title: Role of glutathione conjugate efflux in cellular protection against benzo[a]pyrene-7,8-diol-9,10-epoxide-induced DNA damage.
abstract: Glutathione (GSH) conjugation of (+)-anti-benzo[a]pyrene-7,8-diol-9,10-epoxide [(+)-anti-BPDE], the activated metabolite of benzo[a]pyrene, is believed to be an important mechanism in detoxification of this environmental and dietary carcinogen. Here, we demonstrate that the intracellular accumulation of GSH conjugate of (+)-anti-BPDE (BPD-SG) caused a statistically significant increase in (+)-anti-BPDE-induced DNA adduction. The relationship between intracellular accumulation of BPD-SG and (+)-anti-BPDE-induced DNA adduction was studied using a canine kidney epithelial cell line (MDCKII) and its variants overexpressing multidrug resistance transporter (MDR1) or canalicular multispecific organic anion transporter (cMOAT; also known as multidrug resistance protein 2). MDR1 and cMOAT are implicated in ATP-dependent efflux of anticancer drugs or GSH-xenobiotic conjugates, or both. The GST activity toward (+)-anti-BPDE in parental MDCKII cells did not differ from that in subline overexpressing MDR1 (MDCKII-MDR1) or cMOAT (MDCKII-cMOAT). Intracellular accumulation of BPD-SG, after a 5- or 10-min incubation with 1 microM (+)-anti-BPDE, was significantly higher in parental (41- to 67-fold) and MDCK II-MDR1 cells (31- to 43-fold) than in the MDCKII-cMOAT cells. Interestingly, the levels of DNA adducts of (+)-anti-BPDE, after a 30-min incubation with 0.1 or 0.5 microM [(3)H](+)-anti-BPDE, were significantly higher (about 2.1- and 1.7-fold, respectively) in parental cells than in the MDCKII-cMOAT cells. The results of the present study indicate that in addition to GSH conjugation, the efflux of BPD-SG may be essential for cellular protection against (+)-anti-BPDE-induced DNA damage.
authors.affiliation: Department of Pharmacology and University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Srivastava
authors.forename: Simon C
authors.initials: SC
authors.lastname: Watkins
authors.forename: Erin
authors.initials: E
authors.lastname: Schuetz
authors.forename: Shivendra V
authors.initials: SV
authors.lastname: Singh
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism* / Q000633:toxicity*; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D004249:DNA Damage; D004285:Dogs; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D026901:Membrane Transport Proteins; D018613:Microscopy, Confocal; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D014162:Transfection
chemical_list: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002273:Carcinogens; D005978:Glutathione; D005982:Glutathione Transferase; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C113118:glutathione-BPDE conjugate; C421109:multidrug resistance-associated protein 1