Chemical probes to potently and selectively inhibit endocannabinoid cellular reuptake

The role of monoglyceride lipase gene in promoting proliferation, metastasis, and free fatty acid accumulation in uveal melanoma cells

Uveal melanoma is a malignant tumor originating from melanocytes in the eye's uvea, often detected during routine ophthalmic examinations due to its typically asymptomatic nature. Despite effective local treatments, up to 50% of patients develop hematogenous metastases, highlighting the need for better prognostic markers and therapeutic targets. In this study, we developed an innovative Metastasis-Related Gene Signature (MERGS) score to classify patients from various cohorts. By establishing this scoring method, we discovered underlying mechanisms responsible for significant differences between samples with high and low MERGS scores. We identified a set of ten genes to construct MERGS, which showed a high predictive accuracy for patient survival. Further, Monoglyceride Lipase (MGLL) emerged as the most important gene in distinguishing uveal melanoma metastasis. Functional studies demonstrated that knocking down MGLL significantly inhibited proliferation, invasion, and migration of uveal melanoma cells in vitro and in vivo, while overexpression of MGLL enhanced these malignant behaviors. Additionally, MGLL modulated free fatty acid (FFA) levels within these cells. Our findings reveal MGLL as a crucial player in uveal melanoma progression and propose it as a novel therapeutic target, potentially leading to improved management and outcomes for patients with this disease.

A Highly Potent, Orally Bioavailable Pyrazole-Derived Cannabinoid CB2 Receptor- Selective Full Agonist for In Vivo Studies

The cannabinoid CB2 receptor (CB2R) is a potential therapeutic target for distinct forms of tissue injury and inflammatory diseases. To thoroughly investigate the role of CB2R in pathophysiological conditions and for target validation in vivo, optimal pharmacological tool compounds are essential. Despite the sizable progress in the generation of potent and selective CB2R ligands, pharmacokinetic parameters are often neglected for in vivo studies. Here, we report the generation and characterization of a tetra-substituted pyrazole CB2R full agonist named RNB-61 with high potency (K i 0.13-1.81 nM, depending on species) and a peripherally restricted action due to P-glycoprotein-mediated efflux from the brain. 3H and 14C labeled RNB-61 showed apparent K d values of <4 nM toward human CB2R in both cell and tissue experiments. The 6,800-fold selectivity over CB1 receptors and negligible off-targets in vitro, combined with high oral bioavailability and suitable systemic pharmacokinetic (PK) properties, prompted the assessment of RNB-61 in a mouse ischemia-reperfusion model of acute kidney injury (AKI) and in a rat model of chronic kidney injury/inflammation and fibrosis (CKI) induced by unilateral ureteral obstruction. RNB-61 exerted dose-dependent nephroprotective and/or antifibrotic effects in the AKI/CKI models. Thus, RNB-61 is an optimal CB2R tool compound for preclinical in vivo studies with superior biophysical and PK properties over generally used CB2R ligands.

CNS Drug Discovery in Academia: Where Basic Research Meets Innovation

The involvement of academic research in drug discovery is consistently growing. However, academic projects seldom advance to clinical trials. Here, we assess the landscape of drug discovery within the National Centre of Competence in Research (NCCR) TransCure launched by the Swiss National Science Foundation to foster basic research and early-stage drug discovery on membrane transporters. This included transporters in central nervous system (CNS) disorders, which represent a huge unmet medical need. While idea championship, sustainable funding, collaborations between disciplines at the interface of academia and industry are important for translational research, Popperian falsifiability, strong intellectual property and a motivated startup team are key elements for innovation. This is exemplified by the NCCR TransCure spin-off company Synendos Therapeutics, a clinical stage biotech company developing the first selective endocannabinoid reuptake inhibitors (SERIs) as novel treatment for neuropsychiatric disorders. We provide a perspective on the challenges related to entering an uncharted druggable space and bridging the often mentioned "valley of death". The high attrition rate of drug discovery projects in the CNS field within academia is often due to the lack of meaningful animal models that can provide pharmacological proof-of-concept for potentially disruptive technologies at the earliest stages, and the absence of solid intellectual property.

Endocannabinoid Hydrolase Inhibitors: Potential Novel Anxiolytic Drugs

Over the past decade, the idea of targeting the endocannabinoid system to treat anxiety disorders has received increasing attention. Previous studies focused more on developing cannabinoid receptor agonists or supplementing exogenous cannabinoids, which are prone to various adverse effects due to their strong pharmacological activity and poor receptor selectivity, limiting their application in clinical research. Endocannabinoid hydrolase inhibitors are considered to be the most promising development strategies for the treatment of anxiety disorders. More recent efforts have emphasized that inhibition of two major endogenous cannabinoid hydrolases, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), indirectly activates cannabinoid receptors by increasing endogenous cannabinoid levels in the synaptic gap, circumventing receptor desensitization resulting from direct enhancement of endogenous cannabinoid signaling. In this review, we comprehensively summarize the anxiolytic effects of MAGL and FAAH inhibitors and their potential pharmacological mechanisms, highlight reported novel inhibitors or natural products, and provide an outlook on future directions in this field.

A highly potent, orally bioavailable pyrazole-derived cannabinoid CB2 receptor-selective full agonist for in vivo studies

The cannabinoid CB2 receptor (CB2R) is a potential therapeutic target for distinct forms of tissue injury and inflammatory diseases. To thoroughly investigate the role of CB2R in pathophysiological conditions and for target validation in vivo, optimal pharmacological tool compounds are essential. Despite the sizable progress in the generation of potent and selective CB2R ligands, pharmacokinetic parameters are often neglected for in vivo studies. Here, we report the generation and characterization of a tetra-substituted pyrazole CB2R full agonist named RNB-61 with high potency (K i 0.13-1.81 nM, depending on species) and a peripherally restricted action due to P-glycoprotein mediated efflux from the brain. 3H and 14C labelled RNB-61 showed apparent K d values < 4 nM towards human CB2R in both cell and tissue experiments. The >6000-fold selectivity over CB1 receptors and negligible off-targets in vitro, combined with high oral bioavailability and suitable systemic pharmacokinetic (PK) properties, prompted the assessment of RNB-61 in a mouse ischemia-reperfusion model of acute kidney injury (AKI) and in a rat model of chronic kidney injury/inflammation and fibrosis (CKI) induced by unilateral ureteral obstruction. RNB-61 exerted dose-dependent nephroprotective and/or antifibrotic effects in the AKI/CKI models. Thus, RNB-61 is an optimal CB2R tool compound for preclinical in vivo studies with superior biophysical and PK properties over generally used CB2R ligands.

Inhibition of fatty acid binding protein-5 in the basolateral amygdala induces anxiolytic effects and accelerates fear memory extinction

RATIONALE

The endocannabinoid (eCB) system critically controls anxiety and fear-related behaviours. Anandamide (AEA), a prominent eCB ligand, is a hydrophobic lipid that requires chaperone proteins such as Fatty Acid Binding Proteins (FABPs) for intracellular transport. Intracellular AEA transport is necessary for degradation, so blocking FABP activity increases AEA neurotransmission.

OBJECTIVE

To investigate the effects of a novel FABP5 inhibitor (SBFI-103) in the basolateral amygdala (BLA) on anxiety and fear memory.

METHODS

We infused SBFI-103 (0.5 μg-5 μg) to the BLA of adult male Sprague Dawley rats and ran various anxiety and fear memory behavioural assays, neurophysiological recordings, and localized molecular signaling analyses. We also co-infused SBFI-103 with the AEA inhibitor, LEI-401 (3 μg and 10 μg) to investigate the potential role of AEA in these phenomena.

RESULTS

Acute intra-BLA administration of SBFI-103 produced strong anxiolytic effects across multiple behavioural tests. Furthermore, animals exhibited acute and long-term accelerated associative fear memory extinction following intra-BLA FABP5 inhibition. In addition, BLA FABP5 inhibition induced strong modulatory effects on putative PFC pyramidal neurons along with significantly increased gamma oscillation power. Finally, we observed local BLA changes in the phosphorylation activity of various anxiety- and fear memory-related molecular biomarkers in the PI3K/Akt and MAPK/Erk signaling pathways. At all three levels of analyses, we found the functional effects of SBFI-103 depend on availability of the AEA ligand.

CONCLUSIONS

These findings demonstrate a novel intra-BLA FABP5 signaling mechanism regulating anxiety and fear memory behaviours, neuronal activity states, local anxiety-related molecular pathways, and functional AEA modulation.

The endocannabinoid system as a putative target for the development of novel drugs for the treatment of psychiatric illnesses

Cannabis is well established to impact affective states, emotion and perceptual processing, primarily through its interactions with the endocannabinoid system. While cannabis use is quite prevalent in many individuals afflicted with psychiatric illnesses, there is considerable controversy as to whether cannabis may worsen these conditions or provide some form of therapeutic benefit. The development of pharmacological agents which interact with components of the endocannabinoid system in more localized and discrete ways then via phytocannabinoids found in cannabis, has allowed the investigation if direct targeting of the endocannabinoid system itself may represent a novel approach to treat psychiatric illness without the potential untoward side effects associated with cannabis. Herein we review the current body of literature regarding the various pharmacological tools that have been developed to target the endocannabinoid system, their impact in preclinical models of psychiatric illness and the recent data emerging of their utilization in clinical trials for psychiatric illnesses, with a specific focus on substance use disorders, trauma-related disorders, and autism. We highlight several candidate drugs which target endocannabinoid function, particularly inhibitors of endocannabinoid metabolism or modulators of cannabinoid receptor signaling, which have emerged as potential candidates for the treatment of psychiatric conditions, particularly substance use disorder, anxiety and trauma-related disorders and autism spectrum disorders. Although there needs to be ongoing clinical work to establish the potential utility of endocannabinoid-based drugs for the treatment of psychiatric illnesses, the current data available is quite promising and shows indications of several potential candidate diseases which may benefit from this approach.

Goods and Bads of the Endocannabinoid System as a Therapeutic Target: Lessons Learned after 30 Years

The cannabis derivative marijuana is the most widely used recreational drug in the Western world and is consumed by an estimated 83 million individuals (∼3% of the world population). In recent years, there has been a marked transformation in society regarding the risk perception of cannabis, driven by its legalization and medical use in many states in the United States and worldwide. Compelling research evidence and the Food and Drug Administration cannabis-derived cannabidiol approval for severe childhood epilepsy have confirmed the large therapeutic potential of cannabidiol itself, Δ9-tetrahydrocannabinol and other plant-derived cannabinoids (phytocannabinoids). Of note, our body has a complex endocannabinoid system (ECS)-made of receptors, metabolic enzymes, and transporters-that is also regulated by phytocannabinoids. The first endocannabinoid to be discovered 30 years ago was anandamide (N-arachidonoyl-ethanolamine); since then, distinct elements of the ECS have been the target of drug design programs aimed at curing (or at least slowing down) a number of human diseases, both in the central nervous system and at the periphery. Here a critical review of our knowledge of the goods and bads of the ECS as a therapeutic target is presented to define the benefits of ECS-active phytocannabinoids and ECS-oriented synthetic drugs for human health. SIGNIFICANCE STATEMENT: The endocannabinoid system plays important roles virtually everywhere in our body and is either involved in mediating key processes of central and peripheral diseases or represents a therapeutic target for treatment. Therefore, understanding the structure, function, and pharmacology of the components of this complex system, and in particular of key receptors (like cannabinoid receptors 1 and 2) and metabolic enzymes (like fatty acid amide hydrolase and monoacylglycerol lipase), will advance our understanding of endocannabinoid signaling and activity at molecular, cellular, and system levels, providing new opportunities to treat patients.

Anxiolytic effects of endocannabinoid enhancing compounds: A systematic review and meta-analysis

The endocannabinoid system is a promising candidate for anxiolytic therapy, but translation to the clinic has been lagging. We meta-analyzed the evidence for anxiety-reduction by compounds that facilitate endocannabinoid signaling in humans and animals. To identify areas of specific potential, effects of moderators were assessed. Literature was searched in Pubmed and Embase up to May 2021. A placebo/vehicle-control group was required and in human studies, randomization. We excluded studies that co-administered other substances. Risk of bias was assessed with SYRCLE's RoB tool and Cochrane RoB 2.0. We conducted three-level random effects meta-analyses and explored sources of heterogeneity using Bayesian regularized meta-regression (BRMA). The systematic review yielded 134 studies. We analyzed 120 studies (114 animal, 6 human) that investigated cannabidiol (CBD, 61), URB597 (39), PF-3845 (6) and AM404 (14). Pooled effects on conditioned and unconditioned anxiety in animals (with the exception of URB597 on unconditioned anxiety) and on experimentally induced anxiety in humans favored the investigational drugs over placebo/vehicle. Publication year was negatively associated with effects of CBD on unconditioned anxiety. Compared to approach avoidance tests, tests of repetitive-compulsive behavior were associated with larger effects of CBD and URB597, and the social interaction test with smaller effects of URB597. Larger effects of CBD on unconditioned anxiety were observed when anxiety pre-existed. Studies reported few side effects at therapeutic doses. The evidence quality was low with indications of publication bias. More clinical trials are needed to translate the overall positive results to clinical applications.

Endocannabinoid signaling in the central nervous system

It is hard to overestimate the influence of the endocannabinoid signaling (ECS) system on central nervous system (CNS) function. In the 40 years since cannabinoids were found to trigger specific cell signaling cascades, studies of the ECS system continue to cause amazement, surprise, and confusion! CB1 cannabinoid receptors are expressed widely in the CNS and regulate cell-cell communication via effects on the release of both neurotransmitters and gliotransmitters. CB2 cannabinoid receptors are difficult to detect in the CNS but seem to "punch above their weight" as compounds targeting these receptors have significant effects on inflammatory state and behavior. Positive and negative allosteric modulators for both receptors have been identified and examined in preclinical studies. Concentrations of the endocannabinoid ligands, N-arachidonoylethanolamine and 2-arachidonoylglycerol (2-AG), are regulated by a combination of enzymatic synthesis and degradation and inhibitors of these processes are available and making their way into clinical trials. Importantly, ECS regulates many essential brain functions, including regulation of reward, anxiety, inflammation, motor control, and cellular development. While the field is on the cusp of preclinical discoveries providing impactful clinical and therapeutic insights into many CNS disorders, there is still much to be learned about this remarkable and versatile modulatory system.

Assay of Endocannabinoid Uptake

Endocannabinoids at nanomolar physiological concentrations cross cellular membranes by facilitated diffusion, a process that can be studied by measuring transport kinetics and endocannabinoid trafficking employing radioligands and mass spectrometry. Here, we describe radiosubstrate-based assays using arachidonoyl[1-³H]ethanolamine and 2-arachidonoyl[1,2,3-³H]glycerol to measure cellular endocannabinoid uptake in a three-phase assay with human U937 cells. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS)-based lipidomics was used to interrogate the roles of serum and albumin for endocannabinoid trafficking in U937 cells.

ABX-1431 inhibits the development of endometrial adenocarcinoma and reverses progesterone resistance by targeting MGLL

Endometrial cancer is a common gynecological malignancy. With the onset of EC patients younger, conservative treatment with progesterone has become an important option for patients trying to preserve reproductive function. However, progesterone resistance is a key factor affecting the efficacy of therapy and it is urgent to clarify the mechanism so as to propose a potential target and inhibit the development of endometrial adenocarcinoma and progesterone resistance. MGLL, an important factor involved in lipid mobilization, is overexpressed in many tumors, however the biological function of MGLL in the development of endometrial adenocarcinoma and the process of progesterone resistance still remains unclear. In this study, we first found MGLL was highly expressed in progesterone resistant samples of endometrial adenocarcinoma, and then we verified its expression was increased in endometrial adenocarcinoma. Through in vitro and in vivo experiments, we demonstrated that overexpression of MGLL promoted tumor proliferation, metastasis and the occurrence of progestogen resistance, knockdown MGLL inhibited tumor proliferation, metastasis and reversed progestogen resistance. In addition, knockdown of MGLL can sensitize endometrial adenocarcinoma cells to progesterone, possibly by affecting ROS generation and reducing the expression of AKR1C1. Finally, it was verified that ABX-1431, MGLL inhibitor, reversed progesterone resistance and enhanced the sensitivity of endometrial adenocarcinoma to progesterone both in vitro and in vivo. In conclusion, the high expression of MGLL is involved in the occurrence and development of endometrial adenocarcinoma and progesterone resistance. Targeted inhibition of MGLL by inhibitors may be an effective method for the treatment of progesterone resistance in endometrial adenocarcinoma.

Targeting the cannabinoid system to counteract the deleterious effects of stress in Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disorder characterized histologically in postmortem human brains by the presence of dense protein accumulations known as amyloid plaques and tau tangles. Plaques and tangles develop over decades of aberrant protein processing, post-translational modification, and misfolding throughout an individual’s lifetime. We present a foundation of evidence from the literature that suggests chronic stress is associated with increased disease severity in Alzheimer’s patient populations. Taken together with preclinical evidence that chronic stress signaling can precipitate cellular distress, we argue that chronic psychological stress renders select circuits more vulnerable to amyloid- and tau- related abnormalities. We discuss the ongoing investigation of systemic and cellular processes that maintain the integrity of protein homeostasis in health and in degenerative conditions such as Alzheimer’s disease that have revealed multiple potential therapeutic avenues. For example, the endogenous cannabinoid system traverses the central and peripheral neural systems while simultaneously exerting anti-inflammatory influence over the immune response in the brain and throughout the body. Moreover, the cannabinoid system converges on several stress-integrative neuronal circuits and critical regions of the hypothalamic-pituitary-adrenal axis, with the capacity to dampen responses to psychological and cellular stress. Targeting the cannabinoid system by influencing endogenous processes or exogenously stimulating cannabinoid receptors with natural or synthetic cannabis compounds has been identified as a promising route for Alzheimer’s Disease intervention. We build on our foundational framework focusing on the significance of chronic psychological and cellular stress on the development of Alzheimer’s neuropathology by integrating literature on cannabinoid function and dysfunction within Alzheimer’s Disease and conclude with remarks on optimal strategies for treatment potential.

Chemical Proteomics Reveals Off-Targets of the Anandamide Reuptake Inhibitor WOBE437

Anandamide or N-arachidonoylethanolamine (AEA) is a signaling lipid that modulates neurotransmitter release via activation of the type 1 cannabinoid receptor (CB₁R) in the brain. Termination of anandamide signaling is thought to be mediated via a facilitated cellular reuptake process that utilizes a purported transporter protein. Recently, WOBE437 has been reported as a novel, natural product-based inhibitor of AEA reuptake that is active in cellular and in vivo models. To profile its target interaction landscape, we synthesized pac-WOBE, a photoactivatable probe derivative of WOBE437, and performed chemical proteomics in mouse neuroblastoma Neuro-2a cells. Surprisingly WOBE437, unlike the widely used selective inhibitor of AEA uptake OMDM-1, was found to increase AEA uptake in Neuro-2a cells. In line with this, WOBE437 reduced the cellular levels of AEA and related N-acylethanolamines (NAEs). Using pac-WOBE, we identified saccharopine dehydrogenase-like oxidoreductase (SCCPDH), vesicle amine transport 1 (VAT1), and ferrochelatase (FECH) as WOBE437-interacting proteins in Neuro-2a cells. Further genetic studies indicated that SCCPDH and VAT1 were not responsible for the WOBE437-induced reduction in NAE levels. Regardless of the precise mechanism of action of WOB437 in AEA transport, we have identified SSCPHD, VAT1, and FECH as unprecedented off-targets of this molecule which should be taken into account when interpreting its cellular and in vivo effects.

Behavioral Studies of p62 KO Animals with Implications of a Modulated Function of the Endocannabinoid System

Elementary emotional states and memory can be regulated by the homeostasis of the endocannabinoid system (ECS). Links between the ECS and the autophagy receptor p62 have been found at the molecular level and in animal studies. This project aimed to validate the anxiety and memory phenotype of p62 knockout (KO) animals and whether the ECS plays a role in this. We examined the behavior of p62 KO animals and analyzed whether endocannabinoid levels are altered in the responsible brain areas. We discovered in age-dependent obese p62-KO mice decreased anandamide levels in the amygdala, a brain structure important for emotional responses. Against our expectation, p62 KO animals did not exhibit an anxiety phenotype, but showed slightly increased exploratory behavior as evidenced in novel object and further tests. In addition, KO animals exhibited decreased freezing responses in the fear conditioning. Administration of the phytocannabinoid delta9-tetrahydrocannabinol (THC) resulted in lesser effects on locomotion but in comparable hypothermic effects in p62 KO compared with WT littermates. Our results do not confirm previously published results, as our mouse line does not exhibit a drastic behavioral phenotype. Moreover, we identified further indications of a connection to the ECS and hence offer new perspectives for future investigations.

Chemical Composition of Leaves, Stem, and Roots of Peperomia pellucida (L.) Kunth

Peperomia pellucida is a species known in the Amazon as “erva-de-jabuti” that has been used in several therapeutic applications based on folk medicine. Herein, we describe the classes, subclasses, and the main compounds of the leaves, stems, and roots from P. pellucida by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry associated with molecular networks, mirror plot on the GNPS library, and machine learning. These data show compounds that were annotated for the first time in the Peperomia genus, such as 2′,4′,5′-trihydroxybutyrophenonevelutin, dehydroretrofractamide C, and retrofractamide B.

Neuropsychopharmacological profiling of scoparone in mice

Scoparone (6,7-dimethoxycoumarin) is a simple coumarin from botanical drugs of Artemisia species used in Traditional Chinese Medicine and Génépi liquor. However, its bioavailability to the brain and potential central effects remain unexplored. We profiled the neuropharmacological effects of scoparone upon acute and subchronic intraperitoneal administration (2.5-25 mg/kg) in Swiss mice and determined its brain concentrations and its effects on the endocannabinoid system (ECS) and related lipids using LC-ESI-MS/MS. Scoparone showed no effect in the forced swimming test (FST) but, administered acutely, led to a bell-shaped anxiogenic-like behavior in the elevated plus-maze test and bell-shaped procognitive effects in the passive avoidance test when given subchronically and acutely. Scoparone rapidly but moderately accumulated in the brain (Cmax < 15 min) with an apparent first-order elimination (95% eliminated at 1 h). Acute scoparone administration (5 mg/kg) significantly increased brain arachidonic acid, prostaglandins, and N-acylethanolamines (NAEs) in the FST. Conversely, subchronic scoparone treatment (2.5 mg/kg) decreased NAEs and increased 2-arachidonoylglycerol. Scoparone differentially impacted ECS lipid remodeling in the brain independent of serine hydrolase modulation. Overall, the unexpectedly potent central effects of scoparone observed in mice could have toxicopharmacological implications for humans.

Association of endocannabinoids with pain in endometriosis

ABSTRACT

Endocannabinoid (eCB) levels fluctuate in inflammatory conditions and as such may take part in endometriosis-associated pain or even in endometriosis pathogenesis. In this case-control (23 cases and 19 controls) study, targeted lipids were measured in the serum and peritoneal fluid collected during laparoscopy. Endometriosis was confirmed histologically. Dysmenorrhea, abdominal pain, and dyspareunia were assessed using the Numeric Rating Scale for pain. Steroids, eCBs, and related lipids were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Tumor necrosis factor alpha, IL-8, PAPP-A, PP14, RANTES, OPG, MIDKINE, MCP-1, VEGF, leptin, and defensins were quantified by ELISA. We found that eCB levels were significantly influenced by both noncyclic and cyclic abdominal pain. Specifically, women suffering from noncyclic abdominal pain were characterized by a higher 2-AG level in the peritoneal fluid throughout the menstrual cycle, whereas women suffering from dysmenorrhea had higher 2-AG levels and lower AEA levels during the proliferative phase alone. In addition, 2-AG positively correlated with prostaglandin E2 (PGE2), and the ratio AEA/2-AG positively correlated with defensins, suggesting a possible link between endocannabinoids system and inflammatory pain. The results of the current study indicate that the eCB system may play a role in endometriosis-associated pain, but additional studies are needed to investigate the causal relationship.

On the Biomedical Properties of Endocannabinoid Degradation and Reuptake Inhibitors: Pre-clinical and Clinical Evidence

The endocannabinoid system (ECS) is composed of endogenous cannabinoids; components involved in their synthesis, transport, and degradation; and an expansive variety of cannabinoid receptors. Hypofunction or deregulation of the ECS is related to pathological conditions. Consequently, endogenous enhancement of endocannabinoid levels and/or regulation of their metabolism represent promising therapeutic approaches. Several major strategies have been suggested for the modulation of the ECS: (1) blocking endocannabinoids degradation, (2) inhibition of endocannabinoid cellular uptake, and (3) pharmacological modulation of cannabinoid receptors as potential therapeutic targets. Here, we focused in this review on degradation/reuptake inhibitors over cannabinoid receptor modulators in order to provide an updated synopsis of contemporary evidence advancing mechanisms of endocannabinoids as pharmacological tools with therapeutic properties for the treatment of several disorders. For this purpose, we revisited the available literature and reported the latest advances regarding the biomedical properties of fatty acid amide hydrolase and monoacylglycerol lipase inhibitors in pre-clinical and clinical studies. We also highlighted anandamide and 2-arachidonoylglycerol reuptake inhibitors with promising results in pre-clinical studies using in vitro and animal models as an outlook for future research in clinical trials.

Δ9-cis-Tetrahydrocannabinol: Natural Occurrence, Chirality, and Pharmacology

The cis-stereoisomers of Δ⁹-THC [(-)-3 and (+)-3] were identified and quantified in a series of low-THC-containing varieties of Cannabis sativa registered in Europe as fiber hemp and in research accessions of cannabis. While Δ⁹-cis-THC (3) occurs in cannabis fiber hemp in the concentration range of (-)-Δ⁹-trans-THC [(-)-1], it was undetectable in a sample of high-THC-containing medicinal cannabis. Natural Δ⁹-cis-THC (3) is scalemic (ca. 80-90% enantiomeric purity), and the absolute configuration of the major enantiomer was established as 6aS,10aR [(-)-3] by chiral chromatographic comparison with a sample available by asymmetric synthesis. The major enantiomer, (-)-Δ⁹-cis-THC [(-)-3], was characterized as a partial cannabinoid agonist in vitro and elicited a full tetrad response in mice at 50 mg/kg doses. The current legal discrimination between narcotic and non-narcotic cannabis varieties centers on the contents of "Δ⁹-THC and isomers" and needs therefore revision, or at least a more specific wording, to account for the presence of Δ⁹-cis-THCs [(+)-3 and (-)-3] in cannabis fiber hemp varieties.

Endocannabinoid-Based Therapies

The endocannabinoids are lipid-derived messengers that play a diversity of regulatory roles in mammalian physiology. Dysfunctions in their activity have been implicated in various disease conditions, attracting attention to the endocannabinoid system as a possible source of therapeutic drugs. This signaling complex has three components: the endogenous ligands, anandamide and 2-arachidonoyl-sn-glycerol (2-AG); a set of enzymes and transporters that generate, eliminate, or modify such ligands; and selective cell surface receptors that mediate their biological actions. We provide an overview of endocannabinoid formation, deactivation, and biotransformation and outline the properties and therapeutic potential of pharmacological agents that interfere with those processes. We describe small-molecule inhibitors that target endocannabinoid-producing enzymes, carrier proteins that transport the endocannabinoids into cells, and intracellular endocannabinoid-metabolizing enzymes. We briefly discuss selected agents that simultaneously interfere with components of the endocannabinoid system and with other functionally related signaling pathways. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Fit-for-purpose based testing and validation of antibodies to amino- and carboxy-terminal domains of cannabinoid receptor 1

Specific and selective anti-CB₁ antibodies are among the most powerful research tools to unravel the complex biological processes mediated by the CB₁ receptor in both physiological and pathological conditions. However, low performance of antibodies remains a major source of inconsistency between results from different laboratories. Using a variety of techniques, including some of the most commonly accepted ones for antibody specificity testing, we identified three of five commercial antibodies against different regions of CB₁ receptor as the best choice for specific end-use purposes. Specifically, an antibody against a long fragment of the extracellular amino tail of CB₁ receptor (but not one against a short sequence of the extreme amino-terminus) detected strong surface staining when applied to live cells, whereas two different antibodies against an identical fragment of the extreme carboxy-terminus of CB₁ receptor (but not one against an upstream peptide) showed acceptable performance on all platforms, although they behaved differently in immunohistochemical assays depending on the tissue fixation procedure used and showed different specificity in Western blot assays, which made each of them particularly suitable for one of those techniques. Our results provide a framework to interpret past and future results derived from the use of different anti-CB₁ antibodies in the context of current knowledge about the CB₁ receptor at the molecular level, and highlight the need for an adequate validation for specific purposes, not only before antibodies are placed on the market, but also before the decision to discontinue them is made.

Efficacy of Phytocannabinoids in Epilepsy Treatment: Novel Approaches and Recent Advances

Epilepsy is a neurological disorder mainly characterised by recurrent seizures that affect the entire population diagnosed with the condition. Currently, there is no cure for the disease and a significant proportion of patients have been deemed to have treatment-resistant epilepsy (TRE). A patient is deemed to have TRE if two or more antiepileptic drugs (AEDs) fail to bring about seizure remission. This inefficacy of traditional AEDs, coupled with their undesirable side effect profile, has led to researchers considering alternative forms of treatment. Phytocannabinoids have long served as therapeutics with delta-9-THC (Δ⁹-THC) receiving extensive focus to determine its therapeutic potential. This focus on Δ⁹-THC has been to the detriment of analysing the plethora of other phytocannabinoids found in the cannabis plant. The overall aim of this review is to explore other novel phytocannabinoids and their place in epilepsy treatment. The current review intends to achieve this aim via an exploration of the molecular targets underlying the anticonvulsant capabilities of cannabidiol (CBD), cannabidavarin (CBDV), delta-9-tetrahydrocannabivarin (Δ⁹-THCV) and cannabigerol (CBG). Further, this review will provide an exploration of current pre-clinical and clinical data as it relates to the aforementioned phytocannabinoids and the treatment of epilepsy symptoms. With specific reference to epilepsy in young adult and adolescent populations, the exploration of CBD, CBDV, Δ⁹-THCV and CBG in both preclinical and clinical environments can guide future research and aid in the further understanding of the role of phytocannabinoids in epilepsy treatment. Currently, much more research is warranted in this area to be conclusive.

Characterization of pepcan-23 as pro-peptide of RVD-hemopressin (pepcan-12) and stability of hemopressins in mice

Hemopressins ((x)-PVNFKLLSH) or peptide endocannabinoids (pepcans) can bind to cannabinoid receptors. RVD-hemopressin (pepcan-12) was shown to act as endogenous allosteric modulator of cannabinoid receptors, with opposite effects on CB1 and CB2, respectively. Moreover, the N-terminally elongated pepcan-23 was detected in different tissues and was postulated to be the pro-peptide of RVD-hemopressin. Currently, data about the pharmacokinetics, tissue distribution and stability of hemopressin-type peptides are lacking. Here we investigated the secondary structure and physiological role of pepcan-23 as precursor of RVD-hemopressin. We assessed the metabolic stability of these peptides, including hemopressin. Using LC-ESI-MS/MS, pepcan-23 was measured in mouse tissues and human whole blood (~50 pmol/mL) and in plasma was the most stable endogenous peptide containing the hemopressin sequence. Using peptide spiked human whole blood, mouse adrenal gland and liver homogenates demonstrate that pepcan-23 acts as endogenous pro-peptide of RVD-hemopressin. Furthermore, administered pepcan-23 converted to RVD-hemopressin in mice. In circular dichroism spectroscopy, pepcan-23 showed a helix-unordered-helix structure and efficiently formed complexes with divalent metal ions, in particular Cu(II) and Ni(II). Hemopressin and RVD-hemopressin were not bioavailable to the brain and showed poor stability in plasma, in agreement with their overall poor biodistribution. Acute hemopressin administration (100 mg/kg) did not modulate endogenous RVD-hemopressin/pepcan-23 levels or influence the endocannabinoid lipidome but increased 1-stearoyl-2-arachidonoyl-sn-glycerol. Overall, we show that pepcan-23 is a biological pro-peptide of RVD-hemopressin and divalent metal ions may regulate this process. Given the lack of metabolic stability of hemopressins, administration of pepcan-23 as pro-peptide may be suitable in pharmacological experiments as it is converted to RVD-hemopressin in vivo.

Selective Endocannabinoid Reuptake Inhibitor WOBE437 Reduces Disease Progression in a Mouse Model of Multiple Sclerosis

The modulation of the endocannabinoid system (ECS) has shown positive results in animal models of multiple sclerosis (MS) and immune and inflammatory disorders. However, chronic administration of CB1 receptor agonists and degrading enzyme inhibitors can lead to CB1 receptor desensitization and sedation. WOBE437 is the prototype of a new class of ECS modulators named selective endocannabinoid reuptake inhibitors (SERIs), which mildly and selectively increase central endocannabinoid levels with a self-limiting mode of action. In previous studies, WOBE437 demonstrated analgesic, anxiolytic, and anti-inflammatory effects. Here, we tested the therapeutic potential of WOBE437 in a clinically relevant mouse model of MS (experimental autoimmune encephalomyelitis). C57BL/6 mice were administered WOBE437 (10 mg/kg, 20 days) or vehicle using two therapeutic options: (1) starting the treatment at the disease onset or (2) before reaching the peak of the disease. In both strategies, WOBE437 significantly reduced disease severity and accelerated recovery through CB1 and CB2 receptor-dependent mechanisms. At the peak of the disease, WOBE437 increased endocannabinoid levels in the cerebellum, concurring with a reduction of central nervous system (CNS)-infiltrating immune cells and lower microglial proliferation. At the end of treatment, endocannabinoid levels were mildly increased in brain, cerebellum, and plasma of WOBE437-treated mice, without desensitization of CB1 receptor in the brain and cerebellum. In a mouse model of spasticity (Straub test), WOBE437 (10 mg/kg) induced significant muscle relaxation without eliciting the typical sedative effects associated with muscle relaxants or CB1 receptor agonists. Collectively, our results show that WOBE437 (and SERIs) may represent a novel therapeutic strategy for slowing MS progression and control major symptoms.

Modulators of the endocannabinoid system influence skin barrier repair, epidermal proliferation, differentiation and inflammation in a mouse model

Endocannabinoids (ECs) are important regulators of cell signalling. Cannabinoid receptors are involved in keratinocyte proliferation/differentiation. Elevation of the endogenous cannabinoid tone leads to strong anti-inflammatory effects. Here, we explored the influence of endocannabinoid system (ECS) modulators on skin permeability barrier repair, epidermal proliferation, differentiation and inflammation in hairless mice. We used WOBE440, a selective fatty acid amide hydrolase (FAAH) inhibitor, WOL067-531, an inhibitor of endocannabinoid reuptake with no relevant FAAH activity, which both signal via cannabinoid receptor-1 and cannabinoid receptor-2 (CB-1R and CB-2R) and compared them to WOBE15 which signals via CB-2R. Barrier disruption and skin irritation were induced by tape stripping or by sodium dodecyl sulphate (SDS) patch testing. Immediately after barrier disruption, 30 μL of 0.5% WOBE440, WOL067-531 and WOBE15 solutions or the vehicle was applied topically. Barrier repair was monitored by transepidermal water loss at 1.5, 3, 5 and 7 hours. We found that barrier repair was significantly delayed by WOL067-531. A tendency for a delay was noticed for WOBE440, whereas for WOBE15, no effect was observed. Immunohistology showed that the tape-stripping-induced increase in epidermal proliferation and filaggrin expression was significantly reduced by topical applications of WOL067-531 and WOBE440, but not by WOBE15. Also, the SDS-induced inflammation, as determined by the number of inflammatory cells, was reduced by WOL067-531 and WOBE440. In summary, we showed that WOL067-531 exhibits a significant effect on skin barrier repair, epidermal proliferation/differentiation and inflammation.

Design, synthesis and biological evaluation of second-generation benzoylpiperidine derivatives as reversible monoacylglycerol lipase (MAGL) inhibitors

An interesting enzyme of the endocannabinoid system is monoacylglycerol lipase (MAGL). This enzyme, which metabolizes the endocannabinoid 2-arachidonoylglycerol (2-AG), has attracted great interest due to its involvement in several physiological and pathological processes, such as cancer progression. Experimental evidences highlighted some drawbacks associated with the use of irreversible MAGL inhibitors in vivo, therefore the research field concerning reversible inhibitors is rapidly growing. In the present manuscript, the class of benzoylpiperidine-based MAGL inhibitors was further expanded and optimized. Enzymatic assays identified some compounds in the low nanomolar range and steered molecular dynamics simulations predicted the dissociation itinerary of one of the best compounds from the enzyme, confirming the observed structure-activity relationship. Biological evaluation, including assays in intact U937 cells and competitive activity-based protein profiling experiments in mouse brain membranes, confirmed the selectivity of the selected compounds for MAGL versus other components of the endocannabinoid system. An antiproliferative ability in a panel of cancer cell lines highlighted their potential as potential anticancer agents. Future studies on the potential use of these compounds in the clinical setting are also supported by the inhibition of cell growth observed both in cancer organoids derived from high grade serous ovarian cancer patients and in pancreatic ductal adenocarcinoma primary cells, which showed genetic and histological features very similar to the primary tumors.

Endocannabinoid metabolism and transport as targets to regulate intraocular pressure

Cannabinoids are part of an endogenous signaling system found throughout the body, including the eye. Hepler and Frank showed in the early 1970s that plant cannabinoids can lower intraocular pressure (IOP), an effect since shown to occur via cannabinoid CB1 and GPR18 receptors. Endocannabinoids are synthesized and metabolized enzymatically. Enzymes implicated in endocannabinoids breakdown include monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), but also ABHD12, NAAA, and COX-2. Inhibition of MAGL activity raises levels of the endocannabinoid 2-arachidonoyl glycerol and substantially lowers IOP. Blocking other cannabinoid metabolizing enzymes or cannabinoid transporters may similarly contribute to lowering IOP and so serve as therapeutic targets for treating glaucoma. We have tested blockers for several cannabinoid-metabolizing enzymes and transporters (FABP5 and membrane reuptake) for their ability to alter ocular pressure in a murine model of IOP. Of FAAH, ABHD12, NAAA, and COX2, only FAAH was seen to play a role in regulation of IOP. Only the FAAH blocker URB597 lowered IOP, but in a temporally, diurnally, and sex-specific manner. We also tested two blockers of cannabinoid transport (SBFI-26 and WOBE437), finding that each lowered IOP in a CB1-dependent manner. Though we see a modest, limited role for FAAH, our results suggest that MAGL is the primary cannabinoid-metabolizing enzyme in regulating ocular pressure, thus pointing towards a role of 2-arachidonoyl glycerol. Interestingly, inhibition of cannabinoid transport mechanisms independent of hydrolysis may prove to be an alternative strategy to lower ocular pressure.

Targeting Endocannabinoid Metabolism: an Arrow with Multiple Tips Against Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, immune-mediated disease of the central nervous system. At present, there is no definitive cure, and the few available disease-modifying options display either poor efficacy or life-threatening side effects. There is clear evidence that relapsing-remitting clinical attacks in MS are driven by inflammatory demyelination and that the subsequent disease steps, being irresponsive to immunotherapy, result from neurodegeneration. The endocannabinoid system (ECS) stands halfway between three key pathomechanisms underlying MS, namely inflammation, neurodegeneration and oxidative stress, thus representing a kingpin for the identification of novel therapeutic targets in MS. This review summarizes the current state of the art in the field of endocannabinoid metabolism modulators and their in vivo effects on relevant animal models. We also highlight key molecular underpinnings of their therapeutic efficacy as well as the potential to turn them into promising clinical candidates.

Diacylglycerol lipase alpha in astrocytes is involved in maternal care and affective behaviors

Genetic deletion of cannabinoid CB1 receptors or diacylglycerol lipase alpha (DAGLa), the main enzyme involved in the synthesis of the endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG), produced profound phenotypes in animal models of depression-related behaviors. Furthermore, clinical studies have shown that antagonists of CB1 can increase the incidence and severity of major depressive episodes. However, the underlying pathomechanisms are largely unknown. In this study, we have focused on the possible involvement of astrocytes. Using the highly sensitive RNAscope technology, we show for the first time that a subpopulation of astrocytes in the adult mouse brain expresses Dagla, albeit at low levels. Targeted lipidomics revealed that astrocytic DAGLa only accounts for a minor percentage of the steady-state brain 2-AG levels and other arachidonic acid derived lipids like prostaglandins. Nevertheless, the deletion of Dagla in adult mouse astrocytes had profound behavioral consequences with significantly increased depressive-like behavioral responses and striking effects on maternal behavior, corresponding with increased levels of serum progesterone and estradiol. Our findings therefore indicate that lipids from the DAGLa metabolic axis in astrocytes play a key regulatory role in affective behaviors.

The endocannabinoid system in modulating fear, anxiety, and stress

The endocannabinoid system is widely expressed in the limbic system, prefrontal cortical areas, and brain structures regulating neuroendocrine stress responses, which explains the key role of this system in the control of emotions. In this review, we update recent advances on the function of the endocannabinoid system in determining the value of fear-evoking stimuli and promoting appropriate behavioral responses for stress resilience. We also review the alterations in the activity of the endocannabinoid system during fear, stress, and anxiety, and the pathophysiological role of each component of this system in the control of these protective emotional responses that also trigger pathological emotional disorders. In spite of all the evidence, we have not yet taken advantage of the therapeutic implications of this important role of the endocannabinoid system, and possible future strategies to improve the treatment of these emotional disorders are discussed.


Neurobiology of cannabinoid receptor signaling

The endocannabinoid system (ECS) is a highly versatile signaling system within the nervous system. Despite its widespread localization, its functions within the context of distinct neural processes are very well discernable and specific. This is remarkable, and the question remains as to how such specificity is achieved. One key player in the ECS is the cannabinoid type 1 receptor (CB₁), a G protein-coupled receptor characterized by the complexity of its cell-specific expression, cellular and subcellular localization, and its adaptable regulation of intracellular signaling cascades. CB₁ receptors are involved in different synaptic and cellular plasticity processes and in the brain's bioenergetics in a context-specific manner. CB₂ receptors are also important in several processes in neurons, glial cells, and immune cells of the brain. As polymorphisms in ECS components, as well as external impacts such as stress and metabolic challenges, can both lead to dysregulated ECS activity and subsequently to possible neuropsychiatric disorders, pharmacological intervention targeting the ECS is a promising therapeutic approach. Understanding the neurobiology of cannabinoid receptor signaling in depth will aid optimal design of therapeutic interventions, minimizing unwanted side effects.
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Targeting Endocannabinoid Signaling: FAAH and MAG Lipase Inhibitors

Inspired by the medicinal properties of the plant Cannabis sativa and its principal component (-)-trans-Δ⁹-tetrahydrocannabinol (THC), researchers have developed a variety of compounds to modulate the endocannabinoid system in the human brain. Inhibitors of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), which are the enzymes responsible for the inactivation of the endogenous cannabinoids anandamide and 2-arachidonoylglycerol, respectively, may exert therapeutic effects without inducing the adverse side effects associated with direct cannabinoid CB₁ receptor stimulation by THC. Here we review the FAAH and MAGL inhibitors that have reached clinical trials, discuss potential caveats, and provide an outlook on where the field is headed.

Gene Expression Analysis of Astrocyte and Microglia Endocannabinoid Signaling during Autoimmune Demyelination

The endocannabinoid system is associated with protective effects in multiple sclerosis (MS) that involve attenuated innate immune cell responses. Astrocytes and microglia are modulated by endocannabinoids and participate in the biosynthesis and metabolism of these compounds. However, the role of neuroglial cells as targets and mediators of endocannabinoid signaling in MS is poorly understood. Here we used a microfluidic RT-qPCR screen to assess changes in the expression of the main endocannabinoid signaling genes in astrocytes and microglia purified from female mice during the time-course of experimental autoimmune encephalomyelitis (EAE). We show that astrocytes and microglia upregulate the expression of genes encoding neurotoxic A1 and pro-inflammatory molecules at the acute disease with many of these transcripts remaining elevated during the recovery phase. Both cell populations exhibited an early onset decrease in the gene expression levels of 2-arachidonoylglycerol (2-AG) hydrolytic enzymes that persisted during EAE progression as well as cell-type-specific changes in the transcript levels for genes encoding cannabinoid receptors and molecules involved in anandamide (AEA) signaling. Our results demonstrate that astrocytes and microglia responses to autoimmune demyelination involve alterations in the expression of multiple endocannabinoid signaling-associated genes and suggest that this system may regulate the induction of neurotoxic and pro-inflammatory transcriptional programs in both cell types during MS.

Synthesis and Biological Evaluation of Endocannabinoid Uptake Inhibitors Derived from WOBE437

WOBE437 ((2E,4E)-N-(3,4-dimethoxyphenethyl)dodeca-2,4-dienamide, 1) is a natural product-derived, highly potent inhibitor of endocannabinoid reuptake. In this study, we synthesized almost 80 analogues of 1 with different types of modifications in the dodecadienoyl domain as well as the dimethoxyphenylethyl head group, and we investigated their effects on anandamide uptake into U937 cells. Intriguingly, none of these analogues was a more potent inhibitor of anandamide uptake than WOBE437 (1). At the same time, a number of WOBE437 variants exhibited potencies in the sub-100 nM range, with high selectivity over inhibition of the endocannabinoid-degrading enzyme fatty acid amide hydrolase; two compounds were virtually equipotent with 1. Interestingly, profound activity differences were observed between analogues in which either of the two methoxy substituents in the head group had been replaced by the same bulkier alkoxy group. Some of the compounds described here could be interesting departure points for the development of potent endocannabinoid uptake inhibitors with more drug-like properties.

The Application of Fluorine-Containing Reagents in Structural Proteomics

Structural proteomics refers to large-scale mapping of protein structures in order to understand the relationship between protein sequence, structure, and function. Chemical labeling, in combination with mass-spectrometry (MS) analysis, have emerged as powerful tools to enable a broad range of biological applications in structural proteomics. The key to success is a biocompatible reagent that modifies a protein without affecting its high-order structure. Fluorine, well-known to exert profound effects on the physical and chemical properties of reagents, should have an impact on structural proteomics. In this Minireview, we describe several fluorine-containing reagents that can be applied in structural proteomics. We organize their applications around four MS-based techniques: a) affinity labeling, b) activity-based protein profiling (ABPP), c) protein footprinting, and d) protein cross-linking. Our aim is to provide an overview of the research, development, and application of fluorine-containing reagents in protein structural studies.

The ACSL3-LPIAT1 signaling drives prostaglandin synthesis in non-small cell lung cancer

Enhanced prostaglandin production promotes the development and progression of cancer. Prostaglandins are generated from arachidonic acid (AA) by the action of cyclooxygenase (COX) isoenzymes. However, how cancer cells are able to maintain an elevated supply of AA for prostaglandin production remains unclear. Here, by using lung cancer cell lines and clinically relevant Kras^G12D-driven mouse models, we show that the long-chain acyl-CoA synthetase (ACSL3) channels AA into phosphatidylinositols to provide the lysophosphatidylinositol-acyltransferase 1 (LPIAT1) with a pool of AA to sustain high prostaglandin synthesis. LPIAT1 knockdown suppresses proliferation and anchorage-independent growth of lung cancer cell lines, and hinders in vivo tumorigenesis. In primary human lung tumors, the expression of LPIAT1 is elevated compared with healthy tissue, and predicts poor patient survival. This study uncovers the ACSL3-LPIAT1 axis as a requirement for the sustained prostaglandin synthesis in lung cancer with potential therapeutic value.

The cannabinoid agonist WIN-2 affects acquisition but not consolidation of a spatial information in training and retraining processes: Relation with transcriptional regulation of the endocannabinoid system?

The endocannabinoid system is capable of modulating multiple physiological brain functions including learning and memory. Moreover, there is evidence that the processes of acquisition and consolidation have distinct biological basis. We used the cannabinoid agonist WIN 55,212-2 (WIN-2) to investigate whether chronic CB1 activation affects acquisition and consolidation differently by evaluating gene expression in the hippocampus (HIP) and prefrontal cortex (PFC). Swiss mice were treated with WIN-2 (2 mg/kg) and submitted to the Morris water maze to evaluate different aspects of memory. We observed short-term memory impairment in acquisition of the spatial task while consolidation remained unchanged. In the PFC, animals that received WIN-2 prior to the task exhibited increased expression of the 2-AG synthesis enzyme diacylglycerol lipase and decreased levels of the degradation enzyme monoacylglycerol lipase, while mice that were treated after the task for the evaluation of consolidation exhibited the opposite profile. With respect to genes related to AEA metabolism, no correlation between the molecular and behavioral data could be established. In this sense, the cognitive impairment in the acquisition promoted by WIN-2 treatment may be related to a possible increase in the concentration of 2-AG in the PFC. Overall, this study confirms the relevance of the endocannabinoid system in the modulation of cognitive processes. A better understanding of the mechanisms underlying endocannabinoids roles in cognition could provide guidance for the development of treatments to reduce the cognitive deficits caused by drug abuse.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

The (endo)cannabinoid signaling in female reproduction: What are the latest advances?

Cannabis extracts like marijuana have the highest consumption rate worldwide. Yet, their societal acceptance as recreational and therapeutic drugs could represent a serious hazard to female human reproduction, because cannabis ingredients [termed (phyto)cannabinoids] can perturb an endogenous system of lipid signals known as endocannabinoids. Accumulated evidence on animal models and humans has demonstrated a crucial role of these endogenous signals on different aspects of female reproduction, where they act through an ensamble of proteins that synthesize, transport, degrade and traffic them. Several reports have recently evidenced the potential role of endocannabinoids as biomarkers of female infertility for disease treatment and prevention, as well as their possible epigenetic effects on pregnancy. The purpose of this review is to provide an update of data collected in the last decade on the effects of cannabinoids and endocannabinoids on female reproductive events, from development and maturation of follicles and oocytes, to fertilization, oviductal transport, implantation and labor. In this context, a particular attention has been devoted to the ovary and the production of fertilizable oocytes, because recent studies have addressed this hot topic with conflicting results among species.

Double blinded, vehicle controlled, crossover study on the efficacy of a topical endocannabinoid membrane transporter inhibitor in atopic Beagles

The endocannabinoid system is important for skin homeostasis and alterations are linked to inflammatory diseases like atopic dermatitis (AD). Importantly, activation of cannabinoid receptor CB2 decreases pruritus and inflammation in mouse models. Reduction of inactivation of endogenous cannabinoids could, therefore, be a therapeutic option for AD. Dogs spontaneously develop AD, which closely mimics the human disease making them suitable to test new therapies. Our study aimed to test the effects of a topical endocannabinoid membrane transporter inhibitor (WOL067-531, 1% gel) on pruritus and dermatitis in a canine model of AD. Nineteen Beagles allergic to dust mites (DM) were randomized to receive either active ingredient or vehicle on inguinal area while challenged epicutaneously with DM twice weekly for 28 days. Treatment was administered twice daily and started after three challenges (day 8). Dermatitis and pruritus were scored weekly by personnel blinded to treatment allocation. Dermatitis was scored using a validated scoring system and pruritus was scored using camera recordings. After a 4-week washout, dogs were crossed over and the study was repeated. On days 15 and 22, dermatitis scores were significantly increased after DM challenge in the vehicle group (16.34, p = 0.0089 and 7.42, p = 0.04845, respectively) but not in the active ingredient group (p = 0.3177 and p = 0.3190, respectively). Significant decrease on pruritus both on inguinal area and overall (p = 0.048 and p = 0.032, respectively) occurred in the active ingredient group. No adverse effects were noted. In conclusion, the newly developed topical endocannabinoid membrane transporter inhibitor (WOL067-531) minimized allergic flares and pruritus in a canine model of AD.

Cannabinoid interventions for PTSD: Where to next?

Cannabinoids are a promising method for pharmacological treatment of post-traumatic stress disorder (PTSD). Despite considerable research devoted to the effect of cannabinoid modulation on PTSD symptomology, there is not a currently agreed way by which the cannabinoid system should be targeted in humans. In this review, we present an overview of recent research identifying neurological pathways by which different cannabinoid-based treatments may exert their effects on PTSD symptomology. We evaluate the strengths and weaknesses of each of these different approaches, including recent challenges presented to favourable options such as fatty acid amide hydrolase (FAAH) inhibitors. This article makes the strengths and challenges of different potential cannabinoid treatments accessible to psychological researchers interested in cannabinoid therapeutics and aims to aid selection of appropriate tools for future clinical trials.

Role of pannexin-1 in the cellular uptake, release and hydrolysis of anandamide by T84 colon cancer cells

The large pore ion channel pannexin-1 (Panx1) has been reported to play a role in the cellular uptake and release of anandamide (AEA) in the hippocampus. It is not known whether this is a general mechanism or limited to the hippocampus. We have investigated this pharmacologically using T84 colon cancer cells. The cells expressed Panx1 at the mRNA level, and released ATP in a manner that could be reduced by treatment with the Panx1 inhibitors carbenoxolone and mefloquine and the Panx1 substrate SR101. However, no significant effects of these compounds upon the uptake or hydrolysis of exogenously applied AEA was seen. Uptake by T84 cells of the other main endocannabinoid 2-arachidonoylglycerol and the AEA homologue palmitoylethanolamide was similarly not affected by carbenoxolone or mefloquine. Total release of tritium from [³H]AEA-prelabelled T84 cells over 10 min was increased, rather than inhibited by carbenoxolone and mefloquine. Finally, AEA uptake by PC3 prostate cancer and SH-SY5Y neuroblastoma cells, which express functional Panx1 channels, was not inhibited by carbenoxolone. Thus, in contrast to the hippocampus, Panx1 does not appear to play a role in AEA uptake and release from the cells studied under the conditions used.

FABP1 controls hepatic transport and biotransformation of Δ9-THC

The increasing use of medical marijuana highlights the importance of developing a better understanding of cannabinoid metabolism. Phytocannabinoids, including ∆⁹-tetrahydrocannabinol (THC), are metabolized and inactivated by cytochrome P450 enzymes primarily within the liver. The lipophilic nature of cannabinoids necessitates mechanism(s) to facilitate their intracellular transport to metabolic enzymes. Here, we test the central hypothesis that liver-type fatty acid binding protein (FABP1) mediates phytocannabinoid transport and subsequent inactivation. Using X-ray crystallography, molecular modeling, and in vitro binding approaches we demonstrate that FABP1 accommodates one molecule of THC within its ligand binding pocket. Consistent with its role as a THC carrier, biotransformation of THC was reduced in primary hepatocytes obtained from FABP1-knockout (FABP1-KO) mice. Compared to their wild-type littermates, administration of THC to male and female FABP1-KO mice potentiated the physiological and behavioral effects of THC. The stark pharmacodynamic differences were confirmed upon pharmacokinetic analyses which revealed that FABP1-KO mice exhibit reduced rates of THC biotransformation. Collectively, these data position FABP1 as a hepatic THC transport protein and a critical mediator of cannabinoid inactivation. Since commonly used medications bind to FABP1 with comparable affinities to THC, our results further suggest that FABP1 could serve a previously unrecognized site of drug-drug interactions.

The Endocannabinoid System as a Target in Cancer Diseases: Are We There Yet?

The endocannabinoid system (ECS) has been placed in the anti-cancer spotlight in the last decade. The immense data load published on its dual role in both tumorigenesis and inhibition of tumor growth and metastatic spread has transformed the cannabinoid receptors CB1 (CB1R) and CB2 (CB2R), and other members of the endocannabinoid-like system, into attractive new targets for the treatment of various cancer subtypes. Although the clinical use of cannabinoids has been extensively documented in the palliative setting, clinical trials on their application as anti-cancer drugs are still ongoing. As drug repurposing is significantly faster and more economical than de novo introduction of a new drug into the clinic, there is hope that the existing pharmacokinetic and safety data on the ECS ligands will contribute to their successful translation into oncological healthcare. CB1R and CB2R are members of a large family of membrane proteins called G protein-coupled receptors (GPCR). GPCRs can form homodimers, heterodimers and higher order oligomers with other GPCRs or non-GPCRs. Currently, several CB1R and CB2R-containing heteromers have been reported and, in cancer cells, CB2R form heteromers with the G protein-coupled chemokine receptor CXCR4, the G protein-coupled receptor 55 (GPR55) and the tyrosine kinase receptor (TKR) human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2). These protein complexes possess unique pharmacological and signaling properties, and their modulation might affect the antitumoral activity of the ECS. This review will explore the potential of the endocannabinoid network in the anti-cancer setting as well as the clinical and ethical pitfalls behind it, and will develop on the value of cannabinoid receptor heteromers as potential new targets for anti-cancer therapies and as prognostic biomarkers.

Plant-Based Modulators of Endocannabinoid Signaling

Extracts from Cannabis species have aided the discovery of the endocannabinoid signaling system (ECSS) and phytocannabinoids that possess broad therapeutic potential. Whereas the reinforcing effects of C. sativa are largely attributed to CB1 receptor agonism by Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the observed medicinal effects of Cannabis arise from the combined actions of various compounds. In addition to compounds bearing a classical cannabinoid structure, naturally occurring fatty acid amides and esters resembling anandamide and 2-arachidonoyl glycerol isolated from non- Cannabis species are also valuable tools for studying ECSS function. This review highlights the potential of plant-based secondary metabolites from Cannabis and unrelated species as ECSS modulators.