The orphan nuclear receptor, shp, mediates bile acid-induced inhibition of the rat bile acid transporter, ntcp

LA Denson, E Sturm, W Echevarria, TL Zimmerman, M Makishima, DJ Mangelsdorf, SJ Karpen*

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    329 Citations (Scopus)

    Abstract

    Background & Aims: Hepatic bile acid homeostasis is regulated by negative feedback inhibition of genes involved in the uptake and synthesis of bile acids. Bile acids down-regulate the rate-limiting gene for bile acid synthesis, cholesterol 7 alpha -hydroxylase (cyp7a), via bile acid receptor (fxr) activation of an inhibitory nuclear receptor, shp. We hypothesized that shp would also mediate negative feedback regulation of ntcp, the principal hepatic bile acid transporter. Methods: Primary rat hepatocytes or transfected HepG2 and Cos cells were treated with retinoids with or without bile acids, and effects on bile acid transport and ntcp and shp gene expression and promoter activity were determined. Gel shift assays were performed using synthetic fry, rxr, and rar proteins. Results: Bile acid treatment of primary rat hepatocytes prevented retinoid activation of ntcp gene expression and function; this corresponded temporally with shp gene activation. Bile acid-mediated down-regulation occurred via fxr-dependent suppression of the ntcp RXR:RAR response element. Moreover, cotransfected shp directly inhibited retinoid activation of the ntcp promoter. Conclusions: These studies show negative feedback regulation of ntcp by bile acid-activated fxr via induction of shp. This novel regulatory pathway provides a means for coordinated down-regulation of bile acid import and synthesis, thereby protecting the hepatocyte from bile acid-mediated damage in cholestatic conditions.

    Original languageEnglish
    Pages (from-to)140-147
    Number of pages8
    JournalGastroenterology
    Volume121
    Issue number1
    Publication statusPublished - Jul-2001
    Event51st Annual Meeting of the American-Association-for-the-Study-of-Liver-Diseases -
    Duration: 21-May-200022-May-2000

    Keywords

    • SALT EXPORT PUMP
    • GENE-EXPRESSION
    • DOWN-REGULATION
    • VITAMIN-A
    • LIVER
    • CHOLESTASIS
    • TRANSACTIVATION
    • COTRANSPORTER
    • MECHANISMS
    • DISEASE

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