Individuals with Primary Sclerosing Cholangitis Have Elevated Levels of Biomarkers for Apoptosis but Not Necrosis

Possible role of the HMGB1 and RAGE inflammatory pathway in primary sclerosing cholangitis

BACKGROUND

Activation of the receptor for advanced glycation end products (RAGE) and its ligand High Mobility Group Box Protein 1 (HMGB1), a nuclear protein with proinflammatory properties, has been implicated in several inflammatory disorders.

OBJECTIVE

To analyse the influence of RAGE and HMGB1 signalling in patients with primary sclerosing cholangitis (PSC).

METHODS

Levels of HMGB1 and bile acid in serum and bile samples of 69 PSC patients and 32 controls were measured. Additionally, 640 patients with PSC and other liver diseases were analysed for the gain-of-function RAGE G82S SNP by PCR. Laboratory and clinical parameters were retrieved by chart review.

RESULTS

ELISA analysis showed significantly higher biliary HMGB1 concentrations in PSC patients (n=69, median 124,1 ng/ml) than in the control group (n=32, median 6,85 ng/ml, p<0,001). Median serum HMGB1 (n=22, median 2,4 ng/ml) was significantly lower than median biliary HMGB1 of the concomitant bile samples (n=22, median 151 ng/ml, p =0,001). There was no correlation of biliary HMGB1 levels with laboratory parameters or clinical end points. Analysis of the gain-of-function G82SSNP RAGE SNP in PSC patients showed 8 patients with heterozygote mutant alleles (8/324, 2,5%). Patients carrying the mutation developed more often dominant strictures of the large bile ducts (100.0% vs. 61.3%; p=0.04) and had reduced transplantation-free survival in the mutant allele group (p<0.001).

CONCLUSIONS

Biliary HMGB1 levels are elevated in PSC patients compared to controls and a gain-of-function SNP in RAGE is associated with development of dominant strictures and reduced survival in PSC patients.

Association between appendectomy and risk of primary sclerosing cholangitis: A systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Recent epidemiologic studies have suggested that appendectomy could be a risk factor for primary sclerosing cholangitis (PSC) although the results were inconsistent. This systematic review and meta-analysis was conducted to summarize all available evidence.

METHODS

A comprehensive literature review was conducted using MEDLINE and EMBASE database through January 2018 to identify all studies that reported the risk of PSC among individuals who had appendectomy versus those with no history of appendectomy. Effect estimates from each study were extracted and combined together using the random-effect, generic inverse variance method of DerSimonian and Laird.

RESULTS

A total of 6 case-control studies with 2432 participants met the eligibility criteria and were included in the meta-analysis. The risk of PSC in individuals who had appendectomy was significantly higher than those with no history of appendectomy with the pooled odds ratio of 1.37 (95% CI: 1.15-1.63). The statistical heterogeneity was insignificant with an I2 of 0%.

CONCLUSIONS

A significantly increased risk of PSC among individuals who had a history of appendectomy was found in this study.

N-3 Polyunsaturated Fatty Acids Stimulate Bile Acid Detoxification in Human Cell Models

Cholestasis is characterized by the accumulation of toxic bile acids (BAs) in liver cells. The present study aimed to evaluate the effects of n-3 polyunsaturated fatty acids (n-3 PUFAs), such as docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, on BA homeostasis and toxicity in human cell models. The effects of EPA and/or DHA on the expression of genes involved in the maintenance of BA homeostasis were analyzed in human hepatoma (HepG2) and colon carcinoma (Caco-2) cells, as well as in primary culture of human intestinal (InEpC) and renal (RPTEC) cells. Extracellular BA species were quantified in culture media using LC-MS/MS. BA-induced toxicity was evaluated using caspase-3 and flow cytometry assays. Gene expression analyses of HepG2 cells reveal that n-3 PUFAs reduce the expression of genes involved in BA synthesis (CYP7A1, CYP27A1) and uptake (NTCP), while activating genes encoding metabolic enzymes (SULT2A1) and excretion transporters (MRP2, MRP3). N-3 PUFAs also generate a less toxic BA pool and prevent the BA-dependent activation of apoptosis in HepG2 cells. Conclusion. The present study reveals that n-3 PUFAs stimulate BA detoxification.

Serum high mobility group box 1 protein levels are not associated with either histological severity or treatment response in children and adults with nonalcoholic fatty liver disease

Aim

Serum high mobility group box 1 protein (HMGB1) is a proinflammatory molecule that could potentially serve as a biomarker for non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) due to its correlation with degree of liver fibrosis. The aim of the current study was to examine the cross-sectional and longitudinal relationships between serum HMGB1 levels and liver histology in adults and children with NAFLD participating in two large randomized controlled trials.

Methods

Serum HMGB1 levels were measured at various time points in adults and children with NAFLD, who participated in PIVENS and TONIC clinical trials respectively. PIVENS trial compared vitamin E or pioglitazone to placebo in adults whereas TONIC trial compared vitamin E or metformin to placebo in children. Participants had liver biopsies at baseline and the end of treatment (96 weeks), and liver histology was reviewed by a central committee of study pathologists.

Results

In the cross-sectional analyses (n = 205 for PIVENS and 109 for TONIC), there was no significant relationship between serum HMGB1 levels and histological features such as steatosis, ballooning, inflammation, fibrosis, or presence of steatohepatitis in either adults or children. Serum HMGB1 levels did not change significantly during treatment either with placebo, vitamin E therapy (P = 0.81) or pioglitazone (P = 0.09) in the PIVENS trial. Similarly, serum HMGB1 levels did not change significantly during treatment either with placebo, metformin (P = 0.15) or vitamin E (P = 0.23) in the TONIC trial. In the longitudinal analyses (n = 105 for PIVENS and 109 for TONIC), changes in serum HMGB1 levels did not correlate with histologic improvement or resolution of NASH in either adults or children. There was no relationship between serum HMGB1 and ALT levels in either adults or children with NAFLD.

Conclusion

Serum HMGB1 levels were not associated with histological severity or treatment response in either children or adults with NAFLD.

Pathological features of primary sclerosing cholangitis identified by bile proteomic analysis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown origin. Previous bile proteomic analyses in patients with PSC have revealed changes in disease activity specific to malignant transformation. In this study, we established a reference bile duct-derived bile proteome for PSC that can be used to evaluate biliary pathophysiology. Samples were collected from patients with PSC or with choledocholithiasis (control) (n=6 each). Furthermore, patients with PSC-associated cholangiocarcinoma (CC) and with CC without concomitant PSC were analyzed. None of the patients showed signs of inflammation or infection based on clinical and laboratory examinations. Proteins overexpressed in patients with PSC relative to control patients were detected by two-dimensional difference gel electrophoresis and identified by liquid chromatography-tandem mass spectrometry. Functional proteomic analysis was performed using STRING software. A total of 101 proteins were overexpressed in the bile fluid of patients with PSC but not in those of controls; the majority of these were predicted to be intracellular and related to the ribosomal and proteasomal pathways. On the other hand, 91 proteins were found only in the bile fluid of controls; most were derived from the extracellular space and were linked to cell adhesion, the complement system, and the coagulation cascade. In addition, proteins associated with inflammation and the innate immune response-e.g., cluster of differentiation 14, annexin-2, and components of the complement system-were upregulated in PSC. The most prominent pathways in PSC/CC-patients were inflammation associated cytokine and chemokine pathways, whereas in CC-patients the Wnt signaling pathway was upregulated. In PSC/CC-patients DIGE-analysis revealed biliary CD14 and Annexin-4 expression, among others, as the most prominent protein that discriminates between both cohorts. Thus, the bile-duct bile proteome of patients with PSC shows disease-specific changes associated with inflammation and the innate immune response even in the absence of obvious clinical signs of cholangitis, malignancy, or inflammation. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni and Peter Jansen.

Inhibition of microRNA-24 increases liver fibrosis by enhanced menin expression in Mdr2-/- mice

BACKGROUND

Liver transplantation remains the primary treatment for primary sclerosing cholangitis (PSC). Mdr2-/- mice provide a reliable in vivo model of PSC and develop characteristic biliary inflammation and fibrosis. We tested the hypothesis that the tumor suppressor protein menin is implicated in the progression of liver fibrosis and that menin expression can be regulated in the liver via microRNA-24 (miR-24).

MATERIALS AND METHODS

Menin expression was measured in human PSC and Mdr2-/- mice. Twelve-week-old FVB/NJ wild-type (WT) and Mdr2-/- mice were treated with miR-24 Vivo-Morpholino to knockdown miR-24 expression levels. Liver fibrosis was evaluated by Sirius Red staining and quantitative polymerase chain reaction (qPCR) for genes associated with liver fibrosis, such as fibronectin 1, collagen type 1 alpha 1, transforming growth factor-β1 (TGF-β1), and α-smooth muscle actin. Studies were also performed in vitro using immortalized murine cholangiocyte lines treated with miR-24 hairpin inhibitor and mimic.

RESULTS

Menin gene expression was increased in Mdr2-/- mice and late-stage human PSC samples. Treatment of FVB/NJ WT and Mdr2-/- mice with miR-24 Vivo-Morpholino increased menin expression, which correlated with increased expression of fibrosis genes. In vitro, inhibition of miR-24 also significantly increased the expression of fibrosis genes.

CONCLUSIONS

Inhibition of miR-24 increases menin and TGF-β1 expression, subsequently increasing hepatic fibrosis in FVB/NJ WT and Mdr2-/- mice. Modulation of the menin/miR-24 axis may provide novel targeted therapies to slow the progression of hepatic fibrosis into cirrhosis in PSC patients by altering TGF-β1 expression.

Biliary bile acids in hepatobiliary injury - What is the link?

The main trigger for liver injury in acquired cholestatic liver disease remains unclear. However, the accumulation of bile acids (BAs) undoubtedly plays a role. Recent progress in deciphering the pathomechanisms of inborn cholestatic liver diseases, decoding mechanisms of BA-induced cell death, and generating modern BA-derived drugs has improved the understanding of the regulation of BA synthesis and transport. Now is the appropriate time to reassess current knowledge about the specific role of BAs in hepatobiliary injury.

The changing faces of cholangitis

A variety of diseases are included under the umbrella term ‘cholangitis’, including hepatobiliary diseases with an autoimmune pathogenesis (such as primary sclerosing cholangitis, primary biliary cholangitis, and IgG4-associated sclerosing cholangitis) and disease processes associated with intraductal stones and infectious etiologies (such as ascending bacterial cholangitis, recurrent pyogenic cholangitis, and liver fluke-associated cholangitis). Recent advances in the pathophysiologic bases of these disorders, particularly with respect to the autoimmune variety, are allowing improved diagnosis and prognostication as well as providing the opportunity to refine and re-imagine treatment modalities. The aim of this review is to highlight selected advances in cholangitis research that point to novel insights into the pathophysiology, diagnosis, and treatment of this diverse array of disorders.