RT Journal Article
SR Electronic
T1 Induction of CYP3A by 2,3-Oxidosqualene:Lanosterol Cyclase Inhibitors Is Mediated by an Endogenous Squalene Metabolite in Primary Cultured Rat Hepatocytes
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1302
OP 1312
DO 10.1124/mol.65.5.1302
VO 65
IS 5
A1 Sarita D. Shenoy
A1 Thomas A. Spencer
A1 Nancy A. Mercer-Haines
A1 Masumeh Abdolalipour
A1 William L. Wurster
A1 Melissa Runge-Morris
A1 Thomas A. Kocarek
YR 2004
UL http://molpharm.aspetjournals.org/content/65/5/1302.abstract
AB The effects of inhibitors of 2,3-oxidosqualene:lanosterol cyclase (cyclase) on cytochrome P450 expression were investigated in primary cultures of rat hepatocytes. Treatment of hepatocyte cultures for 24 h with either of the inhibitors [4′-(6-allyl-methyl-amino-hexyloxy)-2′-fluoro-phenyl]-(4-bromophenyl)-methanone fumarate (Ro 48-8071) or trans-N-(4-chlorobenzoyl)-N-methyl-(4-dimethylaminomethylphenyl)-cyclohexylamine (BIBX 79) selectively increased CYP3A mRNA and immunoreactive protein contents, with maximal accumulations occurring at 3 × 10-5 M Ro 48-8071 and 10-4 M BIBX 79. The abilities of Ro 48-8071, BIBX 79, and 3β-(2-diethylaminoethoxy)androst-5-en-17-one·HCl (U18666A) to induce murine CYP3A were abolished in hepatocyte cultures prepared from pregnane X receptor (PXR)-null mice, and cotransfection of primary cultured rat hepatocytes with a dominant-negative PXR prevented cyclase inhibitor-inducible luciferase expression from a PXR-responsive reporter plasmid. Cyclase inhibitor-mediated CYP3A mRNA induction was eliminated when primary cultured rat hepatocytes were cotreated with any of the following agents that inhibit steps upstream of cyclase in the cholesterol biosynthetic pathway: squalestatin 1 (squalene synthase inhibitor), (E)N-ethyl-N-(6,6-dimethyl-2-hepten-4-ynyl)-3-[(3,3′-bithiophen-5-yl)methoxy]benzenemethanamine (NB-598, squalene monooxygenase inhibitor), or pravastatin (HMG-CoA reductase inhibitor). Ro 48-8071-inducible CYP3A mRNA expression was restored when pravastatin-treated cultures were incubated with medium containing mevalonate. The concentration-dependence of Ro 48-8071-mediated CYP3A mRNA induction corresponded to the cellular contents of metabolically labeled squalene 2,3-oxide and squalene 2,3:22,23-dioxide, but not 24(S),25-epoxycholesterol. These results indicate that cyclase inhibitors are capable of inducing CYP3A expression in primary cultured rat and mouse hepatocytes and that the effect is mediated as a consequence of cyclase blockade through the evoked accumulation of one or more squalene metabolites that activate the PXR.