RT Journal Article
SR Electronic
T1 Selective Agonism of Human Pregnane X Receptor by Individual Ginkgolides
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP dmd.112.045013
DO 10.1124/dmd.112.045013
A1 Aik Jiang Lau
A1 Guixiang Yang
A1 Chun Wei Yap
A1 Thomas K. H. Chang
YR 2012
UL http://dmd.aspetjournals.org/content/early/2012/03/05/dmd.112.045013.abstract
AB Ginkgolide A, ginkgolide B, ginkgolide C, and ginkgolide J are structurally-related terpene trilactones present in Ginkgo biloba extract. Pregnane X receptor (PXR), glucocorticoid receptor (GR), and constitutive androstane receptor (CAR) regulate the expression of genes involved in diverse biological functions. In the present study, we investigated the effects of individual ginkgolides as single chemical entities on the function of human PXR (hPXR), human GR (hGR), and human CAR (hCAR). In cell-based reporter gene assays, none of the ginkgolides activated hGR or hCAR (wild-type and its SV23, SV24, and SV25 splice variants). Concentration-response experiments showed that ginkgolide A and ginkgolide B activated hPXR and rat PXR to a greater extent than ginkgolide C, whereas ginkgolide J had no effect. As determined by a time-resolved fluorescence resonance energy transfer competitive binding assay, ginkgolide A and ginkgolide B, but not ginkgolide C or ginkgolide J, were shown to bind to the ligand-binding domain of hPXR, consistent with molecular docking data. When compared with SR12813 (a known agonist of hPXR), ginkgolide A and ginkgolide B were considerably less potent in binding to hPXR. These two ginkgolides recruited steroid receptor coactivator-1 to hPXR and increased hPXR target gene (CYP3A4) expression, as assessed by a mammalian two-hybrid assay and real-time polymerase chain reaction, respectively. In conclusion, the individual ginkgolides regulate the function of nuclear receptors in a receptor-selective and chemical-dependent manner. This study identifies ginkgolide A and ginkgolide B as naturally-occurring agonists of hPXR and provides mechanistic insight into the structure-activity relationship in ligand-activation of hPXR.