The potential of inhibitors of endocannabinoid metabolism as anxiolytic and antidepressive drugs--A practical view

Highly Specific Miniaturized Fluorescent Monoacylglycerol Lipase Probes Enable Translational Research

Monoacylglycerol lipase (MAGL) is the pivotal catabolic enzyme responsible for signal termination in the endocannabinoid system. Inhibition of MAGL offers unique advantages over the direct activation of cannabinoid receptors in treating cancer, metabolic disorders, and inflammatory diseases. Although specific fluorescent molecular imaging probes are commonly used for the real-time analysis of the localization and distribution of drug targets in cells, they are almost invariably composed of a linker connecting the pharmacophore with a large fluorophore. In this study, we have developed miniaturized fluorescent probes targeting MAGL by incorporating a highly fluorescent boron-dipyrromethene (BODIPY) moiety into the inhibitor structure that interacts with the MAGL active site. These miniaturized fluorescent probes exhibit favorable drug-like properties such as high solubility and permeability, picomolar potency for MAGL across various species, and high cell selectivity and specificity. A range of translational investigations were conducted, including cell-free fluorescence polarization assays, fluorescence-activated cell sorting analysis, and confocal fluorescence microscopy of live cancer cells, live primary neurons, and human-induced pluripotent stem cell-derived brain organoids. Furthermore, the application of red-shifted analogs or 18F positron emission labeling illustrated the significant versatility and adaptability of the fluorescent ligands in various experimental contexts.

Early life stress induces decreased expression of CB1R and FAAH and epigenetic changes in the medial prefrontal cortex of male rats

Several studies in both animal models and in humans have provided substantial evidence that early life stress (ELS) induces long-term changes in behavior and brain function, making it a significant risk factor in the aetiology of various mental disorders, including anxiety and depression. In this study, we tested the hypothesis that ELS in male rats (i) leads to increased anxiety and depressive-like symptoms; and (ii) that these behavioral changes are associated with functional alterations in the endocannabinoid system of the medial prefrontal cortex (mPFC). We further assessed whether the predicted changes in the gene expression of two key components of the endocannabinoid system, cannabinoid receptor 1 (CB1R) and the fatty acid amide hydrolase (FAAH), are regulated by epigenetic mechanisms. Behavioral profiling revealed that the proportion of behaviorally affected animals was increased in ELS exposed male rats compared to control animals, specifically showing symptoms of anhedonia and impaired social behavior. On the molecular level we observed a decrease in CB1R and FAAH mRNA expression in the mPFC of adult ELS exposed animals. These gene expression changes were accompanied by reduced global histone 3 acetylation in the mPFC, while no significant changes in DNA methylation and no significant changes of histone-acetylation at the promoter regions of the analyzed genes were detected. Taken together, our data provide evidence that ELS induces a long-term reduction of CB1R and FAAH expression in the mPFC of adult male rats, which may partially contribute to the ELS-induced changes in adult socio-emotional behavior.

Neurolipidomic insights into anxiety disorders: Uncovering lipid dynamics for potential therapeutic advances

Anxiety disorders constitute a spectrum of psychological conditions affecting millions of individuals worldwide, imposing a significant health burden. Historically, the development of anxiolytic medications has been largely focused on neurotransmitter function and modulation. However, in recent years, neurolipids emerged as a prime target for understanding psychiatric pathogenesis and developing novel medications. Neurolipids influence various neural activities such as neurotransmission and cellular functioning, as well as maintaining cell membrane integrity. Therefore, this review aims to elucidate the alterations in neurolipids associated with an anxious mental state and explore their potential as targets of novel anxiolytic medications. Existing evidence tentatively associates dysregulated neurolipid levels with the etiopathology of anxiety disorders. Notably, preclinical investigations suggest that several neurolipids, including endocannabinoids and polyunsaturated fatty acids, may hold promise as potential pharmacological targets. Overall, the current literature tentatively suggests the involvement of lipids in the pathogenesis of anxiety disorders, hinting at potential prospects for future pharmacological interventions.

Sex-Related and Brain Regional Differences of URB597 Effects on Modulation of MAPK/PI3K Signaling in Chronically Stressed Rats

Gender differences exist in depression incidence and antidepressant efficacy. In addition to the neurotransmission theory of depression, inflammation and disrupted signaling pathways play crucial roles in the pathophysiology of depression. Endocannabinoids offer a novel approach to treat inflammatory and emotional disorders like depression. URB597, a FAAH inhibitor, reduces endocannabinoids breakdown. In this study, URB597 effects were investigated on the pro-inflammatory cytokine interleukin-1β (IL-1β), nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3(NLRP3), and mitogen-activated protein kinase (MAPK)/ phosphatidylinositol 3-hydroxy kinase/ protein kinase B (PI3K) signaling in the hippocampus and the medial prefrontal cortex (mPFC) of male and female rats subjected to chronic unpredictable stress (CUS). The results show that CUS induces depression-like behaviors, and the URB597 exhibited antidepressant-like effects inboth sexes. URB597 reduced the CUS-induced NLRP3 and IL-1β increase in the hippocampus and mPFC of both sexes. URB597 increased the reduced pERK1/2 levels in the mPFC of both sexes and hippocampus of CUS males. URB597 also prevented the increase in p38 phosphorylation after chronic stress in the mPFC of both sexes and in the hippocampus of the females. The CUS suppressed the downstream Akt phosphorylation in the mPFC and hippocampi of both sexes. URB597 produced an up-regulation of the pAkt in the hippocampus of the CUS animals but did not affect the pAkt in the mPFC. These data demonstrated a sexual dimorphism in the neural cell signaling, and in the effects of endocannabinoids, and indicated these dimorphisms are region-specific.

Molecular Basis for Non-Covalent, Non-Competitive FAAH Inhibition

Fatty acid amide hydrolase (FAAH) plays a key role in the control of cannabinoid signaling and it represents a promising therapeutic strategy for the treatment of a wide range of diseases, including neuropathic pain and chronic inflammation. Starting from kinetics experiments carried out in our previous work for the most potent inhibitor 2-amino-3-chloropyridine amide (TPA14), we have investigated its non-competitive mechanism of action using molecular dynamics, thermodynamic integration and QM-MM/GBSA calculations. The computational studies highlighted the impact of mutations on the receptor binding pockets and elucidated the molecular basis of the non-competitive inhibition mechanism of TPA14, which prevents the endocannabinoid anandamide (AEA) from reaching its pro-active conformation. Our study provides a rationale for the design of non-competitive potent FAAH inhibitors for the treatment of neuropathic pain and chronic inflammation.

Inactivation Mechanism of the Fatty Acid Amide Hydrolase Inhibitor BIA 10-2474

BIA 10-2474 is a time-dependent inhibitor of fatty acid amide hydrolase(FAAH) that was under clinical development for the treatment of neurological conditions when the program was terminated after one subject died and four were hospitalized with neurological symptoms during a first-in-human clinical study. The present manuscript describes the mechanism of FAAH inhibition by BIA 10-2474 as a target-specific covalent inhibition, supported by quantum mechanics and molecular modelling studies. The inhibitor incorporates a weakly reactive electrophile which, upon specific binding to the enzyme's active site, is positioned to react readily with the catalytic residues. The reactivity is enhanced on-site by the increased molarity at the reaction site and by specific inductive interactions with FAAH. In the second stage, the inhibitor reacts with the enzyme's catalytic nucleophile to form a covalent enzyme-inhibitor adduct. The hydrolysis of this adduct is shown to be unlikely under physiological conditions, therefore leading to irreversible inactivation of FAAH. The results also reveal the important role played by FAAH Thr236 in the reaction with BIA 10-2474, which is specific to FAAH and is not present in other serine hydrolases.

Rapid treatments for depression: Endocannabinoid system as a therapeutic target

Current first-line treatments for major depressive disorder (MDD), i.e., antidepressant drugs and psychotherapy, show delayed onset of therapeutic effect as late as 2-3 weeks or more. In the clinic, the speed of beginning of the actions of antidepressant drugs or other interventions is vital for many reasons. Late-onset means that depression, its related disability, and the potential danger of suicide remain a threat for some patients. There are some rapid-acting antidepressant interventions, such as sleep deprivation, ketamine, acute exercise, which induce a significant response, ranging from a few hours to maximally one week, and most of them share a common characteristic that is the activation of the endocannabinoid (eCB) system. Activation of this system, i.e., augmentation of eCB signaling, appears to have anti-depressant-like actions. This article puts the idea forward that the activation of eCB signaling represents a critical mechanism of rapid-acting therapeutic interventions in MDD, and this system might contribute to the development of novel rapid-acting treatments for MDD.

The endocannabinoid system and drug-associated contextual memories

Drug abuse and addiction can be initiated and reinstated by contextual stimuli previously paired with the drug use. The influence exerted by the context on drug-seeking behaviour can be modelled in experimental animals with place-conditioning protocols. Here, we review the effects of cannabinoids in place conditioning and the therapeutic potential of the endocannabinoid system for interfering with drug-related memories. The phytocannabinoid Δ9-tetrahydrocannabinol (THC) tends to induce conditioned place preference (CPP) at low doses and conditioned place aversion at high doses; cannabidiol is devoid of any effect, yet it inhibits CPP induced by some drugs. Synthetic CB1 receptor agonists tend to recapitulate the biphasic profile observed with THC, whereas selective antagonists/inverse agonists inhibit CPP induced by cocaine, nicotine, alcohol and opioids. However, their therapeutic use is limited by potential psychiatric side effects. The CB2 receptor has also attracted attention, because selective CB2 receptor agonists inhibit cocaine-induced CPP. Inhibitors of endocannabinoid membrane transport and hydrolysis yield mixed results. In targeting the endocannabinoid system for developing new treatments for drug addiction, future research should focus on 'neutral' CB1 receptor antagonists and CB2 receptor agonists. Such compounds may offer a well-tolerated pharmacological profile and curb addiction by preventing drug-seeking triggered by conditioned contextual cues.

Higher trait neuroticism is associated with greater fatty acid amide hydrolase binding in borderline and antisocial personality disorders

Borderline personality disorder (BPD) and antisocial personality disorder (ASPD) are the two most frequently diagnosed and researched DSM-5 personality disorders, and both are characterized by high levels of trait neuroticism. Fatty acid amide hydrolase (FAAH), an enzyme of the endocannabinoid system (ECS), has been linked to regulation of mood through modulation of anandamide, an endocannabinoid. We hypothesized that prefrontal cortex (PFC) FAAH binding would relate to trait neuroticism in personality disorders. Thirty-one individuals with personality disorders (20 with BPD and 11 with ASPD) completed the investigation. All participants completed the revised NEO Personality Inventory, which yields standardized scores (e.g., T scores) for the traits of neuroticism, openness, conscientiousness, agreeableness, and extraversion. All participants were medication free and were not utilizing illicit substances as determined by drug urinalysis. Additionally, none of the participants had a comorbid major depressive episode, bipolar disorder, psychotic disorder, or substance use disorder. Each participant underwent one [¹¹C]CURB PET scan. Consistent with our hypothesis, neuroticism was positively correlated with PFC FAAH binding (r = 0.42, p = 0.021), controlling for genotype. Neuroticism was also positively correlated with dorsal putamen FAAH binding (r = 0.53, p = 0.0024), controlling for genotype. Elevated brain FAAH is an endophenotype for high neuroticism in BPD and ASPD. Novel pharmacological therapeutics that inhibit FAAH could emerge as potential new treatments for BPD and ASPD with high neuroticism.

Inhibition of anandamide hydrolysis does not rescue respiratory abnormalities observed in an animal model of Parkinson's disease

NEW FINDINGS

What is the central question of this study? The respiratory frequency to hypercapnia is attenuated in an animal model of Parkinson's disease (PD): what is the therapeutic potential of inhibition of anandamide hydrolysis for this respiratory deficit? What is the main finding and its importance? In an animal model of PD there is an increased variability in resting respiratory frequency and an impaired tachypnoeic response to hypercapnia, which is accompanied by diminished expression of Phox2b immunoreactivity in the retrotrapezoid nucleus (RTN). Inhibition of anandamide hydrolysis also impaired the response to hypercapnia and decreased the number of Phox2b immunoreactive cells in the RTN. This strategy does not reverse the respiratory deficits observed in an animal model of PD.

ABSTRACT

Parkinson's disease (PD) is characterized by severe classic motor symptoms along with various non-classic symptoms. Among the non-classic symptoms, respiratory dysfunctions are increasingly recognized as contributory factors to complications in PD. The endocannabinoid system has been proposed as a target to treat PD and other neurodegenerative disorders. Since symptom management of PD is mainly focused on the classic motor symptoms, in this work we aimed to test the hypothesis that increasing the actions of the endocannabinoid anandamide by inhibiting its hydrolysis with URB597 reverses the respiratory deficits observed in an animal model of PD. Results show that bilateral injection of 6-hydroxydopamine hydrochloride (6-OHDA) in the dorsal striatum leads to neurodegeneration of the substantia nigra, accompanied by reduced expression of Phox2b in the retrotrapezoid nucleus (RTN), an increase in resting respiratory frequency variability and an impaired tachypnoeic response to hypercapnia. URB597 treatment in control animals was associated with an impaired tachypnoeic response to hypercapnia and a reduced expression of Phox2b in the RTN, whereas treatment of 6-OHDA-lesioned animals with URB597 was not able to reverse the deficits observed. These results suggest that targeting anandamide may not be a suitable strategy to treat PD since this treatment mimics the respiratory deficits observed in the 6-OHDA model of PD.

Reviewing the Role of the Endocannabinoid System in the Pathophysiology of Depression

Major depressive disorder is a high-impact, debilitating disease and it is currently considered the most prevalent mental illness. It is associated with disability, as well as increased morbidity and mortality. Despite its significant repercussions in our society, its exact pathophysiology remains unclear and therefore, available antidepressant treatment options are limited and, in some cases, ineffective. In the past years, research has focused on the development of a multifactorial theory of depression. Simultaneously, evidence supporting the role of the endocannabinoid system in the neurobiology of neuropsychiatric diseases has emerged. Studies have shown that the endocannabinoid system strongly impacts neurotransmission, and the neuroendocrine and neuroimmune systems, which are known to be dysfunctional in depressive patients. Accordingly, common antidepressants were shown to have a direct impact on the expression of cannabinoid receptors throughout the brain. Therefore, the relationship between the endocannabinoid system and major depressive disorder is worth consideration. Nevertheless, most studies focus on smaller pieces of what is undoubtedly a larger mosaic of interdependent processes. Therefore, the present review summarizes the existing literature regarding the role of the endocannabinoid system in depression aiming to integrate this information into a holistic picture for a better understanding of the relationship between the two.

The endocannabinoid system - current implications for drug development

In this review, the state of the art for compounds affecting the endocannabinoid (eCB) system is described with a focus on the treatment of pain. Amongst directly acting CB receptor ligands, clinical experience with ∆⁹ -tetrahydracannabinol and medical cannabis in chronic non-cancer pain indicates that there are differences between the benefits perceived by patients and the at best modest effect seen in meta-analyses of randomized controlled trials. The reason for this difference is not known but may involve differences in the type of patients that are recruited, the study conditions that are chosen and the degree to which biases such as reporting bias are operative. Other directly acting CB receptor ligands such as biased agonists and allosteric receptor modulators have not yet reached the clinic. Amongst indirectly acting compounds targeting the enzymes responsible for the synthesis and catabolism of the eCBs anandamide and 2-arachidonoylglycerol, fatty acid amide hydrolase (FAAH) inhibitors have been investigated clinically but were per se not useful for the treatment of pain, although they may be useful for the treatment of post-traumatic stress disorder and cannabis use disorder. Dual-acting compounds targeting this enzyme and other targets such as cyclooxygenase-2 or transient potential vanilloid receptor 1 may be a way forward for the treatment of pain.

Inhibition of fatty acid amide hydrolase prevents pathology in neurovisceral acid sphingomyelinase deficiency by rescuing defective endocannabinoid signaling

Acid sphingomyelinase deficiency (ASMD) leads to cellular accumulation of sphingomyelin (SM), neurodegeneration, and early death. Here, we describe the downregulation of the endocannabinoid (eCB) system in neurons of ASM knockout (ASM‐KO) mice and a ASMD patient. High SM reduced expression of the eCB receptor CB₁ in neuronal processes and induced its accumulation in lysosomes. Activation of CB₁ receptor signaling, through inhibition of the eCB‐degrading enzyme fatty acid amide hydrolase (FAAH), reduced SM levels in ASM‐KO neurons. Oral treatment of ASM‐KO mice with a FAAH inhibitor prevented SM buildup; alleviated inflammation, neurodegeneration, and behavioral alterations; and extended lifespan. This treatment showed benefits even after a single administration at advanced disease stages. We also found CB₁ receptor downregulation in neurons of a mouse model and a patient of another sphingolipid storage disorder, Niemann–Pick disease type C (NPC). We showed the efficacy of FAAH inhibition to reduce SM and cholesterol levels in NPC patient‐derived cells and in the brain of a NPC mouse model. Our findings reveal a pathophysiological crosstalk between neuronal SM and the eCB system and offer a new treatment for ASMD and other sphingolipidoses.

Antidepressant-like effects of pharmacological inhibition of FAAH activity in socially isolated female rats

Pharmacological inhibition of the enzyme fatty acid amide hydrolase (FAAH), which terminates signaling of the endocannabinoid N-arachidonoylethanolamine (or anandamide, AEA), exerts favourable effects in rodent models of stress-related depression. Yet although depression seems to be more common among women than men and in spite of some evidence of sex differences in treatment efficacy, preclinical development of FAAH inhibitors for the pharmacotherapy of stress-related depression has been predominantly conducted in male animals. Here, adult female rats were exposed to six weeks of social isolation and, starting from the second week, treated with the FAAH inhibitor URB694 (0.3 mg/kg/day, i.p.) or vehicle. Compared to pair-housed females, socially isolated female rats treated with vehicle developed behavioral (mild anhedonia, passive stress coping) and physiological (reduced body weight gain, elevated plasma corticosterone levels) alterations. Moreover, prolonged social isolation provoked a reduction in brain-derived neurotrophic factor (BDNF) and AEA levels within the hippocampus. Together, these changes are indicative of an increased risk of developing a depressive-like state. Conversely, pharmacological inhibition of FAAH activity with URB694 restored both AEA and BDNF levels within the hippocampus of socially isolated rats and prevented the development of behavioral and physiological alterations. These results suggest a potential interplay between AEA-mediated signaling and hippocampal BDNF in the pathogenesis of depression-relevant behaviors and physiological alterations and antidepressant action of FAAH inhibition in socially isolated female rats.

Dual pharmacological inhibitor of endocannabinoid degrading enzymes reduces depressive-like behavior in female rats

Major depressive disorder (MDD) is common, often under-treated and a leading cause of disability and mortality worldwide. The causes of MDD remain unclear, including the role of the endocannabinoid system. Intriguingly, the prevalence of depression is significantly greater in women than men. In this study we examined the role of endocannabinoids in depressive behavior. The levels of endocannabinoids, N-arachidonoyl ethanolamide (AEA) and 2-arachidonoyl glycerol (2-AG) were measured along with brain derived neurotrophic factor (BDNF) in postmortem ventral striata of female patients with MDD and non-psychiatric controls, and in Wistar Kyoto (WKY) rat, a selectively inbred strain of rat widely used for testing the depressive behavior. The effect of pharmacological elevation of endocannabinoids through inhibition of their catabolizing enzymes (fatty acid amide hydrolase [FAAH] and monoacyl glycerol lipase [MAGL]) on depressive-like phenotype was also assessed in WKY rat. The findings showed lower levels of endocannabinoids and BDNF in the ventral striata of MDD patients and WKY rats. A dual inhibitor of FAAH and MAGL, JZL195, elevated the endocannabinoids and BDNF levels in ventral striatum, and reduced the depressive-like phenotype in female WKY rats. Collectively, our study suggests a blunted ventral striatal endocannabinoid and BDNF signaling in depressive behavior and concludes that endocannabinoid enhancing agents may have an antidepressant effect.

The Association between Physical Activity and Anxiety Symptoms for General Adult Populations: An Analysis of the Dose-Response Relationship

OBJECTIVE

The aim of this study is to determine the dose-response relationship between physical activity and anxiety symptoms.

METHODS

We included data of 124,434 participants who had comprehensive health-screening examinations from January 1st, 2012, to December 31st, 2016, in Kangbuk Samsung Hospital, Seoul and Suwon, South Korea. We measured the level of physical activity using the International Physical Activity Questionnaire-short form (IPAQ-SF) and estimated anxiety symptoms using the Beck Anxiety Inventory (BAI). BAI scores of 19 and above were defined as cases. Logistic regression was used to analyze the association between physical activity and BAI-defined anxiety. Furthermore, we assessed whether sex differences might affect the relationship between physical activity and BAI-defined anxiety by stratifying our data.

RESULTS

Compared with the sedentary group (0-600 METs-min/week), individuals achieving 600-6,000 METs-min/wk had a significantly lower risk of BAI-defined anxiety with a U-shaped relationship in general adults. After stratifying our data by sex, we found that optimal ranges of physical activity were 600-9,000 METs-min/wk for men, but 1,200-3,000 METs-min/wk for women.

CONCLUSION

We identified a U- or J-shaped association between physical activity and anxiety symptoms, suggesting an optimal dose and upper limit of physical activity for decreasing anxiety symptoms. Optimal levels and upper limits of physical activity for reducing anxiety symptoms were higher for men than for women.

Physical activity and the prevention of depression: A cohort study

OBJECTIVE

This study aims to identify the optimal amount and appropriate state of physical activity for reducing incident depressive symptoms.

METHOD

The data of 107,901 Korean adults who had undergone at least two annual health examinations from 2012 to 2015 were analyzed. At baseline, the amount of physical activity was measured using the International Physical Activity Questionnaire-Short Form and metabolic equivalents (METs)-min/wk., which is the amount of oxygen consumed while sitting at rest per week. In addition, one-year changes in physical activity were categorized into four groups: persistent sedentary, maintenance, relapse, and adoption groups. For the study's endpoint, new-onset depressive symptoms (score of ≥21) were considered, defined by the Center for Epidemiologic Studies Rating Scale for Depression. A Cox proportional hazards model was used to identify the optimal amount and appropriate state of physical activity for reducing incident depressive symptoms.

RESULTS

Compared with sedentary status (<600 METs-min/wk), achieving 1200-3000 METs-min/wk. was associated with a lower risk of incident depressive symptoms, illustrating a U-shaped relationship. The results show that the amount of physical activity for reducing the onset of depressive symptoms was higher for men (1800-3000 METs-min/wk.: HR, 0.84 [95% CI, 0.74-0.95]) than women (1200-1800 METs-min/wk.: HR, 0.84 [95% CI, 0.71-0.99]). In terms of one-year changes in physical activity, compared to the persistent sedentary group, the maintenance group was associated with a lower risk of the development of depressive symptoms in both sexes (men: HR, 0.81 [95% CI, 0.71-0.93]; women: HR, 0.84 [95% CI, 0.75-0.94]). Women in the adoption group showed a positive effect in terms of a decrease in incident depressive symptoms (HR, 0.87 [95% CI, 0.76-0.99]).

CONCLUSIONS

This study suggests an optimal amount of physical activity for reducing the onset of depressive symptoms. In addition, maintaining an appropriate level of physical activity for one year proved beneficial for decreasing incident depressive symptoms.

Benzylamides and piperazinoarylamides of ibuprofen as fatty acid amide hydrolase inhibitors

Fatty Acid Amide Hydrolase (FAAH) is a serine hydrolase that plays a key role in controlling endogenous levels of endocannabinoids. FAAH inhibition is considered a powerful approach to enhance the endocannabinoid signalling, and therefore it has been largely studied as a potential target for the treatment of neurological disorders such as anxiety or depression, or of inflammatory processes. We present two novel series of amide derivatives of ibuprofen designed as analogues of our reference FAAH inhibitor Ibu-AM5 to further explore its structure-activity relationships. In the new amides, the 2-methylpyridine moiety of Ibu-AM5 was substituted by benzylamino and piperazinoaryl moieties. The obtained benzylamides and piperazinoarylamides showed FAAH inhibition ranging from the low to high micromolar potency. The binding of the new amides in the active site of FAAH, estimated using the induced fit protocol, indicated arylpiperazinoamides binding the ACB channel and the cytosolic port, and benzylamides binding the ACB channel.

Cannabinoid CB1 receptors mediate the anxiolytic effects induced by systemic alprazolam and intra-periaqueductal gray 5-HT1A receptor activation

The endocannabinoid system has been implicated in the modulation of behaviors related to anxiety and panic disorders. Accordingly, facilitation of CB₁ receptor signaling reduces the consequences of aversive stimuli in animal models. However, the role of the CB₁ receptor in the effects of anxiolytic drugs has remained unclear. Here, we tested the hypothesis that the anxiolytic and panicolytic responses to systemic alprazolam injection and local 5-HT_1A receptor activation in the dorsolateral periaqueductal gray (dlPAG) depend on CB₁ receptor activation. Systemic injection of alprazolam (4 mg/kg) induced an anxiolytic-like effect in the elevated T maze (ETM) model of panic and anxiety, which was prevented by the CB₁ antagonist AM251 (0.3 mg/kg). Likewise, intra-dlPAG injection of the 5-HT_1A receptor agonist 8-OH-DPAT (3.2 nmol/0.2 u L) also reduced anxiety-like behavior, a response prevented by intra-dlPAG injection of AM251 (100 pmol/0.2 µL). 8-OH-DPAT (8 nmol/0.2 µL) also presented a panicolytic-like activity in the escape reaction induced by chemical stimulation of the dlPAG, which was not prevented by AM251 (100 pmol/0.2 µL). These results suggest that CB₁ receptor signaling is involved in the effects of anxiolytic drugs, with potential implications for developing new treatments for anxiety disorders.

The endocannabinoid system: Overview of an emerging multi-faceted therapeutic target

The endocannabinoids anandamide (AEA) and 2-arachidonoylglyerol (2-AG) are endogenous lipid mediators that exert protective roles in pathophysiological conditions, including cardiovascular diseases. In this brief review, we provide a conceptual framework linking endocannabinoid signaling to the control of the cellular and molecular hallmarks, and categorize the key components of endocannabinoid signaling that may serve as targets for novel therapeutics. The emerging picture not only reinforces endocannabinoids as potent regulators of cellular metabolism but also reveals that endocannabinoid signaling is mechanistically more complex and diverse than originally thought.

Therapeutic endocannabinoid augmentation for mood and anxiety disorders: comparative profiling of FAAH, MAGL and dual inhibitors

Recent studies have demonstrated anxiolytic potential of pharmacological endocannabinoid (eCB) augmentation approaches in a variety of preclinical models. Pharmacological inhibition of endocannabinoid-degrading enzymes, such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), elicit promising anxiolytic effects in rodent models with limited adverse behavioral effects, however, the efficacy of dual FAAH/MAGL inhibition has not been investigated. In the present study, we compared the effects of FAAH (PF-3845), MAGL (JZL184) and dual FAAH/MAGL (JZL195) inhibitors on (1) anxiety-like behaviors under non-stressed and stressed conditions, (2) locomotor activity and body temperature, (3) lipid levels in the brain and (4) cognitive functions. Behavioral analysis showed that PF-3845 or JZL184, but not JZL195, was able to prevent restraint stress-induced anxiety in the light-dark box assay when administered before stress exposure. Moreover, JZL195 treatment was not able to reverse foot shock-induced anxiety-like behavior in the elevated zero maze or light-dark box. JZL195, but not PF-3845 or JZL184, decreased body temperature and increased anxiety-like behavior in the open-field test. Overall, JZL195 did not show anxiolytic efficacy and the effects of JZL184 were more robust than that of PF-3845 in the models examined. These results showed that increasing either endogenous AEA or 2-AG separately produces anti-anxiety effects under stressful conditions but the same effects are not obtained from simultaneously increasing both AEA and 2-AG.

The Potential of Cannabidiol Treatment for Cannabis Users With Recent-Onset Psychosis

A major factor associated with poor prognostic outcome after a first psychotic break is cannabis misuse, which is prevalent in schizophrenia and particularly common in individuals with recent-onset psychosis. Behavioral interventions aimed at reducing cannabis use have been unsuccessful in this population. Cannabidiol (CBD) is a phytocannabinoid found in cannabis, although at low concentrations in modern-day strains. CBD has a broad pharmacological profile, but contrary to ∆9-tetrahydrocannabinol (THC), CBD does not activate CB1 or CB2 receptors and has at most subtle subjective effects. Growing evidence indicates that CBD acts as an antipsychotic and anxiolytic, and several reports suggest neuroprotective effects. Moreover, CBD attenuates THC's detrimental effects, both acutely and chronically, including psychotogenic, anxiogenic, and deleterious cognitive effects. This suggests that CBD may improve the disease trajectory of individuals with early psychosis and comorbid cannabis misuse in particular-a population with currently poor prognostic outcome and no specialized effective intervention.

Considering Sex as a Biological Variable Will Be Valuable for Neuroscience Research

The recently implemented National Institutes of Health policy requiring that grant applicants consider sex as a biological variable in the design of basic and preclinical animal research studies has prompted considerable discussion within the neuroscience community. Here, we present reasons to be optimistic that this new policy will be valuable for neuroscience, and we suggest some ways for neuroscientists to think about incorporating sex as a variable in their research.

Novel propanamides as fatty acid amide hydrolase inhibitors

Fatty acid amide hydrolase (FAAH) has a key role in the control of the cannabinoid signaling, through the hydrolysis of the endocannabinoids anandamide and in some tissues 2-arachidonoylglycerol. FAAH inhibition represents a promising strategy to activate the cannabinoid system, since it does not result in the psychotropic and peripheral side effects characterizing the agonists of the cannabinoid receptors. Here we present the discovery of a novel class of profen derivatives, the N-(heteroaryl)-2-(4-((2-(trifluoromethyl)pyridin-4-yl)amino)phenyl)propanamides, as FAAH inhibitors. Enzymatic assays showed potencies toward FAAH ranging from nanomolar to micromolar range, and the most compounds lack activity toward the two isoforms of cyclooxygenase. Extensive structure-activity studies and the definition of the binding mode for the lead compound of the series are also presented. Kinetic assays in rat and mouse FAAH on selected compounds of the series demonstrated that slight modifications of the chemical structure could influence the binding mode and give rise to competitive (TPA1) or non-competitive (TPA14) inhibition modes.

Design and synthesis of uracil urea derivatives as potent and selective fatty acid amide hydrolase inhibitors

Fatty acid amide hydrolase (FAAH) is one of the key enzymes involved in the biological degradation of endocannabinoids, especially anandamide.

Dorsal hippocampus cannabinoid type 1 receptors modulate the expression of contextual fear conditioning in rats: Involvement of local glutamatergic/nitrergic and GABAergic neurotransmissions

The cannabinoid receptor type 1 (CB1) is highly expressed in the dorsal portion of hippocampus - a brain region that has been involved in the control of conditioned emotional response (CER) in the contextual fear conditioning (CFC) model. These responses are characterized by increased freezing behavior and autonomic parameters. Moreover, CB1 receptors activation negatively modulate the release of several neurotransmitters, including glutamate and GABA, which also have been related to modulation of CER. Therefore, our aim was to investigate the involvement of CB1 receptors in the dorsal hippocampus on CER expression. Independent groups of male Wistar rats submitted to the contextual fear conditioning received bilateral intra-hippocampal injections (500 nL/side) of the following drugs or vehicle before re-exposure to the aversive context: AM251 (CB1 antagonist; 0.1, 0.3 and 1nmol); AP7 (NMDA antagonist; 1nmol)+AM251 (0.3nmol); NPLA (0.01nmol; nNOS inhibitor)+AM251 (0.3nmol); Bicuculline (1.3pmol; GABAA antagonist)+AM251 (0.1 and 1nmol). In the present paper, AM251 (0.3nmol) increased CER, while this response was prevented by both AP7 and NPLA pretreatment. After pretreatment with Bicuculline, the lower and higher ineffective doses of AM251 were able to increase the CER, supporting the balance between GABAergic and glutamatergic mechanisms controlling this response. Our results suggest that increased CER evoked by CB1 blockade in the dorsal hippocampus depends on NMDA receptor activation and NO formation. Moreover, a fine-tune control promoted by GABAergic and glutamatergic mechanisms in this brain area modulate the CER after CB1 blockade.

FAAH inhibitors in the limelight, but regrettably

Abstract. This short review focuses on the recent drug development of FAAH inhibitors, as recent serious adverse events have been reported in a phase I study with a compound of this class. The authors overview the potential interest in targeting FAAH inhibition, the current programs, and the available information on the recent dramatic events.

Ketamine and MAG Lipase Inhibitor-Dependent Reversal of Evolving Depressive-Like Behavior During Forced Abstinence From Alcohol Drinking

Although alcoholism and depression are highly comorbid, treatment options that take this into account are lacking, and mouse models of alcohol (ethanol (EtOH)) intake-induced depressive-like behavior have not been well established. Recent studies utilizing contingent EtOH administration through prolonged two-bottle choice access have demonstrated depression-like behavior following EtOH abstinence in singly housed female C57BL/6J mice. In the present study, we found that depression-like behavior in the forced swim test (FST) is revealed only after a protracted (2 weeks), but not acute (24 h), abstinence period. No effect on anxiety-like behavior in the EPM was observed. Further, we found that, once established, the affective disturbance is long-lasting, as we observed significantly enhanced latencies to approach food even 35 days after ethanol withdrawal in the novelty-suppressed feeding test (NSFT). We were able to reverse affective disturbances measured in the NSFT following EtOH abstinence utilizing the N-methyl D-aspartate receptor (NMDAR) antagonist and antidepressant ketamine but not memantine, another NMDAR antagonist. Pretreatment with the monoacylglycerol (MAG) lipase inhibitor JZL-184 also reduced affective disturbances in the NSFT in ethanol withdrawn mice, and this effect was prevented by co-administration of the CB1 inverse agonist rimonabant. Endocannabinoid levels were decreased within the BLA during abstinence compared with during drinking. Finally, we demonstrate that the depressive behaviors observed do not require a sucrose fade and that this drinking paradigm may favor the development of habit-like EtOH consumption. These data could set the stage for developing novel treatment approaches for alcohol-withdrawal-induced mood and anxiety disorders.

Cardioprotective effects of fatty acid amide hydrolase inhibitor URB694, in a rodent model of trait anxiety

In humans, chronic anxiety represents an independent risk factor for cardiac arrhythmias and sudden death. Here we evaluate in male Wistar rats bred for high (HAB) and low (LAB) anxiety-related behavior, as well as non-selected (NAB) animals, the relationship between trait anxiety and cardiac electrical instability and investigate whether pharmacological augmentation of endocannabinoid anandamide-mediated signaling exerts anxiolytic-like and cardioprotective effects. HAB rats displayed (i) a higher incidence of ventricular tachyarrhythmias induced by isoproterenol, and (ii) a larger spatial dispersion of ventricular refractoriness assessed by means of an epicardial mapping protocol. In HAB rats, acute pharmacological inhibition of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), with URB694 (0.3 mg/kg), (i) decreased anxiety-like behavior in the elevated plus maze, (ii) increased anandamide levels in the heart, (iii) reduced isoproterenol-induced occurrence of ventricular tachyarrhythmias, and (iv) corrected alterations of ventricular refractoriness. The anti-arrhythmic effect of URB694 was prevented by pharmacological blockade of the cannabinoid type 1 (CB₁), but not of the CB₂, receptor. These findings suggest that URB694 exerts anxiolytic-like and cardioprotective effects in HAB rats, the latter via anandamide-mediated activation of CB₁ receptors. Thus, pharmacological inhibition of FAAH might be a viable pharmacological strategy for the treatment of anxiety-related cardiac dysfunction.

Rapid and profound rewiring of brain lipid signaling networks by acute diacylglycerol lipase inhibition

Diacylglycerol lipases (DAGLα and DAGLβ) convert diacylglycerol to the endocannabinoid 2-arachidonoylglycerol. Our understanding of DAGL function has been hindered by a lack of chemical probes that can perturb these enzymes in vivo. Here, we report a set of centrally active DAGL inhibitors and a structurally related control probe and their use, in combination with chemical proteomics and lipidomics, to determine the impact of acute DAGL blockade on brain lipid networks in mice. Within 2 h, DAGL inhibition produced a striking reorganization of bioactive lipids, including elevations in DAGs and reductions in endocannabinoids and eicosanoids. We also found that DAGLα is a short half-life protein, and the inactivation of DAGLs disrupts cannabinoid receptor-dependent synaptic plasticity and impairs neuroinflammatory responses, including lipopolysaccharide-induced anapyrexia. These findings illuminate the highly interconnected and dynamic nature of lipid signaling pathways in the brain and the central role that DAGL enzymes play in regulating this network.