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

Association of Cannabis Use with Complications Among Patients with Gastroesophageal Reflux Disease: Insights from National Inpatient Sample

Background/Objective: Cannabis, one of the most widely used recreational drug in the United States, has had a significant surge in usage following its legalization in 1996. In recent years, there has been research into the physiological effects of cannabis on the gastrointestinal (GI) system. Our study aims to systematically examine the association between cannabis use and complications of gastroesophageal reflux disease (GERD). Materials and Methods: We queried the 2016-2020 National Inpatient Sample database to identify patient encounters with GERD. Patients with eosinophilic esophagitis or missing demographics were excluded. We compared patient demographics, comorbidities, and complications among cannabis users and nonusers. Multivariate logistic regression analysis was used to investigate the relationship between cannabis use and complications of GERD. Results: A total of 27.2 million patient encounters were included in the analysis, out of which 507,190 were cannabis users. Majority of the cannabis users were aged between 45-64 years (46.6%), males (57.4%), White (63.84%), and belonged to the lowest income quartile (40.6%). Cannabis users demonstrated a higher prevalence of esophagitis compared to nonusers (6.11% vs. 3.23%, p<0.001). However, they exhibited a lower rates of esophageal stricture (0.6% vs. 0.8%, p<0.001) and esophageal cancer (0.2% vs. 0.24%, p<0.001). After adjusting for confounding factors, cannabis users were noted to have higher odds of esophagitis (adjusted odds ratio [aOR]: 1.34, 95% confidence interval [CI]: 1.30-1.39, p<0.001). A lower odds of esophageal stricture (aOR: 0.88, 95% CI: 0.81-0.96, p=0.02) and esophageal cancer (aOR: 0.48,95% CI: 0.42-0.57, p<0.001) were noted. Conclusion: Our cross-sectional study using the nationally available database indicates an association between cannabis use and higher odds of esophagitis, along with lower odds of esophageal stricture and cancer. While these findings suggest a potential relationship between cannabis use and esophageal complications, it is limited in establishing causality. Therefore, further long-term studies are warranted to understand the mechanism behind this association and to determine if cannabis use has an impact on esophagus.

Ghrelin Recruits the Endocannabinoid System to Modulate Food Reward

Ghrelin enhances feeding by activating the growth hormone secretagogue receptor (GHSR). In the brain, GHSRs are expressed in regions responsible for regulating food motivation including the ventral tegmental area (VTA). Endogenous cannabinoids also promote food-seeking behaviors through the cannabinoid receptor-1 (CB-1Rs) in brain regions including the VTA. It is not known, however, if ghrelin and endocannabinoids interact in the VTA to produce these effects. We therefore examined if GHSR and CB-1R interact within the VTA to enhance food motivation. Results show that GHSR and CB-1R mRNA are expressed in the VTA cells in male and female rats and mice, with the GHSR being expressed in dopamine cells and the CB-1R being expressed primarily in nondopaminergic cells with no obvious sex differences. Ghrelin directly activated and increased excitatory tone onto dopamine cells of male and female mice. Male rats lacking fully functional GHSR signaling showed disrupted gene expression of transcripts important for regulating the synthesis, release, and degradation of endocannabinoids and lowered the levels of 2-arachidonoylglycerol (2-AG) within the VTA. Moreover, pharmacological antagonism of VTA CB-1Rs attenuates the orexigenic and appetitive effects of intra-VTA ghrelin in rats and blocks the ability of ghrelin to promote excitatory drive to VTA dopamine neurons. Finally, blocking the breakdown of cannabinoids in the VTA enhances the effects of ghrelin on food motivation. Together, our data show that ghrelin stimulates VTA dopamine cells and ultimately food motivation in part through a mechanism that involves endocannabinoid signaling at the CB-1R.

Development of Yin-Yang ligand for cannabinoid receptors

Cannabinoid receptors (CBs), including CB1 and CB2, are the key components of a lipid signaling endocannabinoid system (ECS). Development of synthetic cannabinoids has been attractive to modulate ECS functions. CB1 and CB2 are structurally closely related subtypes but with distinct functions. While most efforts focus on the development of selective ligands for single subtype to circumvent the undesired off-target effect, Yin-Yang ligands with opposite pharmacological activities simultaneously on two subtypes, offer unique therapeutic potential. Herein we report the development of a new Yin-Yang ligand which functions as an antagonist for CB1 and concurrently an agonist for CB2. We found that in the pyrazole-cored scaffold, the arm of N1-phenyl group could be a switch, modification of which yielded various ligands with distinct activities. As such, the ortho-morpholine substitution exerted the desired Yin-Yang bifunctionality which, based on the docking study and molecular dynamic simulation, was proposed to be resulted from the hydrogen bonding with S173 and S285 in CB1 and CB2, respectively. Our results demonstrated the feasibility of structure guided ligand evolution for challenging Yin-Yang ligand.

Anandamide and other N-acylethanolamines: A class of signaling lipids with therapeutic opportunities

N-acylethanolamines (NAEs), including N-palmitoylethanolamine (PEA), N-oleoylethanolamine (OEA), N-arachidonoylethanolamine (AEA, anandamide), N-docosahexaenoylethanolamine (DHEA, synaptamide) and their oxygenated metabolites are a lipid messenger family with numerous functions in health and disease, including inflammation, anxiety and energy metabolism. The NAEs exert their signaling role through activation of various G protein-coupled receptors (cannabinoid CB₁ and CB₂ receptors, GPR55, GPR110, GPR119), ion channels (TRPV1) and nuclear receptors (PPAR-α and PPAR-γ) in the brain and periphery. The biological role of the oxygenated NAEs, such as prostamides, hydroxylated anandamide and DHEA derivatives, are less studied. Evidence is accumulating that NAEs and their oxidative metabolites may be aberrantly regulated or are associated with disease severity in obesity, metabolic syndrome, cancer, neuroinflammation and liver cirrhosis. Here, we comprehensively review NAE biosynthesis and degradation, their metabolism by lipoxygenases, cyclooxygenases and cytochrome P450s and the biological functions of these signaling lipids. We discuss the latest findings and therapeutic potential of modulating endogenous NAE levels by inhibition of their degradation, which is currently under clinical evaluation for neuropsychiatric disorders. We also highlight NAE biosynthesis inhibition as an emerging topic with therapeutic opportunities in endocannabinoid and NAE signaling.

Acute and long-term effects of cannabinoids on hypertension and kidney injury

Cannabinoids and their endogenous and synthetic analogs impact blood pressure and contribute to the incidence of hypertension. It was previously reported that the endocannabinoid system plays an important role in developing hypertension; however, it was also shown that cannabinoids elicit profound hypotension associated with hemorrhagic, cardiogenic, and endotoxic shock. This study aimed to test acute and chronic effects of an endogenous ligand of cannabinoid receptor anandamide (AEA) on blood pressure and kidney injury in vivo in conscious Dahl salt-sensitive (SS) rats. We demonstrated that acute i.v. bolus administration of a low or a high doses (0.05 or 3 mg/kg) of AEA did not affect blood pressure for 2 h after the injection in Dahl SS rats fed a normal salt diet (0.4% NaCl). Neither low nor high doses of AEA had any beneficial effects on blood pressure or kidney function. Furthermore, hypertensive rats fed a HS diet (8% NaCl) and chronically treated with 3 mg/kg of AEA exhibited a significant increase in blood pressure accompanied by increased renal interstitial fibrosis and glomerular damage at the late stage of hypertension. Western blot analyses revealed increased expression of Smad3 protein levels in the kidney cortex in response to chronic treatment with a high AEA dose. Therefore, TGF-β1/Smad3 signaling pathway may play a crucial role in kidney injury in SS hypertension during chronic treatment with AEA. Collectively, these data indicate that prolonged stimulation of cannabinoid receptors may result in aggravation of hypertension and kidney damage.

Synthesis, Biological Evaluation, and Molecular Modeling Studies of 3,4-Diarylpyrazoline Series of Compounds as Potent, Nonbrain Penetrant Antagonists of Cannabinoid-1 (CB1R) Receptor with Reduced Lipophilicity

In the present report, we describe the synthesis and structure-activity relationships of novel "four-arm" dihydropyrazoline compounds designed as peripherally restricted antagonists of cannabinoid-1 receptor (CB1R). A series of racemic 3,4-diarylpyrazolines were synthesized and evaluated initially in CB1 receptor binding assays. The novel compounds, designed to limit brain penetrance and decreased lipophilicity, showed high affinity for CB1R and potent in vitro CB1R antagonist activities. Promising compounds with potent CB1R activity were evaluated in tissue distribution studies. Compounds 6a, 6f, and 7c showed limited brain penetrance attesting to its peripheral restriction. The 4S-enantiomer of these compounds further showed a stereoselective affinity for the CB1 receptor and behaved as inverse agonists. In vivo studies on food intake and body weight reduction in diet-induced obese (DIO) mice showed that these compounds could serve as potential leads for the development of selective CB1R antagonists with improved potency and peripheral restriction.

[18F]MAGL-4-11 positron emission tomography molecular imaging of monoacylglycerol lipase changes in preclinical liver fibrosis models

Monoacylglycerol lipase (MAGL) is a pivotal enzyme in the endocannabinoid system, which metabolizes 2-arachidonoylglycerol (2-AG) into the proinflammatory eicosanoid precursor arachidonic acid (AA). MAGL and other endogenous cannabinoid (EC) degrading enzymes are involved in the fibrogenic signaling pathways that induce hepatic stellate cell (HSC) activation and ECM accumulation during chronic liver disease. Our group recently developed an ¹⁸F-labeled MAGL inhibitor ([¹⁸F]MAGL-4-11) for PET imaging and demonstrated highly specific binding in vitro and in vivo. In this study, we determined [¹⁸F]MAGL-4-11 PET enabled imaging MAGL levels in the bile duct ligation (BDL) and carbon tetrachloride (CCl₄) models of liver cirrhosis; we also assessed the hepatic gene expression of the enzymes involved with EC system including MAGL, NAPE-PLD, FAAH and DAGL that as a function of disease severity in these models; [¹⁸F]MAGL-4-11 autoradiography was performed to assess tracer binding in frozen liver sections both in animal and human. [¹⁸F]MAGL-4-11 demonstrated reduced PET signals in early stages of fibrosis and further significantly decreased with disease progression compared with control mice. We confirmed MAGL and FAAH expression decreases with fibrosis severity, while its levels in normal liver tissue are high; in contrast, the EC synthetic enzymes NAPE-PLD and DAGL are enhanced in these different fibrosis models. In vitro autoradiography further supported that [¹⁸F]MAGL-4-11 bound specifically to MAGL in both animal and human fibrotic liver tissues. Our PET ligand [¹⁸F]MAGL-4-11 shows excellent sensitivity and specificity for MAGL visualization in vivo and accurately reflects the histological stages of liver fibrosis in preclinical models and human liver tissues.

Rimonabant ameliorates hepatic ischemia/reperfusion injury in rats: Involvement of autophagy via modulating ERK- and PI3K/AKT-mTOR pathways

Hepatic ischemia/reperfusion (HIR), which can result in severe liver injury and dysfunction, is usually associated with autophagy and endocannabinoid system derangements. Whether or not the modulation of the autophagic response following HIR injury is involved in the hepatoprotective effect of the cannabinoid receptor 1(CB1R) antagonist rimonabant remains elusive and is the aim of the current study. Rats pre-treated with rimonabant (3 mg/kg) or vehicle underwent 30 min hepatic ischemia followed by 6 hrs. reperfusion. Liver injury was evaluated by serum ALT, AST, bilirubin (total and direct levels) and histopathological examination. The inflammatory, profibrotic and oxidative responses were investigated by assessing hepatic tumor necrosis factor α (TNFα), nuclear factor kappa B (NF-κB), transforming growth factor (TGF-β), lipid peroxidation and reduced glutathione. The hepatic levels of CB1R and autophagic markers p62, Beclin-1, and LC3 as well as the autophagic signaling inhibitors ERK1/2, PI3K, Akt and mTOR were also determined. Rimonabant significantly attenuated HIR-induced increases in hepatic injury, inflammation, profibrotic responses and oxidative stress and improved the associated pathological features. Rimonabant modulated the expression of p62, Beclin-1, and LC3, down-regulated CB1R, and dcreased pERK1/2, PI3K, Akt, and mTOR activities. The current study suggests that rimonabant can protect the liver from IR injury at least in part by inducing autophagy, probably by modulating ERK- and/or PI3K/AKT-mTOR signaling.

The Potential Use of Cannabis in Tissue Fibrosis

Fibrosis is a condition characterized by thickening or/and scarring of various tissues. Fibrosis may develop in almost all tissues and organs, and it may be one of the leading causes of morbidity and mortality. It provokes excessive scarring that excels the usual wound healing response to trauma in numerous organs. Currently, very little can be done to prevent tissue fibrosis, and it is almost impossible to reverse it. Anti-inflammatory and immunosuppressive drugs are among the few treatments that may be efficient in preventing fibrosis. Numerous publications suggest that cannabinoids and extracts of Cannabis sativa have potent anti-inflammatory and anti-fibrogenic properties. In this review, we describe the types and mechanisms of fibrosis in various tissues and discuss various strategies for prevention and dealing with tissue fibrosis. We further introduce cannabinoids and their potential for the prevention and treatment of fibrosis, and therefore for extending healthy lifespan.

Liver Fibrosis: Therapeutic Targets and Advances in Drug Therapy

Liver fibrosis is an abnormal wound repair response caused by a variety of chronic liver injuries, which is characterized by over-deposition of diffuse extracellular matrix (ECM) and anomalous hyperplasia of connective tissue, and it may further develop into liver cirrhosis, liver failure or liver cancer. To date, chronic liver diseases accompanied with liver fibrosis have caused significant morbidity and mortality in the world with increasing tendency. Although early liver fibrosis has been reported to be reversible, the detailed mechanism of reversing liver fibrosis is still unclear and there is lack of an effective treatment for liver fibrosis. Thus, it is still a top priority for the research and development of anti-fibrosis drugs. In recent years, many strategies have emerged as crucial means to inhibit the occurrence and development of liver fibrosis including anti-inflammation and liver protection, inhibition of hepatic stellate cells (HSCs) activation and proliferation, reduction of ECM overproduction and acceleration of ECM degradation. Moreover, gene therapy has been proved to be a promising anti-fibrosis method. Here, we provide an overview of the relevant targets and drugs under development. We aim to classify and summarize their potential roles in treatment of liver fibrosis, and discuss the challenges and development of anti-fibrosis drugs.

Cannabinoid receptor-1 signaling in hepatocytes and stellate cells does not contribute to NAFLD

The endocannabinoid system regulates appetite and energy expenditure and inhibitors of the cannabinoid receptor-1 (CB-1) induce weight loss with improvement in components of the metabolic syndrome. While CB-1 blockage in brain is responsible for weight loss, many of the metabolic benefits associated with CB-1 blockade have been attributed to inhibition of CB-1 signaling in the periphery. As a result, there has been interest in developing a peripherally restricted CB-1 inhibitor for the treatment of nonalcoholic fatty liver disease (NAFLD) that would lack the unwanted centrally mediated side effects. Here, we produced mice that lacked CB-1 receptors in hepatocytes or stellate cells to determine if CB-1 signaling contributes to the development of NAFLD or liver fibrosis. Deletion of CB-1 receptors in hepatocytes did not alter the development of NAFLD in mice fed a high sucrose high fat diet or high fat diet (HFD). Similarly, deletion of CB-1 deletion specifically in stellate cells also did not prevent the development of NAFLD in mice fed the HFD nor did it protect mice for carbon tetrachloride (CCl4)-induced fibrosis. Combined, these studies do not support a direct role for hepatocyte or stellate cell CB-1 signaling in the development of NAFLD or liver fibrosis.

Epigenetic Regulation of Cannabinoid-Mediated Attenuation of Inflammation and Its Impact on the Use of Cannabinoids to Treat Autoimmune Diseases

Chronic inflammation is considered to be a silent killer because it is the underlying cause of a wide range of clinical disorders, from cardiovascular to neurological diseases, and from cancer to obesity. In addition, there are over 80 different types of debilitating autoimmune diseases for which there are no cure. Currently, the drugs that are available to suppress chronic inflammation are either ineffective or overtly suppress the inflammation, thereby causing increased susceptibility to infections and cancer. Thus, the development of a new class of drugs that can suppress chronic inflammation is imperative. Cannabinoids are a group of compounds produced in the body (endocannabinoids) or found in cannabis (phytocannabinoids) that act through cannabinoid receptors and various other receptors expressed widely in the brain and immune system. In the last decade, cannabinoids have been well established experimentally to mediate anti-inflammatory properties. Research has shown that they suppress inflammation through multiple pathways, including apoptosis and inducing immunosuppressive T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Interestingly, cannabinoids also mediate epigenetic alterations in genes that regulate inflammation. In the current review, we highlight how the epigenetic modulations caused by cannabinoids lead to the suppression of inflammation and help identify novel pathways that can be used to target autoimmune diseases.

Alcoholic and Non-Alcoholic Liver Diseases: Promising Molecular Drug Targets and their Clinical Development

Alcoholic and non-alcoholic fatty liver diseases have become a serious concern worldwide. Both these liver diseases have an identical pathology, starting from simple steatosis to cirrhosis and, ultimately to hepatocellular carcinoma. Treatment options for alcoholic liver disease (ALD) are still the same as they were 50 years ago which include corticosteroids, pentoxifylline, antioxidants, nutritional support and abstinence; and for non-alcoholic fatty liver disease (NAFLD), weight loss, insulin sensitizers, lipid-lowering agents and anti-oxidants are the only treatment options. Despite broad research in understanding the disease pathophysiology, limited treatments are available for clinical use. Some therapeutic strategies based on targeting a specific molecule have been developed to lessen the consequences of disease and are under clinical investigation. Therefore, focus on multiple molecular targets will help develop an efficient therapeutic strategy. This review comprises a brief overview of the pathogenesis of ALD and NAFLD; recent molecular drug targets explored for ALD and NAFLD that may prove to be effective for multiple therapeutic regimens and also the clinical status of these promising drug targets for liver diseases.

Molecular and cellular mechanisms of liver fibrosis and its regression

Chronic liver injury leads to liver inflammation and fibrosis, through which activated myofibroblasts in the liver secrete extracellular matrix proteins that generate the fibrous scar. The primary source of these myofibroblasts are the resident hepatic stellate cells. Clinical and experimental liver fibrosis regresses when the causative agent is removed, which is associated with the elimination of these activated myofibroblasts and resorption of the fibrous scar. Understanding the mechanisms of liver fibrosis regression could identify new therapeutic targets to treat liver fibrosis. This Review summarizes studies of the molecular mechanisms underlying the reversibility of liver fibrosis, including apoptosis and the inactivation of hepatic stellate cells, the crosstalk between the liver and the systems that orchestrate the recruitment of bone marrow-derived macrophages (and other inflammatory cells) driving fibrosis resolution, and the interactions between various cell types that lead to the intracellular signalling that induces fibrosis or its regression. We also discuss strategies to target hepatic myofibroblasts (for example, via apoptosis or inactivation) and the myeloid cells that degrade the matrix (for example, via their recruitment to fibrotic liver) to facilitate fibrosis resolution and liver regeneration.

Δ9-Tetrahydrocannabinolic Acid markedly alleviates liver fibrosis and inflammation in mice

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the Western world, and it is closely associated to obesity, type 2 diabetes mellitus, and dyslipidemia. Medicinal cannabis and some neutral cannabinoids have been suggested as a potential therapy for liver diseases.

HYPOTHESIS

Δ⁹-tetrahydrocannabinolic acid (Δ⁹-THCA), the non-psychotropic precursor of Δ⁹-THC, is one of the most abundant cannabinoids presents in Cannabis Sativa. However, its biological activities have been poorly investigated. Herein, we studied the antifibrotic and antiinflammatory activities of Δ⁹-THCA in two different animal models of liver injury, providing a rationale for additional studies on the medicinal use of this cannabinoid in the treatment of liver fibrosis and the management of NAFLD.

STUDY DESIGN

The antifibrotic activity of Δ⁹-THCA in vitro was investigated in the cell lines LX-2 and NIH-3T3-Col1A2-luc. Non-alcoholic liver fibrosis was induced in mice by CCl₄ treatment or, alternatively, by 23-week high fat diet (HFD) feeding. Δ⁹-THCA was administered daily intraperitoneally during the CCl₄ treatment or during the last 3 weeks in HFD-fed mice.

METHODS

TGFβ-induced profibrotic gene expression was analyzed by luciferase and qPCR assays. Liver fibrosis and inflammation were assessed by immunochemistry and qPCR. Blood glucose, insulin, leptin and triglyceride levels were measured in HFD mice.

RESULTS

Δ⁹-THCA inhibited the expression of Tenascin C (TNC) and Col3A1 induced by TGFβ in LX-2 cells and the transcriptional activity of the Col1A2 promoter in fibroblasts. Δ⁹-THCA significantly attenuated CCl₄-induced liver fibrosis and inflammation and reduced T cell and macrophage infiltration. Mice fed HFD for 23 weeks developed severe obesity (DIO), fatty liver and marked liver fibrosis, accompanied by immune cell infiltration. Δ⁹-THCA, significantly reduced body weight and adiposity, improved glucose tolerance, and drastically attenuated DIO-induced liver fibrosis and immune cell infiltration.

CONCLUSIONS

Δ⁹-THCA prevents TGFβ-induced fibrotic markers in vitro and liver inflammation and fibrogenesis in vivo, providing a rationale for additional studies on the medicinal use of this cannabinoid, as well as cannabis preparations containing it, for the treatment of liver fibrosis and the management of NAFLD.

Efficacy and safety of anti-hepatic fibrosis drugs

Recent progress in our understanding of the pathways linked to progression from hepatic insult to cirrhosis has led to numerous novel therapies being investigated as potential cures and inhibitors of hepatic fibrogenesis. Liver cirrhosis is the final result of prolonged fibrosis, which is an intimate balance between fibrogenesis and fibrinolysis. A number of these complex mechanisms are shared across the various etiologies of liver disease. Thankfully, investigation has yielded some promising results in regard to reversal of fibrosis, particularly the indirect benefits associated with antiviral therapy for the treatment of hepatitis B and C and the farnesoid receptor agonist for the treatment of primary biliary cholangitis and metabolic associated fatty liver disease. A majority of current clinical research is focused on targeting metabolic associated fatty liver disease and its progression to metabolic steatohepatitis and ultimately cirrhosis, with some hope of potential standardized therapeutics in the near future. With our ever-evolving understanding of the underlying pathophysiology, these therapeutics focus on either controlling the primary disease (the initial trigger of fibrogenesis), interrupting receptor ligand interactions and other intracellular communications, inhibiting fibrogenesis, or even promoting resolution of fibrosis. It is imperative to thoroughly test these potential therapies with the rigorous standards of clinical therapeutic trials in order to ensure the highest standards of patient safety. In this article we will briefly review the key pathophysiological pathways that lead to liver fibrosis and present current clinical and experimental evidence that has shown reversibility of liver fibrosis and cirrhosis, while commenting on therapeutic safety.

The Synthetic Cannabinoid URB447 Reduces Brain Injury and the Associated White Matter Demyelination after Hypoxia-Ischemia in Neonatal Rats

The number of functions controlled by the endocannabinoid system in health and disease continues growing over the years. In the brain, these include the modulation of harmful events such as glutamate excitotoxicity, oxidative stress, and inflammation, mainly regulated by activation/blockade of CB₁/CB₂ cannabinoid receptors. In the present work, we evaluated the capacity of the CB₁ antagonist/CB₂ agonist synthetic cannabinoid URB447 on reducing neurodegeneration after brain injury. By using a model of hypoxia-ischemia (HI) in neonatal rats, we found that URB447 strongly reduced brain injury when administered before HI. A comparable effect was observed with the CB₁ antagonist SR141716A, whereas the CB₁ agonist WIN-55,212-2 reduced the effect of URB447. When administered 3 h after HI, which is considered a clinically feasible therapeutic window to treat perinatal brain injury in humans, URB447 reduced neurodegeneration and white matter damage. Markers of astrogliosis and microglial activation also appeared reduced. These results confirm the important role played by the endocannabinoid system in the neurodegenerative process and strongly encourage further research into the mechanisms of URB447-induced neuroprotection.

Novel targeted therapies for the management of liver fibrosis

Introduction: Prolonged liver injury results in tissue damage and replacement by extracellular matrix and fibrosis. Cirrhosis represents a leading cause of mortality worldwide and imposes a major financial burden on health-care systems. Fortunately, fibrogenesis has proven to be reversible if halted early, encouraging the development of novel anti-fibrotic agents that may accelerate histological restoration. Preclinical data have elucidated numerous potential therapeutic targets and many anti-fibrotic agents are currently at various stages of clinical research.Areas covered: The present review summarizes recent clinical data regarding anti-fibrotic drugs including monoclonal antibodies, targeted conjugates, and small molecule agents.Expert opinion: Although undeniable progress has been made in the development of anti-fibrotic agents in recent years, most data currently available are derived from preclinical and early clinical studies. The efficacy and safety of these agents will need to be corroborated by larger clinical trials, some of which are ongoing with results expected in the upcoming years. Combination therapy with agents targeting different pathways of fibrogenesis will also be of great interest for the future and will need to be explored in clinical trials.

Roles of the Hepatic Endocannabinoid and Apelin Systems in the Pathogenesis of Liver Fibrosis

Hepatic fibrosis is the consequence of an unresolved wound healing process in response to chronic liver injury and involves multiple cell types and molecular mechanisms. The hepatic endocannabinoid and apelin systems are two signalling pathways with a substantial role in the liver fibrosis pathophysiology-both are upregulated in patients with advanced liver disease. Endogenous cannabinoids are lipid-signalling molecules derived from arachidonic acid involved in the pathogenesis of cardiovascular dysfunction, portal hypertension, liver fibrosis, and other processes associated with hepatic disease through their interactions with the CB₁ and CB₂ receptors. Apelin is a peptide that participates in cardiovascular and renal functions, inflammation, angiogenesis, and hepatic fibrosis through its interaction with the APJ receptor. The endocannabinoid and apelin systems are two of the multiple cell-signalling pathways involved in the transformation of quiescent hepatic stellate cells into myofibroblast like cells, the main matrix-producing cells in liver fibrosis. The mechanisms underlying the control of hepatic stellate cell activity are coincident despite the marked dissimilarities between the endocannabinoid and apelin signalling pathways. This review discusses the current understanding of the molecular and cellular mechanisms by which the hepatic endocannabinoid and apelin systems play a significant role in the pathophysiology of liver fibrosis.

Cannabinoid receptor-1 antagonism: a new perspective on treating a murine schistosomal liver fibrosis model

BACKGROUND

Formation of schistosomal granulomata surrounding the ova can result in schistosomiasis-associated liver fibrosis (SSLF). The current standard of treatment is praziquantel (PZQ), which cannot effectively reverse SSLF. The role of the cannabinoid (CB) receptor family in liver fibrosis has recently been highlighted.

OBJECTIVES

This study aimed to assess the therapeutic effect of CB1 receptor antagonism in reversing SSLF in a murine model of Schistosoma mansoni infection.

METHODS

One hundred male Swiss albino mice were divided equally into five groups: healthy uninfected control (group I), infected control (group II), PZQ treated (group III), rimonabant (RIM) (SR141716, a CB1 receptor antagonist)-treated (group IV) and group V was treated with combined PZQ and RIM. Liver sections were obtained for histopathological examination, alpha-1 smooth muscle actin (α-SMA) immunostaining and assessment of CB1 receptor expression using real-time polymerase chain reaction (RT-PCR).

FINDINGS

The most effective reduction in fibrotic marker levels and granuloma load was achieved by combined treatment with PZQ+RIM (group V): CB1 receptor expression (H = 26.612, p < 0.001), number of α-SMA-positive cells (F = 57.086, p < 0.001), % hepatic portal fibrosis (F = 42.849, p < 0.001) and number of granulomata (F = 69.088, p < 0.001).

MAIN CONCLUSIONS

Combining PZQ with CB1 receptor antagonists yielded the best results in reversing SSLF. To our knowledge, this is the first study to test this regimen in S. mansoni infection.

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.

Development of Oxygen-Bridged Pyrazole-Based Structures as Cannabinoid Receptor 1 Ligands

In this work, the synthesis of the cannabinoid receptor 1 neutral antagonists 8-chloro-1-(2,4-dichlorophenyl)-N-piperidin-1-yl-4,5-dihydrobenzo-1H-6-oxa-cyclohepta[1,2-c]pyrazole-3-carboxamide 1a and its deaza N-cyclohexyl analogue 1b has led to a deepening of the structure-activity studies of this class of compounds. A series of novel 4,5-dihydrobenzo-oxa-cycloheptapyrazoles analogues of 1a,b, derivatives 1c–j, was synthesized, and their affinity towards cannabinoid receptors was determined. Representative terms were evaluated using in vitro tests and isolated organ assays. Among the derivatives, 1d and 1e resulted in the most potent CB₁ receptor ligands (K_iCB₁ = 35 nM and 21.70 nM, respectively). Interestingly, both in vitro tests and isolated organ assays evidenced CB₁ antagonist activity for the majority of the new compounds, excluding compound 1e, which showed a CB₁ partial agonist behaviour. CB₁ antagonist activity of 1b was further confirmed by a mouse gastrointestinal transit assay. Significant activity of the new CB₁ antagonists towards food intake was showed by preliminary acute assays, evidencing the potentiality of these new derivatives in the treatment of obesity.

Long-term administration of fatty acid amide hydrolase inhibitor (URB597) to rats with spontaneous hypertension disturbs liver redox balance and phospholipid metabolism

PURPOSE

The effect of chronic administration of [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate (URB597), inhibitor of fatty acid amide hydrolase (FAAH) that hydrolyzes anandamide, on cross-talk between endocannabinoid system, oxidative status and pro-inflammatory factors in the liver of spontaneously hypertensive rats (SHRs) was investigated.

MATERIALS/METHODS

Experiments were conducted using SHRs and normotensive control Wistar-Kyoto rats treated by intraperitoneal injection with URB597 for 14 days. The biochemical parameters were assayed in the rat's livers.

RESULTS

In the liver of SHRs an increase in endocannabinoids level, the activity of enzymes degrading them and expression of the cannabinoid receptor type 2 (CB₂) receptor as well as a decrease in the expression of the CB₁ and vanilloid 1 receptor (TRPV1) were shown. These changes were related to inflammatory conditions as well as oxidative stress resulting from increased reactive oxygen species (ROS) generation due to enhanced activity of enzymes generating ROS accompanied by decrease in the effectiveness of transcription activity of nuclear factor erythroid 2 and the activity of antioxidant enzymes, as well as level of glutathione and vitamins. Chronic administration of URB597 to SHRs caused a decrease in FAAH activity and an increase in anandamide and N-arachidonoyl-dopamine level as well as a decrease in CB₂ and an increase in TRPV1 receptor expression. The levels/activities of pro- and antioxidant and inflammatory factors tended to normalize, but phospholipid peroxidation and DNA modifications were increased.

CONCLUSION

In conclusion, long-term chronic administration of URB597 to SHRs by altering interactions between endocannabinoid and redox systems enhances some liver metabolic disturbances observed in hypertension.

Matrix metalloproteinases and liver fibrosis (translational aspects)

Liver fibrosis, a reversible wound-healing response to chronic cellular injury, reflects a balance between liver repair and progressive substitution of the liver parenchyma by scar tissue. Complex mechanisms that underlie liver fibrogenesis are summarized to provide the basis for generating targeted therapies to reverse fibrogenesis and improve the outcomes of patients with chronic liver disease. This minireview presents some pathophysiological aspects of liver fibrosis as a dynamic process and elucidates matrix metalloproteinases (MMPs) and their role within as well as beyond matrix degradation. Open questions remain, whether inhibition of fibrogenesis or induction of fibrolysis is the key mechanism to resolve fibrosis. And a point of principle might be whether regeneration of liver cirrhosis is possible. Will we ever cure fibrosis?

Mosapride Stabilizes Intestinal Microbiota to Reduce Bacterial Translocation and Endotoxemia in CCl4-Induced Cirrhotic Rats

BACKGROUND

Impaired intestinal motility may lead to the disruption of gut microbiota equilibrium, which in turn facilitates bacterial translocation (BT) and endotoxemia in cirrhosis. We evaluated the influence of mosapride, a prokinetic agent, on BT and DNA fingerprints of gut microbiota in cirrhotic rats.

METHODS

A rat model of cirrhosis was set up via subcutaneous injection of carbon tetrachloride (CCl₄). The portal pressure, liver and intestinal damage, plasma endotoxin, BT, and intestinal transit rate (ITR) of cirrhotic rats were determined. Fecal DNA fingerprints were obtained by ERIC-PCR. The expressions of tight junction proteins were evaluated by western blotting.

RESULTS

Mosapride treatment to cirrhotic rats significantly reduced the plasma endotoxin level and incidence of BT, accompanied by increased ITR. Cirrhotic rats (including those treated with mosapride) suffered from BT exhibited significantly lower ITR than those who are free of BT. Pearson coefficient indicated a significant and negative correlation between the plasma endotoxin level and ITR. The genomic fingerprints of intestinal microbiota from the three groups fell into three distinctive clusters. In the mosapride-treated group, Shannon's index was remarkably increased compared to the model group. Significantly positive correlation was detected between Shannon's index and ITR. Mosapride did not improve hepatic and intestinal damages and ileal expressions of occludin and ZO-1.

CONCLUSIONS

Mosapride significantly increases intestinal motility in cirrhotic rats, thus to recover the disordered intestinal microbiota, finally resulting in decreased plasma endotoxin and BT.

Network analyses identify liver-specific targets for treating liver diseases

We performed integrative network analyses to identify targets that can be used for effectively treating liver diseases with minimal side effects. We first generated co-expression networks (CNs) for 46 human tissues and liver cancer to explore the functional relationships between genes and examined the overlap between functional and physical interactions. Since increased de novo lipogenesis is a characteristic of nonalcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC), we investigated the liver-specific genes co-expressed with fatty acid synthase (FASN). CN analyses predicted that inhibition of these liver-specific genes decreases FASN expression. Experiments in human cancer cell lines, mouse liver samples, and primary human hepatocytes validated our predictions by demonstrating functional relationships between these liver genes, and showing that their inhibition decreases cell growth and liver fat content. In conclusion, we identified liver-specific genes linked to NAFLD pathogenesis, such as pyruvate kinase liver and red blood cell (PKLR), or to HCC pathogenesis, such as PKLR, patatin-like phospholipase domain containing 3 (PNPLA3), and proprotein convertase subtilisin/kexin type 9 (PCSK9), all of which are potential targets for drug development.

Targeting cannabinoid signaling for peritoneal dialysis-induced oxidative stress and fibrosis

Long-term exposure to bioincompatible peritoneal dialysis (PD) solutions frequently results in peritoneal fibrosis and ultrafiltration failure, which limits the life-long use of and leads to the cessation of PD therapy. Therefore, it is important to elucidate the pathogenesis of peritoneal fibrosis in order to design therapeutic strategies to prevent its occurrence. Peritoneal fibrosis is associated with a chronic inflammatory status as well as an elevated oxidative stress (OS) status. Beyond uremia per se, OS also results from chronic exposure to high glucose load, glucose degradation products, advanced glycation end products, and hypertonic stress. Therapy targeting the cannabinoid (CB) signaling pathway has been reported in several chronic inflammatory diseases with elevated OS. We recently reported that the intra-peritoneal administration of CB receptor ligands, including CB₁ receptor antagonists and CB₂ receptor agonists, ameliorated dialysis-related peritoneal fibrosis. As targeting the CB signaling pathway has been reported to be beneficial in attenuating the processes of several chronic inflammatory diseases, we reviewed the interaction among the cannabinoid system, inflammation, and OS, through which clinicians ultimately aim to prolong the peritoneal survival of PD patients.

Hepatic expression of cannabinoid receptors CB1 and CB2 correlate with fibrogenesis in patients with chronic hepatitis B

BACKGROUND

The endocannabinoid system is involved in the pathogenesis of liver fibrosis. However, most of the findings in this area have come from experimental studies in animal models or clinical trials on chronic hepatitis C. The roles of cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2) in hepatofibrosis in patients with chronic hepatitis B (CHB) have not been studied fully. This study aimed to explore the relationship between liver fibrosis and the expression of CB1 and CB2 in patients with CHB.

METHODS

Eighty liver biopsy specimens from patients with CHB (52 male, 28 female) were analyzed in this study. Fibrosis was staged on a scale of 1 to 4 (F1 to F4, with F4 defining cirrhosis). There were 20 samples for each fibrosis stage. The expression of hepatic alpha-smooth muscle actin (α-SMA), CB1, and CB2 was detected by immunohistochemistry.

RESULTS

Hepatic CB1 and CB2 were expressed in all patients with CHB. The degree of fibrosis was significantly associated with the increased expression of CB1 and CB2 in CHB. Furthermore a significant increase in cells positive for both CB1 and CB2 was detected in stage 3 and stage 4 disease compared to stage 1 and stage 2 disease. There was a strong positive association between CB1 expression and α-SMA expression. Moreover, double immunofluorescence staining for CB1 and α-SMA demonstrated that activated hepatic stellate cells (HSCs) express CB1.

CONCLUSIONS

The hepatic expression of CB1 and CB2 plays an important role during the progression of fibrosis induced by CHB. Endogenous activation of CB1 receptors in patients with CHB enhances fibrogenesis by direct effect on activated HSCs.

Reversal of liver cirrhosis: current evidence and expectations

In the past, liver cirrhosis was considered an irreversible phenomenon. However, many experimental data have provided evidence of the reversibility of liver fibrosis. Moreover, multiple clinical studies have also shown regression of fibrosis and reversal of cirrhosis on repeated biopsy samples. As various etiologies are associated with liver fibrosis via integrated signaling pathways, a comprehensive understanding of the pathobiology of hepatic fibrogenesis is critical for improving clinical outcomes. Hepatic stellate cells play a central role in hepatic fibrogenesis upon their activation from a quiescent state. Collagen and other extracellular material components from activated hepatic stellate cells are deposited on, and damage, the liver parenchyma and vascular structures. Hence, inactivation of hepatic stellate cells can lead to enhancement of fibrolytic activity and could be a potential target of antifibrotic therapy. In this regard, continued efforts have been made to develop better treatments for underlying liver diseases and antifibrotic agents in multiple clinical and therapeutic trials; the best results may be expected with the integration of such evidence. In this article, we present the underlying mechanisms of fibrosis, current experimental and clinical evidence of the reversibility of liver fibrosis/cirrhosis, and new agents with therapeutic potential for liver fibrosis.

Design, Synthesis, and Biological Evaluation of Novel, Non-Brain-Penetrant, Hybrid Cannabinoid CB1R Inverse Agonist/Inducible Nitric Oxide Synthase (iNOS) Inhibitors for the Treatment of Liver Fibrosis

We report the design, synthesis, and structure-activity relationships of novel dual-target compounds with antagonist/inverse agonist activity at cannabinoid receptor type 1 (CB1R) and inhibitory effect on inducible nitric oxide synthase (iNOS). A series of 3,4-diarylpyrazolinecarboximidamides were synthesized and evaluated in CB1 receptor (CB1R) binding assays and iNOS activity assays. The novel compounds, designed to have limited brain penetrance, elicited potent in vitro CB1R antagonist activities and iNOS inhibitory activities. Some key compounds displayed high CB1R binding affinities. Compound 7 demonstrated potent in vivo pharmacological activities such as reduction of food intake mediated by the antagonism of the CB1Rs and antifibrotic effect in the animal models of fibrosis mediated by iNOS inhibition and CB1R antagonism.

Hybrid inhibitor of peripheral cannabinoid-1 receptors and inducible nitric oxide synthase mitigates liver fibrosis

Liver fibrosis, a consequence of chronic liver injury and a way station to cirrhosis and hepatocellular carcinoma, lacks effective treatment. Endocannabinoids acting via cannabinoid-1 receptors (CB1R) induce profibrotic gene expression and promote pathologies that predispose to liver fibrosis. CB1R antagonists produce opposite effects, but their therapeutic development was halted due to neuropsychiatric side effects. Inducible nitric oxide synthase (iNOS) also promotes liver fibrosis and its underlying pathologies, but iNOS inhibitors tested to date showed limited therapeutic efficacy in inflammatory diseases. Here, we introduce a peripherally restricted, orally bioavailable CB1R antagonist, which accumulates in liver to release an iNOS inhibitory leaving group. In mouse models of fibrosis induced by CCl4 or bile duct ligation, the hybrid CB1R/iNOS antagonist surpassed the antifibrotic efficacy of the CB1R antagonist rimonabant or the iNOS inhibitor 1400W, without inducing anxiety-like behaviors or CB1R occupancy in the CNS. The hybrid inhibitor also targeted CB1R-independent, iNOS-mediated profibrotic pathways, including increased PDGF, Nlrp3/Asc3, and integrin αvβ6 signaling, as judged by its ability to inhibit these pathways in cnr1-/- but not in nos2-/- mice. Additionally, it was able to slow fibrosis progression and to attenuate established fibrosis. Thus, dual-target peripheral CB1R/iNOS antagonists have therapeutic potential in liver fibrosis.

Effect of total flavone from Litchi chinensis Sonn on Smad3, Smad4 and TIMP-1 expression in a rat model of liver fibrosis

AIM: To observe the effect of total flavone from Litchi chinensis Sonn (TFL) on dimethylnitrosamine (DMN) induced hepatic fibrosis and the expression of Smad3, Smad4 and TIMP-1 in rat liver tissue, to explore the antifibrotic mechanism of TFL.

METHODS: Ninety male SD rats were randomly divided into a normal control group, a fibrosis model group, a colchicine positive control group, and high-, medium-, and low-dose TFL groups [200, 100, and 50 mg/(kg•d), respectively]. Liver fibrosis was induced in rats by intraperitoneal injection of 0.5% DMN solution. Colchicine or TFL was given during modelling by gavage, once a day, for 6 wk. Rats were killed after 6 wk, and the levels of alanine aminotransferase (ALT) and aspartate transaminase (AST) were tested using an automatic biochemical analyzer. Liver tissue samples were taken for Masson staining to observe the pathological changes and the degree of liver fibrosis in rats. The protein and mRNA expression of Smad3, Smad4, and TIMP-1 was detected by immunohistochemistry and real-time quantitative PCR (RT-PCR), respectively.

RESULTS: Compared with the model group, the levels of ALT and AST were significantly decreased in the TFL groups. Compared with the normal control group, the extent of fibrosis in the model group increased significantly, and the expression of Smad3, Smad4 and TIMP-1 in liver tissue was significantly enhanced (P < 0.05). Compared with the model group, the expression of Smad3, Smad4 and TIMP-1 showed varying degrees of down-regulation in the TFL groups and colchicine groups.

CONCLUSION: TFL can reduce liver injury and improve liver fibrosis in rats with liver fibrosis, and the underlying mechanism may be closely related with decreasing the expression of Smad3, Smad4 and TIMP-1.

The hepatic cannabinoid 1 receptor as a modulator of hepatic energy state and food intake

The cannabinoid 1 receptor (CB1R) has a well-established role in appetite regulation. Central CB1R antagonists, notably rimonabant, induced weight loss and improved the metabolic profile in obese individuals, but were discontinued due to psychiatric side-effects. The CB1R is also expressed peripherally, where its effects include promotion of liver fat accumulation, which consumes ATP. Type 2 diabetes in obese subjects is linked to excess liver fat, whilst there is a negative correlation between hepatic ATP content and insulin resistance. A decreased hepatic ATP/AMP ratio increases food intake by signals via the vagus nerve to the brain. The hepatic cannabinoid system is highly upregulated in obesity, and the effects of hepatic CB1R activation include increased activity of lipogenic and gluconeogenic transcription factors. Thus, blockade of hepatic CB1Rs could contribute significantly to the weight-reducing and insulin-sensitizing effects of CB1R antagonists. Additionally, upregulation of the hepatic CB1R may contribute to chronic liver inflammation, fibrosis and cirrhosis from causes including obesity, alcoholism and viral hepatitis. Peripheral CB1R antagonists induce weight loss and metabolic improvements in obese rodents; however, as there is evidence that hepatic CB1Rs are predominately intracellular, due to high intrinsic clearance, many drugs may not effectively block these receptors and therefore have limited efficacy. Hepatoselective CB1R antagonists may be effective at reducing hepatic steatosis, insulin resistance and bodyweight in obese, diabetic patients, with far fewer side-effects than first-generation CB1R antagonists. Additionally, such compounds may be effective in treating inflammatory liver disease, such as non-alcoholic steatohepatitis, reducing the likelihood of disease progression to cirrhosis or cancer.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Role of adiponectin in the metabolic effects of cannabinoid type 1 receptor blockade in mice with diet-induced obesity

The adipocyte-derived hormone adiponectin promotes fatty acid oxidation and improves insulin sensitivity and thus plays a key role in the regulation of lipid and glucose metabolism and energy homeostasis. Chronic cannabinoid type 1 (CB1) receptor blockade also increases lipid oxidation and improves insulin sensitivity in obese individuals or animals, resulting in reduced cardiometabolic risk. Chronic CB1 blockade reverses the obesity-related decline in serum adiponectin levels, which has been proposed to account for the metabolic effects of CB1 antagonists. Here, we investigated the metabolic actions of the CB1 inverse agonist rimonabant in high-fat diet (HFD)-induced obese adiponectin knockout (Adipo(-/-)) mice and their wild-type littermate controls (Adipo(+/+)). HFD-induced obesity and its hormonal/metabolic consequences were indistinguishable in the two strains. Daily treatment of obese mice with rimonabant for 7 days resulted in significant and comparable reductions in body weight, serum leptin, free fatty acid, cholesterol, and triglyceride levels in the two strains. Rimonabant treatment improved glucose homeostasis and insulin sensitivity to the same extent in Adipo(+/+) and Adipo(-/-) mice, whereas it reversed the HFD-induced hepatic steatosis, fibrosis, and hepatocellular damage only in the former. The adiponectin-dependent, antisteatotic effect of rimonabant was mediated by reduced uptake and increased β-oxidation of fatty acids in the liver. We conclude that reversal of the HFD-induced hepatic steatosis and fibrosis by chronic CB1 blockade, but not the parallel reduction in adiposity and improved glycemic control, is mediated by adiponectin.

The peripheral cannabinoid receptor 1 antagonist VD60 efficiently inhibits carbon tetrachloride-intoxicated hepatic fibrosis progression

This study investigated a peripheral selective CB₁ antagonist 3,4,22-3-demethoxycarbonyl-3-hydroxylmethyl-4-deacetyl-vindoline 3,4-thionocarbonate (VD60) that efficiently inhibited hepatic fibrosis with lower psychological side effects. A competitive radiolabeled ligand binding experiment and 3'-5'-cyclic adenosine monophosphate (cAMP) response element-driven luciferase analysis were performed to evaluate the antagonistic activity of VD60. Cell viability and collagen production were examined in the human hepatic stellate cell (HSC) line LX-2 and primary cultured rat HSCs. The antifibrotic effects of VD60 were investigated in a CCl₄-induced liver fibrosis mouse model. The concentration of VD60 in the blood and the brain was determined by high-performance liquid chromatography-mass spectrum analysis. Furthermore, the potential underlying mechanisms of VD60 were investigated by Western blot. VD60 selectively competed with the radiolabeled CB1 agonist to bind to CB1. VD60 antagonized CB1 agonist-induced Akt phosphorylation and increased the accumulation of intracellular cAMP. VD60 strongly reduced the expression of α₂(I) pro-collagen mRNA and exerted potent antiproliferative effects on primary HSCs and LX-2 cells. The inhibition of reactive oxygen species production and phosphorylation of Akt, extracellular-signal-regulated kinase (ERK), and Smad3 may explain the underlying mechanisms behind the antiproliferative effect of VD60. Moreover, the in vivo antifibrotic activity of VD60 was confirmed in a CCl4-induced liver fibrosis mouse model. Most importantly, the concentration of VD60 in the peripheral blood was much higher than in the brain, suggesting that VD60 could act as a novel peripheral CB1 antagonist to efficiently inhibit hepatic fibrosis and could be used as a lead compound with low brain side effects in peripheral antifibrotic agents.

Marijuana use in hepatitis C infection does not affect liver biopsy histology or treatment outcomes

BACKGROUND

Marijuana smoking is prevalent among hepatitis C virus-infected patients. The literature assessing the influence of marijuana on liver disease progression and hepatitis C virus antiviral treatment outcomes is conflicting.

METHODS

The authors evaluated hepatitis C virus RNA-positive patients followed at The Ottawa Hospital Viral Hepatitis Clinic (Ottawa, Ontario) from 2000 to 2009. Using The Ottawa Hospital Viral Hepatitis Clinic database and charts, information regarding demographics, HIV coinfection, alcohol use, liver biopsy results, treatment outcomes and self-reported marijuana use was extracted. Biopsy characteristics and hepatitis C virus antiviral treatment outcomes were assessed for association with categorized marijuana use by adjusted logistic regression; covariates were specified according to clinical relevance a priori.

RESULTS

Information regarding marijuana use was available for 550 patients, 159 (28.9%) of whom were using marijuana at the time of first assessment. Biopsy fibrosis stage and marijuana use data were available for 377 of these 550 (F0-2 = 72.3%). Overall, marijuana use did not predict fibrosis stage, inflammation grade or steatosis. Sustained virological response and marijuana use data were available for 359 of the 550 cohort participants; a total of 211 (58.8%) achieved a sustained virological response. Marijuana use was not associated with premature interruption of therapy for side effects, the likelihood of completing a full course of therapy or sustained virological response.

CONCLUSION

Marijuana use did not influence biopsy histology or alter key hard outcomes of hepatitis C virus antiviral therapy.

Suppression of collagen synthesis by Dicer gene silencing in hepatic stellate cells

MicroRNAs (miRNAs) have emerged as important mediators of hepatic stellate cells (HSCs) and are pivotal in the pathogenesis of liver fibrosis. Dicer, the key enzyme in the RNA interference (RNAi) pathway, is involved in cutting precursor miRNAs to functionally mature forms. Emerging evidence has demonstrated that Dicer expression is dysregulated in embryo development and tumors. In the present study, we aimed to address whether Dicer expression was correlated with the activity of HSCs. We used a recombinant lentivirus to generate short hairpin RNAs (shRNAs) targeting Dicer. The mRNA and protein expression of Dicer was effectively inhibited by three pairs of Dicer shRNA vectors, of which the shRNA1 vector exhibited the strongest inhibitory effect. The shRNA1 vector demonstrated a marked inhibitory effect on the activity of HSCs, resulting in the reduction of cell proliferation and the decrease of fibrosis-related genes, including type Ⅰ collagen (Col1A1), α-smooth muscle actin (α-SMA) and tissue inhibitor of metalloproteinases (TIMP). The mRNA expression of Col1A1, α-SMA and TIMP were decreased by 60, 56 and 49%, respectively. The protein expression was reduced by 56, 52 and 42%, respectively. Additionally, the inhibition of Dicer resulted in a decrease of miR-138, -143, -140 and -122 levels, of which miR-138 exhibited the strongest decline. The firefly luciferase reporter experiments and RT-PCR indicated that phosphatase and tension homolog deleted on chromosome 10 (PTEN), Ras GTPase activating-like protein 1 (RASAL1), acyl-CoA synthetase long-chain family member 1 (ACSL1) and p27 3' untranslated region sequences were targeted by miR-138, -143, -140 and -122, respectively. Taken together, the present study contributes important new findings for the role of Dicer-mediated miRNA processing in collagen synthesis of HSCs, which may serve as a foundation for RNAi study of liver fibrosis in vivo.

Cannabinoid signaling and liver therapeutics

Over the last decade, the endocannabinoid system has emerged as a pivotal mediator of acute and chronic liver injury, with the description of the role of CB1 and CB2 receptors and their endogenous lipidic ligands in various aspects of liver pathophysiology. A large number of studies have demonstrated that CB1 receptor antagonists represent an important therapeutic target, owing to beneficial effects on lipid metabolism and in light of its antifibrogenic properties. Unfortunately, the brain-penetrant CB1 antagonist rimonabant, initially approved for the management of overweight and related cardiometabolic risks, was withdrawn because of an alarming rate of mood adverse effects. However, the efficacy of peripherally-restricted CB1 antagonists with limited brain penetrance has now been validated in preclinical models of NAFLD, and beneficial effects on fibrosis and its complications are anticipated. CB2 receptor is currently considered as a promising anti-inflammatory and antifibrogenic target, although clinical development of CB2 agonists is still awaited. In this review, we highlight the latest advances on the impact of the endocannabinoid system on the key steps of chronic liver disease progression and discuss the therapeutic potential of molecules targeting cannabinoid receptors.

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.

Marijuana smoking does not accelerate progression of liver disease in HIV-hepatitis C coinfection: a longitudinal cohort analysis

Background. Marijuana smoking is common and believed to relieve many symptoms, but daily use has been associated with liver fibrosis in cross-sectional studies. We aimed to estimate the effect of marijuana smoking on liver disease progression in a Canadian prospective multicenter cohort of human immunodeficiency virus/hepatitis C virus (HIV/HCV) coinfected persons.

Methods. Data were analyzed for 690 HCV polymerase chain reaction positive (PCR-positive) individuals without significant fibrosis or end-stage liver disease (ESLD) at baseline. Time-updated Cox Proportional Hazards models were used to assess the association between the average number of joints smoked/week and progression to significant liver fibrosis (APRI ≥ 1.5), cirrhosis (APRI ≥ 2) or ESLD.

Results At baseline, 53% had smoked marijuana in the past 6 months, consuming a median of 7 joints/week (IQR, 1–21); 40% smoked daily. There was no evidence that marijuana smoking accelerates progression to significant liver fibrosis (APRI ≥ 1.5) or cirrhosis (APRI ≥ 2; hazard ratio [HR]: 1.02 [0.93–1.12] and 0.99 [0.88–1.12], respectively). Each 10 additional joints/week smoked slightly increased the risk of progression to a clinical diagnosis of cirrhosis and ESLD combined (HR, 1.13 [1.01–1.28]). However, when exposure was lagged to 6–12 months before the diagnosis, marijuana was no longer associated with clinical disease progression (HR, 1.10 [0.95–1.26]).

Conclusions In this prospective analysis we found no evidence for an association between marijuana smoking and significant liver fibrosis progression in HIV/HCV coinfection. A slight increase in the hazard of cirrhosis and ESLD with higher intensity of marijuana smoking was attenuated after lagging marijuana exposure, suggesting that reverse causation due to self-medication could explain previous results.

Glycyrrhizic acid attenuates CCl4-induced hepatocyte apoptosis in rats via a p53-mediated pathway

AIM: To investigate the effect of glycyrrhizic acid (GA) on carbon tetrachloride (CCl₄)-induced hepatocyte apoptosis in rats via a p53-dependent mitochondrial pathway.

METHODS: Forty-five male Sprague-Dawley rats were randomly and equally divided into three groups, the control group, the CCl₄ group, and the GA treatment group. To induce liver fibrosis in this model, rats were given a subcutaneous injection of a 40% solution of CCl₄ in olive oil at a dose of 0.3 mL/100 g body weight biweekly for 8 wk, while controls received the same isovolumetric dose of olive oil by hypodermic injection, with an initial double-dose injection. In the GA group, rats were also treated with a 40% solution of CCl₄ plus 0.2% GA solution in double distilled water by the intraperitoneal injection of 3 mL per rat three times a week from the first week following previously published methods, with modifications. Controls were given the same isovolumetric dose of double distilled water. Liver function parameters, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined. Pathologic changes in the liver were detected by hematoxylin and eosin staining. Collagen fibers were evaluated by Sirius red staining. Hepatocyte apoptosis was investigated using the terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick end labeling (TUNEL) assay and the cleaved caspase-3 immunohistochemistry assay. The expression levels of p53 and apoptosis-related proteins were evaluated by immunohistochemistry or Western blotting analysis.

RESULTS: After 8 wk of treatment, GA significantly reduced serum activity of ALT (from 526.7 ± 57.2 to 342 ± 44.8, P < 0.05) and AST (from 640 ± 33.7 to 462.8 ± 30.6, P < 0.05), attenuated the changes in liver histopathology and reduced the staging score (from 3.53 ± 0.74 to 3.00 ± 0.76, P < 0.05) in CCl₄-treated rats. GA markedly reduced the positive area of Sirius red and the ratio of the hepatic fibrotic region (from 7.87% ± 0.66% to 3.68% ± 0.32%, P < 0.05) compared with the CCl₄ group. GA also decreased the expression level of cleaved caspase-3 compared to the CCl₄ group. TUNEL assay indicated that GA significantly diminished the number of TUNEL-positive cells compared with the CCl₄ group (P < 0.05). GA treatment clearly decreased the level of p53 (P < 0.05) detected by immunohistochemistry and Western blotting analysis. Compared with the CCl₄ group, we also found that GA reduced the Bax/Bcl-2 ratio (P < 0.05), the expression of cleaved caspase-3 (P < 0.05), cleaved caspase-9 (P < 0.05), and inhibited cytochrome C and second mitochondria-derived activator of caspases (Smac) release from mitochondria to cytoplasm, i.e., GA reduced the expression level of Smac, which inhibited c-IAP1 activity (P < 0.05), ultimately inhibiting the activity of caspase-3, according to Western blotting analysis. As a result, GA suppressed activation of the caspase cascades and prevented hepatocyte apoptosis.

CONCLUSION: GA can inhibit CCl₄-induced hepatocyte apoptosis via a p53-dependent mitochondrial pathway to retard the progress of liver fibrosis in rats.

Cannabinoid receptors as therapeutic targets for dialysis-induced peritoneal fibrosis

BACKGROUND

Long-term exposure to bioincompatible peritoneal dialysis solutions is frequently complicated with peritoneal fibrosis and ultrafiltration failure. As cannabinoid receptor (CBR) ligands have been reported to be beneficial to ameliorate the process of liver fibrosis, we strove to investigate their therapeutic potential to prevent peritoneal fibrosis.

METHODS

We used the rat model of peritoneal fibrosis induced by intraperitoneal injection of methylglyoxal and in vitro mesothelial cell culture to test the effects of CBR ligands, including the type 1 CBR (CB(1)R) antagonist and the type 2 CBR (CB(2)R) agonist.

RESULTS

In the methylglyoxal model, both intraperitoneal CB(1)R antagonist (AM281) and CB(2)R agonist (AM1241) treatment significantly ameliorated peritoneal fibrosis. In addition, CB(1)R antagonist was able to alleviate TGF-β(1)-induced dedifferentiation of mesothelial cells and to maintain epithelial integrity in vitro.

CONCLUSIONS

Intraperitoneal administration of CBR ligands (CB(1)R antagonist and CB(2)R agonist) offers a potential therapeutic strategy to reduce dialysis-induced peritoneal fibrosis and to prolong the peritoneal survival in peritoneal dialysis patients.