GPR55 and its interaction with membrane lipids: comparison with other endocannabinoid-binding receptors.

A number of integral membrane G protein-coupled receptors (GPCRs) share common structural features (including palmytoilated aminoacid residues and consensus sequences specific for interaction with cholesterol) that allow them to interact with lipid rafts, membrane cholesterol-rich microdomains able to regulate GPCR signalling and functions. Among GPCRs, type-1 and type-2 cannabinoid receptors, the molecular targets of endocannabinoids (eCBs), control many physiological and pathological processes through the activation of several signal transduction pathways. Recently, the orphan GPR55 receptor has been proved to be activated by many eCBs, thus leading to the hypothesis that it might be the "type-3" cannabinoid receptor. While the biological activity of eCBs and the influence of membrane lipids on their functions are rather well established, information regarding GPR55 is still scarce and often controversial. Based on this background, here we shall review current data about GPR55 pharmacology and signalling, highlighting its involvement in several pathophysiological conditions. We shall also outline the structural features that allow GPR55 to interact with cholesterol and to associate with lipid rafts; how the latter lipid microdomains impact the biological activity of GPR55 is also addressed, as well as their potential for the discovery of new therapeutics useful for the treatment of those human diseases that might be associated with alterations of GPR55 activity.

Human platelets express authentic CB1 and CB2 receptors.

In the last decade, the neurovascular effects exerted by endocannabinoids (eCBs) have attracted growing interest, because they hold the promise to open new avenues of therapeutic intervention against major causes of death in Western society. Several actions of eCBs are mediated by type-1 (CB1) or type-2 (CB2) cannabinoid receptors, yet there is no clear evidence of the presence of these proteins in platelets. To demonstrate that CB1 and CB2 are expressed in human platelets, we analyzed their protein level by Western blotting and ELISA, visualized their cellular localization by confocal microscopy, and ascertained their functionality by binding assays. We found that CB1, and to a lesser extent CB2, are expressed in highly purified human platelets. Both receptor subtypes were predominantly localized inside the cell, thus explaining why they might remain undetected in preparations of plasma membranes. The identification of authentic CB1 and CB2 in human platelets supports the potential exploitation of selective agonists or antagonists of these receptors as novel therapeutics to combat neurovascular disorders. It seems remarkable that some of these substances have been already used in humans to treat disease states.

Alterations of the endocannabinoid system in an animal model of migraine: evaluation in cerebral areas of rat.

Endocannabinoids are involved in the modulation of pain and hyperalgesia. In this study we investigated the role of the endocannabinoid system in the migraine model based on nitroglycerin-induced hyperalgesia in the rat. Male rats were injected with nitroglycerin (10 mg/kg, i.p.) or vehicle and sacrificed 4 h later. The medulla, the mesencephalon and the hypothalamus were dissected out and utilized for the evaluation of activity of fatty acid amide hydrolase (that degrades the endocannabinoid anandamide), monoacylglycerol lipase (that degrades the endocannabinoid 2-arachidonoylglycerol), and binding sites specific for cannabinoid (CB) receptors. The findings obtained show that nitroglycerin-induced hyperalgesia is associated with increased activity of both hydrolases and increased density of CB binding sites in the mesencephalon. In the hypothalamus we observed an increase in the activity of fatty acid amide hydrolase associated with an increase in density of CB binding sites, while in the medulla only the activity of fatty acid amide hydrolase was increased. Anandamide also proved effective in preventing nitroglycerin-induced activation (c-Fos) of neurons in the nucleus trigeminalis caudalis. These data strongly support the involvement of the endocannabinoid system in the modulation of nitroglycerin-induced hyperalgesia, and, possibly, in the pathophysiological mechanisms of migraine.

High levels of anandamide, an endogenous cannabinoid, block the growth of sheep preimplantation embryos by inducing apoptosis and reversible arrest of cell proliferation.

BACKGROUND: The process of implantation is mediated by various molecules, one of which is anandamide (AEA), a lipid signalling ligand belonging to the family of endocannabinoids. AEA exerts its effects on implantation by binding to the Type 1 Cannabinoid Receptor (CB1-R), expressed in both blastocysts and uterus. We wanted to know whether the endocannabinoid signalling system was present also in the sheep reproductive tract and which kind of effect(s) AEA had on the development of sheep blastocysts in vitro. METHODS: We analysed the expression and activity of the endocannabinoid system in sheep reproductive tracts and blastocysts. Hatched sheep blastocysts were then exposed to AEA and its effect(s) were determined by TUNEL assay and by measuring the rate of necrosis and 5-bromo-deoxyuridine incorporation. RESULTS: We show that the AEA signalling system is present in sheep and that high concentrations of AEA induce apoptosis and inhibit cell proliferation via a CB1-R-dependent mechanism. Indeed, AEA effects were blocked when sheep blastocysts were cultured in the presence of the CB1-R antagonist SR161417A. Moreover, AEA inhibition of cell proliferation was reversible, as arrested embryos resumed a normal growth rate upon AEA removal from the medium. CONCLUSIONS: Our results suggest that disturbed regulation of AEA signalling via CB1-R may be associated with pregnancy failure. AEA could lower the quality of blastocysts by inducing apoptosis and inhibiting cell proliferation, thus making them incompetent for implantation.

Cortical expression of brain derived neurotrophic factor and type-1 cannabinoid receptor after striatal excitotoxic lesions.

An involvement of one particular neurotrophin, namely, the brain-derived neurotrophic factor (BDNF), has been demonstrated in the pathophysiology Huntington's disease. Type-1 cannabinoid (CB1) receptor has been postulated to upregulate BDNF gene transcription. To better understand the relationship between CB1 and BDNF levels in a situation where the striatum is degenerating, we studied, by dual label immunofluorescence, the distribution of CB1 and BDNF in cortical neurons projecting to the striatum in our rat quinolinic acid model of striatal excitotoxicity. We completed our study with quantitative analyses of BDNF protein levels and CB1 binding activity in the cortex. We show that, 2 weeks post lesion, cortical neurons contain more BDNF compared with controls and to earlier time points. Such BDNF up-regulation coincides with a higher binding activity and an increased protein expression of CB1. We suggest that after excitotoxic lesions, CB1 might, at least transiently, upregulate BDNF in the attempt to rescue striatal neurons from degeneration.

5-Lipoxygenase and anandamide hydrolase (FAAH) mediate the antitumor activity of cannabidiol, a non-psychoactive cannabinoid.

It has been recently reported that cannabidiol (CBD), a non-psychoactive cannabinoid, is able to kill glioma cells, both in vivo and in vitro, independently of cannabinoid receptor stimulation. However, the underlying biochemical mechanisms were not clarified. In the present study, we performed biochemical analysis of the effect of CBD both in vivo, by using glioma tumor tissues excised from nude mice, and in vitro, by using U87 glioma cells. In vivo exposure of tumor tissues to CBD significantly decreased the activity and content of 5-lipoxygenase (LOX, by approximately 40%), and of its end product leukotriene B4 ( approximately 25%). In contrast cyclooxygenase (COX)-2 activity and content, and the amount of its end product prostaglandin E2, were not affected by CBD. In addition, in vivo treatment with CBD markedly stimulated ( approximately 175%) the activity of fatty acid amide hydrolase (FAAH), the main anandamide-degrading enzyme, while decreasing anandamide content ( approximately 30%) and binding to CB1 cannabinoid receptors ( approximately 25%). In vitro pre-treatment of U87 glioma cells with MK-886, a specific 5-LOX inhibitor, significantly enhanced the antimitotic effect of CBD, whereas the pre-treatment with indomethacin (pan-COX inhibitor) or celecoxib (COX-2 inhibitor), did not alter CBD effect. The study of the endocannabinoid system revealed that CBD was able to induce a concentration-dependent increase of FAAH activity in U87 cells. Moreover, a significantly reduced growth rate was observed in FAAH-over-expressing U87 cells, compared to wild-type controls. In conclusion, the present investigation indicates that CBD exerts its antitumoral effects through modulation of the LOX pathway and of the endocannabinoid system, suggesting a possible interaction of these routes in the control of tumor growth.

Biological abnormalities of peripheral A(2A) receptors in a large representation of polyglutamine disorders and Huntington's disease stages.

Huntington's disease is one of a group of hereditary neurodegenerative diseases characterized by a glutamine expansion (polyQ) in proteins which are expressed in various cell populations. In agreement with this widespread distribution, we have previously shown that A(2A) receptor signaling is affected in mouse brain as well as in peripheral blood cells from a small cohort of HD patients. Here we analyzed a total of 252 subjects, including 126 HD gene-positive individuals, from different clinical sites. Consistent with our previous data we show that A(2A) receptor B(max) values are robustly increased at all HD stages as well as in 32 pre-symptomatic subjects. We report that the same abnormality is present also in other polyQ but not in non-polyQ inherited neurological disorders. Finally, we demonstrate that the same peripheral cells exhibit an altered membrane fluidity, a finding that may explain the observed change in receptor density. We argue that the observed alteration in lymphocytes reflects the presence of the mutant protein, and we suggest that the measure of the A(2A) receptor binding activity might be of potential interest for a peripheral assessment of chemicals capable of interfering with the immediate toxic effects of the mutation.

Endocannabinoids in adipocytes during differentiation and their role in glucose uptake.

The molecular basis for the control of energy balance by the endocannabinoid anandamide (AEA) is still unclear. Here, we show that murine 3T3-L1 fibroblasts have the machinery to bind, synthesize and degrade AEA, and that their differentiation into adipocytes increases by approximately twofold the binding efficiency of cannabinoid receptors (CBR), and by approximately twofold and approximately threefold, respectively, the catalytic efficiency of the AEA transporter and AEA hydrolase. In contrast, the activity of the AEA synthetase and the binding efficiency of vanilloid receptor were not affected by the differentiation process. In addition, we demonstrate that AEA increases by approximately twofold insulin-stimulated glucose uptake in differentiated adipocytes, according to a CB1R-dependent mechanism that involves nitric oxide synthase, but not lipoxygenase or cyclooxygenase. We also show that AEA binding to peroxisome proliferator-activated receptor-gamma, known to induce differentiation of 3T3-L1 fibroblasts into adipocytes, is not involved in the stimulation of glucose uptake.

Human adipose tissue binds and metabolizes the endocannabinoids anandamide and 2-arachidonoylglycerol.

Endocannabinoids are a group of biologically active endogenous lipids that have recently emerged as important mediators in energy balance control. The two best studied endocannabinoids, anandamide (N-arachidonoylethanolamine, AEA) and 2-arachidonoylglycerol (2-AG) are the endogenous ligands of the central and peripheral cannabinoid receptors. Furthermore, AEA binds to the transient receptor potential vanilloid type-1 (TRPV1), a capsaicin-sensitive, non-selective cation channel. The synthesis of these endocannabinoids is catalyzed by the N-acylphosphatidylethanolamine-selective phospholipase D (NAPE-PLD) and the sn-1-selective diacylglycerol lipase (DAGL), whereas their degradation is accomplished by the fatty acid amide hydrolase (FAAH) and the monoglyceride lipase (MGL), respectively. We investigated the presence of a functional endocannabinoid system in human adipose tissue from seven healthy subjects. Subcutaneous abdominal adipose tissue underwent biochemical and molecular biology analyses, aimed at testing the expression of this system and its functional activity. AEA and 2-AG levels were detected and quantified by HPLC. Real time PCR analyzed the expression of the endocannabinoid system and immunofluorescence assays showed the distribution of its components in the adipose tissue. Furthermore, binding assay for the cannabinoid and vanilloid receptors and activity assay for each metabolic enzyme of the endocannabinoid system gave clear evidence of a fully operating system. The data presented herein show for the first time that the human adipose tissue is able to bind AEA and 2-AG and that it is endowed with the biochemical machinery to metabolize endocannabinoids.

New insights into endocannabinoid degradation and its therapeutic potential.

Endocannabinoids are amides, esters and ethers of long chain polyunsaturated fatty acids, which act as new lipidic mediators. Anandamide (N-arachidonoylethanolamine; AEA) and 2-arachidonoylglycerol (2-AG) are the main endogenous agonists of cannabinoid receptors, able to mimic several pharmacological effects of (-)-Delta9-tetrahydrocannabinol (THC), the active principle of Cannabis sativa preparations like hashish and marijuana. The activity of AEA and 2-AG at their receptors is limited by cellular uptake through an anandamide membrane transporter (AMT), followed by intracellular degradation. A fatty acid amide hydrolase (FAAH) is the main AEA hydrolase, whereas a monoacylglycerol lipase (MAGL) is critical in degrading 2-AG. Here, we will review growing evidence that demonstrates that these hydrolases are pivotal regulators of the endogenous levels of AEA and 2-AG in vivo, overall suggesting that specific inhibitors of AMT, FAAH or MAGL may serve as attractive therapeutic targets for the treatment of human disorders. Recently, the N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD), which synthesizes AEA from N-arachidonoylphosphatidylethanolamine (NArPE), and the diacylglycerol lipase (DAGL), which generates 2-AG from diacylglycerol (DAG) substrates, have been characterized. The role of these synthetic routes in maintaining the endocannabinoid tone in vivo will be discussed. Finally, the effects of inhibitors of endocannabinoid degradation in animal models of human disease will be reviewed, with an emphasis on their ongoing applications in anxiety, cancer and neurodegenerative disorders.

Self-rated quality of life in celiac disease.

As much as 1% of the gluten-consuming world is gluten-intolerant. New screening methods are increasingly identifying gluten intolerance in individuals previously free from health problems. The often-abrupt major change in diet may adversely affect the patient's quality of life. Our aim was to evaluate self-perceived quality of life in a large cohort of adult celiac patients after at least one year of a gluten-free diet. In all 581 members (410 females) of five regional celiac societies were on a gluten-free regimen for at least one year. In this cross-sectional study, a modified version of the Zung Self-Rating Depression Scale was administered to the 581 patients from five Italian regions. Most patients correctly defined celiac disease, and compliance with the gluten-free diet was high, although reporting bias cannot be excluded. Most felt well (83.6% "very well" and "well"); consequently, anxiety and depression scores were low. Happiness also scored low. Most participants did not feel that a gluten-free life differentiated them from the general population. Women and patients diagnosed after 20 years of age had better dietary compliance, but more problems in their social life. Happiness scores were higher in patients diagnosed before 20 years of age. Anxiety and depression were infrequent in this group; however, anxiety was frequently related to feeling different from the general population, and depression to an unsatisfactory sexual life. In conclusion, celiac disease does not appear to be associated to a low level of self-perceived quality of life in members of the Italian Celiac Society.

Appropriateness of urea breath test: a prospective observational study based on Maastricht 2000 guidelines.

BACKGROUND: The urea breath test is routinely used for diagnosing or confirming the eradication of Helicobacter pylori. AIM: To evaluate the appropriateness of urea breath test referrals. METHODS: The age, sex, symptoms, endoscopic findings, use of non-steroidal anti-inflammatory drugs, family history of gastric cancer or H. pylori infection and concomitant diseases of patients referred for urea breath testing in a 1-year period were recorded. The appropriateness of urea breath test referrals was judged according to Maastricht guidelines. RESULTS: One thousand, three hundred and twenty subjects (47 +/- 16 years) were referred in 2001: 578 (43.8%) for the diagnosis and 742 (56.2%) for confirmation of the eradication of H. pylori. The urea breath test was considered to be appropriate in 836 (63.3%) patients, inappropriate in 192 (14.5%) and appropriate but avoidable in 292 (22.1%). The appropriateness ratios of urea breath test referrals were 4.6 and 9.0 (P < 0.0001) for general practitioners and gastroenterologists, respectively. Of the patients (n=230) with un investigated dyspepsia, who underwent urea breath testing according to a 'test and treat' strategy, 98 (42.6%) presented at least one risk factor for organic disease. CONCLUSIONS: In Italy, nearly 36% of urea breath test referrals are inappropriate or could be avoided if all dyspeptic patients with risk factors were referred for endoscopy or all dyspeptic patients undergoing endoscopy were tested for H. pylori infection with biopsy methods. Both general practitioners and, to a lesser extent, gastroenterologists require educational programmes to deal effectively with H. pylori.

The first large population based twin study of coeliac disease.

BACKGROUND AND AIMS: The genetic load in coeliac disease has hitherto been inferred from case series or anecdotally referred twin pairs. We have evaluated the genetic component in coeliac disease by estimating the concordance rate for the disease among twin pairs in a large population based study. METHODS: The Italian Twin Registry was matched with the membership lists of a patient support group. Forty seven twin pairs were recruited and screened for antiendomysial (EMA) and antihuman-tissue transglutaminase (anti-tTG) antibodies; zygosity was verified by DNA fingerprinting and twins were typed for HLA class II DRB1 and DQB1 molecules. RESULTS: Concordance rates for coeliac disease differ significantly between monozygotic (MZ) (0.86 probandwise and 0.75 pairwise) and dizygotic (DZ) (0.20 probandwise and 0.11 pairwise) twins. This is the highest concordance so far reported for a multifactorial disease. A logistic regression model, adjusted for age, sex, number of shared HLA haplotypes, and zygosity, showed that genotypes DQA1*0501/DQB1*0201 and DQA1*0301/DQB1*0302 (encoding for heterodimers DQ2 and DQ8, respectively) conferred to the non-index twin a risk of contracting the disease of 3.3 and 1.4, respectively. The risk of being concordant for coeliac disease estimated for the non-index twin of MZ pairs was 17 (95% confidence interval 2.1-134), independent of the DQ at risk genotype. CONCLUSION: This study provides substantial evidence for a very strong genetic component in coeliac disease, which is only partially due to the HLA region.