Polycyclic aromatic hydrocarbon (PAH) o-
quinones produced by
aldo-keto reductases are
ligands for the
aryl hydrocarbon receptor (AhR) (Burczynski, M. E., and Penning, T. M. (2000)
Cancer Res. 60, 908-915). They induce oxidative DNA lesions (
reactive oxygen species-mediated
DNA strand breaks and
8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo) formation) in human lung cells. We tested whether the AhR enhances PAH o-
quinone-mediated oxidative DNA damage by translocating these
ligands to the nucleus. Using the single cell gel electrophoresis (comet) assay to detect
DNA strand breaks in murine
hepatoma Hepa1c1c7 cells and its AhR- and
aryl hydrocarbon receptor nuclear translocator-deficient variants,
benzo[a]pyrene-7,8-dione (B[a]P-7,8-dione) produced fewer
DNA strand breaks in AhR-deficient cells compared with
aryl hydrocarbon receptor nuclear translocator-deficient and wild type Hepa1c1c7 cells. Decreased
DNA strand breaks were also observed in human bronchoalveolar H358 cells in which the AhR was silenced by
siRNA. The
antioxidant alpha-tocopherol and the
iron chelator/
antioxidant desferal decreased the formation of B[a]P-7,8-dione-mediated
DNA strand breaks indicating that they were
reactive oxygen species-dependent. By coupling the comet assay to
8-oxoguanine glycosylase (hOGG1), which excises 8-oxo-Gua, strand breaks dependent upon this lesion were measured. hOGG1 treatment produced more
DNA single strand breaks in B[a]P-7,8-dione-treated Hepa cells and H358 cells than in its absence. The levels of hOGG1-dependent
DNA strand breaks mediated by B[a]P-7,8-dione were lower in AhR-deficient Hepa and AhR knockdown H358 cells. The AhR antagonist
alpha-naphthoflavone also attenuated B[a]P-7,8-dione-mediated
DNA strand breaks. The decrease in
8-oxo-dGuo levels in AhR-deficient Hepa cells and AhR knockdown H358 cells was validated by immunoaffinity capture stable
isotope dilution ([(15)N(5)]8-oxo-dGuo) liquid chromatography-electrospray ionization/multiple reaction monitoring/mass spectrometry. We conclude that the AhR shuttles PAH o-
quinone genotoxins to the nucleus and enhances oxidative DNA damage.