Endocannabinoids acting at vascular CB1 receptors mediate the vasodilated state in advanced liver cirrhosis

Cirrhotic cardiomyopathy: Pathogenesis, clinical features, diagnosis, treatment and prognosis

Cardiac dysfunction among cirrhotic patients has long been recognized in the medical community. While it was originally believed to be a direct result of alcohol toxicity, in the last 30 years cirrhotic cardiomyopathy (CCM) has been described as a syndrome characterized by chronic cardiac dysfunction in cirrhotic patients in the absence of known cardiac disease, regardless of the etiology of cirrhosis. CCM occurs in about 60% of patients with cirrhosis and plays a critical role in disease progression and treatment outcomes. Due to its predominantly asymptomatic course, diagnosing CCM is challenging and requires a high index of suspicion and a multiparametric approach. Patients with CCM usually present with the following triad: impaired myocardial contractile response to exercise, inadequate ventricular relaxation, and electrophysiological abnormalities (notably prolonged QT interval). In recent years, research in this area has grown expeditiously and a new set of diagnostic criteria has been developed by the Cirrhotic Cardiomyopathy Consortium, to properly identify patients with CCM. Nevertheless, CCM is still largely unknown among clinicians, and a major part of its pathophysiology and treatment is yet to be understood. In the present work, we aim to compile and summarize the available data on the pathogenesis, clinical features, diagnosis, treatment, and prognosis of CCM.

The Contemporary Role of Speckle Tracking Echocardiography in Cirrhotic Cardiomyopathy

Cirrhotic cardiomyopathy (CCM) is characterized by elevated cardiac output at rest, an inability to further increase contractility under stress, and diastolic dysfunction. The diagnosis of CCM is crucial as it can lead to complications during liver transplantation. However, its recognition poses challenges with conventional echocardiography techniques. Speckle tracking echocardiography (STE), particularly global longitudinal strain (GLS), is a novel index that enhances the diagnostic efficacy of echocardiography for both ischemic and non-ischemic cardiomyopathies. GLS proves more sensitive in identifying early systolic dysfunction and is also influenced by advanced diastolic dysfunction. Consequently, there is an expanding scope for GLS utilization in cirrhotic cases, with newly updated diagnostic criteria for CCM incorporating GLS. Specifically, systolic dysfunction is now defined as either a left ventricular ejection fraction below 50% or an absolute GLS below 18%. However, conflicting data on GLS alterations in liver cirrhosis patients persist, as many individuals with advanced disease and a poor prognosis exhibit a hyperdynamic state with preserved or increased GLS. Consequently, the presence of CCM, according to the updated criteria, does not exhibit a significant association-in the majority of studies-with the severity of liver disease and prognosis. Furthermore, information on other indices measured with STE, such as left atrial and right ventricular strain, is promising but currently limited. This review aims to offer a critical assessment of the existing evidence concerning the application of STE in patients with liver cirrhosis.

[Hemodynamic Changes in Chronic Liver Disease]

Chronic liver disease causes hemodynamic changes in the body depending on the degree of progression. These hemodynamic changes begin with splanchnic vasodilation, with complications beginning to appear as the hyperdynamic changes occur. As chronic liver disease progresses, increased splanchnic vasodilation and hyperdynamic changes worsen portal hypertension and help cause or worsen chronic liver disease complications, such as ascites. Ultimately, the effective plasma volume and blood pressure decrease in the terminal stage.

The Glymphatic System May Play a Vital Role in the Pathogenesis of Hepatic Encephalopathy: A Narrative Review

Hepatic encephalopathy (HE) is a neurological complication of liver disease resulting in cognitive, psychiatric, and motor symptoms. Although hyperammonemia is a key factor in the pathogenesis of HE, several other factors have recently been discovered. Among these, the impairment of a highly organized perivascular network known as the glymphatic pathway seems to be involved in the progression of some neurological complications due to the accumulation of misfolded proteins and waste substances in the brain interstitial fluids (ISF). The glymphatic system plays an important role in the clearance of brain metabolic derivatives and prevents aggregation of neurotoxic agents in the brain ISF. Impairment of it will result in aggravated accumulation of neurotoxic agents in the brain ISF. This could also be the case in patients with liver failure complicated by HE. Indeed, accumulation of some metabolic by-products and agents such as ammonia, glutamine, glutamate, and aromatic amino acids has been reported in the human brain ISF using microdialysis technique is attributed to worsening of HE and correlates with brain edema. Furthermore, it has been reported that the glymphatic system is impaired in the olfactory bulb, prefrontal cortex, and hippocampus in an experimental model of HE. In this review, we discuss different factors that may affect the function of the glymphatic pathways and how these changes may be involved in HE.

Emerging Therapeutic Targets for Portal Hypertension

Purpose of Review

Portal hypertension is responsible of the main complications of cirrhosis, which carries a high mortality. Recent treatments have improved prognosis, but this is still far from ideal. This paper reviews new potential therapeutic targets unveiled by advances of key pathophysiologic processes.

Recent Findings

Recent research highlighted the importance of suppressing etiologic factors and a safe lifestyle and outlined new mechanisms modulating portal pressure. These include intrahepatic abnormalities linked to inflammation, fibrogenesis, vascular occlusion, parenchymal extinction, and angiogenesis; impaired regeneration; increased hepatic vascular tone due to sinusoidal endothelial dysfunction with insufficient NO availability; and paracrine liver cell crosstalk. Moreover, pathways such as the gut-liver axis modulate splanchnic vasodilatation and systemic inflammation, exacerbate liver fibrosis, and are being targeted by therapy. We have summarized studies of new agents addressing these targets.

Summary

New agents, alone or in combination, allow acting in complementary mechanisms offering a more profound effect on portal hypertension while simultaneously limiting disease progression and favoring regression of fibrosis and of cirrhosis. Major changes in treatment paradigms are anticipated.

Hepatic targeting of the centrally active cannabinoid 1 receptor (CB1R) blocker rimonabant via PLGA nanoparticles for treating fatty liver disease and diabetes

Over-activation of the endocannabinoid/CB1R system is a hallmark feature of obesity and its related comorbidities, most notably type 2 diabetes (T2D), and non-alcoholic fatty liver disease (NAFLD). Although the use of drugs that widely block the CB1R was found to be highly effective in treating all metabolic abnormalities associated with obesity, they are no longer considered a valid therapeutic option due to their adverse neuropsychiatric side effects. Here, we describe a novel nanotechnology-based drug delivery system for repurposing the abandoned first-in-class global CB1R antagonist, rimonabant, by encapsulating it in polymeric nanoparticles (NPs) for effective hepatic targeting of CB1Rs, enabling effective treatment of NAFLD and T2D. Rimonabant-encapsulated NPs (Rimo-NPs) were mainly distributed in the liver, spleen, and kidney, and only negligible marginal levels of rimonabant were found in the brain of mice treated by iv/ip administration. In contrast to freely administered rimonabant treatment, no CNS-mediated behavioral activities were detected in animals treated with Rimo-NPs. Chronic treatment of diet-induced obese mice with Rimo-NPs resulted in reduced hepatic steatosis and liver injury as well as enhanced insulin sensitivity, which were associated with enhanced cellular uptake of the formulation into hepatocytes. Collectively, we successfully developed a method of encapsulating the centrally acting CB1R blocker in NPs with desired physicochemical properties. This novel drug delivery system allows hepatic targeting of rimonabant to restore the metabolic advantages of blocking CB1R in peripheral tissues, especially in the liver, without the negative CB1R-mediated neuropsychiatric side effects.

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.

Expression of cannabinoid (CB1 and CB2) and cannabinoid-related receptors (TRPV1, GPR55, and PPARα) in the synovial membrane of the horse metacarpophalangeal joint

Background

The metacarpophalangeal joint undergoes enormous loading during locomotion and can therefore often become inflamed, potentially resulting in osteoarthritis (OA). There are studies indicating that the endocannabinoid system (ECS) modulates synovium homeostasis, and could be a promising target for OA therapy. Some cannabinoid receptors, which modulate proliferative and secretory responses in joint inflammation, have been functionally identified in human and animal synovial cells.

Objective

To characterize the cellular distribution of the cannabinoid receptors 1 (CB1R) and 2 (CB2R), and the cannabinoid-related receptors transient receptor potential vanilloid type 1 (TRPV1), G protein-related receptor 55 (GPR55) and peroxisome proliferator-activated receptor alpha (PPARα) in the synovial membrane of the metacarpophalangeal joint of the horse.

Animals

The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir.

Materials and methods

The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir. The expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in synovial tissues was studied using qualitative and quantitative immunofluorescence, and quantitative real-time reverse transcriptase PCR (qRT-PCR). Macrophage-like (MLS) and fibroblast-like (FLS) synoviocytes were identified by means of antibodies directed against IBA1 and vimentin, respectively.

Results

Both the mRNA and protein expression of the CB2R, TRPV1, GPR55, and PPARα were found in the synoviocytes and blood vessels of the metacarpophalangeal joints. The synoviocytes expressed the mRNA and protein of the CB1R in some of the horses investigated, but not in all.

Conclusions and clinical importance

Given the expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in the synovial elements of the metacarpophalangeal joint, these findings encouraged the development of new studies supporting the use of molecules acting on these receptors to reduce the inflammation during joint inflammation in the horse.

Invasive Hemodynamic Evaluation of the Fontan Circulation: Current Day Practice and Limitations

PURPOSE OF REVIEW

Establishing the Fontan circulation has led to improved survival in patients born with complex congenital heart diseases. Despite early success, the long-term course of Fontan patients is complicated by multi-organ dysfunction, mainly due to a combination of low resting and blunted exercise-augmented cardiac output as well as elevated central venous (Fontan) pressure. Similarly, despite absolute hemodynamic differences compared to the normal population with biventricular circulation, the "normal" ranges of hemodynamic parameters specific to age-appropriate Fontan circulation have not been well defined. With the ever-increasing population of patients requiring Fontan correction, it is of utmost importance that an acceptable range of hemodynamics in this highly complex patient cohort is better defined.

RECENT FINDINGS

Multiple publications have described hemodynamic limitations and potential management options in patients with Fontan circulation; however, an acceptable range of hemodynamic parameters in this patient population has not been well defined. Identification of "normal" hemodynamic parameters among patients with Fontan circulation will allow physicians to more objectively define indications for intervention, which is a necessary first step to eliminate institutional and regional heterogeneity in Fontan management and potentially improve long-term clinical outcomes.

Cannabis use may reduce healthcare utilization and improve hospital outcomes in patients with cirrhosis

INTRODUCTION AND OBJECTIVES

Previous studies reveal conflicting data on the effect of cannabis use in patients with cirrhosis. This research evaluates the impact of cannabis on hepatic decompensation, health care utilization, and mortality in patients with cirrhosis.

MATERIAL AND METHODS

A retrospective analysis of the State Inpatient Database (SID) was performed evaluating patients from Colorado and Washington in 2011 to represent pre-cannabis legalization and 2015 to represent post-cannabis legalization. Multivariable analysis was performed to study the impact of cannabis on the rate of admissions with hepatic decompensations, healthcare utilization, and mortality in patients with cirrhosis.

RESULTS

Cannabis use was detected in 370 (2.1%) of 17,520 cirrhotics admitted in 2011 and in 1162 (5.3%) of 21,917 cirrhotics in 2015 (p-value <0.001). On multivariable analysis, cirrhotics utilizing cannabis after its legalization experienced a decreased rate of admissions related to hepatorenal syndrome (Odds Ratio (OR): 0.51; 95% Confidence Interval (CI): 0.34-0.78) and ascites (OR: 0.73; 95% CI: 0.63-0.84). Cirrhotics with an etiology of disease other than alcohol and hepatitis C had a higher risk of admission for hepatic encephalopathy if they utilized cannabis [OR: 1.57; 95% CI: 1.16-2.13]. Decreased length of stay (-1.15 days; 95% CI: -1.62, -0.68), total charges (-$15,852; 95% CI: -$21,009, -$10,694), and inpatient mortality (OR: 0.68; 95% CI: 0.51-0.91) were also observed in cirrhotics utilizing cannabis after legalization compared to cirrhotics not utilizing cannabis or utilizing cannabis prior to legalization.

CONCLUSION

Cannabis use in patients with cirrhosis resulted in mixed outcomes regarding hospital admissions with hepatic decompensation. A trend towards decreased hospital utilization and mortality was noted in cannabis users after legalization. These observations need to be confirmed with a longitudinal randomized study.

Mechanistic insights into the pathophysiology of cirrhotic cardiomyopathy

Myocardial dysfunction in end stage cirrhotic liver disease, termed cirrhotic cardiomyopathy, is a long known, but little understood comorbidity seen in ∼50% of adults and children who present for liver transplantation. Structural, functional, hemodynamic and electrocardiographic aberrations that occur in the heart as a direct consequence of a damaged liver, is associated with multi-organ failure and increased mortality and morbidity in patients undergoing surgical procedures such as porto-systemic shunt placement and liver transplantation. Despite its clinical significance and rapid advances in science and pharmacotherapy, there is yet no specific treatment for this disease. This may be due to a lack of understanding of the pathogenesis and mechanisms behind how a cirrhotic liver causes cardiac pathology. This review will focus specifically on insights into the molecular mechanisms that drive this liver-heart interaction. Deeper understanding of the etio-pathogenesis of cirrhotic cardiomyopathy will allow us to design and test treatments that can be targeted to prevent and/or reverse this co-morbid consequence of liver failure and improve health care delivery and outcomes in patients with cirrhosis.

The Endocannabinoid System and Cannabidiol: Past, Present, and Prospective for Cardiovascular Diseases

In the past, cannabis was commonly associated with mysticism and illegality. Fortunately, in recent years perspectives and discourses have changed. More prominence has been given to the rigorous scientific effort that led to the discovery of cannabis' many physiological actions and endogenous signalling mechanisms. The endocannabinoid system is a complex and heterogeneous pro-homeostatic network comprising different receptors with several endogenous ligands, numerous metabolic enzymes and regulatory proteins. Therefore, it is not surprising that alterations and dysfunctions of the endocannabinoid system are observed in almost every category of disease. Such high degree of pathophysiological involvement suggests the endocannabinoid system is a promising therapeutic target and prompted the translation of resurgent scientific findings into clinical therapies. Shifting attitudes toward cannabis also raised other matters such as increased patient awareness, prescription requests, self-medication, recreational use, recognition of new knowledge gaps, renewed scientific activity, and seemingly exponential growth of the cannabis industry. This review, following a general overview of cannabis and the endocannabinoid system, assiduously describes its role within the context of cardiovascular diseases, paying particular attention to the Janus influence that endocannabinoid system modulators can have on the cardiovascular system.

Hepatorenal syndrome in children: a review

Hepatorenal syndrome (HRS) occurs in patients with cirrhosis or fulminant hepatic failure and is a kind of pre-renal failure due to intense reduction of kidney perfusion induced by severe hepatic injury. While other causes of pre-renal acute kidney injury (AKI) respond to fluid infusion, HRS does not. HRS incidence is 5% in children with chronic liver conditions before liver transplantation. Type 1 HRS is an acute and rapidly progressive form that often develops after a precipitating factor, including gastrointestinal bleeding or spontaneous bacterial peritonitis, while type 2 is considered a slowly progressive form of kidney failure that often occurs spontaneously in chronic ascites settings. HRS pathogenesis is multifactorial. Cirrhosis causes portal hypertension; therefore, stasis and release of vasodilator substances occur in the hepatic vascular bed, leading to vasodilatation of splanchnic arteries and systemic hypotension. Many mechanisms seem to work together to cause this imbalance: splanchnic vasodilatation; vasoactive mediators; hyperdynamic circulation states and subsequent cardiac dysfunction; neuro-hormonal mechanisms; changes in sympathetic nervous system, renin-angiotensin system, and vasopressin. In patients with AKI and cirrhosis, fluid expansion therapy needs to be initiated as soon as possible and nephrotoxic drugs discontinued. Once HRS is diagnosed, pharmacological treatment with vasoconstrictors, mainly terlipressin plus albumin, should be initiated. If there is no response, other options can include surgical venous shunts and kidney replacement therapy. In this regard, extracorporeal liver support can be a bridge for liver transplantation, which remains as the ideal treatment. Further studies are necessary to investigate early biomarkers and alternative treatments for HRS.

Dual inhibition of CB1 receptors and iNOS, as a potential novel approach to the pharmacological management of acute and long COVID-19

COVID‐19 (SARS‐CoV‐2) causes multiple inflammatory complications, resulting not only in severe lung inflammation but also harm to other organs. Although the current focus is on the management of acute COVID‐19, there is growing concern about long‐term effects of COVID‐19 (Long Covid), such as fibroproliferative changes in the lung, heart and kidney. Therefore, the identification of therapeutic targets not only for the management of acute COVID‐19 but also for preventing Long Covid are needed, and would mitigate against long‐lasting health burden and economic costs, in addition to saving lives. COVID‐19 induces pathological changes via multiple pathways, which could be targeted simultaneously for optimal effect. We discuss the potential pathologic function of increased activity of the endocannabinoid/CB₁ receptor system and inducible NO synthase (iNOS). We advocate a polypharmacology approach, wherein a single chemical entity simultaneously interacts with CB₁ receptors and iNOS causing inhibition, as a potential therapeutic strategy for COVID‐19‐related health complications.

Angiotensin II-Induced Cardiac Effects Are Modulated by Endocannabinoid-Mediated CB1 Receptor Activation

Angiotensin II (Ang II) has various cardiac effects and causes vasoconstriction. Ang II activates the type-1 angiotensin receptor-Gq/11 signaling pathway resulting in the release of 2-arachidonoylglycerol (2-AG). We aimed to investigate whether cardiac Ang II effects are modulated by 2-AG-release and to identify the role of type-1 cannabinoid receptors (CB1R) in these effects. Expression of CB1R in rat cardiac tissue was confirmed by immunohistochemistry. To characterize short-term Ang II effects, increasing concentrations of Ang II (10-9-10-7 M); whereas to assess tachyphylaxis, repeated infusions of Ang II (10-7 M) were administered to isolated Langendorff-perfused rat hearts. Ang II infusions caused a decrease in coronary flow and ventricular inotropy, which was more pronounced during the first administration. CB agonist 2-AG and WIN55,212-2 administration to the perfusate enhanced coronary flow. The flow-reducing effect of Ang II was moderated in the presence of CB1R blocker O2050 and diacylglycerol-lipase inhibitor Orlistat. Our findings indicate that Ang II-induced cardiac effects are modulated by simultaneous CB1R-activation, most likely due to 2-AG-release during Ang II signalling. In this combined effect, the response to 2-AG via cardiac CB1R may counteract the positive inotropic effect of Ang II, which may decrease metabolic demand and augment Ang II-induced coronary vasoconstriction.

Integrating Endocannabinoid Signalling In Depression

Depression is a common mental disorder and is the leading cause of suicide globally. Because of the significant diversity in mental disorders, accurate diagnosis is difficult. Hence, the investigation of novel biomarkers is a key research perspective in psychotherapy to enable an individually tailored treatment approach. The prefrontal cortex (PFC) is a vital cortical region whose circuitry has been implicated in the development of depressive disorder. The endocannabinoid system (ECS) has garnered increasing attention because of its involvement in several diverse physiological brain processes including regulation of emotional, motivational and cognitive functions. The current review article explores the function of the key elements of the ECS as a biomarker in depressive disorder. The activity of endocannabinoids is thought to be moderated by the CB1 receptors in the central nervous system (CNS). Variations in the concentration of endocannabinoids and the binding affinity of CB1 receptors and their density have been identified in the PFC of persons with depression. Such discoveries support our theory that alteration in endocannabinoid function leads to the pathophysiological features of depressive disorders. Moreover, evidence from animal and human studies has revealed that dysfunction in endocannabinoid signalling can produce depression-like behaviours; therefore, improvement of endocannabinoid signalling may represent a new therapeutic approach for the management of depressive disorders.

Hepatocyte cannabinoid 1 receptor nullification alleviates toxin-induced liver damage via NF-κB signaling

Cannabinoid 1 receptor (CB1R) expression is upregulated in the liver with viral hepatitis, cirrhosis, and both alcoholic and non-alcoholic fatty liver disease (FLD), whereas its expression is muted under usual physiological conditions. Inhibiting CB1R has been shown to be beneficial in preserving hepatic function in FLD but it is unclear if inhibiting CB1R during an inflammatory response to an acute hepatic injury, such as toxin-induced injury, would also be beneficial. We found that intrinsic CB1R in hepatocytes regulated liver inflammation-related gene transcription. We tested if nullification of hepatocyte-specific CB1R (hCNR1^−/−) in mice protects against concanavalin A (Con A)-induced liver injury. We looked for evidence of liver damage and markers of inflammation in response to Con A by measuring liver enzyme levels and proinflammatory cytokines (e.g., TNF-α, IL-1β, IL-6, IL-17) in serum collected from hCNR1^−/− and control mice. We observed a shift to the right in the dose-response curve for liver injury and inflammation in hCNR1^−/− mice. We also found less inflammatory cell infiltration and focal necrosis in livers of hCNR1^−/− mice compared to controls, resulting from downregulated apoptotic markers. This anti-apoptotic mechanism results from increased activation of nuclear factor kappa B (NF-κB), especially cAMP-dependent cannabinoid signaling and membrane-bound TNF-α, via downregulated TNF-α receptor 2 (TNFR2) transcription levels. Collectively, these findings provide insight into involvement of CB1R in the pathogenesis of acute liver injury.

Interplay of cardiovascular mediators, oxidative stress and inflammation in liver disease and its complications

The liver is a crucial metabolic organ that has a key role in maintaining immune and endocrine homeostasis. Accumulating evidence suggests that chronic liver disease might promote the development of various cardiac disorders (such as arrhythmias and cardiomyopathy) and circulatory complications (including systemic, splanchnic and pulmonary complications), which can eventually culminate in clinical conditions ranging from portal and pulmonary hypertension to pulmonary, cardiac and renal failure, ascites and encephalopathy. Liver diseases can affect cardiovascular function during the early stages of disease progression. The development of cardiovascular diseases in patients with chronic liver failure is associated with increased morbidity and mortality, and cardiovascular complications can in turn affect liver function and liver disease progression. Furthermore, numerous infectious, inflammatory, metabolic and genetic diseases, as well as alcohol abuse can also influence both hepatic and cardiovascular outcomes. In this Review, we highlight how chronic liver diseases and associated cardiovascular effects can influence different organ pathologies. Furthermore, we explore the potential roles of inflammation, oxidative stress, vasoactive mediator imbalance, dysregulated endocannabinoid and autonomic nervous systems and endothelial dysfunction in mediating the complex interplay between the liver and the systemic vasculature that results in the development of the extrahepatic complications of chronic liver disease. The roles of ageing, sex, the gut microbiome and organ transplantation in this complex interplay are also discussed.

PET/SPECT Molecular Probes for the Diagnosis and Staging of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a significant public health challenge afflicting approximately 1 billion individuals both in the Western world and in the East world. While liver biopsy is considered as gold standard in the diagnosis and staging of liver fibrosis, noninvasive imaging technologies, including ultrasonography, computed tomography, single-photon emission computed tomography (SPECT), magnetic resonance imaging, and positron emission tomography (PET) could offer more sensitive, comprehensive, and quantitative measurement for NAFLD. In this review, we focus on recent development and applications of PET/SPECT molecular probes that enable multispatial/temporal visualization and quantification of physiopathological progress at the molecular level in the NAFLD. We shall also discuss the limitations of current radioligands and future direction for PET/SPECT probe development.

Cannabinoid-2 receptor activation ameliorates hepatorenal syndrome

STUDY RATIONALE

Hepatorenal syndrome (HRS) is a life-threatening complication of end-stage liver disease characterized by the rapid decline of kidney function. Herein, we explored the therapeutic potential of targeting the cannabinoid-2 receptor (CB₂-R) utilizing a commonly used mouse model of liver fibrosis and hepatorenal syndrome (HRS), induced by bile duct ligation (BDL).

METHODS

Gene expression analysis, histological evaluation, determination of serum levels of renal injury-biomarkers were used to characterize the BDL-induced organ injury; laser speckle analysis to measure microcirculation in the kidneys.

KEY RESULTS

We found that liver injury triggered marked inflammation and oxidative stress in the kidneys of BDL-operated mice. We detected pronounced histopathological alterations with tubular injury paralleled with increased inflammation, oxidative/nitrative stress and fibrotic remodeling both in hepatic and renal tissues as well as endothelial activation and markedly impaired renal microcirculation. This was accompanied by increased CB₂-R expression in both the liver and the kidney tissues of diseased animals. A selective CB₂-R agonist, HU-910, markedly decreased numerous markers of inflammation, oxidative stress and fibrosis both in the liver and in the kidneys. HU-910 also attenuated markers of kidney injury and improved the impaired renal microcirculation in BDL-operated mice.

CONCLUSIONS

Our results suggest that oxidative stress, inflammation and microvascular dysfunction are key events in the pathogenesis of BDL-associated renal failure. Furthermore, we demonstrate that targeting the CB₂-R by selective agonists may represent a promising new avenue to treat HRS by attenuating tissue and vascular inflammation, oxidative stress, fibrosis and consequent microcirculatory dysfunction in the kidneys.

Interactions Between Alcohol and the Endocannabinoid System

Endocannabinoids are lipid mediators that interact with the same cannabinoid receptors that recognize Δ⁹ -tetrahydrocannabinol (THC), the psychoactive constituent of marijuana, to induce similar effects in the brain and periphery. Alcohol and THC are both addictive substances whose acute use elicits rewarding effects that can lead to chronic and compulsive use via engaging similar signaling pathways in the brain. In the liver, both alcohol and endocannabinoids activate lipogenic gene expression leading to fatty liver disease. This review focuses on evidence accumulated over the last 2 decades to indicate that both the addictive neural effects of ethanol and its organ toxic effects in the liver and elsewhere are mediated, to a large extent, by endocannabinoids signaling via cannabinoid-1 receptors (CB₁ R). The therapeutic potential of CB₁ R blockade globally or in peripheral tissues only is also discussed.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

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.

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.

Vascular syndromes in liver cirrhosis

Liver cirrhosis is associated with multiple vascular syndromes affecting almost all body systems. Many of these syndromes are directly related to impaired liver function and sometimes reversible after liver transplantation while others arise secondary to portal hypertension and ascites. Altered expression of angiogenic and vasoactive compounds (most importantly nitric oxide), endothelial dysfunction, dysregulated neurohormonal control, and systemic inflammatory state play differential roles in mediating homeostatic instability and abnormal vasogenic response. Important vascular features encountered in liver disease include portal hypertension, splanchnic overflow, abnormal angiogenesis and shunts, portopulmonary syndrome, hepatopulmonary syndrome, and systemic hyperdynamic circulation. Redistribution of effective circulatory volume deviating from vital organs and pooling in splanchnic circulation is also encountered in liver patients which may lead to devastating outcomes as hepatorenal syndrome. Etiologically, vascular syndromes are not isolated phenomena and vascular dysfunction in one system may lead to the development of another in a different system. This review focuses on understanding the pathophysiological factors underlying vascular syndromes related to chronic liver disease and the potential links among them. Many of these syndromes are associated with high mortality, thus it is crucial to look for early biomarkers for these syndromes and develop novel preventive and therapeutic strategies.

Cannabinoids and Cardiovascular System

Cannabinoids influence cardiovascular variables in health and disease via multiple mechanisms. The chapter covers the impact of cannabinoids on cardiovascular function in physiology and pathology and presents a critical analysis of the proposed signalling pathways governing regulation of cardiovascular function by endogenously produced and exogenous cannabinoids. We know that endocannabinoid system is overactivated under pathological conditions and plays both a protective compensatory role, such as in some forms of hypertension, atherosclerosis and other inflammatory conditions, and a pathophysiological role, such as in disease states associated with excessive hypotension. This chapter focuses on the mechanisms affecting hemodynamics and vasomotor effects of cannabinoids in health and disease states, highlighting mismatches between some studies. The chapter will first review the effects of marijuana smoking on cardiovascular system and then describe the impact of exogenous cannabinoids on cardiovascular parameters in humans and experimental animals. This will be followed by analysis of the impact of cannabinoids on reactivity of isolated vessels. The article critically reviews current knowledge on cannabinoid induction of vascular relaxation by cannabinoid receptor-dependent and -independent mechanisms and dysregulation of vascular endocannabinoid signaling in disease states.

Endocannabinoid-mediated modulation of Gq protein-coupled receptor mediates vascular hyporeactivity to nor-adrenaline during polymicrobial sepsis

BACKGROUND

Endocannabinoids level are reported to increase in sepsis, however, the role of vascular cannabinoid receptor-1 (CB1R) in sepsis-induced vascular hyporeactivity is yet to be unravelled.

METHODS

Polymicrobial sepsis was induced by caecal ligation and puncture in mice. Isometric tension in isolated aortic rings during early (6 h) and late (20 h) phases of sepsis was recorded and expression of mRNA of monoacylglycerol lipase (MAGL) and cannabinoid receptor-1 (CB1R) was investigated.

RESULTS

Sepsis significantly (p < 0.001) reduced the mean survival time in mice along with increase in bacterial load in blood and peritoneal lavage. Compared to Sham-operated (SO) mice, vascular reactivity to nor-adrenaline (NA) was significantly (p < 0.05) attenuated in both early and late phases of sepsis. NA-induced vasoconstriction was significantly (p < 0.05) potentiated by inhibition of diacylglycerol lipase (DAGL) and attenuated by inhibition of MAGL in SO mice. Pre-incubation with KT 109, a DAGL inhibitor, significantly (p < 0.05) improved the vascular hypo-reactivity to NA during both the phases of sepsis. mRNA expression of MAGL in aorta was significantly (p < 0.05) attenuated during both the phases of sepsis. But in the presence of AM 251, specific antagonist of CB1R, vascular reactivity to NA was significantly (p < 0.05) restored along with significant (p < 0.05) increase in mRNA expression of CB1R in aortic rings from both early and late phases of septic mice.

CONCLUSION

2-AG regulates vascular response to NA and increased aortic expression of CB1R is responsible for vascular hyporeactivity to NA in sepsis, and in vitro inhibition of this receptor by AM 251 restored the vascular reactivity.

Aldehyde dehydrogenase 2 activation ameliorates CCl4 -induced chronic liver fibrosis in mice by up-regulating Nrf2/HO-1 antioxidant pathway

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is critical in the pathogenesis of alcoholic liver cirrhosis. However, the effect of ALHD2 on liver fibrosis remains to be further elucidated. This study aimed to demonstrate whether ALDH2 regulates carbon tetrachloride (CCl₄)‐induced liver fibrosis and to investigate the efficacy of Alda‐1, a specific activator of ALDH2, on attenuating liver fibrosis. ALDH2 expression was increased after chronic CCl₄ exposure. ALDH2 deficiency accentuated CCl₄‐induced liver fibrosis in mice, accompanied by increased expression of collagen 1α1, α‐SMA and TIMP‐1. Moreover, ALDH2 knockout triggered more ROS generation, hepatocyte apoptosis and impaired mitophagy after CCl₄ treatment. In cultured HSC‐T6 cells, ALDH2 knockdown by transfecting with lentivirus vector increased ROS generation and α‐SMA expression in an in vitro hepatocyte fibrosis model using TGF‐β1. ALDH2 overexpression by lentivirus or activation by Alda‐1 administration partly reversed the effect of TGF‐β1, whereas ALDH2 knockdown totally blocked the protective effect of Alda‐1. Furthermore, Alda‐1 administration protected against liver fibrosis in vivo, which might be mediated through up‐regulation of Nrf2/HO‐1 cascade and activation of Parkin‐related mitophagy. These findings indicate that ALDH2 deficiency aggravated CCl₄‐induced hepatic fibrosis through ROS overproduction, increased apoptosis and mitochondrial damage, whereas ALDH2 activation through Alda‐1 administration alleviated hepatic fibrosis partly through activation of the Nrf2/HO‐1 antioxidant pathway and Parkin‐related mitophagy, which indicate ALDH2 as a promising anti‐fibrotic target and Alda‐1 as a potential therapeutic agent in treating CCl₄‐induced liver fibrosis.

Enhanced endocannabinoid tone as a potential target of pharmacotherapy

The endocannabinoid system is up-regulated in numerous pathophysiological states such as inflammatory, neurodegenerative, gastrointestinal, metabolic and cardiovascular diseases, pain, and cancer. It has been suggested that this phenomenon primarily serves an autoprotective role in inhibiting disease progression and/or diminishing signs and symptoms. Accordingly, enhancement of endogenous endocannabinoid tone by inhibition of endocannabinoid degradation represents a promising therapeutic approach for the treatment of many diseases. Importantly, this allows for the avoidance of unwanted psychotropic side effects that accompany exogenously administered cannabinoids. The effects of endocannabinoid metabolic pathway modulation are complex, as endocannabinoids can exert their actions directly or via numerous metabolites. The two main strategies for blocking endocannabinoid degradation are inhibition of endocannabinoid-degrading enzymes and inhibition of endocannabinoid cellular uptake. To date, the most investigated compounds are inhibitors of fatty acid amide hydrolase (FAAH), an enzyme that degrades the endocannabinoid anandamide. However, application of FAAH inhibitors (and consequently other endocannabinoid degradation inhibitors) in medicine became questionable due to a lack of therapeutic efficacy in clinical trials and serious adverse effects evoked by one specific compound. In this paper, we discuss multiple pathways of endocannabinoid metabolism, changes in endocannabinoid levels across numerous human diseases and corresponding experimental models, pharmacological strategies for enhancing endocannabinoid tone and potential therapeutic applications including multi-target drugs with additional targets outside of the endocannabinoid system (cyclooxygenase-2, cholinesterase, TRPV1, and PGF_2α-EA receptors), and currently used medicines or medicinal herbs that additionally enhance endocannabinoid levels. Ultimately, further clinical and preclinical studies are warranted to develop medicines for enhancing endocannabinoid tone.

Cannabinoid receptors in the kidney

PURPOSE OF REVIEW

The endocannabinoid system modulates cell signaling targets that are essential for energy homeostasis. Endocannabinoids bind to G protein-coupled receptors in the central nervous system and periphery, including the kidney. Modulation of cannabinoid receptor 1 (CB1) and CB2 activity in the kidney in diabetes and obesity has been identified as potential therapeutic target to reduce albuminuria and renal fibrosis. This review will highlight the results of recent studies that have identified a role for CB1 and CB2 in normal and pathological renal conditions.

RECENT FINDINGS

CB1 and CB2 have been reported to play key roles in renal function and dysfunction. Recent studies have determined that antagonism of CB1 and agonism of CB2 in diabetic nephropathy and obesity associated kidney disease can reduce albuminuria, potentially by acting on both the glomeruli and tubules. Emerging studies have also identified a role for CB1 in renal diseases associated with fibrosis, with CB1 upregulated in multiple models of human nephropathies.

SUMMARY

Emerging studies using isolated cells, rodent models, and human studies have identified a critical role for the endocannabinoid system in renal function and disease. Thus, therapeutics that modulate the activity of CB1 and CB2 in renal disease could become clinically relevant.

Endocannabinoid-related compounds in gastrointestinal diseases

The endocannabinoid system (ECS) is an endogenous signalling pathway involved in the control of several gastrointestinal (GI) functions at both peripheral and central levels. In recent years, it has become apparent that the ECS is pivotal in the regulation of GI motility, secretion and sensitivity, but endocannabinoids (ECs) are also involved in the regulation of intestinal inflammation and mucosal barrier permeability, suggesting their role in the pathophysiology of both functional and organic GI disorders. Genetic studies in patients with irritable bowel syndrome (IBS) or inflammatory bowel disease have indeed shown significant associations with polymorphisms or mutation in genes encoding for cannabinoid receptor or enzyme responsible for their catabolism, respectively. Furthermore, ongoing clinical trials are testing EC agonists/antagonists in the achievement of symptomatic relief from a number of GI symptoms. Despite this evidence, there is a lack of supportive RCTs and relevant data in human beings, and hence, the possible therapeutic application of these compounds is raising ethical, political and economic concerns. More recently, the identification of several EC-like compounds able to modulate ECS function without the typical central side effects of cannabino-mimetics has paved the way for emerging peripherally acting drugs. This review summarizes the possible mechanisms linking the ECS to GI disorders and describes the most recent advances in the manipulation of the ECS in the treatment of GI diseases.

Decreasing CB1 receptor signaling in Kupffer cells improves insulin sensitivity in obese mice

Objective

Obesity-induced accumulation of ectopic fat in the liver is thought to contribute to the development of insulin resistance, and increased activity of hepatic CB₁R has been shown to promote both processes. However, lipid accumulation in liver can be experimentally dissociated from insulin resistance under certain conditions, suggesting the involvement of additional mechanisms. Obesity is also associated with pro-inflammatory changes which, in turn, can promote insulin resistance. Kupffer cells (KCs), the liver's resident macrophages, are the major source of pro-inflammatory cytokines in the liver, such as TNF-α, which has been shown to inhibit insulin signaling in multiple cell types, including hepatocytes. Here, we sought to identify the role of CB₁R in KCs in obesity-induced hepatic insulin resistance.

Methods

We used intravenously administered β-D-glucan-encapsulated siRNA to knock-down CB₁R gene expression selectively in KCs.

Results

We demonstrate that a robust knock-down of the expression of Cnr1, the gene encoding CB₁R, results in improved glucose tolerance and insulin sensitivity in diet-induced obese mice, without affecting hepatic lipid content or body weight. Moreover, Cnr1 knock-down in KCs was associated with a shift from pro-inflammatory M1 to anti-inflammatory M2 cytokine profile and improved insulin signaling as reflected by increased insulin-induced Akt phosphorylation.

Conclusion

These findings suggest that CB₁R expressed in KCs plays a critical role in obesity-related hepatic insulin resistance via a pro-inflammatory mechanism.

•

CB₁R signaling promotes hepatic insulin resistance by promoting hepatic steatosis and hepatic inflammation.

•

CB₁R knock-down in liver macrophages (Kupffer cells, KCs) improves global insulin resistance and glucose homeostasis.

•

CB₁R expressed in KCs play a critical role in hepatic insulin resistance independent of ectopic fat in the liver or adipose tissue inflammation.

Daytime-Dependent Changes of Cannabinoid Receptor Type 1 and Type 2 Expression in Rat Liver

The present study was performed to investigate the diurnal expression pattern of cannabinoid receptor type 1 (CB₁) and type 2 (CB₂) in liver tissue of 12- and 51-week-old normoglycemic Wistar rats. By using real-time RT-PCR, daytime dependent changes in both age groups and, for both, hepatic Cnr1 and Cnr2 receptor mRNA levels were measured. Highest amount of mRNA was detected in the light period (ZT3, ZT6, and ZT9) while the lowest amount was measured in the dark period (ZT18 and ZT21). Diurnal transcript expression pattern was accompanied by comparable changes of protein level for CB₁, as shown by Western blotting. The current results support the conclusion that expression pattern of cannabinoid receptors are influenced by light/dark cycle and therefore seems to be under the control of a diurnal rhythm. These findings might explain the differences in the efficacy of cannabinoid receptor agonists or antagonists. In addition, investigation of liver of streptozotocin (STZ)-treated 12- and 51-week-old rats show alterations in the diurnal profile of both receptors Cnr1 and Cnr2 compared to that of normoglycemic Wistar rats. This suggests an influence of diabetic state on diurnal expression levels of cannabinoid receptors.

Cannabinoids in the Cardiovascular System

Cannabinoids are known to modulate cardiovascular functions including heart rate, vascular tone, and blood pressure in humans and animal models. Essential components of the endocannabinoid system, namely, the production, degradation, and signaling pathways of endocannabinoids have been described not only in the central and peripheral nervous system but also in myocardium, vasculature, platelets, and immune cells. The mechanisms of cardiovascular responses to endocannabinoids are often complex and may involve cannabinoid CB₁ and CB₂ receptors or non-CB_1/2 receptor targets. Preclinical and some clinical studies have suggested that targeting the endocannabinoid system can improve cardiovascular functions in a number of pathophysiological conditions, including hypertension, metabolic syndrome, sepsis, and atherosclerosis. In this chapter, we summarize the local and systemic cardiovascular effects of cannabinoids and highlight our current knowledge regarding the therapeutic potential of endocannabinoid signaling and modulation.

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.

Molecular Mechanisms Leading to Splanchnic Vasodilation in Liver Cirrhosis

In liver cirrhosis, portal hypertension is a consequence of enhanced intrahepatic vascular resistance and portal blood flow. Significant vasodilation in the arterial splanchnic district is crucial for an increase in portal flow. In this pathological condition, increased levels of circulating endogenous vasodilators, including nitric oxide, prostacyclin, carbon monoxide, epoxyeicosatrienoic acids, glucagon, endogenous cannabinoids, and adrenomedullin, and a decreased vascular response to vasoconstrictors are the main mechanisms underlying splanchnic vasodilation. In this review, the molecular pathways leading to splanchnic vasodilation will be discussed in detail.

The endogenous lipid N-arachidonoyl glycine is hypotensive and nitric oxide-cGMP-dependent vasorelaxant

N-arachidonoyl glycine (NAGLY), is the endogenous lipid that activates the G protein-couple receptor 18 (GPR18) with vasodilatory activity in resistance arteries. This study investigates its hemodynamic effects and mechanisms of vasorelaxation. Hemodynamic effects of NAGLY in rats were assessed using a Biopac system and its vascular responses were assessed using a wire myograph. NAGLY (1mg/kg) decreased blood pressure by 69.4±5.5% and reduced renal blood flow by 88±12% and the effects were not sensitive to inhibition by O-1918 (3mg/kg). In resistant vessels, NAGLY (1-30µM) induced concentration- and endothelium-dependent vasorelaxation and the effect was inhibited by the nitric oxide synthase inhibitor, L-NAME (300µM), a cGMP synthase inhibitor, ODQ (10µM), the antagonists of "endothelial anandamide" receptor, rimonabant (3µM) and O-1918 (10µM) and the inhibitor of Na⁺/Ca²⁺ exchanger (NCX), KB-R7943 (10µM). On the other hand, NAGLY-induced vasorelaxation was not affected by CID 16020046 (GPR55 antagonist), AM 251 (cannabinoid CB₁ receptor antagonist), AM 630 (cannabinoid CB₂ receptor antagonist), capsazepine (TRPV1 antagonist), indomethacin (cyclooxygenase inhibitor), TRAM34 (IKCa channel blocker), iberiotoxin (BKCa channel blocker) and GW9662 (PPARɤ antagonist). At low concentrations of carbachol, NAGLY potentiated carbachol-induced vasorelaxation. NAGLY is an endothelium-dependent vasodilator and hypotensive lipid. The vasorelaxation is predominantly via activation of nitric oxide-cGMP pathway and NCX and probably mediated by the "endothelial anandamide" receptor, while the hypotensive effect of NAGLY appears not to involve the anandamide receptor. NAGLY also potentiates carbachol-induced vasorelaxation, the mechanism of which might involve stimulation of NO release.

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS). This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs. In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.

Marijuana Use Is Not Associated With Progression to Advanced Liver Fibrosis in HIV/Hepatitis C Virus-coinfected Women

BACKGROUND

Marijuana (hereafter "tetrahydrocannabinol [THC]") use has been associated with liver fibrosis progression in retrospective analyses of patients with chronic hepatitis C (HCV). We studied long-term effects of THC on fibrosis progression in women coinfected with human immunodeficiency virus (HIV)/HCV enrolled in the Women's Interagency HIV Study (WIHS).

METHODS

Liver fibrosis was categorized according to FIB-4 scores as none, moderate, or significant. THC and alcohol use were quantified as average exposure per week. Associations between THC use and progression to significant fibrosis were assessed using Cox proportional hazards regression.

RESULTS

Among 575 HIV/HCV-coinfected women followed for a median of 11 (interquartile range, 6-17) years, 324 (56%) reported no THC use, 141 (25%) less than weekly use, 70 (12%) weekly use, and 40 (7%) daily use at WIHS entry. In univariable analysis, entry FIB-4 score (hazard ratio [HR], 2.26 [95% confidence interval {CI}, 1.88-2.73], P < .001), log HCV RNA (HR, 1.19 [95% CI, 1.02-1.38], P = .02), tobacco use (HR, 1.37 [95% CI, 1.02-1.85], P = .04), CD4(+) count (risk per 100-cell increase: HR, 0.90 [95% CI, .86-.95], P < .001), and log HIV RNA (HR, 1.18 [95% CI, 1.05-1.32], P = .005) were associated with progression to significant fibrosis, as was cumulative alcohol use in follow-up (HR, 1.03 [95% CI, 1.02-1.04], P < .001). In multivariable analysis, entry FIB-4, entry CD4(+) count, and cumulative alcohol use remained significant. Cumulative THC use was not associated with fibrosis progression (HR, 1.01 [95% CI, .92-1.10], P = .83).

CONCLUSIONS

In this large cohort of HIV/HCV-coinfected women, THC was not associated with progression to significant liver fibrosis. Alcohol use was independently associated with liver fibrosis, and may better predict fibrosis progression in HIV/HCV-coinfected women.

Endocannabinoids in cerebrovascular regulation

The cerebral blood flow is tightly regulated by myogenic, endothelial, metabolic, and neural mechanisms under physiological conditions, and a large body of recent evidence indicates that inflammatory pathways have a major influence on the cerebral blood perfusion in certain central nervous system disorders, like hemorrhagic and ischemic stroke, traumatic brain injury, and vascular dementia. All major cell types involved in cerebrovascular control pathways (i.e., smooth muscle, endothelium, neurons, astrocytes, pericytes, microglia, and leukocytes) are capable of synthesizing endocannabinoids and/or express some or several of their target proteins [i.e., the cannabinoid 1 and 2 (CB1 and CB2) receptors and the transient receptor potential vanilloid type 1 ion channel]. Therefore, the endocannabinoid system may importantly modulate the regulation of cerebral circulation under physiological and pathophysiological conditions in a very complex manner. Experimental data accumulated since the late 1990s indicate that the direct effect of cannabinoids on cerebral vessels is vasodilation mediated, at least in part, by CB1 receptors. Cannabinoid-induced cerebrovascular relaxation involves both a direct inhibition of smooth muscle contractility and a release of vasodilator mediator(s) from the endothelium. However, under stress conditions (e.g., in conscious restrained animals or during hypoxia and hypercapnia), cannabinoid receptor activation was shown to induce a reduction of the cerebral blood flow, probably via inhibition of the electrical and/or metabolic activity of neurons. Finally, in certain cerebrovascular pathologies (e.g., subarachnoid hemorrhage, as well as traumatic and ischemic brain injury), activation of CB2 (and probably yet unidentified non-CB1/non-CB2) receptors appear to improve the blood perfusion of the brain via attenuating vascular inflammation.

Cirrhotic Multiorgan Syndrome

Patients with cirrhosis and portal hypertension are at an increased risk of the development of circulatory dysfunction that may potentially result in multiple organ failure. Apart from the liver, this may involve the heart, lungs, kidneys, the immune system, the adrenal glands, and other organ systems. As the disease progresses, the circulation becomes hyperdynamic, and signs of cardiac, pulmonary, and renal dysfunction are observed, in addition to reduced survival. Infections and an altered cardiac function known as cirrhotic cardiomyopathy may be precipitators for the development of other complications such as hepatorenal syndrome. In patients with chronic organ dysfunction, various precipitating events may induce an acute-on-chronic renal failure and acute-on-chronic liver failure that negatively affect the prognosis. Future research on the pathophysiologic mechanisms of the complications and the precipitating factors is essential to understand the basics of the treatment of these challenging conditions. The aim of the present review is to focus on the development and precipitating factors of various organ failures in patients with decompensated cirrhosis.

Blunted cardiac response to hemorrhage in cirrhotic rats is mediated by local macrophage-released endocannabinoids

BACKGROUND & AIMS

Cirrhosis is associated with blunted cardiovascular response to stimuli such as hemorrhage, but the mechanism remains unclear. We aimed to clarify the role of endocannabinoids in blunted hemorrhage response in cirrhotic rats.

METHODS

Cirrhosis was induced by bile duct ligation (BDL). Hemodynamics were measured. Cannabinoid receptor-1 (CB1) antagonist, AM251, and macrophage inhibitor gadolinium chloride (GdCl3) were administered. Myocardial levels of anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) were measured and resident monocytes and macrophages quantified by immunohistochemistry. Isolated cardiomyocyte contractility was measured before and after incubation with monocytes from BDL and sham controls.

RESULTS

Hemorrhage significantly decreased arterial pressure and left ventricular dP/dT. After hemorrhage, these changes quickly reversed in controls, but were severely prolonged in BDL rats. Chronic AM251 treatment restored this impaired response. AEA and 2-AG levels were increased in BDL hearts and further increased after hemorrhage. Sham hearts showed virtually no monocytes or macrophages before or after hemorrhage, whereas BDL hearts had significantly more white blood cells which further increased after hemorrhage. GdCl3 treatment significantly reduced cardiac endocannabinoid levels both at baseline and after hemorrhage. This treatment also restored cardiovascular response to hemorrhage in BDL rats but did not affect sham controls. Monocytes isolated from BDL rats more potently inhibited cardiomyocyte contractility than sham control monocytes.

CONCLUSIONS

The cirrhotic heart showed increased monocyte recruitment and endocannabinoid levels. CB1 blockade or GdCl3 treatment restored blunted cardiovascular response to hemorrhage. Endocannabinoids released by monocytes blunt cardiac response to hemorrhage. Preventing monocyte recruitment or blocking endocannabinoid signaling may improve cardiovascular homeostasis in cirrhosis.

Rimonabant Improves Oxidative/Nitrosative Stress in Mice with Nonalcoholic Fatty Liver Disease

The present study deals with the effects of rimonabant on oxidative/nitrosative stress in high diet- (HFD-) induced experimental nonalcoholic fatty liver disease (NAFLD). Male mice C57BL/6 were divided into the following groups: control group fed with control diet for 20 weeks (C; n = 6); group fed with HFD for 20 weeks (HF; n = 6); group fed with standard diet and treated with rimonabant after 18 weeks (R; n = 9); group fed with HFD and treated with rimonabant after 18 weeks (HFR; n = 10). Daily dose of rimonabant (10 mg/kg) was administered to HFR and R group by oral gavage for two weeks. Treatment induced a decrease in hepatic malondialdehyde concentration in HFR group compared to HF group (P < 0.01). The concentration of nitrites + nitrates in liver was decreased in HFR group compared to HF group (P < 0.01). Liver content of reduced glutathione was higher in HFR group compared to HF group (P < 0.01). Total liver superoxide dismutase activity in HFR group was decreased in comparison with HF group (P < 0.01). It was found that rimonabant may influence hepatic iron, zinc, copper, and manganese status. Our study indicates potential usefulness of cannabinoid receptor type 1 blockade in the treatment of HFD-induced NAFLD.

Molecular pathophysiology of portal hypertension

Over the past two decades the advances in molecular cell biology have led to significant discoveries about the pathophysiology of portal hypertension (PHT). In particular, great progress has been made in the study of the molecular and cellular mechanisms that regulate the increased intrahepatic vascular resistance (IHVR) in cirrhosis. We now know that the increased IHVR is not irreversible, but that both the structural component caused by fibrosis and the active component caused by hepatic sinusoidal constriction can be, at least partially, reversed. Indeed, it is now apparent that the activation of perisinusoidal hepatic stellate cells, which is a key event mediating the augmented IHVR, is regulated by multiple signal transduction pathways that could be potential therapeutic targets for PHT treatment. Furthermore, the complexity of the molecular physiology of PHT can also be appreciated when one considers the complex signals capable of inducing vasodilatation and hyporesponsiveness to vasoconstrictors in the splanchnic vascular bed, with several vasoactive molecules, controlled at multiple levels, working together to mediate these circulatory abnormalities. Added to the complexity is the occurrence of pathological angiogenesis during the course of disease progression, with recent emphasis given to understanding its molecular machinery and regulation. Although much remains to be learned, with the current availability of reagents and new technologies and the exchange of concepts and data among investigators, our knowledge of the molecular basis of PHT will doubtless continue to grow, accelerating the transfer of knowledge generated by basic research to clinical practice. This will hopefully permit a better future for patients with PHT.

Endocannabinoid signaling at the periphery: 50 years after THC

In 1964, the psychoactive ingredient of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC), was isolated. Nearly 30 years later the endogenous counterparts of THC, collectively termed endocannabinoids (eCBs), were discovered: N-arachidonoylethanolamine (anandamide) (AEA) in 1992 and 2-arachidonoylglycerol (2-AG) in 1995. Since then, considerable research has shed light on the impact of eCBs on human health and disease, identifying an ensemble of proteins that bind, synthesize, and degrade them and that together form the eCB system (ECS). eCBs control basic biological processes including cell choice between survival and death and progenitor/stem cell proliferation and differentiation. Unsurprisingly, in the past two decades eCBs have been recognized as key mediators of several aspects of human pathophysiology and thus have emerged to be among the most widespread and versatile signaling molecules ever discovered. Here some of the pioneers of this research field review the state of the art of critical eCB functions in peripheral organs. Our community effort is aimed at establishing consensus views on the relevance of the peripheral ECS for human health and disease pathogenesis, as well as highlighting emerging challenges and therapeutic hopes.

Pathophysiology of Portal Hypertension

The bases of our current knowledge on the physiology of the hepatic portal system are largely owed to the work of three pioneering vascular researchers from the sixteenth and the seventeenth centuries: A. Vesalius, W. Harvey, and F. Glisson. Vesalius is referred to as the founder of modern human anatomy, and in his influential book, De humani corporis fabrica libri septem, he elaborated the first anatomical atlas of the hepatic portal venous system (Vesalius 2013). Sir William Harvey laid the foundations of modern cardiovascular research with his Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (Harvey 1931) in which he established the nature of blood circulation. Finally, F. Glisson characterized the gastrointestinal-hepatic vascular system (Child 1955). These physiological descriptions were later complemented with clinical observations. In the eighteenth and nineteenth centuries, Morgagni, Puckelt, Cruveilhier, and Osler were the first to make the connection between common hepatic complications – ascites, splenomegaly, and gastrointestinal bleeding – and obstruction of the portal system (Sandblom 1993). These were the foundations that allowed Gilbert, Villaret, and Thompson to establish an early definition of portal hypertension at the beginning of the twentieth century. In this period, Thompson performed the first direct measurement of portal pressure by laparotomy in some patients (Gilbert and Villaret 1906; Thompson et al. 1937). Considering all these milestones, and paraphrasing Sir Isaac Newton, if hepatologists have seen further, it is by standing on the shoulders of giants.

Nowadays, our understanding of the pathogenesis of portal hypertension has largely improved thanks to the progress in preclinical and clinical research. However, this field is ever-changing and hepatologists are continually identifying novel pathological mechanisms and developing new therapeutic strategies for this clinical condition. Hence, the aim of this chapter is to summarize the current knowledge about this clinical condition.