Cannabinoid receptor type 2 functional variant influences liver damage in children with non-alcoholic fatty liver disease. PLoS One. 2012;7:e42259. [PMID: 22927922 PMCID: PMC3426511 DOI: 10.1371/journal.pone.0042259]

Single nucleotide polymorphisms in the cannabinoid CB2 receptor: Molecular pharmacology and disease associations

Preclinical evidence implicating cannabinoid receptor 2 (CB2) in various diseases has led researchers to question whether CB2 genetics influence aetiology or progression. Associations between conditions and genetic loci are often studied via single nucleotide polymorphism (SNP) prevalence in case versus control populations. In the CNR2 coding exon, ~36 SNPs have high overall population prevalence (minor allele frequencies [MAF] ~37%), including non-synonymous SNP (ns-SNP) rs2501432 encoding CB2 63Q/R. Interspersed are ~27 lower frequency SNPs, four being ns-SNPs. CNR2 introns also harbour numerous SNPs. This review summarises CB2 ns-SNP molecular pharmacology and evaluates evidence from ~70 studies investigating CB2 genetic variants with proposed linkage to disease. Although CNR2 genetic variation has been associated with a wide variety of conditions, including osteoporosis, immune-related disorders, and mental illnesses, further work is required to robustly validate CNR2 disease links and clarify specific mechanisms linking CNR2 genetic variation to disease pathophysiology and potential drug responses.

Exploring the role of genetic variations in NAFLD: implications for disease pathogenesis and precision medicine approaches

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases, affecting more than one-quarter of people worldwide. Hepatic steatosis can progress to more severe forms of NAFLD, including NASH and cirrhosis. It also may develop secondary diseases such as diabetes and cardiovascular disease. Genetic and environmental factors regulate NAFLD incidence and progression, making it a complex disease. The contribution of various environmental risk factors, such as type 2 diabetes, obesity, hyperlipidemia, diet, and sedentary lifestyle, to the exacerbation of liver injury is highly understood. Nevertheless, the underlying mechanisms of genetic variations in the NAFLD occurrence or its deterioration still need to be clarified. Hence, understanding the genetic susceptibility to NAFLD is essential for controlling the course of the disease. The current review discusses genetics' role in the pathological pathways of NAFLD, including lipid and glucose metabolism, insulin resistance, cellular stresses, and immune responses. Additionally, it explains the role of the genetic components in the induction and progression of NAFLD in lean individuals. Finally, it highlights the utility of genetic knowledge in precision medicine for the early diagnosis and treatment of NAFLD patients.

Increased expression of CB2 receptor in the intestinal biopsies of children with inflammatory bowel disease

OBJECTIVES

The Cannabinoid Receptor type 2 (CB2) is involved in inflammation and immune cell modulation. In previous studies, we demonstrated the association between the CNR2 rs35761398 polymorphism and the risk for pediatric inflammatory bowel disease (IBD). In this study, we analyzed the intestinal biopsies from Crohn disease (CD) and ulcerative colitis (UC) pediatric patients at the diagnosis to evaluate the expression of CB2 and several factors associated with IBD inflammatory pathways.

METHODS

We enrolled five patients with CD, five with UC, and five controls (CTR). We analyzed ileum and rectum biopsies from patients of each group evaluating the expression of CB2, Toll-like receptor 4, interleukin-6, and interleukin-1β by western blot and immunofluorescence.

RESULTS

Western blot analysis showed a significant increase of CB2 in the CD ileum and in the UC rectum biopsies and an increase of TLR4 in the UC rectum. We also observed a significant over-expression of the IL-6 in UC rectum. The immunofluorescence analysis confirmed western blot data, showing also a T-lymphocytes infiltration colocalized with CB2 expression in the CD ileum and UC rectum.

CONCLUSIONS

Our results show an upregulation of CB2 in pediatric IBD, which might have implications for drug discovery.

IMPACT

The Cannabinoid Receptor type 2 (CB2) is involved in the inflammation and modulation of the immune response in pediatric inflammatory bowel disease (IBD). CB2 receptor is more expressed in the inflamed intestine of pediatric IBD patients. CB2 could be used as a potential therapeutic target to reduce IBD-related inflammatory state in childhood.

Safety and Efficacy of Lenabasum, a Cannabinoid Receptor Type 2 Agonist, in Patients with Dermatomyositis with Refractory Skin Disease: A Randomized Clinical Trial

BACKGROUND

Treatment options are limited for skin disease in dermatomyositis. Lenabasum is a cannabinoid receptor type 2 agonist that triggers the resolution of inflammation.

OBJECTIVE

The objective of this study was to evaluate the safety and efficacy of lenabasum in patients with refractory cutaneous dermatomyositis.

DESIGN

This study was a single-center, double-blind, randomized, placebo-controlled phase 2 study conducted from July 2015 to August 2017.

POPULATION

The population included subjects aged ≥18 years with at least moderately active dermatomyositis skin activity by Cutaneous Dermatomyositis Disease Area and Severity Index activity ≥ 14 and failure or intolerance to hydroxychloroquine.

INTERVENTION

Participants received 20 mg lenabasum daily for 28 days and then 20 mg twice per day for 56 days or placebo.

MAIN OUTCOMES AND MEASURES

The primary outcome was a change in Cutaneous Dermatomyositis Disease Area and Severity Index activity. Safety and other secondary efficacy assessments were performed till day 113.

RESULTS

A total of 22 subjects were randomized to lenabasum (n = 11) or placebo (n = 11). No serious or severe adverse events were related to lenabasum, and no participants discontinued the study. The adjusted least-squares mean for Cutaneous Dermatomyositis Disease Area and Severity Index activity decreased more for lenabasum, and the difference was significant on day 113 (least-squares mean [standard error] difference = ‒6.5 [3.1], P = 0.038). Numerically greater improvements were seen in multiple secondary efficacy outcomes and biomarkers with lenabasum.

CONCLUSION

Lenabasum treatment was well tolerated and was associated with greater improvement in Cutaneous Dermatomyositis Disease Area and Severity Index activity and multiple efficacy outcomes.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov, NCT02466243.

Effects of CB2 and TRPV1 Stimulation on Osteoclast Overactivity Induced by Iron in Pediatric Inflammatory Bowel Disease

BACKGROUND

The reduction of bone mineral density and osteoporosis have high impacts on the health of patients with inflammatory bowel diseases (IBD). We have previously shown that a dysregulated iron metabolism occurs in IBD and leads to a decrease in circulating iron concentration and excessive intracellular sequestration of iron. Studies suggest that iron overload significantly affects the bone, accelerating osteoclast (OC) differentiation and activation, promoting bone resorption. Moreover, we demonstrated that iron overload causes OC overactivity. The cannabinoid receptor type 2 (CB2) and the transient receptor potential vanilloid type-1 (TRPV1) are potential therapeutic targets for bone diseases. The aim of this study was to evaluate the roles of CB2 and TRPV1 receptors and of iron in the development of osteoporosis in pediatric IBD.

METHODS

We differentiated OCs from peripheral blood mononuclear cells of patients with IBD and healthy donors and evaluated CB2 and TRPV1 receptor expression; OC activity, and iron metabolism by Western blot, TRAP assays, bone resorption assays, and iron assays. Moreover, we analyzed the effects of the pharmacological modulation of CB2 and TRPV1 receptors on OC activity and on the iron metabolism.

RESULTS

We confirmed the well-known roles of CB2 and TRPV1 receptors in bone metabolism and suggested that their stimulation can reduce the OC overactivity induced by iron, providing new insights into the pathogenesis of pediatric IBD-related bone resorption.

CONCLUSIONS

Stimulation of CB2 and TRPV1 could reduce IBD-related osteoporosis due to their direct effects on OC activity and to modulating the iron metabolism.

Effects of CB2 Receptor Modulation on Macrophage Polarization in Pediatric Celiac Disease

Celiac Disease (CD) represents an autoimmune disorder triggered by the exposure to gluten in genetically susceptible individuals. Recent studies suggest the involvement of macrophages in CD pathogenesis. Macrophages are immune cells, present as pro-inflammatory classically activated macrophages (M1) or as anti-inflammatory alternatively activated macrophages (M2). The Cannabinoid Receptor 2 (CB2) has important anti-inflammatory and immunoregulatory properties. We previously demonstrated that a common CB2 functional variant, Q63R, causing CB2 reduced function, is associated with several inflammatory and autoimmune diseases The first aim of this study was to investigate the phenotype of macrophages isolated from peripheral blood of CD patients and CB2 expression. The second aim was to evaluate the effects of CB2 pharmacological modulation on CD macrophage polarization. Moreover, by an in vitro model of “immunocompetent gut” we investigated the role of CD macrophages in inducing intestinal barrier damage and the possibility to restore its functionality modulating their polarization. We found an increased expression of M1 macrophages and a CB2 reduced expression. We also demonstrated CD M1 macrophages in inducing the typical mucosal barrier damage of CD. CB2 stimulation switches macrophage polarization towards the anti-inflammatory M2 phenotype thus reducing inflammation but also limiting the epithelial dysfunction. Therefore, we suggest CB2 receptor as a possible novel therapeutic target for CD by regulating macrophages polarization and by preventing mucosal barrier damage.

Signaling through the type 2 cannabinoid receptor regulates the severity of acute and chronic graft-versus-host disease

Graft-versus-host disease (GVHD) pathophysiology is a complex interplay between cells that comprise the adaptive and innate arms of the immune system. Effective prophylactic strategies are therefore contingent upon approaches that address contributions from both immune cell compartments. In the current study, we examined the role of the type 2 cannabinoid receptor (CB2R), which is expressed on nearly all immune cells, and demonstrated that absence of the CB2R on donor CD4+ or CD8+ T cells or administration of a selective CB2R pharmacological antagonist exacerbated acute GVHD lethality. This was accompanied primarily by the expansion of proinflammatory CD8+ T cells, indicating that constitutive CB2R expression on T cells preferentially regulated CD8+ T-cell alloreactivity. Using a novel CB2ReGFP reporter mouse, we observed significant loss of CB2R expression on T cells, but not macrophages, during acute GVHD, indicative of differential alterations in receptor expression under inflammatory conditions. Therapeutic targeting of the CB2R with the agonists Δ9-tetrahydrocannabinol (THC) and JWH-133 revealed that only THC mitigated lethal T cell-mediated acute GVHD. Conversely, only JWH-133 was effective in a sclerodermatous chronic GVHD model where macrophages contributed to disease biology. In vitro, both THC and JWH-133 induced arrestin recruitment and extracellular regulated kinase phosphorylation via CB2R, but THC had no effect on CB2R-mediated inhibition of adenylyl cyclase. This study shows that the CB2R plays a critical role in the regulation of GVHD and suggests that effective therapeutic targeting is dependent upon agonist signaling characteristics and receptor selectivity in conjunction with the composition of pathogenic immune effector cells.

Cannabinoid Receptor Type 2: A Possible Target in SARS-CoV-2 (CoV-19) Infection?

In late December 2019, a novel coronavirus (SARS-CoV-2 or CoV-19) appeared in Wuhan, China, causing a global pandemic. SARS-CoV-2 causes mild to severe respiratory tract inflammation, often developing into lung fibrosis with thrombosis in pulmonary small vessels and causing even death. COronaVIrus Disease (COVID-19) patients manifest exacerbated inflammatory and immune responses, cytokine storm, prevalence of pro-inflammatory M1 macrophages and increased levels of resident and circulating immune cells. Men show higher susceptibility to SARS-CoV-2 infection than women, likely due to estrogens production. The protective role of estrogens, as well as an immune-suppressive activity that limits the excessive inflammation, can be mediated by cannabinoid receptor type 2 (CB2). The role of this receptor in modulating inflammation and immune response is well documented in fact in several settings. The stimulation of CB2 receptors is known to limit the release of pro-inflammatory cytokines, shift the macrophage phenotype towards the anti-inflammatory M2 type and enhance the immune-modulating properties of mesenchymal stromal cells. For these reasons, we hypothesize that CB2 receptor can be a therapeutic target in COVID-19 pandemic emergency.

Nonalcoholic Fatty Liver Disease in Children: Unique Considerations and Challenges

Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence in concert with the global epidemic of obesity and is being diagnosed at increasingly younger ages. The unique histologic features and early presentation of disease in pediatrics suggest that children and adults may differ with regard to etiopathogenesis, with children displaying a greater vulnerability to genetic and environmental factors. Of significant relevance to pediatrics, in utero and perinatal stressors may alter the lifelong health trajectory of a child, increasing the risk of NAFLD and other cardiometabolic diseases. The development and progression of disease in childhood is likely to carry increased risk of long-term morbidity. Novel biomarkers and therapeutic agents are needed to avoid the otherwise inevitable health and societal consequences of this rapidly expanding pediatric population.

New Perspectives on Genetic Prediction for Pediatric Metabolic Associated Fatty Liver Disease

Non-alcoholic or recently re-defined metabolic associated fatty liver disease (MAFLD), a spectrum of progressive hepatic disease, has become a public health issue in obese children and adolescents. MAFLD is a complex metabolic disease strongly associated with obesity and insulin resistance. It is not known why not every obese subject will develop MAFLD. Different ethnic/racial groups display differences in MAFLD prevalence, indicating genetic factor plays a role. In the past two decades, sequence variations in genetic loci, including PNPLA3, TM6SF2, GCKR, MBOAT7, HSD17B13, etc. have been shown to confer susceptibility to MAFLD in children and adults. This review article provides an updated viewpoint of genetic predictors related to pediatric MAFLD. We discuss whether these susceptible genes can be clinically used for risk stratification and personalized care. Understanding human genetics and molecular mechanisms can give important information not only for prediction of risk but also on how to design drugs. In view of current epidemic of MAFLD worldwide, it is necessary to identify which children with MAFLD progress rapidly and need earlier intervention. In the future, a comprehensive analysis of individualized genetic and environmental factors may help assess the risk of children with MAFLD and personalize their treatment.

The Endocannabinoid System in Pediatric Inflammatory and Immune Diseases

Endocannabinoid system consists of cannabinoid type 1 (CB1) and cannabinoid type 2 (CB2) receptors, their endogenous ligands, and the enzymes responsible for their synthesis and degradation. CB2, to a great extent, and CB1, to a lesser extent, are involved in regulating the immune response. They also regulate the inflammatory processes by inhibiting pro-inflammatory mediator release and immune cell proliferation. This review provides an overview on the role of the endocannabinoid system with a major focus on cannabinoid receptors in the pathogenesis and onset of inflammatory and autoimmune pediatric diseases, such as immune thrombocytopenia, juvenile idiopathic arthritis, inflammatory bowel disease, celiac disease, obesity, neuroinflammatory diseases, and type 1 diabetes mellitus. These disorders have a high social impact and represent a burden for the healthcare system, hence the importance of individuating more innovative and effective treatments. The endocannabinoid system could address this need, representing a possible new diagnostic marker and therapeutic target.

Endocannabinoid System in Hepatic Glucose Metabolism, Fatty Liver Disease, and Cirrhosis

There is growing evidence that glucose metabolism in the liver is in part under the control of the endocannabinoid system (ECS) which is also supported by its presence in this organ. The ECS consists of its cannabinoid receptors (CBRs) and enzymes that are responsible for endocannabinoid production and metabolism. ECS is known to be differentially influenced by the hepatic glucose metabolism and insulin resistance, e.g., cannabinoid receptor type 1(CB₁) antagonist can improve the glucose tolerance and insulin resistance. Interestingly, our own study shows that expression patterns of CBRs are influenced by the light/dark cycle, which is of significant physiological and clinical interest. The ECS system is highly upregulated during chronic liver disease and a growing number of studies suggest a mechanistic and therapeutic impact of ECS on the development of liver fibrosis, especially putting its receptors into focus. An opposing effect of the CBRs was exerted via the CB₁ or CB₂ receptor stimulation. An activation of CB₁ promoted fibrogenesis, while CB₂ activation improved antifibrogenic responses. However, underlying mechanisms are not yet clear. In the context of liver diseases, the ECS is considered as a possible mediator, which seems to be involved in the synthesis of fibrotic tissue, increase of intrahepatic vascular resistance and subsequently development of portal hypertension. Portal hypertension is the main event that leads to complications of the disease. The main complication is the development of variceal bleeding and ascites, which have prognostic relevance for the patients. The present review summarizes the current understanding and impact of the ECS on glucose metabolism in the liver, in association with the development of liver cirrhosis and hemodynamics in cirrhosis and its complication, to give perspectives for development of new therapeutic strategies.

Maternal high-fat diet consumption induces sex-dependent alterations of the endocannabinoid system and redox homeostasis in liver of adult rat offspring

Maternal diet plays a critical role in health development. Perinatal overnutrition induces metabolic dysfunctions and obesity in the offspring. Obesity is associated with endocannabinoid system (ECS) over activation and oxidative stress. Liver ECS activation induces hepatic steatosis, inflammation and fibrosis while the antagonism of cannabinoid receptors ameliorates these alterations. Here, we investigated the effect of perinatal maternal high-fat diet (HF, 29% of calories as fat) on the ECS and antioxidant system in liver of male and female adult rat offspring (180 days old). Maternal HF diet increased hepatic cannabinoid receptors, ECS metabolizing enzymes and triglyceride content, with male offspring more affected. ECS changes are likely independent of estradiol serum levels but associated with increased hepatic content of estrogen receptor, which can stimulate the expression of ECS components. Differently, maternal HF diet decreased the activity of the antioxidant enzymes glutathione peroxidase, superoxide dismutase and catalase, and increased oxidative stress markers in both sexes. Alterations in the redox homeostasis were associated with mitochondria damage but not with liver fibrosis. Our data suggest that maternal HF diet induces ECS over activation in adulthood, and that male offspring are at higher risk to develop liver disease compared with female rats.

The Genetics of Pediatric Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children. Severe fibrosis and cirrhosis are potential consequences of pediatric NAFLD and can occur within a few years of diagnosis. Observations suggest that genetics may be a strong modifying factor in the presentation, severity, and natural history of the disease. There is increasing interest in determining at-risk populations based on genetics in the hope of finding genotypes that correlate to NAFLD phenotype. Ultimately, the hope is to be able to tailor therapeutics to genetic predispositions and decrease disease morbidity in children with NAFLD.

Genome-Wide Associations Related to Hepatic Histology in Nonalcoholic Fatty Liver Disease in Hispanic Boys

OBJECTIVE

To identify genetic loci associated with features of histologic severity of nonalcoholic fatty liver disease in a cohort of Hispanic boys.

STUDY DESIGN

There were 234 eligible Hispanic boys age 2-17 years with clinical, laboratory, and histologic data enrolled in the Nonalcoholic Steatohepatitis Clinical Research Network included in the analysis of 624 297 single nucleotide polymorphisms (SNPs). After the elimination of 4 outliers and 22 boys with cryptic relatedness, association analyses were performed on 208 DNA samples with corresponding liver histology. Logistic regression analyses were carried out for qualitative traits and linear regression analyses were applied for quantitative traits.

RESULTS

The median age and body mass index z-score were 12.0 years (IQR, 11.0-14.0) and 2.4 (IQR, 2.1-2.6), respectively. The nonalcoholic fatty liver disease activity score (scores 1-4 vs 5-8) was associated with SNP rs11166927 on chromosome 8 in the TRAPPC9 region (P = 8.7^-07). Fibrosis stage was associated with SNP rs6128907 on chromosome 20, near actin related protein 5 homolog (p = 9.9^-07). In comparing our results in Hispanic boys with those of previously reported SNPs in adult nonalcoholic steatohepatitis, 2 of 26 susceptibility loci were associated with nonalcoholic fatty liver disease activity score and 2 were associated with fibrosis stage.

CONCLUSIONS

In this discovery genome-wide association study, we found significant novel gene effects on histologic traits associated with nonalcoholic fatty liver disease activity score and fibrosis that are distinct from those previously recognized by adult nonalcoholic fatty liver disease genome-wide association studies.

A Guide to Non-Alcoholic Fatty Liver Disease in Childhood and Adolescence

Non-Alcoholic Fatty Liver Disease (NAFLD) is now the most prevalent form of chronic liver disease, affecting 10%–20% of the general paediatric population. Within the next 10 years it is expected to become the leading cause of liver pathology, liver failure and indication for liver transplantation in childhood and adolescence in the Western world. While our understanding of the pathophysiological mechanisms underlying this disease remains limited, it is thought to be the hepatic manifestation of more widespread metabolic dysfunction and is strongly associated with a number of metabolic risk factors, including insulin resistance, dyslipidaemia, cardiovascular disease and, most significantly, obesity. Despite this, ”paediatric” NAFLD remains under-studied, under-recognised and, potentially, undermanaged. This article will explore and evaluate our current understanding of NAFLD in childhood and adolescence and how it differs from adult NAFLD, in terms of its epidemiology, pathophysiology, natural history, diagnosis and clinical management. Given the current absence of definitive radiological and histopathological diagnostic tests, maintenance of a high clinical suspicion by all members of the multidisciplinary team in primary and specialist care settings remains the most potent of diagnostic tools, enabling early diagnosis and appropriate therapeutic intervention.

Systematic review of genetic association studies involving histologically confirmed non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease has an increasing prevalence in Western countries, affecting up to 20% of the population.

Iron overload causes osteoporosis in thalassemia major patients through interaction with transient receptor potential vanilloid type 1 (TRPV1) channels

The pathogenesis of bone resorption in β-thalassemia major is multifactorial and our understanding of the underlying molecular and cellular mechanisms remains incomplete. Considering the emerging importance of the endocannabinoid/endovanilloid system in bone metabolism, it may be instructive to examine a potential role for this system in the development of osteoporosis in patients with β-thalassemia major and its relationship with iron overload and iron chelation therapy. This study demonstrates that, in thalassemic-derived osteoclasts, tartrate-resistant acid phosphatase expression inversely correlates with femoral and lumbar bone mineral density, and directly correlates with ferritin levels and liver iron concentration. The vanilloid agonist resiniferatoxin dramatically reduces cathepsin K levels and osteoclast numbers in vitro, without affecting tartrate-resistant acid phosphatase expression. The iron chelators deferoxamine, deferiprone and deferasirox decrease both tartrate-resistant acid phosphatase and cathepsin K expression, as well as osteoclast activity. Taken together, these data show that transient receptor potential vanilloid type 1 activation/desensitization influences tartrate-resistant acid phosphatase expression and activity, and this effect is dependent on iron, suggesting a pivotal role for iron overload in the dysregulation of bone metabolism in patients with thalassemia major. Our applied pharmacology provides evidence for the potential of iron chelators to abrogate these effects by reducing osteoclast activity. Whether iron chelation therapy is capable of restoring bone health in humans requires further study, but the potential to provide dual benefits for patients with β-thalassemia major -preventing iron-overload and alleviating associated osteoporotic changes - is exciting.

Nonalcoholic fatty liver disease and the heart in children and adolescents

Over the last two decades, the rise in the prevalence rates of overweight and obesity explains the emergence of nonalcoholic fatty liver disease (NAFLD) as the leading cause of chronic liver disease worldwide. As described in adults, children and adolescents with fatty liver display insulin resistance, glucose intolerance, and dyslipidemia. Thus NAFLD has emerged as the hepatic component of the metabolic syndrome (MetS) and a strong cardiovascular risk factor even at a very early age. Several studies, including pediatric populations, have reported independent associations between NAFLD and markers of subclinical atherosclerosis including impaired flow-mediated vasodilation, increased carotid artery intima-media thickness, and arterial stiffness, after adjusting for cardiovascular risk factors and MetS. Also, it has been shown that NAFLD is associated with cardiac alterations, including abnormal left ventricular structure and impaired diastolic function. The duration of these subclinical abnormalities may be important, because treatment to reverse the process is most likely to be effective earlier in the disease. In the present review, we examine the current evidence on the association between NAFLD and atherosclerosis as well as between NAFLD and cardiac dysfunction in the pediatric population, and discuss briefly the possible biological mechanisms linking NAFLD and cardiovascular changes. We also address the approach to treatment for this increasingly prevalent disease, which is likely to have an important future global impact on the burden of ill health, to prevent not only end-stage liver disease but also cardiovascular disease.

What we know and do not know about the cannabinoid receptor 2 (CB2)

It has been well appreciated that the endocannabinoid system can regulate immune responses via the cannabinoid receptor 2 (CB2), which is primarily expressed by cells of the hematopoietic system. The endocannabinoid system is composed of receptors, ligands and enzymes controlling the synthesis and degradation of endocannabinoids. Along with endocannabinoids, both plant-derived and synthetic cannabinoids have been shown to bind to and signal through CB2 via G proteins leading to both inhibitory and stimulatory signals depending on the biological process. Because no cannabinoid ligand has been identified that only binds to CB2, the generation of mice deficient in CB2 has greatly expanded our knowledge of how CB2 contributes to immune cell development and function in health and disease. In regards to humans, genetic studies have associated CB2 with a variety of human diseases. Here, we review the endocannabinoid system with an emphasis on CB2 and its role in the immune system.

Autophagy protects against palmitate-induced apoptosis in hepatocytes

Background

Non-alcoholic fatty liver disease, one of the most common liver diseases, has obtained increasing attention. Palmitate (PA)-induced liver injury is considered a risk factor for the development of non-alcoholic fatty liver disease. Autophagy, a cellular degradative pathway, is an important self-defense mechanism in response to various stresses. In this study, we investigated whether autophagy plays a protective role in the progression of PA-induced hepatocytes injury.

Results

Annexin V-FITC/PI staining by FCM analysis, TUNEL assay and the detection of PARP and cleaved caspase3 expression levels demonstrated that PA treatment prominently induced the apoptosis of hepatocytes. Meanwhile, treatment of PA strongly induced the formation of GFP-LC3 dots, the conversion from LC3I to LC3II, the decrease of p62 protein levels and the increase of autophagosomes. These results indicated that PA also induced autophagy activation. Autophagy inhibition through chloroquine pretreatment or Atg5shRNA infection led to the increase of cell apoptosis after PA treatment. Moreover, induction of autophagy by pretreatment with rapamycin resulted in distinct decrease of PA-induced apoptosis. Therefore, autophagy can prevent hepatocytes from PA-induced apoptosis. In the further study, we explored pathway of autophagy activation in PA-treated hepatocytes. We found that PA activated PKCα in hepatocytes, and had no influence on mammalian target of rapamycin and endoplasmic reticulum stress pathways.

Conclusions

These results demonstrated that autophagy plays a protective role in PA-induced hepatocytes apoptosis. And PA might induce autophagy through activating PKCα pathway in hepatocytes.

Nonalcoholic Fatty liver disease/non-alcoholic steatohepatitis in childhood: endocrine-metabolic "mal-programming"

CONTEXT

Nonalcoholic Fatty Liver Disease (NAFLD) is the major chronic liver disease in the pediatric population. NAFLD includes a broad spectrum of abnormalities (inflammation, fibrosis and cirrhosis), ranging from accumulation of fat (also known as steatosis) towards non-alcoholic steatohepatitis (NASH). The development of NAFLD in children is significantly increased.

EVIDENCE ACQUISITION

A literature search of electronic databases was undertaken for the major studies published from 1998 to today. The databases searched were: PubMed, EMBASE, Orphanet, Midline and Cochrane Library. We used the key words: "non-alcoholic fatty liver disease, children, non-alcoholic steatohepatitis and fatty liver".

RESULTS

NAFLD/NASH is probably promoted by "multiple parallel hits": environmental and genetic factors, systemic immunological disorders (oxidative stress, persistent-low grade of inflammation) as well as obesity and metabolic alterations (insulin resistance and metabolic syndrome). However its exact cause still underdiagnosed and unknown.

CONCLUSIONS

Pediatric NAFLD/NASH is emerging problem. Longitudinal follow-up studies, unfortunately still insufficient, are needed to better understand the natural history and outcome of NAFLD in children. This review focuses on the current knowledge regarding the epidemiology, pathogenesis, environmental, genetic and metabolic factors of disease. The review also highlights the importance of studying the underlying mechanisms of pediatric NAFLD and the need for complete and personalized approach in the management of NAFLD/NASH.

Association between a polymorphism in cannabinoid receptor 2 and severe necroinflammation in patients with chronic hepatitis C

BACKGROUND & AIMS

The cannabinoid receptor 2 (CB2) has been implicated in liver disease. The single-nucleotide polymorphism rs35761398 in cannabinoid receptor 2 gene (CNR2), which encodes the CB2, substitutes glutamine (Q) 63 with arginine (R), and reduces the function of the gene product. We investigated the effects of CNR2 rs35761398 in patients with hepatitis C virus (HCV) infection.

METHODS

We studied 169 consecutive patients with asymptomatic chronic hepatitis (tested positive for anti-HCV and HCV RNA) at 2 liver units in southern Italy. First, liver biopsy samples were collected from July 2009 through December 2011. All patients were naive to antiviral therapy; CNR2 genotype was determined by polymerase chain reaction analysis.

RESULTS

Patients with the CB2-63 QQ variant had higher serum levels of aminotransferase than those with the CB2-63 QR or RR variants; they also had higher histologic activity index (HAI) scores (8.6 ± 3.8) than patients without the CB2-63 RR variant (5.3 ± 3.6; P < .005) or those with the CB2-63 QR variant (5.8 ± 3.3; P < .001). Patients with the different variants of CNR2 did not differ in fibrosis stage or steatosis score. Moderate or severe chronic hepatitis (HAI score, >8) was identified more frequently (55.5%) in patients with the CB2-63 QQ variant than in those with the 63 QR (20%; P < .005) or RR variants (17.4%; P < .005). In logistic regression analysis, the CB2-63 QQ variant and fibrosis score were independent predictors of moderate or severe chronic hepatitis (HAI score, >8; P < .0001).

CONCLUSIONS

The CB2-63 QQ variant of CNR2 is associated with more severe inflammation and hepatocellular necrosis in patients with HCV infection.

Pharmacogenetics of the G protein-coupled receptors

Pharmacogenetics investigates the influence of genetic variants on physiological phenotypes related to drug response and disease, while pharmacogenomics takes a genome-wide approach to advancing this knowledge. Both play an important role in identifying responders and nonresponders to medication, avoiding adverse drug reactions, and optimizing drug dose for the individual. G protein-coupled receptors (GPCRs) are the primary target of therapeutic drugs and have been the focus of these studies. With the advance of genomic technologies, there has been a substantial increase in the inventory of naturally occurring rare and common GPCR variants. These variants include single-nucleotide polymorphisms and insertion or deletions that have potential to alter GPCR expression of function. In vivo and in vitro studies have determined functional roles for many GPCR variants, but genetic association studies that define the physiological impact of the majority of these common variants are still limited. Despite the breadth of pharmacogenetic data available, GPCR variants have not been included in drug labeling and are only occasionally considered in optimizing clinical use of GPCR-targeted agents. In this chapter, pharmacogenetic and genomic studies on GPCR variants are reviewed with respect to a subset of GPCR systems, including the adrenergic, calcium sensing, cysteinyl leukotriene, cannabinoid CB1 and CB2 receptors, and the de-orphanized receptors such as GPR55. The nature of the disruption to receptor function is discussed with respect to regulation of gene expression, expression on the cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (altered ligand binding, G protein coupling, constitutive activity). The large body of experimental data generated on structure and function relationships and receptor-ligand interactions are being harnessed for the in silico functional prediction of naturally occurring GPCR variants. We provide information on online resources dedicated to GPCRs and present applications of publically available computational tools for pharmacogenetic studies of GPCRs. As the breadth of GPCR pharmacogenomic data becomes clearer, the opportunity for routine assessment of GPCR variants to predict disease risk, drug response, and potential adverse drug effects will become possible.

The cannabinoid receptor type 2 as mediator of mesenchymal stromal cell immunosuppressive properties

Mesenchymal stromal cells are non-hematopoietic, multipotent progenitor cells producing cytokines, chemokines, and extracellular matrix proteins that support hematopoietic stem cell survival and engraftment, influence immune effector cell development, maturation, and function, and inhibit alloreactive T-cell responses. The immunosuppressive properties of human mesenchymal stromal cells have attracted much attention from immunologists, stem cell biologists and clinicians.

Recently, the presence of the endocannabinoid system in hematopoietic and neural stem cells has been demonstrated. Endocannabinoids, mainly acting through the cannabinoid receptor subtype 2, are able to modulate cytokine release and to act as immunosuppressant when added to activated T lymphocytes.

In the present study, we have investigated, through a multidisciplinary approach, the involvement of the endocannabinoids in migration, viability and cytokine release of human mesenchymal stromal cells.

We show, for the first time, that cultures of human mesenchymal stromal cells express all of the components of the endocannabinoid system, suggesting a potential role for the cannabinoid CB2 receptor as a mediator of anti-inflammatory properties of human mesenchymal stromal cells, as well as of their survival pathways and their capability to home and migrate towards endocannabinoid sources.

The endocannabinoid system in advanced liver cirrhosis: pathophysiological implication and future perspectives

Endogenous cannabinoids (EC) are ubiquitous lipid signalling molecules providing different central and peripheral effects that are mediated mostly by the specific receptors CB1 and CB2. The EC system is highly upregulated during chronic liver disease and consistent experimental and clinical findings indicate that it plays a role in the pathogenesis of liver fibrosis and fatty liver disease associated with obesity, alcohol abuse and hepatitis C. Furthermore, a considerable number of studies have shown that EC and their receptors contribute to the pathogenesis of the cardio-circulatory disturbances occurring in advanced cirrhosis, such as portal hypertension, hyperdynamic circulatory syndrome and cirrhotic cardiomyopathy. More recently, the EC system has been implicated in the development of ascites, hepatic encephalopathy and the inflammatory response related to bacterial infection. Rimonabant, a selective CB1 antagonist, was the first drug acting on the EC system approved for the treatment of obesity. Unfortunately, it has been withdrawn from the market because of its neuropsychiatric side effects. Compounds able to target selectively the peripheral CB1 receptors are under evaluation. In addition, molecules stimulating CB2 receptor or modulating the activity of enzymes implicated in EC metabolism are promising areas of pharmacological research. Liver cirrhosis and the related complications represent an important target for the clinical application of these compounds.

Endocannabinoid crosstalk between placenta and maternal fat in a baboon model (Papio spp.) of obesity

INTRODUCTION

Maternal obesity (MO) remains a serious obstetric problem with acute and chronic morbidities for both mothers and offspring. The mechanisms underlying these adverse consequences of MO remain unknown. Endocannabinoids (ECB) are neuromodulatory lipids released from adipocytes and other tissues. Metabolic crosstalk between placenta and adipocytes may mediate sequelae of MO. The goal of this study was to elucidate placental and systemic ECB in MO.

MATERIAL AND METHODS

Placentas, sera, and subcutaneous fat were collected at Cesarean sections performed near term (0.9 G) in four non-obese (nOB) and four obese (OB) baboons (Papio spp.). Concentrations of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured by liquid chromatography coupled to tandem mass spectrometry. AEA and 2-AG pathways were characterized in placentas by Q-RT-PCR, Western blot and immunohistochemistry.

RESULTS

Placental 2-AG levels were lower and maternal fat AEA levels were higher in OB (1254.1 ± 401.3 nmol/kg and 17.3 ± 4 nmol/kg) vs. nOB (3124.2 ± 557.3 nmol/kg and 3.1 ± 0.6 nmol/kg) animals. Concentrations of 2-AG correlated positively between maternal fat and placenta (r = 0.82, p = 0.013), but correlated negatively with maternal leptin concentrations (r = -0.72, p = 0.04 and r = -0.83, p = 0.01, respectively).

CONCLUSION

This is the first study to demonstrate differential ECB pathway regulation in maternal fat and placenta in MO. Differential regulation and function exist for AEA and 2-AG as the major ECB pathways in placenta.

Paediatric nonalcoholic fatty liver disease

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is a multicluster disease ranging from intrahepatic simple steatosis to nonalcoholic steatohepatitis (NASH). During the last decade, NAFLD has reached epidemic proportions in overweight/obese children. In this manuscript, we review all recent advances in paediatric NAFLD.

RECENT FINDINGS

Paediatric NAFLD displays some common aspects with the adult form of disease. However, recent findings have demonstrated that regarding development of NAFLD in children, due to the absence of long-time confounding factors, it may be more appropriate to investigate genetic and pathogenetic origins of the disease. Furthermore, as the histological pattern of paediatric NAFLD is different from those observed in adults, specific diagnostic/management programmes and diagnostic scores have been recently developed. Accordingly, several studies demonstrated that both lifestyle intervention and pharmacological treatments should be adequate to the specific pattern of NAFLD in children.

SUMMARY

Results of this year's investigations further elucidated the histological features and genetic background that characterize paediatric NAFLD; the closed association of disease development with the cross-talk between different cells and organs; limitations of diagnostic tools borrowed from adult studies and the need of further clinical trial.

Altered expression of type-1 and type-2 cannabinoid receptors in celiac disease

Anandamide (AEA) is the prominent member of the endocannabinoid family and its biological action is mediated through the binding to both type-1 (CB₁) and type-2 (CB₂) cannabinoid receptors (CBR). The presence of AEA and CBR in the gastrointestinal tract highlighted their pathophysiological role in several gut diseases, including celiac disease. Here, we aimed to investigate the expression of CBR at transcriptional and translational levels in the duodenal mucosa of untreated celiac patients, celiac patients on a gluten-free diet for at least 12 months and control subjects. Also biopsies from treated celiac patients cultured ex vivo with peptic-tryptic digest of gliadin were investigated. Our data show higher levels of both CB₁ and CB₂ receptors during active disease and normal CBR levels in treated celiac patients. In conclusion, we demonstrate an up-regulation of CB₁ and CB₂ mRNA and protein expression, that points to the therapeutic potential of targeting CBR in patients with celiac disease.

Pediatric non alcoholic fatty liver disease: old and new concepts on development, progression, metabolic insight and potential treatment targets

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children. NAFLD has emerged to be extremely prevalent, and predicted by obesity and male gender. It is defined by hepatic fat infiltration >5% hepatocytes, in the absence of other causes of liver pathology. It includes a spectrum of disease ranging from intrahepatic fat accumulation (steatosis) to various degrees of necrotic inflammation and fibrosis (non-alcoholic steatohepatatis [NASH]). NAFLD is associated, in children as in adults, with severe metabolic impairments, determining an increased risk of developing the metabolic syndrome. It can evolve to cirrhosis and hepatocellular carcinoma, with the consequent need for liver transplantation. Both genetic and environmental factors seem to be involved in the development and progression of the disease, but its physiopathology is not yet entirely clear. In view of this mounting epidemic phenomenon involving the youth, the study of NAFLD should be a priority for all health care systems. This review provides an overview of current and new clinical-histological concepts of pediatric NAFLD, going through possible implications into patho-physiolocical and therapeutic perspectives.