Up-regulation of low-density lipoprotein receptor in human hepatocytes is induced by sequestration of free cholesterol in the endosomal/lysosomal compartment.
Up-regulation of low-density lipoprotein receptor (LDLr) is a key mechanism to control elevated plasma LDL-cholesterol levels. In the present paper, we compare the ability of four distinct pharmacological drugs to up-regulate LDLr expression in human hepatocytes. HepG2 cells were treated with the steroidal analog GW707, the oxidosqualene cyclase inhibitor U18666A, the 3beta-hydroxysterol Delta(7)-reductase inhibitor AY-9944 and the vacuolar-type ATPase inhibitor bafilomycin A1. We found that the four compounds induced sequestration of free cholesterol in the endosomal/lysosomal compartment leading to a positive filipin staining pattern and a complete inhibition of cholesteryl ester synthesis. As a consequence of the sequestration of cholesterol, the expression and the activity of LDLr were strongly induced resulting from a transcriptional effect which was measured by a reporter gene assay. These effects were fully abolished when an exogenous water soluble cholesterol analog was added to the cells. These findings have led to the identification of a common mechanism to up-regulate LDLr expression in human hepatocytes and may represent an interesting alternative approach to identify new hypolipidemic drugs.
Issandou
Marc
M
GlaxoSmithKline, 25 Avenue du Quebec, 91951 Les Ulis Cedex, France. mi18785@gsk.com
Guillard
Raphaëlle
R
Boullay
Anne-Benedicte
AB
Linhart
Valerie
V
Lopez-Perez
Elvira
E
D000736:Androstenes / Q000494:pharmacology; D000924:Anticholesteremic Agents / Q000494:pharmacology; D002784:Cholesterol / Q000096:biosynthesis / Q000378:metabolism*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D011973:Receptors, LDL / Q000096:biosynthesis*; D013256:Steroids / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride / Q000494:pharmacology
D000736:Androstenes; D000924:Anticholesteremic Agents; C442817:GW 707; D018942:Macrolides; D011973:Receptors, LDL; D013256:Steroids; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride; C040929:bafilomycin A1; D002784:Cholesterol