Variation in the human cannabinoid receptor CNR1 gene modulates gaze duration for happy faces.

  “From an early age, humans look longer at preferred stimuli and also typically look longer at facial expressions of emotion, particularly happy faces. Atypical gaze patterns towards social stimuli are common in autism spectrum conditions (ASC). However, it is unknown whether gaze fixation patterns have any genetic basis. In this study, we tested whether variations in the cannabinoid receptor 1 (CNR1) gene are associated with gaze duration towards happy faces. This gene was selected because CNR1 is a key component of the endocannabinoid system, which is involved in processing reward, and in our previous functional magnetic resonance imaging (fMRI) study, we found that variations in CNR1 modulate the striatal response to happy (but not disgust) faces. The striatum is involved in guiding gaze to rewarding aspects of a visual scene. We aimed to validate and extend this result in another sample using a different technique (gaze tracking).

One of the key molecular systems involved in the functioning of the striatal circuit is the endocannabinoid system. It is a neuropeptidergic circuit involved in reward processing and works in tandem with the mesolimbic dopaminergic system. Expressed selectively in the brain, the cannabinoid receptor 1 (CNR1) is the best-studied molecule of this system.

This finding suggests a role for CNR1 in social reward processing and could have significance for clinical conditions such ASC, which are marked by a deficit in social reward processing as well as atypical responses to facial expressions of emotion.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155489/

Variations in the human cannabinoid receptor (CNR1) gene modulate striatal responses to happy faces.

Abstract

“Happy facial expressions are innate social rewards and evoke a response in the striatum, a region known for its role in reward processing in rats, primates and humans. The cannabinoid receptor 1 (CNR1) is the best-characterized molecule of the endocannabinoid system, involved in processing rewards. We hypothesized that genetic variation in human CNR1 gene would predict differences in the striatal response to happy faces. In a 3T functional magnetic resonance imaging (fMRI) scanning study on 19 Caucasian volunteers, we report that four single nucleotide polymorphisms (SNPs) in the CNR1 locus modulate differential striatal response to happy but not to disgust faces. This suggests a role for the variations of the CNR1 gene in underlying social reward responsivity. Future studies should aim to replicate this finding with a balanced design in a larger sample, but these preliminary results suggest neural responsivity to emotional and socially rewarding stimuli varies as a function of CNR1 genotype. This has implications for medical conditions involving hypo-responsivity to emotional and social stimuli, such as autism.”

http://www.ncbi.nlm.nih.gov/pubmed/16623851

Cannabinoid 1 (CB1) receptor–pharmacology, role in pain and recent developments in emerging CB1 agonists.

Abstract

“Cannabinoids are antinociceptive in animal models of acute pain, tissue injury and nerve injury induced nociception and act via their cognate receptors, cannabinoid receptor 1 and 2. This review examines the underlying biology of the endocannabinoids and behavioural, neurophysiological, neuroanatomical evidence supporting the notion of pain modulation by these ligands with a focus on the current evidence encompassing the pharmacological characterization of CB1 agonists in this therapy. Separating the psychotropic effects of CB1 agonists from their therapeutic benefits is the major challenge facing researchers in the field today and with the discovery of peripherally acting agonists there seems to be a ray of hope emerging for the diverse potential therapeutic applications of this class of ligands.”

http://www.ncbi.nlm.nih.gov/pubmed/21631407

CB2 cannabinoid receptor-mediated peripheral antinociception.

  “Cannabinoid receptor agonists diminish responses to painful stimuli. Extensive evidence implicates the CB(1) receptor in the production of antinociception. However, the capacity of CB(2) receptors, which are located outside the central nervous system (CNS), to produce antinociception is not known. Using AM1241, a CB(2) receptor-selective agonist, we demonstrate that CB(2) receptors produce antinociception to thermal stimuli… Peripheral antinociception without CNS effects is consistent with the peripheral distribution of CB(2) receptors. CB(2) receptor agonists may have promise clinically for the treatment of pain without CNS cannabinoid side effects.”

http://www.ncbi.nlm.nih.gov/pubmed/11514083

CB1 cannabinoid receptor antagonism: a new strategy for the treatment of liver fibrosis.

“Hepatic fibrosis, the common response associated with chronic liver diseases, ultimately leads to cirrhosis, a major public health problem worldwide. We recently showed that activation of hepatic cannabinoid CB2 receptors limits progression of experimental liver fibrosis… In conclusion, our study shows that CB1 receptor antagonists hold promise for the treatment of liver fibrosis.”

http://www.ncbi.nlm.nih.gov/pubmed/16715087

Antagonism of the cannabinoid CB-1 receptor protects rat liver against ischaemia-reperfusion injury complicated by endotoxaemia.

  “Endotoxaemia can complicate hepatic ischaemia-reperfusion (IR) injury. Endocannabinoids appear to modulate the haemodynamic alterations and cytokine response induced by lipopolysaccharide (LPS). Thus, we aimed to determine the effect of the endocannabinoid CB1-receptor antagonist Rimonabant in a model of hepatic IR injury complicated by endotoxaemia.”

“Liver injury and neutrophil infiltration occurring in the late-phase of LPS-enhanced IR were significantly reduced by CB1-receptor antagonism.”

“CONCLUSIONS:

This study demonstrates that CB1-receptor antagonism protects the liver against LPS-enhanced IR injury by interfering with the inflammatory response that causes the late, neutrophil-dependent phase of reperfusion injury, although the prevention of the transient endotoxin-related hypotension occurring early during reperfusion may be also involved.”

http://www.ncbi.nlm.nih.gov/pubmed/19282305

Cannabinoid type 1 receptor antagonism delays ascites formation in rats with cirrhosis.

  “Endocannabinoids contribute to hemodynamic abnormalities of cirrhosis. Whether this favors renal sodium retention and ascites formation is unknown. We determined whether cannabinoid type 1 receptor antagonism prevents sodium retention and ascites formation in preascitic cirrhotic rats.”

 

“Cannabinoid type 1 receptor antagonism delays ascites formation in rats with cirrhosis.”

 

“Rimonabant improves sodium balance and delays decompensation in preascitic cirrhosis. This is achieved though an improvement in systemic and renal hemodynamics, although it cannot be excluded that the antifibrotic effect of the drug may play a role.”

http://www.ncbi.nlm.nih.gov/pubmed/19208344

Reversal of liver fibrosis by the antagonism of endocannabinoid CB1 receptor in a rat model of CCl(4)-induced advanced cirrhosis.

Abstract

“The endocannabinoid system is involved in the pathogenesis of liver fibrosis. Although many substances have been proved to reduce fibrosis in experimental models of chronic liver injury, most of them appear to be effective only if given as a prophylactic or early treatment. This study aimed to explore the effect of pharmacological antagonism of the endocannabinoid cannabinoid type 1 (CB1) receptor started after the stage of full-blown cirrhosis had been reached. Wistar-Han rats with carbon tetrachloride (CCl(4))-induced cirrhosis were randomized to receive the CB1 receptor antagonist Rimonabant (10 mg/kg/day) or the vehicle for 2 weeks. Age-matched healthy rats served as controls. Liver fibrosis was assessed using Sirius red staining, hydroxyproline concentration and α-smooth muscle actin expression. Hepatic gene expression of mediators of fibrogenesis and inflammation were evaluated by real-time PCR. We also assessed the hepatic expression of CB1 and CB2 receptors and that of the enzymes implicated in the endocannabinoid metabolism. Fibrosis was significantly reduced in rats treated with Rimonabant compared with rats receiving the vehicle. CB1 receptor antagonism limited the gene upregulation of fibrogenic and inflammatory mediators occurring in untreated cirrhotic rats. CB1 and CB2 receptor expression was increased in cirrhotic animals. Interestingly, pharmacological CB1 receptor antagonism was associated with a further induction of the CB2 receptor expression. Regression of fibrosis can be achieved by pharmacological blockade of the CB1 receptor even when started in an advanced stage of the disease. This effect is associated with the suppression of pro-fibrogenic and inflammatory mediators and may have been indirectly favoured by the induction of CB2 receptor expression.”

http://www.ncbi.nlm.nih.gov/pubmed/22184091

The endocannabinoid system as a key mediator during liver diseases: new insights and therapeutic openings

  “Alcohol abuse, viral hepatitis and non-alcoholic fatty liver disease (NAFLD) represent the major causes of chronic liver injury, resulting in progressive accumulation of fibrosis within the liver parenchyma. Progression to cirrhosis exposes patients to life-threatening complications of portal hypertension liver failure and hepatic encephalopathy, and to a high risk of developing hepatocellular carcinoma. Overall, chronic liver diseases represent a major health problem with an estimated rate of death in the range of 1 400 000 per year worldwide. Recent findings have revealed a role of endocannabinoids and their receptors in the pathogenesis of several key steps of acute and chronic liver injury, therefore identifying pharmacological modulation of cannabinoid receptors as an attractive strategy for the management of morbidity related to liver injury .”

 

“Chronic liver diseases represent a major health problem due to cirrhosis and its complications. During the last decade, endocannabinoids and their receptors have emerged as major regulators of several pathophysiological aspects associated with chronic liver disease progression. Hence, hepatic cannabinoid receptor 2 (CB2) receptors display beneficial effects on alcoholic fatty liver, hepatic inflammation, liver injury, regeneration and fibrosis. Cannabinoid receptor 1 (CB1) receptors have been implicated in the pathogenesis of several lesions such as alcoholic and metabolic steatosis, liver fibrogenesis, or circulatory failure associated with cirrhosis. Although the development of CB1 antagonists has recently been suspended due to the high incidence of central side effects, preliminary preclinical data obtained with peripherally restricted CB1 antagonists give real hopes in the development of active CB1 molecules devoid of central adverse effects. CB2-selective molecules may also offer novel perspectives for the treatment of liver diseases, and their clinical development is clearly awaited. Whether combined treatment with a peripherally restricted CB1 antagonist and a CB2 agonist might result in an increased therapeutic potential will warrant further investigation.”

 

“Cannabis Sativa has a long-standing history of recreational and therapeutic use, starting over 200 years ago. Understanding of pathways involved in the pharmacological properties of cannabinoids has only emerged with the identification of an endocannabinoid system that comprises at least two specific G-protein coupled receptors [cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2)], their endogenous lipidic ligands (endocannabinoids), and enzymes involved in endocannabinoid synthesis and degradation.”

“Over the past 10 years, the endocannabinoid system has emerged as a major player in the pathogenesis of liver diseases. CB1 receptors have been implicated in the pathogenesis of several lesions such as liver fibrogenesis, alcoholic and metabolic steatosis, or circulatory failure associated with cirrhosis. In contrast, stimulation of hepatic CB2 receptors is emerging as an overall protective pathway with antifibrogenic properties and beneficial effects on liver inflammation, alcoholic fatty liver and hepatocyte survival and regeneration. Exciting therapeutic developments expected with the availability of CB1 receptor antagonists have been put to a hold, due to the high incidence of central side effects of first generation compounds. Fortunately, CB1 antagonists devoid of brain penetrance are increasingly being synthetized and initial results suggest that they exhibit beneficial effects expected from previous studies. The clinical development of CB2-selective agonists is also eagerly awaited.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3165953/

Endocannabinoids and Liver Disease. II. Endocannabinoids in the pathogenesis and treatment of liver fibrosis

“Plant-derived cannabinoids such as delta-9-tetrahydrocannabinol (THC) have been used for medicinal purposes for thousands of years. Two G protein-coupled receptors termed CB1 and CB2 were identified in the early 1990s as receptors for cannabinoids…”

“Hepatic fibrosis is the response of the liver to chronic injury and is associated with portal hypertension, progression to hepatic cirrhosis, liver failure, and high incidence of hepatocellular carcinoma. On a molecular level, a large number of signaling pathways have been shown to contribute to the activation of fibrogenic cell types and the subsequent accumulation of extracellular matrix in the liver. Recent evidence suggests that the endocannabinoid system is an important part of this complex signaling network. In the injured liver, the endocannabinoid system is upregulated both at the level of endocannabinoids and at the endocannabinoid receptors CB1 and CB2. The hepatic endocannabinoid system mediates both pro- and antifibrogenic effects by activating distinct signaling pathways that differentially affect proliferation and death of fibrogenic cell types. Here we will summarize current findings on the role of the hepatic endocannabinoid system in liver fibrosis and discuss emerging options for its therapeutic exploitation.”

“There is overwhelming evidence that the endocannabinoid system plays a major role in the pathophysiology of chronic liver injury and wound healing responses and that modulation of the endocannabinoid system may be exploited for the treatment of liver fibrosis. Among all candidates, CB1 represents the most promising target for antifibrotic therapies. In addition to the antifibrogenic effects of CB1 blockade, one can expect positive effects on other complications such as portal hypertension, ascites formation, hepatic encephalopathy, and cardiomyopathy. Moreover, CB1 antagonism appears to have beneficial effects on hepatic steatosis…”

http://ajpgi.physiology.org/content/294/2/G357.long