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This Article Full Text Full Text (PDF) All Versions of this Article: 289/5/G798    most recent 00319.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Zollner, G. Articles by Trauner, M. Search for Related Content PubMed PubMed Citation Articles by Zollner, G. Articles by Trauner, M.

LIVER AND BILIARY TRACT

Role of nuclear receptors and hepatocyte-enriched transcription factors for Ntcp repression in biliary obstruction in mouse liver

¹Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, and ³Department of Pathology, Medical University Graz, Graz; and ⁴University Hospital Innsbruck, Innsbruck, Austria; and ²Department of Internal Medicine III, University of Technology Aachen, Aachen, Germany

Submitted 19 July 2004 ; accepted in final form 26 June 2005

Expression of the main hepatic bile acid uptake system, the Na⁺-taurocholate cotransporter (Ntcp), is downregulated during cholestasis. Bile acid-induced, farnesoid X receptor (FXR)-mediated induction of the nuclear repressor short heterodimer partner (SHP) has been proposed as a key mechanism reducing Ntcp expression. However, the role of FXR and SHP or other nuclear receptors and hepatocyte-enriched transcription factors in mediating Ntcp repression in obstructive cholestasis is unclear. FXR knockout (FXR^–/–) and wild-type (FXR^+/+) mice were subjected to common bile duct ligation (CBDL). Cholic acid (CA)-fed and LPS-treated FXR^–/– and FXR^+/+ mice were studied for comparison. mRNA levels of Ntcp and SHP and nuclear protein levels of hepatocyte nuclear factor (HNF)-1, HNF-3, HNF-4, retinoid X receptor (RXR)-, and retinoic acid receptor (RAR)- and their DNA binding were assessed. Hepatic cytokine mRNA levels were also measured. CBDL and CA led to Ntcp repression in FXR^+/+, but not FXR^–/–, mice, whereas LPS reduced Ntcp expression in both genotypes. CBDL and LPS but not CA induced cytokine expression and reduced levels of HNF-1, HNF-3, HNF-4, RXR, and RAR to similar extents in FXR^+/+ and FXR^–/–. DNA binding of these transactivators was unaffected by CA in FXR^+/+ mice but was markedly reduced in FXR^–/– mice. In conclusion, Ntcp repression by CBDL and CA is mediated by accumulating bile acids via FXR and does not depend on cytokines, whereas Ntcp repression by LPS is independent of FXR. Reduced levels of HNF-1, RXR, and RAR in CBDL FXR^–/– mice and reduced DNA binding in CA-fed FXR^–/– mice, despite unchanged Ntcp levels, indicate that these factors may have a minor role in regulation of mouse Ntcp during cholestasis.

bile acids; cytokines; bile duct obstruction; orphan nuclear receptors; cholestasis

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