QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: dmd.108.022558v1 36/10/2030    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Jackson, N. M. Articles by Kocarek, T. A. PubMed PubMed Citation Articles by Jackson, N. M. Articles by Kocarek, T. A.

Suppression of CYP2B Induction by Alendronate-Mediated Farnesyl Diphosphate Synthase Inhibition in Primary Cultured Rat Hepatocytes

Institute of Environmental Health Sciences, Wayne State University, Detroit, Michigan

We previously reported that squalestatin 1-mediated induction of CYP2B expression is attributable to squalene synthase inhibition and accumulation of an endogenous isoprenoid(s) that is capable of activating the constitutive androstane receptor. To determine whether squalestatin 1-mediated CYP2B induction is strictly dependent on the biosynthesis of farnesyl pyrophosphate (FPP), the substrate for squalene synthase, the effects of alendronate, a nitrogen-containing bisphosphonate inhibitor of farnesyl diphosphate synthase, on basal, squalestatin 1-inducible, and phenobarbital-inducible CYP2B expression in primary cultured rat hepatocytes were assessed. Alendronate treatment alone had no effect on CYP2B or CYP3A mRNA expression in the hepatocyte cultures, but alendronate cotreatment completely suppressed squalestatin 1-mediated CYP2B mRNA induction at concentrations (60 and 100 µM) that effectively inhibited cellular farnesyl diphosphate synthase activity, as assessed by reductions of squalestatin 1-mediated FPP accumulation, and that were not toxic to the cells, as indicated by a lack of effect on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide activity. Alendronate cotreatment also partially suppressed phenobarbital-inducible CYP2B expression, and this suppressive effect was attenuated by additional cotreatment with the upstream pathway inhibitor, pravastatin. These findings not only demonstrate that squalestatin 1-mediated CYP2B induction cannot occur in the absence of FPP biosynthesis but also indicate that one or more upstream isoprenoids, possibly isopentenyl pyrophosphate and/or dimethylallyl pyrophosphate, function to antagonize the CYP2B induction process.