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.
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.
Jiang
Hao
H
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA.
Vudathala
Daljit K
DK
Blair
Ian A
IA
Penning
Trevor M
TM
D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000449:Aldehyde Reductase; D000074408:Aldo-Keto Reductases; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D001580:Benzopyrenes / Q000032:analysis / Q000378:metabolism; D045744:Cell Line, Tumor; D065633:Cytochrome P-450 CYP1B1; D004101:Dihydroxydihydrobenzopyrenes / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D000072317:Polychlorinated Dibenzodioxins; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014316:Tritium
D001580:Benzopyrenes; D004101:Dihydroxydihydrobenzopyrenes; D004791:Enzyme Inhibitors; D000072317:Polychlorinated Dibenzodioxins; D014316:Tritium; C017228:benzo(a)pyrene 7,8-dihydrodiol; C076588:benzo(a)pyrene-7,8-dione; D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1