Serum Gas6 and Axl as non-invasive biomarkers of advanced histological stage in primary biliary cholangitis

Novel noninvasive indices for the assessment of liver fibrosis in primary biliary cholangitis

The present study aimed to investigate the accuracy of new noninvasive markers in predicting liver fibrosis among individuals with primary biliary cholangitis (PBC). This retrospective analysis included subjects with PBC who had liver biopsies. Scheuer's classification was used to determine the fibrosis stage. The bilirubin to albumin (Alb) ratio (BAR), fibrosis index based on the four factors (FIB-4), γ-glutamyl transpeptidase to platelet (PLT) ratio (GPR), red cell distribution width to PLT ratio (RPR), aspartate aminotransferase (AST) to alanine aminotransferase ratio (AAR), AST to PLT ratio index (APRI) and total bilirubin to PLT ratio (TPR) were calculated based on the laboratory parameters. A novel index called BARP was conceived as BAR x RPR. A total of 78 individuals with PBC were included in the study, 84.6% of whom had significant fibrosis, 30.8% had advanced fibrosis and 15.4% had cirrhosis. In the multivariate analysis, Alb was determined to be an independent predictor of advanced fibrosis (odds ratio=0.823, P=0.034). The area under the receiver operating characteristic curves (AUROCs) of the BAR, GPR, TPR and BARP were statistically significant in predicting severe fibrosis (P<0.05) and were 0.747, 0.684, 0.693 and 0.696, respectively. In assessing advanced fibrosis, the AUROCs for the AAR, APRI, BAR, FIB-4, RPR, TPR and BARP were 0.726, 0.650, 0.742, 0.716, 0.670, 0.735 and 0.750, respectively. The AUROCs for the APRI, BAR, FIB-4, RPR, TPR and BARP for cirrhosis prediction were 0.776, 0.753, 0.821, 0.819, 0.808 and 0.832, respectively. By comparing the AUROCs, it was demonstrated that the diagnostic capabilities of the BARP (P=0.021) and TPR (P=0.044) were superior to those of the APRI in predicting advanced fibrosis. In conclusion, the BAR, BARP and TPR were of predictive value for the grade of liver fibrosis in PBC and Alb had a diagnostic value in identifying early fibrosis. The aforementioned noninvasive indices may be used for predicting histologic stages of PBC.

A+T rich interaction domain protein 3a (Arid3a) impairs Mertk-mediated efferocytosis in cholestasis

BACKGROUND & AIMS

Macrophages are key elements in the pathogenesis of cholestatic liver diseases. Arid3a plays a prominent role in the biologic properties of hematopoietic stem cells, B lymphocytes and tumor cells, but its ability to modulate macrophage function during cholestasis remains unknown.

METHODS

Gene and protein expression and cellular localization were assessed by q-PCR, immunohistochemistry, immunofluorescence staining and flow cytometry. We generated myeloid-specific Arid3a knockout mice and established three cholestatic murine models. The transcriptome was analyzed by RNA-seq. A specific inhibitor of the Mertk receptor was used in vitro and in vivo. Promoter activity was determined by chromatin immunoprecipitation-seq against Arid3a and a luciferase reporter assay.

RESULTS

In cholestatic murine models, myeloid-specific deletion of Arid3a alleviated cholestatic liver injury (accompanied by decreased accumulation of macrophages). Arid3a-deficient macrophages manifested a more reparative phenotype, which was eliminated by in vitro treatment with UNC2025, a specific inhibitor of the efferocytosis receptor Mertk. Efferocytosis of apoptotic cholangiocytes was enhanced in Arid3a-deficient macrophages via upregulation of Mertk. Arid3a negatively regulated Mertk transcription by directly binding to its promoter. Targeting Mertk in vivo effectively reversed the protective phenotype of Arid3a deficiency in macrophages. Arid3a was upregulated in hepatic macrophages and circulating monocytes in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Mertk was correspondingly upregulated and negatively correlated with Arid3a expression in PBC and PSC. Mertk+ cells were located in close proximity to cholangiocytes, while Arid3a+ cells were scattered among immune cells with greater spatial distances to hyperplastic cholangiocytes in PBC and PSC.

CONCLUSIONS

Arid3a promotes cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes by macrophages during cholestasis. The Arid3a-Mertk axis is a promising novel therapeutic target for cholestatic liver diseases.

IMPACT AND IMPLICATIONS

Macrophages play an important role in the pathogenesis of cholestatic liver diseases. This study reveals that macrophages with Arid3a upregulation manifest a pro-inflammatory phenotype and promote cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes during cholestasis. Although we now offer a new paradigm to explain how efferocytosis is regulated in a myeloid cell autonomous manner, the regulatory effects of Arid3a on chronic liver diseases remain to be further elucidated.

A large-scale plasma proteome Mendelian randomization study identifies novel causal plasma proteins related to primary biliary cholangitis

Background and aims

Primary biliary cholangitis (PBC) is a progressive chronic autoimmune cholestatic liver disease characterized by the destruction of small intrahepatic bile ducts leading to biliary cirrhosis. Liver biopsy is required in the diagnosis of Antimitochondrial antibody-negative patients. Therefore, novel biomarkers are needed for the non-invasive diagnosis of PBC. To identify novel biomarkers for PBC, we conducted large-scale plasma proteome Mendelian randomization (MR).

Methods

A total of 21,593 protein quantitative trait loci (pQTLs) for 2297 circulating proteins were used and classified into four different groups. MR analyses were conducted in the four groups separately. Furthermore, the results were discovered and replicated in two different cohorts of PBC. Colocalization analysis and enrichment analysis were also conducted.

Results

Three plasma proteins (ficolin-1, CD40 and protein FAM177A1) were identified and replicated as being associated with PBC. All of them showed significant protective effects against PBC. An increase in ficolin-1 (OR=0.890 [0.843-0.941], p=3.50×10^-5), CD40 (OR=0.814 [0.741-0.895], p=1.96×10^-5) and protein FAM177A1 (OR=0.822 [0.754-0.897], p=9.75×10^-6) reduced the incidence of PBC. Ficolin-1 (PP4 = 0.994) and protein FAM177A1 (PP4 = 0.995) colocalized with the expression of the genes FCN1 and FAM177A1 in whole blood, respectively. Furthermore, CD40 (PP4 = 0.977) and protein FAM177A1 (PP4 = 0.897) strongly colocalized with PBC.

Conclusions

We expand the current biomarkers for PBC. In total, three (ficolin-1, CD40, and protein FAM177A1) plasma proteins were identified and replicated as being associated with PBC in MR analysis. All of them showed significant protective effects against PBC. These proteins can be potential biomarkers or drug targets for PBC.

Macrophage Activation Markers Predict Liver-Related Complications in Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) has a wide variation in clinical presentation and course. There is no significant correlation between these symptoms and the disease stage, although patients with more advanced stages generally have more symptoms. It is important to develop biomarkers in order to identify patients with an increased risk of complications and end-stage liver disease. This study investigated surrogate markers for risk estimation of PBC-related complications, including a study population of 77 patients with PBC who underwent liver biopsy and were measured for serum levels of macrophage activation markers, soluble CD163 (sCD163), soluble mannose receptor (sMR), and zonulin. Patients with PBC were divided into symptomatic (Group S, n = 20) and asymptomatic (Group A, n = 57) groups. The correlations of histological stages based on both Scheuer and Nakanuma classifications with the three serum markers were investigated. The Nakanuma classification involves grading for liver fibrosis and bile duct loss. The three biomarkers were assessed for their diagnostic ability to identify patients with PBC having high risk of developing complications. The predictive factors of these complications were examined as well. Group S had significantly higher serum sMR (p = 0.011) and sCD163 (p = 0.048) levels versus Group A. A composite index of sMR and sCD163 measurements had significantly better prediction performance than sCD163 alone (p = 0.012), although not when compared to sMR alone (p = 0.129). Serum sMR was an independent factor for developing complications on both univariate (Odds ratio (OR) = 30.20, 95% confidence interval (95% CI): 3.410−267.0, p = 0.00220), and multivariate (OR = 33.70, 95% CI: 3.6600−311.0, p = 0.0019) analyses. Patients with PBC having sMR of ≥56.6 had a higher incidence of clinical complications versus those with a sMR of <56.6. Serum sMR predicts the development of complications in patients with PBC. sMR plus sCD163 showed better predictive power than either marker alone, although the addition of sCD163 did not improve the predictive power of sMR. Future prospective studies are required in order to validate the findings of the present study.

TAM Receptors in the Pathophysiology of Liver Disease

TAM receptors (Tyro3, Axl and MerTK) are a family of tyrosine kinase receptors that are expressed in a variety of cell populations, including liver parenchymal and non-parenchymal cells. These receptors are vital for immune homeostasis, as they regulate the innate immune response by suppressing inflammation via toll-like receptor inhibition and by promoting tissue resolution through efferocytosis. However, there is increasing evidence indicating that aberrant TAM receptor signaling may play a role in pathophysiological processes in the context of liver disease. This review will explore the roles of TAM receptors and their ligands in liver homeostasis as well as a variety of disease settings, including acute liver injury, steatosis, fibrosis, cirrhosis-associated immune dysfunction and hepatocellular carcinoma. A better understanding of our current knowledge of TAM receptors in liver disease may identify new opportunities for disease monitoring as well as novel therapeutic targets. Nonetheless, this review also aims to highlight areas where further research on TAM receptor biology in liver disease is required.

Novel Therapeutic Targets in Liver Fibrosis

Liver fibrosis is end-stage liver disease that can be rescued. If irritation continues due to viral infection, schistosomiasis and alcoholism, liver fibrosis can progress to liver cirrhosis and even cancer. The US Food and Drug Administration has not approved any drugs that act directly against liver fibrosis. The only treatments currently available are drugs that eliminate pathogenic factors, which show poor efficacy; and liver transplantation, which is expensive. This highlights the importance of clarifying the mechanism of liver fibrosis and searching for new treatments against it. This review summarizes how parenchymal, nonparenchymal cells, inflammatory cells and various processes (liver fibrosis, hepatic stellate cell activation, cell death and proliferation, deposition of extracellular matrix, cell metabolism, inflammation and epigenetics) contribute to liver fibrosis. We highlight discoveries of novel therapeutic targets, which may provide new insights into potential treatments for liver fibrosis.

Enhanced liver fibrosis score as a surrogate of liver-related complications and mortality in primary biliary cholangitis

The presence of bridging fibrosis predicts survival of primary biliary cholangitis (PBC). This study aimed to compare serum parameters for the estimation of liver fibrosis and prediction of clinical outcomes in PBC.Out of 392 patients with PBC, 102 who underwent liver biopsy and in whom fibrosis indices, platelet count, hyaluronic acid, type IV collagen 7 second domain, procollagen type III amino-terminal peptide, tissue inhibitor of metalloproteinases 1, Mac-2 binding protein glycosylation isomer, N-terminal type III collagen propeptide levels; fibrosis index based on 4 factors, aspartate aminotransferase-to-platelet ratio index, and enhanced liver fibrosis (ELF) score were determined, were included. The correlation of histological stages based on both Scheuer and Nakanuma classifications with fibrosis indices was investigated. The Nakanuma system comprises grading for liver fibrosis and bile duct loss. Diagnostic performances of 10 fibrosis indices were evaluated to identify patients with poor prognosis. Moreover, correlations of those with PBC clinical manifestation and survival were also investigated.Enhances liver fibrosis (ELF) score had the highest correlation coefficient for liver fibrosis evaluated according to either the Scheuer or Nakanuma classification among 10 serum fibrosis indices. It also had the highest diagnostic performance in estimating Scheuer stage III and Nakanuma fibrosis score 2, both of which represent portal-bridging fibrosis. Patients with an ELF score of ≥10.0 had shorter survival and presented more frequently clinical complications than those with an ELF score of <10.0.ELF score determines the severity of liver fibrosis and predicts the occurrence of complications and survival in patients with PBC.