Combination of ursodeoxycholic acid and glucocorticoids upregulates the AE2 alternate promoter in human liver cells

Primary biliary cholangitis: molecular pathogenesis perspectives and therapeutic potential of natural products

Primary biliary cirrhosis (PBC) is a chronic cholestatic immune liver disease characterized by persistent cholestasis, interlobular bile duct damage, portal inflammation, liver fibrosis, eventual cirrhosis, and death. Existing clinical and animal studies have made a good progress in bile acid metabolism, intestinal flora disorder inflammatory response, bile duct cell damage, and autoimmune response mechanisms. However, the pathogenesis of PBC has not been clearly elucidated. We focus on the pathological mechanism and new drug research and development of PBC in clinical and laboratory in the recent 20 years, to discuss the latest understanding of the pathological mechanism, treatment options, and drug discovery of PBC. Current clinical treatment mode and symptomatic drug support obviously cannot meet the urgent demand of patients with PBC, especially for the patients who do not respond to the current treatment drugs. New treatment methods are urgently needed. Drug candidates targeting reported targets or signals of PBC are emerging, albeit with some success and some failure. Single-target drugs cannot achieve ideal clinical efficacy. Multitarget drugs are the trend of future research and development of PBC drugs.

Cholestasis: exploring the triangular relationship of gut microbiota-bile acid-cholestasis and the potential probiotic strategies

Cholestasis is a condition characterized by the abnormal production or excretion of bile, and it can be induced by a variety of causes, the factors of which are extremely complex. Although great progress has been made in understanding cholestasis pathogenesis, the specific mechanisms remain unclear. Therefore, it is important to understand and distinguish cholestasis from different etiologies, which will also provide indispensable theoretical support for the development of corresponding therapeutic drugs. At present, the treatment of cholestasis mainly involves several bile acids (BAs) and their derivatives, most of which are in the clinical stage of development. Multiple lines of evidence indicate that ecological disorders of the gut microbiota are strongly related to the occurrence of cholestasis, in which BAs also play a pivotal role. Recent studies indicate that probiotics seem to have certain effects on cholestasis, but further confirmation from clinical trials is required. This paper reviews the etiology of and therapeutic strategies for cholestasis; summarizes the similarities and differences in inducement, symptoms, and mechanisms of related diseases; and provides information about the latest pharmacological therapies currently available and those under research for cholestasis. We also reviewed the highly intertwined relationship between gut microbiota-BA-cholestasis, revealing the potential role and possible mechanism of probiotics in the treatment of cholestasis.

Novel therapeutic targets for cholestatic and fatty liver disease

Cholestatic and non-alcoholic fatty liver disease (NAFLD) share several key pathophysiological mechanisms which can be targeted by novel therapeutic concepts that are currently developed for both areas. Nuclear receptors (NRs) are ligand-activated transcriptional regulators of key metabolic processes including hepatic lipid and glucose metabolism, energy expenditure and bile acid (BA) homoeostasis, as well as inflammation, fibrosis and cellular proliferation. Dysregulation of these processes contributes to the pathogenesis and progression of cholestatic as well as fatty liver disease, placing NRs at the forefront of novel therapeutic approaches. This includes BA and fatty acid activated NRs such as farnesoid-X receptor (FXR) and peroxisome proliferator-activated receptors, respectively, for which high affinity therapeutic ligands targeting specific or multiple isoforms have been developed. Moreover, novel liver-specific ligands for thyroid hormone receptor beta 1 complete the spectrum of currently available NR-targeted drugs. Apart from FXR ligands, BA signalling can be targeted by mimetics of FXR-activated fibroblast growth factor 19, modulation of their enterohepatic circulation through uptake inhibitors in hepatocytes and enterocytes, as well as novel BA derivatives undergoing cholehepatic shunting (instead of enterohepatic circulation). Other therapeutic approaches more directly target inflammation and/or fibrosis as critical events of disease progression. Combination strategies synergistically targeting metabolic disturbances, inflammation and fibrosis may be ultimately necessary for successful treatment of these complex and multifactorial disorders.

Vitexin ameliorates glycochenodeoxycholate-induced hepatocyte injury through SIRT6 and JAK2/STAT3 pathways

Objectives

Vitexin, a natural flavonoid, is commonly found in many foods and traditional herbal medicines and has clear health benefits. However, the role of vitexin in cholestasis is presently unclear. This study investigated whether vitexin mitigated glycochenodeoxycholate (GCDC)-induced hepatocyte injury and further elucidated the underlying mechanisms.

Materials and Methods

A cell counting kit-8 (CCK-8) assay was conducted to evaluate cell viability. The mitochondrial membrane potential (MMP, Δψm), reactive oxygen species (ROS) levels, and apoptosis rate of hepatocytes exposed to GCDC were detected by flow cytometry (FCM). We then measured the cytoprotective effects of vitexin against oxidative stress. The molecular signaling pathway was further investigated by using Western blotting and signaling pathway inhibitors.

Results

Here, we showed that vitexin increased cell viability and reduced cell apoptosis, necroptosis, and oxidative stress in a dose-dependent manner in GCDC-treated hepatocytes. In addition, by using selective inhibitors, we further confirmed that inhibition of the JAK2/STAT3 pathway by vitexin was mediated by prolonged activation of Sirtuin 6 (SIRT6).

Conclusion

Vitexin attenuated GCDC-induced hepatocyte injury via SIRT6 and the JAK2/STAT3 pathways.

Primary biliary cholangitis: pathogenic mechanisms

PURPOSE OF REVIEW

Primary biliary cholangitis (PBC) is characterized by autoimmune damage of intrahepatic bile ducts associated with a loss of tolerance to mitochondrial antigens. PBC etiopathogenesis is intriguing because of different perplexing features, namely: a) although mitochondria are present in all cell types and tissues, the damage is mainly restricted to biliary epithelial cells (BECs); b) despite being an autoimmune disorder, it does not respond to immunosuppressive drugs but rather to ursodeoxycholic acid, a bile salt that induces HCO3- rich choleresis; c) the overwhelming female preponderance of the disease remains unexplained. Here we present an etiopathogenic view of PBC which sheds light on these puzzling facts of the disease.

RECENT FINDINGS

PBC develops in patients with genetic predisposition to autoimmunity in whom epigenetic mechanisms silence the Cl-/HCO3- exchanger AE2 in both cholangiocytes and lymphoid cells. Defective AE2 function can produce BECs damage as a result of decreased biliary HCO3- secretion with disruption of the protective alkaline umbrella that normally prevents the penetration of toxic apolar bile salts into cholangiocytes. AE2 dysfunction also causes increased intracellular pH (pHi) in cholangiocytes, leading to the activation of soluble adenylyl cyclase, which sensitizes BECs to bile salt-induced apoptosis. Recently, mitophagy was found to be inhibited by cytosolic alkalization and stimulated by acidification. Accordingly, we propose that AE2 deficiency may disturb mitophagy in BECs, thus, promoting the accumulation of defective mitochondria, oxidative stress and presentation of mitochondrial antigens to the immune cells. As women possess a more acidic endolysosomal milieu than men, mitophagy might be more affected in women in an AE2-defective background. Apart from affecting BECs function, AE2 downregulation in lymphocytes may also contribute to alter immunoregulation facilitating autoreactive T-cell responses.

SUMMARY

PBC can be considered as a disorder of Cl-/HCO3- exchange in individuals with genetic predisposition to autoimmunity.

Multifaceted Control of GR Signaling and Its Impact on Hepatic Transcriptional Networks and Metabolism

Glucocorticoids (GCs) and the glucocorticoid receptor (GR) are important regulators of development, inflammation, stress response and metabolism, demonstrated in various diseases including Addison's disease, Cushing's syndrome and by the many side effects of prolonged clinical administration of GCs. These conditions include severe metabolic challenges in key metabolic organs like the liver. In the liver, GR is known to regulate the transcription of key enzymes in glucose and lipid metabolism and contribute to the regulation of circadian-expressed genes. Insights to the modes of GR regulation and the underlying functional mechanisms are key for understanding diseases and for the development of improved clinical uses of GCs. The activity and function of GR is regulated at numerous levels including ligand availability, interaction with heat shock protein (HSP) complexes, expression of GR isoforms and posttranslational modifications. Moreover, recent genomics studies show functional interaction with multiple transcription factors (TF) and coregulators in complex transcriptional networks controlling cell type-specific gene expression by GCs. In this review we describe the different regulatory steps important for GR activity and discuss how different TF interaction partners of GR selectively control hepatic gene transcription and metabolism.

Primary biliary cholangitis: pathogenesis and therapeutic opportunities

Primary biliary cholangitis is a chronic, seropositive and female-predominant inflammatory and cholestatic liver disease, which has a variable rate of progression towards biliary cirrhosis. Substantial progress has been made in patient risk stratification with the goal of personalized care, including early adoption of next-generation therapy with licensed use of obeticholic acid or off-label fibrate derivatives for those with insufficient benefit from ursodeoxycholic acid, the current first-line drug. The disease biology spans genetic risk, epigenetic changes, dysregulated mucosal immunity and altered biliary epithelial cell function, all of which interact and arise in the context of ill-defined environmental triggers. A current focus of research on nuclear receptor pathway modulation that specifically and potently improves biliary excretion, reduces inflammation and attenuates fibrosis is redefining therapy. Patients are benefiting from pharmacological agonists of farnesoid X receptor and peroxisome proliferator-activated receptors. Immunotherapy remains a challenge, with a lack of target definition, pleiotropic immune pathways and an interplay between hepatic immune responses and cholestasis, wherein bile acid-induced inflammation and fibrosis are dominant clinically. The management of patient symptoms, particularly pruritus, is a notable goal reflected in the development of rational therapy with apical sodium-dependent bile acid transporter inhibitors.

Epigenetic Modifications in Generalized Autoimmune Epithelitis: Sjögren's Syndrome and Primary Biliary Cholangitis

Sjögren's syndrome (SjS) and primary biliary cholangitis (PBC) can be classified as a model of generalized autoimmune epithelitis based on their frequent coexistence in clinical practice and the highly specific immune mediated injury of target epithelial cells. Both of these autoimmune diseases are characterized by female predominance, highly specific circulating autoantibodies, and immune-mediated destruction of the salivary and lachrymal glands and the biliary epithelial cells, respectively. Although the genetic predisposition has been well described for both diseases, genetic studies have failed to completely elucidate their pathogenesis. The recent integration of epigenetic data, analyzing the different cellular partners, opens new perspectives and allows for better understanding of these complex and still incurable diseases. Epigenetic studies on SjS have elucidated the role of DNA methylation alterations in disease pathogenesis, while epigenetic changes that influence expression of genes on the X chromosome have been implicated in the geo-variability and occurrence of PBC. The aim of this review is to describe the advances in epigenetics in the field of autoimmune epithelitis as well as to highlight how epigenetic changes could contribute to better understanding of disease pathogenesis and progression. These advances could yield insights on novel therapeutic interventions.

Promoter hypermethylation of the AE2/SLC4A2 gene in PBC

Background & Aims

Patients with primary biliary cholangitis (PBC) exhibit reduced AE2/SLC4A2 gene expression in the liver and peripheral blood mononuclear cells (PBMCs). AE2 encodes a Cl^–/HCO₃^– exchanger involved in biliary bicarbonate secretion and intracellular pH regulation. Reduced AE2 expression in PBC may be pathogenic, as Ae2-knockout mice reproduce characteristic PBC features. Herein, we aimed to identify CpG-methylation abnormalities in AE2 promoter regions that might contribute to the reduced gene transcription in PBC livers and PBMCs.

Methods

CpG-cytosine methylation rates were interrogated at 1-base pair resolution in upstream and alternate AE2 promoter regions through pyrosequencing of bisulphite-modified genomic DNA from liver specimens and PBMCs. AE2a and alternative AE2b1 and AE2b2 mRNA levels were measured by real-time PCR. Human lymphoblastoid-T2 cells were treated with 5-aza-2´-deoxycytidine for demethylation assays.

Results

AE2 promoters were found to be hypermethylated in PBC livers compared to normal and diseased liver specimens. Receiver operating characteristic (ROC) curve analysis showed that minimal CpG-hypermethylation clusters of 3 AE2a-CpG sites and 4 alternate-AE2b2-CpG sites specifically differentiated PBC from normal and diseased controls, with mean methylation rates inversely correlating with respective transcript levels. Additionally, in PBMCs a minimal cluster of 3 hypermethylated AE2a-CpG sites distinguished PBC from controls, and mean methylation rates correlated negatively with AE2a mRNA levels in these immune cells. Alternate AE2b2/AE2b1 promoters in PBMCs were constitutively hypermethylated, in line with absent alternative mRNA expression in diseased and healthy PBMCs. Demethylation assays treating lymphoblastoid-T2 cells with 5-aza-2´-deoxycytidine triggered AE2b2/AE2b1 expression and upregulated AE2a-promoter expression.

Conclusions

Disease-specific hypermethylation of AE2 promoter regions and subsequent downregulation of AE2-gene expression in the liver and PBMCs of patients with PBC might be critically involved in the pathogenesis of this complex disease.

Lay summary

Primary biliary cholangitis (PBC) is a chronic immune-associated cholestatic liver disease with unclear complex/multifactorial etiopathogenesis affecting mostly middle-aged women. Patients with PBC exhibit reduced expression of the AE2/SLC4A2 gene. Herein, we found that AE2 promoter regions are hypermethylated in the liver and peripheral blood mononuclear cells of patients with PBC. This increased methylation is associated with downregulated AE2-gene expression, which might contribute to the pathogenesis of PBC. Therefore, novel epigenetic targets may improve treatment in patients with PBC who respond poorly to current pharmacological therapies.

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Patients with PBC have higher AE2 CpG methylation in upstream AE2a and/or AE2b2/AE2b1 promoter regions in liver and PBMCs.

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Combined methylation rates of 2 minimal CpG-clusters in the liver and 1 minimal CpG-cluster in PBMCs specifically distinguished PBC from normal and diseased controls.

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Methylation rates of AE2 promoter regions inversely correlated with levels of respective AE2 mRNAs in liver and PBMCs.

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Alternate AE2b2/AE2b1 promoter regions were found to be densely methylated in both normal and diseased PBMC samples.

Adaptive downregulation of Cl-/HCO3- exchange activity in rat hepatocytes under experimental obstructive cholestasis

In obstructive cholestasis, there is an integral adaptive response aimed to diminish the bile flow and minimize the injury of bile ducts caused by increased intraluminal pressure and harmful levels of bile salts and bilirrubin. Canalicular bicarbonate secretion, driven by the anion exchanger 2 (AE2), is an influential determinant of the canalicular bile salt-independent bile flow. In this work, we ascertained whether AE2 expression and/or activity is reduced in hepatocytes from rats with common bile duct ligation (BDL), as part of the adaptive response to cholestasis. After 4 days of BDL, we found that neither AE2 mRNA expression (measured by quantitative real-time PCR) nor total levels of AE2 protein (assessed by western blot) were modified in freshly isolated hepatocytes. However, BDL led to a decrease in the expression of AE2 protein in plasma membrane fraction as compared with SHAM control. Additionally, AE2 activity (JOH-, mmol/L/min), measured in primary cultured hepatocytes from BDL and SHAM rats, was decreased in the BDL group versus the control group (1.9 ± 0.3 vs. 3.1 ± 0.2, p<0.005). cAMP-stimulated AE2 activity, however, was not different between SHAM and BDL groups (3.7 ± 0.3 vs. 3.5 ± 0.3), suggesting that cAMP stimulated insertion into the canalicular membrane of AE2-containing intracellular vesicles, that had remained abnormally internalized after BDL. In conclusion, our results point to the existence of a novel adaptive mechanism in cholestasis aimed to reduce biliary pressure, in which AE2 internalization in hepatocytes might result in decreased canalicular HCO3- output and decreased bile flow.

MicroRNA-506 promotes primary biliary cholangitis-like features in cholangiocytes and immune activation

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease associated with autoimmune phenomena targeting intrahepatic bile duct cells (cholangiocytes). Although its etiopathogenesis remains obscure, development of antimitochondrial autoantibodies against pyruvate dehydrogenase complex E2 is a common feature. MicroRNA (miR) dysregulation occurs in liver and immune cells of PBC patients, but its functional relevance is largely unknown. We previously reported that miR-506 is overexpressed in PBC cholangiocytes and directly targets both Cl- / HCO3- anion exchanger 2 and type III inositol 1,4,5-trisphosphate receptor, leading to cholestasis. Here, the regulation of miR-506 gene expression and its role in cholangiocyte pathophysiology and immune activation was studied. Several proinflammatory cytokines overexpressed in PBC livers (such as interleukin-8 [IL8], IL12, IL17, IL18, and tumor necrosis factor alpha) stimulated miR-506 promoter activity in human cholangiocytes, as revealed by luciferase reporter assays. Experimental overexpression of miR-506 in cholangiocytes dysregulated the cell proteomic profile (by mass spectrometry), affecting proteins involved in different biological processes including mitochondrial metabolism. In cholangiocytes, miR-506 (1) induced dedifferentiation with down-regulation of biliary and epithelial markers together with up-regulation of mesenchymal, proinflammatory, and profibrotic markers; (2) impaired cell proliferation and adhesion; (3) increased oxidative and endoplasmic reticulum stress; (4) caused DNA damage; and (5) sensitized to caspase-3-dependent apoptosis induced by cytotoxic bile acids. These events were also associated with impaired energy metabolism in mitochondria (proton leak and less adenosine triphosphate production) and pyruvate dehydrogenase complex E2 overexpression. Coculture of miR-506 overexpressing cholangiocytes with PBC immunocytes induced activation and proliferation of PBC immunocytes.

CONCLUSION

Different proinflammatory cytokines enhance the expression of miR-506 in biliary epithelial cells; miR-506 induces PBC-like features in cholangiocytes and promotes immune activation, representing a potential therapeutic target for PBC patients. (Hepatology 2018;67:1420-1440).

Update on pharmacotherapies for cholestatic liver disease

Cholestatic liver diseases are conditions with impaired bile formation and/or flow due to genetic, immunologic, environmental, or other causes. Unless successfully treated, this can lead to chronic liver injury and end‐stage liver disease. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) embody the most prominent adult cholestatic liver diseases with regard to incidence, morbidity, and mortality. A considerable proportion of patients with PBC and PSC experience progressive liver disease and ultimately liver‐related death due to a paucity of effective pharmacotherapy; however, novel pharmacologic developments offer substantial promise in this regard. Here, we provide a brief review and update on current and emerging pharmacotherapies for PBC and PSC. (Hepatology Communications 2017;1:7–17)

Primary Biliary Cholangitis: Disease Pathogenesis and Implications for Established and Novel Therapeutics

Primary Biliary Cholangitis is a progressive, autoimmune cholestatic liver disorder. Cholestasis with disease progression may lead to dyslipidemia, osteodystrophy and fat-soluble vitamin deficiency. Portal hypertension may develop prior to advanced stages of fibrosis. Untreated disease may lead to cirrhosis, hepatocellular cancer and need for orthotopic liver transplantation. Classically, diagnosis is made with elevation of alkaline phosphatase, demonstration of circulating antimitochondrial antibody, and if performed: asymmetric destruction/nonsupperative cholangitis of intralobular bile ducts on biopsy. Disease pathogenesis is complex and results from innate and adaptive (cell-mediated and humoral) responses that lead to inflammation of biliary duct epithelium. Ongoing damage is amplified and sustained through bile acid toxicity. Use of weight based (13-15mg/kg) ursodeoxycholic acid is well established in retarding disease progression and improving survival; however, is ineffective in achieving complete biochemical remission in many. Recently, a Farnesoid X Receptor agonist, obeticholic acid, has been approved for use. A number of ongoing clinical studies are underway to evaluate utility of fibric acid derivatives, biologics, antifibrotics, and stem cells as monotherapy or in combination with ursodeoxycholic acid for primary biliary cholangitis. The aim of this review is to discuss disease pathogenesis and highlight rationale/implications for both established and novel therapeutics.

Recent advances in understanding and managing cholestasis

Cholestatic liver diseases are hereditary or acquired disorders with impaired hepatic excretion and enterohepatic circulation of bile acids and other cholephiles. The distinct pathological mechanisms, particularly for the acquired forms of cholestasis, are not fully revealed, but advances in the understanding of the molecular mechanisms and identification of key regulatory mechanisms of the enterohepatic circulation of bile acids have unraveled common and central mechanisms, which can be pharmacologically targeted. This overview focuses on the central roles of farnesoid X receptor, fibroblast growth factor 19, and apical sodium-dependent bile acid transporter for the enterohepatic circulation of bile acids and their potential as new drug targets for the treatment of cholestatic liver disease.

Metabolomics Coupled with Multivariate Data and Pathway Analysis on Potential Biomarkers in Cholestasis and Intervention Effect of Paeonia lactiflora Pall

Background: The dried root of Paeonia lactiflora Pall. (PLP) is a classical Chinese herbal medicine that has been used to treat hepatic disease for 1000s of years. Our previous work suggested that PLP can be used to treat hepatitis with severe cholestasis. This study explored the mechanism by which PLP affects ANIT-induced cholestasis in rats using a metabolomics approach.

Methods: The effects of PLP on serum indices (TBIL, DBIL, AST, ALT, ALP, and TBA) and the histopathology of the liver were analyzed. Moreover, UHPLC-Q-TOF was performed to identify the possible effect of PLP on metabolites. The pathway analysis was conducted to illustrate the pathways and network by which PLP treats cholestasis.

Result: High-dose PLP remarkably down-regulated the serum indices and alleviated histological damage to the liver. Metabolomics analyses showed that the therapeutic effect of high-dose PLP is mainly associated with the regulation of several metabolites, such as glycocholic acid, taurocholic acid, glycochenodeoxycholic acid, L(D)-arginine, and L-tryptophan. A pathway analysis showed that the metabolites were related to bile acid secretion and amino acid metabolism. In addition, the significant changes in bile acid transporters also indicated that bile acid metabolism might be involved in the therapeutic effect of PLP on cholestasis. Moreover, a principal component analysis indicated that the metabolites in the high-dose PLP group were closer to those of the control, whereas those of the moderate dose or low-dose PLP group were closer to those of the ANIT group. This finding indicated that metabolites may be responsible for the differences between the effects of low-dose and moderate-dose PLP.

Conclusion: The therapeutic effect of high-dose PLP on cholestasis is possibly related to regulation of bile acid secretion and amino acid metabolism. Moreover, these findings may help better understand the mechanisms of disease and provide a potential therapy for cholestasis.

Novel therapeutic targets in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic immune-mediated liver disease characterized by progressive cholestasis, biliary fibrosis and eventually cirrhosis. It results in characteristic symptoms with marked effects on life quality. The advent of large patient cohorts has challenged the view of PBC as a benign condition treated effectively by the single licensed therapy-ursodeoxycholic acid (UDCA). UDCA nonresponse or under-response has a major bearing on outcome, substantially increasing the likelihood that liver transplantation will be required or that patients will die of the disease. In patients with high-risk, treatment-unresponsive or highly symptomatic disease the need for new treatment approaches is clear. Evolution in our understanding of disease mechanisms is rapidly leading to the advent of new and re-purposed therapeutic agents targeting key processes. Notable opportunities are offered by targeting what could be considered as the 'upstream' immune response, 'midstream' biliary injury and 'downstream' fibrotic processes. Combination therapy targeting several pathways or the development of novel agents addressing multiple components of the disease pathway might be required. Ultimately, PBC therapeutics will require a stratified approach to be adopted in practice. This Review provides a current perspective on potential approaches to PBC treatment, and highlights the challenges faced in evaluating and implementing those treatments.

Advances in pharmacotherapy for primary biliary cirrhosis

INTRODUCTION

Primary biliary cirrhosis (PBC) is a chronic autoimmune liver disease mostly seen in middle-aged women characterized by progressive nonsuppurative destruction of small bile ducts resulting in intrahepatic cholestasis, parenchymal injury and ultimately end-stage liver disease. Despite major breakthroughs in our understanding of PBC, there remains only one FDA-approved agent for treatment: ursodeoxycholic acid (UDCA) to which one-third of patients are unresponsive.

AREAS COVERED

Biochemical response to treatment with UDCA is associated with excellent survival rates in PBC patients. However, there is a need for alternative treatments for nonresponders. Results from human epidemiological and genetic studies as well as preclinical studies in PBC animal models have provided a strong impetus for the development of new therapeutic agents. In this review, we discuss the recent advances in translational research in PBC focusing on promising therapeutic approaches, namely immune-based targeted therapies and agents targeting the synthesis and circulation of bile acids.

EXPERT OPINION

We are in a new era for the development of novel therapies for PBC. Data on fibrates, budesonide and obeticholic acid offer encouragement for nonresponders to UDCA.

Large dosage of chishao in formulae for cholestatic hepatitis: a systematic review and meta-analysis

Objective. To evaluate the efficacy and safety of large dosage of Chishao in formulae for treatment of cholestatic hepatitis. Methods. The major databases (PubMed, Embase, Cochrane Library, Chinese Biomedical Database Wanfang, VIP medicine information system, and China National Knowledge Infrastructure) were searched until January 2014. Randomized controlled trials (RCTs) of large dosage of Chishao in formulae that reported on publications in treatment of cholestatic hepatitis with total efficacy rate, together with the biochemical indices including alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL), were extracted by two reviewers. The Cochrane tool was used for the assessment of risk of bias included trials. Data were analyzed with RevMan 5.2.7 software. Results. 11 RCTs involving 1275 subjects with cholestatic hepatitis were included. Compared with essential therapy, large dosage of Chishao in formulae demonstrated more efficiently with down regulation of serum ALT, AST, TBIL, DBIL. Meanwhile, there were no obvious adverse events. Conclusion. As a promising novel treatment approach, widely using large dosage of Chishao in formulae may enhance the curative efficacy for cholestatic hepatitis. Considering being accepted by more and more practitioners, further rigorously designed clinical studies are required.

Clinical application of transcriptional activators of bile salt transporters

Hepatobiliary bile salt (BS) transporters are critical determinants of BS homeostasis controlling intracellular concentrations of BSs and their enterohepatic circulation. Genetic or acquired dysfunction of specific transport systems causes intrahepatic and systemic retention of potentially cytotoxic BSs, which, in high concentrations, may disturb integrity of cell membranes and subcellular organelles resulting in cell death, inflammation and fibrosis. Transcriptional regulation of canalicular BS efflux through bile salt export pump (BSEP), basolateral elimination through organic solute transporters alpha and beta (OSTα/OSTβ) as well as inhibition of hepatocellular BS uptake through basolateral Na(+)-taurocholate cotransporting polypeptide (NTCP) represent critical steps in protection from hepatocellular BS overload and can be targeted therapeutically. In this article, we review the potential clinical implications of the major BS transporters BSEP, OSTα/OSTβ and NTCP in the pathogenesis of hereditary and acquired cholestatic syndromes, provide an overview on transcriptional control of these transporters by the key regulatory nuclear receptors and discuss the potential therapeutic role of novel transcriptional activators of BS transporters in cholestasis.

Role of AE2 for pHi regulation in biliary epithelial cells

The Cl⁻/HCO⁻₃anion exchanger 2 (AE2) is known to be involved in intracellular pH (pH_i) regulation and transepithelial acid-base transport. Early studies showed that AE2 gene expression is reduced in liver biopsies and blood mononuclear cells from patients with primary biliary cirrhosis (PBC), a disease characterized by chronic non-suppurative cholangitis associated with antimitochondrial antibodies (AMA) and other autoimmune phenomena. Microfluorimetric analysis of the Cl⁻/HCO⁻₃ anion exchange (AE) in isolated cholangiocytes showed that the cAMP-stimulated AE activity is diminished in PBC compared to both healthy and diseased controls. More recently, it was found that miR-506 is upregulated in cholangiocytes of PBC patients and that AE2 may be a target of miR-506. Additional evidence for a pathogenic role of AE2 dysregulation in PBC was obtained with Ae2^−/−_a,b mice, which develop biochemical, histological, and immunologic alterations that resemble PBC (including development of serum AMA). Analysis of HCO⁻₃ transport systems and pH_i regulation in cholangiocytes from normal and Ae2^−/−_a,b mice confirmed that AE2 is the transporter responsible for the Cl⁻/HCO⁻₃exchange in these cells. On the other hand, both Ae2^+/+_a,b and Ae2^−/−_a,b mouse cholangiocytes exhibited a Cl⁻-independent bicarbonate transport system, essentially a Na⁺-bicarbonate cotransport (NBC) system, which could contribute to pH_i regulation in the absence of AE2.

Nuclear receptors as drug targets in cholestatic liver diseases

Cholestatic liver diseases encompass a wide spectrum of disorders with different causes, resulting in impaired bile flow and accumulation of bile acids and other potentially hepatotoxic cholephils. The understanding of the molecular mechanisms of bile formation and cholestasis has recently improved significantly through new insights into nuclear receptor (patho)biology. Nuclear receptors are ligand-activated transcription factors, which act as central players in the regulation of genes responsible for elimination and detoxification of biliary constituents accumulating in cholestasis. They also control other pathophysiologic processes such as inflammation, fibrogenesis, and carcinogenesis involved in the pathogenesis and disease progression of cholestasis liver diseases.

Bile acid transporters and regulatory nuclear receptors in the liver and beyond

Bile acid (BA) transporters are critical for maintenance of the enterohepatic BA circulation where BAs exert their multiple physiological functions including stimulation of bile flow, intestinal absorption of lipophilic nutrients, solubilization and excretion of cholesterol, as well as antimicrobial and metabolic effects. Tight regulation of BA transporters via nuclear receptors is necessary to maintain proper BA homeostasis. Hereditary and acquired defects of BA transporters are involved in the pathogenesis of several hepatobiliary disorders including cholestasis, gallstones, fatty liver disease and liver cancer, but also play a role in intestinal and metabolic disorders beyond the liver. Thus, pharmacological modification of BA transporters and their regulatory nuclear receptors opens novel treatment strategies for a wide range of disorders.

Up-regulation of microRNA 506 leads to decreased Cl-/HCO3- anion exchanger 2 expression in biliary epithelium of patients with primary biliary cirrhosis

Cl(-) /HCO3- anion exchanger 2 (AE2) participates in intracellular pH homeostasis and secretin-stimulated biliary bicarbonate secretion. AE2/SLC4A2 gene expression is reduced in liver and blood mononuclear cells from patients with primary biliary cirrhosis (PBC). Our previous findings of hepatic and immunological features mimicking PBC in Ae2-deficient mice strongly suggest that decreased AE2 expression might be involved in the pathogenesis of PBC. Here, we tested the potential role of microRNA 506 (miR-506) - predicted as candidate to target AE2 mRNA - for the decreased expression of AE2 in PBC. Real-time quantitative polymerase chain reaction showed that miR-506 expression is increased in PBC livers versus normal liver specimens. In situ hybridization in liver sections confirmed that miR-506 is up-regulated in the intrahepatic bile ducts of PBC livers, compared with normal and primary sclerosing cholangitis livers. Precursor-mediated overexpression of miR-506 in SV40-immortalized normal human cholangiocytes (H69 cells) led to decreased AE2 protein expression and activity, as indicated by immunoblotting and microfluorimetry, respectively. Moreover, miR-506 overexpression in three-dimensional (3D)-cultured H69 cholangiocytes blocked the secretin-stimulated expansion of cystic structures developed under the 3D conditions. Luciferase assays and site-directed mutagenesis demonstrated that miR-506 specifically may bind the 3'untranslated region (3'UTR) of AE2 messenger RNA (mRNA) and prevent protein translation. Finally, cultured PBC cholangiocytes showed decreased AE2 activity, together with miR-506 overexpression, compared to normal human cholangiocytes, and transfection of PBC cholangiocytes with anti-miR-506 was able to improve their AE2 activity.

CONCLUSION

miR-506 is up-regulated in cholangiocytes from PBC patients, binds the 3'UTR region of AE2 mRNA, and prevents protein translation, leading to diminished AE2 activity and impaired biliary secretory functions. In view of the putative pathogenic role of decreased AE2 in PBC, miR-506 may constitute a potential therapeutic target for this disease.

Dual farnesoid X receptor/TGR5 agonist INT-767 reduces liver injury in the Mdr2-/- (Abcb4-/-) mouse cholangiopathy model by promoting biliary HCO⁻₃ output

Chronic cholangiopathies have limited therapeutic options and represent an important indication for liver transplantation. The nuclear farnesoid X receptor (FXR) and the membrane G protein-coupled receptor, TGR5, regulate bile acid (BA) homeostasis and inflammation. Therefore, we hypothesized that activation of FXR and/or TGR5 could ameliorate liver injury in Mdr2(-/-) (Abcb4(-/-)) mice, a model of chronic cholangiopathy. Hepatic inflammation, fibrosis, as well as bile secretion and key genes of BA homeostasis were addressed in Mdr2(-/-) mice fed either a chow diet or a diet supplemented with the FXR agonist, INT-747, the TGR5 agonist, INT-777, or the dual FXR/TGR5 agonist, INT-767 (0.03% w/w). Only the dual FXR/TGR5 agonist, INT-767, significantly improved serum liver enzymes, hepatic inflammation, and biliary fibrosis in Mdr2(-/-) mice, whereas INT-747 and INT-777 had no hepatoprotective effects. In line with this, INT-767 significantly induced bile flow and biliary HCO 3- output, as well as gene expression of carbonic anhydrase 14, an important enzyme able to enhance HCO 3- transport, in an Fxr-dependent manner. In addition, INT-767 dramatically reduced bile acid synthesis via the induction of ileal Fgf15 and hepatic Shp gene expression, thus resulting in significantly reduced biliary bile acid output in Mdr2(-/-) mice.

CONCLUSION

This study shows that FXR activation improves liver injury in a mouse model of chronic cholangiopathy by reduction of biliary BA output and promotion of HCO 3--rich bile secretion.

Ursodeoxycholic acid in neonatal hepatitis and infantile paucity of intrahepatic bile ducts: review of a historical cohort

We retrospectively reviewed the role of ursodeoxycholic acid in infants having nonsurgical cholestasis attending the Hepatology Clinic, New Children Hospital, Cairo University, Egypt, from 1985 until 2005. Files of 496 infants with neonatal hepatitis and 97 with intrahepatic bile duct paucity were included; of them 241 (48.6%) and 52 (46.4%) received 20-40 mg/kg/day ursodeoxycholic acid for 319.2 +/- 506.9 days and 480.3 +/- 583.3 days, respectively. The outcome of infants with neonatal hepatitis with intake of ursodeoxycholic acid and those without was: 108 (44.8%) and 179 (70.2%) successful (P = 0.000), 11 (4.6%) and 13 (5.1%) improved (P = 0. 474), 112 (46.5%) and 61 (23.9%) suffered failed outcome (P = 0.000), and 10 (4.1%) and 2 (0.78%) died (P = 0.014), respectively. Likelihood of successful outcome with ursodeoxycholic acid intake was 0.345 (P = 0.000), and that of deterioration was 2.76 (P = 0.000). For those having intrahepatic bile duct paucity likelihood of successful outcome with ursodeoxycholic acid intake was 0.418 (P = 0.040) and that of deterioration was 2.64 (P = 0.028). Ursodeoxycholic acid failed in management of this cohort of infants with nonsurgical cholestasis.

Bile acids in treatment of ocular disease

Bear bile has been included in Asian pharmacopeias for thousands of years in treatment of several diseases, ranging from sore throat to hemorrhoids. The hydrophilic bile acids tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) are the major bile acids of bear bile. Both of these are available as synthetic formulations and are approved by the health administrations of several countries for treatment of cirrhosis and gallstones. This review briefly covers the use of bear bile in Traditional Chinese Medicine, bile acid physiology, approved use of UDCA and TUDCA in Western medicine, and recent research exploring their neuroprotective properties, including in models of ocular disease.

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9–10:1) with a prevalence of up to 1 in 1,000 women over 40 years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13–15 mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC.

Molecular physiology and genetics of Na+-independent SLC4 anion exchangers

Plasmalemmal Cl(-)/HCO(3)(-) exchangers are encoded by the SLC4 and SLC26 gene superfamilies, and function to regulate intracellular pH, [Cl(-)] and cell volume. The Cl(-)/HCO(3)(-) exchangers of polarized epithelial cells also contribute to transepithelial secretion and reabsorption of acid-base equivalents and Cl(-). This review focuses on Na(+)-independent electroneutral Cl(-)/HCO(3)(-) exchangers of the SLC4 family. Human SLC4A1/AE1 mutations cause the familial erythroid disorders of spherocytic anemia, stomatocytic anemia and ovalocytosis. A largely discrete set of AE1 mutations causes familial distal renal tubular acidosis. The Slc4a2/Ae2(-/-) mouse dies before weaning with achlorhydria and osteopetrosis. A hypomorphic Ae2(-/-) mouse survives to exhibit male infertility with defective spermatogenesis and a syndrome resembling primary biliary cirrhosis. A human SLC4A3/AE3 polymorphism is associated with seizure disorder, and the Ae3(-/-) mouse has increased seizure susceptibility. The transport mechanism of mammalian SLC4/AE polypeptides is that of electroneutral Cl(-)/anion exchange, but trout erythroid Ae1 also mediates Cl(-) conductance. Erythroid Ae1 may mediate the DIDS-sensitive Cl(-) conductance of mammalian erythrocytes, and, with a single missense mutation, can mediate electrogenic SO(4)(2-)/Cl(-) exchange. AE1 trafficking in polarized cells is regulated by phosphorylation and by interaction with other proteins. AE2 exhibits isoform-specific patterns of acute inhibition by acidic intracellular pH and independently by acidic extracellular pH. In contrast, AE2 is activated by hypertonicity and, in a pH-independent manner, by ammonium and by hypertonicity. A growing body of structure-function and interaction data, together with emerging information about physiological function and structure, is advancing our understanding of SLC4 anion exchangers.

Nuclear receptors as therapeutic targets in cholestatic liver diseases

Cholestasis results in intrahepatic accumulation of cytotoxic bile acids, which cause liver damage ultimately leading to biliary fibrosis and cirrhosis. Cholestatic liver injury is counteracted by a variety of adaptive hepatoprotective mechanisms including alterations in bile acid transport, synthesis and detoxification. The underlying molecular mechanisms are mediated mainly at a transcriptional level via a complex network involving nuclear receptors including the farnesoid X receptor, pregnane X receptor, vitamin D receptor and constitutive androstane receptor, which target overlapping, although not identical, sets of genes. Because the intrinsic adaptive response to bile acids cannot fully prevent liver injury in cholestasis, therapeutic targeting of these receptors via specific and potent agonists may further enhance the hepatic defence against toxic bile acids. Activation of these receptors results in repression of bile acid synthesis, induction of phases I and II bile acid hydroxylation and conjugation and stimulation of alternative bile acid export while limiting hepatocellular bile acid import. Furthermore, the use of nuclear receptor ligands may not only influence bile acid transport and metabolism but may also directly target hepatic fibrogenesis and inflammation. Many drugs already used to treat cholestasis and its complications such as pruritus (e.g. ursodeoxycholic acid, rifampicin, fibrates) may act via activation of nuclear receptors. More specific and potent nuclear receptor ligands are currently being developed. This article will review the current knowledge on nuclear receptors and their potential role in the treatment of cholestatic liver diseases.

Endocrine and liver interaction: the role of endocrine pathways in NASH

This article reviews evidence that causally links hormonal disorders with hepatobiliary disease, and gives particular focus to nonalcoholic steatohepatitis (NASH). The downstream mechanisms by which endocrine disturbances cause liver disease might be similar to those involved in the development of primary liver disease. Hypothyroidism, for example, might lead to NASH, cirrhosis and potentially liver cancer via the development of hyperlipidemia and obesity. Patients with growth hormone deficiency have a metabolic-syndrome-like phenotype that is also associated with the development of NASH. Polycystic ovary syndrome is a common endocrine disorder that is often associated with insulin resistance, the metabolic syndrome, altered levels of liver enzymes and the development of NASH. Recent findings support a role of dehydroepiandrosterone sulfate deficiency in the development of advanced NASH. In addition, adrenal failure is increasingly reported in patients with end stage liver disease and in patients who have received a liver transplant, which suggests a bidirectional relationship between liver and endocrine functions. Clinicians should, therefore, be aware of the potential role of endocrine disorders in patients with cryptogenic liver disease and of the effects of liver function on the endocrine system.

Endocrine and liver interaction: the role of endocrine pathways in NASH

This article reviews evidence that causally links hormonal disorders with hepatobiliary disease, and gives particular focus to nonalcoholic steatohepatitis (NASH). The downstream mechanisms by which endocrine disturbances cause liver disease might be similar to those involved in the development of primary liver disease. Hypothyroidism, for example, might lead to NASH, cirrhosis and potentially liver cancer via the development of hyperlipidemia and obesity. Patients with growth hormone deficiency have a metabolic-syndrome-like phenotype that is also associated with the development of NASH. Polycystic ovary syndrome is a common endocrine disorder that is often associated with insulin resistance, the metabolic syndrome, altered levels of liver enzymes and the development of NASH. Recent findings support a role of dehydroepiandrosterone sulfate deficiency in the development of advanced NASH. In addition, adrenal failure is increasingly reported in patients with end stage liver disease and in patients who have received a liver transplant, which suggests a bidirectional relationship between liver and endocrine functions. Clinicians should, therefore, be aware of the potential role of endocrine disorders in patients with cryptogenic liver disease and of the effects of liver function on the endocrine system.