Palmitoylethanolamide inhibits the expression of fatty acid amide hydrolase and enhances the anti-proliferative effect of anandamide in human breast cancer cells

Cannabinoids and Endocannabinoid System Changes in Intestinal Inflammation and Colorectal Cancer

Despite the multiple preventive measures and treatment options, colorectal cancer holds a significant place in the world's disease and mortality rates. The development of novel therapy is in critical need, and based on recent experimental data, cannabinoids could become excellent candidates. This review covered known experimental studies regarding the effects of cannabinoids on intestinal inflammation and colorectal cancer. In our opinion, because colorectal cancer is a heterogeneous disease with different genomic landscapes, the choice of cannabinoids for tumor prevention and treatment depends on the type of the disease, its etiology, driver mutations, and the expression levels of cannabinoid receptors. In this review, we describe the molecular changes of the endocannabinoid system in the pathologies of the large intestine, focusing on inflammation and cancer.

Mediterranean Diet and Neurodegenerative Diseases: The Neglected Role of Nutrition in the Modulation of the Endocannabinoid System

Neurodegenerative disorders are a widespread cause of morbidity and mortality worldwide, characterized by neuroinflammation, oxidative stress and neuronal depletion. The broad-spectrum neuroprotective activity of the Mediterranean diet is widely documented, but it is not yet known whether its nutritional and caloric balance can induce a modulation of the endocannabinoid system. In recent decades, many studies have shown how endocannabinoid tone enhancement may be a promising new therapeutic strategy to counteract the main hallmarks of neurodegeneration. From a phylogenetic point of view, the human co-evolution between the endocannabinoid system and dietary habits could play a key role in the pro-homeostatic activity of the Mediterranean lifestyle: this adaptive balance among our ancestors has been compromised by the modern Western diet, resulting in a “clinical endocannabinoid deficiency syndrome”. This review aims to evaluate the evidence accumulated in the literature on the neuroprotective, immunomodulatory and antioxidant properties of the Mediterranean diet related to the modulation of the endocannabinoid system, suggesting new prospects for research and clinical interventions against neurodegenerative diseases in light of a nutraceutical paradigm.

Neuroprotective and Immunomodulatory Action of the Endocannabinoid System under Neuroinflammation

Endocannabinoids (eCBs) are lipid-based retrograde messengers with a relatively short half-life that are produced endogenously and, upon binding to the primary cannabinoid receptors CB_1/2, mediate multiple mechanisms of intercellular communication within the body. Endocannabinoid signaling is implicated in brain development, memory formation, learning, mood, anxiety, depression, feeding behavior, analgesia, and drug addiction. It is now recognized that the endocannabinoid system mediates not only neuronal communications but also governs the crosstalk between neurons, glia, and immune cells, and thus represents an important player within the neuroimmune interface. Generation of primary endocannabinoids is accompanied by the production of their congeners, the N-acylethanolamines (NAEs), which together with N-acylneurotransmitters, lipoamino acids and primary fatty acid amides comprise expanded endocannabinoid/endovanilloid signaling systems. Most of these compounds do not bind CB_1/2, but signal via several other pathways involving the transient receptor potential cation channel subfamily V member 1 (TRPV1), peroxisome proliferator-activated receptor (PPAR)-α and non-cannabinoid G-protein coupled receptors (GPRs) to mediate anti-inflammatory, immunomodulatory and neuroprotective activities. In vivo generation of the cannabinoid compounds is triggered by physiological and pathological stimuli and, specifically in the brain, mediates fine regulation of synaptic strength, neuroprotection, and resolution of neuroinflammation. Here, we review the role of the endocannabinoid system in intrinsic neuroprotective mechanisms and its therapeutic potential for the treatment of neuroinflammation and associated synaptopathy.

Palmitoylethanolamide: A Natural Compound for Health Management

All nations which have undergone a nutrition transition have experienced increased frequency and falling latency of chronic degenerative diseases, which are largely driven by chronic inflammatory stress. Dietary supplementation is a valid strategy to reduce the risk and severity of such disorders. Palmitoylethanolamide (PEA) is an endocannabinoid-like lipid mediator with extensively documented anti-inflammatory, analgesic, antimicrobial, immunomodulatory and neuroprotective effects. It is well tolerated and devoid of side effects in animals and humans. PEA's actions on multiple molecular targets while modulating multiple inflammatory mediators provide therapeutic benefits in many applications, including immunity, brain health, allergy, pain modulation, joint health, sleep and recovery. PEA's poor oral bioavailability, a major obstacle in early research, has been overcome by advanced delivery systems now licensed as food supplements. This review summarizes the functionality of PEA, supporting its use as an important dietary supplement for lifestyle management.

Palmitoylethanolamide Modulation of Microglia Activation: Characterization of Mechanisms of Action and Implication for Its Neuroprotective Effects

Palmitoylethanolamide (PEA) is an endogenous lipid produced on demand by neurons and glial cells that displays neuroprotective properties. It is well known that inflammation and neuronal damage are strictly related processes and that microglia play a pivotal role in their regulation. The aim of the present work was to assess whether PEA could exert its neuroprotective and anti-inflammatory effects through the modulation of microglia reactive phenotypes. In N9 microglial cells, the pre-incubation with PEA blunted the increase of M1 pro-inflammatory markers induced by lipopolysaccharide (LPS), concomitantly increasing those M2 anti-inflammatory markers. Images of microglial cells were processed to obtain a set of morphological parameters that highlighted the ability of PEA to inhibit the LPS-induced M1 polarization and suggested that PEA might induce the anti-inflammatory M2a phenotype. Functionally, PEA prevented Ca²⁺ transients in both N9 cells and primary microglia and antagonized the neuronal hyperexcitability induced by LPS, as revealed by multi-electrode array (MEA) measurements on primary cortical cultures of neurons, microglia, and astrocyte. Finally, the investigation of the molecular pathway indicated that PEA effects are not mediated by toll-like receptor 4 (TLR4); on the contrary, a partial involvement of cannabinoid type 2 receptor (CB2R) was shown by using a selective receptor inverse agonist.

The Endocannabinoid System and PPARs: Focus on Their Signalling Crosstalk, Action and Transcriptional Regulation

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors including PPARα, PPARγ, and PPARβ/δ, acting as transcription factors to regulate the expression of a plethora of target genes involved in metabolism, immune reaction, cell differentiation, and a variety of other cellular changes and adaptive responses. PPARs are activated by a large number of both endogenous and exogenous lipid molecules, including phyto- and endo-cannabinoids, as well as endocannabinoid-like compounds. In this view, they can be considered an extension of the endocannabinoid system. Besides being directly activated by cannabinoids, PPARs are also indirectly modulated by receptors and enzymes regulating the activity and metabolism of endocannabinoids, and, vice versa, the expression of these receptors and enzymes may be regulated by PPARs. In this review, we provide an overview of the crosstalk between cannabinoids and PPARs, and the importance of their reciprocal regulation and modulation by common ligands, including those belonging to the extended endocannabinoid system (or "endocannabinoidome") in the control of major physiological and pathophysiological functions.

A Glucuronic Acid-Palmitoylethanolamide Conjugate (GLUPEA) Is an Innovative Drug Delivery System and a Potential Bioregulator

Palmitoylethanolamide (PEA) is an endogenous anti-inflammatory lipid mediator and a widely used nutraceutical. In this study, we designed, realized, and tested a drug-carrier conjugate between PEA (the active drug) and glucuronic acid (the carrier). The conjugate, named GLUPEA, was characterized for its capability of increasing PEA levels and exerting anti-inflammatory activity both in vitro and in vivo. GLUPEA treatment, compared to the same concentration of PEA, resulted in higher cellular amounts of PEA and the endocannabinoid 2-arachidonoyl glycerol (2-AG), and increased 2-AG-induced transient receptor potential vanilloid type 1 (TRPV1) channel desensitization to capsaicin. GLUPEA inhibited pro-inflammatory monocyte chemoattractant protein 2 (MCP-2) release from stimulated keratinocytes, and it was almost as efficacious as ultra-micronized PEA at reducing colitis in dinitrobenzene sulfonic acid (DNBS)-injected mice when using the same dose. GLUPEA is a novel pro-drug able to efficiently mimic the anti-inflammatory and endocannabinoid enhancing actions of PEA.

Palmitoylethanolamide: A Nutritional Approach to Keep Neuroinflammation within Physiological Boundaries-A Systematic Review

Neuroinflammation is a physiological response aimed at maintaining the homodynamic balance and providing the body with the fundamental resource of adaptation to endogenous and exogenous stimuli. Although the response is initiated with protective purposes, the effect may be detrimental when not regulated. The physiological control of neuroinflammation is mainly achieved via regulatory mechanisms performed by particular cells of the immune system intimately associated with or within the nervous system and named "non-neuronal cells." In particular, mast cells (within the central nervous system and in the periphery) and microglia (at spinal and supraspinal level) are involved in this control, through a close functional relationship between them and neurons (either centrally, spinal, or peripherally located). Accordingly, neuroinflammation becomes a worsening factor in many disorders whenever the non-neuronal cell supervision is inadequate. It has been shown that the regulation of non-neuronal cells-and therefore the control of neuroinflammation-depends on the local "on demand" synthesis of the endogenous lipid amide Palmitoylethanolamide and related endocannabinoids. When the balance between synthesis and degradation of this bioactive lipid mediator is disrupted in favor of reduced synthesis and/or increased degradation, the behavior of non-neuronal cells may not be appropriately regulated and neuroinflammation exceeds the physiological boundaries. In these conditions, it has been demonstrated that the increase of endogenous Palmitoylethanolamide-either by decreasing its degradation or exogenous administration-is able to keep neuroinflammation within its physiological limits. In this review the large number of studies on the benefits derived from oral administration of micronized and highly bioavailable forms of Palmitoylethanolamide is discussed, with special reference to neuroinflammatory disorders.

Synthesis, Molecular Modeling and Biological Evaluation of Metabolically Stable Analogues of the Endogenous Fatty Acid Amide Palmitoylethanolamide

Palmitoylethanolamide (PEA) belongs to the class of N-acylethanolamine and is an endogenous lipid potentially useful in a wide range of therapeutic areas; products containing PEA are licensed for use in humans as a nutraceutical, a food supplement, or food for medical purposes for its analgesic and anti-inflammatory properties demonstrating efficacy and tolerability. However, the exogenously administered PEA is rapidly inactivated; in this process, fatty acid amide hydrolase (FAAH) plays a key role both in hepatic metabolism and in intracellular degradation. So, the aim of the present study was the design and synthesis of PEA analogues that are more resistant to FAAH-mediated hydrolysis. A small library of PEA analogues was designed and tested by molecular docking and density functional theory calculations to find the more stable analogue. The computational investigation identified RePEA as the best candidate in terms of both synthetic accessibility and metabolic stability to FAAH-mediated hydrolysis. The selected compound was synthesized and assayed ex vivo to monitor FAAH-mediated hydrolysis and to confirm its anti-inflammatory properties. ¹H-NMR spectroscopy performed on membrane samples containing FAAH in integral membrane protein demonstrated that RePEA is not processed by FAAH, in contrast with PEA. Moreover, RePEA retains PEA’s ability to inhibit LPS-induced cytokine release in both murine N9 microglial cells and human PMA-THP-1 cells.

Pyridostigmine bromide exposure creates chronic, underlying neuroimmune disruption in the gastrointestinal tract and brain that alters responses to palmitoylethanolamide in a mouse model of Gulf War Illness

Gulf War Illness (GWI) is a chronic multisymptom illness that includes gastrointestinal disorders. Although the exact etiology of GWI is unknown, exposure to the drug pyridostigmine bromide (PB) is considered a major factor. Exposure to PB drives enteric neuroinflammation, promotes immunosuppression, and alters physiological functions of the colon in the short term but whether exposure to PB is sufficient to promote long term dysfunction is not known. Here, we tested whether exposure to PB is sufficient to drive long term changes that reflect GWI, and whether the endogenous anti-inflammatory mediator palmitoylethanolamide (PEA) is sufficient to reduce the detrimental effects of PB in the gut and brain of mice. Exposure to PB alone was not sufficient to cause major changes in neuromuscular transmission but did drive major changes by altering the effects of PEA. Calcium imaging data show that the mechanisms responsible include a shift in receptor signaling mediated by TRPV1, endocannabinoids, and peroxisome proliferator-activated receptors alpha (PPARα). Additional mechanisms include the development of glial reactivity and changes in enteric neurochemical coding and survival. PB and PEA caused major shifts in pro-inflammatory cytokines/chemokines in the brain and colon that persisted up to 5 months following exposure. Many of the effects of PB and PEA exhibit significant sex differences. Together, these results highlight novel mechanisms whereby PB promotes long-lasting changes in nervous system and immune function by inducing occult neuroplasticity that is revealed by subsequent exposure to unrelated drugs in a sex dependent manner.

The Basal Pharmacology of Palmitoylethanolamide

Palmitoylethanolamide (PEA, N-hexadecanoylethanolamide) is an endogenous compound belonging to the family of N-acylethanolamines. PEA has anti-inflammatory and analgesic properties and is very well tolerated in humans. In the present article, the basal pharmacology of PEA is reviewed. In terms of its pharmacokinetic properties, most work has been undertaken upon designing formulations for its absorption and upon characterising the enzymes involved in its metabolism, but little is known about its bioavailability, tissue distribution, and excretion pathways. PEA exerts most of its biological effects in the body secondary to the activation of peroxisome proliferator-activated receptor-α (PPAR-α), but PPAR-α-independent pathways involving other receptors (Transient Receptor Potential Vanilloid 1 (TRPV1), GPR55) have also been identified. Given the potential clinical utility of PEA, not least for the treatment of pain where there is a clear need for new well-tolerated drugs, we conclude that the gaps in our knowledge, in particular those relating to the pharmacokinetic properties of the compound, need to be filled.

Cannabinoid control of neurogenic inflammation

A significant number of cannabinoids are known to have analgesic and anti-inflammatory properties in various diseases. Due to their presynaptic/terminal location, cannabinoid receptors can inhibit synaptic transmission and have the potential to regulate neurogenic inflammation. Neurogenic inflammation occurs when a noxious signal is detected in the periphery initiating an antidromic axon reflex in the same sensory neurone leading to depolarization of the afferent terminal. Neuropeptides are subsequently released and contribute to vasodilation, plasma extravasation and modulation of immune cells. Endocannabinoids, synthetic cannabinoids and phytocannabinoids can reduce neuroinflammation by inhibiting afferent firing and inflammatory neuropeptide release. Thus, in addition to a direct effect on vascular smooth muscle and inflammatory cells, cannabinoids can reduce inflammation by silencing small diameter neurones. This review examines the neuropharmacological processes involved in regulating antidromic depolarization of afferent nerve terminals by cannabinoids and the control of neurogenic inflammation in different diseases.

ALIAmides Update: Palmitoylethanolamide and Its Formulations on Management of Peripheral Neuropathic Pain

Neuropathic pain results from lesions or diseases of the somatosensory nervous system and it remains largely difficult to treat. Peripheral neuropathic pain originates from injury to the peripheral nervous system (PNS) and manifests as a series of symptoms and complications, including allodynia and hyperalgesia. The aim of this review is to discuss a novel approach on neuropathic pain management, which is based on the knowledge of processes that underlie the development of peripheral neuropathic pain; in particular highlights the role of glia and mast cells in pain and neuroinflammation. ALIAmides (autacoid local injury antagonist amides) represent a group of endogenous bioactive lipids, including palmitoylethanolamide (PEA), which play a central role in numerous biological processes, including pain, inflammation, and lipid metabolism. These compounds are emerging thanks to their anti-inflammatory and anti-hyperalgesic effects, due to the down-regulation of activation of mast cells. Collectively, preclinical and clinical studies support the idea that ALIAmides merit further consideration as therapeutic approach for controlling inflammatory responses, pain, and related peripheral neuropathic pain.

A New Palmitoylethanolamide Form Combined with Antioxidant Molecules to Improve Its Effectivess on Neuronal Aging

Palmitoylethanolamide is a nutraceutical compound naturally produced in many plants and animal source foods, but the natural form is poorly water-soluble. It has demonstrated an anti-inflammatory role as a neuroprotective mediator, acting on several molecular targets of the central nervous system involved on brain aging process. In healthy adults, palmitoylethanolamide is an endogenous PPAR-α (peroxisome proliferator-activated receptor α) agonist through which it performs anti-inflammatory activity and provides its effects by activating the cannabinoid receptor. The different formulations of palmitoylethanolamide (micronized palmitoylethanolamide, FM-LipoMatrix^® palmitoylethanolamide and FM-LipoMatrix^® palmitoylethanolamide plus lipoic acid and vitamin D3) were analyzed starting from intestinal barrier, to verify their bioavailability, to in primary astrocytes in which cell viability, reactive oxygen species (ROS) and nitric oxide (NO) production, NFKB activity, MAPK, p53 and PPARα activities were investigated. Additionally, cannabinoid and estrogen receptors were analyzed using the western blot technique. The combination of palmitoylethanolamide in FM-LipoMatrix^®, lipoic acid and vitamin D3 shows better absorption predicting an improvement on plasma concentration; this formulation also shows a reduction in ROS and NO production and the data show the interaction of palmitoylethanolamide with cannabinoids and estrogen receptors inhibiting neuroinflammatory markers. All these data support the hypothesis of a new potential strategy to restore brain function and slow down brain aging in humans.

Palmitoylethanolamide and Related ALIAmides: Prohomeostatic Lipid Compounds for Animal Health and Wellbeing

Virtually every cellular process is affected by diet and this represents the foundation of dietary management to a variety of small animal disorders. Special attention is currently being paid to a family of naturally occurring lipid amides acting through the so-called autacoid local injury antagonism, i.e., the ALIA mechanism. The parent molecule of ALIAmides, palmitoyl ethanolamide (PEA), has being known since the 1950s as a nutritional factor with protective properties. Since then, PEA has been isolated from a variety of plant and animal food sources and its proresolving function in the mammalian body has been increasingly investigated. The discovery of the close interconnection between ALIAmides and the endocannabinoid system has greatly stimulated research efforts in this field. The multitarget and highly redundant mechanisms through which PEA exerts prohomeostatic functions fully breaks with the classical pharmacology view of “one drug, one target, one disease”, opening a new era in the management of animals’ health, i.e., an according-to-nature biomodulation of body responses to different stimuli and injury. The present review focuses on the direct and indirect endocannabinoid receptor agonism by PEA and its analogues and also targets the main findings from experimental and clinical studies on ALIAmides in animal health and wellbeing.

Tolerability of Palmitoylethanolamide in a Pediatric Population Suffering from Migraine: A Pilot Study

Background

Palmitoylethanolamide (PEA) is emerging as a new therapeutic approach in pain and inflammatory conditions, and it has been evaluated in studies on various painful diseases. The aim of this open-label study was to evaluate the efficacy of ultramicronized PEA (umPEA) in the prophylactic treatment of migraine.

Methods

The study included 70 patients with mean age of 10.3 ± 2.7 (24.5% M and 75.5% F). All patients had a diagnosis of migraine without aura (ICHD 3 criteria) and received umPEA (600 mg/day orally) for three months. We compared the attack frequency (AF) and attack intensity at baseline and after three months. Patients were asked to classify the intensity of the attack with a value ranging from 1 to 3, where 1 means mild attack, 2 moderate, and 3 severe attack.

Results

Nine patients discontinued treatment before the target time of 12 weeks. After 3 months of treatment with umPEA, the headache frequency was reduced by >50% per month in 63.9% patients. The number of monthly attacks at T₁ decreased significantly compared with the baseline assessment (from 13.9 ± 7.5 SD of T₀ to 6.5 ± 5.9 SD of T₁; p < 0.001). The mean intensity of the attacks dropped from 1.67 ± 0.6 (T₀) to 1.16 ± 0.5 (T₁) (p < 0.001), and the percentage of patients with severe attacks decreased after treatment (from 8.2% to 1.6%; p < 0.05). The monthly assumptions of drugs for the attack reduced from 9.5 ± 4.4 to 4.9 ± 2.5 (p < 0.001). Only one patient developed mild side effects (nausea and floating).

Conclusions

Our preliminary data show that umPEA administered for three month reduces pain intensity and the number of attacks per month in pediatric patients with migraine. Although the small number of patients and the lack of control group do not allow us to consider these initial results as definitely reliable, they encourage us to expand the sample.

Palmitoylethanolamide counteracts substance P-induced mast cell activation in vitro by stimulating diacylglycerol lipase activity

BACKGROUND

Palmitoylethanolamide (PEA) is a pleiotropic endogenous lipid mediator currently used as a "dietary food for special medical purposes" against neuropathic pain and neuro-inflammatory conditions. Several mechanisms underlie PEA actions, among which the "entourage" effect, consisting of PEA potentiation of endocannabinoid signaling at either cannabinoid receptors or transient receptor potential vanilloid type-1 (TRPV1) channels. Here, we report novel molecular mechanisms through which PEA controls mast cell degranulation and substance P (SP)-induced histamine release in rat basophilic leukemia (RBL-2H3) cells, a mast cell model.

METHODS

RBL-2H3 cells stimulated with SP were treated with PEA in the presence and absence of a cannabinoid type-2 (CB2) receptor antagonist (AM630), or a diacylglycerol lipase (DAGL) enzyme inhibitor (OMDM188) to inhibit the biosynthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG). The release of histamine was measured by ELISA and β-hexosaminidase release and toluidine blue staining were used as indices of degranulation. 2-AG levels were measured by LC-MS. The mRNA expression of proposed PEA targets (Cnr1, Cnr2, Trpv1, Ppara and Gpr55), and of PEA and endocannabinoid biosynthetic (Napepld, Dagla and Daglb) and catabolic (Faah, Naaa and Mgl) enzymes were also measured. The effects of PEA on the activity of DAGL-α or -β enzymes were assessed in COS-7 cells overexpressing the human recombinant enzyme or in RBL-2H3 cells, respectively.

RESULTS

SP increased the number of degranulated RBL-2H3 cells and triggered the release of histamine. PEA counteracted these effects in a manner antagonized by AM630. PEA concomitantly increased the levels of 2-AG in SP-stimulated RBL-2H3 cells, and this effect was reversed by OMDM188. PEA significantly stimulated DAGL-α and -β activity and, consequently, 2-AG biosynthesis in cell-free systems. Co-treatment with PEA and 2-AG at per se ineffective concentrations downmodulated SP-induced release of histamine and degranulation, and this effect was reversed by OMDM188.

CONCLUSIONS

Activation of CB2 underlies the inhibitory effects on SP-induced RBL-2H3 cell degranulation by PEA alone. We demonstrate for the first time that the effects in RBL-2H3 cells of PEA are due to the stimulation of 2-AG biosynthesis by DAGLs.

Therapeutic Efficacy of Palmitoylethanolamide and Its New Formulations in Synergy with Different Antioxidant Molecules Present in Diets

The use of a complete nutritional approach seems increasingly promising to combat chronic inflammation. The choice of healthy sources of carbohydrates, fats, and proteins, associated with regular physical activity and avoidance of smoking is essential to fight the war against chronic diseases. At the base of the analgesic, anti-inflammatory, or antioxidant action of the diets, there are numerous molecules, among which some of a lipidic nature very active in the inflammatory pathway. One class of molecules found in diets with anti-inflammatory actions are ALIAmides. Among all, one is particularly known for its ability to counteract the inflammatory cascade, the Palmitoylethanolamide (PEA). PEA is a molecular that is present in nature, in numerous foods, and is endogenously produced by our body, which acts as a balancer of inflammatory processes, also known as endocannabionoid-like. PEA is often used in the treatment of both acute and chronic inflammatory pathologies, either alone or in association with other molecules with properties, such as antioxidants or analgesics. This review aims to illustrate an overview of the different diets that are involved in the process of opposition to the inflammatory cascade, focusing on capacity of PEA and new formulations in synergy with other molecules.

Broad Lipidomic and Transcriptional Changes of Prophylactic PEA Administration in Adult Mice

Beside diverse therapeutic properties of palmitoylethanolamide (PEA) including: neuroprotection, inflammation and pain alleviation, prophylactic effects have also been reported in animal models of infections, inflammation, and neurological diseases. The availability of PEA as (ultra)micronized nutraceutical formulations with reportedly no side effects, renders it accordingly an appealing candidate in human preventive care, such as in population at high risk of disease development or for healthy aging. PEA’s mode of action is multi-facetted. Consensus exists that PEA’s effects are primarily modulated by the peroxisome proliferator-activated receptor alpha (PPARα) and that PEA-activated PPARα has a pleiotropic effect on lipid metabolism, inflammation gene networks, and host defense mechanisms. Yet, an exhaustive view of how the prophylactic PEA administration changes the lipid signaling in brain and periphery, thereby eliciting a beneficial response to various negative stimuli remains still elusive. We therefore, undertook a broad lipidomic and transcriptomic study in brain and spleen of adult mice to unravel the positive molecular phenotype rendered by prophylactic PEA. We applied a tissue lipidomic and transcriptomic approach based on simultaneous extraction and subsequent targeted liquid chromatography-multiple reaction monitoring (LC-MRM) and mRNA analysis by qPCR, respectively. We targeted lipids of COX-, LOX- and CYP450 pathways, respectively, membrane phospholipids, lipid products of cPLA₂, and free fatty acids, along with various genes involved in their biosynthesis and function. Additionally, plasma lipidomics was applied to reveal circulatory consequences and/or reflection of PEA’s action. We found broad, distinct, and several previously unknown tissue transcriptional regulations of inflammatory pathways. In hippocampus also a PEA-induced transcriptional regulation of neuronal activity and excitability was evidenced. A massive downregulation of membrane lipid levels in the splenic tissue of the immune system with a consequent shift towards pro-resolving lipid environment was also detected. Plasma lipid pattern reflected to a large extent the hippocampal and splenic lipidome changes, highlighting the value of plasma lipidomics to monitor effects of nutraceutical PEA administration. Altogether, these findings contribute new insights into PEA’s molecular mechanism and helps answering the questions, how PEA prepares the body for insults and what are the “good lipids” that underlie this action.

Anti-Inflammatory Effects by Pharmacological Inhibition or Knockdown of Fatty Acid Amide Hydrolase in BV2 Microglial Cells

Fatty acid amide hydrolase (FAAH) has been recognized as a therapeutic target for several neurological diseases because its inhibition can exert neuroprotective and anti-inflammatory effects by boosting the endogenous levels of N-acylethanolamines. However, previous studies have shown inconsistent results by pharmacological inhibition and genetic deletion of FAAH in response to inflammation. In this study we used two inhibitors, PF3845 and URB597, together with siRNA knockdown to characterize further the effects of FAAH inhibition in BV2 microglial cells. Treatment with PF3845 suppressed lipopolysaccharide (LPS)-induced prostaglandin E₂ (PGE₂) production, and down-regulated cyclooxygenase-2 and microsomal PGE synthase. PF3845 reduced the expression of pro-inflammatory cytokines but had no effect on the expression of anti-inflammatory cytokines. The anti-inflammatory effects of URB597 were not as potent as those of PF3845. Knockdown of FAAH also suppressed PGE₂ production and pro-inflammatory gene expression. Interestingly, FAAH knockdown enhanced expression of anti-inflammatory molecules in both the absence and presence of LPS treatment. The anti-inflammatory effects of FAAH inhibition and knockdown were not affected by the cannabinoid receptor antagonists or the peroxisome proliferator-activated receptor (PPAR) antagonists. Although inhibition and knockdown of FAAH have potent anti-inflammatory effects and possibly lead to the dynamic change of microglial gene regulation, the underlying mechanisms remain to be elucidated.

Modulation of the Endocannabinoid System as a Potential Anticancer Strategy

Currently, the involvement of the endocannabinoid system in cancer development and possible options for a cancer-regressive effect of cannabinoids are controversially discussed. In recent decades, a number of preclinical studies have shown that cannabinoids have an anticarcinogenic potential. Therefore, especially against the background of several legal simplifications with regard to the clinical application of cannabinoid-based drugs, an extended basic knowledge about the complex network of the individual components of the endocannabinoid system is required. The canonical endocannabinoid system consists of the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol as well as the G_i/o protein-coupled transmembrane cannabinoid receptors CB₁ and CB₂. As a result of extensive studies on the broader effect of these factors, other fatty acid derivatives, transmembrane and intracellular receptors, enzymes and lipid transporters have been identified that contribute to the effect of endocannabinoids when defined in the broad sense as “extended endocannabinoid system.” Among these additional components, the endocannabinoid-degrading enzymes fatty acid amide hydrolase and monoacylglycerol lipase, lipid transport proteins of the fatty acid-binding protein family, additional cannabinoid-activated G protein-coupled receptors such as GPR55, members of the transient receptor family, and peroxisome proliferator-activated receptors were identified as targets for possible strategies to combat cancer progression. Other endocannabinoid-related fatty acids such as 2-arachidonoyl glyceryl ether, O-arachidonoylethanolamine, N-arachidonoyldopamine and oleic acid amide showed an effect via cannabinoid receptors, while other compounds such as endocannabinoid-like substances exert a permissive action on endocannabinoid effects and act via alternative intracellular target structures. This review gives an overview of the modulation of the extended endocannabinoid system using the example of anticancer cannabinoid effects, which have been described in detail in preclinical studies.

Clinical applications of palmitoylethanolamide in pain management: protocol for a scoping review

BACKGROUND

Palmitoylethanolamide (PEA) belong to endocannabinoid family, a group of fatty acid amides. PEA has been proven to have analgesic and anti-inflammatory activity and has been used in several controlled studies focused on the management of chronic pain among adult patients with different underlying clinical conditions.

METHODS/DESIGN

A literature search will be performed using PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL). The population will be patients who have chronic pain, the intervention will be the administration of PEA alone or in combination with other drugs for the pain management; the comparison will be the standard therapy in accordance with the current guidelines for the treatment of pain. The Outcomes will be the reduction of pain not restricted to specific scales laying out the pain outcome data described in the included studies.

DISCUSSION

This scoping review aims to describe the clinical applications of the PEA in chronic pain management and its outcome.

SCOPING REVIEW REGISTRATION

Open Science Framework https://osf.io/74tmx/ .

An Analysis of Endocannabinoid Concentrations and Mood Following Singing and Exercise in Healthy Volunteers

The euphoric feeling described after running is, at least in part, due to increased circulating endocannabinoids (eCBs). eCBs are lipid signaling molecules involved in reward, appetite, mood, memory and neuroprotection. The aim of this study was to investigate whether activities other than running can increase circulating eCBs. Nine healthy female volunteers (mean 61 years) were recruited from a local choir. Circulating eCBs, haemodynamics, mood and hunger ratings were measured before and immediately after 30 min of dance, reading, singing or cycling in a fasted state. Singing increased plasma levels of anandamide (AEA) by 42% (P < 0.05), palmitoylethanolamine (PEA) by 53% (P < 0.01) and oleoylethanolamine (OEA) by 34% (P < 0.05) and improved positive mood and emotions (P < 0.01), without affecting hunger scores. Dancing did not affect eCB levels or hunger ratings, but decreased negative mood and emotions (P < 0.01). Cycling increased OEA levels by 26% (P < 0.05) and tended to decrease how hungry volunteers felt, without affecting mood. Reading increased OEA levels by 28% (P < 0.01) and increased the desire to eat. Plasma AEA levels were positively correlated with how full participants felt (P < 0.05). Plasma OEA levels were positively correlated with positive mood and emotions (P < 0.01). All three ethanolamines were positively correlated with heart rate (HR; P < 0.0001). These data suggest that activities other than running can increase plasma eCBs associated with changes in mood or appetite. Increases in eCBs may underlie the rewarding and pleasurable effects of singing and exercise and ultimately some of the long-term beneficial effects on mental health, cognition and memory.

Metabolic differentiation of early Lyme disease from southern tick-associated rash illness (STARI)

Lyme disease, the most commonly reported vector-borne disease in the United States, results from infection with Borrelia burgdorferi. Early clinical diagnosis of this disease is largely based on the presence of an erythematous skin lesion for individuals in high-risk regions. This, however, can be confused with other illnesses including southern tick-associated rash illness (STARI), an illness that lacks a defined etiological agent or laboratory diagnostic test, and is coprevalent with Lyme disease in portions of the eastern United States. By applying an unbiased metabolomics approach with sera retrospectively obtained from well-characterized patients, we defined biochemical and diagnostic differences between early Lyme disease and STARI. Specifically, a metabolic biosignature consisting of 261 molecular features (MFs) revealed that altered N-acyl ethanolamine and primary fatty acid amide metabolism discriminated early Lyme disease from STARI. Development of classification models with the 261-MF biosignature and testing against validation samples differentiated early Lyme disease from STARI with an accuracy of 85 to 98%. These findings revealed metabolic dissimilarity between early Lyme disease and STARI, and provide a powerful and new approach to inform patient management by objectively distinguishing early Lyme disease from an illness with nearly identical symptoms.

Palmitic Acid: Physiological Role, Metabolism and Nutritional Implications

Palmitic acid (PA) has been for long time negatively depicted for its putative detrimental health effects, shadowing its multiple crucial physiological activities. PA is the most common saturated fatty acid accounting for 20–30% of total fatty acids in the human body and can be provided in the diet or synthesized endogenously via de novo lipogenesis (DNL). PA tissue content seems to be controlled around a well-defined concentration, and changes in its intake do not influence significantly its tissue concentration because the exogenous source is counterbalanced by PA endogenous biosynthesis. Particular physiopathological conditions and nutritional factors may strongly induce DNL, resulting in increased tissue content of PA and disrupted homeostatic control of its tissue concentration. The tight homeostatic control of PA tissue concentration is likely related to its fundamental physiological role to guarantee membrane physical properties but also to consent protein palmitoylation, palmitoylethanolamide (PEA) biosynthesis, and in the lung an efficient surfactant activity. In order to maintain membrane phospholipids (PL) balance may be crucial an optimal intake of PA in a certain ratio with unsaturated fatty acids, especially PUFAs of both n-6 and n-3 families. However, in presence of other factors such as positive energy balance, excessive intake of carbohydrates (in particular mono and disaccharides), and a sedentary lifestyle, the mechanisms to maintain a steady state of PA concentration may be disrupted leading to an over accumulation of tissue PA resulting in dyslipidemia, hyperglycemia, increased ectopic fat accumulation and increased inflammatory tone via toll-like receptor 4. It is therefore likely that the controversial data on the association of dietary PA with detrimental health effects, may be related to an excessive imbalance of dietary PA/PUFA ratio which, in certain physiopathological conditions, and in presence of an enhanced DNL, may further accelerate these deleterious effects.

Endocannabinoid-related compounds in gastrointestinal diseases

The endocannabinoid system (ECS) is an endogenous signalling pathway involved in the control of several gastrointestinal (GI) functions at both peripheral and central levels. In recent years, it has become apparent that the ECS is pivotal in the regulation of GI motility, secretion and sensitivity, but endocannabinoids (ECs) are also involved in the regulation of intestinal inflammation and mucosal barrier permeability, suggesting their role in the pathophysiology of both functional and organic GI disorders. Genetic studies in patients with irritable bowel syndrome (IBS) or inflammatory bowel disease have indeed shown significant associations with polymorphisms or mutation in genes encoding for cannabinoid receptor or enzyme responsible for their catabolism, respectively. Furthermore, ongoing clinical trials are testing EC agonists/antagonists in the achievement of symptomatic relief from a number of GI symptoms. Despite this evidence, there is a lack of supportive RCTs and relevant data in human beings, and hence, the possible therapeutic application of these compounds is raising ethical, political and economic concerns. More recently, the identification of several EC-like compounds able to modulate ECS function without the typical central side effects of cannabino-mimetics has paved the way for emerging peripherally acting drugs. This review summarizes the possible mechanisms linking the ECS to GI disorders and describes the most recent advances in the manipulation of the ECS in the treatment of GI diseases.

Palmitoylethanolamide induces microglia changes associated with increased migration and phagocytic activity: involvement of the CB2 receptor

The endogenous fatty acid amide palmitoylethanolamide (PEA) has been shown to exert anti-inflammatory actions mainly through inhibition of the release of pro-inflammatory molecules from mast cells, monocytes and macrophages. Indirect activation of the endocannabinoid (eCB) system is among the several mechanisms of action that have been proposed to underlie the different effects of PEA in vivo. In this study, we used cultured rat microglia and human macrophages to evaluate whether PEA affects eCB signaling. PEA was found to increase CB2 mRNA and protein expression through peroxisome proliferator-activated receptor-α (PPAR-α) activation. This novel gene regulation mechanism was demonstrated through: (i) pharmacological PPAR-α manipulation, (ii) PPAR-α mRNA silencing, (iii) chromatin immunoprecipitation. Moreover, exposure to PEA induced morphological changes associated with a reactive microglial phenotype, including increased phagocytosis and migratory activity. Our findings suggest indirect regulation of microglial CB2R expression as a new possible mechanism underlying the effects of PEA. PEA can be explored as a useful tool for preventing/treating the symptoms associated with neuroinflammation in CNS disorders.

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.

Palmitoylethanolamide Modulates Inflammation-Associated Vascular Endothelial Growth Factor (VEGF) Signaling via the Akt/mTOR Pathway in a Selective Peroxisome Proliferator-Activated Receptor Alpha (PPAR-α)-Dependent Manner

BACKGROUND AND AIM

Angiogenesis is emerging as a pivotal process in chronic inflammatory pathologies, promoting immune infiltration and prompting carcinogenesis. Ulcerative Colitis (UC) and Crohn's Disease (CD) represent paradigmatic examples of intestinal chronic inflammatory conditions in which the process of neovascularization correlates with the severity and progression of the diseases. Molecules able to target the angiogenesis have thus the potential to synergistically affect the disease course. Beyond its anti-inflammatory effect, palmitoylethanolamide (PEA) is able to reduce angiogenesis in several chronic inflammatory conditions, but no data about its anti-angiogenic activity in colitis have been produced, yet.

METHODS

The effects of PEA on inflammation-associated angiogenesis in mice with dextran sulphate sodium (DSS)-induced colitis and in patients with UC were assessed. The release of Vascular Endothelial Growth Factor (VEGF), the hemoglobin tissue content, the expression of CD31 and of phosphatidylinositol 3-kinase/Akt/mammalian-target-of-rapamycin (mTOR) signaling axis were all evaluated in the presence of different concentrations of PEA and concomitant administration of PPAR-α and -γ antagonists.

RESULTS

Our results demonstrated that PEA, in a selective peroxisome proliferator activated receptor (PPAR)-α dependent mechanism, inhibits colitis-associated angiogenesis, decreasing VEGF release and new vessels formation. Furthermore, we demonstrated that the mTOR/Akt axis regulates, at least partly, the angiogenic process in IBD and that PEA directly affects this pathway.

CONCLUSIONS

Our results suggest that PEA may improve inflammation-driven angiogenesis in colonic mucosa, thus reducing the mucosal damage and potentially affecting disease progression and the shift towards the carcinogenesis.

Mustard vesicants alter expression of the endocannabinoid system in mouse skin

Vesicants including sulfur mustard (SM) and nitrogen mustard (NM) are bifunctional alkylating agents that cause skin inflammation, edema and blistering. This is associated with alterations in keratinocyte growth and differentiation. Endogenous cannabinoids, including N-arachidonoylethanolamine (anandamide, AEA) and 2-arachidonoyl glycerol (2-AG), are important in regulating inflammation, keratinocyte proliferation and wound healing. Their activity is mediated by binding to cannabinoid receptors 1 and 2 (CB1 and CB2), as well as peroxisome proliferator-activated receptor alpha (PPARα). Levels of endocannabinoids are regulated by fatty acid amide hydrolase (FAAH). We found that CB1, CB2, PPARα and FAAH were all constitutively expressed in mouse epidermis and dermal appendages. Topical administration of NM or SM, at concentrations that induce tissue injury, resulted in upregulation of FAAH, CB1, CB2 and PPARα, a response that persisted throughout the wound healing process. Inhibitors of FAAH including a novel class of vanillyl alcohol carbamates were found to be highly effective in suppressing vesicant-induced inflammation in mouse skin. Taken together, these data indicate that the endocannabinoid system is important in regulating skin homeostasis and that inhibitors of FAAH may be useful as medical countermeasures against vesicants.

Endocannabinoids as Guardians of Metastasis

Endocannabinoids including anandamide and 2-arachidonoylglycerol are involved in cancer pathophysiology in several ways, including tumor growth and progression, peritumoral inflammation, nausea and cancer pain. Recently we showed that the endocannabinoid profiles are deranged during cancer to an extent that this manifests in alterations of plasma endocannabinoids in cancer patients, which was mimicked by similar changes in rodent models of local and metastatic cancer. The present topical review summarizes the complexity of endocannabinoid signaling in the context of tumor growth and metastasis.

Cannabinoids as therapeutic agents in cancer: current status and future implications

The pharmacological importance of cannabinoids has been in study for several years. Cannabinoids comprise of (a) the active compounds of the Cannabis sativa plant, (b) endogenous as well as (c) synthetic cannabinoids. Though cannabinoids are clinically used for anti-palliative effects, recent studies open a promising possibility as anti-cancer agents. They have been shown to possess anti-proliferative and anti-angiogenic effects in vitro as well as in vivo in different cancer models. Cannabinoids regulate key cell signaling pathways that are involved in cell survival, invasion, angiogenesis, metastasis, etc. There is more focus on CB1 and CB2, the two cannabinoid receptors which are activated by most of the cannabinoids. In this review article, we will focus on a broad range of cannabinoids, their receptor dependent and receptor independent functional roles against various cancer types with respect to growth, metastasis, energy metabolism, immune environment, stemness and future perspectives in exploring new possible therapeutic opportunities.

The Endocannabinoid System and its Modulation by Phytocannabinoids

The endocannabinoid system is currently defined as the ensemble of the two 7-transmembrane-domain and G protein-coupled receptors for Δ(9)-tetrahydrocannabinol (but not for most other plant cannabinoids or phytocannabinoids)-cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R); their two most studied endogenous ligands, the "endocannabinoids" N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG); and the enzymes responsible for endocannabinoid metabolism. However, anandamide and 2-AG, and also the phytocannabinoids, have more molecular targets than just CB1R and CB2R. Furthermore, the endocannabinoids, like most other lipid mediators, have more than just one set of biosynthetic and degrading pathways and enzymes, which they often share with "endocannabinoid-like" mediators that may or may not interact with the same proteins as Δ(9)-tetrahydrocannabinol and other phytocannabinoids. In some cases, these degrading pathways and enzymes lead to molecules that are not inactive and instead interact with other receptors. Finally, some of the metabolic enzymes may also participate in the chemical modification of molecules that have very little to do with endocannabinoid and cannabinoid targets. Here, we review the whole world of ligands, receptors, and enzymes, a true "endocannabinoidome", discovered after the cloning of CB1R and CB2R and the identification of anandamide and 2-AG, and its interactions with phytocannabinoids.

Antineuropathic profile of N-palmitoylethanolamine in a rat model of oxaliplatin-induced neurotoxicity

Neurotoxicity is a main side effect of the anticancer drug oxaliplatin. The development of a neuropathic syndrome impairs quality of life and potentially results in chemotherapy dose reductions and/or early discontinuation. In the complex pattern of molecular and morphological alterations induced by oxaliplatin in the nervous system, an important activation of glia has been preclinically evidenced. N-Palmitoylethanolamine (PEA) modulates glial cells and exerts antinociceptive effects in several animal models. In order to improve the therapeutic chances for chemotherapy-dependent neuropathy management, the role of PEA was investigated in a rat model of oxaliplatin-induced neuropathy (2.4 mg kg^-1 daily, intraperitoneally). On day 21, a single administration of PEA (30 mg kg^-1 i.p.) was able to reduce oxaliplatin-dependent pain induced by mechanical and thermal stimuli. The repeated treatment with PEA (30 mg kg^-1 daily i.p. for 21 days, from the first oxaliplatin injection) prevented lowering of pain threshold as well as increased pain on suprathreshold stimulation. Ex vivo histological and molecular analysis of dorsal root ganglia, peripheral nerves and spinal cord highlighted neuroprotective effects and glia-activation prevention induced by PEA repeated administration. The protective effect of PEA resulted in the normalization of the electrophysiological activity of the spinal nociceptive neurons. Finally, PEA did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. The efficacy of PEA in neuropathic pain control and in preventing nervous tissue alteration candidates this endogenous compound as disease modifying agent. These characteristics, joined to the safety profile, suggest the usefulness of PEA in chemotherapy-induced neuropathy.

Palmitoylethanolamide normalizes intestinal motility in a model of post-inflammatory accelerated transit: involvement of CB₁ receptors and TRPV1 channels

BACKGROUND AND PURPOSE

Palmitoylethanolamide (PEA), a naturally occurring acylethanolamide chemically related to the endocannabinoid anandamide, interacts with targets that have been identified in peripheral nerves controlling gastrointestinal motility, such as cannabinoid CB1 and CB2 receptors, TRPV1 channels and PPARα. Here, we investigated the effect of PEA in a mouse model of functional accelerated transit which persists after the resolution of colonic inflammation (post-inflammatory irritable bowel syndrome).

EXPERIMENTAL APPROACH

Intestinal inflammation was induced by intracolonic administration of oil of mustard (OM). Mice were tested for motility and biochemical and molecular biology changes 4 weeks later. PEA, oleoylethanolamide and endocannabinoid levels were measured by liquid chromatography-mass spectrometry and receptor and enzyme mRNA expression by qRT-PCR.

KEY RESULTS

OM induced transient colitis and a functional post-inflammatory increase in upper gastrointestinal transit, associated with increased intestinal anandamide (but not 2-arachidonoylglycerol, PEA or oleoylethanolamide) levels and down-regulation of mRNA for TRPV1 channels. Exogenous PEA inhibited the OM-induced increase in transit and tended to increase anandamide levels. Palmitic acid had a weaker effect on transit. Inhibition of transit by PEA was blocked by rimonabant (CB1 receptor antagonist), further increased by 5'-iodoresiniferatoxin (TRPV1 antagonist) and not significantly modified by the PPARα antagonist GW6471.

CONCLUSIONS AND IMPLICATIONS

Intestinal endocannabinoids and TRPV1 channel were dysregulated in a functional model of accelerated transit exhibiting aspects of post-inflammatory irritable bowel syndrome. PEA counteracted the accelerated transit, the effect being mediated by CB1 receptors (possibly via increased anandamide levels) and modulated by TRPV1 channels.

The anti-inflammatory mediator palmitoylethanolamide enhances the levels of 2-arachidonoyl-glycerol and potentiates its actions at TRPV1 cation channels

BACKGROUND AND PURPOSE

Palmitoylethanolamide (PEA) is an endogenous congener of anandamide and potentiates its actions at cannabinoid CB1 and CB2 receptors, and at transient receptor potential vanilloid type-1 (TRPV1) channels. The other endocannabinoid, 2-arachidonoylglycerol (2-AG), was recently suggested to act as a TRPV1 channel agonist. We investigated if PEA enhanced levels of 2-AG in vitro or in vivo and 2-AG activity at TRPV1 channels.

EXPERIMENTAL APPROACH

Endogenous lipid levels were measured by LC-MS in (i) human keratinocytes incubated with PEA (10-20 μM, 40 min, 6 and 24 h, 37°C); (ii) the blood of spontaneously Ascaris suum hypersensitive beagle dogs given a single oral dose of ultramicronized PEA (30 mg·kg(-1), 1, 2, 4 and 8 h from administration); (iii) the blood of healthy volunteers given a single oral dose of micronized PEA (300 mg, 2, 4 and 6 h from administration). Effects of 2-AG at TRPV1 channels were assessed by measuring intracellular Ca(2+) in HEK-293 cells over-expressing human TRPV1 channels.

KEY RESULTS

PEA elevated 2-AG levels in keratinocytes (∼3-fold) and in human and canine plasma (∼2 and ∼20-fold respectively). 2-AG dose-dependently raised intracellular Ca(2+) in HEK-293-TRPV1 cells in a TRPV1-dependent manner and desensitized the cells to capsaicin. PEA only slightly enhanced 2-AG activation of TRPV1 channels, but significantly increased 2-AG-induced TRPV1 desensitization to capsaicin (IC50 from 0.75 ± 0.04 to 0.45 ± 0.02 μM, with PEA 2 μM).

CONCLUSIONS AND IMPLICATIONS

These observations may explain why several effects of PEA are attenuated by cannabinoid receptor or TRPV1 channel antagonists.

LINKED ARTICLES

This article is part of a themed section on Endocannabinoids. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.7/issuetoc.

Palmitoylethanolamide, a naturally occurring lipid, is an orally effective intestinal anti-inflammatory agent

BACKGROUND AND PURPOSE

Palmitoylethanolamide (PEA) acts via several targets, including cannabinoid CB1 and CB2 receptors, transient receptor potential vanilloid type-1 (TRPV1) ion channels, peroxisome proliferator-activated receptor alpha (PPAR α) and orphan G protein-coupled receptor 55 (GRR55), all involved in the control of intestinal inflammation. Here, we investigated the effect of PEA in a murine model of colitis.

EXPERIMENTAL APPROACH

Colitis was induced in mice by intracolonic administration of dinitrobenzenesulfonic acid (DNBS). Inflammation was assessed by evaluating inflammatory markers/parameters and by histology; intestinal permeability by a fluorescent method; colonic cell proliferation by immunohistochemistry; PEA and endocannabinoid levels by liquid chromatography mass spectrometry; receptor and enzyme mRNA expression by quantitative RT-PCR.

KEY RESULTS

DNBS administration caused inflammatory damage, increased colonic levels of PEA and endocannabinoids, down-regulation of mRNA for TRPV1 and GPR55 but no changes in mRNA for CB1 , CB2 and PPARα. Exogenous PEA (i.p. and/or p.o., 1 mg·kg(-1) ) attenuated inflammation and intestinal permeability, stimulated colonic cell proliferation, and increased colonic TRPV1 and CB1 receptor expression. The anti-inflammatory effect of PEA was attenuated or abolished by CB2 receptor, GPR55 or PPARα antagonists and further increased by the TRPV1 antagonist capsazepine.

CONCLUSIONS AND IMPLICATIONS

PEA improves murine experimental colitis, the effect being mediated by CB2 receptors, GPR55 and PPARα, and modulated by TRPV1 channels.

Inhibition of fatty acid amide hydrolase activates Nrf2 signalling and induces heme oxygenase 1 transcription in breast cancer cells

BACKGROUND AND PURPOSE

Endocannabinoids such as anandamide (AEA) are important lipid ligands regulating cell proliferation, differentiation and apoptosis. Their levels are regulated by hydrolase enzymes, the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Here, we investigated whether FAAH or AEA are involved in NF (erythroid-derived 2)-like 2 (Nrf2)/antioxidant responsive element (ARE) pathway.

EXPERIMENTAL APPROACH

The aim of this study was to analyse the effects of AEA or FAAH inhibition by the URB597 inhibitor or FAAH/siRNA on the activation of Nrf2-ARE signalling pathway and heme oxygenase-1 (HO-1) induction and transcription.

KEY RESULTS

Endogenous AEA was detected in the immortalized human mammary epithelial MCF-10A cells (0.034 ng per 10(6) cells) but not in MCF-7 or MDA-MB-231 breast cancer cells. Because breast tumour cells express FAAH abundantly, we examined the effects of FAAH on Nrf2/antioxidant pathway. We found that inhibition of FAAH by the URB597 inhibitor induced antioxidant HO-1 in breast cancer cells and MCF-10A cells. RNAi-mediated knockdown of FAAH or treatment with AEA-activated ARE-containing reporter induced HO-1 mRNA and protein expression, independent of the cannabinoid receptors, CB1, CB2 or TRPV1. Furthermore, URB597, AEA and siRNA-FAAH treatments induced the nuclear translocation of Nrf2, while siRNA-Nrf2 treatment and Keap1 expression blocked AEA, URB597 and si-FAAH from activation of ARE reporter and HO-1 induction. siRNA-HO-1 treatment decreased the viability of breast cancer cells and MCF-10A cells.

CONCLUSIONS AND IMPLICATIONS

These data uncovered a novel mechanism by which inhibition of FAAH or exposure to AEA induced HO-1 transcripts and implicating AEA and FAAH as direct modifiers in signalling mediated activation of Nrf2-HO-1 pathway, independent of cannabinoid receptors.

Quantification of anandamide, oleoylethanolamide and palmitoylethanolamide in rodent brain tissue using high performance liquid chromatography-electrospray mass spectroscopy

Reported concentrations for endocannabinoids and related lipids in biological tissues can vary greatly; therefore, methods used to quantify these compounds need to be validated. This report describes a method to quantify anandamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) from rodent brain tissue. Analytes were extracted using acetonitrile without further sample clean up, resolved on a C18 reverse-phase column using a gradient mobile phase and detected using electrospray ionization in positive selected ion monitoring mode on a single quadrupole mass spectrometer. The method produced high recovery rates for AEA, OEA and PEA, ranging from 98.1% to 106.2%, 98.5% to 102.2% and 85.4% to 89.5%, respectively. The method resulted in adequate sensitivity with a lower limit of quantification for AEA, OEA and PEA of 1.4 ng/mL, 0.6 ng/mL and 0.5 ng/mL, respectively. The method was reproducible as intraday and interday accuracies and precisions were under 15%. This method was suitable for quantifying AEA, OEA and PEA from rat brain following pharmacological inhibition of fatty acid amide hydrolase.

Regulation of circulating endocannabinoids associated with cancer and metastases in mice and humans

BACKGROUND AND AIMS

Endocannabinoids may modify cancer development, progression and associated pain. We determined whether cancer-evoked dysregulations in this system become manifest in altered tissue and plasma endocannabinoids.

METHODS

Endocannabinoid changes due to cancer were explored in a local and metastatic syngeneic mouse melanoma model. Endocannabinoid stratification in human cancer was cross-sectionally assessed in the plasma of 304 patients (147 men, 157 women, aged 32 - 87 years) suffering from several types of cancer at Roman Numeral Staging between I and IVc, mostly IV (n = 220), and compared with endocannabinoids of healthy controls.

RESULTS

In mice with local tumor growth, ethanolamide endocannabinoids, i.e., anandamide (AEA), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) were downregulated, whereas 2-arachidonoylglycerol (2-AG) was increased. Upon spreading of the cancer cells particularly 2-AG steadily increased in parallel to disease progression while OEA modulated cell migration. Results translated into humans, in whom cancer was associated with a decreased AEA, increased 2-AG and increased OEA correlating with the number of metastases.

CONCLUSIONS

The endocannabinoid system was subject to cancer-associated regulations to an extent that led to measurable changes in circulating endocannabinoid levels, emphasizing the importance of the endocannabinoid system in the pathophysiology of cancer.

Changes in endocannabinoid and N-acylethanolamine levels in rat brain structures following cocaine self-administration and extinction training

Preclinical investigations have demonstrated that drugs of abuse alter the levels of lipid-based signalling molecules, including endocannabinoids (eCBs) and N-acylethanolamines (NAEs), in the rodent brain. In addition, several drugs targeting eCBs and/or NAEs are implicated in reward and/or seeking behaviours related to the stimulation of dopamine systems in the brain. In our study, the brain levels of eCBs (anandamide (AEA) and 2-arachidonoylglycerol (2-AG)) and NAEs (oleoylethanolamide (OEA) and palmitoylethanolamide (PEA)) were analyzed via an LC-MS/MS method in selected brain structures of rats during cocaine self-administration and after extinction training according to the "yoked" control procedure. Repeated (14days) cocaine (0.5mg/kg/infusion) self-administration and yoked drug delivery resulted in a significant decrease (ca. 52%) in AEA levels in the cerebellum, whereas levels of 2-AG increased in the frontal cortex, the hippocampus and the cerebellum and decreased in the hippocampus and the dorsal striatum. In addition, we detected increases (>150%) in the levels of OEA and PEA in the limbic areas in both cocaine treated groups, as well as an increase in the tissue levels of OEA in the dorsal striatum in only the yoked cocaine group and increases in the tissue levels of PEA in the dorsal striatum (both cocaine groups) and the nucleus accumbens (yoked cocaine group only). Compared to the yoked saline control group, extinction training (10days) resulted in a potent reduction in AEA levels in the frontal cortex, the hippocampus and the nucleus accumbens and in 2-AG levels in the hippocampus, the dorsal striatum and the cerebellum. The decreases in the limbic and subcortical areas were more apparent for rats that self-administered cocaine. Following extinction, there was a region-specific change in the levels of NAEs in rats previously injected with cocaine; a potent increase (ca. 100%) in the levels of OEA and PEA was detected in the prefrontal cortex and the hippocampus, whilst a drop was noted in the striatal areas versus yoked saline yoked animals. Our findings support the previous pharmacological evidence that the eCB system and NAEs are involved in reinforcement and extinction of positively reinforced behaviours and that these lipid-derived molecules may represent promising targets for the development of new treatments for drug addiction.

PPAR-alpha agonists as novel antiepileptic drugs: preclinical findings

Nicotinic acetylcholine receptors (nAChRs) are involved in seizure mechanisms. Hence, nocturnal frontal lobe epilepsy was the first idiopathic epilepsy linked with specific mutations in α4 or β2 nAChR subunit genes. These mutations confer gain of function to nAChRs by increasing sensitivity toward acetylcholine. Consistently, nicotine elicits seizures through nAChRs and mimics the excessive nAChR activation observed in animal models of the disease. Treatments aimed at reducing nicotinic inputs are sought as therapies for epilepsies where these receptors contribute to neuronal excitation and synchronization. Previous studies demonstrated that peroxisome proliferator-activated receptors-α (PPARα), nuclear receptor transcription factors, suppress nicotine-induced behavioral and electrophysiological effects by modulating nAChRs containing β2 subunits. On these bases, we tested whether PPARα agonists were protective against nicotine-induced seizures. To this aim we utilized behavioral and electroencephalographic (EEG) experiments in C57BL/J6 mice and in vitro patch clamp recordings from mice and rats. Convulsive doses of nicotine evoked severe seizures and bursts of spike-waves discharges in ∼100% of mice. A single dose of the synthetic PPARα agonist WY14643 (WY, 80 mg/kg, i.p.) or chronic administration of fenofibrate, clinically available for lipid metabolism disorders, in the diet (0.2%) for 14 days significantly reduced or abolished behavioral and EEG expressions of nicotine-induced seizures. Acute WY effects were reverted by the PPARα antagonist MK886 (3 mg/kg, i.p.). Since neocortical networks are crucial in the generation of ictal activity and synchrony, we performed patch clamp recordings of spontaneous inhibitory postsynaptic currents (sIPSCs) from frontal cortex layer II/III pyramidal neurons. We found that both acute and chronic treatment with PPARα agonists abolished nicotine-induced sIPSC increases. PPARα within the CNS are key regulators of neuronal activity through modulation of nAChRs. These effects might be therapeutically exploited for idiopathic or genetically determined forms of epilepsy where nAChRs play a major role.

Hub and switches: endocannabinoid signalling in midbrain dopamine neurons

The last decade has provided a wealth of experimental data on the role played by lipids belonging to the endocannabinoid family in several facets of physiopathology of dopamine neurons. We currently suggest that these molecules, being intimately connected with diverse metabolic and signalling pathways, might differently affect various functions of dopamine neurons through activation not only of surface receptors, but also of nuclear receptors. It is now emerging how dopamine neurons can regulate their constituent biomolecules to compensate for changes in either internal functions or external conditions. Consequently, dopamine neurons use these lipid molecules as metabolic and homeostatic signal detectors, which can dynamically impact cell function and fitness. Because dysfunctions of the dopamine system underlie diverse neuropsychiatric disorders, including schizophrenia and drug addiction, the importance of better understanding the correlation between an unbalanced endocannabinoid signal and the dopamine system is even greater. Particularly, because dopamine neurons are critical in controlling incentive-motivated behaviours, the involvement of endocannabinoid molecules in fine-tuning dopamine cell activity opened new avenues in both understanding and treating drug addiction. Here, we review recent advances that have shed new light on the understanding of differential roles of endocannabinoids and their cognate molecules in the regulation of the reward circuit, and discuss their anti-addicting properties, particularly with a focus on their potential engagement in the prevention of relapse.

PPARα regulates cholinergic-driven activity of midbrain dopamine neurons via a novel mechanism involving α7 nicotinic acetylcholine receptors

Ventral tegmental area dopamine neurons control reward-driven learning, and their dysregulation can lead to psychiatric disorders. Tonic and phasic activity of these dopaminergic neurons depends on cholinergic tone and activation of nicotinic acetylcholine receptors (nAChRs), particularly those containing the β2 subunit (β2*-nAChRs). Nuclear peroxisome proliferator-activated receptors type-α (PPARα) tonically regulate β2*-nAChRs and thereby control dopamine neuron firing activity. However, it is unknown how and when PPARα endogenous ligands are synthesized by dopamine cells. Using ex vivo and in vivo electrophysiological techniques combined with biochemical and behavioral analysis, we show that activation of α7-nAChRs increases in the rat VTA both the tyrosine phosphorylation of the β2 subunit of nAChRs and the levels of two PPARα endogenous ligands in a Ca(2+)-dependent manner. Accordingly, in vivo production of endogenous PPARα ligands, triggered by α7-nAChR activation, blocks in rats nicotine-induced increased firing activity of dopamine neurons and displays antidepressant-like properties. These data demonstrate that endogenous PPARα ligands are effectors of α7-nAChRs and that their neuromodulatory properties depend on phosphorylation of β2*-nAChRs on VTA dopamine cells. This reveals an autoinhibitory mechanism aimed at reducing dopamine cell overexcitation engaged during hypercholinergic drive. Our results unveil important physiological functions of nAChR/PPARα signaling in dopamine neurons and how behavioral output can change after modifications of this signaling pathway. Overall, the present study suggests PPARα as new therapeutic targets for disorders associated with unbalanced dopamine-acetylcholine systems.

The Endocannabinoid System in the Postimplantation Period: A Role during Decidualization and Placentation

Although the detrimental effects of cannabis consumption during gestation are known for years, the vast majority of studies established a link between cannabis consumption and foetal development. The complex maternal-foetal interrelationships within the placental bed are essential for normal pregnancy, and decidua definitively contributes to the success of this process. Nevertheless, the molecular signalling network that coordinates strategies for successful decidualization and placentation are not well understood. The discovery of the endocannabinoid system highlighted new signalling mediators in various physiological processes, including reproduction. It is known that endocannabinoids present regulatory functions during blastocyst development, oviductal transport, and implantation. In addition, all the endocannabinoid machinery was found to be expressed in decidual and placental tissues. Additionally, endocannabinoid's plasmatic levels were found to fluctuate during normal gestation and to induce decidual cell death and disturb normal placental development. Moreover, aberrant endocannabinoid signalling during the period of placental development has been associated with pregnancy disorders. It indicates the existence of a possible regulatory role for these molecules during decidualization and placentation processes, which are known to be particularly vulnerable. In this review, the influence of the endocannabinoid system in these critical processes is explored and discussed.

Endocannabinoids and obesity

A safe and effective antiobesity drug is needed to combat the global obesity epidemic. The discovery of cannabinoids from medicinal herbs has revealed the endocannabinoid system (ECS) in animals and humans, which regulates various physiological activities such as feeding, thermogenesis, and body weight (BW). Although cannabinoid receptors 1 (CB1) antagonists have shown antiobesity efficacies in animal models and in the clinic, they failed to establish as a treatment due to their psychological side effects. Recent studies indicate that CB1 in various peripheral tissues may mediate some of the therapeutic effects of CB1 antagonists, such as improved lipid and glucose homeostasis. It rationalizes the development of compounds with limited brain penetration, for minimizing the side effects while retaining the therapeutic efficacies. A survey of the literature has revealed some controversies about how the ECS affects obesity. This review summarizes the research progresses and discusses some future perspectives.