Animal models of primary biliary cirrhosis. Clin Rev Allergy Immunol. 2015;48:142-153. [PMID: 25771770 DOI: 10.1007/s12016-015-8482-y]

Regulatory T cells in inflamed liver are dysfunctional in murine primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune disease characterized by immune-mediated destruction of intrahepatic small bile ducts. CD8 T cells play a critical role in biliary destruction. However, regulatory T cells (Tregs) have also been identified in the portal tracts of PBC patients. This study tested the hypothesis that hepatic Tregs in PBC were dysfunctional in suppressing immune responses in disease by using our human PBC-like autoimmune cholangitis (AIC) mouse model induced by 2-octynoic acid-conjugated ovalbumin (2-OA-OVA). Our results showed that female and male mice immunized with 2-OA-OVA developed AIC; however, female AIC mice had more severe liver inflammation and fibrosis than male AIC mice. Levels of functional effector CD8 T cells and their chemoattractants, CXCL9 and CXCL10, in the liver were markedly elevated in female AIC mice than in male AIC mice. These results reinforce that CD8 T cells are the primary effector cells in PBC. The number of hepatic Tregs in AIC mice was also higher than in saline-treated mice, but there was no difference between male and female AIC mice. The suppressive function of AIC Tregs was evident despite a discrepancy in the changes in their co-inhibitory receptors and inhibitory cytokines. However, the expansion of hepatic Tregs by low-dose IL-2 treatment did not reduce immune responses to AIC, which may be due to the dysfunction of Tregs in inhibiting T cells. In conclusion, the function of Tregs in the inflamed liver of PBC was insufficient, and low-dose IL-2 treatment could not restore their function to suppress pathological immune responses. Transferring normal Tregs or directly targeting effector CD8 T cells may be beneficial for treating PBC.

NOTCH signalling - a core regulator of bile duct disease?

The Notch signalling pathway is an evolutionarily conserved mechanism of cell-cell communication that mediates cellular proliferation, fate determination and maintenance of stem/progenitor cell populations across tissues. Although it was originally identified as a critical regulator of embryonic liver development, NOTCH signalling activation has been associated with the pathogenesis of a number of paediatric and adult liver diseases. It remains unclear, however, what role NOTCH actually plays in these pathophysiological processes and whether NOTCH activity represents the reactivation of a conserved developmental programme that is essential for adult tissue repair. In this Review, we explore the concepts that NOTCH signalling reactivation in the biliary epithelium is a reiterative and essential response to bile duct damage and that, in disease contexts in which biliary epithelial cells need to be regenerated, NOTCH signalling supports ductular regrowth. Furthermore, we evaluate the recent literature on NOTCH signalling as a critical factor in progenitor-mediated hepatocyte regeneration, which indicates that the mitogenic role for NOTCH signalling in biliary epithelial cell proliferation has also been co-opted to support other forms of epithelial regeneration in the adult liver.

Apoptotic biliary epithelial cells and gut dysbiosis in the induction of murine primary biliary cholangitis

Primary biliary cholangitis (PBC) is a female-predominant liver autoimmune disease characterized by the specific immune-mediated destruction of the intrahepatic small bile duct. Although apoptosis of biliary epithelial cells (BECs) and alterations in gut microbiota are observed in patients with PBC, it is still unclear whether these events happen in the early stage and cause the breakdown of tolerance in PBC. In this study, we examined the early events in the loss of tolerance in our well-defined 2-OA-OVA-induced murine autoimmune cholangitis (AIC) model. We report herein that apoptosis of BECs was notable in the early stage of murine AIC. An altered gut microbiota, in particular, an increased percentage of gram-positive Firmicutes in AIC mice was also observed. BECs in AIC mice expressed adhesion molecule ICAM-1, cytokines/chemokines TNF-α, CCL2, CXCL9, CXCL10, and toll-like receptor (TLR) 2. Moreover, BECs treated with TLR2 ligand had elevated apoptosis and CXCL10 production. These data collectively suggest a new mechanism of tolerance breakdown in AIC. Altered gut microbiota induces apoptosis of BECs through TLR2 signaling. BECs secrete chemokines to recruit CD8 T cells to damage BECs further.

Linking Human Betaretrovirus with Autoimmunity and Liver Disease in Patients with Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the production of diagnostic antimitochondrial antibodies (AMA) reactive to the pyruvate dehydrogenase complex. A human betaretrovirus (HBRV) resembling mouse mammary tumor virus has been characterized in patients with PBC. However, linking the viral infection with the disease is not a straight-forward process because PBC is a complex multifactorial disease influenced by genetic, hormonal, autoimmune, environmental, and other factors. Currently, PBC is assumed to have an autoimmune etiology, but the evidence is lacking to support this conjecture. In this review, we describe different approaches connecting HBRV with PBC. Initially, we used co-cultivation of HBRV with biliary epithelial cells to trigger the PBC-specific phenotype with cell surface expression of cryptic mitochondrial autoantigens linked with antimitochondrial antibody expression. Subsequently, we have derived layers of proof to support the role of betaretrovirus infection in mouse models of autoimmune biliary disease with spontaneous AMA production and in patients with PBC. Using Hill’s criteria, we provide an overview of how betaretrovirus infection may trigger autoimmunity and propagate biliary disease. Ultimately, the demonstration that disease can be cured with antiviral therapy may sway the argument toward an infectious disease etiology in an analogous fashion that was used to link H. pylori with peptic ulcer disease.

Potential mesenchymal stem cell therapeutics for treating primary biliary cholangitis: advances, challenges, and perspectives

Primary biliary cholangitis (PBC) is a cholestatic autoimmune liver disease characterized by the gradual destruction of small intrahepatic bile ducts that eventually leads to liver cirrhosis, failure, and even carcinoma. The treatment options for PBC are limited, and the main treatment choices are the US Food and Drug Administration–approved ursodeoxycholic acid and obeticholic acid. However, many patients fail to respond adequately to these drugs and the adverse effects frequently lead to low life quality. For patients with end-stage PBC, liver transplantation remains the only effective treatment. Given their low immunogenicity, prominent immunomodulation property, differentiation potential, and tissue maintenance capacity, mesenchymal stem cells (MSCs) are emerging as new options for treating liver diseases, including PBC. Accumulating evidence from basic research to clinical studies supports the positive effects of MSC-based therapy for treating PBC. In this review, we characterized the underlying roles and mechanisms of MSCs for treating liver diseases and highlight recent basic and clinical advances in MSC-based therapy for treating PBC. Finally, the current challenges and perspectives for MSC-based therapy in clinical application are discussed, which could help accelerate the application of MSCs in clinical practice, especially for refractory diseases such as PBC.

Peroxisome Proliferator-Activated Receptors Regulate Hepatic Immunity and Assist in the Treatment of Primary Biliary Cholangitis

Fibrates, which are agonists of peroxisome proliferator-activated receptor alpha, have received increasing attention in the treatment of primary biliary cholangitis. Reduced alkaline phosphatase levels and improved clinical outcomes were observed in patients with primary biliary cholangitis with an inadequate response to ursodeoxycholic acid (UDCA) monotherapy4 when treated with bezafibrate or fenofibrate combined with UDCA. In contrast to obeticholic acid, which exacerbates pruritus in patients, fibrates have been shown to relieve pruritus. Clinical trial outcomes show potential for the treatment of primary biliary cholangitis by targeting peroxisome proliferator-activated receptors. It is currently agreed that primary biliary cholangitis is an autoimmune-mediated cholestatic liver disease, and peroxisome proliferator-activated receptor is a nuclear receptor that regulates the functions of multiple immune cells, thus playing an important role in regulating innate and adaptive immunity. Therefore, this review focuses on the immune disorder of primary biliary cholangitis and summarizes the regulation of hepatic immunity when peroxisome proliferator-activated receptors are targeted for treating primary biliary cholangitis.

Autoimmunity affecting the biliary tract fuels the immunosurveillance of cholangiocarcinoma

Cholangiocarcinoma (CCA) results from the malignant transformation of cholangiocytes. Primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC) are chronic diseases in which cholangiocytes are primarily damaged. Although PSC is an inflammatory condition predisposing to CCA, CCA is almost never found in the autoimmune context of PBC. Here, we hypothesized that PBC might favor CCA immunosurveillance. In preclinical murine models of cholangitis challenged with syngeneic CCA, PBC (but not PSC) reduced the frequency of CCA development and delayed tumor growth kinetics. This PBC-related effect appeared specific to CCA as it was not observed against other cancers, including hepatocellular carcinoma. The protective effect of PBC was relying on type 1 and type 2 T cell responses and, to a lesser extent, on B cells. Single-cell TCR/RNA sequencing revealed the existence of TCR clonotypes shared between the liver and CCA tumor of a PBC host. Altogether, these results evidence a mechanistic overlapping between autoimmunity and cancer immunosurveillance in the biliary tract.

Deletion of Mcpip1 in Mcpip1fl/flAlbCre mice recapitulates the phenotype of human primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune disease characterized by progressive destruction of the intrahepatic bile ducts. The immunopathology of PBC involves excessive inflammation; therefore, negative regulators of inflammatory response, such as Monocyte Chemoattractant Protein-1-Induced Protein-1 (MCPIP1) may play important roles in the development of PBC. The aim of this work was to verify whether Mcpip1 expression protects against development of PBC. Genetic deletion of Zc3h12a was used to characterize the role of Mcpip1 in the pathogenesis of PBC in 6–52-week-old mice. We found that Mcpip1 deficiency in the liver (Mcpip1^fl/flAlb^Cre) recapitulates most of the features of human PBC, in contrast to mice with Mcpip1 deficiency in myeloid cells (Mcpip1^fl/flLysM^Cre mice), which present with robust myeloid cell-driven systemic inflammation. In Mcpip1^fl/flAlb^Cre livers, intrahepatic bile ducts displayed proliferative changes with inflammatory infiltration, bile duct destruction, and fibrosis leading to cholestasis. In plasma, increased concentrations of IgG, IgM, and AMA autoantibodies (anti-PDC-E2) were detected. Interestingly, the phenotype of Mcpip1^fl/flAlb^Cre mice was robust in 6-week-old, but milder in 12–24-week-old mice. Hepatic transcriptome analysis of 6-week-old and 24-week-old Mcpip1^fl/flAlb^Cre mice showed 812 and 8 differentially expressed genes, respectively, compared with age-matched control mice, and revealed a distinct set of genes compared to those previously associated with development of PBC. In conclusion, Mcpip1^fl/flAlb^Cre mice display early postnatal phenotype that recapitulates most of the features of human PBC.

Primary biliary cholangitis

Primary biliary cholangitis is an autoimmune liver disease that predominantly affects women. It is characterised by a chronic and destructive, small bile duct, granulomatous lymphocytic cholangitis, with typical seroreactivity for antimitochondrial antibodies. Patients have variable risks of progressive ductopenia, cholestasis, and biliary fibrosis. Considerations for the cause of this disease emphasise an interaction of chronic immune damage with biliary epithelial cell responses and encompass complex, poorly understood genetic risks and environmental triggers. Licensed disease-modifying treatment focuses on amelioration of cholestasis, with weight-dosed oral ursodeoxycholic acid. For patients who do not respond sufficiently, or patients with ursodeoxycholic acid intolerance, conditionally licensed add-on therapy is with the FXR (NR1H4) agonist, obeticholic acid. Off-label therapy is recognised as an alternative, notably with the pan-PPAR agonist bezafibrate; clinical trial agents are also under development. Baseline characteristics, such as young age, male sex, and advanced disease, and serum markers of liver injury, particularly bilirubin and ALP, are used to stratify risk and assess treatment responsiveness. Parallel attention to the burden of patient symptoms is paramount, including pruritus and fatigue.

Animal Models of Autoimmune Liver Diseases: a Comprehensive Review

Autoimmune liver diseases (AILDs) are potentially life-threatening chronic liver diseases which include autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and recently characterized IgG4-related sclerosing cholangitis. They are caused by immune attack on hepatocytes or bile ducts, with different mechanisms and clinical manifestations. The etiologies of AILDs include a susceptible genetic background, environment insults, infections, and changes of commensal microbiota, but remain complicated. Understanding of the underlying mechanisms of AILDs is mandatory for early diagnosis and intervention, which is of great importance for better prognosis. Thus, animal models are developed to mimic the pathogenesis, find biomarkers for early diagnosis, and for therapeutic attempts of AILDs. However, no animal models can fully recapitulate features of certain AILD, especially the late stages of diseases. Certain limitations include different living condition, cell composition, and time frame of disease development and resolution. Moreover, there is no IgG4 in rodents which exists in human. Nevertheless, the understanding and therapy of AILDs have been greatly advanced by the development and mechanistic investigation of animal models. This review will provide a comprehensive overview of traditional and new animal models that recapitulate different features and etiologies of distinct AILDs.

An insight into primary biliary cholangitis and its recent advances in treatment: semi-synthetic analogs to combat ursodeoxycholic-acid resistance

INTRODUCTION

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease which on progression causes cirrhosis; various studies also suggested that several diseases can co-exist in patients. In existing depiction of disease PBC, apart from entire use of ursodeoxycholic acid (UDCA), several patients need to step forward to liver-transplantation or death due to resistance or non-responder with UDCA monotherapy.

AREAS COVERED

To overcome this non-respondent treatment, novel bile acid semi-synthetic analogs have been identified which shows their potency against for farnesoid X receptor and transmembrane G protein-coupled receptor-5 which are identified as target for many developing analogs which have desirable pharmacokinetic profiles.

EXPERT OPINION

A range of studies suggests that adding semisynthetic analogs in therapeutic regime improves liver biochemistries in patients with suboptimal response to UDCA. Thus, the aspire of this review is to abridge and compare therapeutic value and current markets affirm of various bile acids semi-synthetic analogs which certainly are having promising effects in PBC monotherapy or in pooled treatment with UDCA for PBC.

Recent advances in understanding the molecular mechanisms of cholestatic pruritus: A review

Cholestasis, a condition characterized by an abnormal decrease in bile flow, is accompanied by various symptoms such as pruritus. Although cholestatic pruritus is a prominent condition, its precise mechanisms have largely been elusive. Recently, advancements have been made for understanding the etiology and pathogenesis of cholestatic pruritus. The current review therefore focuses on summarizing the overall progress made in the elucidation of its molecular mechanisms. We have reviewed the available animal models on cholestasis to compare the differences between them, characterized potential pruritogens involved in cholestatic pruritus, and have summarized the receptor and ion channels implicated in the condition. Finally, we have discussed the available treatment options for alleviation of cholestatic pruritus. As our understanding of the mechanisms of cholestatic pruritus deepens, novel strategies to cure this condition are awaited.

Galectin-3 in Inflammasome Activation and Primary Biliary Cholangitis Development

Primary biliary cholangitis (PBC) is a chronic inflammatory autoimmune liver disease characterized by inflammation and damage of small bile ducts. The NLRP3 inflammasome is a multimeric complex of proteins that after activation with various stimuli initiates an inflammatory process. Increasing data obtained from animal studies implicate the role of NLRP3 inflammasome in the pathogenesis of various diseases. Galectin-3 is a β-galactoside-binding lectin that plays important roles in various biological processes including cell proliferation, differentiation, transformation and apoptosis, pre-mRNA splicing, inflammation, fibrosis and host defense. The multilineage immune response at various stages of PBC development includes the involvement of Gal-3 in the pathogenesis of this disease. The role of Galectin-3 in the specific binding to NLRP3, and inflammasome activation in models of primary biliary cholangitis has been recently described. This review provides a brief pathogenesis of PBC and discusses the current knowledge about the role of Gal-3 in NLRP3 activation and PBC development.

Canal of Hering loss is an initiating step for primary biliary cholangitis (PBC): A hypothesis

The origin and initiating features of PBC remain obscure despite decades of study. However, recent papers have demonstrated loss of canals of Hering (CoH) to be the earliest histologic change in liver biopsy specimens from patients with primary biliary cholangitis (PBC). We posit that CoH loss prior to significant inflammation or evidence of bile duct injury might be a very early, perhaps even an initiating lesion of PBC. As a potential target of inflammatory or toxic injury, CoH loss may initiate rather than follow the cascade of events leading to duct injury and loss and their sequelae. Toxins may be exogenous in origin, such as environmental toxins or drug exposures, or endogenous, resulting from genetic or epigenetic alterations in canalicular bile transporters upstream from the CoH. In turn, this hypothesis suggests that loss of CoH would lead to altered bile flow and composition injurious to downstream bile ducts, because bile composition has not been modulated by normal CoH physiologic functions or because, in the absence of CoH, canalicular fluid flow into the biliary tree is disrupted interfering with soluble trophic factors important for bile duct integrity. Regardless of the pathogenic mechanism causing CoH loss, only following such loss would the characteristic diagnostic findings of PBC become evident: damage to downstream interlobular and sub-lobular bile ducts. To the extent that the causal mechanisms for CoH loss can be identified, clinical identification (as through early identification of CoH loss) and intervention (depending on the inciting cause) may offer promise for treatment of this enigmatic disease.

The toxicity of the methylimidazolium ionic liquids, with a focus on M8OI and hepatic effects

Ionic liquids are a diverse range of charged chemicals with low volatility and often liquids at ambient temperatures. This characteristic has in part lead to them being considered environmentally-friendly replacements for existing volatile solvents. However, methylimidazolium ionic liquids are slow to break down in the environment and a recent study at Newcastle detected 1 octyl 3 methylimidazolium (M8OI) - an 8 carbon variant methylimidazolium ionic liquid - in soils in close proximity to a landfill site. The current M8OI toxicity database in cultured mammalian cells, in experimental animal studies and in model indicators of environmental impact are reviewed. Selected analytical data from the Newcastle study suggest the soils in close proximity to the landfill site, an urban soil lacking overt contamination, had variable levels of M8OI. The potential for M8OI - or a structurally related ionic liquid - to trigger primary biliary cholangitis (PBC), an autoimmune liver disease thought to be triggered by an unknown agent(s) in the environment, is reviewed.

The challenges of primary biliary cholangitis: What is new and what needs to be done

Primary Biliary Cholangitis (PBC) is an uncommon, chronic, cholangiopathy of autoimmune origin and unknown etiology characterized by positive anti-mitochondrial autoantibodies (AMA), female preponderance and progression to cirrhosis if left untreated. The diagnosis is based on AMA- or PBC-specific anti-nuclear antibody (ANA)-positivity in the presence of a cholestatic biochemical profile, histologic confirmation being mandatory only in seronegative cases. First-line treatment is ursodeoxycholic acid (UDCA), which is effective in preventing disease progression in about two thirds of the patients. The only approved second-line treatment is obeticholic acid. This article summarizes the most relevant conclusions of a meeting held in Lugano, Switzerland, from September 23rd-25th 2018, gathering basic and clinical scientists with various background from around the world to discuss the latest advances in PBC research. The meeting was dedicated to Ian Mackay, pioneer in the field of autoimmune liver diseases. The role of liver histology needs to be reconsidered: liver pathology consistent with PBC in AMA-positive individuals without biochemical cholestasis is increasingly reported, raising the question as to whether biochemical cholestasis is a reliable disease marker for both clinical practice and trials. The urgent need for new biomarkers, including more accurate markers of cholestasis, was also widely discussed during the meeting. Moreover, new insights in interactions of bile acids with biliary epithelia in PBC provide solid evidence of a role for impaired epithelial protection against potentially toxic hydrophobic bile acids, raising the fundamental question as to whether this bile acid-induced epithelial damage is the cause or the consequence of the autoimmune attack to the biliary epithelium. Strategies are needed to identify difficult-to-treat patients at an early disease stage, when new therapeutic approaches targeting immunologic pathways, in addition to bile acid-based therapies, may be effective. In conclusion, using interdisciplinary approaches, groundbreaking advances can be expected before long in respect to our understanding of the etiopathogenesis of PBC, with the ultimate aim of improving its treatment.

Anti-drug Antibodies Against a Novel Humanized Anti-CD20 Antibody Impair Its Therapeutic Effect on Primary Biliary Cholangitis in Human CD20- and FcγR-Expressing Mice

There is considerable interest in expanding B cell-targeted therapies in human autoimmune diseases. However, clinical trials in human primary biliary cholangitis (PBC) using a chimeric antibody against human CD20 (hCD20) have showed limited efficacy. Two potential explanations for these disappointing results are the appearance of anti-drug antibodies (ADAs) and the high frequency of patients with moderate PBC or patients who had failed ursodeoxycholic acid treatment. Here, we studied a novel humanized IgG1 antibody against hCD20 and explored its efficacy in early stage PBC using a well-defined murine model. We developed a unique murine model consisting of dnTGF-βRII mice expressing hCD20 and human Fcγ receptors (hFcγRs). Beginning at 4–6 weeks of age, equivalent to stage I/II human PBC, female mice were given weekly injections of an anti-hCD20 antibody (TKM-011) or vehicle control, and monitored for liver histology as well as a broad panel of immunological readouts. After 16 weeks' treatment, we observed a significant reduction in portal inflammation, a decrease in liver-infiltrating mononuclear cells as well as a reduction in liver CD8⁺ T cells. Importantly, direct correlations between numbers of liver non-B cells and B cells (r = 0.7426, p = 0.0006) and between numbers of liver memory CD8⁺ T cells and B cells (r = 0.6423, p = 0.0054) were apparent. Accompanying these changes was a dramatic reduction in anti-mitochondrial antibodies (AMAs), interleukin (IL)-12p40 and IL-5, and elevated levels of the anti-inflammatory chemokine CXCL1/KC. In mice that developed ADAs, clinical improvements were less pronounced. Sustained treatment with B cell-targeted therapies may broadly inhibit effector pathways in PBC, but may need to be administered early in the natural history of PBC.

Endogenous IL-10 maintains immune tolerance but IL-10 gene transfer exacerbates autoimmune cholangitis

The immunomodulatory effect of IL-10 as an immunosuppressive and anti-inflammatory cytokine is well known. Taking advantage of our established mouse model of autoimmune cholangitis using 2-octynoic acid conjugated ovalbumin (2-OA-OVA) induction, we compared liver pathology, immune cell populations and antimitochondrial antibodies between IL-10 knockout and wild type mice immunized with 2-OA-OVA. At 10 weeks post immunization, portal inflammation and fibrosis were more severe in 2-OA-OVA immunized IL-10 knockout mice than in wild type mice. This was accompanied by significant higher levels of collagen I and III expression, T, NK and NKT subsets in liver and IgG anti-mitochondrial autoantibodies (AMAs) compared to 2-OA-OVA immunized wild type mice, suggesting that endogenous IL-10 is necessary for the maintenance of immune tolerance in primary biliary cholangitis (PBC). Further, we investigated whether administration of exogenous IL-10 could prevent PBC by administration of IL-10 expressing recombinant adeno-associated virus (AAV-IL-10) either 3 days before or 3 weeks after the establishment of liver pathology. Interestingly, administration of AAV-IL-10 resulted in increased liver inflammation and fibrosis, accompanied by increases in IFN-γ in liver CD4⁺ T cell, granzyme B, FasL, and CD107a in liver CD8⁺ T and NKT cells, and granzyme B and FasL in liver NK cells of AAV-IL-10 administered mice compared with control mice. Furthermore, administration of AAV-IL-10 significantly increased levels of proinflammatory cytokines and chemokines (IFN-γ, TNF-α, CXCL9 and CXCL10) and collagen I and III production in naïve mice, together with increase in immune cell infiltration and collagen deposition in the liver, suggesting a role of IL-10 in fibrosis. In conclusion, our data demonstrate that endogenous IL-10 is critical in the maintenance of immune tolerance but exogenous administration of IL-10 exacerbates liver inflammation and fibrosis. Furthermore, the distinctive presence of inflammatory immune cell populations and collagen expression in AAV-IL-10 treated naïve mice cautions against the clinical use of exogenous IL-10 in patients with autoimmune cholangitis.

Evolution of our understanding of PBC

The discovery of mitochondrial autoantigens recognized by antimitochondrial antibodies (AMAs) in 1987 marked the dawn of a new era in primary biliary cholangitis (PBC) research. Since then, there has been substantial progress in our understanding of PBC partly bestowed by the development of innovative technologies in molecular biology, immunology, and genetics. Here, we review this evolutionary progress in understanding PBC. We now recognize that the epitopes of AMAs, CD4⁺, and CD8⁺ T cells are all mapped to the same region of the inner lipoyl domain of pyruvate dehydrogenase complex E2 subunit (PDC-E2), and that intrahepatic biliary epithelial cells (BECs) are exclusively targeted in PBC. BECs express PDC-E2 on apotopes in an immunologically intact form during apoptosis, but not other epithelial cells, which could explain the tissue specificity of PBC. In addition, genetic factors, environmental triggers, and epigenetic modifications play crucial roles in the development of PBC. Intact lipoylated PDC-E2, presumably after modification with xenobiotics such as 2-octynamide or 2-nonyamide that are abundantly present in the environment, is endocytosed by antigen-presenting cells and are presented to CD4⁺ or CD8⁺ T cells. An immune complex consisting of PDC-E2 and anti-PDC-E2 autoantibodies cross-present autoantigens in a more efficient manner. Finally, an adenylate uridine-rich element (ARE) Del -/- mouse model has been established, which presents a disease modeling human PBC, including female dominance as one of its most important features, and can be used to dissect the immunopathology of PBC. Expanding our knowledge of the pathology from a very early stage of the disease will provide the key to cure PBC.

Is PBC a viral infectious disease?

The human betaretrovirus and the closely related mouse mammary tumor virus have been linked with the development of cholangitis and mitochondrial antibody production in patients with primary biliary cholangitis (PBC) and mouse models of autoimmune biliary disease, respectively. In vitro, betaretroviruses have been found to stimulate the expression of mitochondrial autoantigens on the cell surface of biliary epithelial cells. In vivo, both mitochondrial autoantigens and viral proteins have been shown to be co-expressed in biliary epithelium and lymphoid tissue. Notably, both mice and humans make poor antibody responses to betaretrovirus infection, whereas proinflammatory responses to viral proteins have been observed in T lymphocyte studies. Furthermore, proviral integration studies have confirmed the presence of human betaretrovirus in biliary epithelium of patients with PBC. Preliminary proof of principal studies using combination antiretroviral therapy have shown that suppression of viral expression is associated with sustained biochemical response. As the previous regimen used was poorly tolerated, further randomized controlled trials are planned to determine whether betaretrovirus infection plays an important role in the development of PBC.

Autoantibodies in Autoimmune Hepatitis: Can Epitopes Tell Us about the Etiology of the Disease?

Autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) are serious autoimmune liver diseases that are characterized by a progressive destruction of the liver parenchyma and/or the hepatic bile ducts and the development of chronic fibrosis. Left untreated autoimmune liver diseases are often life-threatening, and patients require a liver transplantation to survive. Thus, an early and reliable diagnosis is paramount for the initiation of a proper therapy with immunosuppressive and/or anticholelithic drugs. Besides the analysis of liver biopsies and serum markers indicating liver damage, the screening for specific autoantibodies is an indispensable tool for the diagnosis of autoimmune liver diseases. Such liver autoantigen-specific antibodies might be involved in the disease pathogenesis, and their epitope specificity may give some insight into the etiology of the disease. Here, we will mainly focus on the generation and specificity of autoantibodies in AIH patients. In addition, we will review data from animal models that aim toward a better understanding of the origins and pathogenicity of such autoantibodies.

Trichloroethylene Exposure Reduces Liver Injury in a Mouse Model of Primary Biliary Cholangitis

Trichloroethylene (TCE) is a persistent environmental contaminant proposed to contribute to autoimmune disease. Experimental studies in lupus-prone MRL+/+ mice have suggested that TCE exposure can trigger autoimmune hepatitis. The vast majority of studies examining the connection between TCE and autoimmunity utilize this model, and the impact of TCE exposure in other established models of autoimmune liver disease is not known. We tested the hypothesis that TCE exposure exacerbates experimental hepatic autoimmunity in dominant negative transforming growth factor beta receptor type II (dnTGFBRII) mice, which develop serological and histological features resembling human primary biliary cholangitis. Female 8-week-old wild-type and dnTGFBRII mice were exposed to TCE (0.5 mg/ml) or vehicle (1% ethoxylated castor oil) in the drinking water for 12 or 22 weeks. Liver histopathology in 20- and 30-week-old wild-type mice was unremarkable irrespective of treatment. Mild portal inflammation was observed in vehicle-exposed 20-week-old dnTGFBRII mice and was not exacerbated by TCE exposure. Vehicle-exposed 30-week-old dnTGFBRII mice developed anti-mitochondrial antibodies, marked hepatic inflammation with necrosis, and hepatic accumulation of both B and T lymphocytes. To our surprise, TCE exposure dramatically reduced hepatic parenchymal inflammation and injury in 30-week-old dnTGFBRII mice, reflected by changes in hepatic proinflammatory gene expression, serum chemistry, and histopathology. Interestingly, TCE did not affect hepatic B cell accumulation or induction of the anti-inflammatory cytokine IL10. These data indicate that TCE exposure reduces autoimmune liver injury in female dnTGFBRII mice and suggests that the precise effect of environmental chemicals in autoimmunity depends on the experimental model.

Environmental basis of primary biliary cholangitis

Autoimmunity is a consequence of both genetic and environmental factors, occurring in genetically susceptible hosts with environmental triggers. While genome-wide association studies have revealed a number of susceptible genes contributing to etiology, the environmental triggers remain poorly understood. Primary biliary cholangitis, formally known as primary biliary cirrhosis, is considered a model autoimmune disease for which our group has extensively evaluated environmental factors involved in its etiology. Bacterial infection and xenobiotics have been proposed as candidate environmental factors that may explain tolerance breakdown and production of primary biliary cholangitis-specific antimitochondrial autoantibodies. Large-scale case-control studies have consistently detected an association of primary biliary cholangitis with urinary tract infections caused by Escherichia coli, as E. coli PDC-E2 is molecularly similar to human PDC-E2, the immunodominant target of AMAs. Another bacterium of interest is Novosphingobium aromaticivorans, a ubiquitous xenobiotic-metabolizing bacterium that produces lipoylated proteins, which are highly reactive with sera from primary biliary cholangitis patients. Regarding xenobiotics, case-control studies have suggested that frequent use of nail polish is associated with an increased susceptibility to primary biliary cholangitis. We found that 2-octynamide, the conjugate derived from 2-octynoic acid present in cosmetics, lipsticks, and some chewing gums, was unique in both its quantitative structure-activity relationship analysis and reactivity with primary biliary cholangitis sera. 2-nonyamide is another xenobiotic that also has the optimal chemical structure for xenobiotic modification of the PDC-E2 epitope, as demonstrated by the enhanced epitope recognition with AMA-positive PBC sera. Moreover, we found that C57BL/6 mice immunized with 2-octynoic acid-BSA possess many of the features characteristic to primary biliary cholangitis. Impact statement Autoimmunity is believed to develop in genetically susceptible hosts with triggers from the environment. Researchers have recently demonstrated that bacteria and xenobiotics commonly present in our environment are potential triggers of tolerance breakdown against autoantigens and autoimmunity, particularly in primary biliary cholangitis (PBC). The link between xenobiotics and PBC has been further confirmed with the establishment of PBC model mice by immunizing mice with xenobiotics.

The role of natural killer T cells in a mouse model with spontaneous bile duct inflammation

Natural killer T (NKT) cells are activated by lipid antigens presented by CD1d molecules and represent a major lymphocyte subset of the liver. NODc3c4 mice spontaneously develop biliary inflammation in extra- and intrahepatic bile ducts. We demonstrated by flow cytometry that invariant NKT (iNKT) cells were more abundant in the thymus, spleen, and liver of NODc3c4 mice compared to NOD mice. iNKT cells in NODc3c4 mice displayed an activated phenotype. Further, NOD and NODCd1d^-/- mice were irradiated and injected with NODc3c4 bone marrow, and injection of NODc3c4 bone marrow resulted in biliary infiltrates independently of CD1d expression in recipient mice. Activation or blocking of NKT cells with α-galactosylceramide or anti-CD1d antibody injections did not affect the biliary phenotype of NODc3c4 mice. NODc3c4.Cd1d^-/- mice were generated by crossing NODCd1d^-/- mice onto a NODc3c4 background. NODc3c4.Cd1d^-/- and NODc3c4 mice developed the same extent of biliary disease. This study demonstrates that iNKT cells are more abundant and activated in the NODc3c4 model. The portal inflammation of NODc3c4 mice can be transferred to irradiated recipients, which suggests an immune-driven disease. Our findings imply that NKT cells can potentially participate in the biliary inflammation, but are not the primary drivers of disease in NODc3c4 mice.

A Mouse Model of Autoimmune Cholangitis via Syngeneic Bile Duct Protein Immunization

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the destruction of interlobular biliary ductules, which progressively leads to cholestasis, hepatic fibrosis, cirrhosis, and eventually liver failure. Several mouse models have been used to clarify the pathogenesis of PBC and are generally considered reflective of an autoimmune cholangitis. Most models focus on issues of molecular mimicry between the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2), the major mitochondrial autoantigen of PBC and xenobiotic cross reactive chemicals. None have focused on the classic models of breaking tolerance, namely immunization with self-tissue. Here, we report a novel mouse model of autoimmune cholangitis via immunization with syngeneic bile duct protein (BDP). Our results demonstrate that syngeneic bile duct antigens efficiently break immune tolerance of recipient mice, capturing several key features of PBC, including liver-specific inflammation focused on portal tract areas, increased number and activation state of CD4 and CD8 T cells in the liver and spleen. Furthermore, the germinal center (GC) responses in the spleen were more enhanced in our mouse model. Finally, these mice were 100% positive for anti-mitochondrial antibodies (AMAs). In conclusion, we developed a novel mouse model of PBC that may help to elucidate the detailed mechanism of this complex disease.

Chronic Autoimmune Epithelitis in Sjögren's Syndrome and Primary Biliary Cholangitis: A Comprehensive Review

Within the spectrum of autoimmune diseases, Sjögren's syndrome and primary biliary cholangitis are exemplary and can be coined as chronic epithelitis based on their frequent coexistence in clinical practice and the highly specific immune-mediated injury of the small bile ducts and the exocrine glands. The pathogenic mechanisms underlying the diseases are similar, with apoptosis being the key element leading to organ-specific immune-mediated injury directed against the small bile ducts and salivary gland epithelia, respectively along with similar epidemiological features, such as female predominance and the age of onset in the fifth decade of life. Indeed, novel insights into the pathogenesis of the diseases have been obtained in recent years, including a better definition of the role of B and T cells, particularly Th17 cells, and the mechanisms of autoantibody-mediated tissue injury, with anti-mitochondrial antibodies and SS-A/SS-B being identified as specific for primary biliary cholangitis and Sjögren's syndrome, respectively. These findings have opened the possibility to new targeted therapies, but most clinical needs remain unmet, particularly from a therapeutic standpoint where options diverge, with bile acids being the predominant treatment strategy in primary biliary cholangitis and immunomodulators being used to treat Sjögren's syndrome. Here we provide a comprehensive review of the most recent findings on the pathogenesis, clinical manifestations and therapeutic options for Sjögren's syndrome and primary biliary cholangitis, respectively, while stressing the common traits between these conditions. Our cumulative hypothesis is that similarities outnumber differences and that this may prove advantageous towards a better management of patients.

Toward solving the etiological mystery of primary biliary cholangitis

Primary biliary cholangitis (PBC) is considered a model autoimmune disease due to its signature anti‐mitochondrial antibody (AMA) autoantibody, female predominance, and relatively specific portal infiltration and cholestasis. The identification and cloning of the major mitochondrial autoantigens recognized by AMA have served as an immunologic platform to identify the earliest events involved in loss of tolerance. Despite the relatively high concordance rate in identical twins, genome‐wide association studies have not proven clinically useful and have led to suggestions of epigenetic events. To understand the natural history and etiology of PBC, several murine models have been developed, including spontaneous models, models induced by chemical xenobiotic immunization, and by “designer” mice with altered interferon metabolism. Herein, we describe five such models, including 1) NOD.c3c4 mice, 2) dominant negative form of transforming growth factor receptor type II mice, 3) interleukin‐2R α^−/− mice, 4) adenylate‐uridylate‐rich element Del^−/− mice, and 5) 2‐octynoic acid‐conjugated bovine serum albumin immunized mice. Individually there is no perfect murine model, but collectively the models point to loss of tolerance to PDC‐E2, the major mitochondrial autoantigen, as the earliest event that occurs before clinical disease is manifest. Although there is no direct association of AMA titer and PBC disease progression, it is noteworthy that the triad of PBC monocytes, biliary apotopes, and AMA leads to an intense proinflammatory cytokine burst. Further, the recurrence of PBC after liver transplantation indicates that, due to major histocompatibility complex restriction, disease activity must include not only adaptive immunity but also innate immune mechanisms. We postulate that successful treatment of PBC may require a personalized approach with therapies designed for different stages of disease. (Hepatology Communications 2017;1:275–287)

The fingerprint of antimitochondrial antibodies and the etiology of primary biliary cholangitis

The identification of environmental factors that lead to loss of tolerance has been coined the holy grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein, we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177-252 (PDC-228) with a 62-residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 inner lipoyl domain (ILD). We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA-modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the immunoglobulin M isotype and more dominant in early-stage primary biliary cholangitis (PBC), suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition, we analyzed PPL, LA-PPL, and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by enzyme-linked immunosorbent assay, immunoblotting, and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid.

CONCLUSION

A molecular understanding of the conformation of xenobiotic-modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. (Hepatology 2017;65:1670-1682).

Current strategies to generate mature human induced pluripotent stem cells derived cholangiocytes and future applications

Stem cell research has significantly evolved over the last few years, allowing the differentiation of pluripotent cells into almost any kind of lineage possible. Studies that focus on the liver have considerably taken a leap into this novel technology, and hepatocyte-like cells are being generated that are close to resembling actual hepatocytes both genotypically and phenotypically. The potential of this extends from disease models to bioengineering, and even also innovative therapies for end-stage liver disease. Nonetheless, too few attention has been given to the non-parenchymal cells which are also fundamental for normal liver function. This includes cholangiocytes, the cells of the biliary epithelium, without whose role in bile modification and metabolism would impair hepatocyte survival. Such can be observed in diseases that target them, so called cholangiopathies, for which there is much yet to study so as to improve therapeutical options. Protocols that describe the induction of human induced pluripotent stem cells into cholangiocytes are scarce, although progress is being achieved in this area as well. In order to give the current view on this emerging research field, and in hopes to motivate further advances, we present here a review on the known differentiation strategies with sight into future applications.

Proposed therapies in primary biliary cholangitis

Primary biliary cholangitis (PBC), previously known as primary biliary cirrhosis, is a model autoimmune disease with chronic cholestasis characterized by the hallmark of anti-mitochondrial antibodies and treated with ursodeoxycholic acid (UDCA). However, approximately 20-40% of patients incompletely respond to UDCA and have an increased risk of disease progression. Although there have been significant advances in the immunobiology of PBC, these have yet to be translated into newer therapeutic modalities. Current approaches to controlling the immune response include broad immunosuppression with corticosteroids as well as targeted therapies directed against T and B cells. In contrast, ameliorating cholestasis is the focus of other therapies in development, including obeticholic acid. In this article the authors will discuss ongoing clinical trials and, in particular, the rationale for choosing agents that may effectively target the aberrant immune response.

The Natural History and Prognosis of Primary Biliary Cirrhosis with Clinical Features of Autoimmune Hepatitis

Although a variant of primary biliary cirrhosis (PBC) characterized by features of autoimmune hepatitis (AIH) has been recognized for many years, few studies with ample numbers of patients have focused on its natural history. This study aimed to clarify the natural history, prognosis, and response to therapy in a cohort of patients with PBC with AIH features. We retrospectively analyzed 277 PBC patients without AIH features and 46 PBC patients with AIH features seen between September 2004 and April 2014. The 5-year adverse outcome-free survival of PBC patients with AIH features was 58% compared to 81% in PBC patients without AIH features. Multivariate analysis in the patients with AIH features indicated that total bilirubin ≥ 2.70× the upper limit of normal predicted a poor prognosis (p = 0.008, relative risk 8.39, 95% confidence interval (CI) 1.73, 40.73). Combination therapy with ursodeoxycholic acid (UDCA) and immunosuppression provided better short-term responses in PBC patients with AIH features, defined by multiple criteria. Higher aspartate aminotransferase (AST) level at accession suggested better prognosis for PBC patients with AIH features while worse prognosis for PBC patients without AIH features. PBC patients with AIH features differ from those without AIH features in terms of natural history, prognostic indicators, and response to therapy.

MiR-139-5p is associated with inflammatory regulation through c-FOS suppression, and contributes to the progression of primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease characterized pathologically by destruction of intrahepatic bile ducts. PBC is largely classified into three subtypes based on clinical course: (i) gradually progressive, (ii) portal hypertension, and (iii) hepatic failure. Previous studies have indicated that serum levels of the pro-inflammatory cytokine TNF-α, is elevated in PBC patients with fibrosis. Although the severity of cholangitis might also be related to the PBC subtype, its etiology has been unclear. Several studies have shown that microRNAs (miRNAs) demonstrate specific expression patterns in various diseases. In the present study, we evaluated miRNA expression patterns among the PBC subtypes using comprehensive deep sequencing. We also carried out histologic examination by laser capture microdissection and investigated how the identified miRNAs were involved in PBC clinical progression using the miRNA transfection method. On average, ~11 million 32-mer short RNA reads per sample were obtained, and we found that the expression levels of 97 miRNAs differed significantly among the four groups. Heat mapping demonstrated that the miRNA profiles from hepatic failure and portal hypertension type were clustered differently from those of the gradually progressive type and controls. Furthermore, we focused on miR-139-5p, which has an adequate number of total short reads. Quantitative reverse transcription PCR showed that miR-139-5p was significantly downregulated in clinically advanced PBC. Also, examination of liver tissues demonstrated that the expression of lymphocyte-derived miR-139-5p was significantly higher in hepatocytes. In vitro, the level of TNF-α was significantly elevated in supernatant of cells with upregulation of miR-139-5p. Furthermore, c-FOS gene transcription was repressed. Thus, we have demonstrated a novel inflammation-regulatory mechanism involving TNF-α and c-FOS transcription through miR-139-5p in the NF-κB signaling pathway. We conclude that the specific miRNA miR-139-5p might be involved in the pathogenesis of PBC, especially during clinical progression.

Inflammatory Bowel Disease: Influence and Implications in Reproduction

The incidence and prevalence of inflammatory bowel disease (IBD) continues to rise with time, signifying its emergence as a global disease. Clinical onset of IBD, comprising Crohn's disease and ulcerative colitis, typically occurs before or at peak reproductive age. Although active disease in female patients is associated with reduced fertility and adverse obstetric outcomes in pregnancy, the molecular mechanisms underlying this altered reproductive course, and its impact on IBD transmission to offspring, remain poorly understood. Clinical and experimental studies have now begun to elucidate the hormonal, environmental, and microbial factors that modulate immune-reproductive cross talk in IBD and define their impact on maternal health, fetal development, and heritability of disease risk. Evolving insight into maternal-fetal imprinting in IBD has important implications for patient counseling and disease management during pregnancy and may help predict clinical outcomes for both mother and child.

Chronic expression of interferon-gamma leads to murine autoimmune cholangitis with a female predominance

In most autoimmune diseases the serologic hallmarks of disease precede clinical pathology by years. Therefore, the use of animal models in defining early disease events becomes critical. We took advantage of a "designer" mouse with dysregulation of interferon gamma (IFNγ) characterized by prolonged and chronic expression of IFNγ through deletion of the IFNγ 3'-untranslated region adenylate uridylate-rich element (ARE). The ARE-Del(-/-) mice develop primary biliary cholangitis (PBC) with a female predominance that mimics human PBC that is characterized by up-regulation of total bile acids, spontaneous production of anti-mitochondrial antibodies, and portal duct inflammation. Transfer of CD4 T cells from ARE-Del(-/-) to B6/Rag1(-/-) mice induced moderate portal inflammation and parenchymal inflammation, and RNA sequencing of liver gene expression revealed that up-regulated genes potentially define early stages of cholangitis. Interestingly, up-regulated genes specifically overlap with the gene expression signature of biliary epithelial cells in PBC, implying that IFNγ may play a pathogenic role in biliary epithelial cells in the initiation stage of PBC. Moreover, differentially expressed genes in female mice have stronger type 1 and type 2 IFN signaling and lymphocyte-mediated immune responses and thus may drive the female bias of the disease.

CONCLUSION

Changes in IFNγ expression are critical for the pathogenesis of PBC. (Hepatology 2016;64:1189-1201).

Endogenous interleukin-22 protects against inflammatory bowel disease but not autoimmune cholangitis in dominant negative form of transforming growth factor beta receptor type II mice

During chronic inflammation, interleukin (IL)-22 expression is up-regulated in both CD4 and CD8 T cells, exerting a protective role in infections. However, in autoimmunity, IL-22 appears to have either a protective or a pathogenic role in a variety of murine models of autoimmunity and, by extrapolation, in humans. It is not clear whether IL-22 itself mediates inflammation or is a by-product of inflammation. We have taken advantage of the dominant negative form of transforming growth factor beta receptor type II (dnTGF-βRII) mice that develop both inflammatory bowel disease and autoimmune cholangitis and studied the role and the biological function of IL-22 by generating IL-22(-/-) dnTGF-βRII mice. Our data suggest that the influence of IL-22 on autoimmunity is determined in part by the local microenvironment. In particular, IL-22 deficiency exacerbates tissue injury in inflammatory bowel disease, but has no influence on either the hepatocytes or cholangiocytes in the same model. These data take on particular significance in the previously defined effects of IL-17A, IL-12p40 and IL-23p19 deficiency and emphasize that, in colitis, there is a dominant role of IL-23/T helper type 17 (Th17) signalling. Furthermore, the levels of IL-22 are IL-23-dependent. The use of cytokine therapy in patients with autoimmune disease has significant potential, but must take into account the overlapping and often promiscuous effects that can theoretically exacerbate inflammation.

Ustekinumab for patients with primary biliary cholangitis who have an inadequate response to ursodeoxycholic acid: A proof-of-concept study

The interleukin (IL)-12 signaling cascade has been associated with primary biliary cholangitis (PBC). This multicenter, open-label, proof-of-concept study evaluated the anti-IL12/23 monoclonal antibody, ustekinumab (90 mg subcutaneous at weeks 0 and 4, then every 8 weeks through week 20), in adults with PBC and an inadequate response to ursodeoxycholic acid therapy (i.e., alkaline phosphatase [ALP] >1.67× upper limit of normal [ULN] after ≥6 months). ALP response was defined as a >40% decrease from baseline and ALP remission as ALP normalization (if baseline ALP 1.67×-2.8× ULN) or <1.67× ULN (if baseline ALP >2.8× ULN). Changes in Enhanced Liver Fibrosis (ELF) scores and serum bile acids were also assessed. At baseline, patients had median disease duration of 3.2 years, median ELF score of 9.8, and highly elevated total bile acid concentration (median, 43.3 μmol/L); 13 of 20 (65%) patients had baseline ALP >3× ULN. Although steady-state serum ustekinumab concentrations were reached by week 12, no patient achieved ALP response or remission. Median percent ALP reduction from baseline to week 28 was 12.1%. ELF score decreased slightly from baseline to week 28 (median reduction: 0.173), and total serum bile acid concentrations decreased from baseline to week 28 (median reduction: 8.8 μmol/L). No serious infections or discontinuations resulting from adverse events were reported through week 28. One patient had a serious upper gastrointestinal hemorrhage considered unrelated to test agent by the investigator.

CONCLUSION

Open-label ustekinumab therapy, though associated with a modest decrease in ALP after 28 weeks of therapy, did not otherwise appreciably change ALP and overt proof-of-concept was not established as per prespecified primary endpoint of proposed efficacy. No new ustekinumab safety signals were observed. (Hepatology 2016;64:189-199).

Evolving Trends in Female to Male Incidence and Male Mortality of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) has been regarded as female-predominant without evidence of gender difference in survival. We aimed to compare the overall survival, incidence and prevalence of PBC in two well defined population-based studies over a recent decade, considering also sex ratios and mortality. We have taken advantage of population-wide records, during 2000–2009, in Lombardia, Northern Italy, and Denmark. We focused on the incident cases of PBC, including gender and outcome, among 9.7 million inhabitants of Lombardia and 5.5 million of Denmark. In Lombardia there were 2,970 PBC cases with a female:male ratio of 2.3:1. The age/sex-adjusted annual incidence of PBC was 16.7 per million. Point prevalence was 160 per million on January 1^st 2009. In Denmark there were 722 cases of incident PBC, female:male ratio was 4.2:1, and the annual incidence was 11.4 per million, a point prevalence of 115 per million in 2009. Cox regression multivariate analysis identified male sex as an independent predictor of all-cause mortality in both Italian (HR 2.36) and Danish population (HR 3.04). Our data indicate for PBC a sex ratio significantly lower than previously cited, a reversal of the usual latitudinal difference in prevalence and a surprisingly higher overall mortality for male patients.

Role of Fibrin(ogen) in Progression of Liver Disease: Guilt by Association?

Strong experimental evidence indicates that components of the hemostatic system, including thrombin, exacerbate diverse features of experimental liver disease. Clinical studies have also begun to address this connection and some studies have suggested that anticoagulants can improve outcome in patients with liver disease. Among the evidence of coagulation cascade activation in models of liver injury and disease is the frequent observation of thrombin-driven hepatic fibrin(ogen) deposition. Indeed, hepatic fibrin(ogen) deposition has long been recognized as a consequence of hepatic injury. Although commonly inferred as pathologic due to protective effects of anticoagulants in mouse models, the role of fibrin(ogen) in acute liver injury and chronic liver disease may not be universally detrimental. The localization of hepatic fibrin(ogen) deposits within the liver is connected to the disease stimulus and in animal models of liver toxicity and chronic disease, fibrin(ogen) deposition may not always be synonymous with large vessel thrombosis. Here, we provide a balanced review of the experimental evidence supporting a direct connection between fibrin(ogen) and liver injury/disease pathogenesis, and suggest a path forward bridging experimental and clinical research to improve our knowledge on the nature and function of fibrin(ogen) in liver disease.

A contemporary perspective on the molecular characteristics of mitochondrial autoantigens and diagnosis in primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune hepatobiliary disease characterized by immune mediated destruction of the intrahepatic small bile ducts and the presence of antimitochondrial antibodies (AMAs). The mitochondrial autoantigens have been identified as the E2 subunits of the 2-oxo-acid dehydrogenase complex, including the E2 subunits of pyruvate dehydrogenase, branched-chain 2-oxo acid dehydrogenase complex, oxoglutarate dehydrogenase complex, E3 binding protein and PDC E1 alpha subunit. The AMA epitope is mapped within the E2 lipoic acid binding domain, which is particularly important for oxidative phosphorylation. In addition, lipoic acid, which serves as a swinging arm to capture electrons, is particularly susceptible to an electrophilic attack and may provide clues to the etiology of PBC. This review emphasizes the molecular characteristics of AMAs, including detection, immunochemistry and the putative role in disease. These data have significance not only specifically for PBC, but generically for autoimmunity.

Deletion of Galectin-3 Enhances Xenobiotic Induced Murine Primary Biliary Cholangitis by Facilitating Apoptosis of BECs and Release of Autoantigens

Galectin-3 (Gal-3) is a carbohydrate binding lectin, with multiple roles in inflammatory diseases and autoimmunity including its antiapoptotic effect on epithelial cells. In particular, increased expression of Gal-3 in epithelial cells is protective from apoptosis. Based on the thesis that apoptosis of biliary epithelial cells (BECs) is critical to the pathogenesis of Primary Biliary Cholangitis (PBC), we have analyzed the role of Gal-3 in the murine model of autoimmune cholangitis. We took advantage of Gal-3 knockout mice and immunized them with a mimotope of the major mitochondrial autoantigen of PBC, 2-octynoic acid (2-OA) coupled to BSA (2OA-BSA) and evaluated the natural history of subsequent disease, compared to control wild-type mice, by measuring levels of antibodies to PDC-E2, immunohistology of liver, and expression of Gal-3. We report herein that deletion of Gal-3 significantly exacerbates autoimmune cholangitis in these mice. This is manifested by increased periportal infiltrations, bile duct damage, granulomas and fibrosis. Interestingly, the BECs of Gal-3 knockout mice had a higher response to apoptotic stimuli and there were more pro-inflammatory lymphocytes and dendritic cells (DCs) in the livers of Gal-3 knockout mice. In conclusion, Gal-3 plays a protective role in the pathways that lead to the inflammatory destruction of biliary epithelial cells.

Xenobiotics and loss of tolerance in primary biliary cholangitis

Data from genome wide association studies and geoepidemiological studies established that a combination of genetic predisposition and environmental stimulation is required for the loss of tolerance in primary biliary cholangitis (PBC). The serologic hallmark of PBC are the presence of high titer anti-mitochondrial autoantibodies (AMA) that recognize the lipoyl domain of the mitochondrial pyruvate dehydrogenase E2 (PDC-E2) subunit. Extensive efforts have been directed to investigate the molecular basis of AMA. Recently, experimental data has pointed to the thesis that the breaking of tolerance to PDC-E2 is a pivotal event in the initial etiology of PBC, including environmental xenobiotics including those commonly found in cosmetics and food additives, suggesting that chemical modification of the PDC-E2 epitope may render its vulnerable to become a neo-antigen and trigger an immune response in genetically susceptible hosts. Here, we will discuss the natural history, genetics and immunobiology of PBC and structural constraints of PDC-E2 in AMA recognition which makes it vulnerable to chemical modification.

AAV-IL-22 modifies liver chemokine activity and ameliorates portal inflammation in murine autoimmune cholangitis

There remain significant obstacles in developing biologics to treat primary biliary cholangitis (PBC). Although a number of agents have been studied both in murine models and human patients, the results have been relatively disappointing. IL-22 is a member of the IL-10 family and has multiple theoretical reasons for predicting successful usage in PBC. We have taken advantage of an IL-22 expressing adeno-associated virus (AAV-IL-22) to address the potential role of IL-22 in not only protecting mice from autoimmune cholangitis, but also in treating animals with established portal inflammation. Using our established mouse model of 2-OA-OVA immunization, including α-galactosylceramide (α-GalCer) stimulation, we treated mice both before and after the onset of clinical disease with AAV-IL-22. Firstly, AAV-IL-22 treatment given prior to 2-OA-OVA and α-GalCer exposure, i.e. before the onset of disease, significantly reduces the portal inflammatory response, production of Th1 cytokines and appearance of liver fibrosis. It also reduced the liver lymphotropic chemokines CCL5, CCL19, CXCL9, and CXCL10. Secondly, and more importantly, therapeutic use of AAV-IL-22, administered after the onset of disease, achieved a greater hurdle and significantly improved portal pathology. Further the improvements in inflammation were negatively correlated with levels of CCL5 and CXCL10 and positively correlated with levels of IL-22. In conclusion, we submit that the clinical use of IL-22 has a potential role in modulating the inflammatory portal process in patients with PBC.

Obeticholic acid for the treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by progressive nonsuppurative destruction of small bile ducts, resulting in intrahepatic cholestasis, fibrosis and ultimately end-stage liver disease. Timely intervention with ursodeoxycholic acid is associated with excellent survival, although approximately one-third of all patients fail to achieve biochemical response, signifying a critical need for additional therapeutic strategies. Obeticholic acid (OCA) is a potent ligand of the nuclear hormone receptor farnesoid X receptor (FXR). Activation of FXR inhibits bile acid synthesis and protects against toxic accumulation in models of cholestasis and facilitates hepatic regeneration in preclinical studies. Data from recent Phase II and III controlled trials suggest a therapeutic impact of OCA in PBC biochemical nonresponders, as evidenced by change in proven laboratory surrogates of long-term outcome. Dose-dependent pruritus is a common adverse effect, but may be overcome through dose-titration. Longer term studies are needed with focus on safety and long-term clinical efficacy.