CD39 mediated regulation of Th17-cell effector function is impaired in juvenile autoimmune liver disease

Adenosine-mediated immune responses in inflammatory bowel disease

Extracellular ATP and its derivates mediate a signaling pathway that might be pharmacologically targeted to treat inflammatory conditions. Extracellular adenosine, the product of ATP hydrolysis by ectonucleotidase enzymes, plays a key role in halting inflammation while promoting immune tolerance. The rate-limiting ectoenzyme ENTPD1/CD39 and the ecto-5'-nucleotidase/CD73 are the prototype members of the ectonucleotidase family, being responsible for ATP degradation into immunosuppressive adenosine. The biological effects of adenosine are mediated via adenosine receptors, a family of G protein-coupled receptors largely expressed on immune cells where they modulate innate and adaptive immune responses. Inflammatory bowel disease (IBD) is a serious inflammatory condition of the gastrointestinal tract, associated with substantial morbidity and often refractory to currently available medications. IBD is linked to altered interactions between the gut microbiota and the immune system in genetically predisposed individuals. A wealth of studies conducted in patients and animal models highlighted the role of various adenosine receptors in the modulation of chronic inflammatory diseases like IBD. In this review, we will discuss the most recent findings on adenosine-mediated immune responses in different cell types, with a focus on IBD and its most common manifestations, Crohn's disease and ulcerative colitis.

T cells in obesity-associated inflammation: The devil is in the details

Obesity presents a significant health challenge, affecting 41% of adults and 19.7% of children in the United States. One of the associated health challenges of obesity is chronic low-grade inflammation. In both mice and humans, T cells in circulation and in the adipose tissue play a pivotal role in obesity-associated inflammation. Changes in the numbers and frequency of specific CD4+ Th subsets and their contribution to inflammation through cytokine production indicate declining metabolic health, that is, insulin resistance and T2D. While some Th subset alterations are consistent between mice and humans with obesity, some changes mainly characterize male mice, whereas female mice often resist obesity and inflammation. However, protection from obesity and inflammation is not observed in human females, who can develop obesity-related T-cell inflammation akin to males. The decline in female sex hormones after menopause is also implicated in promoting obesity and inflammation. Age is a second underappreciated factor for defining and regulating obesity-associated inflammation toward translating basic science findings to the clinic. Weight loss in mice and humans, in parallel with these other factors, does not resolve obesity-associated inflammation. Instead, inflammation persists amid modest changes in CD4+ T cell frequencies, highlighting the need for further research into resolving changes in T-cell function after weight loss. How lingering inflammation after weight loss affecting the common struggle to maintain lower weight is unknown. Semaglutide, a newly popular pharmaceutical used for treating T2D and reversing obesity, holds promise for alleviating obesity-associated health complications, yet its impact on T-cell-mediated inflammation remains unexplored. Further work in this area could significantly contribute to the scientific understanding of the impacts of weight loss and sex/hormones in obesity and obesity-associated metabolic decline.

B and T cells: (Still) the dominant orchestrators in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe hepatopathy characterized by hypergammaglobulinemia, presence of serum autoantibodies and histological appearance of interface hepatitis. Liver damage in AIH is initiated by the presentation of a liver autoantigen to uncommitted Th0 lymphocytes, followed by a cascade of effector immune responses culminating with the production of inflammatory cytokines, activation of cytotoxic cells and subsequent hepatocyte injury. B cells actively participate in AIH liver damage by presenting autoantigens to uncommitted T lymphocytes. B cells also undergo maturation into plasma cells that are responsible for production of immunoglobulin G and autoantibodies, which mediate antibody dependent cell cytotoxicity. Perpetuation of effector immunity with consequent progression of liver damage is permitted by impairment in regulatory T cells (Tregs), a lymphocyte subset central to the maintenance of immune homeostasis. Treg impairment in AIH is multifactorial, deriving from numerical decrease, reduced suppressive function, poor response to IL-2 and less stable phenotype. In this review, we discuss the role of B and T lymphocytes in the pathogenesis of AIH. Immunotherapeutic strategies that could limit inflammation and halt disease progression while reconstituting tolerance to liver autoantigens are also reviewed and discussed.

Immunopathogenesis of Primary Biliary Cholangitis, Primary Sclerosing Cholangitis and Autoimmune Hepatitis: Themes and Concepts

Autoimmune liver diseases include primary biliary cholangitis, primary sclerosing cholangitis, and autoimmune hepatitis, a family of chronic immune-mediated disorders that target hepatocytes and cholangiocytes. Treatments remain nonspecific, variably effective, and noncurative, and the need for liver transplantation is disproportionate to their rarity. Development of effective therapies requires better knowledge of pathogenic mechanisms, including the roles of genetic risk, and how the environment and gut dysbiosis cause immune cell dysfunction and aberrant bile acid signaling. This review summarizes key etiologic and pathogenic concepts and themes relevant for clinical practice and how such learning can guide the development of new therapies for people living with autoimmune liver diseases.

Silencing of aryl hydrocarbon receptor repressor restrains Th17 cell immunity in autoimmune hepatitis

Th17-cells play a key role in the pathogenesis of autoimmune hepatitis (AIH). Dysregulation of Th17-cells in AIH is linked to defective response to aryl-hydrocarbon-receptor (AhR) activation. AhR modulates adaptive immunity and is regulated by aryl-hydrocarbon-receptor-repressor (AHRR), which inhibits AhR transcriptional activity. In this study, we investigated whether defective Th17-cell response to AhR derives from aberrant AHRR regulation in AIH. Th17-cells, obtained from the peripheral blood of AIH patients (n = 30) and healthy controls (n = 30) were exposed to AhR endogenous ligands, and their response assessed in the absence or presence of AHRR silencing. Therapeutic effects of AHRR blockade were tested in a model of Concanavalin-A (Con-A)-induced liver injury in humanized mice. AHRR was markedly upregulated in AIH Th17-cells, following exposure to l-kynurenine, an AhR endogenous ligand. In patients, silencing of AHRR boosted Th17-cell response to l-kynurenine, as reflected by increased levels of CYP1A1, the main gene controlled by AhR; and decreased IL17A expression. Blockade of AHRR limited the differentiation of naïve CD4-cells into Th17 lymphocytes; and modulated Th17-cell metabolic profile by increasing the levels of uridine via ATP depletion or pyrimidine salvage. Treatment with 2'-deoxy-2'-fluoro-d-arabinonucleic acid (FANA) oligonucleotides to silence human AHRR in vivo, reduced ALT levels, attenuated lymphocyte infiltration on histology, and heightened frequencies of regulatory immune subsets in NOD/scid/gamma mice, reconstituted with human CD4 cells, and exposed to Con-A. In conclusion, blockade of AHRR in AIH restores Th17-cell response to AHR, and limits Th17-cell differentiation through generation of uridine. In vivo, silencing of AHRR attenuates liver damage in NOD/scid/gamma mice. Blockade of AHRR might therefore represent a novel therapeutic strategy to modulate effector Th17-cell immunity and restore homeostasis in AIH.

Autoimmune Hepatitis: Pathophysiology

Genome-wide association analyses suggest that HLA genes including HLA-DRB*0301, HLA-DRB*0401, and HLA-B*3501 as well as non-HLA genes including CD28/CTLA4/ICOS and SYNPR increased AIH susceptibility. The destruction of hepatocytes is the result of the imbalance between proinflammatory cells and immunosuppressive cells, especially the imbalance between Tregs and Th17 cells. The microbiome in patients with AIH is decreased in diversity with a specific decline in Bifidobacterium and enrichment in Veillonella and Faecalibacterium. Recent evidence has demonstrated the pathogenic role of E. gallinarum and L.reuteri in inducing autoimmunity in the liver.

CD4+ T-cell subsets in autoimmune hepatitis: A review

Autoimmune hepatitis (AIH) is a chronic autoimmune liver disease that can lead to hepatocyte destruction, inflammation, liver fibrosis, cirrhosis, and liver failure. The diagnosis of AIH requires the identification of lymphoblast cell interface hepatitis and serum biochemical abnormalities, as well as the exclusion of related diseases. According to different specific autoantibodies, AIH can be divided into AIH-1 and AIH-2. The first-line treatment for AIH is a corticosteroid and azathioprine regimen, and patients with liver failure require liver transplantation. However, the long-term use of corticosteroids has obvious side effects, and patients are prone to relapse after drug withdrawal. Autoimmune diseases are characterized by an imbalance in immune tolerance of self-antigens, activation of autoreactive T cells, overactivity of B cells, and increased production of autoantibodies. CD4+ T cells are key players in adaptive immunity and can secrete cytokines, activate B cells to produce antibodies, and influence the cytotoxicity of CD8+ T cells. According to their characteristics, CD4+ T cells can be divided into different subsets. In this review, we discuss the changes in T helper (Th)1, Th2, Th17, Th9, Th22, regulatory T cell, T follicular helper, and T peripheral helper cells and their related factors in AIH and discuss the therapeutic potential of targeting CD4+ T-cell subsets in AIH.

CD73, a significant protein in liver diseases

Purine adenosine pathway exists widely in the body metabolism, and is involved in regulating various physiological processes. It is one of the important pathways of environmental regulation in human body. CD73 is essentially a protease that catalyzes further dephosphorylation of extracellular adenine nucleotides, hydrolyzing extracellular AMP to adenosine and phosphate. CD73 is an important part of the adenosine signaling pathway. Studies have shown that CD73-mediated adenosine pathway can convert the inflammatory ATP into the immunosuppressant adenosine. This paper aims to summarize the relevant effects of CD73 in the occurrence, development and prognosis of liver diseases such as viral hepatitis, highlight the important role of CD73 in liver diseases, especially in viral hepatitis such as HBV and HCV, and explore new clinical ideas for future treatment targets of liver diseases.

Blockade of PGK1 and ALDOA enhances bilirubin control of Th17 cells in Crohn's disease

Unconjugated bilirubin (UCB) confers Th17-cells immunosuppressive features by activating aryl-hydrocarbon-receptor, a modulator of toxin and adaptive immune responses. In Crohn's disease, Th17-cells fail to acquire regulatory properties in response to UCB, remaining at an inflammatory/pathogenic state. Here we show that UCB modulates Th17-cell metabolism by limiting glycolysis and through downregulation of glycolysis-related genes, namely phosphoglycerate-kinase-1 (PGK1) and aldolase-A (ALDOA). Th17-cells of Crohn's disease patients display heightened PGK1 and ALDOA and defective response to UCB. Silencing of PGK1 or ALDOA restores Th17-cell response to UCB, as reflected by increase in immunoregulatory markers like FOXP3, IL-10 and CD39. In vivo, PGK1 and ALDOA silencing enhances UCB salutary effects in trinitro-benzene-sulfonic-acid-induced colitis in NOD/scid/gamma humanized mice where control over disease activity and enhanced immunoregulatory phenotypes are achieved. PGK1 and/or ALDOA blockade might have therapeutic effects in Crohn's disease by favoring acquisition of regulatory properties by Th17-cells along with control over their pathogenic potential.

Th17 cells in the liver: balancing autoimmunity and pathogen defense

In addition to carcinogenesis, T helper 17 (Th17) cells (a subtype of CD4 + T lymphocytes) are involved in the acute, chronic, and cirrhotic phases of liver diseases; however, their role in the development and progression of liver diseases remains unclear. It is difficult to elucidate the role of Th17 cells in liver diseases due to their dichotomous nature, i.e., plasticity in terms of pathogenic or host protective function depending on environmental and time phase factors. Moreover, insufficient depletion of Th17 cells by inhibiting the cytokines and transcription factors involved in their production causes difficulties in analyzing their specific role in vitro and in vivo murine models, partially due to complex interaction. This review summarizes the recent progress in understanding the plasticity and function of hepatic Th17 cells and type 3 cytokines.

A reasoned approach to the treatment of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease affecting all ages, characterised by elevated transaminase and immunoglobulin G levels, positive autoantibodies, interface hepatitis on histology and good response to immunosuppressive treatment. If untreated, it has a poor prognosis. The aim of this review is to analyse AIH therapeutic interventions with reference to our knowledge of the pathogenesis of AIH. Standard treatment, based on steroids and azathioprine, leads to disease remission in 80-90% of patients. Alternative first-line treatment with budesonide is effective in adults, but less so in the juvenile form of AIH; first-line treatment with ciclosporin does not provide convincing advantages compared to standard treatment. Second-line treatments are needed for patients not responding or intolerant to first-line standard management. Mycophenolate mofetil is the most widely used second-line drug, and has good efficacy particularly for patients intolerant to azathioprine, but is teratogenic. Only few and heterogeneous data on calcineurin inhibitors and m-TOR inhibitors are available. Biologicals, including anti-tumour necrosis factor- α and anti-CD20 monoclonal antibodies, have given ambivalent results and may have severe side-effects. Clinical trials with new therapeutic options aiming at targeting B lymphocytes and proinflammatory cytokines, or expanding regulatory T cells to restore tolerance are ongoing.

Limited TCR repertoire and ENTPD1 dysregulation mark late-stage COVID-19

T cell exhaustion and dysfunction are hallmarks of severe COVID-19. To gain insights into the pathways underlying these alterations, we performed a comprehensive transcriptome analysis of peripheral-blood-mononuclear-cells (PBMCs), spleen, lung, kidney, liver, and heart obtained at autopsy from COVID-19 patients and matched controls, using the nCounter CAR-T-Characterization panel. We found substantial gene alterations in COVID-19-impacted organs, especially the lung where altered TCR repertoires are noted. Reduced TCR repertoires are also observed in PBMCs of severe COVID-19 patients. ENTPD1/CD39, an ectoenzyme defining exhausted T-cells, is upregulated in the lung, liver, spleen, and PBMCs of severe COVID-19 patients where expression positively correlates with markers of vasculopathy. Heightened ENTPD1/CD39 is paralleled by elevations in STAT-3 and HIF-1α transcription factors; and by markedly reduced CD39-antisense-RNA, a long-noncoding-RNA negatively regulating ENTPD1/CD39 at the post-transcriptional level. Limited TCR repertoire and aberrant regulation of ENTPD1/CD39 could have permissive roles in COVID-19 progression and indicate potential therapeutic targets to reverse disease.

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Transcriptome profiling of COVID-19 autoptic tissue and PBMC was carried out

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There is limited TCR repertoire in lung, kidney and PBMC of severe COVID-19 cases

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There are increased CD39 levels in PBMC of severe COVID-19 patients

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High HIF-1a and STAT-3 and low CD39-antisense might be linked with CD39 increase

Dysfunctional Immune Regulation in Autoimmune Hepatitis: From Pathogenesis to Novel Therapies

Autoimmune hepatitis (AIH) is a chronic inflammatory disorder characterized by hypergammaglobulinemia, presence of serum autoantibodies and histological features of interface hepatitis. AIH therapeutic management still relies on the administration of corticosteroids, azathioprine and other immunosuppressants like calcineurin inhibitors and mycophenolate mofetil. Withdrawal of immunosuppression often results in disease relapse, and, in some cases, therapy is ineffective or associated with serious side effects. Understanding the mechanisms underlying AIH pathogenesis is therefore of paramount importance to develop more effective and well tolerated agents capable of restoring immunotolerance to liver autoantigens. Imbalance between effector and regulatory cells permits liver damage perpetuation and progression in AIH. Impaired expression and regulation of CD39, an ectoenzyme key to immunotolerance maintenance, have been reported in Tregs and effector Th17-cells derived from AIH patients. Interference with these altered immunoregulatory pathways may open new therapeutic avenues that, in addition to limiting aberrant inflammatory responses, would also reconstitute immune homeostasis. In this review, we highlight the most recent findings in AIH immunopathogenesis and discuss how these could inform and direct the development of novel therapeutic tools.

Regulation of immune responses through CD39 and CD73 in cancer: Novel checkpoints

The immunosuppressive tumor microenvironment has been implicated in attenuating anti-tumoral immune responses and tumor growth in various cancers. Inhibitory immune checkpoints have been introduced as the primary culprits for developing the immunosuppressive tumor microenvironment. Therefore, a better understanding of the cross-talk between inhibitory immune checkpoints in the tumor microenvironment can pave the way for introducing novel approaches for treating affected patients. Growing evidence indicates that CD39 and CD73, as novel checkpoints, can transform adenosine triphosphate (ATP)-mediated pro-inflammatory tumor microenvironment into an adenosine-mediated immunosuppressive one via the purinergic signaling pathway. Indeed, enzymatic processes of CD39 and CD73 have crucial roles in adjusting the extent, intensity, and chemical properties of purinergic signals. This study aims to review the biological function of CD39 and CD73 and shed light on their significance in regulating anti-tumoral immune responses in various cancers.

IL-17A/F enable cholangiocytes to restrict T cell-driven experimental cholangitis by upregulating PD-L1 expression

BACKGROUND & AIMS

IL-17A-producing T cells are present in autoimmune cholestatic liver diseases; however, little is known about the contribution of IL-17 to periductal immune responses. Herein, we investigated the role of IL-17 produced by antigen-specific CD8⁺ T cells in a mouse model of cholangitis and in vitro in human cholangiocyte organoids.

METHODS

K14-OVAp mice express a major histocompatibility complex I-restricted ovalbumin (OVA) peptide sequence (SIINFEKL) on cholangiocytes. Cholangitis was induced by the adoptive transfer of transgenic OVA-specific ovalbumin transgene (OT)-1 CD8⁺ T cells that either had OT-1^wt or lacked IL-17A/F (OT-1^IL17ko). The response of mouse and human cholangiocytes/organoids to IL-17A was assessed in vitro.

RESULTS

Transfer of OVA-specific OT-1^IL17ko cells significantly aggravated periductal inflammation in K14-OVAp recipient mice compared with transfer of OT-1^wt T cells. OT-1^IL17ko T cells were highly activated in the liver and displayed increased cytotoxicity and proliferation. IL-17A/F produced by transferred OT-1^wt CD8⁺ T cells induced upregulation of the inhibitory molecule programmed cell death ligand 1 (PD-L1) on cholangiocytes, restricting cholangitis by limiting cytotoxicity and proliferation of transferred cells. In contrast, OT-1^IL17ko T cells failed to induce PD-L1 on cholangiocytes, resulting in uncontrolled expansion of cytotoxic CD8⁺ T cells and aggravated cholangitis. Blockade of PD-L1 after transfer of OT-1^wt T cells with anti-PD-L1 antibody also resulted in aggravated cholangitis. Using human cholangiocyte organoids, we were able to confirm that IL-17A induces PD-L1 expression in cholangiocytes.

CONCLUSIONS

We demonstrate that by upregulating PD-L1 on cholangiocytes, IL-17 has an important role in restricting cholangitis and protecting against CD8⁺ T cell-mediated inflammatory bile duct injury. Caution should be exercised when targeting IL-17 for the treatment of cholangitis.

LAY SUMMARY

IL-17 is assumed to be a driver of inflammation in several autoimmune diseases, such as psoriasis. IL-17 is also present in inflammatory diseases of the bile duct, but its role in these conditions is not clear, as the effects of IL-17 depend on the context of its expression. Herein, we investigated the role of IL-17 in an experimental autoimmune cholangitis mouse model, and we identified an important protective effect of IL-17 on cholangiocytes, enabling them to downregulate bile duct inflammation via checkpoint inhibitor PD-L1.

Ectonucleotidase Modulation of Lymphocyte Function in Gut and Liver

Imbalance between regulatory and effector T lymphocytes contributes to loss of immunotolerance and plays a permissive role in the initiation, perpetuation, and progression of chronic inflammatory diseases and autoimmune disorders. Regulatory/effector cell balance is governed by the CD39 ectonucleotidase, the prototype member of the NTPDase family that hydrolyzes ATP and ADP into AMP, subsequently converted into adenosine by CD73. Generation of adenosine impacts T-cell function as it contributes to the mechanism of suppression of Tregs and confers regulatory properties to pathogenic Th17-cells. CD39 cell distribution, mechanism of regulation and impact on inflammatory and regulatory signaling pathways are also discussed here. Innovative therapeutic strategies to boost CD39 levels and activity by either administering soluble ADPases or interfering with CD39 inhibitory signals are reviewed. Restoration of CD39 levels and function has enormous translational and clinical implications and should be regarded as an additional form of treatment to be deployed in the chronic inflammatory setting. The key role of CD39 in immunoregulation in the context of Crohn's disease, one of the most frequent manifestations of inflammatory bowel disease, and autoimmune hepatitis, an autoimmune disorder of the liver, is reviewed and discussed here.

Altered aryl-hydrocarbon-receptor signalling affects regulatory and effector cell immunity in autoimmune hepatitis

BACKGROUND & AIMS

In autoimmune hepatitis (AIH), the imbalance between regulatory T cells (Tregs) and T-helper type 17 (Th17) cells has been linked to low levels of CD39, an ectoenzyme that hydrolyses ATP, ultimately generating immunosuppressive adenosine. Upregulation of CD39 results from activation of aryl hydrocarbon receptor (AHR), which mediates toxin responses to modulate T-cell immunity. In this study, we investigated whether altered AHR signalling underlies defective CD39 expression and function in AIH Tregs and Th17 cells, therefore contributing to regulatory/effector cell imbalance.

METHODS

Tregs and Th17 cells, obtained from the peripheral blood of 49 patients with AIH and 21 healthy individuals (HI), were tested for response to endogenous and exogenous AHR ligands.

RESULTS

When compared to those of HI, AIH-derived Tregs and Th17 cells displayed impaired responses to AHR activation, reflected by impaired upregulation of CD39, delayed increase in ectoenzymatic activity, and defective Treg suppressive function. These impairments resulted, at least in part, from heightened levels of AHRR and Erα in Tregs and high HIF-1α in Th17 cells, and were reverted upon molecular blockade. Importantly, in AIH-derived Tregs, the binding affinity of AHR was higher for Erα than ARNT.

CONCLUSIONS

In AIH, high levels of AHRR and HIF-1α inhibit AHR signalling in Tregs and Th17 cells. AHR non-canonical binding to Erα further amplifies the lack of effective CD39 upregulation. Blockade of these inhibitory and/or non-canonical activation pathways represents a potential therapeutic approach to restore CD39 and immunohomeostasis in AIH.

LAY SUMMARY

In patients with autoimmune hepatitis, the imbalance between regulatory T cells and T helper type-17 cells is linked to dysfunction of the aryl hydrocarbon receptor pathway, resulting from aberrant inhibition or non-canonical activation. These alterations impair Treg- and Th17 cell-induced upregulation of CD39, an ectoenzyme key to immunoregulation. Blockade of excessive inhibition or non-canonical activation of the aryl hydrocarbon receptor pathway might represent a novel therapeutic strategy to control inflammation while restoring immune balance in autoimmune hepatitis.

Implications of CD39 in immune-related diseases

Extracellular adenosine triphosphate (eATP) mediates pro-inflammatory responses by recruiting and activating inflammatory cells. CD39 can hydrolyze eATP into adenosine monophosphate (AMP), while CD73 can convert AMP into the immunosuppressive nucleoside adenosine (ADO). CD39 is a rate-limiting enzyme in this cascade, which is regarded as an immunological switch shifting the ATP-mediated pro-inflammatory environment to the ADO- mediated anti-inflammatory status. The CD39 expression can be detected in a wide spectrum of immunocytes, which is under the influence of environmental and genetic factors. It is increasingly suggested that, CD39 participates in some pathophysiological processes, like inflammatory bowel disease (IBD), sepsis, multiple sclerosis (MS), allergic diseases, ischemia-reperfusion (I/R) injury, systemic lupus erythematosus (SLE), diabetes and cancer. Here, we focus on the current understanding of CD39 in immunity, and comprehensively illustrate the diverse CD39 functions within a variety of disorders.

Purinergic signalling in liver diseases: Pathological functions and therapeutic opportunities

Extracellular nucleotides, including ATP, are essential regulators of liver function and serve as danger signals that trigger inflammation upon injury. Ectonucleotidases, which are expressed by liver-resident cells and recruited immune cells sequentially hydrolyse nucleotides to adenosine. The nucleotide/nucleoside balance orchestrates liver homeostasis, tissue repair, and functional restoration by regulating the crosstalk between liver-resident cells and recruited immune cells. In this review, we discuss our current knowledge on the role of purinergic signals in liver homeostasis, restriction of inflammation, stimulation of liver regeneration, modulation of fibrogenesis, and regulation of carcinogenesis. Moreover, we discuss potential targeted therapeutic strategies for liver diseases based on purinergic signals involving blockade of nucleotide receptors, enhancement of ectonucleoside triphosphate diphosphohydrolase activity, and activation of adenosine receptors.

The role of the CD39-CD73-adenosine pathway in liver disease

Extracellular adenosine triphosphate (ATP) is a danger signal released by dying and damaged cells, and it functions as an immunostimulatory signal that promotes inflammation. The ectonucleotidases CD39/ectonucleoside triphosphate diphosphohydrolase-1 and CD73/ecto-5'-nucleotidase are cell-surface enzymes that breakdown extracellular ATP into adenosine. This drives a shift from an ATP-driven proinflammatory environment to an anti-inflammatory milieu induced by adenosine. The CD39-CD73-adenosine pathway changes dynamically with the pathophysiological context in which it is embedded. Accumulating evidence suggests that CD39 and CD73 play important roles in liver disease as critical components of the extracellular adenosinergic pathway. Recent studies have shown that the modification of the CD39-CD73-adenosine pathway alters the liver's response to injury. Moreover, adenosine exerts different effects on the pathophysiology of the liver through different receptors. In this review, we aim to describe the role of the CD39-CD73-adenosine pathway and adenosine receptors in liver disease, highlighting potential therapeutic targets in this pathway, which will facilitate the development of therapeutic strategies for the treatment of liver disease.

The use of biologics in the treatment of autoimmune liver disease

Introduction: Autoimmune liver diseases include autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and juvenile autoimmune hepatitis (JAIH). The pathophysiologic features of each disease vary, but generally include presence of autoantibodies, cytokine abnormalities, and/or T and B cell autoreactivity.Areas covered: This article compares conventional therapy with newer biologics available for treatment of autoimmune liver diseases. Conventional therapy involves the use of immunosuppressive agents, or other treatment modalities for specific autoimmune liver diseases such as ursodeoxycholic acid and fibrates for PBC. Biologics were developed to target the production of autoantibodies by B cells, the presence of proinflammatory cytokines, adhesion molecules or T and B cell activation.Expert opinion: Despite the promise of biologics being able to target specific cellular and humoral pathways, results have been generally poor, and safety has not been as expected. Cases of autoimmune hepatitis have also developed with the use of these biologicals. Reasons for the lack of success of biologics in treating autoimmune liver disease has led to a reevaluation of our understanding of underlying pathogenesis, demonstrating that while our knowledge of the immunity has improved over the past two decades, it is far from complete.

Dysregulation of Adenosinergic Signaling in Systemic and Organ-Specific Autoimmunity

Exact causes for autoimmune diseases remain unclear and no cures are available. Breakdown of immunotolerance could set the stage for unfettered immune responses that target self-antigens. Impaired regulatory immune mechanisms could have permissive roles in autoreactivity. Abnormal regulatory immune cell function, therefore, might be a major determinant of the pathogenesis of autoimmune disease. All current treatments are associated with some level of clinical toxicity. Treatment to specifically target dysregulated immunity in these diseases would be a great advance. Extracellular adenosine is a signaling mediator that suppresses inflammation through activation of P1 receptors, most active under pathological conditions. Mounting evidence has linked alterations in the generation of adenosine from extracellular nucleotides by ectonucleotidases, and associated perturbations in purinergic signaling, to the immunological disruption and loss of immunotolerance in autoimmunity. Targeted modulation of the purinergic signaling by either targeting ectonucleotidases or modulating P1 purinergic receptors could therefore restore the balance between autoreactive immune responses; and thereby allow reestablishment of immunotolerance. We review the roles of CD39 and CD73 ectoenzymes in inflammatory states and with the dysregulation of P1 receptor signaling in systemic and organ-specific autoimmunity. Correction of such perturbations could be exploited in potential therapeutic applications.

Dual effect of T helper cell 17 (Th17) and regulatory T cell (Treg) in liver pathological process: From occurrence to end stage of disease

Liver disease is a complicated pathological status with acute or chronic progressions, causing a series of damages to liver and massive burden to public health and society. Th17 and Treg, two subsets of CD4⁺ T helper cells, seem to keep a subtle balance in the maintenance of organic immune homeostasis including liver. The dysfunction of Th17/Treg balance in liver has been proved associated with hepatic injury and disease. Herein, we summarized the research advance of Th17 and Treg cells in different phenotypes of liver diseases in the past decade. It is known to all that hepatic diseases start from stimulations or infections like virus, autoimmune, alcohol and so on in the early stage, which would cause inflammation. With the disease consistently existed, severe outcomes like cirrhosis and hepatocellular carcinoma appear finally. In conclusion, it is found that Th17 and Treg cells serve as an important role in the immune response imbalance of liver diseases from the beginning to the end stage. However, the effect of these two subsets of CD4⁺ T helper cells is not a stereotype. Pathological role which exacerbates the disease and protective character which inhibits damage to liver are co-existed in the effect of Th17 and Treg cells. Still, more studies should be carried out to enrich the understandings of liver disease and Th17/Treg immune balance in the future.

HIF-1α-induced xenobiotic transporters promote Th17 responses in Crohn's disease

In Crohn's disease, pathogenic Th17-cells express low levels of CD39 ectonucleotidase and are refractory to the immunosuppressive effects of unconjugated bilirubin (UCB), an endogenous ligand for aryl-hydrocarbon-receptor (AhR). This resistance to AhR ligation might be associated with alterations in responses to hypoxia. Limited exposure to hypoxia appears beneficial in acute tissue injury. However, in protracted inflammation, hypoxemia may paradoxically result in Th17-cell activation. We report here that in vitro exposure of Th17-cells from Crohn's disease patients to hypoxia limits responsiveness to AhR stimulation by UCB, as reflected by lower CD39 levels. Blockade of hypoxia-inducible-factor-1alpha (HIF-1α) upregulates CD39 and favors Th17-cell regulatory responses. Resistance of Th17-cells to AhR signaling results, in part, from HIF-1α-dependent induction of ATP-binding cassette (ABC) transporters: multidrug-resistance-protein-1 (MDR1) and multidrug-resistance-associated-protein-4 (MRP4). Increased ABC transporters promote efflux of suppressive AhR ligands, such as UCB, from Th17-cells. Inhibition of MDR1, MRP4 and/or HIF-1α with ritonavir (RTV) reconstitutes AhR function in Th17-cells, enhancing therapeutic effects of UCB in dextran-sulfate-sodium-induced experimental colitis. Deleterious effects of hypoxia on Th17-cells in Crohn's disease can be ameliorated either by inhibiting HIF-1α or by suppressing ABC transporters to increase UCB availability as an AhR substrate. Targeting HIF-1α-ABC transporters could provide innovative therapeutic pathways for IBD.

Real-world management of juvenile autoimmune liver disease

Background and aims

Juvenile autoimmune liver disease (JAILD) includes paediatric forms of autoimmune hepatitis (AIH) and autoimmune sclerosing cholangitis (ASC). Since evidence is scarce, there are currently no evidence-based management guidelines for juvenile AIH. This survey was carried out amongst the paediatric members of the International AIH Group (IAIHG) to describe their practices in the management of JAILD.

Methods

An online survey questionnaire was distributed to members of the IAIHG with active practice (https://www.surveymonkey.de/r/Juvenile_AILD). The questionnaire consisted of four clinical scenarios on different presentations of AIH.

Results

Fifty-eight surveys were sent to the IAIHG members, out of which 43 (74%, 22 countries, four continents) were returned. None reported budesonide as a first-line induction agent for the acute presentation of AIH. Sixteen (37%) routinely perform liver biopsy at three years of biochemical remission. Thirty-five respondents (81%) perform magnetic resonance cholangiography (MRC) at presentation. Ciclosporin is the most widely used second-line agent (number of patients treated = ∼360, 21 centres). Mycophenolate mofetil (n = ∼225, 31 centres), tacrolimus (n = ∼130, 21 centres) and sirolimus (n = ∼5, 3 centres) are less often reported. Rescue therapy with infliximab and rituximab has been tried in eight centres (n = ∼19) and nine centres (n = ∼16), respectively.

Conclusions

Prednisolone remains the preferred first-line induction agent in JAILD. MRC at presentation is performed by the large majority of participants. Participants reported a wide variation in performing liver biopsy for therapy evaluation during follow-up. Within the paediatric members of the IAIHG there is considerable experience with second-line therapeutic agents.

The role of adenosinergic pathway in human autoimmune diseases

Autoimmune diseases are characterized by the abnormal immune response against self-tissue, which are caused by the failure of nature immune homeostasis. Nature immune homeostasis represents the normal state of appropriate immune response to nonself-antigen and unresponsiveness to self-antigens. In normal situation, immune homeostasis is regulated by immunosuppressive signal and immunostimulating signal together. Accumulating data have demonstrated that the adenosinergic pathway played key roles in immune suppression and shield body from an excessive inflammatory response. The deficiency of adenosinergic pathway results in the imbalance between the pro- and anti-inflammatory activities. Thus, researchers pay much attention to the role of adenosinergic pathway in autoimmune diseases development. To date, accumulating data have suggested an important role of adenosinergic pathway-related molecules (i.e., CD39, CD73, ADA, adenosine receptors, etc.) in many types of human autoimmune diseases. More importantly, these findings have presented potential value of adenosinergic pathway analysis to be used for autoimmune diseases diagnosis, monitoring and treatment. In this review, we will provide a comprehensive description of the role of adenosinergic pathway in human autoimmune diseases.

Regulatory T-cell conditioning endows activated effector T cells with suppressor function in autoimmune hepatitis/autoimmune sclerosing cholangitis

Imbalance between T regulatory (Treg) and T effector (Teff) cells is likely to contribute to the induction and perpetuation of liver damage in autoimmune hepatitis (AIH) and autoimmune sclerosing cholangitis (AISC) either through inability of Tregs to restrain proliferation and effector cytokine production by responders or through conversion of Tregs into T helper type 1 (Th1) or type 17 (Th17) effector lymphocytes. We investigated the effect of Treg skewing on the phenotypic and functional properties of CD4⁺ CD127⁺ CD25^high cells, an activated subset of Teff, in 32 patients with AIH and 20 with AISC and in 36 healthy subjects. In AIH/AISC we noted a substantial increase in peripheral blood-derived CD4⁺ CD127⁺ CD25^high cells that display a Th1/Th17 phenotypic profile, as reflected by heightened interferon gamma and interleukin 17 (IL-17) production as well as by high levels of T-bet and related orphan receptor 3 expression, which is strongly correlated with disease activity. CD4⁺ CD127⁺ CD25^high cells are unresponsive to low-dose IL-2 and in patients have marked proliferative ability, further enhanced by stimulation with IL-7. CD4⁺ CD127⁺ CD25^high cells obtained from CD4⁺ cells exposed to Treg polarizing conditions display enhanced IL-10 production; up-regulate CD49b and LAG-3, markers of T regulatory 1 cells; and effectively suppress responder cell proliferation in both healthy subjects and AIH/AISC patients through a mechanism which is dependent on interferon gamma and IL-17. The suppressive function of CD4⁺ CD127⁺ CD25^high cells is maintained upon proinflammatory challenge in healthy subjects but not in AIH/AISC.

CONCLUSION

Treg skewing confers activated Teff phenotypic and functional properties of T regulatory 1 cells in health and in AIH/AISC, though suppressive function is lost in patients upon proinflammatory challenge; protracted modulation of the inflammatory environment is required to attenuate the effector potential while boosting immunoregulatory properties in Teff. (Hepatology 2017;66:1570-1584).

Clinical significance of changes in the Th17/Treg ratio in autoimmune liver disease

AIM

To investigate the levels, ratios, and clinical significance of T helper 17 (Th17) cells and regulatory T (Treg) cells in the peripheral blood of patients with autoimmune liver disease (AILD).

METHODS

Forty-two AILD patients were included in the experimental group (group E), and 11 healthy subjects were recruited as the control group (group C). Flow cytometry was performed to determine the percentages of Th17 and Treg cells in peripheral blood lymphocytes. Furthermore, a range of biochemical indices was measured simultaneously in the blood of group E patients.

RESULTS

The percentage of Th17 cells and the Th17/Treg ratio were higher in group E than in group C (P < 0.01), whereas the percentage of Tregs was lower in the group E patients (P < 0.05). Patients in group E who were admitted with AILD in the active stage showed significantly higher Th17 percentages and Th17/Treg ratios than those measured in patients with AILD in remission (P < 0.05). In addition, among patients with AILD in the active stage, individuals that remained unhealed after hospitalization showed significantly higher baseline values of the Th17 percentage and the Th17/Treg ratio than those detected in patients who improved after treatment (P < 0.05). The results suggested that imbalance in the Th17/Treg ratio plays an important role in the pathogenesis and development of AILD.

CONCLUSION

A high Th17/Treg ratio appears to predict poor short-term prognosis in patients with AILD in the active stage.

Innate lymphoid cell-derived cytokines in autoimmune diseases

The most recently recognized types of immune cells, the innate lymphoid cells (ILCs), have been sub-divided according to respective distinct expression profiles of regulatory factors or/and cytokines. ILCs have also been shown to participate in a variety of beneficial immune responses, including participation in attack against pathogens and mediation of the pre-inflammatory and inflammatory responses through their production of pro-inflammatory cytokines. As such, while the ILCs exert protective effects they may also become detrimental upon dysregulation. Indeed, recent studies of the ILCs have revealed a strong association with the advent and pathogenesis of several common autoimmune diseases, including psoriasis, inflammatory bowel disease (IBD) and multiple sclerosis (MS). Though the ILCs belong to lineage negative cells that are distinctive from the Th cells, the profiles of secreted cytokines from the ILCs overlap with those of the corresponding Th subsets. Nevertheless, considering that the ILCs belong to the innate immune system and the Th cells belong to the adaptive immune system, it is expected that the ILCs should function at the early stage of diseases and the Th cells should exert predominant effects at the late stage of diseases. Therefore, it is intriguing to consider targeting of ILCs for therapy by targeting the corresponding cytokines at the early stage of diseases, with the late stage cytokine targeting mainly influencing the Th cells' function. Here, we review the knowledge to date on the roles of ILCs in various autoimmune diseases and discuss their potential as new therapeutic targets.

Immunosuppressive drugs affect interferon (IFN)-γ and programmed cell death 1 (PD-1) kinetics in patients with newly diagnosed autoimmune hepatitis

Autoimmune hepatitis (AIH) is characterized by overwhelming effector immune responses associated with defective regulatory T cells (T_regs ). Several lines of evidence indicate CD4 as the main effectors involved in autoimmune liver damage. Herein we investigate the in-vitro effects of prednisolone, 6-mercaptopurine, cyclosporin, tacrolimus, mycophenolic acid (MPA) and rapamycin, immunosuppressive drugs (ISDs) used in AIH treatment, on the expression of proinflammatory cytokines, co-inhibitory molecules and ability to proliferate of CD4⁺ CD25^- cells, isolated from the peripheral blood of treatment-naive patients with AIH. We note that in healthy subjects (HS) following polyclonal stimulation and in the absence of ISDs, the expression of interferon (IFN)-γ, interleukin (IL)-17 and tumour necrosis factor (TNF)-α by CD4 effectors peaks at 48 h and decreases at 96 h to reach baseline levels. In contrast, in AIH the expression of all these proinflammatory cytokines continue rising between 48 and 96 h. Levels of programmed cell death-1 (PD-1), T cell immunoglobulin and mucin domain-containing molecule-3 (TIM-3) and cytotoxic T lymphocyte antigen-4 (CTLA-4) increase over 96-h culture both in HS and AIH, although with faster kinetics in the latter. Exposure to ISDs contains IFN-γ and PD-1 expression in AIH, where control over CD4⁺ CD25^- cell proliferation is also noted upon exposure to MPA. Treatment with tacrolimus and cyclosporin render CD4⁺ CD25^- cells more susceptible to T_reg control. Collectively, our data indicate that in treatment-naive patients with AIH, all ISDs restrain T helper type 1 (Th1) cells and modulate PD-1 expression. Furthermore, they suggest that tacrolimus and cyclosporin may ameliorate effector cell responsiveness to T_regs .

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

Novel Immunotherapies for Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a multifactorial autoimmune disease of unknown pathogenesis, characterized by a loss of immunological tolerance against liver autoantigens resulting in the progressive destruction of the hepatic parenchyma. Current treatments are based on non-specific immunosuppressive drugs. Although tremendous progress has been made using specific biological agents in other inflammatory diseases, progress has been slow to come for AIH patients. While current treatments are successful in the majority of patients, treatment discontinuation is difficult to achieve, and relapses are frequent. Lifelong immunosuppression is not without risks, especially in the pediatric population; 4% of patient with type 1 AIH will eventually develop hepatocellular carcinoma with a 2.9% probability after 10 years of treatment. Therefore, future treatments should aim to restore tolerance to hepatic autoantigens and induce long-term remission. Promising new immunotherapies have been tested in experimental models of AIH including T and B cell depletion and regulatory CD4+ T cells infusion. Clinical studies on limited numbers of patients have also shown encouraging results using B-cell-depleting (rituximab) and anti-TNF-α (infliximab) antibodies. A better understanding of key molecular targets in AIH combined with effective site-specific immunotherapies could lead to long-term remission without blanket immunosuppression and with minimal deleterious side effects.