Attenuation of Allergic Contact Dermatitis Through the Endocannabinoid System

Δ9-tetrahydrocannabinol impairs the inflammatory response to influenza infection: role of antigen-presenting cells and the cannabinoid receptors 1 and 2

Δ(9)-tetrahydrocannabinol (Δ(9)-THC) has potent immune modulatory properties and can impair pathogen-induced immune defenses, which in part have been attributed to ligation of the cannabinoid receptors 1 (CB(1)) and 2 (CB(2)). Most recently, dendritic cells (DC) were identified for their potential to enhance influenza-induced immunopathology in mice lacking CB(1) and CB(2) (CB(1) (-/-)CB(2) (-/-)). This study focused on the modulation of the inflammatory immune response to influenza by Δ(9)-THC and the role of CB(1) and/or CB(2) as receptor targets for Δ(9)-THC. C57Bl/6 (wild type) and CB(1) (-/-)CB(2) (-/-) mice were administered Δ(9)-THC (75 mg/kg) surrounding the intranasal instillation of A/PR/8/34 influenza virus. Three days post infection (dpi), Δ(9)-THC broadly decreased expression levels of mRNA induced by the innate immune response to influenza, suppressed the percentage of interferon-gamma (IFN-γ)-producing CD4(+) and interleukin-17-producing NK1.1(+) cells, and reduced the influx of antigen-presenting cells (APC), including inflammatory myeloid cells and monocytes/macrophages, into the lung in a CB(1)- and/or CB(2)-dependent manner. Δ(9)-THC had little effect on the expression of CD86, major histocompatibility complex I (MHC I), and MHC II by APC isolated from the lung. In vitro studies demonstrated that lipopolysaccharide (LPS)-induced maturation was suppressed by Δ(9)-THC in bone marrow-derived DC (bmDC). Furthermore, antigen-specific IFN-γ production by CD8(+) T cells after coculture was reduced by Δ(9)-THC treatment of bmDC in a CB(1)- and/or CB(2)-dependent manner. Collectively, these studies suggest that Δ(9)-THC potently suppresses myeloid cell immune function, in a manner involving CB(1) and/or CB(2), thereby impairing immune responses to influenza infection.

Bioactive lipid mediators in skin inflammation and immunity

The skin is the primary barrier from the outside environment, protecting the host from injury, infectious pathogens, water loss and solar ultraviolet radiation. In this role, it is supported by a highly organized system comprising elements of innate and adaptive immunity, responsive to inflammatory stimuli. The cutaneous immune system is regulated by mediators such as cytokines and bioactive lipids that can initiate rapid immune responses with controlled inflammation, followed by efficient resolution. However, when immune responses are inadequate or mounted against non-infectious agents, these mediators contribute to skin pathologies involving unresolved or chronic inflammation. Skin is characterized by active lipid metabolism and fatty acids play crucial roles both in terms of structural integrity and functionality, in particular when transformed to bioactive mediators. Eicosanoids, endocannabinoids and sphingolipids are such key bioactive lipids, intimately involved in skin biology, inflammation and immunity. We discuss their origins, role and influence over various cells of the epidermis, dermis and cutaneous immune system and examine their function in examples of inflammatory skin conditions. We focus on psoriasis, atopic and contact dermatitis, acne vulgaris, wound healing and photodermatology that demonstrate dysregulation of bioactive lipid metabolism and examine ways of using this insight to inform novel therapeutics.

Lead discovery, chemistry optimization, and biological evaluation studies of novel biamide derivatives as CB2 receptor inverse agonists and osteoclast inhibitors

N,N'-((4-(Dimethylamino)phenyl)methylene)bis(2-phenylacetamide) was discovered by using 3D pharmacophore database searches and was biologically confirmed as a new class of CB(2) inverse agonists. Subsequently, 52 derivatives were designed and synthesized through lead chemistry optimization by modifying the rings A-C and the core structure in further SAR studies. Five compounds were developed and also confirmed as CB(2) inverse agonists with the highest CB(2) binding affinity (CB(2)K(i) of 22-85 nM, EC(50) of 4-28 nM) and best selectivity (CB(1)/CB(2) of 235- to 909-fold). Furthermore, osteoclastogenesis bioassay indicated that PAM compounds showed great inhibition of osteoclast formation. Especially, compound 26 showed 72% inhibition activity even at the low concentration of 0.1 μM. The cytotoxicity assay suggested that the inhibition of PAM compounds on osteoclastogenesis did not result from its cytotoxicity. Therefore, these PAM derivatives could be used as potential leads for the development of a new type of antiosteoporosis agent.

Update of immune events in the murine contact hypersensitivity model: toward the understanding of allergic contact dermatitis

Allergic contact dermatitis (ACD) is one of the most common skin diseases, consisting of sensitization and elicitation phases. With the advancement of technology and the discovery of new types of immune cells, our knowledge of the immunological mechanisms of contact hypersensitivity (CHS) as a murine model of ACD has expanded significantly in the past decade. For example, by introducing regulatory T cells, CD4(+) T-helper 17 cells, and Langerin-positive dermal dendritic cells, the initiation and termination mechanism of CHS has been revealed. In addition, the role of mast cells in CHS, long a matter of debate, has become apparent by developing conditional mast cell-deficient mice. Moreover, the role of the innate immunity system, such as that of Toll-like receptor signaling, has made a breakthrough in this field. In this review, we will integrate the recent advancement of immunological mechanisms of both the sensitization and elicitation phases of CHS into the classic view, and we will discuss updated mechanisms on its development and future directions.

The cannabinoid CB1 receptor antagonists rimonabant (SR141716) and AM251 directly potentiate GABA(A) receptors

BACKGROUND AND PURPOSE

Rimonabant (SR141716) and the structurally related AM251 are widely used in pharmacological experiments as selective cannabinoid receptor CB(1) antagonists / inverse agonists. Concentrations of 0.5-10 µM are usually applied in in vitro experiments. We intended to show that these drugs did not act at GABA(A) receptors but found a significant positive allosteric modulation instead.

EXPERIMENTAL APPROACH

Recombinant GABA(A) receptors were expressed in Xenopus oocytes. Receptors were exposed to AM251 or rimonabant in the absence and presence of GABA. Standard electrophysiological techniques were used to monitor the elicited ionic currents.

KEY RESULTS

AM251 dose-dependently potentiated responses to 0.5 µM GABA at the recombinant α(1) β(2) γ(2) GABA(A) receptor with an EC(50) below 1 µM and a maximal potentiation of about eightfold. The Hill coefficient indicated that more than one binding site for AM251 was located in this receptor. Rimonabant had a lower affinity, but a fourfold higher efficacy. AM251 potentiated also currents mediated by α(1) β(2) , α(x) β(2) γ(2) (x = 2,3,5,6), α(1) β(3) γ(2) and α(4) β(2) δ GABA(A) receptors, but not those mediated by α(1) β(1) γ(2) . Interestingly, the CB(1) receptor antagonists LY320135 and O-2050 did not significantly affect α(1) β(2) γ(2) GABA(A) receptor-mediated currents at concentrations of 1 µM.

CONCLUSIONS AND IMPLICATIONS

This study identified rimonabant and AM251 as positive allosteric modulators of GABA(A) receptors. Thus, potential GABAergic effects of commonly used concentrations of these compounds should be considered in in vitro experiments, especially at extrasynaptic sites where GABA concentrations are low.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.

CB₂: therapeutic target-in-waiting

CB₂ cannabinoid receptor agonists hold promise as a new class of therapeutics for indications as diverse as pain, neuroinflammation, immune suppression and osteoporosis. These potential indications are supported by strong preliminary data from multiple investigators using diverse preclinical models. However, clinical trials for CB₂ agonists, when they have been reported have generally been disappointing. This review considers possible explanations for the mismatch between promising preclinical data and disappointing clinical data. We propose that a more careful consideration of CB₂ receptor pharmacology may help move CB₂ agonists from "promising" to "effective" therapeutics.

Differences in peripheral endocannabinoid modulation of scratching behavior in facial vs. spinally-innervated skin

Cannabinoids suppress nocifensive behaviors in rodents. We presently investigated peripheral endocannabinoid modulation of itch- and pain-related behaviors elicited from facial vs. spinally-innervated skin of rats. Intradermal (id) injection of the pruritogen serotonin (5-HT) elicited significantly more hindlimb scratch bouts, and longer cumulative time scratching, when injected in the rostral back compared to the cheek. Pretreatment of skin with inhibitors of degrading enzymes for the endocannabinoids anandamide (URB597) or 2-arachidonoylglycerol (JZL184) significantly reduced scratching elicited by 5-HT in the rostral back. These effects were prevented by co-treatment with antagonists of the CB₁ (AM251) or CB₂ receptor (AM630), implicating both receptor subtypes in endocannabinoid suppression of scratching in spinally-innervated skin. Conversely, pretreatment with either enzyme inhibitor, or with AM630 alone, increased the number of scratch bouts elicited by id 5-HT injection in the cheek. Moreover, pretreatment with JZL184 also significantly increased pain-related forelimb wipes directed to the cheek following id injection of the algogen, allyl isothiocyanate (AITC; mustard oil). Thus, peripheral endocannabinoids have opposite effects on itch-related scratching behaviors in trigeminally- vs. spinally-innervated skin. These results suggest that increasing peripheral endocannabinoid levels represents a promising therapeutic approach to treat itch arising from the lower body, but caution that such treatment may not relieve, and may even exacerbate, itch and pain arising from trigeminally-innervated skin of the face or scalp.

Latest advances in novel cannabinoid CB(2) ligands for drug abuse and their therapeutic potential

The field of cannabinoid (CB) drug research is experiencing a challenge as the CB(1) antagonist Rimonabant, launched in 2006 as an anorectic/anti-obesity drug, was withdrawn from the European market due to the complications of suicide and depression as side effects. There is interest in developing CB(2) drugs without CB(1) psychotropic side effects for drug-abuse treatment and therapeutic medication. The CB(1) receptor was discovered predominantly in the brain, whereas the CB(2) is mainly expressed in peripheral cells and tissues, and is involved in immune signal transduction. Conversely, the CB(2) receptor was recently detected in the CNS, for example, in the microglial cells and the neurons. While the CB(2) neurons activity remains controversial, the CB(2) receptor is an attractive therapeutic target for neuropathic pain, immune system, cancer and osteoporosis without psychoactivity. This review addresses CB drug abuse and therapeutic potential with a focus on the most recent advances on new CB(2) ligands from the literature as well as patents.

Endocannabinoids regulate growth and survival of human eccrine sweat gland-derived epithelial cells

The functional existence of the emerging endocannabinoid system (ECS), one of the new neuroendocrine players in cutaneous biology, is recently described in the human skin. In this study, using human eccrine sweat gland-derived immortalized NCL-SG3 model cells and a wide array of cellular and molecular assays, we investigated the effects of prototypic endocannabinoids (anandamide, 2-arachidonoylglycerol) on cellular functions. We show here that both endocannabinoids dose-dependently suppressed proliferation, induced apoptosis, altered expressions of various cytoskeleton proteins (e.g., cytokeratins), and upregulated lipid synthesis. Interestingly, as revealed by specific agonists and antagonists as well as by RNA interference, neither the metabotropic cannabinoid receptors (CB) nor the "ionotropic" CB transient receptor potential ion channels, expressed by these cells, mediated the cellular actions of the endocannabinoids. However, the endocannabinoids selectively activated the mitogen-activated protein kinase signaling pathway. Finally, other elements of the ECS (i.e., enzymes involved in the synthesis and degradation of endocannabinoids) were also identified on NCL-SG3 cells. These results collectively suggest that cannabinoids exert a profound regulatory role in the biology of the appendage. Therefore, from a therapeutic point of view, upregulation of endocannabinoid levels might help to manage certain sweat gland-derived disorders (e.g., tumors) characterized by unwanted growth.

Endocannabinoids stimulate human melanogenesis via type-1 cannabinoid receptor

We show that a fully functional endocannabinoid system is present in primary human melanocytes (normal human epidermal melanocyte cells), including anandamide (AEA), 2-arachidonoylglycerol, the respective target receptors (CB(1), CB(2), and TRPV1), and their metabolic enzymes. We also show that at higher concentrations AEA induces normal human epidermal melanocyte apoptosis (∼3-fold over controls at 5 μM) through a TRPV1-mediated pathway that increases DNA fragmentation and p53 expression. However, at lower concentrations, AEA and other CB(1)-binding endocannabinoids dose-dependently stimulate melanin synthesis and enhance tyrosinase gene expression and activity (∼3- and ∼2-fold over controls at 1 μM). This CB(1)-dependent activity was fully abolished by the selective CB(1) antagonist SR141716 or by RNA interference of the receptor. CB(1) signaling engaged p38 and p42/44 mitogen-activated protein kinases, which in turn activated the cyclic AMP response element-binding protein and the microphthalmia-associated transcription factor. Silencing of tyrosinase or microphthalmia-associated transcription factor further demonstrated the involvement of these proteins in AEA-induced melanogenesis. In addition, CB(1) activation did not engage the key regulator of skin pigmentation, cyclic AMP, showing a major difference compared with the regulation of melanogenesis by α-melanocyte-stimulating hormone through melanocortin 1 receptor.

Cannabinoid receptor trafficking in peripheral cells is dynamically regulated by a binary biochemical switch

The cannabinoid G protein-coupled receptors (GPCRs) CB₁ and CB₂ are expressed in different peripheral cells. Localization of GPCRs in the cell membrane determines signaling via G protein pathways. Here we show that unlike in transfected cells, CB receptors in cell lines and primary human cells are not internalized upon agonist interaction, but move between cytoplasm and cell membranes by ligand-independent trafficking mechanisms. Even though CB receptors are expressed in many cells of peripheral origin they are not always localized in the cell membrane and in most cancer cell lines the ratios between CB₁ and CB₂ receptor gene and surface expression vary significantly. In contrast, CB receptor cell surface expression in HL60 cells is subject to significant oscillations and CB₂ receptors form oligomers and heterodimers with CB₁ receptors, showing synchronized surface expression, localization and trafficking. We show that hydrogen peroxide and other nonspecific protein tyrosine phosphatase inhibitors (TPIs) such as phenylarsine oxide trigger both CB₂ receptor internalization and externalization, depending on receptor localization. Phorbol ester-mediated internalization of CB receptors can be inhibited via this switch. In primary human immune cells hydrogen peroxide and other TPIs lead to a robust internalization of CB receptors in monocytes and an externalization in T cells. This study describes, for the first time, the dynamic nature of CB receptor trafficking in the context of a biochemical switch, which may have implications for studies on the cell-type specific effects of cannabinoids and our understanding of the regulation of CB receptor cell surface expression.

Unraveling the complexities of cannabinoid receptor 2 (CB2) immune regulation in health and disease

It has become clear that the endocannabinoid system is a potent regulator of immune responses, with the cannabinoid receptor 2 (CB2) as the key component due to its high expression by all immune subtypes. CB2 has been shown to regulate immunity by a number of mechanisms including development, migration, proliferation, and effector functions. In addition, CB2 has been shown to modulate the function of all immune cell types examined to date. CB2 is a G(i)-protein-coupled receptor and thus exhibits a complex pharmacology allowing both stimulatory and inhibitory signaling that depends on receptor expression levels, ligand concentration, and cell lineage specificities. Here, we discuss both in vitro and in vivo experimental evidence that CB2 is a potent regulator of immune responses making it a prime target for the treatment of inflammatory diseases.

Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects

Tetrahydrocannabinol (THC) has been the primary focus of cannabis research since 1964, when Raphael Mechoulam isolated and synthesized it. More recently, the synergistic contributions of cannabidiol to cannabis pharmacology and analgesia have been scientifically demonstrated. Other phytocannabinoids, including tetrahydrocannabivarin, cannabigerol and cannabichromene, exert additional effects of therapeutic interest. Innovative conventional plant breeding has yielded cannabis chemotypes expressing high titres of each component for future study. This review will explore another echelon of phytotherapeutic agents, the cannabis terpenoids: limonene, myrcene, α-pinene, linalool, β-caryophyllene, caryophyllene oxide, nerolidol and phytol. Terpenoids share a precursor with phytocannabinoids, and are all flavour and fragrance components common to human diets that have been designated Generally Recognized as Safe by the US Food and Drug Administration and other regulatory agencies. Terpenoids are quite potent, and affect animal and even human behaviour when inhaled from ambient air at serum levels in the single digits ng·mL(-1) . They display unique therapeutic effects that may contribute meaningfully to the entourage effects of cannabis-based medicinal extracts. Particular focus will be placed on phytocannabinoid-terpenoid interactions that could produce synergy with respect to treatment of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer, fungal and bacterial infections (including methicillin-resistant Staphylococcus aureus). Scientific evidence is presented for non-cannabinoid plant components as putative antidotes to intoxicating effects of THC that could increase its therapeutic index. Methods for investigating entourage effects in future experiments will be proposed. Phytocannabinoid-terpenoid synergy, if proven, increases the likelihood that an extensive pipeline of new therapeutic products is possible from this venerable plant. http://dx.doi.org/10.1111/bph.2011.163.issue-7.

Endocannabinoids limit excessive mast cell maturation and activation in human skin

BACKGROUND

Mast cells (MCs) crucially contribute to many inflammatory diseases. However, the physiological controls preventing excessive activities of MCs in human skin are incompletely understood.

OBJECTIVE

Since endocannabinoids are important neuroendocrine MC modifiers, we investigated how stimulation/inhibition of cannabinoid 1 (CB1) receptors affect the biology of human skin MCs in situ.

METHODS

This was investigated in the MC-rich connective tissue sheath of organ-cultured human scalp hair follicles by quantitative (immuno)histomorphometry, ultrastructural, and quantitative PCR techniques with the use of CB1 agonists or antagonists, CB1 knockdown, or CB1 knockout mice.

RESULTS

Kit+ MCs within the connective tissue sheath of human hair follicles express functional CB1 receptors, whose pharmacological blockade or gene silencing significantly stimulated both the degranulation and the maturation of MCs from resident progenitor cells in situ (ie, enhanced the number of tryptase+, FcεRIα, or chymase+ connective tissue sheath-MCs). This was, at least in part, stem cell factor-dependent. CB1 agonists counteracted the MC-activating effects of classical MC secretagogues. Similar phenomena were observed in CB1 knockout mice, attesting to the in vivo relevance of this novel MC-inhibitory mechanism.

CONCLUSION

By using human hair follicle organ culture as an unconventional, but clinically relevant model system for studying the biology of MCs in situ, we show that normal skin MCs are tightly controlled by the endocannabinoid system. This limits excessive activation and maturation of MCs from resident progenitors via "tonic" CB1 stimulation by locally synthesized endocannabinoids. The excessive numbers and activation of MCs in allergic and other chronic inflammatory skin diseases may partially arise from resident intracutaneous MC progenitors, for example, because of insufficient CB1 stimulation. Therefore, CB1 stimulation is a promising strategy for the future management of allergy and MC-dependent skin diseases.

Cannabinoid receptor 2 is critical for the homing and retention of marginal zone B lineage cells and for efficient T-independent immune responses

The endocannabinoid system has emerged as an important regulator of immune responses, with the cannabinoid receptor 2 (CB2) and its principle ligand 2-archidonoylglycerol playing a major role. How CB2 regulates B cell functions is not clear, even though they express the highest levels of CB2 among immune cell subsets. In this study, we show that CB2-deficient mice have a significant reduction in the absolute number of marginal zone (MZ) B cells and their immediate precursor, transitional-2 MZ precursor. The loss of MZ lineage cells in CB2(-/-) mice was shown to be B cell intrinsic using bone marrow chimeras and was not due to a developmental or functional defect as determined by B cell phenotype, proliferation, and Ig production. Furthermore, CB2(-/-) B cells were similar to wild type in their apoptosis, cell turnover, and BCR and Notch-2 signaling. We then demonstrated that CB2(-/-) MZ lineage B cells were less efficient at homing to the MZ and that their subsequent retention was also regulated by CB2. CB2(-/-) mice immunized with T-independent Ags produced significantly less Ag-specific IgM. This study demonstrates that CB2 positively regulates T-independent immune responses by controlling the localization and positioning of MZ lineage cells to the MZ.

Deletion of cannabinoid receptors 1 and 2 exacerbates APC function to increase inflammation and cellular immunity during influenza infection

We and others have reported that simultaneous targeted deletion of CB(1) and CB(2) resulted in exacerbation of immune reactivity, suggesting a role of endocannabinoids in down-regulating immune function. In this study, we demonstrate that APC function is enhanced specifically in the absence of CB(1) and CB(2) signaling, resulting in an exacerbated immune response phenotype. After influenza infection, CB(1)(-/-)CB(2)(-/-) mice showed more pronounced pulmonary damage, increased inflammatory cell infiltrate, inflammation, and a greater cellular immune responses compared with WT mice, as evidenced by transcriptome analysis, more robust T cell activation, and effector cell cytokine production. After direct activation in vitro, there were no differences in the percentages of cytokine-producing CD4(+) T cells between CB(1)(-/-)CB(2)(-/-) and WT mice. However, untreated CB(1)(-/-)CB(2)(-/-) mice routinely had fewer naïve T cells compared with WT, suggesting dysregulation of APC immune homeostasis. Moreover, bmDCs and AM isolated from CB(1)(-/-)CB(2)(-/-) mice exhibited a more mature phenotype, with and without TLR stimulation, and bmDCs elicited T cells more robustly than WT mice. Collectively, these findings implicate a role for CB(1) and CB(2) on APCs in regulating immune responses and immune homeostasis.

CB1 receptors mediate rimonabant-induced pruritic responses in mice: investigation of locus of action

RATIONALE

Cannabinoids have recently been identified as potential neuronal modulators of pruritic response, representing a potential target in the treatment of itch associated with a variety of pathophysiologic conditions. While the selective CB(1) receptor antagonist rimonabant is an established pruritic agent in both animal and clinical testing, its receptor mechanism of action and anatomical loci remain unclear.

OBJECTIVE

The purpose of this study was to determine whether CB(1) receptor blockade is critical to rimonabant-induced scratching and to identify differences in scratching response based on different routes of administration. Furthermore, experiments were designed to elucidate any evidence as to whether rimonabant elicits scratching behavior through common immunologic hypersensitivity mechanisms.

RESULTS

Rimonabant was equally effective at producing scratching via intraperitoneal and local subcutaneous injection. This compound also produced an intense scratching response when administered intrathecally, but had no effects after intracerebroventricular administration. Repeated administration of rimonabant led to a decreased magnitude of scratching. While rimonabant-induced scratching was not attenuated either by pretreatment with the H(1) receptor antagonist loratadine or in mast cell-deficient mice, it lacked efficacy in CB(1) (-/-) mice.

CONCLUSIONS

Rimonabant is a potent and fully effective pruritogen when administered spinally or systemically and requires CB(1) receptors to induce scratching, suggesting an important spinal CB(1) receptor component of action. The lack of responsiveness to H(1) antagonism or mast cell deficiency supports previous findings that cannabinoids modulate itch through neuronal mechanisms, and not by traditional hypersensitivity activation.

Δ9-tetrahydrocannabinol suppresses cytotoxic T lymphocyte function independent of CB1 and CB 2, disrupting early activation events

Previously, CD8(+) T cells were found to be a sensitive target for suppression by Δ(9)-tetrahydrocannabinol (Δ(9)-THC) in a murine model of influenza infection. To study the effect of Δ(9)-THC on CD8(+) cytotoxic T lymphocytes (CTL), an allogeneic model of MHC I mismatch was used to elicit CTL. In addition, to determine the requirement for the cannabinoid receptors 1 (CB(1)) and 2 (CB(2)) in Δ(9)-THC-mediated CTL response modulation, mice null for both receptors were used (CB(1) (-/-)CB(2) (-/-)). Δ(9)-THC suppressed CTL function independent of CB(1) and CB(2) as evidenced by reduction of (51)Cr release by CTL generated from CB(1) (-/-)CB(2) (-/-) mice. Furthermore, viability in CD4(+) and CD8(+) cells was reduced in a concentration-dependent manner with Δ(9)-THC, independent of CB(1) and CB(2), but no effect of Δ(9)-THC on proliferation was observed, suggesting that Δ(9)-THC decreases the number of T cells initially activated. Δ(9)-THC increased expression of the activation markers, CD69 in CD8(+) cells and CD25 in CD4(+) cells in a concentration-dependent manner in cells derived from WT and CB(1) (-/-)CB(2) (-/-) mice. Furthermore, Δ(9)-THC synergized with the calcium ionophore, ionomycin, to increase CD69 expression on both CD4(+) and CD8(+) cells. In addition, without stimulation, Δ(9)-THC increased CD69 expression in CD8(+) cells from CB(1) (-/-)CB(2) (-/-) and WT mice. Overall, these results suggest that CB(1) and CB(2) are dispensable for Δ(9)-THC-mediated suppression and that perturbation of Ca(2+) signals during T cell activation plays an important role in the mechanism by which Δ(9)-THC suppresses CTL function.

Mechanism of inhibition of fatty acid amide hydrolase by sulfonamide-containing benzothiazoles: long residence time derived from increased kinetic barrier and not exclusively from thermodynamic potency

Fatty acid amide hydrolase (FAAH) has emerged as a potential target for developing analgesic, anxiolytic, antidepressant, sleep-enhancing, and anti-inflammatory drugs, and tremendous efforts have been made to discover potent and selective inhibitors of FAAH. Most known potent FAAH inhibitors described to date employ covalent mechanisms, inhibiting the enzyme either reversibly or irreversibly. Recently, a benzothiazole-based analogue (1) has been described possessing a high potency against FAAH yet lacking a structural feature previously known to interact with FAAH covalently. However, covalent inhibition of FAAH by 1 has not been fully ruled out, and the issue of reversibility has not been addressed. Confirming previous reports, 1 inhibited recombinant human FAAH (rhFAAH) with high potency with IC(50) ~2 nM. It displayed an apparently noncompetitive and irreversible inhibition, titrating rhFAAH stoichiometrically within normal assay times. The inhibition appeared to be time dependent, but the time dependence only improved potency by a small degree (from ~8 to ~2 nM). However, mass spectrometric analyses of the reaction mixture failed to reveal any cleavage product or covalent adduct and showed full recovery of the parent compound, ruling out covalent, irreversible inhibition. Dialysis revealed recovery of enzyme activity from enzyme-inhibitor complex over a prolonged time (>10 h), demonstrating that 1 is indeed a reversible, albeit slowly dissociating inhibitor of FAAH. Molecular docking indicated that the sulfonamide group of 1 could form hydrogen bonds with several residues involved in catalysis, thereby mimicking the transition state. The long residence time displayed by 1 does not appear to derive exclusively from great thermodynamic potency and is consistent with an increased kinetic energy barrier that prevents dissociation from happening quickly.

Anti-inflammatory cannabinoids in diet: Towards a better understanding of CB(2) receptor action?

The endocannabinoid system is an ancient lipid signaling network which in mammals modulates neuronal functions, inflammatory processes, and is involved in the aetiology of certain human lifestyle diseases, such as Crohn's disease, atherosclerosis and osteoarthritis. The system is able to downregulate stress-related signals that lead to chronic inflammation and certain types of pain, but it is also involved in causing inflammation-associated symptoms, depending on the physiological context. The cannabinoid type-2 (CB(2)) receptor, which unlike the CB(1) receptor does not induce central side effects, has been shown to be a promising therapeutic target. While CB(1) receptor antagonists/inverse agonists are of therapeutic value, also CB(2) receptor ligands including agonists are of pharmacological interest. Although the endocannabinoid system is known to be involved in the regulation of energy homoeostasis and metabolism (mainly via CB(1) receptors) there was hitherto no direct link between food intake and cannabinoid receptor activation. Our recent finding that beta-caryophyllene, a ubiquitous lipohilic plant natural product, selectively binds to the CB(2) receptor and acts as a full agonist is unexpected. Maybe even more unexpected is that oral administration of this dietary compound exerts potent anti-inflammatory effects in wild type mice but not in CB(2) receptor (Cnr2(-/-)) knockout mice. Like other CB(2) ligands also beta-caryophyllene inhibits the pathways triggered by activation of the toll-like receptor complex CD14/TLR4/MD2, which typically lead to the expression of proinflammatory cytokines (IL-1beta, IL-6; IL-8 and TNFalpha) and promotes a TH(1) immune response. In this addendum, the CB(2) receptor-dependent effect of beta-caryophyllene on LPS-triggered activation of the kinases Erk1/2 and JNK1/2 are further discussed with respect to the possibility that both CB(2) inverse agonists and agonists, independent of their G-protein signaling, may block LPS-triggered activation of MAPKs, leading to inhibition of proinflammatory cytokine expression and attenuation of inflammation.

Fatty acid amide hydrolase blockade attenuates the development of collagen-induced arthritis and related thermal hyperalgesia in mice

Fatty acid amide hydrolase (FAAH) is the primary degradative enzyme of the endocannabinoid anandamide (N-arachidonoylethanolamine), which activates cannabinoid CB(1) and CB(2) receptors. FAAH disruption reduces nociception in a variety of acute rodent models of inflammatory pain. The present study investigated whether these actions extend to the chronic, collagen-induced arthritis (CIA) model. We investigated the anti-arthritic and anti-hyperalgesic effects of genetic deletion or pharmacological inhibition of FAAH in the CIA model. FAAH (-/-) mice, and FAAH-NS mice that express FAAH exclusively in nervous tissue, displayed decreased severity of CIA and associated hyperalgesia. These phenotypic anti-arthritic effects were prevented by repeated daily injections of the CB(2) receptor antagonist, SR144528, but not the CB(1) receptor antagonist rimonabant. Similarly, repeated administration of the FAAH inhibitor URB597 reduced CIA severity, and acute administration of rimonabant, but not SR144528, blocked the anti-hyperalgesic effects of prolonged FAAH inhibition, suggesting that prolonged CB(2) receptor activation reduces the severity of CIA, whereas acute CB(1) receptor activation reduces CIA-induced hyperalgesia. In contrast, acute administration of URB597 elicited a CB(1) receptor-dependent anti-hyperalgesic effect. The observed anti-arthritic and anti-hyperalgesic properties of FAAH inhibition, coupled with a lack of apparent behavioral alterations, suggest that endocannabinoid modulating enzymes offer a promising therapeutic target for the development of novel pharmacological approaches to treat rheumatoid arthritis and associated hyperalgesia.

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.

Functional role of cannabinoid receptors in urinary bladder

Cannabinoids, the active components of Cannabis sativa (maijuana), and their derivatives produce a wide spectrum of central and peripheral effects, some of which may have clinical applications. The discovery of specific cannabinoid receptors and a family of endogenous ligands of those receptors has attracted much attention to the general cannabinoid pharmacology. In recent years, studies on the functional role of cannabinoid receptors in bladder have been motivated by the therapeutic effects of cannabinoids on voiding dysfunction in multiple sclerosis patients. In this review, we shall summarize the literature on the expression of cannabinoid receptors in urinary bladder and the peripheral influence of locally and systemically administered cannabinoids in the bladder. The ongoing search for cannabinoid-based therapeutic strategies devoid of psychotropic effects can be complemented with local delivery into bladder by the intravesical route. A greater understanding of the role of the peripheral CB₁ and CB₂ receptor system in lower urinary tract is necessary to allow the development of new treatment for pelvic disorders.

A GPR40 agonist GW9508 suppresses CCL5, CCL17, and CXCL10 induction in keratinocytes and attenuates cutaneous immune inflammation

G-protein coupled receptors (GPCR) exert diverse physiological functions, many of which are exploited therapeutically. The roles of GPCR in keratinocytes in immune response in the skin, however, remain poorly defined. In this study, we focused on Gi-coupled GPCR in keratinocytes and defined their actions in immunoactivation of cultured keratinocytes in vitro and immune reaction in the skin in vivo. We first activated HaCaT cells by tumor necrosis factor (TNF)-α and IFN-γ and examined effects of various ligands for GPCR on production of CCL17 and CCL5. Agonists for Gi-coupled receptors, particularly GW9508 for GPR40, inhibited CCL17 and CCL5 expression in a pertussis toxin-sensitive manner. The inhibitory effect by GW9508 was abrogated by depletion of GPR40 with RNA interference. GW9508 further suppressed expression of IL-11, IL-24, and IL-33 induced in HaCaT cells by TNF-α and IFN-γ. GW9508 also inhibited CCL5 and CXCL10 production by normal human epidermal keratinocytes. Administration of GW9508 topically to the skin in the challenging phase suppressed ear swelling in a repeated hapten application model and contact hypersensitivity with downregulation of CCL5 and CXCL10, respectively. Thus, in the skin, stimulation of Gi-coupled receptors attenuates induction of critical cytokines and chemokines by proinflammatory cytokines in keratinocytes and suppresses allergic inflammation in the skin.

Reversible competitive α-ketoheterocycle inhibitors of fatty acid amide hydrolase containing additional conformational constraints in the acyl side chain: orally active, long-acting analgesics

A series of α-ketooxazoles containing conformational constraints in the C2 acyl side chain of 2 (OL-135) were examined as inhibitors of fatty acid amide hydrolase (FAAH). Only one of the two possible enantiomers displayed potent FAAH inhibition (S vs R enantiomer), and their potency is comparable or improved relative to 2, indicating that the conformational restriction in the C2 acyl side chain is achievable. A cocrystal X-ray structure of the α-ketoheterocycle 12 bound to a humanized variant of rat FAAH revealed its binding details, confirmed that the (S)-enantiomer is the bound active inhibitor, shed light on the origin of the enantiomeric selectivity, and confirmed that the catalytic Ser241 is covalently bound to the electrophilic carbonyl as a deprotonated hemiketal. Preliminary in vivo characterization of the inhibitors 12 and 14 is reported demonstrating that they raise brain anandamide levels following either intraperitoneal (ip) or oral (po) administration indicative of effective in vivo FAAH inhibition. Significantly, the oral administration of 12 caused dramatic accumulation of anandamide in the brain, with peak levels achieved between 1.5 and 3 h, and these elevations were maintained over 9 h. Additional studies of these two representative members of the series (12 and 14) in models of thermal hyperalgesia and neuropathic pain are reported, including the demonstration that 12 administered orally significantly attenuated mechanical (>6 h) and cold (>9 h) allodynia for sustained periods consistent with its long-acting effects in raising the endogenous concentration of anandamide.

Rimonabant reduces keratinocyte viability by induction of apoptosis and exerts topical anti-inflammatory activity in mice

BACKGROUND AND PURPOSE

There is growing evidence that the cannabinoid CB(1) receptor antagonist, rimonabant (SR141716) exerts potential anti-proliferative and anti-inflammatory actions. Here, we have assessed the effects of rimonabant in vitro in murine immortalized keratinocytes and in vivo by assaying the topical anti-inflammatory activity.

EXPERIMENTAL APPROACH

Cell viability and death in a keratinocyte cell line (C5N cells) were measured by Trypan blue exclusion assay and cytotoxicity by sulphorhodamine B test. Cell cycle progression was assessed by flow cytometry and the expression of apoptotic and anti-apoptotic markers, cyclins, pathways of signal transduction and CB1 receptor levels were evaluated by Western blot. The topical anti-inflammatory properties of rimonabant were analysed by inhibition of croton oil-induced ear dermatitis in mice.

KEY RESULTS

Rimonabant reduced cell viability and induced apoptosis as shown by the enhanced number of cells in the subG0 phase of the cell cycle, the expression of Bax and reduced levels of Bcl-2 and X-inhibitor of apoptosis protein. In addition, reduced levels of phosphorylated serine/threonine protein kinase Akt and nuclear factor-kappa B were detected associated with regulation of total nuclear factor-kappa B and inhibitor of kappa B-α, phosphorylated inhibitor of kappa B-α, cyclins D1, E and A. In croton oil-induced ear dermatitis, rimonabant significantly reduced oedema and leukocyte infiltrate.

CONCLUSIONS AND IMPLICATIONS

Rimonabant reduced cell viability, inducing cell death in keratinocytes and decreased croton oil-induced ear dermatitis. Our findings suggest a potential application of rimonabant as a topical anti-inflammatory drug. We did not assess the involvement of CB(1) receptors in these effects of rimonabant.

Inhibition of basal and ultraviolet B-induced melanogenesis by cannabinoid CB(1) receptors: a keratinocyte-dependent effect

Ultraviolet radiation is the major environmental insult to the skin and stimulates the synthesis of melanin in melanocytes, which then distribute it to the neighboring keratinocytes where it confers photo-protection. Skin color results from the paracrine interaction between these two cell types. Recent studies suggest that endocannabinoids are potential mediators in the skin. Here, we investigated whether cannabinoid drugs play a role in melanogenesis and if ultraviolet radiation modifies the cutaneous endocannabinoid system. We used human melanotic melanoma cell line (SK-mel-1) in monoculture or co-culture with human keratinocytes (HaCat). Endocannabinoid levels, cannabinoid receptors expression, and melanin content were evaluated under basal conditions and after ultraviolet-B irradiation (311 nm). We provide evidence that human melanoma cells (SK-mel-1) express CB(1) receptors, and when in co-culture with keratinocytes (HaCat), the selective CB(1) receptor agonist arachidonyl-2-chloroethylamide (ACEA 1 and 10 μM) inhibited (by 33.4 and 37.3%, respectively) basal melanogenesis. In addition, ultraviolet-B-induced melanogenesis in co-cultures was abolished by ACEA 10 μM. Both ACEA inhibitory effects were reversed by AM251 (1 μM), a selective CB(1) antagonist. Furthermore, ultraviolet-B radiation increased endocannabinoids levels only in keratinocytes, whereas CB(1) cannabinoid receptor expression was up-regulated only in melanoma cells. Our results collectively suggest that ultraviolet radiation activates paracrine CB(1)-mediated endocannabinoid signaling to negatively regulate melanin synthesis. The endocannabinoid system in the skin may be a possible target for future therapies in pigmentary disorders.

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

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

The endocannabinoid 2-arachidonoyl-glycerol activates human neutrophils: critical role of its hydrolysis and de novo leukotriene B4 biosynthesis

Although endocannabinoids are important players in nociception and obesity, their roles as immunomodulators remain elusive. The main endocannabinoids described to date, namely 2-arachidonoyl-glycerol (2-AG) and arachidonyl-ethanolamide (AEA), induce an intriguing profile of pro- and anti-inflammatory effects. This could relate to cell-specific cannabinoid receptor expression and/or the action of endocannabinoid-derived metabolites. Importantly, 2-AG and AEA comprise a molecule of arachidonic acid (AA) in their structure and are hydrolyzed rapidly. We postulated the following: 1) the released AA from endocannabinoid hydrolysis would be metabolized into eicosanoids; and 2) these eicosanoids would mediate some of the effects of endocannabinoids. To confirm these hypotheses, experiments were performed in which freshly isolated human neutrophils were treated with endocannabinoids. Unlike AEA, 2-AG stimulated myeloperoxidase release, kinase activation, and calcium mobilization by neutrophils. Although 2-AG did not induce the migration of neutrophils, it induced the release of a migrating activity for neutrophils. 2-AG also rapidly (1 min) induced a robust biosynthesis of leukotrienes, similar to that observed with AA. The effects of 2-AG were not mimicked nor prevented by cannabinoid receptor agonists or antagonists, respectively. Finally, the blockade of either 2-AG hydrolysis, leukotriene (LT) B(4) biosynthesis, or LTB(4) receptor 1 activation prevented all the effects of 2-AG on neutrophil functions. In conclusion, we demonstrated that 2-AG potently activates human neutrophils. This is the consequence of 2-AG hydrolysis, de novo LTB(4) biosynthesis, and an autocrine activation loop involving LTB(4) receptor 1.

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.

Deficiency of CB2 cannabinoid receptor in mice improves insulin sensitivity but increases food intake and obesity with age

AIMS/HYPOTHESIS

The endocannabinoid system has a key role in energy storage and metabolic disorders. The endocannabinoid receptor 2 (CB2R), which was first detected in immune cells, is present in the main peripheral organs responsible for metabolic control. During obesity, CB2R is involved in the development of adipose tissue inflammation and fatty liver. We examined the long-term effects of CB2R deficiency in glucose metabolism.

METHODS

Mice deficient in CB2R (Cb2 ( -/- ) [also known as Cnr2]) were studied at different ages (2-12 months). Two-month-old Cb2 (-/-) and wild-type mice were treated with a selective CB2R antagonist or fed a high-fat diet.

RESULTS

The lack of CB2R in Cb2 (-/-) mice led to greater increases in food intake and body weight with age than in Cb2 (+/+) mice. However, 12-month-old obese Cb2 (-/-) mice did not develop insulin resistance and showed enhanced insulin-stimulated glucose uptake in skeletal muscle. In agreement, adipose tissue hypertrophy was not associated with inflammation. Similarly, treatment of wild-type mice with CB2R antagonist resulted in improved insulin sensitivity. Moreover, when 2-month-old Cb2 (-/-) mice were fed a high-fat diet, reduced body weight gain and normal insulin sensitivity were observed.

CONCLUSIONS/INTERPRETATION

These results indicate that the lack of CB2R-mediated responses protected mice from both age-related and diet-induced insulin resistance, suggesting that these receptors may be a potential therapeutic target in obesity and insulin resistance.

Protective role of palmitoylethanolamide in contact allergic dermatitis

BACKGROUND

Palmitoylethanolamide (PEA) is an anti-inflammatory mediator that enhances the activation by anandamide (AEA) of cannabinoid receptors and transient receptor potential vanilloid type-1 (TRPV1) channels, and directly activates peroxisome proliferator-activated receptor-alpha (PPAR-alpha). In mice, 2,4-dinitrofluorobenzene (DNFB)-induced contact allergic dermatitis (CAD) in inflamed ears is partly mediated by the chemokine Monocyte Chemotactic Protein-2 (MCP-2) and accompanied by elevation of AEA levels. No datum is available on PEA regulation and role in CAD.

OBJECTIVE

We examined whether PEA is produced during DNFB-induced CAD, and if it has any direct protective action in keratinocytes in vitro.

METHODS

Eight- to ten-week-old female C57BL/6J wild-type and CB(1)/CB(2) double knock-out mice were used to measure PEA levels and the expression of TRPV1, PPAR-alpha receptors and enzymes responsible for PEA biosynthesis and degradation. Human keratinocytes (HaCaT) cells were stimulated with polyinosinic polycytidylic acid [poly-(I:C)], and the expression and release of MCP-2 were measured in the presence of PEA and antagonists of its proposed receptors.

RESULTS

2,4-Dinitrofluorobenzene increased ear skin PEA levels and up-regulated TRPV1, PPAR-alpha and a PEA-biosynthesizing enzyme in ear keratinocytes. In HaCaT cells, stimulation with poly-(I:C) elevated the levels of both PEA and AEA, and exogenous PEA (10 microM) inhibited poly-(I:C)-induced expression and release of MCP-2 in a way reversed by antagonism at TRPV1, but not PPAR-alpha. PEA (5-10 mg/kg, intraperitoneal) also inhibited DNFB-induced ear inflammation in mice in vivo, in a way attenuated by TRPV1 antagonism.

CONCLUSIONS

We suggest that PEA is an endogenous protective agent against DNFB-induced keratinocyte inflammation and could be considered for therapeutic use against CAD.

Fatty acid amide hydrolase shapes NKT cell responses by influencing the serum transport of lipid antigen in mice

The potent regulatory properties of NKT cells render this subset of lipid-specific T cells a promising target for immunotherapeutic interventions. The marine sponge glycolipid alpha-galactosylceramide (alphaGalCer) is the proto-typic NKT cell agonist, which elicits this function when bound to CD1d. However, our understanding of the in vivo properties of NKT cell agonists and the host factors that control their bioactivity remains very limited. In this report, we isolated the enzyme fatty acid amide hydrolase (FAAH) from mouse serum as an alphaGalCer-binding protein that modulates the induction of key effector functions of NKT cells in vivo. FAAH bound alphaGalCer in vivo and in vitro and was required for the efficient targeting of lipid antigens for CD1d presentation. Immunization of Faah-deficient mice with alphaGalCer resulted in a reduced systemic cytokine production, but enhanced expansion of splenic NKT cells. This distinct NKT response conferred a drastically increased adjuvant effect and strongly promoted protective CTL responses. Thus, our findings identify not only the presence of FAAH in normal mouse serum, but also its critical role in the tuning of immune responses to lipid antigens by orchestrating their transport and targeting for NKT cell activation. Our results suggest that the serum transport of lipid antigens directly shapes the quality of NKT cell responses, which could potentially be modulated in support of novel vaccination strategies.

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.

Regulation of inflammatory pain by inhibition of fatty acid amide hydrolase

Although cannabinoids are efficacious in laboratory animal models of inflammatory pain, their established cannabimimetic actions diminish enthusiasm for their therapeutic development. Conversely, fatty acid amide hydrolase (FAAH), the chief catabolic enzyme regulating the endogenous cannabinoid N-arachidonoylethanolamine (anandamide), has emerged as an attractive target for treating pain and other conditions. Here, we tested WIN 55212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de)-1,4-benzoxazin-6-yl]-1-napthalenylmethanone], a cannabinoid receptor agonist, and genetic deletion or pharmacological inhibition of FAAH in the lipopolysaccharide (LPS) mouse model of inflammatory pain. WIN 55212-2 significantly reduced edema and hot-plate hyperalgesia caused by LPS infusion into the hind paws, although the mice also displayed analgesia and other central nervous system effects. FAAH(-/-) mice exhibited reduced paw edema and hyperalgesia in this model without apparent cannabimimetic effects. Transgenic mice expressing FAAH exclusively on neurons continued to display the antiedematous, but not the antihyperalgesic, phenotype. The CB(2) cannabinoid receptor (CB(2)) antagonist SR144528 [N-[(1S)-endo-1,3,3-trimethyl bicyclo [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide] blocked this non-neuronal, anti-inflammatory phenotype, and the CB(1) cannabinoid receptor (CB(1)) antagonist rimonabant [SR141716, N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide] blocked the antihyperalgesic phenotype. The FAAH inhibitor URB597 [cyclohexylcarbamic acid 3'-carbamoylbiphenyl-3-yl ester] attenuated the development of LPS-induced paw edema and reversed LPS-induced hyperalgesia through the respective CB(2) and CB(1) mechanisms of action. However, the transient receptor potential vanilloid type 1 antagonist capsazepine did not affect either the antihyperalgesic or antiedematous effects of URB597. Finally, URB597 attenuated levels of the proinflammatory cytokines interleukin-1beta and tumor necrosis factor alpha in LPS-treated paws. These findings demonstrate that simultaneous elevations in non-neuronal and neuronal endocannabinoid signaling are possible through inhibition of a single enzymatic target, thereby offering a potentially powerful strategy for treating chronic inflammatory pain syndromes that operate at multiple levels of anatomical integration.

Synthesis and evaluation of paracetamol esters as novel fatty acid amide hydrolase inhibitors

Fatty acid amide hydrolase (FAAH) is the key hydrolytic enzyme for the endogenous cannabinoid receptor ligand anandamide. The synthesis and evaluation for their FAAH inhibitory activities of a series of 18 paracetamol esters are described. Structure-activity relationship studies indicated that the ester (33) with a 2-(4-(2-(trifluoromethyl)pyridin-4-ylamino)phenyl)acetic acid substituent was the most potent analogue in this series. The compound inhibited FAAH activity in a competitive manner with a K(i) value of 0.16 microM. The compound was also able to inhibit the FAAH activity in rat basophilic leukemia cells as assessed by measuring either the hydrolysis of anandamide, the FAAH-dependent cellular accumulation of anandamide, or the FAAH-dependent recycling of tritium to the cell membranes. The compound also inhibited the activity of monoacylglycerol lipase (MGL), the enzyme responsible for the hydrolysis of the endogenous cannabinoid receptor ligand 2-arachidonoylglycerol, with an IC(50) value of 1.9 microM. It is concluded that the compound may be a useful template for the design of potent novel inhibitors of FAAH.

Falcarinol is a covalent cannabinoid CB1 receptor antagonist and induces pro-allergic effects in skin

The skin irritant polyyne falcarinol (panaxynol, carotatoxin) is found in carrots, parsley, celery, and in the medicinal plant Panax ginseng. In our ongoing search for new cannabinoid (CB) receptor ligands we have isolated falcarinol from the endemic Sardinian plant Seseli praecox. We show that falcarinol exhibits binding affinity to both human CB receptors but selectively alkylates the anandamide binding site in the CB(1) receptor (K(i)=594nM), acting as covalent inverse agonist in CB(1) receptor-transfected CHO cells. Given the inherent instability of purified falcarinol we repeatedly isolated this compound for biological characterization and one new polyyne was characterized. In human HaCaT keratinocytes falcarinol increased the expression of the pro-allergic chemokines IL-8 and CCL2/MCP-1 in a CB(1) receptor-dependent manner. Moreover, falcarinol inhibited the effects of anandamide on TNF-alpha stimulated keratinocytes. In vivo, falcarinol strongly aggravated histamine-induced oedema reactions in skin prick tests. Both effects were also obtained with the CB(1) receptor inverse agonist rimonabant, thus indicating the potential role of the CB(1) receptor in skin immunopharmacology. Our data suggest anti-allergic effects of anandamide and that falcarinol-associated dermatitis is due to antagonism of the CB(1) receptor in keratinocytes, leading to increased chemokine expression and aggravation of histamine action.

The effects of targeted deletion of cannabinoid receptors CB1 and CB2 on intranasal sensitization and challenge with adjuvant-free ovalbumin

The mechanisms by which cannabinoid receptors CB(1) and CB(2) modulate immune function are not fully elucidated. Critical tools for the determination of the role of both receptors in the immune system are CB(1)/CB(2) double null mice (CB(1)/CB(2) null), and previous studies have shown that CB(1)/CB(2) null mice exhibit exaggerated responses to various immunological stimuli. The objective of these studies was to determine the magnitude to which CB(1)/CB(2) null mice responded to the respiratory allergen ovalbumin (OVA) as compared with wild-type C57BL/6 mice. The authors determined that in the absence of adjuvant, both wild-type and CB(1)/CB(2) null mice mounted a marked response to intranasally instilled OVA as assessed by inflammatory cell infiltrate in the bronchoalveolar lavage fluid (BALF), eosinophilia, induction of mucous cell metaplasia, and IgE production. Many of the endpoints measured in response to OVA were similar in wild-type versus CB(1)/CB(2) null mice, with exceptions being modest reductions in OVA-induced IgE and attenuation of BALF neutrophilia in CB(1)/CB(2) null mice as compared with wild-type mice. These results suggest that T-cell responses are not universally exaggerated in CB(1)/CB(2) null mice.

Immunoactive effects of cannabinoids: considerations for the therapeutic use of cannabinoid receptor agonists and antagonists

The active constituents of Cannabis sativa have been used for centuries as recreational drugs and medicinal agents. Today, marijuana is the most prevalent drug of abuse in the United States and, conversely, therapeutic use of marijuana constituents are gaining mainstream clinical and political acceptance. Given the documented contributions of endocannabinoid signaling to a range of physiological systems, including cognitive function, and the control of eating behaviors, it is unsurprising that cannabinoid receptor agonists and antagonists are showing significant clinical potential. In addition to the neuroactive effects of cannabinoids, an emerging body of data suggests that both endogenous and exogenous cannabinoids are potently immunoactive. The central premise of this review article is that the immunological effects of cannabinoids should be considered in the context of each prescribing decision. We present evidence that the immunological effects of cannabinoid receptor agonists and antagonists are highly relevant to the spectrum of disorders for which cannabinoid therapeutics are currently offered.

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.

2,3-Dihydro-1-benzofuran derivatives as a series of potent selective cannabinoid receptor 2 agonists: design, synthesis, and binding mode prediction through ligand-steered modeling

We recently discovered and reported a series of N-alkyl-isatin acylhydrazone derivatives that are potent cannabinoid receptor 2 (CB(2)) agonists. In an effort to improve the druglike properties of these compounds and to better understand and improve the treatment of neuropathic pain, we designed and synthesized a new series of 2,3-dihydro-1-benzofuran derivatives bearing an asymmetric carbon atom that behave as potent selective CB(2) agonists. We used a multidisciplinary medicinal chemistry approach with binding mode prediction through ligand-steered modeling. Enantiomer separation and configuration assignment were carried out for the racemic mixture for the most selective compound, MDA7 (compound 18). It appeared that the S enantiomer, compound MDA104 (compound 33), was the active enantiomer. Compounds MDA42 (compound 19) and MDA39 (compound 30) were the most potent at CB(2). MDA42 was tested in a model of neuropathic pain and exhibited activity in the same range as that of MDA7. Preliminary ADMET studies for MDA7 were performed and did not reveal any problems.

Cannabinoid system in the skin - a possible target for future therapies in dermatology

Cannabinoids and their derivatives are group of more than 60 biologically active chemical agents, which have been used in natural medicine for centuries. The major agent of exogenous cannabinoids is Delta(9)-tetrahydrocannabinol (Delta(9)-THC), natural psychoactive ingredient of marijuana. However, psychoactive properties of these substances limited their use as approved medicines. Recent discoveries of endogenous cannabinoids (e.g. arachidonoylethanolamide, 2-arachidonoylglycerol or palmithyloethanolamide) and their receptors initiated discussion on the role of cannabinoid system in physiological conditions as well as in various diseases. Based on the current knowledge, it could be stated that cannabinoids are important mediators in the skin, however their role have not been well elucidated yet. In our review, we summarized the current knowledge about the significant role of the cannabinoid system in the cutaneous physiology and pathology, pointing out possible future therapeutic targets.