Inflammation-associated extracellular β-glucuronidase alters cellular responses to the chemical carcinogen benzo[a]pyrene

Arch Toxicol. 2016 Sep;90(9):2261-2273. doi: 10.1007/s00204-015-1593-7. Epub 2015 Oct 5.


Neutrophils infiltrate tissues during inflammation, and when activated, they release β-glucuronidase. Since inflammation is associated with carcinogenesis, we investigated how extracellular β-glucuronidase changed the in vitro cellular response to the chemical carcinogen benzo(a)pyrene (B[a]P). For this we exposed human liver (HepG2) and lung (A549) cells to B[a]P in the presence or absence of β-glucuronidase. β-Glucuronidase reduced B[a]P-induced expression of CYP1A1 and CYP1B1 at 6 h after exposure, which did not depend on β-glucuronidase activity, because the inhibitor D-saccharic acid 1,4-lactone monohydrate did not antagonize the effect of β-glucuronidase. On the other hand, the inhibitory effect of β-glucuronidase on CYP expression was dependent on signalling via the insulin-like growth factor receptor (IGF2R, a known receptor for β-glucuronidase), because co-incubation with the IGF2R inhibitor mannose-6-phosphate completely abolished the effect of β-glucuronidase. Extracellular β-glucuronidase also reduced the formation of several B[a]P metabolites and B[a]P-DNA adducts. Interestingly, at 24 h of exposure, β-glucuronidase significantly enhanced CYP expression, probably because β-glucuronidase de-glucuronidated B[a]P metabolites, which continued to trigger the aryl hydrocarbon receptor (Ah receptor) and induced expression of CYP1A1 (in both cell lines) and CYP1B1 (in A549 only). Consequently, significantly higher concentrations of B[a]P metabolites and DNA adducts were found in β-glucuronidase-treated cells at 24 h. DNA adduct levels peaked at 48 h in cells that were exposed to B[a]P and treated with β-glucuronidase. Overall, these data show that β-glucuronidase alters the cellular response to B[a]P and ultimately enhances B[a]P-induced DNA adduct levels.

Keywords: Benzo[a]pyrene; Carcinogen metabolism; Cytochrome P450 1A1; DNA adducts; IGF2R; Inflammation; β-Glucuronidase.

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / agonists
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Benzo(a)pyrene / metabolism
  • Benzo(a)pyrene / toxicity*
  • Biotransformation
  • Carcinogens / metabolism
  • Carcinogens / toxicity*
  • Cytochrome P-450 CYP1A1 / genetics
  • Cytochrome P-450 CYP1A1 / metabolism
  • Cytochrome P-450 CYP1B1 / genetics
  • Cytochrome P-450 CYP1B1 / metabolism
  • DNA Adducts / metabolism
  • Disease Models, Animal
  • Glucuronidase / pharmacology*
  • Hep G2 Cells
  • Hepatocytes / drug effects*
  • Hepatocytes / enzymology
  • Hepatocytes / pathology
  • Humans
  • Lipopolysaccharides
  • Lung / drug effects*
  • Lung / enzymology
  • Lung / pathology
  • Pneumonia / chemically induced
  • Pneumonia / enzymology*
  • Pneumonia / genetics
  • Pneumonia / pathology
  • Receptor, IGF Type 2 / agonists
  • Receptor, IGF Type 2 / metabolism
  • Receptors, Aryl Hydrocarbon / agonists
  • Receptors, Aryl Hydrocarbon / metabolism
  • Signal Transduction / drug effects
  • Time Factors


  • AHR protein, human
  • Basic Helix-Loop-Helix Transcription Factors
  • Carcinogens
  • DNA Adducts
  • Lipopolysaccharides
  • Receptor, IGF Type 2
  • Receptors, Aryl Hydrocarbon
  • benzo(a)pyrene-DNA adduct
  • Benzo(a)pyrene
  • CYP1A1 protein, human
  • CYP1B1 protein, human
  • Cytochrome P-450 CYP1A1
  • Cytochrome P-450 CYP1B1
  • Glucuronidase