Distinct immunometabolic signatures in circulating immune cells define disease outcome in acute-on-chronic liver failure.

BACKGROUND AND AIMS: Acute-on-chronic liver failure (ACLF) is a complication of cirrhosis characterized by multiple organ failure and high short-term mortality. The pathophysiology of ACLF involves elevated systemic inflammation leading to organ failure, along with immune dysfunction that heightens susceptibility to bacterial infections. However, it is unclear how these aspects are associated with recovery and nonrecovery in ACLF. APPROACH AND RESULTS: Here, we mapped the single-cell transcriptome of circulating immune cells from patients with ACLF and acute decompensated (AD) cirrhosis and healthy individuals. We further interrogate how these findings, as well as immunometabolic and functional profiles, associate with ACLF-recovery (ACLF-R) or nonrecovery (ACLF-NR). Our analysis unveiled 2 distinct states of classical monocytes (cMons). Hereto, ACLF-R cMons were characterized by transcripts associated with immune and stress tolerance, including anti-inflammatory genes such as RETN and LGALS1 . Additional metabolomic and functional validation experiments implicated an elevated oxidative phosphorylation metabolic program as well as an impaired ACLF-R cMon functionality. Interestingly, we observed a common stress-induced tolerant state, oxidative phosphorylation program, and blunted activation among lymphoid populations in patients with ACLF-R. Conversely, ACLF-NR cMon featured elevated expression of inflammatory and stress response genes such as VIM , LGALS2 , and TREM1 , along with blunted metabolic activity and increased functionality. CONCLUSIONS: This study identifies distinct immunometabolic cellular states that contribute to disease outcomes in patients with ACLF. Our findings provide valuable insights into the pathogenesis of ACLF, shedding light on factors driving either recovery or nonrecovery phenotypes, which may be harnessed as potential therapeutic targets in the future.

Macrophage activation markers are associated with infection and mortality in patients with acute liver failure.

BACKGROUND AND AIMS: Acute liver failure is a multisystem disorder with a high mortality and frequent need for emergency liver transplantation. Following massive innate immune system activation, soluble markers of macrophage activation are released during liver damage and their association with disease severity and prognosis requires exploration. METHODS: Patients ALF from the United States Acute Liver Failure Study Group (USALFSG, n = 224) and King's College Hospital (n = 40) together with healthy controls (HC, n = 50) were recruited. Serum from early (Days 1-3) and late (>Day 3) time points were analysed for MAMs by enzyme-linked immunosorbent assay correlated to markers of illness severity and 21-day spontaneous survival. Surface expression phenotyping was performed via Flow Cytometry on CD14+ monocytes. RESULTS: All MAMs serum concentrations were significantly higher in ALF compared to controls (p < .0001). sCD206 concentration was higher in early and late stages of the disease in patients with bacteraemia (p = .002) and infection in general (p = .006). In MELD-adjusted multivariate modelling, sCD206 and sCD163 were independently associated with mortality. CD14+ monocyte expression of CD206 (p < .001) was higher in patients with ALF compared with controls and correlated with SOFA score (p = .018). sCD206 was independently validated as a predictor of infection in an external cohort. CONCLUSIONS: sCD206 is increased in serum of ALF patients with infections and poor outcome and is upregulated on CD14+ monocytes. Later measurements of sCD163 and sCD206 during the evolution of ALF have potential as mechanistic predictors of mortality. sCD206 should be explored as a biomarker of sepsis and mortality in ALF.

Immune Checkpoint Inhibitor-Induced Liver Injury.

In recent years cancer treatment has been revolutionized by the development and wide application of checkpoint inhibitor (CPI) drugs, which are a form of immunotherapy. CPI treatment is associated with immune-related adverse events, off-target tissue destructive inflammatory complications, which may affect a range of organs, with liver inflammation (hepatitis) being one of the more commonly noted events. This is a novel form of drug-induced liver injury and a rapidly evolving field, as our understanding of both the basic immunopathology of CPI hepatitis (CPI-H) and optimal clinical management, races to catch up with the increasing application of this form of immunotherapy in clinical practice. In this review, we summarize current evidence and understanding of CPI-H, from fundamental immunology to practical patient management.

Lysophosphatidylcholines modulate immunoregulatory checkpoints in peripheral monocytes and are associated with mortality in people with acute liver failure.

BACKGROUND & AIMS: Acute liver failure (ALF) is a life-threatening disease characterised by high-grade inflammation and immunoparesis, which is associated with a high incidence of death from sepsis. Herein, we aimed to describe the metabolic dysregulation in ALF and determine whether systemic immune responses are modulated via the lysophosphatidylcholine (LPC)-autotaxin (ATX)-lysophosphatidylcholinic acid (LPA) pathway. METHODS: Ninety-six individuals with ALF, 104 with cirrhosis, 31 with sepsis and 71 healthy controls (HCs) were recruited. Pathways of interest were identified by multivariate statistical analysis of proton nuclear magnetic resonance spectroscopy and untargeted ultraperformance liquid chromatography-mass spectrometry-based lipidomics. A targeted metabolomics panel was used for validation. Peripheral blood mononuclear cells were cultured with LPA 16:0, 18:0, 18:1, and their immune checkpoint surface expression was assessed by flow cytometry. Transcript-level expression of the LPA receptor (LPAR) in monocytes was investigated and the effect of LPAR antagonism was also examined in vitro. RESULTS: LPC 16:0 was highly discriminant between ALF and HC. There was an increase in ATX and LPA in individuals with ALF compared to HCs and those with sepsis. LPCs 16:0, 18:0 and 18:1 were reduced in individuals with ALF and were associated with a poor prognosis. Treatment of monocytes with LPA 16:0 increased their PD-L1 expression and reduced CD155, CD163, MerTK levels, without affecting immune checkpoints on T and NK/CD56+T cells. LPAR1 and 3 antagonism in culture reversed the effect of LPA on monocyte expression of MerTK and CD163. MerTK and CD163, but not LPAR genes, were differentially expressed and upregulated in monocytes from individuals with ALF compared to controls. CONCLUSION: Reduced LPC levels are biomarkers of poor prognosis in individuals with ALF. The LPC-ATX-LPA axis appears to modulate innate immune response in ALF via LPAR1 and LPAR3. Further investigations are required to identify novel therapeutic agents targeting these receptors. IMPACT AND IMPLICATIONS: We identified a metabolic signature of acute liver failure (ALF) and investigated the immunometabolic role of the lysophosphatidylcholine-autotaxin-lysophosphatidylcholinic acid pathway, with the aim of finding a mechanistic explanation for monocyte behaviour and identifying possible therapeutic targets (to modulate the systemic immune response in ALF). At present, no selective immune-based therapies exist. We were able to modulate the phenotype of monocytes in vitro and aim to extend these findings to murine models of ALF as a next step. Future therapies may be based on metabolic modulation; thus, the role of specific lipids in this pathway require elucidation and the relative merits of autotaxin inhibition, lysophosphatidylcholinic acid receptor blockade or lipid-based therapies need to be determined. Our findings begin to bridge this knowledge gap and the methods used herein could be useful in identifying therapeutic targets as part of an experimental medicine approach.

Potential therapies for acute-on-chronic liver failure.

Acute-on-chronic liver failure (ACLF) is a syndrome that develops in approximately 30% of patients hospitalised with cirrhosis and is characterised by an acute decompensation of liver function associated with extra-hepatic organ failures and a high short-term mortality. At present, no specific therapies are available for ACLF, and current management is limited to treatment of the precipitating event and organ support. Given the high prevalence and high mortality of this severe liver disease, there is an urgent need for targeted treatments. There is increasing evidence of the important role played by systemic inflammation and immune dysfunction in the pathophysiology of ACLF and a better understanding of these immune processes is resulting in new therapeutic targets. The aim of this review is to present an overview of ongoing studies of potentially promising therapies and how they could be utilised in the management of ACLF.

Suppressor CD4+ T cells expressing HLA-G are expanded in the peripheral blood from patients with acute decompensation of cirrhosis.

OBJECTIVE: Identifying components of immuneparesis, a hallmark of chronic liver failure, is crucial for our understanding of complications in cirrhosis. Various suppressor CD4+ T cells have been established as potent inhibitors of systemic immune activation. Here, we establish the presence, regulation and mechanism of action of a suppressive CD4+ T cell subset expressing human leucocyte antigen G (HLA-G) in patients with acute decompensation of cirrhosis (AD). DESIGN: Flow cytometry was used to determine the proportion and immunophenotype of CD4+HLA-G+ T cells from peripheral blood of 20 healthy controls (HCs) and 98 patients with cirrhosis (28 with stable cirrhosis (SC), 20 with chronic decompensated cirrhosis (CD) and 50 with AD). Transcriptional and functional signatures of cell-sorted CD4+HLA-G+ cells were delineated by NanoString technology and suppression assays, respectively. The role of immunosuppressive cytokine interleukin (IL)-35 in inducing this population was investigated through in vitro blockade experiments. Immunohistochemistry (IHC) and cultures of primary human Kupffer cells (KCs) were performed to assess cellular sources of IL-35. HLA-G-mediated T cell suppression was explored using neutralising antibodies targeting co-inhibitory pathways. RESULTS: Patients with AD were distinguished by an expansion of a CD4+HLA-G+CTLA-4+IL-35+ immunosuppressive population associated with disease severity, clinical course of AD, infectious complications and poor outcome. Transcriptomic analyses excluded the possibility that these were thymic-derived regulatory T cells. IHC analyses and in vitro cultures demonstrate that KCs represent a potent source of IL-35 which can induce the observed HLA-G+ phenotype. These exert cytotoxic T lymphocyte antigen-4-mediated impaired responses in T cells paralleled by an HLA-G-driven downregulation of T helper 17-related cytokines. CONCLUSION: We have identified a cytokine-driven peripherally derived suppressive population that may contribute to immuneparesis in AD.

Dysregulation of the Lysophosphatidylcholine/Autotaxin/Lysophosphatidic Acid Axis in Acute-on-Chronic Liver Failure Is Associated With Mortality and Systemic Inflammation by Lysophosphatidic Acid-Dependent Monocyte Activation.

BACKGROUND & AIMS: Acute-on-chronic liver failure (ACLF) is characterized by systemic inflammation, monocyte dysfunction, and susceptibility to infection. Lysophosphatidylcholines (LPCs) are immune-active lipids whose metabolic regulation and effect on monocyte function in ACLF is open for study. APPROACHES & RESULTS: Three hundred forty-two subjects were recruited and characterized for blood lipid, cytokines, phospholipase (PLA), and autotaxin (ATX) concentration. Peripheral blood mononuclear cells and CD14+ monocytes were cultured with LPC, or its autotaxin (ATX)-derived product, lysophosphatidic acid (LPA), with or without lipopolysaccharide stimulation and assessed for surface marker phenotype, cytokines production, ATX and LPA-receptor expression, and phagocytosis. Hepatic ATX expression was determined by immunohistochemistry. Healthy volunteers and patients with sepsis or acute liver failure served as controls. ACLF serum was depleted in LPCs with up-regulated LPA levels. Patients who died had lower LPC levels than survivors (area under the receiver operating characteristic curve, 0.94; P < 0.001). Patients with high-grade ACLF had the lowest LPC concentrations and these rose over the first 3 days of admission. ATX concentrations were higher in patients with AD and ACLF and correlated with Model for End-Stage Liver Disease, Consortium on Chronic Liver Failure-Sequential Organ Failure Assessment, and LPC/LPA concentrations. Reduction in LPC correlated with higher monocyte Mer-tyrosine-kinase (MerTK) and CD163 expression. Plasma ATX concentrations rose dynamically during ACLF evolution, correlating with IL-6 and TNF-α, and were associated with increased hepatocyte ATX expression. ACLF patients had lower human leukocyte antigen-DR isotype and higher CD163/MerTK monocyte expression than controls; both CD163/MerTK expression levels were reduced in ACLF ex vivo following LPA, but not LPC, treatment. LPA induced up-regulation of proinflammatory cytokines by CD14+ cells without increasing phagocytic capacity. CONCLUSIONS: ATX up-regulation in ACLF promotes LPA production from LPC. LPA suppresses MerTK/CD163 expression and increases monocyte proinflammatory cytokine production. This metabolic pathway could be investigated to therapeutically reprogram monocytes in ACLF.

Activation and transcriptional profile of monocytes and CD8+ T cells are altered in checkpoint inhibitor-related hepatitis.

BACKGROUND & AIMS: Checkpoint inhibitor-related hepatitis (CPI-Hep) is an emerging clinical challenge. We aimed to gain insights into the immunopathology of CPI-Hep by comprehensively characterising myeloid and lymphoid subsets. METHODS: CPI-treated patients with or without related hepatitis (CPI-Hep; n = 22 and CPI-noHep; n = 7) were recruited. Phenotypic and transcriptional profiling of peripheral immune subsets was performed and compared with 19 healthy controls (HCs). In vitro monocyte-derived macrophages (MoMFs) were assessed for activation and cytokine production. CD163, CCR2, CD68, CD3, CD8 and granzyme B expression was assessed using immunohistochemistry/immunofluorescence (n = 4). RESULTS: A significant total monocyte depletion was observed in CPI-Hep compared with HCs (p = 0.04), along with a proportionate increase in the classical monocyte population (p = 0.0002) and significant upregulation of CCR2, CD163 and downregulation of CCR7. Soluble CD163 levels were significantly elevated in CPI-Hep compared with HCs (p <0.0001). In vitro MoMFs from CPI-Hep showed enhanced production of pro-inflammatory cytokines. CD8+ T cells demonstrated increased perforin, granzyme B, ICOS and HLA-DR expression in CPI-Hep. Transcriptional profiling indicated the presence of activated monocyte and enhanced effector CD8+ T cell populations in CPI-Hep. Immunohistochemistry demonstrated co-localisation of CD8+/granzyme B+ T cells with CD68+CCR2+/CD68+CD163+ macrophages in CPI-Hep liver tissue. CONCLUSIONS: CPI-Hep is associated with activation of peripheral monocytes and an enhanced cytotoxic, effector CD8+ T cell phenotype. These changes were reflected by liver inflammation composed of CD163+/CCR2+ macrophages and CD8+ T cells. LAY SUMMARY: Some patients who receive immunotherapy for cancer develop liver inflammation, which requires cessation of cancer treatment. Herein, we describe ways in which the white blood cells of patients who develop liver inflammation differ from those of patients who receive the same immunotherapy but do not experience liver-related side effects. Targeting some of the pathways we identify may help to prevent or manage this side effect and facilitate cancer treatment.

CD14+ CD15- HLA-DR- myeloid-derived suppressor cells impair antimicrobial responses in patients with acute-on-chronic liver failure.

OBJECTIVE: Immune paresis in patients with acute-on-chronic liver failure (ACLF) accounts for infection susceptibility and increased mortality. Immunosuppressive mononuclear CD14+HLA-DR- myeloid-derived suppressor cells (M-MDSCs) have recently been identified to quell antimicrobial responses in immune-mediated diseases. We sought to delineate the function and derivation of M-MDSC in patients with ACLF, and explore potential targets to augment antimicrobial responses. DESIGN: Patients with ACLF (n=41) were compared with healthy subjects (n=25) and patients with cirrhosis (n=22) or acute liver failure (n=30). CD14+CD15-CD11b+HLA-DR- cells were identified as per definition of M-MDSC and detailed immunophenotypic analyses were performed. Suppression of T cell activation was assessed by mixed lymphocyte reaction. Assessment of innate immune function included cytokine expression in response to Toll-like receptor (TLR-2, TLR-4 and TLR-9) stimulation and phagocytosis assays using flow cytometry and live cell imaging-based techniques. RESULTS: Circulating CD14+CD15-CD11b+HLA-DR- M-MDSCs were markedly expanded in patients with ACLF (55% of CD14+ cells). M-MDSC displayed immunosuppressive properties, significantly decreasing T cell proliferation (p=0.01), producing less tumour necrosis factor-alpha/interleukin-6 in response to TLR stimulation (all p<0.01), and reduced bacterial uptake of Escherichia coli (p<0.001). Persistently low expression of HLA-DR during disease evolution was linked to secondary infection and 28-day mortality. Recurrent TLR-2 and TLR-4 stimulation expanded M-MDSC in vitro. By contrast, TLR-3 agonism reconstituted HLA-DR expression and innate immune function ex vivo. CONCLUSION: Immunosuppressive CD14+HLA-DR- M-MDSCs are expanded in patients with ACLF. They were depicted by suppressing T cell function, attenuated antimicrobial innate immune responses, linked to secondary infection, disease severity and prognosis. TLR-3 agonism reversed M-MDSC expansion and innate immune function and merits further evaluation as potential immunotherapeutic agent.

MerTK expressing hepatic macrophages promote the resolution of inflammation in acute liver failure.

OBJECTIVE: Acute liver failure (ALF) is characterised by overwhelming hepatocyte death and liver inflammation with massive infiltration of myeloid cells in necrotic areas. The mechanisms underlying resolution of acute hepatic inflammation are largely unknown. Here, we aimed to investigate the impact of Mer tyrosine kinase (MerTK) during ALF and also examine how the microenvironmental mediator, secretory leucocyte protease inhibitor (SLPI), governs this response. DESIGN: Flow cytometry, immunohistochemistry, confocal imaging and gene expression analyses determined the phenotype, functional/transcriptomic profile and tissue topography of MerTK+ monocytes/macrophages in ALF, healthy and disease controls. The temporal evolution of macrophage MerTK expression and its impact on resolution was examined in APAP-induced acute liver injury using wild-type (WT) and Mer-deficient (Mer-/-) mice. SLPI effects on hepatic myeloid cells were determined in vitro and in vivo using APAP-treated WT mice. RESULTS: We demonstrate a significant expansion of resolution-like MerTK+HLA-DRhigh cells in circulatory and tissue compartments of patients with ALF. Compared with WT mice which show an increase of MerTK+MHCIIhigh macrophages during the resolution phase in ALF, APAP-treated Mer-/- mice exhibit persistent liver injury and inflammation, characterised by a decreased proportion of resident Kupffer cells and increased number of neutrophils. Both in vitro and in APAP-treated mice, SLPI reprogrammes myeloid cells towards resolution responses through induction of a MerTK+HLA-DRhigh phenotype which promotes neutrophil apoptosis and their subsequent clearance. CONCLUSIONS: We identify a hepatoprotective, MerTK+, macrophage phenotype that evolves during the resolution phase following ALF and represents a novel immunotherapeutic target to promote resolution responses following acute liver injury.

Increased Expression of Cytotoxic T-Lymphocyte-Associated Protein 4 by T Cells, Induced by B7 in Sera, Reduces Adaptive Immunity in Patients With Acute Liver Failure.

BACKGROUND & AIMS: Patients with acute liver failure (ALF) have defects in innate immune responses to microbes (immune paresis) and are susceptible to sepsis. Cytotoxic T-lymphocyte-associated protein 4 (CTLA4), which interacts with the membrane receptor B7 (also called CD80 and CD86), is a negative regulator of T-cell activation. We collected T cells from patients with ALF and investigated whether inhibitory signals down-regulate adaptive immune responses in patients with ALF. METHODS: We collected peripheral blood mononuclear cells from patients with ALF and controls from September 2013 through September 2015 (45 patients with ALF, 20 patients with acute-on-chronic liver failure, 15 patients with cirrhosis with no evidence of acute decompensation, 20 patients with septic shock but no cirrhosis or liver disease, and 20 healthy individuals). Circulating CD4+ T cells were isolated and analyzed by flow cytometry. CD4+ T cells were incubated with antigen, or agonist to CD3 and dendritic cells, with or without antibody against CTLA4; T-cell proliferation and protein expression were quantified. We measured levels of soluble B7 molecules in supernatants of isolated primary hepatocytes, hepatic sinusoidal endothelial cells, and biliary epithelial cells from healthy or diseased liver tissues. We also measured levels of soluble B7 serum samples from patients and controls, and mice with acetaminophen-induced liver injury using enzyme-linked immunosorbent assays. RESULTS: Peripheral blood samples from patients with ALF had a higher proportion of CD4+ CTLA4+ T cells than controls; patients with infections had the highest proportions. CD4+ T cells from patients with ALF had a reduced proliferative response to antigen or CD3 stimulation compared to cells from controls; incubation of CD4+ T cells from patients with ALF with an antibody against CTLA4 increased their proliferative response to antigen and to CD3 stimulation, to the same levels as cells from controls. CD4+ T cells from controls up-regulated expression of CTLA4 after 24-48 hours culture with sera from patients with ALF; these sera were found to have increased concentrations of soluble B7 compared to sera from controls. Necrotic human primary hepatocytes exposed to acetaminophen, but not hepatic sinusoidal endothelial cells and biliary epithelial cells from patients with ALF, secreted high levels of soluble B7. Sera from mice with acetaminophen-induced liver injury contained high levels of soluble B7 compared to sera from mice without liver injury. Plasma exchange reduced circulating levels of soluble B7 in patients with ALF and expression of CTLA4 on T cells. CONCLUSIONS: Peripheral CD4+ T cells from patients with ALF have increased expression of CTLA4 compared to individuals without ALF; these cells have a reduced response to antigen and CD3 stimulation. We found sera of patients with ALF and from mice with liver injury to have high concentrations of soluble B7, which up-regulates CTLA4 expression by T cells and reduces their response to antigen. Plasma exchange reduces levels of B7 in sera from patients with ALF and might be used to restore antimicrobial responses to patients.

High-volume plasma exchange in patients with acute liver failure: An open randomised controlled trial.

BACKGROUND & AIMS: Acute liver failure (ALF) often results in cardiovascular instability, renal failure, brain oedema and death either due to irreversible shock, cerebral herniation or development of multiple organ failure. High-volume plasma exchange (HVP), defined as exchange of 8-12 or 15% of ideal body weight with fresh frozen plasma in case series improves systemic, cerebral and splanchnic parameters. METHODS: In this prospective, randomised, controlled, multicentre trial we randomly assigned 182 patients with ALF to receive either standard medical therapy (SMT; 90 patients) or SMT plus HVP for three days (92 patients). The baseline characteristics of the groups were similar. The primary endpoint was liver transplantation-free survival during hospital stay. Secondary-endpoints included survival after liver transplantation with or without HVP with intention-to-treat analysis. A proof-of-principle study evaluating the effect of HVP on the immune cell function was also undertaken. RESULTS: For the entire patient population, overall hospital survival was 58.7% for patients treated with HVP vs. 47.8% for the control group (hazard ratio (HR), with stratification for liver transplantation: 0.56; 95% confidence interval (CI), 0.36-0.86; p=0.0083). HVP prior to transplantation did not improve survival compared with patients who received SMT alone (CI 0.37 to 3.98; p=0.75). The incidence of severe adverse events was similar in the two groups. Systemic inflammatory response syndrome (SIRS) and sequential organ failure assessment (SOFA) scores fell in the treated group compared to control group, over the study period (p<0.001). CONCLUSIONS: Treatment with HVP improves outcome in patients with ALF by increasing liver transplant-free survival. This is attributable to attenuation of innate immune activation and amelioration of multi-organ dysfunction.

Multivariate metabotyping of plasma predicts survival in patients with decompensated cirrhosis.

BACKGROUND & AIMS: Predicting survival in decompensated cirrhosis (DC) is important in decision making for liver transplantation and resource allocation. We investigated whether high-resolution metabolic profiling can determine a metabolic phenotype associated with 90-day survival. METHODS: Two hundred and forty-eight subjects underwent plasma metabotyping by (1)H nuclear magnetic resonance (NMR) spectroscopy and reversed-phase ultra-performance liquid chromatography coupled to time-of-flight mass spectrometry (UPLC-TOF-MS; DC: 80-derivation set, 101-validation; stable cirrhosis (CLD) 20 and 47 healthy controls (HC)). RESULTS: (1)H NMR metabotyping accurately discriminated between surviving and non-surviving patients with DC. The NMR plasma profiles of non-survivors were attributed to reduced phosphatidylcholines and lipid resonances, with increased lactate, tyrosine, methionine and phenylalanine signal intensities. This was confirmed on external validation (area under the receiver operating curve [AUROC]=0.96 (95% CI 0.90-1.00, sensitivity 98%, specificity 89%). UPLC-TOF-MS confirmed that lysophosphatidylcholines and phosphatidylcholines [LPC/PC] were downregulated in non-survivors (UPLC-TOF-MS profiles AUROC of 0.94 (95% CI 0.89-0.98, sensitivity 100%, specificity 85% [positive ion detection])). LPC concentrations negatively correlated with circulating markers of cell death (M30 and M65) levels in DC. Histological examination of liver tissue from DC patients confirmed increased hepatocyte cell death compared to controls. Cross liver sampling at time of liver transplantation demonstrated that hepatic endothelial beds are a source of increased circulating total cytokeratin-18 in DC. CONCLUSION: Plasma metabotyping accurately predicts mortality in DC. LPC and amino acid dysregulation is associated with increased mortality and severity of disease reflecting hepatocyte cell death.

Acute alcoholic hepatitis and cellular Th1 immune responses to alcohol dehydrogenase.

BACKGROUND: Alcoholic hepatitis is characterised by florid hepatic inflammation, liver failure, and death within 28 days in 35% of patients. We recently showed proliferative peripheral blood mononuclear cell (PBMC) responses to alcohol dehydrogenase (ADH) in patients with alcohol-related cirrhosis, associated with T-helper-type 1 (Th1) immunity and disease severity. We aimed to define whether ADH-specific cellular immunity is present in alcoholic hepatitis. METHODS: PBMCs were collected from 15 patients with alcoholic hepatitis (modified Maddrey's discriminant function >32), nine with alcohol-related cirrhosis (long-term alcohol abstinence), and three healthy controls. 25 overlapping peptides, spanning the human ADH ß1 subunit, were constructed. Proliferation to ADH peptides (1 × 10(5) cells per well, cultured with 10 mM peptides for 7 days) was assessed by (3)H-thymidine incorporation. A stimulation index (SI) of 2·5 or more was regarded as positive. ELISA measured concentrations of interferon γ (IFNγ), interleukin (IL) 17, and IL4 from supernatant. FINDINGS: PBMCs from seven of 15 patients with alcoholic hepatitis recognised one to three ADH peptides (SI ≤5·7). IFNγ (mean 390·9 pg/mL [SE 31·4]) was detected in 48% of wells, IL17 (20·1 [3 ·4]) in 15%, and IL4 (90·5 [9·3]) in 14%. PBMCs from six of the nine patients with alcohol-related cirrhosis recognised one to five peptides (SI ≤5·2). IFNγ (360·7 [58·9], p>0·05) was detected in 31% of wells, IL17 (57·7 [10·9], p=0·0006) in 19%, and IL4 (219·7 [11·2], p=0·0012) in 28%. PBMCs from two healthy controls recognised one to two peptides (SI ≤3·1); all cytokine levels were below baseline. INTERPRETATION: Proliferative anti-ADH immune responses in alcoholic hepatitis focused on individual epitopic regions. Predominance of proinflammatory Th1 responses was more pronounced in alcoholic hepatitis than in alcoholic-related cirrhosis. This finding requires investigation of targeted therapies to inhibit Th1 immunity in alcoholic hepatitis. FUNDING: Wellcome Trust.

Patients with acute-on-chronic liver failure have increased numbers of regulatory immune cells expressing the receptor tyrosine kinase MERTK.

BACKGROUND & AIMS: Characteristics of decompensated cirrhosis and acute-on-chronic liver failure (ACLF) include susceptibility to infection, immuneparesis, and monocyte dysfunction. MER receptor tyrosine kinase (MERTK) is expressed by monocytes and macrophages and contributes to down-regulation of innate immune responses. We investigated whether MERTK expression is altered on monocytes from patients with liver failure. METHODS: We analyzed blood and liver samples collected from patients admitted to the liver intensive therapy unit at King's College Hospital in London from December 2012 through July 2014. Patients had either ACLF (n = 41), acute decompensation of cirrhosis without ACLF (n = 9), cirrhosis without decompensation (n = 17), or acute liver failure (n = 23). We also analyzed samples from healthy individuals (controls, n = 29). We used flow cytometry to determine the level of innate immune function, and associated the findings with disease severity. We developed an assay to measure recruitment and migration of immune cells from the tissue parenchyma. Immunohistochemistry and confocal microscopy were used to determine levels of MERTK in bone marrow, liver, and lymph node tissues. We performed immunophenotype analyses and measured the production of tumor necrosis factor and interleukin 6 and intracellular killing of Escherichia coli by monocytes and peritoneal macrophages incubated with lipopolysaccharide, with or without an inhibitor of MERTK (UNC569). RESULTS: The number of monocytes and macrophages that expressed MERTK was greatly increased in the circulation, livers, and lymph nodes of patients with ACLF, compared with patients with stable cirrhosis and controls. MERTK expression (mean fluorescence intensity) correlated with the severity of hepatic and extrahepatic disease and systemic inflammatory responses. Based on immunophenotype, migration, and functional analyses, MERTK-expressing monocytes migrate across the endothelia to localize into tissue sites and regional lymph nodes. Expression of MERTK reduced the response of cultured monocytes to lipopolysaccharide; the addition of UNC569 restored production of inflammatory cytokines in response to lipopolysaccharide. CONCLUSIONS: Patients with ACLF have increased numbers of immunoregulatory monocytes and macrophages that express MERTK and suppress the innate immune response to microbes. The number of these cells correlates with disease severity and the inflammatory response. MERTK inhibitors restore production of inflammatory cytokines by immune cells from patients with ACLF, and might be developed to increase the innate immune response in these patients.

Secretory leukocyte protease inhibitor: a pivotal mediator of anti-inflammatory responses in acetaminophen-induced acute liver failure.

UNLABELLED: Acetaminophen-induced acute liver failure (AALF) is characterized both by activation of innate immune responses and susceptibility to sepsis. Circulating monocytes and hepatic macrophages are central mediators of inflammatory responses and tissue repair processes during human AALF. Secretory leukocyte protease inhibitor (SLPI) modulates monocyte/macrophage function through inhibition of nuclear factor kappa B (NF-κB) signaling. The aims of this study were to establish the role of SLPI in AALF. Circulating levels of SLPI, monocyte cluster of differentiation 163 (CD163), human leukocyte antigen-DR (HLA-DR), and lipopolysaccharide (LPS)-stimulated levels of NF-κBp65, tumor necrosis factor alpha (TNF-α) and interleukin (IL)-6 were determined in patients with AALF, chronic liver disease, and healthy controls. Immunohistochemistry and multispectral imaging of AALF explant tissue determined the cellular sources of SLPI and hepatic macrophage phenotype. The phenotype and function of monocytes and macrophages was determined following culture with recombinant human (rh)-SLPI, liver homogenates, and plasma derived from AALF patients in the presence and absence of antihuman (α)SLPI. Hepatic and circulatory concentrations of SLPI were elevated in AALF and immunohistochemistry revealed SLPI expression in biliary epithelial cells and within hepatic macrophages (h-mψ) in areas of necrosis. H-mψ and circulating monocytes in AALF exhibited an anti-inflammatory phenotype and functional characteristics; typified by reductions in NF-κBp65, TNF-α, and IL-6 and preserved IL-10 secretion following LPS challenge. Culture of healthy monocytes with AALF liver homogenates, plasma, or rhSLPI induced monocytes with strikingly similar anti-inflammatory characteristics which were reversed by inhibiting the activity of SLPI. CONCLUSION: SLPI is a pivotal mediator of anti-inflammatory responses in AALF through modulation of monocyte/macrophage function, which may account for the susceptibility to sepsis in AALF.

Patella Fracture After Total Knee Arthroplasty: A Review.

The management and underlying causes of patellar periprosthetic fractures (PPF) after total knee arthroplasty (TKA) constitute an issue of growing importance given the rising frequency of these procedures. Patella periprosthetic fractures, though relatively rare, pose significant challenges and are a frequent indication for revision surgeries. Despite a decrease in overall incidence, PPFs remain the second most common type of periprosthetic fractures after TKA. Several factors have been identified and associated with patient-specific factors, surgical technique errors, and implant-related causes. Currently extensor apparatus integrity, bone stock, and component loosening are the major concerns and indications for the selective treatment approach. In this study, a thorough review of the existing literature was performed summarizing the epidemiology, clinical manifestation, treatment approach, and functional outcome of PPF. This review aims to underline the significance of such predisposing factors, point out the severity of PPF, and offer insights into the optimal intra- and post-operative management of the patella.

Therapeutic inhibition of monocyte recruitment prevents checkpoint inhibitor-induced hepatitis.

BACKGROUND: Checkpoint inhibitor-induced hepatitis (CPI-hepatitis) is an emerging problem with the widening use of CPIs in cancer immunotherapy. Here, we developed a mouse model to characterize the mechanism of CPI-hepatitis and to therapeutically target key pathways driving this pathology. METHODS: C57BL/6 wild-type (WT) mice were dosed with toll-like receptor (TLR)9 agonist (TLR9-L) for hepatic priming combined with anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) plus anti-programmed cell death 1 (PD-1) ("CPI") or phosphate buffered saline (PBS) control for up to 7 days. Flow cytometry, histology/immunofluorescence and messenger RNA sequencing were used to characterize liver myeloid/lymphoid subsets and inflammation. Hepatocyte damage was assessed by plasma alanine transaminase (ALT) and cytokeratin-18 (CK-18) measurements. In vivo investigations of CPI-hepatitis were carried out in Rag2-/- and Ccr2rfp/rfp transgenic mice, as well as following anti-CD4, anti-CD8 or cenicriviroc (CVC; CCR2/CCR5 antagonist) treatment. RESULTS: Co-administration of combination CPIs with TLR9-L induced liver pathology closely resembling human disease, with increased infiltration and clustering of granzyme B+perforin+CD8+ T cells and CCR2+ monocytes, 7 days post treatment. This was accompanied by apoptotic hepatocytes surrounding these clusters and elevated ALT and CK-18 plasma levels. Liver RNA sequencing identified key signaling pathways (JAK-STAT, NF-ΚB) and cytokine/chemokine networks (Ifnγ, Cxcl9, Ccl2/Ccr2) as drivers of CPI-hepatitis. Using this model, we show that CD8+ T cells mediate hepatocyte damage in experimental CPI-hepatitis. However, their liver recruitment, clustering, and cytotoxic activity is dependent on the presence of CCR2+ monocytes. The absence of hepatic monocyte recruitment in Ccr2rfp/rfp mice and CCR2 inhibition by CVC treatment in WT mice was able to prevent the development and reverse established experimental CPI-hepatitis. CONCLUSION: This newly established mouse model provides a platform for in vivo mechanistic studies of CPI-hepatitis. Using this model, we demonstrate the central role of liver infiltrating CCR2+ monocyte interaction with tissue-destructive CD8+ T cells in the pathogenesis of CPI-hepatitis and highlight CCR2 inhibition as a novel therapeutic target.

AXL Expression on Homeostatic Resident Liver Macrophages Is Reduced in Cirrhosis Following GAS6 Production by Hepatic Stellate Cells.

BACKGROUND & AIMS: AXL and MERTK expression on circulating monocytes modulated immune responses in patients with cirrhosis (CD14+HLA-DR+AXL+) and acute-on-chronic liver failure (CD14+MERTK+). AXL expression involved enhanced efferocytosis, sustained phagocytosis, but reduced tumor necrosis factor-α/interleukin-6 production and T-cell activation, suggesting a homeostatic function. Axl was expressed on murine airway in tissues contacting the external environment, but not interstitial lung- and tissue-resident synovial lining macrophages. Here, we assessed AXL expression on tissue macrophages in patients with cirrhosis. METHODS: Using multiplexed immunofluorescence we compared AXL expression in liver biopsies in cirrhosis (n = 22), chronic liver disease (n = 8), non-cirrhotic portal hypertension (n = 4), and healthy controls (n = 4). Phenotype and function of isolated primary human liver macrophages were characterized by flow cytometry (cirrhosis, n = 11; control, n = 14) ex vivo. Also, AXL expression was assessed on peritoneal (n = 29) and gut macrophages (n = 16) from cirrhotic patients. Regulation of AXL expression was analyzed in vitro and ex vivo using primary hepatic stellate cells (HSCs), LX-2 cells, and GAS6 in co-culture experiments. RESULTS: AXL was expressed on resident (CD68+) but not tissue-infiltrating (MAC387+) liver macrophages, hepatocytes, HSCs, or sinusoidal endothelial cells. Prevalence of hepatic CD68+AXL+ cells significantly decreased with cirrhosis progression: (healthy, 90.2%; Child-Pugh A, 76.1%; Child-Pugh B, 64.5%; and Child-Pugh C, 18.7%; all P < .05) and negatively correlated with Model for End-Stage Liver Disease and C-reactive protein (all P < .05). AXL-expressing hepatic macrophages were CD68highHLA-DRhighCD16highCD206high. AXL expression also decreased on gut and peritoneal macrophages from cirrhotic patients but increased in regional lymph nodes. GAS6, enriched in the cirrhotic liver, appeared to be secreted by HSCs and down-regulate AXL in vitro. CONCLUSIONS: Decreased AXL expression on resident liver macrophages in advanced cirrhosis, potentially in response to activated HSC-secreted GAS6, suggests a role for AXL in the regulation of hepatic immune homeostasis.

Lipids in Liver Failure Syndromes: A Focus on Eicosanoids, Specialized Pro-Resolving Lipid Mediators and Lysophospholipids.

Lipids are organic compounds insoluble in water with a variety of metabolic and non-metabolic functions. They not only represent an efficient energy substrate but can also act as key inflammatory and anti-inflammatory molecules as part of a network of soluble mediators at the interface of metabolism and the immune system. The role of endogenous bioactive lipid mediators has been demonstrated in several inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, cancer). The liver is unique in providing balanced immunotolerance to the exposure of bacterial components from the gut transiting through the portal vein and the lymphatic system. This balance is abruptly deranged in liver failure syndromes such as acute liver failure and acute-on-chronic liver failure. In these syndromes, researchers have recently focused on bioactive lipid mediators by global metabonomic profiling and uncovered the pivotal role of these mediators in the immune dysfunction observed in liver failure syndromes explaining the high occurrence of sepsis and subsequent organ failure. Among endogenous bioactive lipids, the mechanistic actions of three classes (eicosanoids, pro-resolving lipid mediators and lysophospholipids) in the pathophysiological modulation of liver failure syndromes will be the topic of this narrative review. Furthermore, the therapeutic potential of lipid-immune pathways will be described.