Cannabinoid receptor 2 counteracts interleukin-17-induced immune and fibrogenic responses in mouse liver

Reviewing the function of macrophages in liver disease

INTRODUCTION

The liver is a central metabolic organ, but is also hosting a unique immune microenvironment to sustain homeostasis and proper defense measures against injury threats in healthy individuals. Liver macrophages, mostly represented by the tissue-resident Kupffer cells and bone marrow- or monocyte-derived macrophages, are intricately involved in various aspects of liver homeostasis and disease, including tissue injury, inflammation, fibrogenesis and repair mechanisms.

AREAS COVERED

We review recent findings on defining the liver macrophage landscape and their functions in liver diseases with the aim of highlighting potential targets for therapeutic interventions. A comprehensive literature search in PubMed and Google Scholar was conducted to identify relevant literature up to date.

EXPERT OPINION

Liver macrophages orchestrate key homeostatic and pathogenic processes in the liver. Thus, targeting liver macrophages represents an attractive strategy for drug development, e.g. to ameliorate liver inflammation, steatohepatitis or fibrosis. However, translation from fundamental research to therapies remains challenging due to the versatile nature of the liver macrophage compartment. Recent and major technical advances such as single-cell and spatially-resolved omics approaches deepened our understanding of macrophage biology at a molecular level. Yet, further studies are needed to identify suitable, etiology- and stage-dependent strategies for the treatment of liver diseases.

Defective autophagy in CD4 T cells drives liver fibrosis via type 3 inflammation

Conventional CD4 T cells represent a major source of inflammatory mediators that drive progression of chronic liver disease to fibrosis and to end-stage cirrhosis. Identification of T cell pathways that limits the inflammatory response could thus have therapeutic relevance. Here we show, using both human samples and mouse models, that autophagy is deficient in CD4 T cells from patients with advanced fibrosis, and that loss of autophagy following genomic deletion of ATG5 in T cells is associated with the emergence of pathogenic IL-17A + IFN-γ + Th17 T cells that drive liver fibrosis in mice. Mechanistically, liver CD4 T cells lacking autophagy display a Th17 glycolytic phenotype associated with enhanced type 3 cytokine (i.e., IL-17A and GM-CSF) release, shifting hepatic myofibroblasts, hepatocytes and macrophages toward a proinflammatory phenotype. We also show that autophagy can be rescued in CD4 T cells from patients with extensive liver fibrosis, leading to decreased frequency of pathogenic Th17 cells and reduced GM-CSF levels; in addition, limited fibrosis is observed in mice in which Rubicon, a negative regulator of autophagy, is deleted specifically in their T cells. Our findings thus implicate autophagy in CD4 T cells as a key therapeutic target to control inflammation-driven fibrosis during chronic liver injury.

Immunoregulation of Liver Fibrosis: New Opportunities for Antifibrotic Therapy

Liver fibrosis develops in response to chronic liver injury and is characterized by a sustained inflammatory response that leads to excessive collagen deposition by myofibroblasts. The fibrogenic response is governed by the release of inflammatory mediators from innate, adaptive, and innate-like lymphoid cells and from nonprofessional immune cells (i.e., epithelial cells, hepatic myofibroblasts, and liver sinusoidal endothelial cells). Upon removal of the underlying cause, liver fibrosis can resolve via activation of specific immune cell subsets. Despite major advances in the understanding of fibrosis pathogenesis, there is still no approved antifibrotic therapy. This review summarizes our current knowledge of the immune cell landscape and the inflammatory mechanisms underlying liver fibrosis progression and regression. We discuss how reprogramming immune cell phenotype, in particular through targeting selective inflammatory pathways or modulating cell-intrinsic metabolism, may be translated into antifibrogenic therapies.

Therapeutic potential of agents targeting cannabinoid type 2 receptors in organ fibrosis

The endocannabinoid system has garnered attention as a potential therapeutic target in a range of pathological disorders. Cannabinoid receptors type 2 (CB2) are a class of G protein-coupled receptors responsible for transmitting intracellular signals triggered by both endogenous and exogenous cannabinoids, including those derived from plants (phytocannabinoids) or manufactured synthetically (synthetic cannabinoids). Recent recognition of the role of CB2 receptors in fibrosis has fueled interest in therapeutic targeting of CB2 receptors in fibrosis. Fibrosis is characterized by the alteration of the typical cellular composition within the tissue parenchyma, resulting from exposure to diverse etiological factors. The pivotal function of CB2 agonists has been widely recognized in the regulation of inflammation, fibrogenesis, and various other biological pathologies. The modulation of CB2 receptors, whether by enhancing their expression or activating their function, has the potential to provide benefits in numerous conditions, particularly by avoiding any associated adverse effects on the central nervous system. The sufficient activation of CB2 receptors resulted in the complete suppression of gene expression related to transforming growth factor β1 and its subsequent fibrogenic response. Multiple reports have also indicated the diverse functions that CB2 agonists possess in mitigating chronic inflammation and subsequent fibrosis development in various types of tissues. While currently in the preclinical stage, the advancement of CB2 compounds has garnered significant attention within the realm of drug discovery. This review presents a comprehensive synthesis of various independent experimental studies elucidating the pivotal role of identified natural and synthetic CB2 agonists in the pathophysiology of organ fibrosis, specifically in the cardiac, hepatic, and renal systems.

T cell activation and lowered T regulatory cell numbers are key processes in severe major depressive disorder: Effects of recurrence of illness and adverse childhood experiences

BACKGROUND

Major depressive disorder (MDD) is characterized by increased T helper (Th)1 polarization, T cell activation (e.g., CD71+ and CD40L+), and cannabinoid receptor type 2 bearing CD20+ B cells; and lower T regulatory (Treg) numbers.

AIMS

To delineate the effects of adverse childhood experiences (ACEs) and recurrence of illness (ROI) on activated T and CB2-bearing B populations, and Tregs, including FoxP3 + CD152+, FoxP3 + GARP+, and FoxP3 + CB1+ cells.

METHODS

We measured ROI, ACEs, the number of activated T cells, Tregs, and CD20 + CB2+ B cells, in 30 MDD patients and 20 healthy controls.

RESULTS

A larger part of the variance in the depression phenome (40.8 %) was explained by increased CD20 + CB2+ and activated T cells, and lowered Tregs. ROI and lifetime suicidal behaviors were significantly and positively associated with CD20 + CB2+, CD3 + CD71+, CD3 + CD40L+, CD4 + CD71+, CD4 + CD40L+, and CD4HLADR+ numbers. ROI was significantly correlated with CD8 + CD40L+ numbers. The sum of ACEs was significantly associated with CD20 + CB2+, CD3 + CD40L+, CD4 + 40 L+ numbers, T cell activation (positively) and Treg (inversely) indices. One replicable latent vector could be extracted from activated T cells, lifetime and current suicidal behaviors, number of depressive episodes, and severity of depression, and 48.8 % of its variance was explained by ACEs.

CONCLUSIONS

ACE-induced activation of T effector and cytotoxic cells and B cells with autoimmune potential, coupled with lowered Treg numbers are a key component of depression. The findings indicate that increasing ROI, the phenome of depression and suicidal behaviors, are caused by autoimmune processes, which are the consequence of ACEs and increasing sensitization of immune responses.

Role of T and B lymphocyte cannabinoid type 1 and 2 receptors in major depression and suicidal behaviours

Early flow cytometry studies revealed T cell activation in major depressive disorder (MDD). MDD is characterised by activation of the immune-inflammatory response system (IRS) and the compensatory immunoregulatory system (CIRS), including deficits in T regulatory (Treg) cells. This study examines the number of cannabinoid type 1 (CB1) and type 2 (CB2) receptor-bearing T/B lymphocytes in MDD, and the effects of in vitro cannabidiol (CBD) administration on CB1/CB2-bearing immunocytes. Using flow cytometry, we determined the percentage of CD20+CB2+, CD3+CB2+, CD4+CB2+, CD8+CB2+ and FoxP3+CB1+ cells in 19 healthy controls and 29 MDD patients in 5 conditions: baseline, stimulation with anti-CD3/CD28 with or without 0.1 µg/mL, 1.0 µg/mL, or 10.0 µg/mL CBD. CB2+ was significantly higher in CD20+ than CD3+ and CD4+ and CD 8+ cells. Stimulation with anti-CD3/CD8 increases the number of CB2-bearing CD3+, CD4+ and CD8+ cells, as well as CB1-bearing FoxP3+ cells. There was an inverse association between the number of reduced CD4+ CB2+ and IRS profiles, including M1 macrophage, T helper-(Th)-1 and Th-17 phenotypes. MDD is characterised by lowered basal FoxP3+ CB1+% and higher CD20+ CB2+%. 33.2% of the variance in the depression phenome (including severity of depression, anxiety and current suicidal behaviours) is explained by CD20+ CB2+ % (positively) and CD3+ CB2+% (inversely). All five immune cell populations were significantly increased by 10 µg/mL of CBD administration. Reductions in FoxP3+ CB1+% and CD3+ /CD4+ CB2+% contribute to deficits in immune homoeostasis in MDD, while increased CD20+CB2+% may contribute to the pathophysiology of MDD by activating T-independent humoral immunity.

Cannabinoids and Their Receptors in Skin Diseases

The therapeutic application of cannabinoids has gained traction in recent years. Cannabinoids interact with the human endocannabinoid system in the skin. A large body of research indicates that cannabinoids could hold promise for the treatment of eczema, psoriasis, acne, pruritus, hair disorders, and skin cancer. However, most of the available data are at the preclinical stage. Comprehensive, large-scale, randomized, controlled clinical trials have not yet been fully conducted. In this article, we describe new findings in cannabinoid research and point out promising future research areas.

The contradictory roles of macrophages in non-alcoholic fatty liver disease and primary liver cancer-Challenges and opportunities

Chronic liver diseases from varying etiologies generally lead to liver fibrosis and cirrhosis. Among them, non-alcoholic fatty liver disease (NAFLD) affects roughly one-quarter of the world population, thus representing a major and increasing public health burden. Chronic hepatocyte injury, inflammation (non-alcoholic steatohepatitis, NASH) and liver fibrosis are recognized soils for primary liver cancer, particularly hepatocellular carcinoma (HCC), being the third most common cause for cancer-related deaths worldwide. Despite recent advances in liver disease understanding, therapeutic options on pre-malignant and malignant stages remain limited. Thus, there is an urgent need to identify targetable liver disease-driving mechanisms for the development of novel therapeutics. Monocytes and macrophages comprise a central, yet versatile component of the inflammatory response, fueling chronic liver disease initiation and progression. Recent proteomic and transcriptomic studies performed at singular cell levels revealed a previously overlooked diversity of macrophage subpopulations and functions. Indeed, liver macrophages that encompass liver resident macrophages (also named Kupffer cells) and monocyte-derived macrophages, can acquire a variety of phenotypes depending on microenvironmental cues, and thus exert manifold and sometimes contradictory functions. Those functions range from modulating and exacerbating tissue inflammation to promoting and exaggerating tissue repair mechanisms (i.e., parenchymal regeneration, cancer cell proliferation, angiogenesis, fibrosis). Due to these central functions, liver macrophages represent an attractive target for the treatment of liver diseases. In this review, we discuss the multifaceted and contrary roles of macrophages in chronic liver diseases, with a particular focus on NAFLD/NASH and HCC. Moreover, we discuss potential therapeutic approaches targeting liver macrophages.

IL-17 Expression in the Perifollicular Fibrosis in Biopsies From Lichen Planopilaris

BACKGROUND

Lichen planopilaris (LPP) is a primary lymphocytic cicatricial alopecia for which therapy is often ineffective and there is no cure.

OBJECTIVES

Looking for a new targetable molecule in the treatment of LPP, we sought to verify whether IL-17 expression is increased in scalp biopsies from patients with active scalp lesions of LPP.

METHODS

Horizontal sections of hematoxylin and eosin-stained slides from 40 scalp biopsies of active LPP were retrospectively collected and stained with the monoclonal antibody against IL-17 (Abcam, Cambridge, MA; ab79056, dilution 1:100). Twenty biopsies from patients with chronic telogen effluvium served as controls because of their morphological resemblance to the normal scalp. Statistical analysis was performed using IBM SPSS Statistics for Windows (IBM Corporation, Armonk, NY).

RESULTS

The main finding was the positive cytoplasmic expression of IL-17 in the perifollicular fibrosis of the affected follicles in LPP which was statistically significant compared with the controls ( P < 0.0001). The labeled cells were identified as fibroblasts based on their spindle shape and fascicular concentric arrangement in tight perifollicular distribution. Although most of the LPP specimens (n = 35; 87.5%) also revealed cytoplasmic IL-17 expression in the lichenoid inflammatory infiltrate, the results were not statistically significant ( P = 0.1351).

CONCLUSION

Our immunohistochemistry results show that blocking the IL-17 inflammatory pathway may interfere with the progression of the perifollicular fibrosis and inflammation in LPP.

Activation of CD4+ T Cell-Derived Cannabinoid Receptor 2 Signaling Exacerbates Sepsis via Inhibiting IL-10

The cannabinoid receptor 2 (CB2) is a receptor mainly expressed in immune cells and believed to be immunosuppressive in infective or inflammatory models. However, its role in sepsis has not been fully elucidated. In this study, we delineate the function and mechanism of CB2 in the cecal ligation and puncture-induced septic model in mice. The activation of CB2 signaling with HU308 led to decreased survival rates and more severe lung injury in septic mice, and lower IL-10 levels in peritoneal lavage fluid were observed in the CB2 agonist group. The mice with conditional knockout of CB2-encoding gene CNR2 in CD4+ T cells (CD4 Cre CNR2fl/fl) improved survival, enhanced IL-10 production, and ameliorated pulmonary damage in the sepsis model after CB2 activation. In addition, double-knockout of the CNR2 gene (Lyz2 Cre CD4 Cre CNR2fl/fl) decreased the susceptibility to sepsis compared with Lyz2 Cre CNR2fl/fl mice. Mechanistically, the blockade of IL-10 with the anti-IL-10 Ab abolished its protection in CD4 Cre CNR2fl/fl mice. In accordance with the animal study, in vitro results revealed that the lack of CNR2 in CD4+ cells elevated IL-10 production, and CB2 activation inhibited CD4+ T cell-derived IL-10 production. Furthermore, in the clinical environment, septic patients expressed enhanced CB2 mRNA levels compared with healthy donors in PBMCs, and their CB2 expression was inversely correlated with IL-10. These results suggested that the activation of CD4+ T cell-derived CB2 increased susceptibility to sepsis through inhibiting IL-10 production.

Cannabinoid Receptor 2 (CB2) Inverse Agonist SMM-189 Induces Expression of Endogenous CB2 and Protein Kinase A That Differentially Modulates the Immune Response and Suppresses Experimental Colitis

The causes of Crohn’s disease (CD) and ulcerative colitis (UC), the two most common forms of inflammatory bowel disease (IBD), are multi-factorial and include dysregulation of immune cells in the intestine. Cannabinoids mediate protection against intestinal inflammation by binding to the G-protein coupled cannabinoid receptors 1 and 2 (CB1 and CB2). Here, we investigate the effects of the CB2 inverse agonist SMM-189 on dextran sodium sulfate (DSS)-induced experimental colitis. We observed that SMM-189 effectively attenuated the overall clinical score, reversed colitis-associated pathogenesis, and increased both body weight and colon length. Treatment with SMM-189 also increased the expression of CB2 and protein kinase A (PKA) in colon lamina propria lymphocytes (LPLs). We noticed alterations in the percentage of Th17, neutrophils, and natural killer T (NKT) cells in the spleen, mesenteric lymph nodes (MLNs), and LPLs of mice with DSS-induced colitis after treatment with SMM-189 relative to DSS alone. Further, myeloid-derived suppressor cells (MDSCs) during colitis progression increased with SMM-189 treatment as compared to DSS alone or with control cohorts. These findings suggest that SMM-189 may ameliorate experimental colitis by inducing the expression of endogenous CB2 and PKA in LPLs, increasing numbers of MDSCs in the spleen, and reducing numbers of Th17 cells and neutrophils in the spleen, MLNs, and LPLs. Taken together, these data support the idea that SMM-189 may be developed as a safe novel therapeutic target for IBD.

Inflammation in alcohol-associated liver disease progression

Chronic alcohol consumption induces stress and damage in alcohol metabolising hepatocytes, which leads to inflammatory and fibrogenic responses. Besides these direct effects, alcohol disrupts intestinal barrier functions and induces gut microbial dysbiosis, causing translocation of bacteria or microbial products through the gut mucosa to the liver and, which induce inflammation indirectly. Inflammation is one of the key drivers of alcohol-associated liver disease progression from steatosis to severe alcoholic hepatitis. The current standard of care for the treatment of severe alcoholic hepatitis is prednisolone, aiming to reduce inflammation. Prednisolone, however improves only short-term but not long-term survival rates in those patients, and even increases the risk for bacterial infections. Thus, recent studies focus on the exploration of more specific inflammatory targets for the treatment of severe alcoholic hepatitis. These comprise, among others interference with inflammatory cytokines, modulation of macrophage phenotypes or targeting of immune cell communication, as summarized in the present overview. Although several approaches give promising results in preclinical studies, data robustness and ability to transfer experimental results to human disease is still not sufficient for effective clinical translation.

Inflammation and Fibrogenesis in MAFLD: Role of the Hepatic Immune System

Metabolic (dysfunction)-associated fatty liver disease (MAFLD) is the definition recently proposed to better circumscribe the spectrum of conditions long known as non-alcoholic fatty liver disease (NAFLD) that range from simple steatosis without inflammation to more advanced liver diseases. The progression of MAFLD, as well as other chronic liver diseases, toward cirrhosis, is driven by hepatic inflammation and fibrogenesis. The latter, result of a "chronic wound healing reaction," is a dynamic process, and the understanding of its underlying pathophysiological events has increased in recent years. Fibrosis progresses in a microenvironment where it takes part an interplay between fibrogenic cells and many other elements, including some cells of the immune system with an underexplored or still unclear role in liver diseases. Some therapeutic approaches, also acting on the immune system, have been probed over time to evaluate their ability to improve inflammation and fibrosis in NAFLD, but to date no drug has been approved to treat this condition. In this review, we will focus on the contribution of the liver immune system in the progression of NAFLD, and on therapies under study that aim to counter the immune substrate of the disease.

Update on Myositis Therapy: from Today's Standards to Tomorrow's Possibilities

Inflammatory myopathies, in short, myositis, are heterogeneous disorders that are characterized by inflammation of skeletal muscle and weakness of arms and legs. Research over the past few years has led to a new understanding regarding the pathogenesis of myositis. The new insights include different pathways of the innate and adaptive immune response during the pathogenesis of myositis. The importance of non-inflammatory mechanisms such as cell stress and impaired autophagy has been recently described. New target-specific drugs for myositis have been developed and are currently being tested in clinical trials. In this review, we discuss the mechanisms of action of pharmacological standards in myositis and provide an outlook of future treatment approaches.

In quest of a new therapeutic approach in COVID-19: the endocannabinoid system

The SARS-Cov-2 virus caused a high morbidity and mortality rate disease, that is the COVID-19 pandemic. Despite the unprecedented research interest in this field, the lack of specific treatments leads to severe complications in a high number of cases. Current treatment includes antivirals, corticosteroids, immunoglobulins, antimalarials, interleukin-6 inhibitors, anti-GM-CSF, convalescent plasma, immunotherapy, antibiotics, circulation support, oxygen therapy, and circulation support. Due to the limited results, until specific treatments are available, other therapeutic approaches need to be considered. The endocannabinoid system is found in multiple systems within the human body, including the immune system. Its activation can lead to beneficial results such as decreased viral entry, decreased viral replication, and a decrease in pro-inflammatory cytokines such as IL-2, IL-4, IL-6, IL-12, TNF-α, or IFN-γ. Moreover, endocannabinoid system activation can lead to an increase in anti-inflammatory cytokines, mainly represented by IL-10. Overall, the cannabinoid system can potentially reduce pulmonary inflammation, increase the immunomodulatory effect, decrease PMN infiltration, reduce fibrosis, and decrease viral replication, as well as decrease the 'cytokine storm'. Although the cannabinoid system has many mechanisms to provide certain benefits in the treatment of SARS-CoV-2 infected patients, research in this field is needed for a better understanding of the cannabinoid impact in this situation.

Cannabinoid Type-2 Receptor Agonist, JWH133 May Be a Possible Candidate for Targeting Infection, Inflammation, and Immunity in COVID-19

The COVID-19 pandemic, caused by SARS-CoV-2, is a deadly disease affecting millions due to the non-availability of drugs and vaccines. The majority of COVID-19 drugs have been repurposed based on antiviral, immunomodulatory, and antibiotic potential. The pathogenesis and advanced complications with infection involve the immune-inflammatory cascade. Therefore, a therapeutic strategy could reduce infectivity, inflammation, and immune modulation. In recent years, modulating the endocannabinoid system, particularly activation of the cannabinoid type 2 (CB2) receptor is a promising therapeutic target for modulation of immune-inflammatory responses. JWH133, a selective, full functional agonist of the CB2 receptor, has been extensively studied for its potent anti-inflammatory, antiviral, and immunomodulatory properties. JWH133 modulates numerous signaling pathways and inhibits inflammatory mediators, including cytokines, chemokines, adhesion molecules, prostanoids, and eicosanoids. In this study, we propose that JWH133 could be a promising candidate for targeting infection, immunity, and inflammation in COVID-19, due to its pharmacological and molecular mechanisms in numerous preclinical efficacy and safety studies, along with its immunomodulatory, anti-inflammatory, organoprotective, and antiviral properties. Thus, JWH133 should be investigated in preclinical and clinical studies for its potential as an agent or adjuvant with other agents for its effect on viremia, infectivity, immune modulation, resolution of inflammation, reduction in severity, and progression of complications in COVID-19. JWH133 is devoid of psychotropic effects due to CB2 receptor selectivity, has negligible toxicity, good bioavailability and druggable properties, including pharmacokinetic and physicochemical effects. We believe that JWH133 could be a promising drug and may inspire further studies for an evidence-based approach against COVID-19.

Pharmacological Properties, Therapeutic Potential and Molecular Mechanisms of JWH133, a CB2 Receptor-Selective Agonist

The endocannabinoid system has attracted attention as a pharmacological target for several pathological conditions. Cannabinoid (CB2)-selective agonists have been the focus of pharmacological studies because modulation of the CB2 receptor (CB2R) can be useful in the treatment of pain, inflammation, arthritis, addiction, and cancer among other possible therapeutic applications while circumventing CNS-related adverse effects. Increasing number of evidences from different independent preclinical studies have suggested new perspectives on the involvement of CB2R signaling in inflammation, infection and immunity, thus play important role in cancer, cardiovascular, renal, hepatic and metabolic diseases. JWH133 is a synthetic agonist with high CB2R selectivity and showed to exert CB2R mediated antioxidant, anti-inflammatory, anticancer, cardioprotective, hepatoprotective, gastroprotective, nephroprotective, and immunomodulatory activities. Cumulative evidences suggest that JWH133 protects against hepatic injury, renal injury, cardiotoxicity, fibrosis, rheumatoid arthritis, and cancer as well as against oxidative damage and inflammation, inhibits fibrosis and apoptosis, and acts as an immunosuppressant. This review provides a comprehensive overview of the polypharmacological properties and therapeutic potential of JWH133. This review also presents molecular mechanism and signaling pathways of JWH133 under various pathological conditions except neurological diseases. Based on the available data, this review proposes the possibilities of developing JWH133 as a promising therapeutic agent; however, further safety and toxicity studies in preclinical studies and clinical trials in humans are warranted.

5-Aza-2-deoxycytidine alleviates the progression of primary biliary cholangitis by suppressing the FoxP3 methylation and promoting the Treg/Th17 balance

Primary biliary cholangitis (PBC) is a common autoimmune liver disease manifested by the infiltration of CD4+ T cells, and the subsequent targeted injury of biliary epithelial cells (BECs). As important components of CD4 subsets, the Treg/Th17 axis maintains an immunological balance between self-tolerance and inflammation in the liver microenvironment. However, the role and regulatory mechanism of the Treg/Th17 axis in PBC remain unclear. In this study, we examined the Treg/Th17 axis in PBC patients and found that the Treg/Th17 axis was imbalanced in PBC at both the transcriptional and cellular levels, with Treg being a weak candidate, which correlates with the PBC progression. This imbalanced Treg/Th17 axis was likely to be affected by the FoxP3 hypermethylation, which was related to the increase of DNA methyltransferase. Furthermore, the effect of 5-Aza-2-deoxycytidine (DAC)-mediated FoxP3 demethylation on PBC mice was investigated. We verified that DAC significantly suppressed the FoxP3 methylation and rebuilt the Treg/Th17 balance, resulting in the alleviation of liver lesions and inflammation. Taken together, our data indicate that DAC plays a positive role in alleviating the progression of PBC through the inhibition of DNA methylation of FoxP3 to rebuild the balanced Treg/Th17 axis. DAC could be considered as a potential candidate for the development of new anti-inflammation strategies in the treatment of PBC.

Interleukin-10 Attenuates Liver Fibrosis Exacerbated by Thermoneutrality

Background: Crosstalk between brown adipose tissue (BAT) and the liver is receiving increasing attention. This study investigated the effect of BAT dysfunction by thermoneutral (TN) housing on liver fibrosis in mice and examined the effect of secreted factors from brown adipocytes on the activation of hepatic stellate cells (HSCs).

Methods: The carbon tetrachloride (CCl₄)-induced liver fibrosis mouse model was used to evaluate fibrotic changes in the livers of mice housed under standard and TN conditions. The effect of BAT on the activation of HSCs was examined using cultured cells treated with conditioned media from brown adipocytes.

Results: Under TN conditions, mice with CCl₄-induced liver fibrosis exhibited increased liver injury, collagen deposition, and alpha smooth muscle actin (α-SMA) expression in the liver compared with mice maintained at room temperature. The numbers of liver-infiltrating immune cells and T cells producing IL-17A and IFN-γ were also significantly increased in the livers of mice housed under TN conditions. Treatment of HSCs with conditioned media from brown adipocytes markedly attenuated HSC activation, as shown by down-regulated α-SMA expression at day 4, day 7 and day 10 of culture. At thermoneutrality, with CCl₄ administration, IL-10-deficient mice exhibited more severe liver fibrosis than wild-type mice. Interestingly, conditioned media from IL-10-deficient brown adipocytes could up-regulate the expression of α-SMA and induce HSCs activation.

Conclusions: BAT inactivation by thermoneutrality contributes to the activation of pro-inflammatory and pro-fibrotic pathways in mice with CCl₄-induced liver fibrosis. Normal brown adipocytes secreted factors that impair the activation of HSCs, while this protective effect was lost in IL-10-deficient brown adipocytes. Thus, the BAT–liver axis may serve as a potential therapeutic target for liver fibrosis, and IL-10 may be a key factor regulating the activation of HSCs by BAT.

Mechanisms and disease consequences of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide. Its more advanced subtype, nonalcoholic steatohepatitis (NASH), connotes progressive liver injury that can lead to cirrhosis and hepatocellular carcinoma. Here we provide an in-depth discussion of the underlying pathogenetic mechanisms that lead to progressive liver injury, including the metabolic origins of NAFLD, the effect of NAFLD on hepatic glucose and lipid metabolism, bile acid toxicity, macrophage dysfunction, and hepatic stellate cell activation, and consider the role of genetic, epigenetic, and environmental factors that promote fibrosis progression and risk of hepatocellular carcinoma in NASH.

Bile acid-activated macrophages promote biliary epithelial cell proliferation through integrin αvβ6 upregulation following liver injury

Cholangiopathies caused by biliary epithelial cell (BEC) injury represent a leading cause of liver failure. No effective pharmacologic therapies exist, and the underlying mechanisms remain obscure. We aimed to explore the mechanisms of bile duct repair after targeted BEC injury. Injection of intermedilysin into BEC-specific human CD59 (hCD59) transgenic mice induced acute and specific BEC death, representing a model to study the early signals that drive bile duct repair. Acute BEC injury induced cholestasis followed by CCR2+ monocyte recruitment and BEC proliferation. Using microdissection and next-generation RNA-Seq, we identified 5 genes, including Mapk8ip2, Cdkn1a, Itgb6, Rgs4, and Ccl2, that were most upregulated in proliferating BECs after acute injury. Immunohistochemical analyses confirmed robust upregulation of integrin αvβ6 (ITGβ6) expression in this BEC injury model, after bile duct ligation, and in patients with chronic cholangiopathies. Deletion of the Itgb6 gene attenuated BEC proliferation after acute bile duct injury. Macrophage depletion or Ccr2 deficiency impaired ITGβ6 expression and BEC proliferation. In vitro experiments revealed that bile acid-activated monocytes promoted BEC proliferation through ITGβ6. Our data suggest that BEC injury induces cholestasis, monocyte recruitment, and induction of ITGβ6, which work together to promote BEC proliferation and therefore represent potential therapeutic targets for cholangiopathies.

Novel Immune Subsets and Related Cytokines: Emerging Players in the Progression of Liver Fibrosis

Liver fibrosis is a pathological process caused by persistent chronic injury of the liver. Kupffer cells, natural killer (NK) cells, NKT cells, and dendritic cells (DCs), which are in close contact with T and B cells, serve to bridge innate and adaptive immunity in the liver. Meanwhile, an imbalanced inflammatory response constitutes a challenge in liver disease. The dichotomous roles of novel immune cells, including T helper 17 (Th17), regulatory T cells (Tregs), mucosa-associated invariant T cells (MAIT), and innate lymphoid cells (ILCs) in liver fibrosis have gradually been revealed. These cells not only induce damage during liver fibrosis but also promote tissue repair. Hence, immune cells have unique, and often opposing, roles during the various stages of fibrosis. Due to this heterogeneity, the treatment, or reversal of fibrosis through the target of immune cells have attracted much attention. Moreover, activation of hepatic stellate cells (HSCs) constitutes the core of fibrosis. This activation is regulated by various immune mediators, including Th17, Th22, and Th9, MAIT, ILCs, and γδ T cells, as well as their related cytokines. Thus, liver fibrosis results from the complex interaction of these immune mediators, thereby complicating the ability to elucidate the mechanisms of action elicited by each cell type. Future developments in biotechnology will certainly aid in this feat to inform the design of novel therapeutic targets. Therefore, the aim of this review was to summarize the role of specific immune cells in liver fibrosis, as well as biomarkers and treatment methods related to these cells.

Phytocannabinoids-A Green Approach toward Non-Alcoholic Fatty Liver Disease Treatment

Non-alcoholic fatty liver disease (NAFLD) is the most frequent chronic liver disease in adults in developed countries, with a global prevalence as high as one billion. The pathogenesis of NAFLD is a multifactorial and multi-step process. Nowadays, a growing body of research suggests the considerable role of the endocannabinoid system (ECS) as a complex cell-signaling system in NAFLD development. Although increased endocannabinoid tone in the liver highly contributes to NAFLD development, the complex effects and impacts of plant-derived cannabinoids in the aspect of NAFLD pathophysiology are yet not fully understood, and effective medications are still in demand. In our review, we present the latest reports describing the role of ECS in NAFLD, focusing primarily on two types of cannabinoid receptors. Moreover, we sum up the recent literature on the clinical use of natural cannabinoids in NAFLD treatment. This review is useful for understanding the importance of ECS in NAFLD development, and it also provides the basis for more extensive clinical phytocannabinoids testing in patients suffering from NAFLD.

Strategies Targeting the Innate Immune Response for the Treatment of Hepatitis C Virus-Associated Liver Fibrosis

Direct-acting antivirals eliminate hepatitis C virus (HCV) in more than 95% of treated individuals and may abolish liver injury, arrest fibrogenesis, and reverse fibrosis and cirrhosis. However, liver regeneration is usually a slow process that is less effective in the late stages of fibrosis. What is more, fibrogenesis may prevail in patients with advanced cirrhosis, where it can progress to liver failure and hepatocellular carcinoma. Therefore, the development of antifibrotic drugs that halt and reverse fibrosis progression is urgently needed. Fibrosis occurs due to the repair process of damaged hepatic tissue, which eventually leads to scarring. The innate immune response against HCV is essential in the initiation and progression of liver fibrosis. HCV-infected hepatocytes and liver macrophages secrete proinflammatory cytokines and chemokines that promote the activation and differentiation of hepatic stellate cells (HSCs) to myofibroblasts that produce extracellular matrix (ECM) components. Prolonged ECM production by myofibroblasts due to chronic inflammation is essential to the development of fibrosis. While no antifibrotic therapy is approved to date, several drugs are being tested in phase 2 and phase 3 trials with promising results. This review discusses current state-of-the-art knowledge on treatments targeting the innate immune system to revert chronic hepatitis C-associated liver fibrosis. Agents that cause liver damage may vary (alcohol, virus infection, etc.), but fibrosis progression shows common patterns among them, including chronic inflammation and immune dysregulation, hepatocyte injury, HSC activation, and excessive ECM deposition. Therefore, mechanisms underlying these processes are promising targets for general antifibrotic therapies.

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 endocannabinoid signaling pathway as an emerging target in pharmacotherapy, earmarking mitigation of destructive events in rheumatoid arthritis

Rheumatoid arthritis is an inflammatory autoimmune disease, characterized by synovial proliferation, destruction to articular cartilage and severe pain. The cannabinoids obtained from Cannabis sativa exhibited their actions via cannabinoid-1 and -2 receptors, which also provides a platform for endocannabinoids to act. The endocannabinoid system comprises endocannabinoid molecules involved in signaling processes, along with G-protein coupled receptors and enzymes associated with ligand biosynthesis, activation and degradation. The action of endocannabinoid system in immune system regulation, via primary CB2 activation, followed by inhibition of production of pro-inflammatory cytokines, auto-antibodies and MMPs, FLSs proliferation and T-cell mediated immune response, are elaborated as potential therapeutic regimes in rheumatoid arthritis. The involvement of endocannabinoid system in immune cells like, B cells, T cells and macrophages, as well as regulatory actions on sensory noniceptors to ameliorate pain is significantly highlighted in the review, elaborating the actions of endocannabinoid signaling in mitigating the disease events. The review also focuses on enhancement of endocannabinoid tone, either by inhibiting the degradation enzymes, like FAAH, MAGL, COX, CytP450, LOX, etc. or by retarding cellular uptake processes. Moreover, the review portrays the optimizing role of endocannabinoid system, in abbreviating the symptoms and complications of rheumatoid arthritis in patients and mitigating inflammation, pain and immune mediated effects significantly.

Safety and Efficacy of Lenabasum in a Phase II, Randomized, Placebo-Controlled Trial in Adults With Systemic Sclerosis

Objective

To assess the safety and efficacy of lenabasum in diffuse cutaneous systemic sclerosis (dcSSc).

Methods

A randomized, double‐blind, placebo‐controlled, phase II study was conducted at 9 SSc clinics in the US. Adults with dcSSc of ≤6 years’ duration who were receiving stable standard‐of‐care treatment were randomized to receive lenabasum (n = 27) or placebo (n = 15). Lenabasum doses were 5 mg once daily, 20 mg once daily, or 20 mg twice daily for 4 weeks, followed by 20 mg twice daily for 8 weeks. Safety and efficacy were assessed at weeks 4, 8, 12, and 16.

Results

Adverse events (AEs) occurred in 63% of the lenabasum group and 60% of the placebo group, with no serious AEs related to lenabasum. Compared to placebo, lenabasum treatment was associated with greater improvement in the American College of Rheumatology Combined Response Index in diffuse cutaneous Systemic Sclerosis (CRISS) score and other efficacy outcome measures that assessed overall disease, skin involvement, and patient‐reported function. The median CRISS score increased in the lenabasum group during the study, reaching 0.33, versus 0.00 in the placebo group, at week 16 (P = 0.07 by 2‐sided mixed‐effects model repeated‐measures analysis). Gene expression in inflammation and fibrosis pathways was reduced, and inflammation and fibrosis were improved on histologic evaluation of skin biopsy specimens, in the lenabasum group compared to the placebo group (all P ≤ 0.05).

Conclusion

Despite a short trial duration in a small number of patients in this phase II study in dcSSc, our findings indicate that lenabasum improves efficacy outcomes and underlying disease pathology with a favorable safety profile.

Cannabinoid Receptor 1/miR-30b-5p Axis Governs Macrophage NLRP3 Expression and Inflammasome Activation in Liver Inflammatory Disease

Nod-like receptor (NLR) family pyrin domain containing 3 (NLRP3) has been regarded as an important initiator or promoter in multiple inflammatory diseases. However, the relationship between cannabinoid receptor 1 (CB1) and macrophage NLRP3 inflammasome and the corresponding molecular mechanism in liver inflammation remain unclear. Mouse liver injury models were induced by carbon tetrachloride (CCl₄) or methionine-choline-deficient and high fat (MCDHF) diet. Human liver tissues were obtained from patients with different chronic liver diseases. CB1 expression was increased in liver tissue and macrophages of CCl₄- and MCDHF-treated mice, positively correlated with NLRP3. CB1 agonist ACEA (Arachiodonyl-2’-Chloroethylamide) promoted NLRP3 expression and NLRP3 inflammasome activation in macrophages. CB1 blockade with its antagonist AM281 reduced NLRP3 expression, inflammasome activation, and liver inflammation in CCl₄- and MCDHF-treated mice. MicroRNA-30b-5p (miR-30b-5p), screened by the intersection of bioinformatics databases and downregulated miRNAs in injured liver, negatively correlated with NLRP3 in mouse and human liver. miR-30b-5p was involved in CB1-mediated activation of NLRP3 inflammasome in macrophages by directly targeting NLRP3. Importantly, administration of miR-30b-5p agomir targeted NLRP3 and attenuated liver inflammation in the injured liver. Altogether, CB1/miR-30b-5p axis modulates NLRP3 expression and NLPR3 inflammasome activation in macrophages during liver inflammation, which provides a potential target for liver disease.

Differential hepatoprotective role of the cannabinoid CB1 and CB2 receptors in paracetamol-induced liver injury

BACKGROUND AND PURPOSE

Protective mechanisms of the endogenous cannabinoid system against drug-induced liver injury (DILI) are actively being investigated regarding the differential regulatory role of the cannabinoid CB₁ and CB₂ receptors in liver fibrogenesis and inflammation.

EXPERIMENTAL APPROACH

The 2-arachidonoylglycerol (2-AG)-related signalling receptors and enzymatic machinery, and inflammatory/fibrogenic factors were investigated in the liver of a mouse model of hepatotoxicity induced by acute and repeated overdoses (750 mg·kg^-1 ·day^-1 ) of paracetamol (acetaminophen), previously treated with selective CB₁ (ACEA) and CB₂ (JWH015) agonists (10 mg·kg^-1 ), or lacking CB₁ and CB₂ receptors.

KEY RESULTS

Acute paracetamol increased the expression of CB₂ , ABHD6 and COX-2, while repeated paracetamol increased that of CB₁ and COX-2 and decreased that of DAGLβ. Both acute paracetamol and repeated paracetamol decreased the liver content of acylglycerols (2-AG, 2-LG and 2-OG). Human liver samples from a patient suffering APAP hepatotoxicity confirmed CB₁ and CB₂ increments. Acute paracetamol-exposed CB₂ KO mice had higher expression of the fibrogenic αSMA and the cytokine IL-6 and lower apoptotic cleaved caspase 3. CB₁ deficiency enhanced the repeated APAP-induced increases in αSMA and cleaved caspase 3 and blocked those of CYP2E1, TNF-α, the chemokine CCL2 and the circulating γ-glutamyltransferase (γGT). Although JWH015 reduced the expression of αSMA and TNF-α in acute paracetamol, ACEA increased the expression of cleaved caspase 3 and CCL2 in repeated paracetamol.

CONCLUSION AND IMPLICATIONS

The differential role of CB₁ versus CB₂ receptors on inflammatory/fibrogenic factors related to paracetamol-induced hepatotoxicity should be considered for designing alternative therapies against DILI.

Interplay of Liver-Heart Inflammatory Axis and Cannabinoid 2 Receptor Signaling in an Experimental Model of Hepatic Cardiomyopathy

BACKGROUND AND AIMS

Hepatic cardiomyopathy, a special type of heart failure, develops in up to 50% of patients with cirrhosis and is a major determinant of survival. However, there is no reliable model of hepatic cardiomyopathy in mice. We aimed to characterize the detailed hemodynamics of mice with bile duct ligation (BDL)-induced liver fibrosis, by monitoring echocardiography and intracardiac pressure-volume relationships and myocardial structural alterations. Treatment of mice with a selective cannabinoid-2 receptor (CB2 -R) agonist, known to attenuate inflammation and fibrosis, was used to explore the impact of liver inflammation and fibrosis on cardiac function.

APPROACH AND RESULTS

BDL induced massive inflammation (increased leukocyte infiltration, inflammatory cytokines, and chemokines), oxidative stress, microvascular dysfunction, and fibrosis in the liver. These pathological changes were accompanied by impaired diastolic, systolic, and macrovascular functions; cardiac inflammation (increased macrophage inflammatory protein 1, interleukin-1, P-selectin, cluster of differentiation 45-positive cells); and oxidative stress (increased malondialdehyde, 3-nitrotyrosine, and nicotinamide adenine dinucleotide phosphate oxidases). CB2 -R up-regulation was observed in both livers and hearts of mice exposed to BDL. CB2 -R activation markedly improved hepatic inflammation, impaired microcirculation, and fibrosis. CB2 -R activation also decreased serum tumor necrosis factor-alpha levels and improved cardiac dysfunction, myocardial inflammation, and oxidative stress, underlining the importance of inflammatory mediators in the pathology of hepatic cardiomyopathy.

CONCLUSIONS

We propose BDL-induced cardiomyopathy in mice as a model for hepatic/cirrhotic cardiomyopathy. This cardiomyopathy, similar to cirrhotic cardiomyopathy in humans, is characterized by systemic hypotension and impaired macrovascular and microvascular function accompanied by both systolic and diastolic dysfunction. Our results indicate that the liver-heart inflammatory axis has a pivotal pathophysiological role in the development of hepatic cardiomyopathy. Thus, controlling liver and/or myocardial inflammation (e.g., with selective CB2 -R agonists) may delay or prevent the development of cardiomyopathy in severe liver disease.

COX-2 in liver fibrosis

As a vital inducible sensor, cyclooxygenase-2 (COX-2) plays an important role in the progress of hepatic fibrogenesis. Activation of hepatic stellate cells (HSCs) in the liver can significantly accelerate the onset and development of liver fibrosis. COX-2 overexpression triggers inflammation that is an important inducer in hepatic fibrosis. Increasing evidence indicates that COX-2 is involved in the main pathogenesis of liver fibrosis, such as inflammation, apoptosis, and cell senescence. Moreover, COX-2 expression is altered in patients and animal models with non-alcoholic fatty liver disease or cirrhosis. These findings suggest that COX-2 has a broad and critical role in the development of liver fibrosis. In this review, we summarize the latest advances in the regulation and signal transduction of COX-2 and its impact on liver fibrosis.

Structure-Effect Relationships of Novel Semi-Synthetic Cannabinoid Derivatives

Background: As a library of cannabinoid (CB) derivatives with (-)-trans-cannabidiol (CBD) or (-)-trans-cannabidivarin (CBDV) scaffold, we synthesized nine novel cannabinoids: 2-hydroxyethyl cannabidiolate (2-HEC), 2-hydroxypentyl cannabidiolate (2-HPC), 2,3-dihydroxypropyl cannabidiolate (GCBD), cyclohexyl cannabidiolate (CHC), n-hexyl-cannabidiolate (HC), 2-(methylsulfonamido)ethyl cannabidiolate (NMSC), 2-hydroxyethyl cannabidivarinolate (2-HECBDV), cyclohexyl cannabidivarinolate (CHCBDV), and n-hexyl cannabidivarinolate (HCBDV). Their binding and intrinsic effects at the CB1- and CB2-receptors and the effects on inflammatory signaling cascades were investigated in in vitro and ex vivo cell models. Materials and Methods: Binding affinity was studied in membranes isolated from CB-receptor-transfected HEK293EBNA cells, intrinsic functional activity in Chinese hamster ovary (CHO) cells, and activation of nuclear factor κB (NF-κB) and nuclear factor of activated T-cells (NFAT) in phorbol 12-myristate 13-acetate (PMA)/ionomycin (IO)-treated Jurkat T-cells. Inhibition of interleukin (IL)-17-induced pro-inflammatory cytokines and chemokines [IL-6, IL-1β, CC-chemokine ligand 2 (CCL2), and tumor necrosis factor (TNF)-α] was studied in RAW264.7 macrophages at the RNA level. Pro-inflammatory cytokine (IL-1β, IL-6, IL-8, and TNF-α) expression and prostaglandin E2 (PGE₂) expression were investigated at the protein level in lipopolysaccharide (LPS)-treated primary human monocytes. Results: Derivatives with long aliphatic side chains at the ester position at R¹ [HC (5)] as well as the ones with polar side chains [2-HECBDV (7), NMSC (6), and 2-HEC (1)] can be selective for CB2-receptors. The CBDV-derivatives HCBDV and CHCBDV demonstrated specific binding at CB1- and CB2-receptors at nanomolar concentrations. 2-HEC, 2-HPC, GCBD, and NMSC were agonists at CB2-receptor and antagonists at CB1-receptor. CHC bound both receptors at submicromolar ranges and was an agonist for these receptors. 2-HECBDV was an agonist at CB2-receptor and an antagonist at the CB1-receptor despite its modest affinity at this receptor (micromolar range). NMSC inhibited NF-κB and NFAT activity, and 2-HEC, 2-HPC, and GCBD dose-dependently inhibited PMA/IO-stimulated NFAT activation. CHC and HC dose-dependently reduced IL-1β and CCL2 messenger RNA (mRNA) expression. NMSC inhibited IL-1β, CCL2, and TNF-α at lower doses. At higher doses, it induced a pronounced increase in IL-6 mRNA. 2-HEC, 2-HPC, and GCBD dose-dependently inhibited LPS-induced IL-1β, TNF-α, and IL-6 synthesis. NMSC further increased LPS-stimulated IL-1β release but inhibited IL-8, TNF-α, and PGE₂. Conclusion: The CBD- and CBDV-derivatives studied are suitable for targeting CB-receptors. Some may be used as selective CB2 agonists. The length of the aliphatic rest at R² of CBD (pentyl) and CBDV (propyl) did not correlate with the binding affinity. Higher polarity at R¹ appeared to favor the agonistic activity at CB2-receptors.

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.

"Let my liver rather heat with wine" - a review of hepatic fibrosis pathophysiology and emerging therapeutics

Cirrhosis is characterized by extensive hepatic fibrosis, and it is the 14th leading cause of death worldwide. Numerous contributing conditions have been implicated in its development, including infectious etiologies, medication overdose or adverse effects, ingestible toxins, autoimmunity, hemochromatosis, Wilson’s disease and primary biliary cholangitis to list a few. It is associated with portal hypertension and its stigmata (varices, ascites, hepatic encephalopathy, combined coagulopathy and thrombophilia), and it is a major risk factor for hepatocellular carcinoma. Currently, orthotopic liver transplantation has been the only curative modality to treat cirrhosis, and the scarcity of donors results in many people waiting years for a transplant. Identification of novel targets for pharmacologic therapy through elucidation of key mechanistic components to induce fibrosis reversal is the subject of intense research. Development of robust models of hepatic fibrosis to faithfully characterize the interplay between activated hepatic stellate cells (the principal fibrogenic contributor to fibrosis initiation and perpetuation), hepatocytes and extracellular matrix components has the potential to identify critical components and mechanisms that can be exploited for targeted treatment. In this review, we will highlight key cellular pathways involved in the pathophysiology of fibrosis from extracellular ligands, effectors and receptors, to nuclear receptors, epigenetic mechanisms, energy homeostasis and cytokines. Further, molecular pathways of hepatic stellate cell deactivation are discussed, including apoptosis, senescence and reversal or transdifferentiation to an inactivated state resembling quiescence. Lastly, clinical evidence of fibrosis reversal induced by biologics and small molecules is summarized, current compounds under clinical trials are described and efforts for treatment of hepatic fibrosis with mesenchymal stem cells are highlighted. An enhanced understanding of the rich tapestry of cellular processes identified in the initiation, perpetuation and resolution of hepatic fibrosis, driven principally through phenotypic switching of hepatic stellate cells, should lead to a breakthrough in potential therapeutic modalities.

RAB18 modulates autophagy in human stellate cells

BACKGROUND

Macroautophagy (or autophagy) is a conserved degradative pathway that breaks down sequestered cytoplasmic proteins and organelles in specialized double-membrane compartments called autophagosomes that fuse with lysosomes. Several proteins orchestrate this process, specifically Rab GTPases that are master regulators of molecular trafficking. RAB18 GTPase, a known mediator of stellate cell activation, is known to modulate autophagic flux in fibroblasts. However, its role in autophagy is unexplored in hepatic stellate cells.

OBJECTIVE

The aim of this study was to investigate the role of RAB18 in modulating autophagy in hepatic stellate cells.

METHODS

Role of RAB18 was determined by genetic depletion, pharmacologic inhibition, and overexpression studies to monitor autophagy flux and proteostasis in human LX2 stellate cell line.

RESULTS

RAB18 knockdown increases autophagy flux and regulates proteostasis. LX2 cells stimulated with transforming growth factor-beta robustly increases expression of profibrotic genes such as COL1A1 and ACTA2 along with RAB18 and its guanine nucleotide exchange factor, RAB3GAP1.

CONCLUSION

The study elucidates a role for RAB18 in autophagy and regulation of proteostasis in human stellate cells. Molecular insights into this process can provide therapeutic opportunities for intervention in liver fibrosis.

A selective CB2 agonist protects against the inflammatory response and joint destruction in collagen-induced arthritis mice

Rheumatoid arthritis (RA) is a chronic, inflammatory, synovitis-dominated systemic disease with unknown etiology. RA is characterized by the involvement of multiple affected joints, symmetry, and invasive arthritis of the limbs, which can lead to joint deformity, cartilage destruction, and loss of function. Cannabinoid receptor 2 (CB₂) has potent immunomodulatory and anti-inflammatory effects and is predominantly expressed in non-neuronal tissues. In the current study, the role of CB₂ in the process of inflammatory bone erosion in RA was examined. The selective agonist or high-affinity ligand of CB₂ (4-quinolone-3-carboxamides CB2 agonist, 4Q3C CB₂ agonist, 4Q3C) significantly reduced the severity of arthritis, decreased histopathological findings, and markedly reduced bone erosion in collagen-induced arthritis (CIA) mice. In addition, 4Q3C prevented an increase in the nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) ratio and inhibited the formation of osteoclasts in CIA mice. Furthermore, the expression of tumor necrosis factor-alpha, interleukin-1β, cyclooxygenase-2, and inducible nitric oxide synthase was lower in 4Q3C-treated CIA mice than in control CIA mice. Micro-computed tomography corroborated the finding that 4Q3C reduced joint destruction. These data clearly indicate that the CB₂-selective agonist, 4Q3C, may have anti-inflammatory and anti-osteoclastogenesis effects in RA and may be considered to be a novel treatment for RA.

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.

Role of macrophages in experimental liver injury and repair in mice

Liver macrophages make up the largest proportion of tissue macrophages in the host and consist of two dissimilar groups: Kupffer cells (KCs) and monocyte-derived macrophages (MoMø). As the liver is injured, KCs sense the injury and initiate inflammatory cascades mediated by the release of inflammatory cytokines and chemokines. Subsequently, inflammatory monocytes accumulate in the liver via chemokine-chemokine receptor interactions, resulting in massive inflammatory MoMø infiltration. When live r injury ceases, restorative macrophages, derived from recruited inflammatory monocytes (lymphocyte antigen 6 complex, locus Chi monocytes), promote the resolution of hepatic damage and fibrosis. Consequently, a large number of studies have assessed the mechanisms by which liver macrophages exert their opposing functions at different time-points during liver injury. The present review primarily focuses on the diverse functions of macrophages in experimental liver injury, fibrosis and repair in mice and illustrates how macrophages may be targeted to treat liver disease.

Autophagy in liver diseases: Time for translation?

Autophagy is a self-eating catabolic pathway that contributes to liver homeostasis through its role in energy balance and in the quality control of the cytoplasm, by removing misfolded proteins, damaged organelles and lipid droplets. Autophagy not only regulates hepatocyte functions but also impacts on non-parenchymal cells, such as endothelial cells, macrophages and hepatic stellate cells. Deregulation of autophagy has been linked to many liver diseases and its modulation is now recognized as a potential new therapeutic strategy. Indeed, enhancing autophagy may prevent the progression of a number of liver diseases, including storage disorders (alpha-1 antitrypsin deficiency, Wilson's disease), acute liver injury, non-alcoholic steatohepatitis and chronic alcohol-related liver disease. Nevertheless, in some situations such as fibrosis, targeting specific liver cells must be considered, as autophagy displays opposing functions depending on the cell type. In addition, an optimal therapeutic time-window should be identified, since autophagy might be beneficial in the initial stages of disease, but detrimental at more advanced stages, as in the case of hepatocellular carcinoma. Finally, identifying biomarkers of autophagy and methods to monitor autophagic flux in vivo are important steps for the future development of personalized autophagy-targeting strategies. In this review, we provide an update on the regulatory role of autophagy in various aspects of liver pathophysiology, describing the different strategies to manipulate autophagy and discussing the potential to modulate autophagy as a therapeutic strategy in the context of liver diseases.

Liver Macrophages: Old Dogmas and New Insights

Inflammation is a hallmark of virtually all liver diseases, such as liver cancer, fibrosis, nonalcoholic steatohepatitis, alcoholic liver disease, and cholangiopathies. Liver macrophages have been thoroughly studied in human disease and mouse models, unravelling that the hepatic mononuclear phagocyte system is more versatile and complex than previously believed. Liver macrophages mainly consist of liver‐resident phagocytes, or Kupffer cells (KCs), and bone marrow‐derived recruited monocytes. Although both cell populations in the liver demonstrate principal functions of macrophages, such as phagocytosis, danger signal recognition, cytokine release, antigen processing, and the ability to orchestrate immune responses, KCs and recruited monocytes retain characteristic ontogeny markers and remain remarkably distinct on several functional aspects. While KCs dominate the hepatic macrophage pool in homeostasis (“sentinel function”), monocyte‐derived macrophages prevail in acute or chronic injury (“emergency response team”), making them an interesting target for novel therapeutic approaches in liver disease. In addition, recent data acquired by unbiased large‐scale techniques, such as single‐cell RNA sequencing, unraveled a previously unrecognized complexity of human and murine macrophage polarization abilities, far beyond the old dogma of inflammatory (M1) and anti‐inflammatory (M2) macrophages. Despite tremendous progress, numerous challenges remain in deciphering the full spectrum of macrophage activation and its implication in either promoting liver disease progression or repairing injured liver tissue. Being aware of such heterogeneity in cell origin and function is of crucial importance when studying liver diseases, developing novel therapeutic interventions, defining macrophage‐based prognostic biomarkers, or designing clinical trials. Growing knowledge in gene expression modulation and emerging technologies in drug delivery may soon allow shaping macrophage populations toward orchestrating beneficial rather than detrimental inflammatory responses.

AM-1241 CB2 Receptor Agonist Attenuates Inflammation, Apoptosis and Stimulate Progenitor Cells in Bile Duct Ligated Rats

BACKGROUND:

The cannabinoid receptor 2 (CB2) plays a pleiotropic role in the innate immunity and is considered a crucial mediator of liver disease. Cannabinoid CB2 receptor activation has been reported to attenuate liver fibrosis in CCl4 exposed mice and also plays a potential role in liver regeneration in a mouse model of I/R and protection against alcohol-induced liver injury.

AIM:

In this study, we investigated the impact of CB2 receptors on the antifibrotic and regenerative process associated with cholestatic liver injury.

METHODS:

Twenty-six rats had bile duct ligation co-treated with silymarin and AM1241 for 3 consecutive weeks. Serum hepatotoxicity markers were determined, and histopathological evaluation was performed.

RESULTS:

Following bile duct ligation (BDL) for 3 weeks, there was increased aminotransferase levels, marked inflammatory infiltration and hepatocyte apoptosis with induced oxidative stress, as reflected by increased lipid peroxidation. Conversely, following treatment with the CB2 agonist, AM-1241, BDL rats displayed a reduction in liver injury and attenuation of fibrosis as reflected by expression of hydroxyproline and α-smooth muscle actin. AM1241 treatment also significantly attenuated lipid peroxidation end-products, p53-dependent apoptosis and also attenuated inflammatory process by stimulating IL-10 production. Moreover, AM1241 treated rats were associated with significant expression of hepatic progenitor/oval cell markers.

CONCLUSION:

In conclusion, this study points out that CB2 receptors reduce liver injury and promote liver regeneration via distinct mechanisms including IL-10 dependent inhibition of inflammation, reduction of p53-reliant apoptosis and through stimulation of oval/progenitor cells. These results suggest that CB2 agonists display potent hepatoregenrative properties, in addition to their antifibrogenic effects.

Prophylactic digoxin treatment reduces IL-17 production in vivo in the neonatal calf and moderates RSV-associated disease

Respiratory syncytial virus (RSV) is a leading cause of morbidity and mortality in human infants. Bovine RSV infection of neonatal calves is pathologically and immunologically similar to RSV infection in infants, and is therefore a useful preclinical model for testing novel therapeutics. Treatment of severe RSV bronchiolitis relies on supportive care and may include use of bronchodilators and inhaled or systemic corticosteroids. Interleukin-17A (IL-17) is an inflammatory cytokine that plays an important role in neutrophil recruitment and activation. IL-17 is increased in children and rodents with severe RSV infection; and in calves with severe BRSV infection. It is currently unclear if IL-17 and Th17 immunity is beneficial or detrimental to the host during RSV infection. Digoxin was recently identified to selectively inhibit IL-17 production by antagonizing its transcription factor, retinoid-related orphan receptor γ t (RORγt). Digoxin inhibits RORγt binding to IL-17 and Th17 associated genes, and suppresses IL-17 production in vitro in human and murine leukocytes and in vivo in rodent models of autoimmune disease. We demonstrate here that in vitro and in vivo digoxin treatment also inhibits IL-17 production by bovine leukocytes. To determine the role of IL-17 in primary RSV infection, calves were treated prophylactically with digoxin and infected with BRSV. Digoxin treated calves demonstrated reduced signs of clinical illness after BRSV infection, and reduced lung pathology compared to untreated control calves. Digoxin treatment did not adversely affect virus shedding or lung viral burden, but had a significant impact on pulmonary inflammatory cytokine expression on day 10 post infection. Together, our results suggest that exacerbated expression of IL-17 has a negative impact on RSV disease, and that development of specific therapies targeting Th17 immunity may be a promising strategy to improve disease outcome during severe RSV infection.

Heterogeneity of cannabinoid ligand-induced modulations in intracellular Ca2+ signals of mouse pancreatic acinar cells in vitro

We recently reported that a CB₂R agonist, GW405833 (GW), reduced both the ACh-induced Ca²⁺ oscillations and the L-arginine-induced Ca²⁺ signal enhancement in mouse pancreatic acinar cells, suggesting that GW-induced inhibition may prevent the pathogenesis of acute pancreatitis. In this study, we aim to evaluate the effects of other cannabinoid ligands on Ca²⁺ signaling in acinar cells. Patch-clamp whole-cell recordings were applied to measure ACh-induced intracellular Ca²⁺ oscillations in pancreatic acinar cells acutely dissociated from wild-type (WT), CB₁R knockout (KO), and CB₂R KO mice, and the pharmacological effects of various cannabinoid ligands on the Ca²⁺ oscillations were examined. We found that all the 8 CB₂R agonists tested inhibited ACh-induced Ca²⁺ oscillations. Among them, GW, JWH133, and GP1a caused potent inhibition with IC₅₀ values of 5.0, 6.7, and 1.2 μmol/L, respectively. In CB₂R KO mice or in the presence of a CB₂R antagonist (AM630), the inhibitory effects of these 3 CB₂R agonists were abolished, suggesting that they acted through the CB₂Rs. The CB₁R agonist ACEA also induced inhibition of Ca²⁺ oscillations that existed in CB₁R KO mice and in the presence of a CB₁R antagonist (AM251), suggesting a non-CB₁R effect. In WT, CB₁R KO, and CB₂R KO mice, a nonselective CBR agonist, WIN55,212-2, inhibited Ca²⁺ oscillations, which was not mediated by CB₁Rs or CB₂Rs. The endogenous cannabinoid substance, 2-arachidonoylglycerol (2-AG), did not show an inhibitory effect on Ca²⁺ oscillations. In conclusion, CB₂R agonists play critical roles in modulating Ca²⁺ signals in mouse pancreatic acinar cells, while other cannabinoid ligands modulate Ca²⁺ oscillations in a heterogeneous manner through a CB receptor or non-CB-receptor mechanism.

Selective CB2 inverse agonist JTE907 drives T cell differentiation towards a Treg cell phenotype and ameliorates inflammation in a mouse model of inflammatory bowel disease

Cannabinoids are known to possess anti-inflammatory and immunomodulatory properties, but the mechanisms involved are not fully understood. CB2 is the cannabinoid receptor that is expressed primarily on hematopoietic cells and mediates the immunoregulatory functions of cannabinoids. In order to study the effect of JTE907, a selective/inverse agonist of CB2 with anti-inflammatory properties, on the differentiation of T cell subtypes, we used an in vitro system of Th lineage-specific differentiation of naïve CD4⁺ T lymphocytes isolated from the mouse spleen. The results indicate that JTE907 was able to induce the differentiation of Th0 cells into the Treg cell phenotype, which was characterized by the expression of FoxP3, TGF-β and IL-10. P38 phosphorylation and STAT5A activation were found to mediate the signaling pathway triggered by JTE907 via the CB2 receptor in Th0 lymphocytes. In mice with DNBS-induced colitis, JTE907 treatment was able to induce an increase in the number of CD4⁺CD25⁺FoxP3⁺ cells in the lamina propria after 24 h of disease onset and reduce disease severity after 48 h. Further, longer JTE907 treatment resulted in less severe colitis even when administered orally, resulting in less body weight loss, reduction of the disease score, prevention of NF-κB activation, and reduction of the expression of adhesion molecules. Collectively, the results of this study indicate that specific signals delivered through the CB2 receptor can drive the immune response towards the Treg cell phenotype. Thus, ligands such as JTE907 may have use as potential therapeutic agents in autoimmune and inflammatory diseases.

VCE-004.3, a cannabidiol aminoquinone derivative, prevents bleomycin-induced skin fibrosis and inflammation through PPARγ- and CB2 receptor-dependent pathways

BACKGROUND AND PURPOSE

The endocannabinoid system and PPARγ are important targets for the development of novel compounds against fibrotic diseases such as systemic sclerosis (SSc), also called scleroderma. The aim of this study was to characterize VCE-004.3, a novel cannabidiol derivative, and study its anti-inflammatory and anti-fibrotic activities.

EXPERIMENTAL APPROACH

The binding of VCE-004.3 to CB1 and CB2 receptors and PPARγ and its effect on their functional activities were studied in vitro and in silico. Anti-fibrotic effects of VCE-004.3 were investigated in NIH-3T3 fibroblasts and human dermal fibroblasts. To assess its anti-inflammatory and anti-fibrotic efficacy in vivo, we used two complementary models of bleomycin-induced fibrosis. Its effect on ERK1/2 phosphorylation induced by IgG from SSc patients and PDGF was also investigated.

KEY RESULTS

VCE-004.3 bound to and activated PPARγ and CB2 receptors and antagonized CB1 receptors. VCE-004.3 bound to an alternative site at the PPARγ ligand binding pocket. VCE-004.3 inhibited collagen gene transcription and synthesis and prevented TGFβ-induced fibroblast migration and differentiation to myofibroblasts. It prevented skin fibrosis, myofibroblast differentiation and ERK1/2 phosphorylation in bleomycin-induced skin fibrosis. Furthermore, it reduced mast cell degranulation, macrophage activation, T-lymphocyte infiltration, and the expression of inflammatory and profibrotic factors. Topical application of VCE-004.3 also alleviated skin fibrosis. Finally, VCE-004.3 inhibited PDGF-BB- and SSc IgG-induced ERK1/2 activation in fibroblasts.

CONCLUSIONS AND IMPLICATIONS

VCE-004.3 is a novel semisynthetic cannabidiol derivative that behaves as a dual PPARγ/CB2 agonist and CB1 receptor modulator that could be considered for the development of novel therapies against different forms of scleroderma.

The endocannabinoid system of the skin. A potential approach for the treatment of skin disorders

The skin is the largest organ of the body and has a complex and very active structure that contributes to homeostasis and provides the first line defense against injury and infection. In the past few years it has become evident that the endocannabinoid system (ECS) plays a relevant role in healthy and diseased skin. Specifically, we review how the dysregulation of ECS has been associated to dermatological disorders such as atopic dermatitis, psoriasis, scleroderma and skin cancer. Therefore, the druggability of the ECS could open new research avenues for the treatment of the pathologies mentioned. Numerous studies have reported that phytocannabinoids and their biological analogues modulate a complex network pharmacology involved in the modulation of ECS, focusing on classical cannabinoid receptors, transient receptor potential channels (TRPs), and peroxisome proliferator-activated receptors (PPARs). The combined targeting of several end-points seems critical to provide better chances of therapeutically success, in sharp contrast to the one-disease-one-target dogma that permeates current drug discovery campaigns.