Global metabolomics and targeted steroid profiling reveal that rifampin, a strong human PXR activator, alters endogenous urinary steroid markers.

Activation of the pregnane X receptor (PXR) alters the expression of metabolic enzymes and transporters involved in the metabolism of xenobiotics and endobiotics. To identify endogenous biomarkers of PXR activation in humans, rifampin, a strong PXR activator, was administered to 12 healthy male subjects, and their urine was analyzed before and after rifampin administration. Ultraperformance liquid chromatography time-of-flight mass spectrometry (UPLC/QTOF-MS)-based global metabolomics and gas chromatography-mass spectrometry (GC-MS)-based profiling of 75 steroids were used to screen the urine samples. Global metabolomics revealed that hydroxytestosterone sulfate and glycochenodeoxycholate sulfate levels were significantly increased and that androsterone sulfate, dehydroepiandrosterone (DHEA) sulfate, and p-cresol sulfate levels were significantly decreased following rifampin administration compared with controls. Urinary steroid profiling showed that 16α-OH-androstenedione (16α-OH-A-dione), 16α-OH-DHEA, 7α-DHEA, 7β-DHEA, and 11β-OH-A-dione levels were increased, whereas DHEA, androsterone, etiocholanolone, estrone, β-cortolone, and allo-tetrahydrocortisone levels were decreased in the rifampin group. The analysis of the metabolic pathway and the metabolic ratio of steroids enabled the estimation of the induction of CYP1A/3A/7B/11B/2C and the inhibition of CYP17A/19A in response to PXR activation. These human urinary biomarkers may be useful for predicting the extent of PXR activation, monitoring the activity of DMEs, and anticipating drug-drug interactions in patients administered PXR-activating drugs.