Machine Learning Identifies Key Proteins in Primary Sclerosing Cholangitis Progression and Links High CCL24 to Cirrhosis.

Primary sclerosing cholangitis (PSC) is a rare, progressive disease, characterized by inflammation and fibrosis of the bile ducts, lacking reliable prognostic biomarkers for disease activity. Machine learning applied to broad proteomic profiling of sera allowed for the discovery of markers of disease presence, severity, and cirrhosis and the exploration of the involvement of CCL24, a chemokine with fibro-inflammatory activity. Sera from 30 healthy controls and 45 PSC patients were profiled with proximity extension assay, quantifying the expression of 2870 proteins, and used to train an elastic net model. Proteins that contributed most to the model were tested for correlation to enhanced liver fibrosis (ELF) score and used to perform pathway analysis. Statistical modeling for the presence of cirrhosis was performed with principal component analysis (PCA), and receiver operating characteristics (ROC) curves were used to assess the useability of potential biomarkers. The model successfully predicted the presence of PSC, where the top-ranked proteins were associated with cell adhesion, immune response, and inflammation, and each had an area under receiver operator characteristic (AUROC) curve greater than 0.9 for disease presence and greater than 0.8 for ELF score. Pathway analysis showed enrichment for functions associated with PSC, overlapping with pathways enriched in patients with high levels of CCL24. Patients with cirrhosis showed higher levels of CCL24. This data-driven approach to characterize PSC and its severity highlights potential serum protein biomarkers and the importance of CCL24 in the disease, implying its therapeutic potential in PSC.

Patients with autoimmune liver disease have glucose disturbances that mechanistically differ from steatotic liver disease.

Autoimmune liver diseases are associated with an increased risk of diabetes, yet the underlying mechanisms remain unknown. In this cross-sectional study, we investigated the glucose-regulatory disturbances in patients with autoimmune hepatitis (AIH, n = 19), primary biliary cholangitis (PBC, n = 15), and primary sclerosing cholangitis (PSC, n = 6). Healthy individuals (n = 24) and patients with metabolic dysfunction-associated steatotic liver disease (MASLD, n = 18) were included as controls. Blood samples were collected during a 120-min oral glucose tolerance test. We measured the concentrations of glucose, C-peptide, insulin, glucagon, and the two incretin hormones, glucose insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1). We calculated the homeostasis model assessment of insulin resistance (HOMA-IR), whole body insulin resistance (Matsuda index), insulin clearance, and insulinogenic index. All patient groups had increased fasting plasma glucose and impaired glucose responses compared with healthy controls. Beta-cell secretion was increased in AIH, PBC, and MASLD but not in PSC. Patients with AIH and MASLD had hyperglucagonemia and hepatic, as well as peripheral, insulin resistance and decreased insulin clearance, resulting in hyperinsulinemia. Patients with autoimmune liver disease had an increased GIP response, and those with AIH or PBC had an increased GLP-1 response. Our data demonstrate that the mechanism underlying glucose disturbances in patients with autoimmune liver disease differs from that underlying MASLD, including compensatory incretin responses in patients with autoimmune liver disease. Our results suggest that glucose disturbances are present at an early stage of the disease.NEW & NOTEWORTHY Patients with autoimmune liver disease but without overt diabetes display glucose disturbances early on in their disease course. We identified pathophysiological traits specific to these patients including altered incretin responses.

The Role of CCL24 in Primary Sclerosing Cholangitis: Bridging Patient Serum Proteomics to Preclinical Data.

Primary sclerosing cholangitis (PSC) is an inflammatory and fibrotic biliary disease lacking approved treatment. We studied CCL24, a chemokine shown to be overexpressed in damaged bile ducts, and its involvement in key disease-related mechanisms. Serum proteomics of PSC patients and healthy controls (HC) were analyzed using the Olink® proximity extension assay and compared based on disease presence, fibrosis severity, and CCL24 levels. Disease-related canonical pathways, upstream regulators, and toxicity functions were elevated in PSC patients compared to HC and further elevated in patients with high CCL24 levels. In vitro, a protein signature in CCL24-treated hepatic stellate cells (HSCs) differentiated patients by disease severity. In mice, CCL24 intraperitoneal injection selectively recruited neutrophils and monocytes. Treatment with CM-101, a CCL24-neutralizing antibody, in an α-naphthylisothiocyanate (ANIT)-induced cholestasis mouse model effectively inhibited accumulation of peribiliary neutrophils and macrophages while reducing biliary hyperplasia and fibrosis. Furthermore, in PSC patients, CCL24 levels were correlated with upregulation of monocyte and neutrophil chemotaxis pathways. Collectively, these findings highlight the distinct role of CCL24 in PSC, influencing disease-related mechanisms, affecting immune cells trafficking and HSC activation. Its blockade with CM-101 reduces inflammation and fibrosis and positions CCL24 as a promising therapeutic target in PSC.

Beta-lapachone ameliorates the progression of primary sclerosing cholangitis pathogenesis in rodent models.

AIMS: Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease characterized by chronic inflammation and severe fibrosis for which effective treatment options are currently lacking. In this study, we explored the potential of beta-lapachone (ßL) as a drug candidate for PSC therapy. MATERIALS AND METHODS: We employed an animal model fed a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to assess the preventive and therapeutic effects of ßL. The beneficial effects of ßL on PSC pathogenic characteristics, including blood biomarkers, inflammation, and fibrosis, were determined by assessing relevant parameters. Differential gene expression between each group was analyzed by RNA sequencing of liver tissues. Mdr2-/- mice were utilized to explore the involvement of Abcb4 in the ßL-induced improvement of PSC pathogenesis. KEY FINDINGS: ßL effectively inhibited key features of PSC pathogenesis, as demonstrated by reduced blood biomarkers and improved pathogenic characteristics. Treatment with ßL significantly mitigated DDC-induced apoptosis, cell proliferation, inflammation, and fibrosis. Analysis of differential gene expression confirmed a new insight that ßL could stimulate the expression of genes related to NAD synthesis and Abcb4. Indeed, ßL-induced NAD exhibited effective functioning, as evidenced by enhanced sirt1/3 and acetyl-lysine levels, leading to improved mitochondrial stability. The role of Abcb4 in response to ßL was confirmed in Mdr2/Abcb4 KO mice, where the beneficial effects of ßL were abolished. SIGNIFICANCE: This study provided a new concept for PSC treatment, suggesting that pharmacological stimulation of the NAD synthetic pathway and Abcb4 via ßL ameliorates PSC pathogenesis.

Telomere dysfunction promotes cholangiocyte senescence and biliary fibrosis in primary sclerosing cholangitis.

Cellular senescence and biliary fibrosis are prototypical features of obliterative cholangiopathies, such as primary sclerosing cholangitis (PSC). Telomere dysfunction can lead to senescence either through telomere erosion or damaged telomeres. Our goal was to investigate a mechanistic relationship between telomere damage and biliary fibrosis in PSC. Telomere attrition was observed in the bile ducts of patients with PSC along with a reduction in telomerase reverse transcriptase (TERT) expression, compared with that in normal livers. Similarly, liver tissue from mouse models of biliary fibrosis showed telomere attrition with increased damage at telomeres measured as telomere-associated foci (TAF). Cellular models of senescence induction increased the TAF in cholangiocytes. This coincided with decreased TERT expression and increased senescence, which was rescued by modulating TERT levels. Epigenetic analysis revealed increased acquisition of repressive histone methylation at the TERT promoter, which correlated with decreased TERT transcription. Cholangiocyte-selective deletion of TERT in mice exacerbated fibrosis, whereas androgen therapy toward telomerase rescued liver fibrosis and liver function in a genetic mouse model of PSC. Our results demonstrate a mechanistic role for telomere dysfunction in cellular senescence and fibrosis that characterize PSC. This suggests that PSC may be, in part, a telomere biology disorder, and identifies TERT as a potential therapeutic target.

Combined Inhibition of the TGF-ß1/Smad Pathway by Prevotella copri and Lactobacillus murinus to Reduce Inflammation and Fibrosis in Primary Sclerosing Cholangitis.

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disease characterized by inflammation and fibrosis of the bile ducts. Cholestasis may lead to hepatic inflammation and fibrosis, and amelioration of cholestasis may allow recovery from inflammatory and fibrotic pathological damage. Prevotella copri (P. copri) interventions have been reported to significantly improve cholestasis and liver fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced PSC mouse models. Even though P. copri treatment alone cannot bring about recovery from DDC-induced inflammation, it increases the abundance of Lactobacillus murinus (L. murinus) compared with DDC treatment, which has been reported to have anti-inflammatory effects. The abundance of L. murinus still not recovering to a normal level may underlie hepatic inflammation in P. copri + DDC mice. Separate or combined interventions of P. copri and L. murinus were used to investigate the molecular mechanism underlying the improvement in PSC inflammation and fibrosis. P. copri and L. murinus significantly reduced the hepatic inflammatory cell aggregation and inflammatory factor expression as well as the hepatic collagen content and fibrin factor expression in the PSC mice. Further analysis of phosphorylation and dephosphorylation levels revealed that treating the PSC mice with the P. copri and L. murinus combined intervention inhibited the activity of the DDC-activated TGF-ß1/Smad pathway, thereby reducing liver inflammation and fibrosis. The combination of P. copri and L. murinus inhibits the TGF-ß1/Smad pathway and reduces inflammation and fibrosis in PSC.

Endothelin Receptor-A Inhibition Decreases Ductular Reaction, Liver Fibrosis, and Angiogenesis in a Model of Cholangitis.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) leads to ductular reaction and fibrosis and is complicated by vascular dysfunction. Cholangiocyte and endothelial cell crosstalk modulates their proliferation in cholestatic models. Endothelin (ET)-1 and ET-2 bind to their receptor, ET-A, and cholangiocytes are a key source of ET-1 after bile duct ligation. We aimed to evaluate the therapeutic potential of ET-A inhibition in PSC and biliary-endothelial crosstalk mediated by this pathway. METHODS: Wild-type and multidrug resistance 2 knockout (Mdr2-/-) mice at 12 weeks of age were treated with vehicle or Ambrisentan (ET-A antagonist) for 1 week by daily intraperitoneal injections. Human control and PSC samples were used. RESULTS: Mdr2-/- mice at 4, 8, and 12 weeks displayed angiogenesis that peaked at 12 weeks. Mdr2-/- mice at 12 weeks had enhanced biliary ET-1/ET-2/ET-A expression and secretion, whereas human PSC had enhanced ET-1/ET-A expression and secretion. Ambrisentan reduced biliary damage, immune cell infiltration, and fibrosis in Mdr2-/- mice. Mdr2-/- mice had squamous cholangiocytes with blunted microvilli and dilated arterioles lacking cilia; however, Ambrisentan reversed these alterations. Ambrisentan decreased cholangiocyte expression of pro-angiogenic factors, specifically midkine, through the regulation of cFOS. In vitro, ET-1/ET-A caused cholangiocyte senescence, endothelial cell angiogenesis, and macrophage inflammation. In vitro, human PSC cholangiocyte supernatants increased endothelial cell migration, which was blocked with Ambrisentan treatment. CONCLUSIONS: ET-A inhibition reduced biliary and liver damage in Mdr2-/- mice. ET-A promotes biliary angiocrine signaling that may, in turn, enhance angiogenesis. Targeting ET-A may prove therapeutic for PSC, specifically patients displaying vascular dysfunction.

The Role of hsa-miR-125b-5p Interaction with S1P/Ceramide Axis in the Potential Development of Inflammation-Associated Colon Cancer in Primary Sclerosing Cholangitis.

Primary sclerosing cholangitis (PSC) is characterised by the co-occurrence of inflammatory bowel diseases, particularly ulcerative colitis (UC). We investigated how the interaction of miR-125b with the sphingosine-1-phosphate (S1P)/ceramide axis may predispose patients with PSC, PSC/UC, and UC to carcinogenesis in the ascending and sigmoid colons. The overexpression of miR-125b was accompanied by the upregulation of S1P, ceramide synthases, ceramide kinases, and the downregulation of AT-rich interaction domain 2 in the ascending colon of PSC/UC, which contributed to the progression of high microsatellite instability (MSI-H) colorectal carcinoma. We also showed that the overexpression of sphingosine kinase 2 (SPHK2) and the genes involved in the glycolytic pathway in the sigmoid colon of UC led to the upregulation of Interleukin 17 (IL-17). In vitro stimulation of human intestinal epithelial cells (Caco-2, HT-29, and NCM460D) with lipopolysaccharide suppressed miR-125b and increased proinflammatory cytokines, whereas the induction of miR-125b activity by either a miR-125b mimetic or lithocholic acid resulted in the inhibition of miR-125b targets. In summary, miR-125b overexpression was associated with an imbalance in the S1P/ceramide axis that can lead to MSI-H cancer progression in PSC/UC. Furthermore, SPHK2 overexpression and a change in the cellular metabolic flux are important players in inflammation-associated colon cancer in UC.

Development of Scaffold-Free Three-Dimensional Cholangiocyte Organoids to Study the Progression of Primary Sclerosing Cholangitis.

Organoids are novel in vitro models to study intercellular cross talk between the different types of cells in disease pathophysiology. To better understand the underlying mechanisms driving the progression of primary sclerosing cholangitis (PSC), scaffold-free multicellular three-dimensional cholangiocyte organoids (3D-CHOs) were developed using primary liver cells derived from normal subjects and patients with PSC. Human liver samples from healthy donors and patients with PSC were used to isolate primary cholangiocytes [epithelial cell adhesion molecule (EpCam)+/ cytokeratin-19+], liver endothelial cells (CD31+), and hepatic stellate cells (HSCs; CD31-/CD68-/desmin+/vitamin A+). 3D-CHOs were formed using cholangiocytes, HSCs, and liver endothelial cells, and kept viable for up to 1 month. Isolated primary cell lines and 3D-CHOs were further characterized by immunofluorescence, quantitative RT-PCR, and transmission electron microscopy. Transcription profiles for cholangiocytes (SOX9, CFTR, EpCAM, AE, SCT, and SCTR), fibrosis (ACTA2, COL1A1, DESMIN, and TGFß1), angiogenesis (PECAM, VEGF, CDH5, and vWF), and inflammation (IL-6 and TNF-α) confirmed PSC phenotypes of 3D-CHOs. Because cholangiocytes develop a neuroendocrine phenotype and express neuromodulators, confocal immunofluorescence was used to demonstrate localization of the neurokinin-1 receptor within cytokeratin-19+ cholangiocytes and desmin+ HSCs. Moreover, 3D-CHOs from patients with PSC confirmed PSC phenotypes with up-regulated neurokinin-1 receptor, tachykinin precursor 1, and down-regulated membrane metalloendopeptidase. Scaffold-free multicellular 3D-CHOs showed superiority as an in vitro model in mimicking PSC in vivo phenotypes compared with two-dimensional cell culture, which can be used in PSC disease-related research.

Prolonged Administration of Melatonin Ameliorates Liver Phenotypes in Cholestatic Murine Model.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is characterized by biliary senescence and hepatic fibrosis. Melatonin exerts its effects by interacting with Melatonin receptor 1 and 2 (MT1/MT2) melatonin receptors. Short-term (1 wk) melatonin treatment reduces a ductular reaction and liver fibrosis in bile duct-ligated rats by down-regulation of MT1 and clock genes, and in multidrug resistance gene 2 knockout (Mdr2-/-) mice by decreased miR200b-dependent angiogenesis. We aimed to evaluate the long-term effects of melatonin on liver phenotype that may be mediated by changes in MT1/clock genes/miR200b/maspin/glutathione-S transferase (GST) signaling. METHODS: Male wild-type and Mdr2-/- mice had access to drinking water with/without melatonin for 3 months. Liver damage, biliary proliferation/senescence, liver fibrosis, peribiliary inflammation, and angiogenesis were measured by staining in liver sections, and by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay in liver samples. We confirmed a link between MT1/clock genes/miR200b/maspin/GST/angiogenesis signaling by Ingenuity Pathway Analysis software and measured liver phenotypes and the aforementioned signaling pathway in liver samples from the mouse groups, healthy controls, and PSC patients and immortalized human PSC cholangiocytes. RESULTS: Chronic administration of melatonin to Mdr2-/- mice ameliorates liver phenotypes, which were associated with decreased MT1 and clock gene expression. CONCLUSIONS: Melatonin improves liver histology and restores the circadian rhythm by interaction with MT1 through decreased angiogenesis and increased maspin/GST activity.

Modulation of Mismatch Repair and the SOCS1/p53 Axis by microRNA-155 in the Colon of Patients with Primary Sclerosing Cholangitis.

Deficient mismatch repair (MMR) proteins may lead to DNA damage and microsatellite instability. Primary sclerosing cholangitis (PSC) is a risk factor for colitis-associated colon cancer. MiR-155 is suggested to act as a key regulating node, linking inflammation and tumorigenesis. However, its involvement in the chronic colitis of PSC-UC patients has not been examined. We investigated the involvement of miR-155 in the dysregulation of MMR genes and colitis in PSC patients. Colon tissue biopsies were obtained from patients with PSC, PSC with concomitant ulcerative colitis (PSC-UC), uncomplicated UC, and healthy controls (n = 10 per group). In the ascending colon of PSC and PSC-UC patients, upregulated miR-155 promoted high microsatellite instability and induced signal transducer and activator of transcription 3 (STAT-3) expression via the inhibition of suppressors of cytokine signalling 1 (SOCS1). In contrast, the absence of miR-155 overexpression in the sigmoid colon of PSC-UC patients activated the Il-6/S1PR1 signalling pathway and imbalanced the IL17/FOXP3 ratio, which reinforces chronic colitis. Functional studies on human intestinal epithelial cells (HT-29 and NCM460D) confirmed the role of miR-155 over-expression in the inhibition of MMR genes and the modulation of p53. Moreover, those cells produced more TNFα upon a lipopolysaccharide challenge, which led to the suppression of miR-155. Additionally, exposure to bile acids induced upregulation of miR-155 in Caco-2 cell lines. Thus, under different conditions, miR-155 is involved in either neoplastic transformation in the ascending colon or chronic colitis in the sigmoid colon of patients with PSC. New insight into local modulation of microRNAs, that may alter the course of the disease, could be used for further research on potential therapeutic applications.

Changes in beta-catenin expression and activation during progression of primary sclerosing cholangitis predict disease recurrence.

Primary sclerosing cholangitis (PSC) is a rare, chronic, cholestatic liver disease characterized by progressive inflammation and fibrosis of the bile ducts. We have previously demonstrated the importance of Wnt/ß-catenin signaling in mouse models of PSC. In this study, we wished to determine the clinical relevance of ß-catenin localization in patient samples. In livers explanted from patients diagnosed with PSC, the majority (12/16; 75%) lacked ß-catenin protein expression. Biopsies from patients post-transplant were classified as recurrent or non-recurrent based on pathology reports and then scored for ß-catenin activation as a function of immunohistochemical localization. Despite lack of statistical significance, patients with recurrent primary disease (n = 11) had a greater percentage of samples with nuclear, transcriptionally active ß-catenin (average 58.8%) than those with no recurrence (n = 10; 40.53%), while non-recurrence is correlated with ß-catenin staining at the cell surface (average 52.63% for non-recurrent vs. 27.34% for recurrent), as determined by three different methods of analysis. ß-catenin score and years-to-endpoint are both strongly associated with recurrence status (p = 0.017 and p = 0.00063, respectively). Finally, there was significant association between higher ß-catenin score and increased alkaline phosphatase, a marker of biliary injury and disease progression. Thus, ß-catenin expression and activation changes during the progression of PSC, and its localization may be a useful prognostic tool for predicting recurrence of this disease.

Aberrant hepatic trafficking of gut-derived T cells is not specific to primary sclerosing cholangitis.

BACKGROUND AND AIMS: The "gut homing" hypothesis suggests the pathogenesis of primary sclerosing cholangitis (PSC) is driven by aberrant hepatic expression of gut adhesion molecules and subsequent recruitment of gut-derived T cells to the liver. However, inconsistencies lie within this theory including an absence of investigations and comparisons with other chronic liver diseases (CLD). Here, we examine "the gut homing theory" in patients with PSC with associated inflammatory bowel disease (PSC-IBD) and across multiple inflammatory liver diseases. APPROACH AND RESULTS: Expression of MAdCAM-1, CCL25, and E-Cadherin were assessed histologically and using RT-PCR on explanted liver tissue from patients with CLD undergoing OLT and in normal liver. Liver mononuclear cells were isolated from explanted tissue samples and the expression of gut homing integrins and cytokines on hepatic infiltrating gut-derived T cells was assessed using flow cytometry. Hepatic expression of MAdCAM-1, CCL25 and E-Cadherin was up-regulated in all CLDs compared with normal liver. There were no differences between disease groups. Frequencies of α4ß7, αEß7, CCR9, and GPR15 expressing hepatic T cells was increased in PSC-IBD, but also in CLD controls, compared with normal liver. ß7 expressing hepatic T cells displayed an increased inflammatory phenotype compared with ß7 negative cells, although this inflammatory cytokine profile was present in both the inflamed and normal liver. CONCLUSIONS: These findings refute the widely accepted "gut homing" hypothesis as the primary driver of PSC and indicate that aberrant hepatic recruitment of gut-derived T cells is not unique to PSC, but is a panetiological feature of CLD.

Induced Pluripotent Stem Cells From Subjects With Primary Sclerosing Cholangitis Develop a Senescence Phenotype Following Biliary Differentiation.

Primary sclerosing cholangitis (PSC) is a chronic fibroinflammatory disease of the biliary tract characterized by cellular senescence and periportal fibrogenesis. Specific disease features that are cell intrinsic and either genetically or epigenetically mediated remain unclear due in part to a lack of appropriate, patient-specific, in vitro models. Recently, our group developed systems to create induced pluripotent stem cell (iPSC)-derived cholangiocytes (iDCs) and biliary epithelial organoids (cholangioids). We use these models to investigate whether PSC cholangiocytes are intrinsically predisposed to cellular senescence. Skin fibroblasts from healthy controls and subjects with PSC were reprogrammed to pluripotency, differentiated to cholangiocytes, and subsequently grown in three-dimensional matrigel-based culture to induce formation of cholangioids. RNA sequencing (RNA-seq) on iDCs showed significant differences in gene expression patterns, including enrichment of pathways associated with cell cycle, senescence, and hepatic fibrosis, that correlate with PSC. These pathways also overlapped with RNA-seq analysis on isolated cholangiocytes from subjects with PSC. Exome sequencing on the subjects with PSC revealed genetic variants of unknown significance in the genes identified in these pathways. Three-dimensional culture revealed smaller size, lack of a central lumen, and increased cellular senescence in PSC-derived cholangioids. Congruent with this, PSC-derived iDCs showed increased secretion of the extracellular matrix molecule fibronectin as well as the inflammatory cytokines interleukin-6, and chemokine (C-C motif) ligand 2. Conditioned media (CM) from PSC-derived iDCs more potently activated hepatic stellate cells compared to control CM. Conclusion: We demonstrated efficient generation of iDCs and cholangioids from patients with PSC that show disease-specific features. PSC cholangiocytes are intrinsically predisposed to cellular senescence. These features are unmasked following biliary differentiation of pluripotent stem cells and have functional consequences in epithelial organoids.

Gut microbiota depletion exacerbates cholestatic liver injury via loss of FXR signalling.

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology for which there are no approved therapeutic options. Patients with PSC display changes in gut microbiota and in bile acid (BA) composition; however, the contribution of these alterations to disease pathogenesis remains controversial. Here we identify a role for microbiota-dependent changes in BA synthesis that modulates PSC pathophysiology. In a genetic mouse model of PSC, we show that loss of microbiota-mediated negative feedback control of BA synthesis results in increased hepatic BA concentrations, disruption of bile duct barrier function and, consequently, fatal liver injury. We further show that these changes are dependent on decreased BA signalling to the farnesoid X receptor, which modulates the activity of the rate-limiting enzyme in BA synthesis, CYP7A1. Moreover, patients with advanced stages of PSC show suppressed BA synthesis as measured by serum C4 levels, which is associated with poor disease prognosis. Our preclinical data highlight the microbiota-dependent dynamics of BA metabolism in cholestatic liver disease, which could be important for future therapies targeting BA and gut microbiome interactions, and identify C4 as a potential biomarker to functionally stratify patients with PSC and predict disease outcomes.

The Role of Microbiota in Primary Sclerosing Cholangitis and Related Biliary Malignancies.

Primary sclerosing cholangitis (PSC) is an immune-related cholangiopathy characterized by biliary inflammation, cholestasis, and multifocal bile duct strictures. It is associated with high rates of progression to end-stage liver disease as well as a significant risk of cholangiocarcinoma (CCA), gallbladder cancer, and colorectal carcinoma. Currently, no effective medical treatment with an impact on the overall survival is available, and liver transplantation is the only curative treatment option. Emerging evidence indicates that gut microbiota is associated with disease pathogenesis. Several studies analyzing fecal and mucosal samples demonstrate a distinct gut microbiome in individuals with PSC compared to healthy controls and individuals with inflammatory bowel disease (IBD) without PSC. Experimental mouse and observational human data suggest that a diverse set of microbial functions may be relevant, including microbial metabolites and bacterial processing of pharmacological agents, bile acids, or dietary compounds, altogether driving the intrahepatic inflammation. Despite critical progress in this field over the past years, further functional characterization of the role of the microbiota in PSC and related malignancies is needed. In this review, we discuss the available data on the role of the gut microbiome and elucidate important insights into underlying pathogenic mechanisms and possible microbe-altering interventions.

Bile acids modulate colonic MAdCAM-1 expression in a murine model of combined cholestasis and colitis.

Primary sclerosing cholangitis (PSC) is a progressive fibrosing cholestatic liver disease that is strongly associated with inflammatory bowel disease (IBD). PSC-associated IBD (PSC-IBD) displays a unique phenotype characterized by right-side predominant colon inflammation and increased risk of colorectal cancer compared to non-PSC-IBD. The frequent association and unique phenotype of PSC-IBD suggest distinctive underlying disease mechanisms from other chronic liver diseases or IBD alone. Multidrug resistance protein 2 knockout (Mdr2-/-) mice develop spontaneous cholestatic liver injury and fibrosis mirroring human PSC. As a novel model of PSC-IBD, we treated Mdr2-/- mice with dextran sulfate sodium (DSS) to chemically induce colitis (Mdr2-/-/DSS). Mdr2-/- mice demonstrate alterations in fecal bile acid composition and enhanced colitis susceptibility with increased colonic adhesion molecule expression, particularly mucosal addressin-cell adhesion molecule 1 (MAdCAM-1). In vitro, ursodeoxycholic acid (UDCA) co-treatment resulted in a dose dependent attenuation of TNF-α-induced endothelial MAdCAM-1 expression. In the combined Mdr2-/-/DSS model, UDCA supplementation attenuated colitis severity and downregulated intestinal MAdCAM-1 expression. These findings suggest a potential mechanistic role for alterations in bile acid signaling in modulating MAdCAM-1 expression and colitis susceptibility in cholestasis-associated colitis. Together, our findings provide a novel model and new insight into the pathogenesis and potential treatment of PSC-IBD.

The Apelin-Apelin Receptor Axis Triggers Cholangiocyte Proliferation and Liver Fibrosis During Mouse Models of Cholestasis.

BACKGROUND AND AIMS: Apelin (APLN) is the endogenous ligand of its G protein-coupled receptor, apelin receptor (APJ). APLN serum levels are increased in human liver diseases. We evaluated whether the APLN-APJ axis regulates ductular reaction and liver fibrosis during cholestasis. APPROACH AND RESULTS: We measured the expression of APLN and APJ and serum APLN levels in human primary sclerosing cholangitis (PSC) samples. Following bile duct ligation (BDL) or sham surgery, male wild-type (WT) mice were treated with ML221 (APJ antagonist) or saline for 1 week. WT and APLN-/- mice underwent BDL or sham surgery for 1 week. Multidrug resistance gene 2 knockout (Mdr2-/- ) mice were treated with ML221 for 1 week. APLN levels were measured in serum and cholangiocyte supernatants, and cholangiocyte proliferation/senescence and liver inflammation, fibrosis, and angiogenesis were measured in liver tissues. The regulatory mechanisms of APLN-APJ in (1) biliary damage and liver fibrosis were examined in human intrahepatic biliary epithelial cells (HIBEpiCs) treated with APLN and (2) hepatic stellate cell (HSC) activation in APLN-treated human HSC lines (HHSteCs). APLN serum levels and biliary expression of APLN and APJ increased in PSC samples. APLN levels were higher in serum and cholangiocyte supernatants from BDL and Mdr2-/- mice. ML221 treatment or APLN-/- reduced BDL-induced and Mdr2-/- -induced cholangiocyte proliferation/senescence, liver inflammation, fibrosis, and angiogenesis. In vitro, APLN induced HIBEpiC proliferation, increased nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) expression, reactive oxygen species (ROS) generation, and extracellular signal-regulated kinase (ERK) phosphorylation. Pretreatment of HIBEpiCs with ML221, diphenyleneiodonium chloride (Nox4 inhibitor), N-acetyl-cysteine (NAC, ROS inhibitor), or PD98059 (ERK inhibitor) reduced APLN-induced cholangiocyte proliferation. Activation of HHSteCs was induced by APLN but reduced by NAC. CONCLUSIONS: The APLN-APJ axis induces cholangiocyte proliferation through Nox4/ROS/ERK-dependent signaling and HSC activation through intracellular ROS. Modulation of the APLN-APJ axis may be important for managing cholangiopathies.

ADAM Metalloproteinase Domain 17 Regulates Cholestasis-Associated Liver Injury and Sickness Behavior Development in Mice.

Disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) is a ubiquitously expressed membrane-bound enzyme that mediates shedding of a wide variety of important regulators in inflammation including cytokines and adhesion molecules. Hepatic expression of numerous cytokines and adhesion molecules are increased in cholestatic liver diseases including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), however, the pathophysiological role of ADAM17 in regulating these conditions remains unknown. Therefore, we evaluated the role of ADAM17 in a mouse model of cholestatic liver injury due to bile duct ligation (BDL). We found that BDL enhanced hepatic ADAM17 protein expression, paralleled by increased ADAM17 bioactivity. Moreover, inhibition of ADAM17 bioactivity with the specific inhibitor DPC 333 significantly improved both biochemical and histological evidence of liver damage in BDL mice. Patients with cholestatic liver disease commonly experience adverse behavioral symptoms, termed sickness behaviors. Similarly, BDL in mice induces reproducible sickness behavior development, driven by the upregulated expression of cytokines and adhesion molecules that are in turn regulated by ADAM17 activity. Indeed, inhibition of ADAM17 activity significantly ameliorated BDL-associated sickness behavior development. In translational studies, we evaluated changes in ADAM17 protein expression in liver biopsies obtained from patients with PBC and PSC, compared to normal control livers. PSC and PBC patients demonstrated increased hepatic ADAM17 expression in hepatocytes, cholangiocytes and in association with liver-infiltrating immune cells compared to normal controls. In summary, cholestatic liver injury in mice and humans is associated with increased hepatic ADAM17 expression. Furthermore, inhibition of ADAM17 activity improves both cholestatic liver injury and associated sickness behavior development, suggesting that ADAM17 inhibition may represent a novel therapeutic approach for treating patients with PBC/PSC.

Hepatic NFAT signaling regulates the expression of inflammatory cytokines in cholestasis.

BACKGROUND & AIMS: The nuclear factor of activated T-cells (NFAT) plays an important role in immune responses by regulating the expression of inflammatory genes. However, it is not known whether NFAT plays any role in the bile acid (BA)-induced hepatic inflammatory response. Thus, we aimed to examine the functional role of NFATc3 in cholestatic liver injury in mice and humans. METHODS: Gene and protein expression and cellular localization were assessed in primary hepatocyte cultures (mouse and human) and cholestatic liver tissues (murine models and patients with primary biliary cholangitis [PBC] or primary sclerosing cholangitis [PSC]) by quantitative PCR, western blot and immunohistochemistry. Specific NFAT inhibitors were used in vivo and in vitro. Gene reporter assays and ChIP-PCR were used to determine promoter activity. RESULTS: NFAT isoforms c1 and c3 were expressed in human and mouse hepatocytes. When treated with cholestatic levels of BAs, nuclear translocation of NFATc3 was increased in both human and mouse hepatocytes and was associated with elevated mRNA levels of IL-8, CXCL2, and CXCL10 in these cells. Blocking NFAT activation with pathway-specific inhibitors or knocking down Nfatc3 expression significantly decreased BA-driven induction of these cytokines in mouse hepatocytes. Nuclear expression of NFATc3/Nfatc3 protein was increased in cholestatic livers, both in mouse models (bile duct ligation or Abcb4-/- mice) and in patients with PBC and PSC in association with elevated tissue levels of Cxcl2 (mice) or IL-8 (humans). Gene reporter assays and ChIP-PCR demonstrated that the NFAT response element in the IL-8 promoter played a key role in BA-induced human IL-8 expression. Finally, blocking NFAT activation in vivo in Abcb4-/- mice reduced cholestatic liver injury. CONCLUSIONS: NFAT plays an important role in BA-stimulated hepatic cytokine expression in cholestasis. Blocking hepatic NFAT activation may reduce cholestatic liver injury in humans. LAY SUMMARY: Bile acid induces liver injury by stimulating the expression of inflammatory genes in hepatocytes through activation of the transcription factor NFAT. Blocking this activation in vitro (in hepatocyte cultures) and in vivo (in cholestatic mice) decreased the expression of inflammatory genes and reduced liver injury.