Differential effects of membrane cholesterol content on the transport activity of multidrug resistance-associated protein 2 (ABCC2) and of the bile salt export pump (ABCB11).

Rat canalicular membranes contain microdomains enriched in cholesterol and ATP-binding cassette transporters. Cholesterol is known to regulate the activity of transporters. Here, we investigated the effect of membrane cholesterol on the transport kinetics of multidrug resistance-associated protein 2 (MRP2) and of bile salt export pump (BSEP) variants and mutants.

Smoothelin, a new marker to determine the origin of liver fibrogenic cells.

Aim: To explore this hypothesis that smooth muscle cells may be capable of acquiring a myofibroblastic phenotype, we have studied the expression of smoothelin in fibrotic conditions.

Methods: Normal liver tissue (n = 3) was obtained from macroscopically normal parts of hepatectomy, taken at a distance from hemangiomas. Pathological specimens included post-burn cutaneous hypertrophic scars (n = 3), fibrotic liver tissue (n = 5), cirrhotic tissue (viral and alcoholic hepatitis) (n = 5), and hepatocellular carcinomas (n = 5).

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME.

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways.

An Arabidopsis T-DNA insertion mutant for galactokinase (AtGALK, At3g06580) hyperaccumulates free galactose and is insensitive to exogenous galactose.

Galactokinase (GALK, EC 2.7.1.

Interaction of bile salts with rat canalicular membrane vesicles: evidence for bile salt resistant microdomains.

Background & Aims: Canalicular phosphatidylcholine and cholesterol secretion requires the coordinate action of the ATP binding cassette transporters: the bile salt export pump (Bsep) for bile salts (BS) and the phosphatidylcholine translocator multidrug resistance protein 2 (Mdr2). After their secretion, phosphatidylcholine and BS form mixed micelles acting as acceptors for canalicular cholesterol. We have shown that the canalicular liver plasma membrane (cLPM) contains lipid raft enriched in sphingomyelin and cholesterol.

Fibrogenic cell phenotype modifications during remodelling of normal and pathological human liver in cultured slices.

Background: The debate concerning the potential remodelling and/or reversibility of cirrhotic lesions and biliary fibrosis is still open.

Aims/methods: In this work, we have used the precision-cut liver slice (PCLS) model, which maintains cell-cell and cell-matrix interactions to study, by immunohistochemistry, the behaviour of the different fibrogenic cells, i.e.

ABC-transporters are localized in caveolin-1-positive and reggie-1-negative and reggie-2-negative microdomains of the canalicular membrane in rat hepatocytes.

Unlabelled: The canalicular plasma membrane is constantly exposed to bile acids acting as detergents. Bile acids are essential to mediate release of biliary lipids from the canalicular membrane. Membrane microdomains (previously called lipid rafts) are biochemically defined by their resistance to detergent solubilization at cold temperature.

Specific activation of the different fibrogenic cells in rat cultured liver slices mimicking in vivo situations.

Due to the loss of cell-cell and cell-matrix interactions, cell culture models poorly mimic the in vivo situation. Therefore, we tested the applicability of precision-cut liver slices (PCLS) to study the early activation of the two main liver fibrogenic cell subpopulations: hepatic stellate cells (HSC) and portal fibroblasts (PF). PCLS were treated with thioacetamide or acetaminophen to induce HSC activation.

Fibrogenic cell fate during fibrotic tissue remodelling observed in rat and human cultured liver slices.

Background/aims: Fibrotic liver remodelling was studied in culture of precision-cut liver slices (PCLS) derived from fibrotic liver.

Methods: Fibrosis was induced in rats by carbon tetrachloride (CCl4) treatment or bile duct ligation. Human fibrotic livers were also used.

The common bile duct ligation in rat: A relevant in vivo model to study the role of mechanical stress on cell and matrix behaviour.

Common bile duct ligation leads to bile accumulation and liver fibrosis. In this model, little attention has been dedicated to the modification of the common bile duct. We have studied by histochemistry and immunohistochemistry, 3 and 5 days after ligation, the connective tissue modifications of the common bile duct wall.

Effects of bile acids on biliary epithelial cell proliferation and portal fibroblast activation using rat liver slices.

During cholestasis, bile acids accumulate in the liver, and induce cellular alterations. Cholestasis is a major cause of liver fibrosis. We have used precision-cut liver slices (PCLS) in culture to investigate the effects of bile acids on hepatic cells.

Hepatic fibrosis and cirrhosis: the (myo)fibroblastic cell subpopulations involved.

Fibrosis, defined as the excessive deposition of extracellular matrix in an organ, is the main complication of chronic liver damage. Its endpoint is cirrhosis, which is responsible for significant morbidity and mortality. The accumulation of extracellular matrix observed in fibrosis and cirrhosis is due to the activation of fibroblasts, which acquire a myofibroblastic phenotype.

The stroma reaction myofibroblast: a key player in the control of tumor cell behavior.

The cooperation between epithelial and mesenchymal cells is essential for embryonic development and probably plays an important role in pathological phenomena such as wound healing and tumor progression. It is well known that many epithelial tumors are characterized by the local accumulation of connective tissue cells and extracellular material; this phenomenon has been called the stroma reaction. One of the cellular components of the stroma reaction is the myofibroblast, a modulated fibroblast which has acquired the capacity to neoexpress alpha-smooth muscle actin, the actin isoform typical of vascular smooth muscle cells, and to synthesize important amounts of collagen and other extracellular matrix components.