High-fat diet modulates bile acid composition and gut microbiota, affecting severe cholangitis and cirrhotic change in murine primary biliary cholangitis.

Increasing evidence suggests that, in addition to a loss of tolerance, bile acid (BA) modulates the natural history of primary biliary cholangitis (PBC). We focused on the impacts of dietary changes on the immunopathology of PBC, along with alterations in BA composition and gut microbiota. In this study, we have taken advantage of our unique PBC model, a Cyp2c70/Cyp2a12 double knockout (DKO), which includes a human-like BA composition, and develops progressive cholangitis following immunization with the PDC-E2 mimic, 2-octynoic acid (2OA). We compared the effects of a ten-week high-fat diet (HFD) (60 % kcal from fat) and a normal diet (ND) on 2OA-treated DKO mice. Importantly, we report that 2OA-treated DKO mice fed HFD had significantly exacerbated cholangitis, leading to cirrhosis, with increased hepatic expression of Th1 cytokines/chemokines and hepatic fibrotic markers. Serum lithocholic acid (LCA) levels and the ratio of chenodeoxycholic acid (CDCA)-derived BAs to cholic acid-derived BAs were significantly increased by HFD. This was also associated with downregulated expression of key regulators of BA synthesis, including Cyp8b1, Cyp3a11, and Sult2a1. In addition, there were increases in the relative abundances of Acetatifactor and Lactococcus and decreases in Desulfovibrio and Lachnospiraceae_NK4A136_group, which corresponded to the abundances of CDCA and LCA. In conclusion, HFD and HFD-induced alterations in the gut microbiota modulate BA composition and nuclear receptor activation, leading to cirrhotic change in this murine PBC model. These findings have significant implications for understanding the progression of human PBC.

PTEN deficiency induces an extrahepatic cholangitis-cholangiocarcinoma continuum via aurora kinase A in mice.

BACKGROUND & AIMS: The PTEN-AKT pathway is frequently altered in extrahepatic cholangiocarcinoma (eCCA). We aimed to evaluate the role of PTEN in the pathogenesis of eCCA and identify novel therapeutic targets for this disease. METHODS: The Pten gene was genetically deleted using the Cre-loxp system in biliary epithelial cells. The pathologies were evaluated both macroscopically and histologically. The characteristics were further analyzed by immunohistochemistry, reverse-transcription PCR, cell culture, and RNA sequencing. Some features were compared to those in human eCCA samples. Further mechanistic studies utilized the conditional knockout of Trp53 and Aurora kinase A (Aurka) genes. We also tested the effectiveness of an Aurka inhibitor. RESULTS: We observed that genetic deletion of the Pten gene in the extrahepatic biliary epithelium and peri-ductal glands initiated sclerosing cholangitis-like lesions in mice, resulting in enlarged and distorted extrahepatic bile ducts in mice as early as 1 month after birth. Histologically, these lesions exhibited increased epithelial proliferation, inflammatory cell infiltration, and fibrosis. With aging, the lesions progressed from low-grade dysplasia to invasive carcinoma. Trp53 inactivation further accelerated disease progression, potentially by downregulating senescence. Further mechanistic studies showed that both human and mouse eCCA showed high expression of AURKA. Notably, the genetic deletion of Aurka completely eliminated Pten deficiency-induced extrahepatic bile duct lesions. Furthermore, pharmacological inhibition of Aurka alleviated disease progression. CONCLUSIONS: Pten deficiency in extrahepatic cholangiocytes and peribiliary glands led to a cholangitis-to-cholangiocarcinoma continuum that was dependent on Aurka. These findings offer new insights into preventive and therapeutic interventions for extrahepatic CCA. IMPACT AND IMPLICATIONS: The aberrant PTEN-PI3K-AKT signaling pathway is commonly observed in human extrahepatic cholangiocarcinoma (eCCA), a disease with a poor prognosis. In our study, we developed a mouse model mimicking cholangitis to eCCA progression by conditionally deleting the Pten gene via Pdx1-Cre in epithelial cells and peribiliary glands of the extrahepatic biliary duct. The conditional Pten deletion in these cells led to cholangitis, which gradually advanced to dysplasia, ultimately resulting in eCCA. The loss of Pten heightened Akt signaling, cell proliferation, inflammation, fibrosis, DNA damage, epigenetic signaling, epithelial-mesenchymal transition, cell dysplasia, and cellular senescence. Genetic deletion or pharmacological inhibition of Aurka successfully halted disease progression. This model will be valuable for testing novel therapies and unraveling the mechanisms of eCCA tumorigenesis.

New insights into the pathogenesis of primary biliary cholangitis asymptomatic stage.

Primary biliary cholangitis (PBC) is a chronic cholestatic progressive liver disease and one of the most important progressive cholangiopathies in adults. Damage to cholangiocytes triggers the development of intrahepatic cholestasis, which progresses to cirrhosis in the terminal stage of the disease. Accumulating data indicate that damage to biliary epithelial cells [(BECs), cholangiocytes] is most likely associated with the intracellular accumulation of bile acids, which have potent detergent properties and damaging effects on cell membranes. The mechanisms underlying uncontrolled bile acid intake into BECs in PBC are associated with pH change in the bile duct lumen, which is controlled by the bicarbonate (HCO3-) buffer system "biliary HCO3- umbrella". The impaired production and entry of HCO3- from BECs into the bile duct lumen is due to epigenetic changes in expression of the X-linked microRNA 506. Based on the growing body of knowledge on the molecular mechanisms of cholangiocyte damage in patients with PBC, we propose a hypothesis explaining the pathogenesis of the first morphologic (ductulopenia), immunologic (antimitochondrial autoantibodies) and clinical (weakness, malaise, rapid fatigue) signs of the disease in the asymptomatic stage. This review focuses on the consideration of these mechanisms.

Spontaneous development of an autoimmune hepatitis - primary biliary cholangitis overlap syndrome in dnTGFßRII Aire-/- mice.

Autoimmune regulator (Aire) and TGF-ß signaling play important roles in central tolerance and peripheral tolerance, respectively, by eliminating or suppressing the activity of autoreactive T cells. We previously demonstrated that dnTGFßRII mice develop a defect in peripheral tolerance and a primary biliary cholangitis (PBC)-like disease. We hypothesized that by introducing the Aire gene to this model, we would observe a more severe PBC phenotype. Interestingly, however, we demonstrated that, while dnTGFßRII Aire-/- mice do manifest key histological and serological features of autoimmune cholangitis, they also develop mild to moderate interface hepatitis and show high levels of alanine transaminase (ALT) and antinuclear antibodies (ANA), characteristics of autoimmune hepatitis (AIH). To further understand this unique phenotype, we performed RNA sequencing (RNA-seq) and flow cytometry to explore the functional pathways and immune cell pathways in the liver of dnTGFßRII Aire-/- mice. Our data revealed enrichments of programmed cell death pathways and predominant CD8+ T cell infiltrates. Depleting CD8+ T cells using an anti-CD8α antibody significantly alleviated hepatic inflammation and prolonged the life span of these mice. Finally, RNA-seq data indicated the clonal expansion of hepatic CD8+ T cells. In conclusion, these mice developed an autoreactive CD8+ T-cell-mediated autoimmune cholangitis with concurrent hepatitis that exhibited key histological and serological features of the AIH-PBC overlap syndrome, representing a novel model for the study of tolerance and autoimmune liver disease. © 2023 The Pathological Society of Great Britain and Ireland.

Inflammatory type 2 conventional dendritic cells contribute to murine and human cholangitis.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is a progressive cholangiopathy characterised by fibrotic stricturing and inflammation of bile ducts, which seems to be driven by a maladaptive immune response to bile duct injury. The histological finding of dendritic cell expansion in portal fields of patients with PSC prompted us to investigate the role of dendritic cells in orchestrating the immune response to bile duct injury. METHODS: Dendritic cell numbers and subtypes were determined in different mouse models of cholangitis by flow cytometry based on lineage-imprinted markers. Findings were confirmed by immunofluorescence microscopy of murine livers, and liver samples from patients with PSC were compared to control samples from bariatric surgery patients. Using genetic tools, selected dendritic cell subsets were depleted in murine cholangitis. The dendritic cell response to bile duct injury was determined by single-cell transcriptomics. RESULTS: Cholangitis mouse models were characterised by selective intrahepatic expansion of type 2 conventional dendritic cells, whereas plasmacytoid and type 1 conventional dendritic cells were not expanded. Expansion of type 2 conventional dendritic cells in human PSC lesions was confirmed by histology. Depletion studies revealed a proinflammatory role of type 2 conventional dendritic cells. Single-cell transcriptomics confirmed inflammatory maturation of the intrahepatic type 2 conventional dendritic cells and identified dendritic cell-derived inflammatory mediators. CONCLUSIONS: Cholangitis is characterised by intrahepatic expansion and inflammatory maturation of type 2 conventional dendritic cells in response to biliary injury. Therefore, type 2 conventional dendritic cells and their inflammatory mediators might be potential therapeutic targets for the treatment of PSC. LAY SUMMARY: Primary sclerosing cholangitis (PSC) is an inflammatory liver disease of the bile ducts for which there is no effective treatment. Herein, we show that the inflammatory immune response to bile duct injury is organised by a specific subtype of immune cell called conventional type 2 dendritic cells. Our findings suggest that this cell subtype and the inflammatory molecules it produces are potential therapeutic targets for PSC.

Regional heritability mapping identifies several novel loci (STAT4, ULK4, and KCNH5) for primary biliary cholangitis in the Japanese population.

While the advent of GWAS more than a decade ago has ushered in remarkable advances in our understanding of complex traits, the limitations of single-SNP analysis have also led to the development of several other approaches. Simulation studies have shown that the regional heritability mapping (RHM) method, which makes use of multiple adjacent SNPs jointly to estimate the genetic effect of a given region of the genome, generally has higher detection power than single-SNP GWAS. However, thus far its use has been mostly limited to agricultural settings, and its potential for the discovery of new genes in human diseases is yet to be fully exploited. In this study, by applying the RHM method to primary biliary cholangitis (PBC) in the Japanese population, we identified three novel loci (STAT4, ULK4, and KCNH5) at the genome-wide significance level, two of which (ULK4 and KCNH5) have not been found associated with PBC in any population previously. Notably, these genes could not be detected by using conventional single-SNP GWAS, highlighting the potential of the RHM method for the detection of new susceptibility loci in human diseases. These findings thereby provide strong empirical evidence that RHM is an effective and practical complementary approach to GWAS in this context. Also, liver tissue mRNA microarray analysis revealed higher gene expression levels in ULK4 in PBC patients (P < 0.01). Lastly, we estimated the common SNP heritability of PBC in the Japanese population (0.210 ± 0.026).

NAFLD exacerbates cholangitis and promotes cholangiocellular carcinoma in mice.

Nonalcoholic fatty liver disease (NAFLD) is an increasingly common condition, affecting up to 25% of the population worldwide. NAFLD has been linked to several conditions, including hepatic inflammation, fibrosis, and hepatocellular carcinoma (HCC), however the role of NAFLD in cholangitis and the development of cholangiocellular carcinoma (CCC) remains poorly understood. This study investigated whether a high-fat diet (HFD) promotes cholangitis and the development of CCC in mice. We used liver-specific E-cadherin gene (CDH1) knockout mice, CDH1∆Liv , which develop spontaneous inflammation in the portal areas along with periductal onion skin-like fibrosis, similar to that of primary sclerosing cholangitis (PSC). An HFD or normal diet (ND) was fed to CDH1∆Liv mice for 7 mo. In addition, CDH1∆Liv mice were crossed with LSL-KrasG12D mice, fed an HFD, and assessed in terms of liver tumor development. The extent of cholangitis and number of bile ductules significantly increased in mice fed an HFD compared with ND-administered CDH1∆Liv mice. The numbers of Sox9 and CD44-positive stem cell-like cells were significantly increased in HFD mice. LSL-KrasG12D /CDH1∆Liv HFD mice exhibited increased aggressiveness along with the development of numerous HCC and CCC, whereas LSL-KrasG12D /CDH1∆Liv ND mice showed several macroscopic tumors with both HCC and CCC components. In conclusion, NAFLD exacerbates cholangitis and promotes the development of both HCC and CCC in mice.

Cholangiopathy and Biliary Fibrosis in Cyp2c70-Deficient Mice Are Fully Reversed by Ursodeoxycholic Acid.

BACKGROUND AND AIMS: Bile acids (BAs) aid intestinal fat absorption and exert systemic actions by receptor-mediated signaling. BA receptors have been identified as drug targets for liver diseases. Yet, differences in BA metabolism between humans and mice hamper translation of pre-clinical outcomes. Cyp2c70-ablation in mice prevents synthesis of mouse/rat-specific muricholic acids (MCAs), but potential (patho)physiological consequences of their absence are unknown. We therefore assessed age- and gender-dependent effects of Cyp2c70-deficiency in mice. METHODS: The consequences of Cyp2c70-deficiency were assessed in male and female mice at different ages. RESULTS: Cyp2c70-/- mice were devoid of MCAs and showed high abundances of chenodeoxycholic and lithocholic acids. Cyp2c70-deficiency profoundly impacted microbiome composition. Bile flow and biliary BA secretion were normal in Cyp2c70-/- mice of both sexes. Yet, the pathophysiological consequences of Cyp2c70-deficiency differed considerably between sexes. Three-week old male Cyp2c70-/- mice showed high plasma BAs and transaminases, which spontaneously decreased thereafter to near-normal levels. Only mild ductular reactions were observed in male Cyp2c70-/- mice up to 8 months of age. In female Cyp2c70-/- mice, plasma BAs and transaminases remained substantially elevated with age, gut barrier function was impaired and bridging fibrosis was observed at advanced age. Addition of 0.1% ursodeoxycholic acid to the diet fully normalized hepatic and intestinal functions in female Cyp2c70-/- mice. CONCLUSION: Cyp2c70-/- mice show transient neonatal cholestasis and develop cholangiopathic features that progress to bridging fibrosis in females only. These consequences of Cyp2c70-deficiency are restored by treatment with UDCA, indicating a role of BA hydrophobicity in disease development.

Primary biliary cholangitis with normal alkaline phosphatase: A neglected clinical entity challenging current guidelines.

BACKGROUND & AIM: The diagnosis of primary biliary cholangitis (PBC), an uncommon immune-mediated cholestatic liver disease, is based on positive circulating anti-mitochondrial (AMA) and/or PBC-specific anti-nuclear autoantibodies (ANA), coupled with elevated serum alkaline phopsphatase (ALP) levels. Timely initiation of treatment with ursodeoxycholic acid prevents progression to cirrhosis and liver failure. We aimed at investigating liver histology in patients with normal ALP level and positive AMA and/or PBC-specific ANA. METHODS: We searched the Swiss PBC Cohort Study database, which includes subjects with positive PBC autoimmune serology and normal ALP levels, for patients who underwent a liver biopsy. Histological slides were centrally reviewed by an expert liver pathologist, and sera were centrally re-tested for AMA and ANA. RESULTS: 30 patients were included; 90% females, median age 53 (range 27-72) years. Twenty-four (80%) had liver histology typical for (n = 2), consistent with (n = 16) or suggestive of (n = 6) PBC, including three of four AMA-negative ANA-positive patients. Among 22 ursodeoxycholic acid treated patients, 14 had elevated GGT levels before treatment; a significant decrease of the median GGT level between pre- (1.46 x ULN) and post- (0.43 x ULN) treatment (p = 0.0018) was observed. CONCLUSIONS: In our series, a high proportion of AMA positive patients with normal ALP levels have PBC. For the first time we show histological diagnosis of PBC in AMA-negative/PBC-specific ANA-positive subjects and the potential role of GGT as a biomarker in PBC patients with normal baseline ALP levels. Current guidelines for the diagnosis of PBC do not cover the whole extent of PBC presentation, with important clinical implications in terms of timely treatment initiation.

Identifying Differentially Expressed MicroRNAs, Target Genes, and Key Pathways Deregulated in Patients with Liver Diseases.

Liver diseases are important causes of morbidity and mortality worldwide. The aim of this study was to identify differentially expressed microRNAs (miRNAs), target genes, and key pathways as innovative diagnostic biomarkers in liver patients with different pathology and functional state. We determined, using RT-qPCR, the expression of 472 miRNAs in 125 explanted livers from subjects with six different liver pathologies and from control livers. ANOVA was employed to obtain differentially expressed miRNAs (DEMs), and miRDB (MicroRNA target prediction database) was used to predict target genes. A miRNA-gene differential regulatory (MGDR) network was constructed for each condition. Key miRNAs were detected using topological analysis. Enrichment analysis for DEMs was performed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). We identified important DEMs common and specific to the different patient groups and disease progression stages. hsa-miR-1275 was universally downregulated regardless the disease etiology and stage, while hsa-let-7a*, hsa-miR-195, hsa-miR-374, and hsa-miR-378 were deregulated. The most significantly enriched pathways of target genes controlled by these miRNAs comprise p53 tumor suppressor protein (TP53)-regulated metabolic genes, and those involved in regulation of methyl-CpG-binding protein 2 (MECP2) expression, phosphatase and tensin homolog (PTEN) messenger RNA (mRNA) translation and copper homeostasis. Our findings show a novel panel of deregulated miRNAs in the liver tissue from patients with different liver pathologies. These miRNAs hold potential as biomarkers for diagnosis and staging of liver diseases.

NLRP3 receptor contributes to protection against experimental antigen-mediated cholangitis.

Inflammatory diseases of the bile ducts like primary sclerosing colangitis (PSC) are characterized by a robust cellular response targeting the biliary epithelium leading to chronic inflammation and fibrosis. Driving fibro-inflammatory diseases, NOD-like receptors such as NLRP3 have been identified as a central component to immune-mediated pathology. However, to date the role of NLRP3 in biliary diseases has been poorly explored. Here, we addressed the role of NLRP3 in the OVAbil mouse model of antigen-mediated cholangitis. As obesity continues to spread worldwide, we also evaluated the NLRP3 response in experimental cholangitis after high-fat diet exposure. We compared the extent of histopathological liver damage between OVAbil and OVAbilxNLRP3-/- mice after either a standard chow or a high-fat diet. Infiltrating immune cells were characterized by flow cytometry and levels of cytokines, chemokines and liver enzymes in blood samples were analyzed at the end of the experiment. We observed a more severe histopathological phenotype of cholangitis in absence of NLRP3, characterized by loss of bile ducts and larger inflammatory foci and higher levels of IL- 6 and CXCL10 as compared with NLRP3 sufficient mice. This phenotype was further exaggerated in the context of obesity, where cholangitis induced in NLRP3-deficient obese mice resulted in further exacerbated histopathology and increased levels of IL-13 and TNFα, suggesting a diet-specific profile. The absence of NLRP3 caused a supressed IL-17 response. In summary, our data suggest that activation of NLRP3 attenuates this antigen-mediated OVAbil model of cholangitis.

Biliary antibiotics irrigation for E. coli-induced chronic proliferative cholangitis and hepatolithiasis: A pathophysiological study in rabbits.

BACKGROUND: The gram-negative bacteria secreted endotoxin, Lipopolysaccharide (LPS), plays important roles in the formation and recurrence of hepatolithiasis and chronic biliary inflammation in patients of Southeast Asia. We aimed to elucidate the anti-inflammatory effect and mechanism of local antibiotics irrigation on chronic proliferative cholangitis (CPC) and hepatolithiasis. METHODS: Escherichia coli was injected into rabbit bile ducts to induce CPC. Rabbits were divided into sham operation (SO), povidone-iodine, Metronidazole plus chlorhexidine, ofloxacin, furacillin, Neosporin® G.U., and CPC groups. Local irrigation was performed for 28 days after CPC was established. Residual E. coli and LPS, and the expression of MCP-1, CD14, COX-2, VEGF, IL-6, NF-κB, TNF-α, Fas, TGF-ß1, α-SMA, Collagen-I, ß-glucuronidase, PKC, C-myc, and Mucin 5AC were assessed in bile duct tissues. RESULTS: The residual E. coli and LPS, and expression of MCP-1, CD14, COX-2, IL-6, NF-κB, TNF-α, Fas, TGF-ß1, α-SMA, ß-glucuronidase, PKC, C-myc, and Mucin 5AC in the SO, povidone-iodine, Metronidazole plus chlorhexidine, ofloxacin, and Neosporin® G.U. groups were significantly lower than those in the furacillin and CPC groups (P<0.05). VEGF and Collagen-I levels in the SO, povidone-iodine, metronidazole plus chlorhexidine, and ofloxacin groups were significantly lower than those in the furacillin, Neosporin® G.U., and CPC groups (P<0.05). CONCLUSIONS: LPS affects the pathophysiology of E. coli caused chronic proliferative cholangitis and hepatolithiasis recurrence. Local antibiotics irrigation could prevent chronic proliferative cholangitis and stones formation by decreasing LPS-induced proinflammatory and profibrotic cytokines release. Povidone iodine, metronidazole plus chlorhexidine, and ofloxacin were more effective than Neosporin® G.U. and furacillin.

Abnormal Expression of ERα in Cholangiocytes of Patients With Primary Biliary Cholangitis Mediated Intrahepatic Bile Duct Inflammation.

ERα, one of the classical receptors of estrogen, has been found to be abnormally up-regulated in patients with primary biliary cholangitis (PBC), which is an important factor leading to ductopenia. ERα-mediated signaling pathways are involved in proliferation of human intrahepatic biliary epithelial cells (HiBECs) and portal inflammation. Our previous studies have shown that the expression levels of ERα in the liver tissues of PBC patients are positively correlated with the levels of serum pro-inflammatory cytokines. The present study was designed to assess the relationship between abnormal ERα expression in small bile ducts and the progression of PBC. We examined the levels of multiple cytokines and analyzed their relationship with clinical parameters of livers functions in a cohort of 43 PBC patients and 45 healthy controls (HC). The levels of ERα expression and the relation with the levels of cytokines were further assessed. The localization of cytokines and ERα-mediated signaling pathways in liver were examined using immunohistochemistry. The possible underlying mechanisms of these alterations in PBC were explored in vitro. Our results demonstrated that the levels of IL-6, IL-8, and TNF-α were increased in PBC patients, and positively correlated with the serum AKP levels and ERα expression levels. Moreover, the expression of these cytokines were up-regulated in HiBECs that were stimulated with 17ß-estradiol and PPT (an ERα agonist) and they also were positive in intrahepatic bile duct of PBC patients. The ERα-mediated expression of pro-inflammatory cytokines was induced by JNK, P38, and STAT3 phosphorylation in HiBECs. In addition, the CD54 expression was increased in HiBECs after ERα activation, which induced peripheral blood monouclear cells (PBMCs) recruitment. In conclusion, the present study highlighted a key role of abnormal ERα expression in inducing an inflammatory phenotype of HiBECs, which was critical in the development of inflammation and damage in small bile duct.

Liver infiltrating T cells regulate bile acid metabolism in experimental cholangitis.

BACKGROUND & AIMS: T cells are central mediators of liver inflammation and represent potential treatment targets in cholestatic liver disease. Whereas emerging evidence shows that bile acids (BAs) affect T cell function, the role of T cells for the regulation of BA metabolism is unknown. In order to understand this interplay, we investigated the influence of T cells on BA metabolism in a novel mouse model of cholangitis. METHODS: Mdr2-/- mice were crossed with transgenic K14-OVAp mice, which express an MHC class I restricted ovalbumin peptide on biliary epithelial cells (Mdr2-/-xK14-OVAp). T cell-mediated cholangitis was induced by the adoptive transfer of antigen-specific CD8+ T cells. BA levels were quantified using a targeted liquid chromatography-mass spectrometry-based approach. RESULTS: T cell-induced cholangitis resulted in reduced levels of unconjugated BAs in the liver and significantly increased serum and hepatic levels of conjugated BAs. Genes responsible for BA synthesis and uptake were downregulated and expression of the bile salt export pump was increased. The transferred antigen-specific CD8+ T cells alone were able to induce these changes, as demonstrated using Mdr2-/-xK14-OVAp recipient mice on the Rag1-/- background. Mechanistically, we showed by depletion experiments that alterations in BA metabolism were partly mediated by the proinflammatory cytokines TNF and IFN-γ in an FXR-dependent manner, a process that in vitro required cell contact between T cells and hepatocytes. CONCLUSION: Whereas it is known that BA metabolism is dysregulated in sepsis and related conditions, we have shown that T cells are able to control the synthesis and metabolism of BAs, a process which depends on TNF and IFN-γ. Understanding the effect of lymphocytes on BA metabolism will help in the design of combined treatment strategies for cholestatic liver diseases. LAY SUMMARY: Dysregulation of bile acid metabolism and T cells can contribute to the development of cholangiopathies. Before targeting T cells for the treatment of cholangiopathies, it should be determined whether they exert protective effects on bile acid metabolism. Herein, we demonstrate that T cell-induced cholangitis resulted in decreased levels of harmful unconjugated bile acids. T cells were able to directly control synthesis and metabolism of bile acids, a process which was dependent on the proinflammatory cytokines TNF and IFN-γ. Understanding the effect of lymphocytes on bile acid metabolism will help in the design of combined treatment strategies for cholestatic liver diseases.

EGFR monoclonal antibody panitumumab inhibits chronic proliferative cholangitis by downregulating EGFR.

In hepatolithiasis, chronic proliferative cholangitis (CPC), an active and longstanding inflammation of stone­containing bile ducts with enhanced mucin­producing activity, not only affects the progression of the disease, it can also induce biliary carcinogenesis. The present study aimed to examine the effect of the epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab (Pani) on CPC. Following the establishment of CPC rat models, periodic acid Schiff staining was used to observe the positive rate of EGFR expression. The expression levels of EGFR, mucin 5AC (MUC5AC), Ki­67, type I collagen and mammalian target of rapamycin (mTOR), and the activity of ß­glucuronidase (ß­G), were measured. The rats treated with Pani demonstrated a significantly lower degree of hyperproliferation of the epithelium and submucosal glands of the bile duct and collagen fibers of the bile duct wall, a significantly decreased positive rate of EGFR, reduced phosphorylation of mTOR, decreased expression of EGFR, MUC5AC, Ki­67 and type I collagen, and reduced ß­G activity. The therapeutic effects in rats treated with 4 and 6 mg/kg of Pani were more marked than those in rats treated with 2 mg/kg of Pani. Collectively, the data obtained in the present study suggest that the EGFR monoclonal antibody Pani can effectively inhibit the excessive proliferation and stone­forming potential of bile duct mucosa in CPC with a receptor saturation effect. Therefore, Pani offers promise as a treatment for the prevention and control of intrahepatic choledocholithiasis caused by CPC.

Proteomics in Primary Biliary Cholangitis.

Primary biliary cholangitis is a chronic cholestatic liver disease characterized by the presence of serum antimitochondrial antibodies and immune-mediated destruction of the small and medium-sized intrahepatic bile ducts. However, the pathophysiology of primary biliary cholangitis has not yet been completely elucidated. In recent years, proteomics has been comprehensively applied in many research fields, including the pathogenesis, prognosis, and diagnosis of disease. Among multiple methods, isobaric tag for relative and absolute quantitation is a powerful analytic method to characterize complex protein mixtures in combination with liquid chromatography-tandem mass spectrometry. In this chapter, we describe a strategy for using isobaric tag for relative and absolute quantitation to discover those differentially expressed proteins in primary biliary cholangitis. The goal is to identify the differences in protein expression between patients with primary biliary cholangitis and healthy controls for defining biomarkers and elucidating molecular mechanisms underlying disease states.

The Critical Role of Chemokine (C-C Motif) Receptor 2-Positive Monocytes in Autoimmune Cholangitis.

The therapy of primary biliary cholangitis (PBC) has lagged behind other autoimmune diseases despite significant improvements in our understanding of both immunological and molecular events that lead to loss of tolerance to the E2 component of pyruvate dehydrogenase, the immunodominant autoepitope of PBC. It is well known that Ly6Chi monocytes are innate immune cells infiltrating inflammatory sites that are dependent on the expression of C-C motif chemokine receptor 2 (CCR2) for emigration from bone marrow. Importantly, humans with PBC have a circulating monocyte pro-inflammatory phenotype with macrophage accumulation in portal tracts. We have taken advantage of an inducible chemical xenobiotic model of PBC and recapitulated the massive infiltration of monocytes to portal areas. To determine the clinical significance, we immunized both CCR2-deficient mice and controls with 2OA-BSA and noted that CCR2 deficiency is protective for the development of autoimmune cholangitis. Importantly, because of the therapeutic potential, we focused on inhibiting monocyte infiltration through the use of cenicriviroc (CVC), a dual chemokine receptor CCR2/CCR5 antagonist shown to be safe in human trials. Importantly, treatment with CVC resulted in amelioration of all aspects of disease severity including serum total bile acids, histological severity score, and fibrosis stage. In conclusion, our results indicate a major role for Ly6Chi monocytes and for CCR2 in PBC pathogenesis and suggest that inhibition of this axis by CVC should be explored in humans through the use of clinical trials.

Osteoporosis in primary biliary cholangitis.

Primary biliary cholangitis (PBC) is an autoimmune cholestatic liver disease with multiple debilitating complications. Osteoporosis is a common complication of PBC resulting in frequent fractures and leading to significant morbidity in this population, yet evidence for effective therapy is lacking. We sought to summarize our current understanding of the pathophysiology of osteoporosis in PBC, as well as current and emerging therapies in order to guide future research directions. A complete search with a comprehensive literature review was performed with studies from PubMed, EMBASE, Web of Science, Cochrane database, and the Countway Library. Osteoporosis in PBC is driven primarily by decreased bone formation, which differs from the increased bone resorption seen in postmenopausal osteoporosis. Despite this fundamental difference, current treatment recommendations are based primarily on experience with postmenopausal osteoporosis. Trials specific to PBC-related osteoporosis are small and have not consistently demonstrated a benefit in this population. As it stands, prevention of osteoporosis in PBC relies on the mitigation of risk factors such as smoking and alcohol use, as well as encouraging a healthy diet and weight-bearing exercise. The primary medical intervention for the treatment of osteoporosis in PBC remains bisphosphonates though a benefit in terms of fracture reduction has never been shown. This review outlines what is known regarding the pathogenesis of bone disease in PBC and summarizes current and emerging therapies.

The CXC Chemokine Receptor 3 Inhibits Autoimmune Cholangitis via CD8+ T Cells but Promotes Colitis via CD4+ T Cells.

CXC chemokine receptor 3 (CXCR3), a receptor for the C-X-C motif chemokines (CXCL) CXCL9, CXCL10, and CXCL11, which not only plays a role in chemotaxis but also regulates differentiation and development of memory and effector T cell populations. Herein, we explored the function of CXCR3 in the modulation of different organ-specific autoimmune diseases in interleukin (IL)-2 receptor deficiency (CD25-/-) mice, a murine model for both cholangitis and colitis. We observed higher levels of CXCL9 and CXCL10 in the liver and colon and higher expression of CXCR3 on T cells of the CD25-/- mice compared with control animals. Deletion of CXCR3 resulted in enhanced liver inflammation but alleviated colitis. These changes in liver and colon pathology after CXCR3 deletion were associated with increased numbers of hepatic CD4+ and CD8+ T cells, in particular effector memory CD8+ T cells, as well as decreased T cells in mesenteric lymph nodes and colon lamina propria. In addition, increased interferon-γ response and decreased IL-17A response was observed in both liver and colon after CXCR3 deletion. CXCR3 modulated the functions of T cells involved in different autoimmune diseases, whereas the consequence of such modulation was organ-specific regarding to their effects on disease severity. Our findings emphasize the importance of extra caution in immunotherapy for organ-specific autoimmune diseases, as therapeutic interventions aiming at a target such as CXCR3 for certain disease could result in adverse effects in an unrelated organ.

An impaired biliary bicarbonate umbrella may be involved in dysregulated autophagy in primary biliary cholangitis.

Dysregulated autophagy may be a central player in trehe pathogenesis of primary biliary cholangitis (PBC) by inducing autoimmune processes via abnormal expression of mitochondrial antigens such as pyruvate dehydrogenase complex, E2 component (PDC-E2) and also by inducing cellular senescence in biliary epithelial cells (BECs) in bile duct lesions in PBC. We examined the association of an impaired "biliary bicarbonate umbrella" due to dysfunction of anion exchanger 2 (AE2) with dysregulated autophagy and cellular senescence in PBC. The expression of AE2 was examined in cultured BECs treated with bile acids such as glycochenodeoxycholic acid (GCDC) and tauro-ursodeoxycholic acid (TUDCA), various cytokines (IL-4, IL-13, IFNγ, TNFα, TGFß), and serum deprivation. The effect of AE2 knockdown using siRNA on autophagy, cell surface expression of PDC-E2, and cellular senescence was also examined. The expression of AE2 and its association with autophagy-related markers and senescent markers p16INK4a and p21WAF1/Cip1 were immunohistochemically determined in livers taken from the patients with PBC (n = 50) and 69 control diseased and normal livers. The expression of AE2 was significantly induced in the cultured BECs shortly treated with GCDC and other stresses, whereas it was significantly decreased in senescent BECs induced by GCDC and other stresses (p < 0.05). Dysregulated autophagy, cell surface expression of PDC-E2, and cellular senescence were significantly increased by knockdown of AE2 (p < 0.05). The expression of AE2 was significantly decreased in cholangitis in PBC, compared to control livers (p < 0.05). The decreased expression of AE2 was correlated with dysregulated autophagy, abnormal expression of PDC-E2, and cellular senescence in bile duct lesions in PBC. In conclusion, an impaired biliary bicarbonate umbrella may be involved in the pathogenesis of PBC by inducing dysregulated autophagy.