Biosynthesis of anandamide and related acylethanolamides in mouse J774 macrophages and N18 neuroblastoma cells

N-Stearoylethanolamine Inhibits Integrin-Mediated Activation, Aggregation, and Adhesion of Human Platelets

N-stearoylethanolamine (NSE), a lipid mediator that belongs to the N-acylethanolamine (NAE) family, has anti-inflammatory, antioxidant, and membranoprotective actions. In contrast to other NAEs, NSE does not interact with cannabinoid receptors. The exact mechanism of its action remains unclear. The aim of this study is to evaluate the action of NSE on activation, aggregation, and adhesion of platelets that were chosen as a model of cellular response. Aggregation of platelets was measured to analyze the action of NSE (10^-6-10^-10 M) on platelet reactivity. Changes in granularity and shape of resting platelets and platelets stimulated with ADP in the presence of NSE were monitored by flow cytometry, and platelet deganulation was monitored by spectrofluorimetry. In vivo studies were performed using obese insulin-resistant rats. Binding of fibrinogen to the GPIIb/IIIa receptor was estimated using indirect ELISA and a scanning electron microscopy (SEM). It was found that NSE inhibits the activation and aggregation of human platelets. Our results suggest that NSE may decrease the activation and subsequent aggregation of platelets induced by ristocetin, epinephrine, and low doses of ADP. NSE also reduced the binding of fibrinogen to GPIIb/IIIa on activated platelets. These effects could be explained by the inhibition of platelet activation mediated by integrin receptors: the GPIb-IX-V complex for ristocetin-induced activation and GPIIb/IIIa when epinephrine and low doses of ADP were applied. The anti-platelet effect of NSE complements its anti-inflammatory effect and allows us to prioritize studies of NSE as a potent anti-thrombotic agent. SIGNIFICANCE STATEMENT: N-stearoylethanolamine (NSE) was shown to possess inhibitory action on platelet activation, adhesion, and aggregation. The mechanism of inhibition possibly involves integrin receptors. This finding complements the known anti-inflammatory effects of NSE.

N-acylethanolamide metabolizing enzymes are upregulated in human neural progenitor-derived neurons exposed to sub-lethal oxidative stress

N-acyl amides (NAAs) are a class of lipids that consist of an acyl group N-linked to an amino acid, neurotransmitter, taurine or ethanolamide group (N-acylethanolamines or NAEs) and include some endocannabinoids (eCB) such as anandamide. These lipids are synthesized in a wide variety of organisms and in multiple cell types, including neurons. NAEs are involved in numerous cellular and physiological processes and their concentrations are elevated in response to ischemia and physical trauma to play a role in neuroprotection. The neuroprotective properties of eCB NAEs make the protein targets of these compounds attractive targets for clinical intervention for a variety of conditions. The most promising of these targets include cannabinoid receptor type 1 (CB1), cannabinoid receptor type 2 (CB2), fatty acid amide hydrolase (FAAH), N-acylethanolamine acid amidase (NAAA), and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). Further characterization of these targets in a more contemporary model system of neurodegeneration and neuroprotection will allow us to fully describe their role and mechanism of action in neuroprotection against oxidative stress leading to better utilization in the clinical setting. Human stem cell-derived or human neural progenitor cell-derived cells, such as ReN cells, have become more utilized for the study of human neuronal development and neurodegenerative diseases. ReN cells can be easily differentiated thereby circumventing the need for using transformed cell lines and primary neurons as cell model systems. In this study, we determined whether ReN cells, a superior cell model system for studying neurodevelopment, differentiation, and neuroprotection, express proteins involved in canonical eCB NAE signaling and whether oxidative stress can induce their expression. We determined that sublethal oxidative stress upregulates the expression of all eCB proteins tested. In addition, we determined that oxidative stress increases the nuclear localization of FAAH, and to a lesser extent, NAAA and NAPE-PLD. This study is a first step toward determining how oxidative stress affects CB1, CB2, FAAH, NAAA, and NAPE-PLD expression and their potential defense against oxidative stress. As such, our data is important for further determining the role of eCB metabolizing proteins and eCB receptors against oxidative stress.

Microglial Inflammatory-Metabolic Pathways and Their Potential Therapeutic Implication in Major Depressive Disorder

Increasing evidence supports the notion that neuroinflammation plays a critical role in the etiology of major depressive disorder (MDD), at least in a subset of patients. By virtue of their capacity to transform into reactive states in response to inflammatory insults, microglia, the brain's resident immune cells, play a pivotal role in the induction of neuroinflammation. Experimental studies have demonstrated the ability of microglia to recognize pathogens or damaged cells, leading to the activation of a cytotoxic response that exacerbates damage to brain cells. However, microglia display a wide range of responses to injury and may also promote resolution stages of inflammation and tissue regeneration. MDD has been associated with chronic priming of microglia. Recent studies suggest that altered microglial morphology and function, caused either by intense inflammatory activation or by senescence, may contribute to depression and associated impairments in neuroplasticity. In this context, modifying microglia phenotype by tuning inflammatory pathways might have important translational relevance to harness neuroinflammation in MDD. Interestingly, it was recently shown that different microglial phenotypes are associated with distinct metabolic pathways and analysis of the underlying molecular mechanisms points to an instrumental role for energy metabolism in shaping microglial functions. Here, we review various canonical pro-inflammatory, anti-inflammatory and metabolic pathways in microglia that may provide new therapeutic opportunities to control neuroinflammation in brain disorders, with a strong focus on MDD.

Anti-Inflammatory Activity of a CB2 Selective Cannabinoid Receptor Agonist: Signaling and Cytokines Release in Blood Mononuclear Cells

The endocannabinoid system (ECS) exerts immunosuppressive effects, which are mostly mediated by cannabinoid receptor 2 (CBR2), whose expression on leukocytes is higher than CBR1, mainly localized in the brain. Targeted CBR2 activation could limit inflammation, avoiding CBR1-related psychoactive effects. Herein, we evaluated in vitro the biological activity of a novel, selective and high-affinity CBR2 agonist, called JT11, studying its potential CBR2-mediated anti-inflammatory effect. Trypan Blue and MTT assays were used to test the cytotoxic and anti-proliferative effect of JT11 in Jurkat cells. Its pro-apoptotic activity was investigated analyzing both cell cycle and poly PARP cleavage. Finally, we evaluated its impact on LPS-induced ERK1/2 and NF-kB-p65 activation, TNF-α, IL-1β, IL-6 and IL-8 release in peripheral blood mononuclear cells (PBMCs) from healthy donors. Selective CB2R antagonist SR144528 and CBR2 knockdown were used to further verify the selectivity of JT11. We confirmed selective CBR2 activation by JT11. JT11 regulated cell viability and proliferation through a CBR2-dependent mechanism in Jurkat cells, exhibiting a mild pro-apoptotic activity. Finally, it reduced LPS-induced ERK1/2 and NF-kB-p65 phosphorylation and pro-inflammatory cytokines release in human PBMCs, proving to possess in vitro anti-inflammatory properties. JT11 as CBR2 ligands could enhance ECS immunoregulatory activity and our results support the view that therapeutic strategies targeting CBR2 signaling could be promising for the treatment of chronic inflammatory diseases.

Cannabinoid Receptor 1 and 2 Signaling Pathways Involved in Sepsis

ABSTRACT

Sepsis is defined as a life-threatening organ dysfunction, caused by a dysregulated host response to an infection and can progress to septic shock, which represents a major challenge in critical care with a high mortality rate. Currently, there is no definitive treatment available for the dysregulated immune response in sepsis. Therefore, a better understanding of the pathophysiological mechanisms may be useful for elucidating the molecular basis of sepsis and may contribute to the development of new therapeutic strategies. The endocannabinoid system is an emerging research topic for the modulation of the host immune response under various pathological conditions. Cannabinoid receptors include the cannabinoid type 1 receptor (CB1) and the cannabinoid type 2 receptor (CB2). This review addresses the main functionality of CB1 and CB2 in sepsis, which can contribute to a better understanding about the pathophysiology of sepsis. Specifically, we discuss the role of CB1 in the cardiovascular system which is one of the biological systems that are strongly affected by sepsis and septic shock. We are also reviewing the role of CB2 in sepsis, specially CB2 activation, which exerts anti-inflammatory activities with potential benefit in sepsis.

The Endocannabinoid System: A Bridge between Alzheimer's Disease and Gut Microbiota

Alzheimer's disease (AD) is a neurodegenerative disease that progresses from mild cognitive impairment to severe dementia over time. The main clinical hallmarks of the disease (e.g., beta-amyloid plaques and neurofibrillary tangles) begin during preclinical AD when cognitive deficits are not yet apparent. Hence, a more profound understanding of AD pathogenesis is needed to develop new therapeutic strategies. In this context, the endocannabinoid (eCB) system and the gut microbiome are increasingly emerging as important players in maintaining the general homeostasis and the health status of the host. However, their interaction has come to light just recently with gut microbiota regulating the eCB tone at both receptor and enzyme levels in intestinal and adipose tissues. Importantly, eCB system and gut microbiome, have been suggested to play a role in AD in both animal and human studies. Therefore, the microbiome gut-brain axis and the eCB system are potential common denominators in the AD physiopathology. Hence, the aim of this review is to provide a general overview on the role of both the eCB system and the microbiome gut-brain axis in AD and to suggest possible mechanisms that underlie the potential interplay of these two systems.

The Interplay between the Immune and the Endocannabinoid Systems in Cancer

The therapeutic potential of Cannabis sativa has been recognized since ancient times. Phytocannabinoids, endocannabinoids and synthetic cannabinoids activate two major G protein-coupled receptors, subtype 1 and 2 (CB1 and CB2). Cannabinoids (CBs) modulate several aspects of cancer cells, such as apoptosis, autophagy, proliferation, migration, epithelial-to-mesenchymal transition and stemness. Moreover, agonists of CB1 and CB2 receptors inhibit angiogenesis and lymphangiogenesis in vitro and in vivo. Low-grade inflammation is a hallmark of cancer in the tumor microenvironment (TME), which contains a plethora of innate and adaptive immune cells. These cells play a central role in tumor initiation and growth and the formation of metastasis. CB2 and, to a lesser extent, CB1 receptors are expressed on a variety of immune cells present in TME (e.g., T cells, macrophages, mast cells, neutrophils, NK cells, dendritic cells, monocytes, eosinophils). The activation of CB receptors modulates a variety of biological effects on cells of the adaptive and innate immune system. The expression of CB2 and CB1 on different subsets of immune cells in TME and hence in tumor development is incompletely characterized. The recent characterization of the human cannabinoid receptor CB2-G_i signaling complex will likely aid to design potent and specific CB2/CB1 ligands with therapeutic potential in cancer.

Synthesis, Quantification, and Characterization of Fatty Acid Amides from In Vitro and In Vivo Sources

Fatty acid amides are a diverse family of underappreciated, biologically occurring lipids. Herein, the methods for the chemical synthesis and subsequent characterization of specific members of the fatty acid amide family are described. The synthetically prepared fatty acid amides and those obtained commercially are used as standards for the characterization and quantification of the fatty acid amides produced by biological systems, a fatty acid amidome. The fatty acid amidomes from mouse N₁₈TG₂ cells, sheep choroid plexus cells, Drosophila melanogaster, Bombyx mori, Apis mellifera, and Tribolium castaneum are presented.

High and Mighty? Cannabinoids and the microbiome in pain

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In this review, we will focus on the potential role of the endogenous cannabinoids in modulating microbiota-driven changes in peripheral and central pain processing.

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We also focus on the overlap in mechanisms whereby commensal gut microbiota and endocannabinoid ligands can regulate inflammation and further aim to exploit our understanding of their role in microbiota-gut-brain axis communication in pain processing.

Within the human gut, we each harbour a unique ecosystem represented by trillions of microbes that contribute to our health and wellbeing. These gut microbiota form part of a complex network termed the microbiota-gut-brain axis along with the enteric nervous system, sympathetic and parasympathetic divisions of the autonomic nervous system, and neuroendocrine and neuroimmune components of the central nervous system. Through endocrine, immune and neuropeptide/neurotransmitter systems, the microbiota can relay information about health status of the gut. This in turn can profoundly impact neuronal signalling not only in the periphery, but also in the brain itself and thus impact on emotional systems and behavioural responses. This may be true for pain, as the top-down facilitation or inhibition of pain processing occurs at a central level, while ascending afferent nociceptive information from the viscera and systemic areas travel through the periphery and spinal cord to the brain. The endogenous cannabinoid receptors are ubiquitously expressed throughout the gut, periphery and in brain regions associated with pain responding, and represent targets for endogenous and exogenous manipulation. In this review, we will focus on the potential role of the endogenous cannabinoids in modulating microbiota-driven changes in peripheral and central pain processing. We also focus on the overlap in mechanisms whereby commensal gut microbiota and endocannabinoid ligands can regulate inflammation and further aim to exploit our understanding of their role in microbiota-gut-brain axis communication in pain processing.

The Immune Endocannabinoid System of the Tumor Microenvironment

Leukocytes are part of the tumor microenvironment (TME) and are critical determinants of tumor progression. Because of the immunoregulatory properties of cannabinoids, the endocannabinoid system (ECS) may have an important role in shaping the TME. Members of the ECS, an entity that consists of cannabinoid receptors, endocannabinoids and their synthesizing/degrading enzymes, have been associated with both tumor growth and rejection. Immune cells express cannabinoid receptors and produce endocannabinoids, thereby forming an “immune endocannabinoid system”. Although in vitro effects of exogenous cannabinoids on immune cells are well described, the role of the ECS in the TME, and hence in tumor development and immunotherapy, is still elusive. This review/opinion discusses the possibility that the “immune endocannabinoid system” can fundamentally influence tumor progression. The widespread influence of cannabinoids on immune cell functions makes the members of the ECS an interesting target that could support immunotherapy.

The endocannabinoid signaling pathway as an emerging target in pharmacotherapy, earmarking mitigation of destructive events in rheumatoid arthritis

Rheumatoid arthritis is an inflammatory autoimmune disease, characterized by synovial proliferation, destruction to articular cartilage and severe pain. The cannabinoids obtained from Cannabis sativa exhibited their actions via cannabinoid-1 and -2 receptors, which also provides a platform for endocannabinoids to act. The endocannabinoid system comprises endocannabinoid molecules involved in signaling processes, along with G-protein coupled receptors and enzymes associated with ligand biosynthesis, activation and degradation. The action of endocannabinoid system in immune system regulation, via primary CB2 activation, followed by inhibition of production of pro-inflammatory cytokines, auto-antibodies and MMPs, FLSs proliferation and T-cell mediated immune response, are elaborated as potential therapeutic regimes in rheumatoid arthritis. The involvement of endocannabinoid system in immune cells like, B cells, T cells and macrophages, as well as regulatory actions on sensory noniceptors to ameliorate pain is significantly highlighted in the review, elaborating the actions of endocannabinoid signaling in mitigating the disease events. The review also focuses on enhancement of endocannabinoid tone, either by inhibiting the degradation enzymes, like FAAH, MAGL, COX, CytP450, LOX, etc. or by retarding cellular uptake processes. Moreover, the review portrays the optimizing role of endocannabinoid system, in abbreviating the symptoms and complications of rheumatoid arthritis in patients and mitigating inflammation, pain and immune mediated effects significantly.

The fundamental role of the endocannabinoid system in endometrium and placenta: implications in pathophysiological aspects of uterine and pregnancy disorders

BACKGROUND

The endocannabinoid system (ECS) consists of the cannabinoid receptors CB1 and CB2, the main endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and their metabolic enzymes N-acylphosphatidylethanolamine-specific phospholipase D, fatty acid amide hydrolase, diacylglycerol lipase and monoacylglycerol lipase. This system is involved in the modulation of essential physiological processes. Its role in the reproductive system has become significantly important in recent years, given its major role in events such as gametogenesis, decidualisation, implantation and placentation.

OBJECTIVE AND RATIONALE

In this paper, we review the literature and summarize the role of the ECS elements in reproduction and their potential as early markers for diagnosis of reproductive disorders or as pharmacological targets for treatment.

SEARCH METHODS

Original research and review papers published from 1964 to June 2019 were selected in terms of relevance, reliability and quality by searching PubMed, MEDLINE and Web of Science, using the following search terms: endocannabinoid system and endometriosis; endocannabinoid system and ectopic pregnancy; endocannabinoid system and miscarriage; endocannabinoid system and pre-eclampsia; endocannabinoid system and endometrial cancer; endocannabinoid system and reproduction; endocannabinoid, endometrium; placenta; N-acylethanolamines; anandamide; 2-arachidonoylglycerol; and cannabinoids.

OUTCOMES

This review demonstrates relevant information concerning ECS alterations in endometriosis, ectopic pregnancy, miscarriage, pre-eclampsia and endometrial cancer. We highlight the importance of the endocannabinoids in endometrial and placental physiology and pathophysiology, from studies in vitro and in vivo and in clinical observations. The most studied of the endogenous cannabinoids is AEA. The levels of AEA were increased in plasma of patients with endometriosis and miscarriage, as well as in the fallopian tube of women with ectopic pregnancy and in endometrial biopsies of endometrial cancer. Changes in the pattern of expression of the cannabinoid receptor CB1 were also observed in endometrial biopsies of endometriosis, fallopian tube and decidua of patients with ectopic pregnancy and pre-eclamptic placenta. Moreover, alterations in CB2 expression have been reported in association with endometrial cancer. In general, studies on the cannabinoid signalling through CB2 and on the biological activities of the other major endocannabinoid, namely 2-AG, as well as its metabolic enzymes are scarce and avidly required.

WIDER IMPLICATIONS

The pathophysiological mechanisms involved in the described endometrial and placental pathologies are still unclear and lack the means for an early diagnosis. Based on current evidence, though alterations in ECS are demonstrated at tissue level, it is difficult to associate plasmatic changes in AEA with specific endometrial and placental diseases. Thus, pairing alterations in AEA levels with 2-AG and/or other endocannabinoid-like molecules may provide more accurate and early diagnoses. In addition, patients may benefit from new therapies that target the ECS and endocannabinoid signalling.

High Fat Diet Increases Circulating Endocannabinoids Accompanied by Increased Synthesis Enzymes in Adipose Tissue

The endocannabinoid system (ECS) controls energy balance by regulating both energy intake and energy expenditure. Endocannabinoid levels are elevated in obesity suggesting a potential causal relationship. This study aimed to elucidate the rate of dysregulation of the ECS, and the metabolic organs involved, in diet-induced obesity. Eight groups of age-matched male C57Bl/6J mice were randomized to receive a chow diet (control) or receive a high fat diet (HFD, 45% of calories derived from fat) ranging from 1 day up to 18 weeks before euthanasia. Plasma levels of the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (N-arachidonoylethanolamine, AEA), and related N-acylethanolamines, were quantified by UPLC-MS/MS and gene expression of components of the ECS was determined in liver, muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) during the course of diet-induced obesity development. HFD feeding gradually increased 2-AG (+132% within 4 weeks, P < 0.05), accompanied by upregulated expression of its synthesizing enzymes Daglα and β in WAT and BAT. HFD also rapidly increased AEA (+81% within 1 week, P < 0.01), accompanied by increased expression of its synthesizing enzyme Nape-pld, specifically in BAT. Interestingly, Nape-pld expression in BAT correlated with plasma AEA levels (R ² = 0.171, β = 0.276, P < 0.001). We conclude that a HFD rapidly activates adipose tissue depots to increase the synthesis pathways of endocannabinoids that may aggravate the development of HFD-induced obesity.

Cannabidiol's Upregulation of N-acyl Ethanolamines in the Central Nervous System Requires N-acyl Phosphatidyl Ethanolamine-Specific Phospholipase D

Introduction: Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are bioactive cannabinoids. We recently showed that acute THC administration drives region-dependent changes in the mouse brain lipidome. This study tested the hypothesis that cell lines representing cell types present in the central nervous system (CNS), neurons (N18 cells), astrocytes (C6 glioma cells), and microglia (BV2 cells) would respond differently to THC, CBD, or their combination. This experimental strategy also allowed us to test the hypothesis that THC and CBD are metabolized differently if presented in combination and to test the hypothesis that responses to CBD are not like the fatty acid amide hydrolase (FAAH) inhibitor URB597. Finally, we tested the hypothesis that CBD's CNS effects would differ in the N-acyl phosphatidyl ethanolamine-specific phospholipase D (NAPE-PLD) knockout (KO) compared to wild-type (WT) mice. Methods: N18, C6, and BV2 cells were stimulated with 1 μM THC, 1 μM CBD, 1 μM THC:CBD, 1 μM URB597, or vehicle for 2 h and lipids extracted. Adult female WT and NAPE-PLD KO mice were injected with 3 mg/kg CBD or vehicle i.p., brains collected 2 h later, eight brain regions dissected, and lipids extracted. Extracted lipids were characterized and quantified using high-pressure liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS). Results: Lipid levels in each cell type were differentially affected by THC, CBD, or THC:CBD with a few exceptions. In all cell lines, THC increased levels of arachidonic acid and CBD increased levels of N-acyl ethanolamines (NAEs), including N-arachidonoyl ethanolamine. More THC remained when cells were coincubated with CBD; however, levels of THC metabolites were cell-type dependent. CBD and URB597 caused very different lipid profiles in the cell-based assays with the primary similarity being increases in NAEs. CBD increased levels of NAEs in the WT hippocampus, cerebellum, thalamus, cortex, midbrain, and brainstem; however, NAEs did not increase in any brain region after CBD in NAPE-PLD KO mice. Conclusions: CBD and THC differentially modify the lipidome of the brain and CNS-type cell lines. Increases in NAEs observed after CBD treatment had previously been attributed to FAAH inhibition; however, data here suggest the alternative hypothesis that CBD is activating NAPE-PLD to increase NAE levels.

Bm-iAANAT and its potential role in fatty acid amide biosynthesis in Bombyx mori

The purpose of this research is to unravel the substrate specificity and kinetic properties of an insect arylalkylamine N-acyltransferase from Bombyx mori (Bm-iAANAT) and to determine if this enzyme will catalyze the formation of long chain N-acylarylalkylamides in vitro. However, the determination of substrates and products for Bm-iAANAT in vitro is no guarantee that these same molecules are substrates and products for the enzyme in the organism. Therefore, RT-PCR was performed to detect the Bm-iAANAT transcripts and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) analysis was performed on purified lipid extracts from B. mori larvae (fourth instar, Bmi4) to determine if long chain fatty acid amides are produced in B. mori. Ultimately, we found that recombinant Bm-iAANAT will utilize long-chain acyl-CoA thioesters as substrates and identified Bm-iAANAT transcripts and long-chain fatty acid amides in Bmi4. Together, these data show Bm-iAANAT will catalyze the formation of long-chain N-acylarylalkylamides in vitro and provide evidence demonstrating that Bm-iAANAT has a role in fatty acid amide biosynthesis in B. mori, as well.

Sensitization of C-fiber nociceptors in mice with sickle cell disease is decreased by local inhibition of anandamide hydrolysis

Chronic pain and hyperalgesia, as well as pain resulting from episodes of vaso-occlusion, are characteristic features of sickle cell disease (SCD) and are difficult to treat. Since there is growing evidence that increasing local levels of endocannabinoids can decrease hyperalgesia, we examined the effects of URB597, a fatty acid amide hydrolase (FAAH) inhibitor, which blocks the hydrolysis of the endogenous cannabinoid anandamide, on hyperalgesia and sensitization of cutaneous nociceptors in a humanized mouse model of SCD. Using homozygous HbSS-BERK sickle mice, we determined the effects of URB597 on mechanical hyperalgesia and on sensitization of C-fiber nociceptors in vivo. Intraplantar administration of URB597 (10 μg in 10 μL) decreased the frequency of withdrawal responses evoked by a von Frey monofilament (3.9 mN bending force) applied to the plantar hind paw. This was blocked by the CB1 receptor antagonist AM281 but not by the CB2 receptor antagonist AM630. Also, URB597 decreased hyperalgesia in HbSS-BERK/CB2R sickle mice, further confirming the role of CB1 receptors in the effects produced by URB597. Electrophysiological recordings were made from primary afferent fibers of the tibial nerve in anesthetized mice. The proportion of Aδ- and C-fiber nociceptors that exhibited spontaneous activity and responses of C-fibers to mechanical and thermal stimuli were greater in HbSS-BERK sickle mice as compared to control HbAA-BERK mice. Spontaneous activity and evoked responses of nociceptors were decreased by URB597 via CB1 receptors. It is suggested that enhanced endocannabinoid activity in the periphery may be beneficial in alleviating chronic pain associated with SCD.

Oxygenation of polyunsaturated fatty acids and oxidative stress within blood platelets

The oxygenation metabolism of arachidonic acid (ArA) has been early described in blood platelets, in particular with its conversion into the potent labile thromboxane A₂ that induces platelet aggregation and vascular smooth muscle cells contraction. In addition, the primary prostaglandins D₂ and E₂ have been mainly reported as inhibitors of platelet function. The platelet 12-lipoxygenase (12-LOX) product, i.e. the hydroperoxide 12-HpETE, appears to stimulate platelet ArA metabolism at the level of its release from membrane phospholipids through phospholipase A₂ (cPLA₂) and cyclooxygenase (COX-1) activities, the first enzymes in prostanoid production cascade. Also, 12-HpETE may regulate the oxygenation of other polyunsaturated fatty acids (PUFA) by platelets, especially that of eicosapentaenoic acid (EPA). On the other hand, the reduced product of 12-HpETE, 12-HETE, is able to antagonize TxA₂ action. This is even more obvious for the 12-LOX end-products from docosahexaenoic acid (DHA), 11- and 14-HDoHE. In addition, 12-HpETE plays a key role in platelet oxidative stress as observed in pathophysiological conditions, but may be regulated by DHA with a bimodal way according to its concentration. Other oxygenated products of PUFA, especially omega-3 PUFA, produced outside platelets may affect platelet functions as well.

The endocannabinoid system in cardiovascular function: novel insights and clinical implications

RATIONALE

Cardiovascular disease is now recognized as the number one cause of death in the world, and the size of the population at risk continues to increase rapidly. The dysregulation of the endocannabinoid (eCB) system plays a central role in a wide variety of conditions including cardiovascular disorders. Cannabinoid receptors, their endogenous ligands, as well as enzymes conferring their synthesis and degradation, exhibit overlapping distributions in the cardiovascular system. Furthermore, the pharmacological manipulation of the eCB system has effects on blood pressure, cardiac contractility, and endothelial vasomotor control. Growing evidence from animal studies supports the significance of the eCB system in cardiovascular disorders.

OBJECTIVE

To summarize the literature surrounding the eCB system in cardiovascular function and disease and the new compounds that may potentially extend the range of available interventions.

RESULTS

Drugs targeting CB1R, CB2R, TRPV1 and PPARs are proven effective in animal models mimicking cardiovascular disorders such as hypertension, atherosclerosis and myocardial infarction. Despite the setback of two clinical trials that exhibited unexpected harmful side-effects, preclinical studies are accelerating the development of more selective drugs with promising results devoid of adverse effects.

CONCLUSION

Over the last years, increasing evidence from basic and clinical research supports the role of the eCB system in cardiovascular function. Whereas new discoveries are paving the way for the identification of novel drugs and therapeutic targets, the close cooperation of researchers, clinicians and pharmaceutical companies is needed to achieve successful outcomes.

Evidence for a GPR18 Role in Diurnal Regulation of Intraocular Pressure

Purpose

The diurnal cycling of intraocular pressure (IOP) was first described in humans more than a century ago. This cycling is preserved in other species. The physiologic underpinning of this diurnal variation in IOP remains a mystery, even though elevated pressure is indicated in most forms of glaucoma, a common cause of blindness. Once identified, the system that underlies diurnal variation would represent a natural target for therapeutic intervention.

Methods

Using normotensive mice, we measured the regulation of ocular lipid species by the enzymes fatty acid amide hydrolase (FAAH) and N-arachidonoyl phosphatidylethanolamine phospholipase (NAPE-PLD), mRNA expression of these enzymes, and their functional role in diurnal regulation of IOP.

Results

We now report that NAPE-PLD and FAAH mice do not exhibit a diurnal cycling of IOP. These enzymes produce and break down acylethanolamines, including the endogenous cannabinoid anandamide. The diurnal lipid profile in mice shows that levels of most N-acyl ethanolamines and, intriguingly, N-arachidonoyl glycine (NAGly), decline at night: NAGly is a metabolite of arachidonoyl ethanolamine and a potent agonist at GPR18 that lowers intraocular pressure. The GPR18 blocker O1918 raises IOP during the day when pressure is low, but not at night. Quantitative PCR analysis shows that FAAH mRNA levels rise with pressure, suggesting that FAAH mediates the changes in pressure.

Conclusions

Our results support FAAH-dependent NAGly action at GPR18 as the physiologic basis of the diurnal variation of intraocular pressure in mice.

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

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

LINKED ARTICLES

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

Glycine N-acyltransferase-like 3 is responsible for long-chain N-acylglycine formation in N18TG2 cells

Long-chain fatty acid amides are signaling lipids found in mammals and other organisms; however, details of the metabolic pathways for the N-acylglycines and primary fatty acid amides (PFAMs) have remained elusive. Heavy-labeled precursor and subtraction lipidomic experiments in mouse neuroblastoma N18TG2 cells, a model cell line for the study of fatty acid amide metabolism, establish the biosynthetic pathways for the N-acylglycines and the PFAMs. We provide evidence that the N-acylglycines are formed by a long-chain specific glycine-conjugating enzyme, glycine N-acyltransferase-like 3 (GLYATL3). siRNA knockdown of GLYATL3 in the N18TG2 cells resulted in a decrease in the levels of the N-acylglycines and the PFAMs. This is the first report of an enzyme responsible for long-chain N-acylglycine production in cellula. The production of the PFAMs in N18TG2 cells was reported to occur by the oxidative cleavage of the N-acylglycines, as catalyzed by peptidylglycine α-amidating monooxygenase (PAM). siRNA knockdown of PAM resulted in an accumulation of [(13)C18]N-oleoylglycine and decreased levels of [(13)C18]oleamide when the N18TG2 cells were grown in the presence of [(13)C18]oleic acid. The addition of [1-(13)C]palmitate to the N18TG2 cell growth media led to the production of a family of [1-(13)C]palmitoylated fatty acid amides, consistent with the biosynthetic pathways detailed herein.

Damage-associated molecular patterns and their pathological relevance in diabetes mellitus

Diabetes, a group of metabolic and age-related diseases, is a major global health problem, the incidence of which has increased dramatically in recent decades. Type 1 diabetes mellitus (T1DM) is a complex, T cell-mediated autoimmune disease characterized by immune cell infiltration and chronic inflammation in the islets of Langerhans. Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by hyperglycemia (high blood sugar) resulting from insulin resistance and β-cell dysfunction. The involvement of inflammatory processes, such as immune cell infiltration, and chronic inflammation in the pathogenesis of diabetes is less well understood in T2DM than in T1DM. However, studies conducted in the past decade have shown a strong link between inflammation and metabolic dysfunction. They have also shown that chronic inflammation plays a key role in the pathogenesis of both T1DM and T2DM. Two immunological factors commonly contribute to the pathogenesis of diabetes: the activation of inflammasomes and the release of proinflammatory cytokines in response to damage-associated molecular patterns (DAMPs). Inflammasomes are intracellular multiprotein molecular platforms. DAMPs act as endogenous danger signals. Here, we review current research on the function(s) of inflammasomes and DAMPs and discuss their pathological relevance and therapeutic implications in diabetes.

Regulation of inflammation by cannabinoids, the endocannabinoids 2-arachidonoyl-glycerol and arachidonoyl-ethanolamide, and their metabolites

2-Arachidonoyl-glycerol (2-AG) and arachidonyl-ethanolamide (AEA) are endocannabinoids that have been implicated in many physiologic disorders, including obesity, metabolic syndromes, hepatic diseases, pain, neurologic disorders, and inflammation. Their immunomodulatory effects are numerous and are not always mediated by cannabinoid receptors, reflecting the presence of an arachidonic acid (AA) molecule in their structure, the latter being the precursor of numerous bioactive lipids that are pro- or anti-inflammatory. 2-AG and AEA can thus serve as a source of AA but can also be metabolized by most eicosanoid biosynthetic enzymes, yielding additional lipids. In this regard, enhancing endocannabinoid levels by using endocannabinoid hydrolysis inhibitors is likely to augment the levels of these lipids that could regulate inflammatory cell functions. This review summarizes the metabolic pathways involved in the biosynthesis and metabolism of AEA and 2-AG, as well as the biologic effects of the 2-AG and AEA lipidomes in the regulation of inflammation.

Minireview: From the bench, toward the clinic: therapeutic opportunities for cannabinoid receptor modulation

The effects of cannabinoids have been known for centuries and over the past several decades two G protein-coupled receptors, CB1 and CB2, that are responsible for their activity have been identified. Endogenous lipid-derived cannabinergic agents have been found, biosynthetic and catabolic machinery has been characterized, and synthetic agents have been designed to modulate these receptors. Selective agents including agonists, antagonists, inverse agonists, and novel allosteric modulators targeting either CB1 or CB2 have been developed to inhibit or augment their basal tone. As a result, the role these receptors play in human physiology and their potential therapeutic applications in disease states are being elucidated. The CB1 receptor, although ubiquitous, is densely expressed in the brain, and CB2 is largely found on cells of immune origin. This minireview highlights the role of CB1 in excitotoxic assaults in the brain and its potential to limit addiction liability. In addition, it will examine the relationship between receptor activity and stimulation of insulin release from pancreatic β-cells, insulin resistance, and feeding behavior leading toward obesity. The roles of CB2 in the neuropathology of amyotrophic lateral sclerosis and in the central manifestations of chronic HIV infection potentially converge at inflammatory cell activation, thereby providing an opportunity for intervention. Last, CB2 modulation is discussed in the context of an experimental model of postmenopausal osteoporosis. Achieving exquisite receptor selectivity and elucidating the mechanisms underlying receptor inhibition and activation will be essential for the development of the next generation of cannabinergic-based therapeutic agents.

Brain innate immunity in the regulation of neuroinflammation: therapeutic strategies by modulating CD200-CD200R interaction involve the cannabinoid system

The central nervous system (CNS) innate immune response includes an arsenal of molecules and receptors expressed by professional phagocytes, glial cells and neurons that is involved in host defence and clearance of toxic and dangerous cell debris. However, any uncontrolled innate immune responses within the CNS are widely recognized as playing a major role in the development of autoimmune disorders and neurodegeneration, with multiple sclerosis (MS) Alzheimer's disease (AD) being primary examples. Hence, it is important to identify the key regulatory mechanisms involved in the control of CNS innate immunity and which could be harnessed to explore novel therapeutic avenues. Neuroimmune regulatory proteins (NIReg) such as CD95L, CD200, CD47, sialic acid, complement regulatory proteins (CD55, CD46, fH, C3a), HMGB1, may control the adverse immune responses in health and diseases. In the absence of these regulators, when neurons die by apoptosis, become infected or damaged, microglia and infiltrating immune cells are free to cause injury as well as an adverse inflammatory response in acute and chronic settings. We will herein provide new emphasis on the role of the pair CD200-CD200R in MS and its experimental models: experimental autoimmune encephalomyelitis (EAE) and Theiler’s virus induced demyelinating disease (TMEV-IDD). The interest of the cannabinoid system as inhibitor of inflammation prompt us to introduce our findings about the role of endocannabinoids (eCBs) in promoting CD200-CD200 receptor (CD200R) interaction and the benefits caused in TMEV-IDD. Finally, we also review the current data on CD200-CD200R interaction in AD, as well as, in the aging brain.

Endocannabinoid signalling in innate and adaptive immunity

The immune system can be modulated and regulated not only by foreign antigens but also by other humoral factors and metabolic products, which are able to affect several quantitative and qualitative aspects of immunity. Among these, endocannabinoids are a group of bioactive lipids that might serve as secondary modulators, which when mobilized coincident with or shortly after first-line immune modulators, increase or decrease many immune functions. Most immune cells express these bioactive lipids, together with their set of receptors and of enzymes regulating their synthesis and degradation. In this review, a synopsis of the manifold immunomodulatory effects of endocannabinoids and their signalling in the different cell populations of innate and adaptive immunity is appointed, with a particular distinction between mice and human immune system compartments.

Diacerein is a potent and selective inhibitor of palmitoylethanolamide inactivation with analgesic activity in a rat model of acute inflammatory pain

Palmitoylethanolamide (PEA) is produced by mammalian cells from its biosynthetic precursor, N-palmitoyl-phosphatidyl-ethanolamine, and inactivated by enzymatic hydrolysis to palmitic acid and ethanolamine. Apart from fatty acid amide hydrolase (FAAH), the N-acylethanolamine-hydrolyzing acid amidase (NAAA), a lysosomal enzyme, was also shown to catalyze the hydrolysis of PEA and to limit its analgesic and anti-inflammatory action. Here we report the finding of a new potential inhibitor of NAAA, EPT4900 (4,5-diacetyloxy-9,10-dioxo-anthracene-2-carboxylic acid, diacerein). EPT4900 exhibited a high inhibitory activity on human recombinant NAAA over-expressed in HEK293 cells (HEK-NAAA cells). EPT4900 selectively increased the levels of PEA in intact HEK-NAAA cells, and inhibited inflammation as well as hyperalgesia in rats treated with an intraplantar injection of carrageenan. This latter effect was accompanied by elevation of PEA endogenous levels in the paw skin.

Localization of peroxisome proliferator-activated receptor alpha (PPARα) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) in cells expressing the Ca(2+)-binding proteins calbindin, calretinin, and parvalbumin in the adult rat hippocampus

The N-acylethanolamines (NAEs), oleoylethanolamide (OEA) and palmithylethanolamide (PEA) are known to be endogenous ligands of PPARα receptors, and their presence requires the activation of a specific phospholipase D (NAPE-PLD) associated with intracellular Ca²⁺ fluxes. Thus, the identification of a specific population of NAPE-PLD/PPARα-containing neurons that express selective Ca²⁺-binding proteins (CaBPs) may provide a neuroanatomical basis to better understand the PPARα system in the brain. For this purpose, we used double-label immunofluorescence and confocal laser scanning microscopy for the characterization of the co-existence of NAPE-PLD/PPARα and the CaBPs calbindin D28k, calretinin and parvalbumin in the rat hippocampus. PPARα expression was specifically localized in the cell nucleus and, occasionally, in the cytoplasm of the principal cells (dentate granular and CA pyramidal cells) and some non-principal cells of the hippocampus. PPARα was expressed in the calbindin-containing cells of the granular cell layer of the dentate gyrus (DG) and the SP of CA1. These principal PPARα⁺/calbindin⁺ cells were closely surrounded by NAPE-PLD⁺ fiber varicosities. No pyramidal PPARα⁺/calbindin⁺ cells were detected in CA3. Most cells containing parvalbumin expressed both NAPE-PLD and PPARα in the principal layers of the DG and CA1/3. A small number of cells containing PPARα and calretinin was found along the hippocampus. Scattered NAPE-PLD⁺/calretinin⁺ cells were specifically detected in CA3. NAPE-PLD⁺ puncta surrounded the calretinin⁺ cells localized in the principal cells of the DG and CA1. The identification of the hippocampal subpopulations of NAPE-PLD/PPARα-containing neurons that express selective CaBPs should be considered when analyzing the role of NAEs/PPARα-signaling system in the regulation of hippocampal functions.

Pharmacology of the capsaicin receptor, transient receptor potential vanilloid type-1 ion channel

The capsaicin receptor, transient receptor potential vanilloid type 1 ion channel (TRPV1), has been identified as a polymodal transducer molecule on a sub-set of primary sensory neurons which responds to various stimuli including noxious heat (> -42 degrees C), protons and vanilloids such as capsaicin, the hot ingredient of chilli peppers. Subsequently, TRPV1 has been found indispensable for the development of burning pain and reflex hyperactivity associated with inflammation of peripheral tissues and viscera, respectively. Therefore, TRPV1 is regarded as a major target for the development of novel agents for the control of pain and visceral hyperreflexia in inflammatory conditions. Initial efforts to introduce agents acting on TRPV1 into clinics have been hampered by unexpected side-effects due to wider than expected expression in various tissues, as well as by the complex pharmacology, of TRPV1. However, it is believed that better understanding of the pharmacological properties of TRPV1 and specific targeting of tissues may eventually lead to the development of clinically useful agents. In order to assist better understanding of TRPV1 pharmacology, here we are giving a comprehensive account on the activation and inactivation mechanisms and the structure-function relationship of TRPV1.

Anandamide produced by Ca(2+)-insensitive enzymes induces excitation in primary sensory neurons

The endogenous lipid agent N-arachidonoylethanolamine (anandamide), among other effects, has been shown to be involved in nociceptive processing both in the central and peripheral nervous systems. Anandamide is thought to be synthesised by several enzymatic pathways both in a Ca(2+)-sensitive and Ca(2+)-insensitive manner, and rat primary sensory neurons produce anandamide. Here, we show for the first time, that cultured rat primary sensory neurons express at least four of the five known Ca(2+)-insensitive enzymes implicated in the synthesis of anandamide, and that application of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-arachidonoyl, the common substrate of the anandamide-synthesising pathways, results in anandamide production which is not changed by the removal of extracellular Ca(2+). We also show that anandamide, which has been synthesised in primary sensory neurons following the application of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-arachidonoyl induces a transient receptor potential vanilloid type 1 ion channel-mediated excitatory effect that is not inhibited by concomitant activation of the cannabinoid type 1 receptor. Finally, we show that sub-populations of transient receptor potential vanilloid type 1 ion channel-expressing primary sensory neurons also express some of the putative Ca(2+)-insensitive anandamide-synthesising enzymes. Together, these findings indicate that anandamide synthesised by primary sensory neuron via a Ca(2+)-insensitive manner has an excitatory rather than an inhibitory role in primary sensory neurons and that excitation is mediated predominantly through autocrine signalling. Regulation of the activity of the Ca(2+)-insensitive anandamide-synthesising enzymes in these neurons may be capable of regulating the activity of these cells, with potential relevance to controlling nociceptive processing.

Activation of the Nlrp3 inflammasome in infiltrating macrophages by endocannabinoids mediates beta cell loss in type 2 diabetes

Type 2 diabetes mellitus (T2DM) progresses from compensated insulin resistance to beta cell failure resulting in uncompensated hyperglycemia, a process replicated in the Zucker diabetic fatty (ZDF) rat. The Nlrp3 inflammasome has been implicated in obesity-induced insulin resistance and beta cell failure. Endocannabinoids contribute to insulin resistance through activation of peripheral CB1 receptors (CB₁Rs) and also promote beta cell failure. Here we show that beta cell failure in adult ZDF rats is not associated with CB₁R signaling in beta cells, but rather in M1 macrophages infiltrating into pancreatic islets, and that this leads to activation of the Nlrp3-ASC inflammasome in the macrophages. These effects are replicated in vitro by incubating wild-type human or rodent macrophages, but not macrophages from CB₁R-deficient (Cnr1(-/-)) or Nlrp3(-/-) mice, with the endocannabinoid anandamide. Peripheral CB₁R blockade, in vivo depletion of macrophages or macrophage-specific knockdown of CB₁R reverses or prevents these changes and restores normoglycemia and glucose-induced insulin secretion. These findings implicate endocannabinoids and inflammasome activation in beta cell failure and identify macrophage-expressed CB₁R as a therapeutic target in T2DM.

Linoleoyl ethanolamide reduces lipopolysaccharide-induced inflammation in macrophages and ameliorates 2,4-dinitrofluorobenzene-induced contact dermatitis in mice

In our previous study, it was found that linoleoyl ethanolamide (LE) is present in sake lees, which are produced as a byproduct during the making of Japanese sake. LE is a fatty acid ethanolamide, which have been demonstrated to exert a variety of biological functions, and in this study, the anti-inflammatory effects of LE were examined using in vitro cell culture and in vivo animal experiments. In mouse RAW264.7 macrophages, LE suppressed the lipopolysaccharide (LPS)-induced expression of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. In addition, LE inhibited LPS-induced increases in the levels of cyclooxygenase enzyme-2 and prostaglandin E(2), which are indicators of inflammation. The inhibitory effect of LE on the release of TNF-α was stronger than that of dipotassium glycyrrhizinate, which is widely used in external human skin care treatments. LE also suppressed the LPS-induced activation of Toll-like receptor 4 signaling and nuclear translocation of nuclear factor-κB (NF-κB) p65. In a contact dermatitis animal model, applying LE to affected ear skin ameliorated 2,4-dinitrofluorobenzene-induced contact dermatitis and pro-inflammatory cytokine expression at inflamed sites. These results indicate that LE exerts anti-inflammatory effects by inhibiting NF-κB signaling, and LE is proposed to be a useful therapeutic agent against contact dermatitis.

Role of cannabinoids in the regulation of bone remodeling

The endocannabinoid system plays a key role in regulating a variety of physiological processes such as appetite control and energy balance, pain perception, and immune responses. Recent studies have implicated the endocannabinoid system in the regulation of bone cell activity and bone remodeling. These studies showed that endogenous cannabinoid ligands, cannabinoid receptors, and the enzymes responsible for ligand synthesis and breakdown all play important roles in bone mass and in the regulation of bone disease. These findings suggest that the endocannabinoid pathway could be of value as a therapeutic target for the prevention and treatment of bone diseases. Here, we review the role of the skeletal endocannabinoid system in the regulation of bone remodeling in health and disease.

Targeting the endocannabinoid system for gastrointestinal diseases: future therapeutic strategies

Cannabinoids extracted from the marijuana plant (Cannabis sativa) and synthetic cannabinoids have numerous effects on gastrointestinal (GI) functions. Recent experimental data support an important role for cannabinoids in GI diseases. Genetic studies in humans have proven that defects in endocannabinoid metabolism underlie functional GI disorders. Mammalian cells have machinery, the so-called endocannabinoid system (ECS), to produce and metabolize their own cannabinoids in order to control homeostasis of the gut in a rapidly adapting manner. Pharmacological manipulation of the ECS by cannabinoids, or by drugs that raise the levels of endogenous cannabinoids, have shown beneficial effects on GI pathophysiology. This review gives an introduction into the functions of the ECS in the GI tract, highlights the role of the ECS in GI diseases and addresses its potential pharmacological exploitation.

Characterisation of cannabinoid 1 receptor expression in the perikarya, and peripheral and spinal processes of primary sensory neurons

The cannabinoid 1 (CB1) receptor is expressed by a sub-population of primary sensory neurons. However, data on the neurochemical identity of the CB1 receptor-expressing cells, and CB1 receptor expression by the peripheral and central terminals of these neurons are inconsistent and limited. We characterised CB1 receptor expression in dorsal root ganglia (DRG) and spinal cord at the lumbar 4-5 level, as well as in the urinary bladder and glabrous skin of the hindpaw. About 1/3 of DRG neurons exhibited immunopositivity for the CB1 receptor, the majority of which showed positivity for the nociceptive markers calcitonin gene-related peptide (CGRP) or/and Griffonia (bandeiraea) simplicifolia IB4 isolectin-binding. Virtually all CB1 receptor-immunostained fibres showed immunopositivity for CGRP in the skin, while very few did in the urinary bladder. No CB1 receptor-immunopositive nerve fibres were IB4 positive in either peripheral tissue. Spinal laminae I and II-outer showed the highest density of CB1 receptor-immunopositive punctae, the majority of which showed positivity for CGRP or/and IB4 binding. These data indicate that a major sub-population of nociceptive primary sensory neurons expresses CB1 receptors that are transported to both peripheral and central terminals of these cells. Therefore, the present data suggest that manipulation of endogenous CB1 receptor agonist levels in these areas may significantly reduce nociceptive input into the spinal cord.

The endocannabinoid system: a revolving plate in neuro-immune interaction in health and disease

Studies of the last 40 years have brought to light an important physiological network, the endocannabinoid system. Endogenous and exogenous cannabinoids mediate their effects through activation of specific cannabinoid receptors. This modulatory homoeostatic system operates in the regulation of brain function and also in the periphery. The cannabinoid system has been shown to be involved in regulating the immune system. Studies examining the effect of cannabinoid-based drugs on immunity have shown that many cellular and cytokine mechanisms are modulated by these agents, thus raising the hypothesis that these compounds may be of value in the management of chronic inflammatory diseases. The special properties of endocannabinoids as neurotransmitters, their pleiotropic effects and the impact on immune function show that the endocannabinoid system represents a revolving plate of neural and immune interactions. In this paper, we outline current information on immune effects of cannabinoids in health and disease.

Palmitoylethanolamide effects on intraocular pressure after Nd:YAG laser iridotomy: an experimental clinical study

PURPOSE

The purpose of this article was to evaluate whether the anti-inflammatory agent palmitoylethanolamide (PEA) can counteract the increase of intraocular pressure (IOP) that may occur after neodymium-doped: yttrium aluminum garnet (Nd:YAG) laser iridotomy.

METHODS

Fifteen patients underwent bilateral laser iridotomy (Visulas YAG III Laser; Zeiss) for the prevention of primary closed-angle glaucoma. The IOP was measured at the beginning of the study (t-1), after 15 days of pretreatment with placebo or PEA (t0), and at 15, 30, and 120 min after the iridotomy (t1, t2, t3). The pretreatment consisted of 2 tablets of placebo or PEA per day for 15 days.

RESULTS

The t-test did not show a significant difference between the preoperative mean values of IOP t-1 and t0 in both the pretreatments. Analysis of variance/Tukey's test pointed out a significant increase of the postoperative IOP values in placebo pretreated patients (P≤0.05), but not in those who were pretreated with PEA. The trend analysis confirmed the significant positive trend in placebo pretreatment. The parallelism test between the 2 regressions showed a significant difference for the slopes (P=0.022) and not for the intercepts (P=0.520).

CONCLUSIONS

PEA can counteract the increase of IOP that occurs after iridotomy. It is likely that PEA controls the inflammatory process after iridotomy.

Fatty acid amide signaling molecules

Key studies leading to the discovery and definition of the role of endogenous fatty acid amide signaling molecules are summarized.

Cannabinoids and bone: friend or foe?

The endocannabinoid system is recognized to play an important role in regulating a variety of physiological processes, including appetite control and energy balance, pain perception, and immune responses. The endocannabinoid system has also recently been implicated in the regulation of bone metabolism. Endogenously produced cannabinoids are hydrophobic molecules derived from hydrolysis of membrane phospholipids. These substances, along with plant-derived and synthetic cannabinoids, interact with the type 1 (CB(1)) and 2 (CB(2)) cannabinoid receptors and the GPR55 receptor to regulate cellular function through a variety of signaling pathways. Endocannabinoids are produced in bone, but the mechanisms that regulate their production are unclear. Skeletal phenotyping of mice with targeted inactivation of cannabinoid receptors and pharmacological studies have shown that cannabinoids play a key role in the regulation of bone metabolism. Mice with CB(1) deficiency have high peak bone mass as a result of an osteoclast defect but develop age-related osteoporosis as a result of impaired bone formation and accumulation of bone marrow fat. Mice with CB(2) deficiency have relatively normal peak bone mass but develop age-related osteoporosis as a result of increased bone turnover with uncoupling of bone resorption from bone formation. Mice with GPR55 deficiency have increased bone mass as a result of a defect in the resorptive activity of osteoclasts, but bone formation is unaffected. Cannabinoids are also produced within synovial tissues, and preclinical studies have shown that cannabinoid receptor ligands are effective in the treatment of inflammatory arthritis. These data indicate that cannabinoid receptors and the enzymes responsible for ligand synthesis and breakdown play important roles in bone remodeling and in the pathogenesis of joint disease.

From Fertilisation to Implantation in Mammalian Pregnancy-Modulation of Early Human Reproduction by the Endocannabinoid System

There is an increasing recognition that the endocannabinoid system is the crucial cytokine-hormone system regulating early human pregnancy. The synchronous development of the fertilized embryo and the endometrium to ensure timely implantation has been shown to be one of the pivotal steps to successful implantation. This development is thought to be regulated by a finely balanced relationship between various components of the endocannabinoid system in the endometrium, the embryo and the Fallopian tube. In addition, this system has also been shown to be involved in the regulation of the development and maturation of the gametes prior to fertilization. In this review, we will examine the evidence from animal and human studies to support the role of the endocannabinoid system in gametogenesis, fertilization, implantation, early pregnancy maintenance, and in immunomodulation of pregnancy. We will discuss the role of the cannabinoid receptors and the enzymes involved in the synthesis and degradation of the key endocannabinoid ligands (e.g., anandamide and 2-arachinoylglycerol) in early reproduction.

Brain CB₂ Receptors: Implications for Neuropsychiatric Disorders

Although previously thought of as the peripheral cannabinoid receptor, it is now accepted that the CB₂ receptor is expressed in the central nervous system on microglia, astrocytes and subpopulations of neurons. Expression of the CB₂ receptor in the brain is significantly lower than that of the CB₁ receptor. Conflicting findings have been reported on the neurological effects of pharmacological agents targeting the CB₂ receptor under normal conditions. Under inflammatory conditions, CB₂ receptor expression in the brain is enhanced and CB₂ receptor agonists exhibit potent anti-inflammatory effects. These findings have prompted research into the CB₂ receptor as a possible target for the treatment of neuroinflammatory and neurodegenerative disorders. Neuroinflammatory alterations are also associated with neuropsychiatric disorders and polymorphisms in the CB₂ gene have been reported in depression, eating disorders and schizophrenia. This review will examine the evidence to date for a role of brain CB₂ receptors in neuropsychiatric disorders.

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.

3-Heterocycle-phenyl N-alkylcarbamates as FAAH inhibitors: design, synthesis and 3D-QSAR studies

Carbamates are a well-established class of fatty acid amide hydrolase (FAAH) inhibitors. Here we describe the synthesis of meta-substituted phenolic N-alkyl/aryl carbamates and their in vitro FAAH inhibitory activities. The most potent compound, 3-(oxazol-2yl)phenyl cyclohexylcarbamate (2 a), inhibited FAAH with a sub-nanomolar IC(50) value (IC(50)=0.74 nM). Additionally, we developed and validated three-dimensional quantitative structure-activity relationships (QSAR) models of FAAH inhibition combining the newly disclosed carbamates with our previously published inhibitors to give a total set of 99 compounds. Prior to 3D-QSAR modeling, the degree of correlation between FAAH inhibition and in silico reactivity was also established. Both 3D-QSAR methods used, CoMSIA and GRID/GOLPE, produced statistically significant models with coefficient of correlation for external prediction (R(2) (PRED)) values of 0.732 and 0.760, respectively. These models could be of high value in further FAAH inhibitor design.