Rimonabant: just an antiobesity drug? Current evidence on its pleiotropic effects

Pyrazole/pyrazoline as an excellent pharmacophore in the design of carbonic anhydrase inhibitors (2018-2022)

Carbonic anhydrase (CA) is a metalloenzyme that catalyzes the interconversion between carbon dioxide and water and dissociated ions of carbonic acid. In addition, CA performs various other functions in animals and plants, depending on the part of the living being. CAs have been found in almost all organisms. Besides, CAs are associated with several diseases, such as glaucoma, obesity, epilepsy, cancer, and so on. CAs are also involved in tumor cell growth and angiogenesis. Thus, inhibition of CA may be an attractive way of control of such diseases. Hence, CA inhibitors have been designed and developed to cure CA-associated diseases. Some examples of approved CA inhibitors are dorzolamide, methazolamide, brinzolamide, and dichlorphenamide. Furthermore, various heterocyclic scaffolds were utilized for the design of CA inhibitors. Among those, pyrazole/pyrazoline derivatives have exhibited greater potency toward CA inhibition. Hence, research that took place in the field of drug design and discovery of CA inhibition has been systematically reviewed and collated. Alongside, the structure-activity relationship has been described, followed by a description of the most potent molecules and their structural features.

Sex differences in cocaine-associated memory: The interplay between CB1, mGluR5, and estradiol

We know surprisingly little about the sex differences in the neurobiology of cocaine addiction, except females are more susceptible to the rewarding effects of cocaine than their male counterparts. Only a handful of recent studies have examined the neurobiology of cocaine-induced conditioned place preference (CPP) memory among female rodents. We contribute to this emerging line of research by documenting sex differences in cocaine-associated memory and illustrating the underlying signaling pathways in five experiments. Rimonabant (Rim), a cannabinoid CB₁ antagonist and inverse agonist, exerted a facilitating effect for low-dose cocaine and an impairing effect for high-dose cocaine CPP memory in male mice, as in our previous study, but not in female mice. Nor did we observe the effect exist among CB₁ knockout male mice, which indicated that the CB₁ receptors played a mediating role. We also found that the metabotropic glutamate receptor 5 (mGluR5) was located in the same signaling pathway as CB₁ in male mice. To clarify the mechanisms behind the sex differences, we used ovariectomized (OVX) female mice with estradiol benzoate (EB) replacement. In the OVX female mice, we showed that Rim-alone and EB-alone, but not Rim-and-EB-combined, facilitated the low-dose cocaine CPP memory. Moreover, 4-hydroxytamoxifen (4-OHT), an estrogen receptor (ER) antagonist, blocked Rim's and EB's facilitating effect. Finally, 2-methyl-6-(phenylethynyl)pyridine (MPEP), an mGluR5 antagonist, partially blocked EB's facilitating effect. In sum, we identified sex-specific effects of Rim on cocaine-induced CPP memory and the respective signaling pathways: mGluR5-CB₁ for male mice and ER-mGluR5-CB₁ for female mice. These findings may have merits for the development of sex-specific treatment for cocaine addiction.

Mycobacterial Membrane Protein Large 3 (MmpL3) Inhibitors: A Promising Approach to Combat Tuberculosis

Tuberculosis is a prominent aliment throughout the world and a leading cause of mortality among infectious diseases. Drug development for multi-drug resistance and reducing the current therapy time is the top priority. Mycobacterial membrane protein large 3 (MmpL3) is a promising target with high potential, however, it has not been explored to its greatest potential. It is a membrane transporter that translocates trehalose-monomycolate which is a precursor for the synthesis of mycolic acid that is essential for the synthesis of the bacterial cell wall and is pathogenic in nature. In this review, we have discussed the current development of MmpL3 inhibitors, different scaffolds, their derivatives, and their synthetic schemes and provide insight into the challenges in developing these inhibitors.

L-Theanine regulates glutamine metabolism and immune function by binding to cannabinoid receptor 1

l-Theanine is a characteristic amino acid in tea with various effects including antioxidant and anti-inflammatory effects. Previously, most studies had reported that l-theanine regulates the immune function in vivo by inhibiting the expression of the inflammatory factors, but how l-theanine regulates the inflammatory factors' pathway is not known. In this study, we innovatively found the binding target of l-theanine in vivo-cannabinoid receptor 1, and demonstrated that l-theanine regulated the immune function and glutamine metabolism by competitively binding cannabinoid receptor 1. Mechanistically, l-theanine competitively binds cannabinoid receptor 1, leading to inhibition of cannabinoid receptor 1 activity, and regulates glutamine metabolism and immune function in normal and E44813-stressed rats. In normal rats, l-theanine inhibits ERK1/2 phosphorylation through Gβy by antagonizing cannabinoid receptor 1, thus affecting GS expression. From the point of view of immune signaling, after LTA antagonizes the activity of cannabinoid receptor 1, it relieves the inhibition of cannabinoid receptor 1 on COX-2 expression, downregulates Pdcd4 expression and NFκB, and ultimately enhances the expression of the anti-inflammatory factor IL-10. In E44813-stressed rats, l-theanine promotes the nuclear translocation of p-ERK1/2 by inhibiting the activity of cannabinoid receptor 1, and finally acts on GS. At the same time, it decreases the expression of the pro-inflammatory factor TNF-α and increases the expression of the anti-inflammatory factor IL-10 in stressed rats through the COX2-Pdcd4-NFκB-IL10 and TNFα pathways. In summary, these results demonstrate that l-theanine regulates glutamine metabolism and immune function by competitively binding to cannabinoid receptor 1.

Obesity-induced changes in human islet G protein-coupled receptor expression: Implications for metabolic regulation

G protein-coupled receptors (GPCRs) are a large family of cell surface receptors that are the targets for many different classes of pharmacotherapy. The islets of Langerhans are central to appropriate glucose homeostasis through their secretion of insulin, and islet function can be modified by ligands acting at the large number of GPCRs that islets express. The human islet GPCRome is not a static entity, but one that is altered under pathophysiological conditions and, in this review, we have compared expression of GPCR mRNAs in human islets obtained from normal weight range donors, and those with a weight range classified as obese. We have also considered the likely outcomes on islet function that the altered GPCR expression status confers and the possible impact that adipokines, secreted from expanded fat depots, could have at those GPCRs showing altered expression in obesity.

Contribution of N-heterocycles towards anti-tubercular drug discovery (2014-2019); predicted and reengineered molecular frameworks

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis, responsible for high death frequency every year all over the world. In this regard, efficient drug-design and discovery towards the prevention of M.tb H₃₇ R_v is of prime concern. Prevention of the infection may include vaccination, and the treatment comprises anti-TB drug regimen. However, the vaccine decreases the risk of tuberculosis infection only to some extent, while drug-resistance limits the efficacy of the existing anti-TB agents. Much improvement has to be achieved to overcome pitfalls such as side effects, high-toxicity, low bioavailability, pharmacokinetics and pharmacodynamics, and hence forth in clinical therapeutics. Amongst heterocyclic compounds, N-heterocycles played a pivotal role in drug-design and discovery. A wide range of microbial diseases are being treated by the N-heterocyclic drugs. The present review comprises description of anti-TB effects of the N-heterocycles such as indoles, triazoles, thiazoles, and pyrazoles. The potent anti-TB activity exerted by the derivatives of these heterocycles is evaluated critically alongside emphasizing structure-activity relationship. Besides, docking studies supporting anti-TB activity is supplemented. Alongside this, based on the potent heterocyclic molecules, the molecular frameworks are designed that would bring about enhanced M. tb H₃₇ R_v inhibitory potencies.

Plant-derived natural therapeutics targeting cannabinoid receptors in metabolic syndrome and its complications: A review

The endocannabinoid system (ECS) is natural physiological system in the humans. The presence of the ECS system involves different roles in body. The endocannabinoid system involves regulation of most of the centers, which regulates the hunger and leads to changes in the weight. In the present article, we reviewed the role of natural cannabinoid compounds in metabolic disorders and related complications. We studied variety of a plant-derived cannabinoids in treating the metabolic syndrome including stoutness, fatty acid liver diseases, insulin obstruction, dementia, hypertension, lipid abnormalities, non-alcoholic steatohepatitis, endothelial damage, and polycystic ovarian syndrome and so on. The activation of cannabinoid receptors demonstrates a significant number of beneficial approaches concerning metabolic syndrome and reduces the pro-inflammatory cytokines on account of aggravation, decreased oxidative stress and uneasiness, diminishes liver fibrosis, with reduces adiponectin. Pre-clinical investigations of plant-derived cannabinoids resulted in promising outcomes. The different distinctive plant-derived cannabinoids were discovered like cannabidiol (CBD), cannabinol (CBN), cannabichromene (CBC), and cannabidiol (CBG). It has been observed that endogenous cannabinoids and plant-derived cannabinoids have an advantageous impact on limiting the metabolic disorder arising due to lifestyle changes.

Innovative Therapeutic Potential of Cannabinoid Receptors as Targets in Alzheimer’s Disease and Less Well-Known Diseases

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The discovery of cannabinoid receptors at the beginning of the 1990s, CB1 cloned in 1990 and CB2 cloned in 1993, and the availability of selective and potent cannabimimetics could only be justified by the existence of endogenous ligands that are capable of binding to them. Thus, the characterisation and cloning of the first cannabinoid receptor (CB1) led to the isolation and characterisation of the first endocannabinoid, arachidonoylethanolamide (AEA), two years later and the subsequent identification of a family of lipid transmitters known as the fatty acid ester 2-arachidonoylglycerol (2-AG).

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The endogenous cannabinoid system is a complex signalling system that comprises transmembrane endocannabinoid receptors, their endogenous ligands (the endocannabinoids), the specific uptake mechanisms and the enzymatic systems related to their biosynthesis and degradation.

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The endocannabinoid system has been implicated in a wide diversity of biological processes, in both the central and peripheral nervous systems, including memory, learning, neuronal development, stress and emotions, food intake, energy regulation, peripheral metabolism, and the regulation of hormonal balance through the endocrine system.

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In this context, this article will review the current knowledge of the therapeutic potential of cannabinoid receptor as a target in Alzheimer’s disease and other less well-known diseases that include, among others, multiple sclerosis, bone metabolism, and Fragile X syndrome.

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The therapeutic applications will be addressed through the study of cannabinoid agonists acting as single drugs and multi-target drugs highlighting the CB2 receptor agonist.

Countering the Modern Metabolic Disease Rampage With Ancestral Endocannabinoid System Alignment

When primitive vertebrates evolved from ancestral members of the animal kingdom and acquired complex locomotive and neurological toolsets, a constant supply of energy became necessary for their continued survival. To help fulfill this need, the endocannabinoid (eCB) system transformed drastically with the addition of the cannabinoid-1 receptor (CB1R) to its gene repertoire. This established an eCB/CB1R signaling mechanism responsible for governing the whole organism's energy balance, with its activation triggering a shift toward energy intake and storage in the brain and the peripheral organs (i.e., liver and adipose). Although this function was of primal importance for humans during their pre-historic existence as hunter-gatherers, it became expendable following the successive lifestyle shifts of the Agricultural and Industrial Revolutions. Modernization of the world has further increased food availability and decreased energy expenditure, thus shifting the eCB/CB1R system into a state of hyperactive deregulated signaling that contributes to the 21st century metabolic disease pandemic. Studies from the literature supporting this perspective come from a variety of disciplines, including biochemistry, human medicine, evolutionary/comparative biology, anthropology, and developmental biology. Consideration of both biological and cultural evolution justifies the design of improved pharmacological treatments for obesity and Type 2 diabetes (T2D) that focus on peripheral CB1R antagonism. Blockade of peripheral CB1Rs, which universally promote energy conservation across the vertebrate lineage, represents an evolutionary medicine strategy for clinical management of present-day metabolic disorders.

Rimonabant, a potent CB1 cannabinoid receptor antagonist, is a Gαi/o protein inhibitor

Rimonabant is a potent and selective cannabinoid CB1 receptor antagonist widely used in animal and clinical studies. Besides its antagonistic properties, numerous studies have shown that, at micromolar concentrations rimonabant behaves as an inverse agonist at CB1 receptors. The mechanism underpinning this activity is unclear. Here we show that micromolar concentrations of rimonabant inhibited Gα_i/o-type G proteins, resulting in a receptor-independent block of G protein signaling. Accordingly, rimonabant decreased basal and agonist stimulated [³⁵S]GTPγS binding to cortical membranes of CB1- and GABA_B-receptor KO mice and Chinese Hamster Ovary (CHO) cell membranes stably transfected with GABA_B or D2 dopamine receptors. The structural analog of rimonabant, AM251, decreased basal and baclofen-stimulated GTPγS binding to rat cortical and CHO cell membranes expressing GABA_B receptors. Rimonabant prevented G protein-mediated GABA_B and D2 dopamine receptor signaling to adenylyl cyclase in Human Embryonic Kidney 293 cells and to G protein-coupled inwardly rectifying K⁺ channels (GIRK) in midbrain dopamine neurons of CB1 KO mice. Rimonabant suppressed GIRK gating induced by GTPγS in CHO cells transfected with GIRK, consistent with a receptor-independent action. Bioluminescent resonance energy transfer (BRET) measurements in living CHO cells showed that, in presence or absence of co-expressed GABA_B receptors, rimonabant stabilized the heterotrimeric Gαi/o-protein complex and prevented conformational rearrangements induced by GABA_B receptor activation. Rimonabant failed to inhibit Gαs-mediated signaling, supporting its specificity for Gα_i/o-type G proteins. The inhibition of Gα_i/o protein provides a new site of rimonabant action that may help to understand its pharmacological and toxicological effects occurring at high concentrations.

High-throughput screening for selective appetite modulators: A multibehavioral and translational drug discovery strategy

How appetite is modulated by physiological, contextual, or pharmacological influence is still unclear. Specifically, the discovery of appetite modulators is compromised by the abundance of side effects that usually limit in vivo drug action. We set out to identify neuroactive drugs that trigger only their intended single behavioral change, which would provide great therapeutic advantages. To identify these ideal bioactive small molecules, we quantified the impact of more than 10,000 compounds on an extended series of different larval zebrafish behaviors using an in vivo imaging strategy. Known appetite-modulating drugs altered feeding and a pleiotropy of behaviors. Using this multibehavioral strategy as an active filter for behavioral side effects, we identified previously unidentified compounds that selectively increased or reduced food intake by more than 50%. The general applicability of this strategy is shown by validation in mice. Mechanistically, most candidate compounds were independent of the main neurotransmitter systems. In addition, we identified compounds with multibehavioral impact, and correlational comparison of these profiles with those of known drugs allowed for the prediction of their mechanism of action. Our results illustrate an unbiased and translational drug discovery strategy for ideal psychoactive compounds and identified selective appetite modulators in two vertebrate species.

Cannabinoid pharmacology and therapy in gut disorders

Cannabis sp. and their products (marijuana, hashish…), in addition to their recreational, industrial and other uses, have a long history for their use as a remedy for symptoms related with gastrointestinal diseases. After many reports suggesting these beneficial effects, it was not surprising to discover that the gastrointestinal tract expresses endogenous cannabinoids, their receptors, and enzymes for their synthesis and degradation, comprising the so-called endocannabinoid system. This system participates in the control of tissue homeostasis and important intestinal functions like motor and sensory activity, nausea, emesis, the maintenance of the epithelial barrier integrity, and the correct cellular microenvironment. Thus, different cannabinoid-related pharmacological agents may be useful to treat the main digestive pathologies. To name a few examples, in irritable bowel syndrome they may normalize dysmotility and reduce pain, in inflammatory bowel disease they may decrease inflammation, and in colorectal cancer, apart from alleviating some symptoms, they may play a role in the regulation of the cell niche. This review summarizes the main recent findings on the role of cannabinoid receptors, their synthetic or natural ligands and their metabolizing enzymes in normal gastrointestinal function and in disorders including irritable bowel syndrome, inflammatory bowel disease, colon cancer and gastrointestinal chemotherapy-induced adverse effects (nausea/vomiting, constipation, diarrhea).

Review: The Role of Cannabinoids on Esophageal Function-What We Know Thus Far

The endocannabinoid system (ECS) primarily consists of cannabinoid receptors (CBRs), endogenous ligands, and enzymes for endocannabinoid biosynthesis and inactivation. Although the presence of CBRs, both CB1 and CB2, as well as a third receptor (G-protein receptor 55 [GPR55]), has been established in the gastrointestinal (GI) tract, few studies have focused on the role of cannabinoids on esophageal function. To date, studies have shown their effect on GI motility, inflammation and immunity, intestinal and gastric acid secretion, nociception and emesis pathways, and appetite control. Given the varying and sometimes limited efficacy of current medical therapies for diseases of the esophagus, further understanding and investigation into the interplay of the ECS on esophageal health and disease may present new therapeutic modalities that may help advance current treatment options. In this brief review, the current understanding of the ECS role in various esophageal functions and disorders is presented.

Role of cannabinoid receptor 1 in human adipose tissue for lipolysis regulation and insulin resistance

We recently showed that the peripheral cannabinoid receptor type 1 (CNR1) gene is upregulated by the synthetic glucocorticoid dexamethasone. CNR1 is highly expressed in the central nervous system and has been a drug target for the treatment of obesity. Here we explore the role of peripheral CNR1 in states of insulin resistance in human adipose tissue. Subcutaneous adipose tissue was obtained from well-controlled type 2 diabetes subjects and controls. Subcutaneous adipose tissue gene expression levels of CNR1 and endocannabinoid synthesizing and degrading enzymes were assessed. Furthermore, paired human subcutaneous adipose tissue and omental adipose tissue from non-diabetic volunteers undergoing kidney donation or bariatric surgery, was incubated with or without dexamethasone. Subcutaneous adipose tissue obtained from volunteers through needle biopsy was incubated with or without dexamethasone and in the presence or absence of the CNR1-specific antagonist AM281. CNR1 gene and protein expression, lipolysis and glucose uptake were evaluated. Subcutaneous adipose tissue CNR1 gene expression levels were 2-fold elevated in type 2 diabetes subjects compared with control subjects. Additionally, gene expression levels of CNR1 and endocannabinoid-regulating enzymes from both groups correlated with markers of insulin resistance. Dexamethasone increased CNR1 expression dose-dependently in subcutaneous adipose tissue and omental adipose tissue by up to 25-fold. Dexamethasone pre-treatment of subcutaneous adipose tissue increased lipolysis rate and reduced glucose uptake. Co-incubation with the CNR1 antagonist AM281 prevented the stimulatory effect on lipolysis, but had no effect on glucose uptake. CNR1 is upregulated in states of type 2 diabetes and insulin resistance. Furthermore, CNR1 is involved in glucocorticoid-regulated lipolysis. Peripheral CNR1 could be an interesting drug target in type 2 diabetes and dyslipidemia.

Cannabinoid receptor CB1 regulates STAT3 activity and its expression dictates the responsiveness to SR141716 treatment in human glioma patients' cells

Herein we show that a majority of human brain tumor samples and cell lines over-expressed cannabinoid receptor CB1 as compared to normal human astrocytes (NHA), while uniformly expressed low levels of CB2. This finding prompted us to investigate the therapeutic exploitation of CB1 inactivation by SR141716 treatment, with regard to its direct and indirect cell-mediated effects against gliomas. Functional studies, using U251MG glioma cells and primary tumor cell lines derived from glioma patients expressing different levels of CB1, highlighted SR141716 efficacy in inducing apoptosis via G1 phase stasis and block of TGF-β1 secretion through a mechanism that involves STAT3 inhibition. According to the multivariate role of STAT3 in the immune escape too, interestingly SR141716 lead also to the functional and selective expression of MICA/B on the surface of responsive malignant glioma cells, but not on NHA. This makes SR141716 treated-glioma cells potent targets for allogeneic NK cell-mediated recognition through a NKG2D restricted mechanism, thus priming them for NK cell antitumor reactivity. These results indicate that CB1 and STAT3 participate in a new oncogenic network in the complex biology of glioma and their expression levels in patients dictate the efficacy of the CB1 antagonist SR141716 in multimodal glioma destruction.

Plasma and brain pharmacokinetic profile of cannabidiol (CBD), cannabidivarine (CBDV), Δ⁹-tetrahydrocannabivarin (THCV) and cannabigerol (CBG) in rats and mice following oral and intraperitoneal administration and CBD action on obsessive-compulsive behaviour

RATIONALE

Phytocannabinoids are useful therapeutics for multiple applications including treatments of constipation, malaria, rheumatism, alleviation of intraocular pressure, emesis, anxiety and some neurological and neurodegenerative disorders. Consistent with these medicinal properties, extracted cannabinoids have recently gained much interest in research, and some are currently in advanced stages of clinical testing. Other constituents of Cannabis sativa, the hemp plant, however, remain relatively unexplored in vivo. These include cannabidiol (CBD), cannabidivarine (CBDV), Δ(9)-tetrahydrocannabivarin (Δ(9)-THCV) and cannabigerol (CBG).

OBJECTIVES AND METHODS

We here determined pharmacokinetic profiles of the above phytocannabinoids after acute single-dose intraperitoneal and oral administration in mice and rats. The pharmacodynamic-pharmacokinetic relationship of CBD (120 mg/kg, ip and oral) was further assessed using a marble burying test in mice.

RESULTS

All phytocannabinoids readily penetrated the blood-brain barrier and solutol, despite producing moderate behavioural anomalies, led to higher brain penetration than cremophor after oral, but not intraperitoneal exposure. In mice, cremophor-based intraperitoneal administration always attained higher plasma and brain concentrations, independent of substance given. In rats, oral administration offered higher brain concentrations for CBD (120 mg/kg) and CBDV (60 mg/kg), but not for Δ(9)-THCV (30 mg/kg) and CBG (120 mg/kg), for which the intraperitoneal route was more effective. CBD inhibited obsessive-compulsive behaviour in a time-dependent manner matching its pharmacokinetic profile.

CONCLUSIONS

These data provide important information on the brain and plasma exposure of new phytocannabinoids and guidance for the most efficacious administration route and time points for determination of drug effects under in vivo conditions.

RP-HPLC Method Development and Its Validation for Quantitative Determination of Rimonabant in Human Plasma

A simple, accurate, and precise HPLC method was developed and validated for determination of rimonabant in human plasma. Following liquid-liquid extraction, chromatographic separation was accomplished using C18 column with mobile phase consisting of acetonitrile : water (90 : 10, v/v), drug was detected at 260 nm using UVdetector. The LOD and LOQ were 3.0 and 10.0 μg/L, respectively. The method is linear in the interval 50.0-1000.0 μg/L. The average extraction recovery of drug from plasma was found to be 92.2%. The percent CV of the method was found to be less than 10.8%, and accuracy was found between 94.5 and 106.7%. The assay may be applied to a pharmacokinetic and bioequivalence study of rimonabant.

Gemcitabine/cannabinoid combination triggers autophagy in pancreatic cancer cells through a ROS-mediated mechanism

Gemcitabine (GEM, 2′,2′-difluorodeoxycytidine) is currently used in advanced pancreatic adenocarcinoma, with a response rate of < 20%. The purpose of our work was to improve GEM activity by addition of cannabinoids. Here, we show that GEM induces both cannabinoid receptor-1 (CB1) and cannabinoid receptor-2 (CB2) receptors by an NF-κB-dependent mechanism and that its association with cannabinoids synergistically inhibits pancreatic adenocarcinoma cell growth and increases reactive oxygen species (ROS) induced by single treatments. The antiproliferative synergism is prevented by the radical scavenger N-acetyl--cysteine and by the specific NF-κB inhibitor BAY 11-7085, demonstrating that the induction of ROS by GEM/cannabinoids and of NF-κB by GEM is required for this effect. In addition, we report that neither apoptotic nor cytostatic mechanisms are responsible for the synergistic cell growth inhibition, which is strictly associated with the enhancement of endoplasmic reticulum stress and autophagic cell death. Noteworthy, the antiproliferative synergism is stronger in GEM-resistant pancreatic cancer cell lines compared with GEM-sensitive pancreatic cancer cell lines. The combined treatment strongly inhibits growth of human pancreatic tumor cells xenografted in nude mice without apparent toxic effects. These findings support a key role of the ROS-dependent activation of an autophagic program in the synergistic growth inhibition induced by GEM/cannabinoid combination in human pancreatic cancer cells.

Genetic and pharmacologic inactivation of cannabinoid CB1 receptor inhibits angiogenesis

In this study we investigated the role of CB1 receptor signaling in angiogenesis and the therapeutic exploitation of CB1 inactivation as an antiangiogenic strategy. We started from the observation that CB1 receptor expression is induced during angiogenesis and that the endocannabinoid anandamide stimulated bFGF-induced angiogenesis in the nanomolar physiologic range. To define the functional involvement of CB1 receptor signaling during angiogenesis, 2 different strategies have been carried out: siRNA-mediated knockdown and pharmacologic antagonism of CB1 receptors. CB1 receptors inactivation resulted in the inhibition of bFGF-induced endothelial proliferation, migration, and capillary-like tube formation, through prosurvival and migratory pathways involving ERK, Akt, FAK, JNK, Rho, and MMP-2. To corroborate the potential therapeutic exploitation of CB1 blockade as an antiangiogenic strategy, we performed in vivo assays founding that CB1 blockade was able to inhibit bFGF-induced neovascular growth in the rabbit cornea assay. A relevant finding was the ability to reduce ocular pathologic neo-vascularization in mouse oxygen-induced retinopathy. These results demonstrate that CB1 signaling participates to the proliferative response elicited by proangiogenic growth factors in angiogenesis and that for this reason CB1 receptor could represent a novel target for the treatment of diseases where excessive neoangiogenesis is the underlying pathology.

Perspectives of CB1 Antagonist in Treatment of Obesity: Experience of RIO-Asia

Rimonabant, a selective cannabinoid-1 (CB1) receptor antagonist, has been shown to reduce weight and enhance improvements in cardiometabolic risk parameters in Western populations. This study assessed these effects of rimonabant in Asian population. A total of 643 patients (BMI 25 kg/m(2) or greater without diabetes) from China, Republic of Korea, and Taiwan were prescribed a hypocaloric diet (600 kcal/day deficit) and randomized to rimonabant 20 mg (n = 318) or placebo (n = 325) for 9months. The primary efficacy variable was weight change from baseline after 9 months of treatment. Results showed that rimonabant group lost more weight than placebo, (LSM ± SEM of -4.7 ± 0.3 kg vs. -1.7 ± 0.3 kg, P < .0001). The 5% and 10% responders were 2 or 3 folds more in the rimonabant group (53.0% vs. 20.0% and 21.5% vs. 5.7%, resp.) (P < .0001). Rimonabant also significantly increased HDL-cholesterol, decreased triglycerides and waist circumference,by 7.1%, 10.6%, and 2.8 cm, respectively (P < .0001). This study confirmed the comparable efficacy and safety profile of rimonabant in Asian population to Caucasians. Owing to the recent suspension of all the CB1 antagonists off the pharmaceutical market for weight reduction in Europe and USA, a perspective in drug discovery for intervening peripheral CB1 receptor in the management of obesity is discussed.

Synthesis and biological evaluation of bivalent ligands for the cannabinoid 1 receptor

Dimerization or oligomerization of many G-protein-coupled receptors (GPCRs), including the cannabinoid 1 (CB1) receptor, is now widely accepted and may have significant implications for medications development targeting these receptor complexes. A library of bivalent ligands composed of two identical CB1 antagonist pharmacophores derived from SR141716 linked by spacers of various lengths were developed. The affinities of these bivalent ligands at CB1 and CB2 receptors were determined using radiolabeled binding assays. Their functional activities were measured using GTP-γ-S accumulation and intracellular calcium mobilization assays. The results suggest that the nature of the linker and its length are crucial factors for optimum interactions of these ligands at CB1 receptor binding sites. Finally, selected bivalent ligands (5d and 7b) were able to attenuate the antinociceptive effects of the cannabinoid agonist CP55,940 (21) in a rodent tail-flick assay. These novel compounds may serve as probes that will enable further characterization of CB1 receptor dimerization and oligomerization and its functional significance and may prove useful in the development of new therapeutic approaches to G-protein-coupled receptor mediated disorders.

Rimonabant-mediated changes in intestinal lipid metabolism and improved renal vascular dysfunction in the JCR:LA-cp rat model of prediabetic metabolic syndrome

Rimonabant (SR141716) is a specific antagonist of the cannabinoid-1 receptor. Activation of the receptor initiates multiple effects on central nervous system function, metabolism, and body weight. The hypothesis that rimonabant has protective effects against vascular disease associated with the metabolic syndrome was tested using JCR:LA-cp rats. JCR:LA-cp rats are obese if they are cp/cp, insulin resistant, and exhibit associated micro- and macrovascular disease with end-stage myocardial and renal disease. Treatment of obese rats with rimonabant (10 mg.kg(-1).day(-1), 12-24 wk of age) caused transient reduction in food intake for 2 wk, without reduction in body weight. However, by 4 wk, there was a modest, sustained reduction in weight gain. Glycemic control improved marginally compared with controls, but at the expense of increased insulin concentration. In contrast, rimonabant normalized fasting plasma triglyceride and reduced plasma plasminogen activator inhibitor-1 and acute phase protein haptoglobin in cp/cp rats. Furthermore, these changes were accompanied by reduced postprandial intestinal lymphatic secretion of apolipoprotein B48, cholesterol, and haptoglobin. While macrovascular dysfunction and ischemic myocardial lesion frequency were unaffected by rimonabant treatment, both microalbuminuria and glomerular sclerosis were substantially reduced. In summary, rimonabant has a modest effect on body weight in freely eating obese rats and markedly reduces plasma triglyceride levels and microvascular disease, in part due to changes in intestinal metabolism, including lymphatic secretion of apolipoprotein B48 and haptoglobin. We conclude that rimonabant improves renal disease and intestinal lipid oversecretion associated with an animal model of the metabolic syndrome that appears to be independent of hyperinsulinemia or macrovascular dysfunction.

Rimonabant (SR141716) induces metabolism and acquisition of fertilizing ability in human sperm

BACKGROUND AND PURPOSE

The endocannabinoid system and the cannabinoid CB(1) receptor have been identified in human sperm, and it is well known that endocannabinoids have pronounced adverse effects on male and female reproduction. In order to elucidate further the pathophysiological role of the endocannabinoid system in male fertility, we investigated the activity of the CB(1) receptor antagonist rimonabant (SR141716) on the fertilizing ability of human sperm.

EXPERIMENTAL APPROACH

We evaluated in vitro the effects of rimonabant on motility, survival, capacitation, acrosin activity and metabolism of human sperm. Particularly, capacitation was studied by using three different approaches: intracellular free Ca(2+) content assay, cholesterol efflux assay and protein tyrosine phosphorylation analysis.

KEY RESULTS

Rimonabant significantly increased sperm motility and viability through the induction of pAkt and pBcl2, key proteins of cell survival and metabolism, and it induced acrosome reaction and capacitation as well. Rimonabant reduced the triglyceride content of sperm, while enhancing lipase and acyl-CoA dehydrogenase activities, implying an overall lipolytic action in these cells. Rimonabant also affected sperm glucose metabolism by decreasing phosphorylation of glycogen synthase kinase 3 and increasing glucose-6-phosphate dehydrogenase activity, suggesting a role in inducing sperm energy expenditure. Intriguingly, agonism at the CB(1) receptor, with an anandamide analogue or a selective inhibitor of fatty acid amide hydrolase, produced opposing effects on human sperm functions.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that blockade of the CB(1) receptor by rimonabant induces the acquisition of fertilizing ability and stimulates energy expenditure in human sperm.

A new role of anandamide in human sperm: focus on metabolism

The endocannabinoid system and the presence of CB1 receptor (CB1-R) target of the anandamide were identified in human sperm, however the anandamide action in this context needs to be further elucidated. At this purpose we analyzed the effects of anandamide on human sperm capacitation and motility. Afterwards, we focused on lipid and glucose sperm metabolism and also investigated the interrelationship between anandamide and insulin secretion by sperm. By intracellular free Ca(2+) content assay and proteins tyrosine phosphorylation, we evidenced that anandamide did not induce capacitation process and a negative effect was obtained on sperm motility. The blockage of CB1-R by the specific antagonist SR141716 increased both capacitation and sperm motility suggesting an involvement of the CB1-R in the acquisition of sperm fertilizing activity. The evaluation of the triglycerides content, lipase and acyl-CoA dehydrogenase activities, suggest that anandamide exerts a lipogenetic effect on human sperm lipid metabolism. Concerning the glucose metabolism, anandamide increases GSK3 phosphorylation indicating that it is involved in the accumulation of energy substrates. G6PDH activity was not affected by anandamide. Interestingly, AEA is involved in insulin secretion by sperm. As insulin had been demonstrated to be an autocrine factor that triggers capacitation, the endocannabinoid might be inserted in the signaling cascade that induces this process. Altogether these findings highlight a pivotal involvement of the CB1-R in the control of sperm energy homeostasis and propose a new site of action for endocannabinoids in the control of energy metabolism.

Rimonabant inhibits human colon cancer cell growth and reduces the formation of precancerous lesions in the mouse colon

The selective CB1 receptor antagonist rimonabant (SR141716) was shown to perform a number of biological effects in several pathological conditions. Emerging findings demonstrate that rimonabant exerts antitumor action in thyroid tumors and breast cancer cells. In our study, human colorectal cancer cells (DLD-1, CaCo-2 and SW620) were treated with rimonabant and analyzed for markers of cell proliferation, cell viability and cell cycle progression. Rimonabant significantly reduced cell growth and induced cell death. In addition, rimonabant was able to alter cell cycle distribution in all the cell lines tested. Particularly, rimonabant produced a G2/M cell cycle arrest in DLD-1 cells without inducing apoptosis or necrosis. The G2/M phase arrest was characterized by a parallel enhancement of the number of mitoses associated to elevated DNA double strand breaks and chromosome misjoining events, hallmarks of mitotic catastrophe. Protein expression analyses of Cyclin B1, PARP-1, Aurora B and phosphorylated p38/MAPK and Chk1 demonstrated that rimonabant-induced mitotic catastrophe is mediated by interfering with the spindle assembly checkpoint and the DNA damage checkpoint. Moreover, in the mouse model of azoxymethane-induced colon carcinogenesis, rimonabant significantly decreased aberrant crypt foci (ACF) formation, which precedes colorectal cancer. Our findings suggest that rimonabant is able to inhibit colorectal cancer cell growth at different stages of colon cancer pathogenesis inducing mitotic catastrophe in vitro.

CB1 receptor-independent actions of SR141716 on G-protein signaling: coapplication with the mu-opioid agonist Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol unmasks novel, pertussis toxin-insensitive opioid signaling in mu-opioid receptor-Chinese hamster ovary cells

The CB(1) cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride (SR141716) has been shown by many investigators to inhibit basal G-protein activity, i.e., to display inverse agonism at high concentrations. However, it is not clear whether this effect is cannabinoid CB(1) receptor-mediated. Using the ligand-stimulated [(35)S]guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) assay, we have found that 10 microM SR141716 slightly but significantly decreases the basal [(35)S]GTPgammaS binding in membranes of the wild-type and CB(1) receptor knockout mouse cortex, parental Chinese hamster ovary (CHO) cells, and CHO cells stably transfected with micro-opioid receptors, MOR-CHO. Accordingly, we conclude that the inverse agonism of SR141716 is CB(1) receptor-independent. Although the specific MOR agonist Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol (DAMGO) saturably and concentration-dependently stimulated [(35)S]GTPgammaS binding, SR141716 (10 microM) inhibited the basal by 25% and competitively inhibited DAMGO stimulation in the mouse cortex. In MOR-CHO membranes, DAMGO caused a 501 +/- 29% stimulation of the basal activity, which was inhibited to 456 +/- 22% by 10 microM SR141716. The inverse agonism of SR141716 was abolished, and DAMGO alone displayed weak, naloxone-insensitive stimulation, whereas the combination of DAMGO and SR141716 (10 microM each) resulted in a 169 +/- 22% stimulation of the basal activity (that was completely inhibited by the prototypic opioid antagonist naloxone) because of pertussis toxin (PTX) treatment to uncouple MORs from G(i)/G(o) proteins. SR141716 proved to bind directly to MORs with low affinity (IC(50) = 5.7 microM). These results suggest the emergence of novel, PTX-insensitive G-protein signaling that is blocked by naloxone when MORs are activated by the combination of DAMGO and SR141716.

Endocannabinoids and cardiac contractile function: pathophysiological implications

Endocannabinoids are part of a bioactive lipid signaling system, not only in the central nervous system but also in various peripheral organs. Accumulating evidence implicates dysregulation of the endocannabinoid system (ECS) in the pathogenesis of various cardiovascular diseases, including hypertension, atherosclerosis, myocardial infarction, hemorrhagic or septic shock, heart failure and cardiovascular complications of liver cirrhosis. Even though the benefit of chronic cannabinoid 1 (CB1) receptor blockade with the currently available compounds may not outweigh the risks in chronic conditions such as obesity, modulation of the ECS may hold great therapeutic promise in various cardiovascular conditions/disorders. In this review we will discuss recent advances in understanding the role of CB1 receptors and endocannabinoids in the regulation of cardiac function in cirrhotic cardiomyopathy and in doxorubicin-induced heart failure.

Cannabinoid receptor antagonists: pharmacological opportunities, clinical experience, and translational prognosis

The endogenous cannabinoid (CB) (endocannabinoid) signaling system is involved in a variety of (patho)physiological processes, primarily by virtue of natural, arachidonic acid-derived lipids (endocannabinoids) that activate G protein-coupled CB1 and CB2 receptors. A hyperactive endocannabinoid system appears to contribute to the etiology of several disease states that constitute significant global threats to human health. Consequently, mounting interest surrounds the design and profiling of receptor-targeted CB antagonists as pharmacotherapeutics that attenuate endocannabinoid transmission for salutary gain. Experimental and clinical evidence supports the therapeutic potential of CB1 receptor antagonists to treat overweight/obesity, obesity-related cardiometabolic disorders, and substance abuse. Laboratory data suggest that CB2 receptor antagonists might be effective immunomodulatory and, perhaps, anti-inflammatory drugs. One CB1 receptor antagonist/inverse agonist, rimonabant, has emerged as the first-in-class drug approved outside the United States for weight control. Select follow-on agents (taranabant, otenabant, surinabant, rosonabant, SLV-319, AVE1625, V24343) have also been studied in the clinic. However, rimonabant's market withdrawal in the European Union and suspension of rimonabant's, taranabant's, and otenabant's ongoing development programs have highlighted some adverse clinical side effects (especially nausea and psychiatric disturbances) of CB1 receptor antagonists/inverse agonists. Novel CB1 receptor ligands that are peripherally directed and/or exhibit neutral antagonism (the latter not affecting constitutive CB1 receptor signaling) may optimize the benefits of CB1 receptor antagonists while minimizing any risk. Indeed, CB1 receptor-neutral antagonists appear from preclinical data to offer efficacy comparable to or better than that of prototype CB1 receptor antagonists/inverse agonists, with less propensity to induce nausea. Continued pharmacological profiling, as the prelude to first-in-man testing of CB1 receptor antagonists with unique modes of targeting/pharmacological action, represents an exciting translational frontier in the critical path to CB receptor blockers as medicines.

Use of cannabinoid CB1 receptor antagonists for the treatment of metabolic disorders

Abdominal obesity is associated with numerous metabolic abnormalities, including insulin resistance, impaired glucose tolerance/type-2 diabetes, and atherogenic dyslipidaemia with low high-density lipoprotein (HDL) cholesterol, high triglycerides, and increased small dense low-density lipoprotein (LDL) cholesterol. A proportion of these metabolic disorders may be attributed to increased endocannabinoid activity. The selective cannabinoid 1 (CB1) receptor antagonist rimonabant has been shown to reduce body weight, waist circumference, insulin resistance, triglycerides, dense LDL, C-reactive protein (CRP), and blood pressure, and to increase HDL and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients. Besides an improvement in glucose tolerance in non-diabetic subjects, a reduction of 0.5-0.7% in haemoglobin A1C (HbA(1c)) levels was consistently observed in various groups of patients with type-2 diabetes. Almost half the metabolic changes could not be explained by weight loss, supporting direct peripheral effects of rimonabant. Ongoing studies should demonstrate whether improved metabolic disorders with CB1 receptor antagonists (rimonabant, taranabant, etc.) would translate into fewer cardiovascular complications among high-risk individuals.

Use of cannabinoid receptor agonists in cancer therapy as palliative and curative agents

Cannabinoids (the active components of Cannabis sativa) and their derivatives have received renewed interest in recent years due to their diverse pharmacological activities. In particular, cannabinoids offer potential applications as anti-tumour drugs, based on the ability of some members of this class of compounds to limit cell proliferation and to induce tumour-selective cell death. Although synthetic cannabinoids may have pro-tumour effects in vivo due to their immunosuppressive properties, predominantly inhibitory effects on tumour growth and migration, angiogenesis, metastasis, and also inflammation have been described. Emerging evidence suggests that agonists of cannabinoid receptors expressed by tumour cells may offer a novel strategy to treat cancer. In this chapter we review the more recent results generating interest in the field of cannabinoids and cancer, and provide novel suggestions for the development, exploration and use of cannabinoid agonists for cancer therapy, not only as palliative but also as curative drugs.

Metformin maintains the weight loss and metabolic benefits following rimonabant treatment in obese women with polycystic ovary syndrome (PCOS)

OBJECTIVE

Rimonabant has been shown to reduce weight, free androgen index (FAI) and insulin resistance in obese patients with polycystic ovary syndrome (PCOS) compared to metformin. Studies have shown that significant weight regain occurs following the cessation of rimonabant therapy. This study was undertaken to determine if subsequent metformin treatment after rimonabant would maintain the improvement in weight, insulin resistance and hyperandrogenaemia in PCOS.

DESIGN

An extension study for 3 months with the addition of metformin to the randomised open labelled parallel study of metformin and rimonabant in 20 patients with PCOS with a body mass index >or= 30 kg/m(2). Patients who were on 3 months of rimonabant were changed over to metformin for 3 months, whereas those on 3 months of metformin were continued on metformin for another 3 months.

MEASUREMENTS

The primary end-point was a change in weight; secondary end-points were a change in FAI and insulin resistance.

RESULTS

The mean weight loss of 6.2 kg associated with 3 months of rimonabant treatment was maintained by 3 months of metformin treatment (mean change +0.2 kg, P = 0.96). Therefore, the percentage reduction in weight remained significantly higher in the rimonabant/metformin group compared to metformin only subjects at 6 months compared to baseline (-6.0 +/- 0.1%vs. -2.8 +/- 0.1%, P = 0.04). The percentage change in testosterone and FAI from baseline to 6 months was also greater in the rimonabant/metformin group. [Testosterone (-45.0 +/- 5.0%vs. -16 +/- 2.0%, P = 0.02); FAI (-53.0 +/- 5.0%vs. -17.0 +/- 12.2%, P = 0.02)]. HOMA-IR continued to fall significantly in the rimonabant/metformin group between 0, 3 and 6 months (4.4 +/- 0.5 vs. 3.4 +/- 0.4 vs. 2.7 +/- 0.3, respectively, P < 0.01) but not at all in the metformin only group (3.4 +/- 0.7 vs. 3.4 +/- 0.8 vs. 3.7 +/- 0.8, respectively, P = 0.80). Total cholesterol and LDL reduced significantly in both groups, but improvements in triglycerides and HDL were limited to the rimonabant/metformin group.

CONCLUSIONS

In these obese patients with PCOS, metformin maintained the weight loss and enhanced the metabolic and biochemical parameters achieved by treatment with rimonabant, compared to 6 months of metformin treatment alone.

The cannabinoid CB1 receptor antagonist rimonabant stimulates 2-deoxyglucose uptake in skeletal muscle cells by regulating the expression of phosphatidylinositol-3-kinase

The endocannabinoid system regulates food intake, energy, and glucose metabolism at both central and peripheral levels. We have investigated the mechanism by which it may control glucose uptake in skeletal muscle cells. Detectable levels of the cannabinoid receptor type 1 (CB1) were revealed in L6 cells. Exposure of differentiated L6 myotubes to the CB1 antagonist rimonabant (SR141716) selectively increased 2-deoxyglucose uptake (2-DG) in a time- and dose-dependent manner. A similar effect was induced by genetic silencing of CB1 by small interfering RNA. Protein expression profiling revealed that both the regulatory p85 and the catalytic p110 subunits of the phosphatidylinositol-3-kinase (PI3K) were increased by SR141716. No significant change in the cellular content of other known molecules regulating PI3K was observed. However, phosphoinositide-dependent kinase-1, Akt/protein kinase B, and protein kinase Czeta activities were rapidly induced after SR141716 treatment of L6 cells in a PI3K-dependent manner. The stimulatory effect of SR141716 on PI3K expression and activity was largely prevented by N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H-89), an inhibitor of the cAMP-dependent protein kinase. Moreover, SR141716-stimulated 2-DG uptake was blunted by the coincubation either with H-89 or with the PI3K inhibitor 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002), both in L6 cells and in mouse primary myocytes. Thus, modulation of CB1 regulates glucose uptake at the level of the PI3K signaling system in skeletal muscle cells. Interfering with CB1 signaling may therefore ameliorate glucoregulatory functions in peripheral tissues.

Cannabinoid CB1 receptor antagonists in therapeutic and structural perspectives

The observed antiobesity effect of rimonabant (1) in a pharmacological rodent model 10 years ago has led to a surge in the search for novel cannabinoid CB1 antagonists as a new therapeutic target for the treatment of obesity. Rimonabant showed clinical efficacy in the treatment of obesity and also improved cardiovascular and metabolic risk factors. Cannabinoid CB1 receptor antagonists have also good prospects in other therapeutic areas, including smoking and alcohol addiction as well as cognitive impairment. Solvay's research achievements in this fast-moving field are reported in relation with the current state of the art. Several medicinal chemistry strategies have been pursued. The application of the concept of conformational constraint led to the discovery of more rigid analogs of the prototypic CB1 receptor antagonist rimonabant. Replacement of the central heterocyclic pyrazole ring in rimonabant yielded imidazoles, triazoles, and thiazoles as selective CB1 receptor antagonists. Dedicated medium-throughput screening efforts delivered one 3,4-diarylpyrazoline hit. Its poor pharmacokinetic properties were successfully optimized which led to the discovery of orally active and highly CB1/CB2 receptor selective analogs in this series. Regioisomeric 1,5-diarylpyrazolines, 1,2-diarylimidazolines, and water-soluble imidazoles have been designed as novel CB1 receptor antagonist structure classes.

Pharmacological characterization and appetite suppressive properties of BMS-193885, a novel and selective neuropeptide Y(1) receptor antagonist

Treatment of obesity is still a large unmet medical need. Neuropeptide Y is the most potent orexigenic peptide in the animal kingdom. Its five cloned G-protein couple receptors are all implicated in the regulation of energy homeostasis evidenced by overexpression or deletion of neuropeptide Y or its receptors. Neuropeptide Y most likely exerts its orexigenic activity via the neuropeptide Y(1) and neuropeptide Y(5) receptors, although the involvement of the neuropeptide Y(2) and neuropeptide Y(4) receptors are also gaining importance. The lack of potent, selective, and brain penetrable pharmacologic agents at these receptors made our understanding of the modulation of food intake by neuropeptide Y-ergic agents elusive. BMS-193885 (1,4-dihydro-[3-[[[[3-[4-(3-methoxyphenyl)-1-piperidinyl]propyl]amino] carbonyl]amino]phenyl]-2,6-dimethyl-3,5-pyridinedicarboxylic acid, dimethyl ester) is a potent and selective neuropeptide Y(1) receptor antagonist. BMS-193885 has 3.3 nM affinity at the neuropeptide Y(1) receptor, acting competitively at the neuropeptide Y binding site. BMS-193885 increased the K(d) of [(125)I]PeptideYY from 0.35 nM to 0.65 nM without changing the B(max) (0.16 pmol/mg of protein) in SK-N-MC cells that endogenously express the neuropeptide Y(1) receptor. It is also found to be a full antagonist with an apparent K(b) of 4.5 nM measured by reversal of forskolin (FK)-stimulated inhibition of cAMP production by neuropeptide Y. Pharmacological profiling showed that BMS-193885 has no appreciable affinity at the other neuropeptide Y receptors, and is also 200-fold less potent at the alpha(2) adrenergic receptor. Testing the compound in a panel of 70 G-protein coupled receptors and ion channels resulted in at least 200-fold or greater selectivity, with the exception of the sigma(1) receptor, where the selectivity was 100-fold. When administered intracerebroventricularly or directly into the paraventricular nucleus of the hypothalamus, it blocked neuropeptide Y-induced food intake in rats. Intraperitoneal administration of BMS-193885 (10 mg/kg) also reduced one-hour neuropeptide Y-induced food intake in satiated rats, as well as spontaneous overnight food consumption. Chronic administration of BMS-193885 (10 mg/kg) i.p. for 44 days significantly reduced food intake and the rate of body weight gain compared to vehicle treated control without developing tolerance or affecting water intake. These results provide supporting evidence that BMS-193885 reduces food intake and body weight via inhibition of the central neuropeptide Y(1) receptor. BMS-193885 has no significant effect of locomotor activity up to 20 mg/kg dose after 1 h of treatment. It also showed no activity in the elevated plus maze when tested after i.p. and i.c.v. administration, indicating that reduction of food intake is unrelated to anxious behavior. BMS-193885 has good systemic bioavailability and brain penetration, but lacks oral bioavailability. The compound had no serious cardiovascular adverse effect in rats and dogs up to 30 and 10 mg/kg dose, respectively, when dosed intravenously. These data demonstrate that BMS-193885 is a potent, selective, brain penetrant Y(1) receptor antagonist that reduces food intake and body weight in animal models of obesity both after acute and chronic administration. Taken together the data suggest that a potent and selective neuropeptide Y(1) receptor antagonist might be an efficacious treatment for obesity in humans.

Effects of Delta9-tetrahydrocannabivarin on [35S]GTPgammaS binding in mouse brain cerebellum and piriform cortex membranes

BACKGROUND AND PURPOSE

We have recently shown that the phytocannabinoid Delta9-tetrahydrocannabivarin (Delta9-THCV) and the CB1 receptor antagonist AM251 increase inhibitory neurotransmission in mouse cerebellum and also exhibit anticonvulsant activity in a rat piriform cortical (PC) model of epilepsy. Possible mechanisms underlying cannabinoid actions in the CNS include CB1 receptor antagonism (by displacing endocannabinergic tone) or inverse agonism at constitutively active CB1 receptors. Here, we investigate the mode of cannabinoid action in [35S]GTPgammaS binding assays.

EXPERIMENTAL APPROACH

Effects of Delta9-THCV and AM251 were tested either alone or against WIN55,212-2-induced increases in [35S]GTPgammaS binding in mouse cerebellar and PC membranes. Effects on non-CB receptor expressing CHO-D2 cell membranes were also investigated.

KEY RESULTS

Delta9-THCV and AM251 both acted as potent antagonists of WIN55,212-2-induced increases in [35S]GTPgammaS binding in cerebellar and PC membranes (Delta9-THCV: pA2=7.62 and 7.44 respectively; AM251: pA2=9.93 and 9.88 respectively). At micromolar concentrations, Delta9-THCV or AM251 alone caused significant decreases in [35S]GTPgammaS binding; Delta9-THCV caused larger decreases than AM251. When applied alone in CHO-D2 membranes, Delta9-THCV and AM251 also caused concentration-related decreases in G protein activity.

CONCLUSIONS AND IMPLICATIONS

Delta9-THCV and AM251 act as CB1 receptors antagonists in the cerebellum and PC, with AM251 being more potent than Delta9-THCV in both brain regions. Individually, Delta9-THCV or AM251 exhibited similar potency at CB1 receptors in the cerebellum and the PC. At micromolar concentrations, Delta9-THCV and AM251 caused a non-CB receptor-mediated depression of basal [35S]GTPgammaS binding.

CB1 receptor blockade and its impact on cardiometabolic risk factors: overview of the RIO programme with rimonabant

Rimonabant, the first selective CB(1) receptor antagonist in clinical use, has been extensively investigated in the Rimonabant in Obesity (RIO) programme, comprising four 1-2 year placebo-controlled randomised clinical trials recruiting more than 6600 overweight/obese patients with or without co-morbidities. Rimonabant 20 mg daily consistently reduced body weight, waist circumference, triglycerides, blood pressure, insulin resistance and C-reactive protein levels, and increased HDL cholesterol concentrations in both non-diabetic and type-2 diabetic overweight/obese patients. Adiponectin levels were increased, an effect that correlated with HDL cholesterol augmentation, while small dense LDL cholesterol levels were decreased in patients receiving rimonabant 20 mg compared with those receiving placebo in RIO Lipids. Furthermore, in RIO Diabetes, a 0.7% reduction in glycated haemoglobin (HbA1c) levels was observed in metformin- or sulphonylurea-treated patients with type-2 diabetes, an effect recently confirmed in the 6-month SERENADE (Study Evaluating Rimonabant Efficacy in drug-NAive DiabEtic patients) trial in drug-naive diabetic patients. Almost half of metabolic changes occurred beyond weight loss, in agreement with direct peripheral effects. The positive effects observed after 1 year were maintained after 2 years. Rimonabant was generally well-tolerated, but with a slightly higher incidence of depressed mood disorders, anxiety, nausea and dizziness compared with placebo. In clinical practice, rimonabant has to be prescribed to the right patient, i.e. overweight/obese subjects with cardiometabolic risk factors and with no major depressive illness and/or ongoing antidepressive treatment, in order to both maximise efficacy and minimise safety issues. New trials are supposed to confirm the potential role of rimonabant in patients with abdominal adiposity, atherogenic dyslipidaemia and/or type-2 diabetes, i.e. at high cardiometabolic risk.

Anandamide biosynthesis catalyzed by the phosphodiesterase GDE1 and detection of glycerophospho-N-acyl ethanolamine precursors in mouse brain

Anandamide (AEA) is an endogenous ligand of cannabinoid receptors and a well characterized mediator of many physiological processes including inflammation, pain, and appetite. The biosynthetic pathway(s) for anandamide and its N-acyl ethanolamine (NAE) congeners remain enigmatic. Previously, we proposed an enzymatic route for producing NAEs that involves the double-O-deacylation of N-acyl phosphatidylethanolamines (NAPEs) by alpha/beta-hydrolase 4 (ABDH4 or Abh4) to form glycerophospho (GP)-NAEs, followed by conversion of these intermediates to NAEs by an unidentified phosphodiesterase. Here, we report the detection and measurement of GP-NAEs, including the anandamide precursor glycerophospho-N-arachidonoylethanolamine (GP-NArE), as endogenous constituents of mouse brain tissue. Inhibition of the phosphodiesterase-mediated degradation of GP-NAEs ex vivo resulted in a striking accumulation of these lipids in brain extracts, suggesting a rapid endogenous flux through this pathway. Furthermore, we identify the glycerophosphodiesterase GDE1, also known as MIR16, as a broadly expressed membrane enzyme with robust GP-NAE phosphodiesterase activity. Together, these data provide evidence for a multistep pathway for the production of anandamide in the nervous system by the sequential actions of Abh4 and GDE1.

Environmental factors as disease accelerators during chronic hepatitis C

Progression of chronic hepatitis is highly variable among individuals, as the result of several host, viral and environmental factors. The latter have been extensively investigated in order to ameliorate hepatitis C outcome, particularly in difficult-to-treat patients. Over the last decade, several studies have shown that a combination of HCV infection and high levels of alcohol abuse results in synergistic acceleration of liver fibrogenesis. In addition, recent data indicate that light alcohol intake may also exacerbate fibrosis progression. It has also been suggested that cigarette smoking may enhance activity grade in patients with chronic hepatitis C, thereby increasing progression of fibrosis. This assumption mostly relies on epidemiological evidences in the absence of pathogenic studies. Finally, cannabis use is increasingly emerging as a novel co-morbidity in patients with chronic hepatitis C. Indeed, regular cannabis smoking is an independent predictor of both fibrosis and steatosis severity in infected patients. In addition, experimental studies have shown that cannabinoid CB1 receptors enhance liver fibrogenesis and steatogenesis by distinct mechanisms, therefore strongly supporting epidemiological findings. Altogether, patients should be informed of the deleterious impact of alcohol, tobacco and cannabis use and should be offered appropriate support to achieve abstinence.