Personalized medicine can pave the way for the safe use of CB1 receptor antagonists

The endocannabinoid system and breathing

Recent changes in cannabis accessibility have provided adjunct therapies for patients across numerous disease states and highlights the urgency in understanding how cannabinoids and the endocannabinoid (EC) system interact with other physiological structures. The EC system plays a critical and modulatory role in respiratory homeostasis and pulmonary functionality. Respiratory control begins in the brainstem without peripheral input, and coordinates the preBötzinger complex, a component of the ventral respiratory group that interacts with the dorsal respiratory group to synchronize burstlet activity and drive inspiration. An additional rhythm generator: the retrotrapezoid nucleus/parafacial respiratory group drives active expiration during conditions of exercise or high CO₂. Combined with the feedback information from the periphery: through chemo- and baroreceptors including the carotid bodies, the cranial nerves, stretch of the diaphragm and intercostal muscles, lung tissue, and immune cells, and the cranial nerves, our respiratory system can fine tune motor outputs that ensure we have the oxygen necessary to survive and can expel the CO₂ waste we produce, and every aspect of this process can be influenced by the EC system. The expansion in cannabis access and potential therapeutic benefits, it is essential that investigations continue to uncover the underpinnings and mechanistic workings of the EC system. It is imperative to understand the impact cannabis, and exogenous cannabinoids have on these physiological systems, and how some of these compounds can mitigate respiratory depression when combined with opioids or other medicinal therapies. This review highlights the respiratory system from the perspective of central versus peripheral respiratory functionality and how these behaviors can be influenced by the EC system. This review will summarize the literature available on organic and synthetic cannabinoids in breathing and how that has shaped our understanding of the role of the EC system in respiratory homeostasis. Finally, we look at some potential future therapeutic applications the EC system has to offer for the treatment of respiratory diseases and a possible role in expanding the safety profile of opioid therapies while preventing future opioid overdose fatalities that result from respiratory arrest or persistent apnea.

Genetic analyses of the endocannabinoid pathway in association with affective phenotypic variants

BACKGORUND

Increasing experimental data confirm the crucial role of the endocannabinoid (eCB) system in the regulation of stress response and emotional processes. Despite of the fact, that genetically determined vulnerability for stress is a widely accepted concept in the pathomechanism of affective disorders, replicable human genetic results with interaction analyses of early life trauma and eCB genes are rare. The aim of this study is to test the associations between genetic variants of the eCB pathway, childhood trauma and affective phenotypes.

METHODS

We selected 18,897 SNPs in the eCB pathway of a GWAS dataset in two general population cohorts (BP sample N = 837; MN sample N = 988). Association analyses were performed on the anxious and depressive subscales of the Brief Symptom Inventory (BSI-ANX and BSI-DEP, respectively). Childhood trauma was assessed by the Childhood Adversity Questionnaire (CAQ). Association analyses were performed in the R 2.0. statistical program using the SNPassoc package.

REULTS

Genetic effect was more robust in the BP sample than in the MN sample. The most comprehensive results showed that SNPs in the CACNA1C gene associated with depressive phenotype in interaction with CAQ in both BP (p = 1.2 × 10^-4) and MN samples (p = 1.6 × 10^-4). Direct association analyses (without interaction) provided significant associations between SNPs in different genesets of the two study populations. SNPs in KCNJ3 and GNB5 genes on the BSI-DEP (p = 6.1 × 10^-5; p = 7.1 × 10^-4) and GNG12 gene on the BSI-ANX (p = 7.4 × 10^-6) in the BP sample, while GABAergic, ADCY1 and HTR2A gene variants can be outlined from results of MN sample with less strong p-values.

CONCLUSION

Our results confirmed the prominent role of CACNA1C gene in the pathogenic effect of early life stress in the development of affective vulnerability in two different study populations using GxE interaction analysis. CACNA1C gene, as it encodes for L-type voltage-gated calcium channel, contributes to neuronal excitability, plasticity and neurogenesis being a crucial effector of both eCB signaling and the BDNF-CREB pathway as well. Our findings suggest that childhood trauma related depression may have more robust genetically determined basis than without early life stress.

A Brain on Cannabinoids: The Role of Dopamine Release in Reward Seeking and Addiction

Cannabis sativa, like all known drugs of abuse, leads to increased dopamine activation within the mesolimbic pathway. Consequent dopamine release within terminal regions of the striatum is a powerful mediator of reward and reinforcement and patterned dopamine release is critical for associative learning processes that are fundamentally involved in addiction. The endocannabinoid system modulates dopamine release at multiple sites, and the receptors, endogenous ligands, and synthetic and metabolic enzymes of the endocannabinoid system may provide key targets for pharmacotherapies to treat disorders of motivation including addiction. Disrupting endocannabinoid signaling decreases drug-induced increases in dopamine release as well those dopamine events evoked by conditioned stimuli during reward seeking. Advances in recording techniques for dopamine are allowing unprecedented examinations of these two interacting systems and elucidating the mechanisms of endocannabinoid modulation of dopamine release in reward and addiction.

New cannabinoid receptor antagonists as pharmacological tool

Synthesis and pharmacological evaluation of a new series of cannabinoid receptor antagonists of indazole ether derivatives have been performed. Pharmacological evaluation includes radioligand binding assays with [³H]-CP55940 for CB1 and CB2 receptors and functional activity for cannabinoid receptors on isolated tissue. In addition, functional activity of the two synthetic cannabinoids antagonists 18 (PGN36) and 17 (PGN38) were carried out in the osteoblastic cell line MC3T3-E1 that is able to express CB2R upon osteogenic conditions. Both antagonists abolished the increase in collagen type I gene expression by the well-known inducer of bone activity, the HU308 agonist. The results of pharmacological tests have revealed that four of these derivatives behave as CB2R cannabinoid antagonists. In particular, the compounds 17 (PGN38) and 18 (PGN36) highlight as promising candidates as pharmacological tools.

Disease-associated polymorphisms within the conserved ECR1 enhancer differentially regulate the tissue-specific activity of the cannabinoid-1 receptor gene promoter; implications for cannabinoid pharmacogenetics

Cannabinoid receptor‐1 (CB1) represents a potential drug target against conditions that include obesity and substance abuse. However, drug trials targeting CB1 (encoded by the CNR1 gene) have been compromised by differences in patient response. Toward addressing the hypothesis that genetic changes within the regulatory regions controlling CNR1 expression contribute to these differences, we characterized the effects of disease‐associated allelic variation within a conserved regulatory sequence (ECR1) in CNR1 intron 2 that had previously been shown to modulate cannabinoid response, alcohol intake, and anxiety‐like behavior. We used primary cell analysis of reporters carrying different allelic variants of the human ECR1 and found that human‐specific C‐allele variants of ECR1 (ECR1(C)) drove higher levels of CNR1prom activity in primary hippocampal cells than did the ancestral T‐allele and demonstrated a differential response to CB1 agonism. We further demonstrate a role for the AP‐1 transcription factor in driving higher ECR1(C) activity and evidence that the ancestral t‐allele variant of ECR1 interacted with higher affinity with the insulator binding factor CTCF. The cell‐specific approaches used in our study represent an important step in gaining a mechanistic understanding of the roles of noncoding polymorphic variation in disease and in the increasingly important field of cannabinoid pharmacogenetics.

A functional variant of CB2 receptor gene interacts with childhood trauma and FAAH gene on anxious and depressive phenotypes

BACKGROUND

Accumulating data suggest that CB2 receptor plays a crucial role in development of anxiety via regulatory function of stress response and neuroimmune crosstalk. Although animal experiments confirm this relationship, relevant human genetic studies on CB2 receptor gene (CNR2) in association with affective phenotype are absent.

METHODS

CNR2 R63Q and FAAH C385A functional polymorphisms were genotyped of 921 volunteers from the general population. Phenotypic variables were measured by the Zung Self-related Depression Scale (ZSDS), The State-Trait Anxiety Inventory (Trait subscale, STAI-T) and the depressive and anxious subscales of the Brief Symptom Inventory (BSI-DEP and BSI-ANX). Early life trauma was assesssed by the Childhood Trauma Questionnaire (CHQ). Using general linear models we tested possible associations between phenotypic variance and genotype distribution.

RESULTS

There was a significant main effect of RR genotype of R63Q on ZSDS score (p = 0.007) and a remarkble interacting effect of CHQ and R63Q on scores of ZSDS, STAI-T and BSI-ANX scales (p = 0.009; p = 0.003; p = 0.001; respectively). R allele of R63Q and A allele of FAAH C385A were associated with significantly higher ZSDS, STAI-T and BSI-ANX scores compared to non-risk allele carriers (p = 0.009; p = 0.007; p = 0.007, respectively). The highest phenotypic scores were observed in GxGxE model (p_ZSDS = 0.04; p_BSI-DEP = 0.006; p_STAI-T = 0.001; p_BSI-ANX = 3.8 × 10^-5).

CONCLUSIONS

In this first human genetic study on CNR2 and childhood trauma we revealed that dysfunctional CB2 receptor and FAAH can contribute to greater sensitivity for childhood trauma possibly via weaker inhibiton of inflammatory and overactivated HPA axis.

Novel pharmacological targets in drug development for the treatment of anxiety and anxiety-related disorders

Current medication for anxiety disorders is suboptimal in terms of efficiency and tolerability, highlighting the need for improved drug treatments. In this review an overview of drugs being studied in different phases of clinical trials for their potential in the treatment of fear-, anxiety- and trauma-related disorders is presented. One strategy followed in drug development is refining and improving compounds interacting with existing anxiolytic drug targets, such as serotonergic and prototypical GABAergic benzodiazepines. A more innovative approach involves the search for compounds with novel mechanisms of anxiolytic action using the growing knowledge base concerning the relevant neurocircuitries and neurobiological mechanisms underlying pathological fear and anxiety. The target systems evaluated in clinical trials include glutamate, endocannabinoid and neuropeptide systems, as well as ion channels and targets derived from phytochemicals. Examples of promising novel candidates currently in clinical development for generalised anxiety disorder, social anxiety disorder, panic disorder, obsessive compulsive disorder or post-traumatic stress disorder include ketamine, riluzole, xenon with one common pharmacological action of modulation of glutamatergic neurotransmission, as well as the neurosteroid aloradine. Finally, compounds such as D-cycloserine, MDMA, L-DOPA and cannabinoids have shown efficacy in enhancing fear-extinction learning in humans. They are thus investigated in clinical trials as an augmentative strategy for speeding up and enhancing the long-term effectiveness of exposure-based psychotherapy, which could render chronic anxiolytic drug treatment dispensable for many patients. These efforts are indicative of a rekindled interest and renewed optimism in the anxiety drug discovery field, after decades of relative stagnation.

Obesity in Childhood and Adolescence, Genetic Factors

Obesity and excess weight are a pandemic phenomenon in the modern world. Childhood and adolescent obesity often ends up in obesity in adults. The costs of obesity and its consequences are staggering for any society, crippling for countries in development. Childhood obesity is also widespread in Macedonia. Metabolic syndrome, dyslipidemia and carbohydrate intolerance are found in significant numbers. Parents and grandparents are often obese. Some of the children are either dysmorphic, or slightly retarded. We have already described patients with Prader-Willi syndrome, Bardet-Biedl syndrome or WAGR syndrome. A genetic screening for mutations in monogenic obesity in children with early, rapid-onset or severe obesity, severe hyperphagia, hypogonadism, intestinal dysfunction, hypopigmentation of hair and skin, postprandial hypoglycaemia, diabetes insipidus, abnormal leptin level and coexistence of lean and obese siblings in the family discovers many genetic forms of obesity. There are about 30 monogenic forms of obesity. In addition, obesity is different in ethnic groups, and the types of monogenic obesity differ. In brief, an increasing number of genes and genetic mechanisms in children continue to be discovered. This sheds new light on the molecular mechanisms of obesity and potentially gives a target for new forms of treatment.

Effects of Different Stressors Are Modulated by Different Neurobiological Systems: The Role of GABA-A Versus CB1 Receptor Gene Variants in Anxiety and Depression

Environmental stress and its interaction with genetic variation are key contributors in the development of depression and anxiety, yet there is a failure to identify replicable genetic variants and gene-interaction effects in the background of these psychiatric symptoms. Recently it has been reported that 5-HTTLPR and NOSI interact with financial but not other types of recent stressors in the development of depression. In the present study we investigated the interaction of GABRA6 rs3219151 and CNR1 rs7766029 in interaction with different types of recent life events on the presence of depression and anxiety in a large general population sample. 2191 participants completed the List of Threatening Experiences questionnaire which covers four categories of stressful life events (financial problems, illness/personal problems, intimate relationships, and social network) experienced over the previous year and the Brief Symptom Inventory for depression and anxiety symptoms. Participants were genotyped for rs3219151 and rs7766029. Data were analyzed with linear regression models with age and gender as covariates. Results indicated that CNR1 rs7766029 interacted significantly with financial but not other types of life events both in case of depression and anxiety symptoms. In contrast, GABRA6 rs3219151 showed a significant interaction with social network related life events in case of anxiety and with illness/personal problem-related life events in case of depression. Our results suggest that the psychological impact of different types of recent stress may be differentially modulated by distinct molecular genetic pathways. Furthermore, in case of certain genetic variants, the occurring psychiatric symptom may depend on the type of stress experienced.

Emerging Evidence for Cannabis' Role in Opioid Use Disorder

Introduction: The opioid epidemic has become an immense problem in North America, and despite decades of research on the most effective means to treat opioid use disorder (OUD), overdose deaths are at an all-time high, and relapse remains pervasive. Discussion: Although there are a number of FDA-approved opioid replacement therapies and maintenance medications to help ease the severity of opioid withdrawal symptoms and aid in relapse prevention, these medications are not risk free nor are they successful for all patients. Furthermore, there are legal and logistical bottlenecks to obtaining traditional opioid replacement therapies such as methadone or buprenorphine, and the demand for these services far outweighs the supply and access. To fill the gap between efficacious OUD treatments and the widespread prevalence of misuse, relapse, and overdose, the development of novel, alternative, or adjunct OUD treatment therapies is highly warranted. In this article, we review emerging evidence that suggests that cannabis may play a role in ameliorating the impact of OUD. Herein, we highlight knowledge gaps and discuss cannabis' potential to prevent opioid misuse (as an analgesic alternative), alleviate opioid withdrawal symptoms, and decrease the likelihood of relapse. Conclusion: The compelling nature of these data and the relative safety profile of cannabis warrant further exploration of cannabis as an adjunct or alternative treatment for OUD.

Effects of repeated long-term psychosocial stress and acute cannabinoid exposure on mouse corticostriatal circuitries: Implications for neuropsychiatric disorders

Introduction

Vulnerability to psychiatric manifestations is achieved by the influence of genetic and environment including stress and cannabis consumption. Here, we used a psychosocial stress model based on resident‐intruder confrontations to study the brain corticostriatal‐function, since deregulation of corticostriatal circuitries has been reported in many psychiatric disorders. CB₁ receptors are widely expressed in the central nervous system and particularly, in both cortex and striatum brain structures.

Aims and methods

The investigation presented here is addressed to assess the impact of repeated stress following acute cannabinoid exposure on behavior and corticostriatal brain physiology by assessing mice behavior, the concentration of endocannabinoid and endocannabinoid‐like molecules and changes in the transcriptome.

Results

Stressed animals urinated frequently; showed exacerbated scratching activity, lower striatal N‐arachidonylethanolamine (AEA) levels and higher cortical expression of cholinergic receptor nicotinic alpha 6. The cannabinoid agonist WIN55212.2 diminished locomotor activity while the inverse agonist increased the distance travelled in the center of the open field. Upon CB₁ activation, N‐oleoylethanolamide and N‐palmitoylethanolamide, two AEA congeners that do not interact directly with cannabinoid receptors, were enhanced in the striatum. The co‐administration with both cannabinoids induced an up‐regulation of striatal FK506 binding protein 5. The inverse agonist in controls reversed the effects of WIN55212.2 on motor activity. When Rimonabant was injected under stress, the cortical levels of 2‐arachidonoylglycerol were maximum. The agonist and the antagonist influenced the cortical expression of cholinergic receptor nicotinic alpha 6 and serotonin transporter neurotransmitter type 4 in opposite directions, while their co‐administration tended to produce a null effect under stress.

Conclusions

The endocannabinoid system had a direct effect on serotoninergic neurotransmission and glucocorticoid signaling. Cholinergic receptor nicotinic alpha‐6 was shown to be deregulated in response to stress and following synthetic cannabinoid drugs thus could confer vulnerability to cannabis addiction and psychosis. Targeting the receptors of endocannabinoids and endocannabinoid‐like mediators might be a valuable option for treating stress‐related neuropsychiatric symptoms.

Endocannabinoid modulation of dopamine neurotransmission

Dopamine (DA) is a major catecholamine neurotransmitter in the mammalian brain that controls neural circuits involved in the cognitive, emotional, and motor aspects of goal-directed behavior. Accordingly, perturbations in DA neurotransmission play a central role in several neuropsychiatric disorders. Somewhat surprisingly given its prominent role in numerous behaviors, DA is released by a relatively small number of densely packed neurons originating in the midbrain. The dopaminergic midbrain innervates numerous brain regions where extracellular DA release and receptor binding promote short- and long-term changes in postsynaptic neuron function. Striatal forebrain nuclei receive the greatest proportion of DA projections and are a predominant hub at which DA influences behavior. A number of excitatory, inhibitory, and modulatory inputs orchestrate DA neurotransmission by controlling DA cell body firing patterns, terminal release, and effects on postsynaptic sites in the striatum. The endocannabinoid (eCB) system serves as an important filter of afferent input that acts locally at midbrain and terminal regions to shape how incoming information is conveyed onto DA neurons and to output targets. In this review, we aim to highlight existing knowledge regarding how eCB signaling controls DA neuron function through modifications in synaptic strength at midbrain and striatal sites, and to raise outstanding questions on this topic. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Recent progress in genetics, epigenetics and metagenomics unveils the pathophysiology of human obesity

In high-, middle- and low-income countries, the rising prevalence of obesity is the underlying cause of numerous health complications and increased mortality. Being a complex and heritable disorder, obesity results from the interplay between genetic susceptibility, epigenetics, metagenomics and the environment. Attempts at understanding the genetic basis of obesity have identified numerous genes associated with syndromic monogenic, non-syndromic monogenic, oligogenic and polygenic obesity. The genetics of leanness are also considered relevant as it mirrors some of obesity's aetiologies. In this report, we summarize ten genetically elucidated obesity syndromes, some of which are involved in ciliary functioning. We comprehensively review 11 monogenic obesity genes identified to date and their role in energy maintenance as part of the leptin-melanocortin pathway. With the emergence of genome-wide association studies over the last decade, 227 genetic variants involved in different biological pathways (central nervous system, food sensing and digestion, adipocyte differentiation, insulin signalling, lipid metabolism, muscle and liver biology, gut microbiota) have been associated with polygenic obesity. Advances in obligatory and facilitated epigenetic variation, and gene-environment interaction studies have partly accounted for the missing heritability of obesity and provided additional insight into its aetiology. The role of gut microbiota in obesity pathophysiology, as well as the 12 genes associated with lipodystrophies is discussed. Furthermore, in an attempt to improve future studies and merge the gap between research and clinical practice, we provide suggestions on how high-throughput '-omic' data can be integrated in order to get closer to the new age of personalized medicine.

Differential effects of cannabinoid CB1 inverse agonists and antagonists on impulsivity in male Sprague Dawley rats: identification of a possibly clinically relevant vulnerability involving the serotonin 5HT1A receptor

RATIONALE

Cannabinoid CB1 inverse agonists hold therapeutic promise as appetite suppressants but have produced suicidal behaviors among a small subpopulation in clinical trials. Anatomical and pharmacological evidence implicate the 5HT_1A serotonin receptor in suicide in humans and impulsivity in humans and animals.

OBJECTIVE

The objective of the study is to assess whether 5HT_1A blockade is necessary for CB1 ligands to produce impulsivity.

METHODS

Sprague Dawley rats were administered the CB1 inverse agonist AM 251, the CB1 antagonist AM 6527, or the peripherally restricted antagonist AM 6545, with or without pretreatment with the 5HT_1A antagonist WAY 100,635 (WAY) on the paced fixed consecutive number (FCN) task, which measures choice to terminate a chain of responses prematurely. As FCN is sensitive to changes in time perception, which have been demonstrated with CB1 blockade, a novel variable consecutive number task with discriminative stimulus (VCN-S _D ) was also performed and proposed to be less sensitive to changes in timing.

RESULTS

Pretreatment with WAY enabled mild but significant reductions in FCN accuracy for AM 251 and AM 6527. No effects were found for AM 6545. On the VCN-S _D task, substantial impairments were found for the combination of WAY and AM 251.

CONCLUSIONS

AM 251, but not the antagonists AM 6527 or AM 6545, produced impulsivity only following systemic 5HT_1A blockade. Although preliminary, the results may indicate that disrupted serotonin signaling produces a vulnerability to undesirable effects of CB1 inverse agonists, which is not evident in the general population. Furthermore, neutral CB1 antagonists do not produce this effect and therefore may have greater safety.

Variants in the CNR1 gene predispose to headache with nausea in the presence of life stress

One of the main effects of the endocannabinoid system in the brain is stress adaptation with presynaptic endocannabinoid receptor 1 (CB1 receptors) playing a major role. In the present study, we investigated whether the effect of the CB1 receptor coding CNR1 gene on migraine and its symptoms is conditional on life stress. In a cross-sectional European population (n = 2426), recruited from Manchester and Budapest, we used the ID-Migraine questionnaire for migraine screening, the Life Threatening Experiences questionnaire to measure recent negative life events (RLE), and covered the CNR1 gene with 11 SNPs. The main genetic effects and the CNR1 × RLE interaction with age and sex as covariates were tested. None of the SNPs showed main genetic effects on possible migraine or its symptoms, but 5 SNPs showed nominally significant interaction with RLE on headache with nausea using logistic regression models. The effect of rs806366 remained significant after correction for multiple testing and replicated in the subpopulations. This effect was independent from depression- and anxiety-related phenotypes. In addition, a Bayesian systems-based analysis demonstrated that in the development of headache with nausea all SNPs were more relevant with higher a posteriori probability in those who experienced recent life stress. In summary, the CNR1 gene in interaction with life stress increased the risk of headache with nausea suggesting a specific pathological mechanism to develop migraine, and indicating that a subgroup of migraine patients, who suffer from life stress triggered migraine with frequent nausea, may benefit from therapies that increase the endocannabinoid tone.

Genetically reduced FAAH activity may be a risk for the development of anxiety and depression in persons with repetitive childhood trauma

Fatty acid amide hydrolase (FAAH) inhibitors are addressed for promising anxiolytics, but human studies on genetically reduced FAAH activity, stress and affective phenotypes are scarce. We investigated the effect of a functional polymorphism of FAAH (FAAH C385A or rs324420; low FAAH activity and high anandamide concentration are associated with the A allele) together with childhood adversity on the anxious and depressive phenotypes in 858 subjects from the general population. Phenotypes were measured by the Zung Self-Rating Depression Scale (ZSDS), the depression and anxiety subscales of the Brief Symptom Inventory (BSI-DEP, BSI-ANX) and the State-Trait Anxiety scales (STAI-S, STAI-T). Childhood Adversity Questionnaire (CHA) was used to assess early life traumas. Frequency of the A allele was greater among subjects with high ZSDS scores compared to the CC genotype. Furthermore, FAAH C385A and the CHA have shown a robust gene-environment interaction, namely, significantly higher anxiety and depression scores were exhibited by individuals carrying the A allele if they had high CHA scores compared to CC carriers. These data provided preliminary evidence that genetically reduced FAAH activity and repetitive stress in the childhood are associated with increased vulnerability for anxiety and depression in later life. Our results together with earlier experimental data suggest that permanently elevated anandamide level together with early life stress may cause a lifelong damage on stress response probably via the downregulation of CB1R during the neurodevelopment in the brain. It may also point to pharmacogenomic consequences, namely ineffectiveness or adverse effects of FAAH inhibitors in this subpopulation.

Neurogenetics and gene therapy for reward deficiency syndrome: are we going to the Promised Land?

INTRODUCTION

Addiction is a substantial health issue with limited treatment options approved by the FDA and as such currently available. The advent of neuroimaging techniques that link neurochemical and neurogenetic mechanisms to the reward circuitry brain function provides a framework for potential genomic-based therapies.

AREAS COVERED

Through candidate and genome-wide association studies approaches, many gene polymorphisms and clusters have been implicated in drug, food and behavioral dependence linked by the common rubric reward deficiency syndrome (RDS). The results of selective studies that include the role of epigenetics, noncoding micro RNAs in RDS behaviors especially drug abuse involving alcohol, opioids, cocaine, nicotine, pain and feeding are reviewed in this article. New targets for addiction treatment and relapse prevention, treatment alternatives such as gene therapy in animal models, and pharmacogenomics and nutrigenomics methods to manipulate transcription and gene expression are explored.

EXPERT OPINION

The recognition of the clinical benefit of early genetic testing to determine addiction risk stratification and dopaminergic agonistic, rather than antagonistic therapies are potentially the genomic-based wave of the future. In addition, further development, especially in gene transfer work and viral vector identification, could make gene therapy for RDS a possibility in the future.

Differences in Anxiety-Like Behavior within a Batch of Wistar Rats Are Associated with Differences in Serotonergic Transmission, Enhanced by Acute SRI Administration, and Abolished By Serotonin Depletion

BACKGROUND

The anxiety-reducing effect of long-term administration of serotonin reuptake inhibitors is usually seen only in subjects with anxiety disorders, and such patients are also abnormally inclined to experience a paradoxical anxiety-enhancing effect of acute serotonin reuptake inhibition. These unique responses to serotonin reuptake inhibitors in anxiety-prone subjects suggest, as do genetic association studies, that inter-individual differences in anxiety may be associated with differences in serotonergic transmission.

METHODS

The one-third of the animals within a batch of Wistar rats most inclined to spend time on open arms in the elevated plus maze were compared with the one-third most inclined to avoid them with respect to indices of brain serotonergic transmission and how their behavior was influenced by serotonin-modulating drugs.

RESULTS

"Anxious" rats displayed higher expression of the tryptophan hydroxylase-2 gene and higher levels of the tryptophan hydroxylase-2 protein in raphe and also higher levels of serotonin in amygdala. Supporting these differences to be important for the behavioral differences, serotonin depletion obtained by the tryptophan hydroxylase-2 inhibitor p-chlorophenylalanine eliminated them by reducing anxiety in "anxious" but not "non-anxious" rats. Acute administration of a serotonin reuptake inhibitor, paroxetine, exerted an anxiety-enhancing effect in "anxious" but not "non-anxious" rats, which was eliminated by long-term pretreatment with another serotonin reuptake inhibitor, escitalopram.

CONCLUSIONS

Differences in an anxiogenic impact of serotonin, which is enhanced by acute serotonin reuptake inhibitor administration, may contribute to differences in anxiety-like behavior amongst Wistar rats.

Variability in the effect of 5-HTTLPR on depression in a large European population: the role of age, symptom profile, type and intensity of life stressors

Background

Although 5-HTTLPR has been shown to influence the risk of life stress-induced depression in the majority of studies, others have produced contradictory results, possibly due to weak effects and/or sample heterogeneity.

Methods

In the present study we investigated how age, type and intensity of life-stressors modulate the effect of 5-HTTLPR on depression and anxiety in a European population cohort of over 2300 subjects. Recent negative life events (RLE), childhood adversity (CHA), lifetime depression, Brief Symptoms Inventory (BSI) depression and anxiety scores were determined in each subject. Besides traditional statistical analysis we calculated Bayesian effect strength and relevance of 5-HTTLPR genotypes in specified models.

Results

The short (s) low expressing allele showed association with increased risk of depression related phenotypes, but all nominally significant effects would turn to non-significant after correction for multiple testing in the traditional analysis. Bayesian effect strength and relevance analysis, however, confirmed the role of 5-HTTLPR. Regarding current (BSI) and lifetime depression 5-HTTLPR-by-RLE interactions were confirmed. Main effect, with other words direct association, was supported with BSI anxiety. With more frequent RLE the prevalence or symptoms of depression increased in ss carriers. Although CHA failed to show an interaction with 5-HTTLPR, in young subjects CHA sensitized towards the depression promoting effect of even mild RLE. Furthermore, the direct association of anxiety with the s allele was driven by young (≤30) individuals.

Limitations

Our study is cross-sectional and applies self-report questionnaires.

Conclusions

Albeit 5-HTTLPR has only weak/moderate effects, the s allele is directly associated with anxiety and modulates development of depression in homogeneous subgroups.

New perspectives on the development of antiobesity drugs

After many years of research, obesity is still a disease with an unmet medical need. Very few compounds have been approved, acting mainly on neuromediators; researches, in recent years, pointed toward compounds potentially safer than first-generation antiobesity drugs, able to interact with one or more (multitarget therapy) receptors for substances produced by the gut, adipose tissue and other targets outside CNS. Other holistic approaches, such as those involving gut microbiota and plant extracts, appeared recently in the literature, and undoubtedly will contribute to the discovery of a valuable therapy for this disease. This review deals with the positive results and the pitfalls obtained following these approaches, with a view on their clinical trial studies.

Transcriptional evidence for the role of chronic venlafaxine treatment in neurotrophic signaling and neuroplasticity including also Glutamatergic [corrected] - and insulin-mediated neuronal processes

OBJECTIVES

Venlafaxine (VLX), a serotonine-noradrenaline reuptake inhibitor, is one of the most commonly used antidepressant drugs in clinical practice for the treatment of major depressive disorder (MDD). Despite being more potent than its predecessors, similarly to them, the therapeutical effect of VLX is visible only 3-4 weeks after the beginning of treatment. Furthermore, recent papers show that antidepressants, including also VLX, enhance the motor recovery after stroke even in non depressed persons. In the present, transcriptomic-based study we looked for changes in gene expressions after a long-term VLX administration.

METHODS

Osmotic minipumps were implanted subcutaneously into Dark Agouti rats providing a continuous (40 mg/kg/day) VLX delivery for three weeks. Frontal regions of the cerebral cortex were isolated and analyzed using Illumina bead arrays to detect genes showing significant chances in expression. Gene set enrichment analysis was performed to identify specific regulatory networks significantly affected by long term VLX treatment.

RESULTS

Chronic VLX administration may have an effect on neurotransmitter release via the regulation of genes involved in vesicular exocytosis and receptor endocytosis (such as Kif proteins, Myo5a, Sv2b, Syn2 or Synj2). Simultaneously, VLX activated the expression of genes involved in neurotrophic signaling (Ntrk2, Ntrk3), glutamatergic transmission (Gria3, Grin2b and Grin2a), neuroplasticity (Camk2g/b, Cd47), synaptogenesis (Epha5a, Gad2) and cognitive processes (Clstn2). Interestingly, VLX increased the expression of genes involved in mitochondrial antioxidant activity (Bcl2 and Prdx1). Additionally, VLX administration also modulated genes related to insulin signaling pathway (Negr1, Ppp3r1, Slc2a4 and Enpp1), a mechanism that has recently been linked to neuroprotection, learning and memory.

CONCLUSIONS

Our results strongly suggest that chronic VLX treatment improves functional reorganization and brain plasticity by influencing gene expression in regulatory networks of motor cortical areas. These results are consonant with the synaptic (network) hypothesis of depression and antidepressant-induced motor recovery after stroke.

Early phytocannabinoid chemistry to endocannabinoids and beyond

Isolation and structure elucidation of most of the major cannabinoid constituents--including Δ(9)-tetrahydrocannabinol (Δ(9)-THC), which is the principal psychoactive molecule in Cannabis sativa--was achieved in the 1960s and 1970s. It was followed by the identification of two cannabinoid receptors in the 1980s and the early 1990s and by the identification of the endocannabinoids shortly thereafter. There have since been considerable advances in our understanding of the endocannabinoid system and its function in the brain, which reveal potential therapeutic targets for a wide range of brain disorders.

Peripheral targets in obesity treatment: a comprehensive update

Obesity is a major epidemic of our time and is associated with diseases such as metabolic syndrome, type 2 diabetes mellitus and atherosclerotic cardiovascular disease. Although weight loss drugs, when accompanied by diet and exercise, could be a very helpful medical tool in treating obese or overweight patients, their usefulness has been questioned due to the complexity of this type of medication, which regards a plethora of issues such as efficacy and safety of the drug and also risks and benefits among different patients. In general, obesity drugs that target peripheral pathophysiological mechanisms can be divided into two main categories. The first category includes anti-obesity agents able to reduce or limit energy absorption, such as pancreatic lipase and microsomal triglyceride transfer protein inhibitors. The second category consists of a heterogeneous group of compounds aiming to decrease fat mass by increasing energy expenditure or by redistributing adipose tissue. Angiogenesis inhibitors, beta-3 receptor agonists, sirtuin-I activators, diazoxide and other molecules belong to this group. The glucagon-like peptide-1 receptor agonists consist the third category of peripheral anti-obesity agents discussed therein. This review aims to provide a general overview of the molecules and substances that are already or could potentially be used as peripheral anti-obesity drugs, the molecular mechanisms by which they act, as well as their current stage of development, production and/or availability.

Angiotensin II-induced activation of central AT1 receptors exerts endocannabinoid-mediated gastroprotective effect in rats

The aim of the present study was to analyze whether angiotensin II via the endocannabinoid system can induce gastric mucosal protection, since transactivation of cannabinoid CB1 receptors by angiotensin AT1 receptor in CHO cells was described. Experimental ulcer was induced by acidified ethanol given orally in male Wistar rats, CB1(+/+) wild type and CB1(-/-) knockout mice. The compounds were administered intracerebroventricularly. It was found, that 1. Angiotensin II inhibited the ethanol-induced gastric lesions (11.9-191pmol); the effect of angiotensin II (191pmol) was inhibited by the CB1 receptor inverse agonist AM 251 (1.8nmol) and the inhibitor of diacylglycerol lipase (DAGL), tetrahydrolipstatin (0.2nmol). 2. Angiotensin II exerted gastroprotection in wild type, but not in CB1(-/-) mice. 3. The gastroprotective effect of angiotensin II (191pmol) was reduced by atropine (1mg/kg i.v.) and bilateral cervical vagotomy. In conclusion, stimulation of central angiotensin AT1 receptors via activation of cannabinoid CB1 receptors induces gastroprotection in a DAGL-dependent and vagus-mediated mechanism.

Antidepressant treatment response is modulated by genetic and environmental factors and their interactions

Although there is a wide variety of antidepressants with different mechanisms of action available, the efficacy of treatment is not satisfactory. Genetic factors are presumed to play a role in differences in medication response; however, available evidence is controversial. Even genome-wide association studies failed to identify genes or regions which would consequently influence treatment response. We conducted a literature review in order to uncover possible mechanisms concealing the direct effects of genetic variants, focusing mainly on reports from large-scale studies including STAR*D or GENDEP. We observed that inclusion of environmental factors, gene-environment and gene-gene interactions in the model improves the probability of identifying genetic modulator effects of antidepressant response. It could be difficult to determine which allele of a polymorphism is the risk factor for poor treatment outcome because depending on the acting environmental factors different alleles could be advantageous to improve treatment response. Moreover, genetic variants tend to show better association with certain intermediate phenotypes linked to depression because these are more objective and detectable than traditional treatment outcomes. Thus, detailed modeling of environmental factors and their interactions with different genetic pathways could significantly improve our understanding of antidepressant efficacy. In addition, the complexity of depression itself demands a more comprehensive analysis of symptom trajectories if we are to extract useful information which could be used in the personalization of antidepressant treatment.

Gene expression analysis indicates CB1 receptor upregulation in the hippocampus and neurotoxic effects in the frontal cortex 3 weeks after single-dose MDMA administration in Dark Agouti rats

BACKGROUND

3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") is a widely used recreational drug known to impair cognitive functions on the long-run. Both hippocampal and frontal cortical regions have well established roles in behavior, memory formation and other cognitive tasks and damage of these regions is associated with altered behavior and cognitive functions, impairments frequently described in heavy MDMA users. The aim of this study was to examine the hippocampus, frontal cortex and dorsal raphe of Dark Agouti rats with gene expression arrays (Illumina RatRef bead arrays) looking for possible mechanisms and new candidates contributing to the effects of a single dose of MDMA (15 mg/kg) 3 weeks earlier.

RESULTS

The number of differentially expressed genes in the hippocampus, frontal cortex and the dorsal raphe were 481, 155, and 15, respectively. Gene set enrichment analysis of the microarray data revealed reduced expression of 'memory' and 'cognition', 'dendrite development' and 'regulation of synaptic plasticity' gene sets in the hippocampus, parallel to the upregulation of the CB1 cannabinoid- and Epha4, Epha5, Epha6 ephrin receptors. Downregulated gene sets in the frontal cortex were related to protein synthesis, chromatin organization, transmembrane transport processes, while 'dendrite development', 'regulation of synaptic plasticity' and 'positive regulation of synapse assembly' gene sets were upregulated. Changes in the dorsal raphe region were mild and in most cases not significant.

CONCLUSION

The present data raise the possibility of new synapse formation/synaptic reorganization in the frontal cortex three weeks after a single neurotoxic dose of MDMA. In contrast, a prolonged depression of new neurite formation in the hippocampus is suggested by the data, which underlines the particular vulnerability of this brain region after the drug treatment. Finally, our results also suggest the substantial contribution of CB1 receptor and endocannabinoid mediated pathways in the hippocampal impairments. Taken together the present study provides evidence for the participation of new molecular candidates in the long-term effects of MDMA.

Neutral antagonism at the cannabinoid 1 receptor: a safer treatment for obesity

Obesity is a global problem with often strong neurobiological underpinnings. The cannabinoid 1 receptor (CB1R) was put forward as a promising drug target for antiobesity medication. However, the first marketed CB1R antagonist/inverse agonist rimonabant was discontinued, as its use was occasionally associated with negative affect and suicidality. In artificial cell systems, CB1Rs can become constitutively active in the absence of ligands. Here, we show that such constitutive CB1R activity also regulates GABAergic and glutamatergic neurotransmission in the ventral tegmental area and basolateral amygdala, regions which regulate motivation and emotions. We show that CB1R inverse agonists like rimonabant suppress the constitutive CB1R activity in such regions, and cause anxiety and reduced motivation for reward. The neutral CB1R antagonist NESS0327 does not suppress constitutive activity and lacks these negative effects. Importantly, however, both rimonabant and NESS0327 equally reduce weight gain and food intake. Together, these findings suggest that neutral CB1R antagonists can treat obesity efficiently and more safely than inverse agonists.

[Anxiogenic and depressogenic side-effects of non-psychiatric drugs]

Although medications such as anticancer, antimicrobial, immunomodulatory, neurological or hormonal therapies may have a negative impact on mood, adequate attention was not paid until the withdrawal of rimonabant in 2008. In the present study the authors review full spectrum of currently available medications discussing anxiety and depression as possible adverse effects of treatment. A relatively high risk of depression should always be considered when pharmacotherapy applied, especially if current depressive episodes, positive family history, or neurotic personality traits increasing susceptibility to depressogenic effects. Prior to start of medical treatment, the potential effectiveness of the given drug should be precisely evaluated, and alternative medical and non-medical treatment options should also be carefully considered. In addition, monitoring patients during treatment for signs of depressive or anxious symptoms is necessary.

Biomarkers for personalised treatment in psychiatric diseases

Biomarker research of psychiatric disorders is delayed by symptom pattern-related diagnostic categories that are only distantly associated with biological mechanisms. In neuropsychiatric disorders that have high heritability (schizophrenia, autism, Alzheimer's disease), genomic research led to significant genome-wide association study (GWAS) results by increasing the number of subjects in case–control studies, and thus provided new hypotheses regarding the aetiology of these disorders and possible targets for research of new treatment approaches. In contrast, in moderately heritable psychiatric disorders (anxiety disorders, unipolar major depression), the development of symptoms, in addition to risk genes, is more dependent on the presence of specific environmental risk factors. Thus, controlling for heterogeneity, and not simply increasing the number of subjects, is crucial for further significant psychiatric GWAS findings that warrant the collection of more detailed individual phenotypic data and information about relevant previous environmental exposures. Gene–gene interactions (epistasis) and intermediate phenotypes or psychiatric and somatic co-morbidities, by identifying similar cases within a diagnostic category, could further increase the generally weak effects of individual genes that limit their usefulness as biomarkers. In conclusion, we argue that methods that are suitable to identify biologically more homogeneous subgroups within a given psychiatric disorder are necessary to advance biomarker research.

The endocannabinoid signaling system in cancer

Changes in lipid metabolism are intimately related to cancer. Several classes of bioactive lipids play roles in the regulation of signaling pathways involved in neoplastic transformation and tumor growth and progression. The endocannabinoid system, comprising lipid-derived endocannabinoids, their G-protein-coupled receptors (GPCRs), and the enzymes for their metabolism, is emerging as a promising therapeutic target in cancer. This report highlights the main signaling pathways for the antitumor effects of the endocannabinoid system in cancer and its basic role in cancer pathogenesis, and discusses the alternative view of cannabinoid receptors as tumor promoters. We focus on new players in the antitumor action of the endocannabinoid system and on emerging crosstalk among cannabinoid receptors and other membrane or nuclear receptors involved in cancer. We also discuss the enzyme MAGL, a key player in endocannabinoid metabolism that was recently recognized as a marker of tumor lipogenic phenotype.

Characteristics of clinically anxious versus non-anxious regular, heavy marijuana users

Both the key mechanism of action for marijuana (the endocannabinoid system) and the symptoms associated with marijuana withdrawal suggest an important link to anxiety. Despite this link, there is a dearth of research on the characteristics of heavy marijuana users with clinical-level anxiety compared to those with heavy marijuana use alone. Over 10,000 participants (friends or affiliates of the National Organization for the Reform of Marijuana Laws) provided data via online survey. After careful, conservative screening, anxiety, other psychopathology, other drug use, and marijuana-related problems were examined in 2567 heavy marijuana users. Subsequently, 275 heavy users with clinical-level anxiety were compared to demographically-equivalent non-anxious heavy users on psychopathology, drug use, and cannabis-related problems. Among several psychological variables (including anxiety, depression, schizotypy, and impulsivity), anxiety was most strongly predictive of amount of marijuana used and marijuana-related problems. Group comparison (n=550 total) revealed that clinically anxious heavy users exhibited more use, more non-anxiety psychopathological symptoms, and a greater number and severity of marijuana-related problems than their non-anxious peers. The findings reveal that anxiety shows an important relation to marijuana use and related problems among regular, heavy users. Further examinations of common and unique factors predisposing individuals for anxiety and marijuana abuse appear warranted.

Genetic variability in the endocannabinoid system and 12-week clinical response to citalopram treatment: the role of the CNR1, CNR2 and FAAH genes

First line treatment of major depression is based on selective serotonin re-uptake inhibitors (SSRIs) that enhance serotonergic neurotransmission by blocking the serotonin transporter. However, clinical response is a complex phenomenon in which other systems such as the endocannabinoid system could be involved. Given the evidence for the role of the endocannabinoid system in the pathogenesis of depression as well as in the mediation of antidepressant drug effects, the aim of this study was to analyze genetic variability in the endocannabinoid system genes (CNR1, CNR2 and FAAH genes) and their role in clinical response (at week 4) and remission (at week 12) in SSRI (citalopram) treatment in a sample of 154 depressive outpatients, all of Spanish origin. All patients were treated with citalopram and followed over 12 weeks. Severity of depressive symptomatology was evaluated by means of the 21-item Hamilton Depression Rating Score (HDRS). No differences were found in any of the genotype distributions according to response or remission. The longitudinal study showed that (i) the CNR1 rs1049353-GG genotype conferred a better response to citalopram treatment in the subgroup of male patients and (ii) G allele carriers (CNR2 rs2501431) presented higher HDRS scores in the follow-up than AA homozygous allele carriers. Our results seem to suggest the involvement of CNR1 and CNR2 genes in clinical responses to citalopram treatment.

Probing the interaction of SR141716A with the CB1 receptor

SR141716A binds selectively to the brain cannabinoid (CB1) receptor and exhibits a potent inverse agonist/antagonist activity. Although SR141716A, also known as rimonabant, has been withdrawn from the market due to severe side effects, there remains interest in some of its many potential medical applications. Consequently, it is imperative to understand the mechanism by which SR141716A exerts its inverse agonist activity. As a result of using an approach combining mutagenesis and molecular dynamics simulations, we determined the binding mode of SR141716A. We found from the simulation of the CB1-SR141716A complex that SR141716A projects toward TM5 to interact tightly with the major binding pocket, replacing the coordinated water molecules, and secures the Trp-356(6.48) rotameric switch in the inactive state to promote the formation of an extensive water-mediated H-bonding network to the highly conserved SLAXAD and NPXXY motifs in TM2/TM7. We identify for the first time the involvement of the minor binding pocket formed by TM2/TM3/TM7 for SR141716A binding, which complements the major binding pocket formed by TM3/TM5/TM6. Simulation of the F174(2.61)A mutant CB1-SR141716A complex demonstrates the perturbation of TM2 that attenuates SR141716A binding indirectly. These results suggest SR141716A exerts inverse agonist activity through the stabilization of both TM2 and TM5, securing the Trp-356(6.48) rotameric switch and restraining it from activation.

Opposing local effects of endocannabinoids on the activity of noradrenergic neurons and release of noradrenaline: relevance for their role in depression and in the actions of CB(1) receptor antagonists

There is strong evidence that endocannabinoids modulate signaling of serotonin and noradrenaline, which play key roles in the pathophysiology and treatment of anxiety and depression. Most pharmacological and genetic, human and rodent studies suggest that the presence of under-functioning endocannabinoid type-1 (CB(1)) receptors is associated with increased anxiety and elevated extracellular serotonin concentration. In contrast, noradrenaline is presumably implicated in the mediation of depression-type symptoms of CB(1) receptor antagonists. Evidence shows that most CB(1) receptors located on axons and terminals of GABA-ergic, serotonergic or glutamatergic neurons stimulate the activity of noradrenergic neurons. In contrast, those located on noradrenergic axons and terminals inhibit noradrenaline release efficiently. In this latter process, excitatory ionotropic or G protein-coupled receptors, such as the NMDA, alpha1 and beta1 adrenergic receptors, activate local endocannabinoid synthesis at postsynaptic sites and stimulate retrograde endocannabinoid neurotransmission acting on CB(1) receptors of noradrenergic terminals. The underlying mechanisms include calcium signal generation, which activates enzymes that increase the synthesis of both anandamide and 2-arachidonoylglycerol, while G(q/11) protein activation also increases the formation of 2-arachidonoylglycerol from diacylglycerol during the signaling process. In addition, other non-CB(1) receptor endocannabinoid targets such as CB(2), transient receptor potential vanilloid subtype, peroxisome proliferator-activated receptor-alpha and possibly GPR55 can also mediate some of the endocannabinoid effects. In conclusion, both neuronal activation and neurotransmitter release depend on the in situ synthesized endocannabinoids and thus, local endocannabinoid concentrations in different brain areas may be crucial in the net effect, namely in the regulation of neurons located postsynaptically to the noradrenergic synapse.

Anti-obesity drugs: past, present and future

The ideal anti-obesity drug would produce sustained weight loss with minimal side effects. The mechanisms that regulate energy balance have substantial built-in redundancy, overlap considerably with other physiological functions, and are influenced by social, hedonic and psychological factors that limit the effectiveness of pharmacological interventions. It is therefore unsurprising that anti-obesity drug discovery programmes have been littered with false starts, failures in clinical development, and withdrawals due to adverse effects that were not fully appreciated at the time of launch. Drugs that target pathways in metabolic tissues, such as adipocytes, liver and skeletal muscle, have shown potential in preclinical studies but none has yet reached clinical development. Recent improvements in the understanding of peptidergic signalling of hunger and satiety from the gastrointestinal tract mediated by ghrelin, cholecystokinin (CCK), peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), and of homeostatic mechanisms related to leptin and its upstream pathways in the hypothalamus, have opened up new possibilities. Although some have now reached clinical development, it is uncertain whether they will meet the strict regulatory hurdles required for licensing of an anti-obesity drug. However, GLP-1 receptor agonists have already succeeded in diabetes treatment and, owing to their attractive body-weight-lowering effects in humans, will perhaps also pave the way for other anti-obesity agents. To succeed in developing drugs that control body weight to the extent seen following surgical intervention, it seems obvious that a new paradigm is needed. In other therapeutic arenas, such as diabetes and hypertension, lower doses of multiple agents targeting different pathways often yield better results than strategies that modify one pathway alone. Some combination approaches using peptides and small molecules have now reached clinical trials, although recent regulatory experience suggests that large challenges lie ahead. In future, this polytherapeutic strategy could possibly rival surgery in terms of efficacy, safety and sustainability of weight loss.

Modulation of the cannabinoid receptors by hemopressin peptides

Changes in the endocannabinoid system are implicated in numerous diseases, making it an attractive target for pharmaceutical development. The endocannabinoid receptors have traditionally been thought to act through the effects of lipophilic messengers called cannabinoids. The exciting finding of endocannabinoid system modulation by the nonapeptide hemopressin and its N-terminal extensions has highlighted the complexity of cannabinoid biology and pharmacology and sparked interest for therapeutic purposes. However, many questions surrounding the generation and regulation of the hemopressin peptides, the self-assembly of hemopressin and the potential for drug development based on hemopressin remain and are discussed in this review.

The endocannabinoid system and the brain

The psychoactive constituent in cannabis, Δ(9)-tetrahydrocannabinol (THC), was isolated in the mid-1960s, but the cannabinoid receptors, CB1 and CB2, and the major endogenous cannabinoids (anandamide and 2-arachidonoyl glycerol) were identified only 20 to 25 years later. The cannabinoid system affects both central nervous system (CNS) and peripheral processes. In this review, we have tried to summarize research--with an emphasis on recent publications--on the actions of the endocannabinoid system on anxiety, depression, neurogenesis, reward, cognition, learning, and memory. The effects are at times biphasic--lower doses causing effects opposite to those seen at high doses. Recently, numerous endocannabinoid-like compounds have been identified in the brain. Only a few have been investigated for their CNS activity, and future investigations on their action may throw light on a wide spectrum of brain functions.

CB₂: therapeutic target-in-waiting

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

Effects induced by cannabinoids on monoaminergic systems in the brain and their implications for psychiatric disorders

The endocannabinoid system and CB(1) receptors participate in the control of emotional behavior and mood through a functional coupling with the classic monoaminergic systems. In general, the acute stimulation of CB(1) receptors increases the activity (spontaneous firing rate) of noradrenergic (NE), serotonergic (5-HT) and dopaminergic (DA) neurons as well as the synthesis and/or release of the corresponding neurotransmitter in specific brain regions. Notably, the antagonist/inverse agonist rimonabant (SR141617A) can decrease the basal activity of NE and 5-HT neurons, suggesting a tonic/constitutive regulation of these neuronal systems by endocannabinoids acting at CB(1) receptors. Monoaminergic systems are modulated via CB(1) receptors by direct or indirect effects depending on the localization of this inhibitory receptor, which can be present on monoaminergic neurons themselves and/or inhibitory (GABAergic) and/or excitatory (glutamatergic) regulatory neurons. The repeated stimulation of CB(1) receptors is not associated with the induction of tolerance (receptor desensitization) on the activity of NE, 5-HT and DA neurons, in contrast to chronic agonist effects on neurotransmitter synthesis and/or release in some brain regions. CB(1) receptor desensitization may alter the direct and/or indirect effects of cannabinoid drugs modulating the functionality of monoaminergic systems. The sustained activation of monoaminergic neurons by cannabinoid drugs can also be related to changes in the function of presynaptic inhibitory α(2)-adrenoceptors or 5-HT(1A) receptors (autoreceptors and heteroreceptors), whose sensitivity is downregulated or upregulated upon chronic CB(1) agonist exposure. The functional interactions between endocannabinoids and monoaminergic systems in the brain indicate a potential role for CB(1) receptor signaling in the neurobiology of various psychiatric disorders, including major depression and schizophrenia as the major syndromes.

Expression pattern of the cannabinoid receptor genes in the frontal cortex of mood disorder patients and mice selectively bred for high and low fear

Although the endocannabinoid system (ECS) has been implicated in brain development and various psychiatric disorders, precise mechanisms of the ECS on mood and anxiety disorders remain unclear. Here, we have investigated developmental and disease-related expression pattern of the cannabinoid receptor 1 (CB1) and the cannabinoid receptor 2 (CB2) genes in the dorsolateral prefrontal cortex (PFC) of humans. Using mice selectively bred for high and low fear, we further investigated potential association between fear memory and the cannabinoid receptor expression in the brain. The CB1, not the CB2, mRNA levels in the PFC gradually decrease during postnatal development ranging in age from birth to 50 years (r2 > 0.6 & adj. p < 0.05). The CB1 levels in the PFC of major depression patients were higher when compared to the age-matched controls (adj. p < 0.05). In mice, the CB1, not the CB2, levels in the PFC were positively correlated with freezing behavior in classical fear conditioning (p < 0.05). These results suggest that the CB1 in the PFC may play a significant role in regulating mood and anxiety symptoms. Our study demonstrates the advantage of utilizing data from postmortem brain tissue and a mouse model of fear to enhance our understanding of the role of the cannabinoid receptors in mood and anxiety disorders.

Design of a Potent CB1 Receptor Antagonist Series: Potential Scaffold for Peripherally-Targeted Agents

Antagonism of cannabinoid-1 (CB1) receptor signaling has been demonstrated to inhibit feeding behaviors in humans, but CB1-mediated central nervous system (CNS) side effects have halted the marketing and further development of the lead drugs against this target. However, peripherally restricted CB1 receptor antagonists may hold potential for providing the desired efficacy with reduced CNS side effect profiles. In this report we detail the discovery and structure-activity-relationship analysis of a novel bicyclic scaffold (3) that exhibits potent CB1 receptor antagonism and oral activity in preclinical feeding models. Optimization of physical properties has led to the identification of analogues which are predicted to have reduced CNS exposure and could serve as a starting point for the design of peripherally targeted CB1 receptor antagonists.

Medications development to treat alcohol dependence: a vision for the next decade

More than 76 million people world-wide are estimated to have diagnosable alcohol use disorders (AUDs) (alcohol abuse or dependence), making these disorders a major global health problem. Pharmacotherapy offers promising means for treating AUDs, and significant progress has been made in the past 20 years. The US Food and Drug Administration approved three of the four medications for alcoholism in the last two decades. Unfortunately, these medications do not work for everyone, prompting the need for a personalized approach to optimize clinical benefit or more efficacious medications that can treat a wider range of patients, or both. To promote global health, the potential reorganization of the National Institutes of Health (NIH) must continue to support the National Institute on Alcohol Abuse and Alcoholism's (NIAAA's) vision of ensuring the development and delivery of new and more efficacious medications to treat AUDs in the coming decade. To achieve this objective, the NIAAA Medications Development Team has identified three fundamental long-range goals: (1) to make the drug development process more efficient; (2) to identify more efficacious medications, personalize treatment approaches, or both; and (3) to facilitate the implementation and adaptation of medications in real-world treatment settings. These goals will be carried out through seven key objectives. This paper describes those objectives in terms of rationale and strategy. Successful implementation of these objectives will result in the development of more efficacious and safe medications, provide a greater selection of therapy options and ultimately lessen the impact of this devastating disorder.

Regulation of endocannabinoid release by G proteins: a paracrine mechanism of G protein-coupled receptor action

In the past years, the relationship between the endocannabinoid system (ECS) and other hormonal and neuromodulatory systems has been intensively studied. G protein-coupled receptors (GPCRs) can stimulate endocannabinoid (eCB) production via activation of G(q/11) proteins and, in some cases, G(s) proteins. In this review, we summarize the pathways through which GPCR activation can trigger eCB release, as well as the best known examples of this process throughout the body tissues. Angiotensin II-induced activation of AT(1) receptors, similar to other G(q/11)-coupled receptors, can lead to the formation of 2-arachidonoylglycerol (2-AG), an important eCB. The importance of eCB formation in angiotensin II action is supported by the finding that the hypertensive effect of angiotensin II, injected directly into the hypothalamic paraventricular nucleus of anaesthetized rats, can be abolished by AM251, an inverse agonist of CB(1) cannabinoid receptors (CB(1)Rs). We conclude that activation of the ECS should be considered as a general consequence of the stimulation of G(q/11)-coupled receptors, and may mediate some of the physiological effects of GPCRs.

Hemopressin forms self-assembled fibrillar nanostructures under physiologically relevant conditions

The nonapeptide hemopressin, which is derived from the α chain of hemoglobin, has been reported to exhibit inverse agonist activity against the CB1 receptor. Administration of this peptide in animal models led to decreased food intake and elicited hypotensive and antinociceptive effects. On the basis of hemopressin's potential in therapeutic applications and the lack of a structure-activity relationship study in literature, we aimed to determine the conformational features of hemopressin under physiological conditions. We conducted transmission electron microscopy experiments of hemopressin, revealing that it self-assembles into fibrils under aqueous conditions at pH 7.4. Circular dichroism and nuclear magnetic resonance experiments indicate that the peptide adopts a mostly extended β-like structure, which may contribute to its self-assembly and fibril formation.