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Abstract
1. This study investigated the mechanism underlying Echinacea-mediated induction of CYP1A2, CYP3A4 and MDR1 in terms of human pregnane X receptor (PXR) activation.
2. Crude extracts and fractions of Echinacea purpurea were tested for PXR activation in HepG2 cells by a reporter gene assay. Quantitative real-time PCR was carried out to determine their effects on CYP1A2 and CYP3A4 mRNA expressions. Capsules and fractions were risk ranked as high, intermediate and remote risk of drug-metabolizing enzymes induction based on EC50 values determined for respective CYPs.
3. Fractions F1, F2 and capsule (2660) strongly activated PXR with 5-, 4- and 3.5-fold increase in activity, respectively. Echinacea preparations potentiated up-regulation of CYP1A2, CYP3A4 and MDR1 via PXR activation.
4. Thus E. purpurea preparations cause herb–drug interaction by up-regulating CYP1A2, CYP3A4 and P-gp via PXR activation.
Acknowledgements
We acknowledge the technical assistance of Olivia R. Dale at NCNPR, USA.
Declaration of interest
All authors have completed the unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare no support from any organization for the submitted work; no financial relationship with any organization that might have interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.
This study was funded by NIH-Fogarty International Center training grant-Brown AIDS International Training and Research Program (Grant# D43TW000237). The United States Department of Agriculture, Agricultural Research Service, Specific Cooperative Agreement No. 58-6408-1-603 is also acknowledged for partial support of this work.