Hep g2 cells: a model for studies on the regulation of human
cholesterol 7[alpha]-hydroxylase at the molecular level.
Pandak, William M., R. Todd Stravitz, Valentina Lucas, Douglas M.
Heuman, and John Y. L. Chiang.
Division of Gastroenterology P.O. Box 980711, Medical College of
Virginia, Richmond, Virginia 23298-0711
APStracts 2:0177G, 1995.
The present study examines the feedback control governing human
cholesterol 7[alpha]-hydroxylase (C7[alpha]H) mRNA expression in the
human hepatoblastoma cell line, Hep G2. Glycochenodeoxycholate and
glycodeoxycholate, hydrophobic bile salts, decreased C7[alpha]H mRNA
levels and bile acid synthesis in a concentration- { 76+/-8% (p <
0.001) and 48+/-3% (p < 0.01), respectively} and time- dependent
manner. C7[alpha]H mRNA levels were repressed with an IC50 < 12.5
[mu]M by glycochenodeoxcholate, and a T1/2 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 glycochenodeoxycholate (100 [mu]M) led to similar
concentration- and time- dependent suppression of C7[alpha]H mRNA.
Glycocholate (100 [mu]M), not internalized based upon absent uptake
of a fluorescent cholate analogue, had no effect on C7[alpha]H mRNA
nor total bile acid synthesis. In cultures transfected with a rat
C7[alpha]H promoter construct, reporter gene activity was decreased (
31%; p < 0.01) by glycochenodeoxycholate (100 [mu]M).
Conclusion: Hep G2 cells maintain the intracellular machinery to
express and rapidly regulate human C7[alpha]H by hydrophobic bile
acids. These data suggest that Hep G2 cells will support functional
studies of the human C7[alpha]H gene.
Received 10 February 1995; accepted in final form 18 August 1995.
APS Manuscript Number G60-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.