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Regulation of CYP3A4 expression in human hepatocytes by pharmaceuticals and natural products

Judy L Raucy1

  • 1California Toxicology Research Institute, Carlsbad, California 92009, USA. jraucy@puracyp.com

Drug Metabolism and Disposition: the Biological Fate of Chemicals
|April 16, 2003
PubMed

Insights

Certain dietary flavonoids and botanicals can significantly increase CYP3A4 mRNA levels in human hepatocytes. This induction, particularly by kava-kava, suggests potential for drug-herbal interactions due to altered drug metabolism.

Area of Science:

  • Pharmacology and Toxicology
  • Drug Metabolism and Pharmacokinetics
  • Molecular Biology

Background:

  • Human CYP3A4 is a key enzyme in drug metabolism, exhibiting significant inter-individual variability in expression.
  • Xenobiotic exposure, including dietary components and botanicals, can influence CYP3A4 expression levels.
  • Understanding factors that modulate CYP3A4 is crucial for predicting drug efficacy and toxicity.

Purpose of the Study:

  • To investigate the inducibility of CYP3A4 mRNA by dietary flavonoids and botanicals in primary human hepatocytes.
  • To explore the role of the human pregnane X receptor (hPXR) in mediating CYP3A4 induction by these agents.
  • To assess the potential for drug-herbal interactions arising from altered CYP3A4 expression.

Main Methods:

  • Primary human hepatocytes from 17 individuals were used to measure CYP3A4 mRNA accumulation.
  • Reporter gene assays with hPXR and CYP3A4 promoter constructs in HepG2 cells were employed.
  • Prototypical inducers, dietary flavonoids (quercetin, resveratrol, curcumin), and botanicals (grapeseed, ginseng, silymarin, kava-kava) were tested.

Main Results:

  • Rifampicin, phenytoin, phenobarbital, and omeprazole significantly increased CYP3A4 mRNA levels.
  • Quercetin induced CYP3A4 mRNA but showed minimal activity in the hPXR reporter assay, suggesting alternative mechanisms.
  • Kava-kava significantly induced CYP3A4 mRNA and luciferase activity in the hPXR assay, indicating PXR-mediated induction. Grapeseed extract also increased CYP3A4 mRNA.

Conclusions:

  • Several botanicals, notably kava-kava and grapeseed extract, can induce CYP3A4 expression in human hepatocytes.
  • The induction of CYP3A4 by kava-kava appears to be mediated through the pregnane X receptor pathway.
  • The findings highlight the potential for significant drug-herbal interactions, impacting the metabolism of CYP3A4 substrates.

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