Expression of toll-like receptors and type 1 interferon specific protein MxA in biliary atresia

Bacterial translocation markers and toll-like receptors in biliary atresia following successful portoenterostomy

AIM

The gut-liver axis may contribute to pathophysiology of cholestatic liver disorders like biliary atresia (BA) by bacterial translocation (BT). Toll-like receptors (TLR) are pattern recognition receptors known to activate innate immunity and secretion of inflammatory cytokines. Herein, we examined BT-associated biomarkers and TLRs in relation to liver injury after successful portoenterostomy (SPE) in BA.

METHODS

Serum levels of lipopolysaccharide-binding protein (LBP), CD14, LAL, TNF-α, IL-6 and FABP2 along with liver expression of TLRs (TLR1, TLR4, TLR7 and TLR9), LBP and CD14 were measured during median 4.9 (1.7-10.6) years follow-up after SPE in 45 BA patients.

RESULTS

Serum LBP, CD14, TNF-α and IL-6 all increased after SPE whereas LAL and FABP-2 remained unchanged. Serum LBP correlated positively with CD14 and markers of hepatocyte injury and cholestasis, but not with Metavir fibrosis stage, transcriptional markers for fibrosis (ACTA2) or ductular reaction. Serum CD14 concentration was significantly higher in patients with portal hypertension than without. While liver expression of TLR4 and LBP remained low, TLR7 and TLR1 showed marked BA-specific increases, and TLR7 correlated with Metavir fibrosis stage and ACTA2.

CONCLUSION

BT does not seem to play a significant role in liver injury after SPE in our series of BA patients.

Distinct breast milk microbiota, cytokine, and adipokine profiles are associated with infant growth at 12 months: an in vitro host-microbe interaction mechanistic approach

Breast milk (BM) is important for adequate infant development, and it contains bioactive compounds, such as bacteria, cytokines and some adipokines which play a role in infant microbial, metabolic, and immunological maturation. However, little is known about its impact on growth and development in early life. The objective of this study was to evaluate the impact of milk microbiota, cytokine, and adipokine profiles on the risk of overweight at 12 months of life to find the possible mechanisms of host-microbe interactions. In this study, BM samples from 100 healthy women collected during 15 d after birth were included. BM microbiota was analysed by 16S rRNA gene sequencing, and cytokine and adipokine levels were measured by the Luminex approach. In addition, infant weight and length were recorded during the first 12 months and z-scores were obtained according to the WHO databases. Infants were classified as risk of overweight (ROW) and no-risk of overweight (NOROW) based on their body mass index z-score (BMIZ) and infant weight-for-length z-score (WLZ) at 12 months. In order to study host-microbe interactions, epithelial intestinal and mammary cell lines were exposed to milk microbes to assess the host response by interleukin (IL)-6 production as a potential inflammatory marker. BM was dominated by Staphylococcus and Streptococcus genera, and the most abundant cytokines were IL-6 and IL-18. Leptin levels were positively correlated with the pregestational body mass index (BMI). Higher relative abundance of the Streptococcus genus was associated with higher IL-10 and higher relative abundance of the Bifidobacterium genus was associated with lower IL-6 concentrations in milk. Infant WLZ at 12 months could be partially predicted by Streptococcus genus proportions and IL-10 and IL-18 levels in BM. BM microbiota significantly induced cytokine responses in mammary epithelial cells. Higher levels of IL-6 production were observed in mammary cells exposed to BM microbiota from mothers with ROW offspring compared to mothers with NOROW offspring. In conclusion, BM microbiota is related to the cytokine profile. IL-10 and IL-18 levels and the abundance of the Streptococcus genus could affect early infant development. Further research is needed to clarify the specific impact of BM microbiota and cytokines on infant growth and the risk of overweight.

Human poliovirus receptor contributes to biliary atresia pathogenesis by exacerbating natural-killer-cell-mediated bile duct injury

BACKGROUND AND AIMS

Natural killer (NK) cells play an important role in biliary atresia (BA) pathogenesis; human poliovirus receptor (PVR) is an important NK-cell modulator. Here, we explored the role of PVR in BA pathogenesis.

METHODS

Poliovirus receptor expression and NK cell-associated genes were detected in human BA samples and a rotavirus-induced BA mouse model using quantitative PCR and immunofluorescence staining. Chemically modified small interfering RNA silenced PVR expression in the BA model, and its effects on the population and function of intrahepatic NK cells were investigated using flow cytometry (FCM). The effects of PVR overexpression and knockdown on proliferation, apoptosis and NK-cell-mediated lysis of cultured human cholangiocytes were analysed using FCM and cell viability assays. Serum PVR, high-mobility group box 1 (HMGB1), and interleukin-1beta (IL-1beta) levels were measured in a cohort of 50 patients using ELISA.

RESULTS

Poliovirus receptor expression was upregulated in the biliary epithelium of BA patients and BA model and was positively correlated with the population and activation of intrahepatic NK cells. Silencing of PVR expression impaired the cytotoxicity of NK cells, reduced inflammation and protected mice from rotavirus-induced BA. Activation of the TLR3-IRF3 signalling pathway induced PVR expression in cultured cholangiocytes. PVR overexpression promoted proliferation and inhibited the apoptosis of cholangiocytes but exacerbated NK cell-mediated cholangiocyte lysis. Serum PVR levels were elevated in BA patients and were positively correlated with HMGB1 and IL-1beta levels.

CONCLUSIONS

Poliovirus receptor contributes to BA pathogenesis by regulating NK cell-mediated bile duct injury; PVR has the value as a biomarker of BA.

mRNA and lncRNA expression profiles of liver tissues in children with biliary atresia

Progressive liver fibrosis is the most common phenotype in biliary atresia (BA). A number of pathways contribute to the fibrosis process so comprehensive understanding the mechanisms of liver fibrosis in BA will pave the way to improve patient's outcome after operation. In this study, the differentially expressed profiles of mRNAs and long non-coding RNAs from BA and choledochal cyst (CC) liver tissues were investigated and analyzed, which may provide potential clues to clarify hepatofibrosis mechanism in BA. A total of two BA and two CC liver tissue specimens were collected, the expression level of mRNAs and lncRNAs was detected by RNA sequencing. Differentially expressed mRNAs (DEmRNAs) were functionally annotated and protein-protein interaction networks (PPI) was established to predict the biological roles and interactive relationships. Differentially expressed lncRNAs (DElncRNAs) nearby targeted DEmRNA network and DElncRNA-DEmRNA co-expression network were constructed to further explore the roles of DElncRNAs in BA pathogenesis. The expression profiles of significant DEmRNAs were validated in Gene Expression Omnibus database. A total of 2,086 DEmRNAs and 184 DElncRNAs between BA and CC liver tissues were obtained. DEmRNAs were enriched in 521 Gene Ontology terms and 71 Kyoto Encyclopedia of Genes and Genomes terms which were mainly biological processes and metabolic pathways related to immune response and inflammatory response. A total of five hub proteins (TYRO protein tyrosine kinase binding protein, C-X-C motif chemokine ligand 8, pleckstrin, Toll-like receptor 8 and C-C motif chemokine receptor 5) were found in the PPI networks. A total of 31 DElncRNA-nearby-targeted DEmRNA pairs and 2,337 DElncRNA-DEmRNA co-expression pairs were obtained. The expression of DEmRNAs obtained from RNA sequencing were verified in GSE46960 dataset, generally. The present study identified key genes and lncRNAs participated in BA associated liver fibrosis, which may present a new avenue for understanding the patho-mechanism for hepatic fibrosis in BA.

Systemic cytokine profiles in biliary atresia

Background

Inflammation and immune dysregulation persuade biliary duct injury in biliary atresia (BA), a leading cause of pediatric liver transplantation given lack of specific biomarkers. We aimed to determine associations between systemic cytokine profiles and clinical parameters in BA patients and to identify potential BA biomarkers.

Methods

Systemic levels of 27 cytokines were measured in 82 BA patients and 25 healthy controls using a multiplex immunoassay. Relative mRNA expressions of candidate cytokines in 20 BA livers and 5 non-BA livers were assessed using quantitative real-time PCR.

Results

Higher levels of 17 cytokines including IL-1β, IL-6, IL-7, IL-8, IL-9, IL-2, IL-15, eotaxin, IP-10, MCP-1, MIP-1α, MIP-1β, G-CSF, IL-1ra, IL-4, IL-5, and IL-10 and lower levels of IFN-α and PDGF were significantly associated with BA. In BA patients, increased levels of IL-7, eotaxin, IP-10, and IL-13 were significantly associated with unfavorable outcomes including jaundice, fibrosis, and portal hypertension. Indeed, systemic levels of those cytokines were significantly correlated with clinical parameters indicating jaundice, fibrosis, and hepatic dysfunction in BA patients. Out of 27 cytokines, 4 (IL-8, IP-10, MCP-1, and PDGF) had potential as sensitive and specific biomarkers of BA. Of these, higher IL-8 levels were significantly associated with reduced survival of BA. In BA livers, relative mRNA expressions of IL-8, IP-10, and MCP-1 were significantly up-regulated.

Conclusions

Higher levels of several cytokines including inflammatory cytokines, immunomodulatory cytokines, chemokines, and anti-inflammatory cytokines and lower levels of growth factors would reflect inflammatory and immune responses related to BA development. Among 27 cytokines, plasma IL-8 might have great potential as a diagnostic and prognostic biomarker for BA.

Immune Characteristics in Biliary Atresia Based on Immune Genes and Immune Cell Infiltration

BACKGROUND

Biliary atresia (BA) is a serious biliary disease in infancy. Jaundice is the most visual and prominent symptom, and it mainly involves bile duct cells leading to the loss of intrahepatic and extrahepatic bile ducts. If left untreated, it will eventually progress to liver cirrhosis. The pathogenesis of BA is not clear, and it is now generally accepted that BA is an autoimmune disease. However, few studies have revealed the infiltration of immune cells in the liver of BA from a global perspective. We used liver tissue sequencing data to predict the infiltration and relative content of immune cells in BA.

METHODS

The BA datasets GSE46960, GSE15235, and GSE84044, and patient information were downloaded from the Gene Expression Omnibus (GEO) database. After batch normalization, the differentially expressed immune genes (DE-IGs) in BA liver, normal liver, and hepatitis B liver were analyzed with the cut-off value of |log₂fold change (log₂FC)| >1 and false discovery rate (FDR) <0.05. CIBERSORT software was used to predict the proportions of 22 immune cells in all samples of the datasets.

RESULTS

73 DE-IGs have been screened out between BA and normal tissue; among them, 20 genes were highly expressed and another 53 were expressed at a low level. A total of 30 DE-IGs existed between inflammation and fibrosis livers of BA, and all of them were expressed at low levels in fibrosis livers of BA. In GO term analysis, these DE-IGs were mainly associated with the MHC protein complex, cytokine, chemokine activity, and MHC-II receptor activity. In KEGG pathway analysis, the DE-IGs were mainly enriched in pathways of Th1 and Th2 cell differentiation, Th17 cell differentiation, IL-17 signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway, and autoimmune diseases. There were significant differences in immune infiltration among different pathological types of BA, and there were also obvious differences in immune infiltration of hepatitis B as a disease control of BA.

CONCLUSION

Based on immune genes and immune cell infiltration, this study reveals the immune characteristics of BA from a global point of view, which provides a new perspective for understanding the pathogenesis of BA and provides a direction for the diagnosis and treatment of BA.

Pattern recognition receptors in health and diseases

Pattern recognition receptors (PRRs) are a class of receptors that can directly recognize the specific molecular structures on the surface of pathogens, apoptotic host cells, and damaged senescent cells. PRRs bridge nonspecific immunity and specific immunity. Through the recognition and binding of ligands, PRRs can produce nonspecific anti-infection, antitumor, and other immunoprotective effects. Most PRRs in the innate immune system of vertebrates can be classified into the following five types based on protein domain homology: Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma-2 (AIM2)-like receptors (ALRs). PRRs are basically composed of ligand recognition domains, intermediate domains, and effector domains. PRRs recognize and bind their respective ligands and recruit adaptor molecules with the same structure through their effector domains, initiating downstream signaling pathways to exert effects. In recent years, the increased researches on the recognition and binding of PRRs and their ligands have greatly promoted the understanding of different PRRs signaling pathways and provided ideas for the treatment of immune-related diseases and even tumors. This review describes in detail the history, the structural characteristics, ligand recognition mechanism, the signaling pathway, the related disease, new drugs in clinical trials and clinical therapy of different types of PRRs, and discusses the significance of the research on pattern recognition mechanism for the treatment of PRR-related diseases.

Current Concepts of Biliary Atresia and Matrix Metalloproteinase-7: A Review of Literature

Biliary atresia (BA) is a rare cholangiopathy of infancy in which the bile ducts obliterate, leading to profound cholestasis and liver fibrosis. BA is hypothesized to be caused by a viral insult that leads to over-activation of the immune system. Patients with BA are surgically treated with a Kasai portoenterostomy (KPE), which aims to restore bile flow from the liver to the intestines. After KPE, progressive liver fibrosis is often observed in BA patients, even despite surgical success and clearance of their jaundice. The innate immune response is involved during the initial damage to the cholangiocytes and further differentiation of the adaptive immune response into a T-helper 1 cell (Th1) response. Multiple studies have shown that there is continuing elevation of involved cytokines that can lead to the progressive liver fibrosis. However, the mechanism by which the progressive injury occurs is not fully elucidated. Recently, matrix metalloproteinase-7 (MMP-7) has been investigated to be used as a biomarker to diagnose BA. MMPs are involved in extracellular matrix (ECM) turnover, but also have non-ECM related functions. The role of MMP-7 and other MMPs in liver fibrosis is just starting to be elucidated. Multiple studies have shown that serum MMP-7 measurements are able to accurately diagnose BA in a cohort of cholestatic patients while hepatic MMP-7 expression correlated with BA-related liver fibrosis. While the mechanism by which MMP-7 can be involved in the pathophysiology of BA is unclear, MMP-7 has been investigated in other fibrotic pathologies such as renal and idiopathic pulmonary fibrosis. MMP-7 is involved in Wnt/β-catenin signaling, reducing cell-to-cell contact by shedding of E-cadherin, amplifying inflammation and fibrosis via osteopontin (OPN) and TNF-α while it also appears to play a role in induction of angiogenesis This review aims to describe the current understandings of the pathophysiology of BA. Subsequently, we describe how MMP-7 is involved in other pathologies, such as renal and pulmonary fibrosis. Then, we propose how MMP-7 can potentially be involved in BA. By doing this, we aim to describe the putative role of MMP-7 as a prognostic biomarker in BA and to provide possible new therapeutic and research targets that can be investigated in the future.

Biliary atresia: pathology, etiology and pathogenesis

Biliary atresia is a progressive fibrosing obstructive cholangiopathy of the intrahepatic and extrahepatic biliary system, resulting in obstruction of bile flow and neonatal jaundice. Histopathological findings in liver biopsies include the expansion of the portal tracts, with edematous fibroplasia and bile ductular proliferation, with bile plugs in duct lumen. Lobular morphological features may include variable multinucleate giant cells, bilirubinostasis and hemopoiesis. The etiopathogenesis of biliary atresia is multifactorial and multiple pathomechanisms have been proposed. Experimental and clinical studies have suggested that viral infection initiates biliary epithelium destruction and release of antigens that trigger a Th1 immune response, which leads to further injury of the bile duct, resulting in inflammation and obstructive scarring of the biliary tree. It has also been postulated that biliary atresia is caused by a defect in the normal remodelling process. Genetic predisposition has also been proposed as a factor for the development of biliary atresia.

Innate Immunity and Pathogenesis of Biliary Atresia

Biliary atresia (BA) is a devastating fibro-inflammatory disease characterized by the obstruction of extrahepatic and intrahepatic bile ducts in infants that can have fatal consequences, when not treated in a timely manner. It is the most common indication of pediatric liver transplantation worldwide and the development of new therapies, to alleviate the need of surgical intervention, has been hindered due to its complexity and lack of understanding of the disease pathogenesis. For that reason, significant efforts have been made toward the development of experimental models and strategies to understand the etiology and disease mechanisms and to identify novel therapeutic targets. The only characterized model of BA, using a Rhesus Rotavirus Type A infection of newborn BALB/c mice, has enabled the identification of key cellular and molecular targets involved in epithelial injury and duct obstruction. However, the establishment of an unleashed chronic inflammation followed by a progressive pathological wound healing process remains poorly understood. Like T cells, macrophages can adopt different functional programs [pro-inflammatory (M1) and resolutive (M2) macrophages] and influence the surrounding cytokine environment and the cell response to injury. In this review, we provide an overview of the immunopathogenesis of BA, discuss the implication of innate immunity in the disease pathogenesis and highlight their suitability as therapeutic targets.

Peripheral blood and hepatic Toll-like receptor 7 expression and interferon lambda 1 levels in chronic hepatitis C: Relation to virus replication and liver injury

BACKGROUND AND AIM

Toll-like receptor 7 (TLR7) can recognize single-stranded RNA viruses like hepatitis C virus (HCV) with subsequent induction of different interferon (IFN) types including IFN lambda (IFNL), which activate an immediate anti-viral response. However, the role of TLR7 in inflammation and fibrosis, characteristics of HCV-induced liver injury, is still controversial. The present work was designed to investigate the potential role of TLR7 and IFNL1 in chronic hepatitis C (CHC) in relation to viral replication and liver injury.

METHODS

Forty two treatment-naïve patients with CHC and 20 healthy subjects were enrolled in the study. TLR7 expression on peripheral blood CD14+ monocytes was studied by color flow cytometry and the frequency of TLR7+CD14+ cells was expressed as percentage of total monocyte count. Quantification of IFNL1 levels in serum was determined using enzyme-linked immunosorbant assay. Liver biopsies were examined for assessment of histological activity grade (A0-A3) and fibrosis stage (F0-F4) according to METAVIR scoring system as well as steatosis grade. Immunohistochemical staining was performed using human antibodies against TLR7 and IFNL1 and was scored semi-quantitatively (score 0-3). Hepatic expression of TLR7 and IFNL1 was further classified using a two-grade scale as low expression (score 0 or 1) and high expression (score 2 or 3).

RESULTS

Percentages of circulating TLR7+CD14+ monocytes and serum IFNL1 levels were significantly higher in patients with CHC than in healthy controls (P = 0.025 and P < 0.001 respectively) and were positively correlated with corresponding hepatic TLR7 and IFNL1 expression (P < 0.001 and P = 0.010 respectively). Significantly lower peripheral blood and hepatic TLR7 expression and IFNL1 levels were found in patients with viral loads between 200,000-600,000 IU/ml and >600,000 IU/ml than in those with viral load <200,000 IU/ml (P < 0.05), in patients with severe necroinflammation than in those with mild-to-moderate necroinflammation (P < 0.05) and in patients with advanced fibrosis than in those with early fibrosis (P < 0.01). Also, changes in TLR7 expression and IFNL1 production in peripheral blood and the liver were inversely correlated with serum levels of aspartate and alanine aminotransferases (P < 0.05) and HCV RNA (P < 0.01), histological activity grade (P < 0.01) and fibrosis stage (P < 0.01). By plotting receiver operating characteristics (ROC) curve, serum IFNL1 showed higher sensitivity and specificity than percentages of circulating TLR7+CD14+ monocytes in discriminating patients with CHC according to the severity of hepatic necroinflammation (area under the curve (AUC) = 0.901 vs. 0.816 respectively) and fibrosis (AUC = 0.971 vs. 0.825 respectively) at a cut-off value of 44.75 pg/ml and 10.25% respectively.

CONCLUSIONS

TLR7 activation and IFNL1 production in CHC may play an important role in controlling viral replication and limiting hepatic inflammation and fibrosis and their downregulation may result in viral persistence and disease progression. The immunoregulatory role of TLR7-IFNL1 pathway in the pathogenesis of chronic HCV infection should be further studied. Clinical trials with a large number of patients are needed to assess the usefulness of serum IFNL1 as a potential biomarker for severity of liver injury in chronic HCV infection and other liver diseases.

Impact of human milk on the transcriptomic response of fetal intestinal epithelial cells reveals expression changes of immune-related genes

Human milk, the best food for infants, is a dynamic and complex fluid that directly influences the immune system and microbiota establishment.

Human milk, the best food for infants, is a dynamic and complex fluid that directly influences the immune system and microbiota establishment. The protective role of human milk is well known although the mechanisms behind it still need to be uncovered. This study aimed to characterize the impact of human milk in the immature intestine of newborns by analyzing the global transcriptomic response of the FHs 74 int cell line (ATCC CCL-241). The expression of intestinal keratins and other genes with a well-annotated intestinal or epithelial function validated FHs 74 int derived from the fetal small intestine as a model of the intestinal epithelium of newborns. Cells exposed to skimmed human milk showed seventeen differentially expressed genes, most of them up-regulated, including four chemokine genes (CXCL1, CXCL2, CXCL3 and CXCL10) and other immune-related genes. qRT-PCR and ELISA analysis confirmed the microarray data and indicated a different pattern of expression upon milk exposure in FHs 74 int as compared to the adult tumorigenic Caco-2 cell line. The evaluation of the functional significance of these transcriptomic changes reveals that human milk exposure may contribute to the regulation of the inflammatory response in the intestine during the perinatal period, which is characterized by the immaturity of the immune system and a pro-inflammatory phenotype.

Update on investigations pertaining to the pathogenesis of biliary atresia

Biliary atresia is a devastating biliary disease of neonates that results in liver transplantation for the vast majority. The etiology of biliary atresia is unknown and is likely multifactorial, with components of genetic predisposition, environmental trigger and autoimmunity contributing to disease pathogenesis. This review highlights recent work related to investigations of disease pathogenesis in biliary atresia.

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Dendritic Cells Regulate Treg-Th17 Axis in Obstructive Phase of Bile Duct Injury in Murine Biliary Atresia

Several cell types are considered to be effector cells in bile duct injury in rhesus rotavirus (RRV)-induced experimental biliary atresia (BA). Here, we identified an increased T helper 17 (Th17) cell population in a BA mode. By depleting the Th17 cells, the BA symptoms (onset of jaundice, acholic stools and retarded growth) were attenuated and the survival rate was improved. Furthermore, we found that in mice with BA, the percentage of CD4⁺CD25^highFoxp3⁺ T regulatory (Treg) cells decreased along with the increased percentage of Th17 cells. However, the absolute numbers of Treg and Th17 cells were both increased in liver of RRV-injected mice compared to saline-injected mice. The proportion of Th17 cells at 7 days post-infection was decreased if Treg cells isolated from normal adult mice, but not Treg cells from the livers of mice with BA, were intraperitoneally transferred on day 5 of life. In vitro experiments also showed that Treg cells from mice with BA had a diminished suppressive effect on Th17 cell generation. To determine the mechanisms, we investigated the production of cytokines in the liver. The level of IL-6, which has been shown to be abundantly secreted by activated dendritic cells (DCs), was remarkably elevated. Importantly, in a Treg/Th17 cell suppression assay, IL-6 was demonstrated to paralyze the Treg cells’ suppressive effect on Th17 cells and eventually the unrestrained increase of Th17 cells contributed to bile duct injury. In conclusion, the DC-regulated Treg-Th17 axis, probably in conjunction with other effector T cells, aggravates progressive inflammatory injury at the time of ductal obstruction.

Rotavirus Infects Human Biliary Epithelial Cells and Stimulates Secretion of Cytokines IL-6 and IL-8 via MAPK Pathway

Biliary atresia (BA) is an infantile inflammatory cholangiopathy of unknown etiology although epidemiologic studies and animal models utilizing rotavirus (RV) have suggested a role for viral infection. Proinflammatory and profibrotic cytokines have been detected in infants with BA. The purpose of our study was to investigate the susceptibility of human cholangiocytes (H69 cells) to infection with RRV and to determine if this infection resulted in cytokine secretion. Infection of H69 cells by RRV was noncytolytic and resulted in a time-dependent increase in the release of both infectious virions and cytokines IL-6 and IL-8 into the supernate. The greatest difference in cytokine supernatant levels between infected and mock-infected cells was noted at 24 hours postinfection (h p.i.) for IL-8, 556 ± 111 versus 77 ± 68 pg/mL (p < 0.0001), and at 48 h p.i. for IL-6, 459 ± 64 versus 67 ± 2 pg/mL (p < 0.0001). Production of both cytokines following RRV infection was significantly reduced by pretreating the H69 cells with inhibitors of mitogen-activated protein kinase (MAPK). Conclusion. RRV can infect human cholangiocytes resulting in the production of proinflammatory and profibrotic cytokines via the MAPK pathway. RRV-infected H69 cells could be a useful model system for investigating the viral hypothesis of BA.

Interleukin-8: A critical chemokine in biliary atresia

Biliary atresia (BA) is characterized by periductular inflammation and fibrosis and is associated with the progressive obliteration of the bile ducts. The induction and maintenance of systemic and local inflammatory responses plays a pivotal role in this process. Interleukin-8 (IL-8) is an important mediator of inflammation and the immune response in human disease. IL-8 is overexpressed in BA, and its expression positively correlates with inflammation and liver fibrosis. In this review, we focus on the available evidence, recent insights, and future clinical and preclinical possibilities regarding the role of IL-8 in BA.

Immune function of biliary epithelial cells

Biliary epithelial cells (BECs) are the epithelial cells lining the bile duct, constituting the biliary system's first line of defense against pathogenic microorganisms. BECs can express many kinds of pathogen recognition receptors, activate intracellular signal transduction pathways, initiate the internal microbial defense system, including the release of pro-inflammatory cytokines and chemokines and antibacterial peptide synthesis, and maintain the integrity of the biliary epithelium. By expressing and releasing adhesion molecules and immune mediators, BECs interact with other cells in the liver, such as lymphocytes and Kupffer's cells. BECs are involved in a complex feedback mechanism of liver cells and thereby regulate the response to microbial infection. BECs actively participate in the biliary duct mucosal immunity and form an important component of liver immunity.

Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease

Biliary atresia (BA) is a progressive fibroinflammatory obstruction of extrahepatic bile ducts that presents as neonatal cholestasis. Due to the overlap in clinical, biochemical, and histological features with other causes of cholestasis, the diagnosis requires an intraoperative cholangiogram. Thus, we determined whether diseased livers express a gene expression signature unique to BA. Applying stringent statistical analysis to a genome-wide liver expression platform of 64 infants with BA at the time of diagnosis, 14 age-appropriate subjects with intrahepatic cholestasis as diseased controls and seven normal controls, we identified 15 genes uniquely expressed in BA with an accuracy of 92.3%. Among these genes, IL8 and LAMC2 were sufficient to classify subjects with BA distinctly from diseased controls with an area under the curve of 0.934 (95% confidence interval [CI]: 0.84-1.03), sensitivity of 96.9%, and specificity of 85.7% using their combined first principal component. Direct measurement of interleukin (IL)8 protein in the serum, however, was not different between the two groups. To investigate whether the liver-restricted increase in IL8 was relevant to disease pathogenesis, we inactivated the signaling of IL8 homologs by genetic targeting of the Cxcr2 receptor in a murine model of experimental BA. Disruption of Cxcr2 shortened the duration of cholestasis, decreased the incidence of bile duct obstruction, and improved survival above wild-type neonatal mice.

CONCLUSION

The hepatic expression of IL8 and LAMC2 has high sensitivity for BA at diagnosis and may serve as a biomarker of disease, with an important role for the IL8 signaling in experimental BA.

Role of myeloid differentiation factor 88 in Rhesus rotavirus-induced biliary atresia

BACKGROUND

Biliary atresia (BA) is a unique neonatal disease resulting from inflammatory and fibrosing obstruction of the extrahepatic biliary tree. Previous studies have demonstrated the critical role of innate immunity and the Th1 response to activated inflammatory cells and overexpressed cytokines in the pathogenesis of BA. Myeloid differentiation factor 88 (MyD88) is a critical adaptor molecule that has been shown to play a crucial role in immunity. We investigated the role of MyD88 in the inflammatory response and development of cholangiopathy in murine BA.

METHODS

MyD88 knockout (MyD88(-/-)) and wild-type (WT) BALB/c pups were injected with Rhesus rotavirus or saline on day 1 of life. The mice were monitored for clinical symptoms of BA, including jaundice, acholic stools, bilirubinuria, and death. The liver and extrahepatic bile ducts were harvested for histologic evaluation and the quantification of viral content, determination of cytokine expression, and detection of inflammatory cells.

RESULTS

Rhesus rotavirus infection produced symptoms in 100% of both MyD88(-/-) and WT pups, with survival of 18% of WT and 0% of MyD88(-/-) mice. Histologic analysis demonstrated bile duct obstruction in both MyD88(-/-) and WT mice. Viral titers obtained 7 d after infection and expression of interferon-γ and tumor necrosis factor-α at day 3, 5, 8, and 12 after infection revealed no significant differences between the WT and MyD88(-/-) mice. Flow cytometry demonstrated similar levels of activated CD8+ T cells and natural killer cells.

CONCLUSIONS

The pathogenesis of murine BA is independent of the MyD88 signaling inflammatory pathway, suggesting alternative mechanisms are crucial in the induction of the model.

Inhibiting heme oxygenase-1 attenuates rat liver fibrosis by removing iron accumulation

AIM: To investigate the effects of the heme oxygenase (HO)-1/carbon monoxide system on iron deposition and portal pressure in rats with hepatic fibrosis induced by bile duct ligation (BDL).

METHODS: Male Sprague-Dawley rats were divided randomly into a Sham group, BDL group, Fe group, deferoxamine (DFX) group, zinc protoporphyrin (ZnPP) group and cobalt protoporphyrin (CoPP) group. The levels of HO-1 were detected using different methods. The serum carboxyhemoglobin (COHb), iron, and portal vein pressure (PVP) were also quantified. The plasma and mRNA levels of hepcidin were measured. Hepatic fibrosis and its main pathway were assessed using Van Gieson’s stain, hydroxyproline, transforming growth factor-β1 (TGF-β1), nuclear factor-E2-related factor 2 (Nrf2), matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1).

RESULTS: Serum COHb and protein and mRNA expression levels of HO-1 and Nrf2 were increased in the BDL group compared with the Sham group and were much higher in the CoPP group. The ZnPP group showed lower expression of HO-1 and Nrf2 and lower COHb. The levels of iron and PVP were enhanced in the BDL group but were lower in the ZnPP and DFX groups and were higher in the CoPP and Fe groups. Hepcidin levels were higher, whereas superoxide dismutase levels were increased and malonaldehyde levels were decreased in the ZnPP and DFX groups. The ZnPP group also showed inhibited TGF-β1 expression and regulated TIMP-1/MMP-2 expression, as well as obviously attenuated liver fibrosis.

CONCLUSION: Reducing hepatic iron deposition and CO levels by inhibiting HO-1 activity though the Nrf2/Keap pathway could be helpful in improving hepatic fibrosis and regulating PVP.

The dynamic biliary epithelia: molecules, pathways, and disease

Cholangiocytes, the cells lining bile ducts, are a heterogenous, highly dynamic population of epithelial cells. While these cells comprise a small fraction of the total cellular component of the liver, they perform the essential role of bile modification and transport of biliary and blood constituents. From a pathophysiological standpoint, cholangiocytes are the target of a diverse group of biliary disorders, collectively referred to as the cholangiopathies. To date, the cause of most cholangiopathies remains obscure. It is known, however, that cholangiocytes exist in an environment rich in potential mediators of cellular injury, express receptors that recognize potential injurious insults, and participate in portal tract repair processes following hepatic injury. As such, cholangiocytes may not be only a passive target, but are likely directly and actively involved in the pathogenesis of cholangiopathies. Here, we briefly summarize the characteristics of the reactive cholangiocyte and cholangiocyte responses to potentially injurious endogenous and exogenous molecules, and in addition, present emerging concepts in our understanding of the etiopathogenesis of several cholangiopathies.

Advances in cholangiocyte immunobiology

Cholangiocytes, or bile duct epithelia, were once thought to be the simple lining of the conduit system comprising the intra- and extrahepatic bile ducts. Growing experimental evidence demonstrated that cholangiocytes are in fact the first line of defense of the biliary system against foreign substances. Experimental advances in recent years have unveiled previously unknown roles of cholangiocytes in both innate and adaptive immune responses. Cholangiocytes can release inflammatory modulators in a regulated fashion. Moreover, they express specialized pattern-recognizing molecules that identify microbial components and activate intracellular signaling cascades leading to a variety of downstream responses. The cytokines secreted by cholangiocytes, in conjunction with the adhesion molecules expressed on their surface, play a role in recruitment, localization, and modulation of immune responses in the liver and biliary tract. Cholangiocyte survival and function is further modulated by cytokines and inflammatory mediators secreted by immune cells and cholangiocytes themselves. Because cholangiocytes act as professional APCs via expression of major histocompatibility complex antigens and secrete antimicrobial peptides in bile, their role in response to biliary infection is critical. Finally, because cholangiocytes release mediators critical to myofibroblastic differentiation of portal fibroblasts and hepatic stellate cells, cholangiocytes may be essential in the pathogenesis of biliary cirrhosis.

Selective activation of Toll-like receptor 7 in activated hepatic stellate cells may modulate their profibrogenic phenotype

Cholestatic liver injury may activate HSCs (hepatic stellate cells) to a profibrogenic phenotype, contributing to liver fibrogenesis. We have previously demonstrated the involvement of TLR (Toll-like receptor) 7 in the pathogenesis of biliary atresia. In the present study we investigated the ability of TLR7 to modulate the profibrogenic phenotype in HSCs. Obstructive jaundice was associated with significant down-regulation of TLR7. Primary HSCs isolated from BDL (bile duct ligation) rats with obstructive jaundice exhibited reduced expression of TLR7 and increased expression of α-SMA (α-smooth muscle actin) and collagen-α1 compared with sham rats, reflecting HSC-mediated changes. Treatment of primary activated rat HSCs and rat T6 cells with CL075, a TLR7 and TLR8 ligand, significantly decreased expression of MCP-1 (monocyte chemotactic protein-1), TGF-β1 (transforming growth factor-β1), collagen-α1 and MMP-2 (matrix metalloproteinase-2), and inhibited cell proliferation and migration. In contrast, silencing TLR7 expression with shRNA (short hairpin RNA) in T6 cells effectively blocked the effects of CL075 stimulation, reversing the changes in MCP-1, TGF-β1 and collagen-α1 expression and accelerating cell migration. Our results indicate that obstructive jaundice is associated with down-regulation of TLR7 and up-regulation of profibrogenic gene expression in HSCs. Selective activation of TLR7 may modulate the profibrogenic phenotype in activated HSCs associated with cholestatic liver injury.

Clues to the etiology of bile duct injury in biliary atresia

Biliary atresia (BA) is an infantile obstructive cholangiopathy of unknown etiology with suboptimal therapy, which is responsible for 40 to 50% of all pediatric liver transplants. Although the etiology of bile duct injury in BA in unknown, it is postulated that a pre- or perinatal viral infection initiates cholangiocyte apoptosis and release of antigens that trigger a Th1 immune response that leads to further bile duct injury, inflammation, and obstructive fibrosis. Humoral immunity and activation of the innate immune system may also play key roles in this process. Moreover, recent investigations from the murine BA model and human data suggest that regulatory T cells and genetic susceptibility factors may orchestrate autoimmune mechanisms. What controls the coordination of these events, why the disease only occurs in the first few months of life, and why a minority of infants with perinatal viral infections develop BA are remaining questions to be answered.

A high serum interleukin-12p40 level prior to Kasai surgery predict a favourable outcome in children with biliary atresia

BACKGROUND

Biliary atresia (BA) is a paediatric cholestatic disease characterized by a progressive fibro-inflammation of the biliary tree. Current treatment of choice is to establish good bile flow via the Kasai operation.

AIMS

We aimed to identify outcome-predictive serum biomarkers in BA infant.

METHODS

Thirty-three BA children recruited from 1986 to 2007 served as the baseline-study group. An additional 11 children recruited from 2008 to 2011 served as the validation group. Serum samples were collected immediately before and 6 months after the Kasai operation for the assessment of serum cytokines, including tumour necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), interferon-γ (IFN-γ), interleukin-2 (IL-2), IL-10, IL-12p40 and IL-12p70 as the candidate biomarkers.

RESULTS

Increased serum TGF-β levels indicated a lower Knodell hepatitis activity index at Kasai operation. The serum TGF-β levels declined after the operation. Serum IL-12p40 levels before the Kasai operation were higher in the subjects with a 3-month jaundice-free status than in others (P = 0.001). A serum pre-operative IL-12p40 level of 33 pg/ml was predictive of a 3-month jaundice-free status after surgery (positive predictive value=81.0%; negative predictive value=83.3%). This biomarker was also predictive of a better outcome, in terms of 3-year survival with native liver (risk ratio [RR = 4.00]; P < 0.001), and 3-year jaundice-free survival with native liver (RR = 12.00; P < 0.001). We confirmed the predictive power of a high pre-operative IL-12p40 level on 3-month jaundice-free status in the validation group.

CONCLUSIONS

The pre-operative IL-12p40 level was a good predictive biomarker of clinical outcome in children with BA undergoing the Kasai operation.

Down-regulation of Toll-like receptor 7 expression in hepatitis-virus-related human hepatocellular carcinoma

Toll-like receptors (TLRs) play a pivotal role in innate immunity, controlling inflammatory responses, and further development of adaptive immunity. Hepatitis virus can establish chronic infection, and the associated inflammatory responses are important determinants of virus-associated liver damage. However, the contributions of the host immune system to chronic presence of virus are not clear in patients with hepatitis virus infection. Chronic inflammatory conditions caused by persistent hepatitis virus infections and interferon (IFN)-γ-related immunopathology are known to be related to carcinogenesis. To gain insight into the role of immune modulation in the pathogenesis of hepatocellular carcinoma (HCC), we studied the expression of TLR7 in cancerous and non-cancerous liver tissue from 87 patients with HCC. Our results showed that TLR7 is significantly down-regulated in neoplastic hepatocytes (P < .001), especially in the patients with hepatitis B (n = 52) or C (n = 24) virus infection. We confirmed this decreased TLR7 expression by quantitative analysis of mRNA using real-time reverse transcription-polymerase chain reaction in 26 liver specimens of HCC patients. Using serial deletion analysis of the TLR7 promoter, a hepatocyte-specific regulatory region was found at nucleotides -156 to -98 in the TLR7 promoter. Furthermore, the effects of IFN-γ on TLR7 expression in a hepatoma cell line (HepG2) were investigated in vitro. We demonstrated that IFN-γ significantly decreased TLR7 promoter activity and expression in a dose-dependent manner. We thus propose that hepatitis virus induces down-regulation of TLR7 gene expression through IFN-γ, thereby modulating inflammatory signaling in hepatoma cells.

Biliary atresia: cellular dynamics and immune dysregulation

The cause of biliary atresia is unknown; in the past few decades, the majority of investigations related to its pathogenesis have centered on viral infections and immunity. The acquired or perinatal form of biliary atresia entails a progressive inflammatory injury of bile ducts, leading to fibrosis and obliteration of both the extrahepatic and intrahepatic bile ducts. Theories of pathogenesis include viral infection, chronic inflammatory or autoimmune-mediated bile duct injury, and abnormalities in bile duct development. This review will focus solely on human studies pertaining to a potential viral trigger of bile duct injury at diagnosis and provide insight into the interplay of the innate and adaptive immune responses in the pathogenesis of disease.

Increased hepatic expression of TLR2 and TLR4 in the hepatic inflammation-fibrosis-carcinoma sequence

We evaluated expression of TLR2, TLR4 and proinflammatory genes [NF-κB, TNF-α, cyclooxygenase-2 (COX-2)] in liver samples of patients in different stages of liver disease. Fifteen patients with unexplained transaminases elevation (reference group), 22 with viral chronic hepatitis (hepatitis group), 14 with virus-induced severe fibrosis/cirrhosis (cirrhosis group) and 10 with hepatocarcinoma (hepatocarcinoma group) were consecutively included in the study. Quantification of TLR2, TLR4, NF-κB, TNF-α and COX-2 mRNA was done by real-time RT-PCR and TLR2 and TLR4 protein expression was evaluated by immunohistochemistry. Compared with reference, TLR2 and TLR4 mRNA was increased in hepatitis (TLR2: 2.66 ± 0.69; TLR4: 3.11 ± 0.79; P < 0.05) and cirrhosis (TLR2: 2.14 ± 0.5; TLR4: 1.74 ± 0.27; P < 0.05) and decreased in hepatocarcinoma (TLR2: 0.48 ± 0.15; TLR4: 0.54 ± 0.10; P < 0.05). This associated with increased TNF-α and COX-2 mRNA in hepatitis (TNF-α: 3.24 ± 0.79; COX-2: 2.47 ± 0.36; P < 0.05) and cirrhosis (TNF-α: 1.73 ± 0.28; COX-2: 1.8 ± 0.35, P < 0.05), whereas NF-κB mRNA was increased in hepatitis (2.42 ± 0.31; P < 0.05) and unchanged in cirrhosis (1.34 ± 0.17; P = 0.3). Hepatocarcinoma presented increased COX-2 mRNA (1.63 ± 0.15; P < 0.05) and maintained (at decreased levels) mRNA of NF-κB (0.52 ± 0.12) and TNF-α (0.52 ± 0.12; P < 0.05, all genes). Immunohistochemistry confirmed increased expression of TLR2 and TLR4 in hepatitis and cirrhosis and maintained expression in hepatocarcinoma. Upregulation of TLR2, TLR4 and their proinflammatory mediators is associated with virus-induced hepatic IFC sequence.

Cholangiopathy with respect to biliary innate immunity

Biliary innate immunity is involved in the pathogenesis of cholangiopathies in cases of biliary disease. Cholangiocytes possess Toll-like receptors (TLRs) which recognize pathogen-associated molecular patterns (PAMPs) and play a pivotal role in the innate immune response. Tolerance to bacterial PAMPs such as lipopolysaccharides is also important to maintain homeostasis in the biliary tree, but tolerance to double-stranded RNA (dsRNA) is not found. Moreover, in primary biliary cirrhosis (PBC) and biliary atresia, biliary innate immunity is closely associated with the dysregulation of the periductal cytokine milieu and the induction of biliary apoptosis and epithelial-mesenchymal transition (EMT), forming in disease-specific cholangiopathy. Biliary innate immunity is associated with the pathogenesis of various cholangiopathies in biliary diseases as well as biliary defense systems.

Toll-like receptor mRNA expression in liver tissue from patients with biliary atresia

BACKGROUND AND AIM

Inappropriate host immunological reactions against unknown ligands via the Toll-like receptor (TLR) cascades may trigger progressive inflammatory biliary destruction that manifests as biliary atresia (BA) in newborns or infants. The aim of the study was to clarify the role of the innate immune system in the development of BA.

PATIENTS AND METHODS

Liver tissue was obtained from 49 patients with pediatric hepatobiliary diseases: 19 with BA, 21 with choledochal cysts, and 9 with other hepatobiliary diseases. BA samples obtained during the initial portoenterostomy and reoperation or liver transplantation (LT) were classified as early and late BA groups, respectively. Of the early BA group, those requiring LT were designated as the LT group, and the others were designated as the non-LT group. The mRNA expression levels of TLRs 2, 3, 4, 7, and 8 were determined by real-time quantitative reverse transcription-polymerase chain reaction and were compared between groups. The correlation between TLR mRNA expression level and age at sampling was examined for each TLR in the patients with BA.

RESULTS

TLR8 mRNA, encoding the receptor for single-stranded RNA, was significantly higher in the early BA group, compared with non-BA groups (P = 0.008). Within the BA group, mRNA levels of TLRs 2 and 8 were significantly higher in the early group than in the late group (P = 0.02 and 0.006, respectively), despite there being no significant correlation between TLR mRNA expression and age at sampling, except for TLR7 (r = 0.77, P = 0.001). Compared with the non-LT group, the LT group demonstrated significantly higher mRNA expression of TLRs 3 and 7 (P = 0.02 and 0.01, respectively).

CONCLUSIONS

Innate immune responses may contribute to the initiation and progression of BA. Severe inflammation characteristic of BA around the time of the first operation may abate postoperatively, but determination of selected TLR mRNA expression levels in the liver at the time of Kasai portoenterostomy may assist in predicting the prognosis of patients with BA.

Toll-like receptors in secondary obstructive cholangiopathy

Secondary obstructive cholangiopathy is characterized by intra- or extrahepatic bile tract obstruction. Liver inflammation and structural alterations develop due to progressive bile stagnation. Most frequent etiologies are biliary atresia in children, and hepatolithiasis, postcholecystectomy bile duct injury, and biliary primary cirrhosis in adults, which causes chronic biliary cholangitis. Bile ectasia predisposes to multiple pathogens: viral infections in biliary atresia; Gram-positive and/or Gram-negative bacteria cholangitis found in hepatolithiasis and postcholecystectomy bile duct injury. Transmembrane toll-like receptors (TLRs) are activated by virus, bacteria, fungi, and parasite stimuli. Even though TLR-2 and TLR-4 are the most studied receptors related to liver infectious diseases, other TLRs play an important role in response to microorganism damage. Acquired immune response is not vertically transmitted and reflects the infectious diseases history of individuals; in contrast, innate immunity is based on antigen recognition by specific receptors designated as pattern recognition receptors and is transmitted vertically through the germ cells. Understanding the mechanisms for bile duct inflammation is essential for the future development of therapeutic alternatives in order to avoid immune-mediated destruction on secondary obstructive cholangiopathy. The role of TLRs in biliary atresia, hepatolithiasis, bile duct injury, and primary biliary cirrhosis is described in this paper.

Glucocorticoid modulates high-mobility group box 1 expression and Toll-like receptor activation in obstructive jaundice

BACKGROUND

Obstructive jaundice is associated with bacterial translocation and inflammatory cytokine induction. It is unknown if toll-like receptors (TLRs) and their upstream molecule high mobility group box-1 (HMGB1) are involved in the pathogenetic mechanism and if glucocorticoid is effective in modulating the process.

MATERIALS AND METHODS

A rat model of cholestasis by ligation of the extrahepatic bile duct (BDL) for 2 wk was created. TLRs, interferon regulatory factors (IRFs), IL-6, IL-8, antimicrobial peptide β-defensin, and cathelicidin, as well as HMGB1 expressions were studied by using real-time quantitative reverse transcription-polymerase chain reaction, immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assay (ELISA). Glucocorticoid treatment was applied to a group of BDL rats.

RESULTS

Obstructive jaundice for 2 wk was associated with significant up-regulation of TLR1, 2, 4, 6, 7, and 9 mRNA expressions. There were significant increases of liver IRF5, IL-6, and β-defensin 1 mRNA levels in the BDL rats than in the sham and nonoperative control rats, which were associated with significant increase of immunoreactive IRF5 protein staining in the nucleus of Kupffer cells and neutrophils. Hepatic HMGB1 expression and release into serum were significantly elevated in the cholestatic rats than in the sham and control rats. Glucocorticoid treatment significantly decreased hepatic HMGB1 expression and release into serum, which was associated with significantly decreased hepatic TLR4 mRNA expression in the cholestatic rats.

CONCLUSIONS

The results indicate that obstructive jaundice may induce hepatic HMGB1 expression with activation of TLR4 and a number of downstream signaling molecules, which can be reversed by glucocorticoid administration.

Cholestasis downregulate hepcidin expression through inhibiting IL-6-induced phosphorylation of signal transducer and activator of transcription 3 signaling

Hepcidin is downregulated during progressive cholestasis in biliary atresia, but the mechanism is unknown. To verify whether downregulation of hepcidin is specific to cholestasis irrespective of the patient's age, we first analyzed liver hepcidin mRNA and protein expression in adults with primary biliary cirrhosis (PBC) (n=4), non-cholestatic cirrhosis (n=19) and in controls (n=9). We evaluated the tyrosine phosphorylation of signal transducer and activator of transcription 3 (pSTAT3) expressions in the liver sections. A rat model of cholestasis by ligation of the extrahepatic bile duct (BDL) was created, and lipopolysaccharide (LPS)-induced cholangitis in cholestatic rats 2 weeks after BDL was also established to study the modulation of hepcidin by interleukin-6 (IL-6) and STAT3 signaling pathway in these models, using real-time quantitative reverse transcription-PCR, immunohistochemistry, western blotting and enzyme-linked immunosorbent assay (ELISA). An in vitro study of the effect of bile acids on hepcidin expression was carried out to re-confirm the in vivo findings. There was significantly lower hepcidin mRNA and pSTAT3 protein expression in cholestatic cirrhosis compared with non-cholestatic cirrhosis in adults. BDL caused significant decrease in hepcidin and gp130 mRNA expression compared with sham-operated group and normal control. Furthermore, there was significantly lower pSTAT3 protein expression and nuclear translocation in the cholestatic liver from the patients and the BDL rats, which was comparable to lower liver hepcidin mRNA and plasma hepcidin expression. Furthermore, BDL for 2 weeks attenuated the upregulation of hepcidin expression induced by LPS. Hydrophobic bile acid glycochenodeoxycholate inhibited IL-6-induced pSTAT3 expression in primary hepatocytes and resulted in the downregulation of hepcidin mRNA expression. In conclusion, the study shows that cholestasis or its important component-hydrophobic bile acids-can downregulate hepcidin expression through inhibiting IL-6-induced STAT3 phosphorylation and pSTAT3 protein nuclear translocation.

Expression of toll-like receptor 9 in peripheral blood mononuclear cells from patients with different hepatitis B and C viral loads

The aim of the present study was to investigate the expression of toll-like receptors (TLR) 9 in peripheral blood mononuclear cells (PBMC) of patients with chronic hepatitis B and C with different virus copies. The study group included 90 patients (60 with chronic hepatitis B, and 30 with chronic hepatitis C), and 20 healthy people served as control group. The protein and mRNA levels of TLR9 were detected by using flow cytometry and real-time PCR. The serum viral copies of HBV and HCV were measured in all patients, and the correlation between HBV-DNA copies or HCV-RNA copies and the TLR9 expression was analyzed. Our results demonstrated that HBV or HCV infection led to a decreased expression of TLR9 mRNA and protein compared to the control group (P<0.05). The TLR9 protein and mRNA levels were negatively correlated with serum viral copies of HBV and HCV (r=-0.632, r=-0.909, P<0.01). It was concluded that TLR9 mRNA and protein are down-regulated in PBMC of HBV-infected or HCV-infected patients, and they are negatively correlated with serum viral copies and play an important role in detecting viral replication of HBV and HCV.

Inflammation and biliary tract injury

PURPOSE OF REVIEW

Primary biliary cirrhosis, primary sclerosing cholangitis and biliary atresia are thought to be immune-mediated cholangiopathies, however, gaps in knowledge remain with regard to the immunopathogenesis of these diseases.

RECENT FINDINGS

In this review, we highlight recent investigations pertaining to the role of both innate and adaptive immunity in bile duct damage. In innate immunity, evidence is presented for the contribution of cholangiocyte toll-like receptor stimulation promoting the ongoing inflammatory response. Innate-like lymphocytes may also be critical in the early phases of small bile duct injury found in primary biliary cirrhosis. With regard to adaptive immunity, the role of specific gene deficiencies in the susceptibility to immune-mediated cholangiopathies is reviewed. Furthermore, recent work analyzing the effector mechanisms of adaptive immunity leading to bile duct epithelial apoptosis are outlined.

SUMMARY

Understanding the intricacies of the inflammatory mechanisms culminating in bile duct epithelial injury are crucial to the future development of therapies aimed at halting the ongoing biliary tract destruction found in immune-mediated cholangiopathies. A paucity of research studies on primary sclerosing cholangitis was noted in this review and future research efforts should focus on primary sclerosing cholangitis, in addition to primary biliary cirrhosis and biliary atresia.

Incidence of hepatotropic viruses in biliary atresia

Biliary atresia (BA) is the most frequent indication for paediatric liver transplantation. We tested the hypothesis of a viral aetiology of this disease by screening liver samples of a large number of BA patients for the common human hepatotropic viruses. Moreover, we correlated our findings to the expression of Mx protein, which has been shown to be significantly up-regulated during viral infections. Seventy-four liver biopsies (taken during Kasai portoenterostomy) were tested by polymerase chain reaction (PCR) for DNA viruses (herpes simplex virus [HSV], Epstein-Barr virus [EBV], varicella zoster virus [VZV], cytomegalovirus [CMV], adenovirus, parvovirus B19 and polyoma BK) and RNA viruses (enteroviruses, rotavirus and reovirus 3). Mx protein expression was assessed by immunohistochemistry. Virus DNA/RNA was found in less than half of the biopsies (8/74 CMV, 1/74 adenovirus; 21/64 reovirus, 1/64 enterovirus). A limited number presented with double infection. Patients that had detectable viral RNA/DNA in their liver biopsies were significantly older than virus-free patients (P = 0.037). The majority (54/59) of the liver biopsies showed expression of Mx proteins in hepatocytes, bile ducts and epithelium. Our data suggest that the known hepatotropic viruses do not play a major role in the aetiology and progression of BA. Their incidence appears to be, rather, a secondary phenomenon. Nonetheless, the inflammatory response in the livers of BA patients mimics that observed during viral infections.

Cholangiocyte secretion of chemokines in experimental biliary atresia

Biliary atresia (BA) is a disease of the newborn that results in obstruction of the biliary tree. The cause of BA remains unknown; however, recent studies using the murine model of biliary atresia have found that rotavirus infection of the biliary epithelial cell (cholangiocyte) triggers an inflammatory response. We hypothesized that rotavirus infection of cholangiocytes results in the release of chemokines, important mediators of the host immune response.

METHODS

In vivo, Balb/c pups were injected with rhesus rotavirus (RRV) or saline, and, their extrahepatic bile ducts were microdissected 2, 5, 7, and 14 days after injection. Next, an immortalized cholangiocyte cell line (mCl) was incubated with RRV or serum-free media. Qualitative and quantitative chemokine assessment was performed using enzyme-linked immunosorbent assay, polymerase chain reaction, and immunohistochemistry.

RESULTS

In vivo, increased levels of the chemokines macrophage inflammatory protein 2, monocyte chemotactic protein 1, KC and Regulated upon Activation, Normal T Expressed and Secreted were found in RRV-infected murine bile ducts. In vitro, infected mCl cells produced increasing amounts of these same chemokines in relation to dose and time.

CONCLUSION

These novel results suggest that chemokine expression by RRV-infected cholangiocytes may trigger a host inflammatory process that causes bile duct obstruction. Understanding how viral infection initiates this response may shed light on the pathogenesis of biliary atresia.

Incidence of hepatotropic viruses in biliary atresia

Biliary atresia (BA) is the most frequent indication for paediatric liver transplantation. We tested the hypothesis of a viral aetiology of this disease by screening liver samples of a large number of BA patients for the common human hepatotropic viruses. Moreover, we correlated our findings to the expression of Mx protein, which has been shown to be significantly up-regulated during viral infections. Seventy-four liver biopsies (taken during Kasai portoenterostomy) were tested by polymerase chain reaction (PCR) for DNA viruses (herpes simplex virus [HSV], Epstein-Barr virus [EBV], varicella zoster virus [VZV], cytomegalovirus [CMV], adenovirus, parvovirus B19 and polyoma BK) and RNA viruses (enteroviruses, rotavirus and reovirus 3). Mx protein expression was assessed by immunohistochemistry. Virus DNA/RNA was found in less than half of the biopsies (8/74 CMV, 1/74 adenovirus; 21/64 reovirus, 1/64 enterovirus). A limited number presented with double infection. Patients that had detectable viral RNA/DNA in their liver biopsies were significantly older than virus-free patients (P = 0.037). The majority (54/59) of the liver biopsies showed expression of Mx proteins in hepatocytes, bile ducts and epithelium. Our data suggest that the known hepatotropic viruses do not play a major role in the aetiology and progression of BA. Their incidence appears to be, rather, a secondary phenomenon. Nonetheless, the inflammatory response in the livers of BA patients mimics that observed during viral infections.

The immunobiology of cholangiocytes

Cholangiocytes, the epithelial cells lining bile ducts, provide the first line of defense against lumenal microbes in the biliary system. Recent advances in biliary immunity indicate that cholangiocytes express a variety of pathogen-recognition receptors and can activate a set of intracellular signaling cascades to initiate a profound antimicrobial defense, including release of proinflammatory cytokines and chemokines, production of antimicrobial peptides and maintenance of biliary epithelial integrity. Cholangiocytes also interact with other cell types in the liver (for example, lymphocytes and Kupffer cells) through expression and release of adhesion molecules and immune mediators. Subsequently, through an intricate feedback mechanism involving both epithelial and other liver cells, a set of intracellular signaling pathways are activated to regulate the functional state of cholangiocyte responses during microbial infection. Thus, cholangiocytes are actively involved in mucosal immunity of the biliary system and represent a fine-tuned, integral component of liver immunity.

Induction of innate immune response and absence of subsequent tolerance to dsRNA in biliary epithelial cells relate to the pathogenesis of biliary atresia

BACKGROUND/AIMS

Biliary epithelial cells (BECs) possess negative regulatory mechanisms of Toll-like receptor (TLR)-based tolerance to bacteria (e.g. endotoxin tolerance). Viral infections of the Reoviridae genus with a dsRNA genome are suspected to be part of the aetiology of biliary atresia (BA), but the negative biliary mechanisms remain unexplored.

METHODS

Cultured human intrahepatic BECs (HIBECs) pretreated with polyinosinic-polycytidylic acid [poly(I:C)] (a synthetic analogue of viral dsRNA) for 24 h were exposed to poly(I:C) in fresh medium. The activation of nuclear factor-kappaB (NF-kappaB) and the expression of myxovirus resistance protein A (MxA) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) mRNAs were evaluated. Moreover, after the pretreatment, the transition of these molecules was examined in poly(I:C)-free conditions.

RESULTS

Treatment with poly(I:C) significantly upregulated NF-kappaB activity in fresh HIBECs, and pretreatment failed to show tolerance to poly(I:C). The production of MxA and TRAIL was also preserved. Moreover, upregulation in the pretreated HIBECs was well preserved in poly(I:C)-free medium for at least 72 h.

CONCLUSIONS

BECs fail to show tolerance to poly(I:C), and once innate immunity is activated it is sustained in poly(I:C)-free conditions, suggesting that the initiation of the immune response to dsRNA in HIBECs and its presence after the clearance of virus are closely associated with the progression of BA.

Toll-like receptor 7 and 9 expression in peripheral blood mononuclear cells from patients with chronic hepatitis B and related hepatocellular carcinoma

AIM

The aim of the present study was to investigate the expression of Toll-like receptors (TLR) 7 and 9 in peripheral blood mononuclear cells (PBMC) of patients with chronic hepatitis B virus (HBV) infection and related hepatocellular carcinoma.

METHODS

The study group was comprised of 52 patients: 41 with chronic hepatitis B and 11 healthy controls. The protein and mRNA levels of TLR7 and TLR9 were evaluated using real-time PCR, Western blot analysis, and flow cytometry. We also detected the serum viral load of HBV in the patients and analyzed the correlation between HBV-DNA copies and the TLR expression.

RESULTS

Our results demonstrated a lower TLR7 expression in all HBV infection groups compared to the controls. We found that HBV infection led to a decreased expression of TLR9 mRNA, but an increased expression of the TLR9 protein compared to the healthy group. The TLR protein levels are related to serum HBV-DNA (P<0.01).

CONCLUSION

There are downregulations of TLR7 expression and TLR9 mRNA in PBMC of HBV-infected patients, but an increased TLR9 expression at the protein level.