Human CYP3A4 and murine Cyp3A11 are regulated by equol and genistein via the pregnane X receptor in a species-specific manner.

TitleHuman CYP3A4 and murine Cyp3A11 are regulated by equol and genistein via the pregnane X receptor in a species-specific manner.
Publication TypeJournal Article
Year of Publication2009
AuthorsLi, Y, Ross-Viola, JS, Shay, NF, Moore, DD, Ricketts, M-L
JournalJ Nutr
Date Published2009 May
KeywordsAnimals, Carcinoma, Hepatocellular, Cell Line, Tumor, Cercopithecus aethiops, Cytochrome P-450 CYP3A, Equol, Gene Expression Regulation, Genistein, Humans, Isoflavones, Kidney, Liver Neoplasms, Male, Membrane Proteins, Mice, Mice, Knockout, Polymerase Chain Reaction, Promoter Regions, Genetic, Receptors, Steroid, RNA, Messenger, Species Specificity, Transfection

Pregnane X receptor (PXR) is an important component of the body's adaptive defense system responsible for the elimination of various toxic xenobiotics. PXR activation by endogenous and exogenous chemicals, including steroids, antibiotics, bile acids, and herbal compounds, results in induction of drug metabolism. We investigated the ability of the isoflavones genistein, daidzein, and the daidzein metabolite equol to activate human and mouse PXR in vitro using cell-based transient transfection studies and primary hepatocytes and in vivo in a mouse model. In transient transfection assays, the isoflavones genistein and daidzein activate full-length, wild-type mouse PXR, but not a mutant form, with genistein being the most potent. In contrast, equol was a more potent activator of human PXR than genistein or daidzein. In a mammalian 2-hybrid assay, isoflavones induced recruitment of the coactivator steroid receptor coactivator 1 to PXR. When tested against the native human Cytochrome P450 3A4 (CYP3A4) promoter, equol was the more potent activator and treatment of human hepatocytes with equol increased CYP3A4 mRNA and immunoreactive protein expression. Treatment of wild-type, but not PXR(-/-), mouse hepatocytes showed that genistein and daidzein induced the expression of Cytochrome P450 3A11 (Cyp3A11) mRNA, whereas equol had no effect. Cyp3A11 mRNA was also induced in vivo in mice fed a soy protein-containing diet. The results presented herein demonstrate that there is a species-specific difference in the activation of PXR by isoflavones and equol.

Alternate JournalJ. Nutr.
PubMed ID19297428
PubMed Central IDPMC2714390
Grant ListAT000862 / AT / NCCIH NIH HHS / United States
R01-DK53366 / DK / NIDDK NIH HHS / United States