Cholangiopathy aggravation is caused by VDR ablation and alleviated by VDR-independent vitamin D signaling in ABCB4 knockout mice.

Background & Aims: Cholangiopathies are chronic liver diseases in which damaged cholangiocytes trigger a proinflammatory and profibrotic reaction. The nuclear vitamin D receptor (VDR) is highly expressed in cholangiocytes and exerts immune-regulatory functions in these cells. In the present study, we examined the protective function of VDR and other vitamin D signaling pathways in chronic cholangiopathy and cholangiocytes.

Expression patterns of nuclear receptors in parenchymal and non-parenchymal mouse liver cells and their modulation in cholestasis.

Nuclear receptors (NR), the largest family of transcription factors, control many physiological and pathological processes. To gain insight into hepatic NR and their potential as therapeutic targets in cholestatis, we determined their expression in individual cell types of the mouse liver in normal and cholestatic conditions. Hepatocytes, cholangiocytes, hepatic stellate cells (HSC), sinusoidal endothelial cells (SEC) and Kupffer cells (KC) were isolated from the liver of mice with acute or chronic cholestasis (i.

Functions of the Gallbladder.

The gallbladder stores and concentrates bile between meals. Gallbladder motor function is regulated by bile acids via the membrane bile acid receptor, TGR5, and by neurohormonal signals linked to digestion, for example, cholecystokinin and FGF15/19 intestinal hormones, which trigger gallbladder emptying and refilling, respectively. The cycle of gallbladder filling and emptying controls the flow of bile into the intestine and thereby the enterohepatic circulation of bile acids.

Nuclear receptors in acute and chronic cholestasis.

Background: Nuclear receptors (NRs) form a family of 48 members. NRs control hepatic processes such as bile acid homeostasis, lipid metabolism and mechanisms involved in fibrosis and inflammation. Due to their central role in the regulation of hepatoprotective mechanisms, NRs are promising therapeutic targets in cholestatic disorders.

E-cadherin, guardian of liver physiology.

E-cadherin is a cell-to-cell adhesion molecule involved in epithelial cell behavior, tissue formation and cancer suppression. In the liver, E-cadherin is expressed by hepatocytes and biliary epithelial cells. However, the exact role of E-cadherin in hepatic pathophysiology remains largely unknown.

Phosphorylation of ABCB4 impacts its function: insights from disease-causing mutations.

Unlabelled: The ABCB4 transporter mediates phosphatidylcholine (PC) secretion at the canalicular membrane of hepatocytes and its genetic defects cause biliary diseases. Whereas ABCB4 shares high sequence identity with the multidrug transporter, ABCB1, its N-terminal domain is poorly conserved, leading us to hypothesize a functional specificity of this domain. A database of ABCB4 genotyping in a large series of patients was screened for variations altering residues of the N-terminal domain.

Vitamin D nuclear receptor deficiency promotes cholestatic liver injury by disruption of biliary epithelial cell junctions in mice.

Unlabelled: Alterations in apical junctional complexes (AJCs) have been reported in genetic or acquired biliary diseases. The vitamin D nuclear receptor (VDR), predominantly expressed in biliary epithelial cells in the liver, has been shown to regulate AJCs. The aim of our study was thus to investigate the role of VDR in the maintenance of bile duct integrity in mice challenged with biliary-type liver injury.

Defects in gallbladder emptying and bile Acid homeostasis in mice with cystic fibrosis transmembrane conductance regulator deficiencies.

Background & Aims: Patients with cystic fibrosis (CF) have poorly defined defects in biliary function. We evaluated the effects of cystic fibrosis transmembrane conductance regulator (CFTR) deficiency on the enterohepatic disposition of bile acids (BAs).

Methods: Bile secretion and BA homeostasis were investigated in Cftr(tm1Unc) (Cftr-/-) and CftrΔF508 (ΔF508) mice.

Role of nuclear receptors in the biliary epithelium.

The biliary epithelium is organized as a single layer of biliary epithelial cells lining the biliary tree. Biliary epithelial cells have three major biological functions: protection, secretion and proliferation. These functions are all controlled by nuclear receptors.

Vitamin D and the vitamin D receptor in liver pathophysiology.

Vitamin D through the vitamin D nuclear receptor (VDR) plays a key role in mineral ion homeostasis. The liver is central in vitamin D synthesis, however the direct involvement of the vitamin D-VDR axis on the liver remains to be evaluated. In this review, we will describe vitamin D metabolism and the mechanisms of homeostatic control.

Implication of metastasis suppressor NM23-H1 in maintaining adherens junctions and limiting the invasive potential of human cancer cells.

Loss of NM23-H1 expression correlates with the degree of metastasis and with unfavorable clinical prognosis in several types of human carcinoma. However, the mechanistic basis for the metastasis suppressor function of NM23-H1 is obscure. We silenced NM23-H1 expression in human hepatoma and colon carcinoma cells and methodologically investigated effects on cell-cell adhesion, migration, invasion, and signaling linked to cancer progression.

Bile salts control the antimicrobial peptide cathelicidin through nuclear receptors in the human biliary epithelium.

Backgrounds & Aims: Under normal conditions, the biliary tract is a microbial-free environment. The absence of microorganisms has been attributed to various defense mechanisms that include the physicochemical and signaling actions of bile salts. Here, we hypothesized that bile salts may stimulate the expression of a major antimicrobial peptide, cathelicidin, through nuclear receptors in the biliary epithelium.

Ezrin-radixin-moesin-binding phosphoprotein (EBP50), an estrogen-inducible scaffold protein, contributes to biliary epithelial cell proliferation.

Ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) anchors and regulates apical membrane proteins in epithelia. EBP50 is inducible by estrogen and may affect cell proliferation, although this latter function remains unclear. The goal of this study was to determine whether EBP50 was implicated in the ductular reaction that occurs in liver disease.

Cleavage of endoplasmic reticulum proteins in hepatocellular carcinoma: Detection of generated fragments in patient sera.

Background & Aims: In the past decade, there has been a rising incidence of hepatocellular carcinoma (HCC) and a progressive increase in HCC-related mortality in the United States and Western Europe. The poor survival of patients with HCC is largely related to the lack of reliable tools for early diagnosis.

Methods: We have applied proteomics tools to the comparative analysis of protein profiles between HCC and adjacent nontumor tissues as a means for discovering novel molecular markers.

Altered hepatobiliary gene expressions in PFIC1: ATP8B1 gene defect is associated with CFTR downregulation.

Recent reports in patients with PFIC1 have indicated that a gene defect in ATP8B1 could cause deregulations in bile salt transporters through decreased expression and/or activity of FXR. This study aimed to: (1) define ATP8B1 expression in human hepatobiliary cell types, and (2) determine whether ATP8B1 defect affects gene expressions related to bile secretion in these cells. ATP8B1 expression was detected by RT-PCR in hepatocytes and cholangiocytes isolated from normal human liver and gallbladder.

VPAC1 expression is regulated by FXR agonists in the human gallbladder epithelium.

Vasoactive intestinal peptide receptor-1 (VPAC1) is the high-affinity receptor of vasoactive intestinal peptide (VIP), a major regulator of bile secretion. To better define the level at which VPAC1 stimulates bile secretion, we examined its expression in the different cell types participating in bile formation (i.e.

[Biliary function and its regulation].

Biliary function is essential for intestinal absorption of fat, homeostasis of cholesterol and elimination of diverse metabolic end-products. Bile is elaborated in hepatocyte canaliculi and modified by cholangiocytes through both secretion and absorption processes. The main determinant of bile formation is an osmotic filtration process resulting from active transport of bile acids and other osmotic solutes.

Proteomics for hepatocellular carcinoma marker discovery.

Refinements of serological markers and screening of patients at high risk for developing hepatocellular carcinoma (HCC) may lead to better HCC detection, earlier intervention, and successful treatment, improving long-term outcomes. Proteomics promises the discovery of biomarkers for early HCC detection and diagnosis. Proteomic-based profiling uniquely allows delineation of global changes in expression patterns resulting from transcriptional and posttranscriptional control, posttranslational modifications, and shifts in proteins between cellular compartments.

Bile salts potentiate adenylyl cyclase activity and cAMP-regulated secretion in human gallbladder epithelium.

Fluid and ion secretion in the gallbladder is mainly triggered by the intracellular second messenger cAMP. We examined the action of bile salts on the cAMP-dependent pathway in the gallbladder epithelium. Primary cultures of human gallbladder epithelial cells were exposed to agonists of the cAMP pathway and/or to bile salts.

Hepatocyte growth factor and c-Met inhibition by hepatic cell hypoxia: a potential mechanism for liver regeneration failure in experimental cirrhosis.

Hepatic resection in cirrhotic patients is associated with impaired liver regeneration and poor clinical outcome. Because experimental cirrhosis is associated with hepatic cell hypoxia, we herein investigated whether hypoxia might alter the mechanisms of liver regeneration in the cirrhotic liver. Cirrhosis was induced by diethylnitrosamine in rats.