The cannabinoid receptor-1 antagonist rimonabant inhibits platelet activation and reduces pro-inflammatory chemokines and leukocytes in Zucker rats

The Role of Cannabinoid-1 Receptor Ligands in the Ovalbumin-Induced Mouse Model of Allergic Asthma: Is It Related to Transient Receptor Potential Vanilloid-1 Channels?

Objectives: The aim of this study was to investigate the role of cannabinoid (CB1) receptors on airway inflammation and hypersensitivity in allergic asthma and the potential interactions with TRPV1 channels. Materials and Methods: BALB/c mice were sensitized and provoked with ovalbumin to create a model of allergic asthma. CB1 selective agonist arachidonoyl 2'-chloroethylamide (ACEA) was administered intraperitoneally at doses of 0.5, 3, and 5 mg/kg. Receptor antagonism studies were performed utilizing selective CB1 antagonists AM251 at a dose of 3 mg/kg. TRPV1 channel was selectively blocked by capsazepine at a dose of 2.5 mg/kg. Penh values were recorded in vivo by a whole-body plethysmograph under methacholine challenge. Inflammatory cell count was performed in bronchoalveolar lavage fluid (BALF). Serum levels of proinflammatory cytokines were measured by Enzyme-Linked ImmunoSorbent Assay (ELISA). Inflammation in the lung tissue was scored histopathologically. Statistical significance was determined using one-way analysis of variance or Kruskal-Wallis test and expressed as p<0.05. Results: In sensitized animals, provocation with inhaled ovalbumin increased Penh values, serum interleukin (IL)-4, IL-5, IL-13 levels, eosinophil, neutrophil, lymphocyte, macrophage counts in BALF, and inflammation in the lung tissue. ACEA applications did not significantly alter Penh values, BALF inflammatory cell levels, and histological changes related to inflammation in the lung tissue according to the disease group; however, only at a dose of 5 mg/kg, it reduced the levels of the inflammatory cytokine IL-4. AM251 decreased Penh values, eosinophil and neutrophil migration in BALF, and inflammation score of lung tissue compared with the disease group. Although BALF inflammatory cell levels and Penh values were higher in the AM251+ACEA group than in the AM251 group, the differences were insignificant. In the CPZ+ACEA group, Penh values were significantly higher, and serum IL-4 and IL-13 levels and BALF eosinophil counts were lower than that in the CPZ group. Conclusions: This study demonstrated an important role of the CB1 receptors in allergic asthma. CB1 antagonism reduced airway hyperresponsiveness and inflammation and showed immunomodulatory effects. The effect of the CB1 agonist ACEA on asthma does not appear to be related to TRPV1 channels.

Female and male obese Zucker rats display differential inflammatory mediator and long non-coding RNA profiles

AIMS

The goal of this study was to identify mediators in peri-lymphatic adipose tissue (PLAT) that are altered in obese versus lean Zucker rats, with focus on potential sex differences MAIN METHODS: Mesenteric PLAT was analyzed with protein and lncRNA arrays. Additional RT-PCR confirmation was performed with epididymal/ovarian fat.

KEY FINDINGS

MCP-1, TCK-1, Galectin-1, Galectin-3, and neuropilin-1 were elevated in PLAT from obese rats of both sexes. However, 11 additional proteins were elevated only in obese males while 24 different proteins were elevated in obese females. Profiling of lncRNAs revealed lean males have elevated levels of NEAT1, MALAT1 and GAS5 compared to lean females. NEAT1, MALAT1, and GAS5 were significantly reduced with obesity in males but not in females. Another lncRNA, HOTAIR, was higher in lean females compared to males, and its levels in females were reduced with obesity. Obese rats of both sexes had similar histologic findings of mesenteric macrophage crown-like structures and hepatocyte fat accumulation.

SIGNIFICANCE

While obese male and female Zucker rats both have increased inflammation, they have distinct signals. Future studies of the proteome and lncRNA landscape of obese males vs. females in various animal models and in human subjects are warranted to better guide development of therapeutics for obesity-induced inflammation.

Cannabinoids and terpenes for diabetes mellitus and its complications: from mechanisms to new therapies

The number of people diagnosed with diabetes mellitus and its complications is markedly increasing worldwide, leading to a worldwide epidemic across all age groups, from children to older adults. Diabetes is associated with premature aging. In recent years, it has been found that peripheral overactivation of the endocannabinoid system (ECS), and in particular cannabinoid receptor 1 (CB1R) signaling, plays a crucial role in the progression of insulin resistance, diabetes (especially type 2), and its aging-related comorbidities such as atherosclerosis, nephropathy, neuropathy, and retinopathy. Therefore, it is suggested that peripheral blockade of CB1R may ameliorate diabetes and diabetes-related comorbidities. The use of synthetic CB1R antagonists such as rimonabant has been prohibited because of their psychiatric side effects. In contrast, phytocannabinoids such as cannabidiol (CBD) and tetrahydrocannabivarin (THCV), produced by cannabis, exhibit antagonistic activity on CB1R signaling and do not show any adverse side effects such as psychoactive effects, depression, or anxiety, thereby serving as potential candidates for the treatment of diabetes and its complications. In addition to these phytocannabinoids, cannabis also produces a substantial number of other phytocannabinoids, terpenes, and flavonoids with therapeutic potential against insulin resistance, diabetes, and its complications. In this review, the pathogenesis of diabetes, its complications, and the potential to use cannabinoids, terpenes, and flavonoids for its treatment are discussed.

Pharmacognosy and Effects of Cannabinoids in the Vascular System

Understanding the pharmacodynamics of cannabinoids is an essential subject due to the recent increasing global acceptance of cannabis and its derivation for recreational and therapeutic purposes. Elucidating the interaction between cannabinoids and the vascular system is critical to exploring cannabinoids as a prospective therapeutic agent for treating vascular-associated clinical conditions. This review aims to examine the effect of cannabinoids on the vascular system and further discuss the fundamental pharmacological properties and mechanisms of action of cannabinoids in the vascular system. Data from literature revealed a substantial interaction between endocannabinoids, phytocannabinoids, and synthetic cannabinoids within the vasculature of both humans and animal models. However, the mechanisms and the ensuing functional response is blood vessels and species-dependent. The current understanding of classical cannabinoid receptor subtypes and the recently discovered atypical cannabinoid receptors and the development of new synthetic analogs have further enhanced the pharmacological characterization of the vascular cannabinoid receptors. Compelling evidence also suggest that cannabinoids represent a formidable therapeutic candidate for vascular-associated conditions. Nonetheless, explanations of the mechanisms underlining these processes are complex and paradoxical based on the heterogeneity of receptors and signaling pathways. Further insight from studies that uncover the mechanisms underlining the therapeutic effect of cannabinoids in the treatment of vascular-associated conditions is required to determine whether the known benefits of cannabinoids thus currently outweigh the known/unknown risks.

Role of microRNA in CB1 antagonist-mediated regulation of adipose tissue macrophage polarization and chemotaxis during diet-induced obesity

Although cannabinoid receptor 1 (CB1) antagonists have been shown to attenuate diet-induced obesity (DIO) and associated inflammation, the precise molecular mechanisms involved are not clear. In the current study, we investigated the role of microRNA (miR) in the regulation of adipose tissue macrophage (ATM) phenotype following treatment of DIO mice with the CB1 antagonist SR141716A. DIO mice were fed high-fat diet (HFD) for 12 weeks and then treated daily with SR141716A (10 mg/kg) for 4 weeks while continuing HFD. Treated mice experienced weight loss, persistent reduction in fat mass, improvements in metabolic profile, and decreased adipose inflammation. CB1 blockade resulted in down-regulation of several miRs in ATMs, including the miR-466 family and miR-762. Reduced expression of the miR-466 family led to induction of anti-inflammatory M2 transcription factors KLF4 and STAT6, whereas down-regulation of miR-762 promoted induction of AGAP-2, a negative regulator of the neuroimmune retention cues, Netrin-1 and its coreceptor UNC5B. Furthermore, treatment of primary macrophages with SR141716A up-regulated KLF4 and STAT6, reduced secretion of Netrin-1, and increased migration toward the lymph node chemoattractant CCL19. These studies demonstrate for the first time that CB1 receptor blockade attenuates DIO-associated inflammation through alterations in ATM miR expression that promote M2 ATM polarization and macrophage egress from adipose tissue. The current study also identifies additional novel therapeutic targets for diet-induced obesity and metabolic disorder.

Peripheral cannabinoid 1 receptor blockade mitigates adipose tissue inflammation via NLRP3 inflammasome in mouse models of obesity

AIM

To analyze the metabolic parameters and adipose tissue inflammation via NLRP3 inflammasome following chronic treatment of mouse models of obesity with AJ5018 as the peripherally restricted cannabinoid 1 receptor (CB1R) antagonist.

MATERIALS AND METHODS

The selectivity for CB1R over CB2R, brain/plasma concentration ratio, and centrally mediated neurobehavioural effects of AJ5018, were assessed. The long-term effects of AJ5018 and rimonabant on the metabolic parameters and adipose tissue inflammation were analyzed in diet-induced obese (DIO) mice and diabetic db/db mice.

RESULTS

AJ5018 had a higher degree of selectivity for CB1R over CB2R and markedly reduced brain penetrance, as reflected by the lower brain/plasma concentration ratio and the attenuated centrally mediated neurobehavioural effects, compared with its brain-penetrant parent compound rimonabant. In DIO and db/db mice, AJ5018 exhibited comparable effects to rimonabant in improving metabolic abnormalities and suppressing macrophage infiltration into white adipose tissue, activation of the NLRP3 inflammasome, and production of proinflammatory cytokines.

CONCLUSIONS

These results suggest that peripheral CB1R blockade improves obesity-induced insulin resistance by suppressing adipose tissue inflammation via the NLRP3 inflammasome.

Orphan nuclear receptor ERRγ is a key regulator of human fibrinogen gene expression

Fibrinogen, 1 of 13 coagulation factors responsible for normal blood clotting, is synthesized by hepatocytes. Detailed roles of the orphan nuclear receptors regulating fibrinogen gene expression have not yet been fully elucidated. Here, we identified estrogen-related receptor gamma (ERRγ) as a novel transcriptional regulator of human fibrinogen gene expression. Overexpression of ERRγ specially increased fibrinogen expression in human hepatoma cell line. Cannabinoid receptor types 1(CB1R) agonist arachidonyl-2'-chloroethylamide (ACEA) up-regulated transcription of fibrinogen via induction of ERRγ, whereas knockdown of ERRγ attenuated fibrinogen expression. Deletion analyses of the fibrinogen γ (FGG) gene promoter and ChIP assays revealed binding sites of ERRγ on human fibrinogen γ gene promoter. Moreover, overexpression of ERRγ was sufficient to increase fibrinogen gene expression, whereas treatment with GSK5182, a selective inverse agonist of ERRγ led to its attenuation in cell culture. Finally, fibrinogen and ERRγ gene expression were elevated in liver tissue of obese patients suggesting a conservation of this mechanism. Overall, this study elucidates a molecular mechanism linking CB1R signaling, ERRγ expression and fibrinogen gene transcription. GSK5182 may have therapeutic potential to treat hyperfibrinogenemia.

Developmental Role of Macrophage Cannabinoid-1 Receptor Signaling in Type 2 Diabetes

Islet inflammation promotes β-cell loss and type 2 diabetes (T2D), a process replicated in Zucker Diabetic Fatty (ZDF) rats in which β-cell loss has been linked to cannabinoid-1 receptor (CB₁R)-induced proinflammatory signaling in macrophages infiltrating pancreatic islets. Here, we analyzed CB₁R signaling in macrophages and its developmental role in T2D. ZDF rats with global deletion of CB₁R are protected from β-cell loss, hyperglycemia, and nephropathy that are present in ZDF littermates. Adoptive transfer of CB₁R^-/- bone marrow to ZDF rats also prevents β-cell loss and hyperglycemia but not nephropathy. ZDF islets contain elevated levels of CB₁R, interleukin-1β, tumor necrosis factor-α, the chemokine CCL2, and interferon regulatory factor-5 (IRF5), a marker of inflammatory macrophage polarization. In primary cultured rodent and human macrophages, CB₁R activation increased Irf5 expression, whereas knockdown of Irf5 blunted CB₁R-induced secretion of inflammatory cytokines without affecting CCL2 expression, which was p38MAPKα dependent. Macrophage-specific in vivo knockdown of Irf5 protected ZDF rats from β-cell loss and hyperglycemia. Thus, IRF5 is a crucial downstream mediator of diabetogenic CB₁R signaling in macrophages and a potential therapeutic target.

Downstream effects of endocannabinoid on blood cells: implications for health and disease

Endocannabinoids (eCBs), among which N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) are the most biologically active members, are polyunsaturated lipids able to bind cannabinoid, vanilloid and peroxisome proliferator-activated receptors. Depending on the target engaged, these bioactive mediators can regulate different signalling pathways, at both central and peripheral levels. The biological action of eCBs is tightly controlled by a plethora of metabolic enzymes which, together with the molecular targets of these substances, form the so-called "endocannabinoid system". The ability of eCBs to control manifold peripheral functions has received a great deal of attention, especially in the light of their widespread distribution in the body. In particular, eCBs are important regulators in blood, where they modulate haematopoiesis, platelet aggregation and apoptosis, as well as chemokine release and migration of immunocompetent cells. Here, we shall review the current knowledge on the pathophysiological roles of eCBs in blood. We shall also discuss the involvement of eCBs in those disorders affecting the haematological system, including cancer and inflammation. Knowledge gained to date underlines a fundamental role of the eCB system in blood, thus suggesting that it may represent a therapeutic promise for a broad range of diseases involving impaired hematopoietic cell functions.

Fatty acids, endocannabinoids and inflammation

From their phylogenetic and pharmacological classification it might be inferred that cannabinoid receptors and their endogenous ligands constitute a rather specialised and biologically distinct signalling system. However, the opposite is true and accumulating data underline how much the endocannabinoid system is intertwined with other lipid and non-lipid signalling systems. Endocannabinoids per se have many structural congeners, and these molecules exist in dynamic equilibria with different other lipid-derived mediators, including eicosanoids and prostamides. With multiple crossroads and shared targets, this creates a versatile system involved in fine-tuning different physiological and metabolic processes, including inflammation. A key feature of this 'expanded' endocannabinoid system, or 'endocannabinoidome', is its subtle orchestration based on interactions between a relatively small number of receptors and multiple ligands with different but partly overlapping activities. Following an update on the role of the 'endocannabinoidome' in inflammatory processes, this review continues with possible targets for intervention at the level of receptors or enzymes involved in formation or breakdown of endocannabinoids and their congeners. Although its pleiotropic character poses scientific challenges, the 'expanded' endocannabinoid system offers several opportunities for prevention and therapy of chronic diseases. In this respect, successes are more likely to come from 'multiple-target' than from 'single-target' strategies.

The monoacylglycerol lipase inhibitor JZL184 decreases inflammatory response in skeletal muscle contusion in rats

Muscle wound healing process is a typical inflammation-evoked event. The monoacylglycerol lipase (MAGL) inhibitor (4-nitrophenyl)4-[bis(1,3-benzodioxol -5-yl)-hydroxymethyl]piperidine-1-carboxylate (JZL184) has been previously reported to reduce inflammation in colitis and acute lung injury in mice, which provide a new strategy for primary care of skeletal muscle injury. We investigated the effect of JZL184 on inflammation in rat muscle contusion model, and found decreased neutrophil and macrophage infiltration and pro-inflammatory cytokine expression. With extension of post-traumatic interval, myofiber regeneration was significantly hindered with increased collagen types I and ІІІ mRNAfibroblast infiltration as well as promoted fibrosis. Furthermore, 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-morpholin-4-ylpyrazole-3-carboxamide (AM281, a selective cannabinoid CB1 receptor antagonist) and [6-iodo-2-methyl-1-(2-morpholin-4-ylethyl)indol-3-yl]-(4-methoxyphenyl)methanone (AM630, a selective cannabinoid CB2 receptor antagonist) treatment alleviated the anti-inflammatory effect of JZL184. Our findings demonstrate that JZL184 is able to inhibit the inflammatory response and interfere with contused muscle healing, in which the anti-inflammatory action may be mediated through cannabinoid CB1 and CB2 receptors.

The endocannabinoid system: an emerging key player in inflammation

PURPOSE OF REVIEW

The purpose of this review is to illustrate the expanding view of the endocannabinoid system (ECS) in relation to its roles in inflammation.

RECENT FINDINGS

According to the formal classification, the ECS consists of two cannabinoid receptors, their endogenous fatty acid-derived ligands, and a number of enzymes involved in their synthesis and breakdown. However, many endogenous congeners of classical endocannabinoids have now been discovered, together with a set of receptors structurally or functionally related to the cannabinoid receptors. Endocannabinoids per se behave 'promiscuously' with regard to their receptor interactions. It is increasingly recognized how tightly this expanded ECS is intertwined with key processes involved in inflammation. A continuous dynamic exchange of substrates and metabolites exists between ECS and eicosanoid pathways. Endocannabinoids can also be oxygenated by cyclooxygenase and other enzymes to biologically active 'hybrid' structures. Diet is among the main factors determining synthesis and release of endocannabinoids and related mediators.

SUMMARY

The complexity of what may be called the 'endocannabinoidome' requires approaches that take into account its dynamics and interconnections with other regulatory systems. This endocannabinoidome continues to offer possibilities for prevention and intervention, but multiple target approaches will probably provide the only keys to success.

Nutritional properties of dietary omega-3-enriched phospholipids

Dietary fatty acids regulate several physiological functions. However, to exert their properties, they have to be present in the diet in an optimal balance. Particular attention has been focused on tissue highly polyunsaturated fatty acids (HPUFAs) n-6/n-3 ratio, influenced by the type and the esterified form of dietary fatty acids. Dietary EPA and DHA when esterified to phospholipids (PLs) are more efficiently incorporated into tissue PLs and seem to possess peculiar properties through specific mechanism(s) of action, such as the capacity to affect endocannabinoid biosynthesis at much lower doses than EPA and DHA in triglyceride form, probably because of the above mentioned higher incorporation into tissue PLs. Downregulation of the endocannabinoid system seems to mediate the positive effects exerted by omega-3-enriched PLs on several parameters of metabolic syndrome. PLs are one of the major dietary forms of EPA and DHA we are exposed to with the everyday diet; therefore, it is not surprising that it guarantees an effective EPA and DHA nutritional activity. Future studies should address whether EPA and DHA in PL form are also more effective than other formulations in ameliorating other pathological conditions where n-3 HPUFAs seem to exert beneficial activities such as cancer and psychiatric disorders.

Blockade of cannabinoid receptors reduces inflammation, leukocyte accumulation and neovascularization in a model of sponge-induced inflammatory angiogenesis

OBJECTIVE

Angiogenesis depends on a complex interaction between cellular networks and mediators. The endocannabinoid system and its receptors have been shown to play a role in models of inflammation. Here, we investigated whether blockade of cannabinoid receptors may interfere with inflammatory angiogenesis.

MATERIALS AND METHODS

Polyester-polyurethane sponges were implanted in C57Bl/6j mice. Animals received doses (3 and 10 mg/kg/daily, s.c.) of the cannabinoid receptor antagonists SR141716A (CB1) or SR144528 (CB2). Implants were collected at days 7 and 14 for cytokines, hemoglobin, myeloperoxidase, and N-acetylglucosaminidase measurements, as indices of inflammation, angiogenesis, neutrophil and macrophage accumulation, respectively. Histological and morphometric analysis were also performed.

RESULTS

Cannabinoid receptors expression in implants was detected from day 4 after implantation. Treatment with CB1 or CB2 receptor antagonists reduced cellular influx into sponges at days 7 and 14 after implantation, although CB1 receptor antagonist were more effective at blocking leukocyte accumulation. There was a reduction in TNF-α, VEGF, CXCL1/KC, CCL2/JE, and CCL3/MIP-1α levels, with increase in CCL5/RANTES. Both treatments reduced neovascularization. Dual blockade of cannabinoid receptors resulted in maximum inhibition of inflammatory angiogenesis.

CONCLUSIONS

Blockade of cannabinoid receptors reduced leukocyte accumulation, inflammation and neovascularization, suggesting an important role of endocannabinoids in sponge-induced inflammatory angiogenesis both via CB1 and CB2 receptors.

Synergic insulin sensitizing effect of rimonabant and BGP-15 in Zucker-obese rats

Abdominal obesity is referred for as a common pathogenic root of multiple risk factors, which include insulin resistance, dyslipidemia, hypertension, and a pro-atherogenic and pro-inflammatory state. Irrespective of its psychiatric side effects, rimonabant through blocking cannabinoid-1 receptor (CB1R) induces an increase in whole body insulin sensitivity. The aim of this work was to study the effect of selected doses of another insulin sensitizer compound BGP-15, and rimonabant on insulin resistance in Zucker obese rats with a promise of inducing insulin sensitization together at lower doses than would have been expected by rimonabant alone. We found that BGP-15 potentiates the insulin sensitizing effect of rimonabant. The combination at doses, which do not induce insulin sensitization by themselves, improved insulin signaling. Furthermore our results suggest that capsaicin-induced signal may play a role in insulin sensitizing effect of both molecules. Our data might indicate that a lower dose of rimonabant in the treatment of insulin resistance and type 2 diabetes is sufficient to administer, thus a lower incidence of the unfavorable psychiatric side effects of rimonabant are to be expected.

Retinol-binding protein 4 : a possible role in cardiovascular complications

BACKGROUND AND PURPOSE

Retinol-binding protein 4 (RBP4) is an adipocyte-secreted hormone proposed to link obesity with insulin resistance. However, the role of RBP4 in cardiovascular complications is yet to be fully understood. The present study is aimed to decipher the association between RBP4 with pro-inflammatory cytokines and low-density lipoprotein (LDL) cholesterol in diet-induced obese and hyperlipidaemic mice. To understand the correlation, rimonabant, an anti-obesity drug, has been used to relieve the atherosclerotic predisposition.

EXPERIMENTAL APPROACH

Adipose and/or aortic tissue expressions of RBP4, pro-inflammatory cytokine genes and circulating LDL levels were measured in high fat (HF)-fed female C57BL/6 and high cholesterol (HC)-fed apolipoprotein E3 (ApoE3) Leiden mice.

KEY RESULTS

Mice fed a HF diet had a significantly increased adipose expression of RBP4, TNF-α and monocyte chemoattractant protein 1 (MCP-1) and down-regulated adiponectin mRNA levels. A significant increase in aortic RBP4 and MCP-1 expression and circulating levels of LDL and C-reactive protein (CRP) was found in the ApoE3 mice fed a HC diet. Interestingly, rimonabant treatment lowered the elevated aortic RBP4, MCP-1 expressions and significantly reduced the serum levels of LDL, CRP, RBP4 and MCP-1.

CONCLUSION AND IMPLICATIONS

Our results indicate that RBP4 is positively associated with markers of inflammation in obese and pro-atherogenic conditions and could play a role in a predisposition to atherosclerosis. Furthermore, our results indicate that rimonabant may improve vascular function by modulating RBP4 along with pro-inflammatory cytokines.

Does innovation in obesity drugs affect stock markets? An event study analysis

OBJECTIVE

This study empirically analyzes the effects of public information about the pharmaceutical R&D process on the market valuation of the sponsoring firm. We examined the market's response to scientific news and regulatory decisions about an antiobesity drug, rimonabant, and the effects on the sponsoring company (Sanofi-Aventis) and its incumbent competitors (Abbott and Roche).

METHODS

Event study methodology was used to test the null hypothesis of no market response. We covered the full life cycle of rimonabant (1994-2008), using a data set of daily closing price and volume.

RESULTS

The results suggest that scientific news in the initial stages of the drug R&D process (i.e., drug discovery, preclinical and clinical trials) had no significant effects. However, news related to regulatory decisions, such as recall or safety warning, had significant negative effects on the company's market value. No spillover/contagion effects on competitor firms were detected.

CONCLUSION

Market reactions occur at the time when the regulator takes decisions about drugs. Scientific news, even those of high-impact, may pass unnoticed.

Effect of the Cannabinoid Receptor-1 antagonist SR141716A on human adipocyte inflammatory profile and differentiation

Background

Obesity is characterized by inflammation, caused by increase in proinflammatory cytokines, a key factor for the development of insulin resistance. SR141716A, a cannabinoid receptor 1 (CB1) antagonist, shows significant improvement in clinical status of obese/diabetic patients. Therefore, we studied the effect of SR141716A on human adipocyte inflammatory profile and differentiation.

Methods

Adipocytes were obtained from liposuction. Stromal vascular cells were extracted and differentiated into adipocytes. Media and cells were collected for secretory (ELISA) and expression analysis (qPCR). Triglyceride accumulation was observed using oil red-O staining. Cholesterol was assayed by a fluorometric method. 2-AG and anandamide were quantified using isotope dilution LC-MS. TLR-binding experiments have been conducted in HEK-Blue cells.

Results

In LPS-treated mature adipocytes, SR141716A was able to decrease the expression and secretion of TNF-a. This molecule has the same effect in LPS-induced IL-6 secretion, while IL-6 expression is not changed. Concerning MCP-1, the basal level is down-regulated by SR141716A, but not the LPS-induced level. This effect is not caused by a binding of the molecule to TLR4 (LPS receptor). Moreover, SR141716A restored adiponectin secretion to normal levels after LPS treatment. Lastly, no effect of SR141716A was detected on human pre-adipocyte differentiation, although the compound enhanced adiponectin gene expression, but not secretion, in differentiated pre-adipocytes.

Conclusion

We show for the first time that some clinical effects of SR141716A are probably directly related to its anti-inflammatory effect on mature adipocytes. This fact reinforces that adipose tissue is an important target in the development of tools to treat the metabolic syndrome.

The cardioprotective effects of marrubiin, a diterpenoid found in Leonotis leonurus extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Leonotis leonurus L. (Lamiaceae) is used as a traditional medicine for a variety of ailments in South Africa. The diterpene marrubiin is the major product constituent in specimens of this plant occurring in South Africa.

MATERIALS AND METHODS

Marrubiin isolated from South African specimens of L. leonurus in addition to an organic extract of L. leonurus were tested in vivo, ex vivo and in vitro for their anticoagulant, antiplatelet and anti-inflammatory activities.

RESULTS

Marrubiin and the organic extract suppressed coagulation, platelet aggregation and inflammatory markers. For the coagulation markers it was found that the organic extract and marrubiin significantly prolonged activated partial thromboplastin time (APTT). Fibrin and D-dimer formation were drastically decreased. These findings were observed in an ex vivo model and an obese rat model. Chemokines enhance leukocyte recruitment to inflammatory sites. TNF-α and RANTES secretion were significantly reduced by the extract and marrubiin when determined in the obese rat model relative to the controls. Calcium mobilization and TXB(2) synthesis were suppressed by the extract and marrubiin. An in vitro model was used to elucidate the antiplatelet mechanism and it was found that the extract and marrubiin inhibited platelet aggregation by inhibiting the binding of fibrinogen to glycoprotein (GP) IIb/IIIa receptor in a concentration dependent manner.

CONCLUSION

The findings reflect that marrubiin largely contributes to the extract's anticoagulant, antiplatelet and anti-inflammatory effects observed.

Cannabinoid 1 receptor activation contributes to vascular inflammation and cell death in a mouse model of diabetic retinopathy and a human retinal cell line

AIMS/HYPOTHESIS

Recent studies have demonstrated that cannabinoid-1 (CB(1)) receptor blockade ameliorated inflammation, endothelial and/or cardiac dysfunction, and cell death in models of nephropathy, atherosclerosis and cardiomyopathy. However the role of CB(1) receptor signalling in diabetic retinopathy remains unexplored. Using genetic deletion or pharmacological inhibition of the CB(1) receptor with SR141716 (rimonabant) in a rodent model of diabetic retinopathy or in human primary retinal endothelial cells (HREC) exposed to high glucose, we explored the role of CB(1) receptors in the pathogenesis of diabetic retinopathy.

METHODS

Diabetes was induced using streptozotocin in C57BL/6J Cb(1) (also known as Cnr1)(+/+) and Cb(1)(-/-) mice aged 8 to 12 weeks. Samples from mice retina or HREC were used to determine: (1) apoptosis; (2) activity of nuclear factor kappa B, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), poly (ADP-ribose) polymerase and caspase-3; (3) content of 3-nitrotyrosine and reactive oxygen species; and (4) activation of p38/Jun N-terminal kinase/mitogen-activated protein kinase (MAPK).

RESULTS

Deletion of CB(1) receptor or treatment of diabetic mice with CB(1) receptor antagonist SR141716 prevented retinal cell death. Treatment of diabetic mice or HREC cells exposed to high glucose with SR141716 attenuated the oxidative and nitrative stress, and reduced levels of nuclear factor κB, ICAM-1 and VCAM-1. In addition, SR141716 attenuated the diabetes- or high glucose-induced pro-apoptotic activation of MAPK and retinal vascular cell death.

CONCLUSIONS/INTERPRETATION

Activation of CB(1) receptors may play an important role in the pathogenesis of diabetic retinopathy by facilitating MAPK activation, oxidative stress and inflammatory signalling. Conversely, CB(1) receptor inhibition may be beneficial in the treatment of this devastating complication of diabetes.

Increasing endogenous 2-arachidonoylglycerol levels counteracts colitis and related systemic inflammation

Inflammatory bowel diseases (IBDs) are chronic inflammatory conditions for which new therapeutic approaches are needed. Genetic and pharmacological data point to a protective role of CB(1) and CB(2) cannabinoid receptor activation in IBD experimental models. Therefore, increasing the endogenous levels of 2-arachidonoylglycerol, the main full agonist of these receptors, should have beneficial effects on colitis. 2-Arachidonoylglycerol levels were raised in the trinitrobenzene sulfonic acid (TNBS)-induced colitis mouse model by inhibiting monoacylglycerol lipase (MAGL), the primary enzyme responsible for hydrolysis of 2-arachidonoylglycerol, using the selective inhibitor JZL184. MAGL inhibition in diseased mice increased 2-arachidonoylglycerol levels, leading to a reduction of macroscopic and histological colon alterations, as well as of colonic expression of proinflammatory cytokines. The restored integrity of the intestinal barrier function after MAGL inhibition resulted in reduced endotoxemia as well as reduced peripheral and brain inflammation. Coadministration of either CB(1) (SR141716A) or CB(2) (AM630) selective antagonists with JZL184 completely abolished the protective effect of MAGL inhibition on TNBS-induced colon alterations, thus demonstrating the involvement of both cannabinoid receptors. In conclusion, increasing 2-arachidonoylglycerol levels resulted in a dramatic reduction of colitis and of the related systemic and central inflammation. This could offer a novel pharmacological approach for the treatment of IBD based on the new protective role of 2-arachidonoylglycerol described here.

Effect of the cannabinoid receptor-1 antagonist rimonabant on inflammation in mice with diet-induced obesity

We studied whether cannabinoid receptor (CB1) blockade with rimonabant has an anti-inflammatory effect in obese mice, and whether this effect depends on weight loss and/or diet consumption. High-fat diet (HFD)-induced obese mice were treated orally with rimonabant (HFD-R) or vehicle (HFD-V) for 4 weeks. Paired-feeding was conducted in two additional groups of obese mice to achieve either the same body weight (HFD-BW) or the same HFD intake (HFD DI) as HFD-R. All these groups of mice were maintained on HFD throughout, with mice on normal diet (ND) throughout as lean controls. Rimonabant treatment of obese mice induced marked diet-intake reduction and weight loss during the first week, which was followed by maintenance of low body weight but not diet-intake reduction. Lower HFD intake was required to reach the same degree of weight loss in HFD-BW. HFD-DI had similar weight loss initially, but then started to gain weight, reaching a higher body weight than HFD-R. Despite the same degree of weight loss, HFD-R had less fat mass and lower adipogenic gene expression than HFD-BW. Compared to HFD-V or HFD-DI, HFD-R had reduced inflammation in adipose tissue (AT) and/or liver indicated primarily by lower monocyte chemoattractant protein-1 (MCP-1) levels. However, MCP-1 levels were not significantly different between HFD-R and HFD-BW. In vitro incubation of rimonabant with AT explants did not change MCP-1 levels. Thus, rimonabant induced weight loss in obese mice by diet-intake-dependent and -independent fashions. Rimonabant decreased inflammation in obese mice, possibly through a primary effect on weight reduction.

2-arachidonyl glycerol activates platelets via conversion to arachidonic acid and not by direct activation of cannabinoid receptors

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

There are conflicting views in the literature as to whether cannabinoids have an impact on platelet activity and to what extent cannabinoid receptors are involved. This is an important issue to resolve because platelet effects of putative therapeutic cannabinoid inhibitors and stimulators will have an impact on their potential benefits and safety.

WHAT THIS PAPER ADDS

The data presented in this manuscript clearly show that the endocannabinoid 2-arrachidonyl glycerol can activate platelet activity, but that the effects are mediated through an aspirin-sensitive pathway that is not affected by cannabinoid receptor antagonists or FAAH inhibition, but is abolished by MAGL inhibition. The findings question the role of cannabinoid receptors in platelet function and suggest that platelet function is unlikely to be directly affected by cannabinoid receptor antagonists, at least in the acute phase.

AIMS

Cannabinoid receptor-1 (CB(1)) antagonists suppress appetite and induce weight loss. Direct antagonism of CB(1) receptors on platelets might be an additional benefit for CB(1) antagonists, but the role of CB(1) receptors in platelets is controversial. We tested the hypothesis that the endocannabinoid, 2-arachidonyl glycerol (2-AG), induces platelet aggregation by a COX-mediated mechanism rather than through CB(1) receptor activation, in blood obtained from healthy volunteers and patients with coronary artery disease receiving low dose aspirin.

METHODS

Aggregatory responses to the cannabinoids 2-AG and Delta(9)-THC were examined in blood sampled from healthy volunteers (n= 8) and patients (n= 12) with coronary artery disease receiving aspirin using whole blood aggregometry. The effects of CB(1) (AM251) and CB(2) (AM630) antagonists, as well as fatty acid amide hydrolase (FAAH) and monoacyl glycerol lipase (MAGL) inhibitors and aspirin on 2-AG-induced aggregation were also assessed.

RESULTS

AM251 (100 nm-30 microm) had no effect on platelet aggregation induced by either ADP (P= 0.90) or thrombin (P= 0.86). 2-AG, but not Delta(9)-THC, induced aggregation. 2-AG-induced aggregation was unaffected by AM251 and AM630 but was abolished by aspirin (P < 0.001) and by the MAGL inhibitor, URB602 (P < 0.001). Moreover, the aggregatory response to 2-AG was depressed (by >75%, P < 0.001) in blood from patients with coronary artery disease receiving aspirin compared with that from healthy volunteers.

CONCLUSIONS

2-AG-mediated activation of platelets is via metabolism to arachidonic acid by MAGL, and not through direct action on CB(1) or CB(2) receptors, at least in the acute phase.

Fatty acid amide hydrolase is a key regulator of endocannabinoid-induced myocardial tissue injury

Previous studies have suggested that increased levels of endocannabinoids in various cardiovascular disorders (e.g., various forms of shock, cardiomyopathies, atherosclerosis) through the activation of CB(1) cannabinoid receptors may promote cardiovascular dysfunction and tissue injury. We have investigated the role of the main endocannabinoid anandamide-metabolizing enzyme (fatty acid amide hydrolase; FAAH) in myocardial injury induced by an important chemotherapeutic drug, doxorubicin (DOX; known for its cardiotoxicity mediated by increased reactive oxygen and nitrogen species generation), using well-established acute and chronic cardiomyopathy models in mice. The DOX-induced myocardial oxidative/nitrative stress (increased 4-hydroxynonenal, protein carbonyl, and nitrotyrosine levels and decreased glutathione content) correlated with multiple cell death markers, which were enhanced in FAAH knockout mice exhibiting significantly increased DOX-induced mortality and cardiac dysfunction compared to their wild type. The effects of DOX in FAAH knockouts were attenuated by CB(1) receptor antagonists. Furthermore, anandamide induced enhanced cell death in human cardiomyocytes pretreated with FAAH inhibitor and enhanced sensitivity to ROS generation in inflammatory cells of FAAH knockouts. These results suggest that in pathological conditions associated with acute oxidative/nitrative stress FAAH plays a key role in controlling the tissue injury that is, at least in part, mediated by the activation of CB(1) receptors by endocannabinoids.

Cannabinoids and endocannabinoids in metabolic disorders with focus on diabetes

The cannabinoid receptors for Δ(9)-THC, and particularly, the CB(1) receptor, as well as its endogenous ligands, the endocannabinoids anandamide and 2-arachidonoylglycerol, are deeply involved in all aspects of the control of energy balance in mammals. While initially it was believed that this endocannabinoid signaling system would only facilitate energy intake, we now know that perhaps even more important functions of endocannabinoids and CB(1) receptors in this context are to enhance energy storage into the adipose tissue and reduce energy expenditure by influencing both lipid and glucose metabolism. Although normally well controlled by hormones and neuropeptides, both central and peripheral aspects of endocannabinoid regulation of energy balance can become dysregulated and contribute to obesity, dyslipidemia, and type 2 diabetes, thus raising the possibility that CB(1) antagonists might be used for the treatment of these metabolic disorders. On the other hand, evidence is emerging that some nonpsychotropic plant cannabinoids, such as cannabidiol, can be employed to retard β-cell damage in type 1 diabetes. These novel aspects of endocannabinoid research are reviewed in this chapter, with emphasis on the biological effects of plant cannabinoids and endocannabinoid receptor antagonists in diabetes.

Rimonabant inhibits TNF-α-induced endothelial IL-6 secretion via CB1 receptor and cAMP-dependent protein kinase pathway

AIM

To investigate whether rimonabant, a cannabinoid receptor antagonist, had inhibitory effects on inflammatory reactions in human umbilical vein endothelial cells (HUVEC).

METHODS

TNF-α-induced IL-6 production was measured by ELISA and effects on related signaling pathways were investigated by immunoblot analysis. Cellular cAMP level was measured using kinase-coupled luciferase reaction.

RESULTS

Rimonabant at 1 and 10 μmol/L significantly inhibited TNF-α-induced IL-6 production when added 15, 30 and 60 minutes before TNF-α treatment. Rimonabant also inhibited TNF-α-induced phosphorylation of IκB kinase (IKK) α/β and IκB-α degradation. ACEA, a cannabinoid receptor subtype 1 (CB1) agonist, added before rimonabant abolished the former effects of rimonabant. H-89, an inhibitor of cAMP-dependent protein kinase (PKA), abolished the inhibitory effects of rimonabant on TNF-α induced IL-6 production. Rimonabant also increased the phosphorylation of PKA regulatory subunit II (PKA-RII), implying the essential role of PKA activation in the inhibitory effects of rimonabant. Treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin did not abolish the inhibitory effects of rimonabant on TNF-α induced IL-6 production.

CONCLUSION

Rimonabant had anti-inflammatory effects on endothelial cells and inhibited TNF-α-induced IKKα/β phosphorylation, IκB-α degradation and IL-6 production in HUVEC. This effect was related to CB1 antagonism and PKA activation.

CB1 cannabinoid receptors promote oxidative/nitrosative stress, inflammation and cell death in a murine nephropathy model

BACKGROUND AND PURPOSE

Accumulating recent evidence suggests that cannabinoid-1 (CB(1)) receptor activation may promote inflammation and cell death and its pharmacological inhibition is associated with anti-inflammatory and tissue-protective effects in various preclinical disease models, as well as in humans.

EXPERIMENTAL APPROACH

In this study, using molecular biology and biochemistry methods, we have investigated the effects of genetic deletion or pharmacological inhibition of CB(1) receptors on inflammation, oxidative/nitrosative stress and cell death pathways associated with a clinically relevant model of nephropathy, induced by an important chemotherapeutic drug cisplatin.

RESULTS

Cisplatin significantly increased endocannabinoid anandamide content, activation of p38 and JNK mitogen-activated protein kinases (MAPKs), apoptotic and poly (ADP-ribose)polymerase-dependent cell death, enhanced inflammation (leucocyte infiltration, tumour necrosis factor-alpha and interleukin-1beta) and promoted oxidative/nitrosative stress [increased expressions of superoxide-generating enzymes (NOX2(gp91phox), NOX4), inducible nitric oxide synthase and tissue 4-hydroxynonenal and nitrotyrosine levels] in the kidneys of mice, accompanied by marked histopathological damage and impaired renal function (elevated creatinine and serum blood urea nitrogen) 3 days following its administration. Both genetic deletion and pharmacological inhibition of CB(1) receptors with AM281 or SR141716 markedly attenuated the cisplatin-induced renal dysfunction and interrelated oxidative/nitrosative stress, p38 and JNK MAPK activation, cell death and inflammatory response in the kidney.

CONCLUSIONS AND IMPLICATIONS

The endocannabinoid system through CB(1) receptors promotes cisplatin-induced tissue injury by amplifying MAPK activation, cell death and interrelated inflammation and oxidative/nitrosative stress. These results also suggest that inhibition of CB(1) receptors may exert beneficial effects in renal (and most likely other) diseases associated with enhanced inflammation, oxidative/nitrosative stress and cell death.

The endocannabinoid system: its roles in energy balance and potential as a target for obesity treatment

Obesity and cardiometabolic risk continue to be major public health concerns. A better understanding of the physiopathological mechanisms leading to obesity may help to identify novel therapeutic targets. The endocannabinoid system discovered in the early 1990s is believed to influence body weight regulation and cardiometabolic risk factors. This article aims to review the literature on the endocannabinoid system including the biological roles of its major components, namely, the cannabinoid receptors, their endogenous ligands the endocannabinoids and the ligand-metabolising enzymes. The review also discusses evidence that the endocannabinoid system constitutes a new physiological pathway occurring in the central nervous system and peripheral tissues that has a key role in the control of food intake and energy expenditure, insulin sensitivity, as well as glucose and lipid metabolism. Based on the important finding that there is a close association between obesity and the hyperactivity of the endocannabinoid system, interest in blocking stimulation of this pathway to aid weight loss and reduce cardiometabolic risk factor development has become an important area of research. Among the pharmacological strategies proposed, the antagonism of the cannabinoid receptors has been particularly investigated and several clinical trials have been conducted. One challenging pharmacological task will be to target the endocannabinoid system in a more selective, and hence, safe way. As the management of obesity also requires lifestyle modifications in terms of healthy eating and physical activity, the targeting of the endocannabinoid system may represent a novel approach for a multifactorial therapeutic strategy.

Effect of rimonabant, the cannabinoid CB1 receptor antagonist, on peripheral nerve in streptozotocin-induced diabetic rat

The aim of this study is to investigate the effect of rimonabant, which has antiatherosclerotic and antiinflammatory properties, on peripheral neuropathy in a diabetic rat. Diabetic rat models were induced by treatment with streptozotocin and then either normal or diabetic rats were treated with an oral dose of 10mg/kg/day rimonabant or placebo for 24 weeks. We quantified the densities of intraepidermal (PGP9.5+) nerve fiber and total skin (RECA-1+) capillary length. We also measured the current perception threshold, as defined by the intensity of sine-wave stimulus, skin blood flow after treadmill running and TNF-alpha level in spinal cord tissue or plasma. After 24 weeks, rimonabant reduced the body weight and food intake in both diabetic and normal rats, but it had no effect on blood sugar levels. In addition, rimonabant treatment significantly improved the decreased intraepidermal nerve fiber density (5.53+/-0.12 vs. 4.36+/-0.27/mm, P<0.05) and alleviated the increased current perception threshold in rimonabant-treated versus control diabetic rats. These responses were closely associated with the attenuation of skin capillary loss (1.98+/-0.07 vs. 1.67+/-0.10 mm/mm(2), P<0.05), increase in skin blood flow (14.93+/-1.08 vs. 12.07+/-0.87 TPU, P<0.05) and reduction in TNF-alpha level in tissue (70.10+/-4.99 vs. 91.18+/-3.34 pg/mg, P<0.05) in rimonabant-treated diabetic rats compared with placebo. These findings suggest that rimonabant can be beneficial for treatment of diabetic peripheral neuropathy, possibly due to its potential role in micro- and macrovessel protection and its anti-inflammatory properties.

Effect of dietary fat on endocannabinoids and related mediators: consequences on energy homeostasis, inflammation and mood

Among the several known fatty acid-derived chemical signals, the endogenous ligands of cannabinoid receptors type-1 and -2, two G-protein-coupled receptors involved in several aspects of mammalian physiology and pathology, are perhaps those the levels of which have proven to be most sensitive to the fatty acid composition of the diet. The two most studied such ligands, known as endocannabinoids, are N-arachidonoyl-ethanolamine and 2-archidonoylglycerol, and are found in tissues together with other N-acyl-ethanolamines and 2-acylglycerols, not all of which activate the cannabinoid receptors, although several of them do exhibit important pharmacological effects. In this review article, we describe literature data indicating that the tissue concentrations of the endocannabinoids and related signalling molecules, and hence the activity of the respective receptors, can be modulated by modifying the fatty acid composition of the diet, and particularly its content in long chain PUFAs or in long chain PUFA precursors. We also discuss the potential impact of these diet-induced changes of endocannabinoid tone on three of the major pathological conditions in which cannabinoid receptors have been involved, that is metabolic dysfunctions, inflammation and affective disorders.

The prostacyclin analog beraprost sodium ameliorates characteristics of metabolic syndrome in obese Zucker (fatty) rats

OBJECTIVE

The prostacyclin analog, beraprost sodium (BPS), was examined for its potential to improve the symptoms of obesity-type diabetes (i.e., hyperglycemia, hyperinsulinemia, dyslipidemia, histopathologic changes, and diabetic complications).

RESEARCH DESIGN AND METHODS

Obese Zucker rats, an experimental model of genetic obesity-induced type 2 diabetes, were repeatedly administered BPS at oral doses of 0.2 or 0.6 mg x kg(-1) x day(-1) b.i.d. for 12 weeks, and serum chemistry, urinalysis, and histopathologic examination were performed.

RESULTS

BPS dose-dependently suppressed serum glucose, insulin, triglyceride, and cholesterol levels in obese animals. In oral glucose tolerance test, BPS suppressed the post-glucose-loading elevation of serum glucose in a dose-dependent manner. Urinary N-acetyl-beta-D-glucosaminidase was significantly lower in BPS-treated obese animals compared with control animals, although no significant differences were observed in urinary protein levels between the BPS-treated groups and the control group. In addition, histopathologic examination revealed significant protective effects of BPS against renal disorder in obese animals. Histopathologically, BPS also inhibited the progression of hepatic steatosis, hypertrophy of adipose tissue, and pancreatic fibrosis. Furthermore, thermographic analysis of the hind limb sole skin surface indicated a significant increase in temperature in BPS-treated animals, compared with control animals, which was likely due to improved blood circulation by administration of BPS.

CONCLUSIONS

BPS suppressed the pathogenesis and development of diabetes and its complication, nephropathy, which was presumably accompanied by improving glucose intolerance and insulin resistance in obese Zucker rats.

Role of platelets in neuroinflammation: a wide-angle perspective

OBJECTIVES

This review summarizes recent developments in platelet biology relevant to neuroinflammatory disorders. Multiple sclerosis (MS) is taken as the "Poster Child" of these disorders but the implications are wide. The role of platelets in inflammation is well appreciated in the cardiovascular and cancer research communities but appears to be relatively neglected in neurological research.

ORGANIZATION

After a brief introduction to platelets, topics covered include the matrix metalloproteinases, platelet chemokines, cytokines and growth factors, the recent finding of platelet PPAR receptors and Toll-like receptors, complement, bioactive lipids, and other agents/functions likely to be relevant in neuroinflammatory diseases. Each section cites literature linking the topic to areas of active research in MS or other disorders, including especially Alzheimer's disease.

CONCLUSION

The final section summarizes evidence of platelet involvement in MS. The general conclusion is that platelets may be key players in MS and related disorders, and warrant more attention in neurological research.

Involvement of adipokines in rimonabant-mediated insulin sensitivity in ob/ob mice

Objectives

It has been recently reported that blockade of type 1 cannabinoid (CB1) receptors by specific antagonists or genetic manipulation alleviates dyslipidaemia, hyperglycaemia and insulin resistance in animal models of obesity and type 2 diabetes. However, the precise role of adipokines in the insulin-sensitising effects of the CB1 antagonist rimonabant is not clear.

Methods

ob/ob mice were treated with different doses of rimonabant and then subjected to an oral glucose tolerance test. The expression of different adipokines in white adipose tissue was analysed by quantitative real-time PCR.

Key findings

Rimonabant (30 mg/kg) significantly inhibited body weight and fat pad weight gain (P &lt; 0.05) and improved glucose tolerance. Gene expression analysis indicated that tumour necrosis factor-α, visfatin and retinol binding protein-4 were downregulated in the adipose tissue of ob/ob mice treated with rimonabant compared with controls, whereas adiponectin was significantly upregulated.

Conclusions

Rimonabant-mediated alteration of adipokines in white adipose tissues may play a role in improving insulin sensitivity in obese animals.

Central and peripheral consequences of the chronic blockade of CB1 cannabinoid receptor with rimonabant or taranabant

The endocannabinoid system plays a crucial role in the pathophysiology of obesity. However, the clinical use of cannabinoid antagonists has been recently stopped because of its central side-effects. The aim of this study was to compare the effects of a chronic treatment with the CB(1) cannabinoid antagonist rimonabant or the CB(1) inverse agonist taranabant in diet-induced obese female rats to clarify the biological consequences of CB(1) blockade at central and peripheral levels. As expected, chronic treatment with rimonabant and taranabant reduced body weight and fat content. Interestingly, a decrease in the number of CB(1) receptors and its functional activity was observed in all the brain areas investigated after chronic taranabant treatment in both lean and obese rats. In contrast, chronic treatment with rimonabant did not modify the density of CB(1) cannabinoid receptor binding, and decreased its functional activity to a lower degree than taranabant. Six weeks after rimonabant and taranabant withdrawal, CB(1) receptor density and activity recovered to basal levels. These results reveal differential adaptive changes in CB(1) cannabinoid receptors after chronic treatment with rimonabant and taranabant that could be related to the central side-effects reported with the use of these cannabinoid antagonists.

Endothelial dysfunction and specific inflammation in obesity hypoventilation syndrome

Background

Obesity hypoventilation syndrome (OHS) is associated with increased cardiovascular morbidity. What moderate chronic hypoventilation adds to obesity on systemic inflammation and endothelial dysfunction remains unknown.

Question

To compare inflammatory status and endothelial function in OHS versus eucapnic obese patients.

Methodology

14 OHS and 39 eucapnic obese patients matched for BMI and age were compared. Diurnal blood gazes, overnight polysomnography and endothelial function, measured by reactive hyperemia peripheral arterial tonometry (RH-PAT), were assessed. Inflammatory (Leptin, RANTES, MCP-1, IL-6, IL-8, TNFα, Resistin) and anti-inflammatory (adiponectin, IL-1Ra) cytokines were measured by multiplex beads immunoassays.

Principal Findings

OHS exhibited a higher PaCO₂, a lower forced vital capacity (FVC) and tended to have a lower PaO₂ than eucapnic obese patients. _HS-CRP, RANTES levels and glycated haemoglobin (HbA1c) were significantly increased in OHS (respectively 11.1±10.9 vs. 5.7±5.5 mg.l⁻¹ for _HS-CRP, 55.9±55.3 vs 23.3±15.8 ng/ml for RANTES and 7.3±4.3 vs 6.1±1.7 for HbA1c). Serum adiponectin was reduced in OHS (7606±2977 vs 13660±7854 ng/ml). Endothelial function was significantly more impaired in OHS (RH-PAT index: 0.22±0.06 vs 0.51±0.11).

Conclusions

Compared to eucapnic obesity, OHS is associated with a specific increase in the pro-atherosclerotic RANTES chemokine, a decrease in the anti-inflammatory adipokine adiponectin and impaired endothelial function. These three conditions are known to be strongly associated with an increased cardiovascular risk.

Trial Registration

ClinicalTrials.gov NCT00603096

Delta-9-tetrahydrocannabinol enhances food reinforcement in a mouse operant conflict test

RATIONALE

Cannabinoid compounds are known to regulate feeding behavior by modulating the hedonic and/or the incentive properties of food.

OBJECTIVES

The aim of this work was to determine the involvement of the cannabinoid system in food reinforcement associated with a conflict situation generated by stress.

METHODS

Mice were trained on a fixed ratio 1 schedule of reinforcement to obtain standard, chocolate-flavored or fat-enriched pellets. Once the acquisition criteria were achieved, the reinforced lever press was paired with foot-shock exposure, and the effects of Delta(9)-tetrahydrocannabinol (THC; 1 mg/kg) were evaluated in this conflict paradigm.

RESULTS

THC did not modify the operant response in mice trained with standard pellets. In contrast, THC improved the instrumental performance of mice trained with chocolate-flavored and fat-enriched pellets. However, the cannabinoid agonist did not fully restore the baseline responses obtained previous to foot-shock delivery. THC ameliorated the performance to obtain high palatable food in this conflict test in both food-restricted and sated mice. The effects of THC on food reinforcement seem to be long-lasting since mice previously treated with this compound showed a better recovery of the instrumental behavior after foot-shock exposure.

CONCLUSIONS

These findings reveal that the cannabinoid system is involved in the regulation of goal-directed responses towards high palatable and high caloric food under stressful situations.

Endocannabinoids may mediate the ability of (n-3) fatty acids to reduce ectopic fat and inflammatory mediators in obese Zucker rats

Dietary (n-3) long-chain PUFA [(n-3) LCPUFA] ameliorate several metabolic risk factors for cardiovascular diseases, although the mechanisms of these beneficial effects are not fully understood. In this study, we compared the effects of dietary (n-3) LCPUFA, in the form of either fish oil (FO) or krill oil (KO) balanced for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content, with a control (C) diet containing no EPA and DHA and similar contents of oleic, linoleic, and alpha-linolenic acids, on ectopic fat and inflammation in Zucker rats, a model of obesity and related metabolic dysfunction. Diets were fed for 4 wk. Given the emerging evidence for an association between elevated endocannabinoid concentrations and metabolic syndrome, we also measured tissue endocannabinoid concentrations. In (n-3) LCPUFA-supplemented rats, liver triglycerides and the peritoneal macrophage response to an inflammatory stimulus were significantly lower than in rats fed the control diet, and heart triglycerides were lower, but only in KO-fed rats. These effects were associated with a lower concentration of the endocannabinoids, anandamide and 2-arachidonoylglycerol, in the visceral adipose tissue and of anandamide in the liver and heart, which, in turn, was associated with lower levels of arachidonic acid in membrane phospholipids, but not with higher activity of endocannabinoid-degrading enzymes. Our data suggest that the beneficial effects of a diet enriched with (n-3) LCPUFA are the result of changes in membrane fatty acid composition. The reduction of substrates for inflammatory molecules and endocannabinoids may account for the dampened inflammatory response and the physiological reequilibration of body fat deposition in obese rats.

Peripheral endocannabinoid dysregulation in obesity: relation to intestinal motility and energy processing induced by food deprivation and re-feeding

BACKGROUND AND PURPOSE

Endocannabinoids in tissues controlling energy homeostasis are altered in obesity, thus contributing to metabolic disorders. Here we evaluate endocannabinoid dysregulation in the small intestine of mice with diet-induced obesity (DIO) and in peripheral tissues of Zucker and lean rats following food deprivation and re-feeding.

EXPERIMENTAL APPROACH

Intestinal transit, evaluated using rhodamine-B-labelled dextran, and small intestinal endocannabinoid levels, measured by liquid chromatography mass spectrometry, were measured in mice fed normal or high-fat diets (HFDs). Endocannabinoid levels were measured also in various tissues of lean and Zucker rats fed ad libitum or following overnight food deprivation with and without subsequent re-feeding.

KEY RESULTS

After 8 weeks of HFD, baseline intestinal transit was increased in DIO mice and enhanced by cannabinoid CB(1) receptor antagonism less efficaciously than in lean mice. Small intestinal anandamide and 2-arachidonoylglycerol levels were reduced and increased respectively. In Zucker rats, endocannabinoids levels were higher in the pancreas, liver and duodenum, and lower in the subcutaneous adipose tissue. Food deprivation increased endocannabinoid levels in the duodenum and liver of both rat strains, in the pancreas of lean rats and in adipose tissues of Zucker rats.

CONCLUSIONS AND IMPLICATIONS

Reduced anandamide levels might account for increased intestinal motility in DIO mice. Regulation of endocannabinoid levels in rat peripheral tissues, induced by food deprivation and re-feeding, might participate in food intake and energy processing and was altered in Zucker rats. These data, together with previous observations, provide further evidence for dysregulation of peripheral endocannabinoids in obesity.

Cannabinoid type 1 receptors in human skeletal muscle cells participate in the negative crosstalk between fat and muscle

AIMS/HYPOTHESIS

Cannabinoid type 1 receptor (CB1R) antagonists such as rimonabant (Rim) represent a novel approach to treat obesity and related metabolic disorders. Recent data suggest that endocannabinoids are also produced by human adipocytes. Here we studied the potential involvement of endocannabinoids in the negative crosstalk between fat and muscle.

METHODS

The protein level of CB1R in human skeletal muscle cells (SkM) during differentiation was analysed using western blotting. SkM were treated with adipocyte-conditioned medium (CM) or anandamide (AEA) in combination with the CB1R antagonists Rim or AM251, and insulin-stimulated Akt phosphorylation and glucose uptake were determined. Furthermore, signalling pathways of CB1R were investigated.

RESULTS

We revealed an increase of CB1R protein in SkM during differentiation. Twenty-four hour incubation of SkM with CM or AEA impaired insulin-stimulated Akt(Ser473) phosphorylation by 60% and up to 40%, respectively. Pretreatment of cells with Rim or AM251 reduced the effect of CM by about one-half, while the effect of AEA could be prevented completely. The reduction of insulin-stimulated glucose uptake by CM was completely prevented by Rim. Short-time incubation with AEA activated extracellular regulated kinase 1/2 and p38 mitogen-activated protein kinase, and impaired insulin-stimulated Akt(Ser473) phosphorylation, but had no effect on Akt(Thr308) and glycogen synthase kinase 3alpha/beta phosphorylation. In addition, enhanced IRS-1 (Ser307) phosphorylation was observed.

CONCLUSIONS/INTERPRETATION

Our results show that the CB1R system may play a role in the development of insulin resistance in human SkM. The results obtained with CM support the notion that adipocytes may secrete factors which are able to activate the CB1R. Furthermore, we identified two stress kinases in the signalling pathway of AEA and enhanced IRS-1(Ser307) phosphorylation, potentially underlying the development of insulin resistance.

Regulation and possible role of endocannabinoids and related mediators in hypercholesterolemic mice with atherosclerosis

In this study we analysed the possible modulation of endocannabinoids and related molecules during atherosclerosis development in mice. Wild-type and apolipoprotein E knockout (ApoE(-/-)) mice were fed either normal chow or high-cholesterol diet for 8-12 weeks, and tissue endocannabinoid levels were measured by liquid chromatography-mass spectrometry. We found increased levels of 2-AG in aortas and visceral adipose tissue (VAT) of ApoE(-/-) mice fed on high-cholesterol diet for 12 weeks as compared to ApoE(-/-) mice fed on normal chow or wild-type mice fed on cholesterol. No significant difference in 2-AG levels was observed after 8 weeks of diet, and no changes in anandamide levels were found in any group. The levels of the anandamide-related mediators with anti-inflammatory or anti-lipogenic properties, palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), decreased or increased only in VAT or in both tissues, respectively. Endocannabinoid- and OEA/PEA-degrading enzymes were expressed by macrophages within atherosclerotic lesions. In vitro, 2-AG and OEA-induced monocyte migration at 0.3-1microM, which corresponds to the levels observed in aortas. PEA 1microM also induced monocyte migration but counteracted the effect of 2-AG, whereas OEA enhanced it. Enhanced 2-AG levels in advanced atherosclerotic lesions may trigger the inflammatory process by recruiting more inflammatory cells and inducing extracellular matrix degradation via CB(2) receptors, and this possibility was supported in vitro but not in vivo by experiments with the CB(2) antagonist, SR144528.

Rimonabant in rats with a metabolic syndrome: good news after the depression

The synthetic cannabinoid CB1 receptor antagonist rimonabant (sold in the United Kingdom under the brand name Acomplia) was reported to improve the profile of cardiovascular risk factors in obese patients with the metabolic syndrome, a cluster of metabolic disorders that often precedes the onset of type II diabetes. Rimonabant is shown in the current issue of British Journal of Pharmacology to attenuate weight gain in Zucker rats, an experimental model of insulin resistance. Neutrophil and monocyte counts were lowered by rimonabant administration. Both platelet activation (by ADP) and aggregation (in response to thrombin) were inhibited. Circulating pro-inflammatory cytokine levels (monocyte chemotactic protein 1, MCP1 and Regulated upon Activation, Normal T-cell Expressed and Secreted, RANTES) were also reduced. Furthermore, fibrinogen levels returned to normal. These favourable anti-inflammatory and anti-thrombotic actions imply for rimonabant a peripheral, direct action on some cardiovascular risk factors.