoids. It is important for health-care professionals to recognize and appropriately treat synthetic cannabinoid-induced toxicity.

Prolonged cannabinoid exposure alters GABA(A) receptor mediated synaptic function in cultured hippocampal neurons

Developing cannabinoid-based medication along with marijuana's recreational use makes it important to investigate molecular adaptations the endocannabinoid system undergoes following prolonged use and withdrawal. Repeated cannabinoid administration results in development of tolerance and produces withdrawal symptoms that may include seizures. Here we employed electrophysiological and immunochemical techniques to investigate the effects of prolonged CB1 receptor agonist exposure on cultured hippocampal neurons. Approximately 60% of CB1 receptors colocalize to GABAergic terminals in hippocampal cultures. Prolonged treatment with the cannabinamimetic WIN 55,212-2 (+WIN, 1 μM, 24 h) caused profound CB1 receptor downregulation accompanied by neuronal hyperexcitability. Furthermore, prolonged +WIN treatment resulted in increased GABA release as indicated by increased mIPSC frequency, a diminished GABAergic inhibition as indicated by reduction in mIPSC amplitude and a reduction in GABA(A) channel number. Additionally, surface staining for the GABA(A) β(2/3) receptor subunits was decreased, while no changes in staining for the presynaptic vesicular GABA transporter were observed, indicating that GABAergic terminals remained intact. These findings demonstrate that agonist-induced downregulation of the CB1 receptor in hippocampal cultures results in neuronal hyperexcitability that may be attributed, in part, to alterations in both presynaptic GABA release mechanisms and postsynaptic GABA(A) receptor function demonstrating a novel role for cannabinoid-dependent presynaptic control of neuronal transmission.

Endocannabinoids modulate human epidermal keratinocyte proliferation and survival via the sequential engagement of cannabinoid receptor-1 and transient receptor potential vanilloid-1

We have recently shown that lipid mediators of the emerging endocannabinoid system (ECS) are key players of growth control of the human pilosebaceous unit. In this study, we asked whether the prototypic endocannabinoid anandamide (N-arachidonoylethanolamine, AEA) has a role in growth and survival of epidermal keratinocytes (KCs). Using human cultured KCs and skin organ-culture models, and by employing combined pharmacological and molecular approaches, we provide early evidence that AEA markedly suppresses KC proliferation and induces cell death, both in vitro and in situ. Moreover, we present that these cellular actions are mediated by a most probably constitutively active signaling mechanism that involves the activation of the metabotropic cannabinoid receptor CB(1) and a sequential engagement of the "ionotropic cannabinoid receptor" transient receptor potential vanilloid-1 (TRPV1). Finally, we demonstrate that the cellular effects of AEA are most probably due to a Ca(2+) influx via the non-selective, highly Ca(2+)-permeable ion channel TRPV1, and the concomitant elevation of intracellular Ca(2+) concentration. The data reported here may encourage one to explore whether the targeted manipulation of the above signaling pathway of the cutaneous ECS could become a useful adjunct treatment strategy for hyperproliferative human dermatoses such as psoriasis or KC-derived skin tumors.

Endocannabinoid 2-arachidonoylglycerol protects neurons against β-amyloid insults

While endocannabinoid modulation of both GABAergic and glutamatergic synaptic transmission and plasticity has been extensively investigated, our understanding of the role of endocannabinoids in protecting neurons from harmful insults remains limited. 2-Arachidonoylglycerol (2-AG), the most abundant endogenous ligand and a full agonist for cannabinoid receptors, exhibits anti-inflammatory and neuroprotective effects via a CB1 receptor (CB1R)-mediated mechanism. However, it is still not clear whether 2-AG is also able to protect neurons from β-amyloid (Aβ)-induced neurodegeneration. Here, we demonstrate that exogenous application of 2-AG significantly protected hippocampal neurons in culture against Aβ-induced neurodegeneration and apoptosis. This neuroprotective effect was blocked by SR141716 (SR-1), a selective CB1R antagonist, but not by SR144528 (SR-2), a selective CB2R antagonist, or capsazepine (CAP), a selective transient receptor potential cation channels, subfamily V, member 1 (TRPV1) receptor antagonist. To determine whether endogenous 2-AG is capable of protecting neurons from Aβ insults, hippocampal neurons in culture were treated with URB602 or JZL184, selective inhibitors of monoacylglycerol lipase (MAGL), the enzyme hydrolyzing 2-AG. MAGL inhibition that elevates endogenous levels of 2-AG also significantly reduced Aβ-induced neurodegeneration and apoptosis. The 2-AG-produced neuroprotective effects appear to be mediated via CB1R-dependent suppression of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and nuclear factor-κB (NF-κB) phosphorylation and cyclooxygenase-2 (COX-2) expression. Our results suggest that elevation of endogenous 2-AG by inhibiting its hydrolysis has potential as a novel efficacious therapeutic approach for preventing, ameliorating or treating Alzheimer's disease.

Synthesis of fatty acid amides of catechol metabolites that exhibit antiobesity properties

A series of fatty acid amides of 3,4-methylenedioxymethamphetamine (MDMA) catechol metabolites were synthesized in order to evaluate their biological activities. Upon administration, all synthesized compounds resulted in negative modulation of food intake in rats. The most active compounds have affinity for the CB(1) receptor and/or PPAR-α; part of their biological activity may be caused by these double interactions.

Overexpression of CB2 cannabinoid receptors decreased vulnerability to anxiety and impaired anxiolytic action of alprazolam in mice

Mice overexpressing CB2r (CB2xP) were exposed to open field (OF), light-dark box (LDB) and elevated plus maze (EPM) tests. Corticotropin-releasing factor (CRF) and pro-opiomelanocortin (POMC) mRNA were measured in paraventricular (PVN) and arcuate (ARC) nuclei of the hypothalamus after 30 minutes of restraint stress (RS). Anxiolytic effects of alprazolam (45 or 70 µg/kg, ip) were evaluated. GABA(A)α(2) and GABA(A)γ(2) mRNA were measured in the hippocampus (HIPP) and amygdala (AMY) of CB2xP and wild type (WT) mice. No differences were observed in the total distance travelled by CB2xP and WT mice in OF. Central and peripheral distances travelled significantly increased and decreased in CB2xP mice. Overexpression of CB2r reduced anxiety-like behaviours in LDB and EPM. In WT mice, RS increased CRF (82%) and POMC (42%) mRNA in the PVN and ARC nuclei, respectively. In CB2xP mice, RS also increased POMC (22%) mRNA in the ARC nucleus, but had no effect on CRF mRNA in the PVN nucleus. Administration of alprazolam was without effect in CB2xP mice. An increase of GABA(A)α(2) and GABA(A)γ(2) mRNA in the hippocampus and amygdala of CB2xP mice was observed. Our findings revealed that increased expression of CB2r significantly reduced anxiogenic-related behaviours, modified the response to stress and impaired the action of anxiolytic drugs.

Effects of a Cannabinoid Receptor 2 Selective Antagonist on the Inflammatory Reaction to Titanium Particles In Vivo and In Vitro

Wear particle-induced inflammation is a major factor contributing to aseptic loosening in peri-prosthetic tissue. The effects of cannabinoid receptor 2 (CB2) on wear particle-induced inflammation remain unclear. Reverse transcription–polymerase chain reaction and enzyme-linked immunosorbent assay were used to assess the effects of a CB2-selective antagonist, AM630, on regulation of the inflammatory reaction and production of pro-inflammatory cytokines in response to in vitro and in vivo stimulation with titanium particles. In vitro studies, in a model for pre-osteoclast-like cells, demonstrated that AM630 inactivation of CB2 profoundly inhibited interleukin (IL)-1β and tumour necrosis factor (TNF)-α production by RAW264.7 cells stimulated with titanium particles. In vivo findings in a murine air-pouch model of titanium-induced inflammatory osteolysis indicated that AM630 reduced titanium-induced tissue inflammation, seen as a reduction in pouch membrane thickness, inflammatory infiltration and levels of the pro-inflammatory cytokines IL-1β and TNF-α. Thus, inactivation of CB2 by AM630 inhibited the titanium particle-induced inflammatory reaction by reducing pro-inflammatory cytokines in vitro and in vivo.

An anatomical and temporal portrait of physiological substrates for fatty acid amide hydrolase

Fatty acid amide hydrolase (FAAH) regulates amidated lipid transmitters, including the endocannabinoid anandamide and its N-acyl ethanolamine (NAE) congeners and transient receptor potential channel agonists N-acyl taurines (NATs). Using both the FAAH inhibitor PF-3845 and FAAH(-/-) mice, we present a global analysis of changes in NAE and NAT metabolism caused by FAAH disruption in central and peripheral tissues. Elevations in anandamide (and other NAEs) were tissue dependent, with the most dramatic changes occurring in brain, testis, and liver of PF-3845-treated or FAAH(-/-) mice. Polyunsaturated NATs accumulated to very high amounts in the liver, kidney, and plasma of these animals. The NAT profile in brain tissue was markedly different and punctuated by significant increases in long-chain NATs found exclusively in FAAH(-/-), but not in PF-3845-treated animals. Suspecting that this difference might reflect a slow pathway for NAT biosynthesis, we treated mice chronically with PF-3845 for 6 days and observed robust elevations in brain NATs. These studies, taken together, define the anatomical and temporal features of FAAH-mediated NAE and NAT metabolism, which are complemented and probably influenced by kinetically distinguishable biosynthetic pathways that produce these lipids in vivo.

Cannabinoid receptors, CB1 and CB2, as novel targets for inhibition of non-small cell lung cancer growth and metastasis

Non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths worldwide; however, only limited therapeutic treatments are available. Hence, we investigated the role of cannabinoid receptors, CB1 and CB2, as novel therapeutic targets against NSCLC. We observed expression of CB1 (24%) and CB2 (55%) in NSCLC patients. Furthermore, we have shown that the treatment of NSCLC cell lines (A549 and SW-1573) with CB1/CB2- and CB2-specific agonists Win55,212-2 and JWH-015, respectively, significantly attenuated random as well as growth factor-directed in vitro chemotaxis and chemoinvasion in these cells. We also observed significant reduction in focal adhesion complex, which plays an important role in migration, upon treatment with both JWH-015 and Win55,212-2. In addition, pretreatment with CB1/CB2 selective antagonists, AM251 and AM630, prior to JWH-015 and Win55,212-2 treatments, attenuated the agonist-mediated inhibition of in vitro chemotaxis and chemoinvasion. In addition, both CB1 and CB2 agonists Win55,212-2 and JWH-133, respectively, significantly inhibited in vivo tumor growth and lung metastasis (∼50%). These effects were receptor mediated, as pretreatment with CB1/CB2 antagonists abrogated CB1/CB2 agonist-mediated effects on tumor growth and metastasis. Reduced proliferation and vascularization, along with increased apoptosis, were observed in tumors obtained from animals treated with JWH-133 and Win55,212-2. Upon further elucidation into the molecular mechanism, we observed that both CB1 and CB2 agonists inhibited phosphorylation of AKT, a key signaling molecule controlling cell survival, migration, and apoptosis, and reduced matrix metalloproteinase 9 expression and activity. These results suggest that CB1 and CB2 could be used as novel therapeutic targets against NSCLC.

1-Bromo-3-(1',1'-dimethylalkyl)-1-deoxy-Δ(8)-tetrahydrocannabinols: New selective ligands for the cannabinoid CB(2) receptor

Δ(8)-Tetrahydrocannabinol (26), 3-(1',1'-dimethylbutyl)- (12), 3-(1',1'-dimethylpentyl)- (13), 3-(1',1'-dimethylhexyl)- (14) and 3-(1',1'-dimethylheptyl)-Δ(8)-tetrahydrocannabinol (15) have been converted into the corresponding 1-bromo-1-deoxy-Δ(8)-tetrahydrocannabinols (25, 8-11). This was accomplished using a protocol developed in our laboratory in which the trifluoromethanesulfonate of a phenol undergoes palladium mediated coupling with pinacolborane. Reaction of this dioxaborolane with aqueous-methanolic copper(II) bromide provides the aryl bromide. The affinities of these bromo cannabinoids for the cannabinoid CB(1) and CB(2) receptors were determined. All of these compounds showed selectivity for the CB(2) receptor and one of them, 1-bromo-1-deoxy-3-(1',1'-dimethylhexyl)-Δ(8)-tetrahydrocannabinol (10), exhibits 52-fold selectivity for this receptor with good (28nM) affinity.

Type I cannabinoid receptor trafficking: all roads lead to lysosome

The majority of G-protein-coupled receptors (GPCRs) function at the cell surface, where they are activated by their ligands present in the extracellular milieu. Interestingly, type I cannabinoid receptor (CB(1) R), one of the most abundant GPCRs in the central nervous system, is predominantly intracellular. The important physiological roles of CB(1) R have sparked interest in the elucidation of the molecular mechanisms underlying the trafficking of this receptor and the role of intracellular CB(1) Rs. Thus far, results from different groups have been, at least in part, contradictory and the basis of CB(1) R intracellular localization remains controversial. In this commentary, by comparing the studies examining CB(1) R trafficking and localization, we identify technical or experimental ground responsible for the conflicting results. Finally, we propose a possible mechanism of CB(1) R trafficking that may reconcile the different models.

Complementary synaptic distribution of enzymes responsible for synthesis and inactivation of the endocannabinoid 2-arachidonoylglycerol in the human hippocampus

Clinical and experimental evidence demonstrates that endocannabinoids play either beneficial or adverse roles in many neurological and psychiatric disorders. Their medical significance may be best explained by the emerging concept that endocannabinoids are essential modulators of synaptic transmission throughout the central nervous system. However, the precise molecular architecture of the endocannabinoid signaling machinery in the human brain remains elusive. To address this issue, we investigated the synaptic distribution of metabolic enzymes for the most abundant endocannabinoid molecule, 2-arachidonoylglycerol (2-AG), in the postmortem human hippocampus. Immunostaining for diacylglycerol lipase-α (DGL-α), the main synthesizing enzyme of 2-AG, resulted in a laminar pattern corresponding to the termination zones of glutamatergic pathways. The highest density of DGL-α-immunostaining was observed in strata radiatum and oriens of the cornu ammonis and in the inner third of stratum moleculare of the dentate gyrus. At higher magnification, DGL-α-immunopositive puncta were distributed throughout the neuropil outlining the immunonegative main dendrites of pyramidal and granule cells. Electron microscopic analysis revealed that this pattern was due to the accumulation of DGL-α in dendritic spine heads. Similar DGL-α-immunostaining pattern was also found in hippocampi of wild-type, but not of DGL-α knockout mice. Using two independent antibodies developed against monoacylglycerol lipase (MGL), the predominant enzyme inactivating 2-AG, immunostaining also revealed a laminar and punctate staining pattern. However, as observed previously in rodent hippocampus, MGL was enriched in axon terminals instead of postsynaptic structures at the ultrastructural level. Taken together, these findings demonstrate the post- and presynaptic segregation of primary enzymes responsible for synthesis and elimination of 2-AG, respectively, in the human hippocampus. Thus, molecular architecture of the endocannabinoid signaling machinery supports retrograde regulation of synaptic activity, and its similar blueprint in rodents and humans further indicates that 2-AG's physiological role as a negative feed-back signal is an evolutionarily conserved feature of excitatory synapses.

WIN55212-2 ameliorates atherosclerosis associated with suppression of pro-inflammatory responses in ApoE-knockout mice

The role of inflammation in all stages of atherosclerosis has been actively investigated, with an emphasis on the discovery of novel and innovative drugs for treatment and prevention. The anti-inflammatory and immunomodulatory capacity of cannabinoids are well established, and these agents have a broad therapeutic potential in various inflammatory diseases, including cardiovascular diseases. The aim of this study was to investigate the effect of WIN55212-2, a synthetic cannabinoid, on atherosclerosis using the apolipoprotein E-knockout (ApoE(-/-)) mouse on a cholate-containing high-fat diet. Our results showed that WIN55212-2 reduced the size of atherosclerotic lesions in the aorta root, and did not affect serum lipid levels significantly. Furthermore, alleviation of atherosclerosis by WIN55212-2 was associated with a smaller content of macrophages in plaque lesion as well as decreasing pro-inflammatory gene expression and NF-κB activation in aortic tissues. Oxidized LDL (ox-LDL) dramatically induced NF-κB activation, and enhanced pro-inflammatory mRNA and protein expression in peritoneal macrophages isolated from ApoE(-/-) mice. It is noteworthy that all of the above-mentioned effects of ox-LDL were attenuated by WIN55212-2. Moreover, WIN55212-2 also attenuated the inflammatory response that LPS induced. AM630, a cannabinoid receptor 2 (CB₂) special antagonist completely abolished the protective effects of WIN55212-2 both in vivo and in vitro. Our data provide strong evidence that WIN55212-2 can potentially inhibit atherosclerosis in ApoE(-/-) mice. Importantly, all the beneficial effects of WIN55212-2 in our model were closely associated with the suppression of pro-inflammatory responses and were mediated by the CB₂ receptor.

The CB2 cannabinoid receptor-selective agonist O-3223 reduces pain and inflammation without apparent cannabinoid behavioral effects

Although Δ(9)-tetrahydrocannabinol (THC) and other mixed CB(1)/CB(2) receptor agonists are well established to elicit antinociceptive effects, their psychomimetic actions and potential for abuse have dampened enthusiasm for their therapeutic development. Conversely, CB(2) receptor-selective agonists have been shown to reduce pain and inflammation, without eliciting apparent cannabinoid behavioral effects. In the present study, we developed a novel ethyl sulfonamide THC analog, O-3223, and compared its pharmacological effects to those of the potent, mixed CB(1)/CB(2) receptor agonist, CP55,940, in a battery of preclinical pain models. Competitive cannabinoid receptor binding experiments revealed that O-3223 was approximately 80-fold more selective for CB(2) than CB(1) receptors. Additionally, O-3223 behaved as a full CB(2) receptor agonist in [(35)S]GTPγS binding. O-3223 reduced nociceptive behavior in both phases of the formalin test, reduced thermal hyperalgesia in the chronic constriction injury of the sciatic nerve (CCI) model, and reduced edema and thermal hyperalgesia elicited by intraplantar injection of LPS. These effects were blocked by pretreatment with the CB(2) receptor-selective antagonist SR144528, but not by the CB(1) receptor antagonist, rimonabant. Unlike CP55,940, O-3223 did not elicit acute antinociceptive effects in the hot-plate test, hypothermia, or motor disturbances, as assessed in the rotarod test. These data indicate that the CB(2) receptor-selective agonist, O-3223, reduces inflammatory and neuropathic nociception, without affecting basal nociception or eliciting overt behavioral effects. Moreover, this compound can serve as a template to develop new CB(2) receptor agonists with increased receptor selectivity and increased potency in treating inflammatory and neuropathic pain.

Chronic monoacylglycerol lipase blockade causes functional antagonism of the endocannabinoid system

Prolonged exposure to drugs of abuse, such as cannabinoids and opioids, leads to pharmacological tolerance and receptor desensitization in the nervous system. Here we show that a similar form of functional antagonism is produced by sustained inactivation of monoacylglycerol lipase (MAGL), the principal degradative enzyme for the endocannabinoid 2-arachidonoylglycerol (2-AG). After repeated administration, the MAGL inhibitor JZL184 lost its analgesic activity and produced cross-tolerance to cannabinoid receptor (CB₁) agonists in mice, effects that were phenocopied by genetic disruption of MAGL. Chronic MAGL blockade also caused physical dependence, impaired endocannabinoid-dependent synaptic plasticity, and desensitization of brain CB₁ receptors. These data contrasted with blockade of fatty acid amide hydrolase (FAAH), an enzyme that degrades the other major endocannabinoid anandamide, which produced sustained analgesia without impairing CB₁ receptors. Thus, individual endocannabinoids generate distinct analgesic profiles that are either sustained or transitory and associated with agonism and functional antagonism of the brain cannabinoid system, respectively.

Synthesis and pharmacology of 1-methoxy analogs of CP-47,497

Three 1-methoxy analogs of CP-47,497 (7, 8, and 19) have been synthesized and their affinities for the cannabinoid CB(1) and CB(2) receptors have been determined. Although these compounds exhibit selectivity for the CB(2) receptor none have significant affinity for either receptor. Modeling and receptor docking studies were carried out, which provide a rationalization for the weak affinities of these compounds for either receptor.

GABA(A) receptor density is altered by cannabinoid treatment in the hippocampus of adult but not adolescent rats

Cannabinoids are known to induce transient psychotic symptoms and cognitive dysfunction in healthy individuals and contribute to trigger schizophrenia in vulnerable individuals, particularly during adolescence. Converging preclinical evidence suggests important interactions between cannabinoid and GABAergic systems. In the present study, we compared the effects of cannabinoid treatment on GABA(A) receptor binding in the brain of adolescent and adult rats. Adolescent (5 weeks old) and adult (10 weeks old) rats were treated with the synthetic cannabinoid HU210 (25, 50 or 100 microg/kg/day) or vehicle for 1, 4 or 14 days. Rats were sacrificed 24 h after the last injection and GABA(A) receptor density was measured in several brain regions using [(35)S]TBPS and in vitro autoradiography. Adolescent rats had higher numbers of GABA(A) receptors compared to adults. A 24% increase of binding in adult rats treated with 100 microg/kg HU210 for 14 days compared to controls was observed in the CA1 region of the hippocampus (16.1 versus 12.9 fmol/mg tissue equivalent, t=2.720, p<0.05). HU210 did not affect GABA(A) receptors in adolescent rats in any treatment regimen and in adult rats treated with HU210 for 1 or 4 days. These data suggest that long-term, high-dose treatment with HU210 increases GABA(A) receptors in the hippocampus of adult rats, changes that may interfere with associated hippocampal cognitive functions such as learning and memory. In addition, our results suggest that the adolescent brain does not display the same compensatory mechanisms that are activated in the adult brain following cannabinoid treatment.

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.

Loss of retrograde endocannabinoid signaling and reduced adult neurogenesis in diacylglycerol lipase knock-out mice

Endocannabinoids (eCBs) function as retrograde signaling molecules at synapses throughout the brain, regulate axonal growth and guidance during development, and drive adult neurogenesis. There remains a lack of genetic evidence as to the identity of the enzyme(s) responsible for the synthesis of eCBs in the brain. Diacylglycerol lipase-alpha (DAGLalpha) and -beta (DAGLbeta) synthesize 2-arachidonoyl-glycerol (2-AG), the most abundant eCB in the brain. However, their respective contribution to this and to eCB signaling has not been tested. In the present study, we show approximately 80% reductions in 2-AG levels in the brain and spinal cord in DAGLalpha(-/-) mice and a 50% reduction in the brain in DAGLbeta(-/-) mice. In contrast, DAGLbeta plays a more important role than DAGLalpha in regulating 2-AG levels in the liver, with a 90% reduction seen in DAGLbeta(-/-) mice. Levels of arachidonic acid decrease in parallel with 2-AG, suggesting that DAGL activity controls the steady-state levels of both lipids. In the hippocampus, the postsynaptic release of an eCB results in the transient suppression of GABA-mediated transmission at inhibitory synapses; we now show that this form of synaptic plasticity is completely lost in DAGLalpha(-/-) animals and relatively unaffected in DAGLbeta(-/-) animals. Finally, we show that the control of adult neurogenesis in the hippocampus and subventricular zone is compromised in the DAGLalpha(-/-) and/or DAGLbeta(-/-) mice. These findings provide the first evidence that DAGLalpha is the major biosynthetic enzyme for 2-AG in the nervous system and reveal an essential role for this enzyme in regulating retrograde synaptic plasticity and adult neurogenesis.

Cannabinoid CB1 receptor facilitation of substance P release in the rat spinal cord, measured as neurokinin 1 receptor internalization

The contribution of CB1 receptors in the spinal cord to cannabinoid analgesia is still unclear. The objective of this study was to investigate the effect of CB1 receptors on substance P release from primary afferent terminals in the spinal cord. Substance P release was measured as neurokinin 1 (NK1) receptor internalization in lamina I neurons. It was induced in spinal cord slices by dorsal root stimulation and in live rats by a noxious stimulus. In spinal cord slices, the CB1 receptor antagonists AM251, AM281 and rimonabant partially but potently inhibited NK1 receptor internalization induced by electrical stimulation of the dorsal root. This was due to an inhibition of substance P release and not of NK1 receptor internalization itself, because AM251 and AM281 did not inhibit NK1 receptor internalization induced by exogenous substance P. The CB1 receptor agonist ACEA increased NK1 receptor internalization evoked by dorsal root stimulation. The effects of AM251 and ACEA cancelled each other. In vivo, AM251 injected intrathecally decreased NK1 receptor internalization in spinal segments L5 and L6 induced by noxious hind paw clamp. Intrathecal AM251 also produced analgesia to radiant heat stimulation of the paw. The inhibition by AM251 of NK1 receptor internalization was reversed by antagonists of mu-opioid and GABA(B) receptors. This indicates that CB1 receptors facilitate substance P release by inhibiting the release of GABA and opioids next to primary afferent terminals, producing disinhibition. This results in a pronociceptive effect of CB1 receptors in the spinal cord.

Anandamide potentiation of miniature spontaneous excitatory synaptic transmission is mediated via IP3 pathway

Although arachidonoyl ethanolamide (AEA or anandamide) is the first identified endocannabinoid, its roles in synaptic signaling and neuronal survival are still controversial. Here we report that AEA induced a dose-dependent elevation of the frequency of miniature excitatory postsynaptic currents (mEPSCs) in mouse hippocampal neurons in culture. This potentiation was not blocked by SR141716 or AM251, selective cannabinoid receptor antagonists, indicating that the AEA elevation of mEPSCs is not mediated via the CB1 receptor. Similarly, capsazepine and iodoresiniferatoxin, selective vanilloid receptor antagonists, and ryanodine also failed to inhibit the effect of AEA on mEPSCs. However, 2-APB and Xestospongin C, IP3 inhibitors, significantly attenuated AEA-induced increase in hippocampal excitatory synaptic transmission. Application of 3-deoxy-3-fluoro-d-myo-inositol 1,4,5-trisphosphate enhanced the frequency of mEPSCs and occluded the effect of AEA on mEPSCs. Our results suggest that AEA-produced stimulatory effect on excitatory glutamatergic synaptic transmission is likely mediated via an IP3 pathway.

Cannabinoid receptor ligands as potential anticancer agents — high hopes for new therapies?

Objectives

The endocannabinoid system is an endogenous lipid signalling network comprising arachidonic-acid-derived ligands, cannabinoid (CB) receptors, transporters and endocannabinoid degrading enzymes. The CB1 receptor is predominantly expressed in neurons but is also co-expressed with the CB2 receptor in peripheral tissues. In recent years, CB receptor ligands, including Δ9-tetrahydrocannabinol, have been proposed as potential anticancer agents.

Key findings

This review critically discusses the pharmacology of CB receptor activation as a novel therapeutic anticancer strategy in terms of ligand selectivity, tissue specificity and potency. Intriguingly, antitumour effects mediated by cannabinoids are not confined to inhibition of cancer cell proliferation; cannabinoids also reduce angiogenesis, cell migration and metastasis, inhibit carcinogenesis and attenuate inflammatory processes. In the last decade several new selective CB1 and CB2 receptor agents have been described, but most studies in the area of cancer research have used non-selective CB ligands. Moreover, many of these ligands exert prominent CB receptor-independent pharmacological effects, such as activation of the G-protein-coupled receptor GPR55, peroxisome proliferator-activated receptor gamma and the transient receptor potential vanilloid channels.

Summary

The role of the endocannabinoid system in tumourigenesis is still poorly understood and the molecular mechanisms of cannabinoid anticancer action need to be elucidated. The development of CB2-selective anticancer agents could be advantageous in light of the unwanted central effects exerted by CB1 receptor ligands. Probably the most interesting question is whether cannabinoids could be useful in chemoprevention or in combination with established chemotherapeutic agents.

The cannabinoid receptor 1 gene (CNR1) and multiple sclerosis: an association study in two case-control groups from Spain

Different studies point to the implication of the endocannabinoid system in multiple sclerosis (MS) and animal models of MS. The purpose of this study was to evaluate a possible association of MS with polymorphic markers at the CNR1 gene, encoding the cannabinoid 1 (CB1) receptor. We have performed a genetic analysis of an AAT repeat microsatellite localized in the downstream region of the CNR1 gene, in two case—control groups of MS patients and healthy controls (HC) from Spain (Madrid and Bilbao). MS patients with primary progressive MS (PPMS) had more commonly long ((AAT) ≥13) alleles and genotypes with a significant difference for genotype 7/8 in Madrid (p = 0.043) and in the sum of both groups (p = 0.016); short alleles were less frequently found in PPMS with a significant difference for allele 5 in the analysis of both groups together (p = 0.039). In patients with relapsing MS, no consistent differences in allele and genotype distribution were found. Disease severity and progression was unrelated to AAT repeat variations. In conclusion, long (AAT) ≥13 CNR1 genotypes could behave as risk factors for PPMS.

Reduced expression of glutamate receptors and phosphorylation of CREB are responsible for in vivo Delta9-THC exposure-impaired hippocampal synaptic plasticity

Chronic use of marijuana impairs synaptic plasticity and cognitive function. However, the molecular mechanisms by which marijuana alters long-term synaptic plasticity are largely unknown. Here, we show that repeated in vivo exposures to Delta9-THC for 7 consecutive days significantly impaired hippocampal long-term potentiation (LTP) of excitatory glutamatergic synaptic transmission. The Delta9-THC exposure-induced decrease in LTP was prevented by pharmacological inhibition or deletion of the cannabinoid 1 receptor (CB1R). To determine the molecular mechanisms underlying Delta9-THC-altered LTP, we targeted expression and function of the glutamate receptors (GluR) and phosphorylation status of cAMP-response element-binding protein (CREB). Chronic in vivo exposure to Delta9-THC produced CB1R-dependent decreases in expression of hippocampal GluR1, NR2A, and NR2B, the ratio of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/NMDA receptor-gated currents, and phosphorylation of CREB. Our results suggest that reduced expression and function of the GluR subunits and phosphorylation of CREB may underlie the impaired long-term synaptic plasticity induced by repeated in vivo exposure to Delta9-THC.

Characterization of monoacylglycerol lipase inhibition reveals differences in central and peripheral endocannabinoid metabolism

Monoacylglycerol lipase (MAGL) is a principal degradative enzyme for the endocannabinoid 2-arachidonoylglycerol (2-AG). We recently reported a piperidine carbamate, JZL184, that inhibits MAGL with high potency and selectivity. Here, we describe a comprehensive mechanistic characterization of JZL184. We provide evidence that JZL184 irreversibly inhibits MAGL via carbamoylation of the enzyme's serine nucleophile. Functional proteomic analysis of mice treated with JZL184 revealed that this inhibitor maintains good selectivity for MAGL across a wide range of central and peripheral tissues. Interestingly, MAGL blockade produced marked, tissue-specific differences in monoglyceride metabolism, with brain showing the most dramatic elevations in 2-AG and peripheral tissues often showing greater changes in other monoglycerides. Collectively, these studies indicate that MAGL exerts tissue-dependent control over endocannabinoid and monoglyceride metabolism and designate JZL184 as a selective tool to characterize the functions of MAGL in vivo.

New therapeutic potential for psychoactive natural products

Much of our knowledge in neuroscience was discovered through the study of mind-altering natural products. However, although much has been learned about human physiology and basic biological processes, the underlying causes of CNS disorders and other disease states are still elusive. Based on its main past successes, the continued study of mind-altering compounds promises to yield novel agents that may be developed into medications and to identify new targets for the treatment of diseases. This Highlight describes the history of investigations into several classes of mind-altering natural products and relates recent and potential therapeutic uses for these agents.

Tetrahydrocannabinol (Delta 9-THC) Treatment in Chronic Central Neuropathic Pain and Fibromyalgia Patients: Results of a Multicenter Survey

Central neuropathic pain is difficult to treat, but delta 9-Tetrahydrocannabinol (delta 9-THC) may be a promising therapeutic agent. We administered in 172 patients on average 7.5 mg delta 9-THC over 7 months. Of these, 48 patients prematurely withdrew due to side effects, insufficient analgesia, or expense of therapy. Thus, 124 patients were assessed retrospectively in a multicenter telephone survey. Reported changes in pain intensity, recorded on a numeric rating scale (NRS), Pain Disability Index (PDI), Medical Outcomes Short-Form (SF-12), Quality of Life Impairment by Pain (QLIP), Hospital Anxiety Depression Scale (HADS), and amount of concomitant pain medication were recorded. Psychometric parameters (PDI, SF-12, QLIP, HADS) and pain intensity improved significantly during delta 9-THC treatment. Opioid doses were reduced and patients perceived THC therapy as effective with tolerable side effects. About 25% of the patients, however, did not tolerate the treatment. Therapy success and tolerance can be assessed by a transient delta 9-THC titration and its maintained administration for several weeks. The present survey demonstrates its ameliorating potential for the treatment of chronic pain in central neuropathy and fibromyalgia. A supplemental delta 9-THC treatment as part of a broader pain management plan therefore may represent a promising coanalgesic therapeutic option.

The endocannabinoid system of the skin in health and disease: novel perspectives and therapeutic opportunities

The newly discovered endocannabinoid system (ECS; comprising the endogenous lipid mediators endocannabinoids present in virtually all tissues, their G-protein-coupled cannabinoid receptors, biosynthetic pathways and metabolizing enzymes) has been implicated in multiple regulatory functions both in health and disease. Recent studies have intriguingly suggested the existence of a functional ECS in the skin and implicated it in various biological processes (e.g. proliferation, growth, differentiation, apoptosis and cytokine, mediator or hormone production of various cell types of the skin and appendages, such as the hair follicle and sebaceous gland). It seems that the main physiological function of the cutaneous ECS is to constitutively control the proper and well-balanced proliferation, differentiation and survival, as well as immune competence and/or tolerance, of skin cells. The disruption of this delicate balance might facilitate the development of multiple pathological conditions and diseases of the skin (e.g. acne, seborrhea, allergic dermatitis, itch and pain, psoriasis, hair growth disorders, systemic sclerosis and cancer).

Opioid receptor and NO/cGMP pathway as a mechanism of peripheral antinociceptive action of the cannabinoid receptor agonist anandamide

AIMS

In this study, we investigated whether the opioid system and the nitric oxide pathway were involved in the peripheral antinociception induced by a cannabinoid receptor agonist anandamide.

MAIN METHODS

Hyperalgesia was induced by a subcutaneous injection of carrageenan (250 microg) into the plantar surface of the rat's hindpaw and measured by the paw pressure test 3h after injection. The weight in grams (g) required to elicit a nociceptive response, paw flexion, was determined as the nociceptive threshold.

KEY FINDINGS

Anandamide elicited a dose-dependent (50, 75, and 100 ng per paw) antinociceptive effect. The highest dose of anandamide did not produce antihyperalgesia in the contralateral paw, indicating a peripheral site of action. The CB(1) receptor antagonist AM251 (20, 40, 80 and 160mug per paw) antagonized peripheral antihyperalgesia induced by anandamide (100 ng), in a dose-dependent manner, suggesting CB(1) receptor activation. Anandamide-induced peripheral antihyperalgesia was reverted by blockers of the l-arginine/NO/cGMP pathway N(G)-nitro-l-arginine (NOARG; 24, 36 and 48 microg per paw) and 1H-[1,2,4] Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 25, 50 and 100 microg per paw), in a dose-dependent manner. Furthermore, opioid receptor antagonist naloxone (12.5, 25 and 50 microg per paw) antagonized the peripheral antihyperalgesia induced by anandamide.

SIGNIFICANCE

This study provides evidence that the peripheral antinociceptive effect of the cannabinoid receptor agonist anandamide may result from l-arginine/NO/cGMP pathway activation and that the opioid system is also involved.