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. Vdr(-/-) mice subjected to bile duct ligation (BDL) displayed increased liver damage compared to wildtype BDL mice. Adaptation to cholestasis, ascertained by expression of genes involved in bile acid metabolism and tissue repair, was limited in Vdr(-/-) BDL mice. Furthermore, evaluation of Vdr(-/-) BDL mouse liver tissue sections indicated altered E-cadherin staining associated with increased bile duct rupture. Total liver protein analysis revealed that a truncated form of E-cadherin was present in higher amounts in Vdr(-/-) mice subjected to BDL compared to wildtype BDL mice. Truncated E-cadherin was also associated with loss of cell adhesion in biliary epithelial cells silenced for VDR. In these cells, E-cadherin cleavage occurred together with calpain 1 activation and was prevented by the silencing of calpain 1. Furthermore, VDR deficiency led to the activation of the epidermal growth factor receptor (EGFR) pathway, while EGFR activation by EGF induced both calpain 1 activation and E-cadherin cleavage in these cells. Finally, truncation of E-cadherin was blunted when EGFR signaling was inhibited in VDR-silenced cells. CONCLUSION: Biliary-type liver injury is exacerbated in Vdr(-/-) mice by limited adaptive response and increased bile duct rupture. These results indicate that loss of VDR restricts the adaptation to cholestasis and diminishes bile duct integrity in the setting of biliary-type liver injury.

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. The biliary tree conveys bile, a complex fluid containing toxics such as endotoxins, from the liver to the duodenum. Active protection against endotoxins can be elicited by the vitamin D receptor or the farnesoid X receptor (FXR), thus avoiding constant inflammation of the biliary epithelium. Anti-inflammatory activities may be triggered by PPAR-α and -γ, which are also able to inhibit the deleterious effect of bacterial products. Secretion, a major function of biliary epithelial cells, is mainly regulated by circulating factors. Luminal factors, such as bile salts, may also control fluid secretion by classical intracellular pathways, membrane receptors or nuclear receptors. FXR or the glucocorticoid receptor have indeed been shown to increase the expression of genes encoding membrane-bound proteins that participate in biliary epithelial cell secretion. Biliary epithelial cells are quiescent cells that are able to proliferate in pathophysiological settings. Inhibition of estrogen receptor signaling decreases pathological biliary epithelial cell proliferation. Furthermore, progesterone, through the progesterone receptor, increases biliary epithelial cells proliferation. Taken together these observations suggest that nuclear receptors are involved in the control of biliary epithelial cell biology. A better delineation of the specific biliary epithelial cell functions controlled by nuclear receptors may shed light on potential therapeutic molecular targets of cholangiopathies.

[Gallstone disease - interdisciplinary treatment]. / Gallensteine ­ interdisziplinäre Behandlung.

Gallstones develop in the gallbladder or the bile ducts. According to their chemical composition, gallstones can be divided into cholesterol stones, which are common, and the rare bile pigment stones. Altogether, up to 20 % of all adults develop gallstones and more than 20 % of them symptoms or complications. Female sex, age, pregnancy, physical inactivity, obesity, overnutrition and genetic factors such as ABCB4 deficiency of the hepatic lecithin transporter are kown risk factors for gallstone formation. In about one half of all patients biliary symptoms precede the three common and potentially life-threatening complications (acute cholecystitis, acute cholangitis and biliary pancreatitis). Although our knowledge about the genetics and pathophysiology of gallstones has improved, current treatment algorithms are predominantly invasive (ERC and surgery). Thus, better strategies are needed to prevent the formation of gallstones in general.

Ezetimibe prevents cholesterol gallstone formation in mice.

BACKGROUND: Intestinal cholesterol absorption may influence gallstone formation and its modulation could be a useful therapeutic strategy for gallstone disease (GSD). Ezetimibe (EZET) is a cholesterol-lowering agent that specifically inhibits intestinal cholesterol absorption. AIMS: To test whether EZET can prevent gallstone formation in mice. METHODS/RESULTS: Gallstone-susceptible C57BL/6 inbred mice were fed control and lithogenic diets with or without simultaneous EZET administration. Lithogenic diet increased biliary cholesterol content and secretion, and induced sludge or gallstone formation in 100% of the animals. EZET administration reduced intestinal cholesterol absorption by 90% in control animals and by 35% in mice receiving the lithogenic diet. EZET prevented the appearance of cholesterol crystals and gallstones. In addition, mice fed the lithogenic diet plus EZET exhibited a 60% reduction in biliary cholesterol saturation index. Of note, EZET treatment caused a significant increase in bile flow (+50%, P<0.01) as well as bile salt, phospholipid and glutathione secretion rates (+60%, +44% and +100%, respectively, P<0.01), which was associated with a moderately increased expression of hepatic bile salt transporters. In addition, relative expression levels of Nieman-Pick C1 like 1 (NPC1L1) in the enterohepatic axis in humans were assessed. Expression levels of NPC1L1 were 15- to 30-fold higher in the duodenum compared with the liver at transcript and protein levels, respectively, suggesting preferential action of EZET on intestinal cholesterol absorption in humans. CONCLUSIONS: In a murine model of GSD, EZET prevented gallstone formation by reducing intestinal cholesterol absorption and increasing bile salt-dependent and -independent bile flow. EZET could be useful in preventing GSD disease in susceptible patients.

Genetics of biliary lithiasis from an ethnic perspective.

Gallstone disease represents one of the most common gastroenterological disorders worldwide. Gallstones affect over 15% of adults in Europe and 25-30% of Hispanic populations in Central and South America. The heritability of gallstones varies considerably according to ethnicity, with Native Americans and Hispanics with Amerindian admixture being the most susceptible populations. Genetic factors have been shown to account for 25-30% of total gallstone risk in Europe, however, in Hispanic populations, this risk percentage may increase to 45-65%. Recent genome-wide association and candidate gene studies have identified common polymorphisms in enterohepatic transporters (ABCG5/8, SLC10A2) and the Gilbert syndrome UGT1A1 variant as genetic determinants of gallstone formation. Together, these polymorphisms cover a significant proportion of the previously predicted genetic background of gallstones in European populations. New lithogenic genes need to be discovered in future studies in high-risk populations. In this review, we address the latest developments in the genetic analysis of gallstones and discuss the ethnic background of this condition in European, Central and South American and Asian populations.

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. We will also address the associations between the vitamin D-VDR axis and pathological liver entities, such as non-alcoholic fatty liver disease, autoimmune liver disease, viral hepatitis and liver cancer. The link between liver diseases and the vitamin D-VDR axis will be discussed in light of evidences arising from in vitro and in vivo studies. Finally, we will consider the therapeutic potential of the vitamin D-VDR axis in liver diseases.

Dosificación de drogas hipertensinógenas en orina de pacientes hipertensos / Dosification of hipertensionogen drugs from the urine of hipertensive patients

Se presentan los resultados del estudio realizado en una gran Unidad de las FAR a 84 combatientes en los que se dosificó la presencia de drogas hipertensinógenas en la orina. Los pacientes se clasificaron en 4 grupos de acuerdo con las cifras tensionales y la presencia o no de alteraciones del pulso. Para la dosificación de las drogas se utilizó el método de cromatografía de capa fina. Se analizan las posibles causas de los hallazgos detectados y se hacen recomendaciones para la solución del problema. Se propone incluir la categoría de hipertensión ficticia (autoprovocada) a la actual clasificación de la entidad