Distinct costimulation dependent and independent autoreactive T-cell clones in primary biliary cirrhosis

Conventional type 1 dendritic cells are essential for the development of primary biliary cholangitis

BACKGROUND & AIMS

Primary biliary cholangitis (PBC) is a progressive-cholestatic autoimmune liver disease. Dendritic cells (DC) are professional antigen-presenting cells and their prominent presence around damaged bile ducts of PBC patients are documented. cDC1 is a rare subset of DC known for its cross-presentation abilities and interleukin 12 production. Our aim was to assess the role of cDC1 in the pathogenesis of PBC.

METHODS

We utilized an inducible murine model of PBC and took advantage of the DC reporter mice Zbtb46gfp and the Batf3-/- mice that specifically lack the cDC1 subset. cDC1 cells were sorted from blood of PBC patients and healthy individuals and subjected to Bulk-MARS-seq transcriptome analysis.

RESULTS

Histopathology assessment demonstrated peri-portal inflammation in wild type (WT) mice, whereas only minor abnormalities were observed in Batf3-/- mice. Flow cytometry analysis revealed a two-fold reduction in hepatic CD8/CD4 T cells ratio in Batf3-/- mice, suggesting reduced intrahepatic CD8 T cells expansion. Histological evidence of portal fibrosis was detected only in the WT but not in Batf3-/- mice. This finding was supported by decreased expression levels of pro-fibrotic genes in the livers of Batf3-/- mice. Transcriptome analysis of human cDC1, revealed 78 differentially expressed genes between PBC patients and controls. Genes related to antigen presentation, TNF and IFN signalling and mitochondrial dysfunction were significantly increased in cDC1 isolated from PBC patients.

CONCLUSION

Our data illustrated the contribution the cDC1 subset in the pathogenesis of PBC and provides a novel direction for immune based cell-specific targeted therapeutic approach in PBC.

Primary Biliary Cholangitis: Epidemiology, Diagnosis, and Presentation

Using ursodeoxycholic acid as a standard treatment and for its ability to test for antimitochondrial antibody to accelerate diagnosis, survival of primary biliary cholangitis patients has approached that of the general population, leading to a change in nomenclature from primary biliary cirrhosis to primary biliary cholangitis to more accurately describe the disease.

Immunologic Responses and the Pathophysiology of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease with a female predisposition and selective destruction of intrahepatic small bile ducts leading to nonsuppurative destructive cholangitis. It is characterized by seropositivity of antimitochondrial antibodies or PBC-specific antinuclear antibodies, progressive cholestasis, and typical liver histologic manifestations. Destruction of the protective bicarbonate-rich umbrella is attributed to the decreased expression of membrane transporters in biliary epithelial cells (BECs), leading to the accumulation of hydrophobic bile acids and sensitizing BECs to apoptosis. A recent X-wide association study reveals a novel risk locus on the X chromosome, which reiterates the importance of Treg cells.

Review article: pathophysiology and management of primary biliary cholangitis

BACKGROUND

Primary biliary cholangitis (PBC), an immune-mediated disease characterised by destruction of intrahepatic bile ducts, results in progressive damage to the biliary tree, cholestasis and ultimately advanced liver disease. In the last decade, advances in practice have improved clinical care, driven novel therapeutic options and improved risk stratification tools.

AIMS

To provide an overview of the disease characteristics of PBC and review a patient-centred management approach for the clinical team caring for those with PBC.

METHODS

We reviewed the current literature and guidelines on PBC with a focus on management and therapies.

RESULTS

A confident diagnosis of PBC is usually made based on serum liver tests and immune serology. Management of PBC should focus on three main 'process' pillars: (a) treat and risk-stratify through use of biochemical and prognostic criteria; (b) manage concurrent symptoms and other associated diseases; and (c) stage disease, monitor progression and prevent complications. With ongoing complexities in management, including a newly licensed therapy (obeticholic acid) and alternative non-licensed treatments and ongoing clinical trials, discussion with PBC expert centres is encouraged.

CONCLUSIONS

PBC is a dynamic disease wherein current treatment goals have become appropriately ambitious. Goals of care should prioritise prevention of end-stage liver disease and amelioration of patient symptom burden for all.

Immunological abnormalities in patients with primary biliary cholangitis

Primary biliary cholangitis (PBC), an autoimmune liver disease occurring predominantly in women, is characterized by high titers of serum anti-mitochondrial antibodies (AMAs) and progressive intrahepatic cholestasis. The immune system plays a critical role in PBC pathogenesis and a variety of immune cell subsets have been shown to infiltrate the portal tract areas of patients with PBC. Amongst the participating immune cells, CD4 T cells are important cytokine-producing cells that foster an inflammatory microenvironment. Specifically, these cells orchestrate activation of other immune cells, including autoreactive effector CD8 T cells that cause biliary epithelial cell (BEC) injury and B cells that produce large quantities of AMAs. Meanwhile, other immune cells, including dendritic cells (DCs), natural killer (NK) cells, NKT cells, monocytes, and macrophages are also important in PBC pathogenesis. Activation of these cells initiates and perpetuates bile duct damage in PBC patients, leading to intrahepatic cholestasis, hepatic damage, liver fibrosis, and eventually cirrhosis or even liver failure. Taken together, the body of accumulated clinical and experimental evidence has enhanced our understanding of the immunopathogenesis of PBC and suggests that immunotherapy may be a promising treatment option. Herein, we summarize current knowledge regarding immunological abnormalities of PBC patients, with emphasis on underlying pathogenic mechanisms. The differential immune response which occurs over decades of disease activity suggests that different therapies may be needed at different stages of disease.

Natural killer T cells mediate inflammation in the bile ducts

Cholangiocytes function as antigen-presenting cells with CD1d-dependent activation of natural killer T (NKT) cells in vitro. NKT cells may act both pro- and anti-inflammatory in liver immunopathology. We explored this immune pathway and the antigen-presenting potential of NKT cells in the bile ducts by challenging wild-type and Cd1d^-/- mice with intrabiliary injection of the NKT cell activating agent oxazolone. Pharmacological blocking of CD1d-mediated activation was performed with a monoclonal antibody. Intrabiliary oxazolone injection in wild-type mice caused acute cholangitis with significant weight loss, elevated serum levels of alanine transaminase, aspartate transaminase, alkaline phosphatase and bilirubin, increased histologic grade of cholangitis and number of T cells, macrophages, neutrophils and myofibroblasts per portal tract after 7 days. NKT cells were activated after intrabiliary injection of oxazolone with upregulation of activation markers. Cd1d^-/- and wild-type mice pretreated with antibody blocking of CD1d were protected from disease. These findings implicate that cells in the bile ducts function as antigen-presenting cells in vivo and activate NKT cells in a CD1d-restricted manner. The elucidation of this biliary immune pathway opens up for potentially new therapeutic approaches for cholangiopathies.

WAVE3 Induces EMT and Promotes Migration and Invasion in Intrahepatic Cholangiocarcinoma

BACKGROUND

Wiskott-Aldrich syndrome protein family verprolin-homologous protein 3 (WAVE3) plays a critical role in cancer progression and metastasis. However, the specific role of WAVE3 in intrahepatic cholangiocarcinoma (ICC) has not been studied.

AIMS

This study aimed to explore the role and mechanism of WAVE3 in the progression and metastasis of ICC.

METHODS

The expression of WAVE3 in ICC tissues and adjacent non-cancerous tissues was detected by immunohistochemistry. Western blot analysis was utilized to detect the expression of WAVE3 in ICC cells. A transwell assay was used to assess the potential for migration and invasion. The expression of WAVE3 in CC-LP-1 cells was knocked down by small interfering RNA (siRNA) interference.

RESULTS

The expression of WAVE3 in ICC tissues was significantly higher than that in adjacent non-cancerous tissues. The overall survival was lower in the subgroup of ICC patients with higher WAVE3 expression compared to the subgroup with a lower level of WAVE3 expression. WAVE3 expression was an adverse prognostic factor for ICC patients. CC-LP-1 cells expressed higher levels of WAVE3 protein compared to RBE cells and human intrahepatic biliary epithelial cells, which correlated with greater migration and invasion capabilities compared with the RBE cells. After the transfection of CC-LP-1 cells with WAVE3 siRNA, the level of WAVE3 protein was significantly decreased, accompanied by a marked reduction in migration, invasion and proliferation. Moreover, after the knockdown of WAVE3 expression in CC-LP-1 cells, the protein levels of Slug and Vimentin were significantly decreased, while that of E-cadherin was significantly increased.

CONCLUSIONS

WAVE3 may represent a new adverse prognostic factor for patients with ICC. This protein enhances migration and invasion capabilities in ICC, most likely through the induction of an epithelial-mesenchymal transition.

Natural killer cells regulate T cell immune responses in primary biliary cirrhosis

The hallmark of primary biliary cirrhosis (PBC) is the presence of autoreactive T- and B-cell responses that target biliary epithelial cells (BECs). Biliary cell cytotoxicity is dependent upon initiation of innate immune responses followed by chronic adaptive, as well as bystander, mechanisms. Critical to these mechanisms are interactions between natural killer (NK) cells and BECs. We have taken advantage of the ability to isolate relatively pure viable preparations of liver-derived NK cells, BECs, and endothelial cells, and studied interactions between NK cells and BECs and focused on the mechanisms that activate autoreactive T cells, their dependence on interferon (IFN)-γ, and expression of BEC major histocompatibility complex (MHC) class I and II molecules. Here we show that at a high NK/BEC ratio, NK cells are cytotoxic for autologous BECs, but are not dependent on autoantigen, yet still activate autoreactive CD4(+) T cells in the presence of antigen presenting cells. In contrast, at a low NK/BEC ratio, BECs are not lysed, but IFN-γ production is induced, which facilitates expression of MHC class I and II molecules on BEC and protects them from lysis upon subsequent exposure to autoreactive NK cells. Furthermore, IFN-γ secreted from NK cells after exposure to autologous BECs is essential for this protective function and enables autoreactive CD4(+) T cells to become cytopathic.

CONCLUSIONS

NK cell-mediated innate immune responses are likely critical at the initial stage of PBC, but also facilitate and maintain the chronic cytopathic effect of autoantigen-specific T cells, essential for progression of disease.

Interleukin-32 production associated with biliary innate immunity and proinflammatory cytokines contributes to the pathogenesis of cholangitis in biliary atresia

Biliary atresia (BA) is thought to be associated with infections by viruses such as Reoviridae and is characterized histologically by fibrosclerosing cholangitis with proinflammatory cytokine-mediated inflammation. Interleukin (IL)-32 affects the continuous inflammation by increasing the production of proinflammatory cytokines. In this study, the role of IL-32 in the cholangitis of BA was examined. Immunohistochemistry for IL-32 and caspase 1 was performed using 21 samples of extrahepatic bile ducts resected from BA patients. Moreover, using cultured human biliary epithelial cells (BECs), the expression of IL-32 and its induction on stimulation with a Toll-like receptor [(TLR)-3 ligand (poly(I:C)] and proinflammatory cytokines was examined. BECs composing extrahepatic bile ducts showing cholangitis expressed IL-32 in BA, but not in controls. Caspase 1 was expressed constantly on BECs of both BA and control subjects. Furthermore, poly(I:C) and proinflammatory cytokines [(IL-1β, interferon (IFN)-γ and tumour necrosis factor (TNF)-α] induced IL-32 expression strongly in cultured BECs, accompanying the constant expression of TLR-3 and caspase 1. Our results imply that the expression of IL-32 in BECs was found in the damaged bile ducts of BA and induced by biliary innate immunity via TLR-3 and proinflammatory cytokines. These findings suggest that IL-32 is involved initially in the pathogenic mechanisms of cholangitis in BA and also plays an important role in the amplification and continuance of periductal inflammatory reactions. It is therefore tempting to speculate that inhibitors of IL-32 could be useful for attenuating cholangitis in BA.

B cell depletion in treating primary biliary cirrhosis: Pros and cons

Primary biliary cirrhosis (PBC) is a progressive autoimmune liver disease of unknown etiology that affects almost exclusively women. Ursodeoxycholic acid (UDCA) is currently the only approved drug by Food and Drug Administration for patients with PBC. Although the precise pathogenesis of PBC remains unclear, it has been postulated that many cell populations, including B cells, are involved in the ongoing inflammatory process, which implicates, not surprisingly, a potential therapeutic target of depleting B cell to treat this disorder. Rituximab is a chimeric anti-CD20 monoclonal antibody that has been approved for the treatment of lymphoma and some autoimmune diseases such as rheumatoid arthritis. Whether it is effective in the treatment of PBC has not been evaluated. Recently, Tsuda et al^[1] demonstrated that B cell depletion with rituximab significantly reduced the number of anti-mitochondrial antibodies (AMA)-producing B cells, AMA titers, the plasma levels of immunoglobulins (IgA, IgM and IgG) as well as serum alkaline phosphatase, and it was well tolerated by all the treated patients with no serious adverse events. This observation provides a novel treatment option for the patients with PBC who have incomplete response to UDCA.

Comparative analysis of portal cell infiltrates in antimitochondrial autoantibody-positive versus antimitochondrial autoantibody-negative primary biliary cirrhosis

Substantial evidence supports dysregulated B-cell immune responses in patients with primary biliary cirrhosis (PBC), including the presence of serum antimitochondrial antibodies (AMAs). However, recent reports from murine models of PBC suggest that B cells may also provide regulatory function, and indeed the absence of B cells in such models leads to exacerbation of disease. The vast majority of patients with PBC have readily detectable AMAs, but a minority (<5%) are AMA negative (AMA(-)), even with recombinant diagnostic technology. This issue prompted us to examine the nature of B-cell infiltrates surrounding the portal areas in AMA-positive (AMA(+)) and AMA(-) patients, because they display indistinguishable clinical features. Of importance was the finding that the degree of bile duct damage around the portal areas was significantly milder in AMA(+) PBC than those observed in AMA(-) PBC patients. The portal areas from AMA(-) patients had a significant increase of cluster of differentiation (CD)5(+) cells infiltrating the ductal regions, and the levels of B-cell infiltrates were worse in the early phase of bile duct damage. The frequency of positive portal areas and the magnitude of CD5(+) and CD20(+) cellular infiltrates within areas of ductal invasion is associated with the first evidence of damage of biliary duct epithelia, but becomes reduced in the ductopenia stage, with the exception of CD5(+) cells, which remain sustained and predominate over CD20(+) cells.

CONCLUSION

Our data suggest a putative role of B-cell autoimmunity in regulating the portal destruction characteristic of PBC.

Plasma cells and the chronic nonsuppurative destructive cholangitis of primary biliary cirrhosis

There has been increased interest in the role of B cells in the pathogenesis of primary biliary cirrhosis (PBC). Although the vast majority of patients with this disease have anti-mitochondrial antibodies, there is no correlation of anti-mitochondrial antibody titer and/or presence with disease severity. Furthermore, in murine models of PBC, it has been suggested that depletion of B cells may exacerbate biliary pathology. To address this issue, we focused on a detailed phenotypic characterization of mononuclear cell infiltrates surrounding the intrahepatic bile ducts of patients with PBC, primary sclerosing cholangitis, autoimmune hepatitis, chronic hepatitis C, and graft-versus-host disease, including CD3, CD4, CD8, CD20, CD38, and immunoglobulin classes, as well as double immunohistochemical staining for CD38 and IgM. Interestingly, CD20 B lymphocytes, which are a precursor of plasma cells, were found in scattered locations or occasionally forming follicle-like aggregations but were not noted at the proximal location of chronic nonsuppurative destructive cholangitis. In contrast, there was a unique and distinct coronal arrangement of CD38 cells around the intrahepatic ducts in PBC but not controls; the majority of such cells were considered plasma cells based on their expression of intracellular immunoglobulins, including IgM and IgG, but not IgA. Patients with PBC who manifest this unique coronal arrangement were those with significantly higher titers of anti-mitochondrial antibodies.

CONCLUSION

These data collectively suggest a role for plasma cells in the specific destruction of intrahepatic bile ducts in PBC and confirm the increasing interest in plasma cells and autoimmunity.

Biochemical and immunologic effects of rituximab in patients with primary biliary cirrhosis and an incomplete response to ursodeoxycholic acid

The aim of this study was to determine the safety and potential efficacy of B-cell depletion with the anti-CD20 monoclonal antibody rituximab in patients with primary biliary cirrhosis (PBC) and an incomplete response to ursodeoxycholic acid (UDCA). This open-label study enrolled six patients with PBC and incomplete responses to UDCA to be treated with 2 doses of 1000 mg rituximab separated by 2 weeks and followed for 52 weeks. The primary endpoints were safety and changes in B-cell function. Two patients received only 1 dose of rituximab, one due to activation of latent varicella and the other due to a viral upper respiratory infection. Serum levels of total IgG, IgM, and IgA as well as anti-mitochondrial autoantibodies (AMAs) IgA and IgM decreased significantly from baseline by 16 weeks and returned to baseline levels by 36 weeks. Stimulation of B cells with CpG produced significantly less IgM at 52 weeks after treatment compared with B cells at baseline. In addition, transient decreases in memory B-cell and T-cell frequencies and an increase in CD25(high) CD4(+) T cells were observed after treatment. These changes were associated with significant increases in mRNA levels of FoxP3 and transforming growth factor-β (TGF-β) and a decrease in tumor necrosis factor-α (TNF-α) in CD4(+) T cells. Notably, serum alkaline phosphatase levels were significantly reduced up to 36 weeks following rituximab treatment.

CONCLUSION

These data suggest that depletion of B cells influences the induction, maintenance, and activation of both B and T cells and provides a potential mechanism for treatment of patients with PBC with an incomplete response to UDCA.

Novel approach to bile duct damage in primary biliary cirrhosis: participation of cellular senescence and autophagy

Primary biliary cirrhosis (PBC) is characterized by antimitochondrial autoantibodies (AMAs) in patients' sera and histologically by chronic nonsuppurative destructive cholangitis in small bile ducts, eventually followed by extensive bile duct loss and biliary cirrhosis. The autoimmune-mediated pathogenesis of bile duct lesions, including the significance of AMAs, triggers of the autoimmune process, and so on remain unclear. We have reported that cellular senescence in biliary epithelial cells (BECs) may be involved in bile duct lesions and that autophagy may precede the process of biliary epithelial senescence in PBC. Interestingly, BECs in damaged bile ducts show characteristicsof cellular senescence and autophagy in PBC. A suspected causative factor of biliary epithelial senescence is oxidative stress. Furthermore, senescent BECs may modulate the microenvironment around bile ducts by expressing various chemokines and cytokines called senescence-associated secretory phenotypes and contribute to the pathogenesis in PBC.

Biliary epithelial apoptosis, autophagy, and senescence in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized serologically by the high prevalence of anti-mitochondrial autoantibodies (AMAs) and histologically by the cholangitis of small bile ducts, eventually followed by extensive loss of the small bile duct. An autoimmune pathogenesis is suggested by clinical and experimental studies, but there remain issues regarding the etiology, the significance of AMAs in the pathogenesis of bile duct lesions, and so on. The unique properties of apoptosis in biliary epithelial cells (BECs), in which there is exposure of autoantigen to the effectors of the immune system, are proposed to be a cause of bile duct lesions in PBC. Recent progress disclosed that cellular senescence and autophagy are involved in bile duct lesions in PBC. Senescent BECs may modulate the periductal microenvironment by expressing senescence-associated secretory phenotypes, including various chemokines, and contribute to the pathogenesis of bile duct lesions in PBC.

Primary biliary cirrhosis: What do autoantibodies tell us?

Primary biliary cirrhosis (PBC) is a chronic, progressive, cholestatic, organ-specific autoimmune disease of unknown etiology. It predominantly affects middle-aged women, and is characterized by autoimmune-mediated destruction of small- and medium-size intrahepatic bile ducts, portal inflammation and progressive scarring, which without proper treatment can ultimately lead to fibrosis and hepatic failure. Serum autoantibodies are crucial tools for differential diagnosis of PBC. While it is currently accepted that antimitochondrial antibodies are the most important serological markers of PBC, during the last five decades more than sixty autoantibodies have been explored in these patients, some of which had previously been thought to be specific for other autoimmune diseases.

B-cell depletion with anti-CD20 ameliorates autoimmune cholangitis but exacerbates colitis in transforming growth factor-beta receptor II dominant negative mice

The treatment of primary biliary cirrhosis (PBC) with conventional immunosuppressive drugs has been relatively disappointing and there have been few efforts in defining a role for the newer biological agents useful in rheumatoid arthritis and other systemic autoimmune diseases. In this study we took advantage of transforming growth factor-beta (TGF-beta) receptor II dominant negative (dnTGF-betaRII) mice, a mouse model of autoimmune cholangitis, to address the therapeutic efficacy of B-cell depletion using anti-CD20. Mice were treated at either 4-6 weeks of age or beginning at 20-22 weeks of age with intraperitoneal injections of anti-CD20 every 2 weeks. We quantitated B-cell levels in all mice as well as antimitochondrial antibodies (AMA), serum and hepatic levels of proinflammatory cytokines, and histopathology of liver and colon. In mice whose treatment was initiated at 4-6 weeks of age, anti-CD20 therapy demonstrated a significantly lower incidence of liver inflammation associated with reduced numbers of activated hepatic CD8(+) T cells. However, colon inflammation was exacerbated. In contrast, in mice treated at 20-22 weeks of age, anti-CD20 therapy had relatively little effect on either liver or colon disease. As expected, all treated animals had reduced levels of B cells, absence of AMA, and increased levels in sera of tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), and chemokine (C-C motif) ligand (CCL2) (monocyte chemoattractant protein 1 [MCP-1]).

CONCLUSION

These data suggest potential usage of anti-CD20 in early PBC resistant to other modalities, but raise a cautionary note regarding the use of anti-CD20 in inflammatory bowel disease.

Deletion of interleukin-12p40 suppresses autoimmune cholangitis in dominant negative transforming growth factor beta receptor type II mice

Our laboratory has reported that mice that express a dominant negative form of transforming growth factor beta receptor restricted to T cells (dnTGFbetaRII) develop an inflammatory biliary ductular disease with elevated serum levels of interleukin (IL)-12p40 and other proinflammatory cytokines and antimitochondrial autoantibodies (AMAs) closely resembling human primary biliary cirrhosis (PBC). We have used this mouse model to address the potential mechanisms of immunomodulation of liver disease by creating two unique genetic strains: IL-12p40 knockout (KO)-dnTGFbetaRII mice and IFN-gamma KO-dnTGFbetaRII mice. The two colonies of genetically modified mice-and, for purposes of controls, the dnTGFbetaRII mice-were monitored for liver immunopathology, AMAs, and intrahepatic cytokine production. Disease expression in the IFN-gamma KO-dnTGFbetaRII mice, including liver immunopathology, were similar to those of dnTGFbetaRII mice, whereas the IL-12p40 KO-dnTGFbetaRII mice had a dramatic reduction in histological autoimmune cholangitis and significant decreases in levels of intrahepatic proinflammatory cytokines, but similar levels of AMAs compared with dnTGFbetaRII controls.

CONCLUSION

These data indicate that in this mouse model of PBC, signaling by way of IL-12p40 is an essential requirement for the development of autoimmune cholangitis. The results of these studies will play an important role in identifying pathways and reagents that will selectively inhibit IL-12 signaling for the outlining of future therapeutic strategies for human PBC.

Periductal interleukin-17 production in association with biliary innate immunity contributes to the pathogenesis of cholangiopathy in primary biliary cirrhosis

An innate immune response to bacterial components is speculated to be involved in the pathogenesis of primary biliary cirrhosis (PBC). Recently, CD4-positive T helper type 17 (Th17) cells, characterized by the secretion of interleukin (IL)-17, have been implicated in the pathogenesis of autoimmune diseases. Human Th17 cells are generated from Th0 cells by IL-6 and IL-1 beta and maintained by IL-23. In this study, the role of IL-17 in PBC and its association with biliary innate immunity were examined. Using cultured human biliary epithelial cells (BECs), the expression of Th17-related cytokines and chemokines and changes therein on treatment with pathogen-associated molecular patterns (PAMPs) and IL-17 were examined. Immunohistochemistry for IL-17 and Th17-related cytokines was performed using tissue samples of human liver. Consequently, the expression of IL-6, IL-1 beta, IL-23p19 and IL-23/IL-12p40 mRNAs, and their up-regulation by PAMPs, were found in BECs. Moreover, BECs possessed IL-17-receptors and stimulation with IL-17 induced production of IL-6, IL-1 beta, IL-23p19 and chemokines. Several IL-17-positive cells had infiltrated damaged bile ducts and the expression of IL-6 and IL-1 beta was enhanced in the bile ducts of PBC patients. In conclusion, IL-17-positive cells are associated with the chronic inflammation of bile ducts in PBC which is associated causally with the biliary innate immune responses to PAMPs.

Lymphocyte recruitment and homing to the liver in primary biliary cirrhosis and primary sclerosing cholangitis

The mechanisms operating in lymphocyte recruitment and homing to liver are reviewed. A literature review was performed on primary biliary cirrhosis (PBC), progressive sclerosing cholangitis (PSC), and homing mechanisms; a total of 130 papers were selected for discussion. Available data suggest that in addition to a specific role for CCL25 in PSC, the CC chemokines CCL21 and CCL28 and the CXC chemokines CXCL9 and CXCL10 are involved in the recruitment of T lymphocytes into the portal tract in PBC and PSC. Once entering the liver, lymphocytes localize to bile duct and retain by the combinatorial or sequential action of CXCL12, CXCL16, CX3CL1, and CCL28 and possibly CXCL9 and CXCL10. The relative importance of these chemokines in the recruitment or the retention of lymphocytes around the bile ducts remains unclear. The available data remain limited but underscore the importance of recruitment and homing.

Epithelial-mesenchymal transition induced by biliary innate immunity contributes to the sclerosing cholangiopathy of biliary atresia

Infections of Reoviridae consisting of a double-stranded RNA (dsRNA) genome and the biliary innate immune response to dsRNA are implicated in the aetiopathogenesis of biliary atresia (BA). Epithelial-mesenchymal transition (EMT) has recently been proposed as a mechanism behind the sclerosing cholangitis in BA. We hypothesized that the innate immune response to dsRNA in biliary epithelial cells plays an important role in peribiliary fibrosis via biliary EMT. Experiments using cultured human biliary epithelial cells revealed that stimulation with poly(I : C) (a synthetic analogue of viral dsRNA) increased the expression of basic fibroblast growth factor (bFGF, an EMT-inducer), S100A4 (a mesenchymal marker) and Snail (a transcriptional factor), and decreased that of epithelial markers (biliary-type cytokeratin 19 and E-cadherin) and Bambi (TGF-beta1 pseudoreceptor). The expression of TGF-beta1 (EMT-inducer) and vimentin (a mesenchymal marker) was not affected by poly(I : C). Both EMT-inducers, bFGF and TGF-beta1, evoked a decrease and increase in the expression of the epithelial markers and of vimentin respectively, and the expression of Bambi was down-regulated on stimulation with bFGF. Combined treatment with bFGF and TGF-beta1 quickly and completely induced a transformation of morphology as well as change from epithelial to mesenchymal features in cultured biliary epithelial cells. Immunohistochemistry revealed that biliary epithelial cells lining extrahepatic bile ducts and peribiliary glands in BA frequently show a lack of epithelial markers and an aberrant expression of vimentin. Moreover, the biliary epithelium showing sclerosing cholangitis expressed bFGF accompanied by bFGF-positive mononuclear cells. In conclusion, the EMT may contribute to the histogenesis of sclerosing cholangiopathy, and the biliary innate immune response to dsRNA viruses induces biliary epithelial cells to undergo EMT via the production of bFGF and the increased susceptibility to TGF-beta1 caused by the down-regulation of Bambi expression.

Liver architecture, cell function, and disease

The liver is an organ consisting of the largest reticulo-endothelial cell network in the body and playing an important role in host defense against invading microorganisms. The organ is comprised of parenchymal cells and many different types of non-parenchymal cells, all of which play a significant role. Even biliary epithelial cells are not only the target in autoimmune liver diseases but also have central role in orchestrating several immune cells involved in both innate and acquired immunity. Tissue damage caused by various agents results in inflammation, necrosis, fibrosis, and, eventually, distortion of normal hepatic architecture, cirrhosis, and functional deterioration.

B cells suppress the inflammatory response in a mouse model of primary biliary cirrhosis

BACKGROUND & AIMS

Mice that express a dominant-negative form of transforming growth factor-beta receptor restricted to T cells (dnTGF-betaRII) develop antimitochondrial antibodies and liver inflammation similar to human primary biliary cirrhosis.

METHODS

To address the role of B cells in this model of primary biliary cirrhosis, we bred B cell-deficient mice (Igmu(-/-)) with dnTGF-betaRII mice, creating Igmu(-/-)dnTGF-betaRII mice, and compared the resulting disease phenotype with that of dnTGF-betaRII mice (controls). We also performed adoptive transfer of dnTGF-betaRII CD8(+) splenocytes, with or without B cells, to 8-week-old female Rag-1(-/-) mice to assess the role of B cells in the inflammatory response.

RESULTS

The B cell-deficient Igmu(-/-)dnTGF-betaRII mice unexpectedly developed a more severe form of cholangitis than controls (dnTGF-betaRII mice) and had a significantly greater frequency of activated CD4(+) and CD8(+) T cells in the liver. They also had reduced frequency of Foxp3(+) regulatory T cells in the hepatic CD4(+) T-cell population and natural killer (NK) T cells (NK1.1(+) CD3(+)) in hepatic inflammatory cell infiltrates. The Igmu(-/-)dnTGF-betaRII mice had increased levels of proinflammatory cytokines (tumor necrosis factor-alpha and interleukin-6) and developed a more severe form of colitis than controls. Adoptive transfer of CD8(+) splenocytes from dnTGF-betaRII mice and peritoneal cavity-derived, but not spleen-derived, CD19(+) B cells into Rag-1(-/-) mice resulted in decreased amounts of liver inflammation and bile duct damage, compared with Rag-1(-/-) mice in which only CD8(+) splenocytes were transferred.

CONCLUSION

B cells have a suppressive effect on the inflammatory response in the dnTGF-betaRII model of primary biliary cirrhosis.

CD4 T-cell autoreactivity to the mitochondrial autoantigen PDC-E2 in AMA-negative primary biliary cirrhosis

Approximately 5% of patients with primary biliary cirrhosis (PBC) lack characteristic anti-mitochondrial antibodies (AMA). Yet clinically AMA+ and AMA- patients are similar. Using both AMA+ and AMA- patients, we quantitated the frequency of autoreactive T cells that respond to the major CD4 T-cell epitope, PDC-E2 163-176, using limiting dilution assays and quantitation of IFN-gamma, IL-10 and IL-4. Further, based on data that both PBC patients and healthy subjects have CD4+ T cells that recognize PDC-E2 163-176 but with differing costimulation requirements, assays were performed using two different antigen-presenting cell (APC) systems: either autologous peripheral blood mononuclear cells (PBMC) or HLA DR53 transfected mouse fibroblast cell lines (L-DR53). When costimulation-incompetent L-DR53 were used as APCs, the PDC-E2 CD4 T-cell frequency and capacity for IFN-gamma production were equivalent in both AMA+ and AMA- patients but the frequencies of such cells were significantly lower in normals, with IL-10 production similar in all three groups. Thus, in PBC there is 'universal' autoreactive CD4+ T-cell immune responsiveness to the critical autoantigen, PDC-E2. These observations emphasize that the mitochondrial autoreactivity in PBC is a multi-lineage response and hence, AMA-negative PBC may be an anachronism that refers only to sera autoantibodies.

Peripheral tolerance and the qualitative characteristics of autoreactive T cell clones in primary biliary cirrhosis

Primary biliary cirrhosis is characterized by autoreactive T cells specific for the mitochondrial Ag PDC-E2(163-176). We studied the ability of eight T cell clones (TCC) specific for PDC-E2(163-176) to proliferate or become anergic in the presence of costimulation signals. TCC were stimulated with either human PDC-E2(163-176), an Escherichia coli 2-oxoglutarate dehydrogenase mimic (OGDC-E2(34-47)), or analogs with amino acid substitutions using HLA-matched allogeneic PBMC or mouse L-DR53 fibroblasts as APC. Based on their differential responses to these peptides (human PDC-E2(163-176), E. coli OGDC-E2(34-47)) in the different APC systems, TCC were classified as costimulation dependent or independent. Only costimulation-dependent TCC could become anergic. TCC with costimulation-dependent responses to OGDC-E2 become anergic to PDC-E2 when preincubated with mimic, even if costimulation is independent for PDC-E2(163-176). Anergic TCC produced IL-10. One selected TCC could not become anergic after preincubation with PDC-E2(163-176)-pulsed L-DR53 but became anergic using L-DR53 pulsed with PDC-E2 peptide analogs with a substitution at a critical TCR binding site. TCC that only respond to peptide-pulsed PBMC, but not L-DR53, proliferate with peptide-pulsed CD80/CD86-transfected L-DR53; however, anergy was not induced with peptide-pulsed L-DR53 transfected with only CD80 or CD86. These data highlight that costimulation plays a dominant role in maintaining peripheral tolerance to PBC-specific Ags. They further suggest that, under specific circumstances, molecular mimicry of an autoantigen may restore rather than break peripheral tolerance.

Autoreactive T-cell responses in primary biliary cirrhosis are proinflammatory whereas those of controls are regulatory

BACKGROUND

Autoreactive T cells that proliferate in response to autoantigens are found in both autoimmune diseases and controls but have important qualitative differences in relative activation states, costimulation signal requirements and pathogenetic significance.

METHODS

To understand the differences between autoreactive T cells in PBC versus controls, we have developed autoreactive T-cell clones (TCC) from patients with PBC and healthy controls, and have used a peptide corresponding to the CD4 major autoantigen (Ag) to define the relative proliferative response. Peripheral blood mononuclear cells (PBMC) from PBC respond to the Ag in a costimulation-independent manner, but PBMC from controls respond to the Ag in a costimulation-dependent manner. Next, we established nine autoreactive TCC from patients with PBC and eight from healthy controls.

RESULTS

Among 17 TCC, eight were the costimulation-dependent type and nine were independent. In addition, costimulation-dependent autoreactive TCC became anergic after stimulation in the presence of APC that did not provide costimulatory signals. Finally, we observed that anergic TCC exhibit regulatory functions.

CONCLUSIONS

In the case of regulatory dendritic cells, we could not induce TCC anergy. On the other hand, when using peptide analog in a costimulation-deficient manner, we could induce TCC anergy, even though these TCC were costimulation independent.

IL-8 expression by biliary epithelial cells is associated with neutrophilic infiltration and reactive bile ductules

BACKGROUND/AIMS

Reactive bile ductule is a non-specific feature of various hepatobiliary diseases, and is not infrequently accompanied by neutrophilic infiltration. Recently, biliary epithelial cells have been shown to secrete cytokines and chemokines and to express components of the mucosal immune system such as Toll-like receptors.

METHODS AND RESULTS

We examined the expression of a neutrophil chemo-attractant, interluekin (IL)-8, in bile ductular cells to clarify the histogenesis of reactive bile ductules with neutrophilic infiltration using human liver tissues (eight cases of chronic viral hepatitis, seven cases of liver cirrhosis (LC), seven cases of sepsis, 11 cases of extrahepatic biliary obstruction (EBO), three cases of fulminant hepatitis (FH), five cases of primary biliary cirrhosis, and three cases of primary sclerosing cholangitis). Human neutrophil peptides 1-3 (HNP1-3) were used as markers of neutrophils. Immunohistochemically, IL-8 was detected in bile ductules in various diseased livers. HNP1-3-positive neutrophils were significantly dense around IL-8-positive bile ductules compared with IL-8-negative ductules in septic liver, LC, EBO, and FH. Experiments in vitro showed that cultured human biliary epithelial cells expressed and secreted IL-8 in response to lipopolysaccharide and also IL-1beta and tumour necrosis factor-alpha.

CONCLUSIONS

Neutrophilic infiltration around reactive bile ductules may be related to the IL-8 expressed in bile ductular epithelia, possibly induced by bacterial components and proinflammatory cytokines released locally.

Expression profiles of MUC mucins and trefoil factor family (TFF) peptides in the intrahepatic biliary system: physiological distribution and pathological significance

Mucin secreted by mucosal epithelial cells plays a role in the protection of the mucosal surface and also is involved in pathological processes. So far, MUC1-4, 5AC, 5B, 6-8, 11-13 and 15-17 genes coding the backbone mucin core protein have been identified in humans. Their diverse physiological distribution and pathological alterations have been reported. Trefoil factor family (TFF) peptides are mucin-associated molecules co-expressed with MUC mucins and involved in the maintenance of mucosal barrier and the biological behavior of epithelial and carcinoma cells. Intrahepatic biliary system is a route linking the bile canaliculi and the extrahepatic bile duct for the excretion of bile synthesized by hepatocytes. Biliary epithelial cells line in the intrahepatic biliary system, secreting mucin and other molecules involved in the maintenance and regulation of the system. In this review, the latest information regarding properties, expression profiles and regulation of MUC mucins and TFF peptides in the intrahepatic biliary system is summarized. In particular, we focus on the expression profiles and their significance of MUC mucins in developmental and normal livers, various hepatobiliary diseases and intrahepatic cholangiocarcinoma.

Primary biliary cirrhosis: what we know and what we want to know about human PBC and spontaneous PBC mouse models

Human autoimmune cholangiopathy comprises several intractable liver diseases that ultimately lead to hepatic failure. Primary biliary cirrhosis (PBC), allograft rejection, graft versus host diseases, and, possibly, primary sclerosing cholangitis are representative of immune-mediated cholangiopathies. Among them, PBC is the best-investigated human autoimmune cholangiopathy. The immunological approach to PBC has provided much critical information regarding its pathogenesis. The breakdown of self-tolerance in both B cells and T cells toward E2 components of the pyruvate dehydrogenase complex is evident. However, a number of questions regarding its etiology are unclear, in particular, the mechanisms involved in the selectivity of cholangiocyte destruction. In this brief review, we discuss what we know and we do not know regarding the pathogenesis of PBC.

Molecular mechanisms of cholangiopathy in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is histologically characterized by chronic nonsuppurative destructive cholangitis (CNSDC) and the progressive loss of intrahepatic small bile ducts. Cellular immune mechanisms involving T-cell reaction are thought to be significantly involved in the formation of CNSDC and bile duct loss. In inflamed portal tracts of PBC, CD4+ T cells of Th1 type expressing IFN-gamma or CXCR3 are aggregated and more commonly detected around injured bile ducts than Th2-type CD4+ T cells expressing IL-4 or CCR4, indicating that Th1-dominant cellular immunity plays a more-prominent role in recruitment of memory T-cell subsets in PBC and may be responsible for the progressive bile duct damage. Biliary epithelial apoptosis is demonstrated to be a major pathogenic process of bile duct loss in PBC. In CNSDC, several biliary apoptotic cells, an aberrant expression of Fas antigen (proapoptotic molecule) and decreased expression of bcl-2 and mcl-1 (antiapoptotic molecules) are found, although interlobular bile ducts express bcl-2 and mcl-2 but lack Fas. In addition, the upregulation of WAF1 and p53 related to biliary apoptosis is found in biliary epithelial cells of PBC, which may be due to cell senescence in response to genotoxic damage such as oxidative stress. Several steps and mechanisms during induction and progression of cholangitis and biliary apoptosis followed by bile duct loss are now being proposed in PBC, but future analysis of an etiopathogenesis to explain the characteristic histopathogenesis of PBC is required.

Endotoxin tolerance in human intrahepatic biliary epithelial cells is induced by upregulation of IRAK-M

BACKGROUND/AIM

Biliary epithelial cells possess an innate immune system consisting of Toll-like receptors (TLRs). Although the human bile contains lipopolysaccharide (LPS) in normal as well as diseased livers, LPS physiologically does not elicit an inflammatory response in the biliary tree. This absence of a response to LPS could be due to the 'endotoxin tolerance' speculated to maintain innate immune homeostasis in organs. Our aim here is to clarify the presence and molecular mechanisms of endotoxin tolerance of biliary epithelium.

METHODS AND RESULTS

In nuclear factor-kappaB (NF-kappaB)-DNA binding assays using three-cultured human intrahepatic biliary epithelial cell (HIBEC) lines, all the cells responded to LPS (TLR4 ligand) by activating NF-kappaB, but pretreatment with LPS for 24 h effectively induced tolerance against any subsequent stimulation with LPS (endotoxin tolerance). This tolerance was also induced by pretreatment with Pam(3)Cys-Ser-(Lys)(4) trihydrochloride (Pam(3)CKS(4), TLR1/2 ligand). Then, real-time polymerase chain treaction and Western blotting revealed that LPS treatment upregulated the expression of IRAK-M (a negative regulator of TLR signaling), but did not affect interleukin-1 receptor-associated kinase-1 (IRAK-1, an essential molecule of TLR signaling), in HIBECs. Moreover, immunohistochemistry revealed that IRAK-M was diffusely expressed in intrahepatic bile ducts.

CONCLUSIONS

This study showed that the mechanism of endotoxin tolerance exists in the intrahepatic biliary tree and is possibly induced by the expression of IRAK-M in the intrahepatic biliary epithelium, suggesting that the endotoxin tolerance is important in maintaining innate immune biliary homeostasis.

Augmented expression of hepatocytes growth factor activator inhibitor type 1 (HAI-1) in intrahepatic small bile ducts in primary biliary cirrhosis

The repair system of damaged biliary mucosa was not fully clarified so far in primary biliary cirrhosis (PBC). Given that related factors of the hepatocyte growth factor (HGF) such as HGF activator (HGFA) and HGFA inhibitor type 1 (HAI-1) participate in the repair of injured gastrointestinal mucosa, we investigated the involvement of the HGF/HGFA/HAI-1 system in PBC and control livers. The expression of HGFA, HAI-1, and c-Met was examined in PBC livers (n=24), diseased livers (control, n=30), and normal livers (n=15) by immunohistochemistry and semiquantitative reverse transcriptase-polymerase chain reaction. We examined the expression of HGFA, HAI-1, and c-Met, and the effect of HGF administration on cell proliferation and wound healing, and HAI expression in cultured mouse biliary epithelial cells (BECs). HAI-1 expression was faint in control livers, whereas it was significantly augmented in damaged small bile ducts, bile ductules, and periportal hepatocytes in PBC (p<0.05). HGFA and c-Met were homogeneously expressed in BECs in PBC and control livers. HAI-1 expression was increased at the front of wound healing and the treatment with HGF-enhanced HAI-1 expression, cell proliferation, and wound healing in cultured BECs. HGF/HGFA/HAI-1 system may participate in biliary mucosal repair as reported in gastrointestinal mucosal repair.

Autoreactive T-cell responses in primary biliary cirrhosis are proinflammatory whereas those of controls are regulatory

BACKGROUND & AIMS

Autoreactive T cells that proliferate in response to autoantigens are found in both autoimmune disease and controls but have important qualitative differences in relative activation states, costimulation signal requirements, and pathogenetic significance. Understanding the mechanism for activation of autoreactive T cells will be critical in the treatment of autoimmune diseases.

METHODS

To understand the differences between autoreactive T cells in primary biliary cirrhosis (PBC) versus controls, we have developed autoreactive T-cell clones (TCCs) from patients with PBC and healthy controls and have used a peptide corresponding to the CD4 major autoepitope to define the relative proliferative and cytokine response.

RESULTS

Using an enzyme-linked immunosorbent spot assay, peripheral blood mononuclear cells (PBMCs) from PBC, but not from controls, produce interferon (IFN)-gamma regardless of whether costimulation-competent or -incompetent antigen-presenting cells (APC) were used. In contrast, a significant number of IFN-gamma-producing cells were found in PBMCs from controls but only if costimulation-competent PBMCs presented an autoantigenic peptide. In addition, costimulation-dependent autoreactive TCCs became anergic after a single round of stimulation in the presence of APC that did not provide a costimulatory signal, whereas some costimulation-independent autoreactive TCCs required repeated stimulation to become anergic and the others did not become anergic. Finally, anergic TCCs produced interleukin-10, but no IFN-gamma, and exhibited regulatory functions in an antigen-dependent, cell contact-independent, and partially interleukin-10-mediated manner.

CONCLUSIONS

These data relate specifically to the functional characteristics of autoreactive T cells in PBC but are also generically important for understanding the mechanisms for generating pathogenetic autoreactive T cells.

Possible regulation of migration of intrahepatic cholangiocarcinoma cells by interaction of CXCR4 expressed in carcinoma cells with tumor necrosis factor-alpha and stromal-derived factor-1 released in stroma

Intrahepatic cholangiocarcinoma (ICC) is highly fatal because of early invasion, widespread metastasis, and lack of an effective therapy. We examined roles of CXCR4 and its ligand, stromal cell-derived factor (SDF)-1, in migration of ICC with respect to tumor-stromal interaction by using two ICC cell lines, a fibroblast cell line (WI-38), and 28 human ICC tissues. The two ICC cell lines expressed CXCR4 mRNA and protein, and WI-38 fibroblasts expressed SDF-1 mRNA and protein. Migration of cultured ICC cells in Matrigel was induced by co-culture with WI-38 fibroblasts and by incubation with SDF-1. Anti-SDF-1 antibody suppressed migration, demonstrating that SDF-1 released from WI-38 fibroblasts was responsible for this migration. Tumor necrosis factor (TNF)-alpha pretreatment of ICC cells up-regulated CXCR4 mRNA and protein expression in a concentration-dependent manner. Administration of SDF-1 and TNF-alpha increased synergistically ICC cell migration, which was suppressed by the CXCR4 antagonist AMD3100. In ICC tissue, TNF-alpha was mainly expressed in infiltrated macrophages, CXCR4 in ICC cells, and SDF-1 in stromal fibroblasts. In conclusion, the interaction of SDF-1 released from fibroblasts and CXCR4 expressed on ICC cells may be actively involved in ICC migration, and TNF-alpha may enhance ICC cell migration by increasing CXCR4 expression. CXCR4 could be a therapeutic target to prevent ICC invasion.

Mitochondrial antigens as targets of cellular and humoral auto-immunity in primary biliary cirrhosis

Several factors point toward an auto-immune pathogenesis for primary biliary cirrhosis(PBC), mostly based on the presence of serum auto-antibodies to mitochondrial antigens(AMAs) and autoreactive T cells (both helper and cytotoxic). Interestingly, epitopes recognized by AMA and T-cell clones are located within overlapping areas of the antigens. Moreover,a role for an imbalance in cytokine pattern and for natural-killer lymphocytes has also been proposed. Despite several experimental reports, no clear evidence is available regarding the interaction of these factors leading to bile duct destruction. This article reviews the current reports regarding the auto-immune reaction against mitochondrial auto-antigens in PBC.

Characterization of biliary intra-epithelial lymphocytes at different anatomical levels of intrahepatic bile ducts under normal and pathological conditions: numbers of CD4+CD28- intra-epithelial lymphocytes are increased in primary biliary cirrhosis

Distribution of intra-epithelial lymphocytes along intrahepatic biliary tree (bIEL), and their density and phenotype were examined in normal and diseased livers, particularly in primary biliary cirrhosis (PBC). Immunohistochemically, bIEL were examined in 28 normal livers, 13 cases of chronic viral hepatitis (CVH), 13 cases of PBC, five cases of primary sclerosing cholangitis (PSC), seven cases of extrahepatic biliary obstruction (EBO), and 16 hepatolithiatic livers. In normal livers, bIEL were relatively dense at large and septal bile ducts compared to interlobular ducts. Most of them were positive for CD3 and CD8, while a few were positive for CD4, CD20 and CD57. In CVH, PSC and EBO, neither distribution, phenotype nor density of bIEL differed from normal liver. In hepatolithiasis, numbers of CD8(+)bIEL were increased in stone-containing ducts. In PBC, numbers of CD4(+)CD28(-)bIEL, which are reportedly responsible for target tissue destruction in autoimmune diseases, were markedly increased in damaged interlobular ducts. In conclusion, CD3(+)CD8(+)bIEL may be involved in immune homeostasis of intrahepatic bile ducts in normal livers and in CVH, PSC and EBO. Altered distribution and phenotypes of bIEL in PBC and hepatolithiasis may reflect their participation in biliary lesions. Increased CD4(+)CD28(-)bIEL in damaged bile ducts of PBC may be related to immune-mediated biliary damage.

Interferon gamma accelerates NF-kappaB activation of biliary epithelial cells induced by Toll-like receptor and ligand interaction

BACKGROUND

The Toll-like receptor (TLR) family recognises pathogen associated molecular patterns (PAMPs) and plays a pivotal role in the innate immune response. Biliary epithelial cells (BECs) lining the intrahepatic bile ducts are potentially exposed to bacterial components in bile, and murine BECs possess TLRs that recognise PAMPs, resulting in nuclear factor kappaB (NF-kappaB) activation.

AIMS

To examine the presence of TLRs in human BECs and the influence of cytokines and PAMPs on TLR expression and NF-kappaB activation.

METHODS

The expression of TLR2-5, MD-2, MyD88, and IRAK1 was examined in human liver tissue and cultured BECs by immunohistochemistry or reverse transcription polymerase chain reaction. The influence of PAMPs (peptidoglycan and lipopolysaccharide) in cultured cells preincubated with interferon gamma (IFNgamma) was evaluated by NF-kappaB activation.

RESULTS

TLR2-5, MyD88, and IRAK-1 proteins were detectable in BECs of the intrahepatic biliary tree in human liver tissue. TLR2-5, MD-2, MyD88, and IRAK-1 mRNA was demonstrated in human cultured BECs. The expression of these TLRs was upregulated by IFNgamma, and TLR2 was upregulated by tumour necrosis factor alpha. Interleukins 4 and 6 failed to induce TLR upregulation. Interestingly, preincubation with IFNgamma synergistically increased the upregulation of NF-kappaB induced by PAMPs in cultured BECs.

CONCLUSION

These results suggest that the TLR family is present in human biliary cells and participates in the innate immunity of the intrahepatic biliary tree. Disordered regulation of TLRs after intracellular signalling by cytokines and PAMPs may be involved in immune mediated biliary diseases.

Th1 cytokine-induced downregulation of PPARgamma in human biliary cells relates to cholangitis in primary biliary cirrhosis

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is known to inhibit the production of proinflammatory cytokines. In Th1-predominant diseases, PPARgamma ligands can ameliorate clinical severity by downregulating the expression of proinflammatory cytokines. Primary biliary cirrhosis (PBC) is characterized by chronic destructive cholangitis with a Th1-predominant cytokine milieu. Unusual immune responses to infectious agents are suspected to underlie its etiopathogenesis. We examined the significance of PPARgamma in biliary inflammation in connection to PBC. To this end, we performed immunohistochemistry, quantitative polymerase chain reaction, and nuclear factor-kappaB (NF-kappaB) DNA-binding assays to clarify the intrahepatic distribution of PPARgamma and the regulation of PPARgamma by inflammatory cytokines and PPARgamma ligand in five cultured biliary cell lines including one derived from PBC liver. In liver specimens from patients with PBC, PPARgamma protein was ubiquitously expressed in intrahepatic biliary epithelium, whereas the expression of PPARgamma protein and mRNA was reduced in damaged bile ducts. PPARgamma expression in cultured cells was upregulated by interleukin-4 (IL-4; Th2-type), but downregulated by IFN-gamma (Th1-type). PPARgamma ligand negatively modulated lipopolysaccharide-induced NF-kappaB activation. Moreover, this inhibitory effect of PPARgamma ligand was attenuated by pretreatment with IFN-gamma. In conclusion, PPARgamma may be important to maintain homeostasis in the intrahepatic biliary epithelium, and its reduction in the bile ducts of PBC liver may be associated with the Th1-predominant milieu and with the development of chronic cholangitis in PBC. Immunosuppression using PPARgamma ligands may be of therapeutic benefit to attenuate biliary inflammation in PBC.

Fractalkine and CX3CR1 are involved in the recruitment of intraepithelial lymphocytes of intrahepatic bile ducts

Fractalkine is a chemokine with both chemoattractant and cell-adhesive functions, and in the intestine it is involved with its receptor CX3CR1 in the chemoattraction and recruitment of intraepithelial lymphocytes. We examined the pathophysiological roles of fractalkine and CX3CR1 in normal and diseased bile ducts. Expression of fractalkine and CX3CR1 were examined in liver tissues from patients with primary biliary cirrhosis (17 cases) and controls (9 cases of primary sclerosing cholangitis, 10 cases of extrahepatic biliary obstruction, 20 cases of chronic viral hepatitis C, and 18 cases of histologically normal livers). Expression of fractalkine in biliary epithelial cells (BECs) in response to cytokine treatments was examined using a human cholangiocarcinoma cell line (HuCC-T1) and human intrahepatic BEC line. The chemotaxis of CX3CR1-expressing monocytes (THP-1) toward fractalkine was assayed using chemotaxis chambers. Fractalkine messenger RNA/protein were expressed on BECs of normal and diseased bile ducts, and their expression was upregulated in injured bile ducts of primary biliary cirrhosis. CX3CR1 was expressed on infiltrating mononuclear cells in portal tracts and on CD3(+), CD4(+), and CD8(+) intraepithelial lymphocytes of injured bile ducts in primary biliary cirrhosis. Fractalkine messenger RNA expression was upregulated in two cultured BECs on treatment with lipopolysaccharide and Th1-cytokines (interleukin 1beta, interferon gamma, and tumor necrosis factor alpha). THP-1 cells showed chemotaxis toward fractalkine secreted by cultured cells. In conclusion, Th1-cytokine predominance and lipopolysaccharide in the microenvironment of injured bile ducts resulting from primary biliary cirrhosis induce the upregulation of fractalkine expression in BECs, followed by the chemoattraction of CX3CR1-expressing mononuclear cells, including CD4(+) and CD8(+) T cells, and their adhesion to BECs and the accumulation of biliary intraepithelial lymphocytes.

Biliary epithelial cells regulate autoreactive T cells: implications for biliary-specific diseases

The biliary epithelial cell (BEC) is the target for several human immune mediated liver diseases, including primary biliary cirrhosis, but it is not always clear whether the BEC functions as an accessory cell or an antigen presenting cell, although it is well documented that BECs express high levels of human leukocyte antigen Class II, intercellular adhesion molecule-1, and lymphocyte function-associated antigen-3. To examine this issue, we established autoreactive T-cell clones from human leukocyte antigen-DR53 patients with primary biliary cirrhosis and characterized BEC function as a function of the ability of BECs to regulate T-cell activation. We report herein that BEC-mediated T-cell activation occurs partially via programmed death 1 ligands in a cell-contact-dependent manner. Further, such activation occurs via prostaglandin E2 production in a cell-contact-independent fashion. Moreover, the production of prostaglandin E2 was partially controlled by interleukin-1beta and tumor necrosis factor alpha. In conclusion, the regulatory activities of BECs are important for the maintenance of peripheral immune tolerance. Further, modulation of BEC function may be used for therapeutic modulation.

Peptide antibiotic human beta-defensin-1 and -2 contribute to antimicrobial defense of the intrahepatic biliary tree

Human beta-defensins (hBDs) are important antimicrobial peptides that contribute to innate immunity at mucosal surfaces. This study was undertaken to investigate the expression of hBD-1 and hBD-2 in intrahepatic biliary epithelial cells in specimens of human liver, and 4 cultured cell lines (2 consisting of biliary epithelial cells and 2 cholangiocarcinoma cells). In addition, hBD-1 and hBD-2 were assayed in specimens of bile. hBD-1 was nonspecifically expressed immunohistochemically in intrahepatic biliary epithelium and hepatocytes in all patients studied, but expression of hBD-2 was restricted to large intrahepatic bile ducts in 8 of 10 patients with extrahepatic biliary obstruction (EBO), 7 of 11 with hepatolithiasis, 1 of 6 with primary biliary cirrhosis (PBC), 1 of 5 with primary sclerosing cholangitis (PSC), 0 of 6 with chronic hepatitis C (CH-C), and 0 of 11 with normal hepatic histology. hBD-2 expression was evident in bile ducts exhibiting active inflammation. Serum C reactive protein levels correlated with biliary epithelial expression of hBD-2. Real-time PCR revealed that in all of 28 specimens of fresh liver, including specimens from patients with hepatolithiasis, PBC, PSC, CH-C and normal hepatic histology, hBD-1 messenger RNA was consistently expressed, whereas hBD-2 messenger RNA was selectively expressed in biliary epithelium of patients with hepatolithiasis. Immunobloting analysis revealed hBD-2 protein in bile in 1 of 3 patients with PSC, 1 of 3 with PBC, and each of 6 with hepatolithiasis; in contrast, hBD-1 was detectable in all bile samples examined. Four cultured biliary epithelial cell lines consistently expressed hBD-1; in contrast these cell lines did not express hBD-2 spontaneously but were induced to express hBD-2 by treatment with Eschericia coli, lipopolysaccharide, interleukin-1beta or tumor necrosis factor-alpha. In conclusion, these findings suggest that in the intrahepatic biliary tree, hBD-2 is expressed in response to local infection and/or active inflammation, whereas hBD-1 may constitute a preexisting component of the biliary antimicrobial defense system.

Cholestatic syndromes

PURPOSE OF REVIEW

This review highlights recent developments in the molecular pathogenesis of cholestasis as well new aspects of pathogenesis and management of clinical cholestatic disorders.

RECENT FINDINGS

Highlights include the role of nuclear receptors including FXR ligands as potential therapeutic agents, new genetic defects for pediatric cholestasis and sclerosing cholangitis, and novel infections and environmental agents as etiologies for primary biliary cirrhosis. Important clinical studies have been published in the area of pediatric cholestatic syndromes, intrahepatic cholestasis of pregnancy, primary biliary cirrhosis, primary and secondary sclerosing cholangitis, cholestasis of sepsis, viral cholestatic syndromes, and drug-induced cholestasis.

SUMMARY

These advances continue to improve understanding of the pathophysiology, diagnosis, and management of cholestatic liver disease.