Hep G2 cells: A model for studies on regulation of human cholesterol 7 alpha-hydroxylase at the molecular level

Hep G2 cells: A model for studies on regulation of human cholesterol 7 alpha-hydroxylase at the molecular level

Pandak W M; Stravitz R T; Lucas V; Heuman D M; Chiang J Y L

American Journal of Physiology-Gastrointestinal and Liver Physiology

1996

1996-03

The present study examines the feedback control governing human cholesterol 7 alpha-hydroxylase mRNA expression in the human hepatoblastoma cell line, Hep G2. Glycochenodeoxycholate (GCDC) and glycodeoxycholate, hydrophobic bile salts, decreased cholesterol 7 alpha-hydroxylase mRNA levels and bile acid synthesis in a concentration-dependent (76 +/- 8%, P < 0.001, and 48 +/- 3%, P < 0.01, respectively) and time-dependent manner. Cholesterol 7 alpha-hydroxylase mRNA levels were repressed with a half-maximal inhibitory concentration of < 12.5 mu M by GCDC and a half-life of 30 min by 100 mu M of the bile acid. The addition of actinomycin D (10 mu g/ml) alone or in combination with GCDC (100 mu M) led to similar concentration- and time-dependent suppression of cholesterol 7 alpha-hydroxylase mRNA. Glycocholate (100 mu M), not internalized based on lack of uptake of a fluorescent cholate analogue, had no effect on cholesterol 7 alpha-hydroxylase mRNA or total bile acid synthesis. In cultures transfected with a rat cholesterol 7 alpha-hydroxylase promoter construct, reporter gene activity was decreased (31%, P < 0.01) by GCDC (100 alpha M). Hep G2 cells maintain the intracellular machinery to express and rapidly regulate human cholesterol 7 alpha-hydroxylase by hydrophobic bile acids. These data suggest that Hep G2 cells will support functional studies of the human cholesterol 7 alpha-hydroxylase gene.

bile acid; bile-acid synthesis; biosynthesis; density-lipoprotein receptors; expression; Gastroenterology & Hepatology; hepatocytes; line; liver; messenger-rna; metabolism; monolayer-cultures; Physiology; primary; rat; transcriptional activity

Journal Article

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G401-G410

3

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