Competing roles of aldo-keto reductase 1A1 and cytochrome P4501B1 in benzo[a]pyrene-7,8-diol activation in human bronchoalveolar H358 cells: role of AKRs in P4501B1 induction

Chem Res Toxicol. 2006 Jan;19(1):68-78. doi: 10.1021/tx0502488.


Benzo[a]pyrene (BP) requires metabolic activation to electrophiles to exert its deleterious effects. We compared the respective roles of aldo-keto reductase 1A1 (AKR1A1, aldehyde reductase) and P4501B1 in the formation of BP-7,8-dione and BP-tetrols, respectively, in intact bronchoalveolar cells manipulated to express either enzyme. Metabolite formation was confirmed by HPLC/MS and quantitatively measured by HPLC/UV/beta-RAM. In TCDD-treated H358 cells (P4501B1 expression), the anti-BPDE hydrolysis product BP-tetrol-1 increased over 3-12 h to a constant level. In H358 AKR1A1 transfectants, formation of BP-7,8-dione was elevated for 3-12 h but significantly decreased after 24 h. Interestingly, BP-tetrols were also detected in AKR1A1 transfectants even though they do not constitutively express P4501A1/P4501B1 enzymes. Northern and Western blotting confirmed the induction of P4501B1 by BP-7,8-dione in parental cells and the induction of P4501B1 by BP-7,8-diol in AKR1A1-transfected cells. P4501B1 induction was blocked in AKR1A1 transfectants by the AKR1A1 inhibitor (sulfonylnitromethane), the o-quinone scavenger (N-acetyl-l-cysteine), or the cytosolic AhR antagonist (diflubenzuron). Attenuation of P4501B1 induction in these cells was verified by measuring a decrease in BP-tetrol formation. Our studies show that the formation of BP-7,8-dione by AKR1A1 in human bronchoalveolar cells leads to an induction of P4501B1 and that a functional consequence of this induction is elevated anti-BPDE production as detected by increased BP-tetrol formation. Therefore, the role of AKR1A1 in the activation of BP-7,8-diol is bifunctional; that is, it directly activates BP-7,8-diol to the reactive and redox-active PAH o-quinone (BP-7,8-dione) and it indirectly trans-activates the P4501B1 gene by generating the aryl hydrocarbon receptor (AhR) ligand BP-7,8-dione.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Alcohol Oxidoreductases / antagonists & inhibitors
  • Alcohol Oxidoreductases / genetics
  • Alcohol Oxidoreductases / metabolism*
  • Aldehyde Reductase
  • Aldo-Keto Reductases
  • Aryl Hydrocarbon Hydroxylases / biosynthesis
  • Aryl Hydrocarbon Hydroxylases / genetics
  • Aryl Hydrocarbon Hydroxylases / metabolism*
  • Benzopyrenes / analysis
  • Benzopyrenes / metabolism
  • Cell Line, Tumor
  • Cytochrome P-450 CYP1B1
  • Dihydroxydihydrobenzopyrenes / pharmacology*
  • Enzyme Induction / drug effects
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Polychlorinated Dibenzodioxins
  • Pulmonary Alveoli / drug effects*
  • Pulmonary Alveoli / enzymology
  • Pulmonary Alveoli / metabolism
  • Time Factors
  • Transfection
  • Tritium


  • Benzopyrenes
  • Dihydroxydihydrobenzopyrenes
  • Enzyme Inhibitors
  • Polychlorinated Dibenzodioxins
  • Tritium
  • benzo(a)pyrene 7,8-dihydrodiol
  • benzo(a)pyrene-7,8-dione
  • Alcohol Oxidoreductases
  • Aldo-Keto Reductases
  • Aldehyde Reductase
  • Aryl Hydrocarbon Hydroxylases
  • CYP1B1 protein, human
  • Cytochrome P-450 CYP1B1