Inhibition of spleen tyrosine kinase activation ameliorates inflammation, cell death, and steatosis in alcoholic liver disease

Inflammasomes in chronic liver disease: hepatic injury, fibrosis progression and systemic inflammation

Chronic liver disease (CLD) leads to hepatocellular injury that triggers a pro-inflammatory state in several parenchymal and non-parenchymal hepatic cell types ultimately resulting in liver fibrosis, cirrhosis, portal hypertension (PH) and liver failure. Thus, an improved understanding of the inflammasomes - as key molecular drivers of liver injury - supports the development of novel diagnostic or prognostic biomarkers and effective therapeutics. In liver disease, innate immune cells respond to hepatic noxes by activating cell-intrinsic inflammasomes via toll-like receptors (TLRs) and nuclear factor kappa-B (NF-κB) and release of pro-inflammatory cytokines (such as IL-1β, IL-18, TNF-α and IL-6). Subsequently, cells of the adaptive immune system are recruited to fuel hepatic inflammation, and liver parenchymal cells may undergo programmed cell-death mediated by gasdermin D, termed pyroptosis. With liver disease progression, there is a shift towards a type 2 inflammatory response, which promotes tissue repair but also fibrogenesis. Inflammasome activation may also occur at extrahepatic sites, such as the white adipose tissue in metabolic dysfunction-associated steatohepatitis (MASH). In end-stage liver disease, flares of inflammation (e.g., in severe alcohol-related hepatitis) that spark on a dysfunctional immune system, contribute to inflammasome-mediated liver injury and potentially result in organ dysfunctions/failures, as seen in acute-on-chronic liver failure (ACLF). This review provides an overview on current concepts regarding inflammasome activation in liver disease progression and related biomarkers and therapeutic approaches that are being developed for patients with liver disease.

NLRP3 inflammasome in hepatic diseases: A pharmacological target

The NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome pathway is mainly responsible for the activation and release of a cascade of proinflammatory mediators that contribute to the development of hepatic diseases. During alcoholic liver disease development, the NLRP3 inflammasome pathway contributes to the maturation of caspase-1, interleukin (IL)-1β, and IL-18, which induce a robust inflammatory response, leading to fibrosis by inducing profibrogenic hepatic stellate cell (HSC) activation. Substantial evidence demonstrates that nonalcoholic fatty liver disease (NAFLD) progresses to nonalcoholic steatohepatitis (NASH) via NLRP3 inflammasome activation, ultimately leading to fibrosis and hepatocellular carcinoma (HCC). Activation of the NLRP3 inflammasome in NASH can be attributed to several factors, such as reactive oxygen species (ROS), gut dysbiosis, leaky gut, which allow triggers such as cardiolipin, cholesterol crystals, endoplasmic reticulum stress, and uric acid to reach the liver. Because inflammation triggers HSC activation, the NLRP3 inflammasome pathway performs a central function in fibrogenesis regardless of the etiology. Chronic hepatic activation of the NLRP3 inflammasome can ultimately lead to HCC; however, inflammation also plays a role in decreasing tumor growth. Some data indicate that NLRP3 inflammasome activation plays an important role in autoimmune hepatitis, but the evidence is scarce. Most researchers have reported that NLRP3 inflammasome activation is essential in liver injury induced by a variety of drugs and hepatotropic virus infection; however, few reports indicate that this pathway can play a beneficial role by inducing liver regeneration. Modulation of the NLRP3 inflammasome appears to be a suitable strategy to treat liver diseases.

CD22 blockade modulates microglia activity to suppress neuroinflammation following intracerebral hemorrhage

Microglia are first responders to acute brain insults and initiate neuroinflammation to drive secondary tissue injury. Yet the key molecular switches in control of the inflammatory activity of microglia remain poorly understood. Intracerebral hemorrhage (ICH) is a devastating stroke subtype whereby a hematoma is formed within the brain parenchyma and associated with high mortality. Using a mouse model of ICH, we found upregulation of CD22 that predominantly occurred in microglia. Antibody blockade of CD22 led to a reduction in neurological deficits, brain lesion and hematoma volume. This was accompanied by reduced inflammatory activity, increased expression of alternative activation markers (CD206 and IL-10) and enhanced phagocytosis activity in microglia after ICH. CD22 blockade also led to an increase of phosphorylated SYK and AKT after ICH. Notably, the benefits of CD22 blockade were ablated in ICH mice subjected to microglial depletion with a colony-stimulating factor 1 receptor inhibitor PLX5622. Additionally, the protective effects of CD22 blockade was diminished in ICH mice receiving a SYK inhibitor R406. Together, our findings highlight CD22 as a key molecular switch to control the detrimental effects of microglia after acute brain injury, and provide a novel strategy to improve the outcome of ICH injury.

Emerging roles of tyrosine kinases in hepatic inflammatory diseases and therapeutic opportunities

Inflammation has been convicted of causing and worsening many liver diseases like acute liver failure, fibrosis, cirrhosis, fatty liver and liver cancer. Pattern recognition receptors (PRRs) like TLRs 4 and 9 localized on resident or recruited immune cells are well known cellular detectors of pathogen and damage-associated molecular patterns (PAMPs/DAMPs). Stimulation of these receptors generates the sterile and non-sterile inflammatory responses in the liver. When these responses are repeated, there will be a sustained liver injury that may progress to fibrosis and its outcomes. Crosstalk between inflammatory/fibrogenic-dependent streams and certain tyrosine kinases (TKs) has recently evolved in the context of hepatic diseases. Because of TKs increasing importance, their role should be elucidated to highlight effective approaches to manage the diverse liver disorders. This review will give a brief overview of types and functions of some TKs like BTK, JAKs, Syk, PI3K, Src and c-Abl, as well as receptors for TAM, PDGF, EGF, VEGF and HGF. It will then move to discuss the roles of these TKs in the regulation of the proinflammatory, fibrogenic and tumorigenic responses in the liver. Lastly, the therapeutic opportunities for targeting TKs in hepatic inflammatory disorders will be addressed. Overall, this review sheds light on the diverse TKs that have substantial roles in hepatic disorders and potential therapeutics modulating their activity.

A Novel TLR4-SYK Interaction Axis Plays an Essential Role in the Innate Immunity Response in Bovine Mammary Epithelial Cells

Mammary gland epithelium, as the first line of defense for bovine mammary gland immunity, is crucial in the process of mammary glands’ innate immunity, especially that of bovine mammary epithelial cells (bMECs). Our previous studies successfully marked SYK as an important candidate gene for mastitis traits via GWAS and preliminarily confirmed that SYK expression is down-regulated in bMECs with LPS (E. coli) stimulation, but its work mechanism is still unclear. In this study, for the first time, in vivo, TLR4 and SYK were colocalized and had a high correlation in mastitis mammary epithelium; protein−protein interaction results also confirmed that there was a direct interaction between them in mastitis tissue, suggesting that SYK participates in the immune regulation of the TLR4 cascade for bovine mastitis. In vitro, TLR4 also interacts with SYK in LPS (E. coli)-stimulated or GBS (S. agalactiae)-infected bMECs, respectively. Moreover, TLR4 mRNA expression and protein levels were little affected in bMECsSYK- with LPS stimulation or GBS infection, indicating that SYK is an important downstream element of the TLR4 cascade in bMECs. Interestingly, IL-1β, IL-8, NF-κB and NLRP3 expression in LPS-stimulated or GBS-infected bMECsSYK- were significantly higher than in the control group, while AKT1 expression was down-regulated, implying that SYK could inhibit the IL-1β, IL-8, NF-κB and NLRP3 expression and alleviate inflammation in bMECs with LPS and GBS. Taken together, our solid evidence supports that TLR4/SYK/NF-κB signal axis in bMECs regulates the innate immunity response to LPS or GBS.

The spleen tyrosine kinase (SYK): A crucial therapeutic target for diverse liver diseases

Spleen tyrosine kinase (SYK) is an enigmatic protein tyrosine kinase, and involved in signal transduction related with lots of cellular processes. It's highly expressed in the cells of hematopoietic origin and acts as an important therapeutic target in the treatment of autoimmune diseases and allergic disorders. In recent years, more and more evidences indicate that SYK is expressed in non-hematopoietic cells and effectively regulates various non-immune biological responses as well. In this review, we mainly summary the role of SYK in different liver diseases. Robust SYK expression has been discovered in hepatocytes, hepatic stellate cells, as well as Kupffer cells, which participates in the regulation of numerous signal transduction in various liver diseases (e.g. hepatitis, liver fibrosis and hepatocellular carcinoma). In addition, the blockage of SYK activity using small molecule modulators is considered as a significant therapeutic strategy against liver diseases, and both hepatic SYK and non-hepatic SYK could become highly promising therapeutic targets. Totally, even though some critical points about the significance of SYK in liver diseases treatment still need further elaboration, more reliable biotechnical or pharmacological therapy modes will be established based on the better understanding of the relationship between SYK and liver diseases.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Spotlight on liver macrophages for halting liver disease progression and injury

INTRODUCTION

Over the past two decades, understanding of hepatic macrophage biology has provided astounding details of their role in the progression and regression of liver diseases. The hepatic macrophages constitute resident macrophages, Kupffer cells, and circulating bone marrow monocyte-derived macrophages, which play a diverse role in liver injury and repair. Imbalance in the macrophage population leads to pathological consequences and is responsible for the initiation and progression of acute and chronic liver injuries. Further, distinct populations of hepatic macrophages and their high heterogeneity make their complex role enigmatic. The unique features of distinct phenotypes of macrophages have provided novel biomarkers for defining the stages of liver diseases. The distinct mechanisms of hepatic macrophages polarization and recruitment have been at the fore front of research. In addition, the secretome of hepatic macrophages and their immune regulation has provided clinically relevant therapeutic targets.

AREAS COVERED

Herein we have highlighted the current understanding in the area of hepatic macrophages, and their role in the progression of liver injury.

EXPERT OPINION

It is essential to ascertain the physiological and pathological role of evolutionarily conserved distinct macrophage phenotypes in different liver diseases before viable approaches may see a clinical translation.

Nanoparticle Delivery of Novel PDE4B Inhibitor for the Treatment of Alcoholic Liver Disease

The incidence of alcoholic liver disease (ALD) is increasing worldwide while no effective treatment has been approved. The progression of ALD has proven to be related to the upregulation of phosphodiesterase 4 (PDE4) expression, and PDE4 inhibitors showed potential to improve ALD. However, the application of PDE4 inhibitors is limited by the gastrointestinal side effects due to PDE4D inhibition. Therefore, we used a novel PDE4B inhibitor KVA-D88 as the therapeutic for ALD treatment. KVA-D88 inhibited inflammatory response, promoted β-oxidation, increased the level of antioxidants in the hepatocytes, and suppressed hepatic stellate cell (HSC) activation in vitro. To improve the solubility and availability in vivo, KVA-D88 was encapsulated into mPEG-b-P(CB-co-LA) nanoparticles (NPs) by solvent evaporation, with a mean particle size of 135 nm and drug loading of 4.2%. We fed the male C57BL/6 mice with a Lieber–DeCarli liquid diet containing 5% (v/v) ethanol for 6 weeks to induce ALD. Systemic administration of KVA-D88 free drug and KVA-D88-loaded NPs at 5 mg/kg significantly improved the ALD in mice. KVA-D88 significantly ameliorated alcohol-induced hepatic injury and inflammation. KVA-D88 also markedly reduced steatosis by promoting fatty acid β-oxidation. Liver fibrosis and reactive oxygen species (ROS)-caused cellular damage was observed to be alleviated by KVA-D88. KVA-D88-loaded NPs proved better efficacy than free drug in the animal study. In conclusion, the novel PDE4B inhibitor KVA-D88-loaded NPs have the potential to treat ALD in mice

Role of the Inflammasome in Liver Disease

The involvement of inflammasomes in the proinflammatory response observed in chronic liver diseases, such as alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD), is widely recognized. Although there are different types of inflammasomes, most studies to date have given attention to NLRP3 (nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3) in the pathogenesis of ALD, NAFLD/nonalcoholic steatohepatitis, and fibrosis. Canonical inflammasomes are intracellular multiprotein complexes that are assembled after the sensing of danger signals and activate caspase-1, which matures interleukin (IL)-1β, IL-18, and IL-37 and also induces a form of cell death called pyroptosis. Noncanonical inflammasomes activate caspase-11 to induce pyroptosis. We discuss the different types of inflammasomes involved in liver diseases with a focus on (a) signals and mechanisms of inflammasome activation, (b) the role of different types of inflammasomes and their products in the pathogenesis of liver diseases, and (c) potential therapeutic strategies targeting components of the inflammasomes or cytokines produced upon inflammasome activation.

Macrophages as key regulators of liver health and disease

Macrophages are a heterogeneous population of innate immune cells and key cellular components of the liver. Hepatic macrophages consist of embryologically-derived resident Kupffer cells (KC), recruited monocyte-derived macrophages (MDM) and capsular macrophages. Both the diversity and plasticity of hepatic macrophage subsets explain their different functions in the maintenance of hepatic homeostasis and in injury processes in acute and chronic liver diseases. In this review, we assess the evidence for macrophage involvement in regulating both liver health and injury responses in liver diseases including acute liver injury (ALI), chronic liver disease (CLD) (including liver fibrosis) and hepatocellular carcinoma (HCC). In healthy livers, KC display critical functions such as phagocytosis, danger signal recognition, cytokine release, antigen processing and the ability to orchestrate immune responses and maintain immunological tolerance. However, in most liver diseases there is a striking hepatic MDM expansion, which orchestrate both disease progression and regression. Single-cell approaches have transformed our understanding of liver macrophage heterogeneity, dynamics, and functions in both human samples and preclinical models. We will further discuss the new insights provided by these approaches and how they are enabling high-fidelity work to specifically identify pathogenic macrophage subpopulations. Given the important role of macrophages in regulating injury responses in a broad range of settings, there is now a huge interest in developing new therapeutic strategies aimed at targeting macrophages. Therefore, we also review the current approaches being used to modulate macrophage function in liver diseases and discuss the therapeutic potential of targeting macrophage subpopulations as a novel treatment strategy for patients with liver disorders.

Targeting SYK of monocyte-derived macrophages regulates liver fibrosis via crosstalking with Erk/Hif1α and remodeling liver inflammatory environment

Liver fibrosis is a danger signal indicating a huge risk of liver cancer occurrence, but there is still no effective clinical means to regulate the progress of liver fibrosis. Although a variety of drugs targeting SYK have been developed for tumors and autoimmune diseases, the mechanism and specific efficacy of SYK's role in liver fibrosis are not yet clear. Our studies based on chronic CCL4, bile duct ligation, and subacute TAA mouse models show that SYK in monocyte-derived macrophages (MoMFs) is fully dependent on phosphorylation of Erk to up-regulate the expression of Hif1α, thereby forming the crosstalk with SYK to drive liver fibrosis progress. We have evaluated the ability of the small molecule SYK inhibitor GS9973 in a variety of models. Contrary to previous impressions, high-frequency administration of GS9973 will aggravate CCL4-induced liver fibrosis, which is especially unsuitable for patients with cholestasis whose clinical features are bile duct obstruction. In addition, we found that inhibition of MoMFs SYK impairs the expression of CXCL1, on one hand, it reduces the recruitment of CD11bhiLy6Chi inflammatory cells, and on the other hand, it promotes the phenotype cross-dress process of pro-resolution MoMFs, thereby remodeling the chronic inflammatory environment of the fibrotic liver. Our further findings indicate that on the basis of the administration of CCR2/CCR5 dual inhibitor Cenicriviroc, further inhibiting MoMFs SYK may give patients with fibrosis additional benefits.

Increased sTREM-1 levels identify cirrhotic patients with bacterial infection and predict their 90-day mortality

BACKGROUND AND AIMS

Patients with cirrhosis are susceptible to bacterial infections (BIs) that are major causes of specific complications and mortality. However, the diagnosis of BIs can often be difficult in advanced disease stage since their symptoms may overlap with the ones of acute decompensation (AD). Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is released from monocytes/macrophages and neutrophils during activation and has been reported to correlate with activity of various inflammatory processes. We investigated its diagnostic and prognostic performance in patients with cirrhosis and BI.

METHODS

Sera of 269 patients were assayed for sTREM-1 by ELISA (172 outpatients and 97 patients with AD of whom 56 had BI). We investigated capacity of sTREM-1 to identify patients with BI and conducted a 90-day follow-up observational study to assess its possible association with short-term mortality.

RESULTS

sTREM-1 levels were significantly higher in patients with more severe liver disease, BI, and acute-on-chronic liver failure than in patients without these conditions. sTREM-1 had similar accuracy to CRP identifying BI [sTREM-1: AUROC (95%CI) 0.804 (0.711-0.897), p < 0.0001; CRP: 0.791 (0.702-0.881), p < 0.0001)] among AD patients. The combination of these two molecules and the presence of ascites into a composite score significantly increased their discriminative power (AUROC: 0.878, 95%CI: 0.812-0.944, p < 0.0001). High sTREM-1 level (>660 pg/mL) was an independent predictor of 90-day mortality in patients with BI [HR: 2.941, (95%CI: 1.009-8.573), p = 0.048] in our multivariate model.

CONCLUSIONS

Use of sTREM-1 could increase the recognition of BIs in cirrhosis and help clinicians in mortality risk assessment of these patients.

Pathological predictive factors for late recurrence of hepatocellular carcinoma in chronic liver disease

BACKGROUND & AIMS

Late recurrence of hepatocellular carcinoma (HCC) is regarded as de novo HCC from chronic hepatitis. This study investigated clinicopathological and molecular factors to develop a nomogram for predicting late HCC recurrence (>2 years after curative resection).

METHODS

The training and validation cohorts included HCC patients with a major aetiology of hepatitis B who underwent curative resection. Clinicopathological features including lobular and porto-periportal inflammatory activity, fibrosis and liver cell change were evaluated. Proteins encoded by genes related to late recurrence were identified using a reverse phase protein array of 95 non-tumourous liver tissues. Immunoexpression of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), plasminogen activator inhibitor-1, phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) and spleen tyrosine kinase (SYK) was measured.

RESULTS

Late recurrence occurred in 74/402 (18%) and 47/243 (19%) in the training and validation cohorts respectively. Cirrhosis, moderate/severe lobular inflammatory activity, and expression of pSTAT3, pERK1/2, and SYK proteins correlated to the gene signature of hepatocyte injury and regeneration were independently associated with late recurrence, with odds ratios (95% confidence intervals) of 2.0 (1.2-3.3), 21.1 (4.3-102.7) and 6.0 (2.1-17.7) respectively (P < .05 for all). A nomogram based on these variables (histological parameters and immunohistochemical marker combinations) showed high reliability in both the training and validation cohorts (Harrell's C index: 0.701 and 0.716; 95% confidence intervals: 0.64-0.76 and 0.64-0.79 respectively).

CONCLUSIONS

The combination of pSTAT3, pERK1/2 and SYK immunoexpression with high lobular inflammatory activity and cirrhosis (fibrosis) predicts late HCC recurrence.

Drug Discovery in Liver Disease Using Kinome Profiling

The liver is one of the most important organs, playing critical roles in maintaining biochemical homeostasis. Accordingly, disease of the liver is often debilitating and responsible for untold human misery. As biochemical nexus, with kinases being master regulators of cellular biochemistry, targeting kinase enzymes is an obvious avenue for treating liver disease. Development of such therapy, however, is hampered by the technical difficulty of obtaining comprehensive insight into hepatic kinase activity, a problem further compounded by the often unique aspects of hepatic kinase activities, which makes extrapolations from other systems difficult. This consideration prompted us to review the current state of the art with respect to kinome profiling approaches towards the hepatic kinome. We observe that currently four different approaches are available, all showing significant promise. Hence we postulate that insight into the hepatic kinome will quickly increase, leading to rational kinase-targeted therapy for different liver diseases.

The Impact of Acute or Chronic Alcohol Intake on the NF-κB Signaling Pathway in Alcohol-Related Liver Disease

Ethanol misuse is frequently associated with a multitude of profound medical conditions, contributing to health-, individual- and social-related damage. A particularly dangerous threat from this classification is coined as alcoholic liver disease (ALD), a liver condition caused by prolonged alcohol overconsumption, involving several pathological stages induced by alcohol metabolic byproducts and sustained cellular intoxication. Molecular, pathological mechanisms of ALD principally root in the innate immunity system and are especially associated with enhanced functionality of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. NF-κB is an interesting and convoluted DNA transcription regulator, promoting both anti-inflammatory and pro-inflammatory gene expression. Thus, the abundancy of studies in recent years underlines the importance of NF-κB in inflammatory responses and the mechanistic stimulation of inner molecular motifs within the factor components. Hereby, in the following review, we would like to put emphasis on the correlation between the NF-κB inflammation signaling pathway and ALD progression. We will provide the reader with the current knowledge regarding the chronic and acute alcohol consumption patterns, the molecular mechanisms of ALD development, the involvement of the NF-κB pathway and its enzymatic regulators. Therefore, we review various experimental in vitro and in vivo studies regarding the research on ALD, including the recent active compound treatments and the genetic modification approach. Furthermore, our investigation covers a few human studies.

Caffeoyl-Prolyl-Histidine Amide Inhibits Fyn and Alleviates Atopic Dermatitis-Like Phenotypes via Suppression of NF-κB Activation

Caffeic acid (CA) is produced from a variety of plants and has diverse biological functions, including anti-inflammation activity. It has been recently demonstrated that caffeoyl-prolyl-histidine amide (CA-PH), which is CA conjugated with proline-histidine dipeptide, relieves atopic dermatitis (AD)-like phenotypes in mouse. In this study, we investigated the molecular mechanism underlying CA-PH-mediated alleviation of AD-like phenotypes using cell line and AD mouse models. We confirmed that CA-PH suppresses AD-like phenotypes, such as increased epidermal thickening, infiltration of mast cells, and dysregulated gene expression of cytokines. CA-PH suppressed up-regulation of cytokine expression through inhibition of nuclear translocation of NF-κB. Using a CA-PH affinity pull-down assay, we found that CA-PH binds to Fyn. In silico molecular docking and enzyme kinetic studies revealed that CA-PH binds to the ATP binding site and inhibits Fyn competitively with ATP. CA-PH further suppressed spleen tyrosine kinase (SYK)/inhibitor of nuclear factor kappa B kinase (IKK)/inhibitor of nuclear factor kappa B (IκB) signaling, which is required for nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. In addition, chronic application of CA-PH, in contrast with that of glucocorticoids, did not induce up-regulation of regulated in development and DNA damage response 1 (REDD1), reduction of mammalian target of rapamycin (mTOR) signaling, or skin atrophy. Thus, our study suggests that CA-PH treatment may help to reduce skin inflammation via down-regulation of NF-κB activation, and Fyn may be a new therapeutic target of inflammatory skin diseases, such as AD.

Recent advances in alcohol-related liver disease (ALD): summary of a Gut round table meeting

Alcohol-related liver disease (ALD), which includes a range of disorders of different severity and is one of the most prevalent types of liver disease worldwide, has recently regained increased attention. Among other reasons, the realisation that any alcohol intake, regardless of type of beverage represents a health risk, and the new therapeutic strategies tested in recently published or undergoing clinical trials spur scientific interest in this area.In April 2019, Gut convened a round table panel of experts during the European Association for the Study of the Liver International Liver Congress in Vienna to discuss critical and up-to-date issues and clinical trial data regarding ALD, its epidemiology, diagnosis, management, pathomechanisms, possible future treatments and prevention. This paper summarises the discussion and its conclusions.

Role of spleen tyrosine kinase in liver diseases

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase expressed in most hematopoietic cells and non-hematopoietic cells and play a crucial role in both immune and non-immune biological responses. SYK mediate diverse cellular responses via an immune-receptor tyrosine-based activation motifs (ITAMs)-dependent signalling pathways, ITAMs-independent and ITAMs-semi-dependent signalling pathways. In liver, SYK expression has been observed in parenchymal (hepatocytes) and non-parenchymal cells (hepatic stellate cells and Kupffer cells), and found to be positively correlated with the disease severity. The implication of SYK pathway has been reported in different liver diseases including liver fibrosis, viral hepatitis, alcoholic liver disease, non-alcoholic steatohepatitis and hepatocellular carcinoma. Antagonism of SYK pathway using kinase inhibitors have shown to attenuate the progression of liver diseases thereby suggesting SYK as a highly promising therapeutic target. This review summarizes the current understanding of SYK and its therapeutic implication in liver diseases.

Inhibition of the Inflammasome Signaling Cascade Reduces Alcohol Consumption in Female But Not Male Mice

BACKGROUND

Alcohol use disorder is a significant societal and medical burden that is associated with both organ pathology and addiction. Excessive alcohol use results in neuroinflammation characterized by activation of the inflammasome, a multiprotein complex, and IL-1β increase in the brain. Recent studies suggest that inflammation could contribute to alcohol addiction. Here, we targeted components of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome cascade, which senses and responds to immunologic stimuli, to determine whether NLRP3 inhibition modulates alcohol consumption.

METHODS

C57BL/6J male and female mice were provided a 2-bottle choice of alcohol at increasing concentrations (3, 6, 9, and 12%, 4 days each) or water, and some were treated with daily injections of an NLRP3 inhibitor (MCC950), a caspase-1 inhibitor (VX765), IL-1 receptor antagonist (IL-1ra; anakinra), or vehicle injection.

RESULTS

Treatment with VX765, MCC950, and IL-1ra significantly reduced alcohol consumption and preference in female mice (p < 0.05). Treatment with MCC950 and IL-1ra reduced alcohol consumption, while IL-1ra reduced alcohol preference in male mice (p < 0.05). VX765 did not affect alcohol consumption or preference in male mice.

CONCLUSIONS

These findings highlight gender differences in alcohol preference and demonstrate that inhibition of different steps in inflammasome signaling can reduce alcohol consumption in females. Inhibition of NLRP3 inflammasome activation and the inflammasome-IL-1β cascade opens novel insights into the development of new therapies to address alcohol use disorder in an era of targeted and precision medicine.

Therapeutic Targeting of Hepatic Macrophages for the Treatment of Liver Diseases

Hepatic macrophages play a central role in maintaining homeostasis in the liver, as well as in the initiation and progression of liver diseases. Hepatic macrophages are mainly derived from resident hepatic macrophages called Kupffer cells or circulating bone marrow-derived monocytes. Kupffer cells are self-renewing and typically non-migrating macrophages in the liver and are stationed in the liver sinusoids in contrast to macrophages originating from circulating monocytes. Kupffer cells regulate liver homeostasis by mediating immunity against non-pathogenic blood-borne molecules, while participating in coordinated immune responses leading to pathogen clearance, leukocyte recruitment and antigen presentation to lymphocytes present in the vasculature. Monocyte-derived macrophages infiltrate into the liver tissue when metabolic or toxic damage instigates and are likely dispensable for replenishing the macrophage population in homeostasis. In recent years, different populations of hepatic macrophages have been identified with distinct phenotypes with discrete functions, far beyond the central dogma of M1 and M2 macrophages. Hepatic macrophages play a central role in the pathogenesis of acute and chronic liver failure, liver fibrosis, non-alcoholic fatty liver disease, alcoholic liver disease, viral hepatitis, and hepatocellular carcinoma, as well as in disease resolution. The understanding of the role of hepatic macrophages in liver diseases provides opportunities for the development of targeted therapeutics for respective malignancies. This review will summarize the current knowledge of the hepatic macrophages, their origin, functions, their critical role in maintaining homeostasis and in the progression or resolution of liver diseases. Furthermore, we will provide a comprehensive overview of the therapeutic targeting strategies against hepatic macrophages developed for the treatment of liver diseases.

Dysregulated Autophagy and Lysosome Function Are Linked to Exosome Production by Micro-RNA 155 in Alcoholic Liver Disease

Cellular homeostais, that is normally maintained through autophagy, is disrupted in alcoholic liver disease (ALD). Because autophagy and exosome biogenesis share common elements, we hypothesized that increased exosome production in ALD may be linked to disruption of autophagic function. We found impaired autophagy both in ALD and alcoholic hepatitis (AH) mouse models and human livers with ALD as indicated by increased hepatic p62 and LC3-II levels. Alcohol reduced autophagy flux in vivo in chloroquine-treated mice as well as in vitro in hepatocytes and macrophages treated with bafilomycin A. Our results revealed that alcohol targets multiple steps in the autophagy pathway. Alcohol-related decrease in mechanistic target of rapamycin (mTOR) and Ras homolog enriched in brain (Rheb), that initiate autophagy, correlated with increased Beclin1 and autophagy-related protein 7 (Atg7), proteins involved in phagophore-autophagosome formation, in ALD. We found that alcohol disrupted autophagy function at the lysosomal level through decreased lysosomal-associated membrane protein 1 (LAMP1) and lysosomal-associated membrane protein 2 (LAMP2) in livers with ALD. We identified that micro-RNA 155 (miR-155), that is increased by alcohol, targets mTOR, Rheb, LAMP1, and LAMP2 in the authophagy pathway. Consistent with this, miR-155-deficient mice were protected from alcohol-induced disruption of autophagy and showed attenuated exosome production. Mechanistically, down-regulation of LAMP1 or LAMP2 increased exosome release in hepatocytes and macrophages in the presence and absence of alcohol. These results suggested that the alcohol-induced increase in exosome production was linked to disruption of autophagy and impaired autophagosome and lysosome function. Conclusion: Alcohol affects multiple genes in the autophagy pathway and impairs autophagic flux at the lysosome level in ALD. Inhibition of LAMP1 and LAMP2 promotes exosome release in ALD. We identified miR-155 as a mediator of alcohol-related regulation of autophagy and exosome production in hepatocytes and macrophages.

The protein tyrosine kinase SYK regulates the alternative p38 activation in liver during acute liver inflammation

Two distinct p38 signaling pathways, classical and alternative, have been identified to regulate inflammatory responses in host defense and disease development. The role of alternative p38 activation in liver inflammation is elusive, while classical p38 signaling in hepatocytes plays a role in regulating the induction of cell death in autoimmune-mediated acute liver injury. In this study, we found that a mutation of alternative p38 in mice augmented the severity of acute liver inflammation. Moreover, TNF-induced hepatocyte death was augmented by a mutation of alternative p38, suggesting that alternative p38 signaling in hepatocytes contributed more significantly to the pathology of acute liver injury. Furthermore, SYK-Vav-1 signaling regulates alternative p38 activation and the downregulation of cell death in hepatocytes. Therefore, it is suggested that alternative p38 signaling in the liver plays a critical role in the induction and subsequent pathological changes of acute liver injury. Collectively, our results imply that p38 signaling in hepatocytes plays a crucial role to prevent excessive liver injury by regulating the induction of cell death and inflammation.

Pharmacological Inhibition of CCR2/5 Signaling Prevents and Reverses Alcohol-Induced Liver Damage, Steatosis, and Inflammation in Mice

Kupffer cell and macrophage (MØ) activation contributes to steatosis, inflammation, and fibrosis in alcoholic liver disease (ALD). We found increased frequency of MØ, T cells, and expression of C-C chemokine receptor type 2 (Ccr2) and C-C chemokine receptor type 5 (Ccr5) in the livers of patients with ALD, and increased circulating chemokines, C-C chemokine ligand types 2 (CCL2), and C-C chemokine ligand types 5 (CCL5) in patients with alcoholic hepatitis. We hypothesized that inhibition of CCL2 signaling with the dual CCR2/5 inhibitor, cenicriviroc (CVC), would attenuate ALD. In a mouse model of ALD, liver injury (alanine aminotransferase [ALT]) and steatosis were prevented by CVC whether administered as "prevention" throughout the alcohol feeding or as "treatment" started after the development of ALD. Alcohol-induced increases in early liver fibrosis markers (sirius red, hydroxyproline, and collagen-1) were normalized by both modes of CVC administration. We found that prevention and treatment with CVC reversed alcohol-related increases in liver mRNA and protein expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and CCL2. CVC administration regimens prevented the increase in infiltrating MØ (F4/80^lo CD11b^hi ) and reduced proinflammatory Ly6C^hi MØ in livers of alcohol-fed mice. CVC increased liver T-cell numbers and attenuated Il-2 expression without an effect on CD69⁺ or CD25⁺ T-cell expression. In vitro, CVC inhibited CCL2-induced increases in hepatocyte fatty acid synthase (Fasn) and adipose differentiation-related protein (Adrp), whereas it augmented acyl-coenzyme A oxidase 1 (Acox-1), proliferator-activated receptor gamma co-activator alpha (Pgc1α) and uncoupling protein 2 expression, suggesting mechanisms for attenuated hepatocyte steatosis. We found that CCL2 and CCL5 sensitized hepatocytes to lipopolysaccharide-induced liver injury (TNF-α, ALT, and lactate dehydrogenase release). Alcohol feeding induced apoptosis (poly ADP-ribose polymerase [PARP] and caspase-3 [CASP-3] cleavage) and pyroptosis (gasdermin D [GSDMD] cleavage) in livers, and CVC prevented both of these forms of cell death. Conclusion: Together, our data demonstrate preclinical evidence for CCR2/CCR5 inhibition with CVC as a potent intervention to ameliorate alcohol-induced steatohepatitis and liver damage.

Inhibition of spleen tyrosine kinase signaling protects against acute lung injury through blockade of NADPH oxidase and IL-17A in neutrophils and γδ T cells respectively in mice

Acute lung injury (ALI) is one of the most serious complications in critically ill patients which often leads to morbidity and mortality. ALI characterized by severe inflammation of lungs occurs due to uncontrolled inflammatory immune response. However, the immunological mechanism(s) are far from being understood. The spleen tyrosine kinase (SYK), a key component of immune receptor signaling, plays a critical role in the modulation of inflammatory signaling in different immune cells. However, its role in ALI remains to be explored. Therefore, in this study, we investigated the effect of R406, a SYK inhibitor in lipopolysaccharide (LPS)-induced ALI mouse model. LPS led to increased SYK expression in neutrophils and gamma delta (γδ) T cells. This was associated with increased neutrophilic airway inflammation, vascular permeability, myeloperoxidase activity in the lung with upregulated expression of NADPH oxidase (NOX2)/MCP-1/TNF-α in neutrophils and IL-17A in γδ T cells/lung. Pulmonary inflammation was associated with higher mortality in mice with ALI. Inhibition of SYK signaling using R406 in the lung led to blockade of neutrophilic airway inflammation, vascular permeability, pro-inflammatory cytokine release and oxidative stress in innate immune cells, i.e. γδ T cells and neutrophils and the lung. R406 administered LPS group had better survival rate than LPS group. This suggests that SYK upregulation in γδ T cells and neutrophils plays an important role in inflammatory process during ALI. In conclusion, R406 exhibited a great potential to block the LPS-induced airway inflammation and mortality which could be developed as a potential future therapy in ALI.

Inhibition of spleen tyrosine kinase attenuates psoriasis-like inflammation in mice through blockade of dendritic cell-Th17 inflammation axis

Psoriasis is a debilitating autoimmune disease of the skin characterized by acanthosis and hyperkeratosis resulting from excessive growth of keratinocytes in the epidermis and inflammatory infiltrates in the dermis. Innate immune cells such as dendritic cells (DCs), perform a critical role in the pathophysiology of psoriasis by presenting inflammatory/costimulatory signals for differentiation of Th17 cells. Recent studies point to the involvement of spleen tyrosine kinase (SYK) in inflammatory signaling cascade of DCs. However, it is yet to be determined whether SYK inhibition in DCs would lead to diminishment of psoriatic inflammation. Therefore, our study evaluated the effects of SYK inhibitor, R406 on imiquimod (IMQ)-induced psoriasis-like inflammation, expression of costimulatory/inflammatory molecules in DCs and their relationship with Th17/Treg cells. Our data show that R406 causes attenuation of IMQ-induced dermal inflammation as shown by reduction in ear/back skin thickness, acanthosis and myeloperoxidase activity. This was concurrent with reduction in inflammatory cytokines and co-stimulatory molecules in CD11c + DCs such as IL-6, IL-23, MHCII, and CD40. This favoured the suppression of Th17 cells and upregulation of Treg cells in R406-treated mice with psoriasis-like inflammation. Direct activation of TLR7 by IMQ in splenocytic cultures led to increased SYK expression in CD11c + DCs and release of IL-23/IL-6. IMQ-induced IL-6/IL-23 levels were significantly diminished by SYK inhibitor, R406 in splenocytic cultures. In essence, our study shows that SYK inhibition supresses psoriasis-like inflammation by modifying DC function in mice. Further, it implies that SYK inhibition could be a prospective therapeutic approach for the treatment of psoriasis-like inflammation.

Inhibition of Triggering Receptor Expressed on Myeloid Cells 1 Ameliorates Inflammation and Macrophage and Neutrophil Activation in Alcoholic Liver Disease in Mice

Alcoholic liver disease (ALD) is characterized by macrophage and neutrophil leukocyte recruitment and activation in the liver. Damage‐ and pathogen‐associated molecular patterns contribute to a self‐perpetuating proinflammatory state in ALD. Triggering receptor expressed on myeloid cells 1 (TREM‐1) is a surface receptor that amplifies inflammation induced by toll‐like receptors (TLRs) and is expressed on neutrophils and monocytes/macrophages. We hypothesized that TREM‐1 signaling contributes to proinflammatory pathway activation in ALD. Using an in vivo ALD model in mice, we tested the effects of ligand‐independent TREM‐1 inhibitory peptides that were formulated into human high‐density lipoprotein (HDL)‐mimicking complexes GF9‐HDL and GA/E31‐HDL. As revealed in vitro, macrophages endocytosed these rationally designed complexes through scavenger receptors. A 5‐week alcohol feeding with the Lieber‐DeCarli diet in mice resulted in increased serum alanine aminotransferase (ALT), liver steatosis, and increased proinflammatory cytokines in the liver. TREM‐1 messenger RNA (mRNA) expression was significantly increased in alcohol‐fed mice, and TREM‐1 inhibitors significantly reduced this increase. TREM‐1 inhibition significantly attenuated alcohol‐induced spleen tyrosine kinase (SYK) activation, an early event in both TLR4 and TREM‐1 signaling. The TREM‐1 inhibitors significantly inhibited macrophage (epidermal growth factor‐like module‐containing mucin‐like hormone receptor‐like 1 [F4/80], clusters of differentiation [CD]68) and neutrophil (lymphocyte antigen 6 complex, locus G [Ly6G] and myeloperoxidase [MPO]) markers and proinflammatory cytokines (monocyte chemoattractant protein 1 [MCP‐1], tumor necrosis factor α [TNF‐α], interleukin‐1β [IL‐1β], macrophage inflammatory protein 1α [MIP‐1α]) at the mRNA level compared to the HDL vehicle. Administration of TREM‐1 inhibitors ameliorated liver steatosis and early fibrosis markers (α‐smooth muscle actin [αSMA] and procollagen1α [Pro‐Col1α]) at the mRNA level in alcohol‐fed mice. However, the HDL vehicle also reduced serum ALT and some cytokine protein levels in alcohol‐fed mice, indicating HDL‐related effects. Conclusion: HDL‐delivered novel TREM‐1 peptide inhibitors ameliorate early phases of inflammation and neutrophil and macrophage recruitment and activation in the liver and attenuate hepatocyte damage and liver steatosis. TREM‐1 inhibition represents a promising therapeutic approach for further investigations in ALD.

FXR and TGR5 Agonists Ameliorate Liver Injury, Steatosis, and Inflammation After Binge or Prolonged Alcohol Feeding in Mice

Bile acids (BAs) activate various dedicated receptors, including the farnesoid X receptor (FXR) and the Takeda G protein‐coupled receptor 5 (TGR5). The FXR agonist obeticholic acid (OCA) is licensed for the treatment of primary biliary cholangitis and has shown promising results in NASH patients, whereas TGR5 agonists target inflammation and metabolism. We hypothesized that FXR and/or TGR5 agonists may be therapeutic in early alcoholic liver disease (ALD) in mice, in which hepatic inflammation plays a major role. OCA, INT‐777, and INT‐767 are BA derivatives with selective agonist properties for FXR, TGR5, or both, respectively. These compounds were tested in two mouse models (3‐day binge model and prolonged Lieber DeCarli diet for 12 days) of early ALD. Serum alanine aminotransferase and liver histology were used to assess liver injury, Oil Red O staining of liver sections to assess steatosis, and real‐time polymerase chain reaction to assess changes in gene expression. In the ethanol binge model, treatment with OCA and INT‐777 decreased hepatic macrovesicular steatosis and protected from ethanol‐induced liver injury. After prolonged ethanol administration, mice treated with OCA, INT‐767, or INT‐777 showed decreased hepatic steatosis, associated with reduced liver fatty acid synthase protein expression, and protection from liver injury. Treatment with BA receptor agonists in both models of ethanol administration modulated lipogenic gene expression, and decreased liver interleukin‐1β mRNA expression associated with increased ubiquitination of NLRP3 inflammasome through cyclic adenosine monophosphate–induced activation of protein kinase A. Conclusion: OCA, INT‐767, or INT‐777 administration is effective in reducing acute and chronic ethanol‐induced steatosis and inflammation in mice, with varying degrees of efficacy depending on the duration of ethanol administration, indicating that both FXR and TGR5 activation can protect from liver injury in ALD models.

Therapeutic inhibition of spleen tyrosine kinase in inflammatory macrophages using PLGA nanoparticles for the treatment of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is the leading cause of cirrhosis worldwide and the most rapidly growing indication for liver transplantation. Macrophages are the important cellular component in the inflammatory milieu in NASH. Inflammatory and pro-fibrotic mediators produced by macrophages causes significant tissue injury in many inflammatory diseases. Therefore, inhibition of the inflammatory macrophages would be a promising approach to attenuate NASH. In this study, we studied the implication of SYK pathway in NASH, and investigated PLGA nanoparticles-based delivery of SYK pathway inhibitor as an effective and promising therapeutic approach for the treatment of NASH. We found positive correlation between SYK expression with the pathogenesis of NASH and alcoholic hepatitis in patients. Importantly, SYK expression was significantly induced in M1-differentiated inflammatory macrophages. To inhibit SYK pathway specifically, we used a small-molecule inhibitor R406 that blocks Fc-receptor signaling pathway and reduces immune complex-mediated inflammation. R406 dose-dependently inhibited nitric-oxide release and M1-specific markers in M1-differentiated macrophages. Thereafter, we synthesized PLGA nanoparticles to deliver R406 to increase the drug pharmacokinetics for the efficient treatment of NASH. We investigated the therapeutic efficacy of R406-PLGA in-vitro in differentiated macrophages, and in-vivo in Methionine-Choline-deficient (MCD)-diet induced NASH mouse model. R406-PLGA inhibited M1-specific differentiation markers in RAW and bone-marrow-derived macrophages. In-vivo, R406 and more strongly R406-PLGA ameliorated fibrosis, inflammation and steatosis in mice. R406 and more significantly R406-PLGA reduced ALT, AST, cholesterol and triglyceride plasma levels. These results suggest that delivery of SYK inhibitor using PLGA nanoparticles can be a potential therapeutic approach for the treatment of Non-alcoholic steatohepatitis.

Tyrosine kinase SYK is a potential therapeutic target for liver fibrosis

Spleen tyrosine kinase (SYK) plays a critical role in immune cell signaling pathways and has been reported as a biomarker for human hepatocellular carcinoma (HCC). We sought to investigate the mechanism by which SYK promotes liver fibrosis and to evaluate SYK as a therapeutic target for liver fibrosis. We evaluated the cellular localization of SYK and the association between SYK expression and liver fibrogenesis in normal, hepatitis B virus (HBV)-infected, hepatitis C virus (HCV)-infected and non-alcoholic steatohepatitis (NASH) liver tissue (n=36, 127, 22 and 30, respectively). A polymerase chain reaction (PCR) array was used to detect the changes in transcription factor (TF) expression in hepatic stellate cells (HSCs) with SYK knockdown. The effects of SYK antagonism on liver fibrogenesis were studied in LX-2 cells, TWNT-4 cells, primary human HSCs, and three progressive fibrosis/cirrhosis animal models, including a CCL₄ mouse model, and diethylnitrosamine (DEN) and bile duct ligation (BDL) rat models. We found that SYK protein in HSCs and hepatocytes correlated positively with liver fibrosis stage in human liver tissue. HBV or HCV infection significantly increased SYK and cytokine expression in hepatocytes. Increasing cytokine production further induced SYK expression and fibrosis-related gene transcription in HSCs. Up-regulated SYK in HSCs promoted HSC activation by increasing the expression of specific TFs related to activation of HSCs. SYK antagonism effectively suppressed liver fibrosis via inhibition of HSC activation, and decreased obstructive jaundice and reduced HCC development in animal models. Conclusion: SYK promotes liver fibrosis via activation of HSCs and is an attractive potential therapeutic target for liver fibrosis and prevention of HCC development. (Hepatology 2018).

Leucodin attenuates inflammatory response in macrophages and lipid accumulation in steatotic hepatocytes via P2x7 receptor pathway: A potential role in alcoholic liver disease

The current study was aimed to reveal that leucodin, a sesquiterpene lactone from Artemisia capillaris could inhibit the inflammatory response in macrophages and the lipid accumulation in hepatocytes via P2x7R-NLRP3 inflammasome activation. Several types of macrophages including mouse peritoneal macrophages, mouse bone marrow-derived macrophages and human macrophages THP-1 cells were pretreated with different concentrations of leucodin for 1 h and then stimulated with LPS and ATP. LPS plus ATP initiated IL-1β cleavage and release in mouse peritoneal macrophages and peaked at 4 h. Leucodin did not show significant toxicity within 200 μM and effectively inhibited pro-IL-1β cleavage and release of mature-IL-1β in macrophages. Also, P2x7R antagonist and caspase-1 inhibitor also decreased IL-1β release and cleavage. Additionally, leucodin suppressed P2x7R, TLR4 and NLRP3 expression in LPS/ATP-stimulated macrophages. HepG2 cells were pretreated with different concentrations of leucodin for 1 h and then exposed to ethanol for 24 h. Leucodin suppressed lipid accumulation and enhanced phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in HepG2 cells exposed to ethanol. In addition, leucodin inhibited the expression of sterol regulatory element binding protein-1 (SREBP1) and ACC in ethanol-treated HepG2 cells. Leucodin possessed the capacity for inhibiting inflammatory response in macrophages and suppressing lipid accumulation in hepatocytes, suggesting a promising therapeutic potential targeting inflammation and lipid metabolism in alcoholic liver disease.

Extracellular vesicles from mice with alcoholic liver disease carry a distinct protein cargo and induce macrophage activation through heat shock protein 90

A salient feature of alcoholic liver disease (ALD) is Kupffer cell (KC) activation and recruitment of inflammatory monocytes and macrophages (MØs). These key cellular events of ALD pathogenesis may be mediated by extracellular vesicles (EVs). EVs transfer biomaterials, including proteins and microRNAs, and have recently emerged as important effectors of intercellular communication. We hypothesized that circulating EVs from mice with ALD have a protein cargo characteristic of the disease and mediate biological effects by activating immune cells. The total number of circulating EVs was increased in mice with ALD compared to pair-fed controls. Mass spectrometric analysis of circulating EVs revealed a distinct signature for proteins involved in inflammatory responses, cellular development, and cellular movement between ALD EVs and control EVs. We also identified uniquely important proteins in ALD EVs that were not present in control EVs. When ALD EVs were injected intravenously into alcohol-naive mice, we found evidence of uptake of ALD EVs in recipient livers in hepatocytes and MØs. Hepatocytes isolated from mice after transfer of ALD EVs, but not control EVs, showed increased monocyte chemoattractant protein 1 mRNA and protein expression, suggesting a biological effect of ALD EVs. Compared to control EV recipient mice, ALD EV recipient mice had increased numbers of F4/80^hi cluster of differentiation 11b (CD11b)^lo KCs and increased percentages of tumor necrosis factor alpha-positive/interleukin 12/23-positive (inflammatory/M1) KCs and infiltrating monocytes (F4/80^int CD11b^hi ), while the percentage of CD206⁺ CD163⁺ (anti-inflammatory/M2) KCs was decreased. In vitro, ALD EVs increased tumor necrosis factor alpha and interleukin-1β production in MØs and reduced CD163 and CD206 expression. We identified heat shock protein 90 in ALD EVs as the mediator of ALD-EV-induced MØ activation.

CONCLUSION

Our study indicates a specific protein signature of ALD EVs and demonstrates a functional role of circulating EVs containing heat shock protein 90 in mediating KC/MØ activation in the liver. (Hepatology 2018;67:1986-2000).

Spliceosome-Associated Protein 130 Exacerbates Alcohol-Induced Liver Injury by Inducing NLRP3 Inflammasome-Mediated IL-1β in Mice

Excessive alcohol consumption leads to chronic liver diseases. Macrophage-inducible C-type lectin (Mincle) is a C-type lectin receptor that recognizes spliceosome-associated protein 130 (SAP130) known as an endogenous ligand released from dying cells. The aim was to examine the role of Mincle-SAP130 in the pathogenesis of alcoholic liver disease. Alcohol-induced liver injury was induced in wild-type (WT) and Mincle knockout (KO) mice by using a chronic-binge ethanol-feeding model. Mincle KO mice showed significant lower hepatic steatosis, inflammation with neutrophil infiltration, and fibrosis compared with WT mice after alcohol feeding. In contrast, Mincle activation exacerbated alcohol-induced liver injury. Kupffer cells (KCs) are major sources of Mincle. IL-1β expression was significantly down-regulated in Mincle KO mice compared with that in WT mice after alcohol consumption. Interestingly, expression and production of IL-1β were significantly decreased in SAP130-treated KCs isolated from leucine-rich-containing family pyrin domain containing-3-deficient mice compared with those in WT KCs. Such results were also observed in cells treated with SAP130 plus Syk inhibitor. Furthermore, infiltration of invariant natural killer T cells was decreased in livers of Mincle KO mice. Finally, inhibition of Syk signaling ameliorated alcohol-induced liver injury. Collectively, these results demonstrated that interaction between Mincle and SAP130 may promote the progression of alcoholic liver disease by IL-1β production in KCs and consequently increase inflammatory immune cell infiltration.

Animal Models of Alcoholic Liver Disease: Pathogenesis and Clinical Relevance

Alcoholic liver disease (ALD), a leading cause of chronic liver injury worldwide, comprises a range of disorders including simple steatosis, steatohepatitis, cirrhosis, and hepatocellular carcinoma. Over the last five decades, many animal models for the study of ALD pathogenesis have been developed. Recently, a chronic-plus-binge ethanol feeding model was reported. This model induces significant steatosis, hepatic neutrophil infiltration, and liver injury. A clinically relevant model of high-fat diet feeding plus binge ethanol was also developed, which highlights the risk of excessive binge drinking in obese/overweight individuals. All of these models recapitulate some features of the different stages of ALD and have been widely used by many investigators to study the pathogenesis of ALD and to test for therapeutic drugs/components. However, these models are somewhat variable, depending on mouse genetic background, ethanol dose, and animal facility environment. This review focuses on these models and discusses these variations and some methods to improve the feeding protocol. The pathogenesis, clinical relevance, and translational studies of these models are also discussed.

Interleukin-1 inhibition facilitates recovery from liver injury and promotes regeneration of hepatocytes in alcoholic hepatitis in mice

BACKGROUND & AIMS

Inflammation and impaired hepatocyte regeneration contribute to liver failure in alcoholic hepatitis (AH). Interleukin (IL)-1 is a key inflammatory cytokine in the pathobiology of AH. The role of IL-1 in liver regeneration in the recovery phase of alcohol-induced liver injury is unknown.

METHODS

In this study, we tested IL-1 receptor antagonist to block IL-1 signalling in a mouse model of acute-on-chronic liver injury on liver inflammation and hepatocyte regeneration in AH.

RESULTS

We observed that inhibition of IL-1 signalling decreased liver inflammation and neutrophil infiltration, and resulted in enhanced regeneration of hepatocytes and increased rate of recovery from liver injury in AH.

CONCLUSION

Our novel findings suggest that IL-1 drives sustained liver inflammation and impaired hepatocyte regeneration even after cessation of ethanol exposure.

Key Events Participating in the Pathogenesis of Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality worldwide. It ranges from fatty liver to steatohepatitis, fibrosis, cirrhosis and hepatocellular carcinoma. The most prevalent forms of ALD are alcoholic fatty liver, alcoholic hepatitis (AH) and alcoholic cirrhosis, which frequently progress as people continue drinking. ALD refers to a number of symptoms/deficits that contribute to liver injury. These include steatosis, inflammation, fibrosis and cirrhosis, which, when taken together, sequentially or simultaneously lead to significant disease progression. The pathogenesis of ALD, influenced by host and environmental factors, is currently only partially understood. To date, lipopolysaccharide (LPS) translocation from the gut to the portal blood, aging, gender, increased infiltration and activation of neutrophils and bone marrow-derived macrophages along with alcohol plus iron metabolism, with its associated increase in reactive oxygen species (ROS), are all key events contributing to the pathogenesis of ALD. This review aims to introduce the reader to the concept of alcohol-mediated liver damage and the mechanisms driving injury.

Over expression of proteins that alter the intracellular signaling pathways in the cytoplasm of the liver cells forming Mallory-Denk bodies

In this study, liver biopsy sections fixed in formalin and embedded in paraffin (FFPE) from patients with alcoholic hepatitis (AH) were used. The results showed that the expression of the SYK protein was up regulated by RNA-seq and real time PCR analyses in the alcoholic hepatitis patients compared to controls. The results were supported by using the IHC fluorescent antibody staining intensity morphometric quantitation. Morphometric quantification of fluorescent intensity measurement showed a two fold increase in SYK protein in the cytoplasm of the cells forming MDBs compared to surrounding normal hepatocytes. The expression of AKT1 was also analyzed. AKT1 is a serine/threonine-specific protein kinase that plays a key role in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription and cell migration. The AKT protein was also increased in hepatocyte balloon cells forming MDBs. This observation demonstrates the role of SYK and its subsequent effect on the internal signaling pathways such as PI3K/AKT as well as p70S6K, as a potential multifunctional target in protein quality control mechanisms of hepatocytes when ER stress is activated.