Pyrene is a Novel Constitutive Androstane Receptor (CAR) Activator and Causes Hepatotoxicity by CAR

Toxicol Sci. 2015 Oct;147(2):436-45. doi: 10.1093/toxsci/kfv142. Epub 2015 Jul 8.


Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous persistent environmental pollutants which are primarily formed from the incomplete combustion of organic materials. Many potential sources of human exposure to PAHs exist, including daily exposures from the ambient environment or occupational settings. PAHs have been found to cause harmful effects on human health. Here, we evaluated the adverse effects of pyrene, a common PAH, on the liver. The present study demonstrates that pyrene is able to activate mouse constitutive androstane receptor (CAR). CAR protein, as measured by Western blot analysis, was observed to translocate into the nucleus from the cytoplasm in mouse liver after exposure to pyrene. Utilizing CAR null mice, we identified that CAR mediates pyrene-induced hepatotoxicity. Increased relative liver weight, hepatocellular hypertrophy, and elevated serum alanine aminotransferase levels were found in wild-type but not CAR null mice after orally administered pyrene. We further show that pyrene induced the expression of mouse liver metabolism enzymes including CYP2B10, CYP3A11, GSTm1, GSTm3, and SULT1A1, and caused hepatic glutathione depletion in wild-type but not CAR null mice. Moreover, by luciferase reporter assay and quantitative real-time PCR analysis, pyrene was found to be a potential inducer of CYP2B6 expression via activation of human CAR in HepG2 cells and human primary hepatocytes. Our observations suggest that pyrene is a novel CAR activator and that CAR is essential for mediating pyrene-induced liver injury.

Keywords: hepatotoxicity; nuclear receptor CAR; pyrene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus / drug effects
  • Alanine Transaminase / blood
  • Animals
  • Blotting, Western
  • Chemical and Drug Induced Liver Injury / etiology*
  • Chemical and Drug Induced Liver Injury / metabolism
  • Constitutive Androstane Receptor
  • Cytochrome P-450 CYP2B6 / metabolism
  • Glutathione / analysis
  • Hep G2 Cells / drug effects
  • Hep G2 Cells / metabolism
  • Humans
  • Liver / chemistry
  • Liver / drug effects
  • Liver / enzymology
  • Liver / metabolism
  • Liver / physiopathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Pyrenes / pharmacology
  • Pyrenes / toxicity*
  • Receptors, Cytoplasmic and Nuclear / agonists*
  • Receptors, Cytoplasmic and Nuclear / analysis
  • Receptors, Cytoplasmic and Nuclear / physiology


  • Constitutive Androstane Receptor
  • Pyrenes
  • Receptors, Cytoplasmic and Nuclear
  • pyrene
  • Cytochrome P-450 CYP2B6
  • Alanine Transaminase
  • Glutathione