Characterisation of TNF-related apoptosis-inducing ligand in peripheral blood in patients with primary biliary cirrhosis

Panic at the Bile Duct: How Intrahepatic Cholangiocytes Respond to Stress and Injury

In the liver, biliary epithelial cells (BECs) line intrahepatic bile ducts (IHBDs) and are primarily responsible for modifying and transporting hepatocyte-produced bile to the digestive tract. BECs comprise only 3% to 5% of the liver by cell number but are critical for maintaining choleresis through homeostasis and disease. To this end, BECs drive an extensive morphologic remodeling of the IHBD network termed ductular reaction (DR) in response to direct injury or injury to the hepatic parenchyma. BECs are also the target of a broad and heterogenous class of diseases termed cholangiopathies, which can present with phenotypes ranging from defective IHBD development in pediatric patients to progressive periductal fibrosis and cancer. DR is observed in many cholangiopathies, highlighting overlapping similarities between cell- and tissue-level responses by BECs across a spectrum of injury and disease. The following core set of cell biological BEC responses to stress and injury may moderate, initiate, or exacerbate liver pathophysiology in a context-dependent manner: cell death, proliferation, transdifferentiation, senescence, and acquisition of neuroendocrine phenotype. By reviewing how IHBDs respond to stress, this review seeks to highlight fundamental processes with potentially adaptive or maladaptive consequences. A deeper understanding of how these common responses contribute to DR and cholangiopathies may identify novel therapeutic targets in liver disease.

Mast Cell and Innate Immune Cell Communication in Cholestatic Liver Disease

Mast cells (MCs) contribute to the pathogenesis of cholestatic liver diseases (primary sclerosing cholangitis [PSC] and primary biliary cholangitis [PBC]). PSC and PBC are immune-mediated, chronic inflammatory diseases, characterized by bile duct inflammation and stricturing, advancing to hepatobiliary cirrhosis. MCs are tissue resident immune cells that may promote hepatic injury, inflammation, and fibrosis formation by either direct or indirect interactions with other innate immune cells (neutrophils, macrophages/Kupffer cells, dendritic cells, natural killer, and innate lymphoid cells). The activation of these innate immune cells, usually through the degranulation of MCs, promotes antigen uptake and presentation to adaptive immune cells, exacerbating liver injury. In conclusion, dysregulation of MC-innate immune cell communications during liver injury and inflammation can lead to chronic liver injury and cancer.

NK Cells in Autoimmune Diseases: Protective or Pathogenic?

Autoimmune diseases generally result from the loss of self-tolerance (i.e., failure of the immune system to distinguish self from non-self), and are characterized by autoantibody production and hyperactivation of T cells, which leads to damage of specific or multiple organs. Thus, autoimmune diseases can be classified as organ-specific or systemic. Genetic and environmental factors contribute to the development of autoimmunity. Recent studies have demonstrated the contribution of innate immunity to the onset of autoimmune diseases. Natural killer (NK) cells, which are key components of the innate immune system, have been implicated in the development of multiple autoimmune diseases such as systemic lupus erythematosus, type I diabetes mellitus, and autoimmune liver disease. However, NK cells have both protective and pathogenic roles in autoimmunity depending on the NK cell subset, microenvironment, and disease type or stage. In this work, we review the current knowledge of the varied roles of NK cell subsets in systemic and organic-specific autoimmune diseases and their clinical potential as therapeutic targets.

TRAIL inhibits HBV replication and expression by down-regulating liver-enriched transcription factors

BACKGROUND AND STUDY AIMS

To investigate the role of low-concentration TRAIL on HBV replication and expression.

MATERIAL AND METHODS

MTT assay was performed to determine the minimum concentrations of TRAIL protein in HepG2 cell apoptosis. HepG2 cells were transfected by HBV replication plasmid pHBV4.1. After the treatment with low concentration of TRAIL, the culture supernatant was collected to detect HBsAg and HBeAg by ELISA. Proteins were extracted from the resulted cells, followed by total RNA and HBV DNA intermediate replication. Southern Blot and Northern Blot were carried out to detect HBV RNA and HBV DNA replication intermediates, respectively. RT-PCR and Western Blot were carried out to detect gene and protein expressions for HNF4α, PPARα, and RXRα, respectively.

RESULTS

50 ng/ml of TRAIL protein led to significant decline on the secretions of HBsAg and HBeAg. Expression levels of HBV RNA and HBV DNA replication intermediates were significantly decreased too. In addition, gene and protein expressions of HNF4α, PPARα and RXRα also dropped, especially for PPARα whose expressions significantly decreased.

CONCLUSION

TRAIL could inhibit HBV replication and expression by downregulating the expressions of liver-enriched transcription factors HNF4α, PPARα, and RXRα.

Epigenetics of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease with non-suppurative destruction of the intrahepatic bile ducts. The interplay of genetics and environmental triggers contributes to the onset of the disease and subsequently results in cholestasis and progressive fibrosis. Recently, genome-wide association studies (GWAS) have identified multiple genes influencing the susceptibility to PBC in HLA and non-HLA loci. However, it is estimated that the known risk variants merely account for no more than 20% of the heritability of PBC and causes of the remaining heritability remain uncertain. Increasing evidence suggests that the presence of epigenetic abnormalities may explain the "missing heritability" that cannot be captured by GWAS. Among these epigenetic mechanisms, DNA methylation, histone modification, and noncoding RNAs (i.e. miRNA and lncRNA) are involved in the pathogenesis of PBC. Additionally, telomere dysregulation in biliary epithelial cells (BECs) may play a role in disease onset, whereas a deficiency in sex chromosome and skewed gene expression in the X chromosome may to some extent explain the female dominance in PBC.

Hepatic Natural Killer Cells: Organ-Specific Sentinels of Liver Immune Homeostasis and Physiopathology

The liver is considered a preferential tissue for NK cells residency. In humans, almost 50% of all intrahepatic lymphocytes are NK cells that are strongly imprinted in a liver-specific manner and show a broad spectrum of cellular heterogeneity. Hepatic NK (he-NK) cells play key roles in tuning liver immune response in both physiological and pathological conditions. Therefore, there is a pressing need to comprehensively characterize human he-NK cells to better understand the related mechanisms regulating their effector-functions within the dynamic balance between immune-tolerance and immune-surveillance. This is of particular relevance in the liver that is the only solid organ whose parenchyma is constantly challenged on daily basis by millions of foreign antigens drained from the gut. Therefore, the present review summarizes our current knowledge on he-NK cells in the light of the latest discoveries in the field of NK cell biology and clinical relevance.

Natural killer cells in liver diseases

The liver has been characterized as a frontline lymphoid organ with complex immunological features such as liver immunity and liver tolerance. Liver tolerance plays an important role in liver diseases including acute inflammation, chronic infection, autoimmune disease, and tumors. The liver contains a large proportion of natural killer (NK) cells, which exhibit heterogeneity in phenotypic and functional characteristics. NK cell activation, well known for its role in the immune surveillance against tumor and pathogen-infected cells, depends on the balance between numerous activating and inhibitory signals. In addition to the innate direct "killer" functions, NK cell activity contributes to regulate innate and adaptive immunity (helper or regulator). Under the setting of liver diseases, NK cells are of great importance for stimulating or inhibiting immune responses, leading to either immune activation or immune tolerance. Here, we focus on the relationship between NK cell biology, such as their phenotypic features and functional diversity, and liver diseases.

Epigenetics in the Primary Biliary Cholangitis and Primary Sclerosing Cholangitis

Epigenomics, the study of modifications to genetic material that do not alter the underlying DNA sequence, is generating increasing interest as a means to help clarify disease pathogenesis and outcomes. Although genome-wide association studies have identified several potential candidate genes that may be implicated in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), it is estimated that these genes explain less than 20% of the heritability of these diseases. Thus, to date, the origins of “missing heritability” for PBC and PSC remain elusive. The epigenome may provide a potentially elegant solution to this phenomenon, as it can be modified by both internal and external exposures (coined the “exposome”). This may explain differences in disease presentation, treatment response, and rates of progression between individuals. Epigenetic changes may also provide a framework for discovering potential biomarkers for diagnosis and screening of PBC and PSC. Importantly, because the epigenome is modifiable, it may also highlight novel pathways for therapeutic discovery and interventions of these diseases.

NK Cell Subtypes as Regulators of Autoimmune Liver Disease

As major components of innate immunity, NK cells not only exert cell-mediated cytotoxicity to destroy tumors or infected cells, but also act to regulate the functions of other cells in the immune system by secreting cytokines and chemokines. Thus, NK cells provide surveillance in the early defense against viruses, intracellular bacteria, and cancer cells. However, the effecter function of NK cells must be exquisitely controlled to prevent inadvertent attack against normal “self” cells. In an organ such as the liver, where the distinction between immunotolerance and immune defense against routinely processed pathogens is critical, the plethora of NK cells has a unique role in the maintenance of homeostasis. Once self-tolerance is broken, autoimmune liver disease resulted. NK cells act as a “two-edged weapon” and even play opposite roles with both regulatory and inducer activities in the hepatic environment. That is, NK cells act not only to produce inflammatory cytokines and chemokines, but also to alter the proliferation and activation of associated lymphocytes. However, the precise regulatory mechanisms at work in autoimmune liver diseases remain to be identified. In this review, we focus on recent research with NK cells and their potential role in the development of autoimmune liver disease.

Infliximab as a treatment option for patients with rheumatoid arthritis and primary biliary cirrhosis

Rheumatoid arthritis (RA) is a chronic inflammatory systemic disease which commonly requires treatment with biologic agents targeting various inflammatory pathways. Tumor necrosis factor alpha is a proinflammatory cytokine which plays a pivotal role not only in the pathogenesis of RA but also in other autoimmune diseases such as primary biliary cirrhosis. The co-existence of more than one autoimmune disorder in the same individual is very challenging in the daily practice as therapy strategies applicable to one disease setting may cause clinical and/or biochemical relapse of the other clinical entity. As a result, treatment options able to control different diseases are highly desirable among rheumatologists and other specialties. In that respect, we present a case of a 61-year-old female patient with RA and concomitant primary biliary cirrhosis with poor clinical response to conventional disease-modifying drugs for RA. The introduction of tumor necrosis factor alpha antagonist infliximab led to significant clinical improvement of RA and to stabilization of liver function. In this case review study, we discuss aspects of pathophysiology of primary biliary cirrhosis associated with tumor necrosis alpha and we review the available data of similar published cases.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

S100A12 expression in patients with primary biliary cirrhosis

OBJECTIVES

S100 calcium binding protein A12 (S100A12) has been supposed to be a pro-inflammatory factor associated with non-infectious inflammatory diseases. However, whether S100A12 is involved in the inflammatory process of primary biliary cirrhosis (PBC) has not been shown.

METHODS

The levels of S100A12 mRNA transcripts in peripheral mononuclear blood cells (PBMCs) of 66 Chinese patients with primary biliary cirrhosis (PBC), 62 healthy controls (HC) and 55 chronic hepatitis B (CHB) were measured by qRT-PCR. S100A12 serum concentrations in 34 PBC patients were measured by ELISA.

RESULTS

The levels of S100A12 mRNA transcripts in PBMCs of patients with PBC were significantly higher than healthy controls (p < 0.01) and that of patients with CHB (p < 0.01). Importantly, the levels of S100A12 mRNA in PBMCs and S100A12 protein levels in serum were positively correlated with biochemical indicators of bile duct and hepatocyte damage.

CONCLUSION

S100A12 might participate in the damage of biliary epithelial cells and hepatocytes in PBC, and analysis of S100A12 expression could be useful as a surrogate marker for the evaluation of PBC activity.

The role of natural killer cells in autoimmune liver disease: a comprehensive review

Natural Killer (NK) cells are important players of the innate arm of the immune system and provide an early defense against pathogens and tumor-transformed cells. Peripheral blood NK (PB-NK) cells were first identified because of their ability to spontaneously kill tumor-cell targets in vitro without the need for specific antigen priming, which is the reason that they were named 'natural killer' cells. The characterization of NK cells in human tissues and body organs represented another important step forward to better understand their physiology and physiopathology. In this regard, many reports revealed over the past decade a differential anatomic distribution of NK cell subsets in several sites such as the intestine, lung, cervix, placenta and liver as well as in secondary lymphoid organs such as spleen, lymph nodes and tonsils. Among all these tissues, the liver is certainly unique as its parenchyma contains an unusually high number of infiltrating immune cells with 30-50% of total lymphocytes being NK cells. Given the constant liver intake of non-self antigens from the gastrointestinal tract via the portal vein, hepatic NK (H-NK) cells must retain a certain degree of tolerance in the context of their immune-surveillance against dangers to the host. Indeed, the breakdown of the tolerogenic state of the liver-associated immune system has been shown to induce autoimmunity. However, the role of NK cells during the course of autoimmune liver diseases is still being debated mainly because a complete characterization of H-NK cells normally resident in healthy human liver has not yet been fully disclosed. Furthermore, the differences in phenotype and functions between human and mouse H-NK cells often preclude translation of results obtained from murine models into experimental approaches to be performed in humans. Here, we provide an extensive characterization of the phenotype of H-NK cells physiologically resident in the human liver by both mentioning data available in literature and including a set of original results recently developed in our laboratory. We then review our current knowledge in regard to the contribution of H-NK cells in regulating local immune homeostasis and tolerance as well as in inducing the development of liver autoimmunity.

Distinct microRNAs expression profile in primary biliary cirrhosis and evaluation of miR 505-3p and miR197-3p as novel biomarkers

BACKGROUND AND AIMS

MicroRNAs are small endogenous RNA molecules with specific expression patterns that can serve as biomarkers for numerous diseases. However, little is known about the expression profile of serum miRNAs in PBC.

METHODS

First, we employed Illumina deep sequencing for the initial screening to indicate the read numbers of miRNA expression in 10 PBC, 5 CH-C, 5 CH-B patients and 5 healthy controls. Comparing the differentially expressed miRNAs in the 4 groups, analysis of variance was performed on the number of sequence reads to evaluate the statistical significance. Hierarchical clustering was performed using an R platform and we have found candidates for specific miRNAs in the PBC patients. Second, a quantitative reverse transcription PCR validation study was conducted in 10 samples in each group. The expression levels of the selected miRNAs were presented as fold-changes (2(-ΔΔCt)). Finally, computer analysis was conducted to predict target genes and biological functions with MiRror 2.0 and DAVID v6.7.

RESULTS

We obtained about 12 million 32-mer short RNA reads on average per sample and the mapping rates to miRBase were 16.60% and 81.66% to hg19. In the statistical significance testing, the expression levels of 81 miRNAs were found to be differentially expressed in the 4 groups. The heat map and hierarchical clustering demonstrated that the miRNA profiles from PBC clustered with those of CH-B, CH-C and healthy controls. Additionally, the circulating levels of hsa-miR-505-3p, 197-3p, and 500a-3p were significantly decreased in PBC compared with healthy controls and the expression levels of hsa-miR-505-3p, 139-5p and 197-3p were significantly reduced compared with the viral hepatitis group.

CONCLUSIONS

Our results indicate that sera from patients with PBC have a unique miRNA expression profile and that the down-regulated expression of hsa-miR-505-3p and miR-197-3p can serve as clinical biomarkers of PBC.

Prevalence of primary biliary cirrhosis in adults referring hospital for annual health check-up in Southern China

BACKGROUND

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by the presence of anti-mitocondrial autoantibodies (AMA) which has an essential role also for diagnosis. In addition, also some anti-nuclear antibodies (ANA) have been shown to be highly specific PBC. The purpose of this study was to assess the prevalence of PBC among the adults referring hospital for annual health check-up in Southern China by screening sera for PBC-specific autoantibodies.

METHODS

AMA and ANA were screened in 8,126 adults (mean age 44 ± 15 years, 48% females) by indirect immunofluorenscence (IIF). Positive sera were tested by ELISA/immunoblotting for AMA-M2, anti-sp100 and anti-gp210. A diagnosis of PBC was re-assessed six months after the initial testing.

RESULTS

Out of 8,126 individuals 35 were positive for AMA and 79 positive for ANA. Nineteen, 4, and 3 of the subjects positive for AMA and/or ANA showed reactivity for AMA-M2, anti-sp100 or gp210, respectively, further tested with ELISA/immunoblotting. Fourteen in the 39 individuals positive for AMA at IIF, AMA-M2, anti-gp210, or anti-sp100 had abnormal cholestatic liver functional indices. One definite and 3 probable PBC diagnosis could be made in 4 cases including 3 females and 1 male after half a year.

CONCLUSIONS

We found a point prevalence rate of PBC among Southern Chinese adults attending for yearly health check-up of 492 cases per million (95% CI, 128 to 1,093) and 1,558 cases per million (95% CI, 294 to 3,815) for women over 40, a finding similar to prevalence reported in other geographical areas.

Immune-mediated liver diseases: programmed cell death ligands and circulating apoptotic markers

Primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are the three major immune-mediated liver diseases. The etiologies of primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis are largely unknown, but seem to be influenced by genetic and environmental factors. Autoantibodies can be found in nearly all patients with primary sclerosing cholangitis and autoimmune hepatitis, and in the vast majority of patients with primary sclerosing cholangitis. In addition, autoimmune hepatitis is associated with high concentrations of serum globulins. Enhanced liver cell death by apoptosis has been described in all of these liver diseases, although the precise mechanisms remain unclear. In general, apoptosis can be initiated via an extrinsic pathway that is triggered by engagement of death receptors on the cell surface, or via an intrinsic pathway that is induced by mitochondrial injury and is influenced by members of the Bcl-2 family. In both pathways, effector caspases are finally activated that cleave and degrade cell structures, resulting in the release of apoptotic products into the circulation. New diagnostic tests can detect these apoptotic markers and programmed cell death ligands such as Fas and Fas-ligands, nucleosomes, caspases, cytokeratin fragments, macrophage migration inhibitory factor, soluble intracellular adhesion molecule, natural killer cells group 2D and programmed death ligands. Several of these markers have been found to be altered in tissue and/or blood of immune-mediated liver diseases, some also in nonimmune-mediated liver diseases. Beyond their potential usefulness as additional diagnostic markers, they may be valuable for the estimation of disease severity and therapy monitoring. This review summarizes current knowledge on apoptotic mechanisms, death receptor ligands and circulating apoptotic markers in immune-mediated liver diseases.